EP1736823A2 - Method for producing printing plates - Google Patents

Abstract

The method involves providing a printing plate with a rewriteable surface. Erasing and illustration of the surface of the plate are implemented for allocation of a permanent and erasable picture image on the surface of the printing plate. The erasing of the surface before the illustration and/or a hydrophilic of the surface is directly implemented after a time interval under application of an atmospheric plasma.

Description

The invention relates to a method for the production of printing plates according to the preamble of patent claim 1.

In principle, when printing with a printing form, a distinction is made between methods which use a write-once printing form on one side or a rewritable printing form on the other side. Printing methods using rewritable printing forms are also summarized under the keyword "computer to press / direct imaging". The present invention relates to a method for producing a permanent and erasable image on such a rewritable printing form.

The applicant sells under the product name "DICOweb" digital printing machines that work with rewritable and erasable printing plates. In the production of such printing plates, a printing master base cylinder is preferably subjected to an erasing step and an imaging step. The imaging of the printing form is followed by fixing and conditioning of the imaged printing form. An erase device which can be used in erasing such a printing form is disclosed, for example, in US Pat DE 100 08 214 A1 disclosed. The DE 100 23 319 A1 discloses a device for imaging such printing forms. Regarding further basic features of the DICOweb technology, reference can be made to " Handbuch der Printmedien, Helmut Kipphan, pages 674 - 680, year 2000, Springer-Verlag ".

In practice, in digital printing machines, which work with rewritable and erasable printing plates, for erasing, imaging, fixing and conditioning, respectively separately formed devices or devices used, resulting in a relatively large space requirement for these devices or devices within the printing press. The higher the number of devices used, the greater the capital expenditure for such a printing machine and the time required to convert the printing press. To reduce the number of required for producing such printing plates devices or devices and thus to reduce the required space, the investment costs and the changeover times, it is from the DE 199 39 240 C2 It is already known to use a laser source which is used for imaging also in fixing the imaged printing plate. Also in the DE 199 39 240 C2 proposed to perform the deletion of an imaged printing form using the laser source. The laser source is operated in each case with different intensity levels. From this prior art, it is therefore already known to use a laser source, which serves the imaging, also for fixing and erasing an imaged printing form.

On this basis, the present invention is based on the problem to provide a novel method for the production of printing plates.

This problem is solved by a method for the production of printing plates according to claim 1. According to the invention, at least the erasing of the surface immediately before its imaging and / or the preparation thereof after a period of time after erasing is carried out using an atmospheric plasma.

For the purposes of the present invention, it is therefore proposed to carry out the erasing of the surface of an imaged printing plate using an atmospheric plasma. With the help of an atmospheric plasma impurities on the printing form or images to be deleted can be effectively removed from the surface of a printing form to be erased. Ideally, if the Imaging immediately without delay, ie without timer deleting follows, a preparation of the printing for imaging can be omitted. If there is a so-called timing element, ie a time delay, between the erasing and the imaging, the same immediately before the actual imaging is subjected to a plasma treatment with atmospheric plasma in preparation for imaging, whereby it is possible to subsequently apply the adhesion with the aid of to increase a thermal transfer applied to the imaging on the printing plate. By the plasma treatment of the printing plate to be imaged before the actual imaging, it is preferably possible to dispense with a separate fixing and optionally on a hydrophilization of the printing plate.

Producing a permanent and erasable image on a rewritable printing form then ideally involves only the steps of erasing and imaging, with the steps of fixing and hydrophilizing through the plasma treatment becoming superfluous. This drastically reduces the number of devices or devices required to produce the rewritable and erasable printing plates. This results in a reduction in the required space, a reduction in investment costs and a reduction in the time required for retooling. Further advantages of the process according to the invention are a clean surface, adhesion support, correct surface tension to support the hydrophilicity.

Furthermore, under certain conditions different variants of the inventive method are conceivable:

Ideally, the method comprises without delays in the sequence of the individual process steps, ie without timers between the individual steps, only the steps deleting, imaging and printing.

However, should there be a timer between erasing and imaging, i. a time delay of about 15 to 30 minutes, so immediately before the actual imaging of the surface with a thermal transfer process, the surface to be imaged subjected to a treatment with atmospheric plasma, this step is a preparation for imaging the surface. Thus, the method comprises the steps of: deleting, timer (15 to 30 minutes), preparing, imaging and printing.

In addition, it is already common in printing technology to provide printing plates on their surfaces to protect them from contamination or damage from atmospheric oxygen with rubber coatings. A Gummiermediurn should conserve and maintain the printing technology differentiation in terms of color and / or water management. For example, the earlier application discloses DE 10 2004 047 456 a method and apparatus for gumming a printing form.

The inclusion of the gumming step in the process of the invention, in turn, allows for a timer between imaging and printing, such that the process includes the steps of erasing, imaging, gumming, timing (15 to 30 minutes), printing.

Furthermore, the method according to the invention including the possible timers can be represented in particular as follows: erase, timer, preparation, imaging, gumming, timer, printing.

• Variante A: Löschen, Bebildern, Fixieren, Drucken.
• Variante B: Löschen, Zeitglied, Vorbereiten, Bebildern, Fixieren, Drucken.
• Variante C: Löschen, Bebildern, Gummieren, Fixieren, Zeitglied, Drucken.
• Variante D: Löschen, Zeitglied, Vorbereiten, Bebildern, Gummieren, Fixieren, Zeitglied, Drucken.

An additional fixation after imaging, or after gumming is of course also possible:

• Variant A: Delete, Imaging, Fixing, Printing.
• Variant B: Delete, Timer, Prepare, Imagine, Fix, Print.
• Variant C: Delete, Imaging, Gum, Fix, Timer, Print.
• Variant D: Delete, Timer, Prepare, Imagine, Gum, Fix, Timer, Print.

According to a preferred embodiment of the invention, the atmospheric plasma acts to extinguish the surface, or fixing, or preparing, in particular hydrophilizing the same with different power densities on the surface to be erased or imaged.

This offers, in a particularly advantageous manner, the possibility of carrying out various steps of the method according to the invention, such as erasing, preparing or fixing in succession, with a single apparatus for the plasma treatment of the printing form surface. That By means of a high power density it is preferred to carry out the quenching, with an average power density, preferably the fixing and, with a preferably low power density, the preparation, in particular the hydrophilization

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. An embodiment of the invention will be explained in more detail below, without being limited thereto.

The present invention relates to a method for producing a printing form, namely to produce a permanent and erasable image on the surface of a rewritable and erasable printing form, wherein the method is preferably carried out within a printing press. To produce such a printing form, a printing form or a printing form base cylinder with a rewritable and erasable surface is provided. The surface is first deleted and then imaged.

For the purposes of the present invention, it is proposed to carry out the deletion of the surface via a plasma treatment using an atmospheric plasma. Through such atmospheric plasma, when the atmospheric plasma with a relatively high power density acts on the surface to be erased, an image to be erased can be removed from the surface, as well as other impurities. The atmospheric plasma for extinguishing the surface is provided by means of a plasma generating device, wherein the plasma generating means comprises at least two electrodes positioned at a distance from the surface of the printing form, between each of which an electric arc is formed. This results in large quantities of positive or negative charge carriers, which are conducted via compressed air onto the surface to be extinguished. With a correspondingly high power density of the atmospheric plasma, the surface of a printing plate can thus be effectively cleaned or extinguished.

For the purpose of preparing the surface of the printing forme, the same is subjected to a plasma treatment with atmospheric plasma in the sense of the present invention immediately before the actual imaging of the surface so that the imaging of the surface takes place directly after the plasma treatment via the thermal transfer process known from the prior art can. Between the plasma treatment for erasing the surface to be imaged with the atmospheric plasma and the actual imaging of the same with the aid of the thermal transfer process can then be a period of up to 30 minutes, preferably a maximum of 15 minutes, ie a timer.

The atmospheric plasma is in turn formed by an electric arc between at least two electrodes of the plasma generating device, which are positioned at a distance from the surface to be imaged. The power density of the plasma treatment or of the atmospheric plasma during preparation and fixing is preferably lower than the power density of the plasma treatment or of the atmospheric plasma when the printing form is extinguished. In the present case, the power density for fixing is preferably larger than the power density for preparing.

The adhesion of the imaging material to be applied by the thermal transfer method can be improved by the plasma treatment immediately before the imaging of the printing form in such a way that it is possible to dispense with a fixing step subsequent to the imaging according to the prior art. Furthermore, the surface of the printing plate, which usually consists of a metal, is influenced by the plasma treatment in such a way that it has good dampening wet-wetting properties in the sections in which no imaging material is applied, thus dispensing with the hydrophilization step required according to the prior art can be. Immediately after imaging is therefore a print-ready printing form, so that immediately after the imaging can be started with the printing. The steps of fixing and hydrophilizing become superfluous by the plasma treatment.

As already mentioned, to extinguish the surface of the printing form and to prepare it or to fix it, the atmospheric plasma with different power densities acts on the surface to be erased or imaged, whereby when the surface is erased, the plasma has a higher power density than when preparing for imaging. The different power densities can be adjusted by operating the plasma generating device with different intensities. It is also possible to adjust the distance of the plasma generating device to the surface of the printing plate. Then, when the printing forme production takes place within a printing press, the plasma generating device is positioned together with an imaging device on a traverse and is moved in translation relative to the printing plate with rotating printing form. In this case, the power density can also be adjusted by adjusting the speed of the translatory relative movement of the plasma generating device relative to the rotating printing plate and / or the rotational speed of the rotating printing plate.

Claims (12)

A method for producing a printing form, in particular within a printing press, wherein a printing form is provided with a rewritable surface, and wherein to provide a permanent and erasable image on the surface of the printing plate at least preferably a deletion of the surface and an imaging thereof is performed, characterized in that at least erasing the surface immediately before imaging it and / or preparing, in particular, hydrophilizing it after a period of time (a timer) after erasing, using an atmospheric plasma. A method according to claim 1, characterized in that the deletion of the surface and the preparation for imaging the surface after a timer after erasing is performed using an atmospheric plasma. A method according to claim 1 or 2, characterized in that after the imaging of the surface by a thermal transfer process additionally a gumming thereof A method according to claim 1 to 3, characterized in that the deletion of the surface and the preparation for imaging after a timer is carried out using an atmospheric plasma, followed by the image gumming, wherein there is a timer between gumming and the printing, so that a Sequence of the steps Delete, Timer, Prepare, Imaging, Gum, Timer, Print is present. Method according to one of the preceding claims, characterized in that an additional fixing after the imaging or after gumming is carried out. Method according to one of the preceding claims, characterized in that between the deletion of the surface to be imaged with the atmospheric plasma and the imaging of the surface by the thermal transfer method, as well as between the imaging or gumming and printing a maximum of 30 minutes, preferably of maximum 15 minutes, lies. Method according to one or more of claims 1 to 6, characterized in that the atmospheric plasma is generated by an electric arc between at least two spaced apart from the surface to be erased or to be imaged surface electrodes. A method according to claim 7, characterized in that the atmospheric plasma is passed via compressed air onto the surface to be erased or imaged. Method according to one or more of Claims 1 to 8, characterized in that the atmospheric plasma acts on the surface to be erased or imaged for erasing the surface and for preparing it to image it, as well as for fixing it with different power densities. A method according to claim 9, characterized in that the atmospheric plasma acts to erase the surface with a higher power density on the surface than in preparation for imaging the same. A method according to claim 9 or 10, characterized in that for this purpose a plasma generating device is operated with different intensities and / or with different distances to the surface. A method according to claim 11, characterized in that the plasma generating device is moved traversing relative to the rotating printing plate, wherein the power density of the plasma treatment is adjustable via the translational movement of the plasma generating device and / or the rotational movement of the printing plate.