Patent Application
20240150062
This invention relates to a manufacturing method of a bottle-shaped can by drawing and ironing a metal sheet (blank) coated with a synthetic resin film or a paint, and printing a predetermined design on a surface.
A bottle-shaped can is manufactured by forming a metal sheet such as an aluminum alloy sheet or a steel sheet into a shape similar to a glass bottle in which a neck portion and a container mouth are drawn thinner than a trunk portion. Glass material of the glass bottles may be colored to decorate the glass bottles in the desired color. Therefore, it is desirable to decorate the bottle-shaped can in the desired color as the glass bottles. However, the bottle-shaped can is formed by drawing a shoulder portion and a neck portion formed between a can trunk and a container mouth on which a cap is mounted into a cylindrical portion whose diameter is smaller than that of the can trunk. That is, the metal sheet as the material of the bottle-shaped can is subjected to severe processing steps to be deformed significantly. To this end, for example, the metal sheet (blank) is coated with a colored layer in advance, and the metal sheet is drawn and ironed to be shaped into the bottle-shaped can. In this case, the metal sheet is subjected to severe processing steps to form the neck portion, the container mouth, and to form a thread on an outer surface of the neck portion. As a result, cracks and ruptures would develop on the coating. In addition, colorful patterns and letters (hereinafter referred to as design) are printed on the outer surface of the bottle-shaped can to advertise the commodity to consumers. To this end, many kinds of inks may be used to print the designs, and a base layer may be seen through the design depending on the kind on the used ink. In this case, the color of the base layer would be mixed with the color of the design. Consequently, a desired color intended by a designer may not be produced.
In order to solve the above-explained problems, in the conventional art, compositions and constituents of resin coatings have been changed in different manners. For example, according to the invention disclosed in the publication of Japanese Patent No. 3957049, chromatic pigment is mixed into an adhesion layer interposed between a transparent thermoplastic resin layer and an aluminum alloy sheet. Therefore, in the thinned trunk portion, the adhesion layer is thinned to serves as a glossy metal base layer of the printed pattern so that the color of the alloy sheet can be seen through the adhesion layer.
Technical Problem to be Solved by the Invention
Given that the blank is coated with a dark colored coating layer to decorate the bottle-shaped can entirely in the desired color as glass bottles, the color of the coating serves as a ground color in the thinned trunk portion which affects the color of the design. The effect of the base color seems likely to be changed depending on the color of the coating layer and a kind of the ink, but the color of the design would be changed in any case by the base color from the color intended by the designer. In addition, the blank is drawn to be thinned differently in each section of the bottle-shaped can, and the color of the coating layer is lightened (or faded) with the progress of drawing of the blank. That is, even if the pattern is designed based on the color (intensity, hue, brightness) of the coating layer applied to the blank, the base color would be changed with the progress of the processing. Therefore, it is difficult to print the design in the desired color. Nonetheless, it is possible to print a redesigned pattern again on the trunk portion of the bottle-shaped can so as to evaluate the finished printed design. However, such designs are not one colored. Therefore, even if the portion printed unsatisfactory by the previous printing process is printed in the desired color, other portions are not always printed in desired color and brightness. Consequently, the pattern would have to be redesigned over again, and the color of the coating would have to be changed over again.
According to the teachings of Japanese Patent No. 3957049, the glossy metal base layer is formed on the alloy sheet so that the color of the alloy sheet can be seen through the base layer thinned as a result of the forming process. However, the color of the resin coating has to be limited to the color similar to the color of the alloy sheet. Therefore, the bottle-shaped can may not be decorated in a colorful manner.
The present invention has been conceived noting the above-explained technical problems, and it is therefore an object of the present invention to provide a method of manufacturing a bottle-shaped can possible to decorate the bottle-shaped can including a can trunk and a neck portion entirely in a colorful manner, and to print the desired pattern easily or to determine the design of a pattern easily.
According to the present invention, there is provided a manufacturing method of a bottle-shaped can formed of a metal sheet coated with a colored resin coating having a forming process including steps of forming a cylindrical can trunk by drawing or ironing the metal sheet coated with the colored resin coating, and thereafter printing a design on an outer surface of the can trunk. In order to achieve the above-explained objective, the manufacturing method comprises: painting a predetermined section of the outer surface of the can trunk multiple times while changing color of ink thereby collecting samples of colors resulting from mixing the colors of the inks with a ground color of the predetermined section; preparing a tone chart by groups of hues of colors having the same brightness and colorfulness; determining a color scheme of the design with reference to the tone chart; and printing the design on the predetermined section in the determined color scheme.
According to the present invention, the remaining area of the outer surface of the can trunk in which the design is not printed may be painted with the ink of the same or similar color as the color of the resin coating.
The bottle-shaped can manufactured by the method according to the present invention may be a bottle-shaped can comprising a bottom lid on which the design is not printed and which is seamed to an opening end of the can trunk. In addition, a color difference ΔE*ab between: the color of the remaining area after painting the remaining area with the ink of the same or similar color as the color of the resin coating, and the color of the resin coating applied to the metal sheet; may be reduced to “10” or smaller.
According to the present invention, the brightness of the color of the resin coating may be lower than that of the ground color of the metal sheet, or colorfulness of the color of the resin coating may be higher than that of the ground color of the metal sheet.
According to the present invention, the tone chart of the colors of the outer surface of the can trunk are prepared after applying the forming process to the metal sheet, and the color scheme of the design is determined with reference to the tone chart. That is, the design is determined based on the ground color deteriorated after execution of the forming process, different from the case of determining a color scheme of the design to be printed e.g., on a plain white paper. Therefore, the design may be printed on the can trunk in the intended color scheme by a single printing process. In a case of printing the design on the can trunk by a trial-and-error approach, the design whose color scheme has been temporarily determined is printed on the can trunk, and the quality of the printed design is evaluated. Then, the color scheme of the design is adjusted and the design is printed on the can trunk again. Thus, in this case, it is necessary to consider the color scheme multiple times and to print the design multiple times. Unlike the trial-and-error approach, according to the present invention, the color scheme of the design is determined taking account of the ground color. Therefore, the design may be printed in the determined color scheme almost without fail. For this reason, the design may be determined easily to be printed on the bottle-shaped can. Specifically, according to the present invention, the design is determined taking account of the deteriorated color of the can trunk. Therefore, a possibility of failure of a determination in color scheme may be reduced significantly.
In addition, according to the present invention, the area of the outer surface of the can trunk in which the design is not printed is painted with the ink of the same or similar color as the color of the resin coating. Therefore, even if the color of the can trunk is deteriorated by the forming process, the design may be printed on the can trunk as intended by restoring the color of the can trunk.
Specifically, the color difference ΔE*ab between: the color of the remaining area after painting the remaining area with the ink of the same or similar color as the color of the resin coating, and the color of the resin coating applied to the metal sheet; is reduced to “10” or smaller. Therefore, color unevenness of the bottle-shaped can may remain inconspicuous, and hence the design may be printed as intended.
The present invention relates to a manufacturing method of a bottle-shaped can in which a can trunk and a neck portion are formed integrally from a metal sheet material. The bottle-shaped can includes a two-piece type bottle-shaped can in which a bottom and the trunk section are formed integrally, and a three-piece type bottle-shaped can in which a bottom lid is seamed to the trunk section. One example of the three-piece type bottle-shaped can 1 is schematically shown in
The neck section 4 and the container mouth 5 serve as a container neck, and the container neck and the trunk section 2 are colored entirely. The bottle-shaped can 1 is formed of a metal sheet (i.e., a blank) such as an aluminum sheet and a steel sheet, and as explained later, a colored resin coating is applied to the metal sheet for the purpose of coloring the bottle-shaped can 1. Accordingly, the blank serves as a “metal sheet coated with a colored resin coating” of the present invention. For example, brightness of the color of the colored resin coating is lower than that of a color of the blank, or colorfulness of the color of the colored resin coating is higher than that of the color of the blank. In
Turning to
Then, at a can trunk shaping step, a drawing treatment or an ironing treatment and a drawing/ironing treatment are applied to stretch the cup 10 in an axial direction. Consequently, the cup 10 is shaped into a bottomed cylinder 11 whose thickness is reduced. After that, at a trimming step, an opening end of the bottomed cylinder 11 is trimmed to align the height of the opening end. During the drawing and the ironing, lubricant is applied to the cup 10, therefore, the lubricant is subsequently removed at a lubricant removal step. Details of such application and removal of the lubricant is described in the above-mentioned Japanese Patent No. 3957049. As explained later in detail, a design is printed on the bottomed cylinder 11, and the bottomed cylinder 11 is then cured.
The method explained herein is a manufacturing method of the three-piece type bottle-shaped can. Accordingly, at a subsequent top dome shaping step, a bottom section of the bottomed cylinder 11 is drawn into a diametrically smaller cylindrical section having a domed circumferential wall. An outer diameter of the diametrically smaller cylindrical section is further reduced gradually to form the container neck while shaping the domed wall into the smooth shoulder section. After thus forming the shoulder section 3 and the neck section 4 continued from the trunk section 2, the leading end of the neck section 4 is cut out (i.e., trimmed) thereby forming the container mouth 5. Then, the male thread 6 is formed on the neck section 4 at a threading step, and an opening edge of the container mouth 5 is curled outwardly at a curling step. Thereafter, a flange is formed on the lower end of the trunk section 2 at a necking/flanging step, and the bottom lid 7 is seamed by the flange at a seaming step. The above-explained top doming, threading, and curling steps, as well as the necking/flanging and seaming steps of the bottom side may be executed by the conventionally known methods.
It is required not only to ensure rigidity and strength of the bottle-shaped can 1 manufactured by the foregoing steps, but also to ensure rigidity and strength of the bottle-shaped can 1 to bear loads applied thereto during execution of the foregoing steps. Therefore, thickness of each section is set to satisfy the above-mentioned requirements and to reduce an amount of the material as much as possible. Turning to
In the bottomed cylinder 11, an interim trunk section b3 corresponding to the trunk section 2 of the bottle-shaped can 1 is a cylindrical section and hence a buckling strength of the interim trunk section b3 is high. Accordingly, a wall thickness of the interim trunk section b3 is reduced thinner than those of the other sections. Whereas, an interim shoulder section b1 of the bottomed cylinder 11 corresponding to the shoulder section 3 and the neck section 4 of the bottle-shaped can 1 inclines with respect to a load (i.e., an axial load) applied to the bottle-shaped can 1 from above. Therefore, a wall thickness of the interim shoulder section b1 is maintained thicker than the wall thickness of the interim trunk section b3. An interim bottom section b5 having an opening is to be drawn to reduce a diameter thereof at the necking step, and the bottom lid 7 is seamed to the interim bottom section b5 by the flange at the seaming step. That is, a portion drawn to reduce the diameter thereof is subjected to the axial load. Therefore, in order to ensure strength to bear the axial load, a wall thickness of the interim bottom section b5 is maintained thicker than the wall thickness of the interim trunk section b3. Thus, in the bottomed cylinder 11, the wall thicknesses of the interim shoulder section b1 formed above the interim trunk section b3 and the interim bottom section b5 formed below the interim trunk section b3 are thicker, and the wall thickness of the bottomed cylinder 11 changes gradually in an upper intermediate section b2 and a lower intermediate section b4.
As explained above, the wall thickness is changed as a result of a flow of the material caused by the above-explained drawing and ironing. That is, the colored resin coating formed on the blank 9 is expanded by the flow of the material during the process of shaping the blank 9 into the cup 10, and consequently the color of the resin coating is changed. As a result of such change in the color of the resin coating, colorfulness and brightness of the color of the resin coating will be increased. That is, the color is deteriorated. Such deterioration of color is schematically shown in
As illustrated in
Therefore, according to the method of the present invention, the bottomed cylinder 11 in which the color of the resin coating has been deteriorated by the forming process is painted experimentally with a plurality of inks of different colors to be used to draw the design Da. Then, a tone chart of samples of colors resulting from mixing the colors of the inks with the deteriorated colors of the resin coating and the initial color of the resin coating is prepared based on the result of experimentation. As known in the conventional art, a tone is a group of hues of colors having the same brightness and colorfulness. As schematically shown in
A color scheme of each part of the design Da and the inks to be used to draw the design Da are determined with reference to the tone chart, and the design Da is printed on a desired site of the bottomed cylinder 11. The remaining area Db in which the design Da is not printed but the color of the resin coating is deteriorated is painted with the ink of the same or similar color as the color of the ink used to paint the interim shoulder section b1 and the interim bottom section b5. In other words, the remaining area Db is painted with the ink of the same or similar color as the color of the resin coating applied to the blank 9. The bottomed cylinder 11 on which the design Da has been printed and in which the deteriorated color of the resin coating has been restored is schematically shown in
Thus, according to the method of the present invention, the color(s) of the ink(s) used to paint the design Da on the bottle-shaped can 1 is/are selected taking account of the ground color of the outer surface of the bottle-shaped can 1 which has been subjected to the forming process. Therefore, the design 8 may be printed on the bottle-shaped can 1 in the intended color(s) and tone(s) as designed by the existing manufacturing process. For this reason, frequencies of redesigning and printing can be reduced significantly compared to a case of printing a design stepwise by a trial-and-error approach such as printing the design tentatively on the bottomed cylinder 11 and thereafter adjusting the color(s) of the design by printing the design again. In other words, the printing process and the manufacturing process of the bottle-shaped can 1 may be simplified, and the design may be printed easily on the bottle-shaped can 1 as designed.
According to the present invention, it is preferable to restore the color deteriorated by the forming process especially in the remaining area Db in which the design Da is not printed. For this purpose, in order to unify the color of the bottle-shaped can 1, it is preferable to paint an area of the remaining area Db where the color of the resin coating is deteriorated indistinguishably from an area of the remaining area Db where the color of the resin coating is not restored. To this end, inventors of the present invention prepared a three-piece type bottle-shaped can 1 from a blank 9 to which a resin coating colored with gold pigment as a medium color is applied, and a three-piece type bottle-shaped can 1 from a blank 9 to which a resin coating colored with black pigment as a deep color is applied. Here, those bottle-shaped cans 1 were manufactured by the above-explained forming process. As described, in the three-piece type bottle-shaped can, a design is not printed on the can bottom (that is, the can bottom cannot be painted or colored). Then, a color difference ΔE*ab (on the basis of the can bottom which cannot be painted) in each of the above-mentioned sections c1 to c5 shown in
ΔE*ab=[(ΔL*)2+(Δa*)2+(Δb*)2]1/2;
where ΔL* is a difference in brightness, Δa* is a difference in brightness, and Δb* is a difference in colorfulness, between two colors compared in a color space Lab.
The measurement results are shown in Table 1.
In Table 1, the definition of “Before Restoration” is the trunk of the can in which the color thereof is deteriorated as a result of the ironing process, and the definition of “After Restoration” is the trunk of the can in which the color thereof has been restored by painting a site where the color thereof deteriorated as a result of the ironing process with the same or similar color as the color of the resin coating. As can be seen from Table 1, the color difference ΔE*ab is largest at the section C3 corresponding to the interim trunk section b3 in both of the can trunk coated with the gold coating and the can trunk coated with the black coating. That is, the deterioration in color is most serious in this section. Especially, in the can trunk coated with the black coating, the color difference ΔE*ab in the section C3 is “23.84”, and it is significantly greater than that in the same section of the can trunk coated with the gold coating. Therefore, it is assumed that the deeper color is deteriorated more significantly by the forming process, and it is necessary to be restored by painting.
The color of the bottomed cylinder 11 deteriorated by the forming process was painted to be restored, and then the color difference ΔE*ab in each of the sections c1 to c5 was individually measured. Specifically, the deteriorated color was restored by the conventional method such as a solid printing using the ink of the same or similar color as the color of the resin coating applied to the blank 9, or a gradation printing using a halftone. The color differences ΔE*ab after restoring the deteriorated color are as shown in Table 1, and degree of a color unevenness on the bottomed cylinder 11 or the bottle-shaped can 1 was monitored.
Specifically, 10 monitors were delegated, and a color unevenness of the bottomed cylinder 11 or the bottle-shaped can 1 after restoring the color was evaluated visually by each monitor. As a result, 2 monitors had an impression that there was a slight color unevenness, but other 8 monitors did not find any color unevenness. Based on the result of such monitoring, in the three-piece type bottle-shaped can according to the present invention in which a design is not printed on the bottom lid, the color difference ΔE*ab on the basis of the initial color of the resin coating (applied to the blank 9) in the area where the design is not printed is set to “10” or smaller. According to the present invention, therefore, color unevenness of the bottle-shaped can may not be sensed by the consumer not only in the case of coating the blank with the resin coating in the color of medium color, but also in the case of coating the blank with the resin coating in the color of dark color such as black. For this reason, an appearance of the bottle-shaped can may be improved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-036099 | Mar 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/005013 | 2/9/2022 | WO |
