JPH1158665A - Laser plate making apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize a plurality of beams applied to the surface of a plate material without performing complicated adjusting work in a multichannel type laser plate making apparatus using a plurality of semiconductor lasers. SOLUTION: In an outer surface cylinder scanning type plate making apparatus, laser beams are independently transmitted from respective semiconductor lasers housed in a laser modulation device 5 to be allowed to be incident on a laser irradiation head 3. Optical fibers 6 on the side of the semiconductor lasers and optical fibers 7 on the side of the laser irradiation head 3 are connected by connectors 8. The core diameter of each of the optical fibers 7 is larger than that of the optical fibers 6 and the number of the apertures of the optical fibers 7 is less than that of the optical fibers 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser plate making apparatus capable of directly manufacturing a lithographic plate from digital data.

[0002]

2. Description of the Related Art A method and an apparatus for performing drawing on a photosensitive material by irradiating a laser beam modulated based on an image forming signal are well known in the art. For example, Japanese Patent Laying-Open No. 60-203071 discloses a laser scanning device that transmits laser beams from a plurality of semiconductor lasers via optical fibers and draws a recording medium with a plurality of beams.

On the other hand, with the recent development of computer and network technologies, a CTP (Computer To Plate) system for producing a printing plate directly from digital data on a computer without using a negative film on the way has become possible. PS, the mainstream of printing plates
(Presensitize) It is attracting attention as an alternative to the plate system.

A plate making apparatus for an offset printing plate for a CTP system uses an organic semiconductor, a silver salt and a photosensitive resin, or a high-sensitivity photosensitive resin as a plate material, and uses an inner surface scanning method or a plane scanning method as a scanning method. Has already been put to practical use.
However, these plate making devices need to be handled in a dark room, as in the case of the conventional PS plate system, and need to be subjected to the development process after the drawing process. Therefore, there are problems in terms of workability and waste liquid treatment. is there.

On the other hand, a plate making apparatus that draws on a heat-sensitive plate material can make a plate in a bright room and can apply a large amount of energy to the plate material in the drawing process. Because there is no need to perform development processing,
Attention has been paid to plate making equipment for TP systems.

In such a plate making apparatus for a heat-sensitive plate material,
A laser beam in the infrared region is used as a drawing light source.
As a laser oscillation device that oscillates a laser beam in the infrared region, a YAG laser having an oscillation wavelength range at 1064 nm, 8
Although there is a semiconductor laser having a center wavelength region near 30 nm, it is preferable to use a semiconductor laser which is inexpensive as compared with a YAG laser in order to keep the apparatus cost low.

In a plate making apparatus using a semiconductor laser, since the focal length of the semiconductor laser is short, the plate material is wound around the outer peripheral surface of the cylinder, and a laser irradiation head disposed near the outer peripheral surface of the cylinder applies a laser beam to the plate material. An outer cylinder scanning method that irradiates a laser beam is adopted.

In a conventional plate making apparatus using an external cylinder scanning method, a plurality of semiconductor lasers are used to increase the number of scans per cylinder rotation in order to increase the plate making speed.
Drawing by a so-called multi-channel method is performed. Each of the semiconductor lasers is independently modulated based on an image forming signal, and laser light from each of the semiconductor lasers is independently transmitted through an optical fiber to be incident on a laser irradiation head.

Here, the semiconductor laser is a collimated light source, generally shows a fan-shaped radiation pattern having a central angle of about 15 to 30 degrees, and is supplied from a manufacturer in a state where an optical fiber is connected to its light emitting surface. The center of the oscillation wavelength range suitable for a laser plate making apparatus for a heat-sensitive plate material is 830.
For example, a semiconductor laser having a diameter of 50 nm has a core diameter of 50 μm.
m to 100 μm, and the numerical aperture (NA) is 0.2 to
An optical fiber of about 0.3 is connected. Since the light emitting surface of the semiconductor laser is several μm and the core diameter is sufficiently large compared to the oscillation wavelength, the laser light oscillated from this semiconductor laser has a Gaussian intensity distribution in the optical fiber connected to the light emitting surface. Is shown.

In a conventional multi-channel laser plate making apparatus, an optical fiber having the same core diameter and the same NA as the optical fiber (optical fiber A) having one end connected to the semiconductor laser is used. One end is connected to the incident side of the laser irradiation head, and the other end is connected to the other end of the optical fiber A.

[0011]

However, when optical fibers having the same core diameter and the same NA are connected to each other, a slight misalignment occurs at the time of coupling, and even when no misalignment occurs, the core diameter does not increase. Has a tolerance of ± 3 μm, the light entrance surface of the optical fiber (optical fiber B) on the laser irradiation head side may be smaller than the light exit surface of the optical fiber A.

As a result, the beam end transmitted through the optical fiber A is cut, and a coupling loss occurs. Further, when the beam end is cut, the intensity distribution of the laser beam in the optical fiber B differs from that in the optical fiber A, and the intensity distribution of the laser beam introduced from the optical fiber B to the laser irradiation head also changes between the optical fibers B. Will be different. The dot diameter and the dot shape drawn on the plate by a plurality of laser beams having such non-uniform intensity distributions are different for each beam even if the energy applied to each semiconductor laser is the same.

Therefore, in order to obtain a high quality printing plate, the oscillation intensity of each semiconductor laser is delicately adjusted so that the diameter and shape of the dots formed on the plate material are constant in all channels. It is indispensable to perform an extremely labor- and time-consuming adjustment work such as connecting the optical fiber A and the optical fiber B while checking the diameter and shape of each laser beam emitted from the laser irradiation head.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and has been developed in a multi-channel laser plate making apparatus using a plurality of semiconductor lasers.
An object of the present invention is to provide a plate making apparatus capable of obtaining a high-quality printing plate without performing complicated adjustment work as in the related art.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a cylinder having a structure in which a plate-like plate material can be wound around an outer peripheral surface and fixed, and the cylinder is disposed at the center of a bottom circle. A rotation mechanism that rotates as an axis, a plurality of semiconductor lasers that oscillate laser light in the infrared region, a laser modulator that independently modulates each semiconductor laser based on an image forming signal, and an independent laser light from each semiconductor laser A laser irradiation head having an optical system for condensing each laser beam incident on the plate material on the outer peripheral surface of the cylinder, and a laser irradiation head at a position separated by a predetermined distance from the cylinder. A head moving mechanism for moving along a line facing the cylinder in parallel with the rotation axis,
In a laser plate making apparatus in which the other end of an optical fiber whose one end is connected to a light emitting portion of a semiconductor laser and the other end of an optical fiber whose one end is connected to an incident side of a laser irradiation head, the light on the semiconductor laser side A laser plate making apparatus characterized in that the core diameter of the optical fiber (optical fiber B) on the laser irradiation head side is larger than the core diameter of the fiber (optical fiber A).

The size of the core diameter is determined based on the size including the tolerance. In the laser plate making apparatus of the present invention, it is preferable that the numerical aperture of the optical fiber on the laser irradiation head side is smaller than that of the optical fiber on the semiconductor laser side.

More specifically, the optical fiber on the semiconductor laser side has a core diameter in the range of 40 μm to 55 μm and a numerical aperture of 0.2 to 0.3, and the optical fiber on the side of the laser irradiation head. It is preferable that the optical fiber has a core diameter in a range of 60 μm or more and 150 μm or less and a numerical aperture of less than 0.2.

When an optical fiber having the same NA as the optical fiber A and having a core diameter including the tolerance larger than the optical fiber A is used as the optical fiber B, the optical fiber A
All of the laser light emitted from the optical fiber B is taken into the optical fiber B. Thereby, the coupling loss is reduced. In addition, since the ratio of the tolerance to the core diameter becomes smaller as the core diameter becomes larger than the conventional one, the optical fiber B
The intensity distribution of the laser light in the area becomes closer to a perfect circle. Further, the laser light is incident on the laser irradiation head from the optical fiber B while the intensity distribution in the optical fiber A is maintained.

Therefore, since the plurality of laser beams emitted from the laser irradiation head maintain the light intensity distribution in the optical fiber A, the diameter and shape of the dot drawn on the plate by the plurality of beams are changed. Although it depends on the variation of the light intensity distribution between the semiconductor lasers, the core diameter of the optical fiber B becomes more uniform than the conventional case where the core diameter of the optical fiber A is made the same.

Further, NA is smaller than that of the optical fiber A,
When a core having a core diameter larger than the optical fiber A including the tolerance is used as the optical fiber B, a radiation mode occurs in the optical fiber B due to a difference in NA, and the power is attenuated. The laser beam is shaped in B. Therefore, the laser light transmitted through the optical fiber B exhibits an intensity distribution according to the characteristics of the optical fiber B.
As a result, the laser light is incident on the laser irradiation head from the optical fiber B in a state where the influence of the variation in the intensity distribution between the semiconductor lasers is reduced. Further, all of the laser light radiated from the optical fiber A at the connecting portion is taken into the optical fiber B in the same manner as described above due to the core diameter.

Therefore, the plurality of laser beams emitted from the laser irradiation head are reduced in the influence of the variation in the intensity distribution between the semiconductor lasers. The diameter and shape will be very uniform.

[0022]

Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram showing a laser plate making apparatus corresponding to one embodiment of the present invention.

This laser plate making apparatus comprises a cylinder 1 on which a plate material is wound, and a motor (rotating mechanism) 2 for rotating the cylinder.
, A laser irradiation head 3, a stage 4 on which the laser irradiation head 3 is mounted, a linear moving mechanism (head moving mechanism) 41 for moving the stage 4, and a laser modulation in which a plurality of semiconductor lasers are housed. A device 5, an optical fiber 6 extending from a light emitting portion of each semiconductor laser, a plurality of optical fibers 7 in which the laser irradiation head 4 side is arranged and bundled in a line in a sheath tube 71, an optical fiber 6 and an optical fiber 7
And a connector 8 for connecting the two.

The cylinder 1 is made of a hollow aluminum material, and its outer peripheral surface is polished with high precision so that surface irregularities are within a range of ± 5 μm. This is because the distance between the laser irradiation head 4 and the outer peripheral surface of the cylinder 1 is always kept constant. Further, the cylinder 1 has a structure in which a plate-shaped plate material can be wound around the outer peripheral surface and fixed.

The motor 2 rotates the cylinder 1 around the center of the bottom circle, and uses a servomotor to obtain smooth rotation, and is directly connected to one end of the rotation shaft of the cylinder 1 via a coupling. Have been. A rotary encoder 21 for detecting the rotation angle of the cylinder 1 and measuring the timing of drawing is attached to the other end of the rotation shaft of the cylinder 1.

The laser irradiation head 3 has an optical system for condensing the laser light incident from the plurality of optical fibers 7 on a plate material wound around the outer peripheral surface of the cylinder 1. here,
After the light incident from the optical fiber 7 is shaped by a plurality of lens groups, it is condensed by an objective lens disposed at the end on the cylinder 1 side at a beam diameter of １ ／ of the core diameter of the optical fiber 7. It is supposed to be.

The linear moving mechanism 41 of the stage 4 is constituted by a ball screw or a linear motor, and is mounted so that the parallelism between the stage 4 and the outer peripheral surface of the cylinder 1 has an accuracy of ± 5 μm. The linear movement mechanism 41 allows the laser irradiation head 3 to move along a line facing the rotation axis of the cylinder 1 at a position separated from the cylinder 1 by a predetermined distance.

The laser modulator 5 has a center wavelength of 830 nm.
A plurality of semiconductor lasers for oscillating the laser light, and each semiconductor laser is independently modulated based on an image forming signal. One end of the optical fiber 6 is connected to the light emitting section of each semiconductor laser.

The other end of the optical fiber 6 is connected by a connector 8 to the other end of the optical fiber 7 whose one end is connected to the incident side of the laser irradiation head 3. The optical fiber 7 has a larger core diameter and a smaller NA than the optical fiber 6.

FIG. 2 shows that a plurality of optical fibers 7 are connected to a sheath tube 71.
It is a schematic front view showing a fiber array bundled in,
FIG. 3 is a diagram of FIG. 2 viewed from the direction of arrow E. As shown in these figures, a plurality of optical fibers 7
1 are roughly grouped in a tube 72 extrapolated to
Are arranged in a row at a pitch corresponding to the cladding diameter. At the tip of the sheath tube 71, a mounting member 73 to the laser irradiation head 3 is fixed.

The fiber array is configured to be rotatable about the center of the line of the fiber array as an axis, and the rotation axis direction of the cylinder 1 (sub-scanning direction) as long as there is no space between adjacent dots on the plate material surface. It is preferable that the resolution in the sub-scanning direction can be changed by tilting the line of the fiber array with respect to ()).

Using the laser plate making apparatus having such a configuration, specifically, the NA of the optical fiber 6 is set to 0.3, the core diameter is set to 50 μm, and the NA and the core diameter of the optical fiber 7 are shown in Table 1 below. In this manner, a drawing experiment was performed on a plate material using 32 fibers.

The laser irradiation energy on the plate material is 350 m
J / cm ² . No special adjustment was made to make the beam diameter on the plate material uniform. As the plate material, a heat-sensitive lithographic plate described in Example 1 of JP-A-7-1850 was used. This plate material is a plate-shaped plate material having a heat-sensitive layer having the following composition formed on a support. [Composition of heat-sensitive layer] Hydrophilic polymer P-1 (15% solid content): 12.0 parts Macrocapsule M-1 (20% solid content): 6.0 parts AIBN: 1.0 part 2,2-dimethoxy -2-Phenylacetone phenone: 0.3 parts Calcium carbonate: 0.8 parts Zinc stearate: 0.5 parts Water: 18.7 parts The beam diameter of each laser beam irradiated from the laser irradiation head 3 is Meles Griot. The peak intensity (e) was measured using a beam profiler 13SPC001
The range up to (1 / e ² ) was defined as the beam diameter. The diameter of the dots formed on the plate was measured using a Nikon majorscope MM-22.

The results are shown in Table 1 below.

[0035]

[Table 1]

As can be seen from this table, the optical fiber 7 has a smaller NA and a larger core diameter than the optical fiber 6 as compared with No. 1, which has the same NA and core diameter as the optical fiber 6. No. 2 and No. 3 have small variations in beam diameter and dot diameter. In particular, in No. 3 in which the NA of the optical fiber 7 was 0.14 and the core diameter was 65 μm, the dot diameter was very uniform, and the printed matter printed using this printing plate had a particularly high quality. Obtained.

[0037]

As described above, according to the laser plate making apparatus of the present invention, in a multi-channel laser plate making apparatus using a plurality of semiconductor lasers, the plate material can be printed without complicated adjustment work. A high quality printing plate can be obtained by making the diameter and shape of each formed dot uniform.

According to the device of the second aspect, the effect is particularly high.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a laser plate making apparatus corresponding to an embodiment of the present invention.

FIG. 2 is a schematic front view showing a fiber array in which a plurality of optical fibers are bundled by a sheath tube in the apparatus of FIG.

FIG. 3 is a view of FIG. 2 as viewed from the direction of arrow E;

[Explanation of symbols]

 Reference Signs List 1 cylinder 2 motor (rotation mechanism) 21 rotary encoder 3 laser irradiation head 4 stage 41 linear movement mechanism (head movement mechanism) 5 laser modulator 6 optical fiber (semiconductor laser side optical fiber) 7 optical fiber (laser irradiation head side) Optical fiber) 71 Sheath tube 72 Tube material 73 Mounting member 8 Connector

Claims (2)

[Claims] 1. A cylinder having a structure in which a plate-shaped plate material can be wound around and fixed to an outer peripheral surface, a rotating mechanism for rotating the cylinder around a center of a bottom circle, and oscillating laser light in an infrared region. A plurality of semiconductor lasers, a laser modulator that independently modulates each semiconductor laser based on an image forming signal, and a laser beam from each semiconductor laser that is independently transmitted via an optical fiber and is incident, and each of the incident lasers A laser irradiation head having an optical system for condensing light on a plate material on the outer peripheral surface of a cylinder, and a head for moving the irradiation head along a line facing a cylinder in parallel with a rotation axis of the cylinder at a predetermined distance from the cylinder. With a moving mechanism,
In a laser plate making apparatus, the other end of an optical fiber having one end connected to a light emitting portion of a semiconductor laser and the other end of an optical fiber having one end connected to an incident side of a laser irradiation head are connected. A laser plate making apparatus characterized in that the core diameter of the optical fiber on the laser irradiation head side is larger than the core diameter of the fiber. 2. The laser plate making apparatus according to claim 1, wherein the numerical aperture of the optical fiber on the laser irradiation head side is smaller than the numerical aperture of the optical fiber on the semiconductor laser side.