JP7713285B2 - Method for producing active energy ray curable ink and printed matter - Google Patents

Description

The present invention relates to an active energy ray-curable ink that can be used to produce a variety of printed materials.

Active energy ray curable inks have superior curing and drying properties compared to other inks, and are therefore used for printing on a variety of recording media, including plastic films.

As the actinic radiation curable ink, for example, an ink composition containing a colorant, a radical polymerization initiator having a specific structure, and a radical polymerizable compound such as tetrahydrofurfuryl acrylate is known (see, for example, Patent Document 1).

However, in recent years, tetrahydrofurfuryl acrylate may contain small amounts of tetrahydrofurfuryl alcohol as an impurity or decomposition product, which has been a concern due to its effects on the human body, such as skin irritation, so the industry has tended to avoid using inks containing tetrahydrofurfuryl acrylate.

On the other hand, inks that do not contain tetrahydrofurfuryl acrylate may cause a decrease in adhesion to plastic substrates.

Therefore, the industry has been calling for the development of an active energy ray-curable ink that does not contain tetrahydrofurfuryl (meth)acrylate or tetrahydrofurfuryl alcohol, or that contains a reduced amount of these compounds, and that has excellent adhesion to plastic substrates. However, such an ink has not yet been developed.

JP 2012-201815 A

The problem that the present invention aims to solve is to provide an active energy ray-curable ink that has excellent adhesion to various substrates including plastic substrates, even if it does not contain tetrahydrofurfuryl (meth)acrylate, tetrahydrofurfuryl alcohol, etc., or contains only a small amount of these substances.

The present inventors have solved the above problem by providing an active energy ray-curable ink that contains a polymerizable compound (A) that includes at least one compound selected from the group consisting of a compound (a2) having a structure represented by the following general formula (2) and a compound (a3) having a structure represented by the following general formula (3).

The active energy ray curable ink of the present invention has excellent adhesion to plastic substrates and the like even when it does not contain tetrahydrofurfuryl (meth)acrylate or tetrahydrofurfuryl alcohol, or when the content of such is low, and can therefore be suitably used, for example, in the production of printed matter using an inkjet recording device or the like.

FIG. 1 is a conceptual diagram showing a method for evaluating the tackiness of a coating film surface.

The active energy ray curable ink of the present invention is characterized by containing a polymerizable compound (A) containing at least one compound selected from the group consisting of a compound (a2) having a structure represented by the following general formula (2) and a compound (a3) having a structure represented by the following general formula (3).

(In general formula (2), ^R1 and ^R2 each independently represent a hydrogen atom or an alkyl group, and ^R3 represents a hydrogen atom or an alkyl group. In general formula (3), ^R3 represents a hydrogen atom or an alkyl group.)

The following describes compounds (a2) and (a3) that can be used in the polymerizable compound (A). As the compound (a2), a compound having a structure represented by the following general formula (2) is used, and as the compound (a3), a compound having a structure represented by the following general formula (3) is used.

(In general formula (2), ^R1 and ^R2 each independently represent a hydrogen atom or an alkyl group, and ^R3 represents a hydrogen atom or an alkyl group. In general formula (3), ^R3 represents a hydrogen atom or an alkyl group.)

The compounds (a2) and (a3) have a high anchoring effect on the substrate, which is the recording medium, and exhibit excellent adhesion to substrates such as plastic substrates.

As the compound (a2) and the compound (a3), compounds having the structure represented by the above general formula (2) or general formula (3) can be used alone or in combination of two or more kinds.

As the compound (a2), it is preferable to use a compound having a structure represented by the general formula (2) in order to further improve the adhesion of the ink to the substrate, and it is more preferable to use a compound in which R ¹ and R ² in the general formula (2) are each independently an alkyl group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, and R ³ is a hydrogen atom.

As the compound (a2), there can be used (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate in which R ¹ is a methyl group, R ² is an ethyl group, and R ³ is a hydrogen atom in general formula (2); a compound in which R ¹ is a methyl group, R ² is an isopropyl group, and R ³ is a hydrogen atom or a methyl group; or a compound in which R ¹ and R ² are methyl groups, and R ³ is a hydrogen atom or a methyl group. Of these, the use of (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate is particularly preferred in terms of obtaining an ink having excellent adhesion to the substrate.

The compound (a2) is preferably contained in the range of 5% by mass to 40% by mass of the entire polymerizable compound (A), and is preferably contained in the range of 8% by mass to 30% by mass in order to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates.

The compound (a3) may be a compound represented by the general formula (3).

The compound (a3) is preferably contained in the range of 5% by mass to 40% by mass of the entire polymerizable compound (A), and is preferably contained in the range of 8% by mass to 30% by mass in order to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates.

By using a polymerizable compound (A) containing either or both of the compound (a2) and the compound (a3), even if the polymerizable compound (A) does not contain the compound (c) having the structure represented by the chemical formula (5) described below, or even if the content ratio of the compound (c) relative to the entire polymerizable compound (A) is preferably 0% by mass to 0.2% by mass, more preferably 0% by mass to 0.1% by mass, and even more preferably 0% by mass to 0.05% by mass, it is possible to obtain an active energy ray-curable ink having excellent adhesion to various substrates including plastic substrates.

As the polymerizable compound (A), it is preferable to use one in which the compound (a2) and the compound (a3) are contained in a total amount within the range of 5% by mass to 40% by mass based on the entire polymerizable compound (A), in order to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates.

As the polymerizable compound (A), in addition to the compound (a2) and the compound (a3), a compound containing a combination of compounds (a1), (a4), and (a5) as described below can be used as necessary.

The compound (a1) that can be used in the polymerizable compound (A) is described below.

As the compound (a1), a compound having a structure represented by the following general formula (1) and a polymerizable unsaturated double bond can be used.

[In the general formula (1), ^R1 is an alkylene group having 1 or more carbon atoms, ^R2 is an alkylene group having 1 or more carbon atoms which may be the same as or different from ^R1 , ^R3 is a hydrogen atom or an alkyl group, and n is an integer of 0 or more.]

Examples of ^R1 and ^R2 constituting the general formula (1) include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, and an isobutylene group. ^R1 and ^R2 may be the same or different. Of the above, it is more preferable that ^{R1 and R2} are ^both ethylene groups in order to obtain an active energy ray-curable ink having excellent adhesion to various substrates including plastic substrates.

Examples of ^R3 constituting the general formula (1) include a hydrogen atom and alkyl groups such as a methyl group, an ethyl group, and a butyl group. Among these, it is more preferable that ^R3 is an ethyl group in order to obtain an active energy ray-curable ink having excellent adhesion to various substrates including plastic substrates.

In the general formula (1), n is preferably an integer in the range of 0 to 20, more preferably in the range of 0 to 3, and more preferably 1 in order to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates.

Specific examples of the compound (a1) that can be used include methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, diethylene glycol monobutyl ether (meth)acrylate, and methoxytriethylene glycol (meth)acrylate. Among them, the use of ethoxyethoxyethyl (meth)acrylate as the compound (a1) is particularly preferred in obtaining an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates, even when the polymerizable compound (A) does not contain a compound (c) having a structure represented by the chemical formula (5) described below, or when the content of the compound (c) relative to the entire polymerizable compound (A) is preferably 0% by mass to 0.2% by mass, more preferably 0% by mass to 0.1% by mass, even more preferably 0% by mass to 0.05% by mass, and particularly preferably 0% by mass.

The compound (a1) is preferably contained in the range of 20% by mass to 40% by mass of the entire polymerizable compound (A), and is preferably contained in the range of 25% by mass to 35% by mass in order to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates.

By using a polymerizable compound (A) containing the compound (a1) having the structure represented by the general formula (1), it is possible to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates, even when the content of the compound (c) having the structure represented by the chemical formula (5) described below is preferably 0% by mass to 0.2% by mass, more preferably 0% by mass to 0.1% by mass, even more preferably 0% by mass to 0.05% by mass, and particularly preferably 0% by mass, based on the total polymerizable compound (A).

Next, we will explain compound (a4) that can be used in the polymerizable compound (A).

As the compound (a4), a compound (a4) represented by the following general formula (4) is used.

(In general formula (4), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an alkyl group, and X ¹ represents a single bond or an alkylene group.)

Examples of the alkyl group include a methyl group, an ethyl group, etc. Specific examples of ^X1 include a methylene group and an ethylene group.

As the compound (a4) represented by the general formula (4), it is preferable to use one in which R ¹ , R ² and R ³ in the general formula (4) are hydrogen atoms, in order to exert an adhesive effect on plastic substrates.

As the compound (a4) represented by the general formula (4), it is preferable to use cyclic trimethylolpropane formal acrylate.

The compound (a4) is preferably contained in the range of 5% by mass to 40% by mass of the entire polymerizable compound (A), and is preferably contained in the range of 8% by mass to 30% by mass in order to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates.

By using a polymerizable compound (A) containing the compound (a4), it is possible to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates, even when the polymerizable compound (A) does not contain the compound (c) having the structure represented by the chemical formula (5) described below, or when the content of the compound (c) relative to the entire polymerizable compound (A) is preferably 0% by mass to 0.2% by mass, more preferably 0% by mass to 0.1% by mass, and even more preferably 0% by mass to 0.05% by mass.

Next, we will explain the 2-allyloxymethyl acrylate (a5) that can be used in the polymerizable compound (A).

The 2-allyloxymethyl acrylate alkyl (a5) is a compound represented by the following general formula (6):

(In general formula (6), R ¹ represents an alkyl group.)

Examples of the alkyl 2-allyloxymethylacrylate (a5) include compounds represented by the general formula (6) in which R ¹ is an alkyl group having 1 to 3 carbon atoms. The use of methyl 2-allyloxymethylacrylate in which R ¹ is a methyl group is more preferable in terms of obtaining an active energy ray-curable ink having excellent adhesion to various substrates including plastic substrates.

The active energy ray curable ink containing the 2-allyloxymethyl acrylate alkyl (a5) forms a heterocyclic structure when it adheres to the surface of a substrate, which is a recording medium, and cures. This makes it possible to obtain an active energy ray curable ink with excellent adhesion to various substrates, including plastic substrates.

The 2-allyloxymethyl alkyl acrylate (a5) is preferably contained in the polymerizable compound (A) in an amount ranging from 5% to 40% by mass, and is preferably contained in an amount ranging from 8% to 30% by mass in order to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates.

By using a polymerizable compound (A) containing the alkyl 2-allyloxymethylacrylate (a5), it is possible to obtain an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates, even when the polymerizable compound (A) does not contain the compound (c) having the structure represented by the chemical formula (5) described below, or when the content of the compound (c) relative to the entire polymerizable compound (A) is preferably 0% by mass to 0.2% by mass, more preferably 0% by mass to 0.1% by mass, and even more preferably 0% by mass to 0.05% by mass.

Here, we will explain compound (c) having the structure shown in chemical formula (5).

Examples of the compound (c) having the structure represented by the chemical formula (5) include tetrahydrofurfuryl (meth)acrylate and tetrahydrofurfuryl alcohol.

The polymerizable compound (A) used in the present invention may contain the compound (c), but the content of the compound (c) is preferably 0% by mass to 0.2% by mass, more preferably 0% by mass to 0.1% by mass, even more preferably 0% by mass to 0.05% by mass, and particularly preferably 0% by mass, based on the total amount of the polymerizable compound (A).

The polymerizable compound (A) preferably contains the compound (a2) or the compound (a3) as an essential component, and further comprises at least one selected from the compound (a1), the compound (a4), and the alkyl 2-allyloxymethyl acrylate (a5) in combination, in order to achieve a good adhesion effect to the substrate. In particular, the polymerizable compound (A) preferably contains the compound (a1), the compound (a2), the compound (a4), and the alkyl 2-allyloxymethyl acrylate (a5) in combination, and the use of the compound (a2), the compound (a4), and the alkyl 2-allyloxymethyl acrylate (a5) in combination is preferable in order to obtain an active energy ray-curable ink that has both better adhesion to various substrates, including plastic substrates, and reduced tackiness of the printed surface (coating).

The polymerizable compound (A) may contain, in addition to the compound (a1), the compound (a2), the compound (a3), the compound (a4), and the alkyl 2-allyloxymethylacrylate (a5), a compound (b) other than the compound (a1), the compound (a2), the compound (a3), the compound (a4), and the alkyl 2-allyloxymethylacrylate (a5), as necessary.

Compounds having a polymerizable unsaturated double bond can be used as the compound (b), and it is preferable to use a compound having 1 to 6 polymerizable unsaturated double bonds, and it is more preferable to use a compound having 1 to 3 polymerizable unsaturated double bonds in order to obtain an ink that is even more excellent in terms of flexibility and adhesion to the plastic substrate, etc.

It is preferable to use the compound (b) in an amount of 50% by mass to 90% by mass based on the total amount of the polymerizable compound (A) in order to obtain an ink that is even more excellent in terms of flexibility and adhesion to the plastic substrate, etc.

As the compound (b), for example, a compound (b-1) having a heterocyclic structure other than that of the chemical formula (5), a compound (b-2) having an aliphatic cyclic structure, etc. can be used.

Examples of the compound (b-1) that can be used include caprolactone-modified tetrahydrofurfuryl acrylate, acryloylmorpholine, N-vinyl-2-caprolactam, N-vinylpyrrolidone, and N-acryloyloxyethylhexahydrophthalimide. Among these, the use of N-vinyl-2-caprolactam as the compound (b-1) is preferable in obtaining an active energy ray-curable ink with excellent adhesion to various substrates including plastic substrates, even when the compound (c) having the structure represented by the chemical formula (5) is not present in the polymerizable compound (A) or the content of the compound (c) is 0% by mass to 0.2% by mass relative to the entire polymerizable compound (A).

The compound (b-1) is preferably used in an amount of 1% by mass to 15% by mass relative to the total amount of the polymerizable compound (A) in order to further improve the long-term storage stability of the ink of the present invention, and it is more preferable to use the compound (b-1) in an amount of 5% by mass to 15% by mass in order to obtain an ink that has excellent adhesion to various substrates including plastic substrates.

The compound (b-2) can be used to produce printed matter that has a level of chemical resistance that does not cause peeling of the coating film even when it comes into contact with chemicals such as alcohol, and is preferably used in combination with the compounds (a2) and (a3) and the compound (b-1) to obtain an active energy ray-curable ink that has even better adhesion to various substrates including plastic substrates.

Examples of the compound (b-2) that can be used include tricyclodecane dimethanol di(meth)acrylate, adamantyl (meth)acrylate, cyclohexane dimethanol mono(meth)acrylate, cyclohexane dimethanol di(meth)acrylate, trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate. Of these, the use of isobornyl (meth)acrylate is more preferable in obtaining an ink that can be used to produce printed matter having a printing coating film with excellent chemical resistance.

The compound (b-2) is preferably used in the range of 5% by mass to 24% by mass relative to the total amount of the polymerizable compound (A), and it is more preferable to use it in the range of 5% by mass to 20% by mass in order to obtain an ink that can be used to produce printed matter having a printing coating film with even better chemical resistance.

In particular, when the compound (a1) is used as the polymerizable compound (A), it is preferable to use the compound (b-2) in combination in order to reduce the tackiness of the coating film, and it is preferable to use them in combination in a range in which the ratio of the structure represented by general formula (1) possessed by the compound (a1) to the sum of the aliphatic cyclic structures possessed by the compounds (a2), (a4), (a5), and (b-2) [the structure represented by general formula (1)/the sum of the aliphatic cyclic structures possessed by the compounds (a2), (a4), (a5), and (b-2)] is 3 to 50.

The active energy ray-curable ink of the present invention may contain a photopolymerization initiator in addition to the polymerizable compound (A).

Examples of the photopolymerization initiator include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 1-hydroxy Cyclohexyl phenyl ketone, benzoin ethyl ether, benzil dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4'-methyl-diphenyl sulfide, and the like can be used.

As the photopolymerization initiator, it is preferable to use an acylphosphine oxide-based photopolymerization initiator among the above.

In addition, when a UV-LED light source is used as the light source of the active energy rays, it is preferable to use, as the photopolymerization initiator, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-(4-morpholinophenyl)-butan-1-one, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, etc., which correspond to the wavelength of light emitted from the UV-LED light source.

The photopolymerization initiator is preferably used in combination with a sensitizer. As the sensitizer, for example, an amine that does not have reactivity with the polymerizable compound (A), such as trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N,N-dimethylbenzylamine, and 4,4'-bis(diethylamino)benzophenone, can be used.

The active energy ray-curable ink of the present invention may contain a colorant, if necessary, in addition to the polymerizable compound (A) and the photopolymerization initiator.

As the colorant, for example, a pigment or a dye can be used. Examples of the pigment include phthalocyanine pigments used in cyan ink, quinacridone pigments used in magenta ink, azo pigments used in yellow ink, carbon black used in black ink, and white pigments that can be used in white ink.

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

Quinacridone pigments used in magenta inks include, for example, C.I. Pigment Red 122, C.I. Pigment Red 202, C.I. Pigment Red 209, and C.I. Pigment Violet 19.

As the azo pigment used in the yellow ink, for example, monoazo and disazo pigments such as C.I. Pigment Yellow 120, 151, 154, 175, 180, 181, 1, 65, 73, 74, 116, 12, 13, 17, 81, 83, 150, 155, 214, and 128 can be used.

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

There are no particular limitations on the white pigment that can be used in the white ink, 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 finely powdered silicic acid and synthetic silicates, calcium silicate, alumina, alumina hydrate, titanium oxide, zinc oxide, talc, clay, and the like. The inorganic white pigments that can be used include those in which the surface of the aforementioned silicas, etc. has been treated by various surface treatment methods.

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.

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 of the total amount of each ink, more preferably in the range of 1 to 10% by mass, and most preferably in the range of 1 to 5% by mass. Furthermore, 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 is 1.2 times or more higher than that of the other color inks, and more preferably 1.2 to 4 times higher.

It is preferable to use titanium oxide with a volume average particle size of 100 to 500 nm, and it is even more preferable to use titanium oxide with a volume average particle size of 150 nm to 400 nm in order to obtain ink with even better ejection stability and high color development of printed images.

The pigment may be used in combination with a pigment dispersant or a pigment derivative (synergist) for the purpose of increasing the dispersion stability with respect to the polymerizable compound (A) etc.

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.

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 with even better ejection stability and pigment dispersibility. In addition, as the pigment derivative, for example, a sulfonic acid derivative of the pigment can be used.

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

The active energy ray curable 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.

The active energy ray curable ink of the present invention can contain a non-reactive resin such as an acrylic resin, an epoxy resin, a terpene phenol resin, or a rosin ester, in order to further improve adhesion to a substrate such as a plastic substrate.

The active energy ray curable 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.

The active energy ray-curable ink of the present invention can be produced, for example, by dispersing the pigment in a mixture of the polymerizable compound (A), optionally a pigment, a pigment dispersant, and a resin, using a conventional dispersing machine such as a bead mill, adding a photopolymerization initiator, and optionally adding additives such as a polymerization inhibitor, a sensitizer, and a surface tension adjuster, and stirring and dissolving the mixture.

The active energy ray-curable ink can also be produced by first producing a high-concentration pigment dispersion (mill base) containing pigment, pigment dispersant, resin, etc., using a conventional dispersing machine such as a bead mill, and then supplying a photopolymerization initiator, polymerizable compound (A), additives, etc., and stirring and mixing the resulting mixture.

As the dispersing machine, in addition to a bead mill, various commonly 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.

The active energy ray curable ink of the present invention is cured by irradiation with active energy rays, preferably ultraviolet light. As a light source for ultraviolet light or the like, a light source typically used for active energy ray curable inkjet recording inks, such as a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, a low pressure mercury lamp, a high pressure mercury lamp, a UV-LED lamp, etc., can be used.

The active energy ray curable ink of the present invention can be suitably used for printing by the inkjet recording method using an inkjet recording device.

Any of the conventional inkjet recording methods can be used. Examples include a method of ejecting droplets using the vibration of a piezoelectric element (a recording method using an inkjet head that forms ink droplets by mechanically deforming an electrostrictive element) and a method that uses thermal energy.

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

The active energy ray-curable ink of the present invention has excellent adhesion to various substrates that are used as recording media, and can therefore be easily printed on the surfaces of substrates that have curved surfaces or irregular shapes.

As the substrate, for example, a plastic substrate can be used. Specific 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, etc., which are used as general-purpose injection molding plastics.

The plastic substrate can also be, for example, a thermoplastic resin film used for packaging materials.

The thermoplastic resin film may be any of those generally used 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: unstretched polypropylene film, OPP: biaxially stretched polypropylene film), polyvinyl alcohol film, and ethylene-vinyl alcohol copolymer film. The thermoplastic resin film may be one that has been stretched uniaxially or biaxially, or one whose surface has been subjected to flame treatment or corona discharge treatment.

The present invention will be explained in more detail below with reference to the following examples.

[Preparation Example of Pigment Dispersion]
Preparation Example of Cyan Pigment Dispersion (1) 10 parts by mass of Fastgen Blue TGR-G (phthalocyanine pigment C.I. Pigment Blue 15:4, manufactured by DIC Corporation), 4.5 parts by mass of Solsperse 32000 (pigment dispersant, manufactured by Lubrizol Corporation), and 85.5 parts by mass of Light Acrylate PO-A (phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) 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).

[Example 1]
According to the blending ratios shown in Example 1 in Table 1, MIRAMER M3130 (ethylene oxide (EO) modified trimethylolpropane triacrylate, manufactured by MIWON Corporation), MIRAMER M240 (ethylene oxide (EO) modified bisphenol A diacrylate, manufactured by MIWON Corporation), MEDOL-10 (2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd., IBXA (isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.), V-CAP (N-vinyl-2-caprolactam, manufactured by ISP), Light Acrylate POA (phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.), and KF-54 (polysiloxane, manufactured by Shin-Etsu Chemical Co., Ltd.) were placed in a container and mixed with stirring, and then Irgacure 819 (BASF Corporation) bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide), Irgacure.TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by BASF), and Kayacure DETX-S (diethylthioxanthone, manufactured by Nippon Kayaku Co., Ltd.) were added and dissolved by mixing at a temperature of 60° C. for 30 minutes.

Next, the cyan pigment dispersion (1) was added and mixed by stirring for 10 minutes to obtain an active energy ray-curable ink (C1) that can also be used for inkjet printing.

[Example 2]
An active energy ray-curable ink (C2) was obtained in the same manner as in Example 1, except that the amount of MEDOL-10 (2-methyl-2-ethyl-1,3-dioxolan-4-yl, manufactured by Osaka Organic Chemical Industry Co., Ltd.) used was changed from 20 parts by mass to 27 parts by mass, and the amount of POA (phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) used was changed from 16.3 parts by mass to 9.3 parts by mass.

[Example 3]
An active energy ray-curable ink (C3) was obtained in the same manner as in Example 1, except that the amount of MEDOL-10 (2-methyl-2-ethyl-1,3-dioxolan-4-yl, manufactured by Osaka Organic Chemical Industry Co., Ltd.) used was changed from 20 parts by mass to 34 parts by mass, and the amount of POA (phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) used was changed from 16.3 parts by mass to 2.3 parts by mass.

[Example 4]
An active energy ray-curable ink (C4) was obtained in the same manner as in Example 1, except that the amount of MEDOL-10 (manufactured by Osaka Organic Chemical Industry Ltd., (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate used was changed from 20 parts by mass to 27 parts by mass, and the amount of V-CAP (manufactured by ISP, N-vinyl-2-caprolactam) used was changed from 12 parts by mass to 5 parts by mass.

[Example 5]
An active energy ray-curable ink (C5) was obtained in the same manner as in Example 1, except that the amount of MEDOL-10 (2-methyl-2-ethyl-1,3-dioxolan-4-yl, manufactured by Osaka Organic Chemical Industry Ltd.) used was changed from 20 parts by mass to 27 parts by mass, the amount of POA (phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) used was changed from 16.3 parts by mass to 19.3 parts by mass, and the amount of IBXA (isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Ltd.) used was changed from 15 parts by mass to 5 parts by mass.

[Example 6]
An active energy ray-curable ink (C6) was obtained in the same manner as in Example 1, except that the amount of MEDOL-10 (2-methyl-2-ethyl-1,3-dioxolan-4-yl, manufactured by Osaka Organic Chemical Industry Ltd.) used was changed from 20 parts by mass to 27 parts by mass, the amount of POA (phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) used was changed from 16.3 parts by mass to 3.3 parts by mass, and the amount of IBXA (isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Ltd.) used was changed from 15 parts by mass to 21 parts by mass.

[Comparative Example 1]
An active energy ray curable ink (C'1) was obtained in the same manner as in Example 1, except that the amount of MEDOL-10 (Osaka Organic Chemical Industry Co., Ltd.: 2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl acrylate used was changed from 20 parts by mass to 0 parts by mass, the amount of POA (Kyoeisha Chemical Co., Ltd.: phenoxyethyl acrylate) used was changed from 16.3 parts by mass to 9.3 parts by mass, and the amount of tetrahydrofurfuryl acrylate used was changed from 0 parts by mass to 27 parts by mass.

[Comparative Example 2]
An active energy ray curable ink (C'2) was obtained in the same manner as in Comparative Example 1, except that the amount of POA (phenoxyethyl acrylate manufactured by Kyoeisha Chemical Co., Ltd.) used was changed from 9.3 parts by mass to 36.1 parts by mass, and the amount of tetrahydrofurfuryl acrylate used was changed from 27 parts by mass to 0.2 parts by mass.

[Comparative Example 3]
An active energy ray curable ink (C'3) was obtained in the same manner as in Comparative Example 1, except that the amount of POA (phenoxyethyl acrylate manufactured by Kyoeisha Chemical Co., Ltd.) used was changed from 9.3 parts by mass to 36.3 parts by mass, and the amount of tetrahydrofurfuryl acrylate used was changed from 27 parts by mass to 0 parts by mass.
[Comparative Example 4]
An active energy ray curable ink (C'4) was obtained in the same manner as in Comparative Example 1, except that the amount of POA (phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) used was changed from 9.3 parts by mass to 30.3 parts by mass, the amount of tetrahydrofurfuryl acrylate used was changed from 27 parts by mass to 0 parts by mass, and the amount of IBXA (isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Ltd.) used was changed from 15 parts by mass to 21 parts by mass.

[Skin irritation]
The evaluation was based on the degree of skin irritation caused by tetrahydrofurfuryl acrylate. Products that were considered to have high skin irritation caused by tetrahydrofurfuryl acrylate were evaluated as "X", products that were considered to have low skin irritation were evaluated as "△", and products that were considered to have no skin irritation caused by tetrahydrofurfuryl acrylate were evaluated as "○".

The abbreviations in Tables 1 and 2 refer to the following compounds.
M3130: MIWON Corporation Ethylene oxide (EO) modified trimethylolpropane triacrylate M240: MIWON Corporation Ethylene oxide (EO) modified bisphenol A diacrylate MEDOL: Osaka Organic Chemical Industry Co., Ltd. (2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl acrylate IBXA: Osaka Organic Chemical Industry Co., Ltd. Isobornyl acrylate V-CAP: ISP Corporation N-vinyl-2-caprolactam POA: Kyoeisha Chemical Co., Ltd. Phenoxyethyl acrylate THFA: Tetrahydrofurfuryl acrylate KF-54: Shin-Etsu Chemical Co., Ltd. Polysiloxane Irgacure 819: BASF Corporation Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide Irgacure TPO: BASF Corporation 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. Kayacure DETX-S: manufactured by Nippon Kayaku Co., Ltd. Diethylthioxanthone [Irgacure 819/Irgacure TPO]: weight ratio of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide to 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide

[Examples 7 to 12]
According to the blending ratios of the components shown in Tables 3 and 4, active energy ray-curable inkjet recording inks were prepared. Specifically, the container was filled with MIRAMER M3130 (ethylene oxide (EO) modified trimethylolpropane triacrylate manufactured by MIWON), MIRAMER M240 (ethylene oxide (EO) modified bisphenol A diacrylate manufactured by MIWON), V-190 (ethoxyethoxyethyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd.), MEDOL-10 ((2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd.), V200 (Viscoat #200, cyclic trimethylolpropane formal acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd.), FX-AO-MA (methyl 2-allyloxymethylacrylate manufactured by Nippon Shokubai Co., Ltd.), IBXA (isobornyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd.), V-CAP (N-vinyl-2-caprolactam manufactured by ISP), and light acrylate. POA (phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.), a tetrahydrofurfuryl acrylate composition containing a trace amount of tetrahydrofurfuryl alcohol, and KF-54 (polysiloxane, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and mixed with stirring, and then Irgacure 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, manufactured by BASF), Irgacure.TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by BASF), and Kayacure DETX-S (diethylthioxanthone, manufactured by Nippon Kayaku Co., Ltd.) were added and dissolved by mixing at a temperature of 60° C. for 30 minutes.

Next, the cyan pigment dispersion (1) was added and stirred for 10 minutes to obtain active energy ray-curable inks (C7 to C12).

[Adhesion to substrate]
The active energy ray curable ink was applied to a polycarbonate plate (Lexan, thickness 1 mm, PC, manufactured by Asahi Glass Co., Ltd.) and a vinyl chloride sheet (vinyl chloride sheet, PVC, manufactured by DIC Corporation) to a thickness of 10 μm using a spin coater, and then irradiated with an LED irradiation device (emission wavelength: 385 nm, peak intensity: 500 mW/cm ² ) manufactured by Hamamatsu Photonics K.K. equipped with a stage movement device until the tack of the coating surface disappeared (until it became tack-free).

The resulting cured coating was cut with a utility knife into 25 squares of 5 x 5, then cellophane tape manufactured by Nichiban Co., Ltd. was applied and rubbed with a fingernail about 10 times. The tape was peeled off vigorously at a peeling speed of about 1 cm/sec, and the number of squares of the coating remaining on the surface of the polycarbonate plate or polyvinyl chloride sheet was counted.

Evaluation criteria: ⊚: The number of squares of the coating remaining on the surface of the polycarbonate plate or vinyl chloride sheet was 25, and no chipping of the coating occurred near the cuts.

◯: The number of coating squares remaining on the surface of the polycarbonate plate or polyvinyl chloride sheet was 20 or more.

△: The number of squares of coating remaining on the surface of the polycarbonate plate or polyvinyl chloride sheet was 15 or more but less than 20.

×: The number of squares of coating remaining on the surface of the polycarbonate plate or polyvinyl chloride sheet was less than 15.

[Solvent resistance]
The active energy ray-curable ink was applied to a polycarbonate plate (Asahi Glass Co., Ltd., Lexan, thickness 1 mm, PC) to a thickness of 10 μm using a spin coater, and then irradiated with an LED irradiation device (emission wavelength: 385 nm, peak intensity: 500 mW/cm ² ) equipped with a stage movement device manufactured by Hamamatsu Photonics K.K. until the tack on the coating surface disappeared (until it became tack-free).

A cotton swab soaked in a mixture of ethanol and water (ethanol content: 70% by mass) was placed on the resulting cured coating film, and the film was rubbed left and right 10 times over an area of approximately 2 cm. Films that left no marks on the coating surface were rated as "○", and films that left marks were rated as "×".

[Coating surface tackiness]
The active energy ray curable ink was applied to a polycarbonate plate (Lexan, thickness 1 mm, PC, manufactured by Asahi Glass Co., Ltd.) and a vinyl chloride sheet (vinyl chloride sheet, PVC, manufactured by DIC Corporation) to a thickness of 10 μm using a spin coater, and then irradiated with an LED irradiation device (emission wavelength: 385 nm, peak intensity: 500 mW/cm ² ) manufactured by Hamamatsu Photonics K.K. equipped with a stage movement device until the tack of the coating surface disappeared (until it became tack-free).

Next, a stainless steel petri dish (Φ75 mm) was prepared and a 15 g weight was attached to the inside side of the dish.

Next, the stainless steel petri dish with the weight attached was fixed by hand in an upright position on the coating surface so that the positional relationship between the weight and the coating surface was as shown in Figure 1.

Next, the hand was removed from the stainless steel petri dish, and the stainless steel petri dish was swung back and forth on the surface of the membrane, and the evaluation was based on the number of times it took for the dish to stop.
○: 8 times or more○-△: 6 to 7 times△: 5 to 6 times△-×: 3 to 4 times×: 0 to 2 times

1 Stainless steel dish 2 Weight 3 Coating surface

Claims (6)

The present invention comprises a compound (a2) having a structure represented by the following general formula (2), and a polymerizable compound (A) including the compound (a2), a compound (a3) represented by the following general formula (3), and a compound (b) having a polymerizable unsaturated double bond other than a compound (a4) represented by the following general formula (4),
The compound (b) includes a compound (b-1) having a heterocyclic structure other than that represented by the following chemical formula (5) and a compound (b-2) having an aliphatic cyclic structure,
the compound (a2) is contained in an amount of 5% by mass to 38% by mass based on the total amount of the polymerizable compound (A);
the compound (b-1) is N-vinyl-2-caprolactam, and is contained in an amount of 1% by mass to 15% by mass based on the total amount of the polymerizable compound (A);
the compound (b-2) is isobornyl (meth)acrylate and is contained in an amount of 5% by mass to 24% by mass based on the total amount of the polymerizable compound (A);
An active energy ray-curable ink, characterized in that it does not contain a compound having a structure represented by the following chemical formula (5):
(In general formula (2), ^R1 and ^R2 each independently represent a hydrogen atom or an alkyl group, and ^R3 represents a hydrogen atom or an alkyl group.)
(In general formula (3), R3 ^represents a hydrogen atom or an alkyl group.)
(In general formula (4), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an alkyl group, and X ¹ represents a single bond or an alkylene group.)
2. The active energy ray-curable ink according to claim 1, wherein the polymerizable compound (A) further contains a compound (a1) having a structure represented by the following general formula (1) and a polymerizable unsaturated double bond:
[In the general formula (1), ^R1 is an alkylene group having 1 or more carbon atoms, ^R2 is an alkylene group having 1 or more carbon atoms which may be the same as or different from ^R1 , ^R3 is a hydrogen atom or an alkyl group, and n is an integer of 0 or more.] The active energy ray curable ink according to claim 2, wherein the polymerizable compound (A) contains the compound (a1) in an amount ranging from 20% by mass to 40% by mass relative to the entire polymerizable compound (A). The active energy ray curable ink according to any one of claims 1 to 3, which has a viscosity at 25°C in the range of 5 to 30 mPa·sec. The active energy ray-curable ink according to any one of claims 1 to 4, further comprising an acylphosphine oxide-based photopolymerization initiator. A method for producing a printed matter, comprising ejecting the active energy ray curable ink according to any one of claims 1 to 5 onto a recording medium using an inkjet recording device, and curing the ink by irradiating the ink with active energy rays.