Laser irradiation device, workpiece, and method for irradiating with laser

Abstract

To improve visibility of an image pattern while suppressing an increase in scan time.SOLUTION: A laser irradiation device 100 for irradiating with a laser beam includes: first deflection means 20 for performing deflective scanning with a laser beam; and second deflection means 30 for causing a laser beam that is caused to deflect by the first deflection means 20 to deflect. The first deflection means 20 includes a non-inertia deflector and emits a laser beam beside a first line along at least one or more lines parallel to the first line while emitting a laser beam along the first line.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laser irradiation device, a workpiece, and a laser irradiation method.

Background Art

[0002] Laser irradiation devices are known that irradiate workpieces such as PET (Poly Ethylene Terephthalate) bottles with laser light to form image patterns such as characters.

[0003] The laser scanning methods used in such laser irradiation devices include a raster scanning method in which laser light is repeatedly scanned in parallel lines regardless of the shape of the image pattern, and a vector scanning method in which laser light is scanned following the shape of the image pattern.

[0004] For example, in Patent Document 1 (Japanese Patent No. 3425553), a laser irradiation device that irradiates laser light following the shape of an image pattern by two-dimensionally scanning laser light with a galvanometer scanner is disclosed as a vector scanning type laser irradiation device.

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, the irradiation accuracy of the laser light was not considered.

[0006] Therefore, an object of the present invention is to improve the irradiation accuracy of laser light and improve the visibility of the image pattern.

Means for Solving the Problems

[0007] To solve the above problems, the present invention provides a laser irradiation device that irradiates laser light, comprising: a first deflection means for deflecting and scanning the laser light; and a second deflection means for deflecting the laser light deflected by the first deflection means, wherein the first deflection means includes a non-inertial deflection device, and while irradiating the laser light along a first line, the laser light is irradiated laterally of the first line along at least one or more lines parallel to the first line.

Effect of the Invention

[0008] According to the present invention, the irradiation accuracy of the laser light can be improved, and the visibility of the image pattern can be enhanced.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32

Figure 33

Figure 34

Figure 35

Figure 36

Figure 37

Figure 38

Figure 39

Figure 40

Figure 41

Figure 42

Figure 43

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the laser irradiation apparatus of the present invention will be described with reference to the drawings. In each of the drawings for explaining the present invention, for components such as members and constituent parts having the same function or shape, the same reference numerals are given as much as possible to omit the explanation after explaining once.

[0011] <Configuration of Laser Irradiation Apparatus> Fig. 1 shows a plan view of a laser irradiation apparatus 100 according to a first embodiment of the present invention.

[0012] The laser irradiation apparatus 100 includes a laser oscillator 10 as a light source, an acousto-optic deflector 20 as a first deflection means or a first scanning means, a galvanometer scanner 30 as a second deflection means or a second scanning means, and an fθ lens 40. Hereinafter, the acousto-optic deflector will be referred to as "AOD" (Acousto-Optic Deflector).

[0013] As the light source, various laser light sources such as solid-state lasers and gas lasers can be used. For example, as the light source, those capable of pulsed oscillation from femtoseconds, picoseconds to nanoseconds are preferred. Examples of solid-state lasers include YAG lasers and titanium sapphire lasers. Examples of gas lasers include argon lasers, helium-neon lasers, and carbon dioxide lasers. Further, as a small light source, a semiconductor laser is preferred. Further, as an example of a light source that is small and can obtain high peak energy, a fiber laser, which is a type of solid-state laser using an optical fiber as an amplification medium, can be mentioned.

[0014] AOD20 includes a piezoelectric transducer coupled to a crystal and a radio frequency (RF) drive unit that drives the piezoelectric transducer. By driving the piezoelectric transducer with the RF drive unit, AOD20 generates sound waves of the RF frequency in the crystal, for example, sound waves within a frequency range between about 50 MHz and about 1500 MHz. When the incident laser light is diffracted in proportion to the RF frequency by the sound waves generated in the crystal, a part of the power of the laser light is deflected as the first-order light (diffracted light). By controlling the RF frequency, the deflection angle of AOD20 can be controlled.

[0015] When the laser light is deflected by AOD20, the first-order light (diffracted light) enters the galvanometer scanner 30. The laser light incident on the galvanometer scanner 30 is scanned by the galvanometer scanner 30.

[0016] The laser light scanned by the galvanometer scanner 30 enters the fθ lens 40, which is a condenser lens. The laser light emitted from the fθ lens 40 irradiates the workpiece 50, which is the object, and forms an image pattern on the surface of the workpiece 50. The workpiece 50 is, for example, a resin container such as a PET bottle. Further, the image pattern formed on the workpiece 50 includes codes such as characters and barcodes, graphics, images, etc., and indicates information such as the name of the contents contained in the container, the identification number, the manufacturer, and the manufacturing date and time. Further, the position where the image pattern is formed on the workpiece 50 may be the outer surface of the container or the inner surface of the container.

[0017] The fθ lens 40 condenses the laser light scanned by the galvanometer scanner 30 onto the workpiece 50. For example, the fθ lens 40 is configured to scan the laser light scanned by the galvanometer scanner 30 at a predetermined pitch on the imaging surface of the workpiece 50 at predetermined angles.

[0018] <Image pattern formation flow> FIG. 2 shows a flow of forming an image pattern on the workpiece 50 using the laser irradiation apparatus 100 according to the first embodiment of the present invention.

[0019] In FIG. 2, the laser light emitted from the light source at S1 enters the AOD 20 at S2, and a part of it is diffracted at an angle corresponding to the wavelength of the incident light beam, the sound velocity of the AOD 20 crystal, and the RF signal frequency applied from the RF driver connected to the AOD 20 to become the first-order light (diffracted light). Among the incident light to the AOD 20, the component that is not diffracted travels straight as the zero-order light (transmitted light) shown in FIG. 1 and is blocked (terminated) by the beam damper 21. Also, if the power of the zero-order light is so low that an image pattern is not formed on the workpiece 50 even when the zero-order light enters the workpiece 50, it is not necessary to block the zero-order light.

[0020] Subsequently, the first-order light enters the galvanometer scanner 30 and is deflected by the galvanometer scanner 30 (S3). The laser light deflected by the galvanometer scanner 30 enters the fθ lens 40, and the laser light is condensed at a position on the workpiece 50 corresponding to the incident angle to the fθ lens 40 (S4). As a result, the portion of the workpiece 50 irradiated with the laser light is denatured, and a visible image pattern is formed (S5).

[0021] In this way, the position where the laser light is irradiated onto the workpiece 50 is controlled by the two deflection means of the AOD 20 and the galvanometer scanner 30. Also, if necessary, an element for converting the beam diameter, an element for shaping the beam profile, or a wave plate may be provided before or after the AOD 20 of the laser irradiation apparatus 100 in FIG. 1.

[0022] <Change in the properties of the workpiece> FIG. 3 is a diagram showing the state of the laser irradiation modified portion 2 (hereinafter simply referred to as "modified portion") formed on the workpiece 50.

[0023] When the surface of the workpiece 50 is irradiated with laser light from the laser irradiation device 100, the surface of the workpiece 50 is modified to form the modified portion 2. FIG. 3(a) is a diagram showing a state in which the surface of the workpiece 50 is evaporated by the irradiation of the laser light, and a concave modified portion 2 is formed. On the other hand, FIG. 3(b) shows the modified portion 2 when the surface of the workpiece 50 is melted. In the case of FIG. 3(b), compared with FIG. 3(a), the peripheral portion of the concave modified portion 2 has a raised shape. Further, FIG. 3(c) shows the state of the modified portion 2 in which the surface of the workpiece 50 is crystallized, and FIG. 3(d) is a diagram showing the state of the modified portion 2 formed by foaming a part of the workpiece 50. In such various modified portions 2, the surface roughness becomes larger than the portion where the laser light is not irradiated, so that the light diffusibility is increased and the visibility is improved. Thereby, a visible image pattern is formed on the workpiece 50.

[0024] To form the modified portion 2 by evaporation, it is preferable to use a pulsed oscillation laser having a wavelength of 355 nm or more and 1064 nm or less and a pulse width of 10 fs or more and 500 nm or less as the light source. Further, when a CW (Continuous Wave) laser having a wavelength of 355 nm or more and 1064 nm or less is used as the light source, the modified portion 2 by melting can be formed. Furthermore, if the laser light is continuously irradiated even after melting, the surface or the subsurface of the workpiece 50 can be foamed to form a modified portion 2 that becomes cloudy. To form the crystallized modified portion 2, for example, it is preferable to irradiate the workpiece 50 made of PET with a CW laser having a wavelength of 355 nm or more and 1064 nm or less to rapidly increase the temperature of the laser irradiation portion on the workpiece 50. Thereafter, by gradually lowering the temperature of the laser irradiation portion while weakening the power of the irradiated laser light, a crystallized and cloudy modified portion 2 can be obtained. Note that if the irradiation of the laser light is suddenly stopped after raising the temperature of the laser irradiation portion, the temperature of the laser irradiation portion rapidly drops to a transparent amorphous state, so that the cloudy modified portion 2 cannot be obtained.

[0025] In addition to forming the white-turbid modified portion 2, a part of the workpiece 50 may be yellowed, or the properties may be changed by an oxidation reaction or surface modification or the like to form the modified portion 2. Further, an absorber (conversion material) that converts light energy into heat energy may be applied in advance to the surface of the workpiece 50, and an uneven modified portion 2 may be formed on the surface of the workpiece 50 by the heat energy converted when the laser light is irradiated.

[0026] Also, by adjusting the light energy of the laser light irradiated to the workpiece 50, the size of the beam of the laser light, the irradiation time, etc., the size, shape, depth, etc. of the modified portion 2 can be changed. Further, the cross-sectional intensity distribution of the laser light is generally a Gaussian distribution, but the intensity distribution can be adjusted by combining the laser lights of the array light source, or a top-hat-shaped intensity distribution with a flat central intensity distribution can be generated by the design of the irradiation optical system. Also, it is preferable to adjust the irradiation size of the laser light by the light source and the optical system and make the irradiation size of the laser light substantially constant in processing. Here, "constant" means that there is substantially no fluctuation within the allowable range of the processing accuracy, and those that fluctuate within the allowable range of about several percent depending on the processing accuracy are also included.

[0027] <Problems with the visibility of the image pattern> Here, the problems regarding the visibility of the image pattern will be described. It is assumed that the light source is a pulsed laser, and a modified portion 2 corresponding to one pixel of the image pattern 1 is formed by one pulse irradiation.

[0028] FIG. 4 is a diagram showing an example of the image pattern 1 formed on the workpiece 50.

[0029] When the laser irradiation device uses a vector scanning method, the laser beam is scanned in arbitrary directions in the X and Y directions in FIG. 4 based on the coordinate data of the desired image pattern 1. At this time, by pulse-irradiating the laser beam along the line based on the coordinate data of the image pattern 1 (by turning the laser irradiation on and off), a plurality of minute dot-shaped modified portions 2 are continuously formed so as to be close to or in contact with each other. Thereby, the image pattern 1 is formed by image lines in which the plurality of modified portions 2 are arranged linearly. For example, when forming the character "B", start irradiating the laser beam from an arbitrary point on the character "B", and form the modified portion 2 while scanning the laser beam following the shape of "B". In this case, the character "B" can be formed by one continuous scan. On the other hand, when forming the character "E", since the character cannot be formed by one continuous scan, for example, the character "E" is decomposed into predetermined line elements of one vertical line and three horizontal lines, and the laser beam is scanned following each line element to form the modified portion 2.

[0030] By the way, as shown in FIG. 4, when the image pattern 1 is formed by one image line, depending on the size of the modified portion 2, there is a problem that the width of the image pattern 1 becomes small and the visibility decreases. For example, when the width of the image pattern 1 becomes 200 μm or less, the visibility particularly decreases, and it becomes difficult to recognize the image pattern 1 with normal eyesight.

[0031] On the other hand, as shown in FIG. 5, by forming the image pattern 1 by two image lines, it is possible to increase the width of the image pattern 1 and improve the visibility. However, the vector scanning method tends to have a longer scanning time compared to the raster scanning method, and when additional image lines are formed to increase the width of the image pattern 1, there arises a problem that the scanning time of the laser beam further increases by the number of additional image lines.

[0032] In the case of the vector scanning method, usually, after forming one image line, in order to additionally form the next image line, the formation timing of the image lines is different between the previously formed image line and the subsequently formed image line. For this reason, when forming the image pattern 1 on the conveyed object (workpiece 50), variations occur in the intervals between adjacent image lines, and stable visibility cannot be obtained.

[0033] Therefore, an object of the present invention is to be able to shorten the laser scanning time and improve the visibility of the image pattern. Therefore, in the present invention, the following laser irradiation device and laser irradiation method are proposed. Hereinafter, the characteristic parts of the present invention will be described by taking the laser irradiation device 100 according to the first embodiment of the present invention as an example.

[0034] <Characteristic parts of the present invention> As shown in FIG. 1, the laser irradiation device 100 according to the first embodiment of the present invention includes an AOD 20, which is a deflection means different from the galvanometer scanner 30, in order to achieve both shortening of the laser scanning time and improvement of the visibility of the image pattern. The deflection control by the AOD 20 is non-inertial deflection control without inertia such as that of a galvanometer scanner 30 or a polygon scanner. For this reason, the AOD 20 can deflect the laser beam at high speed (for example, within a time of 5 μs or less).

[0035] Further, the deflection control by the AOD 20 can give different deflection angles for each pulse even for a pulsed laser with a high repetition frequency (for example, 200 kHz).

[0036] As shown in FIG. 6, in the AOD 20, a sound wave is induced in the crystal by a transducer (vibrator) as an actuator installed at one end of the AOD crystal, and the laser beam is diffracted by the refractive index distribution generated in the AOD crystal by the sound wave. Here, let the diameter of the sound wave beam in the sound wave propagation direction be dx, and the diameter of the sound wave beam in the direction perpendicular thereto be dy.

[0037] If the acoustic wave signal does not propagate through the entire laser beam, the laser beam will not diffract sufficiently. Therefore, assuming the speed of sound in the crystal is V, the response speed of AOD20 is approximately on the order of dx / V. The smaller the beam diameter, the more possible high-speed control (high-speed deflection) becomes.

[0038] However, when using a high-power laser, if the beam diameter is reduced, the light intensity will become too high, causing problems with the light resistance of each optical device. Therefore, by setting dy > dx, it is possible to reduce the light intensity while maintaining the high-speed deflection responsiveness, and it is possible to achieve both high-speed deflection response and the light resistance of the optical device.

[0039] Also, for the deflection angle control of AOD20, there are restrictions on the response characteristics as an AOD element (such as the relationship between the speed of sound and the beam diameter) and the response time due to the electrical characteristics of the control unit. Assuming the pulse lighting interval of the laser beam (the reciprocal of the repetition frequency) is T [s] and the time required for the deflection angle control of AOD20 is τ [s], if T ≥ τ, the deflection angle can be controlled independently for each pulse of the laser beam, so the degree of freedom is high and the effect of speeding up the laser irradiation is large.

[0040] When T < τ, the time required for the deflection angle control is longer than the pulse lighting interval. Therefore, it is necessary to discard the pulse during the deflection angle control (not light the pulse at the timing when it can be pulse-lit). In this case, it may be possible to obtain the effect of speeding up the laser irradiation by performing control with as few deflection angle changes as possible.

[0041] In the first embodiment of the present invention, AOD20 is used as the non-inertial deflection device that performs non-inertial deflection control, but the non-inertial deflection device is not limited to AOD20. The non-inertial deflection device may be any deflection means having a desired response speed, for example, an electro-optic deflector (EOD) or the like.

[0042] As shown in FIG. 7, according to the AOD 20, the laser beam can be deflected by a preset angle θ with respect to the direction orthogonal to the first line L1 (in the +y direction) scanned by the galvanometer scanner 30. Here, the direction of rotation from +x to +y in FIG. 7 (counterclockwise) is defined as the positive angle θ.

[0043] The "first line" along which the laser beam is scanned by the galvanometer scanner 30 means the scanning locus of the laser beam generated by the scanning of the galvanometer scanner 30 when the deflection angle of the AOD 20 is maintained at a certain reference value (predetermined reference value). Therefore, the first line L1 is determined based on the coordinate data of the image pattern 1. For example, when the image pattern 1 is the character "B", the first line L1 is determined based on the coordinate data defining the character shape of "B". Also, when the image pattern 1 is the character "E", the first line L1 is determined based on the respective coordinate data defining the shapes of each line element of, for example, one vertical line and three horizontal lines obtained by decomposing the character "E".

[0044] In this way, by deflecting the laser beam by the angle θ with respect to the direction orthogonal to the first line L1, the AOD 20 can irradiate the laser beam not only along the first line L1 but also beside the first line L1 while irradiating the laser beam along the first line L1. Thereby, for example, an image pattern 1 in which a plurality of modified portions 2 are arranged on two mutually parallel lines L and L2 as shown in FIG. 8 can be formed.

[0045] Subsequently, with reference to FIG. 9, the laser irradiation method according to the first embodiment of the present invention will be described in detail. In the following description, unless otherwise specified, the light source is a pulsed laser, and it is assumed that a modified portion 2 corresponding to one pixel of the image pattern 1 is formed by one pulse irradiation. Also, it is assumed that the laser irradiation pitch (pitch [m] = galvanometer main scanning speed [m / s] / repetition frequency [1 / s]) calculated from the galvanometer main scanning speed and the laser repetition frequency matches the pixel size.

[0046] In FIG. 9, the image pattern 1 in FIG. 8 is partitioned into pixels in a matrix form, and the position of each pixel is indicated by coordinates (x, y) consisting of an x-coordinate and a y-coordinate. Also, in FIG. 9, the solid line arrow indicates the deflection direction of the laser beam by the galvanometer scanner 30, and the dashed line arrow indicates the deflection direction of the laser beam by the AOD 20. In this case, the deflection angle θ of the laser beam by the AOD 20 is set to 0° (+y direction). Also, laser irradiation is started from the position of the coordinates (0, 0) in FIG. 9, and the amounts of deviation in the x-coordinate and y-coordinate of the laser beam due to the deflection angle control of the galvanometer scanner 30 and the AOD 20 from the laser irradiation start position are taken as relative values Δx and Δy (unit: pixel) respectively from the coordinates (0, 0). For example, when x = 2 and Δx = 1, the x-coordinate of the irradiation position of the laser beam becomes 3. Let the maximum value and minimum value of Δx be Δx_max and Δx_min respectively, and the maximum value and minimum value of Δy be Δy_max and Δy_min respectively.

[0047] Also, the scanning angle of the AOD 20 and the fθ lens 40 determine the scanable range of the AOD 20 on the workpiece 50. From the relationship between the scanable range of the AOD 20 and the pixel size, the range within which Δx and Δy can take values is determined. For example, when the focal length of the fθ lens is 200 mm, the scanning angle of the AOD 20 (range of modifiable deflection angle) is 2 mrad, and the pixel size is 200 μm × 200 μm, the scanable range is 200 mm × 2 mrad = 400 μm.

[0048] Here, since θ = 0, Δx_max - Δx_min and Δy_max - Δy_min are Δx_max - Δx_min = 400 μm × cos(θ) / 200 μm = 2 and Δy_max - Δy_min = 400 μm × sin(θ) / 200 μm = 0 respectively. Also, Δy / Δx = tan(θ).

[0049] The first line L1 scanned by the galvanometer scanner 30 with the laser beam is the one when Δx is minimized (i.e., Δx_min = 0), and the pixel size is 200 μm × 200 μm. In this case, Δx can take values in the range 0 ≦ Δx ≦ 2.

[0050] In the first embodiment of the present invention, when laser irradiation is started, first, laser light is irradiated at the coordinate (0, 0) which is the laser irradiation start position on the first line L1. As a result, a modified portion 2 for one pixel is formed at the position of the coordinate (0, 0) on the workpiece 50. At this time, since the laser light is deflected by the AOD 20, the laser light is also irradiated at the coordinate (0, 1). That is, by setting the deviation amount of the laser light to Δy = 1 by the deflection control of the AOD 20, the laser light is also irradiated at the coordinate (0, 1). As a result, a modified portion 2 for one pixel is also formed on the second line L2 adjacent to the first line L1. Subsequently, the laser light is scanned in the +x direction by the galvano scanner 30, and the laser light is irradiated at the position of the coordinate (1, 0). Also at this time, since the laser light is deflected by the AOD 20, the laser light is also irradiated at the coordinate (1, 1). As a result, modified portions 2 are formed at the positions of the coordinate (1, 0) and the coordinate (1, 1). Thereafter, in the same manner, every time the laser light is scanned in the +x direction, the laser light is irradiated on the first line L1 and the second line L2 to form modified portions 2. As a result, two rows of image lines in which a plurality of modified portions 2 are arranged are formed on the first line L1 and the second line L2. Note that the modified portions 2 on each of the lines L1 and L2 are not limited to being formed with a gap in the x-axis direction and the y-axis direction, and may be in contact with each other or partially overlap in the x-axis direction or the y-axis direction.

[0051] As described above, in the first embodiment of the present invention, since the AOD 20 can deflect the laser light in a direction (y-axis direction) intersecting the deflection direction (x-axis direction) of the galvano scanner 30, the laser light can be irradiated on the first line L1 and the second line L2 almost simultaneously. As a result, compared with the conventional vector scanning method, the scanning time of the laser light can be significantly shortened, and parallel image lines can be formed.

[0052] Also, according to the first embodiment of the present invention, since the laser light can be irradiated onto each of the first line L1 and the second line L2 almost simultaneously, even when forming the image pattern 1 on the workpiece 50 to be conveyed, the variation in the interval between adjacent image lines can be suppressed. As a result, an image pattern 1 with a uniform width can be formed.

[0053] Therefore, according to the first embodiment of the present invention, even in the vector scanning method in which the laser scanning time tends to be longer than that of the raster scanning method, a plurality of parallel image lines can be formed in a relatively short time, and the width of the image pattern 1 can be increased to improve the visibility.

[0054] FIG. 10 shows another example of the image pattern 1 formed by the laser irradiation method according to the first embodiment of the present invention.

[0055] In the example shown in FIG. 10, three image lines in which a plurality of modified portions 2 are arranged on three mutually parallel lines L1, L2, and L3 are formed. Thus, according to the first embodiment of the present invention, three mutually parallel image lines can also be formed.

[0056] In this case, first, the laser light is irradiated onto the coordinates (0, 0) shown in FIG. 11. At this time, by controlling the deflection angle of the AOD 20, Δy = 1, and the laser light is also irradiated onto the coordinates (0, 1) on the second line L2. Subsequently, by controlling the deflection angle of the AOD 20, Δy = 2, and the laser light is also irradiated onto the coordinates (0, 2) on the third line L3. As a result, the modified portions 2 are formed at the coordinates (0, 0), the coordinates (0, 1), and the coordinates (0, 2), respectively.

[0057] Next, when the laser beam is scanned in the +x direction by the galvanometer scanner 30 and the laser beam is irradiated at the position of coordinates (1, 0), by controlling the deflection angle of the AOD 20 such that Δy = 1, the laser beam is also irradiated at the coordinates (1, 1) on the second line L2. Subsequently, by controlling the deflection angle of the AOD 20 such that Δy = 2, the laser beam is also irradiated at the coordinates (1, 2) on the third line L3. As a result, the modified portions 2 are formed at each of the coordinates (1, 0), (1, 1), and (1, 2). Thereafter, in the same manner, each time the laser beam is scanned in the +x direction, the laser beam is irradiated on the first line L1, the second line L2, and the third line L3, and the modified portions 2 are formed. As a result, three image lines on which a plurality of modified portions 2 are arranged are formed on each of the lines L1, L2, and L3.

[0058] Thus, according to the first embodiment of the present invention, by controlling the deflection angle of the AOD 20, the laser beam can be irradiated on two lines L2 and L3 parallel to the first line L1 almost simultaneously. Therefore, even when forming three image lines parallel to each other, the scanning time of the laser beam can be shortened. Further, since the laser irradiation timings on each of the lines L1, L2, and L3 can be made substantially the same, even when forming the image pattern 1 on the workpiece 50 to be conveyed, variations in the intervals between adjacent image lines can be suppressed, and an image pattern 1 having a uniform width can be obtained.

[0059] In the examples of FIGS. 10 and 11, the lowermost line among the three lines L1, L2, and L3 is set as the first line L1 on which the laser beam is scanned by the galvanometer scanner 30. However, the first line L1 may be the uppermost line or the middle line. The position at which the first line L1 is set can be changed as appropriate. For example, when the first line L1 is set as the middle line, by controlling the deflection angle of the AOD 20 such that Δy = 1 and Δy = -1, the laser beam can be irradiated on the uppermost second line L2 and the lowermost third line L3 almost simultaneously.

[0060] In the examples of FIGS. 10 and 11, the case of forming three image lines parallel to each other has been described. However, according to the first embodiment of the present invention, by controlling the deflection angle of the AOD 20, it is also possible to form four or more image lines parallel to each other. That is, according to the number of lines added beside the first line L1, by controlling the deflection angle of the AOD 20, laser light can be irradiated almost simultaneously on the added lines to form image lines.

[0061] By the way, according to the first embodiment of the present invention, a plurality of image lines parallel to each other can be formed almost simultaneously. However, from the time when the laser light is irradiated on the first line L1 until the laser light is irradiated on the second line L2, a slight time shift occurs due to the deflection control of the AOD 20. Therefore, when performing laser irradiation on the workpiece 50 being conveyed, even if the deflection angle θ of the AOD 20 is set to 0° (+y direction), actually, as shown in FIG. 8, the modified portion 2 on the second line L2 is slightly displaced in the laser scanning direction (+x direction) of the galvanometer scanner 30 with respect to the modified portion 2 of the first line L1. That is, between the adjacent modified portions 2a and 2b of the first line L1 and the second line L2, a positional shift γ in the laser scanning direction of the galvanometer scanner 30 occurs due to the time shift associated with the deflection control of the AOD 20.

[0062] Such a positional shift γ between the modified portions 2a and 2b will be hereinafter referred to as "positional shift γ in the main scanning direction" for convenience. The magnitude of the positional shift γ in the main scanning direction varies depending on the laser scanning speed on the first line L1, the frequency of the laser light, the deflection speed of the AOD 20, and the like. When the positional shift γ in the main scanning direction is minute, it hardly affects the visibility and designability of the image pattern 1. However, when the positional shift γ in the main scanning direction becomes large, there is a possibility of affecting the visibility and designability of the image pattern 1. In such a case, it is preferable to set the deflection angle θ of the AOD 20 to a positive value. Thereby, the deflection direction of the laser light by the AOD 20 can be corrected in the direction opposite to the laser scanning direction of the galvanometer scanner 30.

[0063] In this way, by correcting the deflection direction of the laser beam by AOD20 in the direction opposite to the laser scanning direction of the galvanometer scanner 30, as shown in FIG. 12, the modified portions 2a and 2b adjacent to each other between the first line L1 and the second line L2 can be aligned so as to be arranged in a direction orthogonal to the first line L1. Thereby, the positional deviation γ in the main scanning direction can be eliminated, and the visibility and design quality of the image pattern 1 can be improved. The setting of the deflection angle θ of the AOD20 may be appropriately changed based on the laser scanning speed on the first line L1, the frequency of the laser beam, the deflection speed of the AOD20, and the like. Further, when forming three or more image lines, similarly, by setting the deflection angle θ of the AOD20, it is possible to eliminate the positional deviation γ in the main scanning direction between the modified portions 2.

[0064] Subsequently, another embodiment different from the first embodiment of the present invention will be described. Hereinafter, mainly the portions different from the first embodiment of the present invention will be described, and the description of the same portions will be omitted as appropriate.

[0065] <The Second Embodiment of the Present Invention> Since the galvanometer scanner 30 includes two galvanometer mirrors or the like capable of deflecting the laser beam, the laser beam can be scanned two-dimensionally. Therefore, the galvanometer scanner 30 can scan the laser beam not only in the x-axis direction but also in the y-axis direction or an oblique direction inclined with respect to the x-axis or y-axis.

[0066] On the other hand, the AOD20 can deflect the laser beam only in a preset one direction such as the y-axis direction. Therefore, when there is only one AOD20, depending on the scanning direction by the galvanometer scanner 30, it may not be possible to effectively increase the width of the image pattern 1.

[0067] For example, as shown in FIG. 13, when the laser scanning direction (solid line arrow) of the galvanometer scanner 30 and the deflection direction (dashed line arrow) of the AOD 20 are in the same direction, the width W of the image pattern 1 cannot be increased. That is, in this case, if an attempt is made to increase the width W of the image line formed along the first line L1, it is necessary to set the deflection direction of the AOD 20 in the x-axis direction. However, since the AOD 20 can only deflect in the y-axis direction, the deflection direction overlaps with the image line on the first line L1, and the width W of the image pattern 1 cannot be increased.

[0068] Also, as shown in FIG. 14, when the laser scanning direction (solid line arrow) of the galvanometer scanner 30 is inclined at 45° with respect to the x-axis, the width W of the image pattern 1 cannot be effectively increased. That is, in this case, since the deflection direction (dashed line arrow) of the AOD 20 is not perpendicular to the laser scanning direction (solid line arrow) of the galvanometer scanner 30, the width W of the image pattern 1 becomes smaller compared to the case where the deflection direction (dashed line arrow) of the AOD 20 is perpendicular to the laser scanning direction (solid line arrow) of the galvanometer scanner 30 as shown in FIG. 11.

[0069] As described above, when only one AOD 20 is provided, there are cases where the width W of the image pattern 1 cannot be increased, or the width W of the image pattern 1 cannot be effectively increased. Therefore, in the second embodiment of the present invention, two AODs are provided so that the width W of the image pattern 1 can be effectively increased regardless of the laser scanning direction of the galvanometer scanner 30.

[0070] FIG. 15 shows a plan view of the laser irradiation device 110 according to the second embodiment of the present invention, and FIG. 16 shows a side view of the laser irradiation device 110 according to the second embodiment of the present invention.

[0071] As shown in FIGS. 15 and 16, the laser irradiation device 110 according to the second embodiment of the present invention includes two AODs 20 and 23. A half-wave plate 22 is disposed between the two AODs 20 and 23.

[0072] In this case, when laser light is emitted from the laser oscillator 10, first, the laser light enters the first AOD 20, and the laser light is diffracted as first-order light (diffracted light) by the first AOD 20. Then, the first-order light diffracted by the first AOD 20 enters the half-wave plate 22, and the first-order light is deflected by the half-wave plate 22 so as to align with the polarization axis of the second AOD 23. Subsequently, the first-order light is diffracted by the second AOD 23 in a direction orthogonal to the diffraction direction of the first AOD 20 (the +y direction in FIG. 16). Note that, among the light incident on the second AOD 23, the component that is not diffracted travels straight as zero-order light (transmitted light) and is blocked (terminated) by the beam damper 24. Then, the first-order light (diffracted light) diffracted by the second AOD 23 enters the galvanometer scanner 30 and is focused onto the workpiece 50 by the fθ lens 40.

[0073] Thus, in the configuration according to the second embodiment, by using the two AODs 20 and 23, the laser light can be two-dimensionally deflected and controlled. Therefore, as shown in FIG. 17, even when the laser scanning direction (solid arrow) of the galvanometer scanner 30 is in the x-axis direction, or the y-axis direction, or an oblique direction with respect to these, the laser light can be deflected in a direction orthogonal to the laser scanning direction of the galvanometer scanner 30 (dashed arrow).

[0074] Therefore, even when the laser light is scanned in the y-axis direction by the galvanometer scanner 30, by deflecting and irradiating the laser light in the x-axis direction orthogonal to the y-axis direction, the width W1 of the image pattern 1 can be ensured to be large. Further, even when the laser light is scanned in the x-axis direction by the galvanometer scanner 30, since the laser light can be deflected and irradiated in the y-axis direction orthogonal to the x-axis direction, the width W2 of the image pattern 1 can be ensured to be large. Similarly, even when the laser light is scanned in an oblique direction inclined with respect to the x-axis by the galvanometer scanner 30, since the laser light can be deflected and irradiated in a direction orthogonal to the scanning direction, the width W3 of the image pattern 1 can be ensured to be large.

[0075] In this case, the deflection direction of the first AOD 20 is set to the +x direction, the deflection direction of the second AOD 23 is set to the +y direction, the focal length of the fθ lens 40 is 300 mm, the scanning angle of each AOD 20, 23 is 2 mrad, and the pixel size is 100 μm × 100 μm. Also, since the scanable range is 600 μm and the pixel size is 100 μm, Δx and Δy can each be selected from the widths corresponding to 6 pixels.

[0076] As described above, in the second embodiment of the present invention, by using two AODs 20, 23, the degree of freedom in the deflection direction is improved compared to the case where there is one AOD, so the number of candidates for the deflection destination of the laser beam can be increased, and the optimal deflection direction can be set. As a result, regardless of the laser scanning direction of the galvanometer scanner 30, the width of the image pattern 1 can be effectively increased, and the visibility of the image pattern 1 having various shapes can be improved. In addition, if it is sufficient to thicken the image pattern 1 only in one direction to improve visibility, a configuration using only one AOD can also be expected to have a sufficient effect.

[0077] Also, if there are two AODs, the laser beam can be deflected in an arbitrary direction with respect to the laser scanning direction of the galvanometer scanner 30. Therefore, as shown in FIG. 12, it is also possible to easily perform alignment in which the modified portions 2a and 2b adjacent to each other on the respective lines L1 and L2 are arranged in a direction orthogonal to the first line L1, and the misalignment in the main scanning direction can be eliminated.

[0078] Note that since the diffraction efficiency of the AOD is not 100% (for example, about 80%), when two AODs are used, the power of the laser beam with respect to the workpiece 50 decreases compared to the case where one AOD is used. For example, when one AOD is used, the laser beam can be irradiated with 80% power, whereas when two AODs are used, the laser beam can only be irradiated with 64% power. Basically, there is a trade-off relationship between the power and the irradiation speed of the laser beam. Therefore, when trying to increase the irradiation speed of the laser beam, the power of the laser beam tends to decrease. Accordingly, when it is desired to secure the power of the laser beam while increasing the irradiation speed, it is preferable to adopt a configuration using only one AOD.

[0079] <Configuration of the control unit> FIG. 18 shows an example of a control unit that controls the laser irradiation apparatus according to each embodiment of the present invention.

[0080] As shown in FIG. 18, the control unit 6 includes an image pattern data input unit 61, a parameter specifying unit 62, a storage unit 63, a processing data generation unit 64, a laser irradiation control unit 65, a first laser scanning control unit 66, and a second laser scanning control unit 67.

[0081] The image pattern data input unit 61 inputs the pattern data of the image pattern to be formed on the workpiece 50 from an external device such as a PC (Personal Computer) or a scanner. The pattern data of the image pattern is, for example, electronic data including information indicating a pattern such as a code or characters such as a barcode or a QR code (registered trademark), a figure, or a photograph. Note that the pattern data of the image pattern is not limited to that input from an external device. The data of the image pattern generated by the user using the keyboard or pointing device of the control unit 6 may be input.

[0082] The image pattern data input unit 61 outputs the input pattern data to each of the processing data generation unit 64 and the parameter specifying unit 62.

[0083] The parameter specifying unit 62 specifies processing parameters for forming an image pattern.

[0084] The processing parameters of the image pattern are information specifying the type and thickness of the image lines of the image pattern, the processing depth, or the interval or arrangement between adjacent image lines in the aggregate of image lines. Further, the processing parameters are information specifying the type, size, processing depth, interval or arrangement between adjacent points (modifying portion 2) of the image pattern. Here, the type of image line means a straight line, a curve, or the like. The type of point (modifying portion 2) is information indicating a shape such as a circle, an ellipse, a rectangle, or a rhombus.

[0085] For at least any one type of image pattern such as characters, codes, figures, or photographs, the processing parameters suitable for improving visibility are determined in advance by experiments or simulations. The storage unit 63 stores a table showing the correspondence between such types of image patterns and processing parameters.

[0086] The parameter specifying unit 62 can acquire and specify the processing parameters of the image pattern by referring to the storage unit 63 based on the information indicating the type of the image pattern input from the image pattern data input unit 61.

[0087] The processing data generation unit 64 generates processing data for forming an image pattern based on the pattern data of the image pattern and the processing parameters.

[0088] The processing data includes conveyance condition data when the workpiece 50 is conveyed by the conveyance means, deflection scanning condition data for the galvanometer scanner 30 and the AOD 20(23) to deflect and scan the laser beam, and irradiation condition data for irradiating the laser beam in synchronization with the conveyance of the workpiece 50. The deflection scanning conditions include coordinate data of a plurality of line elements obtained by decomposing the image pattern.

[0089] The machining data generation unit 64 outputs the generated machining data to each of the laser irradiation control unit 65, the first laser scanning control unit 66, and the second laser scanning control unit 67.

[0090] The laser irradiation control unit 65 includes an optical intensity control unit 651 and a pulse control unit 652, and controls the irradiation of laser light from the laser oscillator 10 to the workpiece 50 based on the irradiation condition data. The optical intensity control unit 651 controls the optical intensity of the laser light, and the pulse control unit 652 controls the pulse width and irradiation timing of the laser light.

[0091] The first laser scanning control unit 66 controls the scanning of the laser light by the galvanometer scanner 30 based on the deflection scanning condition data. Specifically, it performs control such as turning on or off the driving of the galvanometer mirror.

[0092] The second laser scanning control unit 67 controls the deflection angle of the AOD 20(23) based on the deflection scanning condition data, and controls the scanning of the laser light by the AOD 20(23).

[0093] <Regarding image quality> Subsequently, regarding the image quality of the image pattern 1 formed by adopting the present invention, attention will be paid to the positional deviation γ in the main scanning direction between the modified portions 2a and 2b and the distance β between the modified portions of the modified portions 2a and 2b shown in FIGS. 19 and 20 for explanation. FIG. 19 shows the positional deviation γ in the main scanning direction and the distance β between the modified portions when the image pattern 1 is formed by a linear image line, and FIG. 20 shows the positional deviation γ in the main scanning direction and the distance β between the modified portions when the image pattern 1 is formed by a curved image line.

[0094] Here, the misalignment γ in the main scanning direction is defined as the distance in the direction of the first line L1 between the straight lines drawn in the direction orthogonal to the first line L1 from the centers of the modified portions 2a and 2b arranged adjacent to each other between the adjacent first line L1 and second line L2. Also, the distance β between the modified portions is defined as the center-to-center distance (the distance connecting the centers with a straight line) between the modified portions 2a and 2b arranged adjacent to each other between the first line L1 and the second line L2. Note that the modified portions 2a and 2b arranged adjacent to each other between the first line L1 and the second line L2 mean the modified portion 2a formed at an arbitrary position on the first line L1 and the modified portion 2b formed on the second line L2 when the laser beam is deflected when the modified portion 2a is formed. Hereinafter, a set of these modified portions 2a and 2b may be referred to as an "adjacent modified portion set" for convenience.

[0095] The misalignment γ in the main scanning direction and the distance β between the modified portions can be measured from the captured image by imaging the image pattern 1 in a state where the image pattern 1 is formed on the workpiece 50 using a digital microscope or the like. Also, when the image pattern 1 is formed by an arc-shaped image line, the image information of the image pattern 1 can be imported using CAD software, an arc connecting the centers of the modified portions 2 can be drawn, and the radius can be obtained from the properties of the arc.

[0096] Also, here, the evaluation of the image quality of the present invention was performed by comparison with the image pattern 1 formed using a laser irradiation apparatus of a comparative example that does not employ the present invention. Specifically, the laser irradiation apparatus of the present invention was a laser irradiation apparatus including two AODs 20 and 23 as shown in FIGS. 15 and 16, and the laser irradiation apparatus of the comparative example was a normal vector scanning type laser irradiation apparatus that does not use an AOD. Then, with the diameter of the modified portion 2 being about 50 μm, the distance between the modified portions being 70 μm, and the distance between each line L1 and L2 being about 65 μm, the image pattern 1 was formed.

[0097] <Evaluation based on the misalignment γ in the main scanning direction> The evaluation of the positional deviation γ in the main scanning direction was performed by measuring the amount of positional deviation γ (positional deviation amount) at any 10 locations on each image pattern 1 formed using the laser irradiation apparatus of the present invention and the laser irradiation apparatus of the comparative example, and obtaining the standard deviation with respect to the average value of the positional deviation amounts. Note that the average value and the standard deviation do not necessarily have to be calculated using the measured values at 10 locations, but the number of measurement locations should be at least 5 locations, preferably 10 locations or more.

[0098] ●Evaluation in a linear image line First, the standard deviation of the positional deviation γ in the main scanning direction in a linear image line will be described.

[0099] When the image pattern 1 was formed on the stationary workpiece 50 using the laser irradiation apparatus of the comparative example, the standard deviation of the positional deviation γ in the main scanning direction was 12 μm. When the image pattern 1 was formed on the workpiece 50 conveyed at a speed of 60 BPM (60 pieces per minute), the standard deviation of the positional deviation γ in the main scanning direction was 22 μm, and the variation in the positional deviation became larger than when the workpiece 50 was stationary. As a result, in the case of the comparative example, it was difficult to make the standard deviation of the positional deviation γ in the main scanning direction 10 μm or less.

[0100] In contrast, when the image pattern 1 was formed on the stationary workpiece 50 using the laser irradiation device of the present invention, the standard deviation of the positional deviation γ in the main scanning direction was 6 μm. When the image pattern 1 was formed on the workpiece 50 conveyed at a speed of 60 BPM, the standard deviation of the positional deviation γ in the main scanning direction was 9 μm. That is, according to the present invention, in both cases where the image pattern 1 is formed on the stationary workpiece 50 and where the image pattern 1 is formed on the conveyed workpiece 50, in the linear image line, the standard deviation of the positional deviation γ in the main scanning direction is smaller than that of the comparative example. More specifically, according to the present invention, the standard deviation of the positional deviation γ in the main scanning direction can be made 10 μm or less, and particularly when the workpiece 50 is stationary, the standard deviation of the positional deviation γ in the main scanning direction can be made 6 μm or less. Thus, in the present invention, the reason why the standard deviation of the positional deviation γ in the main scanning direction of the linear image line could be reduced is considered to be that the modified portion 2 could be formed almost simultaneously on a plurality of lines by using the AOD. Therefore, according to the present invention, it can be said that the variation in the positional deviation γ in the main scanning direction can be suppressed and good image quality can be ensured.

[0101] Note that such an effect of the present invention (suppression of the variation in the positional deviation γ in the main scanning direction in the linear image line) is not established only between the first line L1 and the second line L2, but can also be established between any adjacent image lines. Therefore, according to the present invention, even when three or more parallel image lines are formed, not only between the first line L1 and the second line L2, but also between the second line L2 and the third line L3, the standard deviation of the positional deviation γ in the main scanning direction can be made 10 μm or less, or 6 μm or less.

[0102] ●Evaluation of the arc-shaped image line Next, the standard deviation of the positional deviation γ in the main scanning direction in the arc-shaped image line will be described.

[0103] When the image pattern 1 was formed on the stationary workpiece 50 using the laser irradiation device of the comparative example, the standard deviation of the positional deviation γ in the main scanning direction was 13 μm. When the image pattern 1 was formed on the workpiece 50 conveyed at a speed of 60 BPM, the standard deviation of the positional deviation γ in the main scanning direction was 24 μm. Therefore, also in this case, it was difficult to make the standard deviation of the positional deviation γ in the main scanning direction 10 μm or less. Also, in the case of the same comparative example, the standard deviation of the positional deviation γ in the main scanning direction became larger in the arc-shaped image line than in the linear image line.

[0104] On the other hand, when the image pattern 1 was formed on the stationary workpiece 50 using the laser irradiation device of the present invention, the standard deviation of the positional deviation γ in the main scanning direction was 3 μm. When the image pattern 1 was formed on the workpiece 50 conveyed at a speed of 60 BPM, the standard deviation of the positional deviation γ in the main scanning direction was 6 μm. That is, in the case of the present invention, the standard deviation of the positional deviation γ in the main scanning direction became smaller than that of the comparative example. This is considered to be because, in the case of the present invention, the modified portions 2 can be formed almost simultaneously on a plurality of lines parallel to each other. Thus, according to the present invention, the standard deviation of the positional deviation γ in the main scanning direction can be made 10 μm or less. Further, in this case, regardless of whether the workpiece 50 was stationary or conveyed, the standard deviation of the positional deviation γ in the main scanning direction could be made 6 μm or less in any case. Note that such an effect of the present invention (suppression of variation in the positional deviation γ in the main scanning direction in the arc-shaped image line) is not established only between the first line L1 and the second line L2, but also between any adjacent image lines.

[0105] <Regarding the mechanism causing the positional deviation γ in the main scanning direction> Here, the mechanism causing the positional deviation γ in the main scanning direction in the arc-shaped image line will be described.

[0106] When forming the arc-shaped image pattern 1 on the workpiece 50 being conveyed at a speed of 60 BPM using the laser irradiation device of the comparative example, as shown in FIG. 21, the positional deviation γ in the main scanning direction tends to gradually increase as it goes in the laser scanning direction (solid line arrow) of the galvanometer scanner 30. That is, since the radius of the second line L2 is larger than that of the first line L1, when the modified part 2 is formed in the same way along each of the first line L1 and the second line L2 by the normal vector scanning method, the positional deviation γ in the main scanning direction accumulates and increases as it goes in the laser scanning direction. Therefore, the positional deviation γ in the main scanning direction is larger in the adjacent modified part set Zn formed at the Nth position than in the adjacent modified part set Z1 formed first.

[0107] Also, as shown in the graph of FIG. 22, in the case of the laser irradiation device of the comparative example, when the radius of the arc-shaped image line becomes smaller, the positional deviation γ in the main scanning direction tends to increase conversely. In FIG. 22, the numbers on the horizontal axis indicate the relative distances from "0" at each measurement position when the irradiation start position of the laser light is set to "0", and the numbers on the vertical axis indicate the deviation amounts at each measurement position when the deviation amount γ of the position in the main scanning direction at the irradiation start position of the laser light is set to "0".

[0108] In FIG. 21, if the number of each modified part 2 arranged on the first line L1 and the second line L2 is N, the center-to-center distance along each of the lines L1 and L2 between the modified parts 2 for each of the first line L1 and the second line L2 is A, the radius of the first line L2 is r, and the radius difference between the first line L1 and the second line L2 is α, then the arc length of the arc de on the first line L1 is AN / 2rπ = θ / 2π, so the arc de = AN = rθ, and the arc length of the arc ac on the second line L2 is (r + α)θ. Furthermore, since AN = rθ, it can be expressed as θ = AN / r. Therefore, the arc length of the arc bc in FIG. 21 is expressed as arc bc = (r + α)θ - rθ = αAN / r. And this arc length of the arc bc appears as the difference S between the arc length (arc length of the arc de) where N modified parts 2 on the first line L1 are arranged and the arc length (arc length of the arc ab) where N modified parts 2 on the second line L2 are arranged.

[0109] Thus, in the comparative example, when forming the curved image line (image pattern 1), even if the same number of modified portions 2 are arranged on the inner line, the first line L1, and the outer line, the second line L2, there is a difference in the length of the range in which the respective modified portions 2 are arranged. Further, since the length of the arc bc, which is the difference S in the arc lengths in which the modified portions 2 are arranged on each of the lines L1 and L2, is expressed as arc bc = αAN / r, when the radius r of the first line L1 becomes smaller, the arc bc becomes larger. Therefore, in the case of the comparative example, as the radius r of the first line L1 becomes smaller, there is a risk that image loss occurs between the arcs bc and the image quality deteriorates. In particular, when the workpiece 50 is conveyed, since the arc bc tends to become larger, there is a risk that the thickness differs for each line of characters with different curvatures, or image disturbance occurs, which adversely affects the visibility of the characters.

[0110] On the other hand, when the image pattern 1 is formed using the laser irradiation device of the present invention, even when the workpiece 50 is conveyed at a speed of 60 BPM, as shown in FIG. 23, the difference S in the arc lengths in which the modified portions 2 are arranged on each of the lines L1 and L2 can be almost eliminated. That is, by using the laser irradiation device of the present invention, in addition to being able to form the modified portions 2 on a plurality of lines L1 and L2 almost simultaneously, the modified portions 2 on the second line L2 can be formed in the direction orthogonal (normal direction) to the first line L1 with respect to the modified portions 2 on the first line L1. Therefore, the adjacent modified portions 2 on each of the lines L1 and L2 can be aligned. For example, when each image line in FIG. 23 is an arc line with a central angle θ, the arc length of the first line L1 is rθ, while the arc length of the second line L2 is (r + α)θ. Therefore, although the arc lengths are different from each other, according to the present invention, by adjusting the center-to-center distance between the modified portions 2 on the second line L2 by αA / r, the misalignment can be almost eliminated. Therefore, according to the present invention, from the first-formed adjacent modified portion set Z1 to the Nth-formed adjacent modified portion set Zn, the misalignment γ in the main scanning direction can be almost eliminated.

[0111] FIG. 24 is a diagram showing the amount of displacement γ in the main scanning direction for each arc radius of the image lines formed using the laser irradiation apparatus of the present invention. Note that the vertical axis and the horizontal axis in FIG. 24 indicate the same content as the vertical axis and the horizontal axis in FIG. 22.

[0112] As shown in FIG. 24, according to the present invention, regardless of the arc radius, the displacement γ in the main scanning direction can be reduced as compared with the comparative example. Therefore, stable image quality can be ensured, and the visibility and designability of the image pattern 1 can be improved.

[0113] However, even when an arc-shaped image line is formed according to the present invention, there is no case where the displacement γ in the main scanning direction does not occur at all, and a displacement of about 1 / 3 of the length (αAN / r) of the arc bc, which is the difference between the image lines in FIG. 21, may occur. That is, in the present invention, there is a possibility that the difference S in the arc length in which the modified portions 2 on each of the lines L1 and L2 are arranged is about 1 / 3 of the length (αAN / r) of the arc bc. Also, the direction of the displacement may be on the downstream side (plus side) or the upstream side (minus side) with respect to the laser scanning direction along the first line L1.

[0114] Therefore, according to the present invention, each image line can be formed so that the difference S in the arc length in which the modified portions 2 on the first line L1 and the second line L2 are arranged satisfies the following relationship (1).

[0115]

Equation

[0116] Note that each symbol N, A, r, and α in the formula (1) has the same meaning as each symbol in FIG. 21. Also, if the number N of the modified portions 2 arranged on each of the lines L1 and L2 is too small, the noise becomes large and it becomes difficult to calculate an accurate value. Therefore, N is preferably 5 or more, and more preferably 10 or more.

[0117] By satisfying the relationship of the difference S in the arc length along which the modified portions 2 on each of the lines L1 and L2 are arranged as shown in Equation (1), an effect of suppressing the variation in the positional deviation γ in the main scanning direction as shown in FIG. 24 can be obtained. Further, the relationship of Equation (1) need not hold only between the first line L1 and the second line L2, but may also hold between any image lines adjacent to each other in the radial direction. That is, the relationship of Equation (1) may hold between an inner line disposed relatively inward and an arc-shaped outer line positioned adjacent to the inner line on the outer side in the radial direction among the arc-shaped lines parallel to each other that constitute a plurality of image lines.

[0118] <Evaluation by distance β between modified portions> Next, evaluation by the distance β between modified portions will be described.

[0119] Evaluation by the distance β between modified portions was performed by measuring the distance β between modified portions at any 10 locations on each image pattern 1 formed using the laser irradiation apparatus of the present invention and the laser irradiation apparatus of the comparative example, and obtaining the standard deviation with respect to the average value thereof. Note that the laser irradiation apparatus of the present invention and the laser irradiation apparatus of the comparative example are the same as those used for evaluating the positional deviation γ in the main scanning direction. Further, the number of measurement locations for calculating the average value and standard deviation of the distance β between modified portions is preferably at least 5 locations, more preferably 10 locations or more.

[0120] ●Evaluation in a linear image line First, the standard deviation of the distance β between modified portions in a linear image line will be described.

[0121] When the image pattern 1 was formed on the stationary workpiece 50 using the laser irradiation apparatus of the comparative example, the standard deviation of the distance β between modified portions was 7 μm. When the image pattern 1 was formed on the workpiece 50 conveyed at a speed of 60 BPM, the standard deviation of the distance β between modified portions was 45 μm, and the variation in the distance became larger than when the workpiece 50 was stationary. Therefore, in the case of the comparative example, the variation in the width of the image pattern 1 became large, and it was difficult to obtain good visibility.

[0122] On the other hand, when the image pattern 1 was formed on the stationary workpiece 50 using the laser irradiation device of the present invention, the standard deviation of the modified portion interval β was 2 μm. Further, when the image pattern 1 was formed on the workpiece 50 conveyed at a speed of 60 BPM, the standard deviation of the modified portion interval β was 5 μm. That is, according to the present invention, in both the case where the image pattern 1 is formed on the stationary workpiece 50 and the case where the image pattern 1 is formed on the conveyed workpiece 50, in the linear image line, the standard deviation of the modified portion interval β became smaller than that of the comparative example. More specifically, according to the present invention, regardless of whether the workpiece 50 is stationary or conveyed, the standard deviation of the modified portion interval β could be made 6 μm or less in any case. Thus, the reason why the standard deviation of the modified portion interval β could be reduced in the linear image line is considered to be that in the case of the present invention, the modified portions 2 could be formed almost simultaneously on a plurality of lines parallel to each other. Therefore, according to the present invention, the width of the image pattern 1 can be made uniform, and good visibility and image quality can be ensured.

[0123] Such an effect of the present invention (suppression of the variation in the modified portion interval β in the linear image line) is not established only between the first line L1 and the second line L2, but can also be established between any adjacent image lines. Therefore, according to the present invention, even when three or more parallel image lines are formed, not only between the first line L1 and the second line L2, but also between the second line L2 and the third line L3, the standard deviation of the modified portion interval β can be made 6 μm or less.

[0124] ●Evaluation of arc-shaped image line Next, the standard deviation of the modified portion interval β in the arc-shaped image line will be described.

[0125] When the image pattern 1 was formed on the stationary workpiece 50 using the laser irradiation device of the comparative example, the standard deviation of the distance β between the modified portions was 8 μm. When the image pattern 1 was formed on the workpiece 50 conveyed at a speed of 60 BPM, the standard deviation of the distance β between the modified portions was 54 μm. Even in the same comparative example, the standard deviation of the distance β between the modified portions was larger in the arc-shaped image line than in the linear image line.

[0126] On the other hand, when the image pattern 1 was formed on the stationary workpiece 50 using the laser irradiation device of the present invention, the standard deviation of the distance β between the modified portions was 3 μm. When the image pattern 1 was formed on the workpiece 50 conveyed at a speed of 60 BPM, the standard deviation of the distance β between the modified portions was 5 μm. Thus, according to the present invention, regardless of whether the workpiece 50 is stationary or conveyed, the standard deviation of the distance β between the modified portions could be made 6 μm or less in all cases. Note that such an effect of the present invention (suppression of variation in the distance β between the modified portions in the arc-shaped image line) is not established only between the first line L1 and the second line L2, but also between any adjacent image lines adjacent to each other.

[0127] <Mechanism for generating the distance β between the modified portions> Here, the mechanism for generating the distance β between the modified portions in the arc-shaped image line will be described.

[0128] When the arc-shaped image pattern 1 is formed on the workpiece 50 being conveyed at a speed of 60 BPM using the laser irradiation device of the comparative example, as shown in FIG. 25, the distance β between the modified portions tends to gradually increase as it goes in the laser scanning direction (solid line arrow) of the galvanometer scanner 30. That is, since the second line L2 has a larger radius than the first line L1, when the modified portions 2 are formed in the same manner along the first line L1 and the second line L2 by the normal vector scanning method, the distance β between the modified portions is accumulated and increases as it goes in the laser scanning direction. Therefore, the distance β between the modified portions is larger in the adjacent modified portion set Zn formed at the Nth time than in the adjacent modified portion set Z1 formed first.

[0129] Moreover, as shown in the graph of Fig. 26, in the case of the laser irradiation device of the comparative example, the distance β between modified parts tends to increase as the radius of the arc-shaped image line decreases. In Fig. 26, the numbers on the horizontal axis indicate the relative distance from "0" at each measurement position when the laser light irradiation start position is set to "0", and the numbers on the vertical axis indicate the distance β between modified parts at each measurement position when the distance β between modified parts at the laser light irradiation start position is set to "0".

[0130] In Figure 25, if the number of denatured portions 2 lined up on the first line L1 and the second line L2 is N, the center-to-center distance between the denatured portions 2 on the first line L1 and the second line L2 is A, the radius of the first line L2 is r, and the radius difference between the first line L1 and the second line L2 is α, the length of the arc bc, which is the difference S in the arc lengths in which the denatured portions 2 on each line L1, L2 are lined up, can be expressed as arc bc = (r + α)θ - rθ = αAN / r, as explained in Figure 21.

[0131] In addition, in FIG. 25, the length of the line segment be, which is the distance β between modified portions in the Nth adjacent modified portion set Zn, is expressed by the following formulas (2) and (3) when the circular arc bc is approximated as a straight line.

[0132]

number

number

[0133] In this way, the length of the line segment be, which is the distance β between the denatured parts, is given by line segment be = {(αAN / r) 2 +α 2} 1 / 2 Therefore, when the radius r of the first line L1 is smaller, the line segment be is larger. Therefore, in the comparative example, as the radius r of the first line L1 is smaller, the distance β between the modified parts is larger, and the width of the image pattern 1 is varied.

[0134] On the other hand, when the image pattern 1 is formed on the workpiece 50 using the laser irradiation apparatus of the present invention, even when the workpiece 50 is conveyed at a speed of 60 BPM, as shown in FIG. 27, variations in the distance β between the modified portions can be almost eliminated. That is, by using the laser irradiation apparatus of the present invention, in addition to being able to form the modified portions 2 on a plurality of lines L1 and L2 almost simultaneously, the modified portions 2 on the second line L2 can be formed in the direction orthogonal (normal direction) to the first line L1 with respect to the modified portions 2 on the first line L1. Therefore, the modified portions 2 adjacent to each other on the respective lines L1 and L2 can be aligned. Accordingly, according to the present invention, variations in the distance β between the modified portions can be almost eliminated from the first formed adjacent modified portion set Z1 to the Nth formed adjacent modified portion set Zn.

[0135] FIG. 28 is a diagram showing the distance β between the modified portions for each arc radius of the image line formed using the laser irradiation apparatus of the present invention. Note that the vertical axis and the horizontal axis in FIG. 28 represent the same content as the vertical axis and the horizontal axis in FIG. 26.

[0136] As shown in FIG. 28, according to the present invention, regardless of the magnitude of the arc radius, variations in the distance β between the modified portions can be reduced as compared with the comparative example. For this reason, stable image quality can be ensured, and the visibility and designability of the image pattern 1 can be improved.

[0137] However, even when an arc-shaped image line is formed according to the present invention, variations in the distance β between the modified portions do not completely disappear. Here, when an arc-shaped image line is formed using the laser irradiation apparatus of the present invention, as shown in FIG. 27, the length of the image line of the second line L2 becomes the length of the arc ac, and thus the ideal distance β between the modified portions in that case is α. Therefore, the variation (transition) in the distance β between the modified portions from the first adjacent modified portion set Z1 to the Nth adjacent modified portion set Zn is represented by the following formula (4).

[0138]

Equation

[0139] In addition, the variation in the distance β between the modified portions in the present invention is the length of the line segment be which is the distance β between the modified portions in the Nth adjacent modified portion set Zn in FIG. 25 ({(αAN / r) 2 +α 2}) 1 / 2 ) can occur to about 1 / 3 of it.

[0140] Therefore, in the present invention, each image line can be formed so that the distance β between the modified portions satisfies the relationship of the following formula (5).

[0141] [Number]

[0142] In addition, each symbol N, A, r, α in formula (5) has the same meaning as each symbol in FIG. 25. Further, if the number N of the modified portions 2 arranged on each of the lines L1 and L2 is too small, noise becomes large and it becomes difficult to calculate an accurate value. Therefore, N is preferably 5 or more, and more preferably 10 or more.

[0143] By the distance β between the modified portions satisfying the relationship of formula (5), an effect of suppressing the variation in the distance β between the modified portions as shown in FIG. 28 can be obtained. Further, the relationship of formula (5) may hold not only between the first line L1 and the second line L2, but also between any image lines adjacent to each other in the radial direction. That is, the relationship of formula (5) may hold between the inner line disposed relatively inside and the arc-shaped outer line located adjacent to the inner line on the outside in the radial direction among the arc-shaped lines parallel to each other constituting a plurality of image lines.

[0144] <Workpiece> The workpiece 50 used in the present invention is not particularly limited in terms of its material, shape, size, structure, color, etc., and can be appropriately selected according to the purpose. Examples of the material of the workpiece 50 include resin and glass.

[0145] In addition, examples of the resin used for the workpiece 50 include polyvinyl alcohol (PVA), polybutylene adipate / terephthalate (PBAT), polyethylene terephthalate succinate, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), vinyl chloride (PVC), polystyrene (PS), polyurethane, epoxy, biodegradable polybutylene succinate (PBS), polylactic acid blend (PBAT), starch blend polyester resin, polyethylene terephthalate succinate, polylactic acid (PLA), polyhydroxybutyrate / hydroxyhexanoate (PHBH), polyhydroxyalkanoic acid (PHA), bio-PET30, bio-polyamide (PA) 610, 410, 510, bio-PA1012, 10T, bio-PA11T, MXD10, bio-polycarbonate, bio-polyurethane, bio-PE, bio-PET100, bio-PA11, bio-PA1010, etc. These may be used alone or in combination of two or more. Among these, from the viewpoint of environmental load, biodegradable resins such as polyvinyl alcohol, polybutylene adipate / terephthalate, and polyethylene terephthalate succinate are preferable.

[0146] In addition, the workpiece 50 may be a bottle-shaped container having a mouth portion, a shoulder portion connected to the mouth portion, a body portion connected to the shoulder portion, and a bottom portion connected to the body portion. The size of the container is not particularly limited and can be appropriately selected according to the use of the container. As the structure of the container, for example, a single-layer structure or a multi-layer structure may be used.

[0147] Further, the container may be one that houses the contents inside. Examples of the contents include liquids, gases, granular solids, etc. Examples of the liquid contents include water, tea, coffee, black tea, soft drinks, etc. When the contents are a liquid beverage, the contents may have a color such as transparent, white, black, brown, or yellow. Examples of the gas contents include oxygen, hydrogen, nitrogen, etc. Examples of the granular solids include pieces or particles such as pulp, vegetables, nata de coco, tapioca, jelly, konjac, etc.

[0148] <Regarding the visibility of the image pattern> Hereinafter, the visibility of the image pattern will be described.

[0149] FIG. 29 shows a cross-section of the workpiece 50 before the image pattern 1 is formed, and FIG. 30 shows a cross-section of the workpiece 50 in a state where the image pattern 1 is formed. In FIGS. 29 and 30, reference numeral 9 denotes the contents housed inside the workpiece 50.

[0150] As shown in FIG. 30, when an image pattern 1 composed of modified portions 2 is formed on the surface of the workpiece 50, the diffuse reflectance on the surface of the workpiece 50 increases compared to the state of FIG. 29 before the image pattern 1 is formed. For this reason, the portion of the image pattern 1 appears whitened. Also, as the plurality of modified portions 2 become denser, the degree of whitening increases, improving visibility. On the other hand, if an attempt is made to form the modified portions 2 densely, it takes time for laser irradiation, productivity decreases, or deformation of the workpiece 50 due to heat generation or color change due to alteration of the material occurs. For this reason, it is preferable to form the modified portions 2 at a density that does not affect visibility. Also, the visibility of the image pattern 1 is determined by not only the diffuse reflectance due to the modified portions 2 but also the influence of transmitted light from the contained material 9 accommodated in the workpiece 50. Therefore, when the workpiece 50 is formed of a transparent material such as a PET bottle or glass, in particular, the influence of the transmitted light from the contained material 9 accommodated in the workpiece 50 becomes significant. Also, when the image pattern 1 is a collection of a plurality of modified portions 2 at a density that does not reduce productivity, it is necessary to consider the influence of the transmitted light of the non-modified portion 3.

[0151] <Method for evaluating visibility> Subsequently, a method for evaluating visibility will be described.

[0152] The evaluation of visibility is performed by photographing the workpiece 50 and measuring from the visible image (image pattern) and the respective brightnesses measured from the portions other than the image.

[0153] The photographing system of the workpiece 50 will be described with reference to FIGS. 31 to 33. FIG. 31 is a diagram showing an example of the photographing system. FIG. 32 is a diagram showing a state in which a white diffusion surface 54 is installed in the photographing system. FIG. 33 is a schematic diagram showing an image 70 of the workpiece 50 photographed by the photographing system and a portion 71 other than the image. The photographing system includes a workpiece 50, a light source 51, a darkroom 52, a camera 53, and a white diffusion surface 54. The workpiece 50 is photographed with the camera 53 while irradiating it with light. It is performed in the environment of the darkroom 52 in order to exclude images unnecessary for the photographing by the camera 53.

[0154] Further, as shown in FIG. 32, the light source 51 is arranged at a predetermined angle as a flat light source so that the specular reflection component of the surface of the workpiece 50 is not photographed. Further, the light source 51 is arranged at a position for diffused illumination. For example, the position where the light source 51 is installed may be a position where the specular reflection component on the irradiation surface such as diagonally above the workpiece 50 is not detected by the camera 53, or may be diagonally below or on the side surface. The white diffusing surface 54 is installed on the side surface of the workpiece 50 in order to reflect the influence of the contents of the workpiece 50 in the photographed image. Thereby, transmitted light from the surroundings can also be considered.

[0155] <Shooting conditions in the method for evaluating visibility> The shooting conditions were set so that the reading value of white did not saturate. Further, the LED tracer was used for the light source 51. The camera 53 is a Basler area scan camera acA3088-57μm, and the lens of the camera 53 is a Ricoh Lens FL-CC2514-2M (F1.4 f25mm 2 / 3”). Shooting was performed with the following shooting conditions. -Shooting conditions- · Aperture: F1.4 · Exposure time: 20,000 (μs) · Shooting distance: 500 mm

[0156] The brightness of the image and the part other than the image were measured from the image taken by the imaging system. Then, the brightness is converted from the output values of the image 70 and the part 71 other than the image shown in FIG. 33. The output value of the camera 53 is several millimeters 2 ~ dozens of millimeters 2 It is preferable to use the average value of an area of about.

[0157] For the conversion of brightness, first, a chart (gray chart) with a known brightness (L * ) is photographed by the camera 53. Next, the brightness is converted using the G signal and the known brightness from the image taken by the camera 53.

[0158] -G signal and brightness conversion- ·Approximate the image captured by the camera 53 with an nth-degree polynomial. As an example, convert the G signal to brightness using the cubic polynomial shown below. L * = Lab_1st × G1 + Lab_2nd × G2 + Lab_3rd × G3 + Lab_const Lab_1st = 0.461535 Lab_2nd = -0.000281 Lab_3rd = 0.000000 Lab_const = 1.211053

[0159] Note that Fig. 34 is a graph showing the relationship between the G signal and the brightness converted from the cubic polynomial. There is a clear correlation between the G signal and the brightness, and since the contribution rate r 2 = 0.997, a completely proportional relationship holds.

[0160] -Subjective evaluation- For the workpiece 50 with the laser irradiation conditions changed, subjective evaluations were performed by changing the contents 9. The statistical subjective evaluation points were obtained for the workpiece 50 to be evaluated using the paired comparison method of Shuffle.

[0161] ·Workpiece: 6 types with different processing conditions ·Contents: water, coffee, tea ·Subjective evaluation method: paired comparison method of Shuffle ·Evaluators: 3 persons (the evaluation was performed 2 times each) ·First evaluation: water was included in all workpieces ·Second evaluation: 2 water, 2 coffee, 2 tea ·Third evaluation: 1 water, 3 coffee, 2 tea ·Evaluation environment: office indoor

[0162] Fig. 35 shows the relationship between the brightness (L * 0 ) of the image and the subjective evaluation points. Fig. 36 shows the difference (ΔL * between the brightness of the image and the brightness of the part other than the image.) shows the relationship with the subjective evaluation points. The subjective evaluation points evaluated by the paired comparison method of Shaffer indicate that the higher the numerical value, the better the visibility in subjective evaluation. There are workpieces with poor correlation, such as the areas surrounded by dotted lines in FIGS. 35 and 36. These are workpieces in a state where the brightness (L * 0 ) of the image is extremely low, the brightness difference (ΔL * ) is small, or both of these states.

[0163] For such workpieces as well, in order to obtain a highly correlated formula, the following formula (6) is derived by multiplying the brightness L of the image * 0 by (1 - exp(ΔL * ))). As shown in FIG. 37, since Y = (1 - exp(-x)) approaches Y = 0 as x decreases, formula (6) expresses the tendency that the visibility deteriorates as the brightness difference (ΔL * ) decreases.

[0164] Therefore, the visibility value is expressed by the following formula (6).

[0165]

Equation

[0166] However, in the above formula (6), L * 0 is the brightness of the image (image pattern), and ΔL * represents the difference between the brightness of the image (image pattern) and the brightness of the part other than the image (image pattern). The visibility value expressed by formula (6) represents the characteristics that the higher the brightness of the image, the higher the visibility, and the visibility disappears when the brightness difference from the part other than the image disappears.

[0167] Also, as shown in FIG. 38, the visibility value expressed by formula (6) has a very high correlation (R 2 = 0.943) with the subjective evaluation points (paired comparison method) when the laser irradiation conditions and the inclusion 9 accommodated in the workpiece 50 are changed. It is evaluated by the visibility value calculated in this way.

[0168] As described above, regarding the visibility value, the case of converting the brightness from the output values of the measurement square P of the portion of the image 70 in a relatively wide range as shown in FIG. 33 and the measurement square Q of the portion other than the portion 71 other than the image has been described as an example.

[0169] Here, in the present invention, one of the problems is to improve the visibility of characters when forming characters on a workpiece by a vector scanning method. For this reason, the visibility evaluation of characters will be described from here.

[0170] When the present inventors earnestly studied an optimal method for measuring the visibility value in evaluating the visibility and readability of each character, it was found that the visibility of the character itself can be evaluated by determining the size of the measurement square based on the size of each character. That is, characters have various fonts or sizes, and as they are, there is no standard for the size of the measurement square, and the visibility value changes depending on the size of the measurement square.

[0171] FIG. 39 shows an evaluation image when one side of the measurement square adjusted to the vertical size of the character "A" is defined as 1.

[0172] FIG. 40 shows the difference in visibility value when the size of the measurement square is changed with respect to the 7-point-sized character "A" written in a single line.

[0173] Since the visibility value is the ratio between the portion of the image pattern and the portion other than the image pattern, when the measurement square becomes larger than the character, the visibility value decreased almost proportionally. Also, when the measurement square became smaller than the character, the numerical value increased, but since this also depends on whether the smaller measurement square is applied to the drawn portion of the character, it can be seen that the measurement using a measurement square smaller than the character is not reliable. Therefore, as the measurement square for measuring the visibility value of a character, a method of measuring with one side of the measurement square adjusted to the vertical size of the character, which is the easiest to measure, highly reliable, and easy to define, was selected.

[0174] First, regarding the character "A", the relationship between the character size and the visibility value was investigated. The measurement square was defined as 1, and the results of shaking the image lines constituting the character with 1 to 3 lines are shown in FIG. 41. It can be seen that the visibility value is significantly improved by using a plurality of image lines to form the character. Also, when using a single line, even if the character size is changed, there is no significant change in its visibility value. However, when using a plurality of lines, it was found that the visibility value improves as the character size decreases. This is presumably because the character is formed by thick lines with respect to the character size, resulting in such measurement results.

[0175] Regarding these visibility values, the relevance to the actual visibility and readability is important. For example, in the case of soft drinks and other food labels, food labeling is regulated by law when selling food, and there is an obligation to label. The labeling contents subject to such labeling obligations include expiration date, storage method, raw material name, additives, name or title and location of food-related business operators, nutritional component labeling, etc. These information require visibility that allows consumers to pick up and read them reliably. Here, the relevance between the above-mentioned visibility value and the results of a subjective evaluation of the visibility of characters when actually distributed as a product was investigated.

[0176] <Subjective evaluation method> Regarding the workpieces obtained by laser processing the image patterns (characters) under the following conditions, subjective evaluation of the image patterns was performed, and the readability was evaluated on a 5-point scale. The relationship between the evaluation rank and the visibility value is shown in FIG. 42. - Evaluation conditions - · Judges: 30 people · Image patterns: The characters were A, B, C, D, and E, and the character sizes were 5.5 pt, 6 pt, 7 pt, and 8 pt. · Workpieces: PET bottles containing water were prepared, and each character was formed on the surface of the PET bottle by laser irradiation. Also, each character was formed by 1, 2, or 3 image lines. · Evaluation environment: General office indoor · Judgment method: The judgment rank is divided into the following five levels, and subjective evaluation is carried out by the judge, showing the average value of each evaluation rank for each character. [Evaluation rank] 1: Almost no characters can be read. 2: Characters are difficult to read even when bringing the eyes close (the distance between the eyes and the characters is 20 cm). 3: Characters can be read when bringing the eyes close (the distance between the eyes and the characters is 20 cm). 4: Characters can be read at a normal distance when picked up by hand (the distance between the eyes and the characters is 40 cm). 5: Characters can be clearly read at a normal distance when picked up by hand (the distance between the eyes and the characters is 40 cm).

[0177] From the results of Fig. 42, since it is a subjective evaluation by people with various visual acuities, there is a certain degree of variation. However, in terms of the average value, the visibility value is approximately rank 3 or above when it is 3 or more. This evaluation rank of "Characters can be read when bringing the eyes close" becomes one of the criteria for visibility when actually distributing the product. Also, when the visibility value is 5 or more, all judges gave an evaluation rank of 5.

[0178] As a result, although there is variation in the evaluation, in evaluation rank 1, 5.5 pt for a single line was mostly ranked, and in evaluation rank 2, 7 pt and 8 pt for a single line were mostly ranked. When there is one image line, even if the characters are enlarged, relatively speaking, the line becomes thinner with respect to the character size. Thus, it was found that not only the character size contributes to visibility. Also, the characters with two lines and three lines basically had an evaluation rank of 3 or above.

[0179] Incidentally, when two or three lines are formed while transporting the workpiece using a normal vector scanning type laser irradiation device without using the laser irradiation device of the present invention, as described above, the writing time takes several times as long. What becomes difficult with such a method is to accurately form image lines parallel to each other while transporting the bottle. Basically, it is almost impossible to form such image lines without using the laser irradiation device of the present invention. In fact, characters formed by forming a plurality of image lines without using the laser irradiation device of the present invention had a large variation in character thickness and received a low evaluation in terms of readability.

[0180] As described above, the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the present invention.

[0181] The processing method for processing an image pattern on a workpiece using the laser irradiation method according to the present invention may include a step of irradiating the workpiece with laser light while transporting the workpiece as long as it includes an irradiation step of irradiating the workpiece with laser light to form an image pattern, or may include a step of irradiating the workpiece with laser light in a stationary state. Further, other steps may be included as necessary. Instead of the method of transporting the workpiece by a belt conveyor or the like, a method of irradiating the surface of the workpiece with laser light while rotating the workpiece may be adopted.

[0182] The spot diameter of the laser light used in the laser irradiation device of the present invention is preferably, for example, 1 μm or more and 200 μm or less, and more preferably 10 μm or more and 100 μm or less. This is because when the spot diameter becomes smaller than 1 μm, it becomes close to the wavelength of visible light, so that light cannot be scattered and it becomes difficult to become cloudy.

[0183] In addition, the wavelength of the laser light is not limited to those in the ultraviolet region and visible light region, but those in the near-infrared region to mid-infrared region are also suitable. Specifically, those in the wavelength range of 1,200 nm or more and 1,500 nm or less are also suitable. For example, wavelengths in the near-infrared region to mid-infrared region are suitable in that they can respond quickly when whitening by foaming (thermal denaturation), and it is also easy to array the devices. The wavelength in the ultraviolet region is suitable in that the light intensity of the laser light can be increased for processing by ablation. Also, for each wavelength band, since there is a wavelength at which the absorption rate for the workpiece is significantly higher than the surrounding wavelengths, it is particularly suitable to use this wavelength.

[0184] In the above embodiment, the case of using the first-order diffracted light of the AOD has been shown, but the same effect can be obtained by using the first-order light or higher-order light of the second order or more. Also, for example, a plurality of orders of light such as both the zero-order light and the first-order light may be used in combination.

[0185] Further, the present invention may be applicable even when the light source is not a pulse laser, or when the laser irradiation pitch and the pixel size do not necessarily match. Even in such a case, according to the present invention, the same effect can be obtained.

[0186] <Modeling device> Further, the laser irradiation device of the present invention can also be applied to a three-dimensional object modeling device.

[0187] FIG. 43 shows the configuration of a powder bed fusion device 400, which is an example of a three-dimensional object modeling device.

[0188] The powder bed fusion device 400 forms a three-dimensional object by melting and bonding a predetermined laser light irradiation region of the powder bed by irradiating a powder bed in which a plurality of powder layers are sequentially formed with laser light. Specifically, first, a powder material is spread flat to form a layer. Next, laser light is irradiated at a desired position on the layer, and the particles contained in the powder material are selectively sintered or melted to bond the particles.

[0189] In this way, one layer is formed as a plurality of layers into which the three-dimensional object is divided in the thickness direction. Further, a powder material is spread over the formed object layer, and a laser beam is irradiated to form the next object layer.

[0190] By repeating this procedure to stack the object layers, a three-dimensional object having a desired shape is manufactured. The powder material includes a resin material, a metal material, etc., and two or more types may be mixed as appropriate, and additives may be further added.

[0191] The powder bed fusion bonding apparatus 400 includes a shaping stage 310, a layer forming unit 320, a preheating unit 330, a temperature measuring device 335, and a laser irradiation device 200. The shaping stage 310 is a stage on which the three-dimensional object is shaped. The stage support portion 350 supports the shaping stage 310 such that its position in the vertical direction is variable.

[0192] The shaping stage 310 is configured to be precisely movable in the vertical direction by the stage support portion 350. As the stage support portion 350, various configurations can be adopted. For example, it can be composed of a holding member that holds the shaping stage 310, a guide member that guides this holding member in the vertical direction, and a ball screw that engages with a screw hole provided in the guide member.

[0193] The layer forming unit 320 forms a layer. The layer forming unit 320 includes a powder supply unit 321 that supplies powder and a recoater 322a that flattens the powder on the shaping stage 310.

[0194] The layer forming unit 320 includes, for example, an edge of an opening where the shaping stage 310 moves up and down, an opening whose edge is substantially on the same horizontal plane, and a powder material storage portion that extends vertically downward from the opening. The powder supply unit 321 includes a supply piston provided at the bottom of the powder material storage portion and moving up and down within the opening. Note that the powder supply unit 321 may include a powder material storage portion provided vertically above the shaping stage 310 and a nozzle, and may be configured to discharge the powder material on the same horizontal plane as the shaping stage.

[0195] The preheating unit 330 preheats the layer formed by the layer forming unit 320. The preheating unit 330 may be any device that can heat at least the area where the shaped object layer is to be formed on the surface of the layer and maintain the temperature thereof.

[0196] For example, the preheating unit 330 may be configured to include a first heater 331a capable of heating the surface of the layer formed on the shaping stage 310, or may be further configured to include a second heater 332 for heating the powder material before it is supplied onto the shaping stage 310. Further, the preheating unit 330 may be configured to selectively heat the area where the shaped object layer is to be formed, or may be configured to heat the entire interior of the apparatus to adjust the temperature of the surface of the formed layer to a predetermined temperature.

[0197] The first heater 331a may be a heater 331a that heats the layer from above, a heater 331b that heats the layer from the side, a heater 331c that heats the layer from below, or any combination thereof. However, the surface temperature of the layer tends to increase in the vicinity of the first heaters 331a, 331b, and 331c, and the surface temperature of the layer is less likely to increase as the distance from the first heaters 331a, 331b, and 331c increases.

[0198] Therefore, from the viewpoint of making it difficult for temperature unevenness to occur on the surface of the layer and making it difficult for deformation of the shaped object layer due to temperature unevenness on the layer surface to occur, the first heater 331a preferably includes a plurality of heaters arranged discretely from each other. At this time, it is preferable that the plurality of arranged first heaters 331a, the plurality of arranged first heaters 331b, and the plurality of arranged first heaters 331c are arranged at equal intervals from each other.

[0199] The temperature measuring device 335 measures the temperature of the layer. It may be any device that can non - contact measure the surface temperature of the area where the shaped object layer is to be formed, and for example, it can be an infrared sensor or an optical pyrometer.

[0200] The laser irradiation device 200 irradiates a powder bed with laser light. By irradiating the laser light, a shaped object layer is formed. The laser irradiation device 200 includes a laser oscillator 10, an AOD 20, and a galvanometer scanner 30.

[0201] The laser irradiation device 200 may include a laser window 343 that transmits laser light. The laser window 343 may be made of a material that transmits laser light.

[0202] In the powder bed fusion bonding device 400, if there is unevenness in the preheating temperature heated by the preheating unit 330, unevenness will also occur in the volume (specific volume) change rate of the powder irradiated with the laser light, and the accuracy of the three-dimensional shaped object will decrease. Therefore, the temperature is measured by the temperature measuring device 335, and the energy of the laser light irradiated by the laser irradiation device 200 is adjusted according to the temperature result.

[0203] Specifically, when the preheating temperature is low, the energy given to the particles that are the irradiated portion from the laser light is increased, and when the preheating temperature is high, the control is performed so as to reduce the energy given to the particles that are the irradiated portion from the laser light.

[0204] The laser irradiation device 200 can deflect the laser light in a direction intersecting the deflection direction of the galvanometer scanner 30 by the AOD 20, so that the laser light can be irradiated on a plurality of mutually parallel lines almost simultaneously. For this reason, a plurality of linear shaped layers can be formed in a relatively short time, and the scanning time can be shortened. In addition, compared with the case where the shaped object is a single linear shape, the visibility of the shaped object is also improved by being configured as a collection of a plurality of linear shapes.

[0205] Summarizing the aspects of the present invention described above, the present invention includes at least the following aspects.

[0206] [First aspect] The first aspect is a laser irradiation device that irradiates laser light, comprising: a first deflection means for deflecting and scanning the laser light; and a second deflection means for deflecting the laser light deflected by the first deflection means, wherein the first deflection means includes a non-inertial deflection device, and irradiates the laser light along at least one or more lines parallel to the first line while irradiating the laser light along the first line, and is a laser irradiation device that irradiates the laser light beside the first line along at least one or more lines parallel to the first line.

[0207] [Second aspect] The second aspect is, in the first aspect, the second deflection means deflects the laser light to irradiate along the first line, and the first deflection means deflects the laser light to irradiate beside the first line along at least one or more lines parallel to the first line.

[0208] [Third aspect] The third aspect is, in the first aspect, provided with a deflection means for deflecting the laser light so as to continuously form minute laser irradiation modified portions by turning on and off the laser irradiation on the surface of the workpiece along the first line based on the coordinate data of a plurality of line elements obtained by decomposing the image pattern.

[0209] [Fourth aspect] The fourth aspect is, in any one of the first to third aspects, the non-inertial deflection device is an acousto-optic deflector.

[0210] [Fifth aspect] The fifth aspect is, in any one of the first to fourth aspects, the first line is the scanning locus of the laser light generated by the scanning of the second deflection means when the deflection angle of the first deflection means is maintained at a predetermined reference value.

[0211] [Sixth aspect] The sixth aspect is, in any one of the first to fifth aspects, the laser irradiation device irradiates the laser light to a resin workpiece.

[0212] [Seventh aspect] In the seventh aspect, in the sixth aspect, the workpiece is a workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of lines parallel to each other, and the standard deviation of the amount of displacement in the direction parallel to the lines of the laser irradiation modified portions arranged adjacent to each other between two adjacent ones of the lines is 10 μm or less.

[0213] [Eighth Aspect] In the eighth aspect, in the sixth aspect, the workpiece is a workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of lines parallel to each other, and the standard deviation of the center-to-center distance of the laser irradiation modified portions arranged adjacent to each other between two adjacent ones of the lines is 6 μm or less.

[0214] [Ninth Aspect] The ninth aspect is a workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of parallel lines including at least an arcuate inner line and an arcuate outer line located adjacent to the inner line on the outer side in the radial direction of the inner line. Let the center-to-center distance between the laser irradiation modified portions on the inner line be A, the radius of the inner line be r, the difference in radius between the inner line and the outer line be α, and the difference in arc length between the arc length of N laser irradiation modified portions on the inner line and the arc length of N laser irradiation modified portions on the outer line be S. Then, the workpiece satisfies the relationship of 2αAN / 3r < S < 4αAN / 3r.

[0215] [Tenth Aspect] The tenth aspect is a workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of lines parallel to each other, and the standard deviation of the amount of displacement in the direction parallel to the lines of the laser irradiation modified portions arranged adjacent to each other between two adjacent ones of the lines is 10 μm or less.

[0216] [Eleventh Aspect] The 11th aspect is a workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of lines parallel to each other, and the standard deviation of the center-to-center distance between the laser irradiation modified portions arranged adjacent to each other between two adjacent ones of the lines is 6 μm or less.

[0217] [12th aspect] The 12th aspect is the workpiece according to the 10th or 11th aspect, wherein the plurality of lines are each a straight line.

[0218] [13th aspect] The 13th aspect is the workpiece according to the 10th or 11th aspect, wherein the plurality of lines are each a curved line.

[0219] [14th aspect] The 14th aspect is a workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of parallel lines including at least an arc-shaped inner line and an arc-shaped outer line located adjacent to the inner line in the radial direction outside the inner line, where the number of the laser irradiation modified portions arranged on each of the inner line and the outer line is N, the center-to-center distance between the laser irradiation modified portions on the inner line is A, the radius of the inner line is r, the radius difference between the inner line and the outer line is α, and the center-to-center distance between the laser irradiation modified portions arranged adjacent to each other between the inner line and the outer line is β. Then, α ≦ β ≦ [{(αAN / r) 2 +α 2} 1 / 2 -α] / 3.

[0220] [15th aspect] The 15th aspect is the workpiece according to any one of the 9th to 14th aspects, wherein the workpiece is a container.

[0221] [16th aspect] Aspect 16 is that, in Aspect 15, in a state where the container contains the contents, the visibility value represented by the following formula of the image pattern including the laser irradiation modified portions formed on the plurality of lines is 3 or more. Visibility value = 0.195·L * 0 ·{1 - exp(-0.193·ΔL * )} However, in the above formula, L * 0 is the brightness of the image pattern, and ΔL * represents the difference between the brightness of the image pattern and the brightness of the portion other than the image pattern.

[0222] [Aspect 17] Aspect 17 is a laser irradiation method of scanning laser light along a first line based on the coordinate data of an image pattern and irradiating the target object with the laser light, and is a laser irradiation method of deflecting the laser light so as to irradiate the laser light beside the first line while irradiating the laser light along the first line.

Explanation of Signs

[0223] 1 Image pattern 2 Modified portion (laser irradiation modified portion) 20 AOD (First deflection means, non-inertial deflection device) 23 AOD (First deflection means, non-inertial deflection device) 30 Galvanometer scanner (Second deflection means) 50 Workpiece 100 Laser irradiation device 110 Laser irradiation device L1 First line L2 Second line β Distance between modified portions γ Position shift in the main scanning direction

Prior Art Documents

Patent Documents

[0224]

Patent Document 1

Claims

1. A laser irradiation device for irradiating a laser beam, comprising: a first deflection means for deflecting and scanning the laser beam; a second deflection means for deflecting the laser beam deflected by the first deflection means; the first deflection means includes a non-inertial deflection device; A laser irradiation device, characterized in that while irradiating the laser beam along a first line, the laser beam is irradiated beside the first line along at least one or more lines parallel to the first line.

2. The laser beam is deflected by the second deflection means so as to be irradiated along the first line, The laser irradiation device according to claim 1, wherein the laser beam is deflected by the first deflection means so as to be irradiated beside the first line along at least one or more lines parallel to the first line.

3. Deflection means for deflecting the laser beam so as to continuously form minute laser irradiation modification portions by turning on and off the laser irradiation on the surface of the workpiece along the first line based on the coordinate data of a plurality of line elements obtained by decomposing the image pattern. The laser irradiation device according to claim 1.

4. The laser irradiation device according to claim 1, wherein the non-inertial deflection device is an acousto-optic deflector.

5. The laser irradiation device according to claim 1, wherein the first line is a scanning locus of the laser beam generated by scanning of the second deflection means when the deflection angle of the first deflection means is maintained at a predetermined reference value.

6. The laser irradiation device according to claim 1, wherein the laser irradiation device irradiates the laser beam onto a resin workpiece.

7. The workpiece is a workpiece on which a plurality of laser irradiation modification portions are formed side by side on a plurality of lines parallel to each other, The laser irradiation device according to claim 6, wherein a standard deviation of a displacement amount in a direction parallel to the line between the laser irradiation modification portions arranged adjacent to each other between two adjacent lines is 10 μm or less.

8. The workpiece is a workpiece on which a plurality of laser irradiation modification portions are formed side by side on a plurality of lines parallel to each other, The laser irradiation device according to claim 6, wherein a standard deviation of a center-to-center distance between the laser irradiation modification portions arranged adjacent to each other between two adjacent lines is 6 μm or less.

9. A workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of parallel lines including at least an arcuate inner line and an arcuate outer line located adjacent to the inner line on the outer side in the radial direction of the inner line, wherein the center-to-center distance between the laser irradiation modified portions on the inner line is A, the radius of the inner line is r, the radius difference between the inner line and the outer line is α, and the difference between the arc length along which N laser irradiation modified portions on the inner line are arranged and the arc length along which N laser irradiation modified portions on the outer line are arranged is S, and the workpiece satisfies the relationship of 2αAN / 3r < S < 4αAN / 3r.

10. A workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of parallel lines, wherein the standard deviation of the amount of displacement in the direction parallel to the lines between the laser irradiation modified portions arranged adjacent to each other between two adjacent ones of the lines is 10 μm or less.

11. A workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of parallel lines, wherein the standard deviation of the center-to-center distance between the laser irradiation modified portions arranged adjacent to each other between two adjacent ones of the lines is 6 μm or less.

12. The workpiece according to claim 10 or 11, wherein the plurality of lines are each a straight line.

13. The workpiece according to claim 10 or 11, wherein the plurality of lines are each a curved line.

14. A workpiece in which a plurality of laser irradiation modified portions are formed side by side on a plurality of parallel lines including at least an arcuate inner line and an arcuate outer line located adjacent to the inner line on the outer side in the radial direction of the inner line, Let the number of the laser irradiation modified portions arranged on the inner line and the outer line be N, the center-to-center distance between the laser irradiation modified portions on the inner line be A, the radius of the inner line be r, the radius difference between the inner line and the outer line be α, and the center-to-center distance between the adjacent laser irradiation modified portions arranged between the inner line and the outer line be β. Then, α ≦ β ≦ [({(αAN / r) ２ + α ２} １／２ − α]) / 3], and the workpiece is characterized by satisfying this relationship.

15. The workpiece according to any one of claims 9, 10, 11, and 14, wherein the workpiece is a container.

16. The workpiece according to claim 15, wherein in a state where a content is accommodated in the container, a visibility value represented by the following formula of an image pattern including the laser irradiation modified portions formed on the plurality of lines is 3 or more. Visibility value = 0.195 · L ＊ ０ · {1 - exp( - 0.193 · ΔL ＊ )} However, in the above formula, L ＊ ０ is the brightness of the image pattern, and ΔL ＊ represents the difference between the brightness of the image pattern and the brightness of the portion other than the image pattern.

17. A laser irradiation method in which laser light is scanned along a first line based on coordinate data of an image pattern to irradiate an object with the laser light, A laser irradiation method, characterized by deflecting the laser beam so as to irradiate the laser beam beside the first line while irradiating the laser beam along the first line.

Images