JP7528642B2 - Printing device, printing method and can body - Google Patents

Description

The present invention relates to a printing device, a printing method, and a can body.

Various images are printed using ink on the outer surface of cans used as beverage cans. When printing images on cans, the printing is often done so that overlapping portions are formed where the circumferential ends of the images overlap each other (see, for example, Patent Document 1).

JP 2003-81267 A

However, in the overlapping areas where the printed layers of this ink overlap, the thickness of the printed layers increases, and the color tone of the overlapping areas becomes darker than the areas adjacent to the overlapping areas, which may reduce the aesthetic appearance.

In particular, when printing images on a can using special inks, such as functional inks containing functional materials such as foaming materials or inorganic inks, to impart added value such as a three-dimensional effect, glossiness, or matte finish, the materials contained in the special inks tend to result in a thicker printed layer than when other inks (basic inks) are used. As a result, there is a risk that the thickness of the printed layer will increase dramatically in overlapping areas where the special ink printed layers overlap.

The present invention has been made in consideration of the above circumstances, and an example of an objective of the present invention is to solve the above problems. That is, an example of an objective of the present invention is to provide a printing device, a printing method, and a can body that can suppress deterioration in the aesthetic appearance of a can body having overlapping parts of images.

The printing device according to the present invention is a printing device equipped with a printing means for printing an image on the outer peripheral surface of a can body using ink, and the image printed on the outer peripheral surface of the can body includes an overlapping portion where the circumferential ends of the image overlap each other, and the overlapping portion includes an overlapping portion of a printing layer of a special ink, which is at least one of a functional ink containing a functional material and an inorganic ink, where the printing layers of the special ink overlap each other , and the printing means forms the printing layer of the special ink formed on the outer peripheral surface of the can body by a first printing layer of the special ink and a second printing layer of the special ink that are overlapped each other, and forms the overlapping portion of the printing layer of the special ink by the overlapping portion of the first printing layer formed by overlapping the first printing layers on each other, and prints the overlapping portion of the first printing layer so that the thickness of the first printing layer at one circumferential end of the can body is smaller than the thickness of the first printing layer at the other circumferential end of the can body in the overlapping portion of the first printing layer.

Preferably, the special ink of the first printed layer and the special ink of the second printed layer are the same color.
Preferably, the printing means prints in the overlapping portion of the first printed layer printed on the outer surface of the can body so that the thickness of the first printed layer at one circumferential end of the can body gradually decreases toward the other circumferential end of the can body.

Preferably, the printing means prints in the overlapping portion of the first printed layer printed on the outer peripheral surface of the can body so that the first printed layer at one circumferential end of the can body is superimposed on the first printed layer at the other circumferential end of the can body.

Preferably, the ink includes a base ink that is different from the special ink, and the printing means prints the portion of the can body where the neck of the can body will be formed using the base ink so as not to form a printing layer of the special ink on the portion of the outer surface of the can body where the neck of the can body will be formed.

Preferably, the functional ink is at least one of a foaming ink, a thermochromic ink, a fluorescent ink, and a varnish-repellent ink.

Preferably, the inorganic ink is at least one of a pearl pigment ink, a silver ink, a gold ink, and an ink containing an inorganic filler.

The printing method according to the present invention is a printing method having a printing step of printing an image on the outer peripheral surface of a can body using ink, wherein the image printed on the outer peripheral surface of the can body includes an overlapping portion where the circumferential ends of the image overlap each other, and the overlapping portion includes an overlapping portion of a printing layer of a special ink, which is at least one of a functional ink containing a functional material and an inorganic ink, whereby printed layers of the special ink overlap each other, and the printing step is characterized in that the printing layer of the special ink formed on the outer peripheral surface of the can body is formed by a first printing layer of the special ink and a second printing layer of the special ink that are overlapped each other, the overlapping portion of the printing layer of the special ink is formed by overlapping the first printing layers on each other, and the overlapping portion of the first printing layer is printed so that the thickness of the first printing layer at one circumferential end of the can body is smaller than the thickness of the first printing layer at the other circumferential end of the can body in the overlapping portion of the first printing layer.

The can body of the present invention is a can body having an image printed on its outer peripheral surface, the image being printed on the outer peripheral surface of the can body using ink, the image printed on the outer peripheral surface of the can body includes an overlapping portion where the circumferential ends of the image overlap each other, the overlapping portion includes an overlapping portion of the special ink printing layer where printed layers of a special ink, which is at least one of a functional ink containing a functional material and an inorganic ink , overlap each other, the special ink printing layer formed on the outer peripheral surface of the can body is formed by a first printed layer of the special ink and a second printed layer of the special ink that overlap each other, the overlapping portion of the special ink printing layer is formed by overlapping the first printed layers on each other, and in the overlapping portion of the first printed layer, the thickness of the first printed layer at one circumferential end of the can body is smaller than the thickness of the first printed layer at the other circumferential end of the can body.

The present invention provides a printing device, a printing method, and a can body that can prevent deterioration in the aesthetic appearance of a can body having overlapping parts of images.

FIG. 1 is a diagram illustrating a basic configuration of a printing apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of the area in which the printing plate and the blanket contact each other shown in FIG. 1 . FIG. 2 is a perspective view of a can body that is a printing substrate. FIG. 2 is a development view of a print image printed on the can body. 1A is a partial cross-sectional view of a fourth printing plate, FIG. 1B is a partial cross-sectional view of a fifth printing plate, and FIG. 1C is a partial cross-sectional view of a sixth printing plate, which are resin relief printing plates. 5A and 5B are partial cross-sectional views of printing plates which are resin relief printing plates, where (a) is a partial cross-sectional view of a part different from the part shown in FIG. 5A in the fourth printing plate, and (b) is a partial cross-sectional view of a part different from the part shown in FIG. 5B in the fifth printing plate. FIG. 7 is a partial cross-sectional view showing a modified example of the printing plate of FIG. 6 which is a resin relief printing plate. 1A and 1B are partial cross-sectional views of a can body (printed can) on which a print image has been printed by a printing device. 8(b) is a partial cross-sectional view of a portion of a can body (printed can) on which a print image has been printed by a printing device, the portion being different from FIG. 8(a), and including an overlapping portion between printed layers. 6 is a flowchart for explaining a printing operation of a printing device on a can body. FIG. 1 is a functional block diagram of a plate-making system that prepares printing plates to be attached to a printing device. 4 is a flowchart for explaining a platemaking operation for producing a printing plate using the platemaking system.

Hereinafter, an embodiment of the present invention (this embodiment) will be described with reference to the drawings.

[Basic configuration of printing device]
Fig. 1 is a diagram showing a basic configuration of a printing apparatus according to the present embodiment, Fig. 2 is an enlarged view of the vicinity of the region where the printing plate and the blanket contact each other shown in Fig. 1.

The printing device 1 shown in FIG. 1 is an offset printing device that performs printing by transferring ink via a blanket to the outer peripheral surface (outer surface) of the can body of a can body (printing object) P that has a roughly cylindrical shape, such as a two-piece can.

As shown in FIG. 1, the printing device 1 includes an inking unit 10, a blanket wheel 20, a transport unit 30, a mandrel wheel 40, a varnish applicator 50, and a transfer unit 60.

The inking unit 10 is a device that supplies ink to the printing plate 14. The inking unit 10 is also called an inker unit. The inking unit 10 is made up of multiple inking units 10, each with a different ink color, namely the first inking unit 10a to the eighth inking unit 10h. These multiple inking units 10 are each arranged along the outer circumferential surface of the blanket wheel 20. The inking unit 10 includes an ink supply section 11 that contains a specific ink, and a plate cylinder 13 on which a printing plate 14 corresponding to the ink of each ink supply section 11 is mounted.

The ink supply units 11 are made up of the first ink supply unit 11a to the eighth ink supply unit 11h. The printing plates 14 are made up of the first printing plate 14a to the eighth printing plate 14h to which ink can be supplied from the first ink supply unit 11a to the eighth ink supply unit 11h, respectively. The plate cylinder 13 is made up of the first plate cylinder 13a to the eighth plate cylinder 13h to which the first printing plate 14a to the eighth printing plate 14h are respectively mounted.

In the example of the printing device 1 shown in FIG. 1, the multiple ink supply units 11 contain the basic inks of the process colors yellow (Y), magenta (M), cyan (C), and black (K), as well as the basic ink of the special color navy (N) and the special ink of navy (N). Specifically, the first ink supply unit 11a contains the basic ink of yellow (Y), the second ink supply unit 11b contains the basic ink of magenta (M), and the third ink supply unit 11c contains the basic ink of cyan (C). The seventh ink supply unit 11g contains the basic ink of black (K).

The fourth ink supply unit 11d and the fifth ink supply unit 11e both contain navy (N: dark blue) special ink. The sixth ink supply unit 11f contains navy (N: dark blue) basic ink.

On the other hand, the eighth ink supply unit 11h does not contain any ink. Therefore, no ink is supplied to the eighth printing plate 14h that corresponds to the eighth ink supply unit 11h.

Here, "special ink" refers to ink that contains functional materials, inorganic materials, and other materials (these materials are also referred to as "special materials") described below, and unlike ordinary printing inks, it not only colors the ink, but also adds added value in terms of appearance and feel, such as a three-dimensional effect (unevenness, roughness), gloss, matte finish, and discoloration. "Basic ink" refers to ink that does not contain such special materials and is normally used to clearly reproduce images when printing on the outside of a can body, and refers to ink that only colors the ink without adding added value such as a three-dimensional effect, gloss, or matte finish.

By storing each ink in this manner, the multiple ink supply units 11 are able to supply darker inks with lower brightness later.

The navy (N) basic ink is used to print the border image, which is the border portion of the background image (specific image) described below. The navy (N) special ink is used to print the area near the border image of the background image, specifically, the inner image, which is the area inside the border portion of the background image.

As shown in FIG. 2, the ink supply unit 11 includes an ink roller group 12 consisting of a fountain roller, a foam roller, etc. The ink supply unit 11 supplies ink stored in an ink storage unit (not shown) to a printing plate 14 attached to a plate cylinder 13 by rotating each roller of the ink roller group 12. Temperature-adjusting water is circulated inside some of the rollers of the ink roller group 12 to maintain the ink at an appropriate temperature.

The plate cylinder 13 has a generally cylindrical shape that can rotate around a support shaft, and the printing plate 14 is removably attached to its outer circumferential surface. The plate cylinder 13 is provided so that the distance from the blanket wheel 20 can be changed. The plate cylinder 13 is also called a plate cylinder.

The multiple printing plates 14 (first printing plate 14a to eighth printing plate 14h) are made based on the original image data by the platemaking system 200 described below, and are made of resin relief plates in which the image areas on which ink is applied are formed with a photosensitive resin layer or the like. Note that the printing plates 14 are not limited to resin relief plates, and may be other printing plates. The printing plates 14 may also be waterless flat plates in which non-image areas are formed with an ink-repellent layer such as silicone resin, and image areas on which ink is applied are formed between the non-image areas.

The print image 104 printed on the can body P, which will be described later, contains an image portion made up of halftone dots (halftone dot image portion). Therefore, in the platemaking system 200, which will be described later, the original image data is color-separated into separate plate image data for each color, and a halftone dot process is applied to parts of the separated plate image data for each color as necessary to generate image data for platemaking for each color. The platemaking system 200 then makes multiple printing plates 14 based on the image data for platemaking for each color.

The halftone image portion in the print image 104 may also include an image portion (multiplication portion) in which at least a portion of halftone dots of multiple colors overlap each other. In other words, the image data for each color for plate making generated by the plate making system 200 may include a halftone image portion for overprinting using a multiplication method in which at least a portion of halftone dots of multiple colors overlap each other.

In the printing device 1, the first ink supply unit 11a supplies the yellow (Y) base ink to the first printing plate 14a (base ink printing plate), the second ink supply unit 11b supplies the magenta (M) base ink to the second printing plate 14b (base ink printing plate), the third ink supply unit 11c supplies the cyan (C) base ink to the third printing plate 14c (base ink printing plate), and the seventh ink supply unit 11g supplies the black (K) base ink to the seventh printing plate 14g (base ink printing plate).

In addition, in the printing device 1, navy (N) special ink is supplied from the fourth ink supply unit 11d to the fourth printing plate 14d (special ink printing plate), navy (N) special ink is also supplied from the fifth ink supply unit 11e to the fifth printing plate 14e (special ink printing plate), and navy (N) basic ink is supplied from the sixth ink supply unit 11f to the sixth printing plate 14f (basic ink printing plate).

The printing device 1 then transfers the corresponding inks from the first printing plate 14a to the seventh printing plate 14g in sequence to the same blanket 25.

In the printing device 1, after all the inks are transferred (laminated) onto the same (single) blanket 25, all the colors of ink on that same blanket 25 are simultaneously transferred onto the outer surface of the can body P, and the can body P is then transferred from the mandrel 41 to a drying device such as an oven (not shown). With this type of printing device 1, a large number of can bodies P can be printed at high speed.

For example, an outlet for blowing cold air may be installed near the plate cylinder 13, in which case the temperature of the plate cylinder 13 and the printing plate 14 is maintained at an appropriate level.

The blanket wheel 20 is a device that rotates a blanket 25 that comes into rolling contact with each of the printing plate 14 and the can body P to transfer the ink supplied to the printing plate 14 to the can body P. As shown in FIG. 1, the blanket wheel 20 has a generally cylindrical shape that can rotate around a support shaft 22. As shown in FIG. 2, a plurality of segments 21 are provided on the outer circumferential surface of the blanket wheel 20 at predetermined intervals along the circumferential direction of the blanket wheel 20. A blanket 25 is attached to the outer surface of each of the plurality of segments 21. In the printing device 1 shown in FIG. 1, 12 blankets 25 are attached to the segments 21.

The blanket 25 is an intermediate transfer body that mediates the transfer of ink from the printing plate 14 to the can body P. The blanket 25 includes a base layer formed of woven fabric and foam, and a rubber layer formed of acrylonitrile butadiene rubber or the like. The base layer is removably attached to the outer surface of the segment 21 via an adhesive or the like. The rubber layer is a layer to which the ink on the printing plate 14 is transferred, and is disposed on the outer surface of the base layer to form the outer surface of the blanket 25.

In the printing device 1, the blanket wheel 20 rotates in the direction of the arrow shown in FIG. 1 (counterclockwise), and the following inks are transferred to the same (single) blanket 25 in the following order: yellow (Y) basic ink on the first printing plate 14a, magenta (M) basic ink on the second printing plate 14b, cyan (C) basic ink on the third printing plate 14c, navy (N) special ink on the fourth printing plate 14d, navy (N) special ink on the fifth printing plate 14e, navy (N) basic ink on the sixth printing plate 14f, and black (K) basic ink on the seventh printing plate 14g.

Here, since the navy (N) special ink is used to print a relatively wide range of image portions (first inner image 104f-21 to third inner image 104f-23 in background image 104f described below), it is preferable to supply it to two printing plates, the fourth printing plate 14d and the fifth printing plate 14e. However, since the fourth printing plate 14d is the printing plate that is always used to print this image portion, it is also called the "main plate." Furthermore, the fifth printing plate 14e is the printing plate that is used as necessary to bring out the color of the navy (N) special ink firmly in this image portion (to make the printing layer of the navy (N) special ink a thick printing layer (thick film)), so it is also called the "dummy plate."

The arrangement of the fourth printing plate 14d (original) and the fifth printing plate 14e (duplicate) in the printing device 1 may be interchanged. In this case, the printing device 1 transfers the navy (N) special ink onto the fifth printing plate 14e (duplicate) to the same blanket 25, and then transfers the navy (N) special ink onto the fourth printing plate 14d (original).

The transport unit 30 is a device that transports the can bodies P before printing to the mandrel wheel 40. As shown in FIG. 1, the transport unit 30 is provided above the mandrel wheel 40. The transport unit 30 is provided upstream in the rotation direction of the mandrel wheel 40 from the area where the can bodies P held by the mandrel 41 contact the blanket 25. The transport unit 30 transports the can bodies P one by one from above the mandrel wheel 40 to the top of the mandrel wheel 40 by the gravity of the can bodies P.

The mandrel wheel 40 is a device that rotates the mandrel 41 that holds the can body P. The mandrel wheels 40 are arranged adjacent to each other in the radial direction of the blanket wheel 20. The mandrel wheel 40 has a generally circular disk shape that can rotate around a support shaft. A plurality of mandrels 41 are provided on the outer periphery of the mandrel wheel 40 at predetermined intervals along the circumferential direction of the mandrel wheel 40.

The mandrel 41 has a generally cylindrical shape that can be inserted into the can body P. A plurality of mandrels 41 are provided so as to protrude in a direction intersecting with the mandrel wheel 40, and are cantilevered on the outer periphery of the mandrel wheel 40. It is preferable that the number of mandrels 41 is an integer multiple of the number of blankets 25. In the printing device 1 shown in FIG. 1, 24 mandrels 41 are provided on the mandrel wheel 40.

The mandrel 41 holds the can body P by adsorbing the inner bottom surface of the can body P at its tip by air suction or the like. The mandrel 41 is provided so that its posture can be changed, and its position in the radial direction of the mandrel wheel 40 can be changed. The mandrel 41 is provided so that it can rotate around its central axis while holding the can body P.

The varnish applicator 50 is a device that applies an overcoat such as a finishing varnish to the can body P to which the ink has been transferred. The varnish applicators 50 are provided adjacent to each other in the radial direction of the mandrel wheel 40. The varnish applicators 50 are provided downstream in the rotation direction of the mandrel wheel 40 from the area where the can body P held by the mandrel 41 comes into contact with the blanket 25.

The transfer unit 60 is a device that transfers the can body P that has passed through the varnish applicator 50 from the mandrel 41 and transports it to a drying device such as an oven where the ink, overcoat, etc. are fixed to the can body P. The transfer units 60 are provided adjacent to each other in the radial direction of the mandrel wheel 40. The transfer units 60 are provided downstream in the rotation direction of the mandrel wheel 40 from the area where the can body P held by the mandrel 41 comes into contact with the varnish applicator 50.

[Can body]
Fig. 3 is a perspective view of a can body P, which is a printing substrate. The can body P, such as a two-piece can, has a substantially cylindrical shape, and an opening 101 is formed in the upper part of the can body P. A bottom 102 is provided in the lower part of the can body P. A printed image 104 with a design, for example as shown in Fig. 4 described later, is printed on an outer peripheral surface 103 of the can body P.

The can body P is then filled with the beverage content through the opening 101, and the opening 101 is then closed with a lid (not shown), thereby creating a canned beverage product.

The beverage filled into the can body P is, for example, a lemon-flavored sour beverage (lemon sour) that contains lemon juice, pulp, and the like. In this case, the can body P is filled with this lemon sour and the opening 101 is closed with the lid, and the canned lemon sour is provided as a beverage product.

The beverage filled into the can body P is not particularly limited, and may be any of non-alcoholic beverages (e.g., soft drinks, fruit drinks, tea, soup drinks, non-alcoholic beverages with the flavor of alcoholic beverages, etc.) and alcoholic beverages (e.g., beer, chuhai, sour drinks, cocktails, sake, wine, etc.).

The can body P is a metal can, and may be any type of metal can, such as a seamless can or a welded can, formed by drawing, drawing and ironing, redrawing, or the like from various metal sheets, such as aluminum sheets, aluminum alloy sheets, surface-treated steel sheets such as tin-free steel, tinplate, chrome-plated steel sheets, aluminum-plated steel sheets, nickel-plated steel sheets, tin-nickel-plated steel sheets, and various alloy-plated steel sheets. The surface of this metal can may be laminated with a resin film, such as a polyester film, a nylon film, or a polypropylene film.

In addition, a white paint layer (solid white print layer) may be formed in advance on the outer peripheral surface 103 of the can body P.

[Printed Image]
4 is a development view of the print image 104 printed on the can body P. As shown in FIG. 4, the print image 104 printed on the can body P has a product name image 104a, a sake mark image 104b, a product related image 104c, an alcohol content image 104d, a background image 104f (specific image) that is the background of these images, an upper end image 104g located on the upper side of the background image 104f, and a lower end image 104h located on the lower side of the background image 104f. As a result, the print image 104 is an image with a design (design image). In addition, the print image 104 has an information image 104e, which displays detailed information about the beverage product to be presented to the consumer.

The product name image 104a is an image of relatively large letters saying "Refreshing Lemon," which is the product name of a beverage product in which lemon sour is filled in a can P. In this embodiment, the product name image 104a is an image printed with magenta (M) as the base ink.

The sake mark image 104b displays the word "sake" (alcohol) within a circular frame to let consumers know that the beverage product is an alcoholic beverage. In this embodiment, the sake mark image 104b is an image in which the inside of the circular frame is printed with a yellow (Y) base ink, and the word image "sake" is printed with a black (K) base ink.

The product-related image 104c is an illustration of a lemon, which is an ingredient of lemon sour. The product-related image 104c is not limited to this, and may be, for example, another image based on the image of lemon sour (for example, a mark dedicated to the product, an illustration of a character, etc.). In this embodiment, the product-related image 104c is, for example, an image printed with a basic ink of yellow (Y) and a basic ink of black (K). Alternatively, the lemon illustration image of this product-related image 104c may be a halftone image in which at least a portion of halftone dots of each color of yellow (Y), magenta (M), cyan (C), and black (K) are superimposed by overprinting using a cross-printing method. By expressing this product-related image 104c by overlapping halftone dots of each color, a clear and three-dimensional image of a lemon can be obtained.

The alcohol content image 104d displays the text "3% alcohol content," which indicates the alcohol content (%) of the lemon sour. In this embodiment, the alcohol content image 104d is an image printed with the basic ink of cyan (C).

The information image 104e is an image showing detailed product information about a beverage product (canned fruit chuhai). This information image 104e displays, within a rectangular frame, a basic information image 104e-1 that lists basic information such as the ingredients, content volume, expiration date, and manufacturer's address for the contents (lemon sour) filled in the can body P, a barcode image 104e-2, a nutritional information image 104e-3 that lists the nutritional components and calorific value of the contents, a recycle mark image 104e-4 necessary for recycling the empty can, and a warning image 104e-5 that lists other warnings (for example, "Please drink immediately after opening the can").

When a white paint layer (solid white print layer) has been formed in advance, this information image 104e is an image in which the basic information image 104e-1, barcode image 104e-2, nutrition information image 104e-3, recycling mark image 104e-4, and warning image 104e-5 are printed in black (K) basic ink within a rectangular frame formed by the white paint layer.

The top image 104g and the bottom image 104h are solid images in a color different from the background image 104f. Such top image 104g and bottom image 104h are line images that provide accents with the basic ink of yellow (Y) at the top and bottom of the printed image 104.

The background image 104f (specific image) is formed over a relatively wide area on the outer circumferential surface 103 of the can body P. Therefore, the ink used to print this background image 104f can increase the value of the can body P as a beverage product.

The printing device 1 uses a special ink containing special materials such as functional materials and inorganic materials as the ink for printing the background image 104f. This allows the printing device 1 to impart added value in terms of appearance and feel, such as a three-dimensional effect (unevenness, roughness), gloss, matte finish, and discoloration, to the outer surface 103 of the can body P, thereby increasing the commercial value of the can body P. However, the background image 104 is not limited to being printed with a special ink, and may be printed with a basic ink, and the color is not particularly limited. For example, the background image 104 may be printed overall with a navy (N) basic ink.

The special ink may be at least one of a functional ink containing a functional material as a special material and an inorganic ink containing an inorganic material as a special material. This special ink has poorer transferability than a basic ink that does not contain a special material, for example, because the special material, such as the functional material or inorganic material, is easily separated from the ink and the particles of the special material are large. Therefore, the special ink supplied to the fourth printing plate 14d and the fifth printing plate 14e is likely to accumulate on the blanket 25 during transfer, and is likely to accumulate in the non-printing areas of the fourth printing plate 14d and the fifth printing plate 14e where the ink does not adhere, causing the blanket 25 and the non-printing areas of the printing plate 14 to become easily soiled.

As a result, when printing is performed using a dirty blanket 25 or dirty fourth printing plate 14d and fifth printing plate 14e, the print image 104 printed on the outer peripheral surface 103 of the can body P is likely to be printed larger than the image area of the printing plate, which is known as "print thickening."

The printing device 1 prints the background image 104f in the following manner so as to reduce (or suppress) the amount of thickening of the print caused by such special ink. The background image 104f may be, for example, a plain image of navy blue (N), which is the image color of the beverage product.

The printing device 1 prints the border images (first border image 104f-11 to seventh border image 104f-17) located within the image area of the background image 104f and at the border between the background image 104f and adjacent images with a navy (N) basic ink that does not contain special material. The printing device 1 then prints the first inner image 104f-21 to third inner image 104f-23 inside the border images in the background image 104f with a navy (N) special ink that contains special material.

The first boundary image 104f-11 (navy (N) base ink) is located within the image area of the background image 104f at the boundary with the top image 104g (yellow (Y) base ink). The first boundary image 104f-11 and top image 104g are images printed on the outer peripheral surface 103 of the can body P in the portion where the neck is formed by neck-in processing. In the printing device 1, the basic ink is transferred to the blanket 25 so that a printing layer of the special ink is not formed on the neck on the outer peripheral surface 103 of the can body P. In other words, the first boundary image 104f-11 is printed with the navy (N) base ink rather than the navy (N) special ink, and the top image 104g is printed with the yellow (Y) base ink.

The second border image 104f-12 (basic ink of navy (N)) is located within the image area of the background image 104f at the border with the product name image 104a (basic ink of magenta (M)), which is a text image of the product name "Sukkiri Lemon."

The third border image 104f-13 (basic ink of navy (N)) is located within the image area of the background image 104f, at the border with the circular portion of the sake mark image 104b (basic ink of yellow (Y)).

The fourth border image 104f-14 (basic ink of navy (N)) is located within the image area of the background image 104f at the border with the product-related image 104c (basic ink of yellow (Y)), which is an illustration image of a lemon.

The fifth border image 104f-15 (basic ink of navy (N)) is located within the image area of the background image 104f at the border with the alcohol content image 104d (basic ink of cyan (C)), which is a text image saying "3% alcohol content."

The sixth border image 104f-16 (navy (N) base ink) is located within the image area of the background image 104f and at the border with the rectangular frame of the information image 104e (white paint layer (white (W) base ink)).

The seventh border image 104f-17 (basic ink of navy (N)) is located within the image area of the background image 104f and at the border with the bottom edge image 104h (basic ink of yellow (Y)).

The first inner image 104f-21 to the third inner image 104f-23 (navy (N) special ink) are located inside the first border image 104f-11 to the seventh border image 104f-17 within the image area of the background image 104f.

The printed image 104 formed when all the ink has been transferred onto the blanket 25 has overlapping portions where the circumferential ends of the printed image 104 overlap each other when transferred to the can body P.

In the printing device 1, in order to prevent the thickness of this overlapping portion on the can body P from increasing, the overlapping portion on the can body P is printed so that the thickness of the printed layer of the image at one circumferential end of the can body is smaller than the thickness of the printed layer of the image at the other circumferential end of the can body.

Here, the printing device 1 may print in this overlapping portion such that the printed layer of the image at one circumferential end of the can body is superimposed on the printed layer of the image at the other circumferential end of the can body.

In the printed image 104, the second inner image 104f-22 and the third inner image 104f-23 form this overlapping portion. In this overlapping portion, the printed layer of the second inner image 104f-22, which is the printed layer of the image at one circumferential end of the can body, is superimposed on the printed layer of the third inner image 104f-23, which is the printed layer of the image at the other circumferential end of the can body.

In addition, in the printed image 104, the first border image 104f-11 in the navy (N) basic ink has a 1-1 border image 104f-111 located above the first inner image 104f-21, a 1-2 border image 104f-112 located above the second inner image 104f-22, and a 1-3 border image 104f-113 located above the third inner image 104f-23.

The top edge image 104g in the basic ink of yellow (Y) has a first top edge image 104g-1 located above the 1-1 border image 104f-111, a second top edge image 104g-2 located above the 1-2 border image 104f-112, and a third top edge image 104g-3 located above the 1-3 border image 104f-113.

The seventh border image 104f-17 in the navy (N) basic ink has a 7-1 border image 104f-171 located below the first inner image 104f-21, a 7-2 border image 104f-172 located below the second inner image 104f-22, and a 7-3 border image 104f-173 located below the third inner image 104f-23.

The bottom edge image 104h in yellow (Y) basic ink has a first bottom edge image 104h-1 located below the 7-1st border image 104f-171, a second bottom edge image 104h-2 located below the 7-2nd border image 104f-172, and a third bottom edge image 104h-3 located below the 7-3rd border image 104f-173.

In the overlapping portion described above, the printed layer of the second upper end image 104g-2, which is the printed layer of the image at one circumferential end of the can body, is superimposed on the printed layer of the third upper end image 104g-3, which is the printed layer of the image at the other circumferential end of the can body.

In addition, in the overlapping portion described above, the printed layer of the 1-2 border image 104f-112, which is the printed layer of the image at one circumferential end of the can body, is superimposed on the printed layer of the 1-3 border image 104f-113, which is the printed layer of the image at the other circumferential end of the can body.

In addition, in the overlapping portion described above, the printed layer of the 7th-2nd border image 104f-172, which is the printed layer of the image at one circumferential end of the can body, is superimposed on the printed layer of the 7th-3rd border image 104f-173, which is the printed layer of the image at the other circumferential end of the can body.

In addition, in the overlapping portion described above, the printed layer of the second bottom end image 104h-2, which is the printed layer of the image at one circumferential end of the can body, is superimposed on the printed layer of the third bottom end image 104h-3, which is the printed layer of the image at the other circumferential end of the can body.

With the printing device 1, printing may be performed in the overlapping portion so that, for example, the thickness of the printed layer of the image at one circumferential end of the can body gradually (in stages) decreases toward the other circumferential end of the can body. This makes it possible to prevent the thickness of the printed layer in the overlapping portion from increasing.

In addition, in the printing device 1, the portion printed with the navy (N) special ink is the inner portion within the image area of the background image 104f, excluding the boundary portion with the image adjacent to the background image 104f. The printing device 1 then prints the boundary portion within the image area of the background image 104f with a navy (N) basic ink of the same color as the special ink. This allows the printing device 1 to reduce (or suppress) the amount of thickening of the print with the special ink. And while maintaining this print size, the background image 104f can be given added value such as a three-dimensional effect (unevenness, roughness), glossiness, matte finish, and discoloration due to the special ink.

[Print version]
Figures 5 to 7 are partial cross-sectional views of printing plates which are resin relief plates. Figure 5(a) is a partial cross-sectional view of a fourth printing plate, Figure 5(b) is a partial cross-sectional view of a fifth printing plate, and Figure 5(c) is a partial cross-sectional view of a sixth printing plate. Figure 6(a) is a partial cross-sectional view of a part of the fourth printing plate different from the part shown in Figure 5(a), and Figure 6(b) is a partial cross-sectional view of a part of the fifth printing plate different from the part shown in Figure 5(b). Figure 7 is a partial cross-sectional view showing a modification of the printing plate of Figure 6 which is a resin relief plate.

The fourth printing plate 14d shown in Fig. 5(a) has an image area 14d-11 to which navy (N) special ink is applied, and non-image areas 14d-12 and 14d-13 to which no ink is applied. Similarly, the fifth printing plate 14e shown in Fig. 5(b) has an image area 14e-11 to which navy (N) special ink is applied, and non-image areas 14e-12 and 14e-13 to which no ink is applied. The sixth printing plate 14f shown in Fig. 5(c) has an image area 14f-11 and 14f-12 to which navy (N) basic ink is applied, and non-image areas 14f-13 to 14f-15 to which no ink is applied. The image areas 14d-11, 14e-11, 14f-11, and 14f-12 shown in Figures 5(a) to (c) are all image areas for forming images in which ink is applied in a solid manner (solid images).

The image area 14d-11 of the fourth printing plate 14d, the image area 14e-11 of the fifth printing plate 14e, and the image areas 14f-11 and 14f-12 of the sixth printing plate 14f form the background image forming region R1 for forming the background image 104f.

The inner image forming region R11 in the background image forming region R1 is an area that forms part of the first inner image 104f-21 in Figure 4 using navy (N) special ink on the image area 14d-11 of the fourth printing plate 14d and the image area 14e-11 of the fifth printing plate 14e.

The border image forming regions R12 and R13 in the background image forming region R1 are regions that form part of the border image (for example, the third border image 104f-13 and the fourth border image 104f-14 in FIG. 4) using the navy (N) basic ink on the image areas 14f-11 and 14f-12 of the sixth printing plate 14f.

The printing device 1 uses the fourth printing plate 14d to the sixth printing plate 14f to print an inner image in navy (N) special ink inside a border image in navy (N) basic ink, thereby reducing (or suppressing) the amount of thickening of the print in the special ink, and printing a background image 104f on the can body P that has added value such as a three-dimensional effect (unevenness, roughness), gloss, matte, and discoloration from the special ink.

The fourth printing plate 14d (main plate) shown in FIG. 6(a) is composed of a plurality of halftone dot image areas 14d-21 to which navy (N) special ink is applied, and non-image areas 14d-22 to which no ink is applied. The plate also includes a halftone dot forming area 14d-2 for forming an image using halftone dots, a non-image area 14d-23 to which no ink is applied, an image area including image areas 14d-31, 14d-32, and 14d-4 to which navy (N) special ink is applied and which form a solid image, and a non-image area 14d-5 to which no ink is applied.

The fifth printing plate 14e (copy) shown in Figure 6(b) has navy (N) special ink applied to it, forming image areas including image areas 14e-31, 14e-32, and 14e-4 for forming a solid image, as well as non-image areas 14e-2 and 14e-5 that do not receive any ink.

The halftone dot forming section 14d-2, which is composed of a plurality of image areas 14d-21 and non-image areas 14d-22 of the fourth printing plate 14d, forms a background image forming region R2 from position S1 to position S2 for forming the third inner image 104f-23, which is one image portion of the overlapping portion of the background image 104f. The length of the background image forming region R2 from position S1 to position S2 may be, for example, about 2 mm. The length of the portion indicated by the double-sided arrow of the background image forming region R2 in FIG. 6(a) corresponds to the length (width T) of the third inner image 104f-23 shown in FIG. 4 in the direction of the X-axis arrow.

A background image forming region R3 is formed from position S2 to position S3 for forming the image portion of the background image 104f other than the overlapping portion by the image portion including image portion 14d-31 and image portion 14d-32 of the fourth printing plate 14d and the image portion including image portion 14e-31 and image portion 14e-32 of the fifth printing plate 14e. Note that this background image forming region R3 may include the background image forming region R1 described above.

The image portion 14d-4 of the fourth printing plate 14d constitutes a background image forming region R4 from position S3 to position S4 for forming the second inner image 104f-22, which is the other image portion of the overlapping portion of the background image 104f. The length of the portion indicated by the double-sided arrows in the background image forming region R4 in FIG. 6(a) corresponds to the length of the second inner image 104f-22 in the X-axis arrow direction shown in FIG. 4.

The image portion including image portion 14e-31 and image portion 14e-32 of the fifth printing plate 14e is a copy of the image portion including image portion 14d-31 and image portion 14d-32 of the fourth printing plate 14d, and is an image portion from position S2 to position S3 where the navy (N) special ink is applied in order to bring out the color of the navy (N) special ink firmly in the background image forming region R3. Similarly, the image portion 14e-4 of the fifth printing plate 14e is a copy of image portion 14d-4 of the fourth printing plate 14d, and is an image portion from position S3 to position S4 where the navy (N) special ink is applied in order to bring out the color of the navy (N) special ink firmly in the background image forming region R4.

As shown in FIG. 6(a), the transfer of navy (N) specialty ink from the fourth printing plate 14d to the blanket 25 starts at position S1 and proceeds in the direction of arrow Q1, which is opposite the x-axis direction, to position S4. As shown in FIG. 6(a), the fourth printing plate 14d first forms the third inside image 104f-23 with halftone dots at one end of the overlapping portion in the circumferential direction of the can body (start of printing), and lastly forms the second inside image 104f-22 with a solid image at the other end of the overlapping portion in the circumferential direction of the can body (end of printing).

Also, as shown in FIG. 6(b), the transfer of the navy (N) specialty ink from the fifth printing plate 14e to the blanket 25 starts at position S2, which is a certain length (e.g., about 2 mm) away from position S1, and proceeds in the direction of arrow Q2, which is opposite the x-axis direction, to position S4.

In this way, the position where the transfer of the navy (N) specialty ink by the fourth printing plate 14d ends (ends printing) and the position where the transfer of the navy (N) specialty ink by the fifth printing plate 14e ends (ends printing) are both S4. Note that the position where the printing ends by the fifth printing plate 14e in FIG. 6(b) (the position at the left end of the image area 14e-4) is not limited to the example of being the same position S4 as the position where the printing ends by the fourth printing plate 14d in FIG. 6(a) (the position at the left end of the image area 14d-4), but may be another position, for example, it may be a position slightly (for example, about 0.2 mm) away from position S4 in the x-axis direction.

On the other hand, the position S1 where the transfer of the navy (N) special ink by the fourth printing plate 14d begins (starts printing) is a certain length (e.g., about 2 mm) away in the x-axis direction from the position S2 where the transfer of the navy (N) special ink by the fifth printing plate 14e begins (starts printing), and the fourth printing plate 14d starts printing earlier by that amount. For this reason, the fourth printing plate 14d forms an overlapping portion where the printed layers of the second inner image 104f-22 overlap on the printed layer of the image of the third inner image 104f-23. And the fifth printing plate 14e does not form an overlapping portion where the printed layers of the images overlap.

In this way, by forming the image area for forming the third inner image 104f-23, which is one of the circumferential ends of the can body in the overlapping portion, as an image area of multiple fine halftone dots, it is possible to make the thickness of the printed layer of this third inner image 104f-23 smaller than the thickness of the printed layer of the second inner image 104f-22, which is the other circumferential end of the can body in the overlapping portion.

In particular, in order to form a halftone image in which the "dot area ratio," which is the ratio (%) of the area of dots per unit area of the halftone image, gradually decreases, as shown in FIG. 6(a), the length in the x-axis direction of each of the multiple image portions 14d-21 of the halftone dot forming unit 14d-2 gradually decreases as one progresses in the x-axis direction in the background image forming region R2 (i.e., the dot area ratio of the background image forming region R2 gradually decreases as one progresses in the x-axis direction). This allows the thickness of the printed layer of the third inside image 104f-23, which is one of the circumferential ends of the can body, to be gradually reduced toward the other circumferential end of the can body in the overlapping portion, as described below.

The dot formation portion 14d-2 of the fourth printing plate 14d is not limited to being composed of a plurality of image portions 14d-21 whose length in the x-axis direction gradually decreases as the background image formation region R2 advances in the x-axis direction, and non-image portions 14d-22 between them. The dot formation portion 14d-2 may be composed of a plurality of image portions 14-211 whose length in the x-axis direction is approximately the same and formed at approximately uniform intervals, and non-image portions 14d-212 between them, as shown in FIG. 7, for example. This allows the thickness of the entire printed layer of the third inner image 104f-23, which is one of the circumferential ends of the can body, to be approximately uniform and smaller than the thickness of the printed layer of the second inner image 104f-22, which is the other circumferential end of the can body, in the overlapping portion, as described below.

In addition, by printing the printed layer (lower layer) at one of the circumferential ends of the can body in the overlapping portion formed with the basic ink using a printing plate 14 having a configuration similar to the halftone dot forming section 14d-2 in FIG. 6 or FIG. 7, the thickness of the lower layer can be made smaller than the thickness of the printed layer (upper layer) at the other circumferential end of the can body.

That is, in the overlapping portion where the printed layer of the second top edge image 104g-2 in yellow (Y) base ink is superimposed on the printed layer of the third top edge image 104g-3 in yellow (Y) base ink, the printed layer of the third top edge image 104g-3 may be a printed layer of a halftone image, and the printed layer of the second top edge image 104g-2 may be a printed layer of a solid image.

In addition, for the overlapping portion where the print layer of the 1-2 border image 104f-112 in the navy (N) base ink is superimposed on the print layer of the 1-3 border image 104f-113 in the navy (N) base ink, the print layer of the 1-3 border image 104f-113 may be a print layer of a halftone image, and the print layer of the 1-2 border image 104f-112 may be a print layer of a solid image.

In addition, for the overlapping portion where the printed layer of the 7-2 border image 104f-172 in the navy (N) base ink is superimposed on the printed layer of the 7-3 border image 104f-173 in the navy (N) base ink, the printed layer of the 7-3 border image 104f-173 may be a printed layer of a halftone image, and the printed layer of the 7-2 border image 104f-172 may be a printed layer of a solid image.

In addition, for the overlapping portion between the print layer of the third bottom edge image 104h-3 printed in the yellow (Y) base ink and the print layer of the second bottom edge image 104h-2 printed in the yellow (Y) base ink, the print layer of the third bottom edge image 104h-3 may be a print layer of a halftone dot image, and the print layer of the second bottom edge image 104h-2 may be a print layer of a solid image.

In this way, the first boundary image 104f-11 and the top end image 104g are images printed on the part of the can body P where the neck will be formed by the neck-in process, but the printed layers of the first boundary image 104f-11 and the top end image 104g are formed with the basic ink, not the special ink. Therefore, the overlapping parts between the first boundary images 104f-11 and the overlapping parts between the top end images 104g are overlapping printed layers of the basic ink, not the special ink. This makes it possible to make the thickness of the printed layer of the overlapping part formed in the part where the neck will be formed by the neck-in process even smaller than the thickness of the overlapping part made of the special ink. This makes it possible to prevent "a large step from occurring between the overlapping part and the rest of the part, causing many wrinkles and the like in the neck, which significantly reduces the aesthetics of the can body."

[Specialty ink]
The special ink for printing the first inner image 104f-21 to the third inner image 104f-23 of the background image 104f will be described. This special ink may be at least one of a functional ink containing a functional material and an inorganic ink, as described below. The special inks exemplified below tend to form a thicker print layer than basic inks that do not contain special materials due to the special material contained in the special ink (for example, due to the fact that the particles of the special material are large, the special material contains microcapsules with a relatively large particle size, or foams).

(1. Functional inks)
The functional inks of the special inks include, for example, microcapsule-based functional inks that contain functional microcapsules in which various materials are encapsulated in microcapsules as the functional material, which is a special material, and other functional inks. The functional inks may further contain other materials (for example, functional fillers, etc.).

(1-1. Microcapsule-based functional ink)
Examples of the microcapsule-based functional ink include foaming ink, thermochromic ink, and photochromic ink, which will be described below.

(1-1-1. Foaming ink)
A foaming ink containing a foaming agent (foaming material) as a functional material is an ink in which a predetermined amount of a foaming agent is mixed and dispersed in a normal printing ink (basic ink). The foaming agent is, for example, a thermally expandable microcapsule. Examples of the foaming agent for such a thermally expandable microcapsule include a volatile solvent such as isobutane, hexane, or heptane coated with a shell wall of a thermoplastic resin such as a copolymer of vinylidene chloride or acrylonitrile, and the softening temperature of the shell wall in this case can be, for example, a temperature in the range of 100 to 200°C.

(1-1-2. Thermochromic ink)
Thermochromic ink is an ink that changes color at a specific temperature, and there are two types: irreversible thermochromic ink, which does not return to its original color even when cooled, and reversible thermochromic ink, which returns to its original color when cooled. In such thermochromic inks, the components that change color depending on the temperature are microencapsulated, and the microcapsules are included as functional materials.

Examples of reversible thermochromic inks include those made by adding a vehicle to a pigment made from iodides of heavy metals such as Hg, Ag, Cu, and Pb, or their complex salts. For example, reversible thermochromic inks with the pigment composition Ag ₂ HgI ₄ and Cu ₂ HgI ₄ change color at specific temperatures of 50°C and 70°C, respectively, but the temperature can be set between 40°C and 70°C depending on the two-component mixture. Other examples of reversible thermochromic inks include those containing a cobalt chloride solution that turns pink at room temperature and blue at a high temperature of about 80°C.

The material contained in the irreversible thermoindicating ink is not particularly limited, and examples thereof include ₃ (NH4 _{) 2O.Fe2O3.12MoO3.19H2O} , Co( _{AsO4 )2(Pyr)2.10H2O, (NH4)3H6 [ Fe ( MoO4 ) 6 ] .7H2O} , CoSiF6 _, Co( _{C6H5O7 ) 2} , [ _Cu (Pyr _{) 2} ] ₍ CNS) ₂ , _{( NH4} ) _{3VO3 , CoNH4PO4.H2O} , _Cu (OH) _{2 ,} [ _Co ( _NH3 ) _5Cl ] _Cl2 , ₃ ( _NH4 ) _{2O.Al2O3.12MoO3 . 19H2O} , ( _NH4 ) _{2U2O7 ,} [Cr( _{NH3 ) 5Cl} ] _SiF6 , [Co( _NH3 ) ₆ ] _H.P2O7 , _{CdCO3 , NH4MnP2O7 , etc.}

(1-1-3. Photochromic ink)
Photochromic ink is an ink that contains microencapsulated photochromic compounds (pigments) that are colorless in an inactive state and develop color when irradiated with ultraviolet light, and these microcapsules are included as functional materials. This photochromic ink has the ability to exhibit different colors such as red, blue, purple, and yellow depending on the amount of ultraviolet light it is irradiated with.

Examples of photochromic compounds include photochromic compounds such as spirooxazine derivatives, spiropyran derivatives, and naphthopyran derivatives that change color with high sensitivity even when blue light is applied, as well as diarylethene-based photochromic compounds.

(1-2. Other functional inks)
Other functional inks include, for example, fluorescent inks and varnish repellent inks, which will be described below.

(1-2-1. Fluorescent ink)
The fluorescent ink may be an ink containing a fluorescent pigment (particles) as a functional material. Examples of the fluorescent pigment include ultraviolet fluorescent pigments. Examples of the ultraviolet fluorescent pigment include those obtained by uniformly dissolving dyes such as fluorescein, eosin, rhodamine 6G, rhodamine B, and basic yellow HG in resins such as polyvinyl chloride resins, alkyd resins, polymethacrylate resins, urea resins, and melamine resins, and pulverizing the resulting resins.

(1-2-2. Varnish-repellent ink)
The varnish-repellent ink is an ink that contains a functional material that has the property of repelling the resin that is the material of the overcoat layer, such as the above-mentioned finishing varnish, etc. Such a functional material may be, for example, a material that forms a film with a surface tension sufficient to repel the resin, such as varnish, and examples of such functional materials include silicon, fluorine, polyethylene, polytetrafluoroethylene (PTFE), etc.

(1-2-3. Ink containing functional filler)
The functional filler-containing ink may contain a functional filler as a functional material, and examples of such functional fillers include organic fibers such as carbon fibers, carbon black, etc. Such functional filler-containing inks may be inks that further contain a functional filler in addition to the above-mentioned foaming ink, thermochromic ink, photochromic ink, fluorescent ink, varnish-repellent ink, etc.

(2. Inorganic inks)
Among the special inks, the inorganic inks are inks that contain various inorganic materials as special materials. The inorganic inks may also contain other materials (e.g., inorganic fillers, etc.).

(2-1. Pearl pigment ink)
Pearl ink, which contains a pearl pigment as an inorganic material, is an ink whose color changes depending on the viewing angle. For example, such pearl ink can be one in which a pigment having a low refractive index, such as mica, silica, alumina, etc., and a metal oxide having a high refractive index, such as silicon oxide, titanium oxide, tin oxide, iron oxide, etc., is arranged in layers and dispersed in a transparent vehicle. In a printed layer printed with pearl ink, incident light is reflected multiple times at the boundaries of layers having different refractive indexes, and the reflected light interferes with each other, reproducing the interference color, high iridescence, and luster characteristic of pearl.

(2-2. Aluminum pigment ink (silver ink))
The aluminum pigment ink (silver ink) is not particularly limited, but examples thereof include ink in which aluminum particles are dispersed as an inorganic material in a vehicle, and the ink exhibits a silver color due to the luster (brightness) of the aluminum particles.

(2-3. Gold ink)
The gold ink is not particularly limited, but examples include an ink in which brass particles (an alloy of copper and zinc) are dispersed in a vehicle as an inorganic material to give it a metallic luster similar to gold, and an ink in which aluminum particles are dispersed in a transparent yellow pigment as an inorganic material, and the gold color is exhibited by the luster (brightness) of the aluminum particles in the transparent yellow pigment.

(2-4. Ink containing inorganic filler)
The inorganic filler-containing ink may be any ink that contains an inorganic filler such as glass fiber or inorganic silica particles as an inorganic material, and may be an ink that further contains an inorganic filler in addition to the above-mentioned pearl pigment ink, aluminum pigment ink (silver ink), gold ink, etc.

[Printed cans]
8(a) and (b) are partial cross-sectional views of a can body P (printed can) on which a printing process of a printed image 104 has been performed by the printing device 1. In the example of Fig. 8, a white paint layer (solid white print layer) A2 is formed in advance on the outer peripheral surface of the can body A1 of the can body P, and a print layer A3 of the printed image 104 is formed on top of that. However, without being limited to this example, the print layer A3 of the printed image 104 may be formed directly on the outer peripheral surface of the can body A1 of the can body P.

As shown in FIG. 8(a), a printed layer A3 having a first printed layer A31 to a fifth printed layer A35 is formed on a white paint layer A2 formed on a can body A1.

The first printed layer A31 is a printed layer of the yellow (Y) base ink of the sake mark image 104b in FIG. 4. The second printed layer A32 is a printed layer of the navy (N) base ink of the third border image 104f-13, which is the border portion with the sake mark image 104b in the background image 104f.

The third printed layer A33 is a printed layer of navy (N) special ink of the first inner image 104f-21 of the background image 104f. This third printed layer A33 is formed by superimposing a 3-2 printed layer A332 formed of navy (N) special ink transferred from the fourth printing plate 14d (main plate) via the blanket 25 on a 3-1 printed layer A331 formed of navy (N) special ink transferred from the fifth printing plate 14e (dummy plate) via the blanket 25.

As described above, if the fourth printing plate 14d (original) and the fifth printing plate 14e (duplicate) are switched in position, the layer structure of the third printing layer A33 will be different from that shown in FIG. 8(a). That is, in this case, the third printing layer A33 will be formed by superimposing the 3-1 printing layer A331 formed with the navy (N) special ink transferred from the fifth printing plate 14e (duplicate) via the blanket 25 on the 3-2 printing layer A332 formed with the navy (N) special ink transferred from the fourth printing plate 14d (original) via the blanket 25.

The fourth printed layer A34 is a printed layer of the navy (N) base ink of the fourth border image 104f-14, which is the border between the background image 104f and the product-related image 104c. The fifth printed layer A35 is a printed layer of the yellow (Y) base ink of the product-related image 104c.

An overcoat layer A4 such as a finishing varnish is formed on the printed layer A3. The can body P on which the overcoat layer A4 has been formed is then baked in a drying device such as an oven. The overcoat layer A4 may be formed of a varnish made of a conventionally known transparent resin. The transparent resin is preferably a transparent thermosetting resin containing a lubricant. Examples of transparent thermosetting resins containing a lubricant include those in which a resin such as an amino resin such as melamine resin or a phenolic resin is added as a hardener to a base resin such as polyester resin, polyacrylic resin, or epoxy resin, and further a lubricant such as paraffin, polyethylene, or silicone is blended.

In the example of Figure 8, the navy (N) special ink of the third printed layer A33 consisting of the 3-1 printed layer A331 and the 3-2 printed layer A332 is a foaming ink. This foaming ink is heated and baked in an oven or the like together with the finishing varnish layer A4. This heating causes the volatile solvent in the shell walls of the thermally expandable microcapsules to vaporize and expand thermally, thereby expanding the thermally expandable microcapsules. This causes the third printed layer A33 (the 3-1 printed layer A331 and the 3-2 printed layer A332) to foam, as shown in Figure 8 (b).

In this heat baking process, the third printed layer A33 foams and the solvent in the overcoat layer A4 is removed, causing the overcoat layer A4 to dry and harden. As the overcoat layer A4 deformed by the foaming of the third printed layer A33 hardens, the surface of the overcoat layer A4 becomes rough and coarse, as shown in FIG. 8(b). In this way, the printed image 104 printed on the can body P by the printing device 1 has a three-dimensional finish (unevenness, roughness) in the relatively wide image area of the background image 104f.

Figure 9 is a partial cross-sectional view of a portion of a can body P (printed can) on which a print image 104 has been printed by the printing device 1, which is a different portion from that shown in Figure 8(a), including an overlapping portion between printed layers. In the example of Figure 9, the same components as those in Figure 9 are given the same reference numerals and will not be described.

As shown in FIG. 9, the printed layer A3 formed on the white paint layer A2 formed on the can body A1 of the can body P is formed by superimposing a seventh printed layer A37 formed of navy (N) special ink transferred from the fourth printing plate 14d (main plate) via the blanket 25 on a sixth printed layer A36 formed of navy (N) special ink transferred from the fifth printing plate 14e (dummy plate) via the blanket 25.

In FIG. 9, the sixth printed layer A36 has a sixth printed layer A361, a sixth printed layer A362, and a sixth printed layer A363. The seventh printed layer A37 has a seventh printed layer A371, a seventh printed layer A372, a seventh printed layer A373, and a seventh printed layer A374.

As shown in this Figure 9, the can body A1 of the can body P rotates in the direction of rotation of the arrow W (clockwise). In this case, the formation of the sixth printed layer A36 with navy (N) special ink supplied (transferred) from the fifth printing plate 14e (copy plate) via the blanket 25 starts from position Sb on the white paint layer A2 and progresses in the printing direction V, which is opposite to the rotation direction of the arrow W of the can body A1.

The formation of this sixth printed layer A36 proceeds from position Sb in the printing direction V (formation of the sixth-first printed layer A361) and goes around the circumference of the can body A1 to the original position Sb (formation of the sixth-second printed layer A362 and sixth-third printed layer A363). The sixth-third printed layer A363 is the printed layer portion located below the overlapping portion of the seventh printed layer A37.

As shown in FIG. 9, the formation of the seventh printed layer A37 using navy (N) special ink supplied (transferred) from the fourth printing plate 14d (positive plate) via the blanket 25 starts from position Sa on the sixth printed layer A36, approximately 2 mm away from position Sb in the direction of arrow W, and proceeds in the printing direction V opposite to the rotation direction of the can body A1 as shown by arrow W (the formation of the 7-1st printed layer A371 and the 7-2nd printed layer A372). The formation of this seventh printed layer A37 goes around the can body A1 in the printing direction V from position Sa (after the formation of the 7-3rd printed layer A373), and then proceeds further in the printing direction V from the original position Sa to position Sb (the formation of the 7-4th printed layer A374).

As a result, the approximately 2 mm portion of the 7th printed layer A37 from position Sa to position Sb becomes an overlapping portion where the 7th-4 printed layer A374 overlaps the 7th-1 printed layer A371. The 7th-1 printed layer A371, which is the lower layer in this overlapping portion, is the printed layer of the third inner image 104f-23, which is a halftone dot image formed by the halftone dot forming unit 14d-2 in Figure 6. The 7th-4 printed layer A374, which is the upper layer in this overlapping portion, is the printed layer of the second inner image 104f-22, which is a solid image formed by the image forming unit 14d-4 in Figure 6.

As a result, the thickness of the 7-1st printed layer A371 is smaller than the thickness of the 7-4th printed layer A374, and gradually decreases from position Sb to position Sa. In other words, the dot area ratio (%) of this 7-1st printed layer A371 gradually decreases from position Sb to position Sa.

In the example of Figure 9, the navy (N) special ink is a foaming ink, so when heated in an oven or the like, the thermally expandable microcapsules expand and foam. As a result, the surface of the overcoat layer A4 on the print layer A3 in Figure 9 becomes deformed and rough, resulting in a three-dimensional finish (unevenness, roughness).

When the 7-1st printing layer A371 is a printing layer of a halftone image formed by the halftone dot forming unit 14d-2 in FIG. 7, its thickness is approximately uniform from position Sa to position Sb and is smaller than the thickness of the printing layer of the 7-4th printing layer A374.

Also, as described above, when the fourth printing plate 14d (original) and the fifth printing plate 14e (duplicate) are switched, the layer structure of the printing layer A3 differs from that shown in FIG. 9. That is, in this case, the printing layer A3 is formed by superimposing the sixth printing layer A36 formed of the navy (N) special ink transferred from the fifth printing plate 14e (duplicate) via the blanket 25 on the seventh printing layer A37 formed of the navy (N) special ink transferred from the fourth printing plate 14d (original) via the blanket 25. In this case, in the printing layer A3, the 6-3 printing layer A363 is located above the overlapping portion of the seventh printing layer A37.

In this way, the printing device 1 uses two printing plates 14, the fourth printing plate 14d (main plate) and the fifth printing plate 14e (copy plate), to form two overlapping printing layers of navy (N) special ink. This allows the printing device 1 to form an image (a relatively thick printing layer) in which the color of the navy (N) special ink is clearly expressed.

The printing device 1 forms a relatively thick printed layer of navy (N) special ink by printing using these two printing plates 14 (original plate, copy plate), but only one of the two printed layers, formed by printing using the original plate, forms an overlapping portion where the circumferential ends of the image of the can body overlap, while the other printed layer, formed by printing using the copy plate, does not form an overlapping portion. This prevents the thickness of the printed layer from increasing in the area on the can body P where the overlapping portion is formed, compared to if overlapping portions were formed in both of the two printed layers.

As described above in the examples of Figures 6, 7, and 9, the printing device 1 prints in the overlapping portion formed by this single printed layer so that the thickness of the printed layer of the image at one circumferential end of the can body is smaller than the thickness of the printed layer of the image at the other circumferential end of the can body. As a result, the printing device 1 can prevent an increase in the thickness of the printed layer at the location where the overlapping portion is formed on the can body P, and prevent a deterioration in the aesthetic appearance of the can body P.

[Printing Operation of Printing Device]
FIG. 10 is a flowchart for explaining the printing operation of the printing device 1 on the can body P.

(Step S101: Can body conveying process)
In the can body conveying process of step S101, the printing apparatus 1 conveys the can body P to the top of the mandrel wheel 40 by the conveying unit 30. The printing apparatus 1 holds the can body P conveyed to the top of the mandrel wheel 40 with the mandrel 41. Before the can body P comes into contact with the blanket 25, the printing apparatus 1 rotates the mandrel 41 to pre-spin the can body P, and rotates the mandrel wheel 40 to move the can body P to the contact area with the blanket 25. That is, the can body P rotates on its axis due to the rotation of the mandrel 41, and revolves due to the rotation of the mandrel wheel 40.

(Step S102: Ink supplying process)
In the ink supply process of step S102 following step S101, the printing device 1 rotates the ink roller group 12 in each of the multiple ink supply sections 11 to supply the ink contained in the ink supply section 11 to the printing plate 14 mounted on the plate cylinder 13.

In step S102, the printing device 1 supplies the yellow (Y) base ink from the first ink supply unit 11a to the first printing plate 14a, the magenta (M) base ink from the second ink supply unit 11b to the second printing plate 14b, and the cyan (C) base ink from the third ink supply unit 11c to the third printing plate 14c. Also, in step S102, the printing device 1 supplies the navy (N) special ink from the fourth ink supply unit 11d to the fourth printing plate 14d, the navy (N) special ink from the fifth ink supply unit 11e to the fifth printing plate 14e, the navy (N) base ink from the sixth ink supply unit 11f to the sixth printing plate 14f, and the black (K) base ink from the seventh ink supply unit 11g to the seventh printing plate 14g.

Each printing plate 14 to which ink has been applied moves to the contact area between the printing plate 14 and the blanket 25 as the plate cylinder 13 rotates.

(Step S103: Blanket transfer process)
In the blanket transfer process of step S103 following step S102, the printing device 1 rotates the blanket wheel 20 to bring the blanket 25 into contact with the printing plate 14 to which ink has been supplied, and transfers the ink supplied to the printing plate 14 to the blanket 25.

In step S103, the printing device 1 transfers the yellow (Y) base ink on the first printing plate 14a, the magenta (M) base ink on the second printing plate 14b, the cyan (C) base ink on the third printing plate 14c, the navy (N) special ink on the fourth printing plate 14d, the navy (N) special ink on the fifth printing plate 14e, the navy (N) base ink on the sixth printing plate 14f, and the black (K) base ink on the seventh printing plate 14g, in that order, to the same blanket 25. As a result, an image corresponding to the pattern of the image area formed on the printing plate 14 is transferred to the blanket 25.

(Step S104: Can body transfer process)
In the can body transfer step of step S104 following step S103, the printing device 1 moves the blanket 25, to which the ink has been transferred, to a contact area between the can body P and the blanket 25 by rotating the blanket wheel 20. Then, the printing device 1 brings the can body P, held by the mandrel 41, into contact with the blanket 25 that has moved to this contact area while pressing the can body P, thereby transferring the ink transferred to the blanket 25 to the can body P. As a result, an image corresponding to the pattern of the image portion formed on the printing plate 14 is transferred to the outer circumferential surface of the can body P via the blanket 25.

(Step S105: Overcoat painting process)
In an overcoat application process in step S105 following step S104, the printing device 1 moves the can body P to which the ink has been transferred to the varnish applicator 50 by rotating the mandrel wheel 40, and further moves the can body P to the transfer unit 60. Then, the printing device 1 operates the varnish applicator 50 to apply an overcoat such as a finishing varnish to the can body P to which the ink has been transferred.

(Step S106: Transfer process)
In a transfer step of step S106 following step S105, the printing apparatus 1 operates the transfer unit 60 to transfer the can body P that has passed through the varnish applicator 50 from the mandrel 41 and transfer it to a drying device (not shown) such as an oven.

The printing device 1 rotates the plate cylinder 13, blanket wheel 20, mandrel 41, and mandrel wheel 40 in synchronization with each other. The printing device 1 also operates the varnish applicator 50 and transfer unit 60 in synchronization with the rotation of these components. Through these operations, the printing device 1 prints on the can body P.

[Prepress system configuration]
Next, a platemaking system 200 that prepares the printing plate 14 to be attached to the printing device 1 will be described. The platemaking system 200 employs DTP (Desktop Publishing) and CTP (Computer To Plate). The platemaking system 200 prepares the printing plate 14 made of the above-mentioned resin relief plate. It should be noted that even if the printing plate 14 is not a resin relief plate but a waterless planographic plate, it can be prepared by this platemaking system 200. However, the specific configuration of the platemaking device (machine) in the platemaking system 200 may be different between preparing a resin relief plate and preparing a waterless planographic plate.

Figure 11 is a functional block diagram of a platemaking system 200 that produces the printing plate 14 to be attached to the printing device 1. The platemaking system 200 shown in Figure 11 is preferably a system that produces the printing plate 14 using a DLE (Direct Laser Engraving) method, in which resin is sublimated by laser heat and engraved to produce a printing plate, or a LAMS (Laser Ablation Masking System) method, in which the surface of the resin plate is scraped and developed with a laser. If the printing plate 14 is a resin letterpress plate, the part where the resin is removed by the heat of the laser becomes a non-printing area, and the other part becomes a printing area on which ink is applied. Also, if the printing plate 14 is a waterless flat plate, the part where the resin (such as silicone resin) is removed by the heat of the laser becomes a printing area on which ink is applied, and the other part where the resin remains becomes a non-printing area (ink-repellent layer).

The platemaking system 200 includes a data processing device 210 that performs various image processing on the original image data to create image data for platemaking, and a platemaking device 220 that creates printing plates according to the image data for platemaking.

The data processing device 210 performs editing such as correcting the layout and color tone of the original image data expressed in a page description language. The data processing device 210 then performs plate separation processing to perform color separation of process colors and halftoning processing to form halftone image portions to create image data for plate making, and transmits the image data to the plate making device 220. The data processing device 210 includes a processor and a storage device, and is configured to include a program that implements the functions of the data processing device 210.

The data processing device 210 includes a plate separation processing unit 211 that performs plate separation processing, a halftone dot processing condition setting unit 212 that sets the conditions for halftone dot processing, a halftone dot processing unit 213 that performs halftone dot processing, and a transmission processing unit 214 that transmits data to the plate making device 220.

The color separation processing unit 211 separates the edited original image data into process colors. The color separation processing unit 211 then creates color separation image data consisting of image data for each basic ink of yellow (Y), magenta (M), cyan (C), and black (K) extracted by this color separation, image data for the basic ink of navy (N), which is a special color, and image data for the special ink of navy (N).

The halftone dot condition setting unit 212 sets halftone dot conditions, which are conditions for partially halftone dotting the divided image data of the colors forming the halftone dot image among the divided image data created by the separation processing unit 211. The halftone dot conditions are set for each divided image data of the colors to be halftone dotted. The halftone dot conditions include the halftone dot shape for each color, the designation of the image portion (halftone dot image) to which the halftone dot process is applied, the halftone dot area ratio, which is the ratio (%) of the halftone dot area per unit area in the halftone dot image, the screen ruling (the number of halftone dots arranged per unit area (1 inch)), and the screen angle (the angle of the halftone dot arrangement line), as well as conditions related to the multiplication method. Examples of conditions related to the multiplication method include conditions for undercolor removal processing in which at least one of the other colors is adjusted or removed in an overlapping portion where at least a portion of the halftone dots of one color overlaps at least a portion of the halftone dots of another color.

The halftone dot processing unit 213 halftones the image data of a specified image portion (such as the lower layer in the overlapping portion, the lemon illustration image in the product-related image 104c, etc.) in the color-separated image data of each color created by the color separation processing unit 211 according to the halftone dot conditions set by the halftone dot condition setting unit 212.

The transmission processing unit 214 performs processing to transmit the plate separation image data after processing by the plate separation processing unit 211 and further the halftone dot processing unit 213 to the plate making device 220 as image data for plate making.

The plate making device 220 makes printing plates 14 corresponding to each ink according to the plate separation image data transmitted from the transmission processing unit 214 of the data processing device 210. That is, the plate making device 220 may make a resin relief printing plate 14 by forming an image area in a photosensitive resin layer or the like by photocuring with ultraviolet light based on the plate separation image data, and then removing the uncured part by development to make that part a non-image area. Alternatively, the plate making device 220 may make a waterless planographic printing plate 14 by exposing an ink repellent layer (such as silicone resin) with a laser based on the plate separation image data, removing the ink repellent layer in the part irradiated with the laser by peeling, and forming an image area on which ink is applied and a non-image area that repels ink. The printing plate 14 made by the plate making device 220 is applied to the printing device 1.

[Plate making operation by plate making system]
FIG. 12 is a flow chart for explaining the plate-making operation for producing the printing plate 14 using the plate-making system 200 .

Steps S201 to S206 shown in FIG. 12 are executed by the data processing device 210 based on operation commands from a user input via a user interface provided in the data processing device 210. Step S207 is executed by the plate making device 220.

(Step S201: submission process)
In the manuscript submission process of step S201, the platemaking system 200 inputs manuscript image data using the data processing device 210.

(Step S202: Editing process)
In an editing process in step S202 following step S201, the platemaking system 200 edits the submitted manuscript image data in the data processing device 210. The platemaking system 200 edits the manuscript image data by modifying the layout in accordance with the printing area of the print substrate and by correcting color tones.

(Step S203: Plate separation process)
In a plate-separating process in step S203 following step S202, the plate-making system 200 performs plate-separating processing on the edited original image data in the data processing device 210. The plate-making system 200 performs color separation for each process color on the edited original image data, and creates plate-separated image data for each ink, including the basic inks of the process colors yellow (Y), magenta (M), cyan (C), and black (K), and the basic ink of navy (N), which is a special color, and the special ink of navy (N).

(Step S204: halftone dot condition setting process)
In step S204, a halftone dot condition setting process following step S203, the platemaking system 200 performs a halftone dot condition setting process for setting halftone dot conditions for partially halftone dotting the plate-separated image data in the data processing device 210. The platemaking system 200 sets the halftone dot shape for each color, the designation of the image portion (halftone dot image) that has been subjected to halftone dot processing, the halftone dot area ratio which is the ratio (%) of the halftone dot area per unit area in the halftone dot image, the screen ruling (the number of halftone dots arranged per unit area (1 inch)), the screen angle (the angle of the halftone dot arrangement lines), as well as conditions related to the multiplication method, etc.

(Step S205: Halftone dot process)
In the halftone dot process of step S205 following step S204, the platemaking system 200 uses the data processing device 210 to halftone dot the image data of specified image portions (such as the lower layer in the overlapping portion, the lemon illustration image in the product-related image 104c, etc.) in the separated image data of each color created in step S203, according to the halftone dot conditions set in step S204.

(Step S206: Transmission process)
In the transmission process of step S206 following step S205, the platemaking system 200 performs a transmission process in which the data processing device 210 transmits the created plate separation image data (or plate separation image data that has subsequently been subjected to halftoning processing) as image data for platemaking from the data processing device 210 to the platemaking device 220.

(Step S207: Plate making process)
In the plate making process of step S207 following step S206, the plate making system 200 uses the plate making device 220 to make each printing plate 14 corresponding to the image data transmitted from the data processing device 210 in the transmission process. With this step 5, the plate making process shown in FIG.

[Modification]
The above-described embodiments, including modified examples, can apply the techniques of each other. The above-described embodiments do not limit the content of the present invention, and can be modified to the extent that they do not depart from the scope of the claims.

For example, in the above embodiment, the process colors are four colors: yellow (Y), magenta (M), cyan (C), and black (K), but it is also possible to add any one of red (R), green (G), and blue (B) to make five colors.

In the above embodiment, the printing device 1 forms the second inner image 104f-22 and the third inner image 104f-23, which constitute the overlapping portion in the printed image 104, with a printing layer of navy (N) special ink, but this is not limited to the example. For example, the printing device 1 may transfer the navy (N) special ink and the navy (N) basic ink to the blanket 25 so that only the second inner image 104f-22, which constitutes this overlapping portion, is formed with a printing layer of navy (N) special ink, and the third inner image 104f-23 is formed with a printing layer of navy (N) basic ink. In this case, in this overlapping portion, the printing layer of the second inner image 104f-22 with navy (N) special ink at one end of the can body in the circumferential direction may be superimposed on the printing layer of the third inner image 104f-23 with navy (N) basic ink at the other end of the can body in the circumferential direction.

In addition, instead of the printing layer of the third inner image 104f-23 described above, the thickness of the printing layer of the second inner image 104f-22 may be reduced in the same manner as in the above example. In this case, for example, the fourth printing plate 14d may be a printing plate having multiple dot image areas for forming a halftone dot image in which the thickness of the printing layer of the second inner image 104f-22, which is one of the circumferential ends of the can body, gradually decreases (the dot area ratio gradually decreases) toward the other circumferential end of the can body.

In other words, the fourth printing plate 14d configures the background image forming region R2 in FIG. 6(a) with an image area for forming a solid image, and the background image forming region R4 in FIG. 6(a) with a halftone dot forming section consisting of multiple image areas for forming a halftone dot image and non-image areas therebetween. This means that in the seventh printing layer A37 in FIG. 9, the thickness of the 7-1st printing layer A371 is substantially constant from position Sa to position Sb, whereas the thickness of the 7-4th printing layer A374 gradually decreases from position Sa to position Sb, i.e., the halftone dot area ratio (%) in the 7-4th printing layer A374 gradually decreases from position Sa to position Sb.

In addition, the printed image 104 shown in FIG. 4 in the above embodiment is an image in which the inner image of the background image 104f is printed in navy (N) special ink, and the border image bordering the inner image is printed in navy (N) basic ink. However, the printed image printed on the outer surface of the can body P is not limited to the printed image 104 in FIG. 4. In addition, the color of the special ink may be another color other than the above-mentioned navy (N).

In addition, in the above embodiment, two printing plates, the fourth printing plate 14d (original plate) and the fifth printing plate 14e (copy plate), were used as printing plates for printing the navy (N) special ink, but this is not limited to this example. For example, if it is not necessary to make the printing layer of the special ink a thick printing layer (thick film) as described above, only the fourth printing plate 14d (original plate) may be used as the printing plate for printing the special ink.

The method of printing an image onto the can body, which is the substrate, is not limited to the printing method using printing plates, blankets, etc. as described above (plate printing), but may be a printing method in which an image is printed directly onto the can body without using printing plates, blankets, etc. (plateless printing).

An example of plateless printing is printing performed using an inkjet method. In a printing device that directly prints an image on a can body using this inkjet method, to form an overlapping portion of the printed image, for example, the amount of special ink required to form the printed layer of the image at one circumferential end of the can body (the above-mentioned third inner image 104f-23) may be less than the amount of special ink required to form the printed layer of the image at the other circumferential end of the can body (the above-mentioned second inner image 104f-22).

In this case, the inkjet printing device may be configured so that the amount of special ink dripped onto the can body per unit time when printing an image at one circumferential end of the can body (the above-mentioned third inner image 104f-23) is less than the amount of special ink dripped onto the can body per unit time when printing an image at the other circumferential end of the can body (the above-mentioned second inner image 104f-22).

As a result, in the overlapping portion of the printed images printed on the can body, the thickness of the printed layer of the image at one circumferential end of the can body (the above-mentioned third inner image 104f-23) can be made smaller than the thickness of the printed layer of the image at the other circumferential end of the can body (the above-mentioned second inner image 104f-22).

1 Printing device, 10 Inking unit, 10a to 10h First inking unit to eighth inking unit, 11 Ink supply section, 11a to 11h First ink supply section to eighth ink supply section, 12 Ink roller group, 13 Plate cylinder, 13a to 13h First plate cylinder to eighth plate cylinder, 14 Printing plate, 14a to 14h First printing plate to eighth printing plate, 20 Blanket wheel, 21 Segment, 22 Support shaft, 25 Blanket, 30 Transport unit, 40 Mandrel wheel, 41 Mandrel, 50 Burnish applicator, 60 Transfer unit, 200 Plate making system, 210 Data processing device, 211 Plate separation processing section, 212 Halftone dot condition setting section, 213 Halftone dot processing section, 214 Transmission processing section, 220 Plate making device

Claims (9)

A printing device having a printing means for printing an image on an outer peripheral surface of a can body using ink,
The image printed on the outer peripheral surface of the can body includes an overlapping portion where the ends of the image in the can body circumferential direction overlap each other,
The overlapping portion includes an overlapping portion of a printing layer of a special ink, which is at least one of a functional ink containing a functional material and an inorganic ink, where the printing layers of the special ink overlap each other,
The printing means includes:
The printed layer of the special ink formed on the outer peripheral surface of the can body is formed by a first printed layer of the special ink and a second printed layer of the special ink that are superimposed on each other;
The overlapping portion of the special ink printing layer is formed by overlapping the first printing layers with each other,
Printing is performed on the overlapping portion of the first printed layer such that the thickness of the first printed layer at one end of the can body in the circumferential direction is smaller than the thickness of the first printed layer at the other end of the can body in the circumferential direction.
A printing device comprising : The special ink of the first printed layer and the special ink of the second printed layer are the same color.
2. The printing device according to claim 1. The printing device described in claim 1 or 2, characterized in that the printing means prints in the overlapping portion of the first printed layer printed on the outer peripheral surface of the can body so that the thickness of the first printed layer at one circumferential end of the can body gradually decreases toward the other circumferential end of the can body. The printing device described in any one of claims 1 to 3, characterized in that the printing means prints in an overlapping portion of the first printed layer printed on the outer peripheral surface of the can body so that the first printed layer at one circumferential end of the can body is superimposed on the first printed layer at the other circumferential end of the can body. The ink includes a base ink different from the special ink,
The printing device described in claim 1, characterized in that the printing means prints on the portion of the outer surface of the can body where the neck of the can body will be formed using the basic ink so as not to form a printing layer of the special ink on the portion where the neck of the can body will be formed. 6. The printing device according to claim 1, wherein the functional ink is at least one of a foaming ink, a thermochromic ink, a photochromic ink, a fluorescent ink, and a varnish-repellent ink. 7. The printing device according to claim 1, wherein the inorganic ink is at least one of a pearl pigment ink, a silver ink, a gold ink, and an ink containing an inorganic filler. A printing method having a printing step of printing an image on an outer peripheral surface of a can body using ink,
The image printed on the outer peripheral surface of the can body includes an overlapping portion where the ends of the image in the can body circumferential direction overlap each other,
The overlapping portion includes an overlapping portion of a printing layer of a special ink, which is at least one of a functional ink containing a functional material and an inorganic ink, where the printing layers of the special ink overlap each other,
In the printing step,
The printed layer of the special ink formed on the outer peripheral surface of the can body is formed by a first printed layer of the special ink and a second printed layer of the special ink that are superimposed on each other,
The overlapping portion of the special ink printing layer is formed by overlapping the first printing layers with each other,
The overlapping portion of the first printed layer is printed so that the thickness of the first printed layer at one end of the can body in the circumferential direction is smaller than the thickness of the first printed layer at the other end of the can body in the circumferential direction.
A printing method comprising: A can body having an image printed on its outer peripheral surface,
the image is printed on the outer peripheral surface of the can body using ink;
The image printed on the outer peripheral surface of the can body includes an overlapping portion where the ends of the image in the can body circumferential direction overlap each other,
The overlapping portion includes an overlapping portion of a printing layer of a special ink, which is at least one of a functional ink containing a functional material and an inorganic ink, where the printing layers of the special ink overlap each other,
The printed layer of the special ink formed on the outer peripheral surface of the can body is formed by a first printed layer of the special ink and a second printed layer of the special ink that are superimposed on each other,
The overlapping portion of the special ink printing layer is formed by overlapping the first printing layers with each other,
A can body, characterized in that, in an overlapping portion of the first printed layer, a thickness of the first printed layer at one circumferential end of the can body is smaller than a thickness of the first printed layer at the other circumferential end of the can body.