Hoechst Aktiengesellschaft

Vaw Aluminium Ag

Vereinigte Aluminum-Werke Aktiengesellschaft

Hydro Aluminium Deutschland Gmbh

Vaw Aluminum Ag

Barbara Grzemba

Wolfgang Von Asten

Bernhard Kernig

Gerhard Sprintschnik

Kurt Reiss

Gunther Scharf

Walter Niederstaetter

Wolfgang V Asten

Helmut Schmiedel

J&uuml;rgen Kaulen

A litho strip for use as an offset printing plate is described which has a composition of 0.05-0.25% Si, 0.30-0.40% Fe, 0.10-0.30% Mg, max. 0.05% Mn, and max. 0.04% Cu. The strip is produced from a continuous cast ingot of the above composition which is hot rolled to a thickness of up to 2-7 mm. The residual resistance ratio of the hot rolled strip is RR=10-20. The cold rolling is carried out with or without intermediate annealing, wherein the degree of rolling reduction after intermediate annealing is &#x3e;60%. The further processing up to the EC roughening takes place with the microstructure adjusted in the rolling process at &#x3c;100&#xb0; C. The litho strip is characterized by a high thermal stability, a good roughening behavior in the EC processes, and a high reverse bending fatigue strength perpendicular to the rolling direction.

Litho strip and method for its manufacture

A litho strip for use as an offset printing plate is described which has a composition of 0.05-0.25% Si, 0.30-0.40% Fe, 0.10-0.30% Mg, max. 0.05% Mn, and max. 0.04% Cu. The strip is produced from a continuous cast ingot of the above composition which is hot rolled to a thickness of up to 2-7 mm. The residual resistance ratio of the hot rolled strip is RR&equals;10-20. The cold rolling is carried out with or without intermediate annealing, wherein the degree of rolling reduction after intermediate annealing is >60%. The further processing up to the EC roughening takes place with the microstructure adjusted in the rolling process at <100&deg; C. The litho strip is characterized by a high thermal stability, a good roughening behavior in the EC processes, and a high reverse bending fatigue strength perpendicular to the rolling direction.

The invention relates to a printing plate substrate made of a rolled and embossed aluminum strip, wherein the surface has depressions with an average diameter of <25 &mgr;m and an aspect ratio of <1.5 (ratio length/width relative to the transport direction of the strip). The number of depressions is >2,500/mm,. The invention also relates to a method of making an aluminum printing plate substrate, wherein the surface of the aluminum strip is roughened using rollers. The surfaces of the rollers have microscopically small, stochastically distributed, dome-shaped projections. In cross-sectional view, the rollers have a round ridge-shaped roughness profile. The invention is also directed to an offset printing plate, wherein a printing plate substrate is produced with the method and provided with an anodically deposited oxide layer. A light-sensitive hydrophobic, oleophilic layer is deposited on the oxide layer.

Printing plate substrate and method of making a printing plate substrate or an offset printing plate

The invention is directed toward a base material for aluminium offset printing plates having improved heat stability comprising an aluminum alloy consisting of from about 0.2 to about 0.6% by weight of iron, less than about 0.25% by weight silicon and copper combined, from about 0.1 to about 0.3% by weight manganese and the remainder being aluminum and trace production impurities, said base material further characterized as containing secondary precipitates in the form of phases of the Al Mn Si: Al Fe: Al Mn type which bear a ratio to one another of from about 1:1:2 to about 1:1:3, the mean particle size being from about 0.25 to about 0.010 micron with a maximum particle size of less than about 0.3 micron and further containing a precipitation structure with a degree of dispersion of less than about 50 phases per cubic micron and a process for producing such material. The sheet material according to this invention may be uniformly roughened in either HCl or HNO.sub.3 electrolyte baths under very similar process parameters.

Base material for an aluminum offset printing plate

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Bonn, Germany

Barbara Grzemba