JP7750337B2 - Label can and its manufacturing method - Google Patents

Description

The present invention relates to a label can having a digital watermark image layer and a film layer, and a method for manufacturing the same.

Metal cans made of aluminum, steel, or other materials have high impact resistance and are impermeable to gases such as oxygen, allowing the contents to be stored for a much longer time than plastic containers. Furthermore, they are lighter than glass bottles, making them widely used as containers for carbonated drinks, alcoholic drinks, and other beverages, as well as various foods.
Methods for applying product names and various designs to the outer surface of metal cans include attaching a label made of a printed film such as plastic via an adhesive layer, thermally attaching a shrink label using a heat-shrinkable film, or printing on the can body by plate-based printing such as offset printing or inkjet printing which does not use a plate.

Labeled cans are often coated with labels using gravure printing, which is widely known for its aesthetic appeal compared to other printing methods, and for the simpler printing process compared to printing directly on the curved surface of the can.
Furthermore, unlike metal cans that are printed on, label cans can be produced as beautifully printed cans regardless of the surface condition, eliminating the need for a base coat or surface treatment process before printing on the metal can, and shortening the manufacturing process.
In the case of metal cans, with the trend toward a greater variety of products and smaller lots, demands for shorter delivery times and lower costs are also increasing, and there is a demand for rapid and timely product shipments with shorter delivery times. To meet these demands, label cans can be manufactured by producing labels in advance, then applying additional printing or painting to the labels according to customer orders, and then coating the metal cans with the labels, or by applying pre-manufactured labels to metal cans, and then applying additional printing or painting to the labels, which is advantageous in terms of shortening product delivery times.

On the other hand, the letters, designs, etc. printed on the label may contain a readable code in the form of an electronic watermark. The readable code printed on the container can be read by a reading device such as a camera or scanner, making it possible to associate various information with each individual container (see Patent Document 1 below).

Patent No. 5984096

Labeled cans coated with labels printed with digital watermark images containing embedded information are then stored in palletizers or other devices before being transported to a filling plant where they are filled, sealed, and sterilized. However, during these processes, the digital watermark image may become scratched or peeled off. If the image is damaged due to such scratches or peeling, it will be difficult to read and the information will be impossible to extract.

Therefore, the object of the present invention is to provide a label can with a digital watermark image that can be reliably read by preventing the digital watermark image from being damaged during processes such as storage and transportation of the label can, and a method for manufacturing such a label can.

The present invention provides a label can in which a label having at least a digital watermark image layer, a film layer, and a printing layer is attached to the outer surface of the can, and the label is characterized in that a transparent layer is disposed outside the digital watermark image layer.

In the label can of the present invention,
1. The label is formed in the following order from the can side: a print layer, a digital watermark image layer, and a transparent film layer;
2. The label has a print layer, a film layer, a digital watermark image layer, and a transparent protective layer arranged in this order from the can side.
3. The label has a film layer, a print layer, a digital watermark image layer, and a transparent protective layer arranged in this order from the can side.
4. The printing layer comprises a solid printing layer and/or a picture layer;
5. The digital watermark image of the digital watermark image layer and the print image constituting the picture layer are present in the same layer;
6. A picture layer is formed below the portion of the digital watermark image layer other than the digital watermark image, or a picture layer is formed below the digital watermark image;
7. A digital watermark image covering layer for adjusting the visibility of the digital watermark image is formed on the upper side of the digital watermark image layer;
8. An adhesive layer is formed on the label.
9. The label is a heat-shrinkable label.
10. A finishing varnish layer is formed on the outermost surface of the label;
is preferred.

The present invention also provides a method for manufacturing labeled cans in which a label having at least a digital watermark image layer, a film layer, and a printing layer is attached to the outer surface of the can, characterized in that a label having a transparent layer disposed outside the digital watermark image layer is attached to the outer surface of the can.

In the label can and its manufacturing method of the present invention, a transparent layer is positioned outside the digital watermark image layer of the label attached to the metal can, which effectively prevents damage to the digital watermark image during processes such as storage and transportation of label cans equipped with a digital watermark image layer, or during processes such as filling and sterilization, without impairing the accuracy of reading the digital watermark image.

1 is a diagram showing a cross-sectional structure of a body portion of an example of a label can of the present invention. FIG. 10 is a diagram showing the cross-sectional structure of the body of another example of a label can of the present invention. FIG. 10 is a diagram showing the cross-sectional structure of the body of another example of a label can of the present invention. FIG. 10 is a diagram showing the cross-sectional structure of the body of another example of a label can of the present invention. 1 is a diagram showing an example of a cross-sectional structure of a label used in a label can of the present invention. FIG. FIG. 10 is a diagram showing another example of the cross-sectional structure of a label used in the label can of the present invention. FIG. 10 is a diagram showing another example of the cross-sectional structure of a label used in the label can of the present invention. FIG. 10 is a diagram showing another example of the cross-sectional structure of a label used in the label can of the present invention. FIG. 10 is a diagram showing another example of the cross-sectional structure of a label used in the label can of the present invention. FIG. 10 is a diagram illustrating the formation of a printing layer of a label. 10A and 10B are diagrams illustrating the formation of an adhesive layer of a label. FIG. 1 is a diagram showing the cross-sectional structure of the body of a printed can of Comparative Example 1. FIG. 10 is a diagram showing the cross-sectional structure of the body of the label can of Comparative Example 2.

(Labeled can)
As described above, an important feature of the label can of the present invention is that a transparent layer is located outside the digital watermark image layer of the label attached to the metal can. Although the present invention is not limited to this embodiment, it will be described using specific examples shown in Figures 1 to 4.
1, a label 10 is formed on the outer surface of the body of the metal can 1, in this order from the metal can 1 side to the outside: a solid print layer 3a, a design layer 3b (hereinafter, the combined layer of the solid print layer 3a and the design layer 3b, or either one of the layers, may be referred to as the print layer 3), a digital watermark image layer 4, and a transparent film layer 5. The label 10 is attached to the body of the metal can 1 by heat shrinking, and then a finishing varnish layer 6 is formed on the transparent film layer 5, which is the outermost layer of the label 10.
In the labeled can of the present invention shown in Figure 2, a label 10 is formed, in order from the metal can 1 side to the outside, with an adhesive layer 2, a solid print layer 3a, a picture layer 3b, a film layer 5, a digital watermark image layer 4, and a transparent protective layer 7, and is attached to the outer surface of the body of the metal can 1 by the adhesive layer 2.
In the labeled can of the present invention shown in Figure 3, the metal can 1 is a printed can with a solid print layer 3a and a picture layer printed in advance on the outer surface of the body, and a label 10 consisting of, in order from the metal can 1 side to the outside, an adhesive layer 2, a digital watermark image layer 4, and a film layer 5 is attached to the body of the metal can 1, and then a finishing varnish layer 6 is formed on the transparent film layer 5, which is the outermost layer of the label 10. This embodiment can be used, for example, when printed cans with a common picture are used and different digital watermark image layers are formed to be applicable to a wide variety of uses.
The label can of the present invention shown in Figure 4 is made up of a heat-shrinkable label 10, which is composed of, in order from the metal can 1 outward, a solid print layer 3a, a picture layer 3b, a film layer 5, an electronic watermark image layer 4, a picture layer 3b, and a transparent protective layer 7, and is then attached to the metal can 1.A finishing varnish layer 6 is then formed on the transparent protective layer 7, which is the outermost layer of the label 10.

[label]
The label used in the label can of the present invention is not limited to the label having the layer structure shown in Figures 1 to 4 described above, and can take various forms as long as the digital watermark image layer can be covered and protected with a transparent film or transparent protective layer.
For example, in the label shown in Figure 5, from the layer (lower layer) that faces the metal can toward the outer side (surface layer), a solid print layer 3a is formed, and on top of this solid print layer 3a, an electronic watermark image layer 4 is formed in which a picture layer 3b is printed together with an electronic watermark image, and on top of that, a transparent film layer 5 is formed.
6, from the bottom to the top, there is formed an adhesive layer 2, a solid print layer 3a, a picture layer 3b, a transparent film layer 5, a digital watermark image layer 4 on the transparent film layer 5 in a position that does not overlap with the underlying picture layer 3b, and a transparent protective layer 7 on top of that. In this type of label, the picture on the picture layer 3b is not damaged by the digital watermark image.

7 further comprises, from bottom to top, a solid print layer 3a, a design layer 3b, a digital watermark image layer 4, a digital watermark image covering layer 8 for making the digital watermark image layer 4 less visible, and a transparent film layer 5. This type of label is suitable for cases where the digital watermark image should not be visible to consumers, and improves the design of the appearance of the label can. The digital watermark image covering layer 8 can be appropriately positioned by appropriately changing the printing design and color tone, etc., as long as readability is not reduced.
The label shown in Figure 8 is an embodiment in which an adhesive layer 2 is formed on the bottom layer of the label used in the labeled can shown in Figure 1. While the label shown in Figure 1 is a heat-shrinkable label, the label shown in Figure 8 is attached to the metal can by the adhesive layer 2.
The label shown in Figure 9 has a layer structure consisting of, from the bottom to the top, a film layer 5, a solid print layer 3a, a picture layer 3b, a digital watermark image layer 4, and a transparent protective layer 7. The digital watermark image layer 4 has digital watermark images 4a and 4b containing different information. By aligning a portion of the digital watermark image 4b with the position of the picture layer 3b located below, it is possible to embed the information of the digital watermark image 4b in the picture layer 3b, making it different from the other digital watermark image layers 4a.
Furthermore, even if the layer structure of the label exemplified does not have an adhesive layer formed on the bottom layer, an adhesive layer can be formed to make a label that can be attached to a metal can via the adhesive layer.

[Film layer]
The film layer 5 serving as the substrate of the label used in the label can of the present invention may be a known thermoplastic resin, for example, an olefin resin such as low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or a random or block copolymer of α-olefins such as ethylene, propylene, 1-butene, or 4-methyl-1-pentene, or a cyclic olefin copolymer; an ethylene-vinyl copolymer resin such as an ethylene-vinyl acetate copolymer, an ethylene-vinyl alcohol copolymer, or an ethylene-vinyl chloride copolymer; polystyrene, acrylic The film can be formed from styrene-based resins such as methylstyrene-styrene copolymer, ABS, and α-methylstyrene-styrene copolymer; vinyl-based resins such as polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymer, polymethyl acrylate, and polymethyl methacrylate; amide resins such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12; polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polycarbonate; polyphenylene oxide; biodegradable resins such as polylactic acid; etc. Among these, polyethylene terephthalate is preferred from the viewpoint of transparency.

The thickness of the film is not particularly limited, but is preferably in the range of 5 to 30 μm. The film may be uniaxially or biaxially stretched, with biaxially stretched films being particularly preferred from the standpoint of strength, such as scratch resistance.
Furthermore, when the film is located outside the digital watermark image layer, it is preferably colorless and transparent, but it may be colored and transparent, or may have a partially opaque portion as long as it does not impair the readability of the digital watermark image. Furthermore, when the film is located closer to the can body than the digital watermark image layer or the printing layer, it may be an opaque film containing a white pigment or the like.

[Digital Watermark Image Layer]
The digital watermark image layer 4 is a layer having a digital watermark image in which watermark information including a read code is embedded by modulating a two-dimensional pattern, and by reading the digital watermark image with a reading device, electronic data including various information can be obtained. The read code is mainly formed by a dot pattern, and the smallest unit of the image containing the information is repeatedly arranged, making it possible to read it from a wide range. The digital watermark image is mainly composed of parameters such as the size of the smallest unit, the dot density, and the dot distribution.
The digital watermark image layer 4 can be formed by a conventionally known printing method such as gravure printing, offset printing, flexographic printing, or inkjet printing, with gravure printing being particularly suitable.
The digital watermark image may be formed on the entire surface of the digital watermark image layer, or may be formed only on a part of the surface. Also, a plurality of digital watermark images having different information may be formed on different parts of the surface.

[Transparent protective layer]
The transparent protective layer is formed to protect the digital watermark image layer 4. The transparent protective layer 7 may be colored and transparent, but is preferably colorless and transparent.
Since the transparent protective layer is formed on the surface of the label, it is overlapped with the adhesive layer in the overlap portion when the label is applied to the metal can. Therefore, it is preferable that the label be maintained in a semi-cured state before being applied to the metal can. This allows the transparent protective layer and the adhesive layer in the overlap portion to be firmly adhered together at the same time as the adhesive layer is thermally cured when the label is attached to the metal can, effectively preventing peeling of the label from the overlap portion. Furthermore, blocking between the transparent protective layer and the adhesive layer can be prevented when the label is wound up in a long length.
The transparent protective layer 7 is preferably made of any one of an epoxy isocyanate-based composition, a urethane isocyanate-based composition, an acrylic isocyanate-based composition, a polycarbonate isocyanate-based composition, and a polyester isocyanate-based composition, or a mixture of two or more of these. These resin compositions generate little gas during the curing reaction, and furthermore, the gas gradually escapes during storage at room temperature, so that blisters do not form in the overlap portion when the resin composition is applied to a metal can.

The resin composition that makes up the transparent protective layer 7 can also contain a lubricant such as paraffin wax, polyethylene wax, or silicone wax in the range of 0.005 to 5% by weight, which improves the prevention of blocking with the adhesive layer 2 when long labels are wound up, or when wound up and then stored with labels cut to fit the size of the metal can.

The transparent protective layer 7 may be a resin composition that not only protects the digital watermark image layer 4 and the printing layer 3, but also serves as the finishing varnish 6 described below. Finishing varnish is primarily applied to printed or label-coated cans to improve the can's transportability and add a glossy finish, but using a transparent protective layer 7 that also serves as a finishing varnish can eliminate the finishing varnish process.

Furthermore, by forming the transparent protective layer 7, it is possible to protect the digital watermark image layer 4 not only in the label can but also in the state of the label before it is coated on the can.
In addition to the above, the transparent protective layer 7 may have the same features as those described in JP 2017-200764, an invention by the present applicant relating to a label can.

[Printing layer]
The printing layer 3 formed on the label can be formed using conventional plate-type printing methods that allow high-speed, mass printing, such as gravure printing, offset printing, and flexographic printing, as well as inkjet printing, but gravure printing is particularly preferred.
The printing layer may also be a combination of a design layer 3b and a solid printing layer 3a, and as shown in Figures 1 to 3, the design layer 3b may be formed on the solid printing layer 3a, or as shown in Figure 4, the design layer 3b may be further formed on the digital watermark image layer 4. By forming such a solid printing layer 3a as a base layer and covering the metal surface of the metal can, it is possible to suppress metallic gloss, making the design layer 3b and digital watermark image layer 4 clearer, and improving the decorative properties of the printing layer 3 and the reading accuracy of the digital watermark image layer 4.
There are no limitations on the color of the solid printing, but solid printing using white ink is particularly preferred for decorative purposes. Two or more solid printing layers may be superimposed, and the thickness and color of each of these solid printing layers may be different. The printing layer may be provided on one or both sides of the film, or, as shown in Figure 3, a label can may be produced by providing a printing layer directly on the outer surface of a metal can and then covering it with a label.

[Adhesive layer]
In the present invention, in the method for covering the outer surface of a can with a label, the adhesive layer 2 for attaching the label can be a known thermosetting adhesive that can be easily adhered to the outer surface of a can by applying heat and pressure, such as an adhesive containing a thermosetting resin component such as a polyurethane-based, thermosetting polyester resin, polyester polyurethane resin, epoxy resin, phenolic resin, or alkyd resin, and a curing agent component such as an isocyanate or melamine resin in an amount of about 0.1 to 10 parts by weight per 100 parts by weight of the thermosetting resin component. Furthermore, in order to ensure stability before curing, adhesives that contain an appropriate amount of a low-molecular-weight compound such as an oxime, lactam, ester, ketone, or amide, and in which functional groups such as isocyanate groups are blocked by such a low-molecular-weight compound, can be preferably used.
The adhesive layer 2 is formed by applying an adhesive solution prepared by dispersing or dissolving such a thermosetting adhesive in various solvents using a roller or the like, and then drying it. It is generally preferable that the thickness of the adhesive layer 2 be in the range of 1 to 10 μm.

If the label does not have a solid print layer 3a to cover the metal surface, a pigment such as titanium oxide may be blended into the adhesive layer 2. Furthermore, by blending a pigment into the adhesive layer 2, as described below, thermal shrinkage of the adhesive layer 2 can be effectively prevented when the label is wrapped around a metal can and attached by heating, effectively preventing distortion of the printed image due to thermal shrinkage. The blending amount of such pigment is preferably 10 to 90% by weight of the adhesive layer.

When the label has a transparent protective layer 7 as its outermost layer and an adhesive layer 2 as its innermost layer, as shown in Figures 2 and 6, the transparent protective layer 7 and adhesive layer 2 are bonded together in the overlapping area. Therefore, to improve adhesion between labels in the overlapping area, it is preferable to select a transparent protective layer 7 made from the same type of resin as the resin that forms adhesive layer 2. For example, when a polyester isocyanate adhesive composition is used for adhesive layer 2, the transparent protective layer should also be made from a polyester isocyanate composition, thereby improving adhesion between labels in the overlapping area and improving retort resistance.

[Finishing varnish layer]
The finishing varnish layer 6 is formed on the label can to improve transportability and gloss. It is made of a transparent thermosetting resin, such as a thermosetting polyester resin, acrylic resin, or epoxy resin. The preferred finishing varnishes include a thermosetting resin component, such as a phenolic resin or melamine resin, or an isocyanate resin, in an amount of approximately 0.1 to 10 parts by weight per 100 parts by weight of the thermosetting resin component. These resin components are dissolved in an organic solvent and may contain lubricants such as paraffin or silicone oil. The main difference between the protective layer 7 and the finishing varnish layer 6 is the method of application. The finishing varnish layer 6 is formed by contacting an applicator roller coated with the finishing varnish with the outer surface of a cylindrical container, such as a printed can or a printed label can.

[Other layers]
The label can of the present invention has the adhesive layer, print layer, digital watermark image layer, transparent film layer and transparent protective layer described above, but may also have other layers.
For example, a glossy layer containing a metallic powder pigment or pearl pigment, a vapor-deposited layer, or a metal foil can be formed, thereby enhancing the metallic luster and brilliance and improving the decorative properties of the label. Also, an anchor coat layer can be formed as a base for the printing layer.
As shown in FIG. 7, a digital watermark image coating layer 8, mainly made of solid printing, can also be provided to adjust the visibility of the digital watermark image.

[Metal can]
The metal can used for the label can of the present invention may be either a seamless can or a welded can, with seamless cans being particularly preferred. Such seamless cans are produced by subjecting various surface-treated steel sheets such as tin-free steel (TFS), various plated steel sheets such as tin-plated steel sheets, light metal sheets such as aluminum or aluminum alloys, inorganic surface-treated light metal sheets that have been subjected to chemical conversion treatments such as chromium phosphate, organic/inorganic surface-treated light metal sheets that contain an organic substance in the inorganic surface treatment, or resin-coated metal sheets in which a thermoplastic resin coating such as polyester resin is formed on any of these metal sheets, to a conventionally known method such as drawing and re-drawing, bending and stretching by drawing and re-drawing (stretching), bending and stretching and ironing by drawing and re-drawing or drawing and ironing, or impact processing of light metal sheets.
A white coat layer may be formed on the outer surface of the metal can, in which case the base color of the metal plate can be hidden, and therefore the formation of a solid print layer can be omitted.
In the present invention, since it is sufficient that the digital watermark image layer is protected by a transparent layer and is not the outermost layer, as shown in Figure 3, a printed can in which a printed layer is formed on a metal can by a known printing method such as offset printing or inkjet printing may be used, and a label in which the digital watermark image layer is formed on a transparent film may be used. Alternatively, a method may be used in which a film is coated on a seamless can, and then the digital watermark image layer is printed on the curved surface, and then a transparent protective layer is applied. However, in order to efficiently meet the demands for small lots and a wide variety of products, a method in which a label in which the digital watermark image 4 is printed on a transparent film layer 5 is produced and then coated on a metal can is suitable.

(Method for manufacturing label cans)
An important feature of the method for manufacturing a label can of the present invention is that it comprises at least a digital watermark image layer, a printing layer, and a film layer, with a transparent layer being disposed outside the digital watermark image layer. There are no limitations on the manufacturing method as long as it has this layer structure, but it is preferable to manufacture the can by creating a label having this layer structure and covering the body of a metal can with it. However, the method is not limited to this, and it may also be an embodiment in which a label having a transparent layer and a digital watermark image layer is attached to a printed can whose body has already been printed, as shown in Figure 3.

[Label manufacturing]
When the label used in the label can of the present invention has a printing layer 3, an electronic watermark image layer 4, and a transparent film layer 5 arranged in this order, as in the labels shown in Figures 1, 3, 5, and 8, the electronic watermark image layer 4 and the picture layer 3b are formed on the transparent film layer 5, which serves as the base material, by gravure printing or the like, and then the solid printing layer 3a is formed.In the label shown in Figure 8, the label can be produced by further forming an adhesive layer 2 on the solid printing layer 3a.
2 and 6 can be produced by forming a digital watermark image layer 4 on a transparent film layer 5, forming a transparent protective layer 7 on the digital watermark image layer 4, and then forming a printing layer 3 and an adhesive layer on the surface of the transparent film 5 opposite the digital watermark image layer 4. As mentioned above, it is preferable that the transparent protective layer 7 be in a semi-cured state.
7 can be produced by forming, in this order, a digital watermark image coating layer 8, a digital watermark image layer 4, and a printing layer 3 on a transparent film layer 5. The label shown in FIG. 9 can be produced by forming, in this order, a printing layer 3, a digital watermark image 4, and a transparent protective layer 7 on a film layer 5.
Of course, when forming these layers, a corona surface treatment can be carried out, which can improve the adhesion between the layers.

Figure 10 is a diagram illustrating an example of the gravure printing process for forming the label printing layer and digital watermark image layer. The film unwound from the unwinding roll 11 is printed by a printing device having, from upstream to downstream, gravure rollers 12a, 12b, 12c, 12d, 12e, 12f corresponding to each ink: yellow (Y), magenta (M), cyan (C), black (K), special color (S), and white (W), and ovens 13a, 13b, 13c, 13e, 13f, and then taken up by the take-up roll 14.

Figure 11 is a diagram to explain an example of a process for forming an adhesive layer 2, in which a raw film 9a having an electronic watermark image layer 4, a printing layer 3, etc. formed on a transparent film layer 5 is unwound from an unwinding roll 20, adhesive is applied by a coater 21, and after passing through a drying furnace 22, a raw film 9b having an electronic watermark image layer 4, a printing layer 3, and an adhesive layer 2 formed on the film 5 is wound onto a winding roll 23.
If the label has a solid print layer, it may be formed by applying and drying an anchor coating agent using an apparatus similar to that shown in Fig. 11. If the label has a transparent protective layer, it may be formed by applying and semi-curing a resin composition that constitutes the transparent protective layer using an apparatus similar to that shown in Fig. 11. Specifically, semi-curing can be performed by semi-curing at 40°C to 200°C for about 1 to 300 seconds, or by adjusting the ratio of curing agent to the main component of the resin composition to achieve a semi-cured state.
When forming a printing layer, an electronic watermark layer, a protective layer, etc. on the opposite side of the adhesive layer and the film layer, the order of formation is not particularly important, but it is desirable to form the adhesive layer last in order to prevent blocking of the raw film during winding.

Next, the original film, which has the adhesive layer 2, printing layer 3, digital watermark layer 4, protective layer 7, etc. formed on the film layer 5, is cut to fit the size of the metal can to form a label.

[Label coating on metal cans]
When the prepared label has an adhesive layer, it can be produced by wrapping the label around a metal can, and then applying a predetermined temperature and pressure to heat and harden the adhesive layer, thereby affixing the label to the entire circumference of the can body and covering it.
In the case of a shrink label that does not have the adhesive layer 2 but has a heat-shrinkable film, the label may be heat-shrunk to cover the can. Labeled cans using shrink labels can be produced by attaching the label to the entire circumference of the can body of a metal can and shrinking it with steam.

[Formation of finishing varnish layer]
After attaching the label to the labelled can of the present invention, a finishing varnish layer is optionally formed on the labelled can, which not only imparts gloss and transportability to the labelled can, but also improves processability in the subsequent neck flange processing.
The labelled can of the present invention may be completed by covering a filled can with a label. After the labelled can is completed, it may be further printed by offset printing, inkjet printing or the like.

Example 1
<Production of seamless cup>
A 20 μm-thick biaxially oriented polyethylene terephthalate/isophthalate copolymer film was attached to the side that would become the inside surface of a can of a 0.24 mm-thick tin-free steel plate with a temper of T3-CA (surface treatment coating amounts of metallic chromium 120 mg/ ^m2 and chromium oxide 15 mg/ ^m2 ), and a 15 μm-thick biaxially oriented polyethylene terephthalate/isophthalate copolymer film containing 20 wt% titanium oxide was attached to the side that would become the outside surface of the can, at the melting point of the film, followed by immediate water cooling to obtain a resin-coated metal plate.
After uniformly applying glamour wax to this resin-coated metal plate, it was punched out into a disk with a diameter of 143 mm, and then subjected to drawing and stretch drawing to obtain a thin-walled deep-drawn recup with a diameter of 52 mm and a height of 112 mm.
After that, doming was performed according to a conventional method, and the thin-walled deep-drawn cup was then heat-treated at 215°C for 1 minute to remove processing strain from the film and volatilize the lubricant. Next, the opening edge was trimmed to obtain a seamless cup with a height of 106 mm.

<Creating labels>
A 12 μm-thick transparent biaxially oriented polyethylene terephthalate (PET) film was unwound and subjected to a standard corona treatment on one side (the can body side). A digital watermark image layer was then applied to the corona-treated side by gravure printing using one of the following colors: white (W), yellow (Y), magenta (M), cyan (C), or black (K). Next, a 2 μm-thick design layer was applied using the five colors mentioned above, and each color was temporarily cured with hot air. A white solid print layer was then applied on top of the design layer, which was then cured with hot air. The film was then wound up so that four individual labels for each can were lined up across the width of the film.
Next, this film was unwound, and a polyester thermosetting resin was applied onto the white solid print layer and cured in a drying oven to form an adhesive layer. The film was then wound up to produce a label having the layer structure shown in FIG.

<Creating and storing label cans>
The label prepared above was unwound, cut into four strips in the film length direction, and wound up to prepare one strip of film having the same width as the height of the can body.
Next, this single-strand film was unwound and cut to a size with a width equal to the height of the can body and a length equal to the circumference of the can body plus a 5 mm overlap. This was then wrapped around the outer surface of the seamless cup heated to 160°C while applying pressure, and the overlap was adhered to produce a labeled can. 3,000 labeled cans were produced in succession. The produced labeled cans were transported through a chute and sorted into 400 cans per stack using a palletizer. Separate sheets were placed between the cans and the cans were stored on pallets stacked eight high.
The exterior specifications and evaluation results are shown in Table 1.

<Scratch resistance evaluation>
The outer surfaces of 10 palletized (labeled cans arranged on a pallet using a palletizer) labeled cans were visually inspected to evaluate the scratch resistance of the gravure printed surface. A rating of (○) was given if there were no scratches on any of the cans, (△) if there were only slight scratches, and (×) if there were any obvious scratches on any of the cans. ○ and △ were considered to be within the acceptable range for the product.

<Digital watermark reading inspection>
The outer surfaces of 10 palletized label cans were inspected using a digital watermark reader at eight locations, above and below the can axis and at 90-degree intervals around the can body, to see if the watermarks could be read. A rating of (○) was given if all locations were readable, (△) if one location was unreadable, and (×) if two or more locations were unreadable. ○ and △ were considered to be within the acceptable range for the product.

Example 2
Label cans were produced and evaluated in the same manner as in Example 1, except that the digital watermark image layer was placed on the opposite side of the film from the picture layer and the solid white print layer, and a transparent protective layer was placed on the outside of the digital watermark image, resulting in a label with the layer structure shown in Figure 2.
The evaluation results are shown in Table 1.

<Comparative Example 1>
The outer surface of the resulting seamless cup was coated with a white solid print layer using a curved surface coater and cured in an oven. Next, a digital watermark image and a design layer were printed using curved surface offset printing with a relief plate and cured in an oven. The cross section of the barrel of the finished printed can is shown in Figure 12. Printed cans were produced and evaluated in the same manner as in Example 1, except that the printed cans were transported and palletized after curing in the oven.
The evaluation results are shown in Table 1.

<Comparative Example 2>
Except for not providing a protective layer, a labeled can was produced in the same manner as in Example 2. The cross section of the body of the finished labeled can is shown in Figure 13.
The results of evaluation of this labeled can are shown in Table 1.

The effect of the label can of the present invention is clear from the results of the examples.
That is, in the case of the labeled cans of the present invention, even when the labeled cans are arranged on a pallet using a palletizer, the digital watermark image is not damaged, a clear image is formed, and the digital watermark can be easily read (Examples 1 and 2). In contrast, when seamless cans are printed with a digital watermark image using plate-type offset printing and arranged on a pallet as in the Examples, the digital watermark image is damaged during palletizing, resulting in poor digital watermark reading (Comparative Example 1). When a digital watermark image layer is disposed on the outermost layer of the labeled can (Comparative Example 2), the digital watermark image is also damaged during palletizing, as in Comparative Example 1, resulting in poor digital watermark reading.
Furthermore, in the plate-type offset printing of Comparative Example 1, replacement of plates, blankets, etc. is required to accommodate different types of products and small lots, which takes time and costs money. However, in the labeled cans of the present invention, printed labels are produced and temporarily stored during the process of manufacturing labeled cans, making it possible to produce a wide variety of printed cans in small lots in a short amount of time.

1 Can body, 2 Adhesive layer, 3 Printing layer, 4 Digital watermark image layer, 5 Film layer, 6 Finishing varnish layer, 7 Transparent protective layer, 8 Digital watermark image coating layer, 11 Unwinding roll, 12 Gravure roller, 13 Oven, 14 Take-up roll, 20 Unwinding roll, 21 Coater, 22 Drying oven, 23 Take-up roll.

Claims (11)

A label can having a label having at least a digital watermark image layer, a film layer, and a printing layer attached to an outer surface of the can,
the label has a transparent layer disposed outside the digital watermark image layer ;
the label is provided with a printing layer, a film layer, a digital watermark image layer, and a transparent protective layer arranged in this order from the can side;
A label can characterized in that a printing layer, an electronic watermark image layer, and a transparent protective layer are formed on the film layer as a substrate . A label can having a label having at least a digital watermark image layer, a film layer, and a printing layer attached to an outer surface of the can,
the label has a transparent layer disposed outside the digital watermark image layer;
the label is provided with a film layer, a printing layer, a digital watermark image layer, and a transparent protective layer arranged in this order from the can side;
A label can characterized in that a printing layer, an electronic watermark image layer, and a transparent protective layer are formed on the film layer as a substrate. 3. The label can according to claim 1, wherein the printed layer comprises a solid printed layer and/or a picture layer. 4. A label can according to claim 3 , wherein the digital watermark image of the digital watermark image layer and the printed image constituting the picture layer are present in the same layer. 4. A label can according to claim 3 , wherein a design layer is formed below the portion of said digital watermark image layer other than the digital watermark image, or a design layer is formed below the digital watermark image. 6. The label can according to claim 1 , wherein an electronic watermark image covering layer for adjusting the visibility of the electronic watermark image is formed on the upper side of the electronic watermark image layer. 7. The label can according to claim 1, wherein an adhesive layer is formed on the label. The label can according to any one of claims 1 to 6 , wherein the label is a heat-shrinkable label. 9. The label can according to claim 1, wherein a finishing varnish layer is formed on the outermost surface of the label. A method for manufacturing a label can in which a label having at least a digital watermark image layer, a film layer, and a printing layer is attached to the outer surface of the can,
a label having a transparent layer disposed outside the digital watermark image layer and attached to an outer surface of the can ;
the label is formed in the following order from the can side: a print layer, a film layer, a digital watermark image layer, and a transparent protective layer;
A method for manufacturing a label can, characterized in that a printing layer, an electronic watermark image layer and a transparent protective layer are formed on the film layer as a substrate . A method for manufacturing a label can in which a label having at least a digital watermark image layer, a film layer, and a printing layer is attached to the outer surface of the can,
a label having a transparent layer disposed outside the digital watermark image layer and attached to an outer surface of the can;
the label is provided with a film layer, a printing layer, a digital watermark image layer, and a transparent protective layer arranged in this order from the can side;
A method for manufacturing a label can, characterized in that a printing layer, an electronic watermark image layer and a transparent protective layer are formed on the film layer as a substrate .