JP2017104875A - Laser processing device and laser processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processing device which can effectively reduce thermal effect on an object due to irradiation of laser beam.SOLUTION: Laser beam scanning for a work-piece W is executed several times thereby forming an irradiation trace over the whole processing line LN of the work-piece W. In each laser beam irradiation, a scan speed V of laser beam is so made as to be equal to or more than the product of an oscillation frequency F and an irradiation diameter D of laser beam so that irradiation traces are not overlapped on one another, whereby thermal effect on the work-piece W by laser beam can be effectively reduced.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a laser processing apparatus and a laser processing method.

  2. Description of the Related Art Conventionally, there are known apparatuses and methods for performing processing such as cutting on an object by irradiating a laser with metal or resin as the object.

  As such a laser processing apparatus, an apparatus that scans a workpiece (object) with a pulsed laser beam has been proposed (for example, Patent Document 1). The laser processing apparatus described in Patent Document 1 is configured to move a laser beam at a constant speed by emitting light while angularly moving the light at a constant speed.

  When an object is processed by laser irradiation in this way, the object is heated by the laser beam and may be affected by heat. For example, when the object is a metal, it may be oxidized by heat, when it is a resin, it may be blackened, and when the object is a thin plate, deformation may occur. It was. Therefore, it is conceivable to reduce the thermal effect by reducing the pulse width of the laser beam (for example, picosecond or femtosecond). However, for example, when a high processing speed is required or when the energy required for processing is large, the thermal effect tends to increase, and further reduction of the thermal effect has been desired.

  The objective of this invention is providing the laser processing apparatus which can reduce effectively the heat influence to the target object by irradiation of a laser beam.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a laser processing apparatus for processing an object by irradiating the object with a laser beam having a pulse width of 1 nanosecond or less. Generating means for generating, scanning means for scanning the laser beam with respect to the object, and control means for controlling the scanning means, wherein the control means determines a scanning speed of the laser beam. The laser beam is scanned along the processing line so that an irradiation mark by the laser beam is formed over the entire predetermined processing line in the object. In the laser processing apparatus, the scanning unit is caused to execute laser scanning a plurality of times.

  According to the laser processing apparatus of the present invention, by making the scanning speed of the laser beam equal to or higher than the product of the oscillation frequency and the irradiation diameter, it is possible to effectively reduce the thermal influence on the object due to the laser beam irradiation. .

1 is a schematic configuration diagram of a laser processing apparatus according to a first embodiment of the present invention. It is a top view which shows typically the irradiation trace formed in the target object by the said laser processing apparatus. It is a top view which shows the example of the said irradiation trace typically. It is a schematic block diagram of the laser processing apparatus which concerns on 2nd Embodiment of this invention. It is a schematic block diagram of the laser processing apparatus which concerns on 3rd Embodiment of this invention. It is a graph which shows the relationship between the heat affected layer width | variety and the scanning speed in Examples 3-7 and Comparative Examples 4 and 5 of this invention.

  Hereinafter, each embodiment of the present invention will be described with reference to the drawings. In the second and third embodiments, the same constituent members as those described in the first embodiment and the constituent members having the same functions are denoted by the same reference numerals as those in the first embodiment and the description thereof is omitted.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. A laser processing apparatus 1A according to this embodiment processes a workpiece W by irradiating a workpiece W as a target with a laser beam. As shown in FIG. Means 3A and control means are provided. In the present embodiment, the workpiece W has a planar processing surface, the directions along the processing surface are the X direction and the Y direction, and the direction substantially orthogonal to the processing surface is the Z direction.

  1 A of laser processing apparatuses of this embodiment are used in order to cut | disconnect the workpiece | work W along this process line, for example by irradiating a workpiece | work W with a laser beam along the linear process line which is mentioned later. .

  The laser oscillator 2 is configured to generate a laser beam having a pulse width of 1 nanosecond or less, and emits a laser beam with the X direction as an emission direction. The pulse width, wavelength, output, and beam diameter of the laser beam may be appropriately set according to the material and shape of the workpiece W, the type of processing, and the like. The laser oscillator 2 may be a solid laser, a gas laser, or the like, and any medium for stimulated emission may be used.

  The scanning unit 3A includes a polygon mirror (movable reflection mirror) 31, an fθ lens 32, and a stage 33, and is configured to scan the workpiece W with a laser beam.

  The polygon mirror 31 is provided at a position facing the laser oscillator 2 in the X direction and facing the stage 33 in the Z direction, has a plurality of reflecting surfaces 31A to 31F, and rotates around a rotation axis along the Y direction. Is configured to do. That is, the laser beam emitted by the laser oscillator 2 with the X direction as the traveling direction is reflected by the polygon mirror 31 so as to move at an equal angle and travels toward the stage 33.

  The fθ lens 32 is provided between the polygon mirror 31 and the stage 33, and changes the laser beam reflected so as to move at an equal angle by the rotating polygon mirror 31 to a constant velocity linear motion. That is, the laser beam generated by the laser oscillator 2 is scanned with respect to the stage 33 with the X direction as the scanning direction. Further, the fθ lens 32 condenses so that the laser beam when irradiating the workpiece W has an appropriate irradiation diameter.

  The stage 33 is configured to be able to place the workpiece W and to be translated along the Y direction. That is, the laser beam generated by the laser oscillator 2 is scanned with respect to the workpiece W on the stage 33. Further, by moving the stage 33, the irradiation position of the laser beam in the Y direction of the workpiece W can be adjusted.

  The scanning unit 3 may be configured to include a beam expander between the laser oscillator 2 and the polygon mirror 31 and adjust the irradiation diameter with the beam expander.

  The control means is, for example, a CPU (central processing unit) of a microcomputer that controls the entire laser processing apparatus, and is configured to control the rotation of the polygon mirror 31.

  Here, the movement of the laser beam when the control means rotates the polygon mirror 31 will be described. In the present embodiment, it is assumed that the polygon mirror 31 rotates counterclockwise in FIG. 1, and the reflecting surfaces 31A to 31F reflect the laser beam in this order. Further, the polygon mirror 31 side (left side in FIG. 1) when viewed from the laser oscillator 2 is one side in the X direction, and the opposite side is the other side.

  First, the vicinity of the first end of the first reflecting surface 31A of the polygon mirror 31 (the end on the reflecting surface 31F side) faces the laser oscillator 2 in the X direction (that is, the laser beam is reflected near the first end). The reflected laser beam travels in a direction inclined from the Z direction to one side in the X direction. When the polygon mirror 31 is rotated and the reflection position of the laser beam on the reflection surface 31A moves to the second end (end on the reflection surface 31B side), the inclination of the laser beam traveling direction with respect to the Z direction decreases. The irradiation position on the workpiece W moves to the other side in the X direction.

  When the polygon mirror 31 continues to rotate, the laser beam proceeds in a direction inclined from the Z direction to the other side in the X direction, and the irradiation position on the workpiece W further moves to the other side in the X direction. When the polygon mirror 31 is further rotated, the laser beam is reflected in the vicinity of the second end portion of the reflecting surface 31A, and then the laser beam in the vicinity of the third end portion (end portion on the reflecting surface 31A side) of the next reflecting surface 31B. Is reflected, and the irradiation position on the workpiece W returns to one side in the X direction again.

  By rotating the polygon mirror 31 as described above, laser beam scanning (laser scanning) is performed on the workpiece W a plurality of times, with the direction from one side to the other side in the X direction being the scanning direction. At this time, the rotational speed of the polygon mirror 31 and the moving speed of the irradiation position of the laser beam have a proportional relationship. Hereinafter, the moving speed of the irradiation position of the laser beam is simply referred to as “laser beam scanning speed”.

  Here, the detail of the irradiation position of the laser beam in the workpiece | work W is demonstrated. The laser oscillator 2 generates a pulse laser, that is, intermittently generates a laser beam. As shown in FIG. 2A, an irradiation mark of the next pulse is irradiated with respect to an irradiation mark A1 by one pulse. A2 is located on the other side in the X direction. At this time, if the scanning speed of the laser beam is V and the oscillation frequency of the laser beam by the laser oscillator 2 is F, the distance L between the irradiation centers of the two adjacent irradiation marks A1 and A2 is L = V / F. expressed.

  FIG. 2 (B) shows an irradiation mark when the distance L is smaller than the irradiation diameter D of the laser beam, and FIG. 2 (C) shows an irradiation mark when the distance L is equal to the irradiation diameter D. The state of the irradiation mark when the distance L is larger than the irradiation diameter D is shown in FIG. In each of FIGS. 2B to 2D, the scanning speed V is assumed to be substantially constant.

In the present embodiment, the diameter (optical diameter) of the pulse laser generated by the laser oscillator 2 is defined as the beam diameter. The beam diameter means, for example, a range in which the intensity of the laser beam has an intensity of 1 / e ² or more of the peak intensity value of a spatial pulse shape (beam profile) obtained as a Gaussian beam. Further, a processing mark formed on the workpiece by irradiation with one pulse of laser beam is set as an irradiation mark, and a diameter of the irradiation mark (an actually irradiated diameter) is set as an irradiation diameter D.

  When the distance L is smaller than the irradiation diameter D (the scanning speed V is smaller than the product of the oscillation frequency F and the irradiation diameter D), as shown in FIG. 2B, adjacent irradiation marks overlap each other. That is, immediately after an irradiation mark is formed by one pulse, a new irradiation mark is formed by the next pulse so as to overlap this irradiation mark.

  When the distance L is equal to the irradiation diameter D (the scanning speed V is equal to the product of the oscillation frequency F and the irradiation diameter D), as shown in FIG. 2C, the ends of the adjacent irradiation marks are in contact with each other. When the distance L is larger than the irradiation diameter D (the scanning speed V is larger than the product of the oscillation frequency F and the irradiation diameter D), the adjacent irradiation marks are separated from each other as shown in FIG. Formed. That is, if the distance L is equal to or greater than the irradiation diameter D, adjacent irradiation marks do not overlap.

  In the present embodiment, the control means controls the polygon mirror 31 so that the distance L is equal to or greater than the irradiation diameter D. That is, the rotational speed of the polygon mirror 31 is set to a predetermined value or more. Hereinafter, a specific method (laser processing method) in the case where the workpiece W is irradiated with the laser beam along the processing line LN along the X direction will be described with reference to FIG.

  First, FIG. 3A shows an irradiation trace when laser scanning is repeated 10 times so that the distance L is equal to the irradiation diameter D, and the irradiation trace by each laser scanning at this time is shown in FIG. Shown in

  In such an example, the irradiation traces in each laser scanning do not overlap each other as in FIG. In addition, the first irradiation center in the second laser scanning is smaller than the irradiation diameter D by an amount ΔX1 (on the other side in the X direction) relative to the center (irradiation center) of the first irradiation mark in the first laser scanning. Along the line LN). Similarly, in the third and subsequent laser scans, the n + 1 first irradiation center is shifted to the other side in the X direction by a fixed shift amount ΔX1 with respect to the nth first irradiation center.

  In addition, since the scanning speed V is substantially constant, the second and subsequent irradiation centers of the (n + 1) th time are also shifted to the other side in the X direction by a shift amount ΔX1 with respect to the corresponding irradiation center of the nth time. By repeating the laser scanning in this way, the irradiation traces do not overlap each other in each laser scanning, and the corresponding irradiation traces in the continuous laser scanning overlap each other, and an irradiation trace is formed over the entire processing line LN. The

  FIG. 3C shows an irradiation mark when the laser scanning is repeated four times so that the distance L is larger than the irradiation diameter D. FIG. 3D shows the irradiation mark by each laser scanning at this time. Show.

  Next, in such an example, the irradiation marks in each laser scanning are separated from each other as in FIG. Also, the first irradiation center in the second laser scanning is on the other side in the X direction by an amount ΔX2 smaller than the irradiation diameter D (along the processing line LN) with respect to the first irradiation center in the first laser scanning. It's off. Similarly, in the third and subsequent laser scans, the first irradiation center of the (m + 1) th time is shifted to the other side in the X direction by a certain shift amount ΔX2 with respect to the first irradiation center of the mth time.

  Further, since the scanning speed V is substantially constant, the second and subsequent irradiation centers of the (m + 1) th time are also shifted to the other side in the X direction by a shift amount ΔX2 with respect to the corresponding irradiation center of the mth time. By repeating the laser scanning in this way, the irradiation traces do not overlap each other in each laser scanning, and the corresponding irradiation traces in the continuous laser scanning overlap each other, and an irradiation trace is formed over the entire processing line LN. The

  As described above, in order to shift the irradiation center in each laser scanning with respect to the corresponding irradiation center in the immediately preceding laser scanning, the reflecting surfaces 31A to 31F of the polygon mirror 31 have different inclination angles with respect to the radial direction. What should I do? Further, the irradiation center may be shifted by adjusting the rotation speed of the polygon mirror 31 when the reflection surface for reflecting the laser beam is switched.

  According to this embodiment, there are the following effects. That is, in each laser scanning, the laser beam scanning speed V is set to be equal to or higher than the product of the laser beam oscillation frequency F and the irradiation diameter D, so that the irradiation marks do not overlap each other. The influence can be effectively reduced.

  Further, the laser beam is irradiated so that the irradiation center in each laser scanning is shifted along the processing line LN by an amount smaller than the irradiation diameter D with respect to the irradiation center corresponding to the immediately preceding laser scanning. Thereby, the corresponding irradiation traces can be overlapped, and the irradiation traces can be formed over the entire processing line LN by executing a suitable number of laser scans.

  In this way, by performing laser scanning a plurality of times to form irradiation marks over the entire processing line LN, the workpiece W can be processed such as cutting along the processing line LN.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 4, the laser processing apparatus 1 </ b> B of the present embodiment includes a laser oscillator 2, a scanning unit 3 </ b> B, and a control unit.

  The scanning means 3B includes two galvanometer mirrors 34 and 35 as movable reflection mirrors, an fθ lens 32, and a stage 36.

  The galvanometer mirror 34 is configured to face the laser oscillator 2 and rotate about a rotation axis along the Z direction. That is, the traveling direction of the laser beam emitted by the laser oscillator 2 is changed in the XY plane by being reflected by the galvanometer mirror 34.

  The galvanometer mirror 35 is configured to face the galvanometer mirror 34 and rotate about a rotation axis along the X direction. In other words, the laser beam emitted by the laser oscillator 2 and reflected by the galvano mirror 34 is reflected by the galvano mirror 35 and proceeds toward the stage 36.

  By appropriately rotating the galvanometer mirrors 34 and 35, the workpiece W of the stage 36 can be scanned with a laser beam with an appropriate direction in the XY plane as a scanning direction.

  The stage 36 is configured to be able to place the workpiece W and to be translated in three dimensions. When scanning the laser beam beyond the scannable region of the laser beam by the galvanometer mirrors 34, 35, the galvanometer mirrors 34, 35 may be rotated and the stage 36 may be moved in parallel. Further, the stage 36 may be translated in the Z direction as necessary. The laser beam may be scanned by moving only the stage 36 in parallel.

  Also in the present embodiment, similarly to the first embodiment, laser scanning is executed a plurality of times to form irradiation traces over the entire processing line LN, so that the irradiation traces do not overlap in each laser scanning.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 5, the laser processing apparatus 1C of the present embodiment includes a laser oscillator 2, a scanning unit 3C, and a control unit. The scanning unit 3 </ b> C includes an fθ lens 32 and a stage 36.

  The stage 36 is configured to be able to place the workpiece W and to be translated in three dimensions. That is, by moving the stage 36 in parallel along the XY plane, the laser beam is scanned with respect to the workpiece W with a predetermined direction in the XY plane as a scanning direction.

  Also in the present embodiment, similarly to the first embodiment, laser scanning is executed a plurality of times to form irradiation traces over the entire processing line LN, so that the irradiation traces do not overlap in each laser scanning.

  Here, the processing conditions of the example and the comparative example, which are specific conditions for processing the workpiece W by irradiating the laser beam, will be described. The material and dimensions of the workpiece W under various processing conditions and various parameters of laser scanning will be described below. For the laser scanning, any of the laser processing apparatuses 1A to 1C of the first to third embodiments described above is used. Also good.

<Examples 1 and 2 and Comparative Examples 1 to 3>
The processing conditions of Examples 1 and 2 and Comparative Examples 1 to 3 are for forming linear grooves on the surface of the workpiece W made of stainless steel by irradiation with a pulse laser. Each processing condition is that the pulse width is 100 ps, the wavelength of the laser beam is 1 μm, the oscillation frequency F is 1 MHz, the average output is 10 W, the irradiation diameter D is 30 μm, and the number of times of laser scanning is 10 Common times.

  The scanning speed V of the laser beam is 30 m / s in Example 1, 40 m / s in Example 2, 1 m / s in Comparative Example 1, 10 m / s in Comparative Example 2, and Comparative Example 3 is 20 m / s. That is, the distance L between the irradiation centers of two adjacent irradiation traces is 30 μm in Example 1, 40 μm in Example 2, 1 μm in Comparative Example 1, 10 μm in Comparative Example 2, and 20 μm in Comparative Example 3. It becomes.

  Note that a deviation amount ΔX between the irradiation center in each laser scanning and the corresponding irradiation center in the immediately preceding laser scanning is 1/10 of the distance L between the irradiation centers. That is, irradiation marks are formed uniformly on the processing line by 10 times of laser scanning.

  Table 1 below shows the main parameters of the machining conditions of Examples 1 and 2 and Comparative Examples 3 to 5 and the state of the machined workpiece W (machining result). The quality of the processing result is judged by the degree of metal oxidation. That is, if the surface of the formed groove has a metallic luster, the processing result is good, and if the oxidation progresses and the metallic luster is lost, the processing result is judged to be bad.

  In Examples 1 and 2 in which the distance L between the irradiation centers is equal to or greater than the irradiation diameter D, that is, the irradiation marks do not overlap each other in each laser scanning, the processing result is good. On the other hand, in Comparative Examples 1 to 3, in which the distance L between the irradiation centers is less than the irradiation diameter D, that is, the irradiation marks overlap each other in each laser scanning, the processing result is poor.

<About Examples 3 to 7 and Comparative Examples 4 and 5>
The processing conditions of Examples 3 to 7 and Comparative Examples 4 and 5 were as follows: a thin plate-like workpiece having a thickness of 100 μm composed of an epoxy resin (GFRP; Glass Fiber Reinforced Plastic) reinforced with glass fiber by irradiation with a pulse laser. This is for cutting W. Each processing condition is such that the pulse width is 10 ps, the wavelength of the laser beam is 344 nm, the oscillation frequency F is 50 kHz, the average output is 4 W, the irradiation diameter D is 7 μm, and the number of times of laser scanning is 10 Common times.

  The scanning speed V of the laser beam is 500 mm / s in Example 3, 600 mm / s in Example 4, 1000 mm / s in Example 5, 1500 mm / s in Example 6, and Example 7 is 3000 mm / s, Comparative Example 4 is 100 mm / s, and Comparative Example 5 is 200 mm / s.

  That is, the distance L between the irradiation centers of two adjacent irradiation marks is 10 μm in Example 3, 12 μm in Example 4, 20 μm in Example 5, 30 μm in Example 6, and 60 μm in Example 7. In Comparative Example 4, it is 2 μm, and in Comparative Example 5, it is 4 μm. Therefore, in Examples 3 to 7, L> D, and in Comparative Examples 4 and 5, L <D.

  Note that the deviation ΔX between the irradiation center in each laser scanning and the corresponding irradiation center in the immediately preceding laser scanning is 3.5 μm.

  FIG. 6 shows the relationship between the heat-affected layer width of the workpiece W and the scanning speed V in Examples 3 to 7 and Comparative Examples 4 and 5 as described above. Note that the heat-affected layer width of the workpiece W refers to the width at which the resin is melted or discolored at the cut end face when cut by a laser beam.

  In Examples 3 to 7 where L> D (irradiation marks do not overlap in each laser scanning), the heat-affected layer width was 40 μm or less, and good results were obtained. On the other hand, in Comparative Examples 4 and 5 in which L <D (irradiation marks overlap each other in each laser scanning), the heat-affected layer width was larger than 40 μm, resulting in failure.

<About Example 8 and Comparative Example 6>
The processing conditions of Example 8 and Comparative Example 6 are for cutting a thin plate-like workpiece W having a thickness of 150 μm made of carbon fiber reinforced plastic (CFRP) by irradiation with a pulsed laser. It is. Each processing condition is that the pulse width is 260 fs, the wavelength of the laser beam is 1 μm, the oscillation frequency F is 50 kHz, the average output is 4 W, the irradiation diameter D is 30 μm, and the number of times of laser scanning is 20 Common times.

  The scanning speed V of the laser beam is 2000 mm / s in Example 8, and 10 mm / s in Comparative Example 6. That is, the distance L between the irradiation centers of two adjacent irradiation marks is 40 μm in Example 8 and 0.2 μm in Comparative Example 6. Therefore, L> D in Example 8, and L <D in Comparative Example 6. Note that the amount of deviation ΔX between the irradiation center in each laser scanning and the corresponding irradiation center in the immediately preceding laser scanning is 1 μm.

  In Example 8 where L> D (irradiation marks do not overlap in each laser scanning), the heat-affected layer width of the workpiece W was 3 μm. That is, the heat-affected layer width was 40 μm or less, and good results were obtained. On the other hand, in Comparative Example 6 where L <D (irradiation marks overlap each other in each laser scanning), the heat-affected layer width was 100 μm. That is, the heat-affected layer width was larger than 40 μm, resulting in failure.

  In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.

  For example, in the first embodiment, the irradiation center in each laser scanning is shifted from the corresponding irradiation center in the immediately preceding laser scanning by a certain amount of shift ΔX1 or Δx2 on the other side in the X direction. Is not limited to this. That is, the amount of deviation may not be constant, may be shifted to one side in the X direction, or may be mixed with a shift toward one side in the X direction and a shift toward the other side.

  In the first to eighth embodiments, various parameters relating to the laser beam have been illustrated. However, these parameters may be appropriately set according to the type of workpiece W and the type of processing, and the scanning speed V oscillates. What is necessary is just to become more than the product of the frequency F and the irradiation diameter D.

  In addition, the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the present invention has been illustrated and described primarily with respect to particular embodiments, but the present invention is not limited to the embodiments described above without departing from the scope of the technical idea and object of the present invention. The trader can add various modifications.

  Therefore, the description which limited the shape, the material, etc. disclosed above is exemplary for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of some or all of those shapes, materials, etc. is included in this invention.

1A to 1C Laser processing equipment 2 Laser oscillator (generation means)
3 Scanning means 31 Polygon mirror (reflection mirror)
33, 36 Stage 34, 35 Galvano mirror (reflection mirror)
W Work (object)
LN processing line

International Publication No. 2012/120892

Claims (6)

A laser processing apparatus for processing an object by irradiating the object with a laser beam having a pulse width of 1 nanosecond or less,
Generating means for generating the laser beam;
Scanning means for scanning the laser beam with respect to the object;
Control means for controlling the scanning means,
The control means sets the scanning speed of the laser beam to be equal to or higher than the product of the oscillation frequency of the laser beam and the irradiation diameter, and an irradiation mark by the laser beam is formed over a predetermined processing line in the object. As described above, the laser processing apparatus is configured to cause the scanning unit to perform laser scanning for scanning the laser beam along the processing line a plurality of times.   The center of the first irradiation mark in each of the plurality of laser scans is shifted along the processing line by a distance smaller than the irradiation diameter with respect to the center of the first irradiation mark in the immediately preceding laser scan. The laser processing apparatus according to claim 1, wherein the laser beam is radiated as it goes.   The laser processing apparatus according to claim 1, wherein the scanning unit includes a movable reflection mirror.   The laser processing apparatus according to claim 3, wherein the reflection mirror is a polygon mirror or a galvanometer mirror.   The laser processing apparatus according to claim 1, wherein the scanning unit includes a stage that moves the object. A laser processing method for processing an object by irradiating the object with a laser beam having a pulse width of 1 nanosecond or less,
Generating the laser beam;
Scanning the laser beam with respect to the object;
The processing is performed so that the scanning speed of the laser beam is equal to or higher than the product of the oscillation frequency of the laser beam and the irradiation diameter, and an irradiation mark by the laser beam is formed over the entire predetermined processing line in the object. A laser processing method, wherein the laser beam is scanned a plurality of times along a line.

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