Laser processing method

Abstract

To provide a laser processing system capable of securing processing quality while maintaining processing accuracy at the time of laser processing, a workpiece processed by using the laser processing system, and a laser processing method.SOLUTION: A laser processing system 1 according to the present invention includes a container 10, a light transmission member 20, and a laser irradiation device 30. The container 10 stores a liquid medium FD through which a laser beam LB can transmit and accommodates a workpiece W in a state where the workpiece W is arranged in the inside of the liquid medium FD. The light transmission member 20 includes: a contact surface 20Aa that contacts the liquid medium FD; and a non-contact surface 20Ab that does not contact with the liquid medium FD. The laser irradiation device 30 causes the laser beam LB to pass the light transmission member 20 and the liquid medium FD in this order and irradiate the inside of the workpiece W with the laser beam LB. The liquid medium FD and the light transmission member 20 have a refraction index equal to that of the workpiece W. The laser beam LB emitted from the laser irradiation device 30 has a pulse width of 200 fs or less and a laser spot diameter of 3 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to , a user processing method, and particularly to a laser processing method for processing the inside of a workpiece using a laser beam. RuRe It relates to a laser processing method.

Background Art

[0002] Conventionally, as a technique for processing the inside of a workpiece, a method of irradiating a workpiece with a laser beam in the air has been widely known (for example, Patent Document 1). However, in such a method, when the incident surface of the laser beam on the workpiece has a non-planar shape (for example, a curved surface shape), the laser beam refracts when it enters the workpiece, resulting in a problem that the processing accuracy decreases due to a shift in the condensing position.

[0003] [[ID=2I]] Therefore, in order to solve such a problem, for example, a laser processing system described in Patent Document 2 has been proposed. The laser processing system described in Patent Document 2 includes a refractive index adjustment layer (for example, water) made of a liquid or an elastic body that contacts the workpiece (a three-dimensional object, for example, glass), an optical waveguide member (for example, glass) that contacts the refractive index adjustment layer, and a laser irradiation device (a laser processing machine), and is configured to irradiate the workpiece with a laser beam through the refractive index adjustment layer and the optical waveguide member.

[0004] According to such a laser processing system, the laser beam can be condensed at the target position (designed position) regardless of the shape of the incident surface of the workpiece, so that the processing accuracy can be improved.

Prior Art Documents

Patent Documents

[0005] <000002G>

Patent Document 1

Patent Document 2

[0006] Incidentally, examples of the workpieces mentioned above include resin-based optical elements such as imaging lenses. In such optical elements, by irradiating them with laser light, the area where the light is focused can be heated and then carbonized, causing it to turn black. This makes it possible to form a light-shielding region of a desired shape (a region that shields unwanted light reflected from the surface or inside) inside the element (for example, Patent Document 1).

[0007] However, when laser processing optical elements, if the focusing intensity of the laser beam is too weak, for example, it may not be possible to achieve a clear black color due to poor carbonization, etc. Conversely, if the focusing intensity is too strong, cracks may form near the point of focus of the laser beam, or if a coating is applied to the surface, it may be damaged, leading to problems such as cracks forming near the point of focus.

[0008] Therefore, in order to correct such problems, it is necessary to adjust the focusing intensity of the laser beam (for example, the pulse width of the laser beam), but such adjustments are often difficult even for those skilled in operating laser irradiation equipment, and in such cases, the processing quality deteriorates. This is also true when laser processing workpieces other than optical elements.

[0009] Considering these circumstances, although the laser processing system described in Patent Document 1 contributes to improving processing accuracy, it does not take into account the adjustment of the focusing intensity of the laser beam, and therefore, from the standpoint of improving processing quality, it cannot be said to be sufficient and there is still room for improvement.

[0010] This invention was made to solve these problems, and makes it possible to ensure processing quality while maintaining processing accuracy during laser processing. Na Re The objective is to provide a processing method. [Means for solving the problem]

[0011] The inventors of this invention conducted thorough research to resolve the problems described above and, as a result, discovered that the balance between the laser pulse width and the laser spot diameter significantly affects processing quality, leading to the completion of this invention. The present invention relates to the present invention below. RuRe I will now explain the processing method.

[0012] Laser processing according to the present invention method Laser processing is a method of processing the inside of a workpiece using laser light. method The apparatus comprises: a container for storing a liquid medium and housing the workpiece in the liquid medium; a light-transmitting member having a contact surface that contacts the liquid medium and a non-contact surface on the opposite side of the contact surface that does not contact the liquid medium, and capable of transmitting laser light; and a laser irradiation device that irradiates the inside of the workpiece by passing the laser light through the light-transmitting member and the liquid medium in that order, wherein the liquid medium and the light-transmitting member have the same refractive index as the workpiece, and the laser Processing method teeth, The process includes a workpiece placement step of placing the workpiece in the liquid medium within the container, and a laser irradiation step of passing the laser light through the light-transmitting member and the liquid medium in that order to irradiate the inside of the workpiece after the workpiece placement step, wherein the laser irradiation step is The laser light having a pulse width of 200 fs or less and a laser spot diameter of 3 μm or less is irradiated. This forms a light-shielding region inside the optical element. do process , that is.

[0013] Furthermore, the laser processing method In the invention relating to this, it is preferable that the laser spot diameter is 1 μm or less.

[0014] Furthermore, the laser processing method In the invention relating to this, it is preferable that the laser irradiation device irradiates laser light having a frequency of 100 kHz or more and 300 kHz or less, and a peak output of 1 W or less.

[0015] Furthermore, the laser processing method In the invention relating to this invention, it is preferable that the laser irradiation device irradiates the laser light having a wavelength of 1100 nm or less.

[0016] In addition, in the invention related to the laser processing method it is preferable that the light transmission member is a member constituting the bottom or side wall of the container.

[0017] Furthermore, in the invention related to the laser processing method it is preferable that the workpiece is made of a resin member having light permeability.

Advantages of the Invention

[0020] As described above, according to the laser processing method according to the present invention RuRe it is possible to surely improve the processing quality while maintaining the processing accuracy during laser processing, although the configuration is relatively simple.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 is a schematic diagram showing an embodiment of a laser processing system according to the present invention. [Figure 2] FIG. 2 is an explanatory diagram for explaining the behavior of laser light irradiated on the workpiece. [Figure 3] FIG. 3 is a flowchart for explaining the laser processing method according to the present invention. [Figure 4] FIG. 4 is a table showing the results of tests conducted on Example 1, Example 2, and Comparative Examples 1 to 6. [Figure 5] FIG. 5 is a graph showing the relationship between the pulse width and the laser spot diameter in the test of FIG. 4 [Figure 6] FIG. 6 is a graph showing the relationship between the pulse width and the frequency in the test of FIG. 4. [Figure 7] FIG. 7 is a graph showing the relationship between the pulse width and the wavelength in the test of FIG. 4. [Figure 8] FIG. 8 is an image diagram of the workpiece used in the test according to Example 2, where (a) is a plan view showing the state before the test and (b) is a plan view showing the state after the test. [Figure 9] Figure 9 is an image of another workpiece used in the test according to Example 2, where (a) is a plan view showing the state after the test, and (b) is an enlarged plan view showing the X portion of (a). [Figure 10] Figure 10 shows images of the workpiece used in the test for Comparative Example 1, where (a) is a plan view showing the state after the test, (b) is a partially enlarged plan view of (a), and (c) is a partially enlarged plan view of (b). [Figure 11] Figure 11 is an image of another workpiece used in the test related to Comparative Example 1, where (a) is a plan view showing the state after the test, and (b) is an enlarged plan view showing the Y portion of (a). [Figure 12] Figure 12 shows images of other workpieces used in the test related to Comparative Example 1, where (a) is a plan view showing the state after the test, and (b) is a partially enlarged plan view of (a). [Figure 13] Figure 13 shows images of other workpieces used in the test related to Comparative Example 1, where (a) is a plan view showing the state after the test, and (b) is an enlarged plan view showing the Z portion of (a). [Figure 14] Figure 14 is a schematic diagram showing a modified version of the laser processing system shown in Figure 1. [Modes for carrying out the invention]

[0022] Hereinafter, the laser processing system of the present invention, the workpiece processed using the same, and the laser processing method will be described with reference to the drawings based on a preferred embodiment thereof. Figure 1 is a schematic diagram showing one embodiment of the laser processing system according to the present invention, Figure 2 is an explanatory diagram for illustrating the behavior of laser light irradiated onto a workpiece, and Figure 3 is a flowchart for illustrating the laser processing method according to the present invention.

[0023] <Laser Processing System 1> As shown in Figure 1, the laser processing system 1 according to this embodiment is a system for processing the inside of a workpiece W using laser light LB, and is composed of a container 10, a light-transmitting member 20, and a laser irradiation device 30. Furthermore, the laser processing system 1, laser beam LB, workpiece W, container 10, light-transmitting member 20, and laser irradiation device 30 correspond to the "laser processing system," "laser beam," "workpiece," "container," "light-transmitting member," and "laser irradiation device" described in the claims, respectively.

[0024] Here, we will describe the workpiece W used in this embodiment. The workpiece W according to this embodiment is an optical element such as an imaging lens, and is formed using a transparent or translucent resin material (for example, plastic). Specifically, the workpiece W is a plate-like member with a planar shape that is approximately circular (see Figure 8, etc.) and a cross-sectional shape that is curved and convex toward one side (the upper side of the paper in Figure 1). It has a central region through which effective light rays can pass and an outer peripheral region (hereinafter referred to as "edge portion Wa") arranged around the central region. Note that the optical element related to the workpiece W is not limited to a resin member, but may be made of other materials, such as optical glass.

[0025] Inside the edge portion Wa, a light-shielding region LS is formed by laser processing to block unwanted light reflected from the surface (surface layer) or interior of the workpiece W. A detailed explanation of the method for forming the light-shielding region LS (laser processing method) will be given later. As a result, for example, if light reflected from inside the workpiece W (unwanted light) is directed toward the edge portion Wa, this light can be blocked by the light-shielding region LS. Consequently, in the workpiece W according to this embodiment, the reflection of stray light on the surface and inside the workpiece W can be suppressed, thereby reducing so-called ghosting and flare. Furthermore, the above-mentioned light-shielding region LS corresponds to the "internal region" as described in the claims.

[0026] (container 10) Container 10 is a device for storing the liquid material FD and for housing the workpiece W in the liquid material FD. Specifically, the container 10 is formed in the shape of a hollow box or cylinder with an open top, and has a side wall portion 10A and a bottom portion 10B. Such a container 10 can be formed using various materials, such as resin members or metal members. Furthermore, the side wall portion 10A and the bottom portion 10B correspond to the "side wall portion" and "bottom portion" as described in the claims.

[0027] Here, we will describe the liquid medium FD stored in container 10. The liquid medium FD is a fluid medium through which laser light LB can pass; that is, a transparent or translucent liquid. Note that the term "liquid" here includes sols (colloidal solutions). As the liquid FD medium, for example, water, various oils such as silicone oil and paraffin oil, organic solvents such as alcohol-based solvents (e.g., methyl alcohol) and ether-based solvents (e.g., diethyl ether), or so-called refractive indices can be used.

[0028] In this embodiment, the workpiece W is configured to be housed in the container 10 while being supported by a pair of support members 11, 11. Each of the pair of support members 11, 11 has a lower support portion 11A and an upper support portion 11B, which are formed in an L-shape in cross-section. The outer edge of the workpiece W can be sandwiched between the upper pieces of the lower support portion 11A and the upper support portion 11B, and the support members can be placed (positioned) on the bottom 10B of the container 10.

[0029] As will be described in more detail later, in this embodiment, a light-shielding region LS is formed inside the workpiece W by irradiating the workpiece W, which is immersed in a liquid medium FD, with laser light LB. As described above, the liquid medium FD is a fluid medium, so when the workpiece W is immersed in it, it can come into contact with the surface without any gaps, even if the surface of the workpiece W has irregularities or depressions.

[0030] In other words, in this embodiment, since there is no air layer between the workpiece W and the liquid medium FD when the workpiece W is immersed in the liquid medium FD, if the curvature of both is equivalent (preferably the same), the workpiece W and the liquid medium FD can be considered as a homogeneous medium. As a result, in this embodiment, it is possible to suppress (prevent) the refraction or reflection of the irradiated laser beam LB at the interface between the workpiece W and the liquid medium FD, so that the laser beam LB can be irradiated to a targeted position inside the workpiece W. Therefore, in this embodiment, it is possible to accurately form a light-shielding region LS inside the laser beam LB. The behavior (refraction) of the laser beam LB irradiated onto the workpiece W will be explained later (see Figure 2).

[0031] If the refractive index of the workpiece W is "1.5" (plastic), then a liquid medium FD with a refractive index of "1.3 to 1.5" can be used. Examples of such liquid media FD include water (refractive index: 1.333), silicone oil (refractive index: 1.4), methyl alcohol (refractive index: 1.329), and ethyl alcohol (refractive index: 1.3618). While it is particularly preferable that the difference in refractive index between the workpiece W and the liquid media FD be 0, if otherwise, it is desirable to have a difference of 0.3 or less, and more preferably 0.2 or less.

[0032] (Light-transmitting member 20) The light-transmitting member 20 is a member for guiding laser light LB to the liquid medium FD stored in the container 10, and comprises a main body portion 20A and leg portions 20B.

[0033] The main body 20A is made of a transparent or translucent plate-shaped member having a refractive index equivalent to that of the workpiece W, and has a contact surface 20Aa that contacts the liquid medium FD stored in the container 10, and a non-contact surface 20Ab on the opposite side of the contact surface 20Aa that does not contact the liquid medium FD. Furthermore, the contact surface 20Aa and the non-contact surface 20Ab correspond to the "contact surface" and "non-contact surface" described in the claims, respectively.

[0034] The main body 20A is preferably formed using a material whose refractive index difference with the liquid medium FD is "0.3 or less", more preferably "0.2 or less", from the viewpoint of irradiating the laser beam LB to a targeted position (design position) within the workpiece W, as described above, and is particularly preferably formed using the same material as the workpiece W. The behavior (refraction) of the laser beam LB irradiated onto the workpiece W will be explained later (see Figure 2). Such a main body 20A can be formed from the same material if the workpiece W is a plastic with a refractive index of 1.5; otherwise, for example, optical glass with a refractive index of 1.4 to 1.6 can be used.

[0035] The leg portion 20B protrudes from the contact surface 20Aa of the main body portion 20A and can be placed on a pair of upper support portions 11B, 11B arranged inside the container 10. The leg portion 20B may be formed from the same material as the main body portion 20A (a transparent or translucent material), or it may be formed from an opaque material. Furthermore, if the main body portion 20A and the leg portion 20B are formed from the same material, they can be integrally molded (for example, by injection molding). Furthermore, as shown in Figure 1, it is preferable that the light-transmitting member 20 has both a non-contact surface 20Ab and a contact surface 20Aa that are flat and parallel to each other, but it may also be formed in other shapes (for example, the output surface may be curved).

[0036] (Laser irradiation device 30) The laser irradiation device 30 is a device for generating and irradiating laser light LB to the outside, and is located under atmospheric pressure. As such a laser irradiation device 30, known laser irradiation devices can be used, for example, a flatbed type device that moves a head (not shown) in the XY direction to irradiate the workpiece W with laser light LB, or a galvanometer type device that moves a mirror (not shown) in the XY direction to irradiate the workpiece W with laser light LB.

[0037] Furthermore, in the laser irradiation device 30 according to this embodiment, similar to known laser irradiation devices, laser light LB corresponding to various preset parameters (e.g., pulse width, laser spot diameter, frequency, wavelength, irradiation distance) is irradiated under the control of a control device (e.g., CPU: Central Processing Unit).

[0038] The laser irradiation device 30 is configured to irradiate the workpiece W, which is immersed in the liquid medium FD, with the optical axis of the laser beam LB being oriented so as to be substantially perpendicular to the non-contact surface 20Ab of the light-transmitting member 20.

[0039] Here, we will explain the behavior of the laser beam LB irradiated onto the workpiece W with reference to Figure 2. In the following, (1) The refractive indices of the workpiece W and the light-transmitting member 20 are "1.5", and the refractive index of the liquid medium FD is "1.3", (2) The incident surface of the laser beam LB on the workpiece W is curved. I will explain based on that premise.

[0040] As shown in Figure 2, when laser light LB is emitted from the laser irradiation device 30 toward the light-transmitting member 20, the laser light LB is refracted at the incident point Ip1 at an angle corresponding to the difference between the refractive index of the atmosphere ("1.0") and the refractive index of the light-transmitting member 20 ("1.5"), and then travels through the light-transmitting member 20.

[0041] Next, at the incident point Ip2 of the light-transmitting member 20, the laser beam LB is refracted at an angle corresponding to the difference between the refractive index of the light-transmitting member 20 (e.g., "1.5") and the refractive index of the liquid medium FD (e.g., "1.3"). However, because the amount of refraction is small, it travels through the liquid medium FD while generally maintaining a straight line, and eventually reaches the incident point Ip3 (curved surface) of the workpiece W.

[0042] In the example shown in Figure 2, since the incident point Ip3 of the workpiece W is located on a curved surface, the question arises as to whether or not the laser beam LB is refracted or reflected at the interface between the workpiece W and the liquid medium FD. However, since the refractive index of the liquid medium FD (e.g., "1.3") and the refractive index of the workpiece W (e.g., "1.5") are equivalent, as mentioned above, it is possible to consider the whole as homogeneous. Therefore, the laser beam LB is refracted at an angle corresponding to the difference between the refractive index of the liquid medium FD and the refractive index of the workpiece W. However, because the amount of refraction is small, it largely maintains a straight line and focuses inside the workpiece W (edge ​​portion Wa) (see "focusing point LBp").

[0043] Thus, in this embodiment, even if the incident surface of the laser beam LB on the workpiece W is curved or uneven, the laser beam LB can be focused to the target position (design position) regardless of this, making it possible to accurately form the light-shielding region LS.

[0044] <Laser processing method> Next, a laser processing method using the laser processing system 1 according to this embodiment will be described with reference to Figures 1 to 3. In the following explanation, we will assume that the refractive index is as described in (1) and the shape is as described in (2) above.

[0045] As shown in Figure 3, the laser processing method according to this embodiment comprises a workpiece placement step S100 and a laser irradiation step S200. Furthermore, the workpiece placement step S100 and the laser irradiation step S200 correspond to the "workpiece placement step" and the "laser irradiation step" described in the claims, respectively.

[0046] (Workpiece placement process S100) The laser processing method according to this embodiment begins with a workpiece placement step S100, as shown in Figure 3.

[0047] In the workpiece placement process S100, the workpiece W is immersed in the liquid medium FD. For example, in the workpiece placement step S100, as shown in Figure 1, (1) The workpiece W is held between a pair of support members 11, 11. (2) The pair of support members 11, 11, on which the workpiece W is held, are placed inside the container 10 in which the liquid medium FD is stored. These tasks are performed in order. In addition, in the example shown in Figure 1, after performing the operations described in (1) and (2) above, the light-transmitting member 20 is placed on the pair of support members 11, 11. In the above example, the workpiece W is placed in a container 10 containing the liquid medium FD, but it is also acceptable to place the workpiece W in an empty container 10 and then fill the container 10 with the liquid medium FD.

[0048] In the laser processing method according to this embodiment, as shown in Figure 3, the laser irradiation step S200 is performed after the workpiece placement step S100.

[0049] (Laser irradiation process S200) In the laser irradiation process S200, the laser beam LB is irradiated into the workpiece W via the light-transmitting member 20 and the liquid member FD (see Figure 1). Specifically, in the laser irradiation process S200, laser light LB is emitted from the laser irradiation device 30 so as to be approximately perpendicular to the incident surface of the plate-shaped light-transmitting member 20, and the laser light LB is irradiated into the inside of the edge portion Wa of the workpiece W. This makes it possible to form a light-shielding region LS inside the workpiece W (edge ​​portion Wa).

[0050] As described above, in this embodiment, the laser beam LB is irradiated into the workpiece W via the liquid medium FD, making it possible to suppress reflection and refraction of the laser beam LB in unintended directions. As a result, in this embodiment, as shown in Figure 2, it is possible to focus the laser beam LB to the target position (design position), so that a light-shielding region LS can be accurately formed inside the edge portion Wa.

[0051] In the laser processing method according to this embodiment, as shown in Figure 3, the process is configured to end after the laser irradiation step S200 is performed.

[0052] <Exam> Incidentally, the inventors concluded that, as a result of performing the workpiece placement step S100 and laser irradiation step S200 described above, the processing accuracy was significantly improved, but that unless the focusing intensity of the laser beam LB is carefully set, the processing quality of the light-shielding region LS cannot be ensured. Therefore, the inventors conducted several tests on the intensity of the laser beam LB and other related factors in order to ensure the processing quality of the light-shielding region LS. The results of the following tests will be explained below.

[0053] In Examples 1 and 2, and Comparative Examples 1 to 6 shown below, tests were conducted to form a light-shielding region LS inside the workpiece W using the laser processing method described above (workpiece placement step S100 and laser irradiation step S200), according to the processing conditions shown in Figure 4. In this test, the following five items were used as processing conditions. • Pulse width of laser beam LB • Laser beam LB spot diameter (laser spot diameter) • Laser beam frequency LB • Wavelength of laser light LB • Peak output of laser beam LB Furthermore, the pulse width, laser spot diameter, wavelength, frequency, and peak output described above correspond to the "pulse width," "laser spot diameter," "wavelength," "frequency," and "peak output" described in the claims, respectively.

[0054] In the tests for Examples 1, 2, and Comparative Examples 1 to 6, the light-shielding region LS formed inside the workpiece W (edge ​​portion Wa) was evaluated visually (visual inspection). Such evaluations are due to excessive carbonization, etc. (1) Whether or not a crack has formed in the light-shielding region LS (see "Crack C" in Figure 10, etc.) (2) Whether or not a carbonized area is formed around the light-shielding region LS (see "Excessive carbonization region LSa" in Figure 12, etc.) These were the criteria used. In Figure 4, under the "Judgment" section, "◎ (double circle)" indicates that the light-shielding area LS is formed in a very good condition, "〇 (circle)" indicates that the light-shielding area LS is formed in a generally good condition, and "× (cross)" indicates that a light-shielding area LS of a certain quality has not been formed.

[0055] (Example 1) In Example 1, a light-shielding region LS was formed on the workpiece W under the following processing conditions. Pulse width: 185 fs (1.85 e-13 s) • Laser spot diameter: 1 μm ·Wavelength: 515nm • Frequency: 200 kHz • Peak output: 1W

[0056] (Example 2) In Example 2, a light-shielding region LS was formed on the workpiece W under the following processing conditions. Pulse width: 200 fs (2.00 e-13 s) • Laser spot diameter: 1 μm ·Wavelength: 1030nm • Frequency: 200 kHz • Peak output: 1W

[0057] (Comparative Example 1) In Comparative Example 1, a light-shielding region LS was formed on the workpiece W under the following processing conditions. Pulse width: 225 fs (2.25 e-13 s) • Laser spot diameter: 4μm ·Wavelength: 513nm • Frequency: 200 kHz • Peak output: 1W

[0058] (Comparative Example 2) In Comparative Example 2, a light-shielding region LS was formed on the workpiece W under the following processing conditions. Pulse width: 6000 fs (6.00 e-12 s) • Laser spot diameter: 4μm ·Wavelength: 513nm • Frequency: 150kHz • Peak output: 0.5W

[0059] (Comparative Example 3) In Comparative Example 3, a light-shielding region LS was formed on the workpiece W under the following processing conditions. Pulse width: 8000 fs (8.00E-12s) • Laser spot diameter: 1 μm ·Wavelength: 515nm • Frequency: 200 kHz • Peak output: 1.5W

[0060] (Comparative Example 4) In Comparative Example 4, a light-shielding region LS was formed on the workpiece W under the following processing conditions. Pulse width: 10000 fs (1.00E-11s) • Laser spot diameter: 7.8 μm ·Wavelength: 515nm • Frequency: 10kHz • Peak output: 0.1W

[0061] (Comparative Example 5) In Comparative Example 5, a light-shielding region LS was formed on the workpiece W under the following processing conditions. Pulse width: 15000 fs (1.50 e-11 s) • Laser spot diameter: 11 μm ·Wavelength: 532nm • Frequency: 200 kHz • Peak output: 0.3W

[0062] (Comparative Example 6) In Comparative Example 6, a light-shielding region LS was formed on the workpiece W under the following processing conditions. Pulse width: 200000fs (2.00E-10s) • Laser spot diameter: 2μm ·Wavelength: 1064nm • Frequency: 20 kHz • Peak output: 1W

[0063] (Test evaluation) The tests conducted for Examples 1, 2, and Comparative Examples 1 to 6 revealed that the light-shielding region LS was formed in a good condition in Examples 1 and 2, while it was formed in an insufficient condition in the other tests (Comparative Examples 1 to 6) (see the "Judgment" section in Figure 4). In particular, the test related to Example 2 confirmed that a very good light-shielding region LS could be formed.

[0064] Figure 8 is an image of the workpiece W used in the test according to Example 2, where (a) shows the state before the test and (b) shows the state after the test. Figure 9 is an image of another workpiece W used in the test according to Example 2, where (a) shows the state after the test and (b) is an enlarged view showing the X portion of (a). As shown in Figures 8 and 9, in the test according to Example 2, a clear black light-shielding region LS was formed inside the workpiece W (edge ​​portion Wa).

[0065] One point to note in this test is that when the pulse width is set to 200 fs (2.00 E-13 s) (see "Example 2" in Figure 4), a very good light-shielding region LS can be formed. However, when it is increased by only 25 fs (0.25 E-13 s) to 225 fs (2.25 E-13 s) (see "Comparative Example 1" in Figure 4), a light-shielding region LS with processing defects is formed.

[0066] Figures 10 to 13 are image diagrams of the workpiece W used in the test related to Comparative Example 1, with each figure showing the workpiece W obtained in a different test. Figure 10(a) shows the state after the test, Figure 10(b) is a magnified section of Figure 10(a), and Figure 10(c) is a magnified section of (b). Figure 11(a) shows the state after the test, and Figure 11(b) is a magnified section showing the Y portion of Figure 11(a). Figure 12(a) shows the state after the test, and Figure 12(b) is a magnified section of Figure 12(a). Figure 13(a) shows the state after the test, and Figure 13(b) is a magnified section showing the Z portion of Figure 13(a). As shown in Figures 10 to 13, in Example 2, each time the test is performed, • Crack C (see Figures 10-13) is formed within the light-shielding region LS. • A carbonized excess region LSa (see Figures 11-13) is formed around the light-shielding region LS. I understood that.

[0067] Comparing the processing conditions for Example 2 and Comparative Example 1, it can be seen that the "spot diameter" is "1 μm" in the former, while it is "4 μm" in the latter (see Figure 4). As a result of our investigation into this point, we found that even when the "pulse width" is "200 fs (2.00 E-13 s)" (see "Example 2" in Figure 4), if the "spot diameter" exceeds "3 μm", a light-shielding region LS (light-blocking area) of processing defects is likely to be formed, similar to the processing conditions in Comparative Example 1.

[0068] Furthermore, it was found that when the "pulse width" is "200 fs (2.00E-13s)" (see "Example 2" in Figure 4), even if the "laser spot diameter" is "less than 1 μm," a very good light-shielding region LS tends to be formed, similar to the processing conditions in Example 2.

[0069] Furthermore, the results of the tests conducted for Example 1, Example 2, and Comparative Example 3 confirmed that even if the "laser spot diameter" is "1 μm", if the "pulse width" exceeds "200 fs (2.00 E-13 s)", a light-shielding region LS (a processing defect) is formed (see "Judgment" in Figure 4).

[0070] Based on these evaluation results, when forming a workpiece region LS on the workpiece W, • Set the "pulse width" to "200 fs (2.00E-13s) or less". • The laser spot diameter should be 3 μm or less, more preferably 1 μm or less. It was found that this was necessary. When these favorable processing conditions are represented in the graph showing the relationship between pulse width and laser spot diameter in Figure 5, they correspond to the region R1 enclosed by the shaded area in the figure.

[0071] Furthermore, as a result of the tests conducted in Example 1, Example 2 and Comparative Example 3, it was concluded that when the pulse width is 200 fs or less and the laser spot diameter is 3 μm or less, it is preferable to set the frequency, peak output, and wavelength to the same values ​​as those in Example 1 and Example 2, from the viewpoint of stably forming a light-shielding region LS on the workpiece W. • Frequency: 100kHz to 300kHz (See "Region R2" in the "Graph showing the relationship between pulse width and laser spot diameter" in Figure 6) • Peak output: 1W or less • Wavelength: 1100 nm or less (See "Region R3" in the "Graph showing the relationship between pulse width and wavelength" in Figure 7)

[0072] As described above, in this embodiment, since the laser beam LB is irradiated into the inside of the workpiece W via the liquid medium FD, it is possible to accurately form a light-shielding region LS inside the edge portion Wa. Furthermore, in this embodiment, by setting the laser beam LB emitted from the laser irradiation device 30 to have a pulse width of 200 fs (2.00 E-13 s) or less and a laser spot diameter of 3 μm or less (more preferably 1 μm or less), it is possible to form a light-shielding region LS in good condition. Therefore, according to this embodiment, it is possible to reliably improve processing quality while maintaining processing accuracy during laser processing.

[0073] In this embodiment, the light-transmitting member 20 is provided separately from the container 10, but it is also possible to provide it integrally with the container 110, as shown in the laser processing system 101 in Figure 14. In the laser processing system 101 shown in Figure 14, the bottom 110B of the container 110 is formed of a light-transmitting member 120 through which the laser beam LB can pass. In the example shown in Figure 14, the "contact surface" and "non-contact surface" described in the claims correspond to the inner surface (contact surface 120a) and outer surface (non-contact surface 120b) of the container 110 of the light-transmitting member 120, respectively.

[0074] By configuring it in this way, the number of parts can be reduced, making it possible to provide a laser processing system 101 with a simple configuration. Furthermore, in the example shown in Figure 14, after immersing the workpiece W in the liquid medium FD, the laser beam LB can be directed at the bottom 110B of the container 110 without having to separately prepare a light-transmitting member 20, as in the laser processing system 1 (see Figure 1), thus ensuring a simplification of the work.

[0075] In the example shown in Figure 14, the bottom 110B of the container 110 is formed using the light-transmitting member 120, but the side wall 110A can also be formed using the light-transmitting member 120.

[0076] Furthermore, although an optical element was exemplified as the workpiece W to be laser-processed in the above embodiment, the present invention can also be applied to other materials (for example, optical glass) as long as the laser beam LB can pass through them.

[0077] Furthermore, in the laser processing methods shown in Figures 8 to 13, the workpiece W is processed by continuously irradiating it with laser light LB (forming an annular light-shielding region LS enclosed by a solid line). However, it is also possible to process it by intermittently irradiating it (for example, forming an annular light-shielding region LS enclosed by a dashed line).

[0078] Although embodiments applying the invention made by the present inventors have been described above, the present invention is not limited by the descriptions and drawings that constitute part of the disclosure of the present invention in these embodiments. In other words, it should be added that all other embodiments, examples, and operational techniques made by those skilled in the art based on these embodiments are all included in the scope of the present invention. [Explanation of symbols]

[0079] 1,101 Laser Processing System 10,110 containers 10A, 110A side wall part 10B,110B bottom 11 Support member 11A Lower support part 11B Upper support part 20,120 Light-transmitting member 20A Main Unit 20Aa contact surface 20Ab Non-contact surface 120a contact surface 120b Non-contact surface 30 Laser irradiation device W Workpiece Wa Koba Club LB laser light LBp focal point FD liquid media Ip1~Ip3 Incidence point LS Shade area (inner area) LSa excess carbonized portion C Crack R1~R3 ​​area

Claims

1. A laser processing method for processing the inside of an optical element as a workpiece using laser light, A container for storing a liquid medium and for housing the workpiece in the liquid medium, A light-transmitting member having a contact surface that contacts the liquid medium and a non-contact surface on the opposite side of the contact surface that does not contact the liquid medium, and capable of transmitting the laser light, A laser irradiation device that irradiates the inside of the workpiece by passing the laser light through the light-transmitting member and the liquid medium in that order, Equipped with, The liquid medium and the light-transmitting member have a refractive index equivalent to that of the workpiece. The aforementioned laser processing method is A workpiece placement step, in which the workpiece is placed in the liquid medium in the container, After the workpiece placement step, a laser irradiation step is performed in which the laser light is passed through the light-transmitting member and the liquid medium in that order to irradiate the inside of the workpiece. Includes, A laser processing method comprising the step of irradiating the optical element with laser light having a pulse width of 200 fs or less and a laser spot diameter of 3 μm or less to form a light-shielding region inside the optical element.

2. The laser processing method according to claim 1, wherein the laser spot diameter is 1 μm or less.

3. The laser processing method according to claim 1, wherein the laser irradiation device irradiates laser light having a frequency of 100 kHz or more and 300 kHz or less, and a peak output of 1 W or less.

4. The laser processing method according to claim 1, wherein the laser irradiation device irradiates the laser light having a wavelength of 1100 nm or less.

5. The laser processing method according to any one of claims 1 to 4, wherein the light-transmitting member is a member that constitutes the bottom or side wall of the container.

6. The laser processing method according to any one of claims 1 to 4, wherein the workpiece is made of a light-transmitting resin member.

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