label

Abstract

[Problem] To provide a label that can be affixed to an adherend without failure, and a method for manufacturing the label. [Solution] The problem can be solved by a label having a paper base material, a recording layer on the obverse surface of the paper base material, and a re-wetting active paste layer on the reverse surface of the paper base material, wherein: the label, which is sized to CD 80 mm × MD 80 mm on the basis of the paper base material, is allowed to stand for 24 hours in an environment at 23°C and a relative humidity of 50%, and a curl value based on a state in which the re-wetting active paste layer faces upward under the same environment after being allowed to stand is 0 mm to 30 mm; and the re-wetting active paste layer is then wetted to the extent that the re-wetting active paste layer exhibits adhesiveness under the same environment, and a curl value based on a state in which the re-wetting active paste layer faces upward, as measured after the elapse of 10 seconds from wetting, is −30 mm to 0 mm.

Description

label

[0001] The present invention relates to a label having a rewettable adhesive layer containing a rewettable adhesive as an adhesive function.

[0002] A label (sticker paper) having a rewettable adhesive layer on its back surface can be attached to an adherend after it has been moistened by adding water to the rewettable adhesive layer to develop its adhesive function. Because the rewettable adhesive layer develops its adhesive function upon wetting, it has the advantage of eliminating the need for a release paper for the adhesive layer, which is typically required for labels with an adhesive layer. Conventional labels having a rewettable adhesive layer on their back surface and a recording surface on their front surface are printed with a rewettable adhesive on one side of printing paper, and then characters or graphics are printed on the surface. The heat roll during printing tends to cause the rewettable adhesive side of the label to shrink, and after printing, the printing paper stretches due to atmospheric humidity, making the label prone to curling. Therefore, when adding water to the rewettable adhesive, there is the problem that it is difficult to apply water by mechanical transport. In order to solve this problem, for example, Patent Document 1 discloses an adhesive tape in which a re-moisturizing adhesive is applied to one side of the printing paper and a surface treatment agent for printing various types of characters, figures, etc. is applied to the other side, thereby preventing curling of the printing paper due to expansion caused by the ambient humidity.

[0003] JP 2013-231256 A

[0004] In addition to the problem of curling occurring before wetting the rewettable adhesive layer as described above, labels having a paper substrate, a recording layer on the front surface of the paper substrate, and a rewettable adhesive layer on the back surface of the paper substrate have a different curling factor that adversely affects application. That is, when the rewettable adhesive layer is moistened by adding water to the rewettable adhesive layer in order to exert its adhesive function before application to an adherend, the added moisture causes a difference in expansion and contraction between the front and back of the label, resulting in curling of the label. A curled label becomes difficult to handle, causing problems when applying it to an adherend. For example, if curling occurs with the rewettable adhesive layer facing inward, wrinkles or bent corners are likely to occur when the label is applied. On the other hand, if curling occurs with the rewettable adhesive layer facing outward, curling or bent corners are likely to occur when the label is applied.

[0005] The object of the present invention is to provide a label having a paper base material, a recording layer on the surface of the paper base material, and a rewettable adhesive layer on the back surface of the paper base material, which can suppress the occurrence of curling due to wetting of the rewettable adhesive layer and can be attached to an substrate without any problems, and to provide a method for manufacturing such a label.

[0006] The object of the present invention can be achieved by the following: [1] A label having a paper substrate, a recording layer on the front side of the paper substrate, and a rewettable adhesive layer on the back side of the paper substrate, wherein the label is cut to a size of 80 mm CD x 80 mm MD based on the paper substrate and left in an environment of 23°C and 50% relative humidity for 24 hours, and after leaving the label in the same environment, the curl value measured before wetting the rewettable adhesive layer is 0 mm to 30 mm, with the rewettable adhesive layer facing upward; and the rewettable adhesive layer is then moistened in the same environment to the extent that it becomes adhesive, and the curl value measured 10 seconds after wetting is -30 mm to 0 mm, with the rewettable adhesive layer facing upward. [2] The label according to [1] above, wherein the ratio of the specific tensile strength in the MD to the specific tensile strength in the CD (MD / CD) is 1.05 to 1.75, as determined in accordance with ISO 1924-2:1994. [3] The label according to the above [1] or [2], wherein the paper substrate contains one or more water-soluble polymers selected from the group consisting of starches and polyvinyl alcohols as a surface sizing agent using a size press. [4] The rewetting active adhesive layer is applied to the label with a coating amount (g / m ２ The label according to any one of [1] to [3] above, wherein the rewetting active adhesive layer is moistened with an aqueous solvent in an amount of water that is 0.5 to 5 times the amount of water relative to the dry solid content, and the curl value measured 10 seconds after wetting is -30 mm to 0 mm, based on the state in which the rewetting active adhesive layer faces upward.

[0007] According to the present invention, it is possible to provide a label having a paper base material, a recording layer on the surface of the paper base material, and a rewettable adhesive layer on the back surface of the paper base material, which can suppress curling caused by wetting of the rewettable adhesive layer and can be attached to an object without any problems, as well as a method for manufacturing such a label.

[0008] The label of the present invention comprises a paper substrate, a recording layer on the front side of the paper substrate, and a rewettable adhesive layer on the back side of the paper substrate, and the label is cut to a size of 80 mm CD x 80 mm MD based on the paper substrate and left in an environment of 23 ° C and 50% relative humidity for 24 hours. After leaving the label in the same environment, the rewettable adhesive layer is moistened, and the curl value measured with the rewettable adhesive layer facing upward is 0 mm to 30 mm. The rewettable adhesive layer is then moistened in the same environment to the extent that the rewettable adhesive layer exhibits adhesiveness, and the curl value measured 10 seconds after wetting is -30 mm to 0 mm with the rewettable adhesive layer facing upward (hereinafter also referred to as the "label of the present invention"). Here, the terms "front side" and "back side" used in this specification are convenient terms for distinguishing between the surfaces of the paper substrate and do not refer to the front and back sides that depend on physical or chemical differences in the paper substrate. In this specification, CD refers to the "direction perpendicular to the paper flow of the paper machine," and MD refers to the "paper flow direction of the paper machine." The labels of the present invention include sheets, tapes, stickers, displays, slips, and the like. The paper substrate in the label of the present invention includes a single paper layer and a laminate of multiple paper layers. In some embodiments, the paper substrate has a single paper layer. This is because it is advantageous in terms of the manufacturing cost of the label of the present invention. The recording layer of the label of the present invention includes a single layer and a laminate of multiple layers. The rewettable adhesive layer of the label of the present invention includes a single layer and a laminate of multiple layers. In some embodiments, the rewettable adhesive layer is a single layer. This is because it is advantageous in terms of the manufacturing cost of the label of the present invention.

[0009] The label of the present invention may be provided with a protective layer conventionally known in the field of recording materials for the recording layer, provided that the effect of the present invention is not impaired. The label of the present invention may also be provided with an intermediate layer conventionally known in the field of recording materials between the paper substrate and the recording layer and / or between the paper substrate and the rewettable adhesive layer for the purposes of improving the adhesion of the layers, assisting recording on the recording layer, and assisting the activity of the rewettable adhesive layer.

[0010] The paper base material can be any of the following: paper made by a conventional papermaking method under acidic, neutral, or alkaline conditions using a stock prepared by adding various additives conventionally known in the papermaking field, such as fillers, sizing agents, binders, fixing agents, retention agents, and paper strength agents, to a slurry of pulp, such as wood pulp and / or non-wood pulp, as needed; sized base paper obtained by size-pressing the above-mentioned paper with a size-press liquid containing a surface sizing agent conventionally known in the papermaking field; surface-treated base paper obtained by surface-treating the above-mentioned paper with a surface treatment liquid containing a surface treatment agent conventionally known in the papermaking field; and plain paper obtained by calendering the above-mentioned paper, sized base paper, or surface-treated base paper. In the paper base material, the surface to be subjected to the size-press treatment or surface treatment may be either both or one side of the paper, and if one side is used, either the front or back side may be used. The surface to be calendered may be either one or both sides of the above-mentioned papermaking paper, sizing base paper or surface-treated base paper, and in the case of one side, either the front or back side may be calendered.

[0011] The paper substrate also includes conventionally known coated papers in the field of coated paper, which are prepared by providing a coating layer containing a pigment and a binder or a resin layer containing a resin on the above-mentioned papermaking paper, sized base paper, surface-treated base paper, or plain paper.Furthermore, the paper substrate also includes existing fine paper, tissue paper, linter paper, kraft paper such as bleached kraft paper or unbleached kraft paper, one-sided glossy paper, one-sided laminated paper, reinforced inter-paper paper, and flame-retardant paper.

[0012] The wood pulp mentioned above includes pulps made of wood fibers conventionally known in the papermaking field. Raw materials for wood fibers include softwoods and hardwoods. The wood pulp includes chemical pulp, mechanical pulp, semi-chemical pulp, and the like conventionally known in the papermaking field. Examples of chemical pulp include LBKP (Leaf Bleached Kraft Pulp) and NBKP (Needle Bleached Kraft Pulp). Examples of mechanical pulp include GP (Groundwood Pulp), PGW (Pressure Groundwood Pulp), RMP (Refiner Mechanical Pulp), TMP (ThermoMechanical Pulp), CTMP (ChemiThermoMechanical Pulp), and CMP (ChemiMechanical Pulp). An example of semi-chemical pulp is CGP (ChemiGroundwood Pulp). Examples of the non-wood pulp include pulps made of non-wood fibers that are conventionally known in the papermaking field. Examples of raw materials for non-wood fibers include the bast of woody plants such as paper mulberry, Mitsumata, and gampi, the bast of herbaceous plants such as flax, hemp, and kenaf, the leaf fibers of Manila hemp, abaca, and sisal, the grasses such as rice straw, wheat straw, sugarcane bacillus, bamboo, and esparto, and the seed hairs of cotton and linter.Further examples of pulp include waste paper pulp such as DIP (Deinked Pulp) and pulp obtained by defibrating spoilage generated in paper mills.

[0013] In some embodiments, the paper substrate is the above-mentioned papermaking paper, the above-mentioned sizing base paper, the above-mentioned surface-treated base paper, the above-mentioned plain paper, or kraft paper. This is because it is advantageous in terms of manufacturing cost or strength of the label of the present invention. In at least one embodiment, the paper substrate is the above-mentioned papermaking paper, sizing base paper, surface-treated base paper, or plain paper. This is because it is advantageous in terms of manufacturing cost of the label of the present invention. In at least one embodiment, the paper substrate is kraft paper. This is because it is advantageous in terms of strength of the label of the present invention. In at least one embodiment, the paper substrate is a sizing base paper containing one or more water-soluble polymers selected from the group consisting of starches and polyvinyl alcohols as a surface sizing agent. This is because it is possible to further suppress the degree of curling of the paper substrate used in the label of the present invention, and the increased stiffness of the paper substrate makes it less likely to wrinkle or bend at the corners when the label is attached.

[0014] Starches are polysaccharides in which glucose is polymerized via glycosidic bonds, and polysaccharides in which the hydroxyl groups of glucose in such polysaccharides are modified with various substituents. Examples of starches include starch, oxidized starch, enzyme-modified starch, etherified starch, cationic starch, amphoteric starch, dialdehyde starch, esterified starches such as phosphate-esterified starch and urea-phosphate-esterified starch, hydroxyethylated starch, and hydroxybutylated starch. In this specification, polyvinyl alcohols are a general term that includes general polyvinyl alcohols and various modified polyvinyl alcohols. Examples of polyvinyl alcohols include polyvinyl alcohols with various degrees of saponification and various average degrees of polymerization, modified polyvinyl alcohols with various functional groups such as silyl groups, carboxy groups, amino groups, and acetoacetyl groups, and modified polyvinyl alcohols in which other monomers such as ethylene are randomly, graft-, or block-incorporated.

[0015] The label of the present invention may have a laminate film layer between the paper substrate and the rewettable adhesive layer. In this case, the strength of the label of the present invention against tearing is easily improved, and after the label of the present invention is attached to an adherend, when removing the information recorded on the recording layer of the label, the laminate film layer functions as a release layer, making it easy to peel between the paper substrate and the laminate film layer. Materials constituting the laminate film layer include, for example, conventionally known resins such as biodegradable resins such as polylactic acid and polybutylene succinate; synthetic resins such as polyethylene and polypropylene; etc. The laminate film layer can be provided between the paper substrate and the rewettable adhesive layer using a conventionally known laminator such as a dry laminator, a wet laminator, or an extrusion laminator.

[0016] The recording layer in the label of the present invention may be a layer on which an image can be recorded or a layer on which an image has been recorded, and is not particularly limited. In some embodiments, by the printing method and image recording method described below, recording can be performed directly on the surface of the paper substrate constituting the label of the present invention, and a recording layer can be formed. This is advantageous from the viewpoint of the manufacturing cost of the label of the present invention. When an image is directly recorded on the surface of the paper substrate, the surface of the paper substrate also serves as the recording layer, resulting in a label of the present invention.

[0017] Examples of recording layers as layers on which an image can be recorded include layers on which an image can be recorded by conventionally known printing methods and image recording methods, such as coating layers for gravure printing, coating layers for offset printing, coating layers for letterpress printing, coating layers for flexographic printing, thermal recording layers, ink-receiving layers for inkjet printing, coating layers for thermal transfer images, image-receiving layers for transfer printing, and coating layers for electrophotographic printing. Furthermore, images can be recorded on a recording layer as a layer on which an image can be recorded either before and / or after affixing the label of the present invention to an adherend.

[0018] In some embodiments, the recording layer in the label of the present invention is a thermosensitive recording layer. This is because thermosensitive recording printers have been widely introduced on the market as label printers. In some embodiments, the recording layer in the label of the present invention is a thermosensitive recording layer and has a protective layer to impart abrasion resistance and / or chemical resistance to the thermosensitive recording layer. In some embodiments, the recording layer in the label of the present invention is a thermosensitive recording layer and has an intermediate layer between the paper substrate and the recording layer to assist recording on the thermosensitive recording layer. In at least one embodiment, the label of the present invention is a thermosensitive recording layer and has a protective layer to impart abrasion resistance and / or chemical resistance to the thermosensitive recording layer, and has an intermediate layer between the paper substrate and the recording layer to assist recording on the thermosensitive recording layer.

[0019] A recording layer capable of recording an image can be obtained by applying and drying a coating composition for forming the recording layer to the surface of a paper substrate using a conventionally known coating device and drying device. Examples of the coating device include those conventionally known in the field of coated paper, such as air knife coaters, various blade coaters, various bar coaters, various gravure coaters, various lip coaters, various curtain coaters, and various roll coaters. Further examples of the coating device include various printing methods, such as lithographic, relief, intaglio, flexographic, gravure, and screen printing. Examples of the drying device include those conventionally known in the field of coated paper, such as hot air dryers such as linear tunnel dryers, arch dryers, air loop dryers, and sine-curve air float dryers, infrared heating dryers, and dryers using microwaves or ultraviolet light.

[0020] In some embodiments, the recording layer in the label of the present invention is subjected to a calendering treatment using a calendering device conventionally known in the papermaking field, such as a machine calender, soft nip calender, super calender, multi-stage calender, or multi-nip calender, in order to make the recording layer uniform and smooth.

[0021] In some embodiments, the coating weight of the recording layer is 2 g / m2 in terms of dry solid content. ２40g / m or more ２ The reason for this is that curling in the label of the present invention can be easily prevented. When an intermediate layer and / or a protective layer are further provided in addition to the recording layer, the coating amount including the recording layer and layers other than the recording layer is 2 g / m2 in terms of dry solid content. ２ 40g / m or more ２ The following is the result.

[0022] Examples of recording layers as layers on which an image is recorded include layers in which a recording material on which an image has already been formed, such as recording paper, patterned paper, colored paper, patterned film, colored film, decorative paper, decorative sheet, or image recording sheet, is laminated, adhered, or pasted onto a paper substrate. The recording layer as a layer on which an image is recorded may be laminated, adhered, or pasted either before and / or after the label of the present invention is affixed to the adherend.

[0023] The rewetting active adhesive layer in the label of the present invention is an adhesive layer in which the rewetting active adhesive agent contained therein exhibits adhesive properties when the rewetting active adhesive layer is moistened with water or a water-containing solution (hereinafter, collectively referred to as "aqueous solvent"). Rewetting active adhesives are conventionally known in the adhesive field. Examples of rewetting active adhesives include starches such as various modified starches, including oxidized starch and esterified starch, and starch; celluloses such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, ethylhydroxyethyl cellulose, and viscose; chloroprene rubbers; polyvinyl alcohols such as various modified polyvinyl alcohols, including carboxy-modified polyvinyl alcohol, and polyvinyl alcohols with various degrees of saponification; polyvinyl ethers such as polyvinyl ethyl ether and polyvinyl isobutyl ether; vinyl acetate copolymers such as vinyl acetate acrylate copolymer and vinyl acetate methacrylate copolymer; casein, gelatin, dextrin, gum arabic, glue, and polyacrylamide. The rewetting active adhesive layer can be obtained by applying a coating composition containing at least a rewetting active adhesive to a paper substrate and drying the coating composition using a conventionally known coating device and drying device. The details of the coating device and drying device are the same as those of the coating device and drying device that can be used to form the recording layer.

[0024] In some embodiments, the rewetting active paste layer contains various auxiliaries in addition to the rewetting active paste agent. This is because it can improve the operability during the application and drying of the coating composition for forming the rewetting active paste layer, as well as the weather resistance of the rewetting active paste layer. Examples of auxiliaries include preservatives, antioxidants, antifoaming agents, surfactants, antifreeze agents, scale inhibitors, and colorants.

[0025] In some embodiments, the coating weight of the rewet active glue layer is 2 g / m2 in terms of dry solids. ２ 25g / m or more ２ The reason for this is that curling in the label of the present invention can be easily suppressed. When an intermediate layer or the like is provided on the back surface of the paper substrate in addition to the rewetting active adhesive layer, the coating amount including the rewetting active adhesive layer and layers other than the rewetting active adhesive layer is 2 g / m2 in terms of dry solid content. ２ 25g / m or more ２ The following is the result.

[0026] In some embodiments, the label of the present invention comprises a paper substrate, a recording layer on the front surface of the paper substrate, and a rewetting active adhesive layer on the back surface of the paper substrate, wherein the paper substrate is made paper, sized base paper, surface-treated base paper, plain paper, or kraft paper, and the rewetting active adhesive agent of the rewetting active adhesive layer is one or more selected from the group consisting of starches, polyvinyl alcohols, vinyl acetate copolymers, and dextrins. The reason for this is that the paper substrate can be easily recovered and defibrated from used labels of the present invention, thereby reducing the environmental impact of disposal.

[0027] In at least one embodiment, the label of the present invention has a paper base material, a recording layer on the surface of the paper base material, and a rewetting active adhesive layer on the back surface of the paper base material, wherein the paper base material is paper-making paper, sized base paper, surface-treated base paper, plain paper, or kraft paper, the recording layer is a thermosensitive recording layer, and the rewetting active adhesive agent of the rewetting active adhesive layer is one or more selected from the group consisting of starches, polyvinyl alcohols, vinyl acetate copolymers, and dextrin.

[0028] The label of the present invention is prepared by leaving a label having a size of 80 mm CD x 80 mm MD based on a paper substrate in an environment of 23°C and 50% relative humidity for 24 hours, and after leaving, the label is measured under the same environment before wetting the rewetting active adhesive layer, and the curl value is 0 mm to 30 mm based on a state in which the rewetting active adhesive layer faces upward.Furthermore, the label of the present invention is prepared by leaving a label having a size of 80 mm CD x 80 mm MD based on a paper substrate in an environment of 23°C and 50% relative humidity for 24 hours, and after leaving and curl measurement, the label is wetted under the same environment to the extent that the rewetting active adhesive layer exhibits adhesiveness, and the curl value is measured 10 seconds after wetting, and the curl value is -30 mm to 0 mm based on a state in which the rewetting active adhesive layer faces upward.

[0029] By satisfying the above curl value, the label of the present invention can suppress curling caused by wetting of the rewetting active adhesive layer, thereby allowing it to be attached to an adherend without any problems. If the above curl value is not satisfied, curling caused by wetting of the rewetting active adhesive layer cannot be suppressed. As a result, the label will not be attached to an adherend properly. The curl value is the distance between the four corner vertices of the label placed on a horizontal surface under the above conditions and the horizontal surface, and refers to the maximum value among the four corner vertices measured. "10 seconds after wetting" refers to measuring the curl value before the wetting of the rewetting active adhesive layer is relaxed by the environmental temperature and humidity. Here, a positive curl value means that curling occurs with the rewetting active adhesive layer facing inward (hereinafter sometimes simply referred to as "positive curl"). A negative curl value means that curling occurs with the rewetting active adhesive layer facing outward (hereinafter sometimes simply referred to as "negative curl"). The curl value is measured by placing the label with the inner side of the curl facing upward.

[0030] The above-mentioned "wet enough to make the rewettable adhesive layer sticky" refers to a state in which an amount of water is added to make the rewettable adhesive layer sticky over the entire rewettable adhesive layer by applying an aqueous solvent to the entire rewettable adhesive layer. The amount of water required for the rewettable adhesive layer to be wet enough to make the rewettable adhesive layer sticky over the entire rewettable adhesive layer surface varies depending on the type of rewettable adhesive and the coating amount of the rewettable adhesive layer, but is determined by the coating amount of the rewettable adhesive layer per unit area (g / m ２ If the amount is 0.5 to 5 times the dry solid content, the rewetting active adhesive layer can exhibit adhesiveness regardless of the type of rewetting active adhesive.

[0031] In some embodiments, the amount of water used for the "wetting to an extent that the rewettable adhesive layer exhibits adhesiveness" is the coating amount of the rewettable adhesive layer per unit area (g / m ２ In at least one embodiment, the amount of water used for the "wetting to an extent that the rewetting active adhesive layer exhibits adhesiveness" is the coating amount of the rewetting active adhesive layer per unit area (g / m ２ The water content is 1 to 4 times the amount of water (amount of water, dry solids content). The reason for this is that, regardless of the type of rewetting active adhesive, the aqueous solvent can be sufficiently supplied throughout the thickness direction of the rewetting active adhesive layer, allowing the rewetting active adhesive layer to fully exhibit adhesion, and dripping of the aqueous solvent can be suppressed.

[0032] In some embodiments, the label of the present invention has a paper substrate, a recording layer on the surface of the paper substrate, and a rewettable adhesive layer on the back surface of the paper substrate. The label is cut to a size of 80 mm CD x 80 mm MD based on the paper substrate and left in an environment of 23°C and 50% relative humidity for 24 hours. After being left in the same environment, the curl value measured before wetting the rewettable adhesive layer is 0 mm or more and 30 mm or less based on a state in which the rewettable adhesive layer faces upward, and then, in the same environment, the coating amount (g / m) of the rewettable adhesive layer is applied to the rewettable adhesive layer. ２The rewetting active adhesive layer is wetted with an aqueous solvent in an amount of water that is 1 to 4 times the amount of water relative to the dry solid content (amount of the rewetting active adhesive layer, dry solid content), and the curl value measured 10 seconds after wetting is -30 mm to 0 mm, based on the state in which the rewetting active adhesive layer faces upward.

[0033] In a conventional label having a paper substrate, a recording layer on the front surface of the paper substrate, and a rewettable adhesive layer on the back surface of the paper substrate, when an aqueous solvent is applied to the rewettable adhesive layer and the rewettable adhesive layer is wetted, the rewettable adhesive layer side of the paper substrate stretches due to the influence of the applied aqueous solvent, generating stress due to the difference in expansion and contraction between the front and back surfaces of the paper substrate. As a result, the label is prone to negative curl, where the curl value is a negative value based on the state in which the rewettable adhesive layer is facing up. On the other hand, the label of the present invention has a tendency to generate positive curl, where the curl value is a positive value based on the state in which the rewettable adhesive layer is facing up, in order to suppress the negative curl. By having the tendency to generate positive curl, the label of the present invention can offset the stress that causes negative curl when the rewettable adhesive layer is wetted. As a result, when the rewettable adhesive layer is wetted to a degree that uniformly exhibits adhesiveness across the entire surface, curling is suppressed and the label can be attached to an adherend without any problems. In some embodiments, the label of the present invention can be attached to an adherend without any problems, and the curl value based on the state in which the rewettable adhesive layer faces upward is in the range of −10 mm or more and 10 mm or less.

[0034] One method for imparting the tendency for positive curl to the label of the present invention is to control the moisture content and / or drying state of the front and back surfaces of the paper substrate constituting the label of the present invention. Paper curl generally results from (1) differences in drying speed or drying state between the front and back surfaces of the paper, (2) differences in fiber orientation between the front and back surfaces of the paper, (3) differences in moisture desorption or moisture absorption between the front and back surfaces of the paper or differences in density between the front and back surfaces of the paper, and (4) differences in shrinkage rates between the front and back surfaces of the paper due to coating layers. For example, (1) is influenced by the dryer part of the papermaking process; (2) by the stock supply, J / W ratio (the ratio of pulp jet speed to Fourdrinier wire speed), slice lip, and wire part of the papermaking process; (3) by the stock supply, J / W ratio, slice lip, wire part, press part, and size press and calendering processes of the papermaking process; and (4) by the pigment component amount, resin component amount, coating weight, and layer drying. Therefore, paper curl can be adjusted by controlling these factors. There are empirical rules for paper curling, such as "the side from which moisture is removed last curls inward" or "the side that dries slower curls inward." Therefore, from the perspective of preventing curling tendency, the method using the above (1), which utilizes the difference in drying speed or drying state between the front and back sides in the dryer part, is highly effective.

[0035] For example, by creating a difference in drying temperature between the front and back of the paper during the dryer section, calendering, or layer drying, moisture migration occurs in the paper thickness direction, resulting in a relatively low moisture content on the side with the higher temperature setting. On this side with a relatively low moisture content, the pulp fibers are more likely to swell when moistened with an aqueous solvent. That is, when moistened, the paper tends to curl with the side with the higher temperature setting facing outward, assuming the side with the higher temperature setting facing upward. Furthermore, for example, a Fourdrinier papermaking machine can be used to adjust the J / W ratio and / or slice slip to make the paper slower in the wire section and dryer section, thereby increasing the density of the paper on the so-called felt side of the dryer section. The denser the pulp fibers on the higher-density side, the greater the elongation caused by wetting. That is, when moistened with an aqueous solvent, the paper tends to curl with the felt side facing outward. Other methods include, for example, applying an aqueous solvent to one side of the paper and drying it. Paper with a relatively high moisture content on one side using this method tends to curl with that side facing inward when wet. Whether the paper substrate constituting the label of the present invention will have a tendency to have a positive or negative curl is determined by the selection of which side of the paper obtained above will be the front or back.

[0036] In some embodiments of the label of the present invention, a method for providing the label with the tendency to form a positive curl may include applying an aqueous solvent to the rewettable adhesive layer of the label and drying the applied solvent to form the label. This increases the relative moisture content of the rewettable adhesive layer, thereby providing the label with a tendency to form a positive curl when wetted, based on the state in which the rewettable adhesive layer faces upward.

[0037] In some embodiments for obtaining the label of the present invention, a method for providing the label with the tendency to produce the positive curl may include first coating a coating composition for forming a recording layer on the surface of the paper substrate and drying the coating composition to form a recording layer, and second coating a coating composition for forming a rewettable adhesive layer on the back surface of the paper substrate and drying the coating composition to form a rewettable adhesive layer. In this way, the label of the present invention can be provided with a tendency to produce a positive curl based on the state in which the rewettable adhesive layer is facing upward by providing the rewettable adhesive layer after the recording layer.

[0038] In some embodiments of the label of the present invention, a method for imparting the tendency to positive curl to the label may include the following: when producing a paper substrate, a difference in drying speed or drying state between the front and back sides is set in the drying part of a paper machine, and a recording layer is provided on the faster drying side and a rewettable adhesive layer is provided on the slower drying side. This allows the label of the present invention to have a tendency to positive curl based on the state in which the rewettable adhesive layer faces upward due to the difference in drying state between the front and back sides of the paper substrate.

[0039] As mentioned above, if the moisture content or dryness of paper differs between the front and back sides, differences in expansion and contraction occur, and the stress caused by this difference in expansion and contraction accumulates in the paper, resulting in curling. According to Åkesson, paper shrinks more on the side with a lower evaporation rate and curls toward this side. That is, in coated paper with coating layers on both sides, for example, when double-coating is performed after drying in the middle, the paper will always curl toward the side that dries last (Rolf Åkesson, "Moisturizing and Decurling of Coated Papers," JAPAN TAPPI JOURNAL, Vol. 44, No. 12, pp. 1267-1274, 1990, p. 1267). The label manufacturing method of the present invention utilizes the above-mentioned Okeson principle, in which a coating composition for forming a recording layer is first applied to the surface of the paper substrate and dried to form a recording layer, and a coating composition for forming a rewettable adhesive layer is second applied to the back surface of the paper substrate and dried to form a rewettable adhesive layer.

[0040] In a label having a paper substrate, a recording layer on the surface of the paper substrate, and a rewettable adhesive layer on the back surface of the paper substrate, in order to avoid damage to the recording layer during production, particularly to recording layers optimized for printing methods and image recording methods such as a thermal recording layer, an ink-receiving layer for inkjet printing, and a coating layer for thermal transfer image receiving, a rewettable adhesive layer is first formed by coating and drying a coating composition for forming a rewettable adhesive layer on the back surface of the paper substrate, and a recording layer is secondly formed by coating and drying a coating composition for forming a recording layer on the surface of the paper substrate. Therefore, it is usually difficult to select a manufacturing method in which a recording layer is first formed by coating and drying a coating composition for forming a recording layer on the surface of the paper substrate, and a rewettable adhesive layer is secondly formed by coating and drying a coating composition for forming a rewettable adhesive layer on the back surface of the paper substrate.

[0041] In some embodiments, the label of the present invention has a paper substrate, a recording layer on the surface of the paper substrate, and a rewettable adhesive layer on the back of the paper substrate, and the label is cut to a size of 80 mm CD x 80 mm MD based on the paper substrate and left in an environment of 23°C and 50% relative humidity for 24 hours. After being left, the label has a curl value of 0 mm or more and 30 mm or less, measured before wetting the rewettable adhesive layer in the same environment, with the rewettable adhesive layer facing upward; the rewettable adhesive layer is then wetted in the same environment to an extent that the rewettable adhesive layer exhibits adhesiveness, and the curl value measured 10 seconds after wetting is -30 mm or more and 0 mm or less, with the rewettable adhesive layer facing upward; and the paper substrate contains one or more water-soluble polymers selected from the group consisting of starches and polyvinyl alcohols as a surface sizing agent using a size press.

[0042] In at least one embodiment, the label of the present invention has a paper substrate, a recording layer on the surface of the paper substrate, and a rewettable adhesive layer on the back surface of the paper substrate, and the label is cut to a size of 80 mm CD x 80 mm MD based on the paper substrate and left in an environment of 23°C and 50% relative humidity for 24 hours, and after being left in the same environment, the curl value measured before wetting the rewettable adhesive layer is 0 mm or more and 30 mm or less based on a state in which the rewettable adhesive layer faces upward, and the coating amount (g / m ２ The rewettable active adhesive layer is wetted with an aqueous solvent in an amount of water that is 0.5 to 5 times the amount of water relative to the dry solid content, and the curl value measured 10 seconds after wetting, based on the state in which the rewettable active adhesive layer faces upward, is -30 mm to 0 mm. The paper substrate contains one or more water-soluble polymers selected from the group consisting of starches and polyvinyl alcohols as a surface sizing agent using a size press.

[0043] In some embodiments, the label of the present invention has a tensile strength measured in accordance with ISO 1924-2:1994 "Paper and board - Determination of tensile properties - Part 2: Constant rate of elongation method," in which the ratio of the tensile strength in the MD to the tensile strength in the CD (MD / CD) is 1.05 or more and 1.75 or less. Here, the tensile strength ratio is calculated by multiplying the tensile strength (kN / m) of the label by the basis weight (g / m) of the label. ２ ) and rounding off the value to two decimal places. When the MD / CD ratio is 1.05 or more and 1.75 or less, "lifting" of the label attached to the adherend can be suppressed, making it easy to prevent curling. Here, in this specification, "lifting" of the label refers to the phenomenon in which, in the case of a label with a negative curl, the edge of the label attached to the adherend slightly lifts up before the rewettable adhesive in the rewettable adhesive layer dries and adhesion is completed.

[0044] The tensile strength of the label of the present invention is substantially determined by the tensile strength of the paper substrate, since the tensile resistance depends on the entanglement of pulp fibers. The tensile strength of the paper substrate is a physical property conventionally known in the papermaking field and can be adjusted by conventionally known methods, for example, by controlling the ash content, density, paper strength, pulp type and freeness of the base paper, the J / W ratio in papermaking, the concentration and amount of pulp ejected, and the dewatering speed of the wire part.

[0045] In at least one embodiment, the label of the present invention is a label having a paper substrate, a recording layer on the surface of the paper substrate, and a rewettable adhesive layer on the back surface of the paper substrate. The label is cut to a size of 80 mm CD x 80 mm MD based on the paper substrate and left in an environment of 23°C and 50% relative humidity for 24 hours. After leaving the label, the curl value measured in the same environment before wetting the rewettable adhesive layer is 0 mm or more and 30 mm or less, based on a state in which the rewettable adhesive layer faces upward. Next, in the same environment, the rewettable adhesive layer is coated with a coating amount (g / m ２The rewetting active adhesive layer is wetted with an aqueous solvent in an amount of 0.5 to 5 times the amount of water relative to the dry solid content, and the curl value measured 10 seconds after wetting, based on the state in which the rewetting active adhesive layer faces upward, is -30 mm to 0 mm. In the tensile strength determined in accordance with ISO 1924-2:1994, the ratio of the specific tensile strength in the MD side to the specific tensile strength in the CD side (MD / CD) is 1.05 to 1.75. The paper base material contains one or more water-soluble polymers selected from the group consisting of starches and polyvinyl alcohols as a surface sizing agent when used with a size press.

[0046] Examples of the adherend to which the label of the present invention can be attached include materials such as metals, glass, resins, plastics, leather, paper, composite materials of these materials, and food, etc. Examples of the form of the adherend include plates, sheets, fabrics, containers, boxes such as cardboard boxes, various types of packaging, and wrapping materials, packaging packs, packaging bags, and packaging containers, etc.

[0047] In some embodiments, the label of the present invention is used for applications such as shipping labels, display labels, tag labels, and barcode labels used in the logistics and retail fields, as well as packaging tape used to seal cardboard boxes. The reason for this is that, in the case of conventionally known labels having a release paper on an adhesive layer, the peeling process and disposal of the release paper are required at the site where the label is used, whereas the label of the present invention does not require these processes. Furthermore, in conventionally known linerless labels having a recording layer on the front surface of a paper substrate, a release layer on the recording layer, and an adhesive layer on the back surface of the paper substrate, the presence of the outermost release layer prevents subsequent printing, rewriting, and / or overlaying at the site of use, whereas the label of the present invention makes these possible.

[0048] In the water or water-containing solution (water and water-containing solutions are collectively referred to as "aqueous solvent") used to wet the rewet active glue layer, the concept of water includes purified water such as pure water, distilled water, ion-exchanged water, RO water filtered through a reverse osmosis membrane (RO membrane), raw water such as river water, spring water, groundwater, and well water, and purified water obtained by purifying the raw water. In some embodiments, the water used to wet the rewet active glue layer is so-called soft water, which has a low content of mineral components such as calcium ions and magnesium ions. This is because it can reduce the adhesion of limescale to rollers, sponges, textiles, paintbrushes, and other items used in the method for wetting the rewet active glue layer described below. In some embodiments, the aqueous solvent contains a conventionally known fungicide and / or preservative. This is because it can prevent the aqueous solvent from spoiling during storage. In some embodiments, the aqueous solvent contains a conventionally known thickener. This is because it can prevent the aqueous solvent from dripping. In some embodiments, the aqueous solvent contains a conventionally known drying inhibitor and / or humectant, such as glycerin, polyethylene glycol, urea, and deliquescent inorganic salts. This is because evaporation of water from the applied aqueous solvent can be inhibited. In some embodiments, the aqueous solvent contains a colorant, such as a coloring dye or a coloring pigment. This is because the wet state of the rewet active glue layer can be visualized. In some embodiments, the aqueous solvent is kept warm or heated. This is because precipitation of components contained in the aqueous solvent and / or freezing of the aqueous solvent can be prevented.

[0049] The method of applying an aqueous solvent to wet the rewetting active adhesive layer includes, for example, conventionally known methods such as roller coating of the aqueous solvent, coating of the aqueous solvent with a sponge or textile, coating of the aqueous solvent with a brush, spray coating of the aqueous solvent, mist or steam spraying of the aqueous solvent, dripping of the aqueous solvent, etc. The method of wetting the rewetting active adhesive layer may be any of batch processing, sequential processing, and continuous processing.

[0050] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Note that parts by mass represent the value of the dry solid content or the amount of the substantial component. The coating amount represents the value of the dry solid content.

[0051] <Paper base material (A)> A pulp slurry consisting of 85 parts by mass of LBKP beaten to a CSF filtration rate of 370 ml and 15 parts by mass of NBKP beaten to a CSF filtration rate of 370 ml was prepared by adding 0.9 parts by mass of a cationized starch and 0.3 parts by mass of an alkyl ketene dimer sizing agent, respectively, per 100 parts by mass of pulp, to obtain a paper stock. The paper stock was then spun onto a Fourdrinier paper machine to obtain a paper stock with a basis weight of 60 g / m. ２ Subsequently, both sides of the paper were subjected to a size press treatment with a size press solution containing oxidized starch as a surface sizing agent to obtain a sized base paper. The coating amount in the size press treatment was 1.5 g / m per side. ２ The obtained sizing base paper was used as a paper substrate for a label.

[0052] <Paper base material (B)> A pulp slurry consisting of 85 parts by mass of LBKP beaten to a CSF filtration rate of 370 ml and 15 parts by mass of NBKP beaten to a CSF filtration rate of 370 ml was prepared by adding 0.9 parts by mass of a cationized starch and 0.3 parts by mass of an alkyl ketene dimer sizing agent, respectively, per 100 parts by mass of pulp, to obtain a paper stock. The paper stock was then spun onto a Fourdrinier paper machine to obtain a paper stock with a basis weight of 60 g / m. ２ Subsequently, both sides of the paper were subjected to a size press treatment with a size press solution containing fully saponified polyvinyl alcohol with an average degree of polymerization of 1500 as a surface sizing agent to obtain a sized base paper. The coating amount in the size press treatment was 1.5 g / m per side. ２ The obtained sizing base paper was used as a paper substrate for a label.

[0053] <Paper base material (C)> A pulp slurry consisting of 85 parts by mass of LBKP beaten to a CSF filtration rate of 370 ml and 15 parts by mass of NBKP beaten to a CSF filtration rate of 370 ml was prepared by adding 0.9 parts by mass of a cationized starch and 0.3 parts by mass of an alkyl ketene dimer sizing agent, respectively, per 100 parts by mass of pulp, to obtain a paper stock. The paper stock was then spun onto a Fourdrinier paper machine to obtain a paper stock with a basis weight of 60 g / m. ２ The obtained paper was used as the paper base material for the label.

[0054] Here, the paper base materials (A) to (C) were prepared by adjusting the concentration and supply amount of the paper stock, the J / W ratio and / or the slice lip, and the dehydration speed of the wire part, so that the label would ultimately have the desired specific tensile strength. Also, the difference in density between the front and back of the paper base material was suppressed in the wire part and dryer part, while the difference in moisture content between the front and back of the paper base material was adjusted in the dryer part and calendar treatment, so that the label would ultimately have the desired curl value.

[0055] <Coating composition for intermediate layer> The coating composition for intermediate layer was prepared by dissolving and / or dispersing the following materials in water: Pigment (calcined kaolin) 1000 parts by mass Dispersant (ammonium polyacrylate) 1 part by mass Dispersant (sodium hexametaphosphate) 1 part by mass Binder (styrene butadiene copolymer) 120 parts by mass Binder (urea-modified starch phosphate) 60 parts by mass

[0056] <Coating composition for recording layer> The recording layer was a thermosensitive recording layer. A coating composition for a thermosensitive recording layer was prepared by mixing and dispersing the following materials in water: a developer dispersion and a sensitizer dispersion, which were prepared by dissolving and / or dispersing the following materials in water: a dye precursor dispersion, a pigment dispersion, and additives.

[0057] <Dispersion of color developer and sensitizer> Electron-accepting color developer (4-hydroxy-4'-isopropoxydiphenyl sulfone) 200 parts by mass Sensitizer (1,2-bis(3-methylphenoxy)ethane) 200 parts by mass Dispersant (sulfonic acid-modified polyvinyl alcohol) 40 parts by mass

[0058] <Dispersion of dye precursor> Electron-donating dye precursor (3-di-n-butylamino-6-methyl-7-anilinofluoran) 100 parts by mass Dispersant (sulfonic acid-modified polyvinyl alcohol) 10 parts by mass

[0059] <Pigment dispersion> Calcium carbonate 300 parts by mass Dispersant (ammonium polyacrylate) 3 parts by mass Binder (fully saponified polyvinyl alcohol) 200 parts by mass

[0060] <Additives> Zinc stearate 80 parts by mass

[0061] <Coating composition for rewetting active adhesive layer> A coating composition for rewetting active adhesive layer was prepared by dissolving and / or dispersing the following materials in water: Partially saponified polyvinyl alcohol 100 parts by mass Antifoaming agent (acetylene glycol) 0.1 parts by mass

[0062] <Recording layer> The coating composition for the intermediate layer having the above-mentioned composition was applied to the surface of the paper substrate using a bar coater and dried using a hot air dryer. Subsequently, the coating composition for the thermosensitive recording layer having the above-mentioned composition was applied to the intermediate layer using an air knife coater and dried using a hot air dryer. The concentration of the coating composition for the thermosensitive recording layer and the drying conditions were adjusted so that the final label would have the desired curl value.

[0063] <Rewetting active adhesive layer> The coating composition for the most wettable active adhesive layer having the above-mentioned composition was applied to the back surface of the paper substrate using a blade coater and dried using a hot air dryer. The concentration of the coating composition for the most wettable active adhesive layer and the drying conditions were adjusted so that the final label would have the desired curl value.

[0064] <Label> Labels were produced by providing an intermediate layer and a recording layer on the front surface of a paper substrate and a rewetting active adhesive layer on the back surface of the paper substrate. The front and back surfaces of the paper substrate were appropriately selected taking into account the direction of curl.

[0065] Example 1 First, a coating composition for a rewetting active adhesive layer was applied to the back surface of a paper substrate (A) and dried. The coating amount of the rewetting active adhesive layer was 15 g / m ２ Second, the intermediate layer coating composition and the thermosensitive recording layer coating composition were applied to the surface of the paper substrate (A) in that order and then dried. The coating amount of the intermediate layer was 10 g / m ２ The coating amount of the thermal recording layer was 4 g / m ２ Next, steam was sprayed onto the rewettable active adhesive layer surface to add moisture and dry it. Finally, a calendering process was carried out to smooth the thermal recording layer, and a label was obtained. No difference in temperature was set on the front and back sides during the calendering process.

[0066] <Examples 2 to 12 and Comparative Examples 1 to 4> First, the intermediate layer coating composition and the thermosensitive recording layer coating composition were sequentially applied to the surface of the paper substrate and then dried. The coating amount of the intermediate layer was 10 g / m ２ The coating amount of the thermal recording layer was 4 g / m ２ Second, a coating composition for a rewetting active adhesive layer was applied to the back side of the paper substrate and dried. The coating amount of the rewetting active adhesive layer was 15 g / m ２ Next, a calendering treatment was carried out to smooth the thermosensitive recording layer, and a label was obtained. No difference in temperature was set between the front and back sides during the calendering treatment. The types of paper substrates used in each example and comparative example are shown in Table 1.

[0067] <Comparative Example 5> First, a coating composition for a rewetting active adhesive layer was applied to the back surface of the paper substrate (A) and dried. The coating amount of the rewetting active adhesive layer was 15 g / m ２ Second, the intermediate layer coating composition and the thermosensitive recording layer coating composition were applied to the surface of the paper substrate (A) in that order and then dried. The coating amount of the intermediate layer was 10 g / m ２ The coating amount of the thermal recording layer was 4 g / m ２ Next, the heat-sensitive recording layer was subjected to a calendering treatment to smooth the layer, thereby obtaining a label. In the calendering treatment, no difference in temperature was set between the front and back sides.

[0068] [Evaluation] The following evaluations were performed on the labels of each Example and Comparative Example. The results are shown in Table 1. <Curl Value of Remoisturizing Active Adhesive Layer Before Wetting (Curl Value A)> The obtained label was cut into a CD 80 mm x MD 80 mm size based on the paper substrate to serve as a sample for measuring the curl value. The measurement sample was supported at the intersection of the diagonal lines and left at 23°C and 50% relative humidity for 24 hours. After leaving, the measurement sample was placed on a horizontal table under the same environment with the curled inner side facing upward. For the left-standing measurement sample, the distance (mm) between each of the four corners of the measurement sample and the horizontal table was measured. The maximum value of the distance among the four corners was determined for one measurement sample. For each Example and Comparative Example, the maximum values ​​were measured for five measurement samples, the average value was calculated, and the curl value was determined by rounding off to the nearest whole number. Note that the curl value was defined as a positive curl when the remoisturizing active adhesive layer was on the inner side of the curl, and a negative curl when the remoisturizing active adhesive layer was on the outer side of the curl.

[0069] <Curl value after wetting of rewetting active adhesive layer (curl value B)> For each measurement sample for which the curl value of the rewetting active adhesive layer before wetting was measured, tap water (20 ml / m) at room temperature (25°C) was applied to the entire surface of the rewetting active adhesive layer using a sponge roller type stamp moistener in an environment of 23°C and a relative humidity of 50% to the extent that the rewetting active adhesive layer exhibits adhesiveness. ２ ) was applied to moisten the sample, and the sample was placed on a horizontal table with the curled inner side facing upward. 10 seconds after the application of tap water, the distance (mm) between each of the four corner vertices of the sample and the horizontal table was measured for the sample that had been placed. The maximum value of the distances among the four corner vertices was determined for one sample. For each example and comparative example, the maximum values ​​for five samples were measured, the average value was calculated, and the value was rounded off to the nearest whole number to obtain the curl value. Note that the curl value was defined as a positive curl when the rewetting active adhesive layer was on the inner side of the curl, and a negative curl when the rewetting active adhesive layer was on the outer side of the curl.

[0070] <Ratio of specific tensile strength (MD / CD)> According to ISO1924-2:1994 "Paper and board - Determination of tensile properties - Part 2: Constant rate of elongation method", the tensile strength on the CD side and the tensile strength on the MD side were measured, and the specific tensile strength on the CD side and the specific tensile strength on the MD side were calculated. Here, the specific tensile strength was calculated by multiplying the tensile strength (kN / m) of the label by the basis weight (g / m) of the label. ２ The ratio of the tensile strength index in the MD to the tensile strength index in the CD (MD / CD) was calculated by dividing the tensile strength index by the basis weight (tensile strength / basis weight) and rounding the value to two decimal places.

[0071] <Applying to Adherend - Suitability Evaluation> The labels obtained in each Example and Comparative Example were cut into a size of 80 mm in CD x 80 mm in MD to prepare application samples. Ten application samples were given to five subjects. The subjects applied tap water (20 ml / m²) at room temperature (25°C) to the entire surface of the rewetting active adhesive layer of each application sample using a sponge roller-type stamp moistener until the rewetting active adhesive layer developed adhesive properties. ２ ) was applied and moistened. Next, while the rewetting active adhesive layer was developing adhesive properties, the subjects applied the application samples one by one to 500 mm x 500 mm corrugated cardboard sheets fixed on a horizontal table as the adherend. The subjects applied 10 application samples for each Example and Comparative Example, and performed a sensory evaluation based on the following criteria. 3 points: 10 sheets could be applied easily and without any problems. 2 points: 10 sheets could be applied generally without any problems, although it took some time. 1 point: One or more sheets had problems with application. Based on the results of the sensory evaluation by five subjects, the application-related problems were evaluated based on the following criteria. The results are shown in Table 1. A: 3 or more people gave a rating of 3 points and 0 people gave a rating of 1 point. B: 3 or more people gave a rating of 2 points and 0 people gave a rating of 1 point. C: 1 person gave a rating of 1 point. D: 2 or more people gave a rating of 1 point.

[0072] <Attachment to substrate - evaluation of lifting> For all samples that had been attached in the above-mentioned proper evaluation, the presence or absence of "lifting" at the edge of the label was checked according to the following criteria before the rewetting active adhesive layer dried. The results are shown in Table 1. A: No "lifting" was observed in any of the samples. B: "Lifting" was observed with a score of 1 to 2. C: "Lifting" was observed with a score of 3 to 4. D: "Lifting" was observed with a score of 5 or more.

[0073]

[0074] From the results in Table 1, it can be seen that Examples 1 to 12, which satisfy the constitution of the present invention, are labels that can be attached to an adherend without any problems, while Comparative Examples 1 to 5, which do not satisfy the constitution of the present invention, have problems when attaching them to an adherend.

[0075] Primarily, comparison of Examples 1 to 8 with Examples 9 to 10 reveals that when the MD / CD ratio of the tensile strength index of the label is 1.05 or more and 1.75 or less, the label is less likely to lift off before the rewettable adhesive layer dries when attached to the substrate. Primarily, comparison of Examples 1 to 10 with Examples 11 and 12 reveals that when the paper substrate contains one or more water-soluble polymers selected from the group consisting of starches and polyvinyl alcohols as a surface sizing agent, the curl amplitude before and after wetting the rewettable adhesive layer is reduced, and although not shown in the above "Attachment to substrate - suitability evaluation" and "Attachment to substrate - lifting evaluation," wrinkles or bent corners are less likely to occur when the label is attached, making it preferable for the label.

Claims

1. A label having a paper base material, a recording layer on the surface of the paper base material, and a re-wettable adhesive layer on the back surface of the paper base material, wherein the label is cut to a size of CD 80 mm x MD 80 mm based on the paper base material and left in an environment of 23°C and relative humidity 50% for 24 hours, and after being left, the label has a curl value of 0 mm or more and 30 mm or less, based on a state in which the re-wettable adhesive layer faces upward, measured before wetting the re-wettable adhesive layer in the same environment, and the re-wettable adhesive layer is then moistened in the same environment to the extent that the re-wettable adhesive layer exhibits adhesiveness, and the curl value of the label has a curl value of -30 mm or more and 0 mm or less, based on a state in which the re-wettable adhesive layer faces upward, measured 10 seconds after wetting.

2. The label according to claim 1, wherein the ratio of the specific tensile strength in the MD to the specific tensile strength in the CD (MD / CD) is 1.05 or more and 1.75 or less in tensile strength determined in accordance with ISO 1924-2:1994.

3. The label according to claim 1 or 2, wherein the paper base material contains one or more water-soluble polymers selected from the group consisting of starches and polyvinyl alcohols as a surface sizing agent using a size press.

4. The coating amount (g / m) of the rewetting active paste layer is determined by the following steps. ２ The label according to claim 1, wherein the re-wetting active adhesive layer is moistened with water or a water-containing solution in an amount of 0.5 to 5 times the amount of water relative to the dry solid content, and the curl value measured 10 seconds after wetting is -30 mm or more and 0 mm or less, based on the state in which the re-wetting active adhesive layer faces upward.

Images