Such a device for satinizing and embossing packaging foils is known from WO 02/076716 A1 to the applicant of the present invention. According to some exemplary embodiments disclosed therein, e.g. according to FIGS. 6 to 9, the embossing device comprises three embossing rollers, two of which are provided with a toothing of regularly arranged teeth while the third roller has either longitudinal or transversal ribs. The modification of individual teeth for creating signs whose reflection varies according to the position of the observer is known from U.S. Pat. No. 7,036,347 to the applicant of the present invention.
The arrangement and the shape of the individual teeth are disclosed in different patents and patent applications to the applicant of the present invention, e.g. in U.S. Pat. No. 6,176,819, WO 00/69622, and in EP-A-1,925,443. The purpose of the individual teeth essentially consists in creating an appearance on the metallized or other surface of the packaging foil intended therefor that has become known under the term “satinizing”. By eliminating teeth, the original surface is conserved in these locations, thereby allowing to create a logo and other such signs. Furthermore, by modifying individual teeth that are involved in the embossing process, however, signs may be created which may serve for identifying the content of the package.
All the aforementioned tooth shapes have in common that they are pyramidal and have an essentially square base, and that the opening angle between adjacent teeth has the same value both in the axial direction and in the radial direction.
In the references cited above, it is further disclosed that satinizing packaging foils not only serves for improving their esthetic appearance but also for treating the paper part of the packaging foil such that its fibers are broken in order to reduce or avoid a so-called memory effect and to achieve better overall folding properties. The term packaging foil encompasses metal-coated, metallized, printed, or otherwise surface-treated and light reflecting paper. The term “memory effect” denotes the backspringing of a fold under the action of the paper fibers which interferes with the subsequent processing of the packaging foil. Since the trend is to continuously reduce or entirely omit the metal layer, the mechanical behavior of the paper of the packaging foil becomes more and more significant for the subsequent procedure, i.e. the packaging of cigarettes, foods, or pharmaceutical products.
One of the possible improvements consists in reducing the distances between the individual teeth. In view of the already attained small dimensions of the teeth, a reduction of that distance below 0.3 mm is limited by the fact that the teeth generally also serve for driving the second embossing roller so that past a certain fineness of the teeth, there is a risk of slippage, particularly if the teeth are worn or the packaging foil has a great thickness.