Laser processing method and laser processing apparatus

Abstract

To provide a laser machining method and a laser machining device capable of forming multiple fine grooves in the surface of a base material.SOLUTION: There are provided a laser machining method and a laser machining device in the present invention. The laser machining method includes: emitting pulsed laser beams L1 from a plurality of laser emission ends 2e arranged apart from each other into a space; causing the laser beams L1 to enter a condensing optical system 1 for reducing intervals to an extent that the laser beams L1 do not intersect each other in a surface 10a to be machined; applying the laser beams L1 emitted from the condensing optical system 1 to the surface 10a to be machined; forming a plurality of condensing spots for causing abrasion to be apart from each other in a first direction; relatively moving the condensing optical system 1 and the surface 10a to be machined along the surface 10a in a second direction orthogonal to the first direction; and simultaneously forming a plurality of grooves in the surface 10a.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laser processing method and a laser processing apparatus.

Background Art

[0002] Conventionally, steel plates have been used for industrial products such as transportation equipment, and spot welding is generally performed to join steel plates together.

[0003] In recent years, in the context of sustainable development goals (SDGs), efficient use of energy has been demanded in various industrial fields. Industrial products such as transportation equipment are no exception, and weight reduction of transportation equipment and the like is required. Therefore, research and development for using lightweight materials instead of conventional steel plates are being carried out.

[0004] For example, an aluminum material is known as one of the lightweight materials to replace steel plates. However, since the aluminum material is not suitable for spot welding, rivet joining may be performed for joining aluminum materials together or for joining an aluminum material and another material. However, rivet joining causes an increase in the number of parts at the joined portion and is a factor that hinders weight reduction. That is, when considering an alternative material for a steel plate, it is necessary to also consider the joining method of the alternative material.

[0005] Recently, as a method for joining various materials, a joining method using an adhesive has attracted attention. Unlike welding, an adhesive can be joined without being affected by the material and thickness of the base material. For example, there is an advantage that even a base material with low electrical resistance or a thin base material, for which appropriate joining is difficult by welding, can be appropriately joined using an adhesive.

[0006] In addition, when performing joining using an adhesive, in order to increase the adhesive force, grooves for filling the adhesive are arranged on the joining surface (see Patent Document 1).

Prior Art Documents

Patent Documents

[0007] Patent Document 1 Japanese Patent Application Laid-Open No. 2011-7250 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In joining using an adhesive, improvement in the joining strength and durability is an issue. Therefore, the present inventor considered forming a large number of fine grooves for filling an adhesive on the surface of a base material to be joined. By increasing the surface area in contact with the adhesive, the joining strength and durability can be improved. As a result of the intensive research by the present inventor, the idea of using laser ablation for forming fine grooves was conceived.

[0009] Therefore, an object of the present invention is to provide a laser processing method and a laser processing apparatus capable of forming a large number of fine grooves on the surface of a base material. MEANS FOR SOLVING THE PROBLEMS

[0010] In the laser processing method of the present invention, pulsed laser light is emitted into space from a plurality of laser emission ends arranged apart from each other, the plurality of laser lights are made incident on a condensing optical system that reduces the separation distance so that the plurality of laser lights do not intersect each other on the surface to be processed, the plurality of laser lights emitted from the condensing optical system are irradiated onto the surface to be processed to form a plurality of condensing spots that cause ablation, which are spaced apart from each other in a first direction, the condensing optical system and the surface to be processed are relatively moved along the surface to be processed and in a second direction orthogonal to the first direction to simultaneously form a plurality of grooves on the surface to be processed.

[0011] By concentrating and irradiating high-energy laser light onto a small-area condensing spot on the surface of a base material, the surface is locally heated, evaporated, or sublimated to form a hole in the base material. This processing method is generally referred to as laser ablation. Also, since the base material is relatively moved while forming a hole by ablation, a groove can be formed. When forming a groove using laser light, a finer groove can be formed more precisely compared to general machining. And the formation of a groove using laser light can be applied to various materials including aluminum materials.

[0012] Also, since pulsed laser light is used, the influence on the material due to temperature rise is small. For example, when irradiating a base material with a high reflectivity and high thermal conductivity such as an aluminum material with a high-power continuous-wave laser light, high energy is applied to the surface of the base material, and the surface may melt or debris may be generated. However, when using pulsed laser light, since the total amount of energy applied to the surface of the base material can be suppressed while maintaining a high peak power density during the pulse, the melting of the surface and the generation of debris can be suppressed.

[0013] Although details will be described later, "a plurality of laser emission ends arranged at intervals from each other" means that the emission ends of the laser light forming adjacent grooves are arranged at intervals without contacting each other. And since the present invention irradiates a plurality of lights that have passed through a condensing optical system that reduces the separation interval of the laser light onto the surface, a plurality of grooves can be formed at a narrow pitch interval. By increasing the density of the grooves, the surface area in contact with the adhesive can be further increased. Also, since a plurality of grooves can be formed simultaneously, a production efficiency applicable to a mass production process can be realized.

[0014] The plurality of the condensing spots are formed side by side in a third arrangement direction and a fourth arrangement direction. The third arrangement direction and the fourth arrangement direction may both be different from the second direction. Thereby, a plurality of grooves can be formed at an even narrower pitch interval, and the number of grooves that can be formed simultaneously can be increased.

[0015] The incident angle θs formed between the optical axis of each of the plurality of laser beams incident on the surface to be processed and the normal line of the surface may be 20 degrees or less. Thereby, a deep groove with suppressed inclination can be formed, the filling amount and filling property of the adhesive can be increased, and the adhesiveness can be kept good. Further, since the groove depths formed by the respective laser beams are more uniform, the adhesiveness is made uniform.

[0016] The condensing optical system includes a single condensing lens that receives the laser beam. The focal length of the condensing lens may be less than 300 mm. Thereby, a plurality of grooves can be formed at a narrow pitch (for example, 100 μm or less).

[0017] At least one diffractive optical element that converts at least one of the laser beams into a plurality of branched laser beams may be disposed between the plurality of laser emission ends and the condensing optical system.

[0018] The at least one diffractive optical element may convert the plurality of laser beams into a plurality of branched laser beams respectively.

[0019] The at least one diffractive optical element may cause the plurality of laser beams to enter the same diffractive optical element.

[0020] The laser emission end is an emission end of a fiber bundle in which a plurality of fibers are bundled. The fibers may be arranged at the emission end so that the condensing spot is formed at a predetermined position.

[0021] The laser emission end is an emission end of a fiber bundle in which a plurality of fibers are bundled. The fibers may be arranged at the emission end so that the third arrangement direction of the condensing spot is the same as the first direction. Although details will be described later, this makes it possible to align the groove formation start positions and reduce the blank area where no grooves are formed.

[0022] A beam shaping optical system corresponding to each of the plurality of laser emission ends may be arranged between the laser emission end and the condensing optical system.

[0023] The beam shaping optical system includes a beam expander that expands the beam diameter of each of the laser lights, and a converging optical system on the emission side of the beam expander. The laser light may be incident on the condensing optical system while gradually reducing the beam diameter of the laser light. Each laser light condensed by the condensing optical system can be made less likely to intersect with each other, and the groove can be made narrower.

[0024] The laser processing method described above may be respectively performed at a plurality of locations spaced apart in the second direction on the same work surface. Thereby, deeper grooves or more grooves can be formed, and as a result, the production efficiency can be increased.

[0025] The laser processing apparatus of the present invention includes a plurality of laser emission ends that are arranged apart from each other and each emit pulsed laser light into space. A condensing optical system that receives the laser light emitted from the plurality of laser emission ends and reduces the separation distance so that the plurality of laser lights do not intersect with each other on the work surface. A drive mechanism that relatively moves the condensing optical system and the work surface along the work surface and in a second direction orthogonal to the first direction. The plurality of laser lights emitted from the condensing optical system are irradiated onto the work surface to form a plurality of condensing spots spaced apart from each other in the first direction, and the drive mechanism relatively moves the condensing optical system and the work surface to control the formation of a plurality of grooves on the work surface simultaneously.

[0026] The plurality of condensing spots are formed side by side in a third arrangement direction and a fourth arrangement direction. The third arrangement direction and the fourth arrangement direction may both be directions different from the second direction.

[0027] At least one diffractive optical element for converting at least one of the laser lights into a plurality of branched laser lights may be disposed between the plurality of laser emission ends and the condensing optical system.

[0028] The laser emission end is an emission end of a fiber bundle in which a plurality of fibers are bundled, The fibers may be arranged at the emission end so that the condensing spot is formed at a predetermined position.

[0029] The laser emission end is an emission end of a fiber bundle in which a plurality of fibers are bundled, The fibers may be arranged at the emission end so that the third arrangement direction of the condensing spot is the same as the first direction.

[0030] A plurality of light sources each connected to the plurality of laser emission ends and outputting a laser with a peak power density of 100 kW / cm 2 or more, Ablation may be caused in the condensing spot.

Advantages of the Invention

[0031] Accordingly, a laser processing method and a laser processing apparatus capable of forming a large number of fine grooves on the surface of a base material can be provided.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13A

Figure 13B

Embodiments for Carrying Out the Invention

[0033] Embodiments of the laser processing apparatus will be described with reference to the drawings. Note that the following drawings are schematically illustrated, the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios do not necessarily match between the drawings.

[0034] In the following, each drawing will be described with reference to the XYZ coordinate system. In this specification, when expressing a direction, if the positive and negative directions are to be distinguished, it is described with a positive or negative sign, such as the "+X direction" and the "-X direction". When expressing a direction without distinguishing between the positive and negative directions, it is simply described as the "X direction". That is, in this specification, when simply described as the "X direction", both the "+X direction" and the "-X direction" are included. The same applies to the Y direction and the Z direction. In the embodiments described below, the XY plane along the X direction and the Y direction is a plane along the substrate surface, and the Z direction represents the normal direction to the substrate surface.

[0035] <First Embodiment> [Overview of Laser Processing Apparatus] FIG. 1 is a diagram showing a laser processing apparatus 100 according to an embodiment of the present invention. The principle of the laser processing apparatus 100 will be described with reference to this figure.

[0036] The laser processing apparatus 100 includes a plurality of laser emission ends 2e, a condensing optical system that receives each laser beam L1 emitted from the laser emission ends 2e, a drive mechanism M1 that moves the substrate 10, and a control unit (not shown). Each laser emission end 2e is connected to a laser light source 3 that generates a pulsed laser beam, and emits a pulsed laser beam L1 into the space from each laser emission end 2e. The optical axis Lc of each laser beam L1 is indicated by a dashed line. For ease of viewing the figure, in each drawing, many of the multiple existing light beams and components are only labeled in part.

[0037] The laser emission end 2e refers to the location where the laser light emitted from the laser light source 3 is first radiated into space. The laser light source 3 may include, in addition to the light source itself, that is, the generation unit that generates the laser light, an amplification unit (for example, a fiber amplifier) that amplifies the laser light. If such an amplification unit exists between the generation of the laser light and the irradiation of the base material 10, the amplification unit and its upstream are included in the laser light source 3. Therefore, when the laser light source includes an amplification unit, the laser emission end 2e refers to the location where the laser light after being amplified in the amplification unit is first radiated into space.

[0038] In order to apply energy capable of causing ablation to the processed surface of the base material 10 to the base material 10, each of the plurality of laser light sources 3 has a peak power density of 100 kW / cm 2 or more, more preferably 1 MW / cm 2 or more and outputs a laser. Although it varies depending on various conditions such as the material of the base material 10, the groove depth, and the repetition frequency of the pulsed laser, when having a peak power density above the above numerical value, it becomes easy to set the relative movement speed between the condensing optical system and the base material 10 to 125 mm / sec or more. The relative movement speed of 125 mm / sec represents, for example, that the time required for laser processing of a 30 m base material is 4 minutes. That is, it suggests that a production efficiency applicable to a mass production process can be realized. When the laser light is branched by a diffractive optical element (detailed in the second embodiment), each of the laser light sources 3 is preferably configured to output a laser with a higher peak power density. The wavelength of the laser output by the laser light source 3 is a wavelength in the infrared region (for example, in the case of a fiber laser or a YAG laser, the wavelength is 1064 nm, and in the case of a CO2 laser, the wavelength is 10600 nm).

[0039] Each laser light emitted from the laser emission end 2e is spaced apart from each other in the X direction (the first direction). In FIG. 1, three laser emission ends 2e are arranged in a row along the X axis, but the laser emission ends 2e may be arranged in two or more rows along the X axis, or four or more laser emission ends 2e may be arranged, or they may not be arranged along the X axis. Details will be described later.

[0040] The base material 10 has a surface to be processed 10a (hereinafter, may be simply referred to as "surface 10a") at a position facing the condensing optical system. In the present embodiment, the laser beam travels in the +Z direction from the laser emission end 2e to the surface 10a, and there is no optical system (for example, a reflection optical system) that entirely changes the traveling direction of the laser beam between the laser emission end 2e and the surface 10a. However, there may be an optical system that changes the traveling direction of the laser beam between the laser emission end 2e and the surface 10a. Further, an optical system capable of sequentially changing the traveling direction of the laser beam may be incorporated into the laser processing apparatus 100, and the traveling direction of the laser beam may be changed according to the shape of the surface 10a while relatively moving the condensing optical system and the surface 10a.

[0041] The laser processing apparatus 100 of the present embodiment has a plurality of laser light sources 3 respectively connected to a plurality of laser emission ends 2e. However, the laser processing apparatus 100 itself may not have the laser light source 3. In that case, each laser emission end 2e is connected to a laser light source outside the laser processing apparatus 100.

[0042] The base material 10 is not a component of the laser processing apparatus 100, but is shown in FIG. 1 for convenience of explanation. Similarly, the base material 10 may be shown in other laser processing apparatuses shown in the drawings. The base material 10 is not limited to an aluminum material. The material of the base material 10 may be other metal materials or may be a resin.

[0043] In each drawing, the surface 10a of the base material 10 is depicted as a plane parallel to the XY plane, but the shape of the surface 10a is not limited thereto. The surface to be processed 10a may include, for example, an inclined plane, a curved surface, and a surface having irregularities. In each drawing, the base material 10 is shown in a plate shape (extending in the XY direction and thin in the Z direction), but is not necessarily limited to such a shape. The base material 10 may have, for example, a rod shape or a block shape, or may have a complex three-dimensional shape partially having a plate shape, a rod shape, or a block shape.

[0044] When a plurality of laser beams L1 are irradiated onto the surface 10a of the substrate 10, a condensing spot Ls is formed for each laser beam L1. The condensing spot Ls is locally heated by the energy of the laser beam, causing ablation. In the condensing spot Ls, since the temperature instantaneously rises to several thousand degrees (°C), the surface 10a at the condensing spot Ls evaporates or sublimes, creating a hole in the surface 10a.

[0045] Since the laser beam output from the laser light source 3 is output in a pulsed manner, the peak power (pulse energy per pulse width (time)) is high, and locally, it gives the substrate 10 energy sufficient to cause the surface 10a to evaporate or sublime. However, due to the pulsed nature, the total energy amount is small, and it is difficult for the laser beam to heat a wide area of the substrate 10 to a high temperature. Therefore, it is possible to suppress unnecessary melting of the surface 10a and the generation of debris, and it is difficult to have an adverse thermal effect on the substrate 10.

[0046] Using the drive mechanism M1, the condenser lens 1 (although details will be described later, it is an embodiment of the condensing optical system) and the surface 10a are relatively moved in the Y direction along the surface 10a and orthogonal to the X direction. In this embodiment, while keeping the condenser lens 1 fixed, the substrate 10 is moved in the +Y direction (second direction) together with the stage 15 on which the substrate 10 is placed. At this time, as shown in FIG. 2, the substrate 10 is moved while irradiating the surface 10a with the laser beam L1. Note that since it is only necessary for the condenser lens 1 and the substrate 10 to relatively move, the condenser lens 1 may be moved without moving the substrate 10, or both the substrate 10 and the condenser lens 1 may be moved.

[0047] FIG. 2 is a diagram showing a state of irradiating a laser beam. As shown in FIG. 2, while irradiating the surface 10a with a plurality of laser beams and scraping the surface 10a, the substrate 10 is moved, thereby forming a plurality of grooves in the surface 10a.

[0048] The light condensing optical system reduces the separation distance between the respective laser beams L1 and irradiates the surface 10a therewith. As a result, the light condensing spot Ls is made smaller and the respective light condensing spots Ls are made dense. Consequently, a plurality of grooves can be formed at a narrow pitch. Since the distance between adjacent grooves is narrow, the surface area increases due to the formation of the grooves, and bonding using an adhesive can be strengthened. However, the plurality of laser beams L1 are designed so as not to intersect with each other and the light condensing spots Ls do not overlap on the surface 10a. Note that this design does not prevent the respective laser beams L1 from intersecting with each other in the optical path from the light condensing optical system to the surface 10a.

[0049] As shown in FIG. 1, the light condensing optical system of the present embodiment is composed of a single light condensing lens 1. Then, all the laser beams L1 are made incident on the same light condensing lens 1. However, the present invention is not limited to the form of a single light condensing lens 1. The light condensing lenses may be arranged in series so that one laser beam passes through a plurality of light condensing lenses in order. The light condensing lenses may be arranged in parallel so that the light condensing lenses on which the respective laser beams are incident are different.

[0050] In the present embodiment, a beam shaping optical system is arranged between the laser emission end 2e and the light condensing lens 1 so as to correspond to each of the plurality of laser emission ends 2e. In the present embodiment, a beam expander 7 is arranged as the beam shaping optical system. The beam expander 7 is an optical system that expands the beam diameter emitted from the laser emission end 2e. By using the beam expander 7, the separation distance between the respective laser beams can be set to a desired value on the incident surface of the light condensing optical system. As a result, the size and separation distance of the light condensing spots Ls on the surface 10a can be adjusted.

[0051] The laser beam L1 emitted from the beam expander 7 that has passed through the light collecting optical system may be collimated light (parallel light), or may be converging light. In the laser processing apparatus 100 shown in FIG. 1, the laser beam L1 emitted from the beam expander 7 is converging light, and the beam diameter is reduced. By making it converging light, the focus point can be intentionally shifted from the surface 10a, and the size and separation distance of the light collecting spot Ls on the surface 10a can be further finely adjusted.

[0052] [Details of Laser Processing Apparatus] FIG. 3 is a diagram showing the laser processing apparatus 100 in detail. In FIG. 3, for ease of viewing the figure, the light flux (dashed-dotted line) of each laser beam L1 shown in FIG. 1 is not shown, and only the optical axis Lc of each laser beam is shown. The plurality of laser light sources 3 each have a light source unit 3s and an optical fiber 3f that guides the laser light from the light source unit 3s. The plurality of optical fibers 3f are bundled to form an optical fiber bundle.

[0053] In the present embodiment, the beam expander 7 is configured by combining two convex lens arrays. However, the beam expander 7 may be configured by combining a convex lens array and a concave lens array. Instead of the lens array, small individual lenses may be arranged. Also, the beam shaping optical system may be located upstream of the laser emission end 2e. In other words, the beam shaping optical system may be built into the laser light source 3. Therefore, the beam shaping optical system is not an essential component for the laser processing apparatus 100 of the present embodiment.

[0054] FIG. 4A is a view of the bundled laser emission end 2e in the laser processing apparatus 100 of FIG. 3, as viewed from the -Z direction from the side of the beam expander 7. FIG. 4A shows a plurality of laser emission ends 2e constituting the fiber bundle, and a core 3c from which laser light is emitted at the center of each laser emission end 2e. The laser emission ends 2e of the fiber 3f are arranged along the W direction and the V direction. Such an arrangement of the laser emission ends 2e is reflected in the arrangement of the condensing spots Ls. As described above, the present embodiment does not have an optical system that globally changes the traveling direction of the laser light between the laser emission end 2e and the surface 10a. In this case, the arrangement direction of the laser emission ends coincides with the arrangement direction of the condensing spots. In the present embodiment, the W direction corresponds to the third arrangement direction of the condensing spots, and the V direction corresponds to the fourth arrangement direction of the condensing spots.

[0055] When each laser emission end 2e arranged in the W direction and the V direction is represented in the form of "2e(W,V)" based on the arrangement order of each laser emission end, for example, 2e(1,1), 2e(2,1), 2e(10,1), 2e(1,3), 2e(1,5), (1,7), and 2e(10,7) are shown as in FIG. 4A.

[0056] The laser emission end 2e is formed such that the third arrangement direction and the fourth arrangement direction (the W direction and the V direction in the present embodiment) are different from the second direction (Y direction) which is the relative movement direction. As a result, the condensing spots Ls of the laser light emitted from 2e(1,1), 2e(1,3), 2e(1,5), and (1,7), which are the laser emission ends 2e arranged in the V direction, are different in position in the X direction without overlapping each other. The effect of this will be described later.

[0057] In the present embodiment, the arrangement of the laser emission ends 2e adopts a staggered arrangement in which the laser emission ends 2e are arranged at the intersections of the grid and the center of the grid. Even in the case of a staggered arrangement, the positions of the laser emission ends 2e in the X direction are all different. Therefore, a plurality of grooves can be formed with a narrower pitch. The arrangement of the laser emission ends 2e may be a grid arrangement in which the laser emission ends 2e are arranged only at the intersections of the grid.

[0058] In FIG. 4A, 9 to 10 fibers are arranged along the W direction and 3 to 4 fibers are arranged along the V direction. However, the number of arranged fibers is not particularly limited and may be more or less than that in FIG. 4A. In designing a laser processing apparatus having a production efficiency applicable to a mass production process, usually, it is preferable that the number of fibers is larger than that in FIG. 4A. For example, the number of fibers may be 100 or more, preferably 200 or more. The width of the entire fiber bundle at the laser emission end 2e (dimension in the X direction) may be 20 mm or more, or may be 40 mm or more.

[0059] FIG. 4B is a view of the surface 10a seen from the position where the condenser lens 1 is arranged. It shows the state during processing with the laser light. The laser light L1 emitted from each of the laser emission ends 2e forms a condensing spot Ls. As described above, at the condensing spot Ls, the surface 10a is ablated by laser ablation. As a result, the locus of the condensing spot Ls formed by relative movement in the Y direction appears as a groove Lg along the Y direction.

[0060] At this time, since the positions of the laser emission ends 2e in the X direction are all different, the positions of the condensing spots Ls formed by each laser light in the X direction are all different. As a result, the positions of the grooves Lg formed by each laser light in the X direction are also all different.

[0061] In FIG. 4B, a laser emission end 2e that does not exist on the surface 10a is virtually shown. Among the laser emission ends 2e shown in FIG. 4A, 2e(1,1), 2e(2,1), 2e(10,1), 2e(1,3), 2e(1,5), (1,7), and 2e(10,7) are respectively labeled and illustrated in FIG. 4B. The laser emission ends 2e shown in FIG. 4B are represented by reducing them by a predetermined magnification by the amount of the condenser lens 1, assuming the condensing spot Ls as the core 3c at the laser emission end 2e. FIG. 4B shows that by using the laser emission ends 2e arranged such that the condensing spots Ls are different in position in the X direction, the interval between adjacent grooves Lg and Lg can be made smaller than the fiber diameter. In this specification, "a plurality of laser emission ends arranged separately from each other" means, for example, that the emission ends of the laser light for forming adjacent grooves, such as the laser emission end 2e(1,1) and the laser emission end 2e(1,3), are arranged separately from each other without contact.

[0062] It is preferable to design the laser processing apparatus 100 such that the interval between adjacent grooves Lg and Lg is constant. The pitch p1 of the grooves is the sum of the width of one groove (the dimension of the groove in the X direction) and the interval in the X direction between adjacent grooves Lg and Lg. The pitch p1 is preferably 100 μm or less, and more preferably 50 μm. The smaller the pitch p1, the higher the density of the grooves and the larger the surface area can be increased. To reduce the pitch p1, it is preferable that the width (the dimension in the X direction) of the groove Lg is also small. The width of the groove Lg is preferably 50 μm or less, and more preferably 25 μm.

[0063] By arranging the laser emission ends 2e as described above, the pitch p1 of the grooves can be reduced. However, the pitch p1 can also be reduced by reducing the diameter of each fiber 3f constituting the laser emission end 2e or by shortening the focal length of the condensing optical system. For example, when using a condenser lens 1 with a focal length of 300 mm or less, it is easy to form the pitch p1 to be 100 μm or less.

[0064] FIG. 5 shows a cross-sectional view along the optical axis Lc of the laser beam L1 when the laser beam L1 is incident on the substrate 10. The angle formed between the optical axis Lc of the laser beam L1 incident on the surface 10a and the normal line N10 of the surface 10a is defined as the incident angle θs. As the incident angle θs becomes smaller (as the incident angle of the laser beam L1 with respect to the surface 10a approaches 90 degrees), a deep groove with suppressed inclination can be formed. As a result, the amount and filling property of the adhesive filled in the groove can be increased, and the adhesiveness can be kept good. In addition, since the groove depth formed by each laser beam becomes more uniform, it leads to the uniformity of the adhesive force. The incident angle θs of the laser beam L1 is preferably 20 degrees or less, more preferably 10 degrees or less, and even more preferably 7 degrees or less.

[0065] When the condenser lens 1 is used in the condenser optical system as in the present embodiment, the incident angle θs becomes larger for the laser beam L1 passing through a position closer to the edge of the condenser lens 1. Therefore, the condenser lens 1 is preferably designed so that the incident angle θs of the laser beam L1 passing through the outermost edge of the condenser lens 1, where the incident angle θs tends to be large, satisfies the above numerical range. The design for reducing the incident angle θs may be, for example, setting the focal length of the condenser lens 1 to a specified value or more (for example, 100 mm or more). For example, before incidence, the laser beam may be condensed so that the laser beam L1 is not incident on the edge of the condenser lens 1, or the numerical aperture of the condenser lens 1 may be increased. For example, instead of a single condenser lens 1, a condenser optical system combining a plurality of lenses may be used to condense a plurality of laser beams while maintaining the incident angle θs as small as possible.

[0066] FIG. 6 shows a modified example of the laser processing apparatus. The laser processing apparatus 150 includes, as a beam shaping optical system, a beam expander 7 and a focusing optical system 8 corresponding to each of a plurality of laser emission ends 2e on the emission side of the beam expander 7. The focusing optical system 8 converges the laser beam L1 and makes the laser beam L1 with a reduced beam diameter enter the condenser lens 1. Thereby, the condensing point can be intentionally shifted from the surface 10a, and the size of the condensing spot Ls on the surface 10a and the separation distance between adjacent condensing spots Ls can be finely adjusted. When the beam shaping optical system has the focusing optical system 8, the laser beam L1 emitted from the beam expander 7 may be a divergent beam instead of a collimated beam (parallel beam) or a convergent beam. Note that other components of the laser processing apparatus 150 are the same as those of the laser processing apparatus 100.

[0067] FIG. 7A shows a modified example of the laser emission end 2e of the laser processing apparatus. FIG. 7A is a view of the bundled laser emission ends 2e as seen from the -Z direction side of the beam expander 7. The laser emission ends 2e of the fiber 3f are arranged along the W2 direction and the V direction. The W2 direction and the V direction are directions different from the second direction (Y direction) which is the relative movement direction. Thereby, all the positions of the laser emission ends 2e in the X direction are different.

[0068] In this modified example, the W2 direction is the same direction as the X direction. For example, in FIG. 7A, the laser emission ends 2e(1,1), 2e(2,1), and 2e(10,1) arranged in the W2 direction all have the same position regarding the Y direction.

[0069] FIG. 7B is a view of the surface 10a as seen from the position where the condenser lens 1 is arranged in the laser processing apparatus having the laser emission end 2e of FIG. 7A. In FIG. 7B, the laser emission ends 2e that do not exist on the surface 10a are virtually shown. Among the laser emission ends 2e shown in FIG. 7A, the laser emission ends 2e(1,1), 2e(2,1), and 2e(10,1) are respectively labeled and shown in FIG. 7B.

[0070] The effect of the laser emission end 2e shown in FIG. 7A will be described with reference to FIGS. 7B and 8. FIG. 8 is a view of the surface 10a of the substrate 10 in the +Z direction from the position where the condenser lens 1 is disposed with respect to the laser emission end in the first embodiment, which is the same as FIG. 4B. In FIG. 8, since the laser emission ends 2e are arranged in the W direction, the groove formation start positions (the Y-direction end positions of the grooves) are different between 2e(1,1) to 2e(10,1). When the groove formation start positions are different, a margin area A1 where no groove is formed (the area surrounded by the dashed-dotted line in FIG. 8) is generated.

[0071] On the other hand, in FIG. 7B, since the laser emission ends 2e(1,1) to 2e(10,1) are arranged in the W2 direction parallel to the X direction, no margin area A1 where no groove is formed is generated, and the groove start positions are aligned. As a result, the margin area where no groove is formed can be reduced, and the bonding strength by the adhesive can be improved. However, even if the arrangement of the laser emission ends 2e in FIG. 8 is adopted, when the laser emission start timing of the laser light can be made different by the laser emission ends 2e, the groove start positions can be aligned.

[0072] The laser processing apparatus 100 has a drive mechanism M1 and a control unit (not shown) that controls the lighting of the light source. Further, the control unit may control a condenser optical system such as the condenser lens 1, a beam shaping optical system, a converging optical system, etc. The control unit is not an essential configuration for the laser processing apparatus 100. For example, the laser processing apparatus 100 may be controlled by a control unit outside the laser processing apparatus 100, or may be controlled by an operator.

[0073] <Second Embodiment> FIG. 9 is a view showing a laser processing apparatus 200 according to the second embodiment. Regarding the matters shown below, the description will be centered on the parts where the second embodiment is different from the first embodiment. Matters not shown below are the same as those in the first embodiment. The same applies to the third embodiment.

[0074] A diffractive optical element (DOE) 9 that converts laser light into a plurality of branched laser lights is disposed between the plurality of laser emission ends 2e and the condenser lens 1. In the present embodiment, the diffractive optical element 9 is composed of a single optical element, and all the laser lights emitted from the plurality of laser emission ends 2e are made to enter the diffractive optical element 9 which is a single optical element. For ease of viewing the drawings, in FIG. 9 and FIG. 11 described later, each laser light is represented only by its optical axis. Each laser light including the optical axis Lc1 enters the diffractive optical element 9 from the position Li, is converted into a plurality of branched laser lights inside the diffractive optical element 9, and exits from the position Lo as each branched laser light including the optical axis Lc3.

[0075] FIG. 10 is a view of the diffractive optical element 9 as seen from the -Z direction on the condenser lens 1 side. The position Li where each laser light enters is on the back surface side of the diffractive optical element 9 shown in FIG. 10. One laser light incident from the position Li is converted into nine branched laser lights, and the branched laser lights exit from nine positions Lo within the periphery Ln of the position Li. The number of branched laser lights branched from one laser light is not particularly limited. However, since the laser power decreases as the number of branches increases, it is preferably branched into 25 or less, more preferably 16 or less, and even more preferably 9 or less from one laser light. In FIG. 10, the laser lights are made to enter so that the position Li is spaced apart in the X direction (first direction), and are configured to emit branched laser lights respectively. Specifically, a group of branched laser lights branched from one laser light into nine are formed in plurality in the X direction (first direction).

[0076] The positions Lo of the branched laser lights emitted from the diffractive optical element 9 are arranged along the W direction and the V direction orthogonal to the W direction. In the present embodiment, there is no optical system between the laser emission end 2e and the surface 10a that globally changes the traveling direction of the laser light. In this case, the arrangement direction of the branched laser lights coincides with the arrangement direction of the condensing spots. In the present embodiment, the W direction corresponds to the third arrangement direction of the condensing spots, and the V direction corresponds to the fourth arrangement direction of the condensing spots.

[0077] The emission position Lo of the branched laser light is inclined with respect to the X and Y directions. The line h1 represents a reference line extending in the Y direction from the position Lo respectively. The reference line h1 does not overlap with other reference lines h1. This indicates that the positions of the position Lo in the X direction are all different. It is preferable that the interval between the reference line h1 and the adjacent reference line h1 is constant (that is, exhibits a constant pitch). Assuming that the reference line h1 is projected onto the base material 10, the reference line h1 will overlap with the locus of the condensing spot Ls formed by relative movement as shown in Fig. 4B, that is, with the groove. This shows that even when the diffractive optical element 9 is used, by arranging the position Lo of the branched laser light in an inclined manner, a plurality of grooves can be formed at a narrow pitch interval.

[0078] Fig. 11 shows a laser processing apparatus 250 which is a modified example of the laser processing apparatus 200. In the laser processing apparatus 250, the diffractive optical element 11 has the same number as the number of laser emission ends 2e, and is provided corresponding to each of the plurality of laser emission ends 2e. Since the diffractive optical element 11 used in this modified example is smaller than a single diffractive optical element, there is an advantage that the degree of freedom in the layout design of the laser processing apparatus is high. As a further modified example, the diffractive optical element may have two or more and have a number less than the number of laser emission ends 2e.

[0079] Fig. 12 is a view of the diffractive optical element 11 seen from the -Z direction. The position Li where each laser light is incident is on the back side of the diffractive optical element 11 shown in Fig. 12. One laser light incident from the position Li is converted into nine branched laser lights, and the branched laser lights are emitted from nine positions Lo of the same diffractive optical element 11. In order to arrange a plurality of diffractive optical elements 11 close to each other in the X direction, in the laser processing apparatus 250, the disc-shaped diffractive optical element 11 is arranged in a staggered manner as shown in Fig. 12. However, the shape and layout of the diffractive optical element 11 are not limited to this.

[0080] Similar to FIG. 10, the diffraction optical element 11 is designed such that the position Lo of the laser light emitted from the diffraction optical element 11 is arranged along the W direction (third arrangement direction) and the V direction (fourth arrangement direction). The line h1 represents a reference line extending in the Y direction from the position Lo. The reference line h1 does not overlap with other reference lines h1. It is preferable that the interval between the reference line h1 and the adjacent reference line h1 is constant (i.e., exhibits a constant pitch).

[0081] <Third Embodiment> FIGS. 13A and 13B illustrate an embodiment in which laser processing is performed by combining a plurality of laser processing apparatuses. In each figure, laser processing is performed by individual laser processing apparatuses at a plurality of locations spaced apart in the Y direction (second direction) on the same surface 10a. Each individual laser processing apparatus has a control unit, and the laser processing apparatuses may perform laser processing in cooperation by communication between the control units. Alternatively, each individual laser processing apparatus may have a shared control unit, and the shared control unit may control each laser processing apparatus to perform laser processing in cooperation by the laser processing apparatuses.

[0082] In the first example of FIG. 13A, the laser light L2 is irradiated from the second laser processing apparatus so as to overlap with the groove formed by irradiating the surface 10a with the laser light L1 from the first laser processing apparatus. Thereby, the groove can be dug deeper.

[0083] In the second example of FIG. 13B, with respect to the groove formed by irradiating the surface 10a with the laser light L1 from the first laser processing apparatus, the laser light L2 is irradiated from the second laser processing apparatus with a slight shift in the X direction. Thereby, more grooves can be formed with a single relative movement.

[0084] The above describes each embodiment and its modification. However, the present invention is not limited to each of the above-described embodiments and modifications, and various changes or improvements can be made to each of the above embodiments without departing from the spirit of the present invention. Also, each embodiment or modification may be combined.

[0085] In the first and second embodiments, the condensing spots are arranged in two different directions. However, in these embodiments, the condensing spots may be arranged in only one direction, or the condensing spots may not be arranged (i.e., do not form a row side by side).

Explanation of Reference Numerals

[0086] 1: Condensing lens 2e: Laser emission end 3: Laser light source 3c: Core 3f: Fiber 3s: Light source unit 7: Beam expander 8: Converging optical system 9: Diffractive optical element 10: Substrate 10a: Work surface (of the substrate) 11: Diffractive optical element 15: Stage 100, 150, 200, 250: Laser processing apparatus L1, L2: Laser light Lc, Lc1, Lc3: Optical axis Lg: Groove Ls: Condensing spot M1: Driving mechanism

Claims

1. Pulse-shaped laser light is emitted into space from a plurality of laser emission ends arranged at intervals from each other, The plurality of laser lights are incident on a condensing optical system that reduces the separation distance so that the plurality of laser lights do not intersect with each other on the surface to be processed, The plurality of laser lights emitted from the condensing optical system are irradiated onto the surface to be processed to form a plurality of condensing spots that cause ablation, which are spaced apart from each other in a first direction, The condensing optical system and the surface to be processed are relatively moved along the surface to be processed and in a second direction orthogonal to the first direction to simultaneously form a plurality of grooves on the surface to be processed. At least one diffractive optical element that converts the plurality of laser lights into a plurality of branched laser lights respectively is arranged between the plurality of laser emission ends and the condensing optical system. A laser processing method characterized by this.

2. The plurality of condensing spots are formed side by side in a third arrangement direction and a fourth arrangement direction, The third arrangement direction and the fourth arrangement direction are both directions different from the second direction. The laser processing method according to claim 1, characterized by this.

3. The incident angle θs formed between the optical axis of each of the plurality of laser lights incident on the surface to be processed and the normal line of the surface to be processed is 20 degrees or less respectively. The laser processing method according to claim 1, characterized by this.

4. The condensing optical system includes a single condensing lens that receives the laser light, The focal length of the condensing lens is less than 300 mm. The laser processing method according to claim 1, characterized by this.

5. The at least one diffractive optical element is characterized in that the plurality of laser lights are incident on the same diffractive optical element. The laser processing method according to claim 1, characterized by this.

6. The laser emission end is the emission end of a fiber bundle in which a plurality of fibers are bundled, The laser processing method according to any one of claims 1 to 5, characterized in that the fibers are arranged at the emission end so that the condensing spot is formed at a predetermined position.

7. Pulse-shaped laser light is emitted into space from a plurality of laser emission ends arranged apart from each other, The plurality of laser lights are incident on a condensing optical system that reduces the separation distance so that the plurality of laser lights do not intersect each other on the surface to be processed, The plurality of laser lights emitted from the condensing optical system are irradiated onto the surface to be processed to form a plurality of condensing spots that cause ablation, which are spaced apart from each other in a first direction. The condensing optical system and the surface to be processed are relatively moved along the surface to be processed and in a second direction orthogonal to the first direction to simultaneously form a plurality of grooves on the surface to be processed. The plurality of condensing spots are formed side by side in a third arrangement direction and a fourth arrangement direction. Both the third arrangement direction and the fourth arrangement direction are directions different from the second direction. The laser emission end is an emission end of a fiber bundle in which a plurality of fibers are bundled, A laser processing method, characterized in that the fibers are arranged at the emission end so that the third arrangement direction of the condensing spots is the same as the first direction.

8. The laser processing method according to claim 6, characterized in that a beam shaping optical system corresponding to each of the plurality of laser emission ends is arranged between the laser emission end and the condensing optical system.

9. Pulse-shaped laser light is emitted into space from a plurality of laser emission ends arranged apart from each other, The plurality of laser lights are incident on a condensing optical system that reduces the separation distance so that the plurality of laser lights do not intersect each other on the surface to be processed, Irradiate the plurality of laser beams emitted from the light condensing optical system onto the surface to be processed to form a plurality of light condensing spots that are spaced apart from each other in a first direction and generate ablation. Relatively move the light condensing optical system and the surface to be processed along the surface to be processed and in a second direction orthogonal to the first direction to simultaneously form a plurality of grooves on the surface to be processed. The laser emission end is the emission end of a fiber bundle in which a plurality of fibers are bundled. The fibers are arranged at the emission end so that the light condensing spots are formed at predetermined positions. A beam shaping optical system corresponding to each of the plurality of laser emission ends is arranged between the laser emission end and the light condensing optical system. The beam shaping optical system includes a beam expander that expands the beam diameter of each laser beam and a converging optical system on the emission side of the beam expander. A laser processing method, characterized in that the laser beam is incident on the light condensing optical system while gradually reducing the beam diameter of the laser beam.

10. A laser processing method, characterized in that the laser processing method according to any one of claims 1 to 5 is respectively performed at a plurality of locations on the same surface to be processed that are spaced apart in the second direction.

11. A plurality of laser emission ends that are arranged to be spaced apart from each other and each emit pulsed laser light into space, A light condensing optical system that receives the laser light emitted from the plurality of laser emission ends and reduces the separation interval so that the plurality of laser beams do not intersect each other on the surface to be processed, A drive mechanism that relatively moves the light condensing optical system and the surface to be processed along the surface to be processed and in a second direction orthogonal to the first direction. The plurality of laser beams emitted from the light condensing optical system are irradiated onto the work surface to form a plurality of light condensing spots spaced apart from each other in the first direction, while relatively moving the light condensing optical system and the work surface by the drive mechanism, and are controlled to simultaneously form a plurality of grooves on the work surface. The plurality of light condensing spots are formed side by side in a third arrangement direction and a fourth arrangement direction. Both the third arrangement direction and the fourth arrangement direction are directions different from the second direction. The laser emission end is an emission end of a fiber bundle in which a plurality of fibers are bundled. A laser processing apparatus, characterized in that the fibers are arranged at the emission end such that the third arrangement direction of the light condensing spots is the same as the first direction.

12. The plurality of light condensing spots are formed side by side in a third arrangement direction and a fourth arrangement direction. The laser processing apparatus according to claim 11, wherein both the third arrangement direction and the fourth arrangement direction are directions different from the second direction.

13. The laser processing apparatus according to claim 11 or 12, characterized in that at least one diffractive optical element for converting at least one of the laser beams into a plurality of branched laser beams is arranged between the plurality of laser emission ends and the light condensing optical system.

14. The laser emission end is an emission end of a fiber bundle in which a plurality of fibers are bundled. The laser processing apparatus according to claim 11 or 12, characterized in that the fibers are arranged at the emission end such that the light condensing spots are formed at predetermined positions.

15. A plurality of light sources each connected to the plurality of laser emission ends and outputting lasers with a peak power density of 100 kW / cm ２ or more, are provided. The laser processing apparatus according to claim 11 or 12, characterized in that ablation is caused in the light collecting spot.

16. A plurality of laser emission ends that are arranged at intervals from each other and each emit pulsed laser light into space, a condensing optical system that receives the laser light emitted from the plurality of laser emission ends and reduces the separation distance so that the plurality of laser lights do not intersect each other on the surface to be processed, a drive mechanism that relatively moves the condensing optical system and the surface to be processed along the surface to be processed and in a second direction orthogonal to the first direction, at least one diffractive optical element that is arranged between the plurality of laser emission ends and the condensing optical system and converts each of the plurality of laser lights into a plurality of branched laser lights, The laser processing apparatus is characterized in that the plurality of laser lights emitted from the condensing optical system are irradiated onto the surface to be processed to form a plurality of light collecting spots that are separated from each other in the first direction, and while the drive mechanism relatively moves the condensing optical system and the surface to be processed, it is controlled to simultaneously form a plurality of grooves on the surface to be processed.

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