Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
1999-08-24
2001-04-10
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S286100, C430S905000, C430S913000, C430S909000, C430S307000, C430S306000
Reexamination Certificate
active
06214521
ABSTRACT:
The present invention relates to a material for gravure recording by means of coherent electromagnetic radiation, consisting of a substrate, a crosslinkable layer, optionally a release layer and optionally a cover sheet, the crosslinkable layer containing at least one ethylenically unsaturated compound and a polymerization initiator and at least one polymeric binder which consists of a polyvinyl alcohol having a degree of hydrolysis of 50-99% and/or one or more copolymers which have a significant proportion of the structural unit
Such materials are known for printing plates for letterpress printing.
WO 93/23252 describes a process for laser gravure recordings on an elastomeric one-layer flexographic printing plate, where mechanical, photochemical or thermochemical strengthening of the one-layer material and engraving with a selected pattern are to be effected for the production of the completely engraved flexographic printing plate. The one-layer material contains reinforcing agents which are to act mechanically and/or thermochemically and/or photochemically. Such reinforcing agents are advantageous for rubber-like flexographic materials, for improving the gravure with respect to higher image resolution for the printing of packaging. Mechanical reinforcing agents used are radiation-absorbing pigments, for example finely divided metal particles, such as aluminum, copper or zinc, alone or in combination with carbon black, graphite, copper chromite, chromium oxide, cobalt-chromium-aluminum and other dark, inorganic pigments. Further reinforcing agents which may be mentioned are: various synthetic or natural fibers, e.g. cellulose, cotton, cellulose acetate, viscose, paper, glass wool, nylon and polyester. Such mechanical reinforcing agents cannot be used for crosslinkable PVA binders for letterpress printing plates.
Owing to the large amount of energy produced and its reliability, the CO
2
laser permits a good material removal rate during the gravure process.
The use of solid-state lasers, in particular of neodymium-YAG lasers, is also known and has the advantage of 10 times better resolution, since the wavelength is about 1 &mgr;m, and the disadvantage of a lower removal rate owing to the fact that the performance is lower with a highly focused beam.
EP-A 767 406 discloses an IR laser process for the ablation of an IR-sensitive layer for the production of a mask for imagewise UV exposure of a letterpress printing plate. Production of a mask in this manner differs in principle from the gravure of a printing plate.
It is an object of the present invention to provide material for gravure recording for letterpress printing plates, with which recordings or printing products having high resolution can be produced in a short time by means of coherent electromagnetic radiation.
We have found that this object is achieved, according to the invention, by a material for gravure recording, by means of coherent electromagnetic radiation, consisting of a substrate, a crosslinkable layer, optionally a release layer, and optionally a cover sheet, the crosslinkable layer containing at least one ethylenically unsaturated compound and a polymerization initiator and at least one polymeric binder which consists of a polyvinyl alcohol having a degree of hydrolysis of from 50 to 99% and/or one or more copolymers which have a significant portion of the structural unit
and a polymeric filler which has a ceiling temperature of less than 800K, and in particular less than 600K, is additionally provided.
(Ceiling temperature is understood as meaning the temperature at which the depolymerization of a macromolecule begins from the chain end.)
The particular advantage of using the filler having a specified ceiling temperature limit is that the material is surprisingly suitable for letterpress printing and the gravure rate can be significantly increased without sacrificing the printing quality.
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patent: 5344744 (1994-09-01), Ueda et al.
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Brandrup et al.,Polymer Handbook, 3rd ed., 1989, pp. 316-322.
Sandig Hartmut
Stebani Uwe
Telser Thomas
Tensierowski Klaus-Dieter
BASF Drucksysteme GmbH
Baxter Janet
Clarke Yvette M.
Keil & Weinkauf
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