JP3273139B1 - PIXEL DENSITY OF PRINTING PLATES Plural-Step Sequential Exposure Method and Apparatus - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To record and form a printing image having a plurality of pixel densities on a printing plate, and to sequentially record a high-density image and a low-density image at high speed. A method of sequentially exposing a plurality of levels of pixel density of a printing plate according to the present invention includes the steps of: forming a high-density image in a step of forming a high-density image; The narrow high-density image band 26H is formed on the printing plate 4 while the electronic mask ML is added so as to block the light beam from the low-density image area, and the high-density image 28H is recorded. Then, in the step of forming the low-density image 28L, the low-density exposure lens 24bL
To increase the image bandwidth to a wide low-density image bandwidth BL so as to reduce the irradiation density of the light beam, and to add the electronic mask MH so as to block the light beam in the high-density image area. An image band 26L is formed on the printing plate 4 to record a low-density image 28L, and the high-density image forming process and the low-density image forming process are sequentially performed on the printing plate 4 in a desired order. Print image 28
Is recorded.

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 using image signals, and more particularly, to a high-density exposure lens and a low-density exposure lens having different focal lengths. The present invention relates to a method and an apparatus for sequentially exposing a printing plate having a plurality of pixel densities capable of sequentially printing a high-density image and a low-density image in a desired order at a high speed by sequentially exposing the printing plate.

[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. 15 is a schematic configuration diagram of a conventional drum rotation system using multiple beams. 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 bandwidth B, which is the irradiation width of the light beam, is 0.1408 inches (hereinafter referred to as 0.14 inches), and when 128 light beams are used, 0.14 inches is used. Information is recorded at a density of 128 dots in width. When converted, image information is 90 per inch
Recording is performed at a pixel density of 9 dots.

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, if the relative moving speed of the optical system is set to move by the band width B per rotation of the drum 2, the surface of the printing plate 4 becomes an image by the continuous rotation of the drum 2 and the continuous movement of the optical system. The spiral of the band 26 completely fills the space. The drum 2 may be moved while the optical system is stopped. That is, the relative movement means that the movement of the optical system or the movement of the drum may be performed.

Since the exposing unit 22 is also inclined at the angle θ, the image band 26 is also formed in parallel with the top line 10 of the printing plate 4 without distortion. Therefore, 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 on the printing plate 4 without 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.

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, at a high speed. An object of the present invention is to realize a stepwise exposure method and an apparatus therefor.

[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, in a process of forming a high-density image, a high-density exposure lens is used to narrow the image bandwidth with a high-density image bandwidth. The narrow high-density image band is formed on a printing plate while applying an electronic mask so as to block a light beam with respect to the low-density image area, and a high-density image is recorded. In the step of forming, the image bandwidth is set to be wide to a low-density image bandwidth so as to reduce the irradiation density of the light beam by the low-density exposure lens, and the light beam is blocked to the high-density image area. Add an electronic mask The low-density image band is formed on a printing plate to record a low-density image, and the high-density image forming step and the low-density image forming step are sequentially performed on the printing plate in a desired order. A printing step of printing a printing image by printing the printing plate at a plurality of pixel densities.

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 pixel density of the printing plate is increased in multiple stages.

According to a third aspect of the present invention, when the high-density image forming step is performed, the printing plate is shifted in the axial direction by a narrow high-density image bandwidth during one rotation of the high-density drum. The plate is spirally wound around a high-density drum at a high-density inclination angle, and a high-density image band is spirally formed so that high-density dots formed by the light beam do not overlap with each other to record a high-density image. When performing the high-density image forming step, the printing plate is spirally wound around the low-density drum at a low-density tilt angle so that the low-density drum is shifted in the axial direction by a wide low-density image bandwidth during one rotation. 3. The pixel density of a printing plate for printing according to claim 2, wherein a low-density image band is spirally formed so that low-density dots formed by the light beam do not overlap each other to record a low-density image. An optical method.

According to a fourth aspect of the present invention, when the high-density image forming step is performed, the printing plate is arranged in a plane.
The high-density exposure lens is moved relative to the printing plate in a plane so that the high-density dots do not overlap each other to form a high-density image band, and a high-density image is recorded. When performing the printing, the printing plate is rearranged in a plane, and the low-density exposure lens is moved relative to the printing plate in a plane so that the low-density dots do not overlap each other. 3. The method according to claim 2, wherein a low-density image is recorded while forming a high-density image band.

According to a fifth aspect of the present invention, when printing images are printed from three or more images having different pixel densities, the high-density image forming steps and / or the low-density image forming steps corresponding to the different pixel densities are performed. 2. A method for sequentially exposing a plurality of levels of pixel density of a printing plate according to claim 1 provided.

According to a sixth aspect of the present invention, there is provided a printing plate exposure apparatus for irradiating a plurality of light beams from an exposure lens onto a surface of a printing plate to record image information in a band shape with a bandwidth of a plurality of pixels. A high-density exposure lens with a short focal length to form a narrow, high-density image band, a high-density moving mechanism for moving this high-density exposure lens relative to the printing plate, and a high-density printing plate to which the printing plate is attached A high-density exposure device consisting of a fixed device, a low-density exposure lens with a long focal length that forms a wide low-density image band, a low-density moving mechanism that moves the low-density exposure lens relative to a printing plate, and printing. A low-density exposure device comprising a low-density plate fixing device for mounting a printing plate, and an electronic mask for a specific image area when these high-density exposure devices and low-density exposure devices are sequentially driven for exposure in a desired order. A pixel density multi-stage sequential exposure apparatus of the printing plate, characterized in that it comprises a control device for controlling an output to an exposure image signal while applying.

According to a seventh aspect of the present invention, the high-density plate fixing device is a high-density drum rotatable around an axis, and the low-density plate fixing device is also a low-density plate rotatable around an axis. Claims 1. A drum comprising a high-density exposure lens and a low-density exposure lens disposed opposite to a printing plate wound around an outer peripheral surface or an inner peripheral surface of the high-density drum or the low-density drum. Item 7. A sequential exposure apparatus having a plurality of levels of pixel densities of a printing plate according to Item 6.

The invention according to claim 8 is that the high-density printing plate fixing device is a high-density flat plate, and the low-density printing plate fixing device is also a low-density flat plate. A high-density exposure lens and a low-density exposure lens arranged opposite to a printing plate arranged in a plane on the table, and both exposure lenses X parallel to the printing plate relative to the printing plate;
7. The exposure apparatus according to claim 6, further comprising a high-density moving mechanism and a low-density moving mechanism for performing Y movement.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method and an apparatus for sequentially exposing a plurality of levels of pixel density of a printing plate according to the present invention 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. Drum rotation system of the first embodiment is performed using a two-step exposure apparatus of a high-density exposure apparatus 1 _H and a low-density exposure apparatus 1 _L, the H subsequent subscripts relate to high density exposure step, subscripts L Indicates that it is related to the low density exposure step.

The high-density exposure apparatus 1 _H includes a high-density drum 2 _H ,
The low-density exposure apparatus 1 _L includes a high-density optical system A _H and a high-density moving mechanism H _H , and includes a low-density drum 2 _L and a low-density optical system A _L
And a low-density moving mechanism _HL . The high-density optical system A _H includes a high-density exposure unit 22 _H and a high-density exposure lens 24 b _H , and the low-density optical system A _L includes a low-density exposure unit 22 _L and a low-density exposure lens 24 b _L.

High density drum 2_HPrinting plate on the outer peripheral surface of
4 is the drum axis direction g_HHigh-density tilt angle θ_HJust tilt
It is wound obliquely. That is, a high-density image is printed on the printing plate 4.
Image bandwidth B_HDensity image band 26 with_HThe spy
High density image 28 _HWhen you record
Drum 2_HStart line 6 or end line when 1 turns
8 is the high-density image bandwidth B_HPrinting plate
4 are arranged.

When the circumference of the high-density drum 2 _H is CL, the inclination angle θ _H is given by tan θ _H = B _H / CL. When the oblique arrangement is made so as to satisfy this relationship, the above-mentioned spiral condition is satisfied. Accordingly, the ceiling wire 10 and the ground wire 12 are also inclined at an angle θ _H with respect to the drum axis direction g _H. Further, since the high-density image 28 _H is formed in parallel with the heaven line 10 and the ground line 12, the high-density exposure device 22 _H has two axial directions.
2a _H to be the drum axial direction g _H is set to the separable by an angle theta _H.

The low-density exposure apparatus _1L is arranged almost in the same manner as the high-density exposure apparatus _1H . The difference is the low density image band 26
Bandwidth B _L of _L is that it is larger than the high density image bandwidth B _H to allow high speed recording. That is, the low-density inclination angle θ _L is also set to be larger than the high-density inclination angle θ _H by the relational expression of tan θ _L = B _L / CL.

[0029] Thus, in the low-density exposure step, the printing plate 4 is low density drum 2 _L direction that the drum axis on the outer circumferential surface of the g _L
Is wound with a low density tilt angle θ _L. The low since the density image 28 _L is parallel to the Tensen 10 and ground wire 12, to low-density exposure device 22 _L axis direction 22a _L of relative Drum axially g _L by an angle theta _L separable Is set.

High density exposure apparatus _1H and low density exposure apparatus _1L
In, the directions of the top line 10 and the ground line 12 of the printing plate 4 are commonly set in parallel so as to face the Y direction. As shown in the figure, the X axis and the Y axis which are both sides of the printing plate 4 are at the c position, d
It is arranged in the same direction at the position and the position e. Here, c, d, and e mean a position and an arrow direction.

The operation of the above configuration will be described. The printing plate 4 is moved from the position c in the direction of the arrow c, and is wound around the high-density drum 2 _H arranged obliquely in the direction g _H. High density exposure lens 2
When 4b _H recording high density images 28 _H by ends, the plate 4 is singled d position from the dense drum 2 _H. Furthermore, the plate 4 is moved from the position d in the direction of arrow d are wound in a low density drum 2 _L that is inclined largely located in g _L direction. When the low-density exposure lens 24b _L with low density images 28 _L recording is finished, the plate 4 is removed to e position from the low-density drum 2 _L, recording of print image 28 to the printing plate 4 is completed . Finally, the printing plate 4 is moved in the direction of the arrow e, developed, and loaded into the printing press.

The printing plate 4 is commonly moved in the X-axis direction throughout the high-density exposure and low-density exposure steps, and the top line 10 of the printing plate 4 is parallel to the Y-axis direction perpendicular to the X-axis. And the ground line 12 are arranged. The angle θ _H with respect to the Y-axis direction,
theta _L dense drum 2 _H and a low-density drum 2 _L in the direction of are arranged in an inclined manner, at all times these inclined arranged drum unit X-axis direction in the plate 4 is to proceed.

In the high-density optical system A _H and the low-density optical system A _L , the light beam group for exposure is controlled on / off by an image signal output from the control device C. In this figure, the high-density exposure unit _22H and the low-density exposure unit _22L are on / off controlled,
Controlled light beams to form a high density exposure lens 24b _H and low density exposure lens 24b _L high density image on the plate 4 through the band 26 _H and the low-density image band 26 _L.

In the high-density exposure stage, the low-density image area is not exposed by the action of the electronic mask.
Only 8 _H is recorded. Similarly, in the low density exposure stage,
The high density image area is not exposed by the action of the electronic mask, and only the low density image _28L is recorded. Thus, the high-density image _28H and the low-density image _28L are recorded by the two-step exposure method while preventing double exposure. The electronic mask is to completely block the light beam group by turning off all the image signals output from the control device C. That is, the electronic mask and the image exposure are all executed by the image signal from the control device C.

FIG. 2 is a schematic configuration diagram of a high-density exposure apparatus. High density exposure apparatus 1 _H is composed of high-density printing plate fixing apparatus 3 _H and dense optical system A _H, high density printing plate fixing apparatus 3 _H is dense drum 2 _H and density for rotating this previously described It consists of a motor _MH . High-density optical system A _H
H , high-density laser light source 16 _H , high-density multi-beam generator 18 _H , high-density acousto-optic modulator group 20 _H , high-density exposure unit 2
2 _H , high density exposure lens 24b _H and high density moving mechanism H _H
Consists of

This device uses a laser beam as a light beam. One laser beam emitted from a laser light source 16 _H such as a semiconductor laser passes through a multi-beam generating element 18 _H such as a grating or a Wollaston prism, and is divided into, for example, 128 multi-beams. Many of these multi-beams are incident on the high-density AOM group 20 _H, but acousto-optic modulator AOM is its components are present by the number of multi-beams, one of the acousto single laser beam Will be incident on the container AOM.

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 lasers beams enters the dense exposure device 22 _H consisting of a light source array constituted by optical fiber, high-density exposure lens 24
through b _H is applied to the plate 4.

[0038] by the movement in the arrow b direction of rotation and dense moving mechanism H _H high-density optical bench 14 _H in the direction of arrow a high-density motor M _H, irradiation light P _2H high density drum 2
_The high-density image band 26H is spirally formed on the printing plate 4 wound around _H. High density moving mechanism H _H is high density drum 2 _H
The movement of the high-density drum 2 _H and the movement of the optical bench 14 _H are relative, for example, they may be moved in opposite directions.

FIG. 3 is a schematic configuration diagram of the low-density exposure apparatus. The low-density exposure apparatus _1L includes a low-density printing plate fixing device _3L and a low-density optical system A _{L. The} low-density printing plate fixing device _3L includes the above-described low-density drum _2L and a low-density rotary driving device. a motor M _L. The low-density optical system _AL is a low-density optical table 14
_L , low-density laser light source 16 _L , low-density multi-beam generator 18 _L , low-density acousto-optic modulator group 20 _L , low-density exposure unit 2
2 _L , low density exposure lens 24b _L and low density moving mechanism H _L
Consists of

The operation and effect of the low-density exposure apparatus 1 _L is omitted the same as the high-density exposure apparatus 1 _H described above.
Importantly, for bandwidth B _L of the low-density image band 26 _L is set larger than the high density image bandwidth B _H formed in the plate 4 by the irradiation light P _2L, according to the enlargement ratio rotational speed by the moving speed and low-density motor M _L with low-density moving mechanism H _L Te is that is much larger. Therefore, the recording time of the low density image 28L can be reduced,
Efficiency of plate recording work and cost reduction can be realized.

As described above, the control device C is a device for outputting an image signal, and is composed of a computer and a dedicated electronic device. From this control device C, a high-density image signal for controlling the high-density optical system A _H and a low-density image signal for controlling the low-density optical system A _L are simultaneously output, and the acousto-optic modulator group 20 _H , 20 _L is controlled simultaneously, and high-density multi-beam and low-density multi-beam are simultaneously turned on and off.

The multi-beam can be formed by other methods. For example, in the case where one laser beam is divided into a large number in combination with an exposure device during one oscillation in the width direction, the laser beam source is turned on / off by an image signal each time the division is performed, thereby obtaining a multi-beam. Overall on / off control can be realized. For example, the exposing device is composed of 128 optical fibers, and if the laser light source itself is turned on and off each time a laser beam is incident on each optical fiber, one end results.
On / off control of each of the 28 multi-beams is performed individually.

If the group of acousto-optic modulators is used as an exposing device, there is no need to provide an exposing device as a separate member. At this time, the control device C is set so as to directly control on / off of the exposure units 22 _H and 22 _L. The exposing device is constituted by a multi-beam generator composed of a large number of laser generating elements, light emitting diodes, and the like.
Can be turned on and off.

Next, a specific example of the number of dots in the image band will be described. Assuming that the number of multi-beams is 128, each laser beam is controlled to be turned on and off by a control signal, and a light and shade pattern composed of a 128-dot on-off pattern has image bandwidths B _H and B _{L of the} printing plate 4. Will be recorded. While the drums 2 _H and 2 _L make one rotation, the optical table 14 _H ,
14 _L of the direction of the arrow b on the bandwidth B _H, is moved by B _L, image band 26 _H, 26 _L is just enough continuously formed in a spiral shape on the plate 4.

The image density is 909 dots per inch,
When the circumference of the drum 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 128-dot time series signal corresponding to the bandwidth is repeatedly input for 41814 times per circumference.

In this specific example, since the case where the total number of laser beams passing through the exposure units 22 _H and 22 L is 128 has been described, the image density of the image bandwidths BH and BL is 1
28 / band. Since there are 128 dots in the narrow width BH, a high-density image band 26H is formed, and since there are 128 dots in the wide width BL, a low-density image band 26L is formed.

In order to reduce the group of 128 laser beams to a high-density image bandwidth BH or expand the low-density image bandwidth BL, a high-density exposure lens 24bH having a short focal length is used.
Or a low-density exposure lens 24bL having a long focal length.

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.

When the focal length of the high-density exposure lens is represented by f _H and the focal length of the low-density exposure lens is represented by f _L , when the focal length of the exposure lens is changed from f _H to f _L , the low-density image bandwidth B _L Is 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, the diameter S (hereinafter referred to as the dot diameter) of the dot formed by one of the beams constituting the band is also expressed as S _L = S _{H for} the high-density dot diameter and S _L for the low-density dot diameter. _H × f _L
It changes in proportion to the focal length according to the formula of / f _H. As described above, the image density and the dot diameter can be changed by changing the focal length of the exposure lens.

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 arbitrarily adjusted so as to form a predetermined image band.

FIG. 4 is an explanatory diagram of a method of changing the image density according to the focal length. A dotted line indicates a low-density image state, and a solid line indicates a high-density image state. These two image states correspond to the exposure lens 2
4b. The focal length f _H of the high-density exposure lens 24b _H is imaged from printing plate 4 distance D _H
The exposure lens 24b _L located at a distance of (Δf _H ) and also at a low density position is also located at a distance of an image formation distance D _L (Δf _L ). At this time, f _L > f _H , and thus D _L >
The relationship of D _H is established.

[0052] When the incident light P _IH is incident on the high-density exposure lens 24b _H, high density radiation beam P _2H reaches the printing plate 4 as shown by the solid line, forms the narrow high-density image band 26 _H I do. 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, for example, 128 laser beams are included in the image bandwidth.
A 4-inch high-density image 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, in the case of recording a low density image, using a Low-Density exposure lens 24b _L. In this case, the incident light P _1L spreads as dotted lines, a low-density image band 26 _L wide low-density image band width B _L is formed on printing plate 4. The reciprocal of the bandwidth enlargement ratio BL / BH is the density reduction index, and the higher the enlargement ratio, the lower the density.

For example, let us enlarge B _H = 0.14 inch (128 dots) from B _H = 0.187 inch (128 dots). Since the enlargement factor is 4/3, the focal length f _L to be used is given by f _L = f _H × 4/3, and consequently 3 /
4, the density is reduced. The above is the case where the exposure lens is installed at a position separated by the focal length from the drum surface. If the focus position deviates, the enlargement ratio or the density reduction ratio is calculated by actually measuring B _H and B _L.

Next, consider one dot formed by one laser beam in an image band. FIG. 5 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 photosensitive material.
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. 6 is a schematic illustration of a dot image. Low density
Degree exposure lens 24b_LFocal length f_LThe high density exposure lens
24b_HIs set to twice that of the
Let's say you were imaged on the floor. At this time, the high sensitivity position X₁so
Is the low density dot diameter S_LIs the high-density dot diameter S_HTwice as large as
Large, low density dots 32_LArea is high density dot 32 _H
2 × 2 = 4 times as large as However, the low sensitivity position X_Two
Then, the low density dot diameter S _LIs the high-density dot diameter S_HBigger
It does, but does not double. Therefore, the dot area
Even if it does not reach four times.

As described above, when the 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 set to an arbitrary ratio by adjusting the sensitivity. You can also. When an image is formed shifted from the focal position, the ratio between the dot diameters of the high density and the low density does not always match the ratio of the focal length, and can be freely changed by adjusting the sensitivity.

FIG. 7 is a schematic explanatory diagram of a high-density image band. The high-density image band 26 _H is formed on the plate 4 by the high density exposure lens 24b _H arranged in a high density exposure apparatus 1 _H of the first stage, high-density dots obtained by the high-sensitivity position X ₁ 32 and consists of _H. When 6 beams total beam number for simplicity, a high density image band 26 _H bandwidth B _H consists of 6 dots dense dots 32 _H. S _H = 1/2 × S _L from the condition of high sensitivity position X ₁
It is.

Exposure by the high-density exposure lens 24b _H
Dense drum 2 _H during rotation is carried out continuously in a low density mask M _L As for the low-density image region to block the entire beam is applied. Therefore, the line H ₁ for the high density image region, row H _2, line H _3, is continuously exposed to the row H ₄ · ·, high density image band 26 _H Yuku formed on bets spiral. Here, the rotation speed of the high-density drum 2 _H is V _aH , and the relative movement speed of the optical system is V _bH .

FIG. 8 is a schematic explanatory diagram of a low-density image band. This low density image band 26 _L is formed on the plate 4 by the low-density exposure lens 24b _L arranged in the low-density exposure apparatus 1 _L of second stage, low-density dots obtained in the high-sensitivity position X ₁ consisting of 32 _L. Like the high-density image band, the total number of beams is six, so the low-density image band _26L is composed of six dots. It is from sensitive position X ₁ of the condition S _L = 2 × S _H, dot magnification is doubled. Therefore, from B _L = 2 × B _H , the low-density image bandwidth B _L is twice the high-density image bandwidth B _H , and the image density is １ ／ of the high-density image bandwidth.

Exposure by the low-density exposure lens 24b _L is continuously performed during rotation of the low-density drum 2L, and a high-density mask _MH for blocking all beams is applied to a high-density image area. Therefore, the row L only for the low-density image area
₁ , row L _2.
L is formed spirally.

An important point of the present invention is that it is not necessary to match the high-density image bandwidth B _H with the low-density image bandwidth B _L. In the above example, since B _L = 2 × B _H , the rotation speed V _aL of the low-density drum 2 _L and the relative movement speed V _bL of the low-density optical system A _L are twice the high-speed exposure, That is,
V _aL = 2 × V _aH and V _bL = 2 × V _bH hold. Accordingly, the low-density exposure speed is significantly increased, and the efficiency of the exposure process of the printing plate can be improved.

FIG. 9 is an explanatory view of a printing plate on which a high-density image is recorded. The high-density exposure lens 24b _H forms narrow high-density image bands 26 _H , 26 _H ... To record a high-density image 28 _H. Since the low-density image region low density electron mask M _L is added, the low-density region is not exposed by the high-density exposure lens 24b _H.

FIG. 10 is an explanatory view of a printing plate on which a low-density image is recorded. The low-density exposure lens 24b _L is a low-density image band 26 _L, 26 _L ·· is formed low-density image 28 _L is recorded. Since the electronic mask M _H applied for the high density image region, this is the high-density regions exposed by a low-density exposure lens 24b _L is not performed. Thereby preventing double exposure by the action of high-density electronic mask M _H and low density electron mask M _L.

FIG. 11 is an explanatory view of a printing plate on which a high-density image and a low-density image are recorded. As described above, the high density image 28 _H and a low-density image 28 _L is formed in two steps. In this embodiment, the high-density exposure is performed first, and then the low-density exposure is performed. However, the order of the high-density exposure and the low-density exposure may be either. Therefore, high-density exposure may be performed after low-density exposure is performed first.

In this embodiment, the two optical systems A _H and A _L are controlled by the control signal from the same control device C. However, the control devices C for the two optical systems A _H and A _L are separately provided. Is also good. In this case, if necessary, the timing and signal speed of both signals are adjusted.

FIG. 12 is a schematic configuration diagram of a planar recording system for explaining a second embodiment of the present invention. High density exposure equipment _1H
Consists density printing plate fixing apparatus 3 _H and dense optical system A _H,
Low density exposure apparatus 1 _L consists low density printing plate fixing device 3 _L with low density optical system A _L. High density printing plate fixing apparatus 3 _H consists of a dense planar base 3 _H placing the plate 4 in a plane, similarly low density printing plate fixing device 3 _L is made from a low-density plane boards 3 _L.

The high-density optical system A _H comprises a high-density exposure unit 22 _H , a high-density exposure lens 24b _H and a high-density moving mechanism H _H , and the low-density optical system A _L includes a low-density exposure unit 22 _L and a low-density exposure It comprises a lens 24b _L and a low-density moving mechanism _HL .

[0070] First, the Suriban 4 is a plane disposed high density flat base 30 _H, to record high-density images 28 _H to form a narrow high-density image band 26 _H. In this high-density exposure step to prevent the exposure by adding an electronic mask M _L for the low-density image region. Next, the printing plate 4 is removed, moved in the direction of the arrow i, and placed on the low-density flat base _30L . In the low-density exposure step, an electron while applying a mask M _H, to form a wide low-density image band 26 _L for recording low-density images 28 _L high-density image areas. By this two-stage drawing, the printing plate 4
The printing image 28 is recorded and completed.

The high-density optical system A _H is individually driven by the high-density moving mechanism H _H , and the low-density optical system A _L is individually driven by the low-density moving mechanism H _L. Conversely, the printing plate 4 may be moved. In the low density exposure stage, the low density image bandwidth HL
Is wider, the moving speed of the low-density moving mechanism HL is correspondingly increased. Needless to say, low-density exposure may be performed first, and high-density exposure may be performed later.

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
High-density optical system A
_H is within the dense drum 2 _H, low density optical system A _L is located within the low-density drum 2 _L. Other procedures are the same as those of the drum exterior rotation method, and therefore, the details thereof are omitted.

As described above, the exposure units 22 _H and 22 _L are
For example, it can be composed of 128 light emitting diodes or laser light sources. In this case, control signals and image signals from the control device C are directly input to the exposure units _22H and _22L ,
The individual light sources are turned on / off by this signal, and a high-density image _28H and a low-density image _28L are formed on the printing plate 4. Therefore, the laser light source 1 shown in FIGS.
6 _H , 16 _L , multi-beam generators 18 _H , 18 _L and acousto-optic modulator groups 20 _H , 20 _L are not required in this example.
Of course, the acousto-optic modulator groups 20 _H and 20 _L are connected to the exposure units 22 _H and
Various known techniques such as the use of 22 _L may be used.

For a print image having three or more different pixel densities, multi-stage exposure is performed by arranging the same number of exposure devices. For example, in the case of three-stage exposure, although the order is not limited, a three-stage exposure process of high-density exposure, medium-density exposure, and low-density exposure is performed, and a printing image is recorded on a printing plate.

The printing plate sequential exposure method and apparatus according to the present invention are not limited to the above embodiment, and various modifications and design changes may be made without departing from the spirit of the present invention. It goes without saying that they are included in the range.

[0076]

According to the first aspect of the present invention, a high-density image and a low-density image can be sequentially formed in a desired order by exposure.
The printing image can be reliably recorded on the printing plate. As a result, printing with various image densities that can satisfy various requests from advertisers and the like can be realized.

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

According to the third aspect of the present invention, a high-density image and a low-density image are sequentially recorded at a high speed so that dots do not overlap with each other by applying to a drum rotation system in which a printing plate is externally or internally mounted. It is possible to create a printing plate while printing.

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 can be formed on an existing apparatus so that dots do not overlap each other. And the ability to simultaneously form low density images at high speed.

According to the fifth aspect of the present invention, three or more images having different pixel densities can be recorded on a printing plate at a high speed by disposing the same number of exposure devices in multiple stages, and can cover a wide area on a paper such as a newspaper. Image diversity can be introduced.

According to the sixth aspect of the present invention, a high-density exposure apparatus equipped with a high-density exposure lens and a low-density exposure lens having different focal lengths and a low-density exposure apparatus are sequentially driven for exposure. It is possible to provide a multi-stage sequential exposure apparatus having a pixel density capable of sequentially and reliably recording a high-density image and a low-density image.

According to the seventh aspect of the present invention, by using a two-stage drum type exposure apparatus equipped with a high-density exposure lens and a low-density exposure lens, printing is performed while sequentially forming a high-density image and a low-density image. It is possible to provide a drum rotary type pixel density multiple-stage sequential exposure apparatus capable of recording an image on a printing plate at high speed.

According to the eighteenth aspect of the present invention, by using a two-stage flat type exposure apparatus equipped with a high-density exposure lens and a low-density exposure lens, a high-density image and a low-density image are sequentially formed, and It is possible to provide a planar type pixel density multiple-stage sequential exposure apparatus capable of recording an image on a printing plate at high speed. 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 configuration diagram of a high-density exposure apparatus.

FIG. 3 is a schematic configuration diagram of a low-density exposure apparatus.

FIG. 4 is an explanatory diagram of a method of changing an image density according to a focal length.

FIG. 5 is an intensity distribution diagram of one laser beam formed on a drum.

FIG. 6 is a schematic explanatory diagram of a dot image.

FIG. 7 is a schematic explanatory diagram of a high-density image band.

FIG. 8 is a schematic explanatory diagram of a low-density image band.

FIG. 9 is an explanatory diagram of a printing plate on which a high-density image is recorded.

FIG. 10 is an explanatory diagram of a printing plate on which a low-density image is recorded.

FIG. 11 is an explanatory diagram of a printing plate on which a high-density image and a low-density image are recorded.

FIG. 12 is a schematic configuration diagram of a flat recording method for explaining a second embodiment of the present invention.

FIG. 13 is a schematic configuration diagram of a conventional drum rotation system using a multi-beam.

[Explanation of symbols]

 1_HIs a high-density exposure apparatus, 1_LIs a low density exposure apparatus, 2_HIs high
Density drum, 2_LIs a low density drum, 3_HIs high-density printing plate fixing
Device, 3_LIs a low-density printing plate fixing device, 4 is a printing plate, 6 is start
The side line, 8 is the end side line, 10 is the top line of the printing plate, and 12 is the
Ground line, 14_LIs a low-density optical bench, 14_HIs a high-density optical bench, 1
6_LIs a low density laser light source, 16_HIs a high-density laser light source, 1
8_LIs a low-density multi-beam generator, 18_HIs high density multi
Beam generator, 20_LIs a group of low-density acousto-optic modulators, 20_H
Is a group of high-density acousto-optic modulators, 22 _LIs a low-density exposure device, 2
2_HIs a high-density exposure device, 24b_LIs a low density exposure lens, 24
b_HIs a high-density exposure lens, 26 is an image band, 26_LIs low
Density image band, 26_HIs high density image band, 28 is mark
Printing image, 28_LIs the low density image, 28_HIs a high-density image, 3
0_HIs a high-density flat base, 30_LIs a low-density flat base, 32_LIs low
Density dot, 32_HIs a high-density dot, A_LIs low density optics
System, A_HIs high-density optical system, B is bandwidth, B_LIs a low density
Command width, B_HIs the high density bandwidth, C is the controller, H_LIs low
Density transfer mechanism, H _HIs the high-density moving mechanism, M_LIs a low density electron
Mask area, M_HIs the high-density electron mask area, P_1LIs low density
Degree incident light, P_1HIs high-density incident light, P_2LIs low-density irradiation light,
P_2HIs high-density irradiation light, S_HIs the high-density dot diameter, S_LIs low density
Degree dot diameter, V_aHIs the high-speed drum rotation speed, V_aLIs low density
Degree drum rotation speed, V_bHIs the high-speed moving speed, V_bLIs low density
Degree moving speed.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03F ^7/ 20-7/24 G03F 9/00-9/02

Claims (8)

(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 method of exposing a printing plate for recording an image, in the step of forming a high-density image, a high-density exposure lens is used to set the image bandwidth to a narrow high-density image bandwidth, The step of forming the narrow high-density image band on the printing plate to record a high-density image while adding an electronic mask so as to block the light beam, and forming a low-density image, using a low-density exposure lens The image bandwidth is set to be wide to a low-density image bandwidth so as to reduce the irradiation density of the light beam, and the low-density image band is added while adding an electronic mask so as to block the light beam with respect to the high-density image area. For printing A low-density image is recorded on a printing plate, and the high-density image forming process and the low-density image forming process are sequentially processed on the printing plate in a desired order to record the printing image. A method for sequentially exposing a plurality of levels of pixel density of a printing plate. 2. A low-density image band, wherein a dot diameter of one dot formed by one light beam is increased in accordance with an enlargement ratio of the bandwidth than a dot diameter of a high-density image band. 2. The method for sequentially exposing a plurality of levels of pixel density of a printing plate according to item 1. 3. A high-density image forming step, wherein the printing plate is tilted at a high density so as to be shifted in the axial direction by a narrow high-density image bandwidth during one rotation of the high-density drum. Spirally wound on a high-density drum at an angle, and high-density image bands are spiral-formed so that high-density dots formed by the light beam do not overlap each other, and a high-density image is recorded. In this case, the printing plate is spirally wound around the low-density drum at a low-density tilt angle so that the low-density drum is shifted in the axial direction by a wide low-density image bandwidth during one rotation of the low-density drum. 3. The method according to claim 2, wherein the low-density image bands are spirally formed so that the low-density dots formed by the low-density dots do not overlap each other to record the low-density image. 4. When the high-density image forming step is performed, a printing plate is arranged in a plane, and a high-density exposure lens is arranged on the printing plate so that high-density dots do not overlap each other. When a high-density image is recorded while forming a high-density image band by relative movement in a plane, and the low-density image forming step is performed, the printing plate is rearranged in a plane, and The printing method according to claim 2, wherein the low-density exposure lens is moved relative to the printing plate in a planar manner so that the low-density dots do not overlap each other to form a low-density image band, and the low-density image is recorded. A method of sequentially exposing a plurality of levels of pixel density of a printing plate. 5. When printing images from three or more images having different pixel densities, high-density image forming steps and / or low-density image forming steps corresponding to the number of different pixel densities are provided. A method for sequentially exposing a plurality of levels of pixel density of the printing plate described in the above. 6. A printing plate exposure apparatus which irradiates a plurality of light beams from an exposure lens onto the surface of the printing plate to record image information in a band shape with a bandwidth of a plurality of pixels. A high-density exposure lens having a short focal length for forming a high-density image band, a high-density moving mechanism for moving the high-density exposure lens relative to the printing plate, and a high-density printing plate fixing device for mounting the printing plate A low-density exposure apparatus, a low-density exposure lens having a long focal length to form a wide low-density image band, a low-density moving mechanism for relatively moving the low-density exposure lens relative to the printing plate, and a low-density mounting plate. A low-density exposure device comprising a high-density printing plate fixing device, and when the high-density exposure device and the low-density exposure device are sequentially exposed and driven in a desired order, image signals are applied while applying an electronic mask to a specific image area. And a control unit for controlling exposure by outputting a signal. 7. The high-density plate fixing device is a high-density drum rotatable around an axis, and the low-density plate fixing device is also a low-density drum rotatable around an axis. 7. The high-density exposure lens and the low-density exposure lens according to claim 6, further comprising: a high-density exposure lens and a low-density exposure lens arranged to face a printing plate wound around an outer peripheral surface or an inner peripheral surface of the high-density drum or the low-density drum. A multi-stage sequential exposure device with a pixel density of a printing plate. 8. The high-density plate fixing device is a high-density flat plate, and the low-density plate fixing device is also a low-density flat plate. A high-density exposure lens and a low-density exposure lens arranged opposite to the printing plate to be arranged, and a high-density moving mechanism for moving the two exposure lenses XY relatively parallel to the printing plate 7. The exposure apparatus according to claim 6, further comprising a low-density moving mechanism.