Printing – Planographic – Lithographic printing plates
Reexamination Certificate
2000-03-16
2002-01-29
Colilla, Daniel J. (Department: 2854)
Printing
Planographic
Lithographic printing plates
C101S401100, C101S463100, C101S465000, C101S467000, C101S466000, C430S300000, C430S302000
Reexamination Certificate
active
06341559
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a process and a device for illustrating a printing form for wet offset printing. The present invention is used especially in newspaper offset printing and preferably in web-fed newspaper offset printing.
BACKGROUND OF THE INVENTION
In newspaper offset printing, the preliminary printing stage has changed greatly as a consequence of the progressive development of computer technology. Operations that were previously carried out manually have been replaced by so-called computer-to technologies. The current stage of development has been reached with computer-to-plate in newspaper printing. The further development is toward computer-to-press, i.e., toward direct illustration in the press.
A printing form cylinder that can be illustrated directly has been known from U.S. Pat. No. 5,293,817. The printing form cylinder has a porous outer jacket. The moistening is performed through the interior of the cylinder through the porous outer jacket. The porosity of the cylinder jacket is between 20% and 45%. The diameter of the pores of the cylinder jacket decreases toward the outside of the cylinder jacket and is between 3 &mgr;m and 100 &mgr;m. The pores of the cylinder jacket communicate with one another. The illustration is performed according to a thermo transfer or ink jet process by means of an image information transfer means. As an alternative, the use of a heated electrode in the form of a pin in order to apply oleophilic material to the cylinder jacket is mentioned.
SUMMARY AND OBJECTS OF THE INVENTION
The object of the present invention is to make possible the illustrating of a printing form in a wet offset printing press in a simple, inexpensive and accurate manner.
According to the invention, a process for illustrating a printing form for wet offset printing is provided, in which a printing style is produced on an ink-transferring surface of the said printing form by forming ink-absorbing and ink-repelling areas. For illustration, the steps are as follows:
a) the ink-transferring surface is wetted with a moistening agent,
b) the areas of the moistened surface that are to be made into ink-absorbing areas, are dried in a specific manner, and
c) a material that absorbs printing ink is uniformly applied to the ink-transferring surface with the areas still dry.
According to another aspect of the invention, a process for illustrating a printing form for wet offset printing is provided in which a printing style is produced on an ink-transferring surface of the said printing form by forming ink-absorbing and ink-repelling areas. For illustration, the steps are as follows:
a) a flowable material that absorbs printing ink is uniformly applied to the ink-transferring surface,
b) the material is cured in a specific manner on the areas that are to be made into ink-absorbing areas, and
c) it is removed from the areas that are to be made into ink-repelling areas by means of moistening agent.
According to another aspect of the invention, a device for illustrating a printing form of a rotary printing press for wet offset printing is provided. The device includes a printing form cylinder with the printing form a moistening means for wetting an ink-transferring surface of the said printing form with moistening agent, and an application and image transfer means, with which a printing style with ink-absorbing areas and moistening agent-absorbing areas is produced on the ink-transferring surface by applying a material absorbing printing ink. The application and image transfer means comprises an application means for the uniform application of the material absorbing printing ink over the ink-transferring surface and an image transfer means. The printing style is produced by the uniform application of printing ink-absorbing material by means of the application means and by specific irradiation of the areas of the ink-transferring surface that are to be made into ink-absorbing areas by means of the irradiation means.
The present invention is based on a process for illustrating a printing form for wet offset printing, in which a printing style is produced on a non-illustrated surface of the printing form by preparing ink-absorbing and ink-repelling areas. The surface will hereinafter be called the ink-transferring surface in both the illustrated and non-illustrated state because of its ink transfer function.
According to the present invention, the printing style, i.e., the illustration, is produced by wetting the yet non-illustrated ink-transferring surface with a moistening agent, drying the areas of the moistened surface that are intended to absorb ink in a specific manner, i.e., in the pattern of an image, and subsequently applying material that absorbs printing ink and preferably repels moistening agent to the ink-transferring surface with the still dry areas. Like printing ink itself, the material is repelled by the moistening agent, i.e., it is not transferred to the moist areas. Since the supply of moistening agent preferably takes place uniformly and continuously during the illustration as well, the material is preferably applied as quickly as possible after the drying of the ink-transferring surface, which drying is performed in the pattern of the image, so that the dried areas are not wetted again with moistening agent prior to the application of the ink-absorbing material.
The thickness of a film of moistening agent wetting the ink-transferring surface should be at most 1 &mgr;m, averaged over the area of one image pixel, in order to keep the energy of evaporation low. The thickness is preferably set at a value between 0.2 &mgr;m and 0.5 &mgr;m.
Without leaving the scope of the present invention, the process may be modified such that for illustration, a flowable material is first applied uniformly to the ink-transferring surface, which absorbs printing ink and preferably repels moistening agent, after which this material is specifically cured or is brought to a curing in the areas that are to be made into ink-absorbing areas, and it is removed by means of moistening agent in the areas that are to be made into ink-repelling areas, where it is still flowable.
The said two alternatives of the process have the advantage that the ink-transferring surface is first wetted or covered uniformly, for which moistening water is used in one case and ink-absorbing and moistening agent-repelling material in the other, and the uniformly wetted or covered surface of the printing form is then specifically provided with the printing style by drying the moistening agent or curing, especially by drying in the ink-absorbing/moistening agent-repelling material, where the dried areas or the areas with the cured material form the ink-absorbing areas in the printing style. An applicator, with which an ink-absorbing and moistening agent-repelling material is directly applied in the pattern of an image, is not needed for carrying out the process. By performing only a uniform application of material to produce the printing style in both alternatives of the process, the cost for the applicator for the illustration is markedly reduced.
Uniform application is defined according to the present invention as any application of material for illustration which is not performed in the pattern of an image itself. The material is preferably applied over the entire surface of the printing form or at least in strips of the surface.
The ink-absorbing/moistening agent-repelling material is preferably printing ink, especially printing ink of the current production, in which the illustrated printing form will then be used.
A special advantage of both alternatives of the process according to the present invention is that an ink applicator, e.g., an inking roller, which is present for the current production anyway, can be used to apply the ink-absorbing and preferably moistening agent-repelling material in the course of the illustration. The use of such an ink applicator, especially an inking roller, also corresponds to an especially preferred exemplary embodiment of the present invent
Jiang Yufan
Riepenhoff Matthias
Colilla Daniel J.
Maschinenfabrik WIFAG
McGlew and Tuttle , P.C.
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