JP2022059729A - Laser decoration method and coated and decorated metal member - Google Patents

Abstract

To suppress a decoration part from discoloring, rusting and so on.SOLUTION: The present invention relates to a manufacturing method for a decorated metal member with a thin film having the following characteristics of a coating layer that includes (process 1) and (process 2) mentioned below. The thin film is characterized in not peeling off even when irradiated with a CO2 laser beam (wavelength: 10,600 nm) under conditions of 30 W output, 100% of power, a scan speed of 10 mm/sec, a painting-out interval of 0.01 mm pitch, and five-time printing (repetitive printing frequency). In (process 1), a metal raw material is a metal base material itself, or the metal base material having a surface processed layer formed thereon, and a coating layer is formed by coating the metal raw material with paint including a pigment or paint including no pigment and drying the paint. In (process 2), light which has a wavelength absorbed by the coating film and hardly absorbed by a metal raw material surface is used and the coating layer is peeled into the thin film for decoration.SELECTED DRAWING: Figure 2

Description

The present invention relates to a laser decoration method.

Laser marking is used as a method of printing a logo, product name, serial number, model number, etc. by irradiating an object with laser light to melt, burn, peel, oxidize, scrape, or discolor the surface. ..
Among these, Non-Patent Document 1 discloses that a technique of laser printing by peeling off the coating, printing, plating, etc. on the surface of an object and producing a contrast with the base color is generally used.

KEYENCE, Marking Cram School, URL https://www.keyence.co.jp/ss/products/marker/lasermarker/basics/laser_marking.jsp

It is conceivable to apply the conventional technique of peeling off the coating film with a laser to a metal member such as a container in which a surface treatment such as a chemical conversion treatment or a coating treatment is applied to the surface of an aluminum base material to form a surface treatment layer. However, when applied to a metal member having a surface-treated surface-treated layer, it was found to affect the surface-treated layer.
That is, when the coating film layer is irradiated with laser light to decorate it with markings or the like, the coating film layer is removed at the irradiation position of the laser light, and further, the surface treatment layer is removed and the aluminum base material is surfaced. There are many cases where it is exposed to. In such a state, it was found that the surface of the exposed aluminum base material turns black (hereinafter referred to as black) when heat sterilization such as retort sterilization is subsequently performed.

An object of the present invention is to deal with such a problem. That is, it is an object of the present invention to suppress discoloration and rust of the decorative portion.

In order to solve such a problem, the present invention has the following configuration as one form.
A method for manufacturing a decorated metal member provided with a thin film having the following characteristics of a coating film layer including the following (step 1) and (step 2). Characteristics: The thin film can be peeled off even if it is irradiated with a CO ₂ laser (wavelength 10600 nm) at an output of 30 W, a power of 100%, a scan speed of 10 mm / sec, a fill interval of 0.01 mm, and a printing count (repetition count) of 5 times. (Step 1) The metal material is the metal base material itself, or a paint or pigment containing a pigment on the metal base material and having a surface treatment layer formed on the metal base material. The process of forming a coating layer by painting with a paint that does not contain the above and drying it. (Step 2) A step of decorating by using light having a wavelength that is absorbed by the coating film layer and having a wavelength that is difficult to be absorbed on the surface of the metal material, and peeling off the coating film layer until it becomes the thin film.

Further, in order to solve such a problem, the present invention has, as another form, a metal material, a coating film layer, and a decorative portion, and the metal material is the metal base material itself or the metal base material. A surface treatment layer is formed, the coating layer is formed on the surface of the metal material, the decorative portion is made of a thin film, and the thin film is a CO ₂ laser (wavelength 10600 nm). ) Is an output of 30 W, a power of 100%, a scan speed of 10 mm / sec, a fill interval of 0.01 mm, and a number of prints (repetition count) of 5 times. I will provide a.

According to the laser decoration method of the present invention having such characteristics and the metal material in which the thin film is left in the decoration portion, it was possible to suppress discoloration and rust of the decorated portion.

Explanatory drawing of decoration by fiber laser (wavelength 1064 nm) (a) Explanation of decoration process of fiber laser (wavelength 1064 nm) and retort sterilization (hot water sterilization) treatment process (b) Decoration by fiber laser (wavelength 1064 nm) Photo (c) Photo before and after retort sterilization (hot water sterilization) by fiber laser (wavelength 1064 nm) Explanatory drawing of decoration by CO ₂ laser (wavelength 10600 nm) (a) Explanatory drawing of decoration process by CO ₂ laser (wavelength 10600 nm) and retort sterilization (hot water sterilization) treatment process (b) CO ₂ laser (wavelength 10600 nm) Photograph immediately after decoration by (c) Enlarged view of the decoration area Explanatory drawing of clear layer (a) Explanatory drawing of Embodiment 1 (b) Explanatory drawing of Embodiment 2 (c) Photograph of Embodiment 1 and photograph of Embodiment 2.

An embodiment of the present invention will be described with reference to the drawings. In the following description, the same reference numerals in different figures indicate parts having the same function, and duplicate description in each figure will be omitted as appropriate.

(Embodiment 1)
Embodiment 1 of the present invention will be described with reference to the drawings. The first embodiment is an example in which an aluminum container having a chemical conversion-treated surface-treated layer L2 is used as a metal member L6.
The metal base material L3 means a metal or an alloy. See FIG. 1 (a). In the case of the metal base material L3 having no surface treatment layer L2, the metal base material L3 becomes the metal material L5. On the other hand, in the case of a metal or alloy having a surface treatment layer L2 such as aluminum, the surface treatment layer L2 and the metal base material (aluminum base material) L3 under the surface treatment layer L2 are collectively referred to as a metal material L5.
The metal member L6 is a member of a product in which a coating film layer L1 is provided on a metal material L5. For example, in the case of an aluminum container, it is painted and becomes a metal member L6.

(Conventional example)
FIG. 1A is an example in which the aluminum container is a metal member L6. The surface of the metal base material (aluminum base material) L3 is subjected to chemical conversion treatment to form a surface treatment layer L2, and a colored coating film layer L1 having a pigment is provided on the surface treatment layer L2. A commonly used fiber laser (wavelength 1064 nm) was used as the decorative laser. In the chemical conversion treatment, a phosphoric acid chromate treatment (CP treatment) was performed to form a surface treatment layer L2 on the surface of the metal base material (aluminum base material) L3, and further to form a coating film layer L1 on the surface treatment layer L2. After the coating film layer L1 was completely dried, a fiber laser (wavelength 1064 nm) was applied to the coating film layer L1.

The result is photographed in FIG. 1 (b). The star shape is accurately decorated. It can be seen that decoration with extremely good visibility can be performed even with complicated shapes. It can be seen that the edge of the decorative area is slightly uneven as a remnant of the laser light of the fiber laser (wavelength 1064 nm) swept by the galvano mirror and the filling interval of 0.1 mm.
However, as shown in the photograph of FIG. 1 (c), the coating film of the decorative portion 2 is completely peeled off. It should be noted that the portion that looks black does not turn black, but only looks black under the shooting conditions (ghost due to light reflection), and the coating film does not exist at all. Then, when retort sterilization (hot water sterilization) is performed as shown in the photograph of FIG. 1 (c), a blackened portion B is generated over the entire decorative portion 2.
When the decorated region of FIG. 1B was examined, the surface-treated layer L2 was damaged by the fiber laser (wavelength 1064 nm), and the surface-treated layer L2 remained slightly in the decorated region, but the metal substrate (the metal substrate (wavelength 1064 nm) was examined. It was found that the aluminum base material) L3 was greatly exposed.

That is, as shown in FIG. 1A, when the treatment is performed with a commonly used decorative fiber laser (wavelength 1064 nm), the surface treatment layer L2 is peeled off, and the metal base material (aluminum base material) L3 is peeled off. The influence of the laser beam will be affected. After that, when retort sterilization (hot water sterilization) treatment is performed, blackening site B occurs. As a result of analyzing the blackening site B, a trace amount of metal ions (Ca, Mg, Si, etc.) contained in the hot water being treated during the retort sterilization may be taken into the metal base material (aluminum base material) L3 and discolored. found. In any case, it was found that the exposed metal base material (aluminum base material) L3, which lost the surface treatment layer L2, caused a reaction during retort sterilization and turned black.

(Discovery by the present inventor)
The discovery of the present inventor will be described.
(Experiment 1)
FIG. 2A is a conceptual diagram using decoration using a CO ₂ laser (wavelength 10600 nm). 2 (b) and 2 (c) are photographs showing the results.
(Step 1) A metal base material (aluminum base material) L3 having a surface treatment layer L2 formed on the surface thereof was used as a metal material L5 and coated on the metal material L5 with a paint containing a pigment.
(Step 2) After that, the paint was baked and dried to obtain a coating film layer L1.

In the decoration by the fiber laser (wavelength 1064 nm), as shown in FIG. 1 (b), all the colored coating film layer L1 having the pigment is peeled off. On the other hand, in the decoration by the CO ₂ laser (wavelength 10600 nm), as shown in the photograph of FIG. 2 (b) and the enlarged photograph of the thin film L4 of FIG. 2 (c), the decoration portion 2 is covered. , Thin film L4 remains. The decoration conditions by the CO ₂ laser (wavelength 10600 nm) at this time were an output of 30 W, a power of 100%, a scan speed of 4000 mm / sec, a fill interval of 0.1 mm pitch, and a printing count (repetition count) of 1 time.
As shown in FIG. 2C, the thin film L4 of the remaining coating film layer L1 was so thin that the metal material surface L5a (surface treatment layer L2) could be seen, and the film thickness was uniform. In taking the photographs of FIGS. 2 (b) and 2 (c), a red paint having a high pigment concentration was intentionally used so that the thin film L4 could be known to be present. ing.

In any case, since the coating layer L1 is so thin that the metal material surface L5a (surface treatment layer L2) can be seen, retort sterilization (hot water sterilization) was performed as shown in FIG. 2A, but black was used. It didn't change at all. If there are even a few holes in the thin film L4, the holes will turn black, so the thin film L4 does not have holes that expose the metal material surface L5a (surface treatment layer L2), resulting in a uniform thin film L4. It was confirmed that it remained.

(Experiment 2)
Therefore, an experiment was conducted to increase the output of the CO ₂ laser (wavelength 10600 nm). As a result, no matter how much the output is increased, the thin film L4 remains in the decorative portion 2 of the colored coating film layer L1 having the pigment, and the coating film layer L1 can be completely peeled off by the CO ₂ laser (wavelength 10600 nm). It turned out to be difficult.

(Experiment 3)
An experiment was conducted to investigate the characteristics of the thin film L4 with respect to the thin film L4 prepared in Experiment 1. The characteristics investigation conditions were a CO ₂ laser (wavelength 10600 nm), output 30 W, power 100%, scan speed 10 mm / sec, fill interval 0.01 mm pitch, and printing count (repetition count) 5 times.
As a result, the thin film L4 did not peel off.
The characteristic investigation conditions are the above-mentioned decorative output conditions: CO ₂ laser (wavelength 10600 nm), output 30 W, power 100%, scan speed 4000 mm / sec, fill interval 0.1 mm pitch, printing count (repetition count) once. By comparison, it turns out that the conditions are very harsh.
Under this condition, the scan speed is extremely slow, the fill interval is 0.01 mm, and the print areas overlap, and the number of prints is 5, and the same print area is irradiated with a CO ₂ laser (wavelength 10600 nm) many times. It is a strict condition.
It was found that the thin film L4 did not peel off even when irradiated under these conditions, and was a thin film L4 having characteristics that could not be peeled off by a CO ₂ laser (wavelength 10600 nm) due to some physical phenomenon.
From Experiment 3, it was found that the characteristic investigation conditions are effective in identifying the thin film L4.

(Experiment 4)
As a result of an experiment to clarify the cause, a CO ₂ laser with a long wavelength (wavelength 10600 nm) has a wavelength that is difficult to be absorbed by the surface treatment layer L2 (absorption rate is larger than 0% and 5% or less). It was found that the wavelength was absorbed by the pigment and the resin contained in the coating film layer L1.
The reason why the coating film layer L1 becomes the thin film L4 and remains thin is that the particle size of the pigment is thinner than the wavelength of the CO ₂ laser (wavelength 10600 nm), so that the diffraction limit is exceeded and it is difficult for light to be absorbed. This is considered to be one of the causes. Moreover, since it is reflected without being absorbed by the surface treatment layer L2, it is conceivable that the coating film layer L1 remains thin. Further, it is presumed that the metal base material L3 has good thermal conductivity, and the thin film L4 remains due to multiple factors such as heat escaping from the metal base material L3.

From the results of Experiment 2, the decoration performed in Experiment 1 has a wavelength that is substantially absorbed by the coating film layer L1, and is hardly absorbed by the surface of the surface treatment layer L2 (metal material surface L5a) (absorption). Using a CO ₂ laser (wavelength 10600 nm) with a wavelength of more than 0% and 5% or less, the coating layer L1 was peeled off leaving the thin film L4 to form a decorated metal member L6. It will be.

(Experiment 5)
In the above experiment, in order to confirm that the thin film L4 of the coating film layer L1 remains, an experiment was carried out in which a colored paint containing a pigment was intentionally applied thickly. The experimental conditions are paint (red paint pigment addition amount 3.2 (PHR), coating film amount 70 mg / dm ² ).
As a result, in the photographs of FIGS. 2 (b) and 2 (c), a considerable amount of pigment remained on the thin film L4, but the lower metal material surface L5a (surface treatment layer L2) was visible through the thin film L4. It was found that the thin film L4 of the coating film layer L1 remained even in the colored coating film layer L1 containing the thick pigment, and it was found that the thin film L4 remaining was irrelevant to the thickness of the coating film layer L1.
We also conducted experiments using paints with low pigment concentrations. Since the concentration of the pigment contained in the remaining coating film layer L1 was low, it was found that the residual pigment was small and the metal material surface L5a (surface treatment layer L2) was clearly visible and the thin film L4 had a uniform film thickness.

From this, it was found that in order to improve the visibility of the decorative portion 2, it can be achieved by applying a thicker paint as the pigment concentration is lowered. That is, by using the thick colored coating layer L1, the color of the coating layer L1 other than the decorative portion 2 becomes darker. On the other hand, since the pigment concentration is low in the region of the thin film L4, the decorative portion 2 becomes a transparent thin film L4. Since the color of the portion of the coating film layer L1 is dark and the color of the portion of the thin film L4 is light, visibility is improved.

(Experiment 6)
Based on the results of Experiment 5, an experiment was conducted to investigate the effects of the amount of pigment added and the amount of coating film. In addition, the colors of the pigments were red, green and black, and the influence of the color on the thin film L4 was investigated. A chemical conversion-treated aluminum plate (material 5182 alloy) was used as the metal material L5 as the experimental material. Then, a colored paint having a predetermined pigment addition amount and coating film amount was applied, and then baked and dried to obtain a coated plate.
As the paint, three colors of paint, a red paint, a black paint, and a green paint, were used.
A CO ₂ laser (wavelength 10600 nm) manufactured by KEYENCE Corporation was used to leave the thin film L4 as the decorative portion 2 (the portion of the thin film L4).
The colors of the painted part and the decorative part 2 (the part of the thin film L4) were measured using L ^* a ^* b ^* value: X-rite (integrating sphere type colorimeter) (manufactured by x-rite). The color difference ΔE ^* between the painted portion and the decorative portion 2 (the portion of the thin film L4) was determined based on the color of the painted portion.
In addition, visual evaluation of visibility was also performed. Visibility The visual evaluation was made as ⊚>○>Δ> × in order from the one in which the decorative portion 2 (the portion of the thin film L4) was most easily visible in each color.
(Experimental result R) Red paint

Experiment R3 to Experiment R5 are common in that the pigment addition amount is 3.2 PHR, and the coating film amount is different. Further, Experiment R6 and Experiment R7 also have a common pigment addition amount of 2.5 PHR, and the coating film amount is different.
From this result, it was found that the color difference ΔE ^* and the visual evaluation of visibility are better when the amount of the coating film is increased in the red paint.
Further, since the visibility is affected by the color difference between the coating film layer L1 and the thin film L4, as in Experiment R3 and Experiment R6, even with the same film thickness of 70 mg / dm ² , the amount of pigment added is small in R6. It was a little inferior.
(Experimental result B) Black paint

In Experiments B3 to B5 and Experiments B6 to B7 using the black paint, it was found that the color difference ΔE ^* and the visual evaluation of visibility were better when the amount of the coating film was increased as in the case of the red paint. The experimental result B using the black paint showed the same tendency as the experimental result R using the red paint.
(Experimental result G) Green paint

In Experiments G3 to G5 and Experiments G6 to G7 using green paint, the color difference ΔE ^* and visual evaluation of visibility may be better when the amount of coating is increased as in the case of red paint and black paint. found. The experimental result G using the green paint showed the same tendency as the experimental result R using the red paint and the experimental result B using the black paint. When the combination of pigments was examined as described above, the wavelength of the CO ₂ laser was examined. Light at 10600 nm was found to be a wavelength absorbed by the pigment regardless of color.
Therefore, it was found that a CO ₂ laser (wavelength 10600 nm) is effective for a very wide range of pigments.
From this result, in principle, any wavelength may be used as long as the laser has a wavelength that is absorbed by the coating film layer L1 and is not easily absorbed by the metal material surface L5a. Do you get it.

Visibility is related to the large color difference ΔE ^* between the coating film layer L1 and the thin film L4. In Experiment 6, by lowering the pigment concentration and using a thick coating layer L1 to compensate for the decrease in the pigment concentration, the measured values of the L ^* , a ^* , and b ^* color spaces of the portion of the coating layer L1 become large. On the other hand, since the thin film L4 has a low pigment concentration, the amount of pigment remaining in the thin film L4 is small, and the measured values of the L ^* , a ^* , and b ^* color spaces of the decorative portion 2 (thin film L4) are small. As a result, it was found that the color difference ΔE ^* between the coating film layer L1 and the decorative portion 2 (thin film L4) became large, and the visibility was improved.
(Summary of experiment)

When the above experimental results R, experimental results B, and experimental results G are combined, the following can be found.
The main components of the paint are pigments, solvents, and coating film components (synthetic resin, etc.), but the solvent does not volatilize and remain in the dried paint. After all, the coating film layer L1 is composed of a pigment, a coating film component (synthetic resin or the like), an additive or the like. The CO ₂ laser (wavelength 10600 nm) is a laser beam having a wavelength at which the pigment is absorbed, and a wavelength at which the coating film component (synthetic resin or the like) is absorbed, though not as much as the pigment. When the coating film layer L1 composed of the pigment and the coating film component (synthetic resin, etc.) is irradiated with a CO ₂ laser (wavelength 10600 nm), the laser beam is absorbed by the pigment and the coating film component (synthetic resin, etc.) and heated. The coating film layer L1 is peeled off. However, the last thin film L4 remained.
It was found that the surface treatment layer L2 did not absorb the laser beam and reflected it.
Finally, the object heated by the CO ₂ laser (wavelength 10600 nm) disappears, and as a result of the coating film components (synthetic resin and the like) and the pigment remaining, the thin film L4 remains.

(principle)
The reason why the coating film layer L1 becomes the thin film L4 and remains thin is that the particle size of the thin film pigment and the thickness of the coating film component (synthetic resin, etc.) are smaller than the wavelength of the CO ₂ laser (wavelength 10600 nm). One of the causes is considered to be that the diffraction limit is exceeded and absorption is difficult. Moreover, since it is reflected without being absorbed by the surface treatment layer L2, it is conceivable that the coating film layer L1 remains thin. Further, it is presumed that the metal base material L3 has good thermal conductivity, and the thin film L4 remains due to multiple factors such as heat escaping from the metal base material L3.

(Characteristics of thin film)
In any case, since the coating layer L1 is so thin that the metal material surface L5a (surface treatment layer L2) can be seen, retort sterilization (hot water sterilization) was performed as shown in FIG. 2A, but black was used. It didn't change at all. If there are even a few holes in the thin film L4, the holes will turn black, so the thin film L4 does not have holes that expose the metal material surface L5a (surface treatment layer L2), resulting in a uniform thin film L4. It was confirmed that it remained.
The thin film L4 can be peeled off even under the conditions of CO ₂ laser (wavelength 10600 nm), output 30 W, power 100%, scan speed 10 mm / sec, fill interval 0.01 mm pitch, and printing count (repetition count) 5 times. It turned out to have the property of not having.
This property has been found to be an effective experimental tool for identifying the thin film L4.

(Presence / absence of surface treatment layer)
As the first embodiment, an aluminum alloy was used as a metal in a number of experiments, and a metal material L5 having a surface-treated layer L2 by phosphoric acid chromate treatment (CP treatment) was used.
However, in principle, it can also be applied to the metal material L5 in which the surface treatment layer L2 does not exist. For example, even if steel (metal material L5) that does not have the surface treatment layer L2 intentionally provided, a thin film is used if a laser having a wavelength that is absorbed by the coating film layer L1 and is hardly absorbed by the steel surface that is the metal material surface L5a is used. It is clear that L4 is left behind. Then, by leaving the thin film L4, it is possible to prevent corrosion of the steel (metal material L5) and the like.

(Application to other than hot water sterilization container)
Further, although the container for retort sterilization has been described in the first embodiment and the experiment, it can also be applied to a retort pouch having an aluminum foil between the resin layers. The metal material L5 may be a thin film coated with a resin or the like.
Furthermore, even if the retort sterilization is not performed, if the exposed metal base material L3 (especially steel) is exposed to dirt or rainwater, corrosion (rust) may proceed, and the container is not limited to the retort sterilization (hot water sterilization) container. , Contributes to the protection of the decorative part 2 of any container.
Further, the present invention is not limited to containers, and can be applied to decoration of any metal material L5 having a coating film layer L1 such as parts and products of various devices.

(Wavelength of light)
Further, in the above-mentioned numerous experiments, a CO ₂ laser (wavelength 10600 nm) was used for decoration, but according to the above-mentioned principle, the wavelength is absorbed by the coating film layer L1 and is absorbed by the metal material surface L5a. The present invention is not limited to a CO ₂ laser (wavelength 10600 nm), as light having a wavelength that is difficult to be used may be used. For example, the metal (alloy) to be decorated can be various, and different types of metal (alloy) have different wavelengths of light that are difficult to be absorbed by the metal material surface L5a. Further, the physical characteristics of the surface treatment layer L2 differ depending on the type of surface treatment, and the wavelength of light that is difficult to be absorbed by the metal material surface L5a also differs.
The present invention can be carried out as long as light having a wavelength that is absorbed by the coating film layer L1 and is difficult to be absorbed by the metal material surface L5a is used.

(Laser light)
According to this principle, the light source (heating source) does not have to be a laser. For example, even if a masking tape is attached on the coating film layer L1 and a lamp in the far infrared region (wavelength 10600 nm) is used, the thin film L4 remains. The decorative part 2 can be obtained.

(Commercialization of decorated metal parts)
As described above, the decorated metal member L6 is made from the painted metal material L5. The metal member L6 becomes a product by inserting or assembling other members or materials. For example, in the case of a decorated beverage can body, the beverage is put in the can body and commercialized. In addition, the decorated metal member L6 can be used to decorate various parts of the can, such as the can body, the panel of the can lid, and the tab of the can lid. Furthermore, the product is not limited to beverage cans, but cans such as food cans (canned foods, etc.) and aerosol cans, regardless of the type of product.

(Embodiment 2)
In order to confirm that the thin film L4 does not depend on the pigment contained in the coating film layer L1, a clear layer C is formed under the coating film layer L1 using a paint containing no pigment at all, and it is confirmed whether the thin film L4 remains. rice field.
In the first embodiment, a blue paint to which a large amount of pigment was added was applied at a film thickness of 45 mg / dm ² in order to clarify the effect, and decoration was performed using a CO ₂ laser (wavelength 10600 nm). FIG. 3A is the first embodiment, and the thin film L4 remains. As a result, the pigment remains in the thin film L4 as shown in the photograph shown as the first embodiment in FIG. 3 (c).
On the other hand, FIG. 3B is the second embodiment. A clear layer C made of a transparent paint is applied on a metal base material L3 so as to be 25 mg / dm ² , and a blue paint in which a large amount of the same pigment as in the first embodiment is added on the clear layer C is 45 mg / dm. ² is applied and the colored coating film layer L1 is overlapped.
In the metal member L6 of the second embodiment, as shown in the photograph of FIG. 3C, almost no pigment remained, and only the thin film L4 made of the clear layer C remained. By forming the clear layer C, the color difference between the colored coating film layer L1 and the decorative portion 2 becomes clear, and the visibility is enhanced. Further, in the second embodiment, since the thin film L4 of the clear layer C remains, it did not turn black even after retort sterilization (hot water sterilization).

The experiment using the clear layer C in the second embodiment was to confirm that the thin film L4 remains even in the clear layer C containing no pigment at all.
It is also possible to intentionally add a small amount of pigment to the clear layer C so that it can be seen through to color it. The clear layer C also contains a substance to which a small amount of pigment is added.

Further, in the second embodiment, it was found that the thin film L4 of the lower layer (clear layer C) remains even if the paint is repeatedly applied. From this result, if paints of different colors are applied repeatedly to form two layers, a thin film L4 in which the pigment of the lower layer paint remains is formed. In that case, it is also possible to intentionally add a large amount of pigment to the lower layer paint and add a pigment having a color different from that of the lower layer to the upper layer to form a two-layer structure. When decoration is performed using a CO ₂ laser (wavelength 10600 nm), a thin film L4 in which the color of the pigment derived from the lower layer, which is different from the color of the upper layer, remains is formed. Since the color of the decorative portion 2 is different from the color of the periphery of the decorative portion 2, visibility can be improved. In addition, it can be a decorative section 2 having a strange taste.

In the second embodiment, in the decorative portion 2, the clear layer C itself serves as a protective film covering the metal material surface L5a, and discoloration due to retort sterilization (hot water sterilization) and stains (particularly, salt adhesion due to salt wind near the coast). Protects the metal member L6 from corrosion (rust) caused by such factors.

The principle of laser decoration is that the coating film layer L1 absorbs laser light. When exposed to laser light, the coating film layer L1 is heated to a high temperature. In the second embodiment, the coating film component (synthetic resin), which is a component of the clear layer C, also absorbs the laser beam, though not as much as the pigment, so it is presumed that the clear layer C is also heated and peeled off.

Further, if the clear layer C is made extremely thin and the colored coating film layer L1 is provided on the clear layer C, the thin film L4 composed of the clear layer C and the coating film layer L1 remains.

(Paint [with or without pigment])
As described above, it was found that the clear layer C formed of the pigment-free paint was also decorated and the thin film L4 remained. The presence or absence of pigments is irrelevant to the practice of the present invention. Therefore, the coating film layer L1 in the present invention includes the case where only the clear layer C is formed, and even the coating film layer L1 in which the paint does not contain a pigment is included in the present invention.
In the above-mentioned first and second embodiments, the clear layer C and the coating film layer L1 have been described as separate layers, but there is no difference between the two layers being the layers formed of the paint, and the clear layer. C is also a kind of the coating film layer L1.

(Visibility)
By combining the results of the experiment 6 of the first embodiment and the results of the second embodiment, it is possible to consider an experiment using a colored paint. Visibility is related to the large color difference ΔE ^* between the coating film layer L1 and the thin film L4. By lowering the pigment concentration and using a thick coating layer L1 to compensate for the decrease in the pigment concentration, the measured values of the L ^* , a ^* , and b ^* color spaces of the portion of the coating layer L1 become large. On the other hand, since the thin film L4 has a low pigment concentration, the amount of pigment remaining in the thin film L4 is small, and the measured values of the L ^* , a ^* , and b ^* color spaces of the decorative portion 2 (thin film L4) are small. As a result, the color difference ΔE ^* between the coating film layer L1 and the decorative portion 2 (thin film L4) becomes large, and the visibility is improved. By doing so, the visibility of the decorative portion 2 (printing) can be improved. Further, by providing the clear layer C, the amount of pigment remaining in the decorative portion 2 (thin film L4) is further reduced, the color difference ΔE ^* is further widened, and the visibility of the decorative portion 2 (printing) is improved.

On the other hand, when the coating film layer L1 using a paint having a high pigment concentration is decorated, a large amount of pigment remains in the thin film L4 (printed portion), and the visibility of the decorated portion 2 (printed) may be inferior. .. In such cases, it can be used to decorate the product so that it is not noticeable to consumers. For example, printing information that is not necessary for consumers, such as lot numbers.
Further, "decoration (printing)" is not limited to characters, but includes patterns, patterns, barcodes, two-dimensional codes, machine-readable information, and the like. In addition, the purpose of use of decoration (printing) does not matter.

Further, in the second embodiment, it was found that the clear layer C containing no pigment is also decorated. Even if the coating film layer L1 containing no pigment is used and decorated, a transparent thin film L4 (printed portion) remains on the transparent coating film layer L1, and the visibility is extremely poor.
However, it is advantageous when printing a lot number or the like that does not need to be communicated to consumers. By shining light from a specific direction, the print emerges, and it can be used for purposes such as knowing information such as lot numbers only when you want to confirm the manufacturer.

Although the embodiments according to the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the design does not deviate from the gist of the present invention. Even if there is a change or the like, it is included in the present invention.
Further, each of the above-described embodiments can be combined by diverting the technologies of each other as long as there is no particular contradiction or problem in the purpose and configuration thereof.

L1: Coating film layer,
L2: Surface treatment layer,
L3: Metal base material (aluminum base material)
L4: Thin film L5: Metal material L5a: Metal material surface L6: Metal member 2: Decorative part B: Blackening part C: Clear layer

Claims (9)

A method for manufacturing a decorated metal member provided with a thin film having the following characteristics of a coating film layer including the following (step 1) and (step 2).
Characteristics: The thin film can be peeled off even if it is irradiated with a CO ₂ laser (wavelength 10600 nm) at an output of 30 W, a power of 100%, a scan speed of 10 mm / sec, a fill interval of 0.01 mm, and a printing count (repetition count) of 5 times. It ’s something that never happens,
(Step 1) The metal material is the metal base material itself or a surface treatment layer formed on the metal base material, and is coated on the metal material with a paint containing a pigment or a paint not containing a pigment. The process of drying to form a coating layer.
(Step 2) A step of decorating by using light having a wavelength that is absorbed by the coating film layer and having a wavelength that is difficult to be absorbed on the surface of the metal material, and peeling off the coating film layer until it becomes the thin film.
In the above (step 1), the metal material is the metal base material itself or a surface treatment layer formed on the metal base material, and a clear layer coated with a paint containing no pigment and dried is provided. The method for manufacturing a decorated metal member according to claim 1, wherein the step is to form a coating film layer by coating a paint containing a pigment on the clear layer.
The method for manufacturing a painted metal member according to claim 1 or 2, wherein the metal member is a can.
One of claims 1 to 3, wherein the light having a wavelength that is difficult to be absorbed by the surface of the metal material is light having a wavelength that is greater than 0% and absorbed by 5% or less on the surface of the metal material. The method for manufacturing a metal member according to an item.
It has a metal material, a coating film layer, and a decorative part.
The metal material is the metal base material itself or a surface treatment layer formed on the metal base material.
The coating film layer is formed on the surface of the metal material, and is formed on the surface of the metal material.
The decorative portion is made of a thin film, which has a CO ₂ laser (wavelength 10600 nm) output of 30 W, a power of 100%, a scan speed of 10 mm / sec, a fill interval of 0.01 mm, and a printing count (repetition count) of 5 times. A metal member that does not come off even when irradiated under the above conditions.
The metal according to claim 5, wherein the coating film layer has a clear layer made of a paint having no pigment formed on the surface of a metal material and a colored coating film layer made of a paint having a pigment on the clear layer. Element.
The metal member according to claim 5 or 6, wherein the metal member is a member of a can including a can body, a panel of a can lid, or a tab of the can lid.
A product comprising the metal member according to any one of claims 4 to 7 and having other parts or materials.
The product according to claim 8, wherein the product is a can containing a beverage.

Images