JP3302979B2 - PIXEL DENSITY MULTI-STAGE EXPOSURE METHOD AND APPARATUS FOR PRINTING PLATE - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing plate exposure method for recording image information on a printing plate by using image signals, and more particularly, to a method for mixing high-density images and low-density images on a printing plate. The present invention relates to a method and an apparatus for exposing a plurality of levels of pixel density of a printing plate for printing by printing.

[0002]

2. Description of the Related Art In recent years, with the advance of information processing and image processing technology by a computer, even in the field of newspaper printing and the like, direct printing with a laser beam based on an image signal from a computer without using a photographic film. A method of drawing on a printing plate has been developed and put to practical use.

[0003] These printing plates are well known in the industry, for example, under the name of a PS plate. As the PS plate, a printing plate having a structure in which a light-sensitive material is applied in advance to an aluminum substrate is very often used. . The photosensitive material surface is exposed to laser light to record and form a print image on a printing plate.

Heretofore, as a method of drawing on such a printing plate, a drum rotating method in which a printing plate is wound around a drum surface and laser drawing is performed, and a method in which the printing plate is fixed on a flat table are conventionally used. 2. Description of the Related Art A plane method for performing laser drawing is known. The present applicant has already disclosed various inventions regarding the drum rotation method,
Among them, the invention described in Japanese Patent Application Laid-Open No. 10-142805 will be described below as a prior art.

FIG. 17 is a schematic configuration diagram of a conventional drum rotation system using a multi-beam. In the figure, reference numeral 2 denotes a horizontally arranged drum which is driven to rotate in the direction of arrow a by a motor M, and a printing plate 4 is spirally wound around the outer peripheral surface of the drum 2. That is, the top wire 10 and the ground wire 12 of the printing plate 4 are arranged at an angle θ with respect to the direction of the drum axis g.

[0006] A plurality of light beams (for example, 1
28) are emitted and irradiated on the printing plate 4 via the exposure lens 24b. The irradiation width of this light beam group is the width B of the image band 26, and the number of light beams is
Gives a dot number of 6. Rotation of drum 2 and exposure lens 2
The movement of the optical system such as 4b causes the image band 26 to be spirally recorded on the printing plate 2.

As a specific example, when the image band width B, which is the irradiation width of the light beam, is composed of 0.14 inches and the light beam is composed of 128 lines, information is recorded at a density of 128 dots in a width of 0.14 inches. Is done. When converted, the image information is recorded at a pixel density of 909 dots per inch.

The inclination angle θ of the printing plate 4 is set so that the start side line 6 and the end side line 8 are shifted by the image bandwidth B when the drum 2 makes one rotation. At this time, the moving speed of the optical system is set to the bandwidth B per one rotation of the drum 2.
With such a configuration, the surface of the printing plate 4 is completely and completely filled with the spiral of the image band 26 by the continuous rotation of the drum 2 and the continuous movement of the optical system. The drum 2 may be moved while the optical system is stopped.

As described above, the spiral continuum of the image band 26 becomes the printing image 28, and the printing plate 4 is inclined by the angle θ to form the printing image 2.
8 is recorded and formed correctly on the printing plate 4 without tilt distortion.

[0010]

The conventional drum rotation method developed by the present inventors uses a printing image 28.
Is excellent in that it has no tilt distortion, but has the following weak points. As described above, since the printing image 28 is a spiral continuum of the image band 26, the pixel density thereof is equal to the pixel density of the image band 26. Moreover, the entire surface of the printing plate 4 is formed with the same pixel density. For example, as described above, the entire surface of the printing plate 4 becomes a monotonous image in which the pixel density is 909 dots per inch.

In the printing of newspapers, the printing plate 4 corresponds to one page of a newspaper, which means that the entire surface of one page of the newspaper is formed with the same pixel density. However, various types of information such as articles and advertisements are posted on newspapers. Advertisers are more likely to want ads printed more clearly than regular articles.

In order to satisfy such a demand, it is necessary to form the printing plate 4 with a plurality of different pixel densities. However, with the conventional drum rotation method, it is possible to form a print image with a single pixel density, but it is difficult to form a print image with a plurality of pixel densities.

In the above, the case where the printing plate 4 is wound around the outer peripheral surface of the drum 2 (referred to as a drum exterior rotation system) has been described. However, the printing plate 4 is wound around the inner peripheral surface of the drum 2. In the case (drum interior rotation system), there is the same difficulty. Further, this problem is not limited to the drum rotation method, but also occurs in the plane method.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a printing plate having a plurality of pixel densities capable of recording and forming a printing image having a plurality of pixel densities such as a high-density image and a low-density image on the printing plate. A method and an apparatus for implementing the method.

[0015]

According to the first aspect of the present invention, a predetermined number of light beams are irradiated onto the surface of a printing plate through an exposure lens to form a high image band on the printing plate. In a printing plate exposure method for recording a printing image in which a density image and a low density image are mixed, when recording a high density image, an image band formed on the printing plate by adjusting the exposure lens is used. The width is set to a narrow high-density image band width, and the narrow high-density image band is formed on a printing plate while adding an electronic mask so as to block a light beam for a low-density image area. When recording a high-density image and recording a low-density image, the exposure lens is readjusted to enlarge the image bandwidth to a wide low-density image bandwidth so as to reduce the irradiation density of the light beam. , One or both sides of this low density image bandwidth The low-density image bandwidth is set to be reduced so as to be equal to the high-density image bandwidth by making a part of the light beam idle, and the low-density image band is added while an electronic mask is added so as to block the light beam for the high-density image area. A method of exposing a printing plate having a plurality of pixel densities, wherein a low-density image is recorded by forming a density image band on the printing plate.

According to the present invention, the dot diameter of one dot formed by one light beam in the low-density image band corresponds to the enlargement ratio of the band width more than the dot diameter of the high-density image band. 2. The method according to claim 1, wherein the speed of forming the low-density image band is increased in accordance with the enlargement ratio than that of the high-density image band. 3.

According to a third aspect of the present invention, the printing plate is wound around the outer peripheral surface or the inner peripheral surface of the drum, and the printing is performed by rotating the drum while relatively moving the exposure lens in the axial direction of the drum. 2. The pixel density of a printing plate according to claim 1, wherein an image band is spirally formed on the printing plate, and a printing image in which a high-density image and a low-density image are mixed is recorded in the spiral forming process. Is the way.

According to a fourth aspect of the present invention, the printing plate is arranged in a plane, an exposure lens is opposed to the printing plate, and the exposure lens is moved relatively to the surface of the printing plate. 2. The pixel density of a printing plate according to claim 1, wherein an image band is formed in a plane on the printing plate, and a printing image in which a high-density image and a low-density image are mixed is recorded in the process of forming the image band. This is a multi-stage exposure method.

According to a fifth aspect of the present invention, when a printing image is composed of three or more images having different pixel densities, the highest density image is defined as the high density image, and the lower density image is defined as the lower density image. 5. The printing plate of claim 1, 2, 3 or 4, wherein an electronic mask is added so as to block the light beam for all other image areas when recording an image having a certain pixel density. This is a pixel density multi-stage exposure method.

According to a sixth aspect of the present invention, there is provided a printing plate exposure apparatus for irradiating a plurality of light beams onto a surface of a printing plate via an exposure lens to record image information in a band shape with a plurality of pixel bandwidths. In the apparatus, an exposure lens unit equipped with an exposure lens capable of variably adjusting an image bandwidth on a printing plate, an exposure unit for projecting a plurality of light beams into the exposure lens unit, and a plurality of images having different pixel densities. It is equipped with a control device that can turn on and off each light beam output from the exposure lens unit to form a band, and can completely block the light beam group to apply an electronic mask to an arbitrary image area. A printing plate having a pixel density of a plurality of stages, wherein a printing image in which a high-density image and a low-density image are mixed is recorded on the printing plate.

According to a seventh aspect of the present invention, there is provided a drum rotatable around an axis, a printing plate wound on an outer peripheral surface or an inner peripheral surface of the drum, and the exposing lens unit and the exposing unit fixed. The multi-stage exposure apparatus for printing plates having a pixel density according to claim 6, further comprising: an optical table having the above configuration, and a moving mechanism for relatively moving the optical table in the axial direction of the drum.

The invention according to an eighth aspect of the present invention is directed to a flat plate, a printing plate fixed to the flat plate, an exposure lens unit arranged opposite to the printing plate by a predetermined distance, and an exposure lens unit. Move the lens unit XY parallel to the printing plate
7. The exposure apparatus according to claim 6, further comprising a movable mechanism capable of moving the plate.

According to a ninth aspect of the present invention, the exposure lens device is
A turret type exposure lens device comprising a cylindrical body and a plurality of exposure lenses having different focal lengths arranged inside the cylindrical body at different positions in the axial direction, rotating the cylindrical body around the axial direction to emit light. 7. The exposure apparatus according to claim 6, wherein an exposure lens for beam incidence can be selected.

According to a tenth aspect of the present invention, the exposure lens unit includes a cylindrical body, an exposure lens mounted inside the cylindrical body, and a zoom mechanism for moving the exposure lens in an axial direction to change a focal length. 7. The exposure apparatus according to claim 6, wherein the exposure apparatus is a multi-stage exposure apparatus having a pixel density of a printing plate.

According to an eleventh aspect of the present invention, the exposure lens unit forms a composite exposure lens body by connecting a plurality of exposure lenses having different focal lengths, and selects the exposure lens by rotating the composite exposure lens body. 7. The exposure apparatus according to claim 6, wherein the exposure apparatus is a seesaw-type exposure lens device.

According to a twelfth aspect of the present invention, the exposure lens unit includes an exposure lens group in which a plurality of exposure lenses having different focal lengths are integrated, and one exposure lens is taken out of the exposure lens group and arranged. 7. The exposure apparatus according to claim 6, wherein the exposure apparatus is a take-out type exposure lens device comprising a mechanism.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method and an apparatus for exposing a plurality of levels of pixel density of a printing plate according to the present invention will be described.
This will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of a drum exterior rotation system for explaining a first embodiment of the present invention. In the figure, 2 is a drum, 4 is a printing plate, 6 is a start side line, 8 is an end side line, 1
0 is a heaven line, 12 is a ground line, 22 is an exposure unit, 26 is an image band, 28 is a print image, M is a motor, B is an image band width, θ is an inclined arrangement angle, and a is a drum rotation direction. Since the operation and effect of these code members are the same as those described with reference to FIG. 18, the description thereof will be omitted, and other members will be described.

The optical system members mounted on the optical table 14 include a laser light source 16, a multi-beam generator 18, and an acousto-optic modulator group 20. A large number of acousto-optic modulators AOM are arranged in a row in the acousto-optic modulator group 20.
The exposure lens 24b is mounted in the exposure lens unit 24.

The exposing lens unit 24 and the exposing unit 22 are also the optical bench 1
4. Further, a moving mechanism H for moving the optical table 14 relative to the drum 2 in the g direction is provided.
The same result can be obtained by moving the drum 2 in the opposite direction with respect to the stationary optical bench 14. An image signal is output from the control device C, and the acousto-optic modulator group 20 and the laser light source 1 are output.
6 to convert the image signal into an on / off signal of the laser beam. The control device C includes a computer and a dedicated electronic device.

Next, the operation of the above configuration will be described.
One laser beam emitted from a laser light source 16 such as a semiconductor laser passes through a multi-beam generating element 18 such as a grating or a Wollaston prism, and is split into, for example, 128 multi-beams. These many multi-beams are incident on the acousto-optic modulator group 20, and the acousto-optic modulators AOM which are the constituent members exist by the number of multi-beams, and one laser beam is applied to one acousto-optic modulator AOM. Will be incident.

The control device C outputs an image signal consisting of an on / off time-series signal, and controls a large number of acousto-optic modulators AOM simultaneously based on the on / off signal. By this switch control, a large number of laser beams arranged in a row are transmitted or cut off. These laser beams enter an exposure unit 22 composed of a light source array composed of optical fibers, and further irradiate the printing plate 4 via an exposure lens unit 24.

If the acousto-optic modulator group 20 is used as the exposure unit 22, there is no need to provide an exposure unit as a separate member. At this time, the control device C is set so as to directly control the exposure device 22 to be turned on and off. Further, the exposure unit 22 may be constituted by a multi-beam generator including a large number of laser generating elements and light-emitting diodes, and each of the beam generators may be controlled on / off by the control device C.

Next, a specific example of the number of dots will be described. Assuming that the number of multi-beams is 128, each laser beam is turned on / off by a control signal, and a light and shade pattern composed of a 128-dot on / off pattern is recorded in the image bandwidth B of the plate 4. . When the optical bench 14 is moved by the band width B in the direction of the arrow b while the drum 2 makes one rotation, the image band 26 is continuously formed on the printing plate 4 in a spiral shape with no excess or shortage.

The image density is 909 dots per inch,
If the drum circumference is 46 inches, the circumferential direction of the image band 26 is composed of 46 * 909 = 41814 dots. Therefore, the control signal input from the control device C is such that a signal time series of 128 dots corresponding to the bandwidth is input repeatedly 41814 times per circumference.

In this specific example, the case where the total number of laser beams passing through the exposure unit 22 is 128 is described, so that the maximum density of the image bandwidth B is 128 lines / band. The formed image is a high-density image,
This high-density image bandwidth B is represented by _BH . On the other hand, by reducing the number of laser beams forming the bandwidth B, the image band can be reduced in density to a desired density, and an image formed at this low density will be a low-density image.

The change from the high-density image to the low-density image is realized by switching the exposure lens to another exposure lens having a longer focal length. That is, by changing the exposure lens, the length of the image formed on the drum 2, that is, the band width B _H is enlarged and changed to B _L. At this time, B _L > B _H holds. Since there are 128 beams in B _L ,
An appropriate number of beams on one or both sides of the 128 beams are paused to reduce the low density bandwidth from _BL to _BH . That is, in the high-density image, the band width B _H includes 128 beams, whereas in the low-density image, the bandwidth B _H has, for example, 100 beams.

This situation will be described using the lens formula. When the distance from the incident side to the exposure lens is the object distance α, the distance from the exposure lens to the drum is the imaging distance β, and the focal length of the exposure lens is f, the magnification m is obtained from the lens formula.
Is given by m = β / α. In order to form an image as sharp as possible, the band image of the drum 2 is formed near the focal point of the exposure lens. Therefore, since the imaging distance β is set to be substantially equal to the focal length f, the magnification becomes m = f / α.

The focal length f _H of the high density exposure lens, to represent the focal length of the low density exposure lens f _L, and the focal length of the exposure lens is changed from f _H to f _L, low density image band width B _L becomes B _L = B _H × f _L / f _H , and it can be seen that the longer the focal length, the longer the bandwidth in proportion.
At this time, even one of the dots forming the diameter (hereinafter referred to dot diameter) S of a beam constituting the band, it expressed a high density dot size S _H, the low density dot size in S _L, S _L = S _H × f
According to the formula _L / f _H varies in proportion to the focal length. As described above, by exchanging the exposure lens and changing the focal length, the image density and the dot diameter can be changed.

To stop the beam on one or both sides of the image band 26, the following is performed. Since each beam is controlled to be turned on and off by the acousto-optic modulator AOM, the acousto-optic modulator AO corresponding to an appropriate number of beams on one side or both sides is provided.
If M is set to be always off, the number of dots in the image band can be arbitrarily reduced from 128 dots. Therefore, the image density can be easily changed by changing the bandwidth by changing the lens and arbitrarily changing the number of dots by controlling the beam.

FIG. 2 is a schematic oblique view of a turret type exposure lens unit.
FIG. The exposure lens unit 24 is a cylindrical turret.
Three exposure lenses 2 having different focal lengths in a cylindrical body 24a
4b ₁, 24b_Two, 24b_ThreeAre arranged on the same circumference
Is done. Exposure lens 24b₁, 24b_Two, 24b_ThreeIs irradiation
Mounting distance L from surface 24d₁, L_Two, L_ThreeFixed in position
Have been. These mounting distances are from the exposure lens to the drum.
The distance to 2 is set to match the focal length.
The number of the exposed lenses 24b is arbitrarily adjusted.

In this lens arrangement, the exposure lens 24b ₁
Has the shortest focal length, and becomes longer as the exposure lenses 24b ₂ and 24b ₃ become closer. Since the imaging distance is set to be equal to this focal length, the turret type exposure lens unit 24 switches the image density to three stages.

FIG. 3 shows the entrance side of the turret type exposure lens unit.
FIG. Exposure lens 24b ₁, 24b_Two, 24b
_ThreeAre clearly arranged on the same circumference.
You. As can be seen from FIGS. 2 and 3, the incident light P₁Is the circumference
Exposure lens 24b from one point above₁And the irradiation light P_Twoage
And go out. This exposure is performed by a rotating mechanism (not shown).
When the optical lens unit 24 is rotated by a required angle, the exposure lens
24b₁Exposure lens 24b instead of_Two, 24b_Threechoose
can do.

In the above description, the lens position is adjusted so that the distance from the exposure lens to the drum is equal to the focal length of the exposure lens. However, if the entire beam is focused, the image may be too small. For example, if the bandwidth B is set to 0.
To set it to 14 inches (about 3.5 mm), use drum 2
It is necessary to form an image so that the width of the upper image is about 3.5 mm, and it is necessary to shift the image forming position from the focal position. Therefore, the image forming distance from the exposure lens to the drum is not only always set to the focal length, but also adjusted so as to form a predetermined image band.

FIG. 4 is a schematic perspective view of a zoom type exposure lens unit. The zoom cylinder 24c is loaded with one or a combination of exposure lenses 24b.
b can be continuously moved back and forth by rotation of the zoom cylinder 24c. The multi-beam enters the center of the zoom cylinder 24c. That is, the incident light P ₁ is irradiation light P ₂ become through an exposure lens 24b, and expose the printing plate 4.

In this zoom type exposure lens unit 24, since the position of the exposure lens 24b can be continuously adjusted, the image forming distance of the exposure lens 24b to the printing plate 4 can be continuously adjusted. Therefore, the image band 2 formed on the printing plate 4
The image bandwidth B of 6 can be adjusted arbitrarily, making it possible to continuously adjust the image density.

FIG. 5 is a schematic perspective view of a seesaw type exposure lens unit. Exposure lenses 24b ₁ and 24 with different focal lengths
b ₂ composite exposure lens body 24e are integrated by bonding material 24d is formed. The exposure lens is switched by rotating the composite exposure lens body 24e around an alternate long and short dash line in the direction of arrow c in a seesaw manner. If the entire composite exposure lens body 24e can be moved, the position of the exposure lens can be easily adjusted.

FIG. 6 is a schematic perspective view of a seesaw type exposure lens unit similar to FIG. The difference from FIG. 5 is that the compound exposure lens body 24e is rotated around the dashed line in the direction of arrow d. Also in this case, the composite exposure lens body 24e
If the entire lens is movable, the position of the exposure lens can be easily adjusted.

FIG. 7 is a schematic explanatory view of a take-out type exposure lens unit. This take-out type exposure lens unit 24 has a plurality of exposure lenses 24b _{1 to} 24b _n having different focal lengths arranged as an exposure lens group 24f, and a take-out mechanism 24g (not shown).
Is set to take out a desired exposure lens from the exposure lens unit group 24f. The take-out mechanism 24g has a structure in which a lens is pushed out or pulled out by, for example, a solenoid or an air cylinder.

FIG. 8 is an explanatory diagram of a first method of changing the image density. A dotted line indicates a low-density image state, and a solid line indicates a high-density image state. These two image states are determined by the focal length of the exposure lens 24b. The focal length of the exposure lens 24b _{H at} the high density position is f _H , and the exposure lens 24b _H is disposed at a distance from the printing plate 4 by an image forming distance D _H (≒ f _H ) so as to be substantially equal to the focal length. The exposure lens 24b _{L at the} low-density position is spaced apart by an imaging distance D _L substantially equal to its focal length f _L. At this time, f _L > f _H , and therefore D
The relationship of _L > D _H holds.

[0051] When the incident light P ₁ is incident on the high density position lens 24b _H, high-density irradiation light P _2H reaches the printing plate 4 as shown by the solid line, to form a high density image band 26 _H.
The narrow high-density image bandwidth B _H is the image bandwidth of 0.14 inches (3.6 mm) in the above-described example, and includes, for example, 128 laser beams.
Information is recorded with a definition of 128 dots. That is, 12
A high density image of 8 dots / 0.14 inch is formed.
Therefore, to record a high density image band 26 _H in printing plate 4 by a high density position lens 24b _H.

Meanwhile, when recording low-density image is to replace the exposure lens 24b and low density position lens 24b _L. In this case, the incident light P ₁ is spread as a dotted line, a low-density image band 26 _L wide low-density image band width B _L is formed on printing plate 4. At this time, since the high-density image bandwidth B _H is used as a reference, the laser beam in the hatched area protruding from both ends is cut off, and the idle areas 26a,
6a, the low-density image bandwidth B _L is reduced to the high-density image bandwidth B _H. That is, the low-density image band 26 _L fewer laser beam than 128 are included within the width B _H is formed.

For example, consider the case of forming a low-density image of 96 dots / 0.14 inch. This is
Because 3/4 of 8 dots /0.14 inch high density images, the focal distance using a low density position lens _{f L = f H * 4/} 3, image formation distance the low density position lens 24b _L Is D _L
= D _H * 4/3. At this time, B _L = B _H *
Since it is 4/3, to remove the protruding idle area 26a, 32 lines (128 * 1/4 = 32) located on both sides are removed.
May be cut off by the acousto-optic modulator group 20. In this example, since the idle area 26a appears on both sides of the low-density image bandwidth _BL , it is necessary to block the laser beams on both sides.

FIG. 9 is an explanatory diagram of a second method of changing the image density. In this case, less dense position lens 24b _L density position lens 24b _H, not only retracts the drawing, arranged slightly downward. In this way, the upper end of the low-density irradiation light P _2L coincides with the upper end of the high-density irradiation light P _2H at the position of the printing plate 4, and the idle area 26a appears only on one side of the low-density image bandwidth B _L. I do. Therefore, since the laser beam to be blocked is concentrated on one side, the blocking operation of the acousto-optic modulator group 20 by the control signal is simplified.

In the above description, the image forming position of the exposure lens is set to its focal position. However, it is necessary to set the image band width to a predetermined predetermined width. In some cases. In this case, the image is formed by shifting the image forming position from the focal position.

Next, consider one dot formed by one laser beam in an image band. FIG. 10 shows an intensity distribution formed by one laser beam on the drum. The horizontal axis represents the radial direction of the dots, and the vertical axis represents the intensity. The solid line indicates the intensity distribution of dots formed in the high-density image band, and the broken line indicates the intensity distribution of dots formed in the low-density image band.

The printing plate 4 is coated with a sensitizer,
A dot image is photosensitively formed by the irradiation of the laser beam according to the sensitivity of the photosensitive material. Since sensitive photosensitive material is sensitive to all to weak light, for example, cross-sectional image obtained is dot image at the position of X _1. In this case, a high density dot size is given by S _H, the low density dot size is given by S _L. Conversely, cross-sectional images obtained at the position of X ₂ in the photosensitive material of low sensitivity is a dot image, a high density dot size is given by S _H, the low density dot size S _L.

FIG. 11 is a schematic illustration of a dot image. The focal length fL of the low-density locations lens 24b _L is set to 2 times the density position lens 24b _H, suppose imaged in focus position. At this time, at the high-sensitivity position X1, the low-density dot diameter S _L is enlarged to twice the high-density dot diameter S _H ,
The area of the high-density dot 32 _H is 2 × 2 of the low-density dot 32 _L.
= Magnified 4 times. However, at the low-sensitivity position X ₂ , the low-density dot diameter S _L is larger than the high-density dot diameter S _H but is not doubled. Therefore, the dot area is 4
Do not double.

As described above, when an image is formed at the focal position, the ratio between the dot diameters of the high density and the low density can be made to match the ratio of the focal length, and can be arbitrarily set by adjusting the sensitivity. Can also. Also, when an image is formed shifted from the focal position, the ratio between the high-density and low-density dot diameters does not necessarily match the ratio of the focal length.
It can be set freely by adjusting the sensitivity.

FIG. 12 is a schematic explanatory diagram of an image band in which low density and high density are mixed. The image band 26 is comprised of the resulting dot sensitive position X _1. For simplicity, low density image band 26 _L is the bandwidth is composed of 3 dots, high sensitivity position S from X ₁ condition _L = 2 × S
_H , so that the high-density image band 26 _H has a bandwidth of 6 dots.

At this time, the low density dots 32_LThe size of
High-density dots 32 in both the longitudinal and width directions of the band_H2
The drum rotation speed V_aAnd movement of optical bench 14
Speed V _bNeeds to be changed according to the magnification. Toes
The low-density drum rotation speed V_aLIs the high-speed drum rotation speed
V_aHAnd the low-density moving speed V_bLIs high density transfer
Dynamic speed V_bHNeeds to be set to twice.

[0062] The magnification may be set to match the ratio of the low density dot size S _L and the high-density dot diameter S _H, set to 1.5 times the speed ratio if the ratio is 1.5 times do it. Therefore, it is efficient to form a high-density image after forming a low-density image, or to form a low-density image after forming a high-density image. Hereinafter, an image forming method will be described.

FIG. 13 is an explanatory diagram in the case where a low-density image such as an article is formed on a printing plate. Set the exposure lens 24b to the low density position lens 24b _L, the low-density image band 26 _L continuously formed on printing plate 4, finally recorded completing the low-density image 28 _L.

[0064] For the area of the high density image 28 _H, shut off all laser beams by the action of the acousto-optic modulator group 20 by a control signal from the controller C, the region of high density images 28 _H The electronic mask Is a high-density electron mask region M _H. Therefore, the image bands 26 are successively formed on the printing plate 4 by the rotation of the drum 2, a high-density image band 26 _H because it is masked, recording only the low-density image 28 _L is in the printing plate 4 Is done. The drum rotation speed and the optical bench movement speed are set to the high speed state described above.

FIG. 14 is an explanatory diagram in the case where a high-density image such as an advertisement is formed on a printing plate on which a low-density image is recorded. Set the exposure lens 24b in a high density position lens 24b _H, by the movement of rotation of the drum 2 and the optical bench 14, slide into continuously form a dense image band 26 _H in printing plate 4. As a result, a high-density image _28H is finally formed. The drum rotation speed and the optical bench moving speed are set to the low speed state described above.

In this case, all the laser beams are cut off by the control signal from the control device C for the area of the low density image 28 _L on which recording has already been completed, and the low density image 28 _L
The entire area of the _H is in the low-density electronic mask region M _L. Therefore, only the high-density image 28 _H is recorded on the printing plate 4.

FIG. 15 is a plan view of a printing plate on which a high-density image and a low-density image are recorded. 13 and as shown in FIG. 14, second low density images 28 _L and a high-density image 28 _H
By the step recording operation, the low-density image _28L and the high-density image _28H are separately formed on one printing plate 4.

[0068] In the above method, a low-density image 28 is _L was formed earlier, it may be after the low-density image 28 _L formed first high-density image 28 _H. When three or more images having different densities exist, at the stage of forming an image of a specific density, all other images are operated with an electronic mask, and this operation is repeated to sequentially form all images. It will go. The drum rotation speed and the optical bench moving speed are changed in each stage according to the dot magnification.

FIG. 16 is a schematic configuration diagram of a planar recording system for explaining a second embodiment of the present invention. In the figure, reference numeral 30 denotes a flat table on which the printing plate 4 is placed. An exposure lens unit 24 is arranged to face a photosensitive surface of the printing plate 4 at a predetermined image forming distance. As the exposure lens unit 24, the above-mentioned turret type exposure lens unit, zoom type exposure lens unit, seesaw type exposure lens unit, and take-out type exposure lens unit can be freely selected and used.

The exposure lens unit 24 is adjusted to set the low-density exposure lens 24b _L first. The high-density image area is covered with an electronic mask by the control device to form a high-density electronic mask area _MH . In this state, the moving lens unit H scans the exposure lens unit 24 in the XY direction in parallel with the printing plate 4. In this way, the low density image band 26
_L is a low-density image 28 _L is completed are sequentially formed.

Next, the exposure lens 24b is set to a high density exposure lens 24b _H, region of low density images 28 _L with respect to applying an electron mask, successively form a dense image band 26 _H. As a result, a high-density image _28L is completed. In this way, low-density images 28 _L with high density image 28 _H is formed on the printing plate 4, the printing plate 4 is completed.

The present invention can also be applied to a drum interior rotation system (not shown). This drum interior rotation system is a system in which a printing plate 4 is installed inside the drum 2 and an optical system is arranged inside the drum 2. Figure 1 shows the basic configuration
The optical table 14 is connected to the drum 2
The image band 26 is recorded on the printing plate 4 arranged inside by the exposure lens unit 24.
Other procedures are the same as the drum exterior rotation method,
The details are omitted.

As described above, the exposure device 22 is set to, for example, 1
It can be composed of 28 light emitting diodes or laser light sources. In this case, the control signal and the image signal from the control device C are directly input to the exposure unit 22, and the individual light sources are turned on / off by this signal, and the high-density image _28H and the low-density image _28L are printed. It is formed on the printing plate 4. Therefore,
The laser light source 16, the multi-beam generator 18, and the acousto-optic modulator group 20 shown in FIG. 1 are not required in this example. Of course, various known techniques can be used, such as using the acousto-optic modulator group 20 as an exposure device.

The printing plate exposure apparatus according to the present invention is not limited to the above-described embodiment, but includes various modifications and design changes within the technical scope thereof without departing from the gist of the present invention. It goes without saying that it does.

[0075]

According to the first aspect of the present invention, the image bandwidth formed on the surface of the printing plate is changed only by exchanging the exposure lenses having different focal lengths, and the high-density image and the low Since a printing image in which density images are mixed can be recorded on a printing plate, multiple image density printing that satisfies various demands of an advertiser or the like can be performed.

According to the second aspect of the present invention, when the image density is changed, not only the number density of the light beams but also the dot diameter formed on the printing plate by one beam is changed, so that the low-density image can be obtained. The difference in the image definition of the high-density image can be emphasized.

According to the third aspect of the present invention, a printing plate in which a high-density image and a low-density image are mixed at a high speed is produced by applying the printing plate to a drum rotating system having an exterior or interior. be able to.

According to the fourth aspect of the present invention, by applying the method of the present invention to a flat-plate exposure method of a printing plate widely used, a high-density image and a low-density image can be mixed at a high speed in an existing apparatus. The ability to form can be provided.

According to the fifth aspect of the present invention, three or more images having different pixel densities can be formed on a printing plate at high speed, and a wide variety of images can be introduced to a paper such as a newspaper.

According to the sixth aspect of the present invention, a printing plate in which a high-density image and a low-density image are mixed can be produced at high speed by loading a plurality of exposure lenses having different focal lengths into an exposure lens unit. It is possible to provide a multi-stage exposure apparatus having a pixel density.

According to the seventh aspect of the present invention, a high-density image and a low-density image are mixed at a high speed by using a drum type exposure apparatus in which a plurality of exposure lenses having different focal lengths are loaded in an exposure lens unit. It is possible to provide a drum rotation type pixel density multi-stage exposure apparatus capable of producing a printing plate.

According to the eighth aspect of the present invention, a high-density image and a low-density image are mixed at a high speed by using a flat type exposure apparatus in which a plurality of exposure lenses having different focal lengths are mounted on an exposure lens unit. It is possible to provide a plane type pixel density multi-stage exposure apparatus capable of producing a printing plate.

According to the ninth aspect of the present invention, a turret type exposure lens unit in which a plurality of exposure lenses are arranged inside the cylinder at different positions in the axial direction is used, and this exposure lens unit is a drum rotary type or a planar type. By arranging in the exposure device of
It is possible to provide a pixel density multiple exposure apparatus capable of recording and forming a plurality of pixel densities on a printing plate at high speed.

According to the tenth aspect of the present invention, a plurality of pixel densities can be recorded and formed on a printing plate at a high speed by arranging a zoom type exposure lens unit in a drum rotation type or flat type exposure device. It is possible to provide a multi-stage exposure apparatus having a high density.

According to the eleventh aspect of the present invention, a plurality of pixel densities can be recorded and formed on a printing plate at a high speed by arranging a seesaw type exposure lens unit in a drum rotation type or flat type exposure device. It is possible to provide a multi-stage exposure apparatus having a high density.

According to the twelfth aspect of the present invention, a plurality of pixel densities can be recorded and formed on a printing plate at a high speed by arranging a take-out type exposure lens unit in a drum rotation type or a plane type exposure apparatus. It is possible to provide a multi-stage exposure apparatus having a high density. As described above, the present invention can provide excellent practical effects as described above.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a drum exterior rotation system for explaining a first embodiment of the present invention.

FIG. 2 is a schematic perspective view of a turret type exposure lens device.

FIG. 3 is a side view on the incident side of the turret type exposure lens unit.

FIG. 4 is a schematic perspective view of a zoom exposure lens device.

FIG. 5 is a schematic perspective view of a seesaw type exposure lens device.

FIG. 6 is a schematic perspective view of a seesaw type exposure lens device having different rotation directions.

FIG. 7 is a schematic perspective view of a take-out type exposure lens device.

FIG. 8 is an explanatory diagram of a first method of changing the image density.

FIG. 9 is an explanatory diagram of a second method of changing the image density.

FIG. 10 is an intensity distribution diagram of dots formed by one laser beam on a drum.

FIG. 11 is a schematic explanatory diagram of a dot image.

FIG. 12 is a schematic explanatory diagram of an image band in which low density and high density are mixed.

FIG. 13 is an explanatory diagram when a low-density image such as an article is formed on a printing plate.

FIG. 14 is a diagram illustrating a case where a high-density image such as an advertisement is formed on a printing plate on which a low-density image is recorded.

FIG. 15 is a plan view of a printing plate on which a high-density image and a low-density image are recorded.

FIG. 16 is a schematic configuration diagram of a flat recording method for explaining a second embodiment of the present invention.

FIG. 17 is a schematic configuration diagram of a conventional drum rotation system using a multi-beam.

[Explanation of symbols]

2 is a drum, 4 is a printing plate, 6 is a start side line, 8 is an end side line,
10 is the top line of the printing plate, 12 is the ground line of the printing plate, 14 is the optical bench,
16 a laser light source, 18 is a multi-beam generator, 20 is an acousto-optic modulator group, 22 exposing unit, 24 exposure lens unit, 24b, 24b ₁ ~24b ₃ exposure lens, the image bands 26, 26 _L is low density image band, 26 _H high-density image band, the 28 printing image, 28 _L is a low-density image, 2
_8H is high density image, 30 is flat board, _32H is high density dot, _32L is low density dot, B is bandwidth, B _L is low density bandwidth, B _H is high density bandwidth, C is control apparatus, H is the moving mechanism, M _L is a low-density electronic mask region, M _H is a high-density electronic mask area, P ₁ is the incident light, P ₂ is irradiation light, P _2L is a low density irradiation light, P _2H high density Irradiation light, S _H is high density dot diameter, S _L is low density dot diameter, V _aH is high density drum rotation speed, V _aL is low density drum rotation speed, V _bH is high density movement speed, V _bL is low density The moving speed.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03F ^7/ 20-7/24 G03F 9/00-9/02

Claims (12)

(57) [Claims] 1. A printing method in which a high-density image and a low-density image are mixed while forming an image band on a printing plate by irradiating a predetermined number of light beams to the surface of the printing plate through an exposure lens. In the printing plate exposure method for recording an image, when recording a high-density image, the image band width formed on the printing plate by adjusting the exposure lens to a narrow high-density image bandwidth. Setting, forming the narrow high-density image band on the printing plate while adding an electronic mask so as to block the light beam with respect to the low-density image area, and recording the high-density image, During recording, readjust the exposure lens to increase the image bandwidth to a wide low-density image bandwidth so as to reduce the irradiation density of the light beam,
A part of the light beam on one side or both sides of this low-density image bandwidth is idled to reduce the low-density image bandwidth to be equal to the high-density image bandwidth, and block the light beam for the high-density image area. Forming the low-density image band on a printing plate while adding an electronic mask to record a low-density image. 2. In the low-density image band, the dot diameter of one dot formed by one light beam is increased in accordance with the enlargement ratio of the bandwidth than the dot diameter of the high-density image band. 2. The method according to claim 1, wherein the formation speed of the high density image band is increased in accordance with the enlargement ratio as compared with the high density image band. 3. A high-density image narrow during one rotation of a drum.
The printing plate is displaced in the axial direction by the image band width.
Spiral on the outer or inner surface of the drum at the required inclination angle
The drum is rotated while moving the exposure lens relatively in the axial direction of the drum to form a spiral image band on the printing plate. 2. The method according to claim 1, wherein a printing image in which images are mixed is recorded. 4. The printing plate is arranged in a plane, an exposure lens is arranged to face the printing plate, and the exposure lens is moved relatively to the surface of the printing plate to form a printing plate. 2. The method according to claim 1, wherein an image band is formed two-dimensionally, and a printing image in which a high-density image and a low-density image are mixed is recorded in the process of forming the image band. 5. When forming a printing image from three or more images having different pixel densities, a high-density image is defined as the high-density image, and a lower-density image is defined as the low-density image. 5. A multi-step exposure of a printing plate according to claim 1, wherein an electronic mask is added so as to block a light beam in all other image areas when recording an image having a high density. Method. 6. A printing plate exposure apparatus which irradiates a plurality of light beams onto a surface of a printing plate via an exposure lens and records image information in a band shape with a bandwidth of a plurality of pixels. the image band width on the plate in order to variably adjust
Short focal length to form high-density images and long focal length
An exposure lens device loaded with an exposure lens capable of forming a low-density image, an exposure device for projecting a plurality of light beams into the exposure lens device, and an exposure lens for forming a plurality of image bands having different pixel densities. A control device that controls on / off of each light beam output from the printer and that can completely shut off the light beam group to apply an electronic mask to an arbitrary image area is provided. A multi-stage exposure apparatus having a pixel density of a printing plate, which records a printing image in which density images are mixed. 7. A drum rotatable around an axis, a printing plate wound on an outer peripheral surface or an inner peripheral surface of the drum,
The multi-stage exposure of a printing plate for printing according to claim 6, comprising: an optical bench on which the exposure lens unit and the exposure unit are fixed; and a moving mechanism for relatively moving the optical bench in the axial direction of the drum. apparatus. 8. A flat board, a printing plate fixed to the flat board, an exposure lens unit facing the printing plate at a predetermined distance from the printing plate, and printing the exposure lens unit on the printing plate. 7. The exposure apparatus according to claim 6, further comprising a moving mechanism capable of moving the XY plate relatively parallel to the printing plate. 9. The exposure lens unit is a turret type exposure lens unit comprising a cylindrical body and a plurality of exposure lenses having different focal lengths and arranged inside the cylindrical body at different axial positions. 7. The exposure apparatus according to claim 6, wherein the body is rotated around the axial direction so that an exposure lens for light beam incidence can be selected. 10. An exposure lens device, comprising: a cylindrical body; an exposure lens mounted in the cylindrical body; and a zoom mechanism configured to move the exposure lens in an axial direction to change a focal length. The multi-stage exposure apparatus according to claim 6, which is a lens unit. 11. A seesaw-type exposure lens, wherein the exposure lens unit forms a composite exposure lens body by connecting a plurality of exposure lenses having different focal lengths, and rotates the composite exposure lens body to select an exposure lens. The multi-stage exposure apparatus for pixel density of a printing plate according to claim 6, which is a container. 12. The exposure lens unit includes an exposure lens group in which a plurality of exposure lenses having different focal lengths are integrated, and an extraction mechanism for extracting and arranging one exposure lens from the exposure lens group. 7. The exposure apparatus according to claim 6, wherein the exposure apparatus is a take-out type exposure lens unit.