JPH0558073A - Plate making method - Google Patents

Abstract

PURPOSE:To provide a plate making method capable of forming an image on a plate cylinder many times without using a disposable raw plate comparatively high in cost. CONSTITUTION:In a plate making method, the outer peripheral surface of the plate cylinder of a printing press is subjected to hydrophilic treatment in on- machine plate making and a photosensitive film is laminated to the treated outer peripheral surface of the plate cylinder by the nip press of the roller or printing cylinder being in contact with the plate cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate producing method for on-press plate making in a printing press.

[0002]

2. Description of the Related Art Conventional on-machine platemaking involves wrapping a platemaking paper (hereinafter referred to as a raw plate) in which a base material such as a plastic plate or an aluminum plate is coated with a photosensitizer on the outer peripheral surface of the plate cylinder, The front side and the bite side are clamped and mounted on the plate cylinder, and then a laser beam is irradiated to create an image. After the image is formed, a special chemical treatment is performed to remove the photosensitizer in the portion which forms the non-image area where the laser beam is not applied, so that a plate used for printing (hereinafter referred to as a printing plate) is produced.

FIG. 2 shows the above-described on-press plate making method in a plate cylinder of an offset sheet-fed printing press. 1 is a plate cylinder, 2 is a plate biting device, 3 is a raw plate, 4 is a laser beam irradiation device, 5 is a chemical treatment device, and 6 is a gap for mounting the plate biting device 2 of the plate cylinder 1. Ink is supplied to the generated image (image area) of the printing plate 7, dampening water is supplied to the non-image area from a swimsuit roller (not shown), and the ink in the image area is blanketed. After being transferred to the cylinder 9, it is retransferred to the printing machine passing between the impression cylinder 10 and the blanket cylinder 9. In the case of direct printing (direct lithographic printing plate), the ink in the image area is transferred to the printing paper passing between the plate cylinder 1 and the impression cylinder 10 (because no blanket cylinder is provided).

Further, the above-mentioned on-press plate making is used for an offset proofing machine, and there is no example applied to a rotary type offset sheet-fed machine as shown in FIG. Therefore, the plate is never mounted on the plate cylinder of this sheet-fed press.

[0005]

The above-mentioned prior art has the following problems. (1) Raw plates that have been plate-made by on-press printing cannot be reused. In addition, the price of this disposable version is relatively high.
After use, it was possible to remove the dust remaining on the printing plate, remove the imaged photosensitizer on the base member, and reuse the base member.However, since the base member is thin, stainless steel is used. If the plate is not hydrophilic and has a strong strength, cracks will be generated during printing on the gripping side and the gripping edge of the printing plate and it cannot be reused. Even if it is made of stainless steel, it can be reused for 4 to 5 times and is more expensive than an aluminum plate.

(2) In order to remove the non-image area of the raw plate which has been plate-made by the machine, a special chemical treatment including rinsing must be performed. At this time, it may be difficult to find a space on the outer peripheral surface of the plate cylinder for temporarily inserting the apparatus for performing the chemical treatment. (3) A plate biting device must be provided in order to mount the plate on the plate cylinder. Therefore, a gap is required to install the plate biting device on the plate cylinder, and the outer diameter of the plate cylinder becomes large.

It is an object of the present invention to propose a plate producing method capable of forming an image on a plate cylinder many times without using a disposable expensive raw plate.

[0008]

[Means for Solving the Problems]

(1) The outer peripheral surface of the plate cylinder is hydrophilized. (2) A photosensitive film coated with a sensitizer is used instead of the raw plate. (3) After wrapping the photosensitive film around the plate cylinder, a laser beam is irradiated to form an image.

[0009]

[Action]

(1) When the photosensitive film is peeled off from the plate cylinder, the sensitizer which is irradiated with a laser beam and becomes an image firmly adheres to the plate cylinder, and the sensitizer which is not irradiated with the laser beam remains adhered to the photosensitive film. It is removed from the plate cylinder together with the film. (2) Since the outer peripheral surface of the plate cylinder is hydrophilized,
Fountain solution adheres and repels ink, forming non-image line areas on the printed surface.

(3) The photosensitive film is adhered to the plate cylinder by a nip pressure between the plate cylinder and an inking roller, a blanket cylinder or an impression cylinder which is in contact with the plate cylinder. At, it never leaves the plate cylinder.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a plate generation method according to the invention. The photosensitive film 12 rolled into a roll has a sensitizing surface in contact with the outer peripheral surface of the plate cylinder 11, and has a hydrophilic surface treatment such as graining or chrome plating on the outer peripheral surface.
Then, the ink is applied to the plate cylinder 11 by the rotational force of the inking roller 8 and the blanket cylinder 9 and the nip pressure, which is then pressed and then cut. Next, the laser beam irradiation device 4 irradiates a laser beam to form an image. After the image formation, when the photosensitive film 12 is peeled off from the plate cylinder 11, the image portion firmly adheres to the outer peripheral surface of the plate cylinder 11, and the sensitizer in the portion not irradiated with the laser beam remains adhered to the photosensitive film 12. 12 is peeled off and removed from the plate cylinder 11, and the hydrophilic surface of the outer peripheral surface of the plate cylinder 11 is exposed later. Therefore, when the ink and the dampening water are supplied from the ink and the swimsuit roller, respectively, as described above, an image is printed on the printing paper. When printing is completed, the image portion adhering to the outer peripheral surface of the plate cylinder 11 is removed and an image for the next printing is formed by the above-described image generation process. Therefore, it is possible to generate the plate by the number of on-screen plate making.

When the photosensitive film 12 is peeled off from the plate cylinder 11, if the sensitizers which are not irradiated with the laser beam remain on the plate cylinder 11 and remain, these sensitizers can be easily wiped off with a cleaning liquid. ..

[0013]

According to the method of producing a plate according to the present invention, in the on-press plate making, the outer peripheral surface of the plate cylinder of the printing machine is hydrophilized, and the plate cylinder is subjected to the nip pressure of the roller contacting the plate cylinder or the printing cylinder. The following effects can be obtained by laminating the photosensitive film on the outer peripheral surface of. It is possible to produce the plate on the plate cylinder many times, and an inexpensive photosensitive film can be used for producing the plate.

Since the plate is directly generated on the outer peripheral surface of the plate cylinder,
Since it is not necessary to provide a clamp device and a gap for mounting a raw plate on the plate cylinder as in the conventional case, the outer diameter of the plate cylinder can be reduced. Furthermore, no special chemical treatment is required.

[Brief description of drawings]

FIG. 1 is a side view showing the concept of an embodiment of the present invention.

FIG. 2 is a side view showing the concept of a conventional method.

[Explanation of symbols]

 4 Laser beam irradiation device 8 Inking roller 9 Blanket cylinder 11 Plate cylinder 12 Photosensitive film

Claims (1)

[Claims] 1. In on-press platemaking, the outer peripheral surface of a plate cylinder of a printing machine is hydrophilized, and a photosensitive film is laminated on the outer peripheral surface of the plate cylinder by a roller contacting the plate cylinder or the nip pressure of the printing cylinder. A method of generating a version characterized by: