JPH10309900A - Laser coating removing method and laser treating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove a coated film by emitting a laser beam of an infrared region to an object to be treated formed with a coated film on the surface, removing the film by ablation, and removing residue which could not have been removed by ablation for emitting the beam of an ultraviolet region. SOLUTION: Infrared laser beam 63 incident to a laser emitting head 10 is emitted to a surface of an object 1 to be treated via a laser transmission arm 62 to remove a coated film by ablation. In this case, a height from a surface of the object 1 to a condenser lens 23 is adjusted to regulate energy density, thereby always providing the ablation by suitable energy density. At this time, if a thin coated film remains on the surface, a laser beam generator is switched, an ultraviolet laser beam is incident to the head 10, the ultraviolet beam is used to similarly remove the thinly remained film by the ablation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating removing method using laser light and a laser processing apparatus suitable for the coating removing method.

[0002]

2. Description of the Related Art A highly toxic chemical called methylene chloride is mainly used for removing paint on an outer body of an aircraft or the like. Conventionally, this agent is sprayed on the painted surface,
After weakening the paint, the paint film was manually removed by scraping off the surface of the fuselage skin.

[0003]

The above-mentioned conventional method for removing a coating film is not only dangerous, but also has low working efficiency. There is also a problem in the collection and disposal of the removed material.

An object of the present invention is to provide a paint film removing method capable of removing a paint film without using a chemical, and a laser processing apparatus suitable for removing the paint film.

[0005]

According to one aspect of the present invention, a surface of a processing target having a coating film formed on a surface thereof is provided with:
Irradiating a laser beam in an infrared region to remove the coating film by ablation, and irradiating a laser beam in an ultraviolet region to a surface of the object to be processed; Removing the remaining residue that could not be removed by irradiation by ablation.

According to another aspect of the present invention, an infrared laser light source for outputting laser light in an infrared region, an ultraviolet laser light source for outputting laser light in an ultraviolet region, and an output from the infrared laser light source are provided. A first lens for condensing or diverging the infrared laser light, and irradiating the surface of the processing object with the first lens, and condensing or diverging the ultraviolet laser light output from the ultraviolet laser light source to the surface of the processing object. A laser processing apparatus having an irradiating second lens is provided.

[0007] When only infrared laser light is applied, the coating film remains thin on the base surface, and it may be difficult to remove the thin remaining coating film. By irradiating with ultraviolet light, a thin remaining coating film can be easily removed.

[0008]

FIG. 1 is a schematic perspective view of a laser processing apparatus according to an embodiment of the present invention. The laser irradiation head 10 is in contact with the surface of the processing target 1. The laser irradiation head 10 is a box-shaped container 1 having an opening on the processing object 1 side.
1 and optical components housed therein. A transparent window 12 is attached to a side surface of the box-shaped container 11, and the inside can be visually observed through the transparent window 12. Note that the box-shaped container 11 itself may be formed of a transparent material.

[0009] The laser irradiation head 10 is attached to the tip of a manipulator arm 50. The manipulator arm 50 is controlled by the manipulator body 51 and moves and supports the laser irradiation head 10 to a desired position on the surface of the processing target 1.

A laser beam output from a laser light generator 60 is guided into a laser irradiation head 10 through a beam shaping optical component 61 and a beam transmission arm 62.

The laser light generator 60 is, for example, a laterally pumped atmospheric pressure type CO ₂ laser device (TEA-CO ₂ laser device). The TEA-CO ₂ laser device has a wavelength of 9-1.
A 1 μm laser beam is output as a pulse.

The beam shaping optical component 61 shapes the cross section of the laser beam output from the laser light generator 60 into a desired shape. For example, it is constituted by an aperture having a rectangular through-hole, and shapes the cross-sectional shape of the laser beam into a rectangular shape.

The beam transmitting arm 62 is, for example, a bendable arm having a plurality of joints. The beam transmitting arm 62 follows the movement of the laser irradiation head 10 and transmits the laser beam passing through the beam shaping optical component 61 to the laser irradiation head 10. Lead.

The laser irradiation head 10 has a gas introduction tube 13
And a gas exhaust pipe 15. The gas introduction pipe 13 is connected to a gas supply device 14, and is supplied from the gas supply device 14 through the gas introduction pipe 13.
Gas is introduced into 0. The gas exhaust pipe 15 is connected to a gas exhaust device 16, and the gas exhaust device 16 exhausts the gas in the laser irradiation head 10 through the gas exhaust pipe 15.

FIG. 2 is a schematic sectional view of the laser irradiation head 10 of FIG. A box-shaped container 11 having an open surface on the processing object 1 side is held so that the periphery of the opening is almost in contact with the surface of the processing object 1. A laser transmission arm 62 is connected to a through hole 17 formed on a surface of the box-shaped container 11 facing the opening. The laser beam 63 transmitted through the laser transmission arm 62 is introduced into the box-shaped container 11 through the through hole 17.

The laser beam introduced into the box-shaped container 11 passes through the half mirror 20 and the homogenizer 31, is reflected by the deflectors 21 and 22, and enters the condenser lens 23. The laser beam focused by the focusing lens 23 is applied to the surface of the processing target 1.

The half mirror 20 reflects a part of the laser beam and makes it incident on the energy sensor 30. The energy sensor 30 measures the energy of the laser beam.

The homogenizer 31 makes the intensity distribution in the cross section of the laser beam substantially uniform. Deflectors 21 and 22
Indicates the irradiation position of the laser beam,
Are moved in the Y-axis direction and the X-axis direction which are orthogonal to each other in the surface of. The deflectors 21 and 22 are constituted by, for example, galvanomirrors. When the deflectors 21 and 22 are galvanomirrors, it is preferable that the condenser lens 23 be an arc sine lens in order to keep the moving speed of the laser irradiation position constant. When the deflection angle of the laser beam by the deflectors 21 and 22 changes in proportion to time, it is preferable that the condenser lens 23 be an fθ lens for the same reason. Note that rotating polygon mirrors may be used as the deflectors 21 and 22. Even when the fθ lens is used, the moving speed at the laser irradiation position can be kept constant by operating the galvanomirror so that the angle change becomes non-linear with respect to time.

The condenser lens 23 has a condenser lens support mechanism 2
4 attached to the side surface of the box-shaped container 11. The condenser lens support mechanism 24 can adjust the height from the surface of the processing target 1 to the condenser lens 23. A height sensor 25 is attached to the condenser lens 23. The height sensor 25 is provided between the surface of the processing target 1 and the condenser lens 2.
Detects a height up to 3 and sends a detection signal to the height controller 26.

The height control unit 26 stores a height target value in advance. The height control device 26 includes a height sensor 25
And controls the condenser lens support mechanism 24 so that the height of the condenser lens 23 approaches the target value, and adjusts the height of the condenser lens 23 based on the detection signal received from.

A visible light laser device 32 is provided in the box-shaped container 11.
Is installed. The visible light laser device 32 is, for example, H
An eNe laser device or the like. The visible laser beam output from the visible light laser device 32 is reflected by the half mirror 20 and propagates along the same optical axis as the laser beam incident through the through hole 17. Therefore, the visible laser beam irradiates a region of the surface of the processing target 1 that is substantially the same as the TEA-CO ₂ laser beam. Therefore, the irradiation position of the laser beam can be visually observed through the transparent window 12 shown in FIG. Note that a visible light beam may be used instead of the visible laser beam.

In the box-shaped container 11, nozzles 40 and 41 are arranged. The nozzles 40 and 41 communicate with the gas introduction pipe 13 attached to the side wall of the box-shaped container 11. The nozzle 40 ejects gas to the laser beam irradiation position on the surface of the processing target 1 and its vicinity. With this gas flow,
The surface of the processing object 1 can be cooled, and a rise in temperature can be suppressed. The nozzle 41 ejects gas toward the surface of the condenser lens 23 on the processing object 1 side. By this gas flow, scattered matter from the surface of the processing target 1 is collected by the condenser lens 23.
Can be suppressed from adhering to the surface of the substrate.

Gas suction port 4 arranged in box type container 11
2 communicates with a gas exhaust pipe 15 attached to the side wall of the box-shaped container 11. The tip of the gas suction port 42 faces the laser irradiation position on the surface of the processing target 1. The gas suction port 42 can exhaust the gas in the box-shaped container 11 and discharge the scattered matter scattered from the laser irradiation part.

The color sensor 4 is located near the tip of the gas suction port 42.
3 and a temperature sensor 44 are attached.

The color sensor 43 includes, for example, a charge-coupled device (CCD), and detects a laser beam irradiation position of the processing target 1 and a color in the vicinity thereof. Color sensor 4
The output signal of No. 3 is input to the color determination device 46. In the color determination device 46, a range of a reference color serving as a determination reference is stored in advance. The range of the reference color is specified by, for example, a certain reference area specified in the chromaticity diagram.

The color determination device 46 determines whether or not the color detected by the color sensor 43 is within the range of the reference color, that is, whether or not the color matches or approximates the reference color. For example, the position of the detected color in the chromaticity diagram is obtained, and it is determined whether or not this position is within the reference area in the chromaticity diagram.

If the color of the undercoat surface of the paint film is different from the color of the paint film, a certain range including the undercoat surface color is set as a reference color range to determine whether the undercoat surface is exposed. Can be determined.

The temperature sensor 44 is, for example, a radiation thermometer, and detects a laser beam irradiation position on the surface of the processing object 1 and a temperature in the vicinity thereof. The output signal of the temperature sensor 44 is input to the temperature abnormality detection device 45. The temperature abnormality detection device 45 stores a reference temperature serving as a determination reference in advance.

The temperature abnormality detecting device 45 includes a temperature sensor 44
Is compared with the reference temperature. If the detected temperature is higher than the reference temperature, an abnormality process is performed. The abnormality processing is, for example, stopping laser beam irradiation.

Next, the operation of the laser processing apparatus shown in FIGS. 1 and 2 will be described by taking as an example a case where the coating film on the surface of the object to be processed is removed.

The laser beam incident on the laser irradiation head 10 shown in FIG. 2 is irradiated on the surface of the processing object 1, and the coating film is removed by ablation. Processing object 1
If the energy density (fluence) of the laser beam on the surface of the substrate is too low, the coating film is not ablated. On the other hand, if the energy density is too high, the base material of the coating film will be damaged. Therefore, it is preferable to set the energy density of the laser beam in a range where the underlying material is not damaged and the coating film is ablated. When the energy density of the laser beam output from the laser light generator 60 is sufficiently high, a diverging lens may be used instead of the condenser lens 23.

The energy density can be adjusted by adjusting the height from the surface of the processing object 1 to the condenser lens 23 by the condenser lens support mechanism 24 to change the area of the irradiation area. The preferable range of the energy density differs depending on the type of the base material and the coating film. Therefore, it is preferable that preliminary experiments are performed in advance at different energy densities to determine a suitable energy density range, that is, a suitable height of the condenser lens 23.

The preferred height of the condenser lens 23 is stored in the height controller 26. The height controller 26 compares the height detected by the height sensor 25 with a suitable height stored in advance, and controls the condenser lens support mechanism 24 so as to approach the suitable height. With this height control, ablation can always be performed with a suitable energy density.

The irradiation position of the laser beam is swept by the deflector 22 in the X-axis direction, and then the irradiation position is shifted by the deflector 21 in the Y-axis direction. The irradiation position is again swept in the X-axis direction by the deflector 22, and the laser beam is irradiated in the same range as the previous sweep in the X-axis direction. By repeating this sweep, the coating film in a certain area on the surface of the processing target 1 can be removed by ablation.

The position of the laser irradiation head 10 is moved by driving the manipulator arm 50 shown in FIG.
The sweep in the axis and Y axis directions is repeatedly executed. In this manner, the coating film in a wide area on the surface of the processing target 1 can be removed by ablation.

When the laser irradiation head 10 is moved, the height from the surface to the condensing lens 23 may fluctuate due to a change in the curvature of the surface of the processing object 1 or unevenness. In this case, the height of the condenser lens 23 can be kept constant by the height sensor 25 and the height control device 26.
Therefore, the energy density of the laser beam on the surface of the processing target 1 can be kept constant, and stable ablation can be performed.

The sweep direction by the deflector 21 and the sweep direction by the deflector 22 do not necessarily need to be orthogonal. It suffices that the two sweep directions cross each other.

In the above-described sweeping method, a case has been described in which the two-dimensional sweep is performed using the deflectors 21 and 22, but the one-dimensional sweep may be performed using only one of the deflectors. Good. In this case, the laser irradiation head 10 is moved by the manipulator arm 50 shown in FIG. 1 in a direction crossing the sweep direction. In this manner, the laser beam can be applied to a wide area on the surface of the processing target 1.

By blowing a gas from the nozzle 40 onto the surface of the processing object 1, a rise in surface temperature can be suppressed. In addition, the processing target 1
It is preferable to use a gas that does not oxidize, for example, an inert gas such as an Ar gas or a He gas, or an N ₂ gas.
In the case of processing a material having high oxidation resistance, air may be blown. The removed matter scattered from the surface of the processing object 1 is discharged from the gas suction port 42.

The temperature abnormality detection device 45 monitors the normality of the surface temperature of the processing object 1 even during the removal of the coating film by laser ablation. When the surface temperature of the processing target 1 exceeds a preset reference temperature, abnormal processing is executed. The abnormality processing is, for example, stopping laser beam irradiation, sounding an alarm, or the like. When the detected temperature exceeds the reference temperature, the pulse repetition frequency of the laser light may be reduced.

As described above, by using laser ablation, the coating film can be removed without using toxic chemicals.

Since the surface temperature of the processing target 1 is monitored during the ablation, it is possible to prevent the processing target 1 from being damaged or deteriorated due to a rise in temperature.

According to the International Air Transport Association (IATA) standards, the temperature of the aircraft surface must be kept below 80 ° C. when removing the paint film on the surface of the aircraft body. For example, the reference temperature set in the temperature abnormality detection device is 75 ° C.
By doing so, it is possible to remove the coating film while checking whether the body surface temperature satisfies the IATA standard.

Further, since the color of the surface of the processing object 1 is observed by the color determination device 46, it can be determined whether or not the coating film has been completely removed. Aircraft coatings usually consist of two layers, a primer layer for adhesion and rust prevention, and a cosmetic topcoat layer applied thereon. When the colors of the primer layer and the top coat layer are different, the color determination device 46 can detect that the top coat layer has been removed and the primer layer has been exposed.

In the case where the thickness of the coating film is uneven, if the entire surface is irradiated with the laser under the same conditions, an area where the coating film cannot be completely removed occurs. By performing laser irradiation while determining whether or not the base surface has been exposed by the color determination device 46, even if the coating film has uneven thickness, it is possible to prevent the removal remaining from occurring.

Next, referring to FIG. 3, a description will be given of an experimental result of removing the coating film. In the experiment, a sample in which a coating film having a thickness of about 80 μm used for coating an aircraft body was formed on an aluminum plate surface was used. Laser light generator 60
Is a TEA-CO ₂ laser device that outputs pulsed laser light at a repetition frequency of 100 Hz. The energy density of the laser beam on the surface of the object 1 is about 5 J / c.
m ² , the shape of the irradiation area is a rectangle of about 14 mm × 1 mm. At this time, the area to be ablated is a rectangle of about 5 mm × 0.5 mm. The moving distance between shots is about 0.5 mm. Further, the sweep speed of the laser beam irradiation position in the X-axis direction was set to 25 mm / s.

FIG. 3 shows a laser beam irradiation history. First, as shown by the arrow S1, the beam is swept by about 5 cm in the X-axis direction by the deflector 22. Next, it is shifted by about 0.5 cm in the Y-axis direction by the deflector 21, and the same range is swept again by the deflector 22 in the X-axis direction as shown by the arrow S2. Further, it is shifted by about 0.5 cm in the Y-axis direction, and sweeps the same range in the X-axis direction as shown by an arrow S3. Arrow S1
By the sweep of S3, a rectangular area of about 5 cm × 1.5 cm can be irradiated with a laser beam. Arrow S1
The sweep of S3 is repeated three times. As a result, the coating film on the surface of the aluminum plate was almost removed. No damage was observed on the surface of the aluminum plate.

In the above experiment, laser irradiation was performed three times on the same region of the surface of the processing object. By reducing the number of laser irradiations, it is possible to leave the lower layer of the coating film and remove only the upper layer. The coating film on the aircraft body surface is
It usually consists of a primer layer for adhesion and rust prevention, and a cosmetic topcoat layer applied thereon. By adjusting the number of laser irradiations, for example, only the top coat layer can be removed.

FIGS. 1 to 3 show the case where the coating film is removed by irradiating the infrared laser light. However, in the case of irradiating only the infrared laser light, a part of the coating film is on the surface of the object to be processed. May remain thin. The present inventors have found that by irradiating an ultraviolet laser beam, a thin remaining coating film can be removed.

FIG. 4 schematically shows a laser processing apparatus for irradiating infrared laser light and ultraviolet laser light. The infrared laser light output from the infrared laser light generation device 60 is condensed by the condensing lens 23 and is irradiated on the surface of the processing target 1. The ultraviolet laser light output from the ultraviolet laser light generator 60A is condensed by the condenser lens 23A, and is irradiated on the surface of the processing target 1. Infrared laser light generator 6
The mechanical and optical configuration from 0 to the condenser lens 23 and the mechanical and optical configuration from the ultraviolet laser light generator 60A to the condenser lens 23A are the same as those shown in FIGS.

As the infrared laser light generator 60, for example, a TEA-CO ₂ laser device, a Nd: YAG laser device, a Nd: YLF laser device, a CO laser device, a semiconductor laser device, or the like can be used.

As the ultraviolet laser light generator 60A, for example, a KrF excimer laser device (oscillation wavelength 248 n
m) etc. can be used. Also, a YAG laser device or Y
A combination of an AL laser device and a wavelength conversion crystal may use a harmonic of a laser beam output from the laser device.

Using a laser processing apparatus shown in FIG. 4, the coating film on the surface of the processing object 1 is ablated and removed by irradiating infrared laser light. At this time, a thin coating film may remain on the surface. Next, an ultraviolet laser beam is irradiated to ablate and remove the thin remaining coating film. By observing the color of the laser irradiation part with the color sensor 43 shown in FIG. 2, it can be determined whether or not the coating film has been completely removed. A plurality of pulses of pulsed ultraviolet laser light are applied until the thin remaining coating film is completely removed. At this time, it is preferable that the energy density of the ultraviolet laser light on the surface of the processing target 1 be set to a value that does not ablate the base surface of the coating film.

It is difficult to completely remove the thin remaining coating film by irradiation with only infrared laser light, but it can be easily removed by irradiation with ultraviolet laser light.

Using the laser processing apparatus shown in FIG. 4, a coating film (having a thickness of 80 to 10) on the surface of an aircraft aluminum body is used.
0 μm, made of polyurethane). Wavelength 10.
When a 6 μm TEA-CO ₂ laser beam was irradiated under the same conditions as in FIG. 3, a thin coating film remained on the surface of the aluminum plate. After irradiation with TEA-CO ₂ laser light, wavelength 24
8 nm excimer laser beam with energy density of 1.7 J / c
When irradiation was performed under the conditions of m ² and a repetition frequency of 10 Hz, a thin remaining coating film could be removed cleanly.
The same location was irradiated two to three times. At this time, there was no damage on the surface of the aluminum plate.

FIG. 5 shows a modification of the laser processing apparatus shown in FIG. The infrared laser light output from the infrared laser light generator 60 passes through the mirror 65, and the ultraviolet laser light output from the ultraviolet laser light generator 60A is
Is reflected by The infrared laser light transmitted through the mirror 65 and the ultraviolet laser light reflected by the mirror 65 propagate along the same optical axis. Both the infrared laser light and the ultraviolet laser light are condensed by the condensing lens 23 and are irradiated on the surface of the processing target 1.

The ultraviolet laser light generator 60A and the mirror 65
, An adjustment optical system 64 is arranged. The adjustment optical system 64 eliminates chromatic aberration of the condenser lens 23 and corrects a difference in focal position between the infrared laser light and the ultraviolet laser light. The adjustment optical system 64 only needs to be arranged corresponding to one of the infrared laser light generator 60 and the ultraviolet laser light generator 60A.

When the coating film is removed using the laser processing apparatus shown in FIG. 5, ultraviolet laser light may be irradiated after irradiating infrared laser light, or two laser lights may be simultaneously irradiated. You may. When irradiating two laser beams separately, the height of the condenser lens 23 is adjusted so that a suitable energy density is obtained at each irradiation of the laser beams. When irradiating two laser beams simultaneously, for example, the height of the condenser lens 23 is adjusted so that the energy density of the infrared laser beam becomes a suitable value, and the energy density of the ultraviolet laser beam becomes
The adjustment is performed by the adjustment optical system 64. In this way, the energy densities of the infrared laser light and the ultraviolet laser light can be simultaneously set to suitable values.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0060]

As described above, according to the present invention,
By using laser ablation, the coating film formed on the surface of the processing object can be removed without using a chemical. In addition, by irradiating the ultraviolet laser light after or simultaneously with the irradiation with the infrared laser light, it is possible to remove the coating film without leaving the coating film.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a laser processing apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view schematically showing the laser irradiation head shown in FIG.

FIG. 3 is a diagram for explaining how a laser beam is swept.

FIG. 4 is a schematic diagram of a laser processing apparatus capable of irradiating infrared laser light and ultraviolet laser light.

FIG. 5 is a schematic diagram of a laser processing apparatus according to a modification of the laser processing apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing object 10 Laser irradiation head 11 Box-shaped container 12 Transparent window 13 Gas introduction pipe 14 Gas supply device 15 Gas exhaust pipe 16 Gas exhaust device 17 Through hole 20 Half mirror 21, 22 Deflector 23, 23A Condensing lens 24 Collection Optical lens support mechanism 25 Height sensor 26 Height control device 30 Energy sensor 31 Homogenizer 32 Visible light laser device 40, 41 Nozzle 42 Gas suction port 43 Color sensor 44 Temperature sensor 45 Temperature abnormality detection device 46 Color judgment device 50 Manipulator arm 51 Manipulator body 60, 60A Laser light generator 61 Beam shaping optical component 62 Laser transmission arm 63 Laser beam 64 Adjustment optical system 65 Mirror

Claims (4)

[Claims] A step of irradiating a laser beam in an infrared region on the surface of the processing object having a coating film formed on the surface to remove the coating film by ablation; Irradiating a laser beam in an ultraviolet region and removing remaining residues of the coating film, which could not be removed by the laser beam irradiation in the infrared region, by ablation. 2. An infrared laser light source for outputting laser light in an infrared region, an ultraviolet laser light source for outputting laser light in an ultraviolet region, and an infrared laser light output from the infrared laser light source. A first lens that emits or diverges light and irradiates the surface of the object to be processed; and a second lens that condenses or diverges ultraviolet laser light output from the ultraviolet laser light source and irradiates the surface of the object to be processed. A laser processing apparatus having: 3. The two laser lights so that the infrared laser light output from the infrared laser light source and the ultraviolet laser light output from the ultraviolet laser light source propagate along the same optical axis. And a mixing optical system that mixes the first and second lenses, wherein the first lens also functions as the second lens.
A laser processing apparatus according to claim 1. 4. The laser according to claim 3, further comprising a first lens support mechanism that supports the first lens and that can adjust a height from a surface of the processing target to the first lens. Processing equipment.