Security paper and method for the production thereof

Abstract

The invention relates to a security paper for producing value documents, such as bank notes, passports, identification documents or the like, having a flat substrate ( 12 ) provided at least partly with a dirt-repellent protective layer ( 14 ) for extending the life time and fitness for circulation. According to the invention, the protective layer ( 14 ) comprises at least two lacquer layers ( 16, 18 ), a first lower lacquer layer ( 16 ) being formed by a physically drying lacquer layer applied to the substrate ( 12 ) which makes contact with the substrate ( 12 ) therebelow and closes its pores, and a second upper lacquer layer ( 18 ) being present which protects the substrate ( 12 ) from physical and chemical influences.

1 . A security paper for producing value documents, exemplified by bank notes, passports or identification documents, comprising a flat substrate provided at least partly with a dirt-repellent protective layer for extending the life time and fitness for circulation, wherein the protective layer comprises at least two lacquer layers, a first lower one of said lacquer layers being formed by a physically drying lacquer layer applied to the substrate which makes contact with the substrate therebelow and closes its pores, and a second upper one of said lacquer layers protecting the substrate from physical and chemical influences.  
   
   
       2 . The security paper according to  claim 1 , wherein the substrate is formed by an unprinted or printed cotton paper.  
   
   
       3 . The security paper according to  claim 1 , wherein the lower lacquer layer forms a smooth and contiguous layer on the substrate.  
   
   
       4 . The security paper according to  claim 1 , wherein the first lower lacquer layer is elastic.  
   
   
       5 . The security paper according to  claim 1 , wherein the first lower lacquer layer is formed by a water-based dispersion lacquer layer.  
   
   
       6 . The security paper according to  claim 1 , wherein the first lower lacquer layer comprises a polyurethane.  
   
   
       7 . The security paper according to  claim 1 , wherein the first lower lacquer layer is based on a water-based dispersion of aliphatic polyester polyurethanes or styrene-acrylic polyurethanes.  
   
   
       8 . The security paper according to  claim 1 , wherein the second upper lacquer layer is formed by a radiation-curing and/or physically drying lacquer layer.  
   
   
       9 . The security paper according to  claim 8 , wherein the each lacquer layer is selected from the group consisting of a UV-crosslinked lacquer layer, a water-based dispersion lacquer layer and a hybrid lacquer layer.  
   
   
       10 . The security paper according to  claim 1 , wherein the second upper lacquer layer comprises silicones and/or wax.  
   
   
       11 . The security paper according to  claim 9 , wherein the UV-crosslinked lacquer layer is based on an acrylate system, the water-based dispersion lacquer layer on a styrene-acrylic system, and the hybrid lacquer layer on a system comprising aliphatic urethane acrylates and acrylates with photoinitiators.  
   
   
       12 . The security paper according to  claim 8 , wherein the composition of the upper lacquer layer is selected with respect to brittleness and surface tension so as to obtain a predetermined haptics of the security paper, in particular a predetermined smoothness, sound and/or flexural stiffness.  
   
   
       13 . The security paper according to  claim 1 , wherein the second upper lacquer layer is disposed directly on the first lower lacquer layer.  
   
   
       14 . The security paper according to  claim 1 , wherein a further lacquer layer comprising water-based dispersion lacquer is disposed between the second upper and first lower lacquer layers.  
   
   
       15 . The security paper according to  claim 1 , wherein the lacquer layers of the protective layer are conditioned with each other in their adhesion properties so as to form a highly resistant bond.  
   
   
       16 . The security paper according to  claim 1 , wherein the first lower lacquer layer has a low glass transition temperature to increase the adhesion and adhesion promotion.  
   
   
       17 . The security paper according to  claim 1 , wherein either or both the second upper and first lower lacquer layer is transparent and colorless.  
   
   
       18 . The security paper according to  claim 1 , wherein the second upper lacquer layer has antibacterial fungus proofing.  
   
   
       19 . The security paper according to  claim 1 , wherein the first lower lacquer layer is present on the substrate in a coating weight of from 1 to 6 g/m 2 , preferably 2 to 4 g/m 2 .  
   
   
       20 . The security paper according to  claim 1 , wherein the first upper lacquer layer is present on the substrate in a coating weight of from 0.5 to 3 g/m 2 , preferably 1 to 2 g/m 2 .  
   
   
       21 . The security paper according to  claim 1 , wherein at least the substrate is printed with characters or patterns, and the protective layer is applied to the printed substrate and/or the first lower lacquer layer is printed to which the second upper lacquer layer is applied, and/or the second upper lacquer layer is printed.  
   
   
       22 . The security paper according to  claim 1 , wherein the protective layer contains at least one gap.  
   
   
       23 . The security paper according to  claim 21 , wherein the gap has a security element incorporated therein.  
   
   
       24 . The security paper according to  claim 1 , wherein the protective layer is applied to the flat substrate all over.  
   
   
       25 . The security paper according to  claim 1 , wherein the flat substrate is provided with the dirt-repellent protective layer on its two main faces.  
   
   
       26 . A value document, exemplified by a bank note, passport or identification document, comprising security paper according to  claim 1 .  
   
   
       27 . A method for producing a security paper in particular for a value document, exemplified by a bank note, passport or identification document, comprising the following steps: 
 a) supplying a flat substrate;    b) applying a dirt-repellent protective layer to the substrate, the protective layer being applied by 
 b 1 ) applying a physically drying lacquer layer to the substrate as a first lower layer of the protective layer to make contact with substrate therebelow and close its pores; and  
 b 2 ) applying a second upper layer of the protective layer to protect the substrate from physical and chemical influences.  
   
   
   
       28 . The method according to  claim 27 , wherein 
 b 2 ) the second upper layer applied is either or both a radiation-curing and physically drying layer, and    c) the second upper layer is crosslinked, cured and/or dried by irradiation with electromagnetic radiation.    
   
   
       29 . The method according to  claim 27 , wherein the flat substrate supplied is a printed or unprinted cotton paper.  
   
   
       30 . The method according to  claim 27 , wherein the first lower layer applied is an elastic material.  
   
   
       31 . The method according to  claim 27 , wherein the first lower lacquer layer is applied in an amount of coating which closes the pores of the substrate and forms a smooth and cohesive surface on the substrate.  
   
   
       32 . The method according to  claim 27 , wherein the first lower lacquer layer is applied to the substrate in an amount of from 2.5 to 15 g/m 2 , preferably 5 to 10 g/m 2  (wet weight).  
   
   
       33 . The method according to  claim 27 , wherein the first lower layer is dried prior to application of the second upper layer.  
   
   
       34 . The method according to  claim 27 , wherein the second upper lacquer layer applied is a UV-crosslinking lacquer layer, a water-based dispersion lacquer layer or a hybrid lacquer.  
   
   
       35 . The method according to  claim 27 , wherein the composition of the second upper lacquer layer is selected with respect to brittleness and surface tension so as to obtain a predetermined haptics of the security paper, in particular a predetermined smoothness, sound and/or flexural stiffness.  
   
   
       36 . The method according to  claim 27 , wherein a printed image is printed on the substrate prior to application of the protective layer.  
   
   
       37 . The method according to  claim 27 , wherein a printed image is printed on the first lower lacquer layer after application of the first lower lacquer layer, and/or a printed image is printed on the second upper lacquer layer after application of the second upper lacquer layer.  
   
   
       38 . The method according to  claim 27 , wherein the unlacquered or lacquered substrate is printed by the intaglio printing process.  
   
   
       39 . The method according to  claim 27 , wherein the first lower and/or second upper lacquer layer is applied by a flexographic printing process.  
   
   
       40 . The method according to  claim 39 , wherein the lacquer layers applied by a flexographic printing process are applied in an amount of coating of altogether 3 to 12 g/m 2 .  
   
   
       41 . A method according to  claim 27 , wherein the first lower and/or second upper lacquer layer is applied by a screen printing process.  
   
   
       42 . The method according to  claim 41 , wherein the lacquer layers applied by a screen printing process are applied in an amount of coating of altogether 5 to 15 g/m 2 .  
   
   
       43 . The method according to  claim 27 , wherein the first lower and/or second upper lacquer layer is applied by the offset printing process or by the indirect letterpress printing process.  
   
   
       44 . The method according to  claim 27 , wherein the protective layer is applied to the substrate all over.  
   
   
       45 . The method according to  claim 27 , wherein the flat substrate is provided with the dirt-repellent protective layer on its two main faces.  
   
   
       46 . The method according to  claim 27 , wherein the flat substrate supplied in step a) is a paper-of-value sheet comprising a plurality of single copies for which the steps b), b 1 ) and b 2 ) are performed in the same run in each case.  
   
   
       47 . The method according to  claim 27 , wherein the first lower and second upper lacquer layers are applied to the substrate in-line in a sheet-fed lacquering machine.