JPH07148583A - Laser beam processing method of metallic surface - Google Patents

Abstract

PURPOSE:To obtain a metallic product exhibiting iridescent and beautiful reflection luster by forming fine ruggedness corresponding to the intensity distribution of the interference patterns generated on an irradiation surface to the metallic surface. CONSTITUTION:A laser beam R1 emitted from a laser beam source D1 is composed of two bright pattern components B1, B2. Bright pattern components B1, B2 are multiplexed by a multiplexing lens L1 and a multiplexed beam is magnified by a magnifying lens L2, is directionally switched 90 deg. by a reflection mirror M1 for direction switching and is converted by a condenser lens L3 for processing. A work piece W1 placed on an X-Y table T is so placed as to be irradiated with the beam B in a position further from a focus F of the condenser lens L3. The fine ruggedness corresponding to the intensity distribution of the interference patterns generated by the metallic surface of the work piece W1 on the surface irradiated with the laser beam B are formed on the metallic surface. As a result, ornamental working of various kinds of patterns is efficiently executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for densely forming fine irregularities on a metal surface by a laser beam, and for example, it can be used for various metal ornaments, metal home appliances, metal industrial products, and the like. It is used when a beautiful reflection gloss such as iridescent is imparted to the whole or a part of the surface of a metal product.

[0002]

2. Description of the Related Art Laser light is coherent light of a constant wavelength with a uniform phase and has excellent directivity as a beam, and since it can be converged by a lens and high energy can be concentrated on a minute spot, it has recently become a metal. It is often used for cutting, drilling, welding, etc. However, in the conventional metal processing using such a laser beam, high heat is used at the focal position of the processing condensing lens, that is, at the position where the energy density of the beam is maximum, and the spot of the beam at this focal position is used. It is a diameter that melts and evaporates metal instantaneously.

However, even if the laser beam is emitted as perfect parallel light from the laser oscillator, it spreads due to diffraction and the accuracy of the optical system forming the optical path is limited. The spot diameter is generally several μm to 10 μm, and it is extremely difficult to narrow it down to the wavelength of the laser beam. Therefore, the conventional laser processing could not form fine irregularities of 1 μm or less on the metal surface.

By the way, stainless steel products have been increasingly used in various fields due to advantages such as rustlessness, mechanical strength, and heavy weight. However, the product surface gives a metallic ground color and gives a cold feeling. Therefore, in recent years, attempts have been made to form various patterns by applying coloring to the surface while maintaining the original metallic luster to some extent. As a typical coloring processing means, for example, the surface of a stainless steel material is masked with a synthetic resin or the like, the mask is removed into a large number of stripes by a laser beam, and the stripes are immersed in a coloring chemical solution. A method of removing the remaining mask after chemically coloring the mask-removed portion has been adopted.

[0005]

However, with the above-mentioned coloring processing means, it is only possible to impart a certain shade to the processed portion, and for example, coloring such as rainbow colors or iridescent colors that causes a color change depending on the viewing angle. There is a problem that the decoration processing method that treats multi-colored coloring is not applied, and many steps are required for coloring, which is very troublesome and costly.

Therefore, the inventors of the present invention have various hues of various metal surfaces such as the above-mentioned stainless steel as a whole or a part of the surface of the metal, and various colors depending on the viewing angle and the incident direction of external light. As a result of repeated studies on the changing method, when minute unevenness of about 1 μm or less close to the wavelength range of visible light was densely formed on this surface, this uneven surface splits incident light like a diffraction grating. We have obtained the knowledge that a variety of rainbow-colored reflection glosses are generated from the reflection. However, such fine irregularities are difficult to form by the conventional metal processing means using the laser beam as described above, and even if the focal spot diameter by the processing condenser lens is sufficiently reduced, Since it is necessary to form the unevenness one by one, it takes a huge amount of time for processing and cannot be put to practical use at all.

In view of such circumstances, the present invention provides an epoch-making laser processing method capable of easily forming dense fine irregularities on a metal surface in a short time, unlike the conventional metal processing means using a laser beam. Therefore, it is an object of the present invention to realize various metal products in which the reflection gloss of, for example, the whole or a part of the surface is varied in various colors such as iridescent depending on the viewing angle and a so-called iridescent color is exhibited.

[0008]

As a means for achieving the above object, a laser processing method for a metal surface according to the present invention corresponds to the intensity distribution of an interference pattern generated on the irradiation surface by irradiating the metal surface with a laser beam. The structure in which the fine irregularities are formed on the metal surface is adopted.

[0009]

As is well known, the laser beam is coherent light and has perfect coherence, so that an interference pattern is produced when beams having the same frequency and a certain phase difference are superposed. Therefore, the laser beam is converged by a converging means such as a condenser lens or a concave mirror, a metal surface is positioned at a position deviating from the focal point to either shallow or shallow, and a bright and dark striped pattern of the interference pattern is generated on the surface. If the bright part has an energy density capable of melting and evaporating the metal,
On the metal surface, unevenness in which the bright part of the pattern is concave and the dark part is convex, that is, dense unevenness corresponding to the intensity distribution of the interference pattern is formed.

However, since the interference pattern in the irradiation spot is composed of hundreds of minute bright and dark stripes with a mutual interval of about 1 μm or less close to the wavelength range of visible light, irradiation of the beam interference light is performed. X along the metal surface
A single scan with relative displacement in the Y-direction or in the Y-direction results in a large number (eg, a Y with medium power) on the metal surface.
Even with an AG laser processing machine, about 300 concave and convex stripes are formed at once. Thus, since the metal surface obtained by repeating the above scanning has minute irregularities densely, it acts in the same way as a diffraction grating to disperse and reflect the incident light, and to see it in various hues like rainbow colors. Also, it shows a reflective gloss that changes variously depending on the direction of incident light.

On the other hand, in the conventional method of positioning the workpiece surface at the focal position of the processing-like condensing lens, such as metal working with a laser beam, the focal spot diameter of the lens can be narrowed down to about 1 μm. However, since only one groove can be formed by one scanning, a scanning number of several hundred times or more is required to obtain the same reflective gloss as that of the method of the present invention, which requires a huge processing time. Become.

In order to generate an interference pattern on the irradiation surface of the laser beam, the light pattern components of the low-order multi-mode laser light are overlapped with each other or the beams divided from a single laser light are overlapped. Therefore, it is sufficient to irradiate the laser beam as the interference light, but it is possible to generate an interference pattern depending on the irradiation condition even if the laser beam does not interfere. Further, the beam irradiation intensity required to form fine irregularities corresponding to the interference pattern on the metal surface differs depending on the metal material and the irradiation time per unit area (length), and accordingly the output of the laser light source Various conditions such as the focal spot diameter of the processing condensing lens and the depth of the irradiation surface with respect to the focal position may be appropriately set.

In order to displace the irradiation position of the laser beam on the metal surface in the XY directions, the mounting portion of the workpiece may be moved to displace the workpiece side, or two sheets for displacement in each of the XY directions. The interference light side may be displaced by an XY scanner (see FIG. 6) or the like in which the rotating mirrors are combined. This X
When processing a metal surface using a Y scanner, the beam length up to the metal surface changes depending on the angle of the rotating mirror. Therefore, in order to correct this, a focus displacement means such as a Z scanner described later is used. It is desirable to combine them.

Further, by displacing the focal position of the converging means in the optical axis direction, the focal position can be changed in accordance with the Z direction position of the irradiation surface even on a metal surface having a three-dimensional shape such as a curved surface. This makes it possible to keep the intensity of the interference light on the irradiation surface constant and form uniform unevenness on the entire processed portion of the metal surface. The focus displacing means does not necessarily have to move the converging means itself, and may be any one that displaces any of the lenses interposed in the optical path in the optical axis direction. In the focus displacement operation, the surface shape of the workpiece is measured in advance, the measurement result is input to the control system, and the lens is automatically displaced in the optical axis direction by numerical control. The Z scanner (Dynamic Focus) used for processing can be used.

According to the method of the present invention, however, it is possible to form a rainbow-like shining pattern by drawing various patterns on the metal surface by moving the irradiation position of the laser beam. To form such a pattern, a program of the pattern is inputted to the control system of the XY displacement means or the Z direction displacement means, and the irradiation area of the interference light is changed to the XY direction or the Z direction based on the signal of this control system. It may be changed automatically.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on illustrated embodiments.

[0017] Figure 1 shows a device configuration of a laser processing method of the first embodiment using the laser light source D ₁ of the TEM ₁₀ mode.
In this case, the laser light R ₁ emitted from the laser light source D ₁
Is composed of _two bright pattern components B ₁ and B ₂ , and these bright pattern components B ₁ and B ₂ are combined lenses L ₁
Are combined by the magnifying lens L ₂
After being enlarged by, the direction is changed by 90 ° by the direction-changing reflecting mirror M ₁ , and is converged by the processing condenser lens L ₃ . Then, in the workpiece W ₁ placed on the XY table T, the flat metal surface thereof has the condenser lens L.
_The position is set so that the beam B is irradiated at a position farther than the focal point F of ₃ . In addition, CL is a cylindrical lens for deforming the light beam cross section into a slender shape, and in this case, the direction is set so that the light beam cross section becomes long in the direction in which the bright pattern components B ₁ and B ₂ are arranged. The interference pattern becomes clearer.

In the above structure, the surface of the workpiece W ₁ is scanned by the beam B by moving the XY table T in the X direction, and the XY table T is moved in the Y direction each time this one scanning is completed. By moving a distance corresponding to the beam spot diameter on the irradiation surface and repeating the scanning sequentially, the beam irradiation is performed on the entire surface of the workpiece W ₁ or the entire region such as a partial pattern. Since the beam irradiation position is in the interference area of the bright patterns B ₁ and B ₂ farther than the focal point F, the phantom line circle in FIG. As shown in the enlarged view inside, hundreds of recesses I corresponding to the bright parts of the interference fringes of the interference pattern are formed.

As a laser light source D ₁ , YAG (Nd ³⁺
・ Y ₃ Al ₅ O ₁₂ ) laser oscillator is used, and TEM ₁₀ mode laser pulse light (oscillation wavelength 1.06 μm, pulse width 100 ns, pulse repetition frequency 1 kHz, average output 4 w) is focused for processing with a focal depth of 100 mm. Lens L ₃
And the surface of the workpiece W ₁ made of a stainless steel plate is positioned 4 mm below the focal point F, and XY
When processing was performed by setting the moving speed of the table T in the X direction to 100 / min, the beam spot diameter on the irradiation surface was about 0.3 mm, and the mutual spacing and depth within 0.3 mm width for each scan. About 300 concave streaks I each having a size of about 1 μm were formed. Then, the processed surface of the workpiece that has been irradiated shows a variety of rainbow-colored reflective gloss under both sunlight and indoor illumination light, and this hue changes variously depending on the illumination direction and the viewing angle.

[0020] Figure 2 shows a device configuration of a laser processing method of the second embodiment using the laser light source D ₂ of the TEM ₀₀ mode, i.e. single mode. In this case, the laser light R ₂ emitted from the laser light source D ₂ is split into a transmitted light beam B ₃ and a reflected light beam B ₄ by a 50% transmissive semi-transparent mirror BS, and the beam B ₄ is reflected by the reflecting mirror M ₂ At 90 ° and is combined with the beam B ₃ by the combining lens L ₁ , and this combined beam B passes through the magnifying lens L ₂ and the reflecting mirror M ₁ as in the first embodiment, and is collected for processing. The light is converged by the optical lens L _3, and the workpiece W ₁ is placed on the XY table T with its position set as in the first embodiment. Even in this case, therefore, the moving operation of the XY table T similar to that of the first embodiment causes the interference light of the beams B ₃ and B ₄ to be irradiated on the surface of the workpiece W ₁ . Like the enlarged view shown in the virtual circle 2 of FIG. 2, hundreds of recesses I corresponding to the bright portions of the interference fringes of the interference pattern are formed as in the first embodiment.

FIG. 3 shows the apparatus construction of the laser processing method of the third embodiment using a 45 ° spectral prism P as the beam splitting means. The construction is the same as that of the second embodiment except for the splitting portion. In this case, TEM ₀₀ emitted from the laser light source D ₂
The mode laser light R ₂ is split into two directions of reflected light beams B ₅ and B ₆ by the prism P, and both beams B ₅ and B ₆ are redirected by the reflecting mirror M ₂ and then combined with each other. L
After being combined at _1, the surface of the workpiece W ₂ is irradiated as interference light through the same optical path as in the second embodiment, and the same processing as described above is performed.

The semi-transparent mirror BS in the second embodiment is 2
It is possible to divide the beam into three beams by using a single prism or by using a triangular pyramid prism as the prism P in the third embodiment.

FIG. 4 shows the apparatus construction of the laser processing method of the fourth embodiment in which the image rotating prism DP is interposed in the optical path in front of the combining lens L ₁ , and the second embodiment except the image rotating prism DP is shown. It has the same configuration as. In this case, since the direction of the interference fringes of the interference pattern of the beam B changes with the rotation of the prism DP, for example, by intermittently rotating the prism DP during one scan, the workpiece W ₁ On the surface, a group of concave stripes I having different orientations are sequentially formed on one scanning line as shown in an enlarged view in an imaginary line circle in FIG. 4, and if the prism DP is continuously rotated, the concave stripes are formed. I becomes continuous in the waveform. Although the laser beam R ₂ emitted from the laser light source D _{2 in the} TEM ₀₀ mode is split by the semitransparent mirror BS in the drawing, when the spectral prism P as in the third embodiment is used as the beam splitting means. Also, when the TEM ₁₀ mode laser light source D ₁ as in the first embodiment is used, the same uneven processing can be performed by interposing the image rotation prism DP in the optical path. According to this processing method, however, the incident light is variously changed and reflected on the processed surface, so that the reflective gloss just like opal stone is obtained.

FIG. 5 shows a workpiece W having a curved surface.₂To
The apparatus configuration of the laser processing method of the fifth embodiment applied is shown.
You In this case, the combining lens L₁Can be moved along the optical axis
It is configured and the combining lens L₁Processing along with the movement of
Condensing lens L₃The focal point F of the
Move. Therefore, the workpiece W₂Pre-measure the surface shape of
Then, the result is input to the control system C, and the beam
Workpiece W at the irradiation position of B₂Z position on the surface of
The lens L is automatically controlled by the control system C corresponding to₁Strange
Position to keep the intensity of the interference light on the irradiation surface constant
It is possible to maintain and perform uniform unevenness processing. In addition,
Wave lens L₁Condensing lens L instead of ₃Change itself
You may make it rank. Also, such focus displacement
The means can be applied to any of the methods of the first to fourth embodiments.
It

FIG. 6 shows an embodiment in which the irradiation position of the beam interference light is displaced in the XY directions on the beam side by the XY scanner S. The XY scanner S includes a rotating mirror MX for displacing in the X direction and a rotating mirror MY for displacing in the Y direction, and irradiates the surface of the workpiece W ₁ with a beam focused by the processing condenser lens L ₃ . Since the position is displaced in the X direction by the rotation of the rotary mirror MX and is displaced in the Y direction by the rotation of the rotary mirror MY, it is possible to perform the scanning while the workpiece W ₁ is fixed. By the way, in this case, since the beam length reflected by the turning mirror MX is equal on the spherical surface centered on the reflection point as indicated by the imaginary line l, for example, as shown in the drawing, the surface to be processed is flat. In the object W ₁ , the distance from the focal point F changes depending on the irradiation position in any scanning in the XY directions. This change controls the displacement of the focal point F position in combination with the focal point displacing means as in the fifth embodiment. It can be corrected by Since a beam scanning device combining an XY scanner and a Z scanner for laser processing is commercially available, this commercially available device can also be used in the present invention.

FIG. 7 shows an embodiment in which a transmissive object O is interposed in the optical path of the beam B ₄ of the two beams B ₃ and B ₄ split from the TEM ₀₀ mode laser beam R ₂ . In this case, since the information of the two-dimensional transmission shape of the transmission object O is included in the interference pattern of the combined interference light, the above information is also recorded as unevenness on the surface of the workpiece W ₁ .
Since this corresponds to the dry plate of the hologram, the transmissive shape is reproduced during the reflective gloss of the surface. For example, if the shape is a triangle, a triangle appears to appear in the reflective gloss. Therefore, by selecting the transparent object O, it is possible to provide an extremely peculiarly decorated metal product in which various shapes appear as holography in the iridescent reflection gloss. Of course, the bright pattern component B in the first embodiment of FIG.
The same holography can be achieved by interposing the transmissive object D in one of the optical paths of ₁ and B ₂ .

In the present invention, the design of the optical system can be modified in various ways other than the illustrated one. For example, although the converging lens L ₃ is used as the converging means in the above embodiments, a concave mirror is used instead. You may. Although in the embodiment uses a magnifying lens L ₂ and the diverting reflector M _2, can omit the magnifying lens L ₂ by combining lens L ₁ and the depth of focus of the machining condenser lens L _3, also the It is also possible to omit the reflecting mirror M ₂ and position the workpiece on the optical axis of the laser light emitted from the laser light source, or to change the beam direction to several orders by using a plurality of reflecting mirrors M _2. is there. Furthermore,
As in the first embodiment, the light pattern components of the low-order multi-mode laser light are overlapped with each other, and as in the second to fourth embodiments, the beams divided from the single laser light are overlapped to form interference light. In addition to the laser beam, it is possible to generate an interference pattern on the irradiation surface depending on the irradiation conditions even with a laser beam that does not interfere.

Further, in the laser processing method shown in each of the above-described embodiments, the laser-induced thermochemical reaction is utilized to process the metal surface with a smaller laser light output as compared with the case of processing in the atmosphere when the reaction gas atmosphere is used. can do. Further, when the metal surface processed by the laser processing method according to the present invention is damaged, the reflection efficiency of the fine uneven strips decreases,
In order to provide the processed metal surface with durability, if a transparent oxide film, for example, alumina is coated on the metal surface by a method such as sputtering, it can be used in a field requiring durability.

The metal surface having fine irregularities formed by the method of the present invention can also be used as a transfer mold. For example, if the irregularities are transferred to the plastic surface by heat transfer and aluminum or the like is vapor-deposited, it becomes a packaging paper or the like. The decorative film to be used can be easily produced.

The laser oscillator used as the laser light source in the present invention is not particularly limited as long as it can emit a laser beam having good coherence. For example, in addition to the YAG laser shown in the embodiment, a ruby laser or glass. Solid-state lasers such as lasers and gas lasers such as CO ₂ lasers and excimer lasers may be mentioned, but laser light of pulse oscillation is particularly preferable.

[0031]

EFFECTS OF THE INVENTION According to the method of the present invention, it is possible to easily form extremely fine dense irregularities of about 1 μm or less on a metal surface using laser light in a short time. It is possible to provide a metal product in which the entire surface or a part of the pattern is rainbow-colored and has a beautiful iridescent reflection gloss that changes variously depending on the viewing angle and the direction of incident light. Therefore, the apparatus applied to the above method is structurally extremely simple and can be manufactured at low cost, and the existing laser processing apparatus can be used without making a great modification.

Further, the method of the present invention is characterized by the characteristics of laser processing,
That is, it is suitable for high-mix low-volume production, and it is possible to efficiently decorate various types of patterns. However, the metal surface to be processed does not necessarily have to be a flat surface, and even a metal surface having a crystal cut or a little unevenness can be processed without being affected by this, and non-contact processing is also possible. For this reason, it is not necessary to firmly support the work piece in the course of processing, and only temporary fixing is sufficient, so that the working operation is easy.

Further, the fine concave-convex grooves on the metal surface processed according to the present invention can be transferred onto the surface of the resin film by, for example, heat transfer, and post-processing such as aluminum vapor deposition is performed on the surface of the transferred resin film. As a result, a decorative film used for wrapping paper or the like can be easily manufactured, and the present invention can also be applied as a transfer technology for these.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of a laser processing apparatus used in a first embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a laser processing apparatus used in the second embodiment.

FIG. 3 is a schematic structural diagram of a laser processing apparatus used in the third embodiment.

FIG. 4 is a schematic structural diagram of a laser processing apparatus used in the fourth embodiment.

FIG. 5 is a schematic structural diagram of a laser processing apparatus used in the fifth embodiment.

FIG. 6 is a schematic perspective view of a main part of an embodiment using an XY scanner.

FIG. 7 is a schematic structural diagram of the same apparatus of the embodiment to which holography is applied.

[Explanation of symbols]

B laser beam B ₁ , B ₂ bright pattern component B _{3 to} B ₆ divided beam D ₁ , D ₂ laser light source F focus L ₃ processing condenser lens, R ₁ , R ₂ laser light T XY table W ₁ , W ₂ Workpiece

 ─────────────────────────────────────────────────── ─── 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 (1)

[Claims] 1. A laser processing method for a metal surface, which comprises irradiating a laser beam on the metal surface, and forming fine irregularities on the metal surface corresponding to the intensity distribution of an interference pattern generated on the irradiation surface.