Patent EP-2511094-A1 (EP)
Inventor: KOCHER CHRISTOPH
IPC: D21H21/40
Filed: 2012-04-13
Abstract: The method of preparing a multilayer substrate (60) such as a print substrate including security paper, comprises: connecting a plastic layer (30) of the substrate with a first paper layer (10) and a second paper layer, where the substrate comprises first sides on first regions, in which a surface of the substrate is formed by the freely lying paper layer, and second regions, in which substrate surface is formed by the freely lying plastic layer; and bringing the paper layers and the plastic layer together and/or embedding the plastic layer in the paper layers. The method of preparing a multilayer substrate (60) such as a print substrate including security paper, comprises: connecting a plastic layer (30) of the substrate with a first paper layer (10) and a second paper layer, where the substrate comprises first sides on first regions, in which a surface of the substrate is formed by the freely lying paper layer, and second regions, in which substrate surface is formed by the freely lying plastic layer; bringing the paper layers and the plastic layer together and/or embedding the plastic layer in the paper layers; subjecting the resulting multilayer substrate on the first side in the second regions to continuous flame treatment and/or hot-air application; and pressing the paper layers between a pair of rollers (50) in a continuous process using heat and/or pressure, where a cohesive connection is obtained between the paper layers and the plastic layer under the formation of a penetration zone in which parts of the plastic layer are connected with the mass of the fiber composite of the paper layers. The plastic layer is made of a thermoplastic polymeric material and arranged between the paper layers. During the hot-air treatment, a temperature of the multi-layer substrate at the point of impingement of corresponding hot air flow is greater than 125[deg] C that is less than the temperature of the melting point or the glass transition point of the plastic layer. The hot air application is carried out by a slot nozzle, which lies with its longitudinal axis parallel to a transport direction (80) of the multilayer substrate produced as a web during the continuous process and which is directed above and toward the second regions. The paper layers comprise through recesses, and the plastic layer, in the molten state, is supplied between the paper layers. The plastic layer comprises a basis weight of 20-100 g/m 2>, and is supplied as a plastic film having the same width as the paper layers or is supplied in the form of a strip. The recesses are fed in such a way that they form a transparent side panel window. The thermoplastic polymeric material of the plastic layer is a transparent material with a light transmission of 80% and a haze of 5. The hot-air application and/or flame treatment is carried out in the continuous process at a point at which the substrate web is freely guided or at which the substrate web is guided in a vertical direction from top to bottom. A gas/air flame and/or a gas/oxygen flame is used in the flame treatment process, where an energy input is in the range of 0.6-1 J/mm 2>. The hot-air application is carried out, using a blower, directly on the surface of the multilayer substrate to be treated, where a hot air stream is applied on the substrate surface in an amount of 600-800 l/minute and at a transport speed of 70-100 m/minute in such a manner that the surface has a temperature of 180-250[deg] C. A distance between an outlet of the combustible gas mixture of the hot air and the substrate web is 10-50 mm in the hot-air application and/or flame treatment. The multilayer substrate is performed with the hot-air application or the flame treatment in a web speed of 70-120 m/seconds. The substrate web has strip regions along the transport direction over the first surface. The surface of the paper layer is solely formed by the webs. The plastic film has the strip regions on the second surface such that the hot-air application or the flame treatment is carried out as strip-hot-air-strip flame treatment on the first and second surfaces. The paper layers comprise a security feature comprising gray-scale watermarks, security threads, optically variable devices, mottled fibers, security pigments, iridescent color applications, radio frequency identification device chips, transponders and magnetic strips and/or the plastic layer comprises a security feature comprising mottled fibers, planchettes, metal fibers, marking materials, infrared or UV dyes, security pigments, fluorescent dyes, effect pigments, interference pigments, metal pigments, reactive dyes, UV absorbers and stabilizers, where these security features are added to the melt as additives or sprinkled on the surface of the substrate. The plastic layer comprises the security feature in the form of a security thread. An independent claim is included for a multilayer substrate.