Metal container, device for manufacturing metal container, and method for printing metal container

Abstract

The purpose of the present invention is to obtain a metal container having a highly durable recognition display, a device for manufacturing the metal container, and a method for printing the metal container. A metal container according to the present invention is provided with a main body comprising a metal plate, the main body having a cylindrical part and a lid part attached so as to close both ends of the cylindrical part, the main body having formed thereon a coating layer constituting the outer surface of the main body, the printing part is arranged by changing the color of a part including the surface of the coating layer through laser light with visible light or UV wavelength.

Description

Technical Field

[0001] The present invention relates to a metal container, a manufacturing device for the metal container and a printing method for the metal container, and in particular to a technology for attaching an identification display on the surface using a laser. Background Art

[0002] In the past, metal containers such as barrels and cans have many paint colors, and are provided with surface identification displays to distinguish the types. There are many combinations of paint colors and surface identification displays, and barrels and cans are manufactured while managing the types according to manufacturing instructions. The surface identification display can be achieved, for example, by spraying paint, screen printing, printing with a seal, etc., or by mounting a sheet.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-285811 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The manufacturing process of metal containers such as barrels and cans requires the circulation of a variety of barrels and cans of various colors on a single production line, so complex identification displays need to be applied in a short production cycle. When printing on the surface of metal containers by spraying, screen printing, stamping, etc., there are problems such as the printed characters sometimes appearing blurred and unclear, or there are limitations in the expression of complex characters or symbols. In addition, the printed characters sometimes peel off when the metal containers are used, which poses a problem in terms of the durability of the identification display.

[0008] The present invention aims to solve the above-mentioned problems and to provide a metal container having a clear and highly durable identification display, a metal container manufacturing device, and a metal container printing method.

[0009] Solutions to Solve Problems

[0010] The metal container involved in the present invention has a main body made of metal, which has a cylindrical portion and a cover portion installed in a manner to close both ends of the above-mentioned cylindrical portion. The above-mentioned main body forms a coating layer constituting the outer surface of the main body. The above-mentioned main body has a printing portion, and the printing portion is set by discoloring a part of the above-mentioned coating layer including the surface by laser with a visible light or UV wavelength.

[0011] The manufacturing apparatus of the metal container according to the present invention includes a processing head for printing on the above-mentioned metal container, and the processing head emits the above-mentioned laser light in the wavelength region of visible light or UV.

[0012] The metal container printing method according to the present invention is a printing method for printing on the above-mentioned metal container, wherein the band gap of at least one pigment contained in the above-mentioned coating layer is smaller than the light energy hν of the above-mentioned laser light to be irradiated.

[0013] Effects of the Invention

[0014] According to the present invention, since a part of the coating layer including the surface is discolored by laser light of a visible light or UV wavelength to provide a printed portion, a metal container having an identification display with excellent durability, a metal container manufacturing device, and a metal container printing method can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a perspective view showing an appearance of an example of the metal container 100 according to the first embodiment.

[0016] Figure 2 This is an enlarged view of the cross-sectional structure of the printing portion 10 of the metal container 100 according to the first embodiment.

[0017] Figure 3 This is a schematic diagram of the laser beam 30 irradiated onto the metal container 100 according to the first embodiment.

[0018] Figure 4 This is a schematic diagram of a part of a manufacturing apparatus 90 for a metal container 100 according to the first embodiment.

[0019] Figure 5 This is a diagram showing an example of a functional configuration related to control of a laser marking process of a manufacturing apparatus 90 for a metal container 100 according to the first embodiment.

[0020] Figure 6 This is an example of a flowchart of control of a laser marking process of the manufacturing apparatus 90 of the metal container 100 according to the first embodiment.

[0021] Figure 7 These are examples of the respective coating colors, paint and contained components of the metal container 100 according to the first embodiment, and the coloring of the printing portion 10 using the respective coating colors.

[0022] Figure 8 This is an example of the appearance of the printing portion 10 of the metal container 100 .

[0023] Fig. 9 The figures show examples in which laser marking was performed on each paint color and the evaluation results thereof.

[0024] Fig.10 The figures show examples and comparative examples in which printing such as laser marking was performed on each paint color, and the evaluation results thereof.

[0025] Fig.11 This is an example of component analysis results of the discolored portion in the printed portion 10 of the metal container 100 according to the first embodiment obtained by X-ray reflection analysis.

[0026] Fig.12 This is an example of component analysis results of the discolored portion in the printed portion 10 of the metal container 100 according to the first embodiment obtained by X-ray reflection analysis.

[0027] Fig.13 This is a schematic diagram of the reduction reaction of Fe 2 O 3 in the printing portion 10 of the metal container 100 according to the first embodiment by laser irradiation.

[0028] Fig.14 This is an example of the laser beam irradiated onto the metal container 100 according to the first embodiment.

[0029] Fig.15 The band gap of the substance contained in the coating layer 21 of the metal container 100 according to the first embodiment is shown. DETAILED DESCRIPTION

[0030] The following is an explanation of the embodiments based on the accompanying drawings. In addition, in each figure, the elements marked with the same reference numerals are the same or equivalent elements, which are common throughout the entire text of the specification. Furthermore, the modes of the constituent elements shown in the entire text of the specification are merely illustrative and are not limited to these records.

[0031] Implementation method 1.

[0032] <Configuration of Metal Container 100>

[0033] Figure 1 1 is a perspective view showing an external appearance of an example of a metal container 100 according to the first embodiment. The metal container 100 according to the first embodiment is, for example, a metal barrel, for example, a barrel with an internal capacity of about 200 L as specified in JIS Z 1601:2017. However, the metal container 100 is not limited thereto, and is a concept including metal containers such as barrels, cans, buckets, or storage tanks exceeding 200 L. In addition, barrels include not only a closed type (closed can) in which a bottom plate and a top plate are crimped and joined to a can body, but also an open type in which a top plate can be freely attached to and detached from the can body.

[0034] Figure 1The metal container 100 shown is a barrel can, and includes: a cylindrical portion 101 which is a cylindrical portion called a can body; and a cover portion 102 located at both ends of the central axis direction of the cylindrical portion 101. The cover portion 102 is composed of a cover portion 102A called a top plate provided at one end of the central axis direction of the cylindrical portion 101 and a cover portion 102B called a bottom plate provided at the other end. The cylindrical portion 101 and the cover portion 102 are sometimes collectively referred to as a body.

[0035] The cover 102 is fixed to both ends of the tube 101 by crimping. However, the fixing of the cover 102 is not limited to crimping, and may be performed by welding, riveting, brazing, or the like. In addition, the metal container 100 is not limited to the method of fixing the cover 102A and 102B at both ends of the tube 101 in the central axis direction to close the tube 101, but may be a method of fixing only one side.

[0036] The cover 102A is provided with two openings 103 and 104. The openings 103 and 104 are formed by attaching caps to metal ports, for example, and are used as holes for injecting or discharging liquid from one side and exhausting air from the other side. The metal ports and caps forming the openings 103 and 104 are formed so as not to protrude compared to the bead 107 formed at the end of the cylinder 101 of the metal container 100 and protruding in the central axis direction.

[0037] The barrel 101 is substantially cylindrical and has protruding annular ribs 105 (reinforcement ribs) in the middle of the central axis direction. The annular ribs 105 are formed over the entire circumference of the cylindrical barrel 101. In addition, the annular ribs 105 are provided at multiple locations in the central axis direction. In addition, the metal container 100 may not be provided with annular ribs 105.

[0038] The cylindrical portion 106 between the annular rib 105 and the curled edge 107 is a substantially smooth cylindrical surface.

[0039] Figure 2 It is an enlarged view of the cross-sectional structure of the printing portion 10 of the metal container 100 according to Embodiment 1. The cylinder portion 101 of the metal container 100 includes a metal base material 20 and a coating layer 21. The base material 20 is made of steel and may have a chemically synthesized film on the surface.

[0040] The coating layer 21 is, for example, Figure 7 As shown in FIG. 1 , the coating layer 21 is composed of paints for forming DM-1 to DM-14 as standard colors of barrels or paints for forming other user-specified colors. The paint constituting the coating layer 21 may contain necessary pigments according to various colors, and the pigments may contain compounds such as titanium dioxide, carbon black, yellow iron oxide, iron oxide, chlorinated ketone phthalocyanine green, copper phthalocyanine (pigment blue 15), iron hydroxide, and polybrominated chlorinated copper phthalocyanine.

[0041] like Figure 1 As shown in FIG. 1 , a printed portion 10 is provided on a cylindrical portion 101 of a metal container 100. In the first embodiment, the printed portion 10 is formed by discoloring a coating layer 21 by laser marking. Figure 1 In the embodiment, the printing section 10 is provided at a portion 106 of the barrel, and is provided at a portion above a curling edge 107 on the bottom plate side.

[0042] like Figure 2 As shown in FIG. 1 , the printing portion 10 is formed with a discolored portion 22 formed by discoloring a portion of the coating layer 21 including the surface 23 by laser marking. The discolored portion 22 is formed within a range of 0.3 μm or more and 10 μm or less from the surface 23 and is formed so as not to reach the base material 20. Figure 2 In the embodiment, the surface 23 constitutes the outer surface of the metal container 100. In addition, the color-changing portion 22 is sometimes referred to as a color-changing layer, and the portion of the color-changing portion 22 on the base material 20 side of the coating layer 21 that is not color-changed is sometimes referred to as a non-color-changing layer.

[0043] Figure 3 Schematic diagram of laser 30 irradiating metal container 100 according to Embodiment 1. Laser 30 is composed of light in the wavelength region of visible light or ultraviolet light. Lasers are classified into levels 1 to 4, and laser 30 according to Embodiment 1 is a high-output laser of level 4. Figure 3 As shown in (a) to (c) of FIG. 1 , the focal point can be moved relative to the surface 23 of the coating layer 21 . Figure 3 (a) is a state where the focus is on the surface 23 of the coating layer 21. Figure 3 (b) is a position where the focus is located on the depth side (i.e., the base material 20 side) relative to the surface 23. Figure 3 (c) shows a state where the focus is closer to the front side than the surface 23. Figure 3 When the focus is closer to the depth side or the front side than the surface 23 as in (b) and (c), the range of the laser 30 is as follows: Figure 3 The case where the focus is achieved on surface 23 as in (a) is large. Figure 3 The dimension D shown indicates the amount of change in the focal position relative to the state where the laser light 30 is focused on the surface 23. That is, as the dimension D increases, the range of the surface 23 that is hit by the laser light 30 increases.

[0044] When the laser 30 Figure 3When the surface 23 is focused as in (a), the amount of energy given to the surface 23 per unit area becomes larger, while the irradiation area becomes smaller. Therefore, it is easy to discolor a part of the coating layer 21, but the area of ​​the discolored portion 22 is small, and sometimes the visibility is low. Therefore, in the metal container 100 involved in the first embodiment, the position of the focus of the laser 30, the output of the laser 30, and the scanning speed of the laser 30 are changed according to the ease of discoloration of the coating material constituting the coating layer 21, and the visibility of the printing portion 10 as a collection of the discolored portion 22 is adjusted.

[0045] Figure 4 It is a schematic diagram of a part of the manufacturing device 90 of the metal container 100 involved in Embodiment 1. The manufacturing device 90 of the metal container 100 includes: a conveying device 40 for moving at least the metal container 100; a processing head 31 for irradiating the metal container 100 with a laser 30; and a positioning fixture 32 for determining the position of the metal container 100 when performing laser marking.

[0046] The conveying device 40 is, for example, a belt conveyor, etc., which carries a plurality of metal containers 100 and moves them to a predetermined position for each process. The conveying device 40 is sent to the laser marking process. The conveying device 40 moves the metal container 100 to the front of the processing head 31 for laser marking. The moved metal container 100 abuts against the positioning fixture 32 and is positioned so that the distance from the processing head 31 becomes a predetermined value. In addition, the position of the metal container 100 in the conveying direction x can be positioned by controlling the conveying device 40 or using a fixture 33 that abuts from the conveying direction x side relative to the metal container 100. The positioning fixtures 32 and 33 only need to be configured to determine the distance in the y direction and the position in the x direction from the processing head 31 with high precision. For example, the metal container 100 can be pushed toward the positioning fixture 32 from the opposite side where the positioning fixture 32 is arranged relative to the positioning fixture 32 so as to abut against it.

[0047] The processing head 31 irradiates the laser 30 and is arranged on the side of the conveying device 40. At least one processing head 31 is arranged on the side of the conveying device 40, and the laser 30 is irradiated from the processing head 31 to perform laser marking on the metal container 100 to be the target. The manufacturing device 90 according to the first embodiment particularly shows the case where the laser marking process is performed using two processing heads 31, but it is not limited to this.

[0048] exist Figure 4In the embodiment, two processing heads 31 are arranged in the z direction, and the laser beam 30 is irradiated from each of the processing heads to a metal container 100 placed on the conveying device 40. The laser beam 30 irradiated from one processing head can irradiate, for example, an irradiation range 35 of 25 cm square. The irradiation ranges 35 of each of the two adjacent processing heads partially overlap each other. By configuring in this way, the time for attaching a predetermined identification display to the printing portion 10 of the metal container 100 can be shortened. In addition, even when the area of ​​the printing portion 10 is large, the irradiation ranges 35 of the two processing heads 31 can cover the entire area of ​​the printing portion 10, and there is no need to divide the laser marking process into two. In addition, since a plurality of processing heads 31 are used to print on the printing portion 10 at the same time, it is possible to suppress the mutual deviation of the characters or marks printed by the two processing heads 31. If the two processing heads 31 are separately arranged in the two laser marking processes, the two laser marking processes need to respectively position the metal container 100 with respect to the processing heads 31 with high precision. Therefore, the color changing parts 22 of the printing part 10 formed by the two laser marking processes may be offset from each other. On the other hand, as described above, since a plurality of processing heads 31 are used to simultaneously print using a plurality of lasers 30, the positional offset of the display printed by each laser 30 can be suppressed to a minimum.

[0049] In addition, when the metal container 100 is a barrel, the printing unit 10 needs to display a lot of information such as JIS, UN, etc. marks, numbers, codes, etc. Therefore, in the past, in addition to printing on the barrel with a seal, a countermeasure such as attaching a label with identification information is also implemented. On the other hand, according to the processing head 31 involved in the first embodiment, since the identification display is printed by the laser 30, detailed text or symbols can be printed with high precision. In addition, Figure 4 Since the manufacturing apparatus 90 shown automatically performs the laser marking process, it is possible to suppress the occurrence of problems such as a wrong label being attached to the metal container 100.

[0050] The manufacturing device 90 in the first embodiment may also be provided with a color recognition sensor 36. For example, the manufacturing device 90 is provided with a color recognition sensor 36 at a position corresponding to the metal container 100 before entering the laser marking process. Figure 4 In the embodiment, for the metal container 100 at position A, the color recognition sensor 36 detects the color of the surface of the tube 101. In addition, the color recognition sensor 36 may also be arranged at Figure 4 The processing head 31 shown is located inside the processing head 31, and can be arranged at any position as long as the surface of the metal container 100 that has been subjected to the same coating as the portion irradiated with the laser beam 30 can be detected by the color recognition sensor 36.

[0051] The color recognition sensor 36 irradiates the surface of the metal container 100 irradiated with laser light, detects the reflected light from the surface with the light receiving element, and discriminates the color of the surface. The type of the coating layer 21 of the metal container 100 is discriminated by pre-registering the color of the coating layer 21 of the metal container 100 as a specimen, and detecting whether the color of the metal container 100 flowing through the manufacturing device 90 matches any of the registered colors. The control device 50 has a database that associates the registered colors with the irradiation conditions of the laser 30, and instructs the processing head 31 with the irradiation conditions corresponding to the color of the coating layer 21.

[0052] In addition, the color of the coating layer 21 may be determined by the imaging device 34 provided in the processing head 31. In addition, the color recognition sensor 36 may be provided in the processing head 31.

[0053] The manufacturing device 90 is provided with a control device 50 for controlling each part of the manufacturing device 90. The control device 50 controls, for example, the irradiation conditions of the laser 30 of the processing head 31, the movement of the conveying device 40 and the image capturing of the imaging device, and determines the type of the coating layer 21. The control device 50 is connected to each part of the manufacturing device 90 in a communicative manner to obtain information from each part and send information to each part. The control unit 51 is provided with, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory). The CPU is also called a central processing unit, a central arithmetic unit, a processor, a microprocessor, a microcomputer or a DSP (Digital Signal Processor). In the control unit 51, the CPU reads the programs and data stored in the ROM, uses the RAM as a work area, and performs overall control of the control device 50.

[0054] The storage unit 52 is a nonvolatile semiconductor memory such as a flash memory, an EPROM (Erasable Programmable ROM), or an EEPROM (Electrically Erasable Programmable ROM), and functions as a so-called secondary storage device. In the first embodiment, the storage unit 52 stores information acquired by each part of the manufacturing device 90. Furthermore, the storage unit 52 stores programs and data for the control device 50 to communicate with each part constituting the manufacturing device 90.

[0055] Figure 51 is a diagram showing an example of a functional configuration related to control of a laser marking process of the manufacturing apparatus 90 of the metal container 100 according to the first embodiment. Figure 4 The hardware structure shown in the figure performs laser marking on the metal container 100 flowing through the manufacturing device 90. The control device 50 communicates with the processing head 31, the color recognition sensor 36 and the conveying device 40 in a wireless or wired manner to control the laser marking. In addition, the control device 50 may also have Figure 5 Functions other than those shown may also communicate with other control devices provided in the manufacturing device 90 to perform the laser marking process in conjunction with functions implemented by other control devices. In addition, some of the functional blocks provided by the control unit 51 may also be provided in control devices provided by other hardware.

[0056] like Figure 5 As shown in the figure, the control unit 51 includes a color recognition sensor control unit 51a, a color recognition unit 51b, an irradiation condition setting unit 51c, a printing control unit 51d, and a conveying device control unit 51e. The color recognition sensor control unit 51a activates the color recognition sensor 36 based on the information about the position of the metal container 100 to be laser-marked on the conveying device 40 obtained from the conveying device control unit 51e. The color recognition sensor 36 is, for example, a reflective photoelectric sensor, and obtains the color information of the surface of the metal container 100 by using reflected light, and sends it to the color recognition unit 51b. The color recognition unit 51b reads the information of the color information data 52a of the specimen stored in the storage unit 52, compares it with the color information obtained by the color recognition sensor 36, and sends it to the irradiation condition setting unit 51c. In the irradiation condition setting unit 51c, the irradiation condition is read from the irradiation condition data 52b of the storage unit 52 according to the result of the comparison of the color information, and sends it to the printing control unit 51d. If there is a change in the printing design, the printing control unit 51d reads the printing design from the printing design data 52c and sends it to the processing head 31 together with the irradiation conditions.

[0057] The printing control unit 51d issues a command to execute laser marking to the processing head 31 based on the position information of the metal container 100 to be laser marked obtained from the conveying device control unit 51e. Figure 5In the above, the conveying device control unit 51e obtains information related to the operation of the conveying device 40 from the conveying device 40, but for example, the position of the metal container 100 may be detected by a sensor as the information related to the operation of the conveying device 40. The conveying device control unit 51e at least sends information related to the position of the metal container 100 to be laser marked to the printing control unit 51d. In addition, the conveying device control unit 51e sends information related to the position of the metal container 100 to be color-recognized to the color recognition sensor control unit 51a. The conveying device control unit 51e receives information on the completion of laser marking by the processing head 31 from the printing control unit 51d, and operates the conveying device 40.

[0058] Figure 6 This is an example of a flow chart of the control of the laser marking process of the manufacturing device 90 of the metal container 100 according to the first embodiment. When the metal container 100 to be laser marked on the conveying device 40 reaches a predetermined position, Figure 4 When the color recognition sensor 36 reaches position A of the target metal container 100, the color recognition sensor 36 acquires the color information of the surface (step S1). The color recognition unit 51b checks the color information of the surface of the target metal container 100 with the color information data of the specimen, and determines which data of the color information data of the specimen the surface of the target metal container 100 matches. Based on the result of the determination, the irradiation condition setting unit 51c reads the irradiation condition from the irradiation condition data 52b (step S2). When the irradiation condition matches the irradiation condition of the metal container 100 that was laser-marked before the target metal container 100 (in the case of yes in step S3), the irradiation condition setting unit 51c does not output the irradiation condition to the printing control unit 51d (step S4). In addition, when the irradiation condition does not match the irradiation condition of the metal container 100 that was laser-marked just before the target metal container 100 (in the case of no in step S3), the irradiation condition setting unit 51c outputs the new irradiation condition to the printing control unit 51d (step S5).

[0059] Next, if there is no instruction to change the printing design (in the case of YES in step S6), the printing control unit 51d does not acquire the printing design but maintains the already set printing design (step S7). Alternatively, if there is an instruction to change the printing design (in the case of NO in step S6), the printing control unit 51d acquires a new printing design from the printing design data 52c (step S8).

[0060] Next, the printing control unit 51d receives information from the conveying device control unit 51e that the metal container 100 to be laser-marked has reached an appropriate position, and issues an instruction to the processing head 31 to execute printing. At this time, the printing control unit 51d appropriately rewrites the instruction content according to the irradiation conditions and printing design set in the process from step S3 to step S8, and instructs the processing head 31 (step S9). In addition, the change of the printing design can be performed manually from an input device (not shown), for example, or it can be pre-programmed in the control device 50 according to the manufacturing plan.

[0061] In implementation mode 1, if Figure 4 As shown, it will be in the position for laser marking ( Figure 4 Position B) Near the front position ( Figure 4 The metal container 100 at position A) is taken as the object, and the color of the surface of the tube 101 is detected by the color recognition sensor 36. That is, Figure 6 The steps S1 to S8 shown in the figure are performed when the metal container 100 to be laser marked is set to Figure 4 By configuring in this way, the manufacturing device 90 preliminarily recognizes the color of the metal container 100 to be laser-marked, and preliminarily completes the setting of the irradiation conditions when the metal container 100 reaches the position to be irradiated with the laser 30, thereby shortening the overall tact time of the laser marking process. Furthermore, the printing by laser marking can be completed without increasing the overall tact time of the metal container 100.

[0062] In addition, the color recognition sensor 36 is not limited to Figure 4 The metal container 100 at position A in the laser marking process can be identified as an object, for example, at position B where the laser marking process is performed. However, when the color is identified at position B, the time the metal container 100 stays at position B increases. Figure 6 The portion of time for the process from step S3 to step S8 shown.

[0063] Figure 7 The following are examples of the coloring of the metal container 100 according to the first embodiment, the paint and the components contained therein, and the coloring of the printing portion 10 using the paint colors. The paint colors include DM-1 to DM-14, which are standard paint colors for barrels and cans, and two other colors specified by the user. The color of the color-changing portion 22 formed by irradiation with the laser 30 is different for each paint color.

[0064] The color in the color-changing portion 22 is mainly formed by (1) foaming, (2) condensation, (3) carbonization, and (4) chemical changes. (1) For foaming, if the coating layer 21 is irradiated with laser 30, bubbles are generated in the base material due to its thermal effect, and the base material bulges whitely. In particular, in a dark-colored paint, the coating color is changed to a light color, which improves visibility. (2) For condensation, if the coating layer 21 is irradiated with laser 30, the molecular density of the coating layer 21 is increased due to its thermal effect, and the coating layer 21 condenses and changes to a dark color. (3) For carbonization, if the coating layer 21 is irradiated with laser 30, the irradiated portion of the coating layer 21 is carbonized and changes to black. (4) For chemical changes, the color changes due to the following phenomenon. Since the coating layer 21 contains a pigment substance containing metal ions, the irradiation of the laser 30 causes a change in the valence of the metal ions, a change in the crystal structure, a change in the hydration amount in the crystal, etc. As a result, the state of the components contained in the coating layer 21 changes, and color is generated. The chemical change also includes a form in which the light energy of the laser 30 causes the metal compound contained in the coating layer 21 to undergo a photochemical change, and the mechanism will be described later.

[0065] Figure 7 The "Printing Color Change" column shows that each coating color changes to either black (a color that makes each coating color darker) or white (a color that makes each coating color lighter). Whether the color of either the dark color or the light color is easy to be seen depends on each coating color. For example, DM-1 is a white coating, and the coating layer 21 is discolored to a dark color (black) by laser 30, and the discolored portion 22 is easy to be seen. On the other hand, DM-2 is a black coating, and the coating layer 21 is discolored to a light color (white) by laser 30.

[0066] in addition, Figure 7 The right column of the table shows the main compounds contained in the coating layer 21 and their amounts, and describes the range of the ratio of the content.

[0067] The paint colors other than DM-2 and DM-12 among DM-1 to DM-14, which are standard paint colors for barrels, and the paint color designated by the user B contain titanium dioxide as a component. Titanium dioxide is chemically changed into titanium pentoxide by irradiation with the laser 30. Titanium dioxide is mainly white, and changes into dark colors such as black gray and reddish brown by chemically changing into titanium pentoxide. Therefore, the paint color containing titanium dioxide as a component has a tendency that the color change portion 22 changes into a relatively black or dark color.

[0068] The paint colors DM-2, DM-3, and DM-9 contain carbon black as a component. Carbon black easily changes the paint layer 21 to white by foaming.

[0069] Among the paint colors, DM-8, DM-9, DM-12, DM-13, and the paint color designated by the user B contain yellow iron oxide as a component. In addition, the paint colors DM-5, DM-13, and the paint color designated by the user A contain iron oxide as a component. Yellow iron oxide and iron oxide are changed into ferrous oxide or ferroferric oxide by irradiation with the laser 30. Ferrous oxide and ferroferric oxide are black, and have a tendency to change the color change portion 22 of the paint layer 21 into black or dark color.

[0070] Figure 7 Each of the coating colors shown forms a discolored portion 22 mainly through the change of the above-mentioned components. The discolored portion 22 is formed in the portion irradiated with the laser 30, but the degree of coloring varies according to the intensity of the laser 30, the focal position of the laser 30, and the scanning speed of the laser 30. For example, the more energy of the laser 30 irradiated per unit area, the stronger the above-mentioned discoloration appears. For the focal position of the laser 30, even if the intensity of the laser 30 is the same, if the focus is not aligned, the energy irradiated per unit area is reduced, so the discoloration can be suppressed. In addition, if the scanning speed is increased, the energy irradiated per unit area is reduced, so the discoloration can be suppressed. In the metal container 100 involved in embodiment 1, the visibility of the printed portion 10 under each coating color can be ensured, and adjustment is made so that the time spent on the laser marking process does not increase.

[0071] Figure 8 This is an example of the appearance of the printing portion 10 of the metal container 100 . Figure 8 (a) is correct Figure 7 The example of the color change portion 22 when the paint color DM-1 is laser marked is shown. Figure 8 (b) is correct Figure 7 The paint color DM-2 shown is an example of a color change portion when laser marking is performed. Figure 8 (c) is correct Figure 7 The paint color DM-5 shown is an example of a color change portion when laser marking is performed. Figure 8 The table of color change samples (a), (b), and (c) is created by changing the output, scanning speed, and focus position of the laser 30. The sample of the coating color DM-1 is white, which is a relatively bright color, and changes color to a dark color by irradiation with the laser 30, forming a color change portion 22. In addition, the sample of the coating color DM-2 is black, and changes color to a light color by irradiation with the laser 30, forming a color change portion 22.

[0072] In addition, the example of implementation mode 1 is to make a sample by using MD-U1020C manufactured by Keyence Corporation. The laser is a YVO4 laser with a wavelength of 355nm and an output of 2.5W (at 40kHz). The printable range is 330mm×330mm in the vertical and horizontal directions and 42mm in the depth direction. That is, the barrel 101 of the metal container 100 becomes a cylindrical surface with a depth in the irradiation direction of the laser 30, and if it is within the range of 42mm in the depth direction, it can be printed by the laser 30. The sample is formed on a steel plate arranged in the above-mentioned printable range. Figure 7 The coating layer 21 of each coating color shown is obtained. Fig.10 Samples No. 27 to No. 30 using IR laser were produced by using MD-X1020 manufactured by Keyence Corporation. The laser was YVO4 laser with a wavelength of 1064 nm and an output of 13 W. The printable range was 330 mm × 330 mm in the vertical and horizontal directions and 42 mm in the depth direction.

[0073] exist Figure 8 In the table printed on the color change sample, the color change portion 22 shown in each column of symbols "A" to "O" allocated in the left and right directions is obtained by irradiating with the focus spot diameter of the laser 30 varied from -21mm to +21mm. The center "H" column is obtained by irradiating with the focus spot diameter minimized, that is, with the focus on the surface 23.

[0074] In the right Figure 8 In the table printed on the color change samples in the upper section (a-1) and (b-1) of (a) and (b), the symbols in rows "1" to "5" indicate that the scanning speed of the laser 30 is changed to 2000 mm / min to 6000 mm / min, and the scanning speed of the sample in row "5" is faster.

[0075] In the right Figure 8 In the table printed on the color change samples in the lower section (a-2) and (b-2) of (a) and (b), the symbols in rows "1" to "5" indicate that the output of the laser 30 is changed to 60% to 100%, and the output of the sample in row "5" is larger.

[0076] First, for any color-changing sample, the color-changing portion 22 of the sample in the "H" column arranged in the left-right direction changes less. This is because the focused spot diameter of the laser 30 is small, the color-changing range becomes smaller, and the area of ​​overall color change becomes smaller. The processing head 31 sets the laser 30 to pulse for irradiation. If the focus is on the surface 23, the area of ​​the surface 23 irradiated with the laser 30 for each point of the pulse is small, and the color-changing portion 22 is difficult to recognize. On the other hand, as the focused spot diameter increases toward the "A" column or the "O" column of the color-changing sample, the focused spot diameter increases, and therefore, the area of ​​the surface 23 irradiated with the laser 30 for each point of the pulse is large, and the color-changing portion 22 is easy to recognize. However, due to the relationship between the output of the laser 30 and the focused spot diameter, if the energy received per unit area of ​​the surface 23 becomes lower, the color change becomes lighter and difficult to recognize. For example, in the tables of the color-changing samples in the lower rows (a-2) and (b-2), the color-changing portions 22 are difficult to recognize at "1A", "1O" and the vicinity thereof.

[0077] If you watch Figure 8 As can be seen from the upper sections (a-1) and (b-1) of (a) and (b), as the scanning speed increases, the energy received per unit area of ​​the surface 23 decreases, and the color becomes lighter.

[0078] If you watch Figure 8 As can be seen from the lower sections (a-2) and (b-2) of (a) and (b), when the output of the laser 30 decreases, the energy received per unit area of ​​the surface 23 decreases, and the color becomes thinner.

[0079] In addition, if Figure 8 As shown in (c), in the example of the color change portion 22 when laser marking is performed on the coating color DM-5, the tendency of the color change portion 22 shown in each column of the symbols "A" to "O" assigned in the left and right directions is the same as the above-mentioned DM-1 and DM-2. The color of the "H" column is the lightest, and the color becomes darker as it goes toward the "A" column or the "O" column. However, in the case of DM-5, since the coloration due to bubbling and the coloration due to chemical changes occur simultaneously, there is a change in which the coloration due to bubbling (white) or the coloration due to chemical changes (black) is dominant depending on the scanning speed and intensity conditions of the laser 30. As for the tendency of coloration, if the energy of the laser 30 received per unit area of ​​the surface 23 increases, white is dominant, and if the energy is low, black is dominant. If the output of the laser 30 is 100%, white is dominant in almost the entire area of ​​the "A" column to the "O" column where the focus spot diameter changes. In addition, in DM-15, although the color (white) due to foaming and the color (black) due to chemical changes are generated, black is dominant in the entire area.

[0080] Fig. 9 The figures show examples in which laser marking was performed on each paint color and the evaluation results thereof. Fig.10 The figure shows an embodiment and a comparative example in which printing such as laser marking is performed for each coating color and the evaluation results thereof. By using the manufacturing method of the metal container 100 having the above-mentioned laser marking process, the coating layer 21 is irradiated with a laser 30 for each coating color, and the depth of the discolored portion 22 and the thickness of the undiscolored portion of the coating layer 21 (the distance from the discolored portion 22 to the base material 20) are measured, and their visibility, rust resistance, and abrasion resistance are evaluated. The visibility, rust resistance, and abrasion resistance are evaluated on a scale of "1" to "5", and a level of "3" or above is a qualified standard.

[0081] The visibility evaluation standard is a standard that evaluates the ease of visual recognition at a distance of 1 meter. At a distance of 1 meter, level "1" means that the text cannot be recognized, level "2" means that it is difficult to recognize 10mm text, level "3" means that 10mm square text can be recognized, level "4" means that 10mm square text can be clearly recognized, and level "5" means that 5mm square text can be clearly recognized.

[0082] The evaluation standard for rust resistance refers to the standard obtained by peeling off the tape after the sample has been subjected to the salt spray test for the specified time described below and observing the difference in peeling between the printed part and the non-printed part. Level "1" means that peeling of the printed part becomes noticeable by peeling off the tape after 120 hours of salt spray test, level "2" means that peeling of the printed part becomes noticeable by peeling off the tape after 168 hours of salt spray test, level "3" means that there is no difference between the printed part and the non-printed part by peeling off the tape after 168 hours of salt spray test, level "4" means that there is no difference between the printed part and the non-printed part by peeling off the tape after 240 hours of salt spray test, and level "5" means that there is no difference between the printed part and the non-printed part by peeling off the tape after 336 hours of salt spray test.

[0083] The abrasion resistance refers to the evaluation of the state of the printing for a specified number of times by rubbing the printed surface with a friction part applying a load of 1 kg through a grinding test. The surface of the friction part is made of felt. Level "1" means that more than half of the printing is missing until 10 reciprocating times, level "2" means that more than half of the printing is missing until 50 reciprocating times, level "3" means that the printing can be recognized even though part of the printing is missing after 50 reciprocating times, level "4" means that the printing can be recognized even though part of the printing is missing after 100 reciprocating times, and level "5" means that there is no part of the printing missing after 100 reciprocating times.

[0084] In addition, about Fig. 9 as well as Fig.10 The irradiation conditions of the laser beam 30 included therein include the laser beam output [W], scanning speed [mm / sec], distance variable amount [mm], and number of overlapping printing times [times]. Fig. 9 as well as Fig.10 The evaluation results of each of No. 1 to No. 31 shown are a collection of results of evaluating a plurality of samples, and irradiation conditions and evaluation results are shown with some margin.

[0085] exist Fig. 9 In the embodiment shown, in the case of coloration of the coating layer 21 due to foaming or photochemical reaction, even the coloration of the extreme surface layer where the color-changing portion 22 is 0.3 μm or more and 2.5 μm or less can be visually recognized. In addition, in the case of coloration due to foaming or photochemical reaction, if the color-changing portion 22 is 2.5 μm or more and 10 μm or less, there is a tendency for higher visibility. However, in the case of coloration due to foaming, as can be seen from samples No. 3, 4, 12, and 13, a certain degree of depth of the color-changing portion 22 is required. Therefore, if the depth of the color-changing portion 22 is shallow, there is a tendency for visibility to be unfavorable compared to the case of coloration due to chemical changes.

[0086] exist Fig. 9 In the examples shown, the rust resistance satisfies the standard when the thickness of the non-discolored portion is 2.5 to 5 μm, and the rust resistance is higher when the thickness is 5 μm or more. However, in the case of discoloration due to photochemical reaction, there is a tendency that the rust resistance is high even when the thickness is 2.5 to 5 μm (comparison of samples No. 1 to 9 and No. 10 to 18). This is because the example has a bonus point that the coating layer 21 is less damaged.

[0087] exist Fig. 9 In the embodiment shown, when the color change is caused by a photochemical reaction, the polishing resistance tends to be evaluated high regardless of the depth of the color change. However, when the color change is caused by carbonization, the color change portion 22 bleeds due to friction, so although the acceptable standard is met, the evaluation is not high.

[0088] exist Fig.10 In the samples No. 19 to No. 22 shown in the figure, although the laser 30 in the UV wavelength region is used, the thickness of the coating layer 21 other than the discolored portion 22 (non-discolored layer) is thin, and sometimes the rust resistance does not meet the qualified standard (refer to samples No. 19 to No. 22). Fig. 9The embodiment shown is inferior in visibility, rust resistance and abrasion resistance, but is superior in abrasion resistance to the stamp printing shown in No. 31. In addition, the samples No. 19 to No. 22 are laser-marked without using ink, etc., and therefore, compared with stamp printing and other printing using ink, etc., there is no white spot due to insufficient supply of ink, etc. during the printing process, and the printing is clearer than the sample shown in No. 31.

[0089] In addition, Fig.10 In the samples No. 23 to No. 26 shown in the figure, although the laser 30 in the UV wavelength region is used, the thickness of the color changing portion 22 is thin (0.1 μm to 0.3 μm). Fig. 9 The examples shown in the figure have a tendency to have low visibility and abrasion resistance. Furthermore, for samples No. 23 to No. 26, which are colored by foaming, their abrasion resistance is lower than that of samples that are colored by chemical changes. Fig. 9 Although the embodiment shown is inferior in visibility, rust resistance and abrasion resistance, it is advantageous in abrasion resistance compared with the seal printing shown in No. 31 in terms of the structure of color change caused by chemical change. In addition, samples No. 23 to No. 26 are also laser marked like samples No. 19 to No. 22, and no white spots will appear in the printing process, which is superior to the sample shown in No. 31 in terms of clear printing.

[0090] Fig.10 The samples No. 27 to No. 30 are printed by carbonization or foaming of the coating resin accompanied by heat using IR (infrared) laser. Therefore, in these samples, it is difficult to control the depth dimension of the discolored portion 22 within 5 μm from the surface 23. The depth of the discolored portion 22 is more than 5 μm, and the thickness of the coating layer 21 other than the discolored portion 22 is easily thinned, and the rust resistance and abrasion resistance are reduced.

[0091] Fig.10 The sample No. 31 is a stamp printing type. In this case, since the ink is placed on the surface of the coating layer 21, the standards for visibility and rust resistance are met. However, since the polishing resistance depends on the strength of the ink, the standards are not met.

[0092] The printed portion 10 of the metal container 100 according to the first embodiment can ensure visibility, rust resistance, and abrasion resistance by laser marking the depth of the discolored portion 22 to be 0.3 μm or more and 10 μm or less from the surface. Furthermore, laser marking can be performed so that the depth of the discolored portion 22 is set to be 0.3 μm or more and 2.5 μm or less from the surface, thereby ensuring visibility, rust resistance, and abrasion resistance.

[0093] In the printed portion 10 of the metal container 100 according to Embodiment 1, it is preferred that the thickness of the coating layer 21 other than the discolored portion 22 (non-discolored layer) is at least 2.5 μm. This maintains good rust resistance and polishability of the printed portion 10.

[0094] The printed portion 10 of the metal container 100 according to the first embodiment is formed by discoloration due to chemical change or foaming using laser light 30 in the wavelength region of visible light or UV, so that the depth of the discolored portion 22 can be controlled from the surface, and the depth of the discolored portion 22 can be appropriately ensured while ensuring visibility. In addition, the printed portion 10 of the metal container 100 according to the first embodiment has an advantage over discoloration due to carbonization in that discoloration due to chemical change, and has high abrasion resistance.

[0095] The printed portion 10 of the metal container 100 according to the first embodiment is formed mainly by discoloration due to chemical changes or foaming by using laser light 30 in the wavelength region of visible light or UV, so that the depth of the discoloration portion 22 is not too deep, and the thickness of the non-discoloration layer can be sufficiently ensured to ensure rust resistance and polishing resistance. Therefore, the metal container 100 does not need to increase the thickness of the coating layer 21 in order to ensure the durability of the printed portion 10. In the case of laser marking using IR laser, it is necessary to form the printing by foaming or carbonization in order to ensure the necessary visibility, so it is difficult to control the depth of the discoloration portion 22 within the range of 0.3 μm or more and 10 μm or less. As can be seen from the samples No. 27 to No. 30 of the comparative example, the discoloration portion 22 becomes darker and the non-discoloration layer becomes thinner. Therefore, the printed portion using IR laser tends to have a thinner non-discoloration layer than the printed portion 10 of the metal container 100 according to the first embodiment, and is inferior in rust resistance and polishing resistance.

[0096] Fig.11 This is an example of the result of component analysis using X-ray reflection analysis of the discolored portion in the printed portion 10 of the metal container 100 according to the first embodiment. Fig.11 (a) shows the analysis result obtained by X-ray reflection method when X-rays are incident on the coating layer 21 before discoloration. Fig.11 (b) shows the results of X-ray reflection analysis in which X-rays are made incident on the discolored portion 22 of the coating layer 21 after the discoloration. Fig.11 As an example, the results of component analysis of the color-changing portion 22 before and after irradiation with the laser beam 30 of the paint color DM-5 are shown. Figure 7 As shown, the coating layer 21 contains 10 to 15% of iron oxide as a component. The coating layer 21 of DM-5 mainly changes color to black by irradiation with the laser 30, but if the intensity of the laser 30 is high, the foaming of the coating layer 21 takes precedence and changes color to white. In addition, Fig.11 The line graphs shown on the upper side of (a) and (b) are X-ray reflection patterns of the measurement results obtained from the sample. Fig.11 The columns shown below (a) and (b) show the crystalline phases determined from the measurement results. Column P shows the position and intensity of the fold line of iron oxide (Fe2O3), and column Q shows the position and intensity of the fold line of ferrous oxide (FeO). Fig.11 The horizontal axis of (a) and (b) represents the folding angle 2θ (°), and shows a range of 5° to 70°. Fig.11 The vertical axes of (a) and (b) show the intensity (CPS) of the reflected X-rays, and show a range of 0 to 2000 CPS.

[0097] Compare Fig.11 In (a) and (b), ferrous oxide (FeO) which did not exist before the irradiation of the laser 30 appears after the irradiation {refer to Fig.11 In addition, after irradiation, the peak of iron oxide (Fe2O3) attenuates {refer to Fig.11 That is, the following reduction reaction occurs in the coating layer 21 of DM-5 by irradiation with the laser beam 30 .

[0098] Fe2O3+e-→2FeO+1 / 2O 2－ …(Formula 1)

[0099] The iron oxide is reduced to ferrous oxide by irradiation with the laser light 30. Therefore, the color-changing portion 22 appears black.

[0100] Fig.12 This is an example of the result of component analysis using X-ray reflection analysis of the discolored portion in the printed portion 10 of the metal container 100 according to the first embodiment. Fig.12 (a) shows the analysis results obtained by X-ray reflection method when X-rays are incident on the coating layer 21 before discoloration. Fig.12 (b) is an X-ray reflection analysis result obtained by causing X-rays to enter the discolored portion 22 of the coating layer 21 after the discoloration. Fig.12 The results of component analysis of the color-changing portion 22 before and after irradiation with the laser beam 30 of the paint color DM-12 are shown. Figure 7As shown, the coating layer 21 contains 5 to 10% yellow iron oxide as a component. The coating layer 21 of DM-12 mainly changes color to black by irradiation with the laser 30, but if the intensity of the laser 30 is strong, the foaming of the coating layer 21 sometimes takes precedence and changes color to white. In addition, Fig.12 The line graphs shown on the upper side of (a) and (b) are X-ray reflection patterns of the measurement results obtained from the sample. Fig.12 The columns shown below (a) and (b) show the crystalline phases determined from the measurement results. The P column shows the position and intensity of the fold line of iron oxide (Fe2O3), the Q column shows the position and intensity of the fold line of ferrous oxide (FeO), and the R column shows the position and intensity of the fold line of yellow iron oxide (Fe2O3·H2O). Fig.12 The horizontal axes of (a) and (b) show the folding angle 2θ (°), and show a range of 5° to 70°. Fig.12 The vertical axes of (a) and (b) show the intensity (CPS) of the reflected X-rays, and show a range of 0 to 2000 CPS.

[0101] If you compare Fig.12 (a) and (b), the ferrous oxide (FeO) that did not exist before the irradiation of the laser 30 appears after the irradiation {refer to Fig.12 In addition, after irradiation, Fe 3+ The peak attenuation of O(OH) Fig.12} in (a) and (b) R column. That is, the following reduction reaction occurs in the coating layer 21 of DM-12 by irradiation with the laser beam 30 .

[0102] Fe2O3·H2O+e-→2FeO+1 / 2O 2－ +H2O

[0103] …(Formula 2)

[0104] Yellow iron oxide (Fe2O3·H2O) is reduced to ferrous oxide by irradiation with the laser beam 30. Therefore, the color-changing portion 22 appears black.

[0105] Fig.13 This is a schematic diagram for explaining the reduction reaction of Fe2O3 by laser irradiation of the printing portion 10 of the metal container 100 according to the first embodiment. Fig.11 as well as Fig.12The analysis results shown in the figure show that the iron oxide and yellow iron oxide contained in the coating layer 21 are reduced by the irradiation of the laser 30. Since the light energy hν of the laser 30 is larger than the band gap (i.e., energy gap) Eg of the substance (here, the iron oxide and the yellow iron oxide), the electrons in the valence band (i.e., the valence band) are excited by the conduction band (i.e., the conduction band) to become free electrons, and a reduction reaction occurs. In addition, h is Planck's constant, and ν is the vibration number of the laser 30.

[0106] Fig.14 This is an example of the laser beam irradiated to the metal container 100 according to the first embodiment. Fig. 9 In the illustrated embodiment, the laser 30 used for irradiation is a YVO4 laser in the UV wavelength region (355 nm), and the light energy hν is 3.49 eV.

[0107] Fig.15 The band gap of the substance contained in the coating layer 21 of the metal container 100 according to Embodiment 1 is shown. Generally, in semiconductors and insulators, the energy level from the outermost layer of the valence band to the bottom of the conduction band is large, and in order to transfer electrons from the valence band to the conduction band, it is necessary to absorb energy (light or heat) above the band gap Eg. For example, Fig.11 In the case of the coating layer 21 of the coating color DM-5 whose analysis results are shown in FIG, the band gap of the iron oxide contained therein is 2.0 to 2.2 eV. Therefore, if the laser 30 of the manufacturing device 90 involved in the first embodiment is used, the light energy hν exceeds the band gap of the iron oxide, and the coating layer 21 can undergo a reduction reaction. In addition, the laser 30 of the manufacturing device 90 involved in the first embodiment can undergo a reduction reaction of the coating layer 21 even if the output is suppressed, and it can be adjusted so that the blackening caused by the photochemical reaction is dominant over the whitening caused by the foaming.

[0108] in addition, Fig.14 The YAG laser or YVO4 laser with a wavelength of 532 nm, or the argon laser with a wavelength of 488 nm, 514.4 nm, or 315 nm shown above can also cause the iron oxide to undergo a reduction reaction in the same manner as described above. That is, if the light energy hν of the laser 30 exceeds the band gap of the color-changing substance contained in the coating layer 21, the laser 30 with a wavelength in the visible light region can also be used. In other words, the above Fig. 9 In the embodiment shown, even if the laser light 30 in the visible wavelength region is used instead of the laser light 30 in the UV wavelength region, color development by photochemical reaction can be achieved.

[0109] On the other hand, Fig.14 In the case of the laser 30 with a wavelength of 1064 nm or 10600 nm, for example, Fig.15Since the light energy hν is smaller than the band gap of the material shown in FIG. 1, the color change caused by the reduction reaction shown in the above (Formula 1) and (Formula 2) does not occur. In this case, the heat energy of the laser 30 carbonizes or foams the resin constituting the coating layer 21, causing the color change.

[0110] In addition, if the light energy hν is high, a 355nm YAG laser or a YVO4 laser can also promote Figure 7 The chemical reaction of titanium dioxide (TiO2) contained in the paint colors DM-1 to DM-14 except DM-2 and DM-12 and the paint color designated by the user B is shown.

[0111] As described above, according to the metal container 100, the manufacturing device 90 of the metal container 100, and the printing method of the metal container 100 involved in the first embodiment, since the color-changing portion 22 can be provided on the coating layer 21 by laser marking, it is possible to suppress the disappearance of the printing due to, for example, the transportation and use of barrels and cans. For example, in the case where the printing portion 10 is formed by means of a stamp, screen printing, etc., ink for identification display is provided on the surface of the coating layer 21, and therefore, the ink is easily shed due to friction, etc., and the durability of the printing portion 10 is low. On the other hand, the printing portion 10 involved in the first embodiment using laser marking is Fig. 9 As shown, it is excellent in visibility, rust resistance and abrasion resistance.

[0112] In addition, according to the metal container 100, the manufacturing device 90 of the metal container 100, and the printing method of the metal container 100 according to the first embodiment, the discolored portion 22 is provided in the region of the coating layer 21 that is 5 μm or less from the surface 23, so that the metal of the base material 20 of the metal container 100 is not damaged. In addition, the base material 20 is not exposed in the laser marking process, and the thickness of the undiscolored coating layer 21 from the discolored portion 22 to the surface of the base material 20 can be sufficiently ensured. Therefore, even if the metal container 100 is used for a long time, damage such as corrosion due to rust from the printing portion 10 can be suppressed.

[0113] In addition, according to the metal container 100, the manufacturing device 90 of the metal container 100, and the printing method of the metal container 100 involved in the first embodiment, since the laser 30 of the visible light or UV wavelength region is used, at least one substance contained in the coating layer 21 is chemically reacted by the light energy hv to change color, so that not only the damage of the base material 20 but also the damage of the coating layer 21 itself can be suppressed. The coating layer 21 contains a resin constituting the paint, Figure 7 The coating layer 21 of each coating color shown may contain aminoalkyd resin as an example. In addition, the coating layer 21 is preferably 30 μm or less, and more preferably 20 μm or less in consideration of the surface strength, weight and cost of the coating layer 21.

[0114] In addition, since the laser marking process directly changes the color of the coating layer 21, no consumables such as ink or cleaning fluid are required, and thus there is an advantage of no consumables and no management costs for consumables. In addition, by arranging multiple processing heads 31 for laser marking and processing the printing part 10 in one process, even if the area of ​​the printing part 10 is large and the amount of printed information is large, it will not affect the production cycle time of the metal container 100 and a high-precision printing part 10 can be obtained. Furthermore, the laser marking process uses a plurality of processing heads 31 for laser marking to process the printing part 10 in one process. Fig.14 The metal container 100 includes a discolored portion 22 formed by a photochemical reaction using the light energy hv of the laser 30 using a YAG laser, a YVO4 laser, or an argon laser in the wavelength region shown. Therefore, the printed portion 10 changes the color of only a portion of the coating layer 21 for identification display, etc., without impairing the performance of the metal container 100. In addition, the discolored portion 22 of the metal container 100 is not limited to the discolored portion formed only by the photochemical reaction, and may also include the discolored portion formed by other chemical reactions.

[0115] The metal container 100 according to the first embodiment has the printed portion 10 on the side surface of the tube portion 101 , but the printed portion 10 may be provided on the lid portion 102 .

[0116] The present invention has been described above based on the embodiments, but the present invention is not limited to the configuration of the above embodiments. In particular, the combination of constituent elements is not limited to the combination of the embodiments, and the constituent elements described in each embodiment can be appropriately changed. In addition, for the sake of caution, for example, the key points (technical scope) of the present invention also include the scope of various changes, applications, and utilizations that can be realized by the so-called technicians in this field as needed.

[0117] Description of Reference Numerals

[0118] 10 printing unit, 20 base material, 21 coating layer, 22 color changing unit, 23 surface, 30 laser, 31 processing head, 32 positioning fixture, 33 fixture, 34 shooting device, 35 irradiation range, 36 color recognition sensor, 40 conveying device, 50 control device, 51 control unit, 51a color recognition sensor control unit, 51b color recognition unit, 51c irradiation condition setting unit, 51d printing control unit, 51e conveying device control unit, 52 storage unit, 52a specimen color information data, 52b irradiation condition data, 52c printing design data, 90 manufacturing device, 100 metal container, 101 cylinder, 102 cover, 102A cover, 102B cover, 103 opening, 104 opening, 105 annular rib, 106 part, 107 curling.

Claims

1. A metal container, wherein: The metal container includes a main body made of metal, the main body having a cylindrical portion and a cover portion attached so as to close both ends of the cylindrical portion. The main body is formed with a coating layer constituting the outer surface of the main body. The main body includes a color-changing portion provided to change the color of a portion including a surface of the coating layer by laser light having a wavelength of visible light or UV.

2. The metal container according to claim 1, wherein: The color-changing portion is formed in a range of 0.3 μm to 10 μm from the surface of the coating layer.

3. The metal container according to claim 1 or 2, wherein: The coating layer includes a non-color-changing layer between the color-changing portion and the base material. The non-color-changing layer has a thickness of 2.5 μm or more.

4. The metal container according to any one of claims 1 to 3, wherein The coating layer contains at least one of titanium dioxide, carbon black, yellow iron oxide, iron oxide, copper phthalocyanine, iron hydroxide, and polybrominated copper phthalocyanine chloride as a pigment.

5. The metal container according to any one of claims 1 to 4, wherein The coating layer changes color due to photochemical reduction of a part of the pigment by irradiation with the laser beam.

6. A device for manufacturing a metal container, wherein: The manufacturing apparatus of the metal container includes a processing head for printing on the metal container according to any one of claims 1 to 5, wherein the processing head emits the laser light in the visible light or UV wavelength region.

7. The manufacturing device of a metal container according to claim 6, wherein: The processing head irradiates the laser light having a light energy (hν) larger than a band gap of at least one pigment contained in the coating layer.

8. The manufacturing device of a metal container according to claim 6 or 7, wherein: The processing head includes a plurality of processing heads arranged in an array. Two adjacent processing heads among the plurality of processing heads are arranged so that the irradiable ranges of the laser beam overlap with each other.

9. The manufacturing device for a metal container according to any one of claims 6 to 8, wherein: The manufacturing device of the metal container further comprises: A control device, the control device controls the processing head; and A color recognition sensor recognizes the color of the surface of the coating layer.

10. The manufacturing device of a metal container according to claim 9, wherein: The control device discriminates the type of the coating layer using the color recognition sensor, and irradiates the laser beam at a focal point position corresponding to the type of the coating layer.

11. The manufacturing device of a metal container according to claim 9 or 10, wherein: The control device discriminates the type of the coating layer using the color recognition sensor, and irradiates the laser light at an output corresponding to the type of the coating layer.

12. The manufacturing device for a metal container according to any one of claims 9 to 11, wherein: The control device discriminates the type of the coating layer using the color recognition sensor, and irradiates the laser light at a scanning speed corresponding to the type of the coating layer.

13. The manufacturing device for a metal container according to any one of claims 9 to 12, wherein: The manufacturing apparatus of the metal container further includes a jig that abuts against the metal container and secures the distance between the processing head and the main body.

14. A method for printing on a metal container, the method for printing on a metal container being for printing on the metal container according to any one of claims 1 to 5, wherein: The band gap of at least one pigment contained in the coating layer is smaller than the light energy (hν) of the irradiated laser light.

15. The method for printing characters on a metal container according to claim 14, wherein: The laser beam includes a plurality of laser beams emitted from a plurality of processing heads arranged in an array. The color changing portion is formed by the plurality of lasers.

16. The method for printing characters on a metal container according to claim 14 or 15, wherein: The type of the coating layer is determined based on the color of the surface of the main body. The laser beam is irradiated at a focal point corresponding to the type of the coating layer.

17. The method for printing on a metal container according to any one of claims 14 to 16, wherein: The type of the coating layer is determined based on the color of the surface of the coating layer. The laser beam is irradiated at an output corresponding to the type of the coating layer.

18. The method for printing on a metal container according to any one of claims 14 to 17, wherein: The type of the coating layer is determined based on the color of the surface of the coating layer. The laser beam is irradiated at a scanning speed corresponding to the type of the coating layer.

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