JP2006227261A - Platemaking apparatus for printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a platemaking apparatus for a printing plate, the apparatus which varies a beam diameter at an extremely low cost. <P>SOLUTION: When a movable mirror 81 is placed at a deviation position, a laser beam exiting from a laser light source 14 toward an objective lens 46 and modulated by an AOM (acoustooptic modulator) 41, is reflected on a reflecting surface 81a of the movable mirror 81 to be deflected. After the laser beam is reflected on reflecting surfaces 82a, 82b of a fixed mirror 82, the beam is reflected on the reflecting surface 81b of the movable mirror 81 and again returns in the optical path from the laser light source 14 to the objective lens 46. On the other hand, when the movable mirror is placed at a retreating position, the laser beam exiting from the laser light source 14 toward the objective lens 46 and modulated by the AOM 41 directly, enters the objective lens 46. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for making a printing plate for making a printing plate such as a relief printing plate such as a flexographic printing plate or an intaglio printing plate such as a gravure plate.

Conventionally, for example, a laser engraving machine described in Patent Document 1 is known as such a plate making apparatus. This laser engraving machine scans a recording material with a laser beam emitted from a laser light source to engrave the surface of the recording material to make a relief printing plate. The laser light source and the laser light source A modulator for modulating the laser beam, a recording drum that rotates with a recording material mounted on the outer periphery thereof, and a structure that is movable in a direction parallel to the axis of the recording drum. And a recording head that irradiates a recording material mounted on the unit with a laser beam emitted from a laser light source.
In such a plate making apparatus, the main scanning speed of the laser beam, that is, the rotational speed of the recording drum is set to the maximum required based on the power of the laser light source and the sensitivity of the recording material. The engraving depth is set to a value that can be obtained. In the engraving area shallower than the maximum engraving depth, engraving is executed in a state where the power of the laser beam irradiated to the recording material is reduced.

  At this time, the engraving of the recording material by the laser beam requires a relatively large energy, so that there is a problem that it takes a relatively long time to make the printing plate.

  For this reason, the present applicant uses a laser beam having a first beam diameter to sculpt by irradiating a recording material at a first pixel pitch, and then performs a second different from the first beam diameter. A printing plate making apparatus that uses a laser beam having a beam diameter and performs engraving by irradiating a recording material at a second pixel pitch different from the first pixel pitch has been proposed (Japanese Patent Application No. 2004-286175, Japanese Patent Application No. 2004-357586). According to such a plate making apparatus, it is possible to shorten the plate making time by using the laser beam efficiently.

  By the way, the above-described printing plate making apparatus needs to include a beam diameter changing mechanism for changing the beam diameter of the laser beam emitted from the laser light source. As such a beam diameter changing mechanism, a beam diameter changing mechanism is used in which a plurality of beam expanders comprising a pair of lenses are used, and the beam diameter of the laser beam is changed by selectively using the beam expander. can do. However, a beam expander composed of a pair of lenses is expensive, and a beam diameter changing mechanism using a plurality of beam expanders becomes more expensive.

  The present invention has been made to solve the above-mentioned problems. After engraving by irradiating a recording material at a first pixel pitch using a laser beam having a first beam diameter, the first When engraving by using a laser beam having a second beam diameter different from the beam diameter and irradiating the recording material at a second pixel pitch different from the first pixel pitch, the beam diameter is extremely low cost. It is an object of the present invention to provide a printing plate making apparatus capable of changing the above.

  According to the first aspect of the present invention, after engraving by irradiating a recording material with a first pixel pitch using a laser beam having a first beam diameter, a second beam diameter different from the first beam diameter is used. A printing plate making apparatus for engraving by irradiating a recording material at a second pixel pitch different from the first pixel pitch using a laser beam having a beam diameter of: a laser light source; and the laser light source A beam diameter changing mechanism that changes a beam diameter of the laser beam emitted from the laser beam, and the beam diameter changing mechanism changes a beam diameter of the laser beam by changing an optical path length from the laser light source to the recording material. It is characterized by doing.

  According to a second aspect of the present invention, in the first aspect of the invention, the beam diameter changing mechanism includes a fixed mirror, a deflection position in an optical path from the laser light source to the recording material, and a retreat separated from the optical path. A movable mirror that is movable between positions, and by disposing the movable mirror at a deflection position, the laser beam emitted from the laser light source toward the recording material is deflected toward the fixed mirror. Thereafter, the laser beam from the moving mirror is returned again to the optical path from the laser light source to the recording material by the fixed mirror.

  According to a third aspect of the present invention, after engraving by irradiating a recording material with a first pixel pitch using a laser beam having a first beam diameter, a second beam diameter different from the first beam diameter is used. A printing plate making apparatus for engraving by irradiating a recording material at a second pixel pitch different from the first pixel pitch using a laser beam having a beam diameter of: a laser light source; and the laser light source A beam diameter changing mechanism for changing the beam diameter of the laser beam irradiated from the above, and an objective lens having a positive power for condensing the laser beam whose beam diameter has been changed by the beam diameter changing mechanism on the recording material And the beam diameter changing mechanism changes the beam diameter of the laser beam by changing an optical path length from the laser light source to the objective lens.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the beam diameter changing mechanism includes a fixed mirror, a deflection position in an optical path from the laser light source to the objective lens, and a retreat separated from the optical path. A movable mirror that is movable between positions, and by disposing the movable mirror at a deflection position, the laser beam emitted from the laser light source toward the objective lens is deflected toward the fixed mirror. After that, the fixed mirror returns the laser beam from the moving mirror again to the optical path from the laser light source to the objective lens.

  According to a fifth aspect of the present invention, in the invention of the fourth aspect, a beam diameter of a laser beam irradiated to a recording material when the movable mirror is arranged at the deflection position is such that the movable mirror is moved to the retracted position. Smaller than the beam diameter of the laser beam applied to the recording material when the recording material is disposed.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, a modulator for modulating a laser beam emitted from the laser light source is disposed so as to be movable in synchronization with the movable mirror, and the movable mirror is provided. Is placed at the deflection position, the laser beam emitted from the laser light source is incident on the moving mirror via the modulator, and is emitted from the laser light source when the moving mirror is arranged at the retracted position. The laser beam is incident on the objective lens without passing through the modulator, and when the moving mirror is placed at the deflection position, the laser beam is modulated by the modulator, and the moving mirror is placed at the retracted position. When done, the laser beam is modulated by the laser light source itself.

  According to a seventh aspect of the present invention, in the fifth aspect of the present invention, when the movable mirror is disposed at the deflection position, a laser beam emitted from the laser light source toward the objective lens is deflected. After that, a modulator for modulating the laser beam emitted from the laser light source is disposed again in the optical path from the laser light source to the optical path from the laser light source to the objective lens. When arranged at the deflection position, the modulator modulates the laser beam, and when the moving mirror is arranged at the retracted position, the laser light source itself modulates the laser beam.

  The invention according to claim 8 is the invention according to claim 4, wherein a beam diameter of a laser beam applied to the recording material when the moving mirror is arranged at the deflection position is such that the moving mirror is moved to the retracted position. Larger than the beam diameter of the laser beam applied to the recording material when the recording material is disposed.

  According to the inventions described in claims 1 to 5 and claim 8, it is possible to change the beam diameter at an extremely low cost.

  According to the sixth and seventh aspects of the invention, when the moving mirror is arranged at the deflection position, precise engraving is performed with a laser beam having a small beam diameter while performing high-speed modulation by the modulator, and the moving mirror is When placed in the retracted position, it is possible to efficiently engrave by modulating a laser beam having a larger beam diameter on the laser light source itself without using a modulator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an outline of a laser engraving machine which is a printing plate making apparatus according to the present invention.

  This laser engraving machine includes a recording drum 11 on which a flexo direct photosensitive material (hereinafter referred to as “flexo-sensitive material”) 10 as a recording material for a relief printing plate is mounted on the outer periphery thereof, and an axis of the recording drum 11 The recording head 12 is configured to be movable in a direction parallel to the head, a personal computer 13 serving as an input / output unit and a display unit, a laser light source 14 formed of a gas laser, and a control unit 15 that controls the entire apparatus.

  The recording drum 11 is connected to a rotary motor 21 and rotates around a shaft 22. The rotary motor 21 is connected to a motor driver 23. The motor driver 23 receives a rotational speed command from the control unit 15 and controls the rotation of the rotary motor 21. The rotational speed of the rotary motor 21 and the rotational angular position of the recording drum 11 rotated by the rotary motor 21 are measured by the encoder 24, and the information is transmitted to the control unit 15.

  The recording head 12 can be moved in a direction parallel to the axis of the recording drum 11 by being guided by guide means (not shown). The recording head 12 is installed in parallel with the axis of the recording drum 11, is driven by a ball screw 32 that is rotated by a moving motor 31, and reciprocates in a direction parallel to the axis of the recording drum 11. This moving motor 31 is connected to a motor driver 33. The motor driver 33 receives a rotation speed command from the control unit 15 and controls the rotation of the moving motor 31. The rotational speed of the moving motor 31 and the position of the recording head 12 moved by the moving motor 31 are measured by the encoder 34, and the information is transmitted to the control unit 15.

  An AOM (acousto-optic modulator) 41 as a modulator is disposed at the subsequent stage of the laser light source 14. The AOM 41 receives a control signal from the control unit 15 via the AOM driver 42. After the laser beam emitted from the laser light source 14 is modulated by the AOM 41, the beam diameter changing mechanism 51, the pair of folding mirrors 43 and 44 fixed to the apparatus, the folding mirror 45 fixed to the recording head 12, and the objective lens The flexo sensitive material 10 mounted on the outer peripheral portion of the recording head 12 is irradiated through 46.

  The beam diameter changing mechanism 51 is for changing the beam diameter of the laser beam applied to the flexographic material 10 by changing the beam diameter of the laser beam emitted from the laser light source 14. The beam diameter changing mechanism 51 will be described in detail later.

  In this laser engraving machine, the laser beam emitted from the laser light source 14 is modulated by the AOM 41, the beam diameter is changed by the beam diameter changing mechanism 51, and then passed through the folding mirrors 43, 44, 45 and the objective lens 46. And is emitted from the recording head 12. Then, in a state where the recording drum 11 having the flexo sensitive material 10 mounted on the outer peripheral portion thereof is rotated, the recording head 12 is moved in a direction parallel to the axis of the recording drum 11, so that the laser beam is placed on the flexo sensitive material 10. Are engraved and a relief is formed on the flexo sensitive material 10.

  At this time, in this laser engraving machine, the precision engraving beam L1 having a small beam diameter is used, the flexo sensitive material 10 is irradiated with the precision engraving pixel pitch pp, and engraving is performed up to the maximum depth dp with the precision engraving beam L1. Using the precision engraving process to be performed and the coarse beam L2 having a large beam diameter, the flexo sensitive material 10 is irradiated with the coarse engraving pixel pitch pc (equal to the halftone dot pitch) larger than the precise engraving pixel pitch pp, and the relief depth d Engraving is performed by two processes including a rough engraving process for engraving until the plate making time is shortened.

  FIG. 2 is an explanatory view schematically showing the shape of the surface of the flexo sensitive material 10 after engraving using this laser engraving machine. 2A is a plan view of seven reliefs formed in the main scanning direction on the flexo sensitive material 10, and FIG. 2B is a cross-sectional view thereof. In this figure, for the convenience of explanation, seven reliefs having a halftone dot area ratio of 0%, 1%, 1%, 2%, 2%, 0%, and 0% are formed from the left side of the figure. Shows the case.

  As shown in this figure, in the precision engraving process, a precision engraving beam L1 having a small beam diameter is used. Then, this precision engraving beam L1 is irradiated onto the flexo sensitive material 10 at a precise engraving pixel pitch pp, and the flexo sensitive material 10 is engraved from its surface to the maximum depth dp.

  This maximum depth dp coincides with the engraving depth of the boundary portion of these reliefs when the reliefs having very small halftone dot area ratios are adjacent to each other. When the maximum depth dp is smaller than this, it is impossible to express fine halftone dots satisfactorily. Although it is possible to make the maximum depth dp larger than this, the engraving efficiency deteriorates in this case. In this embodiment, when the reliefs having a halftone dot area ratio of 1% are adjacent to each other, the engraving depth of the boundary portion between these reliefs is set to the maximum depth dp.

  In this precision engraving process, engraving of the portion that directly affects the shape of the halftone dots from the surface of the flexo sensitive material 10 to the maximum depth dp is executed. Therefore, a relatively small precision engraving pixel pitch pp is adopted as the engraving pixel pitch at this time, and engraving is performed in minute units as schematically shown in FIG. As the beam diameter of the precision engraving beam L1 at this time, a small beam diameter capable of engraving with the precision engraving pixel pitch pp is employed.

  After the precision engraving process, a rough engraving process is performed. In this rough engraving process, a rough engraving beam L2 having a large beam diameter is used. Then, the rough engraving beam L2 is irradiated onto the flexo sensitive material 10 at the coarse engraving pixel pitch pc, and the flexo sensitive material 10 is engraved from the maximum depth dp to the relief depth d. Thus, since the area engraved in the precision engraving process is engraved again in the coarse engraving process, the relief depth d from the surface of the flexographic photosensitive material 10 after execution of the coarse engraving process is larger than the maximum depth dp by the precision engraving. large. In this rough engraving process, the engraving of the portion that does not directly affect the shape of the halftone dots is performed, so that the coarse engraving pixel pitch pc can be increased.

  As the coarse engraving pixel pitch pc at this time, the halftone pitch w can be adopted. The rough engraving pixel pitch pc can be arbitrarily set in the range of the above-described precision engraving pixel pitch pp and the halftone dot pitch w. However, the closer this is to the halftone pitch w, the better the engraving efficiency.

  FIG. 3 is an explanatory view showing the relief shape formed on the flexo sensitive material 10 more accurately.

  As parameters representing the relief shape, there are a relief angle θ, a relief depth d, a step dt for forming the top hat portion T, and a plateau wt. The relief angle θ is a value common to all reliefs. The relief depth d is the engraving depth in an area where the halftone dot percentage is zero. Step dt is provided to improve the dot gain, and the plateau wt is provided to increase the mechanical strength of the relief. However, when the top hat portion T itself is not formed, The value of the plateau wt is zero. In the above description, the case where step dt and plateau wt are omitted is described.

  When the relief shape shown in FIG. 3 is adopted, the above-described maximum depth dp can be calculated by the following equation (1).

dp = (2 ^1/2 · pc / 2−wt) tan (θπ / 180) + dt (1)
When the top hat portion T itself is not formed, zero may be substituted for step dt and plateau wt.

  Next, the plate making process of the flexographic printing plate which engraves the flexographic sensitive material 10 using this laser engraving machine will be described. 4 and 5 are flowcharts showing the plate making process.

  When making a flexographic printing plate, the operator first specifies the relief shape and the number of screen lines (step S1). The relief shape and the number of screen lines are input from the personal computer 13 and transmitted to the control unit 15.

  Next, the halftone dot pitch w is determined from the screen line number designated in advance (step S2). This halftone pitch w is the reciprocal of the number of screen lines.

  Next, the maximum depth dp in the precision engraving process is calculated (step S3). This calculation is performed using the above-described equation (1).

  Next, the operator designates the resolution (step S4). This resolution is selected from, for example, 1200 dpi, 2400 dpi, and 4000 dpi.

  Next, the precise engraving pixel pitch pp is determined from the designated resolution (step S5). The beam spot size of the precision engraving beam L1 is adjusted so that the precision engraving pixel pitch pp and the width of the precision engraving beam L1 in the sub-scanning direction substantially coincide with each other.

  Next, the main scanning speed v1 during precision engraving is determined (step S6). The main scanning speed v1 is determined by the following equation (2) based on the precision engraving pixel pitch pp, the maximum depth dp, the engraving sensitivity Y of the flexographic photosensitive material 10, and the power P of the laser light source 14. .

pp · dp · v1 · Y = P (2)
Here, the engraving sensitivity is a value obtained by dividing the energy E of the laser beam by the volume V engraved by the laser beam. The energy E of the laser beam is a value obtained by multiplying the power of the laser light source 14 and the irradiation time.

  FIG. 6 is a graph showing the relationship between the engraving sensitivity Y and the S / V ratio obtained by dividing the surface area of the recess engraved by the laser beam by the volume.

  In this graph, the horizontal axis represents the S / V ratio obtained by dividing the surface area of the recess engraved by the laser beam by the volume, and the vertical axis represents the engraving sensitivity obtained experimentally. As is apparent from this graph, the value of the engraving sensitivity is large (that is, the sensitivity is poor) almost in proportion to S / V. This is presumably because the greater the S / V ratio, the greater the ratio of the heat dissipation to the volume, and the applied energy is not effectively used for engraving. For this reason, in order to execute engraving efficiently, it is effective to use a region having a small S / V ratio.

  In the graph shown in FIG. 6, when the engraving sensitivity is Y and the S / V ratio is X, the following approximate expression (3) is established.

Y = 3.221748 + 0.0577759X (3)
Next, the precise engraving sub-scanning speed s1 corresponding to the precise engraving pixel pitch pp is determined (step S7). The precision engraving sub-scanning speed s1 is set to a speed at which the recording head 12 can move in the sub-scanning direction by the precision engraving pixel pitch pp while the recording drum 11 rotates once.

  Note that the sub-scan feed of the recording head 12 may be a continuous feed in which the recording head 12 is continuously fed in synchronization with the rotation of the recording drum 11, or a step of moving the recording head 11 in the sub-scanning direction by a predetermined amount each time the recording drum 11 rotates once. Either feed or any may be used.

  4 and 5 again, next, engraving depth dc in the rough engraving process is calculated (step S8). The engraving depth dc is a value obtained by subtracting the maximum depth dp at the time of precision engraving from the relief depth d.

  Next, the coarse engraving pixel pitch pc for executing the coarse engraving is determined (step S9). The rough engraving pixel pitch pc coincides with the halftone dot pitch w as described above.

  Next, the main scanning speed v2 at the time of rough engraving is determined (step S10). The main scanning speed v2 is based on the coarse engraving pixel pitch pc, the engraving depth dc, the engraving sensitivity Y of the flexo sensitive material 10, and the power P of the laser light source 14 as in the case of the main scanning speed v1. It is determined by the following equation (4).

pc · dc · v2 · Y = P (4)
Next, a coarse engraving sub-scanning speed s2 corresponding to the coarse engraving pixel pitch pc is determined (step S11). The coarse engraving sub-scanning speed s2 is set to a speed at which the recording head 12 can move in the sub-scanning direction by the coarse engraving pixel pitch pc while the recording drum 11 rotates once. The sub-scan feed of the recording head 12 may be a continuous feed in which the recording head 12 is continuously fed in synchronism with the rotation of the recording drum 11, or a step of moving the recording head 12 in the sub-scanning direction by a predetermined amount every time the recording drum 11 rotates once. Either feed or any may be used. However, when the recording head 12 is sub-scan fed by continuous feeding in the rough engraving process, the inclination angle of the scanning line with respect to the axis of the recording drum 11 is increased, which may affect the recorded image. For this reason, in the rough engraving process, it is desirable to feed the recording head 12 by sub-scanning by step feeding.

  In this embodiment, the precision engraving process and the coarse engraving process are performed separately. For this reason, it is possible to selectively execute the optimum sub-scan feed method according to the characteristics of each engraving process.

  Furthermore, the precision engraving process and the rough engraving process are performed separately, and the sub-scan feed speed in each engraving process can be set to an arbitrary value, so that the engraving scanning in each engraving process is the same scan There is no need to do it along the line. For this reason, engraving scanning can be executed along a scanning line that faithfully matches the recording resolution required in each engraving process.

  Next, relief data indicating the relief shape to be engraved is created from the image data to be formed on the flexo sensitive material 10 (step S12). The basic image data is transferred to the control unit 15 via the personal computer 13 online or offline. Relief data is created based on this image data. This relief data is data obtained by superimposing the data of each relief, and in a region overlapping each other, priority is given to data having a shallower depth.

  FIG. 7 is an explanatory diagram schematically showing a method for creating relief data.

  This figure shows a state in which the relief 1 and the relief 2 are formed. The relief 1 side relief data is used for the area on the relief 1 side from the point where the inclined part of the relief 1 and the relief 2 abuts, and the area on the relief 2 side from the point where the inclined part of the relief 1 and the relief 2 abuts is used. Two relief data are used.

  Next, multi-value data for controlling the output of the precision engraving laser light source 14 is created from the relief data (step S13). This multi-value data is multi-value data such that engraving up to the maximum depth dp is executed by the laser beam emitted from the laser light source 14 in a region where the dot area ratio is 0%. This multi-value data is created as data that can form a relief slope in a staircase pattern as shown in FIG. 2C in a region where the dot area ratio is 0% to 100%.

  Next, multivalue data for controlling the output of the laser light source 14 for rough engraving is created from the relief data (step S14). This multivalued data is finally obtained by engraving a region having a halftone dot area ratio of 0% with the engraving depth dc using a laser beam emitted from the laser light source 14 in consideration of the relief angle θ. This is multi-value data such that engraving with a relief depth d is executed.

  Next, under the control of the control unit 15, the laser beam that has passed through the beam diameter changing mechanism 51 is made to have a required beam diameter as the precision engraving beam L 1. (Step S15). Thereby, the beam spot diameter of the precision engraving beam L1 is adjusted so that the precision engraving pixel pitch pp and the width of the precision engraving beam L1 in the sub-scanning direction substantially coincide with each other.

  Then, precision engraving is executed (step S16). At this time, the control unit 15 controls the motor drivers 23 and 33 so that the precision engraving beam L1 scans the flexo sensitive material 10 at the main scanning speed v1 and the sub-scanning speed S1 described above. The rotational speed and the moving speed of the recording head 12 are controlled. Further, when the control unit 15 controls the AOM driver 42, engraving such as an inclined surface up to the maximum depth dp is executed.

  Next, under the control of the control unit 15, the laser beam that has passed through the beam diameter changing mechanism 51 has a beam diameter necessary for the rough engraving beam L2 (step S17). Thereby, the beam spot diameter of the coarse engraving beam L2 is adjusted so that the coarse engraving pixel pitch pc and the width of the coarse engraving beam L2 in the sub-scanning direction substantially coincide with each other.

  Then, rough engraving is executed (step S18). At this time, the control unit 15 controls the motor drivers 23 and 33 so that the rough engraving beam L2 scans the flexo sensitive material 10 at the main scanning speed v2 and the sub-scanning speed S2 described above. The rotational speed and the moving speed of the recording head 12 are controlled. Further, when the control unit 15 controls the AOM driver 42, engraving such as an inclined surface from the maximum depth dp to the relief depth d is executed. Through the above steps, the relief engraving as shown in FIG. 2 is completed.

  In the above description, the rough engraving process is performed after the precision engraving process. However, the precision engraving process may be performed after the rough engraving process.

  Next, the configuration of the beam diameter changing mechanism 51 described above will be described. 8 and 9 are schematic views of the beam diameter changing mechanism 51 according to the first embodiment of the present invention.

  The beam diameter conversion mechanism 51 includes a moving mirror 81 fixed to the moving member 80 and a fixed mirror 82 fixed to the apparatus main body. The moving member 80 reciprocates between the deflection position shown in FIG. 8 and the retracted position shown in FIG. 9 by driving the movement motor 56 shown in FIG. The moving motor 56 is connected to the control unit 15 via the motor driver 57 shown in FIG. 1 and rotates under the control of the control unit 15.

  As shown in FIG. 8, when the moving mirror 81 is arranged at the deflection position, the laser beam emitted from the laser light source 14 toward the objective lens 46 and modulated by the AOM 41 is reflected on the reflecting surface 81a of the moving mirror 81. Reflected by and deflected. The laser beam is reflected by the reflecting surfaces 82 a and 82 b of the fixed mirror 82, then reflected by the reflecting surface 81 b of the moving mirror 81, and returns to the optical path from the laser light source 14 toward the objective lens 46 again. .

  On the other hand, as shown in FIG. 9, when the movable mirror 81 is disposed at the retracted position, the laser beam emitted from the laser light source 14 toward the objective lens 46 and modulated by the AOM 41 is directly applied to the objective lens 46. Incident.

  8 and 9, for convenience of explanation, the moving mirror 81 and the fixed mirror 82 are shown close to each other. However, in actuality, the moving mirror 81 and the fixed mirror 82 are arranged at a distance from each other. . Therefore, the optical path length of the laser beam from the laser light source 14 to the objective lens 46 when the moving mirror 81 is arranged at the deflection position is the same as the optical path length from the laser light source 14 to the objective lens 46 when the moving mirror 81 is arranged at the deflection position. It is about 4 times the optical path length of the laser beam.

  On the other hand, the spread angle of the laser beam emitted from the laser light source 14 is, for example, about 4 milliradians in the case of a gas laser. For this reason, the beam diameter of the laser beam incident on the objective lens 46 when the moving mirror 81 is arranged at the deflection position is the beam diameter of the laser beam incident on the objective lens 46 when the moving mirror 81 is arranged at the retracted position. It becomes larger than the diameter.

  The objective lens 46 described above is composed of a convex lens having positive power. In this case, the laser beam can be narrowed so that the beam diameter of the laser beam becomes smaller as the NA (numerical aperture) becomes larger. In other words, the larger the beam diameter of the laser beam incident on the objective lens 46, the smaller the beam diameter of the laser beam irradiated on the flexo sensitive material 10 mounted on the outer periphery of the recording drum 11.

  For example, the beam diameter of the laser beam emitted from the laser light source 14 is 4 mm, the optical path length from the laser light source 14 to the objective lens 46 when the moving mirror 81 is arranged at the deflection position is 6.5 m, and the moving mirror 81 is retracted. When the optical path length from the laser light source 14 to the objective lens 46 is 1.5 m, the beam diameter of the laser beam incident on the objective lens 46 when the moving mirror 81 is arranged at the deflection position is 30 mm, When the moving mirror is disposed at the retracted position, the beam diameter of the laser beam incident on the objective lens 46 is 10 mm, and when the moving mirror 81 is disposed at the deflection position by appropriately setting the magnification of the objective lens 46. The beam diameter of the laser beam applied to the flexographic photosensitive material 10 is 25 μm, and the flexo-sensitive material 10 has a flexible beam when the movable mirror 81 is disposed at the retracted position. The beam diameter of the laser beam irradiated to the Soviet sensitive material 10 becomes 100 [mu] m.

  As described above, in this embodiment, the beam diameter of the laser beam incident on the objective lens 46 can be changed by moving the movable mirror 81 between the deflection position and the retracted position. It becomes possible to change the beam diameter of the laser beam irradiated to the photosensitive material 10.

  Next, another embodiment of the beam diameter changing mechanism 51 described above will be described. 10 and 11 are schematic views of a beam diameter changing mechanism 51 according to the second embodiment of the present invention.

  In the beam diameter conversion mechanism 51 according to the second embodiment, the moving mirror 81 is fixed to the moving member 88. The AOM 41 is also fixed to the fixing member, and the AOM 41 and the moving mirror 81 are configured to be movable in synchronization. The moving member 88 reciprocates between the deflection position shown in FIG. 10 and the retracted position shown in FIG. 11 by driving the movement motor 56 shown in FIG. Further, the control signal sent from the control unit 15 shown in FIG. 1 to the AOM driver 42 is also sent to the laser light source 14, and the laser light source 14 itself can modulate the laser beam. . Other configurations are the same as those of the first embodiment described above.

  In the beam diameter conversion mechanism 51 according to the second embodiment, when the moving mirror 81 is arranged at the deflection position shown in FIG. 10, the laser beam emitted from the laser light source 14 is transmitted through the AOM 41 to the moving mirror 81. Incident on the reflecting surface 81a. On the other hand, when the movable mirror 81 is disposed at the retracted position shown in FIG. 11, the laser beam emitted from the laser light source 14 is directly incident on the objective lens 46 without passing through the AOM 41.

  For example, the AOM 41 can perform high-speed modulation of about 1 MHz, but germanium used for the AOM 41 has a low laser beam transmittance, and the laser beam causes a loss of about several percent in the AOM 41. Therefore, if the laser beam is modulated by the laser light source 14 itself in the rough engraving process and engraving is performed by the AOM 41 in the precision engraving process, the laser beam can be used efficiently. For this reason, when the configuration according to the second embodiment is adopted, it is possible to shorten the plate making time while maintaining high plate making accuracy.

  Next, still another embodiment of the beam diameter changing mechanism 51 described above will be described. 12 and 13 are schematic views of a beam diameter changing mechanism 51 according to the third embodiment of the present invention.

  The beam diameter conversion mechanism 51 according to the third embodiment includes a pair of moving mirrors 84 and 87 fixed to the moving member 83 and a pair of fixed mirrors 85 and 86 fixed to the apparatus main body. The moving member 83 reciprocates between the deflection position shown in FIG. 12 and the retracted position shown in FIG. 13 by driving the movement motor 56 shown in FIG.

  As shown in FIG. 12, when the pair of moving mirrors 84 and 87 are disposed at the deflection position, the laser beam emitted from the laser light source 14 toward the objective lens 46 is moved to the moving mirror 84, the fixed mirror 85, The light is deflected by the fixed mirror 86 and the moving mirror 87, and returns to the optical path from the laser light source 14 toward the objective lens 46 again. Then, after the laser beam emitted from the laser light source 14 toward the objective lens 46 is deflected, it is again in the optical path until returning to the optical path from the laser light source 14 to the objective lens 46 (in this embodiment, An AOM 41 that modulates the laser beam emitted from the laser light source 14 is disposed at a position between the fixed mirror 85 and the fixed mirror 86.

  On the other hand, as shown in FIG. 13, when the pair of moving mirrors 84 and 87 are arranged at the retracted position, the laser beam emitted from the laser light source 14 toward the objective lens 46 does not pass through the AOM 41. Then, it enters the objective lens 46 as it is.

  Also in this embodiment, as in the case of the first and second embodiments described above, by moving the pair of moving mirrors 84 and 87 between the deflection position and the retracted position, the laser beam incident on the objective lens 46 is changed. The beam diameter can be changed, whereby the beam diameter of the laser beam applied to the flexographic photosensitive material 10 can be changed.

  Also in this embodiment, as in the case of the second embodiment described above, engraving is performed by modulating the laser beam with the laser light source 14 itself in the rough engraving process, and by the AOM 41 in the precision engraving process. By performing the above, it is possible to efficiently use the laser beam, and it is possible to shorten the plate making time while maintaining high plate making accuracy.

  In this embodiment, the optical path length changing means for changing the beam diameter changes the optical path of the laser beam emitted from the laser beam source 14 to either an optical path passing through the AOM 41 or an optical path not passing through this. Since it is also used as a means, the apparatus configuration can be simplified.

  In each of the above-described embodiments, a flexographic material, which is one of the relief printing plates, is used as a recording material. However, the present invention can also be applied to the case where a concave portion is formed by laser engraving on an intaglio printing plate such as a gravure plate.

  The means for changing the optical path length from the laser light source 41 to the objective lens 46 is not limited to those in the above-described embodiments, but particularly when the beam diameter changing mechanism 51 according to the first embodiment is used. Since the optical path length can be changed with few movable parts, there is an effect that the optical axis adjustment is easy.

  Further, in each of the above-described embodiments, the optical path length when executing rough engraving is set to be shorter than the optical path length when executing precise engraving, but the optical path length when executing rough engraving executes fine engraving. It may be set longer than the optical path length at the time. In this case, when the moving mirror 81 or the like is disposed in the optical path from the laser light source 14 to the objective mirror 46, the beam spot diameter emitted from the objective mirror 46 and imaged on the flexo sensitive material 10 becomes relatively large. On the other hand, when the moving mirror 81 or the like is arranged at a position separated from the optical path, the beam spot diameter emitted from the objective mirror 46 and imaged on the flexo sensitive material 10 becomes relatively small.

It is a block diagram which shows the outline | summary of a laser engraving machine. It is explanatory drawing which shows the shape of the flexo sensitive material 10 surface typically. It is explanatory drawing which shows a relief shape. It is a flowchart which shows a plate making process. It is a flowchart which shows a plate making process. It is a graph which shows the relationship between the engraving sensitivity Y and the S / V ratio of the recessed part processed with the laser beam. It is explanatory drawing which shows the production method of relief data typically. It is a schematic diagram of the beam diameter change mechanism 51 which concerns on 1st Embodiment of this invention. It is a schematic diagram of the beam diameter change mechanism 51 which concerns on 1st Embodiment of this invention. It is a schematic diagram of the beam diameter change mechanism 51 which concerns on 2nd Embodiment of this invention. It is a schematic diagram of the beam diameter change mechanism 51 which concerns on 2nd Embodiment of this invention. It is a schematic diagram of the beam diameter change mechanism 51 which concerns on 3rd Embodiment of this invention. It is a schematic diagram of the beam diameter change mechanism 51 which concerns on 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flexo sensitive material 11 Recording drum 12 Recording head 13 Personal computer 14 Laser light source 15 Control part 21 Rotating motor 23 Motor driver 24 Encoder 31 Moving motor 32 Ball screw 33 Motor driver 34 Encoder 41 AOM
42 AOM driver 46 Objective lens 51 Beam diameter changing mechanism 56 Moving mechanism 57 Motor driver 80 Moving member 81 Moving mirror 82 Fixed mirror 83 Moving member 84 Moving mirror 85 Fixed mirror 86 Moving mirror 87 Fixed mirror 88 Moving member L1 Precision engraving beam L2 Rough Engraving beam d Relief depth dp Maximum depth dc Engraving depth pp Precision engraving pixel pitch pc Coarse engraving pixel pitch

Claims (8)

After engraving by irradiating a recording material at a first pixel pitch using a laser beam having a first beam diameter, a laser beam having a second beam diameter different from the first beam diameter is used. A printing plate making apparatus for engraving by irradiating a recording material at a second pixel pitch different from the first pixel pitch,
A laser light source;
A beam diameter changing mechanism that changes the beam diameter of the laser beam emitted from the laser light source,
The plate making apparatus for a printing plate, wherein the beam diameter changing mechanism changes a beam diameter of a laser beam by changing an optical path length from the laser light source to the recording material. In the plate-making apparatus of the printing plate of Claim 1,
The beam diameter changing mechanism includes a fixed mirror, and a movable mirror that is movable between a deflection position in an optical path from the laser light source to the recording material and a retracted position separated from the optical path. By arranging at the deflection position, the laser beam emitted from the laser light source toward the recording material is deflected toward the fixed mirror, and then the laser beam from the moving mirror is again transmitted by the fixed mirror. A printing plate making apparatus for returning to a light path from a laser light source to the recording material. After engraving by irradiating a recording material at a first pixel pitch using a laser beam having a first beam diameter, a laser beam having a second beam diameter different from the first beam diameter is used. A printing plate making apparatus for engraving by irradiating a recording material at a second pixel pitch different from the first pixel pitch,
A laser light source;
A beam diameter changing mechanism for changing the beam diameter of the laser beam emitted from the laser light source;
An objective lens having a positive power for condensing the laser beam having a beam diameter changed by the beam diameter changing mechanism on the recording material;
The plate making apparatus for a printing plate, wherein the beam diameter changing mechanism changes a beam diameter of a laser beam by changing an optical path length from the laser light source to the objective lens. In the plate-making apparatus of the printing plate of Claim 3,
The beam diameter changing mechanism includes a fixed mirror, and a movable mirror movable between a deflection position in an optical path from the laser light source to the objective lens and a retracted position separated from the optical path. By disposing the laser beam emitted from the laser light source toward the objective lens by deflecting the laser beam toward the fixed mirror, the laser beam from the moving mirror is again transmitted by the fixed mirror. A plate making apparatus for a printing plate that is returned in an optical path from a laser light source to the objective lens. In the plate-making apparatus of the printing plate of Claim 4,
The beam diameter of the laser beam applied to the recording material when the moving mirror is arranged at the deflection position is smaller than the beam diameter of the laser beam applied to the recording material when the moving mirror is arranged at the retracted position. Printing plate making equipment. In the plate-making apparatus of the printing plate of Claim 5,
A modulator that modulates the laser beam emitted from the laser light source is arranged to be movable in synchronization with the moving mirror, and the laser beam emitted from the laser light source when the moving mirror is arranged at the deflection position Is incident on the moving mirror via the modulator, and when the moving mirror is disposed at the retracted position, the laser beam emitted from the laser light source is incident on the objective lens without passing through the modulator. ,
A printing plate making apparatus that modulates a laser beam by the modulator when the moving mirror is arranged at the deflection position, and modulates a laser beam by the laser light source itself when the moving mirror is arranged at the retracted position. In the plate-making apparatus of the printing plate of Claim 5,
When the moving mirror is disposed at the deflection position, the laser beam emitted from the laser light source toward the objective lens is deflected and then returned to the optical path from the laser light source to the objective lens again. A modulator for modulating the laser beam emitted from the laser light source in the optical path until
A printing plate making apparatus that modulates a laser beam by the modulator when the moving mirror is arranged at the deflection position, and modulates a laser beam by the laser light source itself when the moving mirror is arranged at the retracted position. In the plate-making apparatus of the printing plate of Claim 4,
The beam diameter of the laser beam applied to the recording material when the moving mirror is arranged at the deflection position is larger than the beam diameter of the laser beam applied to the recording material when the moving mirror is arranged at the retracted position. Printing plate making equipment.

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