Adhesive labels

Abstract

To provide an adhesive label that can effectively prevent tampering even when the label is applied to the substrate by hand. [Solution] An adhesive label having a base material, a display portion that can be peeled off from the base material, and an adhesive layer, wherein the loop tack value to polyethylene is 1.5 N / 25 mm or less, and the adhesive force to stainless steel is 10 N / 25 mm or more.

Description

Technical Field

[0001] The present invention relates to an adhesive label.< /

Background Art

[0002] The tamper-evident adhesive label prevents the contents from being modified or replaced due to improper peeling of the label or tape sealing the lid or packaging of the product.< /

[0003] As such a tamper-evident adhesive label, there is a type in which when the adhesive label is peeled off from the adherend, a peeling mark remains on the adherend.< /

[0004] For example, in the adhesive label described in Patent Document 1, a transparent ink layer is provided on the surface of a transparent plastic film, and further an adhesive layer having specific viscoelastic properties is provided, so that when the adhesive label is peeled off, the transparent ink layer and the adhesive layer having a display function remain on the adherend.< /

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Adhesive labels are often attached to an adherend using a labeling device (labeler), but on a curved surface or the like where it is difficult to use a labeling device, a person may attach it by hand. Also, tamper-evident labels may be used at the storefront of a retail store or the like, and in many cases, a store clerk attaches the label to the package by hand.< /

[0007] When applying an adhesive label to a substrate by hand, the hand inevitably comes into contact with the adhesive layer of the label. As described in Patent Document 1, in the case of a tamper-proof label having an ink layer with a tamper-evident display function, if the hand sticks to the adhesive layer, the display portion may lift up before the label is applied to the substrate, rendering the label unusable.

[0008] Therefore, the present invention aims to provide an adhesive label that can appropriately exhibit tamper-proof effects even when the adhesive label is applied to the substrate by hand. [Means for solving the problem]

[0009] The present invention relates to an adhesive label having a base material, a display portion that can be peeled off from the base material, and an adhesive layer, wherein the loop tack value for polyethylene is 1.5 N / 25 mm or less, and the adhesive strength for stainless steel is 10 N / 25 mm or more. [Effects of the Invention]

[0010] According to the present invention, even when an adhesive label is applied to a substrate by hand, it is possible to prevent the tamper-evident label from becoming unusable. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing one embodiment of an adhesive label. [Figure 2] Figure 1 is a schematic cross-sectional view of the process of peeling the adhesive label from the object it is attached to. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0013] In this specification, the range "X~Y" means "X or greater and Y or less". Unless otherwise specified, operations and physical properties are measured under room temperature (20~25°C) / relative humidity 45~55%RH.

[0014] Figure 1 is a schematic cross-sectional view showing one embodiment of an adhesive label. In Figure 1, the adhesive label 10 has a base material 11, an adhesive layer 12, and a release liner 13 in that order. The adhesive layer 12 is positioned adjacent to the base material 11. The display section 14 is partially positioned on the base material 11. In the embodiment of Figure 1, the surface of the base material 11 is roughened and has a finely uneven surface (pearlescent surface). When the adhesive layer 12 and the display section 14 provided on the roughened surface 15 of the base material 11 (hereinafter, this surface is also referred to as the "roughened surface") are in close contact with the base material 11, for example, when the adhesive label 10 is stored or when the adhesive label 10 is attached to an object 20, the fine irregularities of the roughened surface 15 are filled in by the adhesive layer 12 and the display section 14.

[0015] Figure 2 is a schematic cross-sectional view showing the process when the release liner 13 is removed from the adhesive label in Figure 1, and the adhesive label is applied to the substrate 20 before attempting to peel it off. When attempting to peel the adhesive label 10 applied to the substrate 20 off the substrate 20, external forces are applied to the interface between the base material 11 and the adhesive layer 12, and the interface between the base material 11 and the display portion 14. The adhesive layer 12 adheres well to the base material 11, so the adhesive layer 12 does not peel off from the base material 11. However, the display portion 14 has low adhesion to the surface of the base material 11, so the display portion 14 peels off from the surface of the base material 11. In addition to the display portion 14 peeling off from the base material 11, the portion of the adhesive layer 12 that is in contact with the display portion 14 is separated from the rest of the adhesive layer 12, and parts of the display portion 14 and the adhesive layer 12 remain on the surface of the substrate 20. In this manner, when peeling occurs, the display portion detaches from the adhesive label, causing light transmitted to the substrate 11 to undergo diffuse reflection at the detached portion of the substrate 11, resulting in an opaque state. On the other hand, the parts other than the display portion remain transparent. As a result, the characters formed by the display portion become visible, and the tamper-evident function is activated. Furthermore, in this configuration, even if one attempts to put the adhesive label back on, gaps are created in the uneven surface of the textured material, making it easy to discover that the package has been opened.

[0016] Another example of a substrate having a roughened surface to provide an open indication function is an adhesive layer in which a transparent release agent layer (this release agent layer corresponds to the indication part) is formed on the substrate 11, a vapor-deposited film is formed on and over the entire surface of the release agent layer, and an adhesive is laminated on the vapor-deposited film.

[0017] In the adhesive labels of FIGS. 1 and 2, when the adhesive of the adhesive layer sticks to the hand, the display portion may peel off from the base material and the display function may be exerted unintentionally before being attached to the adherend. According to the adhesive label of the present invention, even when the adhesive label is attached to the adherend by hand, since the loop tack value with respect to polyethylene is 1.5 N / 25 mm or less, the adhesive layer of the adhesive label is difficult to stick to the hand, so that unintended display can be suppressed. On the other hand, since the adhesive force with respect to stainless steel is 10 N / 25 mm or more, the adhesiveness to the adherend is high, and thus the forgery prevention function can be appropriately exerted.

[0018] The concept of "label" includes those referred to as film, sheet, tape, etc.

[0019] In this specification, "(meth)acrylate" refers to "acrylate and / or methacrylate", and "(meth)acrylic acid" refers to "acrylic acid and / or methacrylic acid".

[0020] Hereinafter, each component will be described.

[0021] <Base material> The base material is not particularly limited, and examples thereof include paper base materials such as kraft paper and Japanese paper, resin base materials, synthetic paper, and the like. Among them, from the viewpoint of durability, the base material is preferably a resin base material.

[0022] Examples of the resin constituting the resin substrate include olefin resins having α-olefins such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), etc. as monomer components; polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), etc.; polyvinyl chloride (PVC); vinyl acetate resins; polycarbonate (PC); acrylic resins; polyurethane, etc. These resins may be used alone or in combination of two or more. Among these, from the viewpoints of weather resistance and flexibility, the resin constituting the resin substrate is preferably polyvinyl chloride, acrylic resin, or polyurethane.

[0023] The thickness of the substrate is appropriately selected depending on the type of the substrate used, but is preferably 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm.

[0024] The substrate may be transparent or opaque. In one form, the substrate is transparent.

[0025] Also, the substrate may be colored or colorless. In the case of being colored, any colorant can be used. The production of the colored substrate can be carried out by blending a colorant with the raw material resin, melt-kneading, and molding into a film, or by the cast film method of casting on a process film, drying, and molding.

[0026] The base material may contain various additives such as UV absorbers, plasticizers, heat stabilizers, dispersion solvents, and dilution dispersion solvents. Examples of UV absorbers include salicylic acid-based UV absorbers, benzophenone-based UV absorbers, and triazole-based UV absorbers. Examples of plasticizers include phosphate-based plasticizers, phthalate-based plasticizers, adipic acid-based plasticizers, and polyester-based plasticizers. Examples of heat stabilizers include lead salt-based heat stabilizers, metal soap-based heat stabilizers, and organotin compound-based heat stabilizers. Examples of dispersion solvents include ketones such as diisobutyl ketone and methyl isobutyl ketone, esters such as butyl acetate, and glycol ethers such as butyl cellosolve. Examples of dilution dispersion solvents include paraffinic hydrocarbons, naphthenic hydrocarbons, aromatic hydrocarbons, and terpenes.

[0027] The surface of the substrate (especially the side with the adhesive layer) may be roughened. The roughened surface creates fine irregularities on the surface, which makes it easier for the label to peel off the substrate when attempting to remove the adherend from the adhesive label. The roughening treatment is not particularly limited as long as it can create fine irregularities that cause diffuse reflection of light, and examples include sandblasting, shot blasting, grit blasting, bead blasting, and embossing. On the other hand, the surface of the substrate may be a smooth surface (not roughened).

[0028] Furthermore, the surface of the substrate facing the adhesive layer (i.e., the roughened surface) may be subjected to a surface treatment, such as a primer treatment, to improve the adhesion between the adhesive layer and the substrate.

[0029] The thickness of the substrate is not particularly limited, but may be, for example, 10-300 μm, 20-200 μm, or 25-100 μm.

[0030] <Display section> The display portion delaminates at the interface with the substrate when the adhesive label is peeled off from the adherend. The display portion is partially provided on the substrate between the substrate and the adhesive layer, and the adhesion between the substrate and the display portion is lower than the adhesion between the substrate and the adhesive layer, making it prone to delamination at the interface with the substrate.

[0031] The patterns displayed are not particularly limited and can include letters, numbers, symbols, and shapes. For example, patterns can be letters or pictures indicating peeling, such as "VOID," "Opened," "Invalid," or "×," or graphic information such as dots or stripes, when viewed from above.

[0032] For the display area, it is preferable that the pattern is latent before the adhesive label is peeled off, and therefore, especially when the substrate is transparent, it is preferable that the display area be transparent. Here, transparency means that the haze is preferably 25% or less (the lower limit is, for example, 0%). The haze is measured using a haze meter (NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136:2000 and the value adopted is used.

[0033] Materials used to form the patterns constituting the display area include cellulose-based resins such as methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose; acrylic resins such as poly(meth)acrylate and polymethyl(meth)acrylate; urethane resins; acrylic urethane resins; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polyarylate; epoxy resins; polyvinyl alcohol resins; and vinyl chloride resins. They may also contain release agents such as fluorine-based resins and silicones. Among these, cellulose-based resins and acrylic resins are preferred as materials for forming the patterns constituting the display area.

[0034] In addition to the above-mentioned materials, the material used to form the display area may also contain components such as inorganic pigments like silica, defoamers, and leveling agents.

[0035] The material constituting the display section is preferably made of a resin having a lower adhesive strength than the adhesive strength of the adhesive layer, and more preferably made of a non-adhesive resin.

[0036] The method for forming the display portion is not particularly limited, and for example, it can be formed on a substrate using a general printing method, such as gravure printing, screen printing, offset printing, or flexographic printing, using an ink containing the above-mentioned resin material and solvent.

[0037] Furthermore, as mentioned above, if the display area corresponds to the release agent layer, the display area includes a release agent. Examples of this release agent include silicone resin, wax, long-chain alkyl group-containing resin, and perfluoro resin. The release agent can be applied by printing methods such as letterpress printing and screen printing.

[0038] The thickness of the display area does not need to be greater than the thickness of the adhesive layer, for example, 0.01 to 20 μm, 0.05 to 10 μm, 0.1 to 8 μm, or 0.1 to 6 μm.

[0039] After forming the display portion, a colored layer or metal vapor deposition layer may be provided over the entire substrate surface of the formed portion. Providing such a colored layer or metal vapor deposition layer improves the visibility of the display portion when it peels off from the substrate. In this case, the colored layer or metal vapor deposition layer is present on the portion where the display portion is formed, and on the substrate where the display portion is not formed. Examples of metals or metal compounds used to form the metal vapor deposition layer include aluminum, chromium, nickel, gold, platinum, silver, tin, copper, palladium, titanium oxide, and titanium nitride. The thickness of the colored layer or metal vapor deposition layer is not particularly limited, but is typically 0.03 to 0.1 μm.

[0040] <Adhesive layer> The adhesive used in the adhesive layer is not particularly limited as long as it satisfies the above requirements. For example, the adhesive layer is formed from an adhesive composition containing a urethane prepolymer and a crosslinking agent, wherein the urethane prepolymer is formed from a mixture containing polyisocyanate, a polyol containing lactic acid-derived structural units (hereinafter also referred to as lactic acid polyol), and any other structural units. Using such an adhesive composition, and especially using lactic acid-derived structural units, makes it easier to control the loop tack value for polyethylene to a low level. This is thought to be due to the polar properties of lactic acid.

[0041] The monomers constituting the lactic acid polyol include lactic acid and a hydroxy compound with a valentity of 2 or higher, and more preferably, a hydroxycarboxylic acid other than lactic acid, from the viewpoint of improving adhesion to the adherend.

[0042] The lactic acid is not particularly limited, but examples include L-lactide, D-lactide, DL-lactide, mesolactide, L-lactic acid, D-lactic acid, and DL-lactic acid. Among these, lactide (L-lactide, D-lactide, DL-lactide, mesolactide) is preferred due to its polymerization efficiency and solubility in solvents. By copolymerizing these lactic acid units, a polyester with desired properties can be obtained. One or more types of lactic acid units can be used.

[0043] The lactic acid content relative to the monomers constituting the lactic acid polyol is preferably 5 to 95% by mass, and more preferably 15 to 65% by mass, considering both the effects of adhesion to the adherend and resistance to sticking to the hands.

[0044] Examples of hydroxy compounds with a valency of 2 or higher include linear aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-pentanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 3-methyl-1,5-pentanediol, and 1,6-hexamethylenediol; branched aliphatic diols such as 1,3-butanediol, 3-methylpentane-1,5-diol, 2-ethylhexane-1,6-diol, 2-methyl-1,3-pentanediol, neopentyl glycol, and 2-methyl-1,8-octanediol; and 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2,2'-bis(4-hydroxycyclohexanediol). Examples of polyols include alicyclic diols such as xyl)propane, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; aromatic diols such as 1,4-benzenedimethanol and bisphenol A; polyfunctional polyols such as trimethylolpropane and pentaerythritol; polyester polyols, polyether polyols (for example, aliphatic polyester polyols are obtained by polycondensation of the above-mentioned aliphatic diols with aliphatic polybasic acids (oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, maleic acid, fumaric acid, etc.)); polyols such as polybutadiene polyols and castor oil polyols; and dipropylene glycol, polyethylene glycol, and polypropylene glycol. These may be used individually or in combination of two or more. Among these, it is preferable to include linear aliphatic diols and / or polyester polyols as divalent or higher hydroxy compounds, as this reduces the likelihood of the adhesive sticking to the hands.

[0045] Examples of hydroxycarboxylic acids other than lactic acid include glycolic acid, tartonic acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, malic acid, tartaric acid, and 6-hydroxycaproic acid; and cyclic esters such as α-acetolactone, β-propiolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone. These may be used individually or in combination of two or more.

[0046] From the viewpoint of the effects of the present invention, the number-average molecular weight of the lactic acid polyol is preferably 1,000 to 10,000.

[0047] Lactic acid polyols can be produced by conventionally known manufacturing methods (bulk polymerization, solution polymerization). In this process, the solvents and catalysts used in the production of urethane prepolymers, as described later, can be used.

[0048] Examples of polyisocyanates used as raw materials for urethane prepolymers include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Polyisocyanates may be used individually or in combination of two or more types.

[0049] Examples of aromatic polyisocyanates include 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 2,4-toleylene diisocyanate (2,4-TDI), 2,6-toleylene diisocyanate (2,6-TDI), 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4',4"-triphenylmethane triisocyanate, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate.

[0050] Examples of aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0051] Examples of alicyclic polyisocyanates include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI: isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanate methyl)cyclohexane, and 1,4-bis(isocyanate methyl)cyclohexane.

[0052] These polyisocyanates may also be trimethylolpropane adduct-type modified compounds of the above-mentioned compounds, biuret-type modified compounds obtained by reaction with water, or isocyanurate-type modified compounds containing an isocyanurate ring.

[0053] Among these polyisocyanate compounds, from the viewpoint of obtaining a urethane polymer with excellent adhesive properties to the adherend, one or more selected from 4,4'-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), hexamethylene diisocyanate (HMDI), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) and their modified forms are preferred, and from the viewpoint of weather resistance, one or more selected from HMDI, IPDI and their modified forms are more preferred.

[0054] The amount of polyisocyanate added to the lactic acid polyol is preferably 1 to 30% by mass. Furthermore, the molar ratio of NCO groups in the polyisocyanate to hydroxyl groups in the lactic acid polyol, NCO / OH, is preferably less than 1, and may be, for example, 0.4 to 0.99.

[0055] Other constituent units that impart cohesive force may include polyols such as polyester polyols and polycarbonate polyols, as well as polyols such as amine-initiated polyols, sugar-initiated polyols with 4 or more carbon atoms, amino polyols, and polyamine polyols. A polyol is a compound having two or more hydroxyl groups, preferably a compound having three or more hydroxyl groups. By including a polyol, a branched skeleton can be generated in the urethane prepolymer, thereby increasing its cohesive force.

[0056] The number-average molecular weight of the polyol is preferably 100 to 5,000, and more preferably 500 to 3,000. Having a number-average molecular weight within this range ensures sufficient crosslinking density upon reaction with the isocyanate crosslinking agent, thereby improving retention.

[0057] The reaction between lactic acid polyol and polyisocyanate may be carried out in the presence or absence of a solvent. Furthermore, the reaction between lactic acid polyol and polyisocyanate may be carried out in the presence or absence of a catalyst.

[0058] When using a solvent, there are no particular limitations on the solvents that can be used, but examples include water, benzene, toluene, xylene, mesitylene, chlorobenzene, o-dichlorobenzene, methylene chloride, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, trichloroethylene, tetrachloroethane, tetrachloroethylene, tetrahydrofuran, 1,4-dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidozolidinone, dimethyl sulfoxide, sulfolane, etc. Furthermore, there are no particular limitations on the catalysts, but examples include dibutyltin dilaurate, dioctyltin dilaurate, tetramethylbutanediamine, 1,4-diaza[2,2,2]bicyclooctane, tin octanoate, 4-methylmorpholine, triethylamine, etc.

[0059] The reaction temperature is preferably 60 to 250°C in the absence of a solvent, as the reaction is usually carried out under molten conditions. In the presence of a solvent, the reaction temperature is preferably in the range of room temperature to the boiling point of the solvent.

[0060] From the viewpoint of the effects of the present invention, the weight-average molecular weight of the urethane prepolymer is preferably 10,000 to 200,000, and more preferably 30,000 to 180,000.

[0061] The crosslinking agent used in the adhesive composition is not particularly limited, but isocyanate-based crosslinking agents are preferred.

[0062] Examples of isocyanate crosslinking agents include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl capeate, lysine diisocyanate, lysine ester triisocyanate, and 1,6,11-undecane triisocyanate. Examples include diisocyanate compounds such as aliphatic diisocyanates like nate, 1,3,6-hexamethylene triisocyanate, trimethylhexamethylene diisocyanate, and decamethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate and xylene diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate; as well as isocyanate derivatives such as adducts of diisocyanate compounds with polyol compounds such as trimethylolpropane, biuret and isocyanurate forms of diisocyanate compounds, and difunctional forms of diisocyanate compounds.

[0063] The amount of crosslinking agent added per 100 parts by mass of urethane prepolymer is, for example, 0.1 to 15 parts by mass, or 0.5 to 10 parts by mass, and from the viewpoint of the effects of the present invention, it is preferably 2 to 7 parts by mass, and more preferably 2.5 to 5.5 parts by mass.

[0064] In addition to the above components, the adhesive composition may also contain other additives such as colorants (dyes, pigments, etc.), antioxidants (anilide-based, phenol-based, etc.), UV absorbers (benzophenone-based, benzotriazole-based, triazine-based, etc.), light stabilizers, tackifiers (rosin, rosin esters, etc.), fillers (smectite, kaolin, talc, mica, calcium carbonate, titanium dioxide, etc.), flame retardants, hydrolysis inhibitors, heat stabilizers, lubricants, antistatic agents, plasticizers, curing accelerators, reaction inhibitors, and other additives. These other additives may be used individually or in combination of two or more.

[0065] The thickness of the adhesive layer is preferably 1 to 200 μm, and more preferably 10 to 100 μm.

[0066] The adhesive layer can be formed on one side of the substrate on which the display area is provided.

[0067] More specifically, an adhesive layer is formed on the areas of the substrate where no display portion is formed, and on top of the display portion.

[0068] The adhesive layer may be formed by applying a coating liquid containing an adhesive layer composition for forming the adhesive layer to the side of the substrate where the display portion is formed (direct formation method), or by applying the above coating liquid to the release surface of a release liner to form the adhesive layer, and then transferring the composition containing the adhesive onto the substrate by bonding this adhesive layer to the side of the substrate where the display portion is formed (transfer method). By employing the transfer method, an adhesive label in which the adhesive layer is protected by a release liner can be suitably obtained.

[0069] <Removable Liner> A release liner is provided to protect the adhesive layer and is peeled off from the adhesive label when it is applied to the substrate. In this case, a release agent is usually provided on the adhesive layer side of the release liner to facilitate the peeling of the release liner from the adhesive layer.

[0070] The material of the release substrate constituting the release liner is not particularly limited, and known materials can be used. Examples include resin materials and paper. Examples of resin materials include polyester and polyolefin. Examples of paper include kraft paper, fine paper, glassine paper, and laminated paper laminated with a thermoplastic resin such as polyethylene.

[0071] The thickness of the release liner is preferably 25 μm or more and 100 μm or less.

[0072] Examples of release agents that make up the release agent layer include silicone-based release agents, long-chain alkyl-based release agents, fluorine-based release agents, and rubber-based release agents. Among these, silicone-based release agents are preferred. The thickness of the release agent layer is usually about 0.01 to 5 μm.

[0073] <Adhesive strength, loop tack value> In this invention, the adhesive strength of the adhesive label to stainless steel is 10 N / 25 mm or more. This strong adhesive strength ensures that when the adhesive label is peeled off, the adhesive layer remains on the adherend, thus effectively preventing tampering. Here, the adhesive strength to stainless steel is measured by attaching the adhesive layer surface to the stainless steel, and can therefore also be called the adhesive strength of the adhesive layer itself.

[0074] The adhesive strength of the adhesive label to stainless steel is preferably 10-30 N / 25 mm, and more preferably 15-25 N / 25 mm.

[0075] The adhesive strength to stainless steel can be measured by the method described in the following examples.

[0076] The adhesive strength to stainless steel can be adjusted by the type of adhesive, the type and amount of crosslinking agent used in the adhesive composition. As the amount of crosslinking agent increases, the adhesive strength to stainless steel tends to decrease.

[0077] In this invention, the loop tack value of the adhesive label against polyethylene is 1.5 N / 25 mm or less. A loop tack value of 1.5 N / 25 mm or less reduces the adhesion of the adhesive layer to the skin, thus preventing the tamper-proof function of the adhesive label from being compromised even when the label is applied to the substrate by hand. Polyethylene has a polarity similar to that of human hands, and the loop tack value against polyethylene can serve as an indicator of how easily a material sticks to hands. Here, the loop tack value against polyethylene is measured by applying the adhesive layer surface to polyethylene, and can therefore also be considered the tack of the adhesive layer.

[0078] The loop tack value of the adhesive label against polyethylene is preferably 0.1 to 1.5 N / 25 mm, and more preferably 0.2 to 1 N / 25 mm.

[0079] The loop tack value for polyethylene can be measured by the method described in the following examples. The loop tack value for polyethylene can be adjusted by the type of adhesive used in the adhesive composition (for example, using a urethane prepolymer that uses lactic acid-derived constituent units as polyols), the type and amount of crosslinking agent, etc. If the amount of crosslinking agent is small, the loop tack value for polyethylene tends to increase.

[0080] <Application> The adhesive label of the present invention is a tamper-proof adhesive label. Specifically, tamper-proof applications include: preventing alteration of the contents of labels on automobile parts, electrical and electronic components, precision machine parts, etc.; preventing improper packaging or opening of goods during consignment or packaging of goods; sealing labels to guarantee the virginity of contents such as pharmaceuticals, cosmetics, and food products; preventing improper opening and closing of various openings on vehicles such as passenger cars, aircraft, trains, and ships (for example, preventing improper foreign matter from entering loading docks or fuel tanks); preventing peeling or alteration of identification or certification labels such as passports and product certifications; and security measures such as preventing improper intrusion into vehicles such as passenger cars, aircraft, trains, and ships, and improper intrusion into various buildings.

[0081] Specifically, one application is as a seal used to seal bags or boxes containing duty-free goods sold in duty-free shops, in order to prevent their use within Japan.

[0082] The present invention also encompasses the following aspects.

[0083] (1) An adhesive label having a base material, a display portion that can be peeled off from the base material, and an adhesive layer, wherein the loop tack value to polyethylene is 1.5 N / 25 mm or less, and the adhesive strength to stainless steel is 10 N / 25 mm or more.

[0084] (2) The adhesive label according to (1), wherein the adhesive layer is formed from an adhesive composition comprising a urethane prepolymer and a crosslinking agent, and the urethane prepolymer is formed from a mixture comprising a polyisocyanate and a polyol containing structural units derived from lactic acid.

[0085] (3) The adhesive label according to (2), wherein the crosslinking agent is an isocyanate compound.

[0086] (4) The adhesive label according to any one of (1) to (3), wherein the display portion is transparent.

[0087] (5) The adhesive label according to any one of (1) to (4), wherein the substrate is transparent. [Examples]

[0088] Next, we will describe the examples. In the examples, the units "parts" or "%" may be used, but unless otherwise specified, they represent "parts by mass" or "mass%". Also, unless otherwise specified, each operation is carried out at room temperature (25°C).

[0089] <Measurement of Loop Tack Value> An adhesive label was cut into a tape-like strip 25 mm wide and 300 mm long (including 25 mm gripping portions at each end) to form a test specimen. Next, the release film was peeled off the test specimen, and with the measurement surface facing outwards, the base material surfaces of the adhesive labels at both ends were aligned to form a loop, which was then attached to the upper grips of the tensile testing machine by clamping the gripping portions at both ends. Meanwhile, a polyethylene plate (Kobe Polyethylene Sheet EL-N-AN, manufactured by Resonaq Co., Ltd.) was horizontally attached to the lower grips of the tensile testing machine. The upper grips were lowered to the polyethylene plate at a speed of 300 mm / min. The test specimen was attached so that the contact area between the measurement surface of the test specimen and the polyethylene plate was 25 × 50 mm. After holding it in that position for 15 seconds, it was peeled off at a speed of 300 mm / min, and the maximum tensile load value obtained under environmental conditions of 23°C was taken as the test value. Measurements were taken 10 times, changing the measurement surface of the test specimen, and the minimum value among the test results was taken as the measured value of the loop tack (N / 25mm).

[0090] <Measurement of adhesive strength to stainless steel> Similarly to the above, the adhesive label was cut to make a test piece, the adhesive layer was attached to a SUS plate (SUS304), and after 24 hours, the tensile strength was measured in the 180° direction at a test speed of 300 mm / min using a tensile testing machine in accordance with JIS Z0237:2022.

[0091] (Manufacturing of adhesive label 1) 1. Formation of the display unit One side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name "Lumirror®") with a textured finish on one side was given a textured finish by sand-matting (thickness: 38 μm). On the textured side of this film, the word "VOID" was formed in a letter-like display area using gravure printing with a resin solution containing an acrylic resin (an acrylic polymer whose main monomer is methyl methacrylate), so that the dried thickness would be 5 μm. Each letter was 3 mm x 2.5 mm in size, and the display area covered 38% of the total film surface area.

[0092] 2. Making adhesive labels A tack composition was prepared by mixing 100 parts by mass of a urethane prepolymer (formed from a mixture containing a polyol with lactic acid-derived structural units and an isocyanate compound) with 6 parts by mass of an isocyanate crosslinking agent.

[0093] After applying the adhesive composition to the display surface of the polyethylene terephthalate film with a display area obtained above, a release film was laminated and dried to obtain an adhesive label 1 with a thickness of 20 μm.

[0094] The loop tack value and adhesive strength to stainless steel of adhesive label 1 were 0.1 N / 25 mm and 10 N / 25 mm, respectively.

[0095] (Manufacturing of adhesive label 2) Adhesive label 2 was obtained in the same manner as adhesive label 1, except that the amount of isocyanate-based crosslinking agent added was changed to 3 parts by mass.

[0096] The loop tack value and adhesive strength to stainless steel of adhesive label 2 were 0.5 N / 25 mm and 15 N / 25 mm, respectively.

[0097] (Manufacturing of adhesive label 3) Adhesive label 2 was obtained in the same manner as adhesive label 1, except that the amount of isocyanate-based crosslinking agent added was changed to 0.5 parts by mass.

[0098] The loop tack value and adhesive strength to stainless steel of adhesive label 3 were 2N / 25mm and 20N / 25mm, respectively.

[0099] (Manufacturing of adhesive labels 4) Adhesive label 2 was obtained in the same manner as adhesive label 1, except that the amount of isocyanate-based crosslinking agent added was changed to 10 parts by mass.

[0100] The loop tack value and adhesive strength to stainless steel of adhesive label 4 were 0.1 N / 25 mm and 0.5 N / 25 mm, respectively.

[0101] (Manufacturing of adhesive labels 5) An adhesive label 5 was obtained in the same manner as in Example 1, except that an adhesive composition was prepared by mixing 100 parts by mass of an acrylic adhesive and 3.5 parts by mass of an isocyanate crosslinking agent, and this adhesive composition was used.

[0102] (Evaluation method 1: Evaluation of missing characters) Press your index finger against the adhesive layer of the resulting adhesive label for 30 seconds, 3 cm in length. 2 (Contact Area) After making contact with the adhesive layer and then separating the index finger from the adhesive layer, the index finger was observed. This was repeated 5 times, and scores were assigned based on the following evaluations, and the average value was calculated.

[0103] 3: The display is not visible to the index finger. 2: Part of the display area touches the index finger (approximately 20% or less of the display area within the contact area). 1: A large portion of the display area touches the index finger (more than 20% of the display area within the contact area).

[0104] The results are shown in Table 1.

[0105] (Evaluation method 2: Evaluation of transcriptional properties) After removing the release liner from each adhesive label, the adhesive layer was applied to a stainless steel plate under conditions of 23°C and 50% RH. After 24 hours, the adhesive labels were peeled off the stainless steel plate. The visibility of the label on the substrate was checked after peeling. This process was repeated five times, and scores were assigned based on the following evaluation criteria, with the average score calculated.

[0106] 3: The entire display area is visible on the substrate (more than 70% of the display area within the application area). 2: Most of the display area is visible on the substrate (50% or more but less than 70% of the display area within the application area). 1: The display area is not sufficiently visible on the substrate (less than 50% of the display area within the application area). The results are shown in Table 1.

[0107] [Table 1]

[0108] From the results above, adhesive labels 1 and 2, which are examples, showed minimal character loss and good transferability to the substrate. On the other hand, adhesive labels 3 and 5, which had loop tack values ​​for polyethylene exceeding 1.5 N / 25 mm, exhibited character loss. Thus, even if the adhesive strength to the substrate is increased to ensure transferability, it is clear that when the loop tack value for polyethylene exceeds 1.5 N / 25 mm, the label tends to stick to the hands and character loss becomes significant. Furthermore, adhesive label 4, which had an adhesive strength of less than 10 N / 25 mm to stainless steel, resulted in poor transferability to the substrate and poor visibility of the displayed area. [Explanation of Symbols]

[0109] 10 labels, 11 base material, 12 Adhesive layer, 13. Release liner, 14 Display section, 15. Roughened surface.

Claims

1. An adhesive label comprising a base material, a display portion detachable from the base material, and an adhesive layer, An adhesive label having a loop tack value of 1.5 N / 25 mm or less for polyethylene and an adhesive strength of 10 N / 25 mm or more for stainless steel.

2. The adhesive label according to claim 1, wherein the adhesive layer is formed from an adhesive composition comprising a urethane prepolymer and a crosslinking agent, and the urethane prepolymer is formed from a mixture comprising a polyisocyanate and a polyol containing structural units derived from lactic acid.

3. The adhesive label according to claim 2, wherein the crosslinking agent is an isocyanate compound.

4. The adhesive label according to claim 1 or 2, wherein the display portion is transparent.

5. The adhesive label according to claim 1 or 2, wherein the substrate is transparent.

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