Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
1998-07-30
2001-03-27
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Composite
Of metal
C428S336000, C428S457000, C428S472200, C428S913000, C427S156000, C427S327000, C427S379000, C427S384000, C427S402000
Reexamination Certificate
active
06207287
ABSTRACT:
TECHNICAL AREA OF THE INVENTION
The invention relates to a dummy plate for offset printing which essentially consists of a mechanically and/or electrochemically roughened anodically oxidized and aluminium support and a non-photosensitive, water-soluble layer applied thereto, and to a process for the production thereof.
PRIOR ART
In a printing machine, a plurality of plates are generally clamped alongside one another and in succession on a printing cylinder. Dummy plates are planographic printing plates without ink-carrying areas. They are used where the paper band is not to be printed completely. A dummy plate has the task of transferring damping solution applied over the entire width of the cylinder to the paper band. At the same time, the dummy plate must not take up the printing ink, so that this is not transferred to the paper (“smearing”). A particularly large number of dummy plates are necessary if, in multicolour offset printing, individual colours are not needed on all pages and the respective inking systems are then not supposed to transfer ink.
Dummy plates are usually roughened and anodically oxidized aluminium plates. If desired, they can also be subjected to hydrophilizing treatment, for example with phosphorus-containing compounds, as described in DE 4423140. The disadvantage of these dummy plates is that they react very sensitively to fingerprints and other external influences. Fingerprints result, for example, in ink take-up and thus smearing in the printing machine. In addition, it is found that the hydrophilicity of such dummy plates worsens with time, and they therefore take up ink in the printing machine and cause smearing. This effect is particularly pronounced if the dummy plates have been exposed to the room air without protection for an extended period and have taken up, for example, moisture, dust or traces of oil. In order to eliminate the consequences of fingerprints and to restore the hydrophilicity of the aluminium surface to the original value, dummy plates are subjected to the normal development process with subsequent gumming. The development cleans and hydrophilizes the surface of the printing plate. Subsequent gumming protects the surface. The dummy plates treated in this way have a significantly lower tendency towards smearing in the printing machine.
EP 96200429 describes dummy plates which do not require a development step before use in the printing machine. These dummy plates consist of an aluminium support of the abovementioned type which has a non-photosensitive, water-soluble protective layer of a water-soluble polymer and an acidic inorganic substance. Preference is given to mixtures of polyvinyl alcohol and inorganic phosphates/sulphates. However, it is found that these materials lose their ink-repellent action after extended storage at elevated temperature—which can be simulated by a forced storage test for 24 hours at 100° C.—and likewise result in smearing during printing. It has furthermore been found that the protective layers become tacky under moist storage conditions.
OBJECT OF THE INVENTION
The object of the invention is therefore to provide a dummy plate in which, even after extended storage at elevated temperature, a development step is not absolutely necessary in order to ensure a sufficiently ink-repellent action during printing and which does not develop a tendency to stick during storage at high atmospheric humidity levels. In addition, it should be processable without problems in an automatic development unit with developer and subsequent gumming. This additional requirement therefore means that, in automatic printing-plate processing units, all plates, including the dummy plates, are subjected to the normal development conditions.
REFERENCES:
patent: 5474885 (1995-12-01), Michiels et al.
patent: 5481084 (1996-01-01), Patrick et al.
patent: 5786127 (1998-07-01), Madoux et al.
patent: 5908706 (1999-06-01), Lehmann et al.
patent: 110 417 (1984-06-01), None
patent: 316 240 (1989-05-01), None
patent: 497 351 (1992-08-01), None
patent: 619 525 (1994-10-01), None
Alba Cornelia
Elsasser Andreas
Grabley Fritz-Feo
Jorg Klaus
Lehmann Peter
AGFA-GEVAERT
Foley & Lardner
Yamnitzky Marie
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