WO2018092439A1

WO2018092439A1 - Method for manufacturing beverage can, printing system, and beverage can

Info

Publication number: WO2018092439A1
Application number: PCT/JP2017/035838
Authority: WO
Inventors: 小島　真一; 和紀池田; 明日美諏訪; 増田　和久
Original assignee: 昭和アルミニウム缶株式会社
Priority date: 2016-11-17
Filing date: 2017-10-02
Publication date: 2018-05-24
Also published as: JP2018079638A; JP6824009B2

Abstract

A star-shaped formed image 201 is formed on a base coat layer BL. In addition, a clear ink part 301 is provided so as to be along a contour of the star-shaped formed image 201. The provision of the clear ink part 301 along the contour of the formed image 201 prevents ink constituting the formed image 201 from moving to the side of the formed image 201. Thus, spreading (moving) of the ink hardly occurs, and the contour of the formed image 201 is prevented from blurring.

Description

Beverage can manufacturing method, printing system, and beverage can

The present invention relates to a beverage can manufacturing method, a printing system, and a beverage can.

Patent Document 1 discloses a printing apparatus in which inkjet printing is performed in at least one inkjet printing station, and a plurality of inkjet heads are arranged in the inkjet printing station.

JP 2012-232771 A

In beverage cans filled with beverages, images such as letters and designs are often formed on the outer surface. Here, when this image is formed using ink, after the image is formed on the can, the ink constituting the image may spread outward and the outline of the image may be blurred.
An object of the present invention is to improve the image quality of an image formed on the outer surface of a beverage can using ink.

The manufacturing method of a beverage can to which the present invention is applied includes an image forming step of forming an image by attaching ink to an outer surface of the beverage can, and a side of the outer surface where the image is formed, And a dot image row forming step of forming two or more dot image rows along the contour of the image.
Here, the dot images included in the two or more dot image rows may be arranged along the axial direction of the beverage can and along the circumferential direction of the beverage can.
In addition, the dot images included in the two or more dot image rows may be arranged in a staggered manner.
Further, the thickness of the layer formed by curing the two or more dot image rows may be 2 μm or more.
Further, the two or more dot image rows may be formed of transparent ink.
In addition, before the image formation by the image forming step, the two or more dot image rows are formed.

From another viewpoint, the method for producing a beverage can to which the present invention is applied includes an image forming step of forming a plurality of images having different colors of each image by attaching ink to the outer surface of the beverage can; Inhibiting ink for suppressing the movement of the ink constituting each image to the side beside the portion where each image is formed and not contacting the other image of each image. An ink adhering step for adhering. A method for producing a beverage can.
Here, in the ink attaching step, the suppression ink is not attached to the side of the formation place of each image and to the side of the portion in contact with the other image. be able to.
Further, in the ink adhering step, a transparent ink can be used as the suppression ink.
In the ink adhering step, two or more dot image rows along the outline of each image may be formed beside a portion that is not in contact with the other image.
In addition, the dot images included in the two or more dot image rows may be arranged along the axial direction of the beverage can and along the circumferential direction of the beverage can.
In addition, the dot images included in the two or more dot image rows may be arranged in a staggered manner.

From another viewpoint, the beverage can manufacturing method to which the present invention is applied includes an image forming step of forming an image by attaching ink to an outer surface of the beverage can, and the image of the outer surface is formed. An ink adhering step for adhering a suppressing ink for suppressing movement of the ink constituting the image to the side of the portion to be formed, after the formation of the image by the image forming step, and the ink And a paint application step of applying a paint on the image and the suppression ink after the suppression ink is attached in the adhesion step.

Further, when the present invention is regarded as a printing system, the printing system to which the present invention is applied includes an image forming unit that forms an image by attaching ink to an outer surface of a beverage can, and the image of the outer surface includes A dot image line forming unit that forms two or more dot image lines along the contour of the image beside a place to be formed.

From another point of view, the printing system to which the present invention is applied includes an image forming unit that forms a plurality of images having different colors of each image by attaching ink to the outer surface of the beverage can, Ink adhesion for adhering suppression ink for suppressing movement of the ink constituting each image to the side of the portion of the image that is not in contact with the other image. And a printing system.

From another point of view, the printing system to which the present invention is applied includes an image forming unit that forms an image by attaching ink to an outer surface of a beverage can, and a portion of the outer surface where the image is formed. An ink adhering means for adhering a restraining ink for suppressing movement of the ink constituting the image to the side to the side, after the formation of the image by the image forming means, and the ink adhering means A printing system comprising: a paint application unit that applies a paint on the image and the suppression ink after the suppression ink is attached.

In addition, when the present invention is regarded as a beverage can, the beverage can to which the present invention is applied is an outer surface, an image provided on the outer surface, and two rows provided on the outer surface along the contour of the image. A beverage can comprising the above dot image array.

From another point of view, the beverage can to which the present invention is applied is an outer surface, a plurality of images provided on the outer surface, each image having a different color, beside each image, and each of the images. A beverage can comprising: an ink layer provided on a side of a portion that does not come into contact with another image and cured with a suppression ink for suppressing movement of the ink constituting each image to the side. .

From another point of view, a beverage can to which the present invention is applied is provided with an outer surface, an image provided on the outer surface, and a side of the image, and movement of ink constituting the image to the side. It is a beverage can comprising: an ink layer obtained by curing a suppression ink for suppressing water; and a transparent layer provided on the image and the ink layer.

According to the present invention, it is possible to improve the image quality of an image formed on the outer surface of a beverage can using ink.

It is a perspective view of the can for beverages concerning this embodiment. It is the figure which showed a part of manufacturing process of the can for drinks. It is a perspective view of a printing apparatus. (A), (B) is the figure which showed the formation image formed in the outer peripheral surface of the drink can. (A) to (C) are cross-sectional views of a beverage can. (A) to (D) are diagrams illustrating the clear ink portion. It is the figure which showed the experimental condition in an Example and a comparative example. It is the figure which showed the experimental result when changing the number of lines of the dot image of a clear ink part, the thickness of a clear ink part, and the thickness of a formation image (ink layer) to various values. It is the figure which showed the actual printing result. (A) and (B) are diagrams showing other printing examples. It is the figure which showed the other structural example of the printing apparatus.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view of a beverage can 100 according to the present embodiment.
The beverage can 100 is provided with a can body 200 formed in a cylindrical shape. A circular opening 210 is formed in the upper portion of the can body 200. In addition, a bottom 220 is provided at the bottom of the can body 200. The can body 200 includes an outer peripheral surface (outer surface) 230.
Printing is performed on the outer peripheral surface 230 by an inkjet head (described later), and a printed image is formed on the outer peripheral surface 230.

In the present embodiment, the beverage, which is the content, is filled into the beverage can 100 through the opening 210 positioned at the top of the beverage can 100. Thereafter, the opening 210 is closed by a can lid (not shown). Thereby, the beverage can filled with the beverage is completed.
In addition, in FIG. 1, illustration of the detailed shape of the drink can 100 was abbreviate | omitted, and the drink can 100 was expressed with the bottomed cylinder. More specifically, the beverage can 100 is generally provided with a neck having a flange, or the bottom of the beverage can 100 is generally a circular shape that is recessed in the interior direction of the beverage can 100. Although a recessed part is provided, illustration of these is abbreviate | omitted in FIG.

The beverage can 100 is formed of a metal material. Specifically, the beverage can 100 is made of, for example, aluminum or an aluminum alloy. Further, the beverage can 100 is formed of, for example, an iron alloy such as tin-free steel.
The beverage can 100 is formed by, for example, drawing and ironing (DI) molding or stretch drawing molding of a flat plate material.
Examples of the beverage filled in the beverage can 100 include alcoholic beverages such as beer and non-alcoholic beverages such as soft drinks.

FIG. 2 is a diagram showing a part of the manufacturing process of the beverage can 100. Specifically, FIG. 2 shows a printing process among a plurality of processes included in the manufacturing process of the beverage can 100. In addition, FIG. 2 shows each process included in the printing system that performs printing on the outer surface of the beverage can 100.
In the printing process of the beverage can 100, as shown in FIG. 2, the base coat layer forming process 10, the first drying process 20, the clear printing process 30, the second drying process 40, the image forming process 50, and the third drying process 60 are performed. The overcoat layer forming step 70 and the fourth drying step 80 are provided.

In printing on the beverage can 100, the beverage can 100 is transported so that the beverage can 100 sequentially passes through these steps. And in the process of this conveyance, the various process with respect to the drink can 100 is performed. In transporting the beverage can 100, a cylindrical support member (mandrel) (described later) is inserted into the beverage can 100, and then the beverage can 100 is transported.
The base coat layer forming step 10, the first drying step 20, and the second drying step 40 can be omitted.

In the base coat layer forming step 10, a base coat layer (underlying layer) is formed on the outer peripheral surface 230 (see FIG. 1) of the beverage can 100.
By forming the base coat layer, the background color of the beverage can 100 can be concealed, and the image formed on the outer peripheral surface 230 of the beverage can 100 can be made clearer.
The base coat layer is formed by roll coating. That is, a base coat layer is formed on the beverage can 100 by bringing the roll-shaped member disposed along the axial direction of the beverage can 100 and having a coating material on the surface thereof into contact with the outer peripheral surface 230 of the beverage can 100. .

The base coat layer is mainly formed of a resin.
As the resin, polyester / epoxy / amino resin, polyester / acryl / amino resin, and the like can be used. In addition, the base coat layer may be formed of an ultraviolet curable paint. In this case, an epoxy / polyethylene resin containing a photopolymerization initiator can be used.
In order to cancel the metallic color of the beverage can 100, a white pigment may be added as an additive. Further, the thickness of the base coat layer can be set to 2 μm to 15 μm, for example.

Next, in the present embodiment, in the first drying step 20, the base coat layer is dried. In the first drying step 20, the beverage can 100 is heated or the beverage can 100 is irradiated with ultraviolet rays, and the base coat layer is dried (cured).
Thereafter, in this embodiment, in the clear printing step 30, clear printing using clear ink (colorless and transparent ink) is performed on the base coat layer, and a clear ink portion (details will be described later) is formed on the base coat layer. ) Is formed.
In this embodiment, ultraviolet curable ink is used as the clear ink. When the clear ink portion is formed on the base coat layer, a functional portion serving as a bank is provided on the base coat layer, and ink bleeding hardly occurs (details will be described later).

Next, in the present embodiment, in the second drying step 40, the outer peripheral surface of the beverage can 100 is irradiated with ultraviolet rays, and the clear ink portion is cured.
When the clear ink portion is cured, the clear ink portion serving as a bank is firmly formed, and the effect of preventing bleeding (described later) is improved. On the other hand, when the 2nd drying process 40 is provided, there exists a possibility that production efficiency may fall. For this reason, the second drying step 40 may be omitted.

Next, in the present embodiment, in the image forming process 50 as an example of the image forming process, the color ink is ejected onto the outer peripheral surface 230 of the beverage can 100 to be applied to the outer peripheral surface 230 of the beverage can 100. Then, an image composed of characters, designs, etc. (hereinafter referred to as “formed image”) is formed.
Here, in the present embodiment, the thickness of the formed image (color ink thickness) is, for example, 2 to 5 μm.

Here, the ink used for forming the formed image preferably has a viscosity at 40 ° C. in the range of 5 mPa · s to 30 mPa · s, and more preferably in the range of 5 mPa · s to 20 mPa · s. . By setting the viscosity of the ink at 40 ° C. in such a range, it is possible to realize good ejection stability when ejecting ink from an inkjet head (described later). The ink viscosity can be measured using a cone plate viscometer.

The ink used for forming the formed image preferably has a surface tension at 25 ° C. in the range of 22 mN / m to 36 mN / m. By setting the surface tension of the ink at 25 ° C. within such a range, it is possible to realize good ejection stability when ejecting ink from the inkjet head.

Thereafter, in the present embodiment, in the third drying step 60, the beverage can 100 is irradiated with ultraviolet rays again, and the formed image formed in the image forming step 50 is cured.
Next, in the present embodiment, in the overcoat layer forming step 70, the coating material is uniformly applied over the entire outer peripheral surface of the beverage can 100, and the outermost layer of the beverage can 100 is an example of a transparent layer. The overcoat layer (transparent protective layer) is formed. Here, the overcoat layer is formed by roll coating in the same manner as the base coat layer.

Examples of the paint used for forming the overcoat layer include alkyd resin-based, acrylic resin-based, vinyl resin-based, polyester resin-based, amino resin-based, polyurethane resin-based, and epoxy resin-based paints.
Among these, it is most preferable to use an amino resin-based paint from the viewpoints of coating film hardness and water resistance.

FIG. 3 is a perspective view of the printing apparatus 500.
In the present embodiment, a printing apparatus 500 shown in FIG. 3 is provided in each of the clear printing process 30 and the image forming process 50.
More specifically, the clear printing step 30 is provided with one printing device 500, and the image forming step 50 is provided with four printing devices 500.
In the image forming process 50, an image is formed using four color inks of YMCK (yellow, magenta, cyan, and black). In the image forming process 50, the four color inks can be ejected. Four printing apparatuses 500 shown in FIG. 3 are provided.

Here, the four printing apparatuses 500 provided in the image forming step 50 function as image forming means, and attach ink to the outer peripheral surface 230 of the beverage can 100 to form a formed image and an ink layer (described later). Form.
Further, in the image forming process 50, the beverage cans 100 are sequentially transported, and the four printing apparatuses 500 are arranged in the transport direction of the beverage cans 100 and the beverage cans 100 are transported. The image formation using the four colors of ink is performed.

More specifically, in the present embodiment, for example, the yellow printing device 500, the magenta printing device 500, the cyan printing device 500, black, from the upstream side in the transport direction of the beverage can 100 to the downstream side in the transport direction. Printing apparatuses 500 are arranged in order.
In this embodiment, each time the beverage can 100 reaches each printing device 500, the beverage can 100 stops, and ink is discharged to the stopped beverage can 100. When ink is discharged to the beverage can 100, the beverage can 100 rotates in the circumferential direction.

As shown in FIG. 3, the printing apparatus 500 is provided with an inkjet head 400. The inkjet head 400 is located above the beverage can 100 that is sequentially conveyed. The ink jet head 400 is disposed along the axial direction of the beverage can 100. As described above, the beverage can 100 is supported by the cylindrical support member (mandrel) 600.
In addition, a plurality of ink discharge ports 610 arranged along the axial direction of the beverage can 100 are provided at the bottom of the inkjet head 400.

The ink discharge ports 610 are provided in a plurality of rows (only three rows are shown in FIG. 3).
In other words, in this embodiment, a plurality of ink discharge port arrays in which the ink discharge ports 610 are arranged in a line are provided. Further, in the present embodiment, the ink discharge ports 610 are arranged in a staggered manner in two adjacent ink discharge port arrays.

More specifically, in the present embodiment, when the positions of the inkjet heads 400 in the longitudinal direction are compared, the position of each ink discharge port 610 included in one ink discharge port array and the one ink discharge port array The positions of the respective ink discharge ports 610 included in the other ink discharge port arrays located next to are shifted from each other.
In addition, in the longitudinal direction of the inkjet head 400, each ink ejection port 610 included in one ink ejection port array is located between two ink ejection ports 610 that are included in another ink ejection port array and are adjacent to each other. .
The ink discharge ports 610 are not limited to being arranged in a zigzag pattern, but are straight along the axial direction of the beverage can 100 as shown in FIG. 11 (a diagram illustrating another configuration example of the printing apparatus 500). And may be arranged linearly along the circumferential direction of the beverage can 100. In addition, the ink discharge ports 610 may be arranged linearly along the longitudinal direction and the short direction of the inkjet head 400. In other words, in the embodiment shown in FIG. 11, the plurality of ink discharge ports 610 are arranged in a grid pattern.
More specifically, in the configuration example shown in FIG. 11, when the positions of the inkjet head 400 in the longitudinal direction are compared, the positions of the respective ink discharge ports 610 included in one ink discharge port array and the one ink discharge port The positions of the respective ink discharge ports 610 included in the other ink discharge port arrays located next to the columns are aligned.

In each of the clear printing process 30 and the image forming process 50, the support member 600 is rotated in the circumferential direction by a driving mechanism (not shown), and the beverage can 100 is rotated in the circumferential direction accordingly.
Then, ink (clear ink, color ink) is ejected to the outer peripheral surface 230 of the beverage can 100 rotating in the circumferential direction.

Furthermore, the printing apparatus 500 of the present embodiment is provided with a print control unit 510 that controls the ejection of ink in the inkjet head 400. The print control unit 510 is configured by a program-controlled CPU (Central Processing Unit).
In the present embodiment, the ink jet head 400 is controlled by the print control unit 510, and ink is ejected from the ink ejection port 610 to the beverage can 100 positioned below and rotating in the circumferential direction. As a result, a clear ink portion (described later) and a formed image are formed on the outer peripheral surface 230 of the beverage can 100.

FIGS. 4A and 4B are views showing formed images formed on the outer peripheral surface 230 of the beverage can 100.
In the example shown in FIG. 4A, a star-shaped formed image 201 is formed on the base coat layer BL. Further, in the example shown in FIG. 4A, the clear ink portion 301 is formed so as to surround the star-shaped formed image 201 and to be in contact with the star-shaped formed image 201.

In this embodiment, the clear ink portion 301 is also formed in a star shape, and a star-shaped formed image 201 is formed inside the clear ink portion 301.
More specifically, in the present embodiment, the clear ink portion 301 is provided along the outline (outer peripheral portion) 201A of the star-shaped formed image 201.

In another example shown in FIG. 4B, a star-shaped base coat layer BL is exposed, and a portion of the star-shaped base coat layer BL is a star-shaped image. In the example shown in FIG. 4B, an ink layer 401 formed by the ink ejected in the image forming process 50 is provided around the star-shaped extracted image.
Further, in the example shown in FIG. 4B, a clear ink portion 301 is provided at a location that contacts the ink layer 401 and faces a star-shaped extracted image. In other words, the clear ink portion 301 that is in contact with the ink layer 401 is provided around the star-shaped extracted image.

When forming the formed image 201 or the extracted image as in the present embodiment on the outer peripheral surface 230 of the beverage can 100, if there is no clear ink portion 301, the formed image 201 and the extracted image are caused by ink bleeding. The outline is blurred.
On the other hand, when the clear ink portion 301 is provided along the outline of the formed image 201 as in the present embodiment, movement of the ink constituting the formed image 201 to the side of the formed image 201 is suppressed. Further, when the clear ink portion 301 is provided along the contour of the ink layer 401 (the contour of the extracted image), the ink constituting the ink layer 401 may move to the side of the ink layer 401 (to the inside of the extracted image). It is suppressed.

As a result, ink bleeding (movement) is less likely to occur, and blurring of the contours of the formed image 201 and the extracted image is suppressed.
Note that the clear ink portion 301 is preferably formed before the formation image 201 and the ink layer 401 are formed, but the clear ink portion 301 can also be formed after the formation image 201 and the ink layer 401 are formed.

FIGS. 5A to 5C are views showing a cross section of the beverage can 100. FIG.
In the example shown in FIG. 5A, a black formed image 201 is formed, and a clear ink portion 301 is provided around the black formed image 201.
Here, the clear ink portion 301 is provided with two dot image rows. In other words, in this embodiment, a dot-like image (dot image) is formed in the clear ink portion 301, and further, this dot image is formed for two rows on the side of the formed image 201.

More specifically, in this example, two dot image rows along the outline 201A of the formed image are formed beside the portion where the formed image 201 is formed.
Thereby, in this embodiment, a dot image for one row is formed on the side close to the formed image 201, and a dot image for another row is formed on the side opposite to the side on which the formed image 201 is sandwiched. It has become a state.
Here, the dot image row formed in the clear ink portion 301 is formed in the clear printing step 30 (see FIG. 2) as an example of the dot image row forming step. More specifically, the dot image row formed in the clear ink portion 301 is formed by a printing apparatus 500 as an example of a dot image row forming unit provided in the clear printing step 30.

Furthermore, in this embodiment, the overcoat layer OL is formed outside the formed image 201 and the clear ink portion 301 (outside in the radial direction of the beverage can 100) (on the formed image 201 and the clear ink portion 301). Is provided.
The overcoat layer OL is formed by applying a paint to the outermost layer of the beverage can 100 in an overcoat layer forming process 70 (see FIG. 2) as an example of a paint applying process.
More specifically, the overcoat layer forming step 70 is provided with a roll-shaped member as an example of a paint application unit, and this roll-shaped member to which the paint adheres is applied to the outer peripheral surface 230 of the beverage can 100. The overcoat layer OL is formed on the outermost layer of the beverage can 100 by contact.

In the present embodiment, the formed image 201, the clear ink portion 301, and the base coat layer BL are provided between the overcoat layer OL and the beverage can 100.
In addition, in the present embodiment, the formed image 201, the clear ink portion 301, and the base coat layer BL are sealed between the overcoat layer OL and the beverage can 100.

In the example shown in FIG. 5B, a color formation image 201 is formed, and a clear ink portion 301 is provided around the color formation image 201.
Also in this example, two lines of dot images are provided in the clear ink portion 301. Further, similarly to the above, the formed image 201, the clear ink portion 301, and the base coat layer BL are sealed between the overcoat layer OL and the beverage can 100.
In the example shown in FIGS. 5A and 5B, the case where the dot images of the clear ink portion 301 are provided for two rows has been described. However, three or more dot images may be provided. . Further, clear ink may be placed on all portions of the base coat layer BL where ink is not placed (portions where image formation by the image forming step 50 is not performed). In other words, not only the side portion of the contour of the formed image 201 and the extracted image, but clear ink may be placed on the side portion.

In the example shown in FIG. 5C, a blank image is formed, and an ink layer 401 is provided around the blank image. Further, a clear ink portion 301 is provided so as to be in contact with a portion of the ink layer 401 that faces the extracted image.
In the clear ink portion 301, two rows of dot images are provided as described above. Also in this example shown in FIG. 5C, the ink layer 401, the clear ink portion 301, and the base coat layer BL are sealed between the overcoat layer OL and the beverage can 100.
Similarly to the above, in the example shown in FIG. 5C, the dot image of the clear ink portion 301 may be provided in three or more rows. Further, the clear ink portion 301 may be formed so that the clear ink is placed on the entire extracted image.

6A to 6D are diagrams illustrating the clear ink unit 301. FIG.
FIG. 6A is a diagram when the clear ink portion 301 is viewed from the direction of the arrow VIA in FIG.
In the present embodiment, as described above, the clear ink portion 301 is provided with two rows of dot images formed by clear ink. FIG. 6A shows the clear ink unit 301 when the printing apparatus 500 shown in FIG. 3 is used. In the printing apparatus 500 shown in FIG. 3, the ink discharge ports 610 (see FIG. 3) are arranged in a staggered manner, and in this case, two rows of dot images are also arranged in a staggered manner.

In other words, the dot image included in the other dot image row is positioned between two dot images included in one dot image row and adjacent to each other in the direction in which the dot image row extends. In other words, in the present embodiment, an overlap occurs between the dot image included in one dot image column and the dot image included in the other dot image column in the direction in which the dot image column extends.
In the present embodiment, a part of the dot image included in the other dot image row enters between two adjacent dot images included in one dot image row.
FIG. 6D shows the clear ink unit 301 when the printing apparatus 500 shown in FIG. 11 is used. In the printing apparatus 500 shown in FIG. 11, the ink discharge ports 610 (see FIG. 11) are arranged side by side along the axial direction and the circumferential direction of the beverage can 100. In this case, two rows of dot images are formed. The included dot images are also arranged side by side along the axial direction and the circumferential direction of the beverage can 100.
The dot image along the axial direction and the circumferential direction of the beverage can 100 can be formed not only in the printing apparatus 500 shown in FIG. 11 but also in the printing apparatus 500 shown in FIG. Specifically, for example, by using the ink discharge ports 610 included in the

columns

3B and 3C in FIG. 3 without using the ink discharge ports 610 included in the column 3A in FIG. A dot image along the axial direction and the circumferential direction of the beverage can 100 can be formed.

Here, for example, as shown in FIG. 6B, if the dot image row is a single row and there is a gap between the dot images, the ink easily moves through the gap, and the ink tends to bleed. .
For example, even when all the necessary dot image rows are ejected, if the ink ejection pressure is low, the ink droplets become smaller, and the dot image becomes smaller accordingly. In this case, as shown in FIG. 6B, a gap is easily generated between the dot images, and the ink is easily moved through the gap. In this case, ink bleeding tends to occur.

Further, as shown in FIG. 6C, even when there is no gap between the dot images, if the dot image row is a single row, it passes through a valley portion located between two adjacent dot images. As a result, the ink easily moves and ink bleeding is likely to occur.
Even when all the necessary dot image rows are not ejected, if the ink ejection pressure is increased, the ink droplets become larger, and the dot image becomes larger accordingly. Even in this case, it is possible to prevent a gap from being generated between the dot images. However, even if there is no gap, if the dot image row is a single row, as described above, the ink is likely to move through the valley portion, and ink bleeding tends to occur.
On the other hand, in the configuration of the present embodiment shown in FIGS. 6A and 6D, dot images adjacent to each other overlap (dots included in one dot image row of two dot image rows). The height of the valley located between two dot images adjacent to each other in one dot image row is determined by the overlap of the image and the dot image included in the other dot image row (FIG. 6B). It becomes larger than the height of the valley in the aspect shown in (C). In this case, it is difficult for ink to pass through the valleys, and ink bleeding is less likely to occur.

Next, examples will be described.
The inventor printed on the beverage can 100 by using the steps shown in FIG. 2 (processing in each step included in the base coat layer forming step 10 to the fourth drying step 80 was sequentially performed). Then, the formed image 201 obtained by printing and the extracted image were evaluated (evaluation of bleeding).

FIG. 7 is a diagram showing experimental conditions when the bleeding is evaluated.
In printing on the beverage can 100, the base coat layer BL, the clear ink portion 301, the formed image 201, and the overcoat layer OL had thicknesses of 13 μm, 1.5 to 4 μm, 2 to 4 μm, and 3 to 4 μm, respectively. .
Further, the base coat layer BL and the overcoat layer OL were formed using a roll coat. Moreover, the clear ink part 301, the formation image 201, and the ink layer 401 were formed using the inkjet head 400 (refer FIG. 3).

Further, the base coat layer BL, the clear ink portion 301, the formed image 201 (ink layer 401), and the overcoat layer OL were formed of polyester / acrylic resin, modified acrylic resin, modified acrylic resin, and amino resin system, respectively. .
The formation image 201 (ink layer 401) was formed using ultraviolet curable ink. More specifically, a modified acrylic resin-based ink composed of an acrylate monofunctional monomer, an acrylate polyfunctional monomer, a photopolymerization initiator, and a colorant was used.

The clear ink portion 301 was formed using an ink having the same composition as that of the ink used for forming the formed image 201 (ink layer 401) and containing no colorant.
The base coat layer BL, the formed image 201 (ink layer 401), and the overcoat layer OL were dried by a 200 ° C. drying oven, ultraviolet (UV) irradiation, and far infrared irradiation, respectively.

Further, the clear ink portion 301 was cured together with the formed image 201 (ink layer 401).
In other words, when the formed image 201 (ink layer 401) is cured, the clear ink portion 301 is also irradiated with ultraviolet rays, and the clear ink portion 301 is cured together with the formed image 201 (ink layer 401).

The ink used for forming the clear ink portion 301 had a viscosity at 40 ° C. of 6 to 8 mPa · s and a surface tension at 25 ° C. of 30 mN / m to 35 mN / m.
In addition, the ink used for forming the formed image 201 (ink layer 401) has a viscosity of 6 to 8 mPa · s at 40 ° C. as in the case of any color ink of cyan, magenta, yellow, and black. The surface tension at 25 ° C. was 30 mN / m to 35 mN / m.

The base coat layer BL was white and the thickness was 13 μm as described above.
Further, the overcoat layer OL was transparent and further had a thickness of 3 to 4 μm as described above. However, when the experiment (described later) shown in FIGS. 8 and 9 was performed, the overcoat layer OL was not formed. In addition, the inventor also conducted experiments other than the experiments shown in FIGS. 8 and 9, but in this experiment (experiments other than the experiments shown in FIGS. 8 and 9), the overcoat layer OL was formed. Formed. On the other hand, when the experiment (described later) shown in FIGS. 8 and 9 was performed, the overcoat layer OL was not formed.
In this experiment, as shown in FIG. 9, characters were printed and bleeding of the characters was observed.

FIG. 8 shows the experimental results when the number of dot images in the clear ink portion 301, the thickness of the clear ink portion 301, and the thickness of the formed image 201 (ink layer 401) are changed to various values. It is a figure.
In this experiment, the number of dot images in the clear ink portion 301 was set to three types: one row, two rows, and three rows. Further, the thickness of the clear ink portion 301 was set to four types of 1.5 μm, 2 μm, 3 μm, and 4 μm. Further, the thickness of the formed image 201 (ink layer 401) was set to three types of 2 μm, 3 μm, and 4 μm.
Moreover, in the clear ink part 301, as shown to FIG 6 (D), the dot image was arranged in the linear form along the axial direction of the drink can 100, and the circumferential direction.
In addition, although the experimental result demonstrated below shows the experimental result at the time of arranging a dot image along the axial direction and circumferential direction of the drink can 100, a dot image is staggered like FIG. 6 (A). The same results as those obtained when the dot images were arranged along the axial direction and the circumferential direction of the beverage can 100 were also obtained.

Here, the thicknesses of the clear ink portion 301 and the formed image 201 (ink layer 401) can be changed, and the thicknesses of the clear ink portion 301 and the formed image 201 (ink layer 401) can be changed from the inkjet head 400. This is done by adjusting the ink discharge amount.
More specifically, the thickness of the clear ink portion 301 and the formed image 201 (ink layer 401) is changed by changing the number of ink droplets ejected per unit time or changing the size of the ink droplets. To change.

Regarding the thickness of the clear ink portion 301 and the thickness of the formed image 201 (ink layer 401), the clear ink portion 301 and the formed image 201 (ink layer 401) of the beverage can 100 are provided. After the portion was cut out and embedded in the resin, the film thickness at five locations was measured while observing the cross section with a microscope, and the average film thickness was determined based on the thickness of the clear ink portion 301 and the formed image 201 (ink layer 401). And the thickness.

The experimental results will be described with reference to FIG.
As shown in FIG. 8, when the dot image row of the clear ink portion 301 is one row, the result is “× (large blur)” under all conditions, and the thickness of the clear ink portion 301 and the formed image 201 ( Regardless of the thickness of the ink layer 401), the bleeding was large.
On the other hand, when the dot image of the clear ink portion 301 has two or more rows, a result of “Δ (with blur)” or “◯ (slight blur)” was obtained, and an effect of preventing blur was obtained.

Further, in this experiment, it has been found that the thickness of the clear ink portion 301 (thickness after the clear ink portion 301 is cured) is preferably 2 μm or more (more preferably 3 μm or more).
When the thickness of the clear ink portion 301 is 1.5 μm, the result of “Δ” is obtained regardless of whether the dot image row of the clear ink portion 301 is 2 rows or 3 rows, but it is 2 μm or more. As a result, a result of “Δ to ○ (bleeding is small)” was obtained. When the thickness was 3 μm or more, a result of “◯ (slight blurring)” was obtained.

FIG. 9 is a diagram showing an actual printing result.
Specifically, FIG. 9 shows actual printing results under the conditions (2) to (8) and (10) to (13) in FIG. 8, and (1) and (9 in FIG. ) Shows a printing result when the clear ink portion 301 is not formed at all.
Further, “normal characters” in FIG. 9 indicate characters in which the character portion is formed by the formed image 201, and “extracted characters” indicate characters in which the character portion is formed by the extracted image.

9 indicates the result when the clear ink portion 301 is not formed, and 9B indicates the result when the dot image row of the clear ink portion 301 is one row. 9C shows a result when the dot image rows of the clear ink portion 301 are two rows and three rows. In this experiment, a normal character was formed with 5 points and 6 points, and a blank character was formed with 5 points.

Explaining the experimental results, in the case where there is no clear ink portion 301 at all and a normal character, as shown in (1) of FIG. 9, a blur occurs around the character and the blur spreads.
Further, in the case where there is no clear ink portion 301 and the character is to be removed, as shown in (9) of FIG. 9, the ink in the ink layer 401 located in the vicinity of most of the extracted character has entered, Most of the extracted letters were covered with ink.

Further, in the case where the dot image row of the clear ink portion 301 is one row and a normal character, as shown in (2) of FIG. 9, a blur occurs around the character and the blur spreads. The part where the outline of the character has collapsed has increased.
Also, in the case where the dot image row of the clear ink portion 301 is one row and the character is to be removed, as shown in (10), there is a portion where the ink has entered the character and the outline of the character has been broken. Increased.

On the other hand, in the case where there are two dot image rows in the clear ink portion 301 and a normal character, as shown in (3) to (8) of FIG. Compared with the case where the dot image row of the ink part 301 is one row, the outline of the character is clear.
Also, in the case where there are three dot image rows in the clear ink portion 301 and a character to be removed, as shown in (11) to (13) in FIG. Compared with the case where the dot image row of the portion 301 is one row, the ink intrusion into the extracted character is suppressed and the outline of the character is clear.

Further, when the thickness of the clear ink portion 301 is 2 μm (in the cases (4), (7), and (12) in FIG. 9), the thickness of the clear ink portion 301 is 1.5 μm (in FIG. 9 ( 3), (6), and (11)), the bleeding was reduced.
In addition, when the thickness of the clear ink portion 301 was 3 μm (in the case of (5), (8), and (13) in FIG. 9), the blur was further reduced and the outline became clearer.

In the example shown in FIG. 9, 5 points and 6 points of normal characters and 5 points of cut characters were printed. In addition, 1 point to 14 points of characters were also printed to confirm the bleeding state. . The result is the same as described above. When the number of dot image rows in the clear ink portion 301 is two or more, bleeding is reduced and the outline of the character is clear.
In addition, when the point of a character becomes large (for example, it becomes 10 points or more), the ratio of the bleeding part to a character will become small, and the malfunction that a character will become unreadable does not arise, but when the clear ink part 301 is not formed, the outline of a character The problem of blurring still occurred.

In FIG. 9, an experiment on bleeding of characters was performed, but the same effect as described above can be obtained even in the case of a pattern instead of a character, and the clear ink portion 301 is formed even in the case of a normal pattern or a blank pattern. By doing so, bleeding was less likely to occur.
Further, the results shown in FIGS. 8 and 9 were obtained regardless of the presence or absence of the base coat layer BL. In other words, the beverage can 100 with the base coat layer BL and the beverage can 100 without the base coat layer BL were prepared, and the above-described experiment was performed. Even with the can 100, the same results as those shown in FIGS. 8 and 9 were obtained.

FIGS. 10A and 10B are diagrams illustrating other printing examples.
In FIG. 10A, a star-shaped formed image 201 (hereinafter referred to as “star-shaped formed image 201S”) is formed as described above. Further, in this example, a round formed image 201 (hereinafter referred to as “round formed image 201C”) is formed so as to be adjacent to the star formed image 201S. Note that the color of the star-shaped image 201S is different from the color of the round-shaped image 201C.

In addition, in this example, in the image forming process 50 as an example of the image forming process, ink is attached to the outer peripheral surface 230 of the beverage can 100, and the star-shaped image 201S and the round-shaped image having different colors are combined. Two formed images 201 of 201C were formed.
In other words, in the image forming process 50, ink was adhered to the outer peripheral surface 230 of the beverage can 100, and a plurality of formed images 201 having different colors were formed on the outer peripheral surface 230.

In the example shown in FIG. 10A, the clear ink portion 301 is not formed over the entire periphery of the star-shaped image 201S, and the clear ink portion 301 is formed in a portion in contact with the round-shaped image 201C. Not done.
Similarly, the clear ink portion 301 is not formed over the entire periphery of the round formed image 201C, and the clear ink portion 301 is not formed in a portion in contact with the star formed image 201S.
In other words, the clear ink portion 301 is not formed between the star-shaped image 201S and the round-shaped image 201C.

More specifically, in the example shown in FIG. 10A, the clear printing process 30 as an example of the ink adhesion process clears the side of the formed image 201 (star-shaped image 201S, round-shaped image 201C). The clear ink portion 301 is formed by attaching ink. In the example shown in FIG. 10A, the clear ink is attached to the side of the formed image 201 that does not contact the other formed image 201. Yes. On the other hand, in the example shown in FIG. 10A, the clear ink is not attached to the side of the portion in contact with the other formed image 201.

In other words, the clear ink functions as a suppression ink, and in the clear printing step 30, the suppression ink is attached to the side of a portion of the formed image 201 that does not contact the other formed image 201. Thereby, the movement of the ink constituting the formed image 201 to the side of the formed image 201 is suppressed, and the outline of the formed image 201 is suppressed from being broken.
On the other hand, in the example illustrated in FIG. 10A, the suppression ink is not attached to the side of the portion of the formed image 201 that is in contact with the other formed image 201.

More specifically, in the clear printing step 30, the printing apparatus 500 as an example of an ink attaching unit attaches clear ink to a side of a part of the formed image 201 that does not contact the other formed image 201. On the other hand, the printing apparatus 500 does not attach clear ink to the side of the portion of the formed image 201 that contacts the other formed image 201.

More specifically, in the example shown in FIG. 10A, the clear ink portion 301 is formed on the side of the star-shaped image 201S and on the side of the portion not in contact with the round-shaped image 201C. On the other hand, the clear ink portion 301 is not formed on the side of the star-shaped image 201S and on the side of the portion in contact with the round-shaped image 201C.
Similarly, in the example shown in FIG. 10A, the clear ink portion 301 is formed on the side of the round formed image 201C and on the side of the portion not in contact with the star formed image 201S. On the other hand, the clear ink portion 301 is not formed on the side of the round shaped image 201C and on the side of the portion in contact with the star shaped image 201S.

Here, in the example shown in FIG. 10A, the round image 201C is located beside (side) the portion of the star image 201S that is in contact with the round image 201C. For this reason, even if the clear ink part 301 is not formed beside the portion of the star-shaped image 201S that is in contact with the round-shaped image 201C, the movement of the ink constituting the star-shaped image 201S is suppressed.
Similarly, the star-shaped image 201S is located beside (side) a portion of the round-shaped image 201C that is in contact with the star-shaped image 201S. For this reason, even if the clear ink part 301 is not formed beside the portion of the round image 201C that contacts the star-shaped image 201S, the movement of the ink constituting the round image 201C is suppressed.

Note that it is not excluded to form the clear ink portion 301 between the star-shaped image 201S and the round-shaped image 201C, and the clear-shaped image 201C is not cleared between the star-shaped image 201S and the round-shaped image 201C. The ink part 301 may be formed.
In this case, color mixing between the ink forming the star-shaped image 201S and the ink forming the round-shaped image 201C can be suppressed.
In the example shown in FIG. 10A as well, two or more dot image rows are provided in the clear ink portion 301 as described above.

In FIG. 10B, a round-shaped image 201C is formed in the star-shaped extracted image as described above. The circular formed image 201C is provided in contact with the ink layer 401 positioned around the extracted image.
Also in the example shown in FIG. 10B, the clear ink portion 301 is formed on the side of the portion of the ink layer 401 that does not contact the round image 201C.
On the other hand, the clear ink portion 301 is not formed on the side of the portion of the ink layer 401 that is in contact with the round formed image 201C.

In addition, for the circular formed image 201C, the clear ink portion 301 is formed on the side of the portion of the circular formed image 201C that does not contact the ink layer 401.
On the other hand, the clear ink portion 301 is not formed on the side of the portion in contact with the ink layer 401 in the round image 201C.
In other words, in the example shown in FIG. 10B as well, the clear ink portion 301 is not provided between the round image 201C and the ink layer 401, as described above.

Also in this example, a clear ink portion 301 is provided beside a portion of the round image 201C that is not in contact with another image (ink layer 401), whereby the contour of the round image 201 is formed. Blurring is suppressed. In addition, another image is located beside the portion of the round image 201C that is in contact with the other image (ink layer 401), and the round image 201C is also formed by this other image. The movement of the constituent ink is suppressed.
Similarly, a clear ink portion 301 is provided beside a portion of the ink layer 401 that is not in contact with another image (round-shaped image 201C), which may blur the outline of the ink layer 401. It is suppressed. In addition, the other image is located beside the portion of the ink layer 401 that is in contact with the other image (the round-shaped image 201C), and the ink layer 401 is also formed by the other image. Ink movement is suppressed.

Similarly to the above, it does not exclude the formation of the clear ink portion 301 between the round image 201C and the ink layer 401, and the clear ink portion between the round image 201C and the ink layer 401. 301 may be formed. In this case, it is possible to suppress the color mixture between the ink constituting the round image 201C and the ink of the ink layer 401.
Also in the example shown in FIG. 10B, the clear ink portion 301 is provided with two or more dot image rows.

(Other)
In the form shown in FIG. 4, the clear ink portion 301 is formed over the entire circumference of the formed image 201 and the extracted image. However, the clear ink portion 301 is not necessarily formed over the entire circumference. The clear ink portion 301 may be formed so as to contact only 201 or a part of the outline of the extracted image.
In some cases, it is desired to obscure a part of the contour. In this case, the clear ink portion 301 can be omitted to make the contour part ambiguous.

In addition, when the clear ink portion 301 is formed around the character string, the clear ink portion 301 may be formed around the character for each character, or the character strings may be grouped together and around the character string. The clear ink portion 301 may be formed.
Further, three or more dot image rows may be formed. Further, clear ink may be placed on all portions of the base coat layer BL where ink is not placed (portions where image formation by the image forming step 50 is not performed). In other words, not only the side portion of the contour of the formed image 201 and the extracted image, but clear ink may be placed on the side portion.

DESCRIPTION OF SYMBOLS 30 ... Clear printing process, 50 ... Image formation process, 100 ... Beverage can, 201 ... Formation image, 201C ... Round formation image, 201S ... Star formation image, 230 ... Outer peripheral surface (outer surface), 301 ... Clear ink part 500 ... Printing apparatus

Claims

An image forming step of forming an image by attaching ink to the outer surface of the beverage can;
On the side of the outer surface where the image is formed, a dot image row forming step of forming two or more dot image rows along the contour of the image;
A method for producing a beverage can comprising:
The method for producing a beverage can according to claim 1, wherein the dot images included in the two or more dot image rows are arranged along an axial direction of the beverage can and along a circumferential direction of the beverage can. .
2. The method for producing a beverage can according to claim 1, wherein the dot images included in the two or more dot image rows are arranged in a staggered pattern.
The method for producing a beverage can according to any one of claims 1 to 3, wherein a thickness of a layer formed by curing the two or more dot image rows is 2 µm or more.
5. The method for producing a beverage can according to any one of claims 1 to 4, wherein the two or more dot image rows are formed of a transparent ink.
The method for producing a beverage can according to any one of claims 1 to 5, wherein the two or more dot image rows are formed before the image is formed by the image forming step.
An image forming step of forming a plurality of images with different colors of each image by attaching ink to the outer surface of the beverage can;
Inhibiting ink for suppressing the movement of the ink constituting each image to the side beside the portion where each image is formed and not contacting the other image of each image. An ink adhering step for adhering;
A method for producing a beverage can comprising:
8. The beverage according to claim 7, wherein, in the ink adhering step, the ink for suppression is not adhering to a side of a portion where the image is formed and a portion of the image in contact with another image. A method for manufacturing cans.
The method for producing a beverage can according to claim 7 or 8, wherein a transparent ink is used as the suppression ink in the ink adhering step.
10. The beverage can according to claim 7, wherein, in the ink adhering step, two or more dot image rows are formed along a contour of each image on a side of a portion not in contact with the other image. Manufacturing method.
The method for producing a beverage can according to claim 10, wherein the dot images included in the two or more dot image rows are arranged along an axial direction of the beverage can and along a circumferential direction of the beverage can. .
The method for producing a beverage can according to claim 10, wherein the dot images included in the two or more dot image rows are arranged in a staggered manner.
An image forming step of forming an image by attaching ink to the outer surface of the beverage can;
An ink adhering step of adhering a suppressing ink for suppressing movement of the ink constituting the image to the side of the portion of the outer surface where the image is formed;
A beverage can comprising: a coating application step of applying a coating material on the image and the suppression ink after the formation of the image by the image formation step and after the suppression ink is adhered by the ink adhesion step; Manufacturing method.
Image forming means for forming an image by attaching ink to the outer surface of the beverage can;
Dot image row forming means for forming two or more dot image rows along the contour of the image on the side of the outer surface where the image is formed;
A printing system comprising:
Image forming means for forming a plurality of images having different colors of each image by attaching ink to the outer surface of the beverage can;
Inhibiting ink for suppressing the movement of the ink constituting each image to the side beside the portion where each image is formed and not contacting the other image of each image. An ink adhering means for adhering;
A printing system comprising:
Image forming means for forming an image by attaching ink to the outer surface of the beverage can;
An ink adhering means for adhering a suppression ink for suppressing movement of the ink constituting the image to the side of the portion of the outer surface where the image is formed;
A printing system comprising: a coating application unit that applies a coating on the image and the suppression ink after the image is formed by the image forming unit and after the suppression ink is deposited by the ink deposition unit.
The outer surface,
An image provided on the outer surface;
Two or more rows of dot images along the contour of the image, provided on the outer surface;
A beverage can comprising:
The outer surface,
A plurality of images provided on the outer surface, each image having a different color;
Provided beside each image and beside a portion of each image that is not in contact with the other image, and the suppression ink for suppressing movement of the ink constituting each image to the side is cured. Ink layer,
A beverage can comprising:
The outer surface,
An image provided on the outer surface;
An ink layer provided on a side of the image and cured with a suppression ink for suppressing movement of the ink constituting the image to the side;
A transparent layer provided on the image and the ink layer;
A beverage can comprising: