JP5589223B2 - Active energy ray curable inkjet ink set - Google Patents

Description

  The present invention relates to an active energy ray-curable inkjet ink set composed of at least two types of color inks selected from cyan ink, magenta ink, and yellow ink, and suppresses a decrease in gloss of printed matter associated with poor curing. However, it outputs high-definition and high-quality images.

  The ink jet printing method is a printing method in which fine droplets of the ink composition are ejected and landed from an ink jet head on a substrate to be printed to print images and characters, and is characterized by not requiring a plate. To do. As a printing method that does not require a plate, the electrophotographic method is widely recognized. However, the ink jet printing method has the initial cost of the device, the running cost at the time of printing, the device size, the high-speed printing characteristics, etc. Excellent in terms.

  A printing method using an active energy ray-curable inkjet ink mainly includes reactive monomers and oligomers, an initiator and a photoacid generator, and the active energy is applied to the ink composition landed on the substrate to be printed by the above method. This is a printing method in which images and characters are formed by irradiating a line and advancing a polymerization reaction.

  In recent years, with the improvement of the performance of inkjet heads, application to the existing printing market by offset printing or the like is expected. Productivity is very important in the existing printing market, but it has been difficult to achieve desired productivity with the multi-pass printing method used in the sign market. For this reason, the inkjet printing method used in the printing market preferably uses a single-pass printing method capable of high-speed printing in order to realize productivity that cannot be obtained by the multi-pass printing method.

  Furthermore, most of the base materials used in the sign market are vinyl chloride sheets, but various base materials such as various coated papers and various films are used in the existing printing market. However, the ink wetting and spreading properties and adhesion to the substrate differ depending on the substrate, so in order to handle various substrates with the same ink, the printing image quality can be applied to any substrate. It is important to ensure the print quality to be achieved at a certain level or higher. In order to achieve productivity and compatibility with multiple substrates at the same time, an active energy ray-curable inkjet ink that can perform high-speed printing and can secure adhesion with many substrates is optimal.

  However, in the multi-pass printing method using the active energy ray-curable ink jet ink, an image is formed by overlapping the ink multiple times. However, in the single-pass printing method, a desired image is formed by a single printing. In the rate portion, it is necessary to cure a large amount of ink at a time, and the problem is that the internal curability is poor. That is, since the active energy ray is irradiated only once when curing a large amount of ink, if the active energy ray does not sufficiently penetrate to the inside of the ink composition, a difference occurs in the reaction rate between the coating film surface and the inside. When the polymerization reaction is sufficiently advanced, the polymer produced in the process contracts and stress acts, but if this stress balance is different between the coating surface and the inside, stress due to the stress difference occurs and the coating surface is affected. A phenomenon occurs in which wrinkles occur and gross loss is significantly impaired.

  When this loss of gloss occurs in one color, the amount of pigment is reduced to increase the internal curability, and the active energy rays are transmitted to the inside of the ink, or are easily cleaved in the long wavelength region (internal curing occurs. It can be solved by using an ink composition with a composition that increases the amount of initiator, but not only at the expense of the color gamut, but also when printing over two or more inks simply It does not solve. When wrinkles occur on the cured film of two or more colors and the gloss is impaired, the texture of the high printing rate portion and the low printing rate portion are different, and a clear image quality cannot be reproduced. Further, when the gloss is reduced in the coating film in which two or more colors of ink are overlapped, the color gamut is greatly impaired, and the image quality is greatly deteriorated.

  In order to solve the above problems, Document 1 proposes an ink that contains a bifunctional acrylate compound having a specific structure and a monofunctional acrylate compound, and has no wrinkles or curls and does not impair the texture of printed matter. However, this ink slightly suppresses single-color wrinkles, but wrinkles on cured films of two or more colors occur, and light is scattered on the surface, resulting in insufficient texture and color gamut as printed matter. It was. Reference 2 contains a monofunctional alicyclic epoxy compound having a specific structure and (meth) acrylate monomer and oligomer, and Reference 3 contains dipentaerythritol hexaacrylate and allyl glycol modified with ε-caprolactone. Thus, in Document 4, an ink containing an internally curable photopolymerization initiator and an ink containing at least an active energy ray-curable monomer, a surface curable photopolymerization initiator, and a polymerization accelerator are used. Thus, an ink free from wrinkles has been proposed. However, as in Reference 1, these inks are somewhat suppressed in single color wrinkles, but wrinkles are generated on cured films of two or more colors, and light is scattered on the surface, resulting in the texture and color as printed matter. The area was not enough.

JP 2004-182808 A WO2006 / 054441 JP 2010-202736 A Patent No. 4706426

  An object of the present invention is to provide an active energy ray-curable inkjet ink set that can suppress a reduction in gloss of a printed matter associated with poor curing and can output a high-definition and high-quality image.

    That is, the present invention relates to an active energy ray-curable inkjet ink set containing at least two or more kinds of color inks selected from cyan, magenta, and yellow. An active energy ray-curable inkjet ink set characterized in that the curing speed is higher as the ink is faster, and the total amount of initiator and sensitizer in each color of cyan ink, magenta ink, and yellow ink is 7 to 25% by weight in the ink. It is about.

The present invention also relates to the above-mentioned active energy ray-curable ink jet ink set, characterized in that, among cyan ink, magenta ink, and yellow ink, the color ink having a faster printing order has a larger total amount of initiator and sensitizer. is there.
The present invention also relates to the above active energy ray-curable inkjet ink set, which is printed by a single-pass inkjet printing method.

  The present invention also relates to the above active energy ray-curable ink jet ink set comprising at least black ink as ink other than cyan ink, magenta ink, and yellow ink.

  The present invention also relates to the above active energy ray-curable ink jet ink set, wherein each color ink has a viscosity at 25 ° C. of 8.5 to 13.0 mPa · s.

  The present invention also includes 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 4-benzoyl-4′-methyl-diphenyl sulfide, ethyl-4- (dimethylamino) -benzoate, bis ( The present invention relates to the above active energy ray-curable inkjet ink set, which contains at least one of 2,4,6-trimethylbenzoyl) -phenylphosphine oxide.

  In an active energy ray curable inkjet ink set composed of two or more color inks selected from cyan, magenta, and yellow, among cyan ink, magenta ink, and yellow ink, the faster the color ink, the faster the curing speed. By using an active energy ray-curable inkjet ink set that is fast and the total amount of initiator in each color is 7 to 25% by weight in the ink, it suppresses the gloss reduction of the printed matter that accompanies poor curing, with high definition and high image quality Was able to output an image.

  Hereinafter, the active energy ray-curable inkjet ink set of the present invention will be described in detail.

(Active energy ray-curable inkjet ink set)
The active energy ray-curable inkjet ink set used in the present invention includes two or more kinds of color inks selected from cyan, magenta, and yellow. The present invention defines the printing order and curing speed among cyan, magenta, and yellow inks, and does not limit the printing order and curing speed with other inks. In the present invention, in addition to these inks, inks such as red, orange, blue, violet, green, white, and clear (anchor coat and overcoat varnish) may be used.
In the present invention, in addition to two or more types of color inks selected from cyan, magenta, and yellow, black ink can be used to draw letters and clean black. Because it is high, the curing speed tends to be slower compared to cyan, magenta, and yellow color inks. To obtain the same curing speed as cyan, magenta, and yellow, more initiator and sensitizer are added. There is a need.

(Active energy ray-curable inkjet ink)
The active energy ray-curable inkjet ink used in the present invention is an active energy ray-curable ink composition containing at least an active energy ray-curable monomer and a photopolymerization initiator, and the total amount of the initiator and the sensitizer is each color. It is characterized by being 7 to 25% by weight in the ink.

(Single pass inkjet printing method)
The single-pass inkjet printing method of the present invention is a printing method that completes printing (printing) once on a medium to be printed, and is suitable for business printing that requires a printing speed. However, compared to the multi-pass inkjet printing method, the single-pass inkjet printing method often irradiates the UV lamp only once after printing all the colors, so the portion where two or more inks overlap is UV down to the lower layer. Irradiation light is difficult to reach, resulting in poor curing and loss of gloss due to generation of wrinkles on the coating surface.

(Curing speed)
The curing speed defined in the present invention defines the fastest printing speed at which a printed matter using an active energy ray-curable inkjet ink is cured. The printed material was rubbed 10 times with a cotton swab, and the state where the ink did not adhere to the cotton swab and the trace of the cotton swab remained on the surface of the printed material was judged as cured.

(Initiator and sensitizer)
The initiator contained in the ink composition of the present invention can be freely selected depending on the curing speed, the cured coating film properties, and the coloring material. Among them, molecular cleavage type or hydrogen abstraction type is suitable for the present invention, and specifically, benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine. Oxide, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, bis (2,4,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, oligo (2-hydroxy-2-methyl) -1- (4- (1-methylvinyl) phenyl) propanone), 4-benzoyl- '- methyl - diphenyl sulfide, 1,2-octane-dione, 1- (4- (phenylthio)-2,2-(O-benzoyl oxime)) is preferably used, such as. These initiators are preferable in that the radical generation reaction due to light absorption of the pigment or the polymerizable compound is not inhibited, and the radical generation efficiency is high and the curability of the ink composition can be improved.

  As initiators other than the above, in the case of molecular cleavage, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and 1- (4- Examples of isopropylphenyl) -2-hydroxy-2-methylpropan-1-one and hydrogen abstraction type polymerization initiators include benzophenone, 4-phenylbenzophenone, and isophthalphenone.

The initiator may be used alone or in combination of two or more in consideration of the wavelength spectrum of the active energy ray and the light absorption spectrum of the initiator.
In addition to the above initiator, trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl-4- (dimethylamino) -benzoate, isoamyl p-dimethylaminobenzoate, N, N- Amines that do not cause an addition reaction with the polymerizable compound such as dimethylbenzylamine and 4,4′-bis (diethylamino) benzophenone can also be used in combination.

  The sensitizers can be used alone or in combination of two or more in consideration of the wavelength spectrum of the active energy ray and the light absorption spectrum of the sensitizer.

  Of course, it is preferable to select and use the initiator and the sensitizer that are excellent in solubility in the ink composition and do not inhibit the ultraviolet light transmittance. Since the sensitizer exhibits an effect of increasing the sensitivity of the initiator, in the present invention, the total amount of the initiator and the sensitizer is considered to affect the curability of the coating film. The total amount of the initiator and the sensitizer used in the present invention represents the sum of the weight% of the initiator and the sensitizer contained in the ink.

  Among the above initiators and sensitizers, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 4-benzoyl-4′-methyl-diphenyl sulfide, ethyl-4- (dimethylamino) -benzoate, bis (2, By containing at least one of 4,6-trimethylbenzoyl) -phenylphosphine oxide, the internal curability and the surface curability in the monochromatic ink can be improved in a well-balanced manner, and therefore it is more preferably used.

  The initiator and sensitizer are preferably contained in an amount of 7 to 25% by weight based on the total amount of ink in each color of cyan ink, magenta ink, and yellow ink. If it is less than 7% by weight, the curing rate is remarkably deteriorated. If it is more than 25% by weight, not only the curing rate is different from that of 25% by weight, but also a dissolution residue may be generated. Even if the undissolved residue is melted, the viscosity of the ink composition rises. As a result, the viscosity of the ink composition cannot be within the above-mentioned preferable range, and there is a problem that the ink cannot be ejected. More preferably, when it is contained in an amount of 7 to 21% by weight, the storage stability of the ink composition can be made extremely stable, and the quality reliability during long-term use can be ensured.

  The difference in the total amount of initiator and sensitizer between two or more color inks selected from cyan, magenta, and yellow is preferably 0.01 wt% to 10 wt%. If the difference is less than 0.01% by weight, the curing speed becomes almost the same, and wrinkles are generated. On the other hand, if the difference is larger than 10% by weight, the difference in curing rate is too large, and stress due to the stress difference is generated, and soot is also generated.

  The ink-jet ink of the present invention is prepared by adding a monomer, an initiator and an additive to a pigment dispersion produced by well dispersing the pigment together with a monomer and a pigment dispersant using an ordinary dispersing machine such as a sand mill. Is done. By this method, sufficient dispersion is possible even with dispersion by a normal disperser. Therefore, excessive dispersion energy is not applied, and a great amount of dispersion time is not required. An ink that is difficult to invite and excellent in stability is prepared. As the conditions for preparing the pigment dispersion, it is preferable to use fine beads. Specifically, it is preferred to use fine beads of 0.1 mm to 2 mm in order to produce a stable dispersion having a low viscosity. After the ink composition is dispersed, it is preferably filtered through a filter having a pore size of 3 μm or less, more preferably 1 μm or less.

(Pigment)
When a colorant is contained in the ink composition of the present invention, a dye or a pigment can be used, but a pigment can be more preferably used from the viewpoint of resistance to printed matter. As the pigment, a pigment generally used for an ink composition for printing or paint can be used, and can be selected according to necessary uses such as color developability and light resistance. As the pigment component, achromatic pigments such as carbon black, titanium oxide, calcium carbonate, or chromatic organic pigments can be used. Examples of organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa Yellow, Benzidine Yellow, and pyrazolone red, soluble azo pigments such as Ritol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B, alizarin, indanthrone, and thioindigo. Derivatives from vat dyes such as maroon, phthalocyanine organic pigments such as phthalocyanine blue and phthalocyanine green, quinacridone organic pigments such as quinacridone red and quinacridone magenta, perylene organic pigments such as perylene red and perylene scarlet, isoindolinone yellow , Isoindolinone organic pigments such as isoindolinone orange, pyranthrone organic pigments such as pyranthrone red and pyranthrone orange, thioy Digo organic pigments, rhodamine lake organic pigments, condensed azo organic pigments, benzimidazolone organic pigments, quinophthalone organic pigments such as quinophthalone yellow, isoindoline organic pigments such as isoindoline yellow, naphthol organic pigments, etc. Examples of the pigment include flavanthrone yellow, acylamide yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet, lake pigment, and the like.

  When organic pigments are exemplified by color index (CI) numbers, C.I. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 8893, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153 154, 155, 166, 168, 180, 185, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 81, 81: 1, 81: 2, 81: 4, 81: 5, 97, 122, 123, 149, 168, 169, 177, 180, 185, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 269, C.I. I. Pigment violet 1, 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment green 7, 36, C.I. I. Pigment brown 23, 25, 26, and the like.

  Specific examples of carbon black include “Special Black 350, 250, 100, 550, 5, 4, 4A, 6” “Printex U, V, 140 U, 140 V, 95, 90, 85, 80, 75, 55, manufactured by Degussa. 45, 40, P, 60, L6, L, 300, 30, 3, 35, 25, A, G ", Cabot's" REGAL 400R, 660R, 330R, 250R "," MOGUL E, L ", Mitsubishi Chemical “MA7, 8, 11, 77, 100, 100R, 100S, 220, 230” “# 2700, # 2650, # 2600, # 200, # 2350, # 2300, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 900, # 850, # 750, # 650, # 52, # 50, # 47, # 45, # 4 5L, # 44, # 40, # 33, # 332, # 30, # 25, # 20, # 10, # 5, CF9, # 95, # 260 ”and the like.

  Specific examples of titanium oxide include “Taipeku CR-50, 50-2, 57, 80, 90, 93, 95, 953, 97, 60, 60-2, 63, 67, 58, 58- manufactured by Ishihara Sangyo Co., Ltd. 2, 85 "" Tipekes R-820, 830, 930, 550, 630, 680, 670, 580, 780, 780-2, 850, 855 "," Tipekes A-100, 220 "," Tipekes W-10 "," Tipekes " PF-740, 744 "" TTO-55 (A), 55 (B), 55 (C), 55 (D), 55 (S), 55 (N), 51 (A), 51 (C) " "TTO-S-1, 2", "TTO-M-1, 2", "Titanics JR-301, 403, 405, 600A, 605, 600E, 603, 805, 806, 701, 800, 808" manufactured by Teika "Titanic EN-1, C, 3, 4, 5 ", DuPont" Taipyua R-900,902,960,706,931 ', and the like.

  Among the above pigments, quinacridone organic pigment, phthalocyanine organic pigment, benzimidazolone organic pigment, isoindolinone organic pigment, condensed azo organic pigment, rhodamine lake organic pigment, quinophthalone organic pigment, isoindoline Organic pigments are preferred because they have a good balance between light resistance and color gamut and are suitable for practical use. The organic pigment is preferably a fine pigment having an average particle diameter of 10 to 300 nm as measured by laser scattering. When the average particle diameter of the pigment is less than 10 nm, the light resistance is lowered due to the small particle diameter, and when it exceeds 300 nm, it is difficult to maintain stable dispersion, and the pigment is likely to precipitate.

The organic pigment can be refined by the following method. That is, a mixture comprising at least three components of an organic pigment, a water-soluble inorganic salt that is at least 3 times the weight of the organic pigment, and a water-soluble solvent is made into a clay-like mixture, and is kneaded strongly with a kneader or the like and then refined. And stirred with a high speed mixer or the like to form a slurry. Next, filtration and washing of the slurry are repeated to remove the water-soluble inorganic salt and the water-soluble solvent. In the miniaturization step, a resin, a pigment dispersant and the like may be added.
Examples of the water-soluble inorganic salt include sodium chloride and potassium chloride. These inorganic salts are used in the range of 3 times by weight or more, preferably 20 times by weight or less of the organic pigment. When the amount of the inorganic salt is less than 3 times by weight, a treated pigment having a desired size cannot be obtained. On the other hand, if the amount is more than 20 times by weight, the washing process in the subsequent step is great, and the substantial amount of the organic pigment is reduced.

  The water-soluble solvent is an organic solvent and a water-soluble inorganic salt that is used as a crushing aid, and is used for efficient crushing efficiently, especially if it is a solvent that dissolves in water. Although not limited, a high boiling point solvent having a boiling point of 120 to 250 ° C. is preferable from the viewpoint of safety because the temperature rises during kneading and the solvent is easily evaporated. Examples of water-soluble solvents include 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (isopentyloxy) ethanol, 2- (hexyloxy) ethanol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether. , Triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, low molecular weight Examples thereof include polypropylene glycol.

  In the present invention, the pigment is preferably contained in the ink composition in the range of 0.1 to 30% by weight in order to obtain a sufficient concentration and sufficient light resistance. More preferably, it is in the range of 1 to 7% by weight.

(Pigment dispersant)
In the present invention, it is preferable to add a pigment dispersant in order to improve the dispersibility of the pigment and the storage stability of the ink composition. Examples of the pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, a high molecular weight unsaturated acid ester, Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene Nonylphenyl ether, stearylamine acetate, etc. can be used.

Specific examples of the dispersant include “Anti-Terra-U (polyaminoamide phosphate)”, “Anti-Terra-203 / 204 (high molecular weight polycarboxylate)”, “Disperbyk-101” (polyamino) manufactured by BYK Chemie. Amide phosphate and acid ester), 107 (hydroxyl group-containing carboxylic acid ester), 110, 111 (copolymer containing an acid group), 130 (polyamide), 161, 162, 163, 164, 165, 166, 167, 168 , 170 (polymer copolymer) ”,“ 400 ”,“ Bykumen ”(high molecular weight unsaturated acid ester),“ BYK-P104, P105 (high molecular weight unsaturated acid polycarboxylic acid) ”,“ P104S, 240S ( High molecular weight unsaturated acid polycarboxylic acid and silicon system ”,“ Lactimon (long chain amine) And unsaturated acid polycarboxylic acid and silicon).
Also, “Efka CHEMICALS” “Efka 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766”, “Efka Polymer 100 (modified polyacrylate), 150 (aliphatic) System modified polymer), 400, 401, 402, 403, 450, 451, 452, 453 (modified polyacrylate), 745 (copper phthalocyanine system) "," Floren TG-710 (urethane oligomer) "," Flownon "manufactured by Kyoeisha Chemical Co., Ltd. “SH-290, SP-1000”, “Polyflow No. 50E, No. 300 (acrylic copolymer)”, “Disparon KS-860, 873SN, 874 (polymer dispersing agent), # 2150 (manufactured by Enomoto Kasei Co., Ltd.) Aliphatic polyvalent carboxylic acid), # 7004 (polyether ester type) ” That.
Further, “Demol RN, N (Naphthalenesulfonic acid formalin condensate sodium salt), MS, C, SN-B (aromatic sulfonic acid formalin condensate sodium salt), EP”, “Homogenol L-18 (poly) Carboxylic acid type polymer), “Emulgen 920, 930, 931, 935, 950, 985 (polyoxyethylene nonyl phenyl ether)”, “Acetamine 24 (coconut amine acetate), 86 (stearyl amine acetate)”, manufactured by Lubrizol "Solsperth 5000 (phthalocyanine ammonium salt type), 13940 (polyesteramine type), 17000 (fatty acid amine type), 24000GR, 32000, 33000, 39000, 41000, 53000, 76400, 76500, J100", Nikko Chemi "Nikkor T106 (polyoxyethylene sorbitan monooleate), MYS-IEX (polyoxyethylene monostearate), Hexagline 4-0 (hexaglyceryl tetraoleate)" manufactured by Luo, "Ajisper PB821, 822," manufactured by Ajinomoto Fine Techno Co., Ltd. 824, 827, 711 "," TEGO Disper 685 "manufactured by Tego Chemi Service, and the like.
Among them, Solsperse 76400, 76500 manufactured by Lubrizol Corporation, J100 and Disperbyk-161, 162, 163, 164, 165, 166, 167, and 168 and Solsperse 24000GR manufactured by Lubrizol Corporation 32000, 33000, 39000, 41000, 53000 are preserved. A pigment dispersion with good stability is obtained.
The amount of the dispersion resin added is arbitrarily selected in order to ensure the desired stability. The fluidity of the ink was excellent when the active ingredient of the dispersion resin was 15 to 75 parts with respect to 100 parts of the pigment. Within this range, when compared with the same drop volume, the discharge speed is relatively fast and high-accuracy image drawing is possible.

(Monomer, oligomer, prepolymer)
In the active energy ray-curable inkjet ink of the present invention, conventionally known active energy ray-curable monomers, oligomers and prepolymers can be used as necessary.

Specific examples of the active energy ray-curable monomer including the above include benzyl (meth) acrylate, (ethoxy (or propoxy)) 2-phenoxyethyl (meth) acrylate, dicyclopentenyl (oxyethyl) (monofunctional monomer) (Meth) acrylate, phenoxydiethylene glycol (meth) acrylate, 2-methoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 2-ethoxyethyl (meth) acrylate, ethoxyethoxyethyl (meth) acrylate, methoxydipropylene glycol (Meth) acrylate, dipropylene glycol (meth) acrylate, β-carboxylethyl (meth) acrylate, trimethylolpropane formal (meth) acrylate, isoamyl ( (Meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isoboronyl (meth) acrylate, dicyclopentanyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, 2-hydroxy-3 -Phenoxypropyl (meth) acrylate, 1,4-cyclohexanedimethanol (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, acryloylmorpholine, Mention may be made of N-vinylcaprolactam, N-vinylpyrrolidone, N-vinylformamide, N-acryloyloxyethylhexahydrophthalimide.
Polyfunctional monomers include dimethylol-tricyclodecane di (meth) acrylate, (ethoxy (or propoxy)) bisphenol A di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, (poly) ethylene glycol di ( (Meth) acrylate, (ethoxy (or propoxy)) 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decandiol di (meth) acrylate, (ethoxy (Or propoxy))) neopentyl glycol di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, (neopentyl glycol modified) trimethylolpropane di (meta) Acrylate, tripropylene glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, pentaerythritol tri (or tetra) (meth) acrylate, trimethylolpropane tri (or tetra) (meth) acrylate, tetramethylol methanetri (Or tetra) (meth) acrylate and dipentaerythritol hexa (meth) acrylate may be mentioned.
The above active energy ray-curable monomers may be used alone or in combination of two or more.

    Among these, in the inkjet ink of the present invention, phenoxyethyl acrylate, ethoxyethoxyethyl acrylate, isobornyl acrylate, isooctyl acrylate, lauryl acrylate, N-vinylcaprolactam, N-acryloyloxyethyl hexahydrophthalimide as monofunctional monomers, Further, dimethylol-tricyclodecane diacrylate, (ethoxy (or propoxy)) bisphenol A diacrylate, (ethoxy (or propoxy)) neopentyl glycol diacrylate, hydroxypivalate neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, di B propylene glycol diacrylate, tripropylene glycol diacrylate, can be used 2- (2-vinyloxy ethoxy) ethyl acrylate more preferably. More preferably, lauryl acrylate, dipropylene glycol diacrylate, N-vinylcaprolactam, 1,10-decanediol diacrylate, and 2- (2-vinyloxyethoxy) ethyl acrylate can be used.

    In addition to the above, what is called an oligomer or a prepolymer can be used for the active energy ray-curable inkjet ink of the present invention. Specifically, “Ebecryl 230, 244, 245, 270, 280 / 15IB, 284, 285, 4830, 4835, 4858, 4883, 8402, 8803, 8800, 254, 264, 265, 294 / 35HD, manufactured by Daicel UCB, 1259, 1264, 4866, 9260, 8210, 1290.1290K, 5129, 2000, 2001, 2002, 2100, KRM7222, KRM7735, 4842, 210, 215, 4827, 4849, 6700, 6700-20T, 204, 205, 6602, 220, 4450, 770, IRR567, 81, 84, 83, 80, 657, 800, 805, 808, 810, 812, 1657, 1810, IRR302, 450, 670, 830, 835, 870, 1 30, 1870, 2870, IRR267, 813, IRR483, 811, 436, 438, 446, 505, 524, 525, 554W, 584, 586, 745, 767, 1701, 1755, 740 / 40TP, 600, 601, 604, 605, 607, 608, 609, 600 / 25TO, 616, 645, 648, 860, 1606, 1608, 1629, 1940, 2958, 2959, 3200, 3201, 3404, 3411, 3412, 3415, 3500, 3502, 3600, 3603, 3604, 3605, 3608, 3700, 3700-20H, 3700-20T, 3700-25R, 3701, 3701-20T, 3703, 3702, RDX63182, 6040, IRR419 ", manufactured by Sartomer CN104, CN120, CN124, CN136, CN151, CN2270, CN2271E, CN435, CN454, CN970, CN971, CN972, CN9782, CN981, CN9873, CN991, "Laromar EA81L, F87" manufactured by BASF LR8800, PE46T, LR8907, PO43F, PO77F, PE55F, LR8967, LR8981, LR8982, LR8992, LR9004, LR8956, LR8985, LR8987, UP35D, UA19T, LR9005, PO83F, PO33F, L8489, L9489 LR8996, LR9013 LR9019, PO9026V, PE9027V "manufactured by Cognis" Photomer 3005, 3015, 3016, 3072, 3982, 3215, 5010, 5429, 5430, 5432, 5662, 5806, 5930, 6008, 6010, 6019, 6184, 6210, 6217, 6230, 6891, 6892, 6893-20R, 6363, 6572, 3660 "," Art Resin UN-9000HP, 9000PEP, 9200A, 7600, 5200, 1003, 1255, 3320HA, 3320HB, 3320HC, 3320HS, 901T " 1200TPK, 6060PTM, 6060P "," Nippon Gosei Chemical Co., Ltd. "" purple light UV-6630B, 7000B, 7510B, 7461TE, 3000B, 320 " 0B, 3210EA, 3310B, 3500BA, 3520TL, 3700B, 6100B, 6640B, 1400B, 1700B, 6300B, 7550B, 7605B, 7610B, 7620EA, 7630B, 7640B, 2000B, 2010B, 2250EA, 2750B, “Kayarad” R-280, R-146, R131, R-205, EX2320, R190, R130, R-300, C-0011, TCR-1234, ZFR-1122, UX-2201, UX-2301, UX3204, UX-3301, UX-4101, UX-6101, UX-7101, MAX-5101, MAX-5100, MAX-3510, UX-4101 ", etc., but are not limited thereto.

  In order to further improve the dispersibility of the pigment and the storage stability of the ink composition, an organic pigment derivative may be added to the inkjet ink set of the present invention when the pigment is dispersed.

(Surface conditioner)
In the present invention, it is preferable to add a surface conditioner in order to improve wettability to the substrate. The surface conditioner in the present invention is a resin that lowers the ink surface tension by 0.5 mN / m or more when 1 wt% is added to the ink.
Specific examples of the surface conditioner include BYK-350, 352, 354, 355, 358N, 361N, 381N, 381, 392, BYK-300, 302, 306, 307, 310, 315, 320, and 322 manufactured by BYK Chemie. 323, 325, 330, 331, 333, 337, 340, 344, 370, 375, 377, 355, 356, 357, 390, UV3500, UV3510, UV3570, "Tegorad-2100, 2200, 2250, 2500" manufactured by Tego Chemie 2700 "or the like, but is not limited thereto. These surface conditioners may be used alone or in combination of two or more as required.

  The surface conditioner is preferably contained in the ink-jet ink in an amount of 0.001 to 5% by weight. If it is less than 0.001% by weight, the wetting spread is poor, and if it is more than 5% by weight, the surface conditioner cannot be fully oriented at the ink interface, and only a certain effect is exhibited.

  In the present invention, it is preferable to use a stabilizer in order to improve the viscosity stability of the ink over time and the on-press viscosity stability in the recording apparatus. As the stabilizer, hindered phenol compounds, phenothiazine compounds, hindered amine compounds, and phosphorus compounds are particularly preferably used. Specifically, as hindered phenol compounds, “IRGANOX 1010, 1010FF, 1035, 1035FF, 1076, 1076FD, 1076DWJ, 1098, 1135, 1330, 245, 245FF, 245DWJ, 259, 3114, 565, manufactured by BASF, 565DD, 295 ", Seiko Chemical Co., Ltd." BHT Swanox "" Nonflex Aruba, MBP, EBP, CBP, BB "" TBH ", ADEKA" AO-20, 30, 50, 50F, 70, 80, 330 ", “H-BHT” manufactured by Honshu Chemical Co., Ltd. “Yoshinox BB, 425, 930” manufactured by API Corporation, phenothiazine as a phenothiazine-based compound, “phenothiazine” “2-methoxyphenothiazine” manufactured by Sakai Chemical Industry, “2 "Cyanophenothiazine", hindered amine compounds, "IRGANOX 5067" "TINUVIN 144, 765, 770DF, 622LD" manufactured by BASF, Seiko Chemical Co., Ltd. "Nonflex H, F, OD-3, DCD, LAS-P" "Stealer STAR “Diphenylamine”, “4-aminodiphenylamine”, “4-oxydiphenylamine”, “HO-TEMPO” manufactured by Evonik Degussa, Hitachi Chemical “Fancryl 711MM, 712HM”, and phosphorous compound “Triphenylphosphine” “IRGAFOS 168, 168FF”, Seiko Chemical Co., Ltd. “Nonflex TNP”, and other compounds such as “IRGASTAB UV-10, 22” manufactured by BASF, “Hydroquinone” “Metoki” manufactured by Seiko Chemical Co., Ltd. “Toluquinone” “MH” “PBQ” “TBQ” “2,5-diphenyl-p-benzoquinone”, Wako Pure Chemical Industries “Q-1300, 1301”, “GENORAD 16, 18, 20” manufactured by RAHN be able to. Among them, Seiko Chemical Co., Ltd. “BHT Swanox”, “Nonflex Alba”, Honshu Chemical Co., Ltd. “H-BHT” as hindered phenol compounds in terms of solubility in ink and the color of the stabilizer itself, “Phenothiazine” manufactured by Seiko Chemical Co., Ltd., “Phenothiazine” manufactured by Sakai Chemical Industry Co., Ltd., “HO-TEMPO” manufactured by Evonik Degussa Co., and “Triphenylphosphine” manufactured by BASF Co., Ltd. are used as phosphorus compounds. Selected.

  The stabilizer is preferably contained in the ink-jet ink in an amount of 0.001 to 5% by weight. If it is less than 0.001% by weight, the ink stability is deteriorated. If it is more than 5% by weight, curing is inhibited and wrinkles are likely to occur.

    The inkjet ink of the present invention preferably has a viscosity at 25 ° C. adjusted to 5 to 50 mPa · s. If it is this viscosity area | region, the stable discharge characteristic is especially shown with the head which has a normal frequency of 5-30 KHz. Here, when the viscosity is less than 5 mPa · s, a decrease in the followability of the discharge is recognized, and when it exceeds 50 mPa · s, the discharge itself is lowered even if a mechanism for reducing the viscosity by heating is incorporated in the head. Discharge stability becomes poor and it becomes impossible to discharge at all. Furthermore, it is more preferable to adjust the viscosity at 25 ° C. to 7 to 14.5 mPa · s, and particularly preferably to 8.5 to 13 mPa · s. In this viscosity region, stable ejection characteristics are exhibited not only in a head having a normal frequency of 5 to 30 KHz but also in a head having a high frequency of 10 to 50 KHz.

    The ink composition of the present invention preferably has an electric conductivity of 10 μS / cm or less in a piezo head and does not cause electrical corrosion inside the head. In the continuous type, it is necessary to adjust the electric conductivity by the electrolyte. In this case, it is necessary to adjust the electric conductivity to 0.5 mS / cm or more.

  In order to use the ink composition of the present invention, the ink composition is first supplied to a printer head of a printer for an ink jet recording system, discharged from the printer head onto a substrate, and then activated energy such as ultraviolet rays or electron beams. Irradiate the line. As a result, the ink composition on the print medium is quickly cured.

    Although there is no limitation in particular about the printing base material used by this invention, Plastic base materials, such as a polycarbonate, a hard vinyl chloride, a soft vinyl chloride, a polystyrene, a foamed polystyrene, PMMA, a polypropylene, polyethylene, PET, these mixed or modified goods, a fine paper And paper base materials such as art paper, coated paper and cast coated paper, and metal base materials such as glass and stainless steel.

[Example]
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the embodiments of the present invention are not limited to these examples. In the following, all parts represent parts by weight.

(Cyan pigment dispersion creation)
Pigment Phthalocyanine pigment (Toyo Color)
"LIONOL BLUE FG-7400G" 15.0 parts Pigment dispersant Solsperse 32000 (manufactured by Lubrizol) 5.0 parts Monomer dipropylene glycol diacrylate 80.0 parts The above materials were stirred with a high-speed mixer or the like until uniform. Thereafter, the obtained mill base was dispersed in a horizontal sand mill for about 1 hour to prepare a cyan pigment dispersion.

(Preparation of magenta pigment dispersion 1)
Pigment 1 Quinacridone pigment (BASF)
"CROMOPHTAL JET Magenta DMQ" 10.0 parts Pigment 2 Quinacridone pigment (manufactured by Clariant)
“Ink Jet Magenta E5B02” 5.0 parts Pigment dispersant Solsperse 32000 (manufactured by Lubrizol) 10.0 parts Monomer dipropylene glycol diacrylate 75.0 parts Like the cyan pigment dispersion, the above materials are mixed with a high speed mixer or the like. Then, the obtained mill base was dispersed in a horizontal sand mill for about 1 hour to prepare a magenta pigment dispersion 1.

(Preparation of magenta pigment dispersion 2)
Pigment Rhodamine lake pigment (manufactured by Daido Kasei Kogyo Co., Ltd.)
“No. 9310 PINK” 20.0 parts Pigment dispersant Solsperse 32000 (manufactured by Lubrizol) 10.0 parts Monomer Dipropylene glycol diacrylate 70.0 parts Like the cyan pigment dispersion, the above materials were mixed with a high speed mixer. Then, the resulting mill base was dispersed with a horizontal sand mill for about 1 hour to prepare a magenta pigment dispersion 2.

(Creation of yellow pigment dispersion)
Pigment Isoindoline pigment (BASF)
“Paliotol Yellow D1155” 20.0 parts Pigment dispersant Solsperse 32000 (manufactured by Lubrizol) 10.0 parts Monomer Dipropylene glycol diacrylate 70.0 parts Like the cyan pigment dispersion, the above materials are mixed with a high speed mixer or the like. The resulting mill base was dispersed in a horizontal sand mill for about 1 hour to prepare a yellow pigment dispersion.

(Creation of black pigment dispersion)
Pigment Carbon black pigment (Degussa)
“Special Black 350” 15.0 parts Pigment dispersant Solsperse 32000 (manufactured by Lubrizol) 5.0 parts Monomer Dipropylene glycol diacrylate 80.0 parts In the same manner as the cyan pigment dispersion, the above materials were mixed with a high speed mixer or the like. After stirring until uniform, the obtained mill base was dispersed in a horizontal sand mill for about 1 hour to prepare a black pigment dispersion.

[Example 1 to Example 5]
Next, in Table 1 formulation, add while stirring sequentially from the top of the table, gently mix until the polymerization initiator is dissolved, then filter through a 1 μm membrane filter to remove coarse particles Inkjet ink composition was obtained.

The ink raw materials in Table 1 are
・ Dipropylene glycol diacrylate (manufactured by BASF)
・ 2- (2-vinyloxyethoxy) ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.)
・ Lauryl acrylate (manufactured by Osaka Organic Chemicals)
・ N-Vinylcaprolactam (manufactured by BASF)
・ LUCIRIN TPO (BASF)
・ KAYACURE BMS (manufactured by Nippon Kayaku Co., Ltd.)
・ Irgacure 819 (manufactured by BASF)
・ SB-PI 704 (manufactured by Sojyo Industrial Co., Ltd.)
・ BHT Swanox (made by Seiko Chemical Co., Ltd.)
・ Phenothiazine (Seiko Chemical Co., Ltd.)
・ BYK-UV3510 (manufactured by BYK Chemie)
It was prepared using.

(Evaluation of ink)
The adjusted ink was printed by OnePass JET manufactured by Tritech Co., Ltd. The adjusted ink was injected into a Kyocera head by a syringe, printed at a head temperature of 40 ° C., cured by a UV lamp (240 W) manufactured by Nordson, and the output image was evaluated. As the evaluation paper, OK top coat + (Oji Paper Co., Ltd.) coated paper was cut into a suitable size and used.

(Curing speed)
The ink composition prepared above is printed from 55 m / min to 25 m / min with a printing speed reduced every 1 m / min, and the 100% solid printing portion of each color is cured at 1 Pass, so that the curability is high. The degree (curing speed) was judged. The printed material was rubbed 10 times with a cotton swab, and the state where the ink did not adhere to the cotton swab and the trace of the cotton swab remained on the surface of the printed material was judged as cured.
As an evaluation standard, a material that is cured at 25 m / min or more that can secure sufficient productivity in actual use is considered to have good curability. It can be said that the faster the printing speed, the faster the curing speed. Those that did not cure even at 25 m / min were evaluated as uncured.

(gross)
Wrinkles are generated when the internal curability is insufficient, and it is possible to detect even wrinkles at a level that is difficult to visually determine by gross measurement.
Gross, using the ink-jet ink composition prepared above, two or more solid print portions (200% solid for 2 colors, 300% solid for 3 colors, 400% solid for 4 colors) Was cured at a printing speed of 25 m / min · 1 Pass, measured with BYK Gardner Micro-Gloss, and judged with a measured value of 20 ° gloss.
The evaluation criteria are as follows. A value of ◯ or more is good with no surface wrinkles. X indicates a level at which wrinkles can be visually confirmed, and Δ indicates a level at which it is difficult to determine wrinkles visually, but when a microscope is used, wrinkles can be confirmed, and the color gamut decreases when colorimetry is performed. Then, the quality of the image is clearly degraded compared to ○.
Gross is affected by the surface shape as well as the degree of wrinkles. When the colors are overlapped, the surface generally becomes uneven, and the gloss tends to decrease in the order of 2>3> quaternary colors.
Secondary color gloss ○: 20 ° gloss is 50 or more Δ: 20 ° gloss is 20 to 50 ×: 20 ° gloss is less than 20 Tertiary color gloss ○: 20 ° gloss is 30 or more Δ : 20 ° gloss is 10 to 30 ×: 20 ° gloss is less than 10 quaternary color gloss ○: 20 ° gloss is 20 or more Δ: 20 ° gloss is 5 to 20 ×: 20 ° gloss Is less than 5

(Initial viscosity)
The viscosity immediately after preparation of the ink composition prepared above was measured. To measure the viscosity, a TVE25L viscometer manufactured by Toki Sangyo Co., Ltd. was used.
(Storage stability)
By comparing 6 mL of the ink composition prepared above into a screw tube bottle (capacity: about 7 mL) and sealing it, and then measuring the viscosity measured after standing at 60 ° C. for 7 days with the initial viscosity immediately after preparation, The stability over time was evaluated. In addition, the evaluation criteria at this time are as follows.
A: Increase in viscosity after a aging test is less than 5% compared to the initial viscosity B: Increase in viscosity after a aging test is less than 10% compared to the initial viscosity Δ: Increase in viscosity after a aging test is an initial viscosity 10% or more and less than 15% in comparison with X: Viscosity increase after aging test is 15% or more compared with initial viscosity

(Discharge stability)
For the ejection performance, the nozzle check pattern was printed on the ink-jet ink composition prepared above with OnePass JET manufactured by Tritech Co., Ltd., and after 100,000 shots were printed, the nozzle check pattern was printed again. Ejectability was evaluated. The evaluation criteria are as follows. A value of ◯ or higher is regarded as good ejection stability.
○: No nozzle missing after 100,000 shots △: Nozzle missing 1 to 5 after 100,000 printing ×: Nozzle missing 6 or more after 100,000 printing

[Examples 6 to 13]
In the same manner as in Examples 1 to 5, an inkjet ink composition was prepared, printed and cured according to Table 2 formulation.

[Comparative Examples 1 to 7]
In the same manner as in Examples 1 to 13, an inkjet ink composition was prepared, printed and cured according to Table 3 formulation.

    The evaluation results are shown in Table 4. Examples 1 to 13 are examples in which the color ink with a faster printing order has a faster curing speed, and the total amount of initiator and sensitizer in each color is 7 to 25% by weight in the ink, and the curing speed, gloss, Good results were obtained in both storage stability and ejection stability.

    Among them, Examples 1, 3, 4, 6, 8, 9, 11, and 12 are examples in which the total amount of initiator and sensitizer in each color is 7 to 21% by weight in the ink, and storage stability is high. In both cases, a very good evaluation result is obtained with ◎ or more.

    Comparative Examples 1-4, 6, and 7 have a sufficient level of curability in a single color, but the gloss of the secondary color or higher is low, and wrinkles are visually confirmed in the tertiary color or higher, and clearly the quality of the printed matter Has fallen. In Comparative Example 5, since the amount of the initiator was small, even a single color did not cure. Further, in Comparative Examples 4 and 5, the viscosity is out of the range suitable for stable ejection, so the ejection stability is poor. In Comparative Example 4, the amount of initiator is so large that the storage stability is very poor. ing. Furthermore, when stored at room temperature, precipitation of the initiator was confirmed over time.

  From the above results, in order to suppress the gloss reduction of the printed matter accompanying the curing failure and output a clear image, the color ink with the earlier printing order has a faster curing speed, and the initiator and sensitizer of each color It was confirmed that it was an essential condition to use an active energy ray-curable inkjet ink composition having a total amount of 7 to 25% by weight in the ink.

The present invention relates to an ink composition used for active energy ray-curable ink jet printing, which has excellent curability, dischargeability, storage stability, and can produce high-definition and high-quality images. For this reason, it can be used for, for example, inkjet printing in industrial applications and industrial applications.

Claims (5)

In an active energy ray-curable inkjet ink set containing at least two or more types of color ink selected from cyan, magenta, and yellow, among cyan ink, magenta ink, and yellow ink, the faster the color ink, the faster the curing order. The total amount of initiator and sensitizer in each color of cyan ink, magenta ink and yellow ink is 7 to 25% by weight in each color ink, and acrylic 2- (2-vinyloxyethoxy) is used as a monomer. ) Ethyl is an essential component, and the total amount of dipropylene glycol diacrylate, acrylic 2- (2-vinyloxyethoxy) ethyl, lauryl acrylate, and N-vinylcaprolactam is 54.4% by weight or more of the total amount of the ink set. And single pass inkjet printing The active energy ray-curable inkjet ink set, characterized in that it is printed by the law. In an inkjet ink set containing two or more color inks selected from cyan, magenta and yellow as essential components and one or more inks selected from black, white and clear as optional components, cyan ink and magenta inks Of the inks and yellow inks, the faster the printing order, the faster the curing speed, and the total amount of initiator and sensitizer in each color of cyan ink, magenta ink and yellow ink is 7 to 25% by weight in each color ink. And, as a monomer, acrylic 2- (2-vinyloxyethoxy) ethyl as an essential component, dipropylene glycol diacrylate, acrylic 2- (2-vinyloxyethoxy) ethyl, lauryl acrylate, and N-vinylcaprolactam The total amount is the total amount of ink set 4.4 used wt% or more, and the active energy ray-curable inkjet ink set, characterized in that printed by a single pass ink jet printing. The active energy ray-curable inkjet ink set according to claim 1 or 2 , wherein among the cyan ink, magenta ink, and yellow ink, the color ink having the earlier printing order has a larger total amount of initiator and sensitizer. Wherein the viscosity at 25 ° C. of each color ink is 8.5~13.0mPa · s, claim 1-3 active energy ray-curable inkjet ink set according to any one. As initiators and sensitizers, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 4-benzoyl-4'-methyl-diphenyl sulfide, ethyl-4- (dimethylamino) -benzoate, bis (2,4,4) 6- trimethyl benzoyl) - at least one, characterized by containing, claim 1-4 active energy ray-curable inkjet ink set according to any one of phenyl phosphine oxide.