JPH09141462A - Laser beam machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the magnetic force generated by a linear motor of an X-Y table from adversely affecting a laser oscillator by devising the laser beam machine in such a manner that the electron beam of an arc lamp built in the laser oscillator is not bent by the influence of the magnetic force of the linear motor. SOLUTION: The outer peripheral part of the laser oscillator 5 is provided with a degaussing cover 42 which consists of a ferromagnetic material and encloses at least the arc lamp 5a. The degaussing cover 42 is composed of two layers of metallic sheets (lower shielding sheet 42a and upper shielding sheet 42b) consisting of silicon steel sheets, iron sheets or 'Permalloy (R)' sheets, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing machine suitable for thin film precision processing.

[0002]

2. Description of the Related Art Recently, a technique for performing precision thin film processing by a YAG laser processing machine has been established. For example, trimming processing of color filters and transparent electrodes necessary for manufacturing a liquid crystal display device can be performed very easily and surely. In various fields where high precision and fine processing are required, much attention has been paid to the fact that the use of such a laser processing machine can reduce the processing time, improve the processing accuracy, and reduce the equipment cost.

A laser beam machine of this type is usually a laser beam (YAG laser) supplied from a laser oscillator.
Machine body that guides the light through an optical system including lens groups and irradiates the workpiece, an XY table that can transfer the mounted workpiece in two directions orthogonal to each other by a linear motor, and the machine body and the XY table. As is well known in the laser oscillator, an arc lamp that emits an electron beam and a YAG rod that emits a laser beam when excited by the electron beam are generally configured, including a base plate on which a table is placed. It is built in. In order to eliminate the influence of vibration, the base board is often installed on a vibration isolation table.

In the laser beam machine having the above-described structure, the workpiece can be moved in the horizontal plane by driving and controlling the XY table, so that the tip end (objective lens) of the optical system is irradiated. By moving the workpiece with respect to the spot-shaped laser beam (beam spot) along a predetermined locus, a desired processing pattern by beam irradiation can be drawn on the workpiece.

[0005]

By the way, in the above-mentioned conventional laser beam machine, since the XY table driven and controlled by the linear motor is used, the workpiece can be moved with high positional accuracy. , Even fine processing such as thin film precision processing can be performed,
Since the linear motor incorporated in such an XY table generates a strong magnetic force to drive a heavy object, the strong magnetic force may affect the laser oscillator. That is, when the electron beam of the arc lamp built in the laser oscillator travels in the magnetic field, its course is bent by the electromagnetic action, so that when the linear motor of the XY table generates a strong magnetic force, this electron beam is emitted. If it is bent greatly, the power and mode of the laser beam may change, and the life of the arc lamp may be shortened.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a laser processing machine in which the magnetic force generated by a linear motor does not adversely affect the laser oscillator.

[0007]

The above-mentioned object of the present invention has a laser oscillator which oscillates a laser beam when excited by an electron beam of an arc lamp incorporated therein, and guides the laser beam by an optical system to be processed. A processing machine body that irradiates objects,
An XY table capable of transferring the mounted work piece in two directions orthogonal to each other by a linear motor, and a base board on which the processing machine body and the XY table are mounted are provided, and a ferromagnetic material is provided on the outer peripheral portion of the laser oscillator. And a degaussing cover surrounding at least the arc lamp. And this degaussing cover
It is more preferable to use a two-layer metal plate made of a silicon steel plate, an iron plate, a permalloy plate, or the like.

[0008]

If a degaussing cover made of a ferromagnetic material and surrounding at least the arc lamp is provided on the outer peripheral portion of the laser oscillator, the demagnetizing effect of the ferromagnetic material causes the magnetic force of the linear motor to be extremely large inside the degaussing cover. Since it is weakened, there is no concern that the electron beam of the arc lamp will be bent due to the magnetic force of the linear motor.

[0009]

Embodiments of the present invention will be described below with reference to FIGS.

Here, FIG. 1 is a front view of an XY table incorporated in a laser processing machine according to the present embodiment, FIG. 2 is a side view of the XY table, a portion of which is not shown, and FIG. 3 includes the XY table. FIG. 4 is a side view of the entire laser processing machine, FIG. 4 is a side view of a portion corresponding to FIG. 3 of a safety cover that covers the laser processing machine, and FIG. 5 is an optical system arranged in the optical path of the laser beam in the laser processing machine. 6 is an explanatory view showing a layout of FIG. 6, FIG. 6 is an explanatory view showing a laser oscillator of the laser processing machine, and FIG.
FIG. 8 is a plan view showing a state in which a degaussing cover is attached to the laser oscillator shown in FIG. 8, FIG. 8 is an explanatory view showing a beam irradiation part of the laser processing machine, and FIG. 9 is a laser beam emitted from an optical fiber by the optical system shown in FIG. 10 is a characteristic diagram showing the energy distribution around the optical axis of FIG. 10, FIG. 10 is a process explanatory view showing a manufacturing method of a liquid crystal display element for trimming a color filter using the laser processing machine, and FIG. 11 is a manufacturing process shown in FIG. FIG. 6 is an explanatory diagram showing a step of laser trimming a color filter in FIG.

As shown in FIG. 3, the laser beam machine according to this embodiment guides a laser beam (YAG laser) supplied from a laser oscillator 5 by an optical system including a lens group, a beam splitter and the like to be processed. Machine body 1 to irradiate
An XY table 2 capable of transferring the mounted workpiece in two directions orthogonal to each other by a linear motor, a surface plate (base plate) 3 on which the processing machine body 1 and the XY table 2 are mounted, and the surface plate 3 and a vibration isolation table 4 on which a cover 3 is placed, and a cover frame 6 shown by a chain line in FIG.
A safety cover 7 (see FIG. 4) having a support frame covers the laser processing machine and the vacuum pump 8. Reference numeral 21 in FIG. 1 indicates an optical surface plate on which the processing machine main body 1 is mounted.
It is supported by.

Then, the X integrated in this laser processing machine
The Y table 2 is a suction table 9 capable of suction-fixing a workpiece to be mounted by sucking air through a large number of suction holes formed on the upper surface, and the suction table 9
Columnar support shaft 10 in the shaft hole that is opened in the center of the bottom of the
X which inserts a and rotatably supports the suction table 9
The table 10, a pair of parallel X-axis rail portions 11a slidably supporting the X-table 10 on both side edges, and a concave cross-sectional support 11 are installed inside the support 11. An X-axis linear motor 12 for linearly moving the X-table 10 back and forth along the X-axis rail portion 11a.
And an X-axis linear encoder 13 that detects the position data of the X table 10, and a Y table 1 on which a support 11 is mounted.
4, three Y-axis rails 15 and 16 extending in a direction orthogonal to the X-axis rail portion 11a and slidably supporting the Y-table 14, and the Y-table along the Y-axis rail groups 15 and 16. A Y-axis linear motor 17 that linearly moves the reciprocating unit 14 and a Y-axis linear encoder 18 that detects position data of the Y table 14 are mainly configured. However, an air gap is formed between the X table 10 and each X-axis rail portion 11a and between the Y table 14 and each Y-axis rail 15 and 16 by blowing out compressed air from an air nozzle provided on the table side. By reducing the frictional force in these air gaps, the workpiece can be smoothly transported in the X-axis direction and the Y-axis direction.

In FIG. 1, reference numeral 3a indicates a mounting groove provided on the upper surface of the surface plate 3 for inserting the bottom portions of the Y-axis rail groups 15 and 16 and positioning them in the width direction.
Reference numerals a, 17b, and 17c denote coils, magnets, and yokes forming the Y-axis linear motor 17, respectively.
Reference numerals 8b respectively indicate a detecting portion such as an optical element and a scale portion (linear scale) which constitute the Y-axis linear encoder 18. Further, in FIG. 2, reference numeral 10b indicates the X table 10.
12a, 12b, 12
Reference characters 13a and 13b respectively denote a coil, a magnet, and a yoke which form the X-axis linear motor 12, and X denote X, respectively.
The axis linear encoder 13 includes a detector, such as an optical element, and a scale (linear scale). Reference numeral 20 denotes the spindle 10.
A motor for driving the suction table 9 to rotate about a is shown. Furthermore, the symbol P in FIG.
Indicates the point of action of the magnetic driving force generated by the X-axis linear motor 12, and in the case of the present embodiment, the X table 10 is started by making the point of action P substantially coincide with the center of gravity of the X table 10. Care is taken to prevent rattling at times and when stopping.

A laser beam machine incorporating such an XY table 2 can move the workpiece mounted on the suction table 9 in the horizontal plane with high positional accuracy by controlling the drive of the XY table 2. Therefore, by moving the workpiece along a predetermined locus with respect to the spot-shaped laser beam (beam spot) emitted from the tip (objective lens) of the optical system of the processing machine body 1, the beam irradiation is performed. A desired processing pattern can be drawn on the workpiece.

Since the linear motors 12 and 17 incorporated in the XY table 2 generate a strong magnetic force for driving a heavy object, in this embodiment, a CRT for a monitor or a monitor arranged in the periphery is used. In order to prevent the magnetic forces of the linear motors 12 and 17 from adversely affecting the machine, the safety machine 7 mainly made of a ferromagnetic material covers the laser machine. That is, the safety cover 7 is, as shown in FIGS.
4 is an iron plate, a degaussing plate, and the like. Specifically, the part A in FIG. 4 is the place where the stainless steel plate of SUS304 is attached, and the parts a and c are the inside of the stainless steel plate of SUS304 and the stainless steel plate of SUS430. It is a two-layer structure where a degaussing plate is attached to enhance the degaussing effect. Among these, the claw part is a double-opening cover that can be opened and closed. In addition, the d part has the same configuration as the claw part on the outside of the colored acrylic plate. It is a part of the three-layer structure. Thus, if the laser processing machine is covered with the safety cover 7 having a degaussing effect, and a strong magnetic force is expected in the vicinity of the linear motors 12 and 17, the degaussing effect is enhanced by forming a two-layer structure. There is no fear that the magnetic forces of 12 and 17 will adversely affect the peripheral equipment, and the optical system of the processing machine main body 1 can be easily adjusted by opening the double-opening cover of the c. Further, when directly confirming whether or not the laser beam is properly applied to the workpiece, if the both-sided covers of the section D are opened, it is possible to perform visual confirmation safely through the colored acrylic plate.

Next, the structure of the processing machine body 1 of the laser processing machine will be described in detail.

As shown in FIG. 6, the laser oscillator 5 is constructed so that the YAG rod 5b oscillates a laser beam by exciting the YAG rod 5b with an electron beam E generated in the arc lamp 5a. In this embodiment, as shown in FIGS. 5 and 7, two laser oscillators 5 are arranged in parallel so that two laser beams can be simultaneously supplied.

Further, in this embodiment, as shown in FIG. 7, a degaussing cover which surrounds both arc lamps 5a with a two-layer structure made of a ferromagnetic metal plate is provided on the outer periphery of these two laser oscillators 5. 42 is provided. Specifically,
The degaussing cover 42 includes a lower shield plate 42a made of an iron plate or a permalloy plate and surrounding both arc lamps 5a with a margin, and an upper shield plate 42b made of a silicon steel plate and having a width dimension matching the size of both arc lamps 5a. The magnetic force generated by the linear motors 12, 17 of the XY table 2 inside the degaussing cover 42 is extremely high due to the degaussing effect of these two layers of shield plates 42a, 42b made of a ferromagnetic material. Being weakened. Therefore, the arc lamp 5a of each laser oscillator 5
There is no fear that the electron beam E of the above will be bent by the influence of the magnetic force of the linear motors 12 and 17, and therefore the power and mode of the laser beam supplied from each laser oscillator 5 will change, and the life of the arc lamp 5a will increase. There is no risk of deterioration.

Next, the optical system of the processing machine main body 1 will be described. The two laser beams supplied from the two laser oscillators 5 are guided along the optical paths shown in FIG. 5, respectively. Since an optical system having the same configuration is provided in the optical path of each laser beam supplied from these two laser oscillators 5, only one optical system for one laser beam is designated by a reference numeral. Explain.

A laser beam emitted from the laser oscillator 5 first passes through an acousto-optic device (AOM) 23, is reflected by a reflection mirror 24, and then is also called a 1 / 4λ plate.
The linearly polarized light is converted into circularly polarized light by being incident on the retardation plate 25 of. Here, the acousto-optic element 23 is a kind of switching element, and when this is switched on, incident light (laser beam) is generated by applying ultrasonic waves to distort the optical axis.
Most of the can be made unusable light. That is,
The acousto-optic element 23 is kept in the off state during the laser processing and allows the laser beam to pass therethrough, but is switched to the off state when the laser processing is desired to be temporarily stopped. .

The circularly polarized laser beam emitted from the first retardation plate 25 is reflected by the reflection mirror 27 through the diffusion preventing lens 26 and then is incident on the first beam splitter 28 to be bidirectional. Split into linearly polarized light toward
As a result, two split beams capable of simultaneously laser processing a plurality of locations can be obtained. However, in order to perform fine processing such as thin film precision processing, the first beam splitter 2
The power (energy level) of each split beam emitted from 8 must be set to the same level, but in reality, the power of the two split beams (linear polarization) may be slightly different due to the mounting error of each member. Variation easily occurs. Therefore, in this embodiment, the first phase difference plate 25 is rotatably installed in the optical path, and the phase difference plate 25 is appropriately rotated so that the power of the two split beams can be easily adjusted. It has become.

One of the split beams emitted from the first beam splitter 28 passes through the reflection mirror 29, the optical fiber 43, and then enters the rotatable second retardation plate 30. It is converted into circularly polarized light again, and this circularly polarized light is expanded into an elliptical shape through the cylindrical lens 31, and then is incident on the second beam splitter 35 to be split into linearly polarized light traveling in two directions. Similarly, the first beam splitter 2
The other split beam emitted from 8 is the reflection mirror 32.
After passing through the optical fiber 44, it is incident on the rotatable third retardation plate 33 and is converted into circularly polarized light again, and this circularly polarized light is expanded into an elliptical shape through the cylindrical lens 34. Then, it is incident on the second beam splitter 35,
It is divided into linearly polarized light in the direction. That is, when one laser beam emitted from the laser oscillator 5 is emitted from the second beam splitter 35 via a predetermined optical path, it is divided into a total of four laser beams. By appropriately rotating the third retardation plates 30 and 33, the power of these four split beams can be easily adjusted.

In this embodiment, as the first and second beam splitters 28 and 35, a type in which two prisms are adhered is used, but a reflection layer is provided on one surface of a glass plate. A type of beam splitter may be used.

The optical fiber 4 installed in front of the second and third retardation plates 30 and 33 in the above-mentioned optical path.
Reference numerals 3 and 44 are publicly known ones which are formed by coating a quartz material with a reflection film, and the laser beam transmitted while being reflected by the reflection film is emitted in a state in which a single mode is converted into a multimode. , The energy distribution curve around the optical axis of the laser beam incident on each of the optical fibers 43 and 44 is in the state of being converted into the multi-mode top-hat shape indicated by the symbol L1 in FIG. 9, in other words, with the optical axis as the center. The light is emitted in a state where the area of the high energy region is increased.

When the four split beams are emitted from the second beam splitter 35 in this way, these split beams pass through the aperture 36 and then pass through the converging lens 37, the imaging lens 38, etc. The light is incident on the objective lens 39 located at the front end, and four parallel beams, which are parallel to each other, are emitted in spots from the objective lens 39 toward the processing surface A. However, in reality,
The laser beam emitted from the other laser oscillator 5 is also irradiated onto the processing surface as the four split beams from the objective lens located at the tip of the optical path. 8 for the workpieces placed on the surface
The divided beams of a book are irradiated in spots so that laser processing can be performed at a plurality of positions at the same time.

It should be noted that at the four positions of the aperture 36, rectangular light transmission holes 36a for passing the respective split beams are provided.
When the divided beams pass through the light transmission hole 36a opened in the optical path, the beam shape is formed into a rectangular shape suitable for high-speed processing. And
Since the split beam incident on the aperture 36 is a multimode laser beam that has passed through the optical fiber 43 or 44, the optical axis of this laser beam and the center of the light transmitting hole 36a opened in the optical path thereof. Unless an extreme displacement occurs, only the high energy portion of the laser beam passes through the aperture 36 and the beam shape is shaped, and there is no fear that an unnecessary low energy portion is guided to the objective lens 39. . That is, as shown in FIG. 9, the optical axis of the laser beam incident on the aperture 36 (the position where the abscissa coordinate is 0) is the center of the light transmission hole 36a (width position w) opened in the optical path ( If it is slightly deviated from the horizontal axis of the one-dot chain line C), the energy distribution curve around the optical axis is assumed to be a Gaussian shape of normal distribution (broken line L
In the case of 2), since the laser beam also passes through the aperture 36 even in the low energy portion, the low energy portion is irradiated to the processing surface A, and the laser processing cannot be performed satisfactorily there. Machining defects such as width dimensional errors and variations will be introduced. However, in this embodiment, since the energy distribution curve around the optical axis of the laser beam incident on the aperture 36 is the top hat type (solid line L1), the optical axis is slightly deviated from the center of the light transmitting hole 36a. However, the low-energy portion of the laser beam does not pass through the aperture 36, so that the beam spot S (see FIG. 8) emitted from the objective lens 39 has a substantially uniform light energy distribution around the optical axis. Since it can be set to laser light, the dimensional error of the processed shape is extremely small.

FIG. 8 shows a beam irradiation unit 40 including an objective lens 39 located at the tip of the above-mentioned optical path,
Here, in addition to the funnel-shaped nozzle 41 that surrounds the beam spot S, an air delivery unit 40 a that blows compressed air between the nozzle 41 and the objective lens 39, and the nozzle 4
1. Air suction unit 4 forcibly sucking air near the tip of 1
0b is provided, and the compressed air flows from the upper side to the lower side along the conical inner wall surface of the nozzle 41 (arrow in FIG. 8).
Are formed. That is, in the present embodiment, most of the smoke generated during laser processing is sucked by the air suction portion 40b and guided to the discharge path, so that the smoke containing metal components and the like adversely affects the health of workers in the vicinity. I have been careful not to. Even if part of the smoke enters the inside of the nozzle 41, the smoke is quickly discharged from the lower part of the nozzle 41 to the outside by the flow of the compressed air and sucked into the air suction portion 40b. Therefore, the possibility that smoke will adversely affect the beam spot S and the objective lens 39 is extremely low.

In the present embodiment, the color filter is trimmed in the manufacturing process of the liquid crystal display device by using such a laser processing machine to form a desired color filter surrounded by a light shielding film. Formed.

The manufacturing technique will be described below.
As shown in FIG. 10A, a transparent substrate 5 such as a glass substrate
By patterning ITO on one surface of 0, a large number of transparent electrodes 51 extending in one direction at a constant pitch interval are formed.
To form Then, as shown in FIG. 10B, R is formed on each transparent electrode 51 by a method such as an electrodeposition method or a printing method.
(Red), G (green), and B (blue) color filters 52 are laminated in a predetermined arrangement. By the way, in the example of FIG. 10B, the color filters 52 are laminated in the order of R, G, B, R, G, B, R .... And after stacking, about 250
The color filter 52 is solidified by firing at ° C.

After that, the transparent substrate 50 is mounted on the suction table 9 of the XY table 2, and the XY table 2 is attached.
Laser trimming in which the R, G, and B color filters 52 are partially removed by irradiating eight divided beams at a constant pitch in a direction orthogonal to the longitudinal direction of the color filters 52 while controlling the above. Processing is performed, and as a result, as shown in FIG. 10C, a color filter 52 in which a light-shielding film is not formed but is arranged in a predetermined arrangement is obtained. In FIG. 11, which schematically shows the laser trimming process of the color filter 52, the transparent substrate 50 on the suction table 9 is transferred in the direction orthogonal to the paper surface of FIG.
Along with the movement, the beam spot S emitted from the objective lens 39 removes unnecessary portions of the color filter 52.

After the unnecessary portion of the color filter 52 is removed, a black resist is applied to the color filter forming surface of the transparent substrate 50 and dried, and then exposure light is irradiated from the other surface side and development is performed after exposure. By processing and removing the unexposed black resist, FIG.
As shown in, the light shielding film 53 was formed in the gap around the color filter 52.

In the manufacturing technique of this embodiment in which the color filter 52 and the light shielding film 53 are formed in this manner, the phase difference plates 25, 30, 33, etc. arranged in the optical path of the laser beam as described above are used. By appropriately rotating, it is possible to adjust the power of the plurality of split beams so that there is no variation in the power. Therefore, as shown in FIG. 11, a predetermined amount necessary to remove only the color filter 52 on the transparent electrode 51 is obtained. It is easy to apply the beam power to each split beam without excess or deficiency, and therefore, by simultaneously irradiating a plurality of (specifically, eight) split beams to a plurality of locations, laser trimming of the color filter 52 is performed. The processing can be performed efficiently and the processing time can be greatly reduced. Further, in this embodiment, as described above, the aperture 3
Since the energy distribution curve around the optical axis of the laser beam incident on 6 is made into a top hat shape so that the low energy portion does not pass through the aperture 36, the beam spot emitted from the objective lens 39 S
Can be set to a laser beam having a substantially uniform distribution of light energy around the optical axis, and thus highly accurate laser processing can be performed with few dimensional errors and variations in the trimming width of the color filter 52. Furthermore, in the present embodiment, since the laser oscillator 5 of the laser processing machine used for trimming is provided with the degaussing cover 42 surrounding the arc lamp 5a, the linear motors 12 and 17 of the XY table 2 cause the demagnetization. There is no fear that the power or mode of the laser beam will change due to the strong magnetic force generated, and therefore, highly reliable trimming processing can always be performed.

Incidentally, if only the color filter 52 is removed while leaving the transparent electrode 51 as in this embodiment, static electricity is less likely to be generated in the subsequent cleaning process and rubbing process step, so that the liquid crystal resulting from static electricity is generated. There is an advantage that display unevenness of the display element and damage to the alignment film can be avoided.

[0034]

As described above, in the laser beam machine according to the present invention, the demagnetizing cover made of a ferromagnetic material is provided on the outer peripheral portion of the laser oscillator containing the arc lamp to surround the arc lamp. Therefore, there is no fear that the electron beam of the arc lamp emitted inside the degaussing cover will be bent by the influence of the magnetic force of the linear motor of the XY table, and therefore the power of the laser beam and the power of the laser beam will be reduced by the influence of the magnetic force of the linear motor. It is possible to achieve a remarkable effect that the reliability is improved because the troubles such as the mode change and the arc lamp life deterioration are not caused.

[Brief description of the drawings]

FIG. 1 is an XY incorporated in a laser processing machine according to this embodiment.
It is a front view of a table.

FIG. 2 is a side view of the XY table with a part thereof omitted.

FIG. 3 is an overall side view of a laser processing machine including the XY table.

FIG. 4 is a side view of a portion corresponding to FIG. 3 of a safety cover that covers the laser beam machine.

FIG. 5 is an explanatory diagram showing a layout of an optical system arranged in an optical path of a laser beam in the laser processing machine.

FIG. 6 is an explanatory diagram showing a laser oscillator of the laser processing machine.

7 is a plan view showing a state in which a degaussing cover is attached to the laser oscillator shown in FIG.

FIG. 8 is an explanatory view showing a beam irradiation unit of the laser processing machine.

9 is a characteristic diagram showing an energy distribution around an optical axis of a laser beam emitted from an optical fiber in the optical system shown in FIG.

FIG. 10 is a process explanatory view showing a method of manufacturing a liquid crystal display element, in which a color filter is trimmed by using the laser beam machine.

11 is an explanatory diagram showing a step of laser-trimming a color filter in the manufacturing process shown in FIG.

[Explanation of symbols]

 1 Processing machine main body 2 XY table 3 Surface plate (base plate) 5 Laser oscillator 5a Arc lamp 5b YAG rod 9 Adsorption table 10 X table 12 X axis linear motor 14 Y table 17 Y axis linear motor 39 Objective lens 42 Degaussing cover 50 Transparent Substrate 51 Transparent electrode 52 Color filter E Electron beam

Claims (3)

[Claims] 1. A processing machine main body which has a laser oscillator excited by an electron beam of a built-in arc lamp to oscillate a laser beam, guides the laser beam by an optical system and irradiates a workpiece, and a mounted object. An XY table capable of transferring a workpiece in two directions orthogonal to each other by a linear motor, and a base board on which the processing machine main body and the XY table are mounted are provided, and at least a ferromagnetic material is provided on an outer peripheral portion of the laser oscillator. A laser beam machine comprising a degaussing cover surrounding the arc lamp. 2. The laser processing machine according to claim 1, wherein the degaussing cover is composed of two layers of metal plates. 3. The laser processing machine according to claim 2, wherein the metal plate is any two of a silicon steel plate, an iron plate and a permalloy plate.