method of fabricating a sheet comprising a region of reduced thickness or of increased thickness in register with a ribbon, and an associated sheet

Abstract

A method of fabricating a sheet by papermaking, the sheet including at least one ply of a fiber substrate and at least one ribbon, wherein the ribbon is introduced in a fiber suspension of a vat former papermaking machine enabling the ply to be formed; or in direct contact with the vat former; or in contact with the already-formed ply; the point at which the ribbon is introduced being selected so as to create at least one region of increased thickness or of reduced thickness in the sheet in register with the ribbon, the reduced thickness being due to a reduction in the de-watering of the fiber suspension caused by the ribbon.

1 . A method of fabricating a sheet by papermaking, the sheet comprising at least one ply of a fiber substrate and at least one ribbon, wherein the ribbon is introduced:
 a) in a fiber suspension of a vat former papermaking machine enabling the ply to be formed; or   b) in direct contact with the vat former; or   c) in contact with the already-formed ply;   the point at which the ribbon is introduced being selected so as to create at least one region of increased thickness or of reduced thickness in the sheet in register with the ribbon, the reduced thickness being due to a reduction in the de-watering of the fiber suspension caused by the ribbon;   at least one security element being incorporated in the region of reduced thickness, the security element being of thickness that is compensated at least in part by the reduced thickness or being juxtaposed with the ribbon at the region of increased thickness, the security element presenting a thickness that is compensated at least in part by the increased thickness.   
     
     
         2 . A method according to  claim 1 , the ribbon being introduced with one of its faces in direct contact with the vat former prior to the ribbon penetrating into the fiber suspension. 
     
     
         3 . A method according to  claim 1 , the ribbon being introduced into the fiber suspension after fibers have already become deposited on the vat former at the point where the ribbon is introduced. 
     
     
         4 . A method according to  claim 1 , the ribbon being introduced in contact with the formed ply of the fiber substrate. 
     
     
         5 . A method according to  claim 1 , the ribbon being a fiber ribbon. 
     
     
         6 . A method according to  claim 1 , the paper ply formed on the vat former and comprising the ribbon being united in the wet portion of the papermaking machine with another paper ply that overlies the ribbon. 
     
     
         7 . A method according to  claim 1 , the paper ply formed on the vat former and comprising the ribbon being united by pasting with another paper ply overlying the ribbon. 
     
     
         8 . A method according to  claim 1 , the ribbon having at least one of its faces that is not completely covered by fibers of the fiber suspension at the outlet from the vat former papermaking machine. 
     
     
         9 . A method according to  claim 1 , the ribbon presenting thickness that is less than the thickness of the vellum of the sheet. 
     
     
         10 . A method according to  claim 1 , the ribbon having thickness greater than the thickness of the vellum of the sheet. 
     
     
         11 . A method according to  claim 1 , the ribbon being subjected to embossing, in particular hot embossing. 
     
     
         12 . A method according to  claim 1 , the thickness reduction having a value greater than or equal to 15 μm. 
     
     
         13 . A method according to  claim 1 , the increase in thickness having a value that is less than or equal to 20 μm. 
     
     
         14 . A method according to  claim 1 , the ribbon being a paper ribbon. 
     
     
         15 . A method according to  claim 1 , the ribbon comprising non-fiber elements. 
     
     
         16 . A method according to  claim 1 , the ribbon having width lying in the range 2 mm to 60 mm. 
     
     
         17 . A method according to  claim 1 , the ribbon having a thickness greater than 10 μm. 
     
     
         18 . A method according to  claim 1 , the ribbon comprising an electronic device. 
     
     
         19 . A method according to  claim 1 , the ribbon comprising at least one adhesive. 
     
     
         20 . A method according to  claim 1 , the ribbon being fabricated from a material that has previously been subjected to wet strength treatment. 
     
     
         21 . A method according to  claim 1 , the ribbon comprising one or more openings. 
     
     
         22 . A method according to  claim 1 , the sheet comprising on either side of the ribbon a region of reduced thickness in which there extends at least part of at least one security element. 
     
     
         23 . A method according to  claim 1 , the security element comprising a film extending parallel to the ribbon and in contact therewith. 
     
     
         24 . A method according to  claim 1 , the ribbon comprising an opening, the security elements being observable, showing through the ribbon. 
     
     
         25 . A method according to  claim 1 , at least one electronic device, being received at least in part in the region of reduced thickness, the thickness reduction compensating the thickness of the electronic device, at least in part. 
     
     
         26 . A sheet comprising a fiber substrate and a ribbon, at least one security element being placed in register with the ribbon, and presenting thickness that is compensated at least in part by a difference in thickness between the ribbon and the vellum of the sheet and/or by an opening in the ribbon. 
     
     
         27 . A sheet according to  claim 26 , the ribbon being a fiber ribbon. 
     
     
         28 . A security document comprising a sheet as defined in  claim 26 .