JP2007070450A - Ultraviolet curing type ink for gravure printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet curing type ink for gravure printing, enabling coating without almost or entirely using any solvent and excellent in printability in gravure printing. <P>SOLUTION: In the ultraviolet curing type ink for gravure printing, the content of an organic compound having ≥2,000 molecular weight is ≤5 wt.% and the viscosity in 60 revolution in Brookfield viscometer is 100-2,000 cps and the thixotropic index is 0.8-10.0. The ultraviolet curing type ink for gravure printing may contain an oxetane compound and an epoxy compound as components or further may contain a photopolymerization initiator. In a plastic label, gravure printing of the above ultraviolet curing type ink for gravure printing is carried out on at least either one surface of a plastic film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultraviolet curable ink excellent in printability in gravure printing.

  Conventionally, gravure printing using solvent-based ink or water-based ink has been performed for printing of plastic films. The solvent-type ink is used by adjusting a viscosity that can be printed by using a polymer compound as a binder and blending a large amount of an organic solvent. For this reason, the solvent odor was intense and it was necessary to treat the exhaust gas. On the other hand, water-based inks are poor in dryness because water is the main diluent solvent, and several tens of percent of alcohol is required for printing plastic films.

  In recent years, ultraviolet curable inks have been used as printing inks that can avoid the above-mentioned problems because no dilution solvent is required. However, the conventional UV curable ink is not suitable for gravure printing because of its high viscosity. For example, Japanese Patent Application Laid-Open No. 2001-46956 discloses a cured film having sufficient surface hardness by a method in which an active energy ray-curable coating composition is applied to a substrate and then cured by sequentially irradiating ultraviolet rays and an electron beam. Is obtained. However, when gravure printing is performed using the active energy ray-curable coating composition, blurring and streaks are likely to occur, which is significantly inferior to the printing finish using solvent-based ink.

JP 2001-46956 A

An object of the present invention is to provide an ultraviolet curable ink for gravure printing which can be applied with little or no solvent and has excellent printability in gravure printing.
Another object of the present invention is to provide an ultraviolet curable ink for gravure printing excellent in heat resistance and scratch resistance, and a plastic label on which the ink is printed.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have excellent viscosity even when used for gravure printing because the UV curable ink having a specific composition and physical properties can reduce the viscosity. The inventors have found that printing aptitude can be exhibited and completed the present invention.

  That is, in the present invention, the content of an organic compound having a molecular weight of 2000 or more is 5% by weight or less, the viscosity at 60 revolutions in a B-type viscometer is 100 to 2000 cps, and the thixotropic index is 0.8 to 10. An ultraviolet curable ink for gravure printing that is in the range of 0 is provided. The ultraviolet curable ink for gravure printing of the present invention may contain an oxetane compound and an epoxy compound as constituent components. The ink may further contain a photopolymerization initiator.

  The present invention provides a plastic label in which the ultraviolet curable ink for gravure printing of the present invention is gravure-printed on at least one surface of a plastic film.

  In the present specification, the “viscosity” of the ink, unless otherwise specified, uses a B-type viscometer (single cylindrical rotational viscometer) under the conditions of 23 ± 2 ° C. and the rotational speed of the cylinder of 60 JIS. It means a value measured according to Z8803. The thixotropic index (TI value) is a viscosity measured under the conditions of 23 ± 2 ° C. and 6 rotations according to JIS Z 8803, using the B-type viscometer, under the same 60 rotations. It means the value divided by.

  Since the UV curable ink for gravure printing of the present invention has a specific composition and physical properties, the viscosity is low and no solvent is required, so there is no problem of odor or exhaust gas due to the solvent, and also when gravure printing is performed. No fading or streaking occurs and an excellent print finish can be obtained. When printing such a gravure UV curable ink on a plastic film, it is excellent in printability during high-speed printing, and therefore a plastic label can be produced efficiently.

  The ultraviolet curable ink for gravure printing of the present invention (hereinafter sometimes simply referred to as “UV ink of the present invention”) contains an organic compound having a molecular weight of 2000 or more (hereinafter sometimes simply referred to as “compound”). The amount is 5% by weight or less, the viscosity at 60 rotations in a B-type viscometer is in the range of 100 to 2000 cps, and the thixotropic index is in the range of 0.8 to 10.0. When a UV ink having such characteristics is used for gravure printing, no blurring or streaking of printing occurs, and the gravure printing suitability can be remarkably improved as compared with conventional UV inks.

  The UV ink having a content of the compound having a molecular weight of 2000 or more is 5% by weight or less means that, among the components constituting the UV ink, an oligomer and a polymer having a molecular weight of 2000 or more are contained by 5% by weight or less. It is preferably 3% by weight or less, more preferably 1% by weight or less. Since the UV ink having the above characteristics has a relatively low viscosity, the ink is likely to be placed in the concave portion (gravure cell) of the gravure printing plate, and has an effect of improving transferability from the gravure plate to the printing material. On the other hand, when the content of the compound having a molecular weight of 2000 or more exceeds 5% by weight, the ink in the gravure cell is reduced because the ink is difficult to be placed in the gravure cell, and pressure is applied at the time of transition from the gravure plate to the film. The transferability is remarkably lowered due to necessity, and the printability is inferior due to blurring and streaking.

  The content of the compound having a molecular weight of 2000 or more in the UV ink can be adjusted by appropriately selecting the molecular weight, molecular weight distribution, usage amount, and the like of the compound used in the UV ink. In the present invention, each of the compounds (such as oxetane compounds and epoxy compounds described later) constituting the UV ink preferably has a low molecular weight, and the molecular weight of each compound is, for example, less than 2000, preferably 1000 or less, more preferably 555 or less. Are preferred. As a preferable aspect in this invention, UV ink which consists of an oxetane compound with a molecular weight of 555 or less, an epoxy compound with a molecular weight of 555 or less, and a photoinitiator is mentioned, for example.

  Since conventional UV inks generally have high viscosity, they are remarkably inferior in printability compared to the case where gravure printing is performed using solvent-based inks, and are not practical as gravure printing inks. Specifically, a UV ink having a viscosity at 60 rotations of more than 2000 cps in a B-type viscometer has poor loading on a gravure cell, is inferior in transferability from a gravure plate to a printing material such as a film, It is easy to produce “blur” and “streaks”. On the other hand, when the viscosity is lower than 100 cps, the storage stability is lowered, which is not preferable. The viscosity of the UV ink can be adjusted within the above range by appropriately selecting the type and amount of the constituents of the UV ink. Specifically, if a compound having a network structure or a compound having a high molecular weight is used as a constituent of UV ink, the viscosity can be increased, and the viscosity can be increased by adding a compound having a low molecular weight, a photopolymerization initiator, a surfactant or a solvent. Can be reduced. In the present invention, it is preferable to adjust the viscosity without adding a solvent.

  The viscosity when the UV ink of the present invention is a transparent UV ink containing no pigment is preferably 100 to 1000 cps. Moreover, the viscosity of the UV ink (colored ink) to which the pigment is added tends to increase. For example, the viscosity of white UV ink containing a white pigment is preferably about 200 to 2000 cps.

  If the thixotropic index (TI value) is less than 0.8, the printing quality at high-speed printing is low, and if it exceeds 1.0, the ink is not placed on the gravure cell, and in any case, the printability is poor. In the present invention, a UV ink having a TI value within the above range is selected and used. The TI value can be adjusted by appropriately selecting the components and viscosity of the UV ink.

  The UV ink of the present invention is not particularly limited as long as it is a UV ink having the above properties, but more preferably a cationic polymerization type ultraviolet curable ink. The composition of the ink varies depending on the conditions of gravure plate, printing speed, film material, etc. and required properties, and is not particularly limited. For example, photopolymerizable oligomer (prepolymer), photopolymerizable monomer (reactive diluent), etc. The resin component, a photopolymerization initiator, and the like. In addition, additives such as pigments, sensitizers, lubricants and the like may be contained depending on the required performance.

  As the resin component, a general photopolymerizable compound such as a cationic polymerizable compound having an epoxy group or a vinyl ether group or a radical polymerizable compound having an acryloyl group or a vinyl group is used within a range not impairing the above characteristics. be able to. Examples of the cationic polymerizable compound include epoxy compounds, vinyl ether compounds, and oxetane compounds. Examples of the radical polymerizable compound include urethane acrylate, epoxy acrylate, ester acrylate, and acrylate compounds. Among these, cationically polymerizable compounds are preferable, and epoxy compounds and oxetane compounds are preferable. These can be used singly or in combination of two or more.

  Among the above, when an oxetane compound and an epoxy compound are used as resin components, the curing rate, the heat resistance after curing, the scratch resistance, and the like are particularly preferable. Examples of the oxetane compound include 3-ethyl-3-[(phenoxy) methyl] oxetane, 3-ethyl-3- (hexyloxymethyl) oxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, Compounds having one oxetane ring in one molecule such as 3-ethyl-3- (hydroxymethyl) oxetane and 3-ethyl-3- (chloromethyl) oxetane; 1,4-bis [(3-ethyl-3oxetanyl And compounds having two oxetane rings in one molecule such as methoxy) methyl] benzene and bis {[1-ethyl (3-oxetanyl) methyl]} ether. These oxetane compounds are used alone or in combination of two or more.

  Especially, the compound which has a 1 or more functional group in a molecule | numerator from a viewpoint of viscosity reduction of an ink is preferable. Examples of such oxetane compounds include compounds having one oxetane ring in one molecule and further having at least one functional group. Specifically, 3-ethyl-3- (hydroxymethyl ) Oxetane, bis {[1-ethyl (3-oxetanyl) methyl]} ether, etc. are preferred, and in particular, 3-ethyl-3- (hydroxymethyl) oxetane, bis {[1-ethyl (3-oxetanyl) methyl]}. Ether or the like is preferably used.

  These oxetane compounds may be produced in accordance with a known method using oxetane alcohol and a halide (for example, xylene dichloride) produced from trimethylolpropane and dimethyl carbonate, and “Aron Oxetane OXT” manufactured by Toagosei Co., Ltd. Commercially available products such as “−101, 121, 211, 221, 212” can also be used.

  The content of the oxetane compound can be appropriately selected from the range that can be coated by gravure printing, and is, for example, 10% by weight or more, preferably 10 to 75% by weight, more preferably 20 to 70% by weight, based on the entire ink. It is. In particular, when the UV ink of the present invention is a white ink (when the UV ink contains a large amount of other additives such as pigments and lubricants), it is preferably 20 to 40% by weight, and is a transparent ink (UV When the amount of other additives such as pigments and lubricants in the ink is small), 50 to 70% by weight is preferred. When the content of the oxetane compound exceeds 75% by weight, the curing start speed of the UV ink becomes slow, so that the curing becomes insufficient, the heat resistance and the solvent resistance are lowered, and the curing is sufficiently performed. May slow down the production speed and reduce productivity. In addition, when the content of the oxetane compound is less than 10% by weight, the termination reaction of the curing reaction tends to proceed, and the cured product may have a low molecular weight or the UV ink layer may become brittle. Furthermore, the viscosity of the UV ink becomes high, and it may be difficult to apply it uniformly by gravure printing.

  Examples of the epoxy compound include aliphatic epoxy compounds such as propylene glycol glycidyl ether; alicyclic rings such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and bis- (3,4-epoxycyclohexyl) adipate. Epoxy compounds: aromatic epoxy compounds such as bisphenol A glycidyl ether, glycidyl ether condensates of bisphenol A, and epichlorohydrin modified products of novolak resins and cresol resins can be used. Among these, from the viewpoint of a high reaction rate, a compound having a glycidyl group or an alicyclic epoxy compound having an epoxycyclohexane ring is preferable, and an epoxy compound having two or more epoxy groups is preferable. From the viewpoint of reducing the viscosity of the UV ink, for example, a relatively low molecular weight epoxy compound having one or more functional groups and having a molecular weight of less than 2000, particularly 555 or less is preferably used.

  As these epoxy compounds, those synthesized by a general method such as synthesis from epichlorohydrin and bisphenol A can be used. For example, “Celoxide 2021”, “Celoxide 2080” manufactured by Daicel Chemical Industries, Ltd., “ “Epolide GT400” is available as a commercial product.

  Content of the epoxy compound of this invention can be suitably selected from the range which can be coated by gravure printing, and 5-70 weight% is preferable with respect to the whole ink. In particular, when the UV ink of the present invention is a white printing ink, 5 to 25% by weight is preferable, and when it is a transparent ink, 15 to 60% by weight is preferable. When the content of the epoxy compound exceeds 70% by weight, the termination reaction of the curing reaction tends to proceed, and the cured product may have a low molecular weight or the UV ink layer may become brittle. Furthermore, the viscosity of the UV ink becomes high, and it may be difficult to apply it uniformly by gravure printing. In addition, when the content of the epoxy compound is less than 5% by weight, the curing start speed of the UV ink is slowed, so that the curing becomes insufficient, the heat resistance and the solvent resistance are lowered, or the curing is sufficiently performed. In order to do so, the manufacturing speed may be slowed down and productivity may be reduced.

  In the UV ink of the present invention, an oxetane compound and an epoxy compound, for example, in a blending ratio (weight ratio) of 2: 8 to 8: 2 (the former / the latter is 0.00) in that a viscosity usable for gravure printing can be obtained. 25-4), preferably 3: 7-8: 2 (the former / the latter is about 0.42-4). When the amount of oxetane compound is larger than the above range, the UV ink curing reaction start speed becomes slow, and it takes time to cure, so that the productivity may be lowered or uncured in a normal curing process. In addition, if the amount of the epoxy compound is larger than the above range, the viscosity of the UV ink becomes large and it becomes difficult to apply uniformly by gravure printing, or the curing reaction is likely to stop, and the cured product has a low molecular weight. Thus, the UV ink layer after curing may become brittle.

  These resin components may further contain silicone having an epoxy group. The silicone having an epoxy group is a silicone having at least one epoxy group in the molecule (epoxy-modified silicone). Note that the base silicone may be a polysiloxane whose main chain is composed of a siloxane bond. When the silicone having such an epoxy group is included, the curing rate of the UV ink is increased and the productivity is improved, which is preferable. As for content of the silicone which has an epoxy group, about 0.1 to 20 weight% is preferable with respect to the whole ink.

  These epoxy group-containing silicones include a method of adding an epoxy compound containing an alkenyl group-containing epoxy compound to a polyorganohydrogensiloxane using a catalyst, etc. It can be obtained by a known method such as a method of cohydrolysis and condensation polymerization with a hydrolyzable silane, a method of condensation polymerization of an epoxy compound containing a hydroxyl group with a silane or siloxane having a hydroxyl group or a hydrolyzable group. The component C may be an existing epoxy-modified silicone compound such as “KF-101, KF-102, KF-105, KF-1001, X-22-163A, X-22” manufactured by Shin-Etsu Silicone Co., Ltd. -163B, X-22-163C, X-22-169AS, X-22-169B, X-22-173DX, X-22-2000 "and the like are commercially available.

  The UV ink of the present invention may also contain one or more of the above exemplified resin components such as acrylic compounds.

  The photopolymerization initiator is not particularly limited, but a photocationic polymerization initiator is preferable. Although it does not specifically limit as a photocationic polymerization initiator, For example, a diazonium salt, a diaryl iodonium salt, a triaryl sulfonium salt, a silanol / aluminum complex, a sulfonic acid ester, an imide sulfonate etc. are mentioned. In this invention, there exists an effect which reduces the viscosity of UV ink by addition of a photoinitiator. Although content of a photoinitiator will not be specifically limited if the viscosity of UV ink is in the said range, For example, it is 0.5-7 weight% with respect to the whole UV ink, Preferably it is 1-5 weight%.

  As the pigment, white pigments such as titanium oxide (titanium dioxide), indigo pigments such as copper phthalocyanine blue, other colored pigments, carbon black, aluminum flakes, mica (mica), and the like can be selected and used according to the application. In addition, extender pigments such as alumina, calcium carbonate, barium sulfate, silica, and acrylic beads can also be used as pigments for the purpose of adjusting gloss.

  When used as white UV ink, titanium oxide is preferably used as the pigment. As the titanium oxide, any of rutile type (tetragonal high temperature type), anatase type (tetragonal low temperature type), and brookite type (orthorhombic type) may be used. For example, titanium oxide particles manufactured by Ishihara Sangyo Co., Ltd. “Taipeke” is available. Moreover, the average particle diameter of the titanium oxide particles (in the case where an aggregate is formed, the particle diameter of the aggregate, so-called secondary particle diameter) is, for example, 0.01 to 1 μm, preferably 0.1 to 0.00. It is about 5 μm. If the average particle size is less than 0.01 μm, the dispersibility is poor, and if it exceeds 1 μm, the film surface becomes rough and the appearance tends to deteriorate.

  The content of the pigment of the present invention is preferably from 20 to 60% by weight, more preferably from 30 to 55% by weight, based on the entire UV ink, from the viewpoint of concealability and suppression of coarse protrusion formation. In general, the UV ink can have a higher pigment content than solvent-based inks. For this reason, by using a white UV ink containing a high concentration of white pigment, the white density of printing can be increased. For example, when two solid coating printings are conventionally required, sufficient concealment can be achieved by one printing. There are effects such as being able to obtain.

  Moreover, it is preferable to add a sensitizer to the UV ink of this invention as needed from a viewpoint of improving production efficiency. This is particularly effective when the titanium oxide pigment is used. In this case, the sensitizer can be selected from existing sensitizers in consideration of the type of active energy ray used. For example, (1) amine sensitizers such as amines containing nitrogen in the ring, such as aliphatic, aromatic amines, piperidine, (2) urea sensitizers such as allyl, o-tolylthiourea, (3) sodium Sulfur compound sensitizers such as diethyldithiophosphate, (4) anthracene sensitizers, (5) nitrile sensitizers such as N, N-disubstituted-p-aminobenzonitrile compounds, (6) tri -Phosphorus compound sensitizers such as n-butylphosphine, (7) Nitrogen compound sensitizers such as N-nitrosohydroxylamine derivatives and oxazolidine compounds, (8) Chlorine compound sensitizers such as carbon tetrachloride, etc. Sensitizers. Also in the above, in particular, anthracene sensitizers are preferred because of their strong sensitizing action. Of these, thioxanthone and 9,10-dibutoxyanthracene are preferably used. The content of the sensitizer is not particularly limited, but is preferably 0.1 to 5% by weight, particularly preferably 0.3 to 3% by weight, based on the entire UV ink.

  Furthermore, in the UV ink of the present invention, if necessary, various waxes such as polyolefin wax such as polyethylene wax, fatty acid amide, fatty acid ester, paraffin wax, polytetrafluoroethylene (PTFE) wax, carnauba wax, etc. A lubricant may be added.

  In addition to the above, the UV ink of the present invention may contain a dispersant, an antioxidant, a fragrance, a deodorant, a stabilizer, a leveling agent, etc. to the extent that the effects of the present invention are not impaired.

  The content of the solvent in the UV ink of the present invention is preferably 5% by weight or less, more preferably 1% by weight or less, and most preferably substantially no solvent. The solvent here means, for example, an organic solvent such as toluene, xylene, methyl ethyl ketone, ethyl acetate, methyl alcohol, and ethyl alcohol, and water. In gravure printing ink, coating processability and UV ink It is usually used for the purpose of improving the compatibility and dispersibility of each component. The UV ink of the present invention may use a solvent to lower the TI value, but can exhibit excellent coating properties and dispersibility between components even without a solvent. For this reason, the amount of the solvent can be extremely reduced, the removal of the solvent becomes unnecessary, the speed can be increased, the cost can be reduced, and the environmental load can be reduced.

  The UV ink of the present invention includes, for example, the above components (oxetane compound, epoxy compound, photopolymerization initiator, pigment, etc.), a mixer such as a butterfly mixer, a planetary mixer, a pony mixer, a dissolver, a tank mixer, a roll mill, and a sand mill. And can be produced by mixing using a mixing means such as a mill such as a ball mill or a kneader. The above components may be mixed simultaneously or sequentially, but are mixed simultaneously when a pigment is used. The mixing time (residence time) is preferably about 10 to 120 minutes. The obtained UV ink may be used after being filtered, if necessary.

  In the plastic label of the present invention, the above-mentioned UV curable ink for gravure printing of the present invention is gravure-printed on at least one surface of a plastic film.

  The plastic label of the present invention includes, for example, a stretch label, a shrink label, a stretch shrink label, an in-mold label, a tack label, a roll label (a wrap-type glued label), a heat-sensitive adhesive label, and the like. Among them, the UV ink of the present invention is particularly preferably used as a shrink label from the viewpoint of heat resistance, toughness and followability during processing.

  The material of the plastic film can be appropriately selected according to the required physical properties, application, cost, etc., and is not particularly limited. For example, polyester, polyolefin, polystyrene, polyvinyl chloride, polyamide, aramid, polyimide Resins such as polyphenylene sulfide and acrylic can be used. Among these, a polyester film, a polyolefin film, a polystyrene film, and a polyvinyl chloride film are preferable, and a polyester film and a polyolefin film are more preferable. As the polyester, polyethylene terephthalate (PET) or poly (ethylene-2,6-naphthalenedicarboxylate) (PEN) can be used, and as the polyolefin, polypropylene, polyethylene, cyclic olefin, or the like can be used. is there. These plastic films may be a single layer film or a laminated film composed of a plurality of layers, and each layer constituting the laminated film may be the same or different layers.

  As the plastic film, any of an unstretched film, a uniaxially oriented film, and a biaxially oriented film may be used. In particular, when the plastic label is a shrink label, a uniaxial or biaxially oriented film is often used. In particular, in the case of a shrink label that is formed in a cylindrical shape and is attached to an attachment, the film width direction A film (a film substantially uniaxially stretched in the width direction) that is strongly oriented in (the direction that becomes the circumferential direction of the label) is generally used. The stretching may be biaxial stretching in the longitudinal direction (longitudinal direction; MD direction) and width direction (transverse direction; TD direction), or may be uniaxial stretching in the longitudinal direction or the width direction. The stretching method may be any of a roll method, a tenter method, and a tube method. The stretching treatment can be performed under appropriate conditions depending on the type and use of the plastic film. For example, in the case where the plastic label is a heat-shrinkable film constituting a cylindrical shrink label, the glass transition temperature (Tg) of the polymer is about Tg + 50 ° C. If necessary, for example, 1.01 to 3 in the longitudinal direction. In many cases, the film is stretched by about 1.05 to 1.5 times, and then stretched by 3 to 10 times, preferably about 4 to 6 times in the width direction.

  The heat shrinkage rate (90 ° C., 10 seconds) of the plastic film is not particularly limited. For example, in the case of shrink label use, the longitudinal direction is −3 to 15% and the width direction from the viewpoint of shrink workability. Is preferably 20 to 80%.

  The surface of the plastic film may be subjected to conventional surface treatment such as corona discharge treatment or primer treatment, if necessary.

  Although the thickness of the said plastic film changes with uses and is not specifically limited, 10-200 micrometers is preferable, for example, in the case of a shrink label use, 20-80 micrometers is preferable, More preferably, it is 20-60 micrometers.

  The thickness of the UV ink layer in the plastic label of the present invention varies depending on the application and is not particularly limited, but is preferably 0.1 to 15 μm, and particularly preferably 0.5 to 10 μm. When the thickness of the UV ink layer is less than 0.1 μm, it may be difficult to provide the UV ink layer uniformly. When used as a UV ink layer, it may be partially blurred. In some cases, it may be difficult to print as designed. In addition, when the UV ink layer thickness exceeds 15 μm, a large amount of UV ink is consumed, which increases the cost, makes it difficult to apply uniformly, and makes the UV ink layer brittle. It becomes easy to peel off. Among these, when the UV ink layer of the present invention is a white UV ink layer, the thickness is preferably 2 to 10 μm from the viewpoint of concealment, and when the UV ink layer is a transparent UV ink layer, the thickness is transparent. In view of the above, 0.2 to 3 μm is preferable. In the present invention, the thickness of the UV ink layer hardly changes before and after curing.

  The plastic label of the present invention may have a layer other than the plastic film and the UV ink layer. However, when the UV ink layer is composed of an oxirane compound and an epoxy compound, the UV ink layer is formed on the plastic label. When it is provided on the outermost layer, it is preferable because it can effectively exhibit excellent heat resistance, scratch resistance, solvent resistance, water repellency and the like. In particular, a transparent UV ink layer may be provided on the outermost layer.

  The plastic label of the present invention may be provided with a printing ink layer different from the UV ink layer. The printing ink layer can be formed by a conventional printing method such as gravure printing or flexographic printing. The printing ink used to form such a printing ink layer is composed of, for example, a pigment, a binder resin, and a solvent. Examples of the binder resin include acrylic, urethane, polyamide, vinyl chloride-vinyl acetate copolymer, cellulose Common resins such as nitrocellulose and nitrocellulose can be used. Moreover, in this invention, it is preferable that the said printing ink layer is provided in the label inner side (side which contacts a container), or the interlayer of the said UV ink layer and a base film. Specifically, what provided the printing ink layer in the base film, and also provided the UV ink layer of this invention containing a white pigment is illustrated. The thickness of the UV ink layer is not particularly limited and is, for example, about 0.1 to 10 μm.

  The plastic label of the present invention may further be provided with an anchor coat layer, a primer coat layer, an adhesive layer, a heat-sensitive adhesive layer, a nonwoven fabric, paper or the like which is different from the UV ink layer of the present invention. Good.

The plastic label of the present invention is produced, for example, by subjecting at least one surface of a plastic film to gravure printing using the UV ink of the present invention and then irradiating it with an ultraviolet lamp to form a UV ink layer. be able to. The printing speed is, for example, about 30 to 300 m / min. According to the UV ink of the present invention, even when gravure printing is performed at a high printing speed of about 80 m / min, no “blurring” or “streaks” occur, and a beautiful printed image can be displayed. it can. For this reason, a high quality label can be manufactured efficiently. Curing is preferably performed using ultraviolet rays having a wavelength of 300 to 460 nm under the conditions of an intensity of 150 mJ / cm ^{2 to} 1000 mJ / cm ² and a time of about 0.1 to 3 seconds.

  Further, as described above, the plastic label of the present invention is any one of a stretch label, a shrink label, a stretch shrink label, an in-mold label, a tack label, a roll label (a wrap-type glued label), a heat-sensitive adhesive label, and the like. However, the UV ink layer of the present invention is most suitably used as a shrink label because it has good adhesion (adhesion) to a film and good followability to deformation during processing such as shrink processing.

  The plastic label obtained by the above method is used after being processed into a desired shape according to the purpose. For example, when the plastic label is a shrink label, the UV ink layer is on the outer side, and the plastic film is rolled into a cylindrical shape so that the width direction is the circumferential direction. It is possible to obtain a cylindrical shrink label by cutting each label into a continuous body of shrink labels.

  Moreover, as a preferable aspect, design printing is performed with gravure printing ink (not limited to the UV ink of the present invention) containing a color pigment on the inner surface of a transparent plastic film, and solid printing of the white UV ink of the present invention is performed on the innermost surface. And a label obtained by solid printing the transparent UV ink of the present invention on the outer surface (outermost surface) of a transparent plastic film.

  The plastic label of the present invention can be manufactured into a labeled container by attaching it to the container using a conventional method. Such a container may be any of a plastic container made of polyester such as polyethylene terephthalate, a glass container, a metal container, etc. The surface may have any shape such as a circular cylinder.

  For example, a container with a label supplies the above-described cylindrical shrink label to an automatic label mounting device, cuts it to a required length, and then externally fits into a container filled with normal contents, It can be produced by allowing it to pass through a steam tunnel or by heating with radiant heat such as infrared rays to cause heat shrinkage. Such a labeled container is particularly suitable for containers for beverages, foods, pharmaceuticals and the like because the plastic label is odorless. Also, depending on the composition of the UV ink layer that forms the outermost surface of the label, it is excellent in scratch resistance and chemical resistance. It is preferably used as a container.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The viscosity of the ink is JIS Z 8803 according to JIS Z 8803, using a B-type viscometer (single cylindrical rotational viscometer) manufactured by Toki Sangyo Co., Ltd. Measurements were performed according to the above. Moreover, also in the measurement of the viscosity used for calculation of the thixotropic index, the B type viscometer (single cylindrical rotational viscometer) manufactured by Toki Sangyo Co., Ltd. was used.

Example 1
As resin components, 3-ethyl-3-hydroxymethyloxetane (manufactured by Toagosei Co., Ltd., trade name “Aronoxetane OXT-101”) 48 parts by weight, and 3,4-epoxycyclohexenylmethyl-3 ′, 4 ′ -Epoxy cyclohexene carboxylate (Daicel Chemical Industries, Ltd., trade name "Celoxide 2021") 47 parts by weight, photopolymerization initiator (Asahi Denka Co., Ltd., trade name "Adekaoptomer SP-150") 3 weights Parts, 1 part by weight of photosensitizer (manufactured by Nippon Kayaku Co., Ltd., trade name “KAYACURE-DETX-S”), 1 weight by weight of silica (manufactured by Tosoh Silica Co., Ltd., trade name “NIPGEL AY-401”) Part was dispersed and mixed with a disperser for 30 minutes to prepare an ultraviolet curable ink (transparent UV ink), but no solvent was used.
This transparent UV ink had an organic compound content of 2,000 or more in molecular weight of 0% by weight, a B-type viscometer with a viscosity of 60 cps at 60 rpm, and a thixotropic index of 1.1.
Using the obtained transparent UV ink, a plate gravure printing machine (manufactured by Nissho Gravure Co., Ltd., trade name “GRAVO PROOF MINI”) and a gravure plate with 60 lines and a plate depth of 40 μm, the plate is rotated 5 times to obtain ink. After acclimatization, gravure printing was performed at a process speed of 50 m / min on one side of a polyester shrink film (manufactured by Toyobo Co., Ltd., trade name “Space Clean (S7042)”: film thickness 50 μm). Next, using an electroded lamp type ultraviolet irradiation device (manufactured by GS Yuasa Lighting Co., Ltd., trade name “4 kW × 1 light conveyor CSOT-40”) under the conditions of a process speed of 30 m / min, an irradiation distance of 8 cm, and an output of 3 kW. UV curing was performed to obtain a plastic label. The obtained plastic label was free from blurring and a beautiful printed image was obtained.

Example 2
In Example 1, it was carried out except that 3 parts by weight of epoxy resin modified at both ends (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “X-22-169B”: alicyclic epoxy group, epoxy equivalent 1700) was used. Using the same method as in Example 1, an ultraviolet curable ink (transparent UV ink) was prepared. This ultraviolet curable ink had an organic compound content of 2,000 or more in molecular weight of 0% by weight, a B-type viscometer with a viscosity of 60 cps at 60 rpm, and a thixotropic index of 1.1.
Using the obtained ultraviolet curable ink, the same operation as in Example 1 was performed to obtain a plastic label. The obtained plastic label was free from blurring and a beautiful printed image was obtained.

Example 3
In Example 1, UV curable type was used in the same manner as in Example 1 except that 60 parts by weight of titanium oxide (Ishihara Sangyo Co., Ltd., trade name “Taipeke PF-736”) was used as a white pigment. An ink (white UV ink) was prepared. This ultraviolet curable ink had an organic compound content of 2,000 or more in molecular weight of 0% by weight, a B-type viscometer with a viscosity of 60 cps at 60 rpm, and a thixotropic index of 1.2.
Using the obtained ultraviolet curable ink, the same operation as in Example 1 was performed to obtain a plastic label. The obtained plastic label was free from blurring and a beautiful printed image was obtained.

Comparative Example 1
In Example 1, an ultraviolet curable ink (transparent UV ink) was prepared in the same manner as in Example 1 except that 7 parts by weight of both-end epoxy-modified silicone (similar to Example 2) was used. This ultraviolet curable ink had an organic compound content of 2000% or more in molecular weight of 0% by weight, a B-type viscometer with a viscosity at 60 rpm of 2200 cps, and a thixotropic index of 1.5.
Using the obtained ultraviolet curable ink, the same operation as in Example 1 was performed to obtain a plastic label. In the obtained plastic label, a part of the printed image was faint and streaks were found in several places and the display was unclear.

Comparative Example 2
In Example 1, an ultraviolet curable ink (transparent) was used in the same manner as in Example 1 except that 3 parts by weight of an anti-settling agent (trade name “T-300-10AK” manufactured by Ito Oil Co., Ltd.) was used. UV ink) was prepared. This ultraviolet curable ink had an organic compound content of 2000% or more, a viscosity of 1000 cps under a B-type viscometer at 60 rpm, and a thixotropic index of 12.0.
Using the obtained ultraviolet curable ink, the same operation as in Example 1 was performed to obtain a plastic label. The obtained plastic label had a part of the printed image faint, streaks in several places, the display was unclear, and the printability was poor.

Claims (4)

A gravure in which the content of an organic compound having a molecular weight of 2000 or more is 5% by weight or less, the viscosity at 60 revolutions in a B-type viscometer is 100 to 2000 cps, and the thixotropic index is 0.8 to 10.0. UV curable ink for printing. The ultraviolet curable ink for gravure printing according to claim 1, comprising an oxetane compound and an epoxy compound as constituent components. Furthermore, the ultraviolet curable ink for gravure printing of Claim 1 or 2 containing a photoinitiator. A plastic label in which the ultraviolet curable ink for gravure printing according to any one of claims 1 to 3 is gravure-printed on at least one surface of the plastic film.