Laser exposure method

0001The present invention can be used for laser plate making in gravure plate making, offset plate making, flexographic plate making, etc., and further, for laser exposure of circuit patterns in electronic components such as printed circuit boards, liquid crystal displays, plasma displays, etc., and for preventing counterfeiting in bills, etc. It relates to a high-resolution laser exposure method that can also be used for special printing and the like, and products manufactured by using the high-resolution laser exposure method.

0002In gravure printing, ink is filled in minute recesses (cells) formed on the surface of a cylindrical plate cylinder (gravure cylinder), and excess ink is scraped off by a doctor while the plate cylinder is printed (paper). Etc.) to transfer the ink in the cell to the object to be printed, and the gradation and shading of the ink are expressed according to the degree of cell depth. Plate making in gravure printing is performed by forming cells on the surface of the gravure cylinder, and there are also conventional mechanical engravings, but in recent years, semiconductor lasers have been used from the viewpoint of high-definition printing and productivity improvement. Laser plate making that directly exposes plate making information (digital data such as characters and images) by the XY scanning type laser exposure apparatus used has become mainstream. Laser plate making is a surface hardening film such as chrome plating, which is exposed to a photosensitive material film coated on the surface of a gravure cylinder that rotates at high speed by photomodulating a semiconductor laser with a wavelength of 830 nm with plate making information, developing, and etching. Is to form. Laser plate making is a so-called CTP (computer to) that outputs digital data of plate making information such as characters and images directly to a plate without going through a film. It is particularly preferably used in plate). Laser plate making is used not only for gravure plate making but also for various plate making such as offset plate making and flexographic plate making. The applicants have already developed a laser plate making system that fully automates the entire process of laser plate making, and have been very well received (for example, Patent Document 1 etc.).

0003Currently, as a laser exposure method for laser gravure plate making, a method having a resolution of about 3200 dpi (dot per inch) is widely used. In this case, one pixel is about 7.9.²μm²It is expressed by. This resolution of 3200dpi can be said to be sufficient performance in the general printing industry such as ordinary books, magazines, catalogs, and packaging films, but it has potential application fields such as printed circuit boards, liquid crystal displays, and plasma displays. In the field of the manufacturing industry of electronic parts such as, in the case of exposing various circuit patterns with an XY scanning type laser exposure device instead of the conventional mask film layered and batch exposure or step exposure, or in bills and the like. Higher resolution is required for anti-counterfeiting special printing.

0004A conventional laser exposure method having a resolution of 3200 dpi in the sub-scanning direction and 3200 dpi in the main scanning direction will be described with reference to FIG.

0005In FIG. 9, a laser light source that oscillates a laser beam, an optical modulator that spatially divides the laser beam into a plurality of laser beams by a plurality of control signals, and an arrayed laser beam from the optical modulator. For a gravure plate making cylinder coated with a photosensitive film by using a conventional laser exposure apparatus including a projection optical unit for reducing and projecting a laser beam and a scanning means for scanning the laser beam with respect to the photosensitive film. The method for exposure will be described. In the illustrated example, 208 laser beams are used, and the size of the laser spot is a square having a height of about 7.9 μm and a width of about 7.9 μm.

0006While rotating the cylinder coated with the photosensitive film, the laser head portion is scanned in a spiral shape for exposure.

0007First, in the first round of rotation of the cylinder, a series of laser spots having a predetermined length is formed on the photosensitive film with 208 laser beams and exposed.

0008The second lap of rotation of the cylinder is sub-scanned based on the following equation (1) so as to overlap only with the 208th beam irradiated on the first lap, and the beam is irradiated. In this case, only the 208th line on the first lap is overexposed. Pitch 25.4 / 3200 × 207 = 1.634mm (1)

0009Next, on the third lap of the rotation of the cylinder, the beam is radiated by overlapping with the 208th beam radiated on the second lap. In this case, only the 208th line on the first lap is overexposed.

0010In this way, laser exposure having a resolution of 3200 dpi × 3200 dpi is performed.

0011Recently, in order to further increase the resolution, a laser exposure apparatus has been developed in which the height of the laser spot is halved from the size of the conventional laser spot, which is about 7.9 μm, to form a rectangular laser spot. The laser exposure apparatus can perform laser exposure having a resolution of 3200 dpi × 6400 dpi.

0012A laser exposure method having such a resolution of 3200 dpi in the sub-scanning direction and 6400 dpi in the main scanning direction will be described with reference to FIG.

0013In FIG. 10, a laser light source that oscillates a laser beam, an optical modulator that spatially divides the laser beam into a plurality of laser beams by a plurality of control signals, and an arrayed laser beam from the optical modulator. For a gravure plate making cylinder coated with a photosensitive film by using a conventional laser exposure apparatus including a laser head unit having a projection optical unit for reducing and projecting a laser beam and a scanning means for scanning the laser beam with respect to the photosensitive film. The method for exposure will be described. In the illustrated example, 208 laser beams are used, the size of the laser spot is about 7.9 μm wide, and the height is half a rectangle.

0014While rotating the cylinder coated with the photosensitive film, the laser head portion is scanned in a spiral shape for exposure.

0015First, in the first round of rotation of the cylinder, a series of laser spots having a predetermined length is formed on the photosensitive film with 208 laser beams and exposed.

0016The second lap of rotation of the cylinder irradiates the beam based on the following equation (1) so as to overlap only the 208th beam radiated on the first lap. In this case, only the 208th line on the first lap is overexposed. Pitch 25.4 / 3200 × 207 = 1.634mm (1)

0017Next, on the third lap of the rotation of the cylinder, the beam is radiated by overlapping with the 208th beam radiated on the second lap. In this case, only the 208th line on the first lap is overexposed.

0018In this way, laser exposure having a resolution of 3200 dpi × 6400 dpi is performed.

0019Recently, even higher definition is required, but even if the height direction of the laser spot can be reduced as described above, it is not possible to develop a laser exposure apparatus in which the size in the width direction of the laser spot is further reduced. It was quite difficult.

0020In addition, a scanning line method using a single stripe laser diode that can be individually driven has also been proposed (Patent Document 2).

0021However, it is preferable to realize high resolution with an existing device from the viewpoint of cost and the like.

0022Therefore, as a result of diligent studies by the present inventors, a laser exposure method capable of achieving high resolution with an existing laser device has been found, and the present proposal is made.

<p num="0023"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 10-193551</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2002-113836</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2000-318195</text></patcit></p>

<p num="0024"> The present invention has been made in view of the above-mentioned problems of the prior art, and gravure plate making, using a laser exposure apparatus having the same performance as the conventional laser exposure apparatus having a resolution of about 3200 dpi, which is relatively inexpensive. High-resolution laser plate making in offset plate making, flexo plate making, etc. can be performed, and further, for laser exposure of circuit patterns in electronic parts such as printed circuit boards, liquid crystal displays, plasma displays, etc., and special printing for anti-counterfeiting on banknotes, etc. It is an object of the present invention to provide a high-resolution laser exposure method that can also be used and a product manufactured by using the method.</p>

<p num="0025"> Of the present invention<u style="single">For laser plate making</u>The laser exposure method includes a laser light source that oscillates a laser beam, an optical modulator that spatially divides the laser beam into a plurality of laser beams by a plurality of control signals, and an array of lasers from the optical modulator. It has a projection optical unit that reduces and projects the beam, and a scanning means that scans the laser beam against the photosensitive film, and each of the plurality of laser spots arranged in the imaging unit of the projection optical unit has a size in the width direction. Includes a laser head portion that is a rectangular laser spot having a rectangular shape larger than the size in the height direction orthogonal to the width direction.<u style="single">For laser plate making</u>By rotating a cylinder coated with a photosensitive film and scanning a laser beam using a laser exposure apparatus, a predetermined length consisting of a plurality of parallel laser spots that do not overlap each other is formed on the photosensitive film for each orbit of the cylinder. In the orbits before and after each other, at least half of the region in the width direction of the laser spots formed on the photosensitive film on the cylinder by the previous orbits is overlapped by the laser spots of the later orbits. It is characterized in that the laser spot sequence of the subsequent orbit is scanned and exposed so as to be performed.</p><p num="0026"> The scanning means includes a main scanning direction in which the photosensitive film is subjected to relative scanning in a direction intersecting the arrangement direction of the laser spot trains irradiated to the photosensitive film, and a sub-scanning direction in which scanning is performed in a direction orthogonal to the main scanning direction. A scanning means for scanning is suitable.</p><p num="0027"> By exposing in this way, the exposure area is increased by the amount obtained by subtracting the overlapping exposure portion from the laser spot sequence scanned earlier from the laser spot sequence scanned later, so that the exposure area is almost parallel as in the conventional case. Since the exposure area is smaller than that in the case of scanning so as to irradiate the laser spot sequence, high resolution can be realized. In particular, it is possible to increase the resolution in the width direction of the laser spot, which has been difficult to achieve in the past, that is, to increase the resolution in the sub-scanning direction of the laser exposure apparatus.</p><p num="0028"> Further, it is preferable that the plurality of laser beams are an odd number.</p><p num="0029"> The laser light source is preferably a semiconductor laser.</p><p num="0030"><u style="single">Book</u>The product is characterized by being manufactured using the laser exposure method of the present invention.</p>

<p num="0031"> According to the present invention, high-resolution laser plate making in gravure plate making, offset plate making, flexo plate making, etc. can be performed by using a laser exposure device having the same performance as the conventional laser exposure device having a resolution of about 3200 dpi, which is relatively inexpensive. A high-resolution laser exposure method that can be used for laser exposure of circuit patterns in electronic components such as printed circuit boards, liquid crystal displays, and plasma displays, and special printing for anti-counterfeiting on banknotes, etc. It has a great effect that it is possible to provide a product manufactured by using a laser.</p>

0032<figref num="1">It is a schematic explanatory drawing which shows the laser exposure method of this invention.</figref><figref num="2">It is a schematic explanatory drawing which explains the 1st lap and the 2nd lap of the cylinder rotation of FIG. 1 in more detail.</figref><figref num="3">It is a block diagram which shows the basic apparatus structure of the laser exposure apparatus used in the laser exposure method of this invention.</figref><figref num="4">It is a schematic diagram which shows the basic apparatus structure of the laser exposure apparatus used in the laser exposure method of this invention.</figref><figref num="5">FIG. 4 is a schematic diagram showing FIG. 4 in more detail.</figref><figref num="6">It is an electron micrograph of a plate-made gravure cylinder, (a) shows the result of Example 1, and (b) shows the result of Comparative Example 1.</figref><figref num="7">It is an enlarged photograph of the upper column of Fig. 6 (a).</figref><figref num="8">It is an enlarged photograph of the upper column of Fig. 6 (b).</figref><figref num="9">It is a schematic explanatory drawing which shows the conventional laser exposure method.</figref><figref num="10">It is a schematic explanatory drawing which shows the conventional laser exposure method.</figref>

0033Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the illustrated examples are shown by way of example, and it goes without saying that various modifications are possible as long as they do not deviate from the technical idea of the present invention. ..

0034First, the laser exposure apparatus used in the laser exposure method of the present invention will be described below with respect to the apparatus configuration. FIG. 3 is a block diagram showing a basic apparatus configuration of the laser exposure apparatus of the present invention. In the figure, reference numeral 10 is a laser exposure apparatus, and the laser exposure apparatus 10 has a main scanning direction and the main scanning direction in which the laser beam is relatively scanned in a direction intersecting the arrangement direction of the laser spot trains irradiated on the photosensitive film. The laser head unit 11 has a laser head unit 11 having a scanning mechanism 4 as a scanning means for scanning in the sub-scanning directions orthogonal to each other, and the laser head unit 11 has a laser light source 1 and a size of the laser beam in the width direction is the same as the width direction. It is composed of a beam forming irradiation unit 2 that forms a rectangular laser spot having a rectangular shape larger than the size in the orthogonal height direction, and based on the plate making information, the laser light source 1, the beam forming irradiation unit 2, It includes a scanning mechanism 4 of the laser head unit 11 and a control unit 3 that controls the operation of the plate cylinder 5. The plate cylinder 5, which is the target of plate making, has a plate surface 6 on which a photosensitive material is applied to form a photosensitive film.

0035The laser light source 1 is, for example, a semiconductor laser having a plurality of laser oscillation units of a semiconductor laser having a wavelength of 830 nm, and continuously oscillates the laser. The laser beam emitted from the laser light source 1 is incident on the beam forming irradiation unit 2.

0036The beam forming irradiation unit 2 is composed of an aperture forming unit 7, an optical modulation unit 8, and a projection optical unit 9. The aperture forming unit 7 forms the beam shape of the incident laser light according to the incident aperture of the light modulation unit 8 and causes the incident laser light to enter the light modulation unit 8. In the present invention, since the shape of the laser spot needs to be rectangular, the beam shape is also formed into a rectangle. The method of forming the beam shape into a rectangle may be a known method, but for example, the laser beam may be passed through a light valve having a rectangular hole (see Patent Document 3).

0037The optical modulation unit 8 is an optical modulation unit composed of a liquid crystal type space modulator having dozens to hundreds of independent optical modulation openings, an electrically driven micromirror array, an acoustic-optical space modulator, and the like. Based on the plate making information, the laser beam is spatially divided into arrangements by a plurality of signals and optical modulation control is performed. For example, in the case of a diffraction grating type mirror array in which a large number of electronically driven micromirrors are arranged, it is possible to modulate the light intensity of a laser beam incident at about 200 kHz by driving and controlling several elements as one channel, and it is independent of about several hundred channels. It can be used as a light modulator. The plate-making information from the control unit 3 is intensity-modulated independently by the modulated signal to which the plate-making information is given, and emitted as pulsed diffracted light arranged for several hundred channels.

0038The light-modulated laser light emitted from the light-modulating unit 8 is an arranged laser beam corresponding to an independent light-modulated aperture, which is incident on the projection optical unit 9. The projection optical unit 9 is a reduction projection optical system composed of a plurality of lenses that reduce and project incident light at a predetermined magnification, has a lens system, an autofocus function, and the like, and uses the light modulation unit 8 as an incident light source surface as a plate surface. 6 This is a reduction optical system with the upper surface as the image plane. The laser beam diameter and the laser beam spacing determined by the shape of the channel at the position of the light modulation unit 8 are reduced and projected on the plate surface so as to be a predetermined laser spot and the laser spot spacing. For example, assuming that the reduction ratio of the projection optical unit is 10: 1, the laser spot trains arranged at 50 μm diameter and 50 μm intervals in the optical modulation unit 8 are reduced to 5 μm diameter and 5 μm intervals on the plate surface 6. Will be done.

0039As is well shown in FIGS. 4 and 5, the laser head unit 11 equipped with the optical system from the laser light source 1 to the projection optical unit 9 sequentially passes through the shaft 12 along the plate cylinder 5 according to the plate making information. The scanning mechanism 4 scans the laser beam in the main scanning direction with respect to the photosensitive film and the sub-scanning direction orthogonal to the main scanning direction. A photosensitive material is applied to the plate surface 6 to form a photosensitive film. The control unit 3 enables the rotation of the plate cylinder 5 and the control of the main scanning direction and the sub-scanning direction of the laser scanning mechanism 4 based on the plate making information.

0040In the exposure method of the present invention, a laser beam is scanned in the main scanning direction or the sub-scanning direction using such a laser exposure apparatus to form a laser spot train having a predetermined length on the photosensitive film and apply it to a plate surface. This is an exposure method for exposing the exposed photosensitive film to form an exposed portion and a non-exposed portion. In the interphase scanning, at least half of the region in the width direction of the previously scanned laser spot array is covered. The laser spot sequence after that is scanned and exposed so that the laser spots are duplicated. An odd number of laser beams is preferable as the plurality of laser beams.

0041Since the laser-irradiated portion of the plate surface 6 is exposed to light and the non-irradiated portion is not exposed to light, plate-making information is given to the entire five plate cylinder surfaces. After that, the plate cylinder 5 is provided as a gravure printing plate by development, etching of a metal surface, resist peeling, and a hard film forming treatment using chrome plating, diamond-like carbon, or the like. When a positive photosensitive liquid is used as the photosensitive material, the exposed portion is photodecomposed, and when a negative photosensitive liquid is used, the exposed area is photocured and remains, and is etched. If this is the case, the unexposed areas will be removed.

0042Examples of the present invention will be described in more detail below, but it goes without saying that each example is shown exemplarily and should not be construed in a limited manner.

0043(Example 1) The laser gravure plate making system was configured as follows. The plate cylinder (gravure cylinder) was an aluminum gravure cylinder with a circumference of 600 mm and a width of 1100 mm, which was plated with 80 μm of copper, and the surface was mirror-polished (surface roughness Ry = 0.12 μm). As the photosensitive liquid, TSER-2104 [a positive photosensitive liquid manufactured and sold by Sink Laboratory Co., Ltd.] was used, and the photosensitive film was air-dried (temperature 23 ° C) for 45 minutes after coating with a film thickness of 3.5 μm. Coating-FX-1300 [Sink Laboratory Co., Ltd.] was used as the photosensitive liquid coating device. LaserStream-FX-1300 [Manufactured and sold by Sink Laboratory Co., Ltd.] is used as a laser exposure device, and the exposure power is 230 mJ / cm.²The cylinder speed during exposure was set to 200 rpm. A TLD developer [manufactured and sold by Sink Laboratory Co., Ltd.] was used as the developer, and the development method was rotary immersion development for 80 seconds (temperature 25 ° C). The laser spot 16 of the laser exposure apparatus in the system configuration is rectangular and can irradiate 208 laser beams.

0044A laser exposure method using such a laser exposure apparatus will be described with reference to FIGS. 1 and 2. The cylinder coated with the photosensitive film is rotated. First, in the first rotation of the cylinder, the 208th laser beam out of the 208 laser beams is turned off, and 207 laser beams have a predetermined length in the photosensitive film. Laser spot row 14a Is formed, irradiated, and exposed.

0045In the second round of rotation of the cylinder, the laser spot row 14b is sub-scanned based on the following equation (2) so that the half area in the width direction of the 207 laser spot rows irradiated on the first round is overexposed. To do. In this case, half of the width direction of the laser spot row 14a on the first round is overexposed on the photosensitive film (see FIG. 2). Pitch 25.4 / 3200 × 103.5 = 0.8215mm (2)

0046Next, in the third round of rotation of the cylinder, the laser spot row is sub-scanned in the same manner so that the half region in the width direction of the 207 laser spot rows irradiated on the second round is overexposed.

0047By exposing one after another in this way, the same effect as that of exposure with a laser exposure apparatus having a resolution of 6400 dpi × 6400 dpi can be obtained.

0048Other than the above laser exposure method, the results of normal laser gravure plate making are shown in FIGS. 6 (a) and 7. As shown in Fig. 6 (a) and Fig. 7, almost no steps or jaggedness appeared in the shaded area, and a nearly completely linear shaded line could be formed, and extremely precise fine exposure and plate making could be performed. ..

0049(Comparative example 1) Using the same laser gravure plate making system as in Example 1, the laser exposure apparatus in the system configuration was subjected to the same laser exposure method as shown in FIG. 10, except that the laser was used in the same manner as in Example 1. Gravure plate making was performed. The results are shown in Fig. 6 (b) and Fig. 8. As shown in Fig. 6 (b) and Fig. 8, jaggedness due to the step appeared in the shaded area, and it was not possible to perform sufficiently fine exposure and plate making.

0050In the above description, the case where it is mainly applied to gravure plate making has been described, but the laser exposure method of the present invention can be used not only for gravure plate making but also for various laser plate making such as offset plate making and flexographic plate making. Also, in the field of manufacturing electronic components such as printed circuit boards, liquid crystal displays, and plasma displays, various circuits are used by XY scanning laser exposure equipment instead of the conventional mask films that are layered for batch exposure or step exposure. It can also be used to expose patterns. Furthermore, it can also be used for special printing for preventing counterfeiting of banknotes and the like.

00511: Laser light source, 2: Beam molding irradiation part, 3: Control part, 4: Laser scanning mechanism, 5: Plate cylinder (gravure cylinder), 6: Plate surface (photosensitive film), 7: Aperture molding part, 8: Optical modulation Part, 9: Projection optics, 10: Laser exposure device, 11: Laser head, 12: Shaft, 14a, 14b: Laser spot row, 16: Laser spot.