Method for manufacturing bottle-shaped can made of colored resin-coated metal sheet

Abstract

The present invention provides a method for easily and precisely creating a design on an outer surface. The method comprises the following steps: subjecting a metal plate coated with a colored resin to a forming process, including drawing or ironing, to form a cylindrical main body; then printing a design on the outer surface of the main body; wherein the design is printed multiple times at predetermined locations on the outer surface of the main body, with the color being varied; obtaining a color mixture sample of the color used for printing the design and the base color at the predetermined location; creating a color tone table of a hue group with the same brightness and saturation as that at the predetermined location; determining the color scheme of the design based on the color tone table; and then printing the design.

Description

Technical Field

[0001] The present invention relates to a method for producing a bottle-shaped can by drawing and ironing a metal plate (blank) coated with a synthetic resin film, a paint, or the like, and then printing an appropriate design on the surface. Background Art

[0002] Bottle-shaped cans are cans whose neck and mouth are drawn and tapered relative to the main body. These cans are molded from sheet metal, such as aluminum, its alloys, or steel, into a shape that mimics the shape of conventional glass bottles. Because glass bottles can be colored to desired colors, they can be made into a variety of colors. Similar to glass bottles, bottle-shaped cans are desired to be made in a variety of colors. However, when bottle-shaped cans are manufactured from sheet metal, the shoulder, neck, and mouth where the lid is attached are drawn to a smaller diameter than the main body, further extending them into a thin, cylindrical shape, subjecting them to harsh processing requiring significant deformation. Therefore, when a colored coating is applied to the sheet metal (blank) before drawing and thinning to create a bottle-shaped can, the harsh deformation of the neck, mouth, and the threads on the outer surface of the mouth can sometimes cause cracks or breaks in the coating. Furthermore, bottle-shaped cans are often printed with colorful graphics and text (hereinafter referred to as design) to showcase the product to consumers. The inks used in this printing vary greatly, and in many cases, light can penetrate through the base color, allowing the base color to be seen. In this case, the base color mixes with the design color, so the color the designer intended or specified may not appear.

[0003] To address this inconvenience, attempts have been made to adjust the composition and ingredients of various resin coatings. For example, in the invention described in Japanese Patent No. 3957049, a color pigment is mixed into the adhesive layer that bonds the transparent thermoplastic resin layer to the aluminum alloy plate. This creates a printed base with a silver metallic luster, allowing the base metal to be visible through the thinned adhesive layer in the main body portion that has been thinned by molding. Summary of the Invention

[0004] When applying a dark coating to the blank to mimic a glass bottle, the color of the coating becomes the base color for printing in the molded body, affecting the design color. While the extent and manner of this influence vary depending on the coating color and the type of printing ink, the coating applied to the blank is a major factor in causing the color to differ from the designer's intended design. Furthermore, the degree to which the blank is stretched and thinned during molding varies depending on the can, causing the color of the coating to degrade (lighten). Therefore, even if a design is based on the color (saturation, hue, and brightness) of the coating applied to the blank, the change in base color caused by molding makes it difficult to achieve the desired color or image. In such cases, the design can be redesigned and the body of the can printed again to observe the final effect. However, since designs are not composed of a single color, even if a location that was previously considered defective becomes the desired chromaticity, the hue and brightness of other parts may not meet expectations, making it inevitable to redo the design, adjust, and change the color of the coating.

[0005] The invention described in Japanese Patent No. 3957049 takes into account the degradation of the base color during molding, and thus provides a printed base with a silver metallic luster, allowing the base metal to be seen through the thinning adhesive layer. However, with this structure, the color of the resin coating is limited to the color of the metal plate or a color close to it, making it impossible to achieve a colorful bottle-shaped can.

[0006] The present invention is completed with a view to the above-mentioned technical problems, and its purpose is to provide a method for manufacturing a bottle-shaped can, which can not only enrich the color of the main body, but also enrich the overall color of the shoulder, mouth and neck, etc., and can make it easy to print or determine the target design.

[0007] To achieve the above-mentioned objectives, the present invention is a method for manufacturing a bottle-shaped can made of a colored resin-coated metal sheet, comprising the following steps: forming a cylindrical main body portion by subjecting the metal sheet coated with the colored resin to a forming process including drawing or ironing, and then printing a design on the outer surface of the main body portion; the method being characterized in that the color is changed and printed multiple times at a predetermined position on the outer surface of the main body portion to obtain a mixed color sample of the color used in the printing and the base color at the predetermined position, creating a color tone table representing a hue group with the same brightness and saturation as the predetermined position, determining a color scheme for the design based on the color tone table, and printing the design at the predetermined position with the determined color scheme.

[0008] In the method of the present invention, the outer surface of the main body portion other than the predetermined portion where the design is printed may be printed in the same color or a color related to the colored resin coating.

[0009] In the method of the present invention, the bottle-shaped can may be configured such that a bottom cap without a printed design is screwed onto the open end of the main body, and the position other than the predetermined position is printed with the same color or a color of the same color family as the colored resin coating, and the color difference ΔE between the color of the colored resin coating on the metal plate and the color of the colored resin coating is ΔE. * ab is less than "10".

[0010] Furthermore, in the present invention, the color of the colored resin coating may be a color with lower brightness or higher saturation than the color of the metal plate body.

[0011] In the present invention, a color chart is created for the resulting colored outer surface of the main body by actually forming the metal sheet. The color scheme of the design is then determined based on this chart. This contrasts with the process of determining the color scheme based on a plain white paper or other substrate, where the design is based on a colored substrate that degrades due to forming. Therefore, by printing the design on the main body using the determined color scheme, the desired color can be printed. This contrasts with the process of actually printing a design with a temporarily determined color scheme on the main body, studying the resulting print quality, and then re-determining the color scheme and then actually printing the design and studying the resulting print quality, which involves repeated trial-and-error color scheme research and printing. Because the main body's base color is considered at the time of color determination and a color scheme is chosen that is appropriate for that base color, the frequency or likelihood of color scheme failures is reduced, making it easier to determine the design and manufacture the bottle-shaped can. In particular, even if the main body degrades in color, the present invention allows for a design that takes this degraded color into account, further reducing the frequency or likelihood of color scheme failures.

[0012] Furthermore, in the present invention, since the locations other than the locations where the design is to be printed are printed with the same color or a color related to the colored resin coating, even if the main body undergoes color degradation due to molding, the color can be corrected to achieve the desired design.

[0013] In this case, the color difference ΔE between the printed color of the same color or the same color series as the colored resin coating and the color of the colored resin coating on the metal plate which is the original color is * Since ab is "10" or less, the deterioration and complementation of color are not noticeable, and in this respect, a desired design can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a front view showing an example of a bottle-shaped can manufactured in the present invention.

[0015] Figure 2 It is a block diagram for explaining the manufacturing process of the present invention.

[0016] Figure 3 This is a diagram schematically showing the wall thickness of a can body obtained by molding, corresponding to each part of the bottle-shaped can.

[0017] Figure 4 (A) to (D) are schematic diagrams showing, in order, a state of color deterioration, a state with design printing, a state with repair of the deteriorated portion, and a bottle-shaped can obtained through processing after repair.

[0018] Figure 5 This is a diagram showing an example of a color tone table in an achromatic manner. DETAILED DESCRIPTION

[0019] The bottle-shaped can manufactured using the method of the present invention is a can with a metal plate as the blank, and the main body and the mouth and neck are integrated. It can be a so-called two-piece bottle-shaped can with the bottom and the main body integrated, or it can be a so-called three-piece bottle-shaped can with the bottom cover screwed and installed on the main body. Figure 1 The figure schematically shows an example of a three-piece bottle-shaped can 1. A shoulder portion 3, whose diameter gradually decreases upward, is formed above a cylindrical main body 2. A cylindrical neck portion 4 is connected to the upper portion of the shoulder portion 3. The upper end of the neck portion 4 is open to form a mouth portion 5. Neck portion 4 is formed with an external thread 6, and a cap (not shown) is attached thereto to seal the bottle-shaped can 1. Furthermore, the cap can be attached and removed, making it a resealable can. It should be noted that a bottom cap 7 is screwed onto the bottom of the main body 2. The open end of the mouth portion 5 is curled outward.

[0020] The neck portion 4 and the mouth portion 5 are collectively referred to as the mouth-neck portion, and the entire body portion 2 is colored starting from the mouth-neck portion. This coloring is performed by applying a colored resin coating to a metal plate (blank) such as aluminum or steel that is the blank material of the bottle-shaped can 1, as will be described later. Therefore, the blank is equivalent to the "colored resin-coated metal plate" in the present invention. An example of the color of the colored resin coating is a color with lower brightness or higher saturation than the color of the blank body. It should be noted that in Figure 1 In the figure, the colored resin coating is indicated by cross hatching. In the main body 2, a design 8 consisting of graphics, characters, etc. is printed on the colored base.

[0021] Figure 2 The manufacturing process of the bottle-shaped can 1 is shown in a block diagram. Figure 2The first step in the process is the cup body forming step, in which a blank plate 9 is drawn to form a cup body 10. As described above, the blank plate 9 is a thin metal plate made of aluminum, steel, or the like, and is punched into a predetermined shape such as a circle. Furthermore, the surface that will become the outer surface of the bottle-shaped can 1 is coated with a colored resin by methods such as film bonding or coating.

[0022] Next, the can body is formed as follows, the cup body 10 is subjected to drawing or thinning processing, and further drawing and thinning processing is performed, the cup body 10 is stretched along the axial direction to become deeper, and the wall thickness is thinned to form the can body 11. Then, the following trimming is performed, and the open end side of the can body 11 is cut off to make the height consistent. Since lubricating oil is used in the drawing, thinning and other processing, the lubricating oil is removed in the process following the trimming. The type of the lubricating oil or the application and removal thereof may be, for example, the contents described in the above-mentioned Japanese Patent Gazette No. 3957049. The can body 11 obtained in this way is printed and the packaging is changed. The printing will be described in detail later.

[0023] Next, dome molding is performed. The method described here is a method for manufacturing a so-called three-piece bottle-shaped can 1. Therefore, during this molding process, the bottom of the can body 11 is stretched into a small-diameter cylindrical shape, and its surrounding area is molded into a dome shape. The outer diameter of the cylindrical portion gradually decreases to form the mouth and neck, and the dome-shaped portion is molded into a smooth shoulder. After the shoulder 3 and neck 4 connected to the main body 2 are molded into a specified shape, the front end of the neck 4 is cut off (trimmed) to form the mouth 5, and then threading is performed on the neck 4 to form an external thread 6, and curling is performed to bend the open end of the mouth 5 outward. On the other hand, the lower end of the main body 2 is necked and flanged (フランジング), and the bottom cap 7 is tightened using this flange. These dome molding, threading and curling molding, and the necking, flange, and tightening of the bottom can be carried out in the same way as previously known technologies.

[0024] The bottle-shaped can 1 obtained through the above-mentioned process is required to have not only strength and rigidity as a product itself, but also strength and rigidity to withstand the loads borne during the manufacturing process. Therefore, the wall thickness of each part is set in a manner to meet these requirements and minimize the amount of blank material. Figure 3 1 is a schematic diagram for explaining the wall thickness, and shows the wall thickness of each portion after the wall thickness is reduced by the ironing process, corresponding to each portion of the can body 11 and the bottle-shaped can 1 .

[0025] First, the tank body portion b3 of the tank body 11, which corresponds to the main body 2 of the bottle-shaped tank 1, is cylindrical in shape and has high buckling strength. Therefore, the wall thickness of the tank body portion b3 is thinner than that of other portions. In contrast, the shoulder portion b1 of the tank body 11, which corresponds to the shoulder 3 and neck 4 of the bottle-shaped tank 1, is weaker than the main body 2 due to its shape, mainly due to its tilt relative to the load (axial load) applied from above when in the state of the bottle-shaped tank 1. Therefore, the wall thickness of the shoulder portion b1 is thicker than that of the tank body portion b3. Furthermore, since the bottom portion b5 of the opening is the portion whose diameter is reduced by the above-mentioned necking and the bottom cover 7 is tightened by the flange, the axial load is borne by the portion with the reduced diameter. Therefore, in order to ensure strength, the wall thickness is made thicker than that of the tank body portion b3. Thus, the wall thickness increases at the shoulder portion b1 above the tank body portion b3 and the bottom portion b5 below the tank body portion b3, with an upper transition portion b2 and a lower transition portion b4 between them where the wall thickness gradually changes.

[0026] Such a wall thickness is set as a result of the material flow during the above-mentioned drawing and ironing process. The colored resin coating provided on the surface of the blank plate 9 and the cup body 10 subjected to the forming process is stretched along with the material flow in the blank plate 9 and the cup body 10, and its color changes. This color change is, for example, a change in saturation or brightness, and is sometimes also called degradation. Figure 4 (A) schematically shows the state of color degradation. Figure 4 In (A), the portions where the horizontal lines are narrowly spaced and cross-hatched are the portions c1 and c5 with the least color degradation, which correspond to the aforementioned portion b1 equivalent to the shoulder and the portion b5 equivalent to the bottom. Furthermore, the portion where the horizontal lines are widest and no cross-hatching is applied is the portion c3 with the greatest color degradation, which corresponds to the aforementioned portion b3 equivalent to the tank body. Furthermore, the portions where the horizontal lines are gradually spaced and no cross-hatching is applied are the portions c2 and c4 with a gradually changing degree of color degradation, which correspond to the aforementioned upper and lower transition portions b2 and b4. These portions c1 to c5 correspond to the aforementioned wall thickness. That is, the color degradation is greatest in the portion b3 equivalent to the tank body, and the degree of color degradation gradually changes from this portion to the upper transition portion b2 and the lower transition portion b4 corresponding to the shoulder b1 or the bottom b5.

[0027] Among these parts with or without color degradation and different degrees, the design Figure 4The printing shown in (B) is carried out from the corresponding portion b3 of the can body to the upper and lower transition portions b2 and b4. In this case, when a design drawn with any color and ink or paint is printed on a backing paper of any color such as white in a location where color degradation occurs, the degraded color and the design may be mixed with each other, resulting in an undesirable design. If the design is made with a silver metallic luster that allows the base metal to be visible, or a light base color similar to it, as described in Japanese Patent Gazette No. 3957049, such as the one described in Japanese Patent Gazette, then in most cases, the design is designed with such a base color in mind, and it is believed that the design is unlikely to be affected by the base color and not be as expected. However, when the coating is a colored resin with high saturation and low brightness, such as black or brown, the influence of the color is more obvious in the design color, and the changes in the degradation (depth) are likely to directly affect the design.

[0028] Therefore, in the method of the present invention, a can body 11, which has undergone color degradation due to molding, is trial-printed using inks of various colors intended for use in the design Da. A color hue chart is created using samples of the degraded or undegraded base and the printed colors obtained as a result. As is well known, a hue is a group of hues with the same brightness and saturation. A color hue chart is created for each ink of the hue intended for use in the design Da. Figure 5 An example of the color tone table is shown schematically in FIG. Figure 5 Although it is recorded in a colorless manner, it is actually a table for inks of various hues.

[0029] Based on this color chart, the color scheme and ink used for each part of the design are determined, and the design Da is printed on a predetermined position on the can body 11. It should be noted that the positions Db where color degradation occurs in areas other than the design Da are printed with ink of the same color or a color related to that used in the non-degraded positions such as the shoulder portion b1 and the bottom portion b5. In other words, the positions Db are printed with ink of the same color or a color related to that used for the colored resin coating applied to the blank 9. Figure 4 (C) schematically shows the can body 11 after printing of the so-called supplement and design Da. Figure 4 In (C), the color is not shown in achromatic form, and the so-called base color and density of the can body 11 are expressed by cross-hatching. Figure 4 (D) in the figure shows the use of Figure 4 The printed can body 11 shown in (C) is an example of a bottle-shaped can 1 obtained by subjecting the can body 11 to dome molding, thread and curling molding, and necking, flange, and bottom cap screwing.

[0030] In the method of the present invention described above, because the color or ink of the design Da is determined based on the color of the outer surface of the can body 11 after molding, a bottle can 1 can be obtained with the design 8 having the same color or hue as the design by printing according to the design during the actual manufacturing process. This significantly reduces the frequency of repeated design and printing compared to a method that gradually determines the design by trial and error, such as actually printing the design on the can body 11, adjusting the colors of various parts, and then printing again. In other words, the design, printing, and manufacturing of the bottle can 1 can be simplified, making it easy to produce a design that is consistent with the desired design.

[0031] It should be noted that in the present invention, it is preferred to print the portion Db other than the design Da in the position where the color deterioration occurs due to the molding process to compensate for the above-mentioned deterioration. In this case, in order to ensure the sense of unity of the color of the bottle-shaped can 1, it is preferred to print in a manner that does not distinguish between the complementary position and the non-complementary position without a base. Therefore, the present inventors carried out the above-mentioned molding process on a so-called three-piece bottle-shaped can 1 in which the bottom of the can is not printed with a design (cannot be coated or colored) using a blank 9 coated with a colored resin of gold as an intermediate color and a blank 9 coated with a colored resin of black as a dark color, and obtained the above-mentioned color of the obtained can body 11. Figure 4 The color difference ΔE*ab of each portion represented by symbols c1 to c5 in (A) (color difference based on the bottom of the can that cannot be printed) was obtained using a Konica Minolta CR-5 colorimeter. The color difference is given by the following formula.

[0032] ΔE*ab=〔(ΔL*) 2 +(Δa*) 2 +(Δb*) 2 〕 1 / 2 …Mode

[0033] ΔL* is the brightness difference between the two colors being compared in the L*a*b* color space, Δa* is the saturation difference, and Δb* is the hue difference.

[0034] The measurement results are shown in Table 1.

[0035] [Table 1]

[0036] (Measure the color difference AE*ab at each position based on the original colored resin coating)

[0037]

[0038] In Table 1, "before supplementation" refers to a can or can body that has undergone color degradation due to the ironing process, and "after supplementation" refers to a can or can body that has undergone color supplementation by printing the area degraded by the ironing process with the same color or a color similar to the color resin coating before the molding process (before degradation). As shown in Table 1, the color difference ΔE at the portion c3 corresponding to the corresponding portion b3 of the can body in each of the gold-coated can body and the black-coated can body is: * ab is the largest, and it is confirmed that the color degradation of this part is large. In particular, in the case of black, which is a dark color, the color difference ΔE * ab is "23.84", and the color difference ΔE is confirmed compared to the case of the intermediate color gold. * Therefore, it is speculated that the darker the color, the greater the color degradation caused by the molding process, and the more necessary it is to print for supplementation.

[0039] The can body 11 whose color has deteriorated due to the molding process is printed to compensate for the color difference ΔE at each of the subsequent parts c1 to c5. * It should be noted that the printing for supplementation is performed by solid printing with ink of the same color or the same color family as the colored resin coating provided on the blank 9, or by gradation printing based on halftone dots or other conventionally known methods. Color difference after supplementation ΔE * As shown in Table 1, the presence and degree of color unevenness of the can body 11 or the bottle-shaped can 1 that was color-compensated in this manner were monitored.

[0040] This monitoring involved providing the can body 11 or bottle-shaped can 1 after color supplementation to 10 randomly selected monitors, who then visually assessed the color unevenness. Two of the 10 monitors judged that the color unevenness was slightly noticeable, while the other eight judged that the color unevenness was not noticeable. Based on the results of this monitoring, the color difference ΔE of the can body, excluding the design printing, was calculated based on the original coloring resin coating color (the coloring resin coating color of the blank 9) of the so-called three-piece bottle-shaped can without a design printed on the bottom cap. * ab is set to be equal to or less than 10. With this configuration, a bottle-shaped can having an excellent appearance without causing consumers or other viewers to perceive color unevenness can be produced regardless of whether the color is a neutral color or a dark color such as black.

Claims

1. A method for manufacturing a bottle-shaped can made of a colored resin-coated metal sheet, the method comprising the steps of: subjecting the metal sheet coated with a colored resin to a forming process including drawing or ironing to form a cylindrical body; and then printing a design on the outer surface of the body. The manufacturing method is characterized in that the color of the predetermined position on the outer surface of the main body is changed and printed multiple times to obtain a mixed color sample of the color used in the printing and the base color of the predetermined position. creating a hue table of hue groups having the same brightness and saturation as those at the predetermined position, Determine the color scheme of the design based on the color tone table, The design is printed at the specified location using the determined color combination.

2. The method for manufacturing a bottle-shaped can made of a colored resin-coated metal sheet according to claim 1, wherein: The outer surface of the main body is printed in the same color or a color related to the colored resin coating at locations other than the predetermined location on the main body where the design is printed.

3. The method for manufacturing a bottle-shaped can made of a colored resin-coated metal sheet according to claim 2, wherein: The bottle-shaped can is constructed by screwing a bottom cover without a printed design onto the open end of the main body. The color difference ΔE between the color of the colored resin coating on the metal plate and the color of the colored resin coating on the metal plate is made such that the color of the colored resin coating on the metal plate is the same color or the same color as the colored resin coating. * ab is less than "10".

4. The method for producing a bottle-shaped can made of a colored resin-coated metal sheet according to any one of claims 1 to 3, wherein: Due to the forming process, the color of the outer surface of the main body portion deteriorates in accordance with the thinning of the metal plate.

5. The method for producing a bottle-shaped can made of a colored resin-coated metal sheet according to any one of claims 1 to 4, wherein: The color of the colored resin coating is a color with lower brightness or higher saturation than the color of the metal plate body.

Images