JP5220794B2 - Multi-beam exposure scanning method and apparatus and printing plate manufacturing method - Google Patents

Description

  The present invention relates to a multi-beam exposure scanning method and apparatus and a printing plate manufacturing method, and more particularly to a multi-beam exposure technique suitable for manufacturing a printing plate such as a flexographic plate and a printing plate manufacturing technique to which the multi-beam exposure technique is applied.

  Conventionally, a technique for engraving a concave shape on the surface of a printing plate using a multi-beam head capable of simultaneously irradiating a plurality of laser beams has been disclosed (Patent Document 1). When engraving a plate by such multi-beam exposure, it is very difficult to stably form fine shapes such as small dots and fine lines due to the influence of heat of adjacent beams.

  In response to such a problem, Patent Document 1 proposes a configuration in which so-called interlaced exposure is performed in order to reduce mutual thermal influence between adjacent beam spots in a beam spot array formed on the surface of a plate material. Yes. That is, in Patent Document 1, a plurality of laser spots are formed on the surface of the plate material at intervals of at least twice the engraving pitch corresponding to the engraving density, and scanning lines formed at a single exposure scan are spaced apart from each other. A method is employed in which scanning lines between lines are exposed in the second and subsequent scans.

JP 09-85927 A

  In flexographic printing, the increase in dot diameter on the printed surface caused by the shape distortion of convex small dots due to printing pressure is particularly significant, and the resulting highlight image quality is a problem. One way to alleviate this problem is to sharpen the edge shape of convex small points. However, it is very difficult to stably sharpen the edge shape of the small convex point by multi-beam exposure.

  FIG. 17 is a schematic diagram showing engraving of a small convex point by 1ch exposure. As shown in the figure, when the flat surface before engraving is exposed and carved, a part of the large amount of heat generated there flows along the uncarved surface. For example, when a large amount of light power is irradiated to the vicinity of the surface of a small dot, heat flows into the surface of the small point at one time before and after that, so a heat pool is created near the surface of the small dot, resulting in damage (melting) to the surface. ), And the edge shape of the convex small point is rounded.

  Therefore, a large amount of optical power cannot be irradiated near the edge. Such a problem occurs even when the interlace exposure described in Patent Document 1 is used.

  SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a multi-beam exposure scanning method and apparatus for forming a stable and sharp convex dot shape in multi-beam exposure, and a printing plate manufacturing method using the same. The purpose is to provide.

  To achieve the above object, the multi-beam exposure scanning method according to claim 1, wherein a plurality of light beams are simultaneously irradiated, and the same scanning line is exposed a plurality of times to engrave the surface of the recording medium. In the method, at least four scans are performed on a first region which is a target planar shape to be left on the exposure surface of the recording medium and is a region around a rectangular planar shape having four sides, and each scan is performed once. In scanning, at least an area adjacent to one of the four sides is exposed, and the one area is sequentially changed to engrave all the first areas.

  According to the first aspect of the present invention, at least four scans are performed with respect to the first area which is the target planar shape to be left on the exposure surface of the recording medium and is a peripheral area of a rectangular planar shape having four sides. In each scan, only the area adjacent to one of the four sides of the first area is exposed, and the one area is sequentially changed so that the first area is entirely engraved. Therefore, a region adjacent to each side of the target planar shape can be exposed one by one, and a steep convex dot shape can be formed.

  According to a second aspect of the present invention, in the multi-beam exposure scanning method according to the first aspect, in the four times of scanning, the second region that is a region around the first region is exposed four times. It is characterized by.

  Thereby, a convex small point can be made into a steep shape.

  The multi-beam exposure scanning method according to claim 1 or 2, wherein the first region is a region of one or two pixels around the target planar shape. .

  Thereby, a convex small dot shape can be formed appropriately.

  In order to achieve the object, the multi-beam exposure scanning apparatus according to claim 4 irradiates a plurality of light beams simultaneously and sculpts the surface of the recording medium by exposing the same scanning line a plurality of times. In the apparatus, an exposure head having a plurality of exits from which the light beam is emitted, main scanning means for main scanning the exposure head relative to the recording medium in a main scanning direction, and exposure of the recording medium At least four scans are performed on a first region that is a target planar shape to be left on the surface and is a region around a rectangular planar shape having four sides, and at least one of the four sides is scanned in each scan. Exposure scanning control means is provided for exposing an area adjacent to one side and engraving all of the first area by sequentially changing the one side.

  According to the fourth aspect of the present invention, at least four scans are performed on the first region which is the target planar shape to be left on the exposure surface of the recording medium and is a region around the rectangular planar shape having four sides. In each of the scans, the region adjacent to one side of the four sides is exposed and the one region is sequentially changed so that the first region is entirely engraved. A region adjacent to each side can be exposed one by one, and a steep convex small dot shape can be formed.

According to a fifth aspect of the present invention , in the multi-beam exposure scanning apparatus according to the fourth aspect, the exposure scanning control means is a second region that is a region around the first region in the at least four main scans. The area is exposed at least four times.

  Thereby, a convex small point can be made into a steep shape.

  6. The multi-beam exposure scanning apparatus according to claim 4, wherein the first region is a region of one or two pixels around the target planar shape. .

  Thereby, a convex small dot shape can be formed appropriately.

  7. The multi-beam exposure scanning apparatus according to claim 4, wherein the exposure head is relatively subordinate to the recording medium in a sub-scanning direction orthogonal to the main scanning direction. Subscanning means for scanning is provided, wherein the subscanning means subscans the exposure head by a predetermined amount after the main scanning means performs main scanning at least four times.

  Accordingly, four main scans can be performed on the first region, and the entire surface of the recording medium can be engraved.

  The multi-beam exposure scanning apparatus according to any one of claims 4 to 6, wherein the exposure head is relatively moved in a sub-scanning direction perpendicular to the main scanning direction with respect to the recording medium. A sub-scanning means for scanning, and assuming that the number of times the same scanning line is exposed is N (N is an integer of 4 or more) and the number of exit ports is T, the sub-scanning means The exposure head and the recording medium are sub-scanned at a constant speed so as to move relative to the main scan by a T / N scan line.

  Accordingly, four main scans can be performed on the first region, and the entire surface of the recording medium can be engraved.

As shown in claim 9, in the multi-beam exposure scanning apparatus according to any one of claims 4 to 8, the plurality of exit ports are arranged on a straight line having a predetermined angle with respect to the main scanning direction, The exposure scanning control means is a second ejection port adjacent to the first ejection port, and the first scanning port is not exposed at the second ejection port located upstream of the main scanning. Exposure is performed with a predetermined amount of light at one exit port, and exposure is performed with a light amount smaller than the predetermined amount of light at the first exit port when exposure is performed at the second exit port. .

  Thereby, even if there is an influence of heat on the main scanning line exposed previously, it can be appropriately engraved.

  In order to achieve the above object, the printing plate manufacturing method according to claim 10 engraves the surface of the plate material corresponding to the recording medium by the multi-beam exposure scanning method according to any one of claims 1 to 3. To obtain a printing plate.

  According to the tenth aspect of the present invention, it is possible to obtain a printing plate in which a small convex dot shape that is stable and steep is formed.

  According to the present invention, it is possible to form a convex small dot shape that is stable and steep in multi-beam exposure.

1 is a configuration diagram of a plate making apparatus to which a multi-beam exposure scanning apparatus according to an embodiment of the present invention is applied. Configuration diagram of optical fiber array unit arranged in exposure head Enlarged view of the light output part of the optical fiber array part Schematic diagram of the imaging optical system in the optical fiber array section Explanatory drawing which shows the relationship between the example of arrangement | positioning of the optical fiber in an optical fiber array part, and a scanning line The top view which shows the outline | summary of the scanning exposure system in the plate-making apparatus of this example Block diagram showing the configuration of the control system in the plate making apparatus of this example Diagram showing the engraving of the plate material The figure which shows the upper surface and cross section of the plate material after the engraving by this embodiment The graph which shows the power control example of the light beam by this embodiment The figure which shows the relationship between a non-exposure area and the convex small point actually formed Graph showing an example of power control for interlaced exposure Schematic diagram showing a modification of the optical fiber array light source The figure shown about the engraving of the plate material by the optical fiber array light source of FIG. Graph showing an example of power control of a light beam by the optical fiber array light source of FIG. Explanatory drawing showing an overview of the flexographic plate making process Schematic showing the sculpture of convex small dots

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Configuration example of multi-beam exposure scanning apparatus>
FIG. 1 is a configuration diagram of a plate making apparatus to which a multi-beam exposure scanning apparatus according to an embodiment of the present invention is applied. The illustrated plate making apparatus 11 fixes a sheet-like plate material F (corresponding to “recording medium”) to the outer peripheral surface of a drum 50 having a cylindrical shape, and the drum 50 is moved in the direction of arrow R (main scanning direction) in FIG. ) And a plurality of laser beams corresponding to image data of an image to be engraved (recorded) on the plate material F are emitted from the exposure head 30 of the laser recording apparatus 10 toward the plate material F, and the exposure head The two-dimensional image is engraved (recorded) on the surface of the plate F at a high speed by scanning 30 at a predetermined pitch in the sub-scanning direction (arrow S direction in FIG. 1) orthogonal to the main scanning direction. Here, a case where a rubber plate or a resin plate for flexographic printing is engraved will be described as an example.

  The laser recording apparatus 10 used in the plate making apparatus 11 of this example includes a light source unit 20 that generates a plurality of laser beams, an exposure head 30 that irradiates the plate material F with a plurality of laser beams generated by the light source unit 20, and And an exposure head moving unit 40 that moves the exposure head 30 along the sub-scanning direction.

  The light source unit 20 includes a plurality of semiconductor lasers 21 (in this case, a total of 32 lasers), and the light from each of the semiconductor lasers 21 individually passes through the optical fibers 22 and 70 to the optical fiber array unit 300 of the exposure head 30. Is transmitted.

  In this example, a broad area semiconductor laser (wavelength: 915 nm) is used as the semiconductor laser 21, and these semiconductor lasers 21 are arranged side by side on the light source substrate 24. Each semiconductor laser 21 is individually coupled to one end of an optical fiber 22, and the other end of the optical fiber 22 is connected to an adapter of an FC type optical connector 25.

  The adapter substrate 23 that supports the FC optical connector 25 is vertically attached to one end of the light source substrate 24. In addition, an LD driver substrate 27 mounted with an LD driver circuit (not shown in FIG. 1, reference numeral 26 in FIG. 7) for driving the semiconductor laser 21 is attached to the other end portion of the light source substrate 24. Each semiconductor laser 21 is connected to a corresponding LD driver circuit via an individual wiring member 29, and each semiconductor laser 21 is individually driven and controlled.

  In this embodiment, a multimode optical fiber having a relatively large core diameter is applied to the optical fiber 70 in order to increase the output of the laser beam. Specifically, in this embodiment, an optical fiber having a core diameter of 105 μm is used. Further, a semiconductor laser 21 having a maximum output of about 10 W is used. Specifically, for example, a core having a core diameter of 105 μm and an output of 10 W (6398-L4) sold by JDS Uniphase can be used.

  On the other hand, the exposure head 30 is provided with an optical fiber array unit 300 that collectively emits the laser beams emitted from the plurality of semiconductor lasers 21. The light emitting section (not shown in FIG. 1, reference numeral 280 in FIG. 2) of the optical fiber array section 300 has a structure in which the emitting ends of the 32 optical fibers 70 guided from the respective semiconductor lasers 21 are arranged in a line. (See FIG. 3).

  Further, in the exposure head 30, a collimator lens 32, an opening member 33, and an imaging lens 34 are arranged in order from the light emitting unit side of the optical fiber array unit 300. An imaging optical system is configured by the combination of the collimator lens 32 and the imaging lens 34. The opening member 33 is disposed so that the opening is positioned at the far field when viewed from the optical fiber array unit 300 side. As a result, an equivalent light amount limiting effect can be given to all laser beams emitted from the optical fiber array unit 300.

  The exposure head moving unit 40 is provided with a ball screw 41 and two rails 42 arranged so that the longitudinal direction is along the sub-scanning direction, and a sub-scanning motor (not shown in FIG. 1) that rotationally drives the ball screw 41. 7 is operated, the exposure head 30 disposed on the ball screw 41 can be moved in the sub-scanning direction while being guided by the rail 42. The drum 50 can be driven to rotate in the direction of the arrow R in FIG. 1 by operating a main scanning motor (not shown in FIG. 1, reference numeral 51 in FIG. 7), thereby performing main scanning.

  FIG. 2 is a configuration diagram of the optical fiber array unit 300, and FIG. 3 is an enlarged view of the light emitting unit 280 (viewed in the direction of arrow A in FIG. 2). As shown in FIG. 3, in the light emitting section 280 of the optical fiber array section 300, optical fibers 70 having a core diameter of 105 μm that emit 32 lights at equal intervals are arranged in a straight line.

  The optical fiber array unit 300 includes a base (V-groove substrate) 302, and the base 302 is formed so that the same number of semiconductor lasers 21, that is, 32 V-shaped grooves 282 are adjacent to each other at a predetermined interval. Has been. One optical fiber end 71 of the other end of the optical fiber 70 is fitted into each V-shaped groove 282 of the base 302. Thereby, the optical fiber end group 301 arranged in a straight line is configured. Accordingly, a plurality (32) of these laser beams are simultaneously emitted from the light emitting part 280 of the optical fiber array part 300.

  FIG. 4 is a schematic diagram of an imaging system of the optical fiber array unit 300. As shown in FIG. 4, the light emitting section 280 of the optical fiber array section 300 is exposed to the exposure surface (surface) FA of the plate material F at a predetermined imaging magnification by the imaging means composed of the collimator lens 32 and the imaging lens 34. The image is formed in the vicinity of. In the present embodiment, the imaging magnification is set to 1/3, whereby the spot diameter of the laser beam LA emitted from the optical fiber end 71 having a core diameter of 105 μm is φ35 μm.

  In the exposure head 30 having such an imaging system, the adjacent fiber interval (L1 in FIG. 3) of the optical fiber array unit 300 described in FIG. 3 and the arrangement of the optical fiber end group 301 when the optical fiber array unit 300 is fixed. By appropriately designing the inclination angle (angle θ in FIG. 5) in the direction (array direction), as shown in FIG. 5, the scanning line (FIG. 5) is exposed with a laser beam emitted from an optical fiber arranged at an adjacent position. The interval P1 between the main scanning lines K can be set to 10.58 μm (corresponding to a resolution of 2400 dpi in the sub-scanning direction).

  By using the exposure head 30 configured as described above, it is possible to simultaneously scan and expose a range of 32 lines (one swath).

  FIG. 6 is a plan view showing an outline of a scanning exposure system in the plate making apparatus 11 shown in FIG. The exposure head 30 includes a focus position changing mechanism 60 and an intermittent feed mechanism 90 in the sub-scanning direction.

  The focus position changing mechanism 60 has a motor 61 and a ball screw 62 that move the exposure head 30 back and forth with respect to the drum 50 surface. Under the control of the motor 61, the focus position can be moved about 339 μm in about 0.1 seconds. it can. The intermittent feed mechanism 90 constitutes the exposure head moving unit 40 described with reference to FIG. 1, and includes a ball screw 41 and a sub-scanning motor 43 that rotates the ball screw 41 as shown in FIG. The exposure head 30 is fixed to the stage 44 on the ball screw 41. Under the control of the sub-scanning motor 43, the exposure head 30 is moved in the direction of the axis 52 of the drum 50 for one swath (in the case of 2400 dpi) in about 0.1 second. (10.58 μm × 64 ch = 677.3 μm) can be intermittently fed.

  In FIG. 6, reference numerals 46 and 47 denote bearings that rotatably support the ball screw 41. Reference numeral 55 denotes a chuck member that chucks the plate material F on the drum 50. The position of the chuck member 55 is a non-recording area where exposure (recording) by the exposure head 30 is not performed. While rotating the drum 50, the plate material F on the rotating drum 50 is irradiated with a laser beam of 32 channels from the exposure head 30 so that the exposure range 92 for 32 channels (one swath) can be formed without any gaps. Exposure is performed, and engraving (image recording) of 1 swath width is performed on the surface of the plate material F. Then, when the chuck member 55 passes in front of the exposure head 30 by the rotation of the drum 50 (at the non-recording area of the plate material F), intermittent feeding is performed in the sub-scanning direction to expose the next one swath. To do. A desired image is formed on the entire surface of the plate F by repeating exposure scanning by intermittent feeding in the sub-scanning direction.

  In this example, a sheet-like plate material F (recording medium) is used, but a cylindrical recording medium (sleeve type) can also be used.

<Control system configuration>
FIG. 7 is a block diagram showing the configuration of the control system of the plate making apparatus 11. As shown in FIG. 7, the plate making apparatus 11 includes an LD driver circuit 26 that drives each semiconductor laser 21 according to two-dimensional image data to be engraved, a main scanning motor 51 that rotates a drum 50, and a main scanning motor. 51, a main scanning motor driving circuit 81 for driving 51, a sub scanning motor driving circuit 82 for driving the sub scanning motor 43, and a control circuit 80. The control circuit 80 controls the LD driver circuit 26 and each motor drive circuit (81, 82).

  Image data indicating an image to be engraved (recorded) on the plate material F is supplied to the control circuit 80. The control circuit 80 controls the driving of the main scanning motor 51 and the sub-scanning motor 43 based on the image data, and outputs the respective semiconductor lasers 21 individually (on / off control and laser beam power control). Control.

  In the plate making apparatus 11 configured as described above, the plate material F (recording medium) can be engraved. Engraving is performed by exposing the exposed area 202 of the plate material F as shown in FIG. 8, and the non-exposed area 201 is not exposed. For the exposure region, the leftmost channel ch1 (first beam) first emits and engraves, then the right adjacent channel ch2 (second beam) emits and engraves, and then sequentially adjacent channels. The ch3 to ch32 beams are emitted to engrave the swath width. When engraving of one swath width is completed, the same engraving is sequentially performed by moving the swath width in the sub-scanning direction.

<Method for forming convex small dots>
Next, an exposure scanning process for forming small convex points having a steep shape in the plate making apparatus 11 configured as described above will be described. In this embodiment, by performing four main scans (exposure scans) at the same sub-scan position, a steep shape is formed while eliminating the influence of heat accumulation.

  FIG. 9 shows a cross section in the main scanning direction and the sub-scanning direction of the non-exposure region 221 including the region to be formed as the convex small points of the plate material F and the exposure region 222 other than the non-exposure region 221. FIG.

  The non-exposure region 221 includes a first non-exposure region 221a that is a region to be formed as a convex small point, and a second non-exposure region 221b that is a peripheral region thereof. The second non-exposure area 221b is a peripheral 1-dot or 2-dot area excluding the peripheral area on one side of the first exposure area having four sides, and has four types of 221b1 to 221b4 depending on the excluded side. Transformed into a region.

  First, the first exposure scan is performed on the exposure region 212. In the first time, the second non-exposure region 221b is a peripheral region excluding the upper side of the first non-exposure region 221a (downstream in the main scanning direction in the drawing) as shown in FIG. 9A. .

  That is, in the first exposure scanning, only the upper side of the boundary of the first non-exposure region 221a is engraved, and the boundary of the lower side and the left and right sides is not engraved as the second non-exposure region 221b. Therefore, the boundary of the upper side of the first non-exposure area 221a can be engraved without the influence of heat accumulation.

  Next, a second exposure scan is performed on the exposure region 212. In the second time, the second non-exposure area 221b is a peripheral area excluding the lower side (upstream in the main scanning direction) of the first non-exposure area 221a as shown in FIG. 9B. Therefore, in the second exposure scanning, the boundary of the lower side of the first non-exposure region 221a can be engraved without the influence of heat accumulation.

  Further, a third exposure scan is performed for the exposure region 212. As shown in FIG. 9C, the third second non-exposure area 221b is a peripheral area excluding the right side (downstream in the sub-scanning direction) of the first non-exposure area 221a. Therefore, in the third exposure scanning, the boundary of the right side of the first non-exposure region 221a can be engraved without the influence of heat accumulation.

  Finally, a fourth exposure scan is performed for the exposure region 212. The fourth second non-exposure area 221b is a peripheral area excluding the left side (upstream side in the sub-scanning direction) of the first non-exposure area 221a as shown in FIG. 9D. Therefore, in the fourth exposure scan, the boundary of the left side of the first non-exposure area 221a can be engraved without the influence of heat accumulation.

  In this way, four main scans are performed at the same sub-scanning position, and in each main scan, the four sides of the rectangular convex small dots are engraved one by one in order, so that the heat pool near the surface of the convex small dots can be obtained. It is possible to prevent the occurrence of rounding of the edge shape of each side of the convex small point by preventing the occurrence, and the exposure region can be deeply engraved by four exposures to form a steep convex small point.

  In the present embodiment, the upper side (downstream side in the main scanning direction), the lower side (upstream side in the main scanning direction), the right side (downstream side in the sub scanning direction), the left side (on the boundary of the region to be formed as the convex small point) The engraving is performed in the order of the upstream side in the sub-scanning direction), but the order is not limited.

  In the present embodiment, the exposure area 222 shown in FIG. 9A is exposed with a uniform light power, but the light power is reduced as the area is closer to the non-exposure area 221. A light amount distribution may be provided in the region.

<Power control between each channel of the light beam>
In FIG. 8, if exposure scanning is performed with the optical powers of the channels ch1 to ch32 set equal, the exposure region 202 is first engraved with the first beam (ch1), and the plate material F is warmed by the remaining heat. It is done. Since the second beam (ch2) for engraving the next adjacent line is irradiated there and engraved, the energy of ch2 is applied while the temperature of the plate material F is high due to the influence of residual heat due to the engraving of ch1. It will be. In this way, a phenomenon occurs in which engraving with the subsequent beam proceeds excessively due to the influence of heat by engraving with the preceding adjacent beam.

  Although the phenomenon that the engraving proceeds excessively always occurs in the exposure area 202, it becomes a problem particularly at the boundary between the non-exposure area 201 and the exposure area 202.

  For example, the outer periphery of the left side of the non-exposed area 201 in FIG. 8B is engraved with ch4, but if the engraving with ch4 proceeds excessively under the influence of heat from engraving of ch1 to ch3, the non-exposed area 201 May not be engraved into the desired shape.

  Note that such a problem does not occur on the outer periphery of the left side of the non-exposure area 201 in FIG. In the case of FIG. 8A, the outer periphery of the left side of the non-exposure area 201 is engraved with ch1, but since there is no scanning beam preceding ch1 in one swath, there is no influence of residual heat. As described above, the influence of heat differs depending on the positional relationship between the small convex point to be formed and the channel of each beam.

  In order to avoid this phenomenon, the plate making apparatus 11 in the present embodiment controls the optical power between the channels of each beam based on information indicating which position is exposed in which channel. An example is shown in FIG. The horizontal axis in FIG. 10 represents the channel number (ch), and the vertical axis represents the optical power of the beam as a relative value (the power of ch1 is normalized to 1). As shown in FIG. 10, the optical powers of the channels ch1, ch2, and ch3 corresponding to the start portion for starting engraving are set as ch1> ch2> ch3, and the optical powers after ch3 (intermediate portion) are made substantially constant. Then, the optical power of the last (end of writing) channel (ch32) in the swath is increased (for example, ch32 = ch2).

  As described with reference to FIG. 8, when convex small dots are formed by the beam arrangement of the channel groups arranged obliquely, a time difference occurs in the light emission timing of each channel (pixel exposure timing). First, the ch1 beam is emitted, and the next ch2 beam is emitted when exposure scanning is performed. At this time, since the surface temperature of the plate material F corresponding to the beam position of the ch2 is increased due to the influence of the heat of the preceding ch1 beam, the optical power of the ch2 is changed to the ch1 in consideration of the influence of the heat of the adjacent beam. Lower than.

  In FIG. 10, the optical power of ch2 is set to 0.7 with respect to the optical power of ch1 (standardized to 1), but the light quantity ratio of adjacent beams to the beam to be scanned first is , 0.4 to 0.9.

  Similarly for ch3, the optical power of ch3 is further reduced below that of ch2 in consideration of heat accumulation by the beams of the preceding ch2 and ch1 (in FIG. 10, it is set to 0.5).

  However, after ch3, the heat condition is saturated and becomes almost the same condition, so that the optical power is substantially constant in the middle part of the line. By controlling in this way, it becomes possible to engrave appropriately regardless of the positional relationship between the convex small point and the channel of each beam.

FIG. 10 shows a beam spot diameter of 35 μm and resolution of 2400 dpi (scanning line interval =
This is merely an example of the case of 10.6 μm), and it is necessary to optimize the optical power between channels according to conditions such as spot diameter, spot arrangement, scanning speed, and plate material. For example, depending on conditions, the optical power relationship between the beams may be ch1 ≧ ch2≈ch3≈ch4... Ch1>
ch2>ch3> ch4 (≈ch5≈ch6...) may be used.

It is effective to control such optical power in the range of several pixels (about 2 to 4 pixels) for writing, and to perform optical power control between beams for at least two adjacent pixels (ch1 and ch2). Is effective.

The last channel (here, ch32) differs from the other intermediate channels (ch4 to ch31) in that there is no heat contribution from the next adjacent beam, so the optical power may be increased, Depending on the conditions, it may be the same as the previous channel (ch31).

As illustrated above, when a desired shape is formed by engraving the vicinity of the surface of the recording medium (plate material F) with a laser by a multi-beam exposure system, based on the emission state of the beam around the pixel emitting laser light, The amount of light emitted is controlled. The amount of light is controlled by a few pixels in the sub-scanning direction centering on the emitted beam, and when the other beams are not emitted first, the amount of light is a. After that, when a certain amount of light is used when the adjacent beam (second beam) exposes the pixel B adjacent to the pixel A, the light amount b is set.

<Relationship between non-exposure area and actually formed small convex point>
In order to form a convex small point, in consideration of the fact that the peripheral area of the non-exposed area is engraved by the residual heat when the boundary of the non-exposed area is engraved, it is actually more than the convex small point. There are cases where exposure is not performed in a large range. For example, as shown in FIG. 11, when forming a 2 × 2 dot small dot under the condition of a spot diameter of 35 μm and a scanning line interval = 10.6 μm, the non-exposure area 211 is set to 1 dot around the small dot. By setting this range, the final convex small dot 214 of 2 × 2 dots may be formed.

  Therefore, when this embodiment is applied under such conditions, it is necessary to engrave the 4 × 4 dot range as the non-exposed area 221 in FIG. 9 and the area outside the one dot as the exposed area 222. is there.

  As described above, the relationship between the non-exposure area and the actually formed small convex point varies depending on various conditions of the light beam and the plate material, but the present embodiment is applied to the non-exposure area as the non-exposure area. do it.

<In case of interlace exposure>
FIG. 10 illustrates an example in which non-interlaced exposure is performed in which all pixels in one swath are exposed at the same time without leaving a pixel interval during exposure scanning. Can be applied similarly.

  FIG. 12 shows an example of the control of the optical power between channels in the case of performing interlaced exposure with a gap of 1 ch under the conditions of a spot diameter of 35 μm and a resolution of 2400 dpi (scan line interval = 10.6 μm).

  Since the interlace exposure is also affected by the heat of the adjacent beam, the optical power after ch2 is lowered with respect to the optical power of ch1 (1 by standardization). In the figure, the optical power of ch2 is set to “0.7”, but the present invention is not limited to this, and the light quantity ratio of the adjacent beam to the beam scanned first is in the range of 0.5 to 0.9. Is set as appropriate.

  In the case of interlaced exposure, since the density of the beam in the sub-scanning direction is lower (sparse) than in non-interlaced exposure, the influence of heat between adjacent beams is smaller than in the case of non-interlaced exposure. For this reason, compared to the case of non-interlaced exposure (FIG. 10), the amount of reduction in optical power after ch2 in interlaced exposure (FIG. 12) is small.

<When using other beam arrangements>
In the above embodiment, the beam arrangement in which 32 lines (one swath) are arranged in an oblique direction by the exposure head 30 having the one optical fiber array arrangement described in FIG. 3 is exemplified. In implementation, the beam arrangement is not limited to such a single row arrangement.

  FIG. 13 shows an example of another optical fiber array unit light source. The illustrated optical fiber array unit light source 500 includes optical fiber array units 501, 502, 503, and 504 combined in four stages. In each stage array, 16 optical fibers 70 having a core diameter of 105 μm are arranged in a line in a straight line, and a total of 64 optical fibers 70 are arranged in an oblique matrix form in four stages. Yes.

  As shown in FIG. 13, the channel number belonging to the uppermost (first) optical fiber array unit 501 is 4M + 1 (M = 0, 1, 2,...) From the right end, and the channel belonging to the second (reference numeral 502). The number of channels is 4M + 2 from the right end, the number of channels belonging to the third stage (reference 503) is 4M + 3 from the right end, and the number of channels belonging to the fourth lowest stage (reference 503) is 4M + 4 from the right end. The block is composed of 16 rows of 4 channels that share a common channel.

  The adjacent fiber spacing (L1 in FIG. 13) and the spacing (L2) in each row of the optical fiber array units 501, 502, 503, and 504 at each stage, and the relative position in the row direction (L3 in FIG. 13), Furthermore, by appropriately designing the inclination angle of the array unit, as shown in FIG. 14, the interval P1 of the scanning lines (main scanning lines) K exposed by the optical fibers of adjacent channels and the rightmost channel of the block consisting of 4 channels The interval P2 between the scanning lines to be exposed in the (channel belonging to the upper stage of the array) and the leftmost channel (channel belonging to the lower stage of the array) adjacent to this is equally 10.58 μm (corresponding to a resolution of 2400 dpi in the sub-scanning direction). Can be set.

  When engraving fine lines along the sub-scanning direction with such a beam arrangement, the optical power between the channels of each beam is controlled as shown in FIG.

  In FIG. 15, the horizontal axis indicates the channel number, and the vertical axis indicates the optical power (ch1 is normalized to 1). As shown in the figure, in correspondence with repetition of swath blocks in units of 4 lines, the optical power between the channels within this repetition unit is expressed as ch (4M + 1)> ch (4M + 2)> ch (4M + 3)> ch (4M + 4). Set as follows.

  Using the above configuration, the plate material F can be engraved as shown in FIG. At this time, by performing exposure scanning four times at the same sub-scanning position and controlling the optical power of the laser beam, convex small dots having a steep shape as shown in FIG. 9D are formed. be able to.

  The form of the optical fiber array unit light source is not limited to the example described with reference to FIG. 13, and an arbitrary number of array stages and swath block repetitions can be realized by the same method as in FIG. 13, and an appropriate two-dimensional array can be realized.

<Spiral exposure method>
The surface of the plate material F is scanned in a spiral shape by moving the exposure head 30 at a constant speed in the sub-scanning direction during drum rotation, not limited to the scanning exposure method using intermittent feeding in the sub-scanning direction described in FIG. A spiral exposure method may be employed.

  For example, if one swath of the exposure head 30 is 32 channels and four scans are required for one main scanning line, the head is equivalent to 32 ÷ 4 = 8 channels during one rotation of the drum 50. What is necessary is just to control 30 to move to a subscanning direction. By performing sub-scanning in this way, each main scanning line can be exposed and scanned a desired number of times (in this case, four times), and the entire surface of the plate material F can be exposed and scanned.

  The intermittent feed method is effective when the rotational speed of the drum is relatively slow. On the other hand, the spiral exposure method is effective when the rotational speed of the drum is relatively high.

<About the flexographic plate manufacturing process>
Next, the exposure scanning process when manufacturing a printing plate by a multi-beam exposure system will be described.

  FIG. 16 shows an outline of the plate making process. An original plate 700 used for plate making by laser engraving has an engraving layer 704 (rubber layer or resin layer) on a substrate 702, and a protective cover film 706 is stuck on the engraving layer 704. At the time of plate making, as shown in FIG. 9A, the cover film 706 is peeled to expose the engraving layer 704, and the engraving layer 704 is irradiated with laser light to remove a part of the engraving layer 704. To form a desired three-dimensional shape (see FIG. 16B). A specific laser engraving method is as described with reference to FIGS. Note that dust generated during laser engraving is sucked and collected by a suction device (not shown).

  After the engraving process is completed, as shown in FIG. 9C, water cleaning is performed by the cleaning device 710 (cleaning process), and then a flexographic plate is completed through a drying process (not shown).

  In this way, a plate making method in which the plate itself is directly laser engraved is called a direct engraving method. The plate making apparatus to which the multi-beam exposure scanning apparatus according to this embodiment is applied can realize a lower price than a laser engraving machine using a CO2 laser. In addition, the processing speed can be improved by using the multi-beam, and the productivity of the printing plate is improved.

<Other application examples>
The present invention can be applied not only to the manufacture of flexographic plates but also to the manufacture of other convex printing plates or concave printing plates. Further, the present invention can be applied not only to the production of a printing plate but also to a drawing recording apparatus and engraving apparatus for various other purposes.

  DESCRIPTION OF SYMBOLS 10 ... Laser recording apparatus, 11 ... Plate making apparatus, 20 ... Light source unit, 21A, 21B, 21C, 21D ... Semiconductor laser, 22A, 22B, 22C, 22D, 70A, 70B, 70C, 70D ... Optical fiber, 30 ... Exposure head, 40 ... exposure head moving unit, 50 ... drum, 80 ... control circuit, 201, 221 ... non-exposure area, 202, 222 ... exposure area, F ... plate material, K ... scanning line

Claims (10)

In a multi-beam exposure scanning method for engraving the surface of a recording medium by simultaneously irradiating a plurality of light beams and exposing the same scanning line multiple times,
At least four scans are performed on a first area which is a target planar shape to be left on the exposure surface of the recording medium and is a peripheral area of a rectangular planar shape having four sides. A multi-beam exposure scanning method comprising exposing an area adjacent to one of the four sides and engraving all of the first area by sequentially changing the one side.   2. The multi-beam exposure scanning method according to claim 1, wherein, in the four times of scanning, the second region which is a region around the first region is exposed four times.   The multi-beam exposure scanning method according to claim 1, wherein the first region is a region of one pixel or two pixels around the target planar shape. In a multi-beam exposure scanning apparatus that engraves the surface of a recording medium by simultaneously irradiating a plurality of light beams and exposing the same scanning line multiple times,
An exposure head having a plurality of exits from which the light beam is emitted;
Main scanning means for causing the exposure head to perform main scanning relative to the recording medium in a main scanning direction;
At least four scans are performed on a first area that is a target plane shape to be left on the exposure surface of the recording medium and is a peripheral area of a rectangular plane shape having four sides, and at least one scan in each scan Exposure scanning control means for engraving all of the first region by exposing a region adjacent to one side of the four sides and changing the one side in order;
A multi-beam exposure scanning apparatus comprising: The multi-scanning apparatus according to claim 4, wherein the exposure scanning control means exposes at least four times for a second region that is a region around the first region in the at least four main scans. Beam exposure scanning device.   6. The multi-beam exposure scanning apparatus according to claim 4, wherein the first region is a region of one pixel or two pixels around the target planar shape. Sub-scanning means for sub-scanning the exposure head relative to the recording medium in a sub-scanning direction orthogonal to the main scanning direction;
7. The multi-beam exposure scanning apparatus according to claim 4, wherein the sub-scanning unit sub-scans the exposure head by a predetermined amount after the main scanning unit performs main scanning at least four times. . Sub-scanning means for sub-scanning the exposure head relative to the recording medium in a sub-scanning direction orthogonal to the main scanning direction;
When the number of times that the same scanning line is exposed is N (N is an integer of 4 or more) and the number of the emission ports is T, the sub-scanning unit performs the exposure head for one main scanning by the main scanning unit. 7. The multi-beam exposure scanning apparatus according to claim 4, wherein the scanning medium and the recording medium are sub-scanned at a constant speed so as to move relative to each other by a T / N scanning line. The plurality of outlets are arranged on a straight line having a predetermined angle with respect to the main scanning direction,
The exposure scanning control means is a second ejection port adjacent to the first ejection port, and the first scanning port is not exposed at the second ejection port located upstream of the main scanning. Exposure is performed with a predetermined amount of light at one exit port, and exposure is performed with a light amount smaller than the predetermined amount of light at the first exit port when exposure is performed at the second exit port. The multi-beam exposure scanning apparatus according to claim 4.   4. A printing plate manufacturing method, wherein a printing plate is obtained by engraving a surface of a plate material corresponding to the recording medium by the multi-beam exposure scanning method according to claim 1.

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