JPH074675B2 - Iridescent coloring method for metal surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a rainbow color that forms a pattern or region in which the hue of reflection gloss changes in a rainbow-like manner on a metal surface depending on the angle of incident light and the viewing direction. It relates to the color processing method,
For example, it is used as a surface decoration means for metal ornaments, metal home appliances, metal industrial products and the like.

(Prior Art) When minute unevenness of about 1 μm or less close to the wavelength range of visible light is densely formed on a metal surface, the surface acts like a diffraction grating to disperse and reflect incident light. Therefore, the hue of the reflection gloss will change in a variety of rainbow colors depending on the direction of incident light and the viewing angle. Therefore, such fine concavo-convex processing is extremely promising as a decorating means for providing a beautiful multicolor variable coloring which is impossible by painting or chemical coloring on the metal surface.

However, in the processing means using an ordinary laser beam, which has been widely used for various kinds of metal processing in recent years, generally, the minimum spot diameter that can be converged by a condenser lens is several μm to 10 μm.
Since it is about m, it is impossible to form the fine irregularities of 1 μm or less as described above. Even if the spot diameter is narrowed down to about 1 μm, one groove can be formed by one scanning, so it takes a huge amount of processing time to form the concave and convex portions in a width or a surface shape visible to the naked eye. Will be required.

Therefore, the present inventors have previously proposed, as Japanese Patent Application No. 1-84326 and Japanese Patent Application No. 1-229567, fine irregularities corresponding to the intensity distribution of interference fringes of the interference light on the metal surface by irradiation of laser interference. It proposes an epoch-making means of forming the.
That is, according to these proposed means, by setting the intensity of the laser light to the energy density at which the metal melts and evaporates in the bright part of the interference fringes, the unevenness in which the bright part is concave on the metal surface and the dark part is convex Thus, hundreds of minute ridges and valleys with a mutual interval of about 1 μm or less can be formed at once by one scanning.

(Problems to be Solved by the Invention) However, as a result of experimental research continued from the above proposals made by the present inventors, since the fine irregularities corresponding to the interference fringes of the laser light as described above are very fine, the laser interference light It has been found that the sharpness of the fine irregularities formed by the surface condition of the metal surface irradiated with is greatly influenced, and it is not possible to stably obtain a processed product exhibiting a good iridescent color by ordinary means.

In view of such circumstances, the present invention provides a processing method in which a processed product exhibiting a good rainbow color development is stably obtained, and thus, it is possible to improve the yield of decorative processing and the decoration quality. Has an aim.

(Means for Solving the Problems) The first method of iridescent coloring of a metal surface according to the present invention is, as a means for achieving the above object, mirror-finishing a metal surface by electrolytic polishing, and applying the mirror-finished surface to the mirror-finished surface. A configuration is adopted in which fine unevenness corresponding to the intensity distribution of interference fringes is formed by irradiating the interference light of a laser.

In addition, the second method of iridescent coloring of a metal surface according to the present invention
Adopts a configuration in which the metal surface to be electrolytically polished in the above-mentioned first method is a surface on which drawing is performed by laser engraving.

(Operation) In the method of the present invention, the surface of the metal to be processed is mirror-finished before the formation of fine irregularities by the irradiation of the laser interference light, and electrolytic polishing is adopted as the mirror-finishing means. Is the greatest feature.

Here, there are various mechanical polishing methods such as buff polishing and chemical polishing as the means for mirror-finishing the metal surface, but the mirror surface necessary for exhibiting a good rainbow color development which is the object of the present invention. The surface is not a surface having a small degree of unevenness that can be defined as so-called surface roughness, but is a surface having no sharp valleys even if the degree of unevenness is somewhat large. Therefore, the present invention requires electrolytic polishing. That is, in electropolishing, the metal surface is smoothed by electrodissolution, but with the start of electrolysis, a viscous polishing film is generated to protect the recesses, and current is concentrated in the recesses and elution proceeds preferentially. A smooth surface without sharpness can be obtained even if large undulations remain.

Then, when the laser interference is applied, even if there are gentle and large undulations on the surface as described above, fine irregularities corresponding to the interference fringes are faithfully formed along the undulations. In particular, on a surface having fine and sharp undulations obtained by mechanical polishing, fine irregularities to be formed are affected by the undulations and lose clarity. Also,
Chemical polishing produces a mirror-like effect similar to electrolytic polishing, but has the drawback that pre-polishing must be performed before processing, and the chemical cost is high.

In addition to the fine irregularities for performing iridescent color development, when drawing is performed on the metal surface by the usual laser engraving process according to the specifications of the product, the drawing is preferably performed before electrolytic polishing. That is, in the engraving process, an oxide film is generally formed around the processed groove, and the film becomes a brownish tint in stainless steel or the like, and if it is as it is, the beauty of the background and the sharpness of the iridescent color are impaired. However, it is convenient because the coating is removed by electrolytic polishing.

(Example) Hereinafter, the method of the present invention will be specifically described based on illustrated examples.

FIG. 1 (A) is an enlarged view showing a surface portion of a metal plate M to be subjected to iridescent coloring in an untreated state, and the surface as shown in the drawing.
There are various large and small sharp irregularities on S ₁ .

However, in the present invention, the surface S ₁ of such a metal plate M is mirror-finished by electrolytic polishing. That is, according to this electrolytic polishing, first, as shown in FIG. 1 (B), the polishing film P generated at the start of electrolysis particularly covers the concave portion, and the electric current is concentrated on the convex portion to preferentially elute from the convex portion. Done. The polishing film P
Also gradually dissolves, but when a new convex portion appears, it elutes more intensively than that portion, so smoothing gradually progresses as shown in FIGS. 1 (C) and (D), and finally a large gentle undulation is left. Becomes a surface S ₂ having no sharp unevenness.

Such electrolytic polishing may be performed according to a conventional method, but the conditions such as the composition of the polishing liquid, the current, the liquid temperature, the electrolysis time, and the like, needless to say, depend on the material of the metal plate M. As an example, the following table shows two examples of polishing liquid and processing conditions for stainless steel.

When the metal surface to be subjected to the above-mentioned electrolytic polishing is previously drawn by the engraving process of a normal laser, an oxide film exists around the processed groove, but such an oxide film is formed by the electrolytic polishing. Will be removed in the process. Therefore, it is possible to prevent the oxide film from adversely affecting the background coloration and the iridescent color development.

In the present invention, after the surface is mirror-finished by the above electrolytic polishing,
The surface is irradiated with laser interference light to form fine irregularities corresponding to the intensity distribution of the interference fringes.

FIG. 2 shows a laser processing step, in which a metal plate M is placed on a ZY table T, and an interference beam B _{1 of a} laser beam is converged by a processing condenser lens L provided above the metal plate M so that the lens is converged. The mirror-finished surface S ₂ of the metal plate M is irradiated at a position farther than the focal point of L. Therefore, by moving the XY table T in the X direction, the surface of the metal plate M is scanned with the converged interference light B ₂ , so that the XY table is scanned every time this scanning is completed.
By moving the table T in the Y direction, a parallel line-shaped or plane-shaped scanning pattern can be obtained. Then, on each surface S ₂ of the metal plate M, the bright portion of the interference fringes of the interference pattern is formed on the surface S ₂ of the metal plate M within the width of the irradiation spot diameter as shown in the enlarged view in the virtual circle of FIG. Corresponding hundreds of recesses I are formed.

Here, the interference light B ₁ is overlapped with the bright pattern components in the low-order multimode laser beam as described in Japanese Patent Application No. 1-84326, or is split from a single laser beam. Or a plurality of beams overlap each other, or the above-mentioned Japanese Patent Application No. 229567.
As disclosed in the publication, a part of the laser beam may be laterally displaced and superposed on the original beam component. Therefore, specific device configurations for generating the interference light B ₁ are disclosed in both of the above patent applications.

By interlocking the movement of the XY table T in both XY directions, or by changing the optical axis direction of the interference light B ₁ by an optical control mechanism such as an XY scanner, the scanning line is curved or has a complicated pattern. You can set it to draw a trajectory that makes
Further, by combining the Z-direction displacement means, it becomes possible to perform fine concavo-convex processing on a three-dimensionally shaped metal surface such as a curved surface.

The irradiation position of the interference light B ₂ may be set to a position shallower than the focal point F of the lens L. Therefore, a concave mirror can also be used as a means for converging the interference light B ₁ .

FIG. 3 shows the surface portion of the metal plate M which has been subjected to the iridescent coloring process. Even if the mirror-finished surface S ₂ has a gentle and large undulation as shown in the figure, each recess I of the fine uneven portion U corresponding to the laser scanning line is clearly engraved.
Then, the fine irregularities U exhibit a reflective gloss whose hue varies in a rainbow-like manner depending on the angle of incident light and the viewing direction. Note that such fine irregularities U may be densely formed so that rainbow color is generated as a surface.

(Effects peculiar to the invention) According to the method of the present invention, the metal surface is mirror-polished by electrolytic polishing before the fine unevenness corresponding to the intensity distribution of the interference fringes is formed on the metal surface by irradiation with laser interference light. It is possible to reliably form the above-mentioned fine fine irregularities, and as a result, a unique iridescent color that varies in a variety of colors depending on the angle of the incident light and the viewing direction is produced. There is an advantage that the decoration can be manufactured stably.

Further, according to the configuration of claim (2) of the present invention, in the case where the metal surface is decorated with the above-described iridescent color and drawing is performed by a usual laser engraving process, the coating film accompanying the engraving process is electrolytic. Since it is removed by polishing, there is an advantage that adverse effects on the background coloring and iridescent coloring due to the coating can be prevented without requiring special treatment.

[Brief description of drawings]

FIG. 1 (A) is an enlarged sectional view showing an untreated surface portion of a metal plate used in the present invention, and FIGS. 1 (B) to (D) show stepwise the surface portion of the metal plate in electrolytic polishing. An enlarged cross-sectional view, FIG. 2 is a schematic perspective view showing a process of forming fine irregularities by laser interference light, and FIG. 3 is an enlarged cross-sectional view of the surface portion of the metal plate on which the fine irregularities are formed. B ₁ , B ₂ ... laser interference light, M ... metal plate, S ₁ ... untreated surface, S ₂ ... mirror-finished surface, U ... fine irregularities.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichiro Oshima 1-9-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture Osaka Fuji Industrial Co., Ltd. (72) Inventor Tokihiko Oshima 1-1-9, Jokoji Temple, Amagasaki City, Hyogo Osaka Fuji Industrial Co., Ltd. (72) Inventor Shigekazu Hirata 1-9-1, Jokoji, Amagasaki City, Hyogo Osaka Fuji Industrial Co., Ltd. (72) Inventor Yoshikazu Okano 1-1-9, Jokoji, Amagasaki City, Hyogo Osaka Fuji Industry Co., Ltd.

Claims (2)

[Claims] 1. A metal which is characterized in that a metal surface is mirror-finished by electrolytic polishing, and the mirror-finished surface is irradiated with laser interference light to form fine irregularities corresponding to the intensity distribution of interference fringes. Surface rainbow color processing method. 2. The method for iridescent coloring of a metal surface according to claim 1, wherein the metal surface to be electropolished is a surface which is drawn by laser engraving.