JP2015061897A - Method for printing ultraviolet-curable coating varnish composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for printing a UV-curable coating varnish composition which has good curability, low yellowing property and light stability, and low toxicity and low migration property for applications to toys and food packages, and which shows excellent curability even at a printing speed in an offset printing machine.SOLUTION: The method for printing a UV-curable coating varnish composition aims for printing a UV-curable coating varnish composition comprising a photopolymerization initiator composition, a polymerizable acylate monomer, and a resin oligomer having a polymerizable group. The photopolymerization initiator composition is an α-hydroxyketone-based photopolymerization initiator having a number average molecular weight of 320 or more and 1300 or less. The varnish composition is favorably cured in an integral luminous energy range of 20 to 200 mJ/cmof UV rays irradiating the composition, and is applied by an in-line coater unit included in an offset printing machine.

Description

  The present invention has a good curability, low yellowing, and light stability under ultraviolet light conditions, and is provided in an offset printing machine in consideration of safety such as low toxicity and low migration for toy and food packaging applications. The present invention relates to an invention of a printing method of an ultraviolet curable coating varnish, which is coated on a printed matter by a coater unit, and the printed matter.

  UV curable coating varnish, which cures under UV conditions, is widely used in the field of package printing for food packaging such as toys and paper containers because of the convenience of instantaneous curing characteristics.

  The coating varnish composition, which has a colorless transparent or translucent appearance and substantially does not contain a coloring component, prevents scratches and rubbing of the ink layer by, for example, overprinting on the colored ink. It is also possible to increase the gloss of the printed matter and improve the design. Furthermore, it is possible to change the appearance of varnish gloss, smoothness, texture, etc. by blending colorless inorganic pigments, waxes, resin beads, etc. in the coating varnish, and it is widely used in the applications shown above. ing.

  UV curable coating varnish is widely used in food packaging applications such as confectionery boxes and beverage packs, but in recent years, the trend toward migration of varnish components to encapsulated foods has become widespread, mainly in European and American countries. There is also a strong demand for improving the safety of coating varnishes, which are also one of various materials for producing printed materials.

  As a prescription for an ultraviolet curable coating varnish, migration of a relatively low molecular weight photopolymerization initiator or sensitizer component to an encapsulated food tends to be a problem.

For example, an ink composition using a polymer material has been proposed as an ink-jet ink composition for toys and food packaging (see, for example, Patent Documents 1 and 2). However, this technology has insufficient curability in offset printing machines with a much higher printing speed (production speed) than inkjet printing, and a sufficiently low migration performance because a large amount of unreacted initiator remains. Cannot be expressed. Although the printing speed (line speed) of the offset printing machine varies depending on the size and type of the machine, it is in the range of about 50 to 600 m / min, which is much higher than that of the head scanning ink jet printing machine. The cumulative amount of ultraviolet light applied to the ultraviolet curable coating composition applied by the inline coater unit provided in the offset printing machine is in the range of about 20 to 200 mJ / cm ^2. It is difficult to cure the ink composition well.

  In addition, it is necessary to consider not only the amount of migration for encapsulated foods, but also the safety and toxicity of the raw materials of the composition itself used for food packaging.

Special table 2011-502188 Special table 2011-500932

  The object of the present invention is to combine excellent curability, low yellowing, light stability, low toxicity for toys and food packaging applications, and low migration, and excellent curability at the printing speed of an offset printing press. It is providing the printing method of the ultraviolet curable coating varnish composition which has.

  The present inventors have found that the above-mentioned problems can be achieved by appropriately adopting a combination of a high-molecular photopolymerization initiator or sensitizer and a polymerizable oligomer that is excellent in reaction curability as compared with conventional ones, leading to the present invention. It was.

A method for printing an ultraviolet curable coating varnish composition comprising a photopolymerization initiator composition, a polymerizable acrylate monomer, and a resin oligomer having a polymerization group, wherein the photopolymerization initiator composition has a number average molecular weight of 320 or more. It is an α-hydroxyketone photopolymerization initiator that is 1300 or less, and cures well in the range of ²⁰ to 200 mJ / cm ² of the cumulative amount of ultraviolet light to be irradiated, and is provided by an inline coater unit provided in an offset printing machine. The present invention provides a method for printing an ultraviolet curable coating varnish composition characterized by being coated.

  The UV curable coating varnish composition of the present invention is applied by an in-line coater unit provided in an offset printing machine, and is suitable for toys and food packaging, which has high curability but high toxicity and migration. UV curable coating varnishes for toys and food packaging can be obtained that have no curing varnish composition, excellent curability, excellent light stability, little yellowing, low toxicity and low migration. .

It is a figure which coats the ultraviolet curable coating varnish composition of the present invention with an in-line coater unit provided in an offset printing machine and cures it with an ultraviolet irradiation lamp. It is a figure which shows the printed matter which irradiated the ultraviolet-ray to the printed matter developed using the ultraviolet curable coating varnish composition of this invention, and hardened the coating varnish layer. It is a figure which superimposes and presses so that the back surface of milk carton white paper may contact the upper surface of the printed matter after ultraviolet irradiation.

  The present invention offsets an ultraviolet curable coating varnish composition containing an appropriate amount of an α-hydroxyketone photopolymerization initiator having a number average molecular weight of 320 to 1300, a polymerizable acrylate monomer, and a resin oligomer having a polymerizable group. The effect of the present invention is achieved by coating with an inline coater unit provided in a printing press.

  The photopolymerization initiator composition used in the printing method of the ultraviolet curable coating varnish print described herein of the present invention is an α-hydroxyketone photopolymerization initiator having a number average molecular weight of 320 or more and 1300 or less.

  When the α-hydroxyketone photopolymerization initiator is less than the number average molecular weight 320, the migration amount tends to increase due to the migration of the photopolymerization initiator component to the inclusion, and the number average molecular weight exceeds 1300. , It leads to a decrease in storage stability due to reprecipitation accompanying crystallization of the photopolymerization initiator and a decrease in coating curability after printing. In addition, the initiator component can be made soluble even if the number average molecular weight exceeds 1300 by chemically bonding a component having no conjugated double bond such as polyhydric alcohols and fatty acids by a method such as esterification. Although it is technically possible to provide an excellent compound, these derivatives having a number average molecular weight of more than 1300 lower the effective component concentration of the initiator in the compound (ratio of conjugated double bonds having ultraviolet absorbing ability). Therefore, it is difficult to obtain sufficient curability.

  An α-aminoalkylphenone photopolymerization initiator 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl)-having a number average molecular weight of 320 or more and 1300 or less and exhibiting excellent low migration properties in a colored ink. Butanone-1 (number average molecular weight: 366.5), 2- (dimethylamino) -2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one ( Number average molecular weight: 380.5), acylphosphine oxide photopolymerization initiator bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (number average molecular weight 418.5), 2,4,6- Trimethylbenzoyl-diphenylphosphine oxide (number average molecular weight 348.0) is a discoloration (yellowing) of the cured film due to the curing reaction, Use of a coating varnish colorless transparent system because of the reduced sexual is undesirable.

  As the α-hydroxyketone photopolymerization initiator having a number average molecular weight of 320 to 1300, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl]- Phenyl} -2-methyl-propan-1-one (number average molecular weight: 340.4), oligo (2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone) (number average Molecular weight: 424.57), 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) phenoxy] phenyl} -2-methylpropanone (number average molecular weight: 342.39), etc. Any one or more of these may be included, and a plurality of these may be used in combination. 1-hydroxy-cyclohexyl-phenyl-ketone (number average molecular weight: 204.3), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (several) which are the same α-hydroxyketone photopolymerization initiator The average molecular weight: 164.2) is not included in these. In addition, 2,2-dimethoxy-1,2-diphenylethane-1-one (number average molecular weight 256.3) is used in a wide range in colorless and transparent coating varnish, but its use is not preferred because of low migration property. .

  The content of the α-hydroxyketone photopolymerization initiator in the coating varnish composition is preferably in the range of 4 to 25% by weight with respect to 100% by weight of the nonvolatile content in the coating varnish. When the addition amount is less than 4% by weight, it is difficult to obtain good curability. When the addition amount exceeds 25% by weight, the initiator amount becomes excessive, resulting in a decrease in storage stability (deposition of the initiator component) and This is not preferable because it causes a decrease in low migration performance.

  In addition to the α-hydroxyketone-based photopolymerization initiator, a phenylketone-based composition group having a polymerizable group introduced into the initiator molecule described in Japanese Patent No. 2514804 also imparts coating varnish curability and low migration properties. Available for purpose. For example, in this composition group, 4- (2-acryloyloxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone has been named “Darocur ZLI3331” in the past by Merck (currently BASF). And are available in the present invention. In addition, a composition (number average molecular weight of about 1100) in which a high molecular weight α-hydroxyketone photopolymerization initiator is introduced and a polymerizable group is introduced is sold by BASF under the name of “Irgacure LEX201” and has excellent low migration performance. Similarly, it can be suitably used in the present invention.

  Specific examples of the safety and toxicity of the photopolymerization initiator itself used for coating varnish for food packaging are as follows: 2-methyl-1- [4- (methylthio) phenyl] -2-monoforinopropane-1- IRGACURE907 (manufactured by BASF), which is ON, has extremely excellent curability and is widely used particularly in UV curable compositions, but is a substance of high concern for reproductive toxicity (GHS classification: reproductive toxicity) Category 1B (reproductive ability) and 1B (fetus)), which do not depend on this, and have higher required properties required for coating varnishes such as low migration, low odor, light stability, and excellent curability. In the present invention, printing can be performed by a coater unit provided in an offset printing machine.

  Furthermore, as an example of a photopolymerization initiator, DAROCURE TPO (manufactured by BASF), which is 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, has excellent internal curing performance and is also widely used. However, in terms of safety, it has been announced as a former type 2 monitoring chemical substance, and there is a suspicion of long-term toxicity, so it does not depend on this, yet it has low migration, low odor, light stability, and excellent curability. The present invention satisfies the higher required characteristics required for a coating varnish printable with a coater unit provided in an offset printing press.

  The polymerizable acrylate monomer, which is an essential component of the ultraviolet curable coating varnish composition used in the printing method of the present invention, is shown in the examples below, but with respect to 100% by weight of the nonvolatile content in the ultraviolet curable coating varnish, It contains 30 to 85% by weight, more preferably 40 to 70% by weight.

  In terms of expressing low migration performance in the ultraviolet curable coating varnish composition used in the printing method of the present invention, it is preferable to use a bifunctional or higher acrylate monomer having higher reactivity. In order to obtain necessary physical properties such as adhesion to the material and flexibility of the cured coating film, a monofunctional acrylate monomer can be used alone or in combination as appropriate. In the printing method of the present invention, a methacrylate monomer can be appropriately used as a monomer component, but an acrylate monomer having better curability is preferably used as a main monomer.

  Examples of the monofunctional acrylate monomer include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, lauryl acrylate, tridecyl acrylate, hexadecyl acrylate, octadecyl acrylate, isoamyl acrylate, isodecyl acrylate, isostearyl acrylate, and cyclohexyl. Acrylate, benzyl acrylate, methoxyethyl acrylate, butoxyethyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, nonylphenoxyethyl acrylate, tetrahydrofurfuryl acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acetate Rate, 3-chloro-2-hydroxypropyl acrylate, diethylaminoethyl acrylate, nonylphenoxyethyl tetrahydrofurfuryl acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, isobornyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxy ethyl acrylate, etc. Is mentioned.

  Examples of the bifunctional or higher acrylate monomer include 1,4-butanediol diacrylate, 3-methyl-1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 2 -Methyl-1,8-octanediol diacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, tricyclodecane dimethanol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, Dihydric alcohol diacrylates such as dipropylene glycol diacrylate and tripropylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate Trivalent or more polyvalent polyacrylates such as acrylate, tris (2-hydroxyethyl) isocyanurate diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol polyacrylate Diacrylate of a diol obtained by adding 2 mol or more of ethylene oxide or propylene oxide to 1 mol of polyhydric alcohol, 1 mol of neopentyl glycol, obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of glycerin Triol triacrylate, 3 moles of ethylene oxide or propylene oxide per mole of trimethylolpropane Pressurized to triol di- or tri-acrylates obtained, polyacrylate polyoxyalkylene polyols and di acrylate of a diol obtained by adding 2 moles or more of ethylene oxide or propylene oxide to bisphenol A1 molar and the like.

  Among the acrylate monomers, it is possible to use an acrylate monomer having 4 or more functionalities in combination for the purpose of developing a better curability and low migration performance in the ultraviolet curable coating varnish composition used in the printing method of the present invention. Examples include ditrimethylolpropane tetraacrylate, ethylene oxide modified pentaerythritol tetraacrylate, propylene oxide modified pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and the like. It may be used. Among them, dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate are preferable materials in terms of greatly improving the curability of the composition, and 5 to 30% by weight with respect to 100% by weight of the nonvolatile content in the ultraviolet curable coating varnish. You may use in the range.

  Furthermore, the resin oligomer which has a polymeric group is mentioned as an essential component of the ultraviolet curable coating varnish composition used for the printing method of this invention. Compared with non-reactive resins (inert resins) having no polymerizable group in the molecule, the reactivity is high, and it is possible to impart more excellent curability and low migration property. As the resin oligomer having a polymerizable group described in the present invention, an epoxy acrylate compound, a urethane acrylate compound, a polyester acrylate compound or the like having at least one polymerizable group in one molecule may be used alone. One or more kinds may be used in combination. The amount of the resin oligomer having a polymerization group is preferably in the range of 10 to 50% by weight with respect to 100% by weight of the nonvolatile content in the ultraviolet curable coating varnish. When the amount used is less than 10% by weight, it is difficult to obtain the flexibility of the cured coating film. When the amount used exceeds 50% by weight, since these polymerizable resin oligomers generally have high viscosity, the present invention is carried out. In the composition described in the examples, it becomes difficult to obtain a viscosity suitable as a coating varnish. On the other hand, if the polymerizable oligomer is added in a proportion exceeding 50 wt% by using a large amount of low molecular weight monomers (generally monofunctional and bifunctional acrylate monomers) for viscosity adjustment, a suitable viscosity is obtained. Even if it can be obtained, the low migration property is impaired.

  Among the resin oligomer components having a polymerizable group, epoxy acrylate is an acrylate obtained by reacting polyepoxide with acrylic acid or its anhydride. Examples of the polyepoxide include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, and the like, and hydrogenated aromatic rings of bisphenol type epoxy resin. As the epoxy acrylate, bisphenol A type epoxy acrylate is preferable.

  The polyepoxide is preferably an epoxy resin having an average of 2 to 5 epoxy groups in one molecule. Among the epoxy resins, a bisphenol type epoxy resin is preferable because it can form a cured coating film having an excellent balance between hardness and elongation. Polyepoxides can be used alone or in combination of two or more. The reaction between polyepoxide and acrylic acid is usually carried out at a temperature in the range of 50 ° C. to 150 ° C. for about 1 to 8 hours. In the reaction, a catalyst is preferably used. Specific examples of the catalyst include amines such as triethylamine, dimethylbutylamine and tri-n-butylamine, quaternary ammonium salts such as tetramethylammonium salt, tetraethylammonium salt, tetrabutylammonium salt and benzyltriethylammonium salt, Alternatively, quaternary phosphonium salts, phosphines such as triphenylphosphine, and imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole can be used.

  Among the resin oligomer components having a polymerizable group described above, urethane acrylate is an acrylate having a urethane bond in the molecule. For example, it can be obtained by reacting a hydroxyl group-containing acrylate, a polyisocyanate, and a polyol. Depending on the purpose, it is possible to use a urethane acrylate composed of a hydroxyl group-containing acrylate and a polyisocyanate without using a polyol as a raw material.

  As the hydroxyl group-containing acrylate, for example, hydroxyalkyl acrylate and its ether extension product, lactone extension product and the like can be used. Further, for various polyols, those having a structure in which a part of the hydroxyl group is acrylate, and the like In addition, various carboxylic acid esters of glycidyl acrylate can also be used. Specifically, C2-C8 hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate, (poly) ethylene glycol monoacrylate, (poly) propylene glycol monoacrylate, poly (ethylene glycol / propylene) Glycol) monoacrylate, poly (propylene glycol tetramethylene glycol) monoacrylate, ε-caprolactone extension of 2-hydroxyethyl acrylate, glycerol monoacrylate, glycerol diacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate , Tris (2-hydroxyethyl) diacrylate, etc., acetic acid of glycidyl acrylate, propionic acid, p-ter - butyl benzoic acid, also acid adducts such as fatty acid can be used.

  Examples of the polyisocyanate used in the urethane acrylate include aromatic polyisocyanate, aliphatic polyisocyanate, cycloaliphatic polyisocyanate, and polyisocyanate having an isocyanurate structure. Specifically, tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexanediol diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated In addition to methylene diphenyl diisocyanate, dimer acid diisocyanate, lysine diisocyanate and the like, 1,6-hexanediol diisocyanate trimer forming isocyanurate skeleton, isophorone diisocyanate trimer and the like can be mentioned.

  As the polyol used for the urethane acrylate, for example, polyether polyol, polyester polyol, polycarbonate polyol, polybutadiene polyol and the like can be used, and in some cases, those modified with polysiloxane, fluoroolefin copolymer, and the like can also be used.

  Among the resin oligomer components having a polymerizable group, the polyester acrylate is a saturated or unsaturated polyester acrylate having at least two acryloyl groups in one molecule. For example, it can be obtained by esterifying a polybasic acid or its anhydride, a polyol, acrylic acid or its anhydride. Depending on the purpose, it is also possible to use a polyester acrylate comprising a polyol and acrylic acid or its anhydride without using a polybasic acid or its anhydride. In addition, a polyester acrylate obtained by reacting a carboxyl group of a polyester synthesized by a conventional method with an acrylate having an epoxy group can also be used.

  As said polybasic acid, an aromatic polybasic acid, a chain | strand-shaped aliphatic polybasic acid, a cyclic aliphatic polybasic acid etc. can be used, for example. As the polyol, for example, an alkylene polyol can be used.

  Examples of the glycol that is a raw material for the polyester include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, hexylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, Alkylene glycols typified by 1,6-hexanediol, 2-methylpropane-1,3-diol, dimethylolcyclohexane, hydrogenated bisphenol A, 2,4,4-trimethyl-1,3-pentanediol; , Polyalkylene glycols represented by triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polybutylene glycol and the like; bisphenol A, Scan phenol F, and the like addition reaction product of bisphenol S, 2 dihydric phenol with an alkylene oxide represented by ethylene oxide or propylene oxide represented by tetrabromobisphenol A and the like. Examples of the triol include glycerin, trimethylolpropane, trimethylolethane, and 1,2,6-hexanetriol. Examples of the tetraol unit include pentaerythritol, diglycerol, and 1,2,3,4-butanetetraol. In addition, polycondensates such as polyethylene terephthalate having a hydroxyl group or a carboxyl group as a part of glycols and an acid component can also be used.

  Examples of the dibasic acid (anhydride) include o-phthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic acid, tetrabromophthalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, There are 1,2-dodecanoic acid, maleic acid, fumaric acid, itaconic acid, himitic acid, hettic acid and the like. Tribasic acid units include trimellitic acid, aconitic acid, butanetricarboxylic acid, 6-carboxy-3-methyl. -1,2,3,6-hexahydrophthalic acid and the like, and examples of the 4-basic acid unit include pyromellitic acid and butanetetracarboxylic acid. Examples of the α, β-unsaturated dibasic acid or acid anhydride thereof include maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, chloromaleic acid, and esters thereof. As aromatic saturated dibasic acid or acid anhydride thereof, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, nitrophthalic acid, tetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, halogenated phthalic anhydride and these Examples of the aliphatic or alicyclic saturated dibasic acid include oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, glutaric acid, hexahydrophthalic anhydride, and esters thereof. These are used alone or in combination.

  Examples of the monoepoxy compound include ethylene oxide, propylene oxide, epichlorohydrin, styrene oxide, and phenyldaricidyl ether. Moreover, as a polyepoxy compound, what is called a diepoxy compound can be used conveniently, for example, the Nikkan Kogyo Shimbun plastic material course 1 "epoxy resin" (issued May 10, 1946, written by Kuniyuki Stripe) Mention may be made of the epoxy resins described on pages 19 to 48.

  Furthermore, in the ultraviolet curable coating varnish composition used in the printing method of the present invention, as a means for further improving the curability, the number average molecular weight is 400 or more and 1500 or less as a sensitizer, and the maximum absorption at a wavelength of 250 to 450 nm is 280. An aromatic tertiary amine compound having a range of ˜340 nm may be added. Among them, poly (ethylene glycol) bisdimethylaminobenzoate (number average molecular weight 488 to 532) as a bifunctional amine derivative which is an alkylaminobenzoate compound (poly (ethylene glycol) bisdimethylaminobenzoate (number average molecular weight 860) as a tetrafunctional amine derivative) Is preferable in that it has a relatively high molecular weight and is difficult to migrate. The same alkylaminobenzoate compounds ethyl-4- (dimethylamino) benzoate (number average molecular weight 193.2), 2- (dimethylamino) ethyl benzoate (number average molecular weight 193.2), 2-ethylhexyl-4- (dimethyl) Amino) benzoate (number average molecular weight 277.4), etc. are not included. Aromatic tertiary amines other than alkylaminobenzoates include alkylaminobenzophenone compounds. Among them, 4,4'-bis (diethylamino) benzophenone (number average molecular weight 324.47) has excellent curability and low migration properties, but has a wavelength. Since the maximum absorption wavelength at 250 to 450 nm is as high as 365 nm, and the discoloration (yellowing) of the cured film due to the curing reaction is severe, it is not preferable to use it in a colorless and transparent composition that does not contain a coloring material such as coating varnish.

  The content of the aromatic tertiary amine compound in the UV curable coating varnish composition is preferably in the range of 1 to 8% by weight with respect to 100% by weight of the nonvolatile content in the UV curable coating varnish. . An addition amount of less than 1% by weight is undesirable in that a further improvement in the curing rate cannot be obtained, and even if it is added in excess of 8% by weight, the effect of just using it is not recognized.

  In the colorless and transparent coating varnish, benzophenone (number average molecular weight 182.22), 4-methylbenzophenone (number average molecular weight 196.24), O-methylbenzoylbenzoate (number average molecular weight), which are hydrogen abstraction type photopolymerization initiators, are used. 240.25) and the like are widely used, but their use is not preferable because of low migration.

[Description of viscosity: Extracted from water-based adhesive patent]
The solution viscosity range of the ultraviolet curable coating varnish composition used in the printing method of the present invention is the Zahn cup viscometer No. The number of seconds at a liquid temperature of 25 ° C. using 4 is preferably in the range of 10 seconds to 80 seconds, more preferably in the range of 20 seconds to 50 seconds, for example, compared with the composition used in inkjet printing. And high viscosity. When the viscosity of the UV curable coating varnish composition used in the printing method of the present invention is less than 10 seconds, that is, a sufficient amount of the resin oligomer as a high viscosity component cannot be used, and the flexibility and mechanical properties of the cured coating film are obtained. I can't. On the other hand, when the viscosity exceeds 80 seconds, good coating suitability cannot be obtained and it becomes difficult to obtain a uniform coating varnish coating film. The coating varnish may be appropriately adjusted in the range of room temperature to 60 ° C by adjusting the liquid temperature of the coating varnish supplied into the coater by installing a heater device having a temperature adjustment function in the varnish supply tank. In order to obtain the surface state, the liquid temperature is changed. In this case as well, the viscosity of the ultraviolet curable coating varnish composition is preferably within the above range. Further, the ultraviolet curable coating varnish composition used in the printing method of the present invention is substantially free of volatile components such as organic solvents, and is in the state of a composition not containing volatile components and has the above-mentioned viscosity. It is preferable to be within the range.

  The printing substrate used in the printing method of the present invention is not particularly limited. For example, it is used for printing catalogs, posters, flyers, CD jackets, direct mails, brochures, cosmetics and beverages, pharmaceuticals, toys, equipment packages, etc. Quality paper, coated paper, art paper, imitation paper, thin paper, cardboard, various synthetic paper, polyester resin, acrylic resin, vinyl chloride resin, vinylidene chloride resin, polyvinyl alcohol, polyethylene, polypropylene, polyacrylonitrile, ethylene acetate Vinyl copolymers, ethylene vinyl alcohol copolymers, ethylene methacrylic acid copolymers, films or sheets of nylon, polylactic acid, polycarbonate, etc., cellophane, aluminum foil, and other various conventional substrates used as printing substrates To mention Can.

  The ultraviolet curable coating varnish composition described in the printing method of the present invention is characterized in that it is applied to a printed material by an inline coater unit provided in an offset printing machine, on the printing substrate and on the surface of the printing substrate. It is coated on the offset ink composition printed by offset printing, and good curability and low migration can be obtained regardless of the presence or absence of underprint offset ink.

  Offset printing machines are manufactured and sold by a large number of printing machine manufacturers. Examples include Heidelberg, Komori Corporation, Mitsubishi Heavy Industries Printing Paper Machine Co., Ltd., Man Roland, Ryobi, and KBA. The present invention can be suitably used in any sheet feeding method, such as a sheet-fed offset printing machine using a printing paper in a form, an offset rotary printing machine using a printing paper in a reel form. More specifically, offset printing machines such as Heidelberg's Speedmaster Series, Komori Corporation's Lislon Series, Mitsubishi Heavy Industries Printing Paper Machinery Co., Ltd.'s Diamond Series, etc. can be mentioned. The product is suitably coated with an in-line coater unit provided in these offset printing machines, and can provide good curability, low yellowing, light stability and low migration.

  As the underprint offset ink used in combination with the ultraviolet curable coating varnish composition used in the printing method of the present invention, publicly known and commonly used ultraviolet curable offset inks and oxidation polymerization type offset inks which are generally manufactured and sold, heat drying It is possible to use a mold (heat set) offset ink, a penetrating dry offset ink, etc., but it is more preferable to select an ultraviolet curable offset ink in terms of obtaining better curability and gloss. Examples of the curable offset ink include Dicure Abilio ink series (manufactured by DIC Graphics).

  As the varnish coating method using an inline coater unit provided in the offset printing machine, a roll coater method and a chamber coater method are widely used, and the UV curable coating varnish composition described in the printing method of the present invention is either method. However, the chamber coater is more preferable in that the coating amount of the coating varnish can be controlled more strictly. The chamber coater has a mechanism that can supply coating varnish inside the pores (cells) uniformly carved on the surface of the anilox roll and scrape the anilox roll with a doctor to make the amount of varnish uniform. Is changed, an anilox roll having a different cell volume is used (see FIG. 1).

  The optimum coating thickness of the ultraviolet curable coating varnish composition used in the printing method of the present invention applied to a printing substrate and printed matter is preferably in the range of 1 to 8 micrometers in a wet state before ultraviolet irradiation. More preferably, it is in the range of -6 micrometers. When the coating thickness of the varnish is less than 1 micrometer, good gloss cannot be obtained, and when it exceeds 8 micrometers, unevenness (swimming) of the varnish surface is likely to occur, and ultraviolet energy given from the ultraviolet irradiation lamp is reduced. Since a large amount of varnish layer is consumed, it is not preferable to use UV curable offset ink as the base because the ink layer is liable to be hardened.

  The UV curable coating varnish composition used in the printing method of the present invention is produced in the same manner as in the conventional UV curable coating varnish, the polymerizable acrylate monomer, the resin oligomer having a polymerizable group, the photopolymerization initiator, and the sensitization. It is manufactured by blending agents, other additives, and the like and stirring and mixing with a mixer or the like.

  Hereinafter, the present invention will be described specifically by way of examples.

[Method for producing coating varnish composition]
According to the composition of Tables 1 to 5, UV curable coating varnishes of Examples 1 to 11 and Comparative Examples 1 to 9 were obtained by dispersing and mixing with a mixer.
As a leveling agent, 0.5% by weight of TEGO GLIDE 450 (manufactured by Evonik), which is a polysiloxane modified with polyether, and 0.2% by weight of S381-N1 (manufactured by Shamrock), which is a polyolefin wax, are used as waxes. In addition, 0.1% by weight of Ubitex OB (manufactured by BASF) as a fluorescent brightening agent was commonly added to all Examples and Comparative Examples.

[Method for producing printed matter]
The UV curable coating varnish composition thus obtained was uniformly stretched onto the rubber roll and metal roll of the RI tester using 0.40 ml of coating varnish using a simple color developing machine (RI tester, manufactured by Toyoe Seiko Co., Ltd.). The color was developed so as to be uniformly applied to the surface area of about 220 cm ^{2 on} the surface of milk carton paper (polyethylene laminated paper, Tetra Rex, Tetra Pak Co., Ltd.) to produce a printed matter. The coating thickness of the coating varnish under these conditions was about 3.5 micrometers. The RI tester is a testing machine that develops ink or coating varnish on paper or film, and can adjust the transfer amount or printing pressure of the ink or coating varnish.

[Curing method using UV lamp light source]
The printed matter after applying the coating varnish was irradiated with UV to cure the coating varnish film. Use a UV irradiation device equipped with a water-cooled metal halide lamp (output 80 W / cm1 light) and a belt conveyor (made by Eye Graphics, with cold mirror), place the printed matter on the conveyor, and directly below the lamp (irradiation distance 11 cm) It was made to pass on the predetermined conditions described in the following. The ultraviolet irradiation amount in each condition was measured using an ultraviolet integrated light quantity system (UNIMETER UIT-150-A / light receiving device UVD-C365 manufactured by USHIO INC.).

[Evaluation Method of Coating Varnish Composition 1: Curability]
The curability was confirmed by the paper rubbing method immediately after irradiation for scratches on the printed material surface. The printed matter was irradiated with ultraviolet rays while changing the conveyor speed (m / min) of the UV irradiation apparatus, and immediately after irradiation, the surface of the varnish cured coating film was coated on paper (“OK Topcoat Plus 57.5 kg, Oji Paper Co., Ltd., A The fastest conveyor speed with no scratches when the coated paper was rubbed vigorously against the surface of the cured coating was described. Therefore, the faster the conveyor speed, the better the curability of the coating varnish.

[Evaluation method 2 of coating varnish composition: light stability]
20 g of the prepared coating varnish was prepared, put in a glass petri dish with a diameter of 5 centimeters and the upper part was opened without a lid, and a fluorescent lamp (manufactured by Panasonic, three-wavelength daylight white, Hf fluorescent lamp, FHF32EX-N- The sample was allowed to stand directly under 30 cm from H), and whether or not the coating varnish was cured after 5 minutes was confirmed by visual inspection and palpation, and evaluated in the following three stages. In the composition where curing can be confirmed in this evaluation item, the coating varnish on the printing press coater unit is increased, and the viscosity of the coating varnish is increased, and defects in printability are likely to occur.
○: Not cured at all.
(Triangle | delta): Some hardening can be confirmed.
X: Curing can be confirmed.

[Coating Varnish Composition Evaluation Method 3: Initiator Solubility]
The prepared coating varnish was stored in a refrigerator (4 ° C.) for 1 week, and then the state of precipitation accompanying a decrease in solubility of the photopolymerization initiator in the coating varnish was visually confirmed and evaluated in the following three stages. When a photoinitiator precipitates and crystallizes, the varnish solution confirms the occurrence of turbidity and precipitate accompanying crystal formation. In the composition where precipitation occurs in this evaluation item, sufficient product performance cannot be exhibited in a low temperature environment such as winter.
○: No precipitation is observed.
Δ: Slight precipitation can be confirmed.
X: Precipitation can be confirmed.

[Evaluation Method for Printed Material 1: Yellowing]
The color change resulting from discoloration (yellowing) of the varnish cured film immediately after UV irradiation was confirmed and evaluated in the following three stages.
○: No or no color change.
Δ: Some yellowing can be confirmed.
X: The color change by yellowing can be confirmed clearly.

[Evaluation method 2 for printed matter: low migration]
Regarding the evaluation of low migration, the basic evaluation procedure is the European Printing Ink Association (EuPIA Guideline on printing contest), the guidelines of the European Printing Ink Council (European Printing Ink Association). articles, November 2011 (Replaces the September 2009 version)).
First, the printed matter has a conveyor speed of 40 m / min. The coating varnish layer was cured by UV irradiation twice. The UV integrated light quantity under these conditions was about 100 mJ / cm ² . Subsequently, a milk press carton white paper (hereinafter referred to as a non-printed milk carton paper on which the coating varnish is not developed) is in contact with the cured coating varnish layer on the upper surface of the printed material, and the hydraulic press machine is The unreacted components in the cured coating varnish layer were migrated to the back side of the milk carton white paper by pressurizing for 48 hours under a press pressure of 40 kg / cm ² and a room temperature of 25 ° C. (see FIGS. 2 and 3). ). After pressing, the milk carton blank paper was removed and molded to prepare a 1000 ml liquid container. In this liquid container, the back surface to which the coating varnish component has transferred faces inward. Next, 1000 ml of an aqueous ethanol solution (mixed solution of 95% by weight of ethanol and 5% by weight of pure water) prepared as a simulated liquid food was poured into a liquid container and sealed. In this condition, the total area of the inner surface of the liquid container in contact with 1000 ml of the ethanol aqueous solution was about 600 cm ² . The sealed liquid container was allowed to stand at room temperature and 25 ° C. for 24 hours, and the coating varnish component transferred to the back of the milk carton white paper was extracted into an aqueous ethanol solution. Thereafter, the ethanol aqueous solution is taken out from the liquid container, and the initiator used in the liquid chromatograph mass spectrometry is identified and each elution concentration (migration concentration) is quantified. From the total value of the migration concentration of each initiator component, three levels are obtained. We evaluated the migration performance. As an example, in a printed matter using an ultraviolet curable coating varnish using three types of initiators A, B, and C, the initiator A migration concentration is 10 ppb, the initiator B migration concentration is 5 ppb, and the initiator C migration concentration. Is 15 ppb, the total migration concentration of the initiator component is evaluated as A + B + C = 10 + 5 + 15 = 30 ppb. In quantification of liquid chromatograph mass spectrometry, a calibration curve using the above ethanol aqueous solution was prepared in advance for each of the initiators used, and calculation was performed by using this.
○: Less than 30 ppb.
(Triangle | delta): 30ppb or more and less than 60ppb.
X: 60 ppb or more.

The numerical values in Tables 1 to 5 are% by weight.
Various raw materials and abbreviations shown in Tables 1 to 5 are shown below.

KIP150: oligo (2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone), number average molecular weight 424.57, manufactured by Lamberti Irgacure 127: 2-hydroxy-1- {4 -[4- (2-Hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one, number average molecular weight 340.4, manufactured by BASF KIP160: 2-hydroxy-1 -{4- [4- (2-hydroxy-2-methylpropionyl) phenoxy] phenyl} -2-methylpropanone, number average molecular weight 342.39, manufactured by Lamberti, Esacure One: oligo (2-hydroxy-2- Methyl-1- [4- (1-methylvinyl) phenyl] propanone), number average molecular weight 424.57, Lamber Irgacure 369: 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, number average molecular weight 366.5, manufactured by BASF Irgacure 819: bis (2,4,6- Trimethylbenzoyl) -phenylphosphine oxide, number average molecular weight 418.5, manufactured by BASF, DAROCURE TPO: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, number average molecular weight 348.0, manufactured by BASF, Irgacure 184: 1-hydroxy-cyclohexyl-phenyl-ketone,
Number average molecular weight 204.3, manufactured by BASF, Irgacure 651: 2,2-dimethoxy-1,2-diphenylethane-1-one, number average molecular weight 256.3, manufactured by BASF, Aronix M-400: dipentaerythritol penta Mixture of acrylate and dipentaerythritol hexaacrylate (ratio of pentaacrylate in the product: 40 to 50% by weight), manufactured by Toagosei Co., Ltd. SR494NS: ethylene oxide modified pentaerythritol tetraacrylate, manufactured by Sartomer Co., Ltd. MIRAMER M-220: Tri Propylene glycol diacrylate, manufactured by MIWON, MIRAMER M-284: Polyethylene glycol molecular weight 300 (PEG300) diacrylate, manufactured by MIWON, Inc., DICLITE UE-8200T: Bisuf Nord A diglycidyl ether diacrylate (epoxy acrylate having a polymerizable group), manufactured by DIC, UNIDIC V3212: 40% by weight of non-reactive polyester resin, DPHA (mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate) Mixture of 30% by weight and 30% by weight of ditrimethylolpropane tetraacrylate, DIC's GENOPOL AB1: poly (ethylene glycol) bisdimethylaminobenzoate, number average molecular weight 860, RAHN AG's Omnipol ASA: poly (ethylene glycol) ) Bisdimethylaminobenzoate, number average molecular weight 488-532, manufactured by IGM, EAB-SS: 4,4'-bis (diethylamino) benzophenone, number average molecular weight 3 4.47, Daido Kasei Kogyo's LUNACUR EDB: ethyl-4- (dimethylamino) benzoate, number average molecular weight 193.24, EUTEC CHEMICAL's DAROCUR EHA: 2-ethylhexyl-4- (dimethylamino) benzoate, Number average molecular weight 277.4, manufactured by BASF

(Measurement of number average molecular weight)
In addition, the measurement of the number average molecular weight (polystyrene conversion) by GPC in this invention was performed on condition of the following using the HLC8220 system by Tosoh Corporation.
Separation column: 4 TSKgelGMH _HR- N manufactured by Tosoh Corporation are used. Column temperature: 40 ° C. Moving layer: Tetrahydrofuran manufactured by Wako Pure Chemical Industries, Ltd. Flow rate: 1.0 ml / min. Sample concentration: 1.0% by weight. Sample injection volume: 100 microliters. Detector: differential refractometer.

  In the printing method using the ultraviolet curable coating varnish composition described in the Examples, good curability was obtained by ultraviolet irradiation. In addition, by blending each raw material in the range of the above weight%, it is good in evaluation items such as light stability on a printing press, initiator solubility, and reduction of migration to inclusions, which are necessary characteristics of the present invention. As a result.

In the results of the comparative examples, there is a problem in light stability, initiator solubility, and yellowing even when the molecular weight is 320 or more with an initiator other than the α-hydroxyketone, and an initiator with a molecular weight of less than 320 has low migration. The result was inferior. As for the sensitizer, alkylaminobenzophenone having a high maximum absorption wavelength has a problem of yellowing, and those having a molecular weight of less than 400 resulted in poor low migration. Further, when a non-reactive resin was used without using a polymerizable resin oligomer, the curability and the low migration property were inferior.
In addition, about the result of Comparative Examples 1 and 2, since the initiator solubility was particularly inferior and the initiator was precipitated at room temperature immediately after production, it was not possible to evaluate the curability and the low migration property. .

  The printing method using the UV curable coating varnish composition of the present invention and the printed matter can be widely used for sanitary / cosmetic / pharmaceutical packaging and filling applications, in addition to toys and various food packaging materials that emphasize safety and hygiene. .

DESCRIPTION OF SYMBOLS 1 Offset ink printing unit 2 Coater unit 3 Printing base material 4 Chamber 5 Anilox roll 6 Blanket cylinder 7 Pressure cylinder 8 Ultraviolet irradiation apparatus 9 Curing coating varnish layer 10 Milk carton paper 11 Milk carton blank paper

Claims (6)

A method for printing an ultraviolet curable coating varnish composition comprising a photopolymerization initiator composition, a polymerizable acrylate monomer, and a resin oligomer having a polymerization group, wherein the photopolymerization initiator composition has a number average molecular weight of 320 or more. It is an α-hydroxyketone photopolymerization initiator that is 1300 or less, and cures well in the range of ²⁰ to 200 mJ / cm ² of the cumulative amount of ultraviolet light to be irradiated, and is provided by an inline coater unit provided in an offset printing machine. A method for printing an ultraviolet curable coating varnish composition, characterized by being applied. The photopolymerization initiator composition comprises 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one, oligo (2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone), 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) phenoxy] phenyl The method for printing an ultraviolet curable coating varnish composition according to claim 1, wherein the printing method is one or more selected from the group consisting of} -2-methylpropanone. The photopolymerization initiator composition is 4 to 25% by weight of the total amount, the polymerizable acrylate monomer is 30 to 85% by weight of the total amount, and the resin oligomer having a polymerization group is 10 to 50% by weight of the total amount. The printing method of the ultraviolet curable coating varnish composition as described in 1 above. Further, the aromatic tertiary amine compound having a number average molecular weight of 400 or more and 1500 or less and having a maximum absorption at a wavelength of 250 to 450 nm in a range of 280 to 340 nm contains 1 to 8% by weight of the total amount. The printing method of the ultraviolet curable coating varnish composition as described in any one. The printed matter printed using the printing method of the ultraviolet curable coating varnish composition as described in any one of Claims 1-4. An ultraviolet curable coating varnish composition comprising a photopolymerization initiator composition, a polymerizable acrylate monomer, and a resin oligomer having a polymerization group, wherein the photopolymerization initiator composition has a number average molecular weight of 320 to 1300. An ultraviolet curable coating varnish composition, which is an α-hydroxyketone photopolymerization initiator.

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