JPH0825045B2 - Iridescent color processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rainbow color which forms a pattern or region in which the hue of the reflection gloss varies in a rainbow-like manner on the surface of various materials such as metal depending on the angle of incident light and the viewing direction. The present invention relates to a coloring method and is suitably used as a surface decorating means for, for example, ornaments, household electrical appliances, industrial articles and the like.

[0002]

2. Description of the Related Art When fine irregularities of about 1 μm or less close to the wavelength range of visible light are densely formed on the surface of a material such as metal, the surface acts like a diffraction grating to disperse incident light. Since it is reflected by the reflected light, the hue of the reflected gloss changes in various colors like rainbow depending on the direction of the incident light and the viewing angle. Therefore, such fine concavo-convex processing is extremely promising as a decorating means for giving a beautiful multicolor variable coloring which cannot be achieved by painting or chemical coloring on the material surface.

However, in the usual laser processing means which has been frequently used for processing various materials such as metal in recent years, the minimum spot diameter which can be converged by the condenser lens is generally several μm to 10 μm. 1μ as above
It is impossible to form fine irregularities of m or less. 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 inventors of the present invention first disclosed in Japanese Patent Laid-Open No. 2-2
No. 63589 and Japanese Patent Laid-Open No. 3-94986 propose an epoch-making means of forming fine unevenness corresponding to the intensity distribution of the interference fringes of the interference light on the metal surface by irradiating the interference light of the laser. That is, according to these proposed means, the intensity of the laser light is melted in the bright part of the interference fringes,
By setting the power density to evaporate, unevenness is formed on the metal surface with the bright portion being concave and the dark portion being convex.
It is possible to form hundreds of minute ridges and valleys with a mutual spacing of about 1 μm or less by one scan.

[0005]

However, in the above-mentioned proposed means, since the laser light is emitted as the interference light,
Bright pattern components in a low-order multimode laser beam are overlapped with each other, or a plurality of beams divided from a single laser beam are overlapped with each other (Japanese Patent Application No. 1-84326).
No.) or a part of the laser beam is laterally displaced and superimposed on the original beam component (Japanese Patent Application No. 1-229567).
No.), and the restrictions on the model and device configuration of the laser oscillator used for that purpose are large, and it is difficult to adjust the optical system to perform the above division and displacement, and a laser beam with good coherence is selected. However, the clarity of the interference pattern cannot be sufficiently increased, and there is a limit to the improvement in the clarity of the rainbow color.In addition, when forming the rainbow color part in a large area or forming a dense pattern, it is necessary to process it. Since it takes a considerable amount of time, shortening the processing time is an issue in terms of manufacturing efficiency and cost of the decorated processed product.

However, as a result of further studies by the present inventors, if the surface of the work piece is in a specific state, interference occurs on the irradiation surface without irradiating the laser light as interference light,
In the same manner as above, fine irregularities are formed in which the bright part of the interference fringe is concave and the dark part is convex, and it is possible to draw a rainbow-colored pattern in which the hue of the reflective gloss changes in various directions depending on the direction of the incident light and the viewing angle. The inventors have found that the light interference is extremely good, and that it is possible to perform decoration processing that produces a very vivid rainbow color, and that the processing time can be significantly shortened, and the present invention has been completed.

[0007]

That is, in the iridescent color processing method according to claim 1 of the present invention, after forming a thin film P serving as a waveguide of laser light on the surface of a workpiece W, the thin film P is formed. The converged pulsed laser light L is irradiated onto the surface where the laser beam is formed so that multiple pulses are applied to the same position, so that the laser light La propagating through the thin film P and the irradiated laser light L interfere with each other, and the interference occurs. The structure employs a feature that fine irregularities G corresponding to the intensity distribution of stripes are formed on the surface of the workpiece W.

A second aspect of the present invention, in the iridescent color processing method according to the first aspect, employs a configuration in which the pulsed laser light L is irradiated at a position shallower than the focal point F of the converging means S in one direction. It was done.

Further, a third aspect of the present invention is the method for forming an iridescent color according to the first or second aspect, wherein the thin film P serving as a waveguide of the laser light is formed by surface modification of the workpiece W. It was done.

According to a fourth aspect of the present invention, a metal material is used as the workpiece W in the iridescent color processing method of the above-mentioned third aspect, and a heat treatment is performed in a reactive gas to obtain a raw material metal and a gas component. The thin film P serving as the waveguide of the laser light is formed by forming a film made of the reaction product.

A fifth aspect of the present invention is the third or fourth aspect of the invention.
Laser light Lp different from the laser light L for forming fine irregularities in the heat treatment in the reactive gas in the iridescent color processing method
The structure is adopted by irradiating with.

According to a sixth aspect of the present invention, in the iridescent color processing method according to any of the first to fifth aspects, a configuration is adopted in which the thin film P serving as the waveguide of the laser light has a thickness of 50 angstroms or more. Is.

According to a seventh aspect of the present invention, in the iridescent color processing method according to any one of the first to sixth aspects, the cylindrical lens SL is interposed in the optical path of the laser beam L for forming the fine irregularities, whereby the laser is produced. A configuration is adopted in which a circular beam of light L is converted into a long beam pattern in a direction orthogonal to the beam scanning direction.

[0014]

Detailed Configuration and Operation of the Invention As shown in FIG. 1 (A), when a thin film P serving as a waveguide of laser light is present on the surface of a workpiece W, a large number of pulsed laser light L are provided at the same position on this surface. When irradiation is performed so that a single pulse is applied, a portion La of the laser light enters the thin film P from minute scratches or crystal grain boundaries of the thin film P as shown by an arrow in FIG. The laser light La that travels in the direction of the surface and the laser light L that is radiating in the surface interfere with each other to generate interference fringes on the surface of the workpiece W. At this time, the intensity of the laser light L is set to a power density sufficient to melt and evaporate the surface in the bright portion of the interference fringes, so that the surface of the workpiece W is exposed as shown in FIG. Fine irregularities G are formed in which the bright portion of the interference fringe is concave and the dark portion is convex.

The groove spacing Δx of the fine concavities and convexities G is given by Δx = λ / sin θ, assuming that the laser beams L and La having the wavelength λ intersect at an angle θ and interfere with each other. Since it is 90 degrees, sin θ = 1, and Δx =
λ, that is, the same as the wavelength of the irradiation laser beam. Therefore,
The fine irregularities G are composed of irregular stripes having a very fine pitch of about 1 μm or less, which is close to the wavelength range of visible light, and are used as a diffraction grating to disperse and reflect incident light to give a reflection gloss shade. Iridescent color is generated that varies in various ways depending on the direction of incident light and the viewing angle.
The formation of the fine irregularities G can be performed by a scanning method in which the irradiation position is continuously moved as shown in FIG. 2, and the scanning method is adopted in a normal drawing pattern.

Therefore, the laser light L traveling in the above plane direction
Since there is almost no optical path difference (distance difference) from the laser light source to the interference position between the laser light L and the irradiating laser light L, the microscopic unevenness G at the initial stage of formation serves as a grating coupler and is a thin film of the waveguide. Since it acts so as to enhance the efficiency of introducing the laser light La into P, and a single mode laser beam can be used, it is possible to generate very clear interference fringes in the entire irradiation spot, and to form a fine pattern. The unevenness G provides a highly vivid rainbow color.

Further, in the processing means according to the above-mentioned conventional proposal, for example, when the metal surface is irradiated with the pulsed laser light L forming interference fringes, the fine irregularities corresponding to the interference fringes have the number of irradiation pulses on the same irradiation surface. It has been found that it is formed rapidly after reaching the number of times, and the irradiation energy up to that time is exclusively consumed for modification of the surface properties as a preparatory step for forming fine irregularities. However, in the method of the present invention, particularly when the workpiece is a metal, since the thin film P as a waveguide formed in advance on the surface thereof functions similarly to the surface portion after the modification of the surface texture, the irradiation energy Almost all of them can be used to form fine irregularities, and thus the number of irradiation pulses of the pulsed laser light at the same position can be reduced (generally 70% or less), and the laser processing speed can be increased and the processing time can be shortened.

A thin film P which serves as a waveguide for the laser light described above.
Means that the laser light La is propagated in the surface direction, so to speak, the waveguide (core portion) of the optical fiber is made flat (plate-shaped).
Since it corresponds to the above, it takes the form of a high refractive index layer surrounded on both sides by a substance with a low refractive index, and therefore a substance in contact with the surface of the thin film P at the time of processing (gas in the gas phase processing,
It becomes a substance with a higher refractive index than the material and the material of the workpiece W in the liquid phase, but when processed in normal air (refractive index 1), it has a higher refractive index than the workpiece material. Just set it. When such a thin film P does not exist, needless to say, the non-absorbed portion of the irradiated laser beam L simply reflects according to Snell's law and does not propagate in the surface direction, so that no interference occurs.

However, theoretically, even if the laser light La propagating through the thin film P travels in the plane direction by one pitch of the interference fringes, it will interfere with the irradiation laser light L, and this one pitch is about 1 μm. Or, since the width is short such as less than that, most materials that are normally opaque within this width behave as translucent. Therefore, the thin film P used as the waveguide is
It does not have to be a transparent substance in the ordinary concept, but naturally, the strongest interference occurs when the intensity ratio of the irradiation laser beam L and the laser beam La propagating in the waveguide is 1: 1, so too much. Good interference fringes cannot be obtained with substances with large light attenuation.

The thickness of the thin film P serving as the waveguide is preferably 50 angstroms or more, more preferably 100 μm or more. If it is too thin, the propagation of the laser light La is insufficient and good coherence can be obtained. On the other hand, for example, a passivation film naturally formed on the surface of a metal material (a polished passivation oxide film of iron has a maximum thickness of about 30 to 40 Å) is too thin to function as a waveguide.

However, particularly when performing groove processing by the scanning method, the wavelength of the irradiation laser beam L and the waveguide are determined by the efficiency of introducing (coupling) the laser beam La into the waveguide by the fine irregularities Ga at the initial stage of formation. It is necessary to prevent the apparent wavelength of the laser light La propagating through the thin film P from changing substantially.
However, when the refractive index of the waveguide is significantly higher than the refractive index of the processing atmosphere (n = 1 in air), if the laser light La propagating in the plane direction is confined in the waveguide and travels, the propagation speed is Is decreased (the apparent wavelength is shortened), and the interval of the interference fringes formed is largely deviated from the wavelength of the irradiation laser beam L, so that the coupling to the waveguide is deteriorated and good fine irregularities cannot be formed.

Therefore, in the waveguide having a high refractive index, as shown in FIG. 3, a thin film thickness is set so that most of the laser light La propagating in the surface direction goes out of the waveguide and the equivalent refractive index is set. It is desirable to make it small to approach the refractive index of the processing atmosphere. From this point of view, when the refractive index of the waveguide is slightly higher than the refractive index of the processing atmosphere, the thickness may be set so that the laser light La propagating in the surface direction of the waveguide is completely confined. However, when the propagating laser light La becomes thicker than the wavelength of the irradiating laser light L and travels by total reflection, the interval of the interference fringes formed also deviates from the wavelength of the irradiating laser light L, and the waveguide in the scanning method is used. Coupling to is bad. However, in the method of forming a groove in a spot shape at a fixed position, there is little problem even if the groove interval of the fine irregularities G to be formed is changed. Therefore, regardless of the refractive index of the waveguide, the thickness of the irradiation laser beam L It can be set to about several times.

In order to form such a thin film P serving as a waveguide on the surface of the workpiece W, the surface layer of the workpiece W itself has a high refractive index either chemically or physically depending on its constituent material. It may be transformed into a waveguide, or a material having a high refractive index to serve as a waveguide may be applied to the surface of the workpiece W. As the former transformation means, there is a method of forming a compound film by a gas phase reaction by heat-treating the workpiece W in a reactive atmosphere, and a compound film is formed by bringing the surface of the workpiece W into contact with a reactive solution. A method, a method of doping an appropriate element into the surface layer portion of the workpiece W, and the like can be mentioned. As the latter deposition means, methods such as vacuum deposition, sputtering, ion plating, and chemical vapor deposition, which are generally known as thin film forming techniques, are used for deposition in a high vacuum, spraying and LB film methods (liquid level). A method of increasing the adhesion by heat treatment after forming a film by the method of transferring the film of the target substance formed in the above to the surface by pulling up the workpiece W from the liquid), a method by plating, and the like.

Of the above-mentioned thin film forming methods, the method of forming a compound film by a gas phase reaction by heat-treating in a reactive atmosphere is the simplest, and particularly when the workpiece W is a metal material, the surface is oxidized. There is an advantage that the thin film P which becomes a good waveguide can be easily formed by nitriding or the like. Therefore, in forming a compound film by such a gas phase reaction, there is a method of forming a waveguide on the entire processed surface or a wide area of the workpiece W by a normal heating means using an electric furnace, an infrared lamp or the like. In addition, a method of irradiating the surface of the workpiece W with a laser beam different from the laser beam L for forming the fine irregularities to cause the gas component in the atmosphere and the material component of the workpiece W to react can be adopted.

According to the above reaction method utilizing laser light, as shown in FIG. 4, the laser light Lp for forming a waveguide is led to the laser light L for forming fine irregularities in a laser processing apparatus to be processed. By arranging so as to irradiate the surface of the object W, it is possible to continuously form the thin film P of the waveguide and the fine concavities and convexities G, and at the same time, the laser light Lp,
If the scanning pattern of L is controlled to be the same, it becomes possible to form the thin film P of the waveguide only in the region where the fine irregularities G need to be formed. Further, when the surface of the workpiece W is brought into contact with a reactive solution to form a compound film to serve as a waveguide, heating by laser light irradiation is used to cause a chemical reaction only in a target region to cause a waveguide. Can be formed. Since such a laser light Lp for forming a waveguide simply heats, it is possible to use a laser light with poor coherence such as a high-order multimode or a continuous wave laser light without any trouble.

A metal material such as stainless steel is generally used as the workpiece W, but various non-metal materials such as ceramics and semiconductors can also be processed, and a transparent material (transparent to the naked eye) of a general concept is used. Even if there is a material, it can be processed as long as it is a material that can absorb an infrared laser light such as a carbon dioxide gas laser and an ultraviolet laser light such as an excimer laser. Furthermore, since the iridescent color can be obtained even if the formed fine irregularities G reach only the thin film P of the waveguide, the thin film P of the waveguide has a lower melting point than the material of the workpiece W. Even if a material having poor absorption of the laser light L used for processing or a material to which laser processing is difficult to apply is applied as a thin film P of the waveguide, iridescent coloring processing can be performed. Therefore, there are almost no restrictions on the object to be processed in the present invention.

A laser beam L for irradiating the surface of the workpiece W having the thin film P of the waveguide to form the fine irregularities G.
Is generally used in a form in which a laser beam emitted from a laser oscillator is converged through a converging means such as a convex lens or a concave mirror.However, when the irradiation surface is positioned near the focus of the converging means, it is like a normal grooving process. Since the entire area of the irradiation spot is uniformly melted and evaporated, in order to form clear fine irregularities G corresponding to the interference fringes, the irradiation is set at a position shifted in the depth direction from the above focal point. There is a need to. FIG. 5 exemplifies the above processing conditions. The range of Z ₀ including the focal point F of the lens S that converges the laser beam L is the damaged area, and the suitable processing areas Z ₁ and Z ₂ are above and below the damaged area. . However, if a strong pulsed laser beam can be obtained, it is possible to form fine irregularities G by irradiating without passing through the converging means.

Further, pulse laser light is used to form the fine irregularities G, and a large number of times are used in both the scanning method of grooving while continuously moving the irradiation position and the method of grooving into spots at a fixed position. The pulse is set to be repeatedly irradiated to the same position on the surface of the workpiece many times (usually several tens of times). Further, as the laser oscillator, it is desirable that the beam pattern has a single mode (TEM ₀₀ ) in order to form a clear interference fringe.

In order to obtain a clear iridescent color, it is desirable that the processing conditions are such that clear fine irregularities G are formed at the final stage of the pulse repeatedly applied to the same position on the surface of the workpiece. Then, in the scanning method in which the irradiation position is continuously moved and the groove is processed, the scanning speed is set so that the pulse of the laser light L strikes the same position of the workpiece many times.
As shown in, even if the laser light La does not penetrate into the thin film P from minute scratches or crystal grain boundaries, the fine unevenness G already formed in the latter half portion can enter the thin film P very efficiently as a grating coupler. The interference becomes stronger than that of the method of processing with the irradiation spot stopped, and more clear fine irregularities G can be formed.

By the way, since the laser beam L emitted from the laser oscillator generally has a beam pattern with a circular cross section, in the processing of the scanning method, the laser beam passes with a wider width toward the central portion of the processing line. The groove formation conditions are different between the central part and both sides. When the beam intensity is strong, the fine irregularities in the central part of the processing line tend to be crushed due to excess energy, while when the beam intensity is weak, the fine irregularities in the peripheral part of the processing line. Tends to become unclear due to lack of energy, and it is difficult to form uniform fine irregularities on the entire processing line. However, as shown in FIG. 6, the cylindrical lens SL is provided in the optical path of the laser beam L for forming the fine irregularities.
, The circular beam pattern is converted into a long beam pattern in the direction orthogonal to the scanning direction by interposing the longitudinal direction orthogonal to the beam scanning direction. The difference between the widths of the irradiation spots along the scanning direction is reduced, the irradiation energy in the line width direction is equalized, and the width of the irradiation spots along the scanning direction is narrow, resulting in fine irregularities formed during scanning. Therefore, it is possible to prevent the laser light from being irradiated more than necessary, and thus it is possible to form uniform and clear fine irregularities G over the entire width of the processing line.

Incidentally, DP in FIG. 6 is a Dope prism interposed in the optical path of the laser beam, and has the function of rotating the transmitted image at a double angle without rotating the plane of polarization by the rotation thereof. Therefore, when the fine irregularities G are formed by the scanning method with the cylindrical lens SL interposed, the vector direction of movement is calculated based on the movement command in the XY directions of the laser beam, and the dope prism DP is set based on this. By controlling the rotation, it is possible to adjust such that the major axis direction of the long beam pattern formed by the cylindrical lens SL is always orthogonal to the scanning direction.

[0032]

Example 1 A stainless steel plate having a machined surface mirror-polished in an electric furnace was heat-treated in air (1 atm) at each temperature shown in the table below for 30 minutes to oxidize a surface of the steel plate into a waveguide. A film was formed. This oxide film is mainly Cr ₂ O ₃ (including NiO)
And the film thickness and refractive index are measured at a wavelength of 0.6.
When the measurement was performed at 328 μm (the attenuation coefficient k of the oxide film was calculated as 0 because the film thickness is thin), the results in the following table were obtained. The damping coefficient k =
The refractive index of the surface portion was 4.3 and the refractive index n was 2.3.

[0033]

[Table 1]

Next, linearly polarized Q-switched Nd: YAG laser (single mode, wavelength 1.06 μm, pulsed) in air on each surface of the stainless steel plates A to C on which the waveguide made of the oxide film is formed. A pulsed laser beam with a width of 100 ns and a laser output of 0.5 mJ) is set 8 mm above the focus focused by the objective lens, and the irradiation position is continuously set at a scanning speed at which a pulse is applied about 40 times. When a line drawing of a predetermined pattern was drawn by irradiation, the width was about 0.5μ over the entire line width of about 0.1mm in each case.
Fine irregularities in which m grooves were densely aggregated at a pitch of about 1 μm were formed. This line drawing is composed of lines showing a variety of iridescent reflection gloss under both sunlight and indoor illumination light, and the shade of the reflection gloss changes variously depending on the illumination direction and the viewing angle. However, the line image of the stainless steel plate of Sample B showed the clearest reflection gloss.

Example 2 Using the same Q-switched Nd: YAG laser as in Example 1,
As shown in FIG. 6, a cylindrical lens SL and a dope prism DP are interposed in the optical path of the laser light,
When the surface of the stainless steel plate on which the waveguide of the oxide film was formed on the processed surface was irradiated with the pulsed laser light while scanning the same under the same conditions as in Example 1, the Dope prism was controlled by the control device in the same manner as in Sample B of Example 1. The rotation was controlled and scanning was performed so that the major axis direction of the oblong irradiation beam pattern was always orthogonal to the scanning direction, and a line image of a predetermined pattern was drawn. as a result,
A finer concavo-convex pattern is formed over the entire line width of about 0.3 mm, in which grooves each having a width of about 0.5 μm are arranged parallel to the line width direction at a pitch of about 1 μm. A line drawing was obtained which consisted of lines showing reflective gloss which changed to color.

Example 3 Two Q-switched Nd: YAG lasers similar to those in Example 1 were used, and the irradiation track of one pulse laser beam was configured so that the other pulse laser beam traced 1 mm apart. The irradiation position of the pulsed laser light is set to a position 8 mm above the focus focused by the objective lens, and the laser beam pulse leading to the same position is adjusted 40 times by adjusting the Q switch, and the pulse of the subsequent laser beam is set. At a scanning speed of 40 times each, the surface of the stainless steel plate mirror-polished in the air (1 atm) was continuously irradiated and a line image of a predetermined pattern was drawn.
Fine irregularities composed of a groove group in which grooves each having a width of about 0.5 μm were densely gathered at a pitch of about 1 μm were formed on the entire line width. This line drawing was composed of lines exhibiting reflective gloss that was variably changed to rainbow colors, as in the case of the processed product of Example 1. In addition, when the irradiation trajectory of only the leading laser beam in this case was examined, an oxide film of about 150 angstrom was formed.

Comparative Example 1 A mirror-polished stainless steel plate was not heat-treated, and its surface was continuously irradiated with pulsed laser light under the same conditions as in Example 1, using the same Q-switched Nd: YAG laser as in Example 1,
A line drawing of a predetermined pattern was drawn. However, no clear fine irregularities were formed on the line of this line drawing, and it showed only a dull gold reflection gloss different from the metallic gloss of the background.

Comparative Example 2 The same Q-switched Nd: YAG laser as in Example 1 was used on the surface of a stainless steel plate having an oxide film waveguide formed on the processed surface in the same manner as in Sample B of Example 1, and the irradiation position was changed. Pulse laser light was continuously irradiated in the same manner as in Example 1 except that the focus was set by the objective lens, and a line image having a predetermined pattern was drawn. However, the line of this line drawing had only one deep groove, and did not show any iridescent reflection gloss.

Example 4 Using an electric furnace, a metal titanium plate having a machined surface mirror-polished was heat-treated at 700 ° C. for 30 minutes in a nitrogen atmosphere (1 atm). The surface had a thickness of about 150 Å and was refracted. Nitride film (T
iN) was formed. Before processing, the damping coefficient k =
The refractive index n of the surface portion was 3.6. Next, the surface of the metal titanium plate having the nitrided film was continuously irradiated with pulsed laser light in air using the same Q-switched Nd: YAG laser as in Example 1 under the same conditions as in Example 1 When I drew a line drawing of the pattern, it was about 0.1 m
Fine concavo-convex formed of a groove group in which grooves having a width of about 0.5 μm were densely gathered at a pitch of about 1 μm was formed over the entire line width of m. This line drawing was composed of lines exhibiting reflective gloss that was variably changed to rainbow colors, as in the case of the processed product of Example 1.

The present invention is not limited to the above-mentioned embodiments, and metal materials other than those used in these embodiments,
Various non-metal materials such as ceramics and semiconductors can be processed, and the thin film of the waveguide can be formed by means other than the heat treatment as illustrated, and the Q switch Nd: YAG illustrated as an example for forming fine unevenness. It goes without saying that various pulsed laser oscillators other than lasers (preferably ones that can obtain laser light with a short pulse width) can be used.

[0041]

According to the iridescent color processing method of claim 1,
It is possible to easily form irregularities consisting of a collection of minute and dense grooves with a mutual spacing of about 1 μm or less corresponding to the interference fringes of laser light on the surface of the work piece in a short time, and based on these minute irregularities, reflection gloss It is possible to inexpensively provide a processed product having a beautiful decoration made up of lines and surfaces that change in a rainbow-like manner depending on the direction of incident light and the viewing angle. Further, in this processing method, a part of the irradiation laser light is propagated in the surface direction by the waveguide on the surface of the workpiece, and the interference between the propagating laser light and the irradiation laser light corresponds to the intensity distribution of the interference fringes. By forming the fine concavo-convex pattern, it is not necessary to intervene a special interference mechanism in the optical path of the laser beam or the laser oscillator itself, and the laser processing apparatus configuration is simple, and the coherence is high. Results in iridescent coloring with a very high degree of sharpness, and the processing speed can be increased and the processing time can be greatly shortened as compared with the conventional case of irradiating with laser light that has been previously made as interference light.

According to the iridescent coloring method of the second aspect, there is an advantage that it is possible to avoid the uniformization due to the melting in the irradiation spot of the pulsed laser light and to form fine fine irregularities corresponding to the interference fringes. .

According to the iridescent coloring method of claim 3, the thin film to be the waveguide can be efficiently formed in a short time by treating the object to be processed in the reactive gas or the reactive liquid. It is also possible to simultaneously form the thin film on the surfaces of many workpieces.

According to the iridescent coloring method of the fourth aspect, when the object to be processed is a metal material, it is easy to form an oxide film, a nitride film, or the like, which becomes a good waveguide, simply by performing heat treatment in the vapor phase. There is an advantage that it can be reliably formed.

According to the iridescent color processing method of the fifth aspect, the laser processing apparatus is arranged so that the laser beam for forming the waveguide is directed to the laser beam for forming the fine irregularities and irradiates the surface of the workpiece. By doing so, it is possible to continuously form the thin film of the waveguide and the formation of fine irregularities, so that it is possible to perform rainbow color development processing efficiently in a very short time and control so that the scanning patterns of both laser beams are the same. As a result, the waveguide can be provided only in the region where the fine irregularities need to be formed.

According to the iridescent color processing method of the sixth aspect, the coupling efficiency of the laser light to the waveguide can be sufficiently enhanced, so that fine irregularities for producing a more vivid iridescent color can be formed. There is.

According to the iridescent color processing method of claim 7, particularly when fine irregularities are continuously formed by a scanning method,
Irradiation energy in the width direction of the workpiece line can be equalized, and more than necessary laser light can be prevented from hitting the fine irregularities formed during scanning, and thus uniform and clear fine irregularities over the entire width of the processing line. Can be formed.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view for explaining a mechanism of forming fine irregularities in the iridescent color processing method of the present invention in the order of steps A to C.

FIG. 2 is a schematic vertical cross-sectional view showing a forming process of a fine unevenness by a scanning method in the processing method.

FIG. 3 is a schematic vertical sectional view showing a propagation state of laser light through a waveguide in the same processing method.

FIG. 4 is a schematic vertical sectional view showing a method of continuously forming a waveguide and fine irregularities by laser light in the same processing method.

FIG. 5 is a schematic diagram showing a processing region of laser light used for forming fine irregularities in the processing method.

FIG. 6 is a schematic front view showing an example in which a cylindrical lens is used to form fine irregularities in the processing method.

[Explanation of symbols]

 W Workpiece P Thin film used as waveguide for laser light L Irradiated laser light La Laser light propagating in waveguide Lb Laser light for forming waveguide S Lens (converging means) F Focus G Fine unevenness SL Cylindrical lens

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tokhiko Oshima, 1-9-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture, Osaka Fuji Kogyo Co., Ltd. (72) Inventor, Shigekazu Hirata 1-9-1, Jokoji Temple, Amagasaki City, 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 (7)

[Claims] 1. A thin film that serves as a waveguide for laser light is formed on the surface of a workpiece, and then the converged pulsed laser light is irradiated onto the surface on which the thin film is formed so that multiple pulses strike the same position. By causing the laser light propagating through the thin film and the irradiation laser light to interfere with each other, fine irregularities corresponding to the intensity distribution of the interference fringes are formed on the surface of the workpiece, iridescent coloring processing. Method. 2. The rainbow color developing method according to claim 1, wherein the pulsed laser light is applied at a position shifted in one direction in a depth direction from a focus of the converging means. 3. The rainbow color developing method according to claim 1, wherein the thin film serving as the waveguide of the laser light is formed by surface modification of the workpiece. 4. A thin film which serves as a waveguide for laser light by forming a coating film made of a reaction product of a material metal and a gas component by heat-treating the work material in a reactive gas. The rainbow color processing method according to claim 3. 5. The iridescent color processing method according to claim 3, wherein the heat treatment in the reactive gas is performed by irradiating a laser beam different from the laser beam for forming the fine irregularities. 6. The rainbow color developing method according to claim 1, wherein the thin film serving as a waveguide for the laser light has a thickness of 50 angstroms or more. 7. The circular beam of the laser light is converted into a long beam pattern in a direction orthogonal to the beam scanning direction by interposing a cylindrical lens in the optical path of the laser light for forming fine irregularities. 6. The iridescent color processing method according to any one of 6 above.