JP2015067825A - Active energy ray-curable inkjet recording ink and ink set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active energy ray-curable inkjet recording ink and ink set having excellent storage stability.SOLUTION: An active energy ray-curable inkjet recording ink comprises a polymerizable compound represented by general formula (1), a colorant, and vitamins. In the formula (1), Ris a hydrogen atom or methyl group, Ris an organic residue having 2 to 20 carbon atoms, Ris a hydrogen atom or an organic residue having 1 to 11 carbon atoms. There is also provided an active energy ray-curable inkjet recording ink set.

Description

  The present invention relates to an active energy ray-curable ink for ink jet recording and an ink set.

  Printing with an inkjet printer recording device is a method that ejects ink from nozzles and adheres to the recording material. Unlike conventional printing methods, this is a printing method that does not use a plate, so on-demand printing that can accommodate a small variety of products This printing method is expected to be used in a wide range of fields. In particular, in recent years, as a recording material, many studies have been made on printing on a non-absorbing substrate such as plastic from printing on a conventional absorbing substrate such as paper.

  As an ink used in this inkjet recording apparatus, an ink that is cured and dried with an active energy ray such as an ultraviolet ray has a short drying time on a non-absorbing material, and has excellent adhesion and durability of a printed image. Many have been proposed. Furthermore, as an ink for performing white printing on a black or dark base material, UV-curable white ink for inkjet recording using titanium oxide, which is a white pigment having excellent hiding power, coloring power, chemical resistance, etc., as a coloring material Has also been proposed. (For example, see Patent Document 1)

On the other hand, an example of using 2- (2-vinyloxyethoxy) ethyl acrylate as a monomer to be used is known (see, for example, Patent Document 2). 2- (2-vinyloxyethoxy) ethyl acrylate is a monomer having an acryloyl group and a vinyl ether group in one molecule, and is excellent in curability and adhesion to a substrate. However, sometimes it gelled.
In particular, titanium oxide used for white ink is generally surface-treated, and sometimes has a tendency to induce gelation due to the influence of active residues. Accordingly, the white ink tends to have storage stability as compared with other color inks.

JP 2008-308692 A JP 2012-207084 A

  An object of the present invention is to provide an active energy ray-curable ink jet recording ink and an ink set which are excellent in storage stability.

  The present inventors solved the above-mentioned problems by using 2- (2-vinyloxyethoxy) ethyl (meth) acrylate in combination with vitamins as an active energy ray polymerizable compound.

  That is, the present invention provides an active energy ray-curable ink jet recording ink containing a polymerizable compound represented by the general formula (1), a colorant, and vitamins.

（１）

(1)

(In formula (1), R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an organic residue having 2 to 20 carbon atoms, and R ₃ represents a hydrogen atom or an organic residue having 1 to 11 carbon atoms. Represents.)

  The present invention is also an active energy ray curable ink jet recording ink set containing a white ink, wherein the white ink is the active energy ray curable ink jet recording ink described in the previous term. Provide an ink set.

  According to the present invention, it is possible to provide an active energy ray-curable white ink for inkjet recording and an ink set which are excellent in storage stability.

(Active Energy Ray Polymerizable Compound Polymerizable Compound Represented by Formula (1))
The active energy ray-curable composition of the present invention uses the polymerizable compound represented by the general formula (1) as an essential component.
In the general formula (1), R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an organic residue having 2 to 20 carbon atoms, and R ₃ represents a hydrogen atom or an organic residue having 1 to 11 carbon atoms. Represents a group.
Specifically, R ₂ is a linear, branched or cyclic alkylene group having 2 to 20 carbon atoms, and having 2 to 20 carbon atoms having an oxygen atom by an ether bond and / or an ester bond in the structure. An alkylene group, an aromatic group having 6 to 11 carbon atoms which may be substituted is represented. Among these, an alkylene group having 2 to 6 carbon atoms and an alkylene group having 2 to 9 carbon atoms having an oxygen atom by an ether bond in the structure are preferable.
Specific examples of the organic residue having 1 to 11 carbon atoms represented by R ₃ include a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, and substitution having 6 to 11 carbon atoms. Represents an aromatic group or the like. Of these, an alkyl group having 1 to 2 carbon atoms and an aromatic group having 6 to 8 carbon atoms are preferable.

  Among them, it is preferable to use 2- (2-vinyloxyethoxy) ethyl (meth) acrylate. Examples of commercially available (meth) acrylic acid 2- (2-vinyloxyethoxy) ethyl include VEEA and VEEM manufactured by Nippon Shokubai Co., Ltd.

  The (meth) acrylic acid 2- (2-vinyloxyethoxy) ethyl is preferably contained in an amount of 10 to 100% by mass, more preferably 15 to 100% by mass, based on the total amount of the polymerizable compound. If it is less than 10% by mass, sufficient curability cannot be obtained, and the back-off to the non-printing surface cannot be suppressed, the adhesion of the ink coating to the substrate is reduced, or the odor emitted from the ink coating is strong. It becomes.

(Active energy ray polymerizable compounds and other polymerizable compounds)
In this invention, there is no limitation in particular except using the said polyester (meth) acrylate and the (meth) acrylate which has the said mercapto group, The said well-known polymeric compound can be used. For example, methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, isooctyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, glycidyl, dimethylaminoethyl, diethylamino (Meth) acrylate having a substituent such as ethyl, isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl, vinylpyrrolidone, N-vinylformamide, N-vinyl-2-caprolaclam,

1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol and other di (meth) acrylates, tris (2-hydroxyethyl) isocyanurate Di (meth) acrylate, neopentyl glycol di (meth) acrylate, bisphenol A di (meth) acrylate, bisphenol F di (meth) acrylate, hydrogenated bisphenol A di (meth) acrylate, trimethylo Rupropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, poly (meth) acrylate of dipentaerythritol, and alkylene oxide modified products such as ethylene oxide and propylene oxide, caprolactone modified products, (meth) acrylic acid 2- Polymerizable compounds such as (2-vinyloxyethoxy) ethyl, urethane (meth) acrylate, and epoxy (meth) acrylate can be used. Two or more of these can be used in combination.

  Among these polymerizable compounds, 2-ethylhexyl, isooctyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, glycidyl, dimethylaminoethyl, diethylaminoethyl, isobornyl , Monoacrylates such as dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecandi Di (meth) acrylates such as methanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol The use of such is preferable from the viewpoint of low viscosity and curing properties. Among them, monoacrylates such as 2-ethylhexyl, isooctyl, phenoxyethyl, and isobornyl, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,6-hexanediol, neopentyl glycol, ethylene glycol, polyethylene Di (meth) acrylates such as glycol, propylene glycol, dipropylene glycol, tripropylene glycol and polypropylene glycol are preferred, and dipropylene glycol diacrylate and ethyl carbitol acrylate are most preferred.

  The composition of the active energy ray-polymerizable compound has a viscosity of about 1 to 100 mPa.s after blending each monomer, depending on the ink jet apparatus used. It is preferable to design so that it may become s.

(Photopolymerization initiator)
In the present invention, when ultraviolet rays are used as active energy rays, it is preferable to use a photopolymerization initiator. As the photopolymerization initiator, a radical polymerization type photopolymerization initiator is used.
Specifically, 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, etc. are preferably used, and other than these As the molecular cleavage type, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2 - Roxy-2-methylpropan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, etc. may be used in combination, and hydrogen abstraction type photopolymerization initiator Benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide and the like can be used in combination.
In particular, when an LED is used, it is preferable to select a photopolymerization initiator in consideration of the emission peak wavelength of the LED. For example, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2- (dimethylamino)-is suitable as a photopolymerization initiator when using a UV-LED. 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 and the like.

  For the above photopolymerization initiator, for example, trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N An amine that does not cause an addition reaction with the polymerizable component, such as dimethylbenzylamine and 4,4′-bis (diethylamino) benzophenone, can also be used in combination.

  The photopolymerization initiator is preferably blended in an amount of 1 to 25% by weight, more preferably 5 to 20% by weight, most preferably 5 to 15% by weight based on the total solid content of the ink composition.

(Vitamins)
Examples of vitamins used in the present invention include vitamin A, vitamin B, vitamin C, vitamin D, vitamin E, and vitamin K. More preferable types of vitamins are vitamin C and vitamin E.

  Vitamin C used in the present invention is not particularly limited, and known ones can be used, and include ascorbic acid, its derivatives, and salts thereof. Vitamin C may be obtained by synthesis, or a commercially available product may be used.

  Ascorbic acid derivatives include ester derivatives of ascorbic acid and acids such as phosphoric acid, sulfuric acid, sulfonic acid, carboxylic acid (eg, aliphatic carboxylic acid, aromatic carboxylic acid, etc.); hydrogen of hydroxy group of ascorbic acid An atom is an alkyl group (for example, an alkyl group having 1 to 22 carbon atoms), an alkenyl group (for example, an alkenyl group having 2 to 12 carbon atoms), an aryl group (for example, an aryl group having 6 to 12 carbon atoms), a sugar residue And ether derivatives substituted with, and the like. Here, phosphoric acid, sulfuric acid, sulfonic acid, and carboxylic acid forming ester derivatives are monoesters (for example, phosphoric monoesters such as monoalkyl phosphates; sulfuric monoesters such as monoalkyl sulfates) and diesters. (For example, phosphoric acid diesters such as phosphoric acid dialkyl esters), alkyl groups (for example, alkyl groups having 1 to 6 carbon atoms) and alkoxy groups (for example, alkoxy groups having 1 to 6 carbon atoms) Etc.), an acyl group (for example, an acyl group having 1 to 7 carbon atoms), a halogen atom, an amino group, a hydroxy group, an oxo group, a phenyl group and the like. Similarly, an alkyl group, an alkenyl group, an aryl group, a sugar residue and the like forming an ether derivative may also be substituted with the above-described substituent.

  More specifically, examples of ascorbic acid derivatives include ester derivatives of ascorbic acid and phosphoric acid, such as ascorbic acid monophosphate, ascorbic acid diphosphate, ascorbyl triphosphate; ascorbic acid-2-sulfate Ascorbic acid and sulfuric acid ester derivatives such as ascorbic acid-2-sulfonic acid ester and other ascorbic acid and sulfonic acid ester derivatives; ascorbyl palmitate, ascorbyl stearate, ascorbyl dipalmitate, ascorbyl tetraisopalmitate ( Ester derivatives of ascorbic acid and carboxylic acid, such as VCIP); ascorbyl-2-phosphate-6-palmitate (APPS), (ascorbyl / tocopheryl) phosphate, ascorbyl aminopro Ester derivatives such as ethyl; ascorbate (for example, 2-O-ethylascorbic acid, 3-O-ethylascorbic acid), 3-O-cetylascorbic acid, methylsilanol ascorbate, ascorbyl glucoside (for example, ascorbic acid 2 -Derivativescorbic acid and the like, including but not limited to ether derivatives such as -glucoside).

  Examples of salts of ascorbic acid or ascorbic acid derivatives include various metals such as alkali metal salts such as sodium and potassium, alkaline earth metal salts such as magnesium, calcium and barium, and polyvalent metal salts such as zinc and aluminum. Salts; ammonium salts such as ammonium and tricyclohexylammonium; various alkanolamine salts such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine; chitosan salts and the like can be used. A metal salt is preferable, an alkali metal salt or an alkaline earth metal salt is more preferable, an alkali metal salt is further preferable, and a sodium salt is particularly preferable.

  More specifically, examples of salts of ascorbic acid or ascorbic acid derivatives include sodium ascorbyl phosphate, disodium ascorbate sulfate, calcium ascorbate, magnesium ascorbate, sodium ascorbate, zinc ascorbate, chitosan ascorbic acid, phosphorus Examples include, but are not limited to, magnesium ascorbyl acid, trisodium ascorbyl palmitate, potassium (ascorbyl / tocopheryl) phosphate, and the like.

Vitamin E used in the present invention is not particularly limited, and known ones can be used, and include vitamin E and its derivatives.
Specific examples of vitamin E derivatives include tocol, α-tocopherol, β-tocopherol, γ-tocopherol, δ-tocopherol, α-tocotrienol, β-tocotrienol, γ-tocotrienol, δ-tocotrienol, etc. And the compounds shown. Specific examples of the compound represented by the general formula 1 include acetic acid-α-tocopherol, acetic acid-β-tocopherol, acetic acid-γ-tocopherol, acetic acid-δ-tocopherol, succinic acid-α-tocopherol, succinic acid-β-tocopherol. , Succinic acid-γ-tocopherol, succinic acid-δ-tocopherol, nicotinic acid-α-tocopherol, nicotinic acid-β-tocopherol, nicotinic acid-γ-tocopherol, nicotinic acid-δ-tocopherol, isonicotinic acid-α-tocopherol , Isonicotinic acid-β-tocopherol, isonicotinic acid-γ-tocopherol, isonicotinic acid-δ-tocopherol, α-tocopherol glycine ester, β-tocopherol glycine ester, γ-tocopherol glycine ester, δ-tocopherol glycine ester , Α-tocopherol sarcosine ester, β-tocopherol sarcosine ester, γ-tocopherol sarcosine ester, δ-tocopherol sarcosine ester, acetic acid-α-tocotrienol, acetic acid-β-tocotrienol, acetic acid-γ-tocotrienol, acetic acid-δ -Tocotrienol, succinic acid-α-tocotrienol, succinic acid-β-tocotrienol, succinic acid-γ-tocotrienol, succinic acid-δ-tocotrienol, nicotinic acid-α-tocotrienol, nicotinic acid-β-tocotrienol, nicotinic acid-γ- Tocotrienol, nicotinic acid-δ-tocotrienol, isonicotinic acid-α-tocotrienol, isonicotinic acid-β-tocotrienol, isonicotinic acid-γ-tocotrienol, isonicotinic acid-δ-tocotrienol Etc.

  A preferable blending amount of vitamins used in the present invention is 0.01 to 0.5% by mass, and more preferably 0.05 to 0.2% by mass.

The vitamins function as a polymerization inhibitor.
In addition, the polymerization inhibitor that can be used in combination with the vitamins is not particularly limited, and known ones can be used. For example, polymerization inhibitors such as hydroquinone, methoquinone, di-t-butylhydroquinone, P-methoxyphenol, butylhydroxytoluene, and nitrosamine salts can be used. When used in combination with the vitamins, it is preferably added in the range of 0.01 to 2% by mass in the ink.

(Pigment)
The active energy ray-curable ink for ink jet recording of the present invention can be applied to all color inks, but the white ink added with a white pigment used when a plastic is used as a recording material is particularly suitable for this ink. The effect of the invention can be exhibited, which is preferable.

(White pigment)
The white pigment used in the white ink is not particularly limited, and a known inorganic white pigment can be used. Examples include silicas such as alkaline earth metal sulfates, carbonates, finely divided silicic acids, synthetic silicates, calcium silicates, alumina, alumina hydrates, titanium oxides, zinc oxides, talc, clays and the like. . The inorganic white pigment may be surface-treated by various surface treatment methods.
Among these, surface-treated titanium oxide is preferable because it exhibits relatively good dispersibility in an aqueous medium. For example, in order to avoid the influence of photocatalytic properties, titanium oxide surface-treated with an inorganic substance is preferable, and titanium oxide surface-treated with silica and alumina is preferable. Furthermore, it is still possible to use titanium oxide that has been surface-treated with the silica and alumina and then surface-treated with a silane coupling agent.

In the titanium oxide surface-treated with silica and alumina, known rutile type / anatase type titanium dioxide can be used as the titanium oxide, and rutile type titanium dioxide is more preferable.
Moreover, as an average particle diameter of the said titanium oxide, it is preferable to use a 100-500 nm thing, and it is more preferable to use a 150-400 nm thing. When the average particle size is 100 nm or less, non-sedimentation and dispersion stability in an aqueous medium are more easily realized, but the whiteness and hiding properties are inferior, and the practicality as an original white ink may be reduced. On the other hand, when the average particle diameter is 500 nm or more, there is no problem in terms of whiteness and hiding properties, but the ejection stability tends to be insufficient. A practically preferable particle diameter is 200 to 300 nm.
In addition, the average particle diameter of the titanium oxide as a raw material shall have taken the average by measuring 20 particle diameters with an electron micrograph.

  In titanium oxide surface-treated with silica and alumina, silica is generally used for the purpose of adjusting the acid / base state of the titanium oxide surface and for imparting durability of the obtained ink / paint film. Is used to improve the wetting of titanium oxide during dispersion. Examples of the titanium oxide surface treatment method include aqueous treatment and vapor phase treatment. From the viewpoint of dispersion stability, the ratio of the amount of treated alumina is preferably 35% by mass or more and 80% by mass or less from the viewpoint of dispersion stability. The amount of the inorganic substance relative to titanium oxide is not necessarily limited, but is generally 30 parts or less with respect to 100 parts of titanium oxide.

  In addition, when using titanium oxide surface-treated with silica and alumina and further surface-treated with a silane coupling agent, the range of the ratio of the treatment amount with alumina to the total amount of alumina and silica treatment amount is 35 to 80 mass. %, Preferably 35 to 65% by mass, more preferably 35 to 50% by mass. Alumina exists in the form of Al-OH (Al represents aluminum and OH represents a hydroxy group) on the surface of titanium oxide. If the amount of alumina treated is too large, a silane coupling agent for adsorbing to this OH. Are required in large quantities, and problems such as thickening during processing are likely to occur.

  Such titanium oxide surface-treated with silica and alumina may be a commercially available product, and is commercially available, for example, from manufacturers of titanium oxide such as Ishihara Sangyo Co., Ltd. and Teika Co., Ltd. For example, varieties with a large amount of silica treated compared to the amount of alumina treated, varieties with a large amount of alumina treated compared to the amount of silica treated are commercially available, and titanium oxide whose amount treated with alumina falls within the above range is also obtained. Can do.

The respective mass ratios of alumina and silica can be estimated from the amount of alumina and silica present together with titanium oxide on the surface of titanium oxide. The abundance ratio of alumina and silica can be confirmed by analyzing and comparing the amount of alumina or silica adsorbed on the titanium oxide surface by fluorescent X-rays or ESCA. In particular, measurement with fluorescent X-rays is simple and accurate. Silica and alumina may exist on the surface of titanium oxide, and some of them may exist as free particles, and the total amount can be measured by measuring with fluorescent X-rays. As for the quantitative method using fluorescent X-rays, an analytical method using a calibration curve using standard data has been established.
Therefore, the mass ratio of alumina and silica present on the surface of commercially available titanium oxide can be confirmed by measurement with fluorescent X-rays, and titanium oxides having various mass ratios can be used.

  As the silane coupling agent used when the surface-treated titanium oxide surface-treated with silica and alumina is treated with a silane coupling agent, it reacts with alumina treatment or hydroxyl groups present on the alumina and silica-treated titanium oxide surfaces. It has a hydrolyzable group and an organic functional group, and its general structure is represented by the following general formula (2)

（１）

(1)

(Wherein (R ₄ ), (R ₅ ), (R ₆ ), and (R ₇ ) are each independently any one of a hydrogen atom, an alkoxy group, a hydroxy group, a chloro group, and an organic group, One is an alkoxy group, a hydroxy group or a chloro group, and at least one is an organic group, a, b, c and d are (R ₄ ), (R ₅ ), (R ₆ ). And an integer of 0 to 3 representing the number of repetitions of (R ₇ ), and a + b + c + d = 4).
These silane coupling agents produce silanols by hydrolysis of hydrolyzable groups, and the silanols condense to form siloxane bonds to form oligomers. On the other hand, it reacts with the oxidized surface or hydroxyl group of the inorganic compound by the same mechanism, moves to the inorganic surface through hydrogen bonds with the hydroxyl group on the inorganic surface, and forms a polysiloxane bond through a dehydration condensation reaction. These reactions proceed in parallel to form an oligomer or polymer coating having a polysiloxane bond, that is, an organopolysiloxane coating on the inorganic surface.

  Specific compounds include vinyltrichlorosilane, vinyltriethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, vinylmethyldimethoxysilane and other vinylsilanes, 3-methacryloxypropyltriethoxysilane, 3-methacrylic Methoxysilanes such as loxypropyltrimethoxysilane, epoxy silanes such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3 -Mercaptosilanes such as mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane; Sulfur silanes such as 3-octanoylthio-1-propyltriethoxysilane; Triethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3- (N Examples include aminosilanes such as -phenyl) aminopropyltrimethoxysilane, ureidosilanes such as 3-ureidopropyltriethoxysilane, and isocyanate silanes such as 3-isocyanatopropyltriethoxysilane and 3-isocyanatopropyltrimethoxysilane.

At least one of (R ₄ ), (R ₅ ), (R ₆ ), and (R ₇ ) in the general formula (2) is a chloro group, a methoxy group, or an ethoxy group, and (R ₄ ) , (R ₅ ), (R ₆ ), and (R ₇ ) are preferably vinyl groups.
These silane coupling agents may be used alone or in combination of two or more.

  As the silane coupling agent used in the present invention, vinyl silane considered to have good adsorptivity to the styrene group of the styrene copolymer used as the pigment dispersant is preferable, and among them, vinyl triethoxysilane or vinyl trimethoxysilane. Vinyltriethoxysilane, which is more excellent in terms of storage stability and safety from the viewpoint of the environment, is even more preferable.

  To treat alumina oxide or titanium oxide treated with alumina and silica with a silane coupling agent, for example, mix titanium oxide and silane coupling agent in water, heat and stir, and then volatilize the water completely. You can do it. The amount of the silane coupling agent used is generally about 0.05 to 20% by mass, but since titanium oxide has a relatively small specific surface area, the effect can be exhibited at about 1 to 10% by mass.

  The white pigment is preferably added in an amount of 5 to 25% by mass of the total solid content of the ink in order to obtain a sufficient image density and light resistance of the printed image.

  The dispersant for dispersing the white pigment may be a known one, and for example, a polymer dispersant or the like can be used. Examples of the polymer dispersant include a polymer dispersant having a basic group having a nitrogen-containing heterocycle such as a primary, secondary, or tertiary amino group, pyridine, pyrimidine, pyrazine, etc., and an acid such as a phosphate ester type. A polymer dispersant having a group can be widely used.

  Specific examples of the polymeric dispersant having a basic group include Ajimoto PB821, PB822, and PB817 manufactured by Ajinomoto Fine Techno, Solsperz 24000GR, 32000 manufactured by Abyssia, Disparon DA-703-50, DA-705 manufactured by Enomoto Kasei. DA-725 and the like, but are not limited thereto. Moreover, the usage-amount of the polymeric dispersing agent which has a basic group has the preferable range of 1-10 mass% with respect to a pigment, and the range of 3-6 mass% is especially preferable.

  Specific examples of the acidic group polymer dispersant include Disperbyk-111 and 110 manufactured by BYK-Chemie. The amount of the polymeric dispersant having an acidic group is preferably in the range of 1 to 10% by mass, particularly preferably in the range of 3 to 6% by mass with respect to the pigment.

  These polymer dispersants are usually used together with a solvent that dissolves the polymer dispersant because the adsorption point to the pigment is not exposed unless the polymer dispersant is dissolved.

In addition to the white ink, pigments that give four basic colors of yellow, magenta, cyan, and black, which are process colors of inkjet ink, can be used. (Hereinafter, pigments other than white pigments are collectively referred to as “pigments other than white pigments”.)
As these pigments, inorganic pigments or organic pigments can be used.

  As the inorganic pigment, titanium oxide or iron oxide, or carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye chelates, acidic dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, and the like.

  Specific examples of the pigment include carbon black, No. manufactured by Mitsubishi Chemical Corporation. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B, etc. are Raven 5750, 5250, 5000, 3500, 1255, 700, etc. made by Columbia, and Regal 400R, 330R, 660R, Mogu L, 700, Monarch 800, 880, made by Cabot, 900, 1000, 1100, 1300, 1400, etc. are Degussa Color Black FW1, FW2, FW2V, FW18, FW200, ColorBlack S150, S160, S170, Printex 35, U, the same V, the same 140 U, the Special Black 6, the same 5, the same 4 A, the same 4, and the like.

  Examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 180, 185, 213 and the like.

  Examples of pigments used for magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209, C.I. I. Pigment violet 19 and the like.

  Examples of pigments used for cyan ink include C.I. I. And CI Pigment Blue 1, 2, 3, 15: 3, 15: 4, 60, 16, and 22.

  The average particle diameter of the pigments other than the white pigment is preferably in the range of 10 to 200 nm, more preferably about 50 to 150 nm. Further, in order to obtain the addition amount of the colorant, sufficient image density, and light fastness of the printed image, it is preferably contained in the range of 1 to 20% by mass of the total amount of the ink.

  When used as an ink set described later, in addition to the basic four colors of yellow, magenta, cyan, and black, the same series of dark and light colors may be added for each color. For example, light magenta in addition to magenta, light red, cyan in addition to light light cyan, dark blue, black in addition to light gray, light black, and dark matte black Can do.

  As for the pigments other than the white pigment, it is preferable to use a pigment dispersant for the purpose of improving the dispersion stability with respect to the active energy ray polymerizable compound or the like, similarly to the white pigment. Specifically, Ajinomoto Fine Techno Co., Ltd. Ajisper PB821, PB822, PB817, Avisia Corp. Solspurs 24000GR, 32000, 33000, 39000, Enomoto Kasei Co., Ltd. Disparon DA-703-50, DA-705, DA-725 However, it is not limited to these. The amount of the pigment dispersant used is preferably in the range of 10 to 80% by mass, particularly preferably in the range of 20 to 60% by mass with respect to the pigment other than the white pigment. When the amount used is less than 10% by mass, the dispersion stability tends to be insufficient, and when it exceeds 80% by mass, the viscosity of the ink tends to increase, and the ejection stability tends to decrease. is there.

  In addition to the above, the surfactant, leveling additive, matting agent, polyester-based resin for adjusting the film physical properties, and polyurethane based on the range as long as the problems of the present invention are not impaired and the ejection stability is not impaired. Resin, vinyl resin, acrylic resin, rubber resin, waxes, acrylic resin, epoxy resin, terpene phenol resin within the range of not impairing the effect of the present invention for the purpose of imparting adhesiveness to the substrate to be printed Non-reactive resins such as rosin esters can be blended.

  As leveling additives, polyester leveling agents and silicon leveling are particularly preferable. Addition of the leveling agent is preferable because it improves physical properties such as gloss accompanying the reduction in surface tension.

(Production method)
The active energy ray-curable ink for ink jet recording of the present invention is produced by mixing a mixture containing a pigment and an active energy ray-polymerizable compound, if necessary, a pigment dispersant, and a resin when a pigment is contained, in a normal dispersion such as a bead mill. After dispersing the pigment using a machine, it can be prepared by adding a photopolymerization initiator and, if necessary, adding an additive such as a surface tension adjuster and stirring and dissolving. Prepare a high-concentration pigment dispersion (mill base) using an ordinary dispersing machine such as a bead mill in advance, and then stir and mix the active energy ray-polymerizable compound in which the photopolymerization initiator is dissolved and additives. You can also

  As a stirring / dispersing device for dispersing a pigment, in addition to a bead mill, for example, 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 disperse mat, an SC mill, and a nanomizer are commonly used. A variety of dispersers can be used.

The active energy ray-curable ink jet recording ink of the present invention thus obtained preferably has a surface tension in the range of 20.0 to 25.0 mN / m. In particular, white ink is preferably in the range of 22.5 to 24.0 mN / m, and color ink is preferably in the range of 20.0 to 22.5 mN / m.
By setting the surface tension within this range, there is an advantage that a good color ink image can be obtained without impairing the leveling property of the white ink.

  The active energy ray-curable ink jet recording ink of the present invention undergoes a curing reaction by irradiation with active energy rays, preferably light such as ultraviolet rays. As a light source such as an ultraviolet ray, it can be cured without problems if it is a light source usually used for UV curable inkjet 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, etc. . For example, a commercially available product such as an H lamp, D lamp, or V lamp manufactured by Fusion System can be used.

  Any conventionally known method can be used as the ink jet recording method. For example, a method of ejecting droplets using vibration of a piezoelectric element (a recording method using an ink jet head that forms ink droplets by mechanical deformation of an electrostrictive element) or a method of using thermal energy can be given.

The active energy ray curable ink jet recording ink of the present invention is excellent in adhesion to a plastic material. Therefore, it is possible to easily print on the surface of a plastic molded body or the like having a curved surface or an irregular irregular shape. Specifically, ABS (acrylonitrile butadiene styrene) resin, PVC (polyvinyl chloride) / ABS resin, PA (polyamide) / ABS resin, PC (polycarbonate) / ABS used as general-purpose injection molding plastics Resins, ABS 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 resin, PC (polycarbonate) resin, acrylic resin, methacrylic resin, PP (polypropylene) resin, and the like.
It is also possible to use a film made of a plastic material such as a thermoplastic resin film for packaging material as a recording material. For example, as thermoplastic resin films used for food packaging, polyethylene terephthalate (PET) film, polystyrene film, polyamide film, polyacrylonitrile film, polyethylene film (LLDPE: low density polyethylene film, HDPE: high density polyethylene film) And polyolefin films such as polypropylene film (CPP: unstretched polypropylene film, OPP: biaxially stretched polypropylene film), polyvinyl alcohol film, ethylene-vinyl alcohol copolymer film, and the like. These may be subjected to stretching treatment such as uniaxial stretching or biaxial stretching. The film surface may be subjected to various surface treatments such as flame treatment and corona discharge treatment as necessary.

A printing layer is formed on the plastic film using the active energy ray-curable ink set for inkjet recording of the present invention.
Any conventionally known method can be used as the ink jet recording method. For example, a method of ejecting droplets using vibration of a piezoelectric element (a recording method using an ink jet head that forms ink droplets by mechanical deformation of a piezoelectric strain element) or a method using thermal energy can be given.

As an overprint method for back printing, black (K), cyan (C), magenta (M), yellow (Y) while preheating the film at about 40 to 80 ° C. with an inkjet recording apparatus having inkjet nozzles. Is printed. In this case, printing and drying are repeated for each color so that bleeding does not occur, or four-color printing is simultaneously performed by drying the surface with ultraviolet rays or an electron beam while printing. Next, an image is printed using the white ink (W), and finally cured sufficiently with ultraviolet rays, EB rays or the like to obtain a printed matter.
Similarly, as the surface overprinting method, white ink (W), yellow (Y), magenta (M), cyan, while preheating the film to about 40 to 80 ° C. in an ink jet recording apparatus having an ink jet nozzle. (C) Black (K) is printed. Printing or drying is repeated for each color so that bleeding does not occur, or the surface is dried with ultraviolet rays or an electron beam while printing. Finally, the printed matter is obtained by sufficiently drying it with ultraviolet rays or electron beams.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited to the following Example at all. In addition, hereinafter, the part in an Example represents a mass part.

[Example of preparation of high concentration pigment dispersion (white mill base)]
(Example of mill base (1) production)
JR-806 48 parts Teica Co., Ltd. Titanium Oxide Azisper PB-821 0.96 parts Ajinomoto Finetech Polymer Pigment Dispersant Solspers 24000GR 1.44 parts Lubrizol Polymer Pigment Dispersant New Frontier PGA 5.6 parts Daiichi Kogyo Seiyaku Phenylglycidyl ether acrylate Miramar M222 64 parts MIWON dipropylene glycol diacrylate was stirred and mixed with a stirrer for 1 hour, and then treated with a bead mill for 2 hours to prepare a mill base (1).

(Examples 1 and 2 Method for producing active energy ray-curable ink jet recording ink)
[Example of white ink adjustment]
As a polyfunctional monomer, 5 parts of trimethylolpropane triacrylate (MIWON M-300), 35 parts of dipropylene glycol diacrylate (Dycelcytec EBECRYL DPGDA), 2- (2-vinyloxyethoxy) ethyl acrylate (Nippon Shokubai Co., Ltd.) VEEA) mixed with 40 parts, Irgacure 819 (manufactured by BASF) as photopolymerization initiator, 4 parts, Irgacure 2959 (manufactured by BASF), 2 parts, Darocur 1173 (manufactured by BASF), 4 parts, Lucyrin TPO 7 parts (manufactured by BASF), 0.1 part of BYK-UV3500 (silicone oil made by BYK) as a surface tension regulator, 0.2 part of KF-351A (silicone oil made by Shin-Etsu Silicone), and tocopherol as a polymerization inhibitor (Vitamin E) or L-ascorbic acid 0.05 part of (Vitamin C) was added, and the mixture was heated and stirred at 60 ° C. for 30 minutes, and then the mill base (1) of Preparation Example was added, and sufficiently stirred and mixed to obtain each ink. Next, active energy ray-curable ink jet recording inks (Examples 1 and 2) were obtained by filtration using a 1.2 μm membrane filter.

(Comparative Examples 1 to 3 Method for producing active energy ray-curable ink for inkjet recording)
The active energy ray-curable ink jet recording ink for Comparative Example (Comparative Example 1) was used in the same manner as in Example 1 except that a hindered amine inhibitor, a hindered phenol inhibitor, and a phosphorus inhibitor were used as the inhibitor. ~ 3) was obtained.

(Physical property measurement method)
Viscosity was measured as a physical property of the active energy ray-curable ink jet recording ink. Moreover, specific gravity was measured in order to fill a predetermined volume in a sealed container for evaluating storage stability. The measuring method is shown below.

[viscosity]
Viscosity measuring device manufactured by Toki Sangyo Co., Ltd .: Viscosity at 40 ° C. was measured with TVE-20L. The measurement rotation speed was 50 rpm / mim. In addition, in order to print stably with the inkjet printing evaluation apparatus used in the Example of this invention, the viscosity of the ink was adjusted between 5-10 mPa * sec.
[specific gravity]
The ink was placed in a plastic light-shielding container, immersed in a constant temperature water bath at 25 ° C., and then measured with a glass specific gravity buoy.

The composition ratio and physical properties are shown in Table 1. Numerical values represent parts.

  The abbreviations in the table are “M-300” is trimethylolpropane triacrylate, “DPGDA” is dipropylene glycol diacrylate, and VEEA is 2- (2-vinyloxyethoxy) ethyl acrylate.

D: Tocopherol (vitamin E)
E; L-ascorbic acid (vitamin C)
G; 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane (hindered phenol type)
H; 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (hindered amine type)
I: Triphenylphosphine (phosphorus)

(Ink evaluation)
The storage stability evaluations of Examples 1 and 2 and Comparative Examples 1 to 3 of the active energy ray-curable ink jet recording ink were performed as follows.

[How to fill containers]
The specific gravity at 25 ° C. was measured using a specific gravity buoy, and a 6 mL brown glass bottle was filled with a necessary weight so as to be 5.4 mL. Specifically, when the specific gravity was 1.13, 6.10 g was filled and sealed.

[Confirmation of gel generation]
The above filled container was left in an oven at 60 ° C. for 20 days, then sampled with a micropipette, spread on a stainless steel petri dish, and the presence or absence of gel generation was visually confirmed. In addition, the following criteria were used for two-level evaluation.
No generation of gel; ○
Generation of gel; x

The results are shown in Table 2.

(Effects of inhibitor types on storage stability)
From the evaluation result of Examples 1-2 and Comparative Examples 1-3, what mix | blended vitamins showed the storage stability. On the other hand, gels were formed when hindered phenols, hindered amines, and phosphorus inhibitors were blended.

Claims (6)

An active energy ray-curable ink jet recording ink comprising a polymerizable compound represented by the general formula (1), a colorant, and vitamins.

(1)
(In formula (1), R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an organic residue having 2 to 20 carbon atoms, and R ₃ represents a hydrogen atom or an organic residue having 1 to 11 carbon atoms. Represents.) The active energy ray-curable ink jet recording ink according to claim 1, wherein the vitamin is vitamin E or vitamin C. The active energy ray-curable ink jet recording ink according to claim 1, wherein the pigment is a white pigment. 4. The active energy ray-curable ink jet recording ink according to claim 3, wherein the surface tension is 22.5 to 23.8 mN / m. An active energy ray-curable ink jet recording ink set comprising a white ink, wherein the white ink is the active energy ray-curable ink jet recording ink according to claim 3 or 4. Ink set for curable inkjet recording. The active energy ray-curable ink jet recording ink set according to claim 5, wherein the white ink has the highest surface tension among the ink sets.