Method and apparatus for producing a structured surface on an embossing steel roll

Abstract

A method of forming structures on the surface of embossing steel rolls using a short-pulse laser, wherein said structures are macroscopic structures with dimensions exceeding 20 μm and depths of 150 μm and more, the structures themselves being differentiated from the following parameter combinations: a) in In single pulse operation, the fluence is in the range of 0.5J / cm2 to 3.5J / cm2, and in the burst mode, the average burst fluence is 0.5J / cm2 to 70J / cm2 per pulse, b) the wavelength is 532nm to 1064nm, c) repetition rate 1kHz to 10MHz, d) pulse-to-pulse spacing on the workpiece, 10% to 50% of beam diameter for femtosecond lasers, 10-25% of beam width and 40% for picosecond lasers -50%, e) the laser pulse position is close to the workpiece surface, and f) the deflection speed is up to 100 m / s and higher. Such a method allows the manufacture of a complete embossing roll with teeth and gaps for producing logos, the teeth having variable height, shape and spacing, for embossing eg the inner liner of a cigarette pack.

Description

technical field [0001] The present invention relates to a method and apparatus for producing a structured surface on an embossing steel roll by means of a short-pulse laser, the structure being a macrostructure with dimensions exceeding 20 μm and a depth of 200 μm and more. Background technique [0002] Embossing steel rollers, for example for embossing foils used as inner liners for so-called cigarette packs, are known primarily by the applicant of the present invention, eg according to WO-2009 / 155720, US-7036347 or EP2336823. With such embossing rolls, the foils are simultaneously polished, ie very fine depressions are provided homogeneously over large areas, and logos are provided where the teeth of the embossing roll are completely or partially removed. Additionally, the teeth and / or gaps on the embossing roll may be shaped to provide identifying features and / or reinforcement, etc. to the foil. Furthermore, according to EP2027994A2 assigned to the applicant of the prese...

AI Technical Summary

Problems solved by technology

[0015] However, no data are disclosed relating to the production of the above-mentioned embossing rolls with macrostructures, i.e. a very large number of teeth with a height of 0.1 to 0.4 mm and a tooth-free surface for producing most different kinds of logos or other structures, in Melting and softening of the material should not occur during embossing roll processing, despite the massive increase in global and local heating observed in prior art laser systems

Images