JP2007229778A - Marking method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a marking method by which multicolor marking is made possible on the surface of a material such as aluminum without using a complicated and chemical machining process. <P>SOLUTION: On the surface of a material such as aluminum which becomes a workpiece held by the X, Y stages 4, an ultra short pulsed laser having an oscillation pulse width of ≤1 picosecond is modulated/emitted using a femtosecond laser device or the like, thereby forming a micro structure on a laser beam irradiation part on the surface of the aluminum material. As a result, a certain specific color tone can be provided, and also by varying an irradiation position and laser power, different color tones are exhibited, and the marking is performed at least in two color tones. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aluminum coloring marking method, and more particularly, to a multicolor marking method and apparatus that exhibits a plurality of color tones by irradiating an aluminum surface with laser.

  In general, for marking on a metal surface, engraving, engraving with a hard metal, mechanical cutting, sandblasting, etching, or the like is used. However, these methods cannot meet the demand for changing the color tone, and other methods have been proposed as follows.

One is to cause physical or chemical changes to the metal surface or the finish layer such as the coating layer, plating layer, etc. by irradiating laser light with a wavelength of about 1 μm or less, such as excimer laser or YAG laser, This is a method of changing the color tone (see, for example, Patent Document 1).
In this method, the color tone once changed exhibits a stable color tone over a long period of time, and a clean display portion can be formed without causing problems such as blurring, distortion, and fading due to the changed color tone. Also, by using very thin laser light, very fine parts such as letters can be reproduced clearly, and the type and wavelength of laser light, irradiation time, etc. depending on the metal material and type of finishing treatment, etc. By selecting the number of shots and the like, there is an advantage that the hue obtained by changing the color tone can be changed, and thereby the hue of the mark can be adjusted.

The other is that after anodizing the aluminum and aluminum alloy materials, an intermediate electrolytic treatment is performed in a bath mainly composed of an organic acid, an inorganic acid or a salt thereof, and then a metal salt. After the electrolytic coloring treatment is performed in a bath containing, the electric power of the paint containing 0.6 to 2.4% by weight of white pigment and 0.04 to 2.4% by weight of black pigment based on the resin solid content This is a method of applying a coating (see, for example, Patent Document 2).
JP-A-6-305241 JP 2001-329397 A

  However, the above prior art is a method of exhibiting a single color tone, and a simple method capable of exhibiting two or more colors is desired.

  In view of the above circumstances, an object of the present invention is to provide a simple multicolor marking method and apparatus.

In order to achieve the above-described object, the present invention irradiates the surface of a workpiece with an ultrashort pulse laser having an oscillation pulse width of 1 picosecond or less, and forms a microstructure in the irradiated portion. Marking having a specific color tone is performed on the surface of the workpiece.
In addition, the present invention is characterized in that marking of a plurality of colors having different color tones is performed by changing the position of irradiating the ultrashort pulse laser and the laser power.

  According to the marking method and apparatus of the present invention, it is not necessary to select various kinds of laser light, such as the type, wavelength, irradiation time, and number of shots by marking with an ultrashort pulse laser, and various acids and pigments. There is no need to perform electrolytic treatment, and good quality marking can be easily performed, and multicolor marking can be easily performed by changing the laser power.

FIG. 1 is a schematic view showing an example of an apparatus for carrying out a multicolor marking method for aluminum using an ultrashort pulse laser according to an embodiment of the present invention.
The X and Y stages 4 position and hold the workpiece 5 made of aluminum and control the movement of the workpiece 5 in the X and Y directions. The femtosecond laser apparatus 1 uses a femtosecond laser as an ultrashort pulse laser. Irradiate with polarization control.
The objective lens 3 converges the laser beam from the femtosecond laser device 1 on the surface of the workpiece 5 held on the X and Y stages 4.

Next, the technical principle of the marking method performed by the apparatus shown in FIG. 1 will be described.
First, as a prior art of the present invention, it has recently been proposed to use an ultrashort pulse laser of 1 picosecond or less for surface processing of a metal material. In particular, non-thermal processing is possible due to the fact that it is a phenomenon shorter than the multiphoton absorption and thermal relaxation time, and the processing resolution is below the diffraction limit of light due to non-linear response. It is known that processing is possible.

In addition, it has been reported that a fine periodic structure smaller than the irradiation laser wavelength can be obtained by low fluence processing (see Japanese Patent Application Laid-Open No. 2001-212796).
In this report, the surface of a solid material is irradiated with a low-fluence ultrashort pulse laser (femtosecond laser) with a polarization controlled to form a microstructure smaller than the wavelength of the irradiated laser.
Then, by irradiating the surface of the solid material with linearly polarized ultrashort pulse laser, it is possible to form a fine structure consisting of elongated protrusions along the direction orthogonal to the polarization direction, and to irradiate with circular polarization A fine structure composed of granular protrusions can be formed. The size of such a microstructure has a positive correlation with the wavelength of the laser to be irradiated, and it is a proposal that the size of the microstructure can be controlled by selecting the wavelength.

In addition, the present inventors ablated a linearly polarized femtosecond laser pulse having a wavelength of 775 μm, a pulse width of 150 femtoseconds, and an optical beam spot diameter of 10 μm on the surface of a quartz substrate optically polished with nanometer smoothness. As a result of single pulse irradiation in the vicinity of the threshold value, a three-dimensional pattern with a processing range of about 2 μm in diameter and a fine structure with a period of about 0.5 μm inside can be obtained (see, for example, JP-A-2005-270992) ).
When this fine structure was subjected to raster scanning with a pulse irradiation interval of 1 μm and a feed interval of 1 μm to attempt two-dimensional dot pattern processing, a pattern having a periodic fine structure of several tens of nanometers over the entire surface was obtained. Can be formed.

  The phenomenon that this periodic microstructure is formed occurs in various solid materials, but it is expected that the plasma temperature generated in the vicinity of the irradiated part by the ultrashort pulse laser irradiation on the material surface will differ from material to material. The Therefore, it is considered that the generation pattern differs depending on the material.

  Therefore, in order to investigate how the generation of this periodic fine structure occurs depending on the material, the laser power is increased from the power at which the periodic fine structure is clearly formed with various materials, and the generation pattern is observed. It was decided to.

In the crystalline lens and glass, the drilling was increased due to the increased irradiation power, and the periodic microstructure could not be confirmed.
However, a unique phenomenon was found in metal materials. For example, when surface processing was performed using stainless steel, a structure having a periodicity with an average height and a period of about 10 μm appeared. A random fine structure of about 0.5 μm was formed on the surface of each individual structure (see FIG. 2).
At this time, the processing depth is about 13 μm, and the structure is 20 times the periodic fine structure. The macroscopic color tone is black.

Further, when the same processing was performed with aluminum, a random microstructure was developed instead of a periodic microstructure (see FIG. 3). In this case, the height is about 0.5 μm at the maximum, but the distribution width is expanded from about 0.1 μm to several μm.
Note that the upper half of FIG. 3 is a portion irradiated by raster scanning at a laser power of 10.5 mW, and the lower half is a portion irradiated by raster scanning at 0.25 mW. The scanning speed and the optical spot diameter are both 1 mm / second and 10 μm.
These exhibited different shades of light gold and whited silver.

  Therefore, in the present embodiment, marking having at least two color tones is realized by using the property that the color tone of the material surface changes by changing the laser power to be irradiated.

Next, Example 1 will be described using specific numerical values.
First, in the marking processing of this example, the femtosecond laser apparatus 1 having an oscillation wavelength of 775 nm, a peak power of 800 mW, a pulse energy of 800 μJ / pulse, a pulse width of 200 femtoseconds, and a pulse repetition frequency of 1 kHz was used.
Moreover, aluminum is used as the target material.

Then, the laser beam 2 is condensed on the surface of the aluminum by the objective lens 3, and the beam spot of the femtosecond laser having an optical beam spot diameter of 10 μm is changed from 0.1 mW to 20 mW. The surface of the aluminum workpiece 5 was two-dimensionally scanned at a speed of 1 mm / second.
In this embodiment, the X and Y stages are used for two-dimensional scanning. However, for example, a galvano scanner may be used, and any means capable of two-dimensional scanning with a laser beam may be used.

The aluminum workpiece 5 can be applied to jewelry, a watch name plate, and the like.
However, as long as aluminum is used as the engraving material, the application form is not restricted, and cards, various home appliances, furniture, automobiles, and the like may be used.

Such a marking method of this example can be used in the following processing examples.
(Processing Example 1) An aluminum plate can be attached to a jewelry, and one color tone can be marked on the surface of the aluminum plate as a background pattern, and the name and birthday of the owner can be marked with another color tone. In addition, a pattern may be drawn using two color tones.
(Processing example 2) Individual information can be marked through glass by using aluminum for the nameplate of the watch.

It is the schematic which shows an example of the apparatus for enforcing the marking method by embodiment of this invention. It is explanatory drawing which shows the fine structure of the marking shape formed in the aluminum surface by embodiment of this invention. It is explanatory drawing which shows the fine structure of the marking shape formed in the stainless steel surface by embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Femtosecond laser apparatus, 2 ... Laser beam, 3 ... Objective lens, 4 ... X, Y stage, 5 ... Aluminum workpiece.

Claims (6)

  By irradiating the surface of the workpiece with an ultrashort pulse laser having an oscillation pulse width of 1 picosecond or less and forming a fine structure on the irradiated portion, a specific color tone is formed on the surface of the workpiece. A marking method characterized by performing marking.   2. The marking method according to claim 1, wherein a marking of a plurality of colors having different color tones is performed by changing a position of irradiating the ultrashort pulse laser and a laser power.   The marking method according to claim 1, wherein the workpiece includes an aluminum material. Holding means for holding the workpiece;
Laser irradiation means for irradiating the surface of the workpiece with an ultrashort pulse laser having an oscillation pulse width of 1 picosecond or less;
A marking device, wherein a marking having a specific color tone is performed on a surface of the workpiece by forming a fine structure in a laser irradiation portion of the workpiece.   It has a control means for changing the position and laser power to irradiate the ultra-short pulse laser, and by changing the position and laser power to irradiate the ultra-short pulse laser, marking of multiple colors having different color tones is performed. The marking device according to claim 4, wherein 6. The marking device according to claim 5, wherein the workpiece includes an aluminum material.

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