JP4649952B2 - Ultraviolet curable resin composition and printing ink using the same - Google Patents

Description

  The present invention relates to an ultraviolet curable resin composition in which the amount of volatilization, elution and migration of a photopolymerization initiator or photopolymerization accelerator from a composition before or after curing is reduced. The photopolymerization accelerator is also called a sensitizer. In this specification, a sensitizer is used as a term.

  Further, the present invention relates to an ultraviolet curable printing ink and an ultraviolet curable varnish containing the resin, wherein the ink before curing and the photopolymerization initiator or sensitizer from the varnish are reduced in volatilization, elution and migration. .

  Further, the present invention relates to a printed matter obtained by using the printing ink or the varnish, wherein the ink or the varnish of the photopolymerization initiator or the sensitizer from the ink or the varnish after curing is reduced, and the amount of migration is reduced. .

  Here, migration refers to a phenomenon in which components of the resin composition, ink, or varnish move to another surface that is in contact with them. For example, even when the ink is dried, the coloring material such as a dye in the ink moves to the surface in contact with the ink film and coloring occurs. In addition, photopolymerization initiators and sensitizers other than colorants may move. These cause the odor of the printed matter, the deterioration of the physical properties of the printing ink film, etc., and may be transferred to the contents in food packaging.

  The phenomenon of migration is also called migration. Color Material Engineering Handbook (published by Asakura Shoten Co., Ltd., 4th April 2000) p. No. 943 describes a phenomenon in which an ink component or a decomposed volatile component is transferred to paper or a film that is in contact with a printed matter or is transferred to the paper or film by sublimation or evaporation to cause discoloration.

  The ultraviolet curable ink and varnish utilizing radical polymerization reaction are composed of an acrylate polymer (oligomer) and a monomer, a photopolymerization initiator (photo radical generator) and, if necessary, a sensitizer, a pigment and an additive. Since the photopolymerization initiator and the sensitizer are required to have fast curability, they are used in an amount of about 1 to 10% by mass with respect to the total amount of ink. However, pigments are not included in clear coatings and overprint varnishes.

  Usually, many photopolymerization initiators and sensitizers have a low molecular weight. These low molecular weight components contained in the ink and varnish cause many problems in printing. For example, before curing, if it elutes from ink or the like, it infiltrates into a rubber roller or the like to swell the rubber, or dissolves the image area of the printing plate. Since these low molecular weight components also function as a kind of solvent, they infiltrate into the rubber, while the fluidity of ink or the like that has lost the solvent is lowered, and printability may be deteriorated. At the time of curing or after curing, the photodecomposition product of the generated initiator, the unreacted initiator remaining in the film, and the sensitizer have volatility and sublimation, which may cause odor of the printing site or printed matter. In addition, the physical properties of the film are lowered. In addition, there is a risk of migration or elution of the solid or liquid in contact with the ink film.

  Accordingly, there is a demand for ultraviolet curable resins, UV inks and UV varnishes, and printed matter using them, which reduce the odor of components such as photopolymerization initiators and sensitizers, and their migration and elution.

  In order to improve the drawbacks of the active energy ray-curable ink containing these photopolymerization initiators, copolymerizable photoinitiators have been proposed. For example, Patent Document 1 proposes a copolymerizable photoinitiator in which 4- (2-hydroxyethoxy) -phenyl-2-hydroxy-2-propylketone (Irgacure 2959 or the like) and acrylic acid chloride are bonded. ing.

  Patent Document 2 discloses a photoinitiator composition in which dimethylaminobenzoic acid or benzoylbenzoic acid is bonded to an epoxy compound to have a molecular weight of 300 to 2,000.

  Patent Document 3 discloses a photoinitiator composition in which a photoinitiator having a molecular weight of 300 or more and a benzophenone derivative are used in combination. All of these are aimed at reducing the odor of the printed matter, but are insufficient to suppress the migration.

  As described above, the term “migration” means that a photopolymerization initiator or a sensitizer, which is contained in an ink or varnish and generally has a low molecular weight, leaches out of the ink or varnish before curing, After curing, the photodecomposition product of the generated initiator, the unreacted initiator remaining on the film, and the sensitizer are volatilized or sublimated to dissipate to the outside, or come into contact with the ink or varnish film. This refers to migration or elution.

JP-A-62-81345 Japanese Patent Laid-Open No. 6-263813 JP-A-8-217814

  An object of the present invention is to provide a photocurable resin composition in which the amount of volatilization, elution or migration of a photopolymerization initiator and / or a sensitizer from a composition before or after curing is reduced. Moreover, it is providing the ultraviolet curable printing ink and ultraviolet curable varnish which reduced the amount of volatilization, elution, or transfer | transfer of a photoinitiator and / or a sensitizer using this resin composition. Then, using the ink or the varnish, to provide a printed matter in which the amount of volatilization, elution or migration of the photopolymerization initiator and / or the sensitizer from the ink and the varnish film after curing is reduced. It is.

  As a result of intensive studies to solve the above problems, the inventors have completed the invention described below. That is, the ultraviolet curable resin composition of the present invention is obtained by chemically bonding a photopolymerization initiator and / or a sensitizer and a resin. UV curable inks and varnishes obtained using this resin composition have fewer initiators than conventional UV curable ink resins because the initiator and sensitizer are bound to the resin. The same amount of photocuring property can be obtained by the post-addition amount of the sensitizer and sensitizer, the odor at the time of curing is reduced, and the amount of the component that volatilizes, migrates or elutes remaining in the cured film can be reduced.

  In addition, by exposing and drying the printing ink and varnish in a low oxygen partial pressure atmosphere, excellent curability can be achieved even with less photopolymerization initiator / sensitizer after addition than exposure in air. Therefore, the odor at the time of curing, the photopolymerization initiator and the sensitizer remaining in the cured film can be reduced, and their volatilization, migration and elution can be further reduced.

  In the ultraviolet curable resin composition of the present invention, a photopolymerization initiator or a sensitizer is bonded to a resin which is a base polymer. Therefore, an ultraviolet curable ink or an ultraviolet curable varnish produced using the resin is an optical material. Odor resulting from the polymerization initiator and sensitizer, and elution and migration of these components can be reduced. As a result, printability such as swelling of the blanket, ink smearing on the blanket, and dissolution of the plate is improved.

  In addition, the printed matter obtained using the ink and varnish is not only excellent as an ink and varnish for food packaging, because the amount of elution and migration of components in the cured coating and the odor generated from the coating are small. Work environment can be improved.

  Furthermore, by combining the ink and varnish with an exposure device that can reduce the oxygen partial pressure in the exposure chamber, even a photopolymerization initiator or sensitizer with a smaller addition amount than when exposed in air is excellent. Therefore, a printed matter with a very small amount of odor, migration of the above components and elution amount can be obtained.

  The 1st form of the ultraviolet curable resin composition of this invention is an ultraviolet curable resin composition which has as a main component the resin which chemically combined the photoinitiator and the ultraviolet curable monomer.

As the resin, any one of known resins can be selected and used. Among them, a polyester resin, a polyurethane resin, a urea resin, an amide resin, and the like are easily synthesized and give desired properties to a cured product. Since it can provide, it is preferable.
There is no restriction | limiting in particular as the manufacturing method of the said polyester resin, Well-known and publicly-known methods, such as direct esterification by block polymerization or solution polymerization, and a transesterification method, are applicable.
Moreover, as the said polyurethane resin, arbitrary things can be selected and used from well-known polyurethane resins. There is no restriction | limiting in particular as the manufacturing method of the said polyurethane resin, Well-known and publicly available methods, such as polyaddition reaction of the polyvalent hydroxyl group and polyvalent isocyanate by block polymerization or solution polymerization, are applicable.

  Any photopolymerization initiator that is chemically bonded to the resin can be selected from known photopolymerization initiators. Specific examples of such a photopolymerization initiator include acylphosphine oxides, acetophenones, benzoins, benzophenones, thioxanthones, and the like.

  Examples of acylphosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide (for example, Lucillin TPO, manufactured by BASF), bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine. And oxides.

  Examples of the acetophenone series include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one (for example, Darocur 1173, manufactured by Ciba Specialty Chemicals) and 4- (2-hydroxyethoxy) phenyl. 2- (2-hydroxy-2-propyl) ketone (for example, Irgacure 2959, manufactured by Ciba Specialty Chemicals), benzyldimethyl ketal (for example, Irgacure 651, manufactured by Ciba Specialty Chemicals, Lucillin BDK, BASF, etc.), 1-hydroxycyclohexyl phenyl ketone (eg, Irgacure 184, Ciba Specialty Chemicals), 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one (eg, Irgacure 907, manufactured by Ciba Specialty Chemicals), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone (for example, Irgacure 369, manufactured by Ciba Specialty Chemicals), oligo [ 2-Hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone] (for example, Esacure KIP, manufactured by Lamberti) and the like.

  Examples of the benzoin system include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and the like. Examples of the benzophenone series include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfite, 2,4,6-trimethylbenzophenone, (4-benzoylbenzyl) trimethylammonium chloride, UVECRYL P-36 (manufactured by Daicel UCB) and the like.

  Examples of the thioxanthone series include 2- or 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, and the like. In addition to these, methylbenzoyl formate (Bicure 55, manufactured by AKZO) and 3,6-bis (2-morpholinoisobutyl) -9-butylcarbazole (A-Cure3, manufactured by Asahi Denka) can also be mentioned.

  Formation of the chemical bond between the resin and the photopolymerization initiator can be performed by using a known chemical reaction. Among them, the chemical bond formation by transesterification or urethane modification is simple and preferable because the cost can be kept low. Used.

  The photopolymerization initiator chemically bonded to the resin may be used alone or in combination of two or more. It can also be combined with a sensitizer. The introduction amount of the photopolymerization initiator with respect to 100 parts by mass of the resin is selected in the range of 1 to 200 parts by mass, preferably 20 to 100 parts by mass. When the introduction amount is too small, the effect as an initiator is not sufficiently exhibited, and when it is too large, properties as a resin for printing ink such as wettability and emulsification ability of the pigment are impaired.

  In addition, as the ultraviolet curable monomer used in the ultraviolet curable resin composition of the present invention, any monomer capable of dissolving the present resin can be used. Since it is easy to be taken in, unreacted monomer remaining in the film after curing can be reduced, and monomer elution and migration are less likely to occur. Examples of such acrylate monomers include pentaerythritol triacrylate, trimethylolpropane triacrylate, isocyanuric acid triacrylate and their ethylene oxide or propylene oxide modified products, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, ditrityl. Examples include methylolpropane tetraacrylate, pentaerythritol tetraacrylate, and their modified ethylene oxide or propylene oxide. The monomer dilution amount is not particularly limited as long as it is within a range suitable for the resin composition viscosity to be used, but it is preferably used within a range of 20 to 400% by mass with respect to the resin amount.

  The second form of the ultraviolet curable resin composition of the present invention is an ultraviolet curable resin composition comprising, as main components, a resin chemically bonded with a sensitizer and an ultraviolet curable monomer.

  As the resin, any one of known resins can be selected and used. Among them, a polyester resin, a polyurethane resin, a urea resin, an amide resin, and the like are easily synthesized and give desired properties to a cured product. Since it can provide, it is preferable.

  There is no restriction | limiting in particular as the manufacturing method of the said polyester resin, Well-known and publicly-known methods, such as direct esterification by block polymerization or solution polymerization, and a transesterification method, are applicable.

  Moreover, as the said polyurethane resin, arbitrary things can be selected and used from well-known polyurethane resins. There is no restriction | limiting in particular as the manufacturing method of the said polyurethane resin, Well-known and publicly available methods, such as polyaddition reaction of the polyvalent hydroxyl group and polyvalent isocyanate by block polymerization or solution polymerization, are applicable.

  As a sensitizer chemically bonded to the resin, an arbitrary one can be selected from known sensitizers. Specific examples of such a sensitizer include 4,4′-diethylaminobenzophenone, 4,4′-dimethylaminobenzophenone, N-methyldiethanolamine, dialkylaminobenzoic acid, and derivatives thereof (for example, 4 -Dimethylaminobenzoic acid, 4-dimethylaminobenzoic acid ester, etc.), phosphine sensitizers (for example, phosphine compounds such as triphenylphosphine and trialkylphosphine) and the like.

  Formation of the chemical bond between the resin and the sensitizer can be performed using a known chemical reaction. Among them, in addition to transesterification, chemical bond formation by urethane modification, urea bond, amide bond is simple and cost-effective. Is also preferable because it can be kept low.

  The sensitizer chemically bonded to the resin may be used alone or in combination of two or more. It can also be combined with a photopolymerization initiator. The introduction amount of the sensitizer with respect to 100 parts by mass of the resin is selected in the range of 1 to 200 parts by mass, preferably 20 to 100 parts by mass. When the introduction amount is too small, the effect as a sensitizer is not sufficiently exhibited, and when it is too large, properties as a printing ink resin such as wettability and emulsification ability of the pigment are impaired.

  In addition, as the ultraviolet curable monomer used in the ultraviolet curable resin composition of the present invention, any monomer capable of dissolving the present resin can be used. Since it is easy to be taken in, unreacted monomer remaining in the film after curing can be reduced, and monomer elution and migration are less likely to occur. Examples of such acrylate monomers include pentaerythritol triacrylate, trimethylolpropane triacrylate, isocyanuric acid triacrylate and their ethylene oxide or propylene oxide modified products, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, ditrityl. Examples include methylolpropane tetraacrylate, pentaerythritol tetraacrylate, and their modified ethylene oxide or propylene oxide. The monomer dilution amount is not particularly limited as long as it is within a range suitable for the resin composition viscosity to be used, but it is preferably used within a range of 20 to 400% by mass with respect to the resin amount.

  The resin used in the present invention is a polyester resin obtained using a monobasic acid, a polybasic acid, and a polyhydric alcohol. The polyester resin suitably has a weight average molecular weight in the range of 2,000 to 50,000, more preferably a weight average molecular weight in the range of 3,000 to 45,000. .

  That is, when the weight average molecular weight is less than 2,000, the pigment dispersibility is poor and the printability of the ink obtained using the pigment is poor, and the UV curability tends to be poor. On the other hand, the higher the molecular weight of the polyester resin, the better the UV curability, misting and emulsification suitability of the UV ink using this polyester. The required amount increases, and as a result, the physical properties of the film after UV curing become inferior.

  There is no restriction | limiting in particular as the manufacturing method of the said polyester, Well-known and publicly used methods, such as direct esterification by block polymerization or solution polymerization, and a transesterification method, are applicable.

  Examples of the monobasic acids that can be used in the present invention include alicyclic monobasic acids such as rosin and hydrogenated rosin; and fatty acids derived from lauric acid, stearic acid, and vegetable oil. Aliphatic monobasic acids such as benzoic acid, and aromatic monobasic acids such as p-tert-butylbenzoic acid.

  Further, only typical examples of the above-mentioned polybasic acids are exemplified. Terephthalic acid, isophthalic acid, (anhydrous) phthalic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, 6-naphthalenedicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, 1,4-cyclohexanedicarboxylic acid or hexahydro (anhydride) phthalic acid, but these acids can be used alone Of course, two or more types may be used in combination.

  On the other hand, only typical examples of the above-mentioned polyhydric alcohols are exemplified by ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, dipropylene glycol, or tripropylene glycol, and the weight average molecular weight is 200 to Tetramethylene glycol in the range of 4,000, 1,4-cyclohexanediol, ethylene oxide or propylene oxide adduct of bisphenol A, ethylene oxide or propylene oxide addition of hydrogenated bisphenol A , 1,4-cyclohexane dimethanol, glycerol, trimethylol ethane, trimethylol propane, pentaerythritol, dipentaerythritol or sorbitol and the like. Of course, these polyhydric alcohols may be used alone or in combination of two or more.

  The polyester resin is diluted with an ultraviolet curable monomer after the production of the polyester resin, and used for blending ink and varnish as a viscous varnish. Any UV curable monomer can be used as long as it dissolves the resin, but among them tri- or higher functional acrylate monomers are easily incorporated into the polymerization system, and therefore remain in the film after curing. The reaction monomer can be reduced and the elution and transfer of the monomer are less likely to occur. Examples of such acrylate monomers include pentaerythritol triacrylate, trimethylolpropane triacrylate, isocyanuric acid triacrylate and their ethylene oxide or propylene oxide modified products, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, ditrityl. Examples include methylolpropane tetraacrylate, pentaerythritol tetraacrylate, and their modified ethylene oxide or propylene oxide.

  The monomer dilution amount is not particularly limited as long as it is in a range where the varnish viscosity is suitable for handling, but it is preferable to use the ultraviolet curable monomer described above in a range of 20 to 400% by mass with respect to the resin.

  The method of bonding the resin and the photopolymerization initiator in the ultraviolet curable resin composition of the present invention is preferably used because chemical bond formation by esterification is simple and low cost. The method for forming the ester bond can be appropriately selected from general esterification reactions, and in particular, dehydration condensation or transesterification reaction of carboxylic acid or acid anhydride with alcohol is preferably used. Photopolymerization having at least one structure or functional group selected from an ester bond, carboxyl group and hydroxyl group in the molecule at the carboxyl group or hydroxyl group at the end of the polyester resin synthesized using polybasic acid and polyhydric alcohol Bind the agent. This modification may be performed after the resin is synthesized or may be performed simultaneously with the synthesis of the polyester resin.

  As the photopolymerization initiator used for esterification, one having an ester bond, a carboxyl group and / or a hydroxyl group in its molecular structure is selected. Specific examples of such a photopolymerization initiator include, for example, methyl o-benzoylbenzoate (for example, OBM100, manufactured by Daicel UCB), methylbenzoylformate (Vicure 55, manufactured by AKZO), 2 -Hydroxy-2-methyl-1-phenylpropan-1-one (for example, Darocur 1173, manufactured by Ciba Specialty Chemicals), 1-hydroxycyclohexyl phenyl ketone (for example, Irgacure 184, manufactured by Ciba Specialty Chemicals) ), Oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone] (for example, Esacure KIP, manufactured by Lamberti) and the like.

  The photopolymerization initiator chemically bonded to the resin may be used alone or in combination of two or more. Moreover, a sensitizer can also be combined. The introduction amount of the photopolymerization initiator with respect to 100 parts by mass of the polyester resin is selected in the range of 1 to 200 parts by mass, preferably 20 to 100 parts by mass.

  Among these, a photopolymerization initiator having an ester bond in the molecule is preferably one having an alkyl ester group having a carbon number of C4 or less. When the number of carbon atoms of the alkyl ester is larger than C5, the transesterification reactivity is reduced when the polyester side chain is modified, and the by-produced alkyl alcohol has a high boiling point and is difficult to remove from the reaction system.

  The method of bonding the polyester resin and the sensitizer in the ultraviolet curable resin composition of the present invention is preferably used because chemical bond formation by esterification is simple and low cost. The method for forming the ester bond can be appropriately selected from general esterification reactions. In particular, dehydration condensation and transesterification of carboxylic acid or acid anhydride and alcohol are preferably used. A sensitizer having at least one structure or functional group selected from an ester bond, a carboxyl group and a hydroxyl group in the molecule at the carboxyl group and hydroxyl group at the end of the polyester resin synthesized using a polybasic acid and a polyhydric alcohol Are combined. This modification may be performed after the polyester resin is synthesized or may be performed simultaneously with the synthesis of the polyester resin.

  As the sensitizer used for esterification, one having an ester bond, a carboxyl group and / or a hydroxyl group in its molecular structure is selected. Specific examples of such a sensitizer include 4-dimethylaminobenzoic acid or a derivative thereof such as 4-dimethylaminobenzoic acid ethyl ester (Kayacure EPA, manufactured by Nippon Kayaku Co., Ltd.), 4-dimethylaminobenzoic acid. Examples include acid isoamyl ester (Kayacure DMBI, manufactured by Nippon Kayaku Co., Ltd.) and 4-dimethylaminobenzoic acid-2-ethylhexyl ester (SPEDCURE EHA, manufactured by Sebel Hegner).

  The sensitizer chemically bonded to the resin may be used alone or in combination of two or more. Moreover, a photoinitiator can also be combined. The introduction amount of the sensitizer with respect to 100 parts by mass of the polyester resin is selected in the range of 1 to 200 parts by mass, preferably 20 to 100 parts by mass.

  Among these sensitizers having an ester bond in the molecule, those having an alkyl ester group having a carbon number of C4 or less are particularly preferable. When the number of carbon atoms of the alkyl ester is larger than C5, the transesterification reactivity is reduced when the polyester side chain is modified, and the by-produced alkyl alcohol has a high boiling point and is difficult to remove from the reaction system.

  The method of bonding the resin and the photopolymerization initiator in the ultraviolet curable resin composition of the present invention is preferably used because chemical bond formation by urethane modification is simple and low cost. Chemical bonding by urethane modification can be performed using a known chemical reaction. For example, a photopolymerization initiator having a hydroxy group, a carboxy group, or an amide group and a hydroxy group of a resin are passed through a diisocyanate. Can be formed. Examples of such diisocyanates include isophorone diisocyanate, toluylene diisocyanate, and hexamethylene diisocyanate. This modification may be performed after the resin is synthesized or may be performed simultaneously with the synthesis of the resin.

  The photopolymerization initiator chemically bonded to the resin may be used alone or in combination of two or more. Moreover, a sensitizer can also be combined. The introduction amount of the photopolymerization initiator with respect to 100 parts by mass of the polyester resin is selected in the range of 1 to 200 parts by mass, preferably 20 to 100 parts by mass.

  The method of bonding the resin and the sensitizer in the ultraviolet curable resin composition of the present invention is preferably used because chemical bond formation by urethane modification is simple and low cost. The chemical bond by urethane modification can be made by using a known chemical reaction. For example, N-methyldiethanolamine, dialkylaminobenzoic acid and the like and the hydroxy group of the resin can be formed via diisocyanate. Examples of such diisocyanates include isophorone diisocyanate, toluylene diisocyanate, and hexamethylene diisocyanate. This modification may be performed after the resin is synthesized or may be performed simultaneously with the synthesis of the resin.

  The sensitizer chemically bonded to the resin may be used alone or in combination of two or more. Moreover, a photoinitiator can also be combined. The introduction amount of the sensitizer with respect to 100 parts by mass of the polyester resin is selected in the range of 1 to 200 parts by mass, preferably 20 to 100 parts by mass.

In addition to the ultraviolet curable resin composition of the present invention, materials used for conventional ultraviolet curable inks and ultraviolet curable varnishes can be appropriately used for the ultraviolet curable ink and the ultraviolet curable varnish of the present invention. Examples are shown in the following a) to e).
A) Photopolymerization initiator and sensitizer,
B) Colorants such as organic pigments and inorganic pigments, inorganic extender pigments, viscosity modifiers or extenders,
C) Polymerization inhibitors such as hydroquinone for imparting ink stability over time or storage stability,
D) Surfactants for adjusting the printability of ink, phosphates for preventing sensitization of the plate,
E) An auxiliary agent for adjusting the surface physical properties of the cured film, such as wax.

  The ultraviolet curable ink and the ultraviolet curable varnish thus obtained can be printed and cured and dried by using the same technique as that of the conventional ultraviolet curable ink and varnish. In the ink and the varnish of the present invention, since an initiator and / or a sensitizer are bonded to the resin, less initiator and sensitizer are used compared to those using a conventional ultraviolet curable ink resin. Equivalent photocurability can be obtained with a post-addition amount. Moreover, the odor at the time of hardening can be reduced, and the quantity of the photoinitiator and sensitizer which remain in the film after hardening and volatilize, migrate or elute can be reduced. Furthermore, problems such as blanket swelling, ink clumping, and dissolution of a plate due to migration or dissolution of a low molecular weight photopolymerization initiator or sensitizer can be improved.

  Furthermore, since the oxygen partial pressure in the exposure chamber is reduced, the oxygen inhibition of radical reaction is suppressed and the reaction efficiency is increased, so the amount of photopolymerization initiator and sensitizer added is less than in air exposure. Can exhibit excellent photocurability. Along with this, the odor and the amount of components that migrate and dissolve can be further reduced.

  As a method for reducing the oxygen partial pressure in the exposure chamber, for example, a method of purging an inert gas such as nitrogen or argon, or a method of reducing the pressure is used. In particular, the nitrogen purge is inexpensive and the apparatus can be easily and preferably used.

  The oxygen partial pressure is preferably 2000 Pa or less, more preferably 1000 Pa or less. If the oxygen partial pressure range is higher than this, the influence of oxygen inhibition appears, which may result in insufficient curing.

  Furthermore, although this invention is demonstrated in detail using an Example and a comparative example, this invention is not limited to these Examples. Parts and% in the examples are based on mass.

[Production of photopolymerization initiator-introduced varnish α]
A total of 9994 parts of neopentyl glycol 198 parts, pentaerythritol 2108 parts, adipic acid 225 parts, isophthalic acid 2279 parts, benzoic acid 2424 parts, coconut oil fatty acid 749 parts, OMB 2011 parts in the presence of an inert gas at 230 ° C. Heating for a time, a polyester resin having a solid content acid value of 16 and a polystyrene-reduced weight average molecular weight of 29,000 by GPC measurement was obtained.

  Next, 35 parts of this polyester and 65 parts of Aronix M408 (ditrimethylolpropane tetraacrylate, manufactured by Toagosei Co., Ltd.) are heated and melted at 100 ° C. for 2 hours, and further 1.4 parts of toluene diisocyanate is added and reacted at 80 ° C. for 3 hours. Thus, a resin varnish α used for ink A and ink C was obtained. OMB is o-methylbenzoylbenzoate.

[Production of sensitizer-introduced varnish β]
1943 parts of trimethylolpropane, 1430 parts of EDB and 0.07 part of lithium hydroxide were heated at 240 ° C. for 2 hours in the presence of an inert gas, then 734 parts of pentaerythritol, 234 parts of adipic acid, 2689 parts of isophthalic acid, benzoic acid 1867, 761 parts of coconut oil fatty acid was added and heated in the presence of an inert gas at 230 ° C. for 6 hours to obtain a polyester resin having a solid content acid value of 14 and a weight average molecular weight of 8,000. .

  Next, 35 parts of this polyester and 65 parts of Aronix M408 are heated and melted at 100 ° C. for 2 hours, 1.0 part of toluene diisocyanate is added, and the mixture is reacted at 80 ° C. for 3 hours to be used for ink B and ink D. Resin varnish β was obtained. EDB is p-dimethylaminobenzoic acid ethyl ester.

[Production of varnish γ for UV ink containing no photopolymerization initiator and sensitizer]
A method for producing a conventional resin varnish γ used for a general UV ink for paperboard printing is shown below. The ink using this varnish is ink E.

  A total of 1000 parts of 20 parts of neopentyl glycol, 240 parts of pentaerythritol, 25 parts of adipic acid, 225 parts of isophthalic acid and 490 parts of benzoic acid are heated at 210 ° C. for 6 hours in the presence of an inert gas, and the solid content acid value Of 9.5 and a weight average molecular weight of 18,000 was obtained.

  Next, 40 parts of this polyester resin, 30 parts of Aronix M402 (dipentaerythritol hexaacrylate, manufactured by Toa Gosei Co., Ltd.) and 100 parts of 30 parts of Aronix M408 were heated and melted at 140 ° C. for 2 hours, and further toluene diisocyanate 1.0. The resin varnish (gamma) used for the ink E was obtained by adding a part and reacting at 80 degreeC for 3 hours.

[Production of ink using photopolymerization initiator-introduced varnish α]
Ink A:
Using a photopolymerization initiator-introduced varnish (varnish α), a pigment, a photopolymerization initiator, a sensitizer, a polymerization inhibitor, etc. are mixed, kneaded with three rolls, and the UV ink process four colors of the present invention (Yellow, red, indigo, ink). Table 1 shows the ink composition. The indigo ink composition in Table 1 is also described in Ink A in Table 2.

Explanation of Table 1:
Color index No. of each pigment Are (* 1) Pigment Yellow 13, (* 2) Pigment Red 57-1, (* 3) Pigment Blue 15-3, (* 4) Pigment Black 17.

Ink B:
Using a sensitizer-introducing varnish (varnish β), a pigment, a photopolymerization initiator, a sensitizer, a polymerization inhibitor, etc. are mixed and kneaded with three rolls to obtain the four colors of the UV ink process of the present invention. Obtained. Table 2 shows the composition of the indigo ink.

Ink C:
Using a photopolymerization initiator-introduced varnish (varnish α), a pigment, a sensitizer, a polymerization inhibitor and the like were mixed and kneaded with three rolls to obtain four colors of the UV ink process of the present invention. Table 2 shows the composition of the indigo ink.

Ink D:
Using a sensitizer-introducing varnish (varnish β), a pigment, a photopolymerization initiator, a polymerization inhibitor, and the like were mixed, and kneaded with three rolls to obtain four process colors of the UV ink of the present invention. Table 2 shows the composition of the indigo ink.

Ink E:
Using a resin varnish for ink (varnish γ) containing no photopolymerization initiator and sensitizer in the resin varnish, mixing the pigment, sensitizer, polymerization inhibitor, etc., kneading with 3 rolls, Four process colors of UV curable ink were obtained. Table 2 shows the composition of the indigo ink.

[Physical property evaluation of the obtained ink]
Example 1:
Using an ink A process 4 colors (yellow, red, indigo, and black), an OK topcoat (57.5) was used on a Rland R704 sheet-fed printing press equipped with an ultraviolet irradiation device (120 W, 3 metal halide lamps). After printing 3000 sheets at a rate of 8000 sheets per hour (5 kg / A total, manufactured by Oji Paper Co., Ltd.), various aptitudes were obtained: (a) water volume dial width, (b) rubber roller / blanket swelling property, (c) A comparative test was conducted on five items: odor from the image area immediately after exposure, (d) ink curability, and (e) the amount of migration (migration) of unreacted initiator from the printed matter. The results are shown in Table 3.

Example 2:
Various printability was evaluated in the same manner as in Example 1 except that the four process colors of ink B were used. The results are shown in Table 3.

Example 3:
For the four colors of ink C, using a UV irradiation device with a conveyor with a nitrogen purge function, the oxygen partial pressure in the exposure chamber was set to 500 Pa, and (c) the odor from the image area immediately after the exposure, (d) Three items were evaluated: ink curability and (e) the amount of migration of the unreacted initiator from the printed matter. The results are shown in Table 3.

Example 4:
Various printability was evaluated in the same manner as in Example 3 except that the process 4 colors of ink D were used. The results are shown in Table 3.

Comparative Example 1:
Various printing aptitudes were evaluated in the same manner as in Example 1 except that the four process colors of ink E were used. The results are shown in Table 3.

Comparative Example 2:
Evaluation was performed in the same manner as in Example 1 using Dycure Scepter DT (manufactured by Dainippon Ink & Chemicals, Inc.) as an example of a UV curable ink currently on the market. The results are shown in Table 3.

Evaluation criteria in Table 3: ◎ (Excellent), ○ (Excellent), △ (Normal), × (Poor).
(B) In an offset printing machine, if the amount of water supplied is too large, problems such as a decrease in density due to excessive emulsification of the ink and ink accumulation in the water rod occur. On the other hand, if the amount of water is too small, the printed matter is smudged. This item indicates the range of adjustment value of the dial that adjusts the amount of water supplied. The wider the ink, the easier it is to print.
(B) evaluated the swelling of rubber by finger touch.
In (c), the odor generated from the image area (solid part) immediately after printing was measured by smell.
(D) The material ink is developed on the original fabric with an RI tester, the printed material is passed through a UV irradiation device with a conveyor, the conveyor speed is changed, the printed material is rubbed with fine paper and nails, and the film is rubbed off. Judged the conveyor speed without. The RI tester is a commonly used name of the apparatus described in Annex 3 “Simple color development method” of JIS K 5701-1: 2000 (Testing method for lithographic ink).
In (e), a polyvinylidene chloride film was placed on the printed matter, pressed with a press machine at a temperature of 70 ° C. and a pressure of 100 kgf / cm ² for 5 hours, and migrated to the polyvinylidene chloride film. The amount of the sensitizer was measured with an ultraviolet-visible spectrophotometer.

Claims (9)

An ultraviolet curable resin composition mainly comprising a resin chemically bonded with a photopolymerization initiator and an ultraviolet curable monomer , the resin obtained using a monobasic acid, a polybasic acid, and a polyhydric alcohol. An ultraviolet curable resin composition which is a polyester resin . An ultraviolet curable resin composition mainly comprising a resin chemically bonded with a sensitizer and an ultraviolet curable monomer , wherein the resin is obtained using a monobasic acid, a polybasic acid, and a polyhydric alcohol. An ultraviolet curable resin composition which is a polyester resin .   The ultraviolet curable resin composition according to claim 1, wherein the chemical bond is an ester bond. The chemical bond is an ester bond, and the photopolymerization initiator has at least one structure or functional group selected from the group consisting of (a) an ester bond, (b) a carboxyl group, and (c) a hydroxyl group. The ultraviolet curable resin composition according to claim 1 or 3 . The chemical bond is an ester bond, and the sensitizer has at least one structure or functional group selected from the group consisting of (a) an ester bond, (b) a carboxyl group, and (c) a hydroxyl group. Item 4. The ultraviolet curable resin composition according to Item 2 or 3 . The ultraviolet curable printing ink containing the ultraviolet curable resin composition in any one of Claims 1-5 . UV-curable varnish containing an ultraviolet-curable resin composition according to any one of claims 1-5. A printed matter obtained by printing the printing ink according to claim 6 and / or the varnish according to claim 7 , and curing and drying the composition by ultraviolet irradiation. A printed matter obtained by printing the printing ink according to claim 6 and / or the varnish according to claim 7 and curing and drying the composition by ultraviolet irradiation in a low oxygen partial pressure atmosphere.