Energy ray curable inkjet printing ink and method for producing printed matter

Abstract

To provide an energy ray-curable inkjet print ink that achieves excellent curable and adhesive properties even in the case where thin-film printing is applied to a recorded medium that is prone to be penetrated by liquid components in the ink.SOLUTION: An energy ray-curable inkjet print ink contains a predetermined polymerizable compound (A) and a hydroxy acetophenone polymerization initiator (B) having two or more hydroxy groups. The hydroxy acetophenone polymerization initiator (B) is contained at a rate of less than 2 mass% to the total amount of the energy ray-curable inkjet print ink.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an energy radiation curable ink jet printing ink that can be used to produce a variety of printed materials. [Background technology]

[0002] Energy ray curable inkjet printing inks are superior in curability and drying properties compared to other inks, and are therefore used for printing on a variety of recording media including, for example, plastic films.

[0003] As the energy ray-curable inkjet printing ink, for example, a photocurable inkjet recording ink composition containing a polymerizable compound containing a predetermined vinyl ether group-containing (meth)acrylic acid ester and phenoxyethyl (meth)acrylate, a photopolymerization initiator, and a coloring material has been described (see, for example, Patent Document 1).

[0004] However, when an ink suitable for printing on a recording medium such as a plastic film into which the liquid component contained in the ink is unlikely or does not penetrate is applied to a recording medium into which the liquid component is likely to penetrate, the curing property of the coating film formed by the ink may decrease, or the adhesion between the coating film and the recording medium may decrease. In particular, when the coating film is thin (thin), a significant decrease in curing property may occur.

[0005] As a recording medium that is easily permeated with the liquid component, for example, synthetic paper containing a resin component such as polypropylene and an inorganic filler, etc. When attempting to form a thin coating film on the surface of the synthetic paper, there are cases where the curing property is reduced due to the influence of oxygen inhibition, etc., and the adhesion to the synthetic paper is reduced. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-121361 A Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide an energy ray curable inkjet printing ink which has excellent curability and adhesion even when a thin film is printed on a recording medium which is easily permeated by the liquid components in the ink. [Means for solving the problem]

[0008] The present inventors have solved the above-mentioned problems by providing an energy ray-curable inkjet printing ink containing a compound (A) represented by the following general formula (1) and a hydroxyacetophenone-based polymerization initiator (B) having two or more hydroxyl groups, wherein the hydroxyacetophenone-based polymerization initiator (B) is contained in an amount of less than 2 mass % based on the total amount of the energy ray-curable inkjet printing ink. CH 2 =CR 1 -CO-OR 2 -O-CH=CH-R 3 (1) (In formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents a structure containing 2 to 20 carbon atoms, and R 3 represents a structure containing a hydrogen atom or 1 to 11 carbon atoms. Effect of the Invention

[0009] The energy ray-curable ink jet printing ink of the present invention has excellent curing properties and excellent adhesion to synthetic paper, even when used for printing on synthetic paper, for example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The energy ray curable inkjet printing ink of the present invention contains a compound (A) represented by the following general formula (1) and a hydroxyacetophenone-based polymerization initiator (B) having two or more hydroxyl groups, and is characterized in that the hydroxyacetophenone-based polymerization initiator (B) is contained in an amount of less than 2 mass % based on the total amount of the energy ray curable inkjet printing ink.

[0011] CH 2 =CR 1 -CO-OR 2 -O-CH=CH-R 3 (1) (In formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents a structure containing 2 to 20 carbon atoms, and R 3 represents a structure containing a hydrogen atom or 1 to 11 carbon atoms.

[0012] The compound (A) used has a structure represented by the general formula (1). 1 represents a hydrogen atom or a methyl group, and R 2 represents a structure containing 2 to 20 carbon atoms, and R 3 represents a structure containing a hydrogen atom or 1 to 11 carbon atoms.

[0013] R 2 Specific examples of the alkylene group include linear alkylene groups having 2 to 20 carbon atoms, branched alkylene groups having 2 to 20 carbon atoms, cyclic alkylene groups having 2 to 20 carbon atoms, structures containing an ether bond or an ester bond and 2 to 20 carbon atoms, and aromatic cyclic structures having 6 to 11 carbon atoms which may be substituted with functional groups of the type having hydrogen atoms partially or entirely.

[0014] Among them, the above-mentioned R 2 As the alkylene group, it is more preferable to use an alkylene group having 2 to 6 carbon atoms or a structure containing an ether bond and 2 to 9 carbon atoms in order to obtain an energy ray-curable inkjet printing ink having excellent curing properties.

[0015] R 3Specific examples of the alkylene group include linear alkylene groups having 1 to 11 carbon atoms, branched alkylene groups having 1 to 11 carbon atoms, cyclic alkylene groups having 1 to 11 carbon atoms, and aromatic groups having 6 to 11 carbon atoms which may be substituted.

[0016] Among them, the above-mentioned R 3 As the alkyl group, it is more preferable to use a hydrogen atom or an alkyl group having 1 to 2 carbon atoms in order to obtain an energy ray-curable inkjet printing ink having excellent curing properties.

[0017] Specifically, it is preferable to use 2-(2-vinyloxyethoxy)ethyl (meth)acrylate as the compound (A).

[0018] The compound (A) including the 2-(2-vinyloxyethoxy)ethyl (meth)acrylate is preferably contained in an amount of 30% by mass or more, more preferably in the range of 35 to 60% by mass, and particularly preferably in the range of 40 to 60% by mass, based on the total amount of the energy ray-curable inkjet printing ink of the present invention, in order to maintain low viscosity and excellent curability of the ink.

[0019] Next, the hydroxyacetophenone-based polymerization initiator (B) used in the present invention will be described.

[0020] The hydroxyacetophenone-based polymerization initiator (B) has two or more hydroxyl groups. Here, when a hydroxyacetophenone-based polymerization initiator having one hydroxyl group is used instead of the hydroxyacetophenone-based polymerization initiator (B), the curing property may be insufficient. In addition, when a hydroxyacetophenone-based polymerization initiator having one hydroxyl group is used, the odor of the printed matter may become an issue.

[0021] The hydroxyacetophenone-based polymerization initiator (B) is used in an amount of less than 2% by mass relative to the total amount of the energy ray-curable inkjet printing ink of the present invention. Here, an energy ray-curable inkjet printing ink containing 2% by mass or more of the hydroxyacetophenone-based polymerization initiator (B) may experience a decrease in adhesion to a recording medium or a decrease in ejection stability. In addition, an energy ray-curable inkjet printing ink containing 2% by mass or more of the hydroxyacetophenone-based polymerization initiator (B) may experience precipitation of the polymerization initiator (B) when stored at low temperatures.

[0022] In this way, in the present invention, by using the compound (A) and the hydroxyacetophenone-based polymerization initiator (B) in a combination at a predetermined content ratio, it is possible to achieve both excellent curability, even better adhesion to the recording medium, and even better ejection stability.

[0023] The content of the hydroxyacetophenone-based polymerization initiator (B) is preferably in the range of 0.2% by mass or more and less than 2.0% by mass, based on the total amount of the energy ray-curable inkjet printing ink of the present invention, and is particularly preferably in the range of 0.3% by mass or more and 1.8% by mass or less, in order to achieve both excellent curability, even better adhesion to the recording medium, and even better ejection stability.

[0024] Specific examples of the hydroxyacetophenone-based polymerization initiator (B) include 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one and 2-hydroxy-1-(4-(4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl)-2-methylpropanone. Among them, as the hydroxyacetophenone-based polymerization initiator (B), it is preferable to use 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one from the viewpoints of curability when thin-film printing is performed and excellent adhesion to the recording medium.

[0025] The energy ray-curable inkjet printing ink of the present invention may contain a polymerizable compound other than the compound (A) as a polymerizable compound that can be cured by irradiation with energy rays, which will be described later. Examples of the polymerizable compound other than the compound (A) include a compound (C) having three or more polymerizable unsaturated double bonds.

[0026] As the compound (C), for example, trimethylolpropane triacrylate, trimethylolpropane ethylene oxide modified triacrylate, glycerin triacrylate, glycerin propoxy triacrylate, trimethylolpropane propoxy modified triacrylate, pentaerythritol can be used. Among them, it is preferable to use trimethylolpropane triacrylate as the compound (C) in order to realize excellent adhesion to the recording medium.

[0027] The compound (C) is preferably used in an amount of 1 to 20% by mass, and particularly preferably 3 to 15% by mass, based on the total amount of the energy ray-curable inkjet printing ink, in order to achieve even better adhesion.

[0028] Examples of the polymerizable compound other than the compound (A) and the compound (C) include compounds having one polymerizable unsaturated double bond. Specific examples of the polymerizable compound include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, amino(meth)acrylate, 2-ethylhexyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, dodecyl(meth)acrylate, hexadecyl(meth)acrylate, octadecyl(meth)acrylate, cyclohexyl(meth)acrylate, benzo(meth)acrylate, and the like. Examples of the acrylates include diethyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, nonylphenoxyethyl (meth)acrylate, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, vinylpyrrolidone, and N-vinylformamide.

[0029] In addition, as the polymerizable compound other than the compound (A) and the compound (C), a compound having two or more polymerizable unsaturated double bonds can also be used. For example, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, Examples of the poly(meth)acrylate include acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, di(meth)acrylate of tris(2-hydroxyethyl)isocyanurate, neopentyl glycol di(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol F di(meth)acrylate, hydrogenated bisphenol A di(meth)acrylate, pentaerythritol tri(meth)acrylate, poly(meth)acrylate of dipentaerythritol, and alkylene oxide modified products such as ethylene oxide and propylene oxide, and caprolactone modified products of these.

[0030] As the polymerizable compound other than the compound (A) and the compound (C), it is preferable to use 1,6-hexanediol diacrylate and dipropylene glycol diacrylate in order to achieve both better discharge stability and better adhesion.

[0031] The polymerizable compound other than the compound (A) and the compound (C) is preferably used in a range of 5 to 60% by mass, and particularly preferably in a range of 15 to 50% by mass, based on the total amount of the energy ray-curable inkjet printing ink, in order to achieve even better adhesion.

[0032] In the energy ray-curable ink jet printing ink of the present invention, a polymerization initiator other than the polymerization initiator (B) can be used in combination with the hydroxyacetophenone-based polymerization initiator (B) as a polymerization initiator.

[0033] Examples of polymerization initiators other than the hydroxyacetophenone-based polymerization initiator (B) include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, benzoin isobutyl ether, benzyl, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone) 1-hydroxycyclohexyl phenyl ketone, benzo isopropyl ether, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, benzophenone, 4-phenylbenzophenone, isophthalphenone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-(4-morpholinophenyl)-butan-1-one), 2,4-diethylthioxanthone, 2-isopropylthioxanthone, and the like.

[0034] Among them, in the present invention, it is particularly preferable to use a combination of a hydroxyacetophenone-based polymerization initiator (B) and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide or 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide as the polymerization initiator in order to maintain excellent curability.

[0035] The polymerization initiator other than the hydroxyacetophenone-based polymerization initiator (B) is preferably used in the range of 1 to 20 mass % based on the total amount of the energy ray-curable inkjet printing ink, and it is particularly preferable to use it in the range of 2 to 15 mass % in order to impart even better adhesion.

[0036] The energy ray-curable ink jet printing ink of the present invention may contain a colorant, if necessary, in addition to the compound (A) and the hydroxyacetophenone-based polymerization initiator (B).

[0037] The colorant may be, for example, a pigment or a dye, and examples of the pigment include a phthalocyanine pigment used in cyan ink, a quinacridone pigment used in magenta ink, an azo pigment used in yellow ink, carbon black used in black ink, and a white pigment usable in white ink.

[0038] Examples of phthalocyanine pigments used in the cyan ink include CI Pigment Blue 1, 2, 3, 15:3, 15:4, 16:6, 16, 17:1, 75, and 79.

[0039] Examples of quinacridone pigments used in magenta inks include CI Pigment Red 122, CI Pigment Red 202, CI Pigment Red 209, CI Pigment Violet 19, and the like.

[0040] Examples of azo pigments used in yellow ink include monoazo and disazo pigments such as CI Pigment Yellow 120, 151, 154, 175, 180, 181, 1, 65, 73, 74, 116, 12, 13, 17, 81, 83, 150, 155, 214, and 128.

[0041] Examples of carbon black used in black inks include Mitsubishi Chemical's No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, and No. 2200B; Columbia's Raven 5750, 5250, 5000, 3500, 1255, and 700; Cabot's Regal 400R, 330R, 660R, Mogul L, 700, Monarch 800, 880, 900, 1000, 1100, 1300, and 1400; and Degussa's Color Black FW1, FW2, FW2V, FW18, FW200, ColorBlack S150, S160, S170, Printex Examples include 35, 35 U, 35 V, 140U, Special Black 6, 5, 4A, and 4.

[0042] The white pigment that can be used in the white ink is not particularly limited, and any known inorganic white pigment can be used. Examples of the inorganic white pigment include sulfates or carbonates of alkaline earth metals, silicas such as fine powdered silicic acid and synthetic silicates, calcium silicate, alumina, alumina hydrate, titanium oxide, zinc oxide, talc, clay, etc. As the inorganic white pigment, the above-mentioned silicas and the like can also be used whose surfaces have been treated by various surface treatment methods.

[0043] The volume average particle size of the pigment is preferably in the range of 10 to 300 nm, and more preferably 50 to 200 nm.

[0044] In order to obtain sufficient image density and lightfastness of the printed image, the pigment is preferably contained in the range of 1 to 20% by mass, more preferably in the range of 1 to 10% by mass, and most preferably in the range of 1 to 5% by mass, based on the total amount of each ink. Also, it is preferable that the pigment concentration of the magenta ink is higher than that of the other color inks. Specifically, it is preferable that the pigment concentration of the magenta ink is 1.2 times or more, and more preferably 1.2 to 4 times, that of the other color inks.

[0045] The titanium oxide used has a volume average particle size of preferably 100 to 500 nm, and in order to obtain an ink having even better ejection stability and high color development of printed images, it is even more preferable to use titanium oxide having a volume average particle size of 150 nm to 400 nm.

[0046] The pigment may be used in combination with a pigment dispersant, a pigment derivative (synergist), or the like, for the purpose of enhancing the dispersion stability with respect to the compound (A) or the like.

[0047] Examples of the pigment dispersant that can be used include Ajisper PB821, PB822, and PB817 manufactured by Ajinomoto Fine-Techno Co., Ltd.; Solspers 24000GR, 32000, 33000, and 39000 manufactured by Avecia Corporation; and Disparlon DA-703-50, DA-705, and DA-725 manufactured by Kusumoto Chemicals Co., Ltd.

[0048] The amount of the pigment dispersant used is preferably in the range of 10 to 100% by mass relative to the pigment, and more preferably in the range of 20 to 60% by mass in order to obtain an ink having even better ejection stability and pigment dispersibility. As the pigment derivative, for example, a sulfonic acid derivative of a pigment can be used.

[0049] In addition to the above-mentioned components, the energy ray curable inkjet printing ink of the present invention may contain, if necessary, a polymerization inhibitor such as hydroquinone, methoquinone, di-t-butylhydroquinone, p-methoxyphenol, butylhydroxytoluene, nitrosamine salt, etc. The polymerization inhibitor may be used in an amount of 0.01% by mass to 2% by mass based on the total amount of the ink of the present invention.

[0050] The energy ray-curable inkjet printing ink of the present invention may contain a sensitizer such as trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N,N-dimethylbenzylamine, and 4,4'-bis(diethylamino)benzophenone.

[0051] As the energy ray-curable inkjet printing ink of the present invention, one containing a non-reactive resin such as an acrylic resin, an epoxy resin, a terpene phenol resin, or a rosin ester can be used in order to further improve adhesion to a substrate such as a plastic substrate.

[0052] The energy ray curable inkjet printing ink of the present invention preferably has a viscosity at 25°C in the range of 3 mPa·sec to 30 mPa·sec, and more preferably in the range of 5 mPa·sec to 20 mPa·sec in order to achieve stable inkjet ejection.

[0053] The energy ray curable inkjet printing ink of the present invention can be produced, for example, by dispersing the pigment using a normal dispersing machine such as a bead mill, a mixture of the compound (A), and optionally a pigment, a pigment dispersant, and a resin, and then adding the hydroxyacetophenone-based polymerization initiator (B), and optionally adding additives such as a polymerization inhibitor, a sensitizer, and a surface tension adjuster, followed by stirring and dissolving.

[0054] The energy ray curable inkjet printing ink can also be produced by previously producing a high-concentration pigment dispersion (mill base) containing a pigment, a pigment dispersant, a resin, and the like using a conventional dispersing machine such as a bead mill, and then supplying the compound (A), the hydroxyacetophenone-based polymerization initiator (B), additives, and the like, and stirring and mixing the resulting mixture.

[0055] As the dispersing machine, in addition to a bead mill, various known and commonly used dispersing machines such as an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a Dyno Mill, a Dispermat, an SC Mill, or a Nanomizer can be used.

[0056] The energy ray-curable inkjet printing ink of the present invention is cured by irradiation with active energy rays, preferably ultraviolet light, etc. As the light source for ultraviolet light, etc., light sources generally used for active energy ray-curable inkjet printing inks, such as metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, UV-LED lamps, etc., can be used.

[0057] The energy ray-curable ink jet printing ink of the present invention can be suitably used exclusively for printing by an ink jet recording method using an ink jet recording apparatus.

[0058] Any of the conventional inkjet recording methods can be used, including a method of ejecting droplets by utilizing the vibration of a piezoelectric element (a recording method using an inkjet head that forms ink droplets by the mechanical deformation of an electrostrictive element) and a method that utilizes thermal energy.

[0059] The energy ray curable inkjet printing ink is ejected onto a substrate, which is a recording medium, using an inkjet recording device, and cured by irradiating with active energy rays to produce a printed matter. Examples of the printed matter include advertisements, signs, guide boards, and promotional item printing.

[0060] The energy ray-curable inkjet printing ink of the present invention has excellent adhesion to various substrates that are recording media, and can therefore be easily printed on the surface of a substrate having a curved surface or an irregular shape with projections and recesses.

[0061] The substrate may be, for example, a plastic substrate, and examples of the plastic substrate include substrates made of ABS (acrylonitrile butadiene styrene) resin, PVC (polyvinyl chloride) / ABS resin, PA (polyamide) / ABS resin, PC (polycarbonate) / ABS resin, ABS-based polymer alloys such as PBT (polybutylene terephthalate) / ABS, AAS (acrylonitrile acrylic rubber styrene) resin, AS (acrylonitrile styrene) resin, AES (acrylonitrile ethylene rubber styrene) resin, MS ((meth)acrylic acid ester styrene)-based resin, PC (polycarbonate)-based resin, acrylic resin, methacrylic resin, PP (polypropylene)-based resin, and the like, which are used as general-purpose injection molding plastics.

[0062] As the plastic substrate, for example, a thermoplastic resin film used for packaging materials can also be used.

[0063] Examples of the thermoplastic resin film include those generally used as thermoplastic resin films for food packaging, such as polyethylene terephthalate (PET) film, polystyrene film, polyamide film, polyacrylonitrile film, polyolefin films such as polyethylene film (LLDPE: low density polyethylene film, HDPE: high density polyethylene film) and polypropylene film (CPP: non-oriented polypropylene film, OPP: biaxially oriented polypropylene film), polyvinyl alcohol film, ethylene-vinyl alcohol copolymer film, etc. As the thermoplastic resin film, those that have been subjected to a stretching treatment such as uniaxial stretching or biaxial stretching, or those whose surfaces have been subjected to a flame treatment or corona discharge treatment, etc., can also be used.

[0064] The energy ray-curable inkjet printing ink of the present invention can be used for printing on various recording media, and is particularly suitable for use in printing on synthetic paper containing polypropylene.

[0065] Synthetic paper containing polypropylene is made from raw materials such as polypropylene, inorganic fillers, and additives, and is produced by a biaxially stretched film forming method while generating fine pores. Due to this process, conventional energy ray curable inkjet printing inks tend to penetrate into synthetic paper, which may cause a decrease in the curability of the coating film formed by the ink and a decrease in the adhesion between the coating film and the synthetic paper. The energy ray curable inkjet printing ink of the present invention is less susceptible to oxygen inhibition and the like, even on such synthetic paper, and therefore has good curability and adhesion, and can be suitably used.

[0066] A manufacturing method will be described in which an energy ray-curable inkjet ink is printed on synthetic paper containing polypropylene, and then the printed surface is irradiated with energy rays to cure the ink, thereby forming a coating film.

[0067] The energy ray curable inkjet ink can be used in an inkjet recording method. The inkjet recording method includes a discharge step of discharging the energy ray curable inkjet ink onto synthetic paper containing polypropylene, and a curing step of irradiating the ink composition discharged in the discharge step with energy rays to cure the ink composition. The energy ray curable inkjet ink is preferably used in the discharge step because of its excellent discharge stability. In addition, in the curing step, the inkjet ink is preferably used even in low energy irradiation because of its excellent curability.

[0068] Next, a method for producing a printed matter in which a coating film formed by an energy ray curable inkjet printing ink on the surface of the synthetic paper has a thickness of 3 μm or less will be described. The inkjet recording method includes a discharge step of discharging an energy ray curable inkjet ink onto the synthetic paper to a coating film thickness of 3 μm or less, and a curing step of irradiating the ink composition discharged in the discharge step with energy rays to cure the ink composition. In the curing step, when the coating film has a thin thickness (thin film), a conventional energy ray curable inkjet printing ink may cause a significant decrease in curability. The energy ray curable inkjet ink is less susceptible to oxygen inhibition and the like even in a thin coating film of 3 μm or less, and can be suitably used. EXAMPLES

[0069] The present invention will now be described in more detail with reference to examples.

[0070] [Example of pigment dispersion preparation] (Preparation Example of Cyan Pigment Dispersion (1)) 10 parts by mass of Fastgen Blue TGR-J (phthalocyanine pigment CI Pigment Blue 15:4 manufactured by DIC), 4.5 parts by mass of Solspers 32000 (polymeric pigment dispersant manufactured by Lubrizol), 18 parts by mass of Light Acrylate PO-A (phenoxyethyl acrylate manufactured by Kyoeisha Chemical Co., Ltd.), and 67.5 parts by mass of Miramar M222 (dipropylene glycol diacrylate manufactured by MIWON) were mixed and stirred with a stirrer for 1 hour, and then treated with a bead mill for 2 hours to obtain a cyan pigment dispersion (1).

[0071] [Example 1] According to the blending ratio shown in Example 1 of Table 1, an energy beam curable inkjet printing ink was prepared. Specifically, 31.84 parts by mass of VEEA-AI (2-(2-vinyloxyethoxy)ethyl acrylate manufactured by Nippon Shokubai Co., Ltd.), 10.5 parts by mass of M300 (trimethylolpropane triacrylate manufactured by MIWON Co., Ltd.), 26.81 parts by mass of M222 (dipropylene glycol diacrylate manufactured by MIWON Co., Ltd.), 1.7 parts by mass of Omnirad 127 (2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one manufactured by IGM Co., Ltd.), 3.4 parts by mass of Omnirad 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide manufactured by IGM Co., Ltd.), 3.4 parts by mass of Omnirad TPO-H (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide manufactured by IGM Co., Ltd.), 1.5 parts by mass of Omnirad 1.7 parts by mass of 1173 (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide manufactured by IGM), 0.8 parts by mass of SPEEDCURE DETX (diethylthioxanthone manufactured by Lambson Japan), 2.5 parts by mass of KAYACURE EPA (4-dimethylaminobenzoic acid ethyl ester manufactured by Nippon Kayaku), 0.04 parts by mass of PP-360 (triphenylphosphine manufactured by K.I. Kasei), and 0.3 parts by mass of Tego Rad 2010 (silicone oil manufactured by Evonik) were added, and the mixture was heated and stirred at 60°C for 30 minutes, and then 15.08 parts by mass of the cyan pigment dispersion (1) was added, thoroughly stirred, and mixed to obtain an ink. Next, the ink was filtered using a 1.2 μm membrane filter to obtain energy beam curable inkjet recording ink 1.

[0072] [Examples 2 to 10] Energy beam-curable ink-jet printing inks 2 to 10 were obtained in the same manner as in Example 1, except that the formulations were changed as shown in Tables 1 and 2.

[0073] [Comparative Examples 1 to 4] Except for changing the formulation as shown in Table 3, the same method as in Example 1 was used to obtain energy beam-curable ink-jet printing inks 11 to 14.

[0074] [Creation of printed matter] The energy beam curable inkjet printing ink of the Example or Comparative Example was applied onto synthetic paper (Yupo 80 (UV) PA-T1 8LK Blue, manufactured by Lintec Corporation) using a spin coater to form a coating film having a thickness of 2 μm. Next, the coating film was irradiated with ultraviolet light using a UV irradiation device manufactured by GS Yuasa (4 kW (160 W) x 1 lamp (metal halide lamp, lamp output 80 W / cm).

[0075] In addition, the energy beam curable inkjet printing ink of the Example or Comparative Example was applied to synthetic paper (Yupo 80 (UV) PA-T1 8LK Blue, manufactured by Lintec Corporation) using a spin coater to form a coating film having a thickness of 9 μm. Next, the coating film was irradiated with ultraviolet light using a UV irradiation device manufactured by GS Yuasa (4 kW (160 W) x 1 lamp (metal halide lamp, lamp output 80 W / cm).

[0076] [Evaluation of Curability] 5. When a printed matter can be produced in which the surface of the coating film has no tack when touched with a finger and the surface of the coating film is not scratched when rubbed with a finger, the cumulative amount of ultraviolet light irradiated to the coating film is 60 mJ / cm 2 It was less than. 4. When a printed matter can be produced in which the surface of the coating film has no tack when touched with a finger and the surface of the coating film is not scratched when rubbed with a finger, the cumulative amount of ultraviolet light irradiated to the coating film is 60 mJ / cm 2 More than 80mJ / cm 2 It was less than. 3. When a printed matter can be produced in which the surface of the coating film has no tack when touched with a finger and the surface of the coating film is not scratched when rubbed with a finger, the cumulative amount of ultraviolet light irradiated to the coating film is 80 mJ / cm 2 More than 100mJ / cm 2 It was less than. 3. When a printed matter can be produced in which the surface of the coating film has no tack when touched with a finger and the surface of the coating film is not scratched when rubbed with a finger, the cumulative amount of ultraviolet light irradiated to the coating film is 80 mJ / cm 2 More than 100mJ / cm 2 It was less than. 2. When a printed matter can be produced in which the surface of the coating film has no tack when touched with a finger and the surface of the coating film is not scratched when rubbed with a finger, the cumulative amount of ultraviolet light irradiated to the coating film is 100 mJ / cm 2 More than 120mJ / cm 2 It was less than. 1. When a printed matter can be produced in which the surface of the coating film has no tack when touched with a finger and the surface of the coating film is not scratched when rubbed with a finger, the cumulative amount of ultraviolet light irradiated to the coating film is 120 mJ / cm 2 That was all.

[0077] [Adhesion to synthetic paper: Cross-cut tape peel test] A print was made according to the above-mentioned [Method of Making a Print]. The ultraviolet rays were irradiated until the surface of the coating film was no longer tacky when touched with a finger and the surface of the coating film was not scratched when rubbed with a finger. After making a cross-shaped cut with a cutter knife on the coating film of the print, Nichiban cellophane tape was attached and rubbed with a fingernail about 10 times. Next, the tape was peeled off vigorously at a peeling speed of about 1 cm / sec, and the presence or absence of peeled parts was confirmed. The following three-level evaluation was performed according to the following criteria.

[0078] ○: No peeling △: Peeling occurred only near the cut ×: Peeling occurred other than near the cut

[0079] [Table 1]

[0080] [Table 2]

[0081] [Table 3]

[0082] In Tables 1, 2, and 3, "VEEA-AI" is 2-(2-vinyloxyethoxy)ethyl acrylate manufactured by Nippon Shokubai Co., Ltd., "M300" is trimethylolpropane triacrylate manufactured by MIWON Co., Ltd., "M3130" is trimethylolpropane ethylene oxide modified triacrylate manufactured by MIWON Co., Ltd., "M-930" is glycerin triacrylate manufactured by Toagosei Co., Ltd., "M320" is glycerin propoxy triacrylate manufactured by MIWON Co., Ltd., "M360" is trimethylolpropane propoxy modified triacrylate manufactured by MIWON Co., Ltd., "M222" is dipropylene glycol diacrylate manufactured by MIWON Co., Ltd., "Omnirad 127" is 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one manufactured by IGM Co., Ltd., and "Omnirad "Omnirad TPO-H" is 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide manufactured by IGM, "Omnirad 1173" is 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide manufactured by IGM, "SPEEDCURE DETX" is diethylthioxanthone manufactured by Lambson Japan, "KAYACURE EPA" is 4-dimethylaminobenzoic acid ethyl ester manufactured by Nippon Kayaku, "PP-360" is triphenylphosphine manufactured by Kei-I Chemicals, and "Tego Rad 2010" is silicone oil manufactured by Evonik.

Claims

1. An energy ray curable inkjet printing ink containing a compound (A) represented by the following general formula (1) and a hydroxyacetophenone-based polymerization initiator (B) having two or more hydroxyl groups, wherein the compound (A) is contained in an amount of 35 to 60% by mass based on a total amount of the energy ray curable inkjet printing ink, the hydroxyacetophenone-based polymerization initiator (B) is 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one and is contained in an amount of less than 2% by mass based on a total amount of the energy ray curable inkjet printing ink, a compound (C) having three or more polymerizable unsaturated double bonds is contained in an amount of 1 to 20% by mass based on a total amount of the energy ray curable inkjet printing ink, and the polymerizable compound other than the compound (A) and the compound (C) is a compound selected from the group consisting of 1,6-hexanediol diacrylate and dipropylene glycol diacrylate. CH ２ =CR １ -CO-O-R ２ -O-CH=CH-R ３ (1) (In formula (1), R １ represents a hydrogen atom or a methyl group, R ２ represents a structure containing 2 to 20 carbon atoms, R ３ represents a hydrogen atom or a structure containing 1 to 11 carbon atoms.

2. 2. The energy ray curable inkjet printing ink according to claim 1, wherein the compound (C) having three or more polymerizable unsaturated double bonds is a compound selected from the group consisting of trimethylolpropane triacrylate, trimethylolpropane ethylene oxide modified triacrylate, glycerin triacrylate, glycerin propoxy triacrylate, trimethylolpropane propoxy modified triacrylate and pentaerythritol.

3. An energy ray curable inkjet printing ink according to claim 1 or 2, wherein the polymerizable compound other than compound (A) and compound (C) is contained in an amount in the range of 15 to 50 mass % relative to the total amount of the energy ray curable inkjet printing ink.

4. An energy ray curable inkjet printing ink as described in claim 1 or 3, wherein the content of the hydroxyacetophenone-based polymerization initiator (B) relative to the total amount of the energy ray curable inkjet printing ink is 0.3 mass% or more and 1.8 mass% or less.

5. The energy ray curable ink jet printing ink according to any one of claims 1 to 4, which is used for printing on synthetic paper containing polypropylene.

6. A method for producing a printed matter, comprising the steps of: printing on synthetic paper containing polypropylene with the energy ray-curable inkjet printing ink according to any one of claims 1 to 5; and irradiating the printed surface with energy rays to cure the ink, thereby forming a coating film.

7. The method for producing a printed matter according to claim 6, wherein a coating film formed on a surface of the synthetic paper by the energy ray curable inkjet printing ink according to any one of claims 1 to 5 has a thickness of 3 µm or less.

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