Method for producing heat-shrinkable label, method for producing labeled container, and heat-shrinkable label

Abstract

A method for producing a heat-shrinkable label (1) includes: a step (102) for transferring an aqueous ink onto a substrate film (11); and a step (103) for drying the aqueous ink transferred onto the substrate film to form an aqueous ink layer. The substrate film (11) includes a polyester-based resin film or a multilayer film obtained by laminating a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer in the stated order. The substrate film, before the aqueous ink is transferred thereon, satisfies the following requirements (1) to (3).　(1) The contraction percentage in the width direction after immersion in a warm bath at 60°C for 10 seconds is 1% or less.　(2) The contraction percentage in the width direction after immersion in the warm bath at 70°C for 10 seconds is 10% or less.　(3) The contraction percentage in the width direction after immersion in the warm bath at 90°C for 10 seconds is 40% or more.

Description

Method for manufacturing heat-shrinkable labels, method for manufacturing labeled containers, and heat-shrinkable labels

[0001] The present disclosure relates to a method for manufacturing a heat-shrinkable label, a method for manufacturing a labeled container, and a heat-shrinkable label.

[0002] For example, labels printed for product identification and the like are attached to the outer surfaces of various containers. Among the plastic labels attached to the outer surfaces of various containers are heat-shrinkable labels that are attached to the containers by thermal shrinkage so that they adhere tightly to the containers. Heat-shrinkable labels have heat-shrinkability such that they hardly shrink naturally at room temperature but shrink rapidly when heated to 60°C or higher.

[0003] For example, Patent Document 1 describes a label in which a water-based ink print layer is formed on a substrate in response to the recent increase in environmental awareness and from the perspective of suppressing the generation of VOCs (volatile organic compounds).

[0004] Japanese Patent Application Laid-Open No. 2023-3150

[0005] Although the substrate in Patent Document 1 is not heat-shrinkable, printing with water-based ink is also required for heat-shrinkable labels. When producing a label by transferring water-based ink onto a substrate and then drying the water-based ink, it is necessary to dry the water-based ink at a high temperature to improve label production efficiency. However, when water-based ink on a heat-shrinkable substrate is dried at a high temperature, the substrate may thermally shrink. If the substrate thermally shrinks, the substrate will flap as it is unwound from the original roll on the printing press, making it difficult to align the print and perform post-processing such as bag making. This requires drying at a low temperature, which reduces printing efficiency.

[0006] In view of the above circumstances, the object of the present disclosure is to provide a method for manufacturing a heat-shrinkable label, a method for manufacturing a labeled container, and a heat-shrinkable label that can improve printing efficiency and do not cause any problems in the finished product even when a container is attached, etc.

[0007] According to the present disclosure, there is provided a method for producing a heat-shrinkable label, the method comprising the steps of transferring an aqueous ink onto a base film and drying the aqueous ink transferred onto the base film to form an aqueous ink layer, wherein the base film comprises a multilayer film formed by laminating a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer in this order, or a polyester-based resin film, and the base film before transferring the aqueous ink satisfies the following requirements (1) to (3): (1) The shrinkage rate in the width direction after immersion in a 60°C warm bath for 10 seconds is 1% or less; (2) The shrinkage rate in the width direction after immersion in a 70°C warm bath for 10 seconds is 10% or less; and (3) The shrinkage rate in the width direction after immersion in a 90°C warm bath for 10 seconds is 40% or more.

[0008] According to the present disclosure, there is provided a heat-shrinkable label suitable for being attached to a container by heat shrinking in close contact with the container, the heat-shrinkable label comprising a base film and an aqueous ink layer on the base film, wherein the base film is a multilayer film formed by laminating a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer in this order, or a polyester-based resin film, and the heat-shrinkable label satisfies the following requirements (1) to (4): (1) a widthwise shrinkage rate of 1% or less after immersion in a 60°C warm bath for 10 seconds; (2) a widthwise shrinkage rate of 10% or less after immersion in a 70°C warm bath for 10 seconds; (3) a widthwise shrinkage rate of 40% or more after immersion in a 90°C warm bath for 10 seconds; and (4) a widthwise shrinkage rate of 0.5% or less after storage for 7 days in an atmosphere at a temperature of 55°C or after storage for 1 day in an atmosphere at a temperature of 55°C and 30% humidity followed by storage for 6 days in an atmosphere at a temperature of 40°C and 90% humidity.

[0009] According to the present disclosure, it is possible to provide a method for manufacturing a heat-shrinkable label, a method for manufacturing a labeled container, and a heat-shrinkable label that can improve printing efficiency and produce a finished product that does not have any problems even when a container is attached, etc.

[0010] FIG. 1 is a flow diagram of an example of a method for producing a heat-shrinkable label of embodiment 1. FIG. 2 is a schematic plan view of an example of a base film. FIG. 3 is a schematic perspective view illustrating an example of a heat-shrinkable label of embodiment 1. FIG. 4 is a schematic cross-sectional view of an example of the heat-shrinkable label shown in FIG. 3, taken along line IV-IV. FIG. 5 is a flow diagram of an example of a method for producing a heat-shrinkable label of embodiment 2. FIG. 6 is a schematic cross-sectional view of an example of the heat-shrinkable label of embodiment 2. FIG. 7 is a schematic perspective view illustrating an example of a step of placing a heat-shrinkable label so as to surround the outer peripheral surface of a container. FIG. 8 is a schematic cross-sectional view of an example taken along line VIII-VIII of FIG. 7. FIG. 9 is a schematic plan view of an example of a labeled container.

[0011] Hereinafter, embodiments will be described. In the drawings used to describe the embodiments, the same reference numerals denote the same or corresponding parts.

[0012] [Embodiment 1] Fig. 1 shows a flow diagram of an example of a method for producing a heat-shrinkable label according to embodiment 1. As shown in Fig. 1, the method for producing a heat-shrinkable label according to embodiment 1 includes step 102 of transferring aqueous ink for printing onto a base film, step 103 of drying the aqueous ink transferred onto the base film to form an aqueous ink layer, and step 104 of forming the printed base film into a cylindrical bag.

[0013] <Step of transferring aqueous ink> Step 102 of transferring aqueous ink can be performed, for example, by transferring the aqueous ink from a gravure printing plate or a flexographic printing plate onto a substrate film. Step 102 can be performed, for example, by gravure printing or flexographic printing. When performing gravure printing or flexographic printing, by setting the temperature of a drying oven installed after transferring the aqueous ink from the gravure printing plate or the flexographic printing plate onto the substrate film high, the drying of the solvent contained in the aqueous ink can be promoted, thereby enabling high-speed printing of the aqueous ink. Step 102 is preferably performed by flexographic printing, and particularly preferably by center-drum flexographic printing, in which each color is printed with the substrate film overlapping and aligned with the peripheral surface of a drum.

[0014] <Substrate Film> Figure 2 shows a schematic plan view of an example of the substrate film used in step 102. The substrate film 11 shown in Figure 2 is a multilayer film formed by laminating a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer in this order, or a heat-shrinkable plastic film containing a polyester-based resin film. The substrate film 11 has a longitudinal direction 2, which is the non-shrinkage direction, and a width direction 3, which is the main shrinkage direction. Before printing, the substrate film 11 is in a long, continuous shape, extending for example several thousand meters in the longitudinal direction 2. In this specification, the non-shrinkage direction (longitudinal direction 2) refers to a direction in which the shrinkage rate is smaller than that of the main shrinkage direction (width direction 3), and does not necessarily mean that the substrate film 11 does not shrink at all. The angle between the longitudinal direction 2 and the width direction 3 of the substrate film 11 is 90°.

[0015] Furthermore, the base film 11 before transferring the water-based ink satisfies the following requirements (1) to (3): (1) The shrinkage rate in the width direction 3 after immersion in a warm bath at 60°C for 10 seconds is 1% or less. (2) The shrinkage rate in the width direction 3 after immersion in a warm bath at 70°C for 10 seconds is 10% or less. (3) The shrinkage rate in the width direction 3 after immersion in a warm bath at 90°C for 10 seconds is 40% or more.

[0016] The widthwise shrinkage rate of the base film 11, which satisfies the above requirements (1) to (3), is calculated by the following (Formula A) from the widthwise lengths of the base film 11 before and after immersion in a warm water bath heated to a temperature of 60°C to 90°C for 10 seconds under no load.

[0017] Width direction shrinkage rate [%]=100×[{(width direction length of base film 11 before immersion)−(width direction length of base film 11 after immersion)} / (width direction length of base film 11 before immersion)] (Equation A)

[0018] Furthermore, from the viewpoint of obtaining a heat-shrinkable label that will not cause any problems in finish even after being attached to a container, etc., it is preferable that the base film 11 before the aqueous ink is transferred further satisfy the following requirement (4): (4) It is preferable that the shrinkage rate in the width direction after storage for 7 days in an atmosphere at a temperature of 55°C, or after storage for 1 day in an atmosphere at a temperature of 55°C and a humidity of 30%, and then storage for 6 days in an atmosphere at a temperature of 40°C and a humidity of 90% is 0.5% or less.

[0019] The widthwise shrinkage percentage of the base film 11, as required by requirement (4), before the transfer of the aqueous ink is calculated as follows: The base film 11 has been continuously stored in an atmosphere at a temperature of 25° C. or less, and then stored for 7 days in an atmosphere at a temperature of 55° C. (humidity 1% to 2%) (hereinafter, "storing for 7 days in an atmosphere at a temperature of 55° C. (humidity 1% to 2%)" is sometimes simply referred to as "aging"), or the base film 11 has been stored for 1 day in an atmosphere at a temperature of 55° C. and humidity 30%, and then stored for 6 days in an atmosphere at a temperature of 40° C. and humidity 90% (hereinafter, sometimes referred to as "humid aging"), and the widthwise shrinkage percentage is calculated from the widthwise lengths of the base film 11 before and after storage using the following formula (B):

[0020] Width direction shrinkage rate [%]=100×[{(width direction length of base film 11 before aging or before humid aging)−(width direction length of base film 11 after aging or after humid aging)} / (width direction length of base film 11 before aging or before humid aging)] (Equation B)

[0021] The substrate film 11 shown in FIG. 2 can be manufactured, for example, as follows. First, a polyester-based resin raw material and a polystyrene-based resin raw material are prepared. The polyester-based resin raw material can be, for example, a resin containing 50 mol% or more of ethylene terephthalate units and containing an amorphous component modified with other glycol components such as 1,4-cyclohexanedimethanol or neopentyl glycol, or other dicarboxylic acid components such as isophthalic acid. The polystyrene-based resin raw material can be, for example, a styrene-based resin such as a styrene-butadiene copolymer resin, which is likely to provide gradual heat shrinkability in the substrate film 11.

[0022] Next, the polyester-based resin raw material and the polystyrene-based resin raw material are used to prepare an unstretched multilayer film, or the polyester-based resin raw material is used to prepare an unstretched polyester-based resin film.

[0023] An unstretched multilayer film can be produced, for example, as follows. First, the polyester-based resin raw material and the polystyrene-based resin raw material are fed into an extruder. Next, the raw material is extruded through a multilayer die into a three-layer sheet having a polystyrene-based resin layer between two polyester-based resin layers (a first polyester-based resin layer and a second polyester-based resin layer). The extruded three-layer sheet is then cooled and solidified. This allows the production of an unstretched multilayer film. The multilayer film is not limited to a three-layer structure. For example, a five-layer structure, a six-layer structure, or a seven-layer structure having another resin layer (e.g., a mixed resin of a polyester-based resin and a polystyrene-based resin, or a resin layer containing other resin components, adhesive components, etc.) between the polyester-based resin layer and the polystyrene-based resin layer can also be used. Furthermore, an unstretched polyester-based resin film can be produced in the same manner as an unstretched multilayer film, except that the polyester-based resin raw material is extruded into a single layer or multiple layers. As an unstretched film of a multilayer polyester-based resin film, for example, a laminate of three polyester-based resin layers of different types (where the middle polyester-based resin layer and the polyester-based resin layers on both sides have different amorphous components in terms of their presence or ratio, or where recycled PET is laminated onto the middle polyester-based resin layer) can be used.

[0024] The unstretched film can be produced by a conventional method such as melt film formation, but the melt film formation method (particularly the T-die method) is preferably used as the method for producing the unstretched film. Furthermore, the resin lamination method can be a conventional method such as co-extrusion (feed block method, multi-manifold method, etc.), with the feed block method being preferred.

[0025] A specific example of the co-extrusion method (feed block method) is a method in which the raw material (polystyrene-based resin layer) forming the intermediate portion and the raw material (polyester-based resin layer) forming the surface portion are respectively fed into multiple extruders set at predetermined temperatures, and co-extruded through a T-die using a feed block to form a predetermined laminate structure. The extrusion temperature varies depending on the type of resin used and is not particularly limited, but is preferably, for example, about 150 to 250°C. An unstretched film (sheet) can be produced by contacting the polymer co-extruded through the T-die with a cooling drum and quenching it.

[0026] Next, the unstretched film produced as described above is stretched to impart heat shrinkability, thereby producing the substrate film 11. The stretching can be performed by biaxial stretching in the longitudinal direction 2 and the width direction 3, or uniaxial stretching in the width direction 3. As the stretching method, for example, any of a roll method, a tenter method, and a tube method can be used. Furthermore, when performing the stretching by biaxial stretching in the longitudinal direction 2 and the width direction 3, the films may be stretched biaxially simultaneously or sequentially.

[0027] A specific example of stretching processing involves introducing the unstretched film prepared as described above into a longitudinal stretching device and then into a transverse stretching device. More specifically, for example, the film can be stretched in the longitudinal direction 2 by roll-type longitudinal stretching at a stretching temperature of 65 to 100°C and a stretching ratio of 1.05 to 1.50, and then stretched in the width direction 3 by tenter-type transverse stretching at a stretching temperature of 70 to 120°C and a stretching ratio of 3 to 8 (preferably 4 to 7). After stretching in the width direction 3, the film can be subjected to heat treatment (heat setting at a temperature lower than the stretching temperature) while clipped by a tenter, or to a relaxation heat treatment in which the tenter is slightly relaxed. The stretching processing may be performed in multiple stages, and heat treatments such as annealing may also be performed. In particular, the heat shrinkage rate and natural shrinkage rate of the substrate film 11 at each temperature and during storage can be adjusted by adjusting the stretching temperature, stretching ratio, and heat treatment temperature and time during the stretching processing.

[0028] <Water-Based Ink> In step 102, the water-based ink to be transferred onto the substrate film 11 may be, for example, a water-based ink containing an aqueous solvent such as water or an alcoholic aqueous solution, a resin, an additive, a pigment, and the like.

[0029] Examples of resins that can be used in aqueous inks include one or more of the following resins: acrylic resins, urethane resins, polyester resins, polyamide resins, cellulose resins, vinyl chloride resins, vinyl acetate resins, polyolefin resins such as polyethylene resins, polybutadiene resins, isocyanate resins, rosin resins, polyvinyl alcohol resins, and imine resins.

[0030] Additives contained in the water-based ink include, for example, plasticizers, anti-settling agents, dispersants, stabilizers, anti-foaming agents, fillers, antioxidants, ultraviolet absorbers, antistatic agents, color separation inhibitors, and lubricants.

[0031] Examples of pigments that can be used in aqueous inks include white pigments such as titanium oxide, black pigments such as carbon black, color pigments of various colors such as red, blue, and yellow, and other pigments such as silver pigments made from aluminum pigments.

[0032] The aqueous ink may contain an aqueous solvent in an amount of 30% by weight or more relative to the total weight of the aqueous ink. The aqueous ink may also contain resins, additives, pigments, etc. other than the aqueous solvent in an amount of 70% by weight or less relative to the total weight of the aqueous ink. The aqueous solvent contained in the aqueous ink may be, for example, 100% water, or an aqueous solution containing an alcohol such as ethanol or isopropyl alcohol. When the aqueous solvent contains alcohol, the concentration of the alcohol relative to the total weight of the aqueous ink including solids is preferably less than 5%.

[0033] <Step of Forming an Aqueous Ink Layer> Step 103 of forming an aqueous ink layer can be performed, for example, by passing the substrate film 11 and the aqueous ink transferred onto the substrate film 11 through a heating zone. This dries the aqueous ink on the substrate film 11 and volatilizes the aqueous solvent from the aqueous ink, thereby forming an aqueous ink layer on the substrate film 11. In step 103, the drying time (time exposed to the drying temperature) of the aqueous ink transferred onto the substrate film 11 is, for example, approximately 1.8 seconds in flexographic printing when the drying oven (60°C) is 6 m long and the printing speed is 200 m / min. Gravure printing and flexographic printing are preferred because they require a small amount of ink application and a thin printed layer, which requires less heating during drying. The ink application amount is 0.1 g / m per color in the case of solid printing. ２ ~5g / m ２ The thickness after drying is about 0.05 μm to 3 μm.

[0034] <Step of Forming a Cylindrical Bag> Heat-shrinkable labels can be produced by processing a printed substrate film into a cylindrical bag. Step 104 of forming a cylindrical bag can be performed, for example, as follows. First, in steps 102 and 103, the long substrate film 11 is unwound from the roll in the longitudinal direction. Water-based ink is transferred onto the substrate film 11 by gravure printing or flexographic printing, the water-based ink is dried to form a water-based ink layer, and the roll is then wound up. The rolled substrate film is then slit (cut) to a predetermined width. Next, the substrate film 11 with the water-based ink layer formed thereon is unwound from the slit roll, and both edges in the width direction 3 are bonded (envelope-sealed) with an adhesive or the like to form a cylindrical bag. The bag is then folded flat and wound up into a roll, thereby producing a long label roll product in which heat-shrinkable labels are connected in the longitudinal direction 2. During the processing, the heat-shrinkable label 1 may be perforated in the longitudinal direction or the like for label removal.

[0035] <Heat-shrinkable label of embodiment 1> Figure 3 shows a schematic perspective view of an example of a single heat-shrinkable label of embodiment 1 manufactured as described above. As shown in Figure 3, the heat-shrinkable label 1 of embodiment 1 has a longitudinal direction 2, which is the non-shrinkage direction, and a width direction 3, which is the main shrinkage direction, and is processed into a tubular shape surrounding an imaginary axis 2' extending along the longitudinal direction 2. Figure 4 shows a schematic cross-sectional view of the heat-shrinkable label 1 shown in Figure 3 taken along line IV-IV. As shown in Figure 4, the heat-shrinkable label 1 includes a base film 11 and an aqueous ink layer 12 on the base film 11.

[0036] From the viewpoint of obtaining a heat-shrinkable label that will not cause any problems in finish even after being attached to a container, the heat-shrinkable label 1 preferably satisfies the following requirements (1) to (4), and more preferably satisfies the following requirements (1) to (5): (1) The shrinkage in the width direction after immersion in a 60°C warm bath for 10 seconds is 1% or less; (2) The shrinkage in the width direction after immersion in a 70°C warm bath for 10 seconds is 10% or less; (3) The shrinkage in the width direction after immersion in a 90°C warm bath for 10 seconds is 40% or more; (4) The shrinkage in the width direction after storage in an atmosphere at a temperature of 55°C for 7 days, or after storage in an atmosphere at a temperature of 55°C and 30% humidity for 1 day and then storage in an atmosphere at a temperature of 40°C and 90% humidity for 6 days is 0.5% or less; and (5) The shrinkage in the width direction after immersion in an 80°C warm water bath for 10 seconds is greater than 10% and less than 50% (more preferably greater than 15% and less than 50%).

[0037] The widthwise shrinkage percentage of the heat-shrinkable label 1 meeting the above requirements (1) to (3) and (5) is calculated by the following formula C from the widthwise lengths of the heat-shrinkable label 1 before and after immersion in a hot water bath heated to a temperature of 60°C to 90°C for 10 seconds under no load, after which the heat-shrinkable label 1, which has been continuously stored in an atmosphere at a temperature of 25°C or less after being processed from the base film 11,

[0038] Width direction shrinkage rate [%]=100×[{(width direction length of heat-shrinkable label 1 before immersion)−(width direction length of heat-shrinkable label 1 after immersion)} / (width direction length of heat-shrinkable label 1 before immersion)] (Equation C)

[0039] The widthwise shrinkage rate of the heat-shrinkable label 1, which is the requirement (4) above, is calculated as follows: After the base film 11 is manufactured and continuously stored in an atmosphere at a temperature of 25° C. or less, the base film 11 is processed into the heat-shrinkable label 1, and then the widthwise shrinkage rate is calculated from the widthwise lengths of the heat-shrinkable label 1 before and after aging or before and after humid aging using the following formula (D):

[0040] Width direction shrinkage rate [%]=100×[{(width direction length of heat shrinkable label 1 before aging or humidity aging)−(width direction length of heat shrinkable label 1 after aging or humidity aging)} / (width direction length of heat shrinkable label 1 before aging or humidity aging)] (Equation D)

[0041] Furthermore, it is preferable that the heat-shrinkable label 1 satisfies at least the above requirements (1) to (3) and (5) both before and after the aging process and both before and after the humidification aging process, which allows for a good finish when the label is fitted onto a container and heat-shrunk to attach it to the container.

[0042] The widthwise shrinkage percentage of the heat-shrinkable label 1 before aging or humidity aging, which satisfies the above requirements (1) to (3) and (5), is calculated using the above formula C. The widthwise shrinkage percentage of the heat-shrinkable label 1 after aging or humidity aging, which satisfies the above requirements (1) to (3) and (5), is calculated as follows: The heat-shrinkable label 1 after aging or humidity aging is immersed in a warm water bath heated to a temperature of 60°C to 90°C for 10 seconds under no load, and the widthwise shrinkage percentage is calculated using the following formula E from the widthwise lengths of the heat-shrinkable label 1 before and after immersion.

[0043] Width direction shrinkage rate [%]=100×[{(width direction length of heat-shrinkable label 1 after aging or humidification aging before immersion)−(width direction length of heat-shrinkable label 1 after aging or humidification aging after immersion)} / (width direction length of heat-shrinkable label 1 after aging or humidification aging before immersion)] (Equation E)

[0044] <Water-Based Ink Layer> The water-based ink layer 12 of the heat-shrinkable label 1 shown in FIG. 4 is not limited to full-surface printing, but may also include a partial printing layer such as letters or a design. It may also include a single-color printing, a multicolor printing layer with 2 to 10 colors, a solid white printing layer, or a solid silver printing layer. Even when a printing configuration with a high solid density (number of colors) that is prone to blocking (e.g., a light-blocking configuration with solid white / white / silver or gray printing) is used on the base film 11, the drying efficiency is improved, thereby preventing blocking. Furthermore, even when a curing agent is added, the water-based ink can be dried at high temperatures, which is believed to be effective in preventing blocking. Furthermore, even when double-sided printing is applied to the base film 11 (e.g., a design color and a solid white background on the back, and a matte medium on the front), high-temperature drying of the water-based ink is believed to reduce blocking caused by contact between the inks on both sides when the film is wound after printing. Blocking refers to the phenomenon in which the aqueous ink printed surface of a rolled-up original sheet transfers to another substrate (film) or printed surface located directly above or below it, or overlapping labels (print and film, print and print) stick together, making it difficult to unwind the sheet from the rolled up state.

[0045] <Effects> In embodiment 1, since the base film 11 satisfies at least the above requirements (1) and (2), thermal shrinkage of the base film 11 can be suppressed even when the aqueous ink transferred onto the base film 11 is dried at high temperatures, thereby improving the printing efficiency of the aqueous ink. Furthermore, if the base film 11 also satisfies the above requirement (3), a heat-shrinkable label 1 that satisfies the above requirements (1) to (3), preferably the above requirements (1) to (3) and (5), can be produced from the base film 11, and the heat-shrinkable label 1 can be used to attach a container or the like without causing any problems in the finished product. If the heat-shrinkable label 1 also satisfies the above requirement (4), the heat-shrinkable label 1 can be used to attach a container or the like without causing any problems in the finished product.

[0046] [Embodiment 2] Fig. 5 shows a flow diagram of an example of a method for producing a heat-shrinkable label according to Embodiment 2. As shown in Fig. 5, the method for producing a heat-shrinkable label according to Embodiment 2 is characterized by including step 102a of transferring a colored water-based ink onto a base film 11, step 103a of drying the colored water-based ink transferred onto the base film 11 to form a first water-based ink layer, step 105a of transferring a white water-based ink containing a curing agent onto the first water-based ink layer, step 106a of drying the white water-based ink containing a curing agent to form a second water-based ink layer, and step 107a of winding up the base film 11 onto which the first water-based ink and the second water-based ink layer have been formed.

[0047] <Step of transferring colored water-based ink> Step 102a of transferring colored water-based ink onto the base film 11 can be carried out, for example, by a step of transferring the colored water-based ink from a gravure printing plate or a flexographic printing plate onto the base film, similar to step 102 described above.

[0048] <Step of forming first water-based ink layer> Step 103a of forming the first water-based ink layer can be carried out, for example, in the same manner as step 103 described above, by drying the base film 11 and the colored water-based ink on the base film 11 by passing them through a heating zone to form the first water-based ink layer on the base film 11.

[0049] <Step of transferring white water-based ink containing a curing agent onto the first water-based ink layer> Step 105a of transferring white water-based ink containing a curing agent onto the first water-based ink layer can be performed by transferring the white water-based ink containing a curing agent onto the first water-based ink layer, for example, by gravure printing or flexographic printing.

[0050] <Step of forming second aqueous ink layer> Step 106a of forming the second aqueous ink layer can be carried out, for example, by transferring the white aqueous ink containing the curing agent onto the first aqueous ink layer from the printing plate onto the base film 11, and then passing it through a heating zone, thereby removing the aqueous solvent from the white aqueous ink containing the curing agent to form the second aqueous ink layer.

[0051] <Step of Winding into a Roll> Step 107a of winding into a roll can be performed, for example, by using a conventionally known winding device to wind the substrate film 11, on which the first and second water-based ink layers have been formed and which is being continuously transported, onto a conventionally known roll. Thereafter, the above-mentioned step of forming the heat-shrinkable label into a cylindrical bag is performed, thereby producing the heat-shrinkable label 1 shown in FIG.

[0052] <Other Forms of Embodiment 2> When performing multicolor printing using inks such as black, blue, red, and yellow, the first water-based ink layer may be formed by transferring each color of water-based ink and repeating the transfer and drying of the colored water-based inks. This is followed by a step of transferring a white water-based ink containing a curing agent onto the first water-based ink layer. Two or more layers of white water-based ink containing a curing agent may be superimposed, in which case the transfer and drying of the white water-based ink containing a curing agent may be repeated two or more times. Furthermore, when performing flexographic printing using the center drum method described above, for example, colored water-based inks of each color, such as black, blue, red, and yellow, may be transferred sequentially from each plate, and then the white water-based ink containing a curing agent may be superimposed and transferred without undergoing a step of drying the colored water-based inks for each color. The entire ink may then be dried in a drying oven. In this case, the first and second water-based ink layers may be formed by simultaneously drying the entire ink.

[0053] <Heat-shrinkable label of embodiment 2> Fig. 6 shows a schematic cross-sectional view of an example of a heat-shrinkable label of embodiment 2. As shown in the schematic cross-sectional view of Fig. 6, the heat-shrinkable label 1 of embodiment 2 is characterized in that the water-based ink layer 12 on the base film 11 includes a first water-based ink layer 12a and a second water-based ink layer 12b.

[0054] <First Water-Based Ink Layer> The first water-based ink layer 12a includes an ink layer formed by transferring and drying a colored water-based ink. The colored water-based ink includes colored pigments such as black, blue, red, and yellow. The colored water-based ink forming the first water-based ink layer 12a may include an aqueous solvent such as water or an alcohol-water solution, a resin, an additive, and a pigment. The first water-based ink layer 12a is not limited to a full-surface print; it may also include a partial print layer such as letters or a design. In addition to a single color print, it may also include multiple design print layers, such as a multicolor print layer with two to ten colors applied over each other. The colored water-based ink does not need to contain a curing agent. By forming the first water-based ink layer 12a with a colored water-based ink that does not contain a curing agent and forming the second water-based ink layer 12b overlying the first water-based ink layer 12a with a white water-based ink that does contain a curing agent, the first water-based ink layer 12a can also be cured, improving the durability of the printed layer. Furthermore, by not adding a curing agent to the colored water-based ink, the remaining amount of the colored water-based ink used in the first water-based ink layer 12a can be reused, making it possible to reduce the amount used.

[0055] <Second Water-Based Ink Layer> The second water-based ink layer 12b includes a layer formed by transferring and drying a white water-based ink containing a curing agent. Examples of the white water-based ink containing a curing agent include a white water-based ink containing an aqueous solvent such as water or an alcohol solution, a binder resin, additives, and a white pigment. It is preferable to use a curing agent that corresponds to the binder resin contained in the white water-based ink. For example, if the binder resin contained in the water-based ink used to form the first water-based ink layer has a hydroxyl group or an amino group, an isocyanate-based curing agent is suitable. Furthermore, if the binder resin contained in the water-based ink used to form the first water-based ink layer has an amino group or a carbonyl group, an epoxy-based curing agent is suitable. Furthermore, if the binder resin contained in the water-based ink used to form the first water-based ink layer has a carbonyl group, a carbodiimide-based curing agent, an aziridine-based curing agent, or a hydrazide-based curing agent is suitable.

[0056] Other than the above, the description of the second embodiment is the same as that of the first embodiment, and therefore will not be repeated.

[0057] <Method for manufacturing labeled container> An example of a method for manufacturing a labeled container will now be described. First, as shown in the schematic perspective view of Figure 3, a step of producing a single heat-shrinkable label 1 of the embodiment is carried out. This step can be carried out, for example, by cutting a long heat-shrinkable label 1 that has been made into a cylindrical shape and folded so as to surround an imaginary axis 2' extending along the longitudinal direction 2 into single heat-shrinkable labels 1, and then unfolding the folded label 1 into a cylindrical shape (approximately cylindrical).

[0058] Next, as shown in the schematic perspective view of Figure 7, a step of installing a heat-shrinkable label 1 so that it surrounds the outer peripheral surface of the container is performed. This step can be performed, for example, by fitting the tubular heat-shrinkable label 1 onto the container 4 so that the inner peripheral surface 1a of the label 1 surrounds the outer peripheral surface 40 of the container 4. Here, the outer peripheral surface 40 of the container 4 has a body portion 41 located at the bottom of the container 4, a shoulder portion 42 located above the body portion 41, and a mouth portion 43 located above the shoulder portion 42. The heat-shrinkable label 1 can be installed, for example, by fitting it onto the outer peripheral surface 40 of the container 4 from the body portion 41 to the shoulder portion 42.

[0059] Figure 8 shows a schematic cross-sectional view of an example taken along line VIII-VIII in Figure 7. The heat-shrinkable label 1 is preferably placed so as to surround the outer peripheral surface 40 of the container 4 such that the circumferential length of the inner peripheral surface 1a of the heat-shrinkable label 1 is 15 mm to 30 mm longer than the circumferential length of the outer peripheral surface 40 of the container 4. In particular, when the circumferential length of the outer peripheral surface 40 of the container 4 is, for example, 180 mm to 250 mm, the heat-shrinkable label 1 is more preferably placed so as to surround the outer peripheral surface 40 of the container 4 such that the circumferential length of the inner peripheral surface 1a of the heat-shrinkable label 1 is 18 mm to 26 mm longer than the circumferential length of the outer peripheral surface 40 of the container 4. Note that, although Figure 8 illustrates a case in which the cross-sectional shapes of the outer peripheral surface 40 of the container 4 and the inner peripheral surface 1a of the heat-shrinkable label 1 are circular, they are not limited to circular shapes and may be polygonal. The heat-shrinkable label 1 may also be in a cylindrical shape with two to four creases remaining when folded flat.

[0060] Next, steam and / or hot air is blown onto the heat-shrinkable label 1 to adhere the heat-shrunk label 1 to the outer peripheral surface 40 of the container 4. This process can be performed, for example, by passing the container 4 fitted with the heat-shrinkable label 1 through a steam tunnel and / or a hot air tunnel, and then blowing steam and / or hot air onto the entire heat-shrinkable label 1 in the atmospheric pressure steam tunnel and / or hot air tunnel. The steam blown onto the heat-shrinkable label 1 can be, for example, water vapor generated in a boiler at 100°C or less, preferably 80°C to 90°C, i.e., a mixture of saturated water vapor and steam condensed from water vapor. The hot air blown onto the heat-shrinkable label 1 can be, for example, hot air at 80°C to 250°C.

[0061] A labeled container can be manufactured through the above steps. Fig. 9 shows a schematic plan view of an example of a labeled container. In the labeled container 50 shown in Fig. 9, the heat-shrinkable label 1 after heat shrinkage is in close contact with the outer peripheral surface 40 of the container 4, and the heat-shrinkable label 10 after heat shrinkage is attached from the body portion 41 to the shoulder portion 42 of the outer peripheral surface 40 of the container 4.

[0062] <Preparation of Base Films for Experimental Examples 1 to 8> Several types of base films with various width-direction shrinkage rates were prepared by appropriately changing the manufacturing conditions, etc., and were used as the base films for Experimental Examples 1 to 8. The base films for Experimental Examples 1 to 3 and 6 were each a 35 μm-thick multilayer film in which a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer were laminated in this order. The base films for Experimental Examples 4, 7, and 8 were polyester-based resin films with a thickness of 20 μm. The base film used in Experimental Example 5 was a polyester-based resin film with a thickness of 30 μm.

[0063] First, the following shrinkage percentages were calculated for the width direction of the base films of Experimental Examples 1 to 8: (i) shrinkage percentage [%] in the width direction when stored at 25°C; (ii) shrinkage percentage [%] in the width direction after storage for 7 days in an atmosphere at a temperature of 55°C; (iii) difference ((i) - (ii)) [%] between the width direction shrinkage percentage when stored at 25°C and the width direction shrinkage percentage after storage for 7 days in an atmosphere at a temperature of 55°C; (iv) maximum shrinkage percentage [%] in the width direction; (v) natural shrinkage percentage [%]; (vi) shrinkage percentage [%] in the width direction after storage for 1 day in an atmosphere at a temperature of 55°C and 30% humidity followed by storage for 6 days in an atmosphere at a temperature of 40°C and 90% humidity; and (vii) difference ((i) - (vi)) [%] between the width direction shrinkage percentage when stored at 25°C and the width direction shrinkage percentage after storage for 1 day in an atmosphere at a temperature of 55°C and 30% humidity followed by storage for 6 days in an atmosphere at a temperature of 40°C and 90% humidity. The results are shown in Table 1.

[0064] (i) The widthwise shrinkage rate [%] when stored at 25°C was calculated by immersing each of the base films of Experimental Examples 1 to 8, which had been stored in an atmosphere at a temperature of 25°C or less since production, in a warm water bath at 60°C to 100°C for 10 seconds under no load, from the widthwise lengths of the base film 11 before and after immersion, using the following formula (A'):

[0065] Width direction shrinkage rate [%]=100×[{(width direction length of base film before immersion)−(width direction length of base film after immersion)} / (width direction length of base film before immersion)] (Equation A′)

[0066] (ii) The widthwise shrinkage percentage [%] after storage in an atmosphere at a temperature of 55°C for 7 days was calculated by immersing the substrate films of Experimental Examples 1 to 8 immediately after storing them in an atmosphere at a temperature of 25°C or less and then immediately after storing (aging) them in an atmosphere at a temperature of 55°C (humidity 1% to 2%) for 7 days in a warm water bath at 60°C to 100°C for 10 seconds under no load, and then calculating the widthwise shrinkage percentage [%] after storing them in an atmosphere at a temperature of 25°C or less and immediately after storing (aging) them in an atmosphere at a temperature of 55°C (humidity 1% to 2%) in a warm water bath at 60°C to 100°C for 10 seconds under no load, using the widthwise lengths of the substrate film 11 before and after the immersion according to the following formula B':

[0067] Width direction shrinkage rate [%]=100×[{(width direction length of the aged base film before immersion)−(width direction length of the aged base film after immersion)} / (width direction length of the aged base film before immersion)] (Equation B′)

[0068] (iii) The difference in shrinkage percentage [%] between (i) the width direction shrinkage percentage when stored at 25°C and (ii) the width direction shrinkage percentage after storage for 7 days in an atmosphere at a temperature of 55°C was calculated by subtracting (ii) the width direction shrinkage percentage [%] after storage for 7 days in an atmosphere at a temperature of 55°C from ((i) - (ii)) the width direction shrinkage percentage [%] when stored at 25°C.

[0069] (iv) The maximum shrinkage rate [%] in the width direction was calculated by immersing each of the substrate films of Experimental Examples 1 to 8, immediately after production and storage in an atmosphere at a temperature of 25°C or less, in a glycerin bath at 140°C for 10 seconds under no load, from the width direction lengths of the substrate film 11 before and after immersion, using the following formula A″:

[0070] Maximum shrinkage rate in width direction [%]=100×[{(width direction length of base film before immersion)−(width direction length of base film after immersion)} / (width direction length of base film before immersion)] (Equation A″)

[0071] (v) The natural shrinkage percentage [%] was calculated from the longitudinal length or width direction length of the base film 11 before and after storage (aging) for 7 days in an atmosphere at a temperature of 55°C or before and after storage (humidification aging) for 6 days in an atmosphere at a temperature of 40°C and a humidity of 90% (without immersion in a hot water bath or a glycerin bath) using the following (formula F). In the following (formula F), the longitudinal length is selected when calculating the longitudinal natural shrinkage percentage [%] after aging or humidification aging, and the width direction length is selected when calculating the width natural shrinkage percentage [%] after aging or humidification aging.

[0072] Natural shrinkage rate [%]=100×[{(longitudinal length or width direction length of base film before aging or humid aging)−(longitudinal length or width direction length of base film after aging or humid aging)} / (longitudinal length or width direction length of base film before aging or after humid aging)] (Equation F)

[0073] (vi) The width direction shrinkage percentage [%] after storage in an atmosphere at a temperature of 55°C and a humidity of 30% for 1 day and then storage in an atmosphere at a temperature of 40°C and a humidity of 90% for 6 days (humidification aging) was calculated by immersing the base films of Experimental Examples 1 to 8 immediately after storage in an atmosphere at a temperature of 25°C or less immediately after production of the base film, immediately after storage in an atmosphere at a temperature of 55°C and a humidity of 30% for 1 day, and immediately after storage in an atmosphere at a temperature of 40°C and a humidity of 90% for 6 days in a warm water bath at 60°C to 100°C for 10 seconds under no load, and calculating the width direction shrinkage percentage [%] after storage in an atmosphere at a temperature of 55°C and a humidity of 30% for 1 day (humidification aging) and then storage in an atmosphere at a temperature of 40°C and a humidity of 90% for 6 days in a warm water bath at 60°C to 100°C for 10 seconds under no load.

[0074] Width direction shrinkage rate [%]=100×[{(width direction length of the base film after the humid aging before immersion)−(width direction length of the base film after the humid aging after immersion)} / (width direction length of the base film after the humid aging before immersion)] (Equation C″)

[0075] (vii) The difference in shrinkage ((i) - (vi) [%] between (i) the width direction shrinkage when stored at 25°C and (vi) the width direction shrinkage after storage for 1 day in an atmosphere at a temperature of 55°C and a humidity of 30% and then storage for 6 days in an atmosphere at a temperature of 40°C and a humidity of 90% (humidification aging) was calculated by subtracting (vi) the width direction shrinkage [%] after storage for 1 day in an atmosphere at a temperature of 55°C and a humidity of 30% and then storage for 6 days in an atmosphere at a temperature of 40°C and a humidity of 90% from (i) the width direction shrinkage [%] when stored at 25°C.

[0076]

[0077] <Printing Evaluation of Base Films of Experimental Examples 1 and 6> Next, base films for Experimental Examples 1 and 6 were selected from the base films of Experimental Examples 1 to 8 above. A roll-shaped raw web measuring 980 mm wide and 2000 m long was prepared as the base film for each of Experimental Examples 1 and 6. A design print of indigo water-based ink was transferred from a flexographic printing machine to the base film using a flexographic printing plate. Subsequently, a white water-based ink was transferred from a flexographic printing plate onto the design on the base film as a solid background print. The film was then dried by passing it through a drying oven approximately 6 meters long and set at 60°C for approximately 1.8 seconds to form an aqueous ink layer. The width and length of each base film for Experimental Examples 1 and 6 before and after passing through the drying oven were measured, and the shrinkage before and after passing through the drying oven was calculated using the following formula (G). The results are shown in Table 2.

[0078] Shrinkage rate [%]=100×[{(length of base film before passing through drying oven)−(length of base film after passing through drying oven)} / (length of base film before passing through drying oven)] (Equation G)

[0079]

[0080] Next, the drying oven was set to 80° C., and printing was performed under the same other conditions. The shrinkage rates of the base films of Experimental Examples 1 and 6 before and after passing through the drying oven are shown in Table 3.

[0081] <Printing Evaluation Results of Base Film> As is clear from the results in Tables 1 to 3, it was confirmed that the base film of Experimental Example 1, which satisfied both of the above requirements (1) and (2), was able to reduce the shrinkage rate when the temperature of the drying oven was set to 80° C., compared to the base film of Experimental Example 6, which satisfied neither of the above requirements (1) nor (2). Therefore, it was confirmed that the use of a base film such as that of Experimental Example 1 enables the aqueous ink transferred onto the base film to dry at 80° C., which is higher than 60° C., and therefore enables an increase in printing speed.

[0082] <Preparation of Heat-Shrinkable Labels of Experimental Examples 1 to 8> Next, a character design and a solid white print were printed using aqueous ink on the prepared base film of each of Experimental Examples 1 to 8, and the film was slit to a predetermined width and then center-sealed (bag-making process) to produce the long tubular heat-shrinkable labels of Experimental Examples 1 to 8. When the above-mentioned properties (i) to (vii) of the heat-shrinkable labels of Experimental Examples 1 to 8 were investigated, it was confirmed that the above-mentioned properties (i) to (vii) of the heat-shrinkable labels of Experimental Examples 1 to 8 were no different from the above-mentioned properties (i) to (vii) of the base film of Experimental Examples 1 to 8, respectively.

[0083] <Evaluation of Finish of Heat-Shrinkable Labels of Experimental Examples 1 to 8 after Steam Heating> The finish of the heat-shrinkable labels of Experimental Examples 1 to 8 was evaluated as follows: First, the flattened cylindrical heat-shrinkable labels of Experimental Examples 1 to 8 (folded diameter (fold width) 114 mm before aging or before humid aging) were unfolded into a roughly cylindrical shape during storage at 25°C, after aging, and after humid aging.

[0084] Next, a PET bottle having a body with a diameter of 65 mm (the diameter is the maximum diameter of the circular part, and is approximately hexagonal with six panels) and a shoulder located above the body and having a smaller diameter than the body was filled with tap water at 15° C. Next, the cylindrical heat-shrinkable labels of Experimental Examples 1 to 8 were fitted into the PET bottle, so that the heat-shrinkable labels of Experimental Examples 1 to 8 were respectively placed around the outer periphery of the PET bottle.

[0085] Next, the PET bottle containers fitted with the heat-shrinkable labels of Experimental Examples 1 to 8 were passed through a normal pressure steam tunnel (tunnel length 3 m, temperature inside the tunnel approximately 85°C (varies between 80°C and 90°C depending on the measurement position, the passage of the container, etc.)), and the heat-shrinkable label was heated for 3 seconds to cause heat shrinkage, thereby attaching it to the outer surface of the PET bottle container in close contact. Here, the steam outlet inside the steam tunnel was adjusted so that it was directed downwards on the PET bottle container in the front section of the steam tunnel, directed to an intermediate position in the middle section, and heated the entire container in the rear section. Furthermore, the required shrinkage rate at the maximum shrinkage position of the heat-shrinkable labels of Experimental Examples 1 to 8 at the uppermost end of the shoulder of the PET bottle container was set to 40 to 45%, taking into account variations in the heat-shrinkable label attachment position.

[0086] Next, the finish of the heat-shrinkable labels of Experimental Examples 1 to 8 attached to the PET bottle containers was visually evaluated according to the following criteria. The results are shown in Table 4.

[0087] (Criteria for evaluation of finish) A... Good finish with no wrinkles etc. B... Good finish with some wrinkles etc. C... Poor finish compared to A and B due to insufficient heat shrinkage D... Natural shrinkage makes it difficult to wear

[0088]

[0089] <Results of evaluation of finish of heat-shrinkable labels of Experimental Examples 1 to 8 after steam heating> As is clear from the results in Table 4, the heat-shrinkable labels of Experimental Examples 1 to 3, which satisfy at least all of the above requirements (1) to (4) for heat-shrinkable labels containing multilayer films, achieved a finish comparable to that of the heat-shrinkable label of Experimental Example 6, which did not satisfy at least the above requirements (1), (2), and (4), before the aging and before the humid aging. After the aging and the humid aging, the heat-shrinkable label of Experimental Example 6 had difficulty in fitting due to natural shrinkage, but Experimental Examples 1 to 3 achieved a good finish with little natural shrinkage.

[0090] Furthermore, as is clear from the results in Table 4, the heat-shrinkable labels of Experimental Examples 4 and 5, which satisfied at least all of the above requirements (1) to (4) for heat-shrinkable labels containing polyester-based resin films, achieved a finish comparable to that of the heat-shrinkable label of Experimental Example 8, which did not satisfy at least requirement (4), before the aging and before the humid aging. After the aging and the humid aging, the heat-shrinkable label of Experimental Example 8 had difficulty in fitting due to natural shrinkage, but Experimental Examples 4 and 5 had little natural shrinkage and achieved a good finish.

[0091] <Evaluation of the Finish of Heat-Shrinkable Labels of Experimental Examples 1 to 8 by Hot Air Heating> Next, the finish of the heat-shrinkable labels of Experimental Examples 1 to 8 attached to PET bottle containers was evaluated in the same manner as the evaluation of the finish by steam heating, except that the PET bottle containers fitted with the heat-shrinkable labels of Experimental Examples 1 to 8 were passed through a hot air tunnel at normal pressure. The results are shown in Table 5. The hot air tunnel used was a Tornado Tunnel PURE 2001 manufactured by Japan Technology Solutions Co., Ltd. The hot air tunnel was 2 m long and had, from upstream to downstream, a first zone and a second zone in which hot air was blown from the sides, and a tornado zone (third zone) in which hot air was blown around the container in a swirling manner. The tunnel passage time was approximately 17 seconds, and the temperatures were set to 90°C in the first zone, 120°C in the second zone, and 180°C in the tornado zone.

[0092]

[0093] <Results of evaluation of finish of heat-shrinkable labels of Experimental Examples 1 to 8 after hot air heating> As is clear from the results in Table 5, the heat-shrinkable labels of Experimental Examples 1 to 3, which satisfy at least all of the above requirements (1) to (4) for heat-shrinkable labels containing multilayer films, achieved a finish comparable to that of the heat-shrinkable label of Experimental Example 6, which did not satisfy at least the above requirements (1), (2), and (4), before the aging and before the humid aging. After the aging and the humid aging, the heat-shrinkable label of Experimental Example 6 had difficulty in fitting due to natural shrinkage, but Experimental Examples 1 to 3 achieved a good finish with little natural shrinkage.

[0094] Furthermore, as is clear from the results in Table 5, the heat-shrinkable labels of Experimental Examples 4 and 5, which satisfied at least all of the above requirements (1) to (4) for heat-shrinkable labels containing polyester-based resin films, showed less natural shrinkage than the heat-shrinkable labels of Experimental Examples 7 and 8, which did not satisfy at least requirement (4). Even before the aging and before or after the humid aging and even after the humid aging, they were fitted into a container and heat-shrunk with hot air, resulting in a good finish.

[0095] Although the embodiments and experimental examples have been described above, it is also planned from the beginning that the configurations of the above-described embodiments and experimental examples may be appropriately combined.

[0096] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0097] The heat-shrinkable label of the embodiment can be used as a label that is attached to a container and displays information, for example, by being thermally shrunk by being blown with steam and / or hot air, and then being attached to the container in close contact with the container.

[0098] REFERENCE SIGNS LIST 1 heat-shrinkable label, 1a inner peripheral surface, 2 longitudinal direction, 2' virtual axis, 3 width direction, 4 container, 11 base film, 12 water-based ink layer, 12a first water-based ink layer, 12b second water-based ink layer, 40 outer peripheral surface, 41 body portion, 42 shoulder portion, 43 mouth portion, 50 labeled container.

Claims

1. A method for producing a heat-shrinkable label, comprising the steps of transferring aqueous ink onto a base film, and drying the aqueous ink transferred onto the base film to form an aqueous ink layer, wherein the base film is a multilayer film formed by laminating a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer in this order, or a polyester-based resin film, and the base film before transferring the aqueous ink satisfies the following requirements (1) to (3): (1) The shrinkage rate in the width direction after immersion in a 60°C warm bath for 10 seconds is 1% or less. (2) The shrinkage rate in the width direction after immersion in a 70°C warm bath for 10 seconds is 10% or less. (3) The shrinkage rate in the width direction after immersion in a 90°C warm bath for 10 seconds is 40% or more.

2. The method for producing a heat-shrinkable label according to claim 1, wherein the base film before transferring the aqueous ink further satisfies the following requirement (4), and the heat-shrinkable label satisfies the following requirements (1) to (4): (1) The shrinkage rate in the width direction after immersion in a 60°C warm bath for 10 seconds is 1% or less; (2) The shrinkage rate in the width direction after immersion in a 70°C warm bath for 10 seconds is 10% or less; (3) The shrinkage rate in the width direction after immersion in a 90°C warm bath for 10 seconds is 40% or more; and (4) The shrinkage rate in the width direction is 0.5% or less after storage in an atmosphere at a temperature of 55°C for 7 days or after storage in an atmosphere at a temperature of 55°C and 30% humidity for 1 day and then storage in an atmosphere at a temperature of 40°C and 90% humidity for 6 days.

3. The method for producing a heat-shrinkable label according to claim 1, wherein the step of transferring the water-based ink includes a step of transferring the water-based ink from a gravure printing plate or a flexographic printing plate onto the base film, and the step of forming the water-based ink layer includes a step of passing the base film and the water-based ink on the base film through a heating zone.

4. A method for producing a heat-shrinkable label according to claim 1, wherein the step of transferring a water-based ink onto a base film includes a step of transferring a colored water-based ink onto the base film and a step of transferring a white water-based ink containing a curing agent, and further includes a step of winding up the base film on which the water-based ink layer has been formed into a roll.

5. A method for manufacturing a labeled container, comprising the steps of: manufacturing the heat-shrinkable label by the method for manufacturing a heat-shrinkable label according to any one of claims 1 to 4; placing the heat-shrinkable label so as to surround the outer periphery of a container; and blowing steam and / or hot air onto the heat-shrinkable label to heat-shrink the heat-shrinkable label and bring the heat-shrinked label into close contact with the outer periphery of the container.

6. A heat-shrinkable label suitable for being attached to a container by heat shrinking in close contact with the container, comprising: a base film; and an aqueous ink layer on the base film, wherein the base film is a multilayer film formed by laminating a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer in this order, or a polyester-based resin film, and satisfies the following requirements (1) to (4): (1) The widthwise shrinkage rate after immersion in a 60°C warm bath for 10 seconds is 1% or less; (2) The widthwise shrinkage rate after immersion in a 70°C warm bath for 10 seconds is 10% or less; (3) The widthwise shrinkage rate after immersion in a 90°C warm bath for 10 seconds is 40% or more; and (4) The widthwise shrinkage rate after storage for 7 days in an atmosphere at a temperature of 55°C, or after storage for 1 day in an atmosphere at a temperature of 55°C and 30% humidity, followed by storage for 6 days in an atmosphere at a temperature of 40°C and 90% humidity is 0.5% or less.

7. The heat-shrinkable label according to claim 6, wherein the water-based ink layer comprises a first water-based ink layer and a second water-based ink layer that is a white solid print layer containing a curing agent.

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