Can Labels

Abstract

To provide a label for a can appropriate for an adhesion onto a can surface while having an electrostatic ink layer by a digital printing machine.SOLUTION: A label for a can is to be laminate-processed onto a can body, and includes a first base material, a primer layer, an electrostatic ink layer, an adhesive layer and a second base material laminated in this order. The adhesive layer includes at least one of: an adhesive composition containing a polyol, a polyisocyanate and an epoxy compound; and a cured product of the adhesive composition.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to labels for cans. [Background technology]

[0002] Digital printing using an electrostatic ink composition is applicable to small lot production, and is therefore used for various packaging materials. For example, Patent Document 1 discloses a technique in which electrostatic printing is performed on a surface of a first flexible substrate such as a PET film coated with a primer resin using a digital printer (Indigo20000 label and package digital printer manufactured by HP), and then a crosslinking composition is applied, followed by laminating the flexible substrate to obtain a packaging material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-530478 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, it has been found that when a laminate having a printed surface of an electrostatic ink composition printed on a digital printer is used to create a can label and then used to manufacture a can container, the state of the label attachment to the manufactured can container may differ from the appropriate state.

[0005] Therefore, the present disclosure provides a can label that has an electrostatic ink layer produced by a digital printer and is suitable for attachment to the surface of a can. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a can label according to one embodiment of the present disclosure is a can label that is laminated onto a can body, in which a first substrate, a primer layer, an electrostatic ink layer, an adhesive layer, and a second substrate are laminated in this order, and the adhesive layer contains at least one of an adhesive composition containing a polyol, a polyisocyanate, and an epoxy compound, and a cured product of the adhesive composition.

[0007] According to the above-mentioned can label, the adhesive composition containing the epoxy compound is cured, so that the deformation of the label due to heating during the production of the can container is suppressed. Therefore, a can label having an electrostatic ink layer produced by a digital printer and suitable for attachment to the surface of a can is obtained.

[0008] At least one of the first substrate and the second substrate may be a polyethylene terephthalate resin film. A can label having a polyethylene terephthalate resin film has excellent heat resistance and water resistance, and is therefore suitable for use as a can label for various applications.

[0009] The polyol may include an aliphatic polyester polyol, and the epoxy compound may include one having epoxy groups at both ends. Such an adhesive layer has high adhesive strength, particularly in a high-temperature environment. Therefore, a can label can be obtained that can further suppress the deformation of the label due to heating or the like during the production of a can container to which the can label is attached.

[0010] The epoxy compound may be an embodiment containing a bifunctional alicyclic epoxy compound. Since such an epoxy compound is bifunctional, it increases the number of crosslinking points with the electrostatic ink composition, and thus promotes crosslinking with the electrostatic ink composition to obtain a strong crosslinked composition. Furthermore, since it is alicyclic, it is possible to suppress the reaction with polyisocyanate due to steric hindrance. Therefore, it is possible to stably cure and to provide sufficiently excellent adhesion at the interface between the adhesive layer and the electrostatic ink layer.

[0011] The polyisocyanate may be a xylylene diisocyanate derivative. Such a polyisocyanate and a polyol have excellent reactivity. This improves the curing property of the adhesive composition, and can suppress deformation of a label attached to a can surface. Effect of the Invention

[0012] According to the present disclosure, a can label is provided that has an electrostatic ink layer produced by a digital printer and is suitable for application to the surface of a can. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing an example of a cross section along the lamination direction (thickness direction) of a label for cans according to one embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a can container to which a can label is attached. [Diagram 3] FIG. 3 is a diagram showing an example of a cross section of a can container. [Figure 4] FIG. 4 is a diagram showing an example of a method for manufacturing a can container. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals and duplicated descriptions will be omitted.

[0015] [Can labels] 1 shows a cross section along the lamination direction (thickness direction) of a label for cans according to one embodiment. The label for cans 1 is a label to be attached to the surface of a can container. Applications of the can container are not particularly limited, and examples include beverage cans for enclosing beverages, food cans for enclosing food, oil, etc., and industrial cans for enclosing chemicals, industrial products, etc.

[0016] 1, the can label 1 has a first base film 10 (first base material), a primer layer 40, an adhesive layer 30, and a second base film 20 (second base material) laminated in this order. The primer layer 40 is provided on one of a pair of main surfaces of the first base film 10 closer to the second base film 20.

[0017] The first base film 10 and the second base film 20 may be flexible base materials. For example, a film-like thermoplastic polymer can be used as the flexible base material. More specifically, a film of biaxially oriented polypropylene (BOPP), polyethylene terephthalate (PET), oriented polyamide (OPA), non-oriented polypropylene (CPP), linear low-density polyethylene (LLDPE), or low-density polyethylene (LDPE) can be used as the flexible base material. As an example, a PET film can be used as the first base film 10 and the second base film 20. Note that, for the second base film 20, a metal foil such as an aluminum foil may be used as the flexible base material. Also, for the second base film 20, a material in which a metal foil such as an aluminum foil and a resin film are combined may be used as the flexible base material.

[0018] The thickness of the first base film 10 and the second base film 20 may be 7 to 150 μm, 15 to 90 μm, or 20 to 80 μm. The thickness of the first base film 10 may be greater than the thickness of the second base film 20. From the viewpoint of the heat resistance of the can label 1 and the rigidity of the can label 1, the thickness of the second base film 20 may be set to 7 μm or more. On the other hand, by increasing the difference in thickness between the first base film 10 and the second base film 20, it is possible to prevent a difference in stress caused by the difference in thickness of the base films from occurring in the first base film 10 and the second base film 20 label.

[0019] The primer layer 40 may contain a resin. Examples of the resin include polyvinyl alcohol resin, cellulose-based resin, polyester, polyamine, polyethyleneimine resin, polyamide resin, polyurethane, polyacrylic polymer, hydroxyl group-containing resin, carboxyl group-containing resin, and amine-based polymer. By having the primer layer 40, printing of the electrostatic ink composition using a digital printer can be smoothly performed. The application amount of the resin constituting the primer layer 40 is, for example, 0.01 to 1.5 g / m. 2 and may be 0.05 to 1.0 g / m 2 may be also possible.

[0020] The can label 1 has an electrostatic ink layer 50 provided on one of a pair of main surfaces of the primer layer 40 closer to the second base film 20. The electrostatic ink layer 50 is made of an electrostatic ink composition and is provided by electrostatic printing using a digital printer. The multiple electrostatic ink layers 50 in FIG. 1 may have the same composition, or may have different compositions and thus different colors. The electrostatic ink layer 50 may be provided so as to be dotted on the primer layer 40, or may be provided so as to cover the entire one surface of the primer layer 40.

[0021] The electrostatic ink composition that constitutes the electrostatic ink layer 50 is an ink composition used in liquid electrophotographic printing, i.e., electrostatic printing, and is printed onto substrates such as paper and plastic. The electrostatic ink composition may include a colorant or pigment, such as a dye, and a resin. In addition to these, the electrostatic ink composition may also include a carrier fluid or liquid. It may further include charge directors, charge adjuvants, surfactants, viscosity modifiers, emulsifiers, and other additives.

[0022] The colorants include, for example, cyan pigments, magenta pigments, yellow pigments, and black pigments.The resins include thermoplastic resins such as ethylene acrylic acid copolymers, propylene acrylic acid copolymers, ethylene methacrylic acid copolymers, propylene methacrylic acid copolymers, and ethylene vinyl acetate copolymers.

[0023] The carrier liquid may include hydrocarbons, silicone oils, vegetable oils, and the like. The hydrocarbons may include aliphatic hydrocarbons, branched-chain aliphatic hydrocarbons, and aromatic hydrocarbons. The electrostatic ink composition may be substantially free of carrier liquid when printed on a printing substrate (e.g., on the first substrate film 10 with the primer layer 40 sandwiched therebetween). The carrier liquid may be removed, for example, by an electrophoretic process or evaporation during printing. This allows substantially only solids to be transferred to the printing substrate.

[0024] Charge directors serve to maintain a sufficient electrostatic charge on the particles contained in the electrostatic ink composition and include, for example, ionic compounds such as metal salts of fatty acids, metal salts of sulfosuccinates, metal salts of oxyphosphates, metal salts of alkylbenzenesulfonic acids, metal salts of aromatic carboxylic or aromatic sulfonic acids, as well as zwitterionic and non-ionic compounds such as polyoxyethylenated alkylamines, lecithin, polyvinylpyrrolidone, and organic acid esters of polyhydric alcohols.

[0025] Charge adjuvants have the effect of increasing or stabilizing the charge of particles contained in the electrostatic ink composition. Examples of charge adjuvants include barium petronate, calcium petronate, naphthenic acid Co salt, naphthenic acid Ca salt, naphthenic acid Cu salt, naphthenic acid Mn salt, naphthenic acid Ni salt, naphthenic acid Zn salt, naphthenic acid Fe salt, stearate Ba salt, stearate Co salt, stearate Pb salt, stearate Zn salt, stearate Al salt, stearate Cu salt, stearate Fe salt, and metal carboxylates.

[0026] The electrostatic ink composition may contain a crosslinked product crosslinked by components contained in the adhesive layer 30 and / or the primer layer 40. This makes it possible to sufficiently increase the strength of the electrostatic ink layer 50 itself, as well as the adhesive strength between the adhesive layer 30 and the electrostatic ink layer 50, and between the electrostatic ink layer 50 and the primer layer 40.

[0027] The adhesive layer 30 is laminated onto the main surface of the primer layer 40 on which the electrostatic ink layer 50 is provided, and is also formed so as to cover the electrostatic ink layer 50. That is, when the electrostatic ink layer 50 is formed so as to cover the entirety of one side of the primer layer 40, the adhesive layer 30 is laminated onto the main surface of the electrostatic ink layer 50 (the main surface opposite to the surface in contact with the primer layer 40). In this manner, at least one of the main surfaces of the electrostatic ink layer 50 (the main surface opposite to the surface in contact with the primer layer 40 ) serves as an adhesive surface for the adhesive layer 30 .

[0028] The adhesive layer 30 may be composed of an adhesive composition, a cured product thereof, or a mixture thereof. The adhesive composition contains a polyol, a polyisocyanate, and an epoxy compound. At least a part of these three components (polyol, polyisocyanate, and epoxy compound) may react with each other and be cured to form a cured product. The adhesive layer 30 containing the above three components and the electrostatic ink layer 50 are in direct contact with each other at their interface. The epoxy compound contained in the adhesive layer 30 and the ink composition contained in the electrostatic ink layer 50 are crosslinked with each other, thereby providing a sufficiently high adhesive strength between the adhesive layer 30 and the electrostatic ink layer 50.

[0029] The polyol has, for example, a number average molecular weight of 400 or more and has two or more hydroxyl groups in one molecule. The polyisocyanate has two or more isocyanate groups in one molecule. The polyol and the polyisocyanate react as a base agent and a curing agent, respectively, to produce polyurethane (polyurethane adhesive). The polyol may have, for example, a number average molecular weight of 10,000 or less.

[0030] The polyol may contain at least one selected from the group consisting of polyester polyols and polyether polyols. Among these, from the viewpoint of sufficiently increasing the adhesive strength of the adhesive layer 30 in a high-temperature environment, the polyol may contain a polyester polyol or may contain an aliphatic polyester polyol.

[0031] The polyester polyol can be obtained, for example, by a condensation reaction or an ester exchange reaction between a polyhydric alcohol and a polybasic acid, its alkyl ester, its acid anhydride, or its acid halide. Examples of the polyhydric alcohol include a low molecular weight diol, a low molecular weight triol, and a low molecular weight polyol having four or more hydroxyl groups.

[0032] Examples of low molecular weight diols include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, neopentyl glycol, 1,6-hexanediol, 2,2-diethyl-1,3-propanediol, 3,3-dimethylolheptane, and 2-ethyl-2-butyl-1,3-propanediol.

[0033] Examples of low molecular weight triols include glycerin, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentane, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-(hydroxymethyl)pentane, and 2,2-bis(hydroxymethyl)-3-butanol.

[0034] Examples of low molecular weight polyols having four or more hydroxyl groups include tetramethylolmethane, pentaerythritol, dipentaerythritol, D-sorbitol, xylitol, D-mannitol, and D-mannite.

[0035] Examples of the alkyl ester of a polybasic acid include methyl ester and ethyl ester of a polybasic acid. Examples of the acid anhydride include acid anhydrides derived from a polybasic acid. For example, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, 2-alkyl (C12-18) succinic anhydride, tetrahydrophthalic anhydride, and trimellitic anhydride can be mentioned.

[0036] The acid halide may be an acid halide derived from the above-mentioned polybasic acid, such as oxalic acid dichloride, adipic acid dichloride, or sebacic acid dichloride.

[0037] The polyether polyol may be a polyalkylene oxide. For example, it may be obtained by addition reaction of an alkylene oxide such as ethylene oxide and / or propylene oxide with a low molecular weight polyol as an initiator. Specific examples include polyethylene glycol, polypropylene glycol, and polyethylene polypropylene glycol (random or block copolymer). In addition, for example, polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran may be mentioned.

[0038] Examples of polyisocyanates include polyisocyanate monomers, polyisocyanate derivatives, and isocyanate-terminated prepolymers. The adhesive composition may contain a plurality of different polyisocyanates. The molar ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate to the hydroxyl groups of the polyol may be 0.5 to 10. Such an adhesive composition can form a cured product having high adhesive strength and excellent flexibility.

[0039] Examples of the polyisocyanate monomer include aliphatic polyisocyanates, aromatic polyisocyanates, araliphatic polyisocyanates, and alicyclic polyisocyanates.

[0040] Examples of aliphatic polyisocyanates include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methylcaprate.

[0041] The aromatic aliphatic polyisocyanate may be a xylylene diisocyanate derivative, such as xylylene diisocyanate (1,3-xylylene diisocyanate or 1,4-xylylene diisocyanate) (XDI), tetramethyl xylylene diisocyanate (1,3-tetramethyl xylylene diisocyanate or 1,4-tetramethyl xylylene diisocyanate) (TMXDI), ω,ω'-diisocyanate-1,4-diethylbenzene, or a polyol modified product of xylylene diisocyanate obtained by reacting xylylene diisocyanate with trimethylolpropane.

[0042] The content of the xylylene diisocyanate derivative relative to the entire polyisocyanate may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more from the viewpoint of improving the reactivity with the base agent (e.g., polyol). By making it 30% by mass or more, the reactivity can be further increased.

[0043] Examples of alicyclic polyisocyanates include 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorodiisocyanate) (IPDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), and norbornane diisocyanate (NBDI).

[0044] Examples of the polyisocyanate derivatives include polymers of the above-mentioned polyisocyanate monomers, allophanate-modified products, polyol-modified products, polyol-modified products produced by the reaction of a monomer with an alcohol, biuret-modified products, urea-modified products, oxadiazinetrione-modified products, carbodiimide-modified products, uretdione-modified products, and uretonimine-modified products.

[0045] The isocyanate-terminated prepolymer is a urethane prepolymer having at least two isocyanate groups at the molecular end. It can be obtained by a urethane reaction between at least one selected from the group consisting of polyisocyanate monomers, polyisocyanate derivatives, and isocyanate-terminated prepolymers, and a polyol. In this case, the molar ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate to the hydroxyl groups of the polyol may be 0.5 or more, 0.6 or more, 0.8 or more, 1 or more, or 1.5 or more. The molar ratio (NCO / OH) may be 10 or less, 5 or less, 4 or less, or 3 or less. Examples of the numerical range of the molar ratio (NCO / OH) include 0.5 to 10, 0.5 to 5, 0.8 to 4, and 0.6 to 3.

[0046] The epoxy compound may be a compound having one or more epoxy groups in one molecule. From the viewpoint of further increasing the adhesive strength of the adhesive layer 30 in a high temperature environment, the epoxy compound may have epoxy groups at both ends. Examples of the epoxy compound include glycidyl ether type epoxy compounds, glycidyl amine type epoxy compounds, glycidyl ester type epoxy compounds, and alicyclic epoxy compounds (alicyclic epoxy compounds).

[0047] The molecular weight of the epoxy compound may be 500 or less, 450 or less, or 400 or less. Such an epoxy compound can be sufficiently permeated into the electrostatic ink composition constituting the electrostatic ink layer. The lower limit of the molecular weight of the epoxy compound may be, for example, 98.

[0048] Examples of alicyclic epoxy compounds include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate and bis(epoxycyclohexyl)adipate.

[0049] Examples of monofunctional alicyclic epoxy compounds having one epoxy group per molecule include 3,4-epoxycyclohexylmethyl methacrylate and 1,2-epoxy-4-vinylcyclohexane. Examples of bifunctional epoxy compounds having two epoxy groups per molecule include 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, and 4-vinylcyclohexene dioxide. Examples of epoxy compounds having one or more epoxy groups per molecule include 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol represented by the following general formula (I).

[0050] [ka]

[0051] In the above general formula (I), n may be an integer of 1-4.

[0052] The epoxy compound preferably contains a bifunctional alicyclic epoxy compound. By being bifunctional, the number of crosslinking points with the electrostatic ink composition and the primer resin can be increased, accelerating the curing reaction of the adhesive, and making it easier to cure. In addition, by being alicyclic, the reaction with the polyisocyanate can be suppressed due to steric hindrance. Therefore, the epoxy compound can be stably cured, and the adhesion at the interface between the electrostatic ink layer 50 and the adhesive layer 30 can be sufficiently excellent.

[0053] In the adhesive composition, the content of the epoxy compound relative to 100 parts by mass of polyol may be 3 to 25 parts by mass, 6 to 25 parts by mass, or 8 to 20 parts by mass, from the viewpoint of achieving both high adhesive strength and excellent shear suppression. If the content of the epoxy compound is too high, the excellent shear suppression tends to be impaired. That is, when the adhesive layer 30 is formed, the adhesive surface may shift or the adhesive composition may protrude. If the amount of the epoxy compound is too small, the adhesive strength under high-temperature hot water treatment conditions tends to decrease.

[0054] In the adhesive composition, the content of polyisocyanate per 100 parts by mass of polyol may be 10 to 50 parts by mass, 15 to 35 parts by mass, or 20 to 30 parts by mass, from the viewpoint of sufficiently increasing the seal strength and the adhesive strength under high-temperature hot water treatment conditions.

[0055] The molar ratio of the epoxy groups contained in the epoxy compound to the isocyanate groups contained in the polyisocyanate may be 0.5 to 10, 1.5 to 9, or 2.0 to 6.5. This makes it possible to maintain a sufficiently high adhesive strength under high-temperature hot water treatment conditions.

[0056] The adhesive composition constituting the adhesive layer 30 may contain optional components such as additives in addition to the above-mentioned components. Examples of additives include antioxidants, UV absorbers, light stabilizers, fillers, silane coupling agents, epoxy resins, catalysts, coating property improvers, leveling agents, nucleating agents, lubricants, release agents, defoamers, plasticizers, surfactants, pigments, dyes, organic fine particles, inorganic fine particles, antifungal agents, and flame retardants. The adhesive composition may contain a solvent such as an organic solvent.

[0057] The adhesive composition constituting the adhesive layer 30 bonds the electrostatic ink layer 50 and the second base film 20. An optional layer may be provided between the second base film 20 and the adhesive layer 30. In this case, the adhesive composition bonds the electrostatic ink layer 50 and the optional layer. The adhesive composition forms a urethane bond by reacting with the polyol and the polyisocyanate, and functions as an adhesive. Even in the presence of an epoxy compound, the formation of the urethane bond proceeds smoothly, so that the electrostatic ink layer 50 can be bonded to the second base film 20 or the optional layer with sufficiently high adhesive strength.

[0058] The adhesive composition constituting the adhesive layer 30 may have a function of forming urethane bonds and cross-linking the electrostatic ink composition forming the electrostatic ink layer 50. This can improve the adhesive strength between the electrostatic ink layer 50 and the second base film 20, or between the electrostatic ink layer 50 and any layer of the adhesive layer 30.

[0059] Even if the ratio of the electrostatic ink in the electrostatic ink layer 50 (ink coverage) increases, the epoxy compound can be sufficiently permeated into the electrostatic ink layer 50 made of the electrostatic ink composition by increasing the content of the epoxy compound in the adhesive composition accordingly. The permeated epoxy compound has the effect of increasing the strength of the electrostatic ink composition (electrostatic ink layer 50) by crosslinking the electrostatic ink composition. Therefore, even if the ink coverage increases, deformation of the electrostatic ink layer 50 (e.g., wrinkles, lifting of a part of the can label 1 along the electrostatic ink layer 50, etc.) during the process of attaching the can label 1 to a can container or the subsequent heating process can be prevented.

[0060] The adhesive composition can maintain high adhesive strength even after heat treatment, while also having an excellent pot life. Therefore, the adhesive composition is excellent in workability such as coating and lamination when adhering the electrostatic ink composition to the substrate. The adhesive composition contains polyol and polyisocyanate that form urethane, and an epoxy compound, and at least a part of these may be cured to form the adhesive layer. This can reduce the number of layers that constitute the can label 1 compared to the case where an adhesive layer containing only polyurethane and an epoxy coating layer are separately provided. Therefore, for example, when a laminate that becomes a can label is produced by roll-to-roll, problems such as roll meandering after aging and the occurrence of wrinkles due to blocking or the like do not occur. In addition, the aging process after coating can be reduced, and the efficiency of production can be improved.

[0061] When the electrostatic ink layer 50 and the adhesive layer 30 are in direct contact as in the can label 1, the epoxy compound and / or polyisocyanate and other components contained in the adhesive composition of the adhesive layer 30 sufficiently penetrate into the electrostatic ink layer 50. This crosslinks the electrostatic ink composition constituting the electrostatic ink layers 50 and 51, improving the strength of the electrostatic ink composition (electrostatic ink layer 50) and improving the adhesive strength between the layers. Even when the electrostatic ink layer 50 includes a region not provided on the primer layer 40 (a plain portion without the electrostatic ink layer 50 and a region not colored by electrostatic ink) as in FIG. 1, the epoxy compound is included in the adhesive layer 30, so that stickiness can be eliminated. On the other hand, when an epoxy coating layer is provided separately from the adhesive layer 30, when the electrostatic ink layer 50 includes a plain portion, the epoxy compound becomes excessive near the plain portion, and stickiness is likely to occur. In this way, even when the can label 1 includes a plain portion where the electrostatic ink layer 50 is not formed, it is possible to eliminate stickiness while adhering with high adhesive strength.

[0062] The thickness of the can label 1 may be, for example, 15 to 200 μm, or 18 to 120 μm.

[0063] The configuration of the can label 1 can be appropriately changed. For example, a primer layer 40 may be provided on each of the opposing surfaces of the first base film 10 and the second base film 20. In addition, a film layer different from the first base film 10 and the second base film 20 (for example, a resin layer such as a nylon film, or a metal layer such as an aluminum foil) may be provided between the first base film 10 and the second base film 20.

[0064] The method for producing the above-mentioned can label 1 is described below. First, the method includes a step of forming a primer layer 40 on one side of the first base film 10, a step of printing an electrostatic ink composition on the primer layer 40 to form an electrostatic ink layer 50, and a step of adhering the electrostatic ink layer 50 and one side of the second base film 20 together using an adhesive composition.

[0065] The primer layer 40 may be formed on one side of the first substrate film 10 by gravure printing. The primer layer 40 may be formed by crosslinking a resin raw material with a crosslinking agent. Crosslinking may be performed by irradiation with ultraviolet light, heat, ionizing radiation such as an electron beam, or non-ionizing radiation such as microwave radiation. The printing of the electrostatic ink composition may be performed by electrostatic printing using a digital printer.

[0066] The adhesion of the laminate of the first base film 10, the primer layer 40, and the electrostatic ink layer 50 to the second base film 20 with the adhesive composition can be performed by lamination. The lamination can be performed using any device. The epoxy compound and / or polyisocyanate contained in the adhesive composition may penetrate into the electrostatic ink composition and the primer layer 40 constituting the electrostatic ink layer 50, and may crosslink with the components contained in the electrostatic ink composition and the primer layer 40. This improves the strength of the electrostatic ink layer 50, and can obtain a can label 1 in which the interfaces of the layers are sufficiently bonded. At least a part of the adhesive composition may be cured to become a cured product during lamination. In this way, a can label 1 having the first base film 10, the primer layer 40, the electrostatic ink layer 50, the adhesive layer 30, and the second base film 20 in this order can be manufactured. In addition, as an aging treatment to promote the curing of the adhesive layer 30, a process of storing the can label 1 at a temperature condition such as 40°C for several hours to several days may be added.

[0067] The can label 1 thus produced has the configuration and properties as described in the above embodiment. The description of the can label 1 also applies to the description of the above embodiment of the production method.

[0068] [Can container with can label attached] FIG. 2 is a perspective view that typically shows a can container to which the above-mentioned can label is affixed.

[0069] The can label 1 is a label that is affixed to the surface of a can container 100. The uses of the can container 100 are not particularly limited, and examples thereof include beverage cans in which beverages are sealed, food cans in which food, oil, etc. are sealed, and industrial cans in which chemicals, industrial products, etc. are sealed.

[0070] The can container 100 includes a body 110, a bottom 120, and a can lid 200. The body 110 is a main body of the can container 100 and has a cylindrical shape. The above-mentioned can label 1 can be attached to the body 110 to display, for example, characters, symbols, patterns, etc. The bottom 120 is provided so as to close one end of the body 110. A lid 115 for attaching a can lid 200 is formed at the end of the body 110 opposite to the end where the bottom 120 is provided. The can lid 200 fixed to the lid 115 may be provided with, for example, a pull tab for opening the can container 100. The can container 100 shown in FIG. 2 is an example of a beverage can, and the shape, etc. may be changed as appropriate.

[0071] The can container 100 is formed by attaching the can label 1 to a can body. The material of the can body may be, for example, aluminum or steel, but is not limited to these. The structure of the can body is not limited to, for example, a two-piece can, a three-piece can, a bottle can, etc. The manufacturing method of the can body is also not particularly limited, and is not limited to any of a welded can, a DR (Draw & Redraw Can) can, a DI (Draw & Ironing Method) can, or a TULC (Toyo Ultimate Can).

[0072] Fig. 3 is a diagram showing an example of a layer structure of a can container 100 with a can label 1 attached. As shown in Fig. 3, the can label 1 is attached to a can body 90 of the can container 100 via an adhesive layer 80 on a body portion 110 of the can container 100. When attaching the can label 1 to the can body 90, for example, the can label 1 is attached to the can body 90 so that the main surface of the second base film 20 faces the can body 90.

[0073] The adhesive layer 80 is composed of, for example, a cured adhesive or a cured semi-cured film, etc. The adhesive used for the adhesive layer 80 may be, for example, an acrylic resin-based, polyurethane-based, polyester-based, or epoxy resin-based adhesive.

[0074] Fig. 4 shows an example of a method for manufacturing the can container 100. The example shown in Fig. 4 is an example of a method for manufacturing the can container 100 filled with the contents by dry molding. As described above, the can container 100 can be manufactured by various methods, and is not limited to the method shown in Fig. 4.

[0075] First, a metal sheet is dry-molded (step S01). In the dry-molding process, for example, a coil-shaped metal sheet is unwound and stretched (uncoiler), and then a polyester resin film such as PET is laminated on one or both sides of the metal sheet. The laminated metal sheet is then punched and drawn using a cupping press to obtain a cylindrical metal material with a bottom. The can body corresponding to the body 110 and bottom 120 is obtained by flattening the metal material.

[0076] Next, a can label is attached to the can body (step S02). The above-mentioned can label 1 is attached so as to cover at least a portion of the can body obtained in step S01. At this time, for example, an adhesive or a semi-cured film derived from an adhesive is placed between the can label 1 and the attachment surface of the can body to which the can label 1 is to be attached, and the can label 1 is attached in this state, thereby attaching the can label 1 to the can body. The attachment method can be appropriately adjusted depending on the type of adhesive used.

[0077] Next, the can body to which the can label is attached is necked (step S03). One end of the can body is shaped by necking to form the lid portion 115, which will enable the can lid 200 to be attached later by seaming. Other parts of the can body may also be processed at this stage. A known method may be used for necking. Note that the necking may be performed before the attachment of the can label (S02).

[0078] Next, the contents are filled into the can container (step S04). After the contents are filled into the can body, the can lid 200 is fixed to the lid portion 115 by, for example, seaming, to obtain the can container 100 with the inside of the can sealed.

[0079] Next, the can container is subjected to a pressurized heat treatment (step S05). For example, the pressurized heat treatment is a treatment (so-called retort treatment) in which the contents are filled and then pressurized and heated to a temperature of 100°C or higher. The heating temperature and time can be changed depending on the contents, but as an example, heating conditions of 105 to 130°C and 30 to 60 minutes can be used. Note that the pressurized heat method can be, for example, a steam method, but is not limited to this. By passing through the pressurized heat treatment, the contents are sterilized, cooked by heating, etc. are performed. After the pressurized heat treatment, the can container 100 can be subjected to various inspections and then processing such as packaging.

[0080] [Effect] As described in the above embodiment, the can label 1 according to this embodiment is formed by laminating, in this order, a first base film 10, a primer layer 40, an electrostatic ink layer 50, an adhesive layer 30, and a second base film 20. The adhesive layer 30 contains at least one of an adhesive composition containing a polyol, a polyisocyanate, and an epoxy compound, and a cured product of the adhesive composition.

[0081] According to the above-mentioned can label 1, the adhesive strength between the adhesive layer 30 and the electrostatic ink layer 50 is increased by crosslinking the epoxy compound contained in the adhesive layer 30 and the electrostatic ink composition contained in the electrostatic ink layer 50. This increases the rigidity of the can label 1, suppressing deformation of the label due to heating during the manufacture of the can container. In this way, a can label having an electrostatic ink layer produced by a digital printer and suitable for application to the surface of a can is obtained.

[0082] As described above, the manufacturing process of can containers often includes a heat treatment, such as a pressurized heat treatment performed after filling the can container with the contents. The heat treatment may cause deformation of the label attached to the can container, as described above. In contrast, in the above-mentioned can label 1, the adhesive strength between the adhesive layer 30 and the electrostatic ink layer 50 is sufficiently high due to crosslinking caused by the epoxy compound contained in the adhesive layer 30. As a result, deformation of the can label during the manufacturing of the can container is suppressed.

[0083] In addition, the electrostatic ink composition produced by a digital printer tends to have poorer heat resistance and strength than other inks. Therefore, when a can label having an electrostatic ink layer derived from an electrostatic ink composition is subjected to a heat treatment, the electrostatic ink layer may be deformed due to heat, and the appearance of the affixed can label may change. In contrast, in the above-mentioned can label 1, the strength of the electrostatic ink composition (electrostatic ink layer 50) is increased by crosslinking between the epoxy compound contained in the adhesive layer 30 and the electrostatic ink composition contained in the electrostatic ink layer 50. As a result, changes in appearance due to deformation of the electrostatic ink layer are also suppressed, making it possible to produce a can container with excellent appearance.

[0084] At least one of the first base film 10 and the second base film 20 may be a polyethylene terephthalate resin film. A can label having a polyethylene terephthalate resin film is excellent in heat resistance and water resistance, and is therefore suitable as a can label for various applications.

[0085] The polyol may include an aliphatic polyester polyol, and the epoxy compound may include one having epoxy groups at both ends. Such an adhesive layer 30 has high adhesive strength, especially in a high-temperature environment. Therefore, it is possible to sufficiently prevent gaps from being generated near the electrostatic ink layer or the electrostatic ink composition from being broken during the manufacture or use of the can container after the can label is attached.

[0086] The epoxy compound may be an embodiment containing a bifunctional alicyclic epoxy compound. Such an epoxy compound is bifunctional, which promotes crosslinking with the electrostatic ink composition to obtain a strong crosslinked composition. In addition, being alicyclic, it is possible to suppress the reaction with the polyisocyanate due to steric hindrance. Therefore, it is possible to stably cure and to provide sufficiently excellent adhesion at the interface between the adhesive layer and the electrostatic ink layer.

[0087] The polyisocyanate may be a xylylene diisocyanate derivative. Such polyisocyanate and polyol have excellent reactivity. This improves the curing property of the adhesive composition, and can suppress deformation of the label attached to the surface of the can.

[0088] Although several embodiments have been described above, the present disclosure is not limited to the above-described embodiments. For example, the position where the can label is attached is not particularly limited, and the label may be attached to, for example, the can lid, the bottom, or the like. EXAMPLES

[0089] The present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to the following examples.

[0090] Example 1 [Laminated body production] A polyethylene terephthalate film (PET film, thickness: 12 μm) was prepared as the first base film. A water-based primer resin (a resin containing polyethyleneimine, manufactured by Michelman, product name: DP050) was applied to one side of this PET film to form a primer layer. The amount of water-based polyethyleneimine applied was 0.10 to 0.18 g / m 2 The coating was applied so that the result was as follows.

[0091] A predetermined printing was performed on the surface of the primer layer using a digital printer (HP Indigo 20000 label and packaging digital printer). The ink coverage rate from one printing was 100%. As the electrostatic ink composition, an electrostatic ink composition (HP Indigo Electroink) containing a thermoplastic resin containing a copolymer of ethylene acrylic acid and ethylene methacrylic acid was used. As the colors of the electrostatic ink composition, white (W), yellow (Y), magenta (M), and cyan (C) were used as shown in Table 1. A plurality of samples with different colors and ink coverage rates of the electrostatic ink composition were prepared. The ink coverage rate of each color and the total were as shown in Table 1. As shown in Table 1, the total ink coverage rate was 200 to 500%.

[0092] An adhesive composition having a solid content concentration of 36.5% by mass was prepared by blending an aliphatic polyester polyol (A) (manufactured by Mitsui Chemicals, Inc., product name: Takelac A626) as a main agent, a polyisocyanate (B) (manufactured by Mitsui Chemicals, Inc., product name: Takenate A50), 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate as an epoxy compound (C), and ethyl acetate as a solvent. The structure of this epoxy compound is as shown in the following formula (1). The blending ratio of each component based on mass is as shown in Table 1. The column [(B) / (A)]×100 in Table 1 shows the blending amount (parts by mass) of polyisocyanate relative to 100 parts by mass of aliphatic polyester polyol. The column [(C) / (A)]×100 in Table 1 shows the blending amount (parts by mass) of epoxy compound relative to 100 parts by mass of aliphatic polyester polyol. The column "Epoxy group / isocyanate group" in Table 1 shows the molar ratio of epoxy groups contained in the epoxy compound (C) to the isocyanate groups contained in the polyisocyanate (B).

[0093] The adhesive composition prepared as described above was applied to the electrostatic ink layer formed by the electrostatic ink composition using a dry laminating device to form an adhesive layer. The application amount of the adhesive composition was 4.0 g / m 2 It was decided.

[0094] [ka]

[0095] As the second base film, a base film having an aluminum foil (manufactured by Toyo Aluminum Co., Ltd., thickness: 7 μm), a nylon film, and a non-oriented polypropylene film in this order was prepared. Using the above-mentioned dry laminating device, the second base film was attached to the adhesive layer so that the adhesive layer and the aluminum foil were in contact with each other, thereby obtaining a laminate. The curing time (aging) was 40° C. for 2 days. In this way, a laminated film (laminate) was produced. Note that the "laminate" described in the following examples has a structure that can be used as a can label described in the above embodiment.

[0096] [Measurement of adhesive strength (room temperature)] The adhesive strength of the prepared laminate was measured in accordance with JIS K 6854-1:1999. Specifically, the prepared laminate was cut into a width of 15 mm to prepare a measurement sample. After peeling between the layers at the end of the measurement sample, the peel strength between the layers of the laminate was measured using a tensile tester under conditions of an angle of 90°, a tensile speed of 300 mm / min, and room temperature. This peel strength was defined as the adhesive strength at room temperature (20°C). The measurement results are shown in Table 1.

[0097] (Examples 2 to 6) A laminate was produced and the adhesive strength was measured in the same manner as in Example 1, except that the formulation of the adhesive composition was changed as shown in Tables 1 and 2. The measurement results are shown in Tables 1 and 2.

[0098] Example 7 A two-liquid adhesive was prepared in which a first liquid consisting of an aliphatic polyester polyol (A) (manufactured by Mitsui Chemicals, Inc., product name: Takelac A626) and a second liquid consisting of a polyisocyanate (B) (manufactured by Mitsui Chemicals, Inc., product name: Takenate A50) and an epoxy compound (C) were separately contained in containers. The first liquid and the second liquid were mixed to prepare an adhesive composition having the composition shown in Table 2. A laminate was produced in the same manner as in Example 1 except that this adhesive composition was used, and the adhesive strength was measured. The measurement results are shown in Table 2.

[0099] Comparative Example 1 A laminate was produced in the same manner as in Example 1, except that the epoxy compound (C) was not added when preparing the adhesive composition, and the adhesive strength was measured. The measurement results are shown in Table 2.

[0100] Comparative Example 2 A laminate was produced in the same manner as in Example 1, except that an epoxy coating layer was provided by applying an epoxy compound of formula (1) on the electrostatic ink layer formed from the electrostatic ink composition, and the adhesive composition of Comparative Example 1 was applied to this epoxy coating layer, and the adhesive strength was measured. The amount of the epoxy coating layer applied was an amount equivalent to 0.53 parts by mass in the composition shown in Table 2. The measurement results were as shown in Table 2.

[0101] [Table 1]

[0102] [Table 2]

[0103] As shown in Tables 1 and 2, it was confirmed that the laminates of Examples 1 to 7 using an adhesive layer containing an epoxy compound had higher adhesive strength than the laminate of Comparative Example 1 using an adhesive layer not containing an epoxy compound. In Comparative Example 2, a relatively high adhesive strength was obtained, but the number of steps had to be increased in order to form an epoxy coating layer in addition to the adhesive layer. It took two days to cure (age) the epoxy coating layer, which reduced productivity.

[0104] In the laminate of Comparative Example 1, peeling occurred near the interface between the electrostatic ink layer and the primer layer. In the laminate of Comparative Example 2, the electrostatic ink layer underwent cohesive failure. On the other hand, in the laminates of Examples 1 to 7, peeling occurred at the interface between the electrostatic ink layer and the adhesive layer, and no cohesive failure of the electrostatic ink layer was observed. This suggests that the cohesive force of the electrostatic ink layer was improved. In Examples 1 to 7, the molar ratio of the isocyanate groups contained in the polyisocyanate (B) to the hydroxyl groups of the aliphatic polyester polyol (A) was within the range of 0.5 to 10.

[0105] Next, the adhesive strength after retort heat treatment and the hot water adhesive strength were measured for the laminates according to Example 5 and Comparative Example 2. For the measurements, the total ink coverage was 500% and 200%. The details of the measurement procedure are as follows.

[0106] [Measurement of adhesive strength after retort (120℃)] A three-sided bag was made using the laminate, and water was sealed in the three-sided bag. After that, a retort heat treatment (120°C x 30 minutes) was performed using a retort treatment device (manufactured by Hisaka Works, Ltd.). Here, a steam-type pressurized heating method was used for the retort heat treatment. After the retort heat treatment, a laminate sample was taken by cutting into a width of 15 mm, and the interlayer strength between the ink layer and the layer in contact with the ink layer was measured. The measured peel strength is shown in the "120°C" column in Table 3. Table 3 also shows the adhesive strength at room temperature before the heat treatment.

[0107] [Measurement of adhesive strength after retort (130℃)] A three-sided bag was made using the laminate, and water was sealed in the three-sided bag. Then, a retort heat treatment (130°C x 30 minutes) was performed using a retort treatment device (manufactured by Hisaka Works, Ltd.). After the retort heat treatment, a laminate sample was taken by cutting it into a width of 15 mm, and the interlayer strength between the electrostatic ink layer and the layer in contact with the electrostatic ink layer was measured. The measured peel strength is shown in the "130°C" column in Table 3.

[0108] [Measurement of hot water adhesive strength] The laminate was cut to a width of 15 mm, and the layers at the edge were peeled off, and the laminate was immersed in hot water at 90° C. and the peel strength was measured using a tensile tester. That is, the peel angle was free and the tensile speed was 300 mm / min. This peel strength is shown in Table 3 as the hot water adhesion strength.

[0109] [Table 3]

[0110] As shown in Table 3, it was confirmed that Example 5 had better hot water adhesive strength than Comparative Example 2.

[0111] Example 8 [Adhesive composition and preparation of laminate] A polyethylene terephthalate film (PET film, thickness: 12 μm) was prepared as the first base film. A water-based primer resin (a resin containing polyethyleneimine, manufactured by Michelman, product name: DP050) was applied to one side of this PET film to form a primer layer. The amount of water-based polyethyleneimine applied was 0.10 to 0.18 g / m 2 The coating was applied so that the result was as follows.

[0112] A predetermined printing was performed on the surface of the primer layer using a printer manufactured by HP Indigo (product name: Indigo 2000). As the electrostatic ink composition, an electrostatic ink composition (HP Indigo Electroink) containing a thermoplastic resin containing a copolymer of ethylene acrylic acid and ethylene methacrylic acid was used. As the colors of the electrostatic ink composition, white (W), yellow (Y), magenta (M), and cyan (C) were used. As the ink coverage, one with W200% and one with C100%+M100%+Y100%+W200% were prepared. In Table 4, the former is referred to as "ink coverage (1)" and the latter is referred to as "ink coverage (2)". In this way, two types of samples with different ink coverage of the electrostatic ink composition were prepared.

[0113] The same adhesive composition as in Example 5 was prepared. The adhesive composition prepared as described above was applied by a hand laminator onto an electrostatic ink layer formed by the electrostatic ink composition to form an adhesive layer. The application amount of the adhesive composition was 4.0 g / m 2 It was decided.

[0114] A base film having a nylon film and a non-oriented polypropylene film in this order was prepared as the second base film. The base film was attached to the adhesive layer so that the adhesive layer and the nylon film were in contact with each other to obtain a laminate. The curing time (aging) was 40°C for 2 days.

[0115] The adhesive strength (room temperature) and hot adhesive strength (120°C) of the laminate thus obtained were measured. The method for measuring adhesive strength (room temperature) was the same as that described above. The hot adhesive strength (120°C) was measured at a temperature of 120°C, similar to the adhesive strength (room temperature), by measuring the adhesive strength of the laminate produced in accordance with JIS K 6854-1:1999. The measurement results are shown in Table 4.

[0116] (Examples 9 to 12) A laminate was produced in the same manner as in Example 8, except that the amount of polyisocyanate (B) used in preparing the adhesive composition was changed as shown in Table 4. The produced laminate was evaluated in the same manner as in Example 8. The evaluation results are shown in Table 4.

[0117] Comparative Example 3 A laminate was produced in the same manner as in Comparative Example 1, except that lamination above the electrostatic ink layer formed from the electrostatic ink composition was performed using a hand laminator machine instead of using a dry laminator. The color and ink coverage of the electrostatic ink composition were as shown in Table 4. The produced laminate was evaluated in the same manner as in Example 8. The evaluation results were as shown in Table 4.

[0118] [Table 4]

[0119] As shown in Table 4, it was confirmed that in each Example, high adhesive strength was obtained even under high-temperature hot water treatment conditions. It was also confirmed that the hot adhesive strength (120°C) could be sufficiently increased by adjusting the blending ratio of polyisocyanate (B) to aliphatic polyester polyol (A). This indicates that a sufficiently high adhesive strength can be maintained even when pressure and heat treatment is performed in a state where the label is attached to a can container, such as a can label. On the other hand, it was confirmed that in Comparative Example 3, which does not use epoxy compound (C), the adhesive strength is significantly reduced when exposed to high-temperature hot water treatment conditions. In Examples 8 to 12, the molar ratio of isocyanate groups contained in polyisocyanate (B) to hydroxyl groups contained in aliphatic polyester polyol (A) was within the range of 0.5 to 10.

[0120] (Examples 13 to 17) An adhesive composition was prepared by blending an aliphatic polyester polyol (A1) (Takelac A525, manufactured by Mitsui Chemicals, Inc.), a polyisocyanate (B1) (Takenate A52, manufactured by Mitsui Chemicals, Inc.), and 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate as the epoxy compound (C). The blending ratios were as shown in Table 5. Except for using such an adhesive composition, laminates were produced and evaluated in the same manner as in Examples 8 to 12. The evaluation results were as shown in Table 5.

[0121] Comparative Example 4 An adhesive composition was prepared by blending an aliphatic polyester polyol (A1) (Takelac A525, manufactured by Mitsui Chemicals, Inc.) as a polyol, and a polyisocyanate (B1) (Takenate A52, manufactured by Mitsui Chemicals, Inc.). The blending ratio was as shown in Table 5. A laminate was produced and evaluated in the same manner as in Comparative Example 3, except that such an adhesive composition was used. The evaluation results were as shown in Table 5.

[0122] [Table 5]

[0123] As shown in Table 5, it was confirmed that high adhesive strength was obtained in each Example even when the combination of aliphatic polyester polyol and polyisocyanate was changed. It was also confirmed that the hot adhesive strength (120°C) could be sufficiently increased by adjusting the blending ratio of polyisocyanate (B1) to aliphatic polyester polyol (A1). On the other hand, it was confirmed that in Comparative Example 4, which did not use epoxy compound (C), the adhesive strength was significantly reduced when exposed to high-temperature hot water treatment conditions. In Examples 13 to 17, the molar ratio of isocyanate groups contained in polyisocyanate (B1) to hydroxyl groups contained in aliphatic polyester polyol (A1) was within the range of 0.5 to 10. [Industrial Applicability]

[0124] According to the present disclosure, it is possible to provide a can label that has an electrostatic ink layer produced by a digital printer and is suitable for attachment to the surface of a can. [Explanation of symbols]

[0125] Reference Signs List 1: can label, 10: first base film, 20: second base film, 30: adhesive layer, 40: primer layer, 50: electrostatic ink layer, 80: adhesive layer, 90: can body, 100: can container.

Claims

1. A can label that is laminated to a can body, A first substrate, a primer layer, an electrostatic ink layer, an adhesive layer, and a second substrate are laminated in this order; The adhesive layer comprises at least one of an adhesive composition containing a polyol, a polyisocyanate and an epoxy compound, and a cured product of the adhesive composition.

2. The can label according to claim 1 , wherein at least one of the first substrate and the second substrate is a polyethylene terephthalate resin film.

3. 3. The can label according to claim 1, wherein the polyol includes an aliphatic polyester polyol, and the epoxy compound includes one having epoxy groups at both ends.

4. The can label according to any one of claims 1 to 3, wherein the epoxy compound comprises a difunctional alicyclic epoxy compound.

5. The can label according to any one of claims 1 to 4, wherein the polyisocyanate comprises a xylylene diisocyanate derivative.

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