JPH06212451A - Method for ornamenting metallic surface - Google Patents

Abstract

PURPOSE:To impart color development variable to multiple colors to a metallic surface without using noble metals by forming a thin film consisting of the reaction product of gaseous components by a heat treatment on the surface of a metallic material provided with fine ruggedness corresponding to interference fringes of a laser beam. CONSTITUTION:The surface of the metallic material M, for example, stainless steel, Ni-Cr alloy, Ti or alloy essentially consisting of Ti, is irradiated with the laser beam L to cause interference on its surface, by which the fine ruggedness G corresponding to the interference fringes is formed. The surface having this fine ruggedness G is thereafter heat-treated in a reactive gas, for example, oxygen-contg. atmosphere or nitrogen atmosphere, by which the thin film P consisting of the reaction product of the metallic component and the above- mentioned gaseous component is formed. The ornaments with which patternssuch as pictures and characters. are visibly observed as reflected gloss of beautiful rainbow color development on the surface color different from the ground color as a background are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a rainbow-colored pattern on a metal surface with a surface color different from the base color and a pattern pattern such as a line drawing or a character depending on the viewing angle and the direction of incident light. The present invention relates to a method of performing a decoration process visually recognized with a reflective gloss.

[0002]

2. Description of the Related Art As a means for providing a beautiful multicolor variable coloring that cannot be achieved by painting or chemical coloring on a metal surface, the applicant of the present invention disclosed in JP-A-2-263589 and JP-A-3-9.
There is a method of irradiating a laser beam applied to a metal surface and causing interference on the surface by a laser processing method or the like proposed as No. 4986 to form fine irregularities corresponding to the intensity distribution of the interference fringes.

That is, the fine unevenness formed by such a method usually has a concave-convex stripe having a bright portion of the interference fringes and a dark portion of a convex portion on one scanning spot or one scanning line of the laser beam, which is usually 1 μm or less. The wavelength range of visible light such as (38
They are densely aggregated at a pitch interval close to 00 to 7800 angstroms) and act like a diffraction grating to disperse and reflect incident light, so that the hue of the reflection gloss varies depending on the direction of the incident light and the viewing angle. A so-called iridescent color that changes in various colors is generated.

At the present time, however, stainless steel is a typical metal material that can easily form the above-mentioned fine irregularities with a general laser processing machine such as a YAG laser which is widely used for surface processing of metals. Steel, Ni-Cr alloy,
Examples thereof include titanium and alloys containing this as a main component.
However, with these metal materials, the decorative pattern itself consisting of spots and lines composed of the fine irregularities described above produces a beautiful rainbow color, but the surface color due to scattered light reflection, that is, the metal base color is cheap. However, there was a dislike that it lacked a high-class feel when used as a decorative item.

Therefore, the applicant of the present invention first disclosed in Japanese Patent Laid-Open No. 4-9.
As No. 1875, scattered light is formed by forming a precious metal coating on the surface of stainless steel or Ni-Cr alloy provided with fine irregularities corresponding to the interference fringes of the laser light described above, with a thickness such that the fine irregularities remain on the surface. It proposes a means for giving a high-class feeling by using the surface color due to reflection as a tint of a precious metal. However, in such a method, since the precious metal is used, the material cost is high, and in order to uniformly deposit the thin precious metal coating that leaves the fine irregularities, a high vacuum such as vacuum deposition or sputtering is used. Since it is necessary to adopt a thin film forming method by deposition inside, there is a problem that processing is very time-consuming and equipment cost is high.

[0006]

In view of the above situation, the inventors of the present invention, in view of the above situation, do not rely on the deposition of a noble metal coating or the like as proposed above, but stainless steel provided with fine irregularities corresponding to interference fringes of laser light. As a result of extensive studies on means for changing the surface color of steel, etc., when the surface portion of the metal having the fine unevenness is transformed into an oxide film or a nitride film by heat treatment, the iridescent coloration due to the fine unevenness is observed. The surface color can be changed to gold or the like without any damage, and the pattern pattern such as line drawings and letters is visually recognized as a reflective rainbow gloss with a beautiful surface color that is different from the base color. The inventors have found that a decorated processed product can be provided, and have completed the present invention.

That is, in the method for decorating a metal surface according to claim 1 of the present invention, the surface of the metal material is irradiated with laser light to cause interference on the surface, thereby forming fine irregularities corresponding to the interference fringes. After the formation, the surface having the fine irregularities is heat-treated in a reactive gas to form a thin film composed of a reaction product of the metal component and the gas component.

A second aspect of the present invention is the decoration processing method according to the first aspect, wherein the metallic material is stainless steel or Ni-C.
It is an r-based alloy and has a structure in which an oxide film is formed by heat treatment in an oxygen-containing atmosphere.

A third aspect of the present invention adopts a structure in which the oxide film in the decorative processing method of the second aspect has a thickness of 100 to 200 angstroms.

According to a fourth aspect of the present invention, in the decoration processing method according to the first aspect, the metal material is titanium or an alloy mainly containing titanium, and the nitride film is formed by heat treatment in a nitrogen atmosphere. It is a thing.

[0011]

In the method of the present invention, as shown in FIG.
First, the surface of the metal material M is irradiated with laser light L to cause interference on the surface to form fine irregularities G corresponding to the interference fringes, and then the surface having the fine irregularities G is heat-treated in a reactive gas. Then, as shown in FIG. 3B, a thin film P made of a reaction product of the metal component on the surface and the gas component is formed.
Thus, in the obtained processed product, the surface color is changed from the background color of the metal material M to the hue through the thin film P, and the pattern formed by the fine irregularities G and the pattern such as characters are viewed and the incident light It will be visually recognized as a reflective gloss that changes in a rainbow-like manner depending on the direction.

By the way, it is known that the surface color becomes golden when an oxide film having a certain thickness is formed on the surface of stainless steel. Then, if the fine irregularities are formed in a required pattern on the surface of stainless steel in advance, and the surface is heated and oxidized in air to form an oxide film,
Although the area of the above pattern will be uniformly oxidized,
The surface condition of the fine irregularities does not change, and its iridescent color development is the same as before the formation of the oxide film, and only the background becomes a golden color that gives a high-class feeling. This is because the iridescent coloration due to the fine irregularities is not affected by the composition of the surface on which it is formed, and the morphological characteristics of the diffraction grating are exclusively used, that is, the mutual spacing is about 1 μm or less. It relies on the spectroscopic effect of the aggregate structure, meaning that it retains its original iridescent color unless the surface state is disturbed, and it has been confirmed that the same applies to metallic materials other than stainless steel. .

The type of the metallic material to be processed in the present invention is not limited, and the surface color based on the coating film formed by the heat treatment in the reactive gas is not particularly limited. From the viewpoint of obtaining a decorative product with a feeling, it is desirable to select a combination of a material and a coating that changes the ground color of metal to a high-grade shade such as gold. For example, in addition to the above-mentioned stainless steel, Ni-Cr alloys also have a gold-colored surface color due to the formation of a similar oxide film, and titanium or an alloy containing titanium as a main component forms a nitride film by heat treatment in a nitrogen atmosphere. By doing so, a golden surface color is obtained. In the case of stainless steel or Ni-Cr alloy, if the oxide film is too thick, it loses its metallic luster and is easily peeled off from the metal base. The thickness of the oxide film that exhibits a good golden color is about 100 to 200 angstroms. However, the thickness of the thin film P is generally 100 to 35 for other metals having no problem of peeling as described above.
It can be set to about 0 angstrom.

As means for forming fine irregularities corresponding to the interference fringes of laser light on the surface of a metal material, it is sufficient that interference can be generated on the irradiation surface of the laser light, and it is described in Japanese Patent Laid-Open No. 263589/1990. As disclosed in, a method of superimposing the light pattern components of low-order multimode laser light on each other, or superimposing beams divided from a single laser light,
Similarly, as disclosed in Japanese Patent Laid-Open No. 3-94986, a method of laterally displacing a part of a laser beam in a laser resonator or in an external optical system to overlap the original beam component and the displaced beam component can be adopted. As a simple means, it is recommended to use a waveguide formed when the pulsed laser light is repeatedly irradiated on the metal surface to cause interference.

That is, when a pulsed laser beam focused on the surface of a metal material in a reactive gas is irradiated so that a large number of pulses hit the same position, the metal component on the surface heated in the preceding stage of the irradiation and the gas described above. The components react with each other, and a thin film of the reactant is formed on the surface in the irradiation spot. When the refractive index is higher than the refractive index of the material on both sides, that is, the material metal of the workpiece and the atmospheric gas, this thin film is equivalent to a planarized (plate-shaped) core of the optical fiber. Will work. For example, when the workpiece is the above-mentioned stainless steel or Ni-Cr alloy, an oxide film formed by irradiation with laser light in an oxygen-containing atmosphere, titanium, or an alloy mainly composed of titanium is exposed in a nitrogen atmosphere. The nitrided film formed by irradiating the laser light of 1) functions as a waveguide.

When the surface on which the waveguide is formed is further irradiated with the pulsed laser light in this way, a part of the laser light penetrates into the waveguide through minute scratches and crystal grain boundaries and advances in the surface direction.
The laser light traveling in the surface direction and the radiated laser light interfere with each other to generate interference fringes on the surface of the metal material. At this time,
By setting the intensity of the laser light to a power density sufficient to melt and evaporate the surface in the bright portion of the interference fringe, fine irregularities are formed on the surface, with the bright portion of the interference fringe being concave and the dark portion being convex. .
The groove spacing Δx of the fine concavities and convexities is given by Δx = λ / sin θ if the laser light of wavelength λ intersects at an angle θ and interferes. In this case, the intersecting angle θ is 90 degrees, so s
in θ = 1, and Δx = λ, that is, the same as the wavelength of the irradiation laser light. Therefore, the fine irregularities G are composed of irregular stripes having an extremely fine pitch of about 1 μm or less, which is close to the wavelength range of visible light, and the incident light is dispersed and reflected as a diffraction grating to generate iridescent color. Become.

According to this method of utilizing the waveguide, there is almost no optical path difference (distance difference) from the laser light source to the interference position between the laser light traveling in the surface direction and the laser light being irradiated, and therefore, the coherence is extremely high. In addition, the fine irregularities at the initial stage of formation act as a grating coupler to improve the efficiency of introducing laser light into the waveguide, and since a single-mode laser beam can be used, very clear interference fringes can be observed over the entire irradiation spot. As a result, the fine irregularities formed are capable of obtaining a rainbow-colored color with high definition. Further, in this fine concavo-convex processing, a method of forming fine concavo-convex for each range of the irradiation spot without changing the irradiation position of the laser light may be used, but at a speed at which the laser light pulse hits the same position on the workpiece many times. If a method of continuously forming fine irregularities while scanning is used, the waveguide is formed in the first half of the moving direction of the moving irradiation spot, and the melting / corresponding to the interference fringes is formed in the latter half.
The fine irregularities are completed by evaporation, and the fine irregularities already formed in the latter half of the laser beam can enter the waveguide very efficiently as a grating coupler, resulting in higher interference than the former processing method in the stopped state. Therefore, clearer fine irregularities can be formed.

As the pulsed laser light to be applied, the laser beam emitted from the laser oscillator is used in the form of being converged through a converging means such as a convex lens or a concave mirror, but a general laser processing device for metal processing is used. In this case, if the irradiation surface is located near the focal point of the converging means, the entire area of the irradiation spot will melt and evaporate uniformly as in normal grooving processing, so clear minute irregularities corresponding to interference fringes will be formed. In order to do so, it is preferable to set so that the light is emitted at a position shifted in one direction in the depth and shallower than the focus.

[0019]

【Example】

Example 1 Pulsed laser light of a linearly polarized Q-switched Nd: YAG laser (single mode, wavelength 1.06 μm, pulse width 100 ns, laser output 0.5 mJ) was used, and the irradiation position was above the focus of the condenser lens. 8 mm, the power density at the irradiation position is set to 22 MW / cm ² , respectively,
The surface of 18-8 stainless steel plate mirror-polished in the air was continuously irradiated while scanning at the same speed as a pulse hitting about 100 times, and a line image of a predetermined pattern was drawn. Fine irregularities in which grooves having a width of about 0.5 μm were densely aggregated at a pitch of about 1 μm were formed. This line drawing was composed of lines in which the hue of the reflective gloss varied in a rainbow-like manner depending on the illumination direction and the viewing angle under both sunlight and indoor illumination light.

Next, with respect to Samples A to E of similar stainless steel plates on which this line drawing was drawn, heat treatment was performed for 30 minutes at different temperatures in the air (1 atm) in the electric furnace. An oxide film mainly containing Cr ₂ O ₃ (including NiO ₂ ) was formed. Table 1 shows the thickness, surface color, and iridescent color development of the line drawing pattern of the oxide film of the processed stainless steel sheet, and FIG. 2 shows the reflectance characteristics (excluding sample E) together with the untreated one. The unit A of the thickness of the oxide film in the table means angstrom.

[0021]

[Table 1]

Examples 2 to 4 In place of the 18-8 stainless steel plate, an 8-8 stainless steel plate, a 22-22 stainless steel plate, and a Ni-Cr alloy plate were used, respectively, and pulsed laser light irradiation was performed in the same manner as in Example 1. When a line drawing pattern was drawn with, a groove with a width of about 0.5 μm was about 1 μ in the entire line width of about 90 μm.
Fine irregularities densely aggregated at a pitch of m were formed. All of these line drawings showed the same clear iridescent color as in Example 1. Next, the metal plate on which these line drawings were drawn was heated in air (1 atm) at 460 ° C. for 30 minutes in an electric furnace.
When heat-treated for minutes, an oxide film was formed on the surface and the surface color became gold in all cases, but the line-drawing patterns all produced the same vivid rainbow coloring as before the heat-treatment.

Example 5 The same Q-switched Nd: YAG laser as in Example 1 was used, the irradiation position was set to 7 mm above the focal point of the objective lens, and the power density was set to 28 MW / cm ² , respectively, and the nitrogen atmosphere (1 atm. ), Pulsed laser light (repeated 2 KHz) was continuously irradiated while scanning the same position of the mirror-polished metal titanium plate at a speed at which the pulse hits about 100 times, and a line drawing of a predetermined pattern was drawn. A groove with a width of about 0.5 μm is about 1 μ in the entire line width of about 90 μm.
Fine irregularities densely aggregated at a pitch of m were formed. This line drawing showed the same clear rainbow color development as in Example 1. Next, when the metal titanium plate on which this line drawing was drawn was heat-treated at 700 ° C. for 30 minutes in an electric furnace in a nitrogen atmosphere (1 atm), a nitride film (TiN) was formed on the surface,
Although the surface color became golden, the line drawing pattern produced the same vivid rainbow color as before the heat treatment.

In each of the above embodiments, the oxide film or the nitride film formed during the irradiation of the pulsed laser light is used as a waveguide to interfere the laser light to form fine irregularities. Fine interference may be formed by utilizing the interference method of. In addition, the present invention can process metal materials other than those used in these examples, and can use various pulse laser oscillators (preferably having a small pulse width) other than the Q-switched Nd: YAG laser exemplified for forming fine irregularities. Needless to say, it can be used.

[0025]

According to the first aspect of the present invention, so-called iridescent coloring processing, in which a drawing pattern such as a pattern or a character is visually recognized as a reflection gloss that is variegated like an iridescent color depending on the viewing angle and the direction of incident light, is provided. The surface color of the applied metal material can be easily changed to another shade without impairing the iridescent color forming property,
For example, using a cheap metal material, it is possible to provide a beautiful, high-class, highly decorative processed product with a bright rainbow-colored drawing pattern emerging in the surface color of gold at a low cost. .

According to the second aspect of the present invention, it is possible to provide a processed product which is made of stainless steel or a Ni-Cr alloy and whose drawing pattern is visually recognized with a reflection gloss of iridescent color with a gold surface as a background.

According to the invention of claim 3, there is an advantage that a processed product made of stainless steel or a Ni-Cr alloy can be surely provided with a gold color having a particularly good surface color.

According to the fourth aspect of the present invention, it is possible to provide a processed product which is made of titanium or an alloy mainly composed of titanium and whose drawing pattern is visually recognized with reflection gloss of iridescent color with a gold surface as a background.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing a decorative processing method of the present invention in the order of A and B steps.

FIG. 2 is a reflectance characteristic diagram of a surface of a processed product obtained in an example of the present invention.

[Explanation of symbols]

 M Metallic material L Laser light G Fine unevenness P Coating

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H01S 3/00 B 8934-4M (72) Inventor Ichiro Oshima 1-9-1 Jokoji, Amakosaki, Hyogo Prefecture No. Osaka Fuji Kogyo Co., Ltd. (72) Inventor Tokihiko Oshima 1-9-1, Jokoji, Amagasaki City, Hyogo Prefecture Osaka Fuji Kogyo Co., Ltd. (72) Inventor Shigekazu Hirata 1-9-1, Jokoji Amagasaki, Hyogo Prefecture In Osaka Fuji Industry Co., Ltd. (72) Inventor Yoshikazu Okano 1-9-1, Jokoji Temple, Amakosaki City, Hyogo Prefecture Inside Fuji Fuji Industry Co., Ltd.

Claims (4)

[Claims] 1. A surface of a metal material is irradiated with laser light to cause interference on the surface to form fine irregularities corresponding to the interference fringes, and then the surface having the fine irregularities is heat-treated in a reactive gas. And then forming a thin film composed of a reaction product of the metal component and the gas component. 2. The metal material is stainless steel or Ni—Cr.
The method for decorating a metal surface according to claim 1, which is a system alloy and is heat-treated in an oxygen-containing atmosphere to form an oxide film. 3. The method for decorating a metal surface according to claim 2, wherein the oxide film has a thickness of 100 to 200 angstroms. 4. The method for decorating a metal surface according to claim 1, wherein the metal material is titanium or an alloy mainly composed of titanium, and the nitride film is formed by heat treatment in a nitrogen atmosphere.