Photosensitive stencils & methods

Abstract

An photosensitive stencil includes a porous stencil carrier that can be a sheet of woven material with crisscrossing filaments. The stencil carrier is coated with a photopolymer emulsion that is water based to form a stencil blank. A pressure sensitive adhesive may disposed on one surface of the emulsion either as a continuous film, in which case the adhesive also is photosensitive, or in the form of spaced and unconnected microdots, in which case the adhesive need not be photosensitive. Alternatively, no adhesive need be applied. In use, a light mask is disposed atop the stencil blank. The light mask can be contained on a sheet of paper or a transparent film. Alternatively the stencil blank is fed through an inkjet printer and the light mask is printed directly onto the stencil blank using common inks. The stencil blank is then exposed to light for a few minutes, which cross-links the photopolymer emulsion in unmasked regions. After exposure, the stencil blank is developed by being washed out with water. The water removes emulsion and adhesive, where present, within areas that were masked by the light mask, revealing open or open regions through which ink or paint can be applied. The adhesive, where present, allows the stencil to stick removably to a surface during decoration. Where no adhesive is present, the stencil may be mounted in a relatively flexible adhesive frame that holds the stencil to a surface.

1 . A photosensitive stencil blank comprising:
 a stencil carrier having openings sized to pass art media;   a photosensitive emulsion coating on the stencil carrier substantially permeating the carrier and defining a surface, the emulsion being formulated to be soluble in water and further being formulated to become insoluble in water upon exposure to electromagnetic radiation having a spectrum comprising wavelengths above about 370 nanometers such that the radiation is safe for human skin and eyes.   
     
     
         2 . A photosensitive stencil blank as claimed in  claim 1  and further comprising an adhesive on at least a portion of the surface, the adhesive having an adhesive strength sufficient to stick to a surface to be decorated but being removable from the surface after decoration. 
     
     
         3 . A photosensitive stencil blank as claimed in  claim 2  and wherein the adhesive comprises a pressure sensitive adhesive. 
     
     
         4 . A photosensitive stencil blank as claimed in  claim 2  and wherein the adhesive comprises an array of microdots of adhesive. 
     
     
         5 . A photosensitive stencil blank as claimed in  claim 4  and wherein the microdots are substantially embedded within the photosensitive emulsion coating. 
     
     
         6 . A photosensitive stencil blank as claimed in  claim 2  and wherein the adhesive comprises a substantially continuous film of adhesive. 
     
     
         7 . A photosensitive stencil blank as claimed in  claim 2  and further comprising a removable protective sheet overlying the adhesive. 
     
     
         8 . A photosensitive stencil blank as claimed in  claim 6  and wherein the protective sheet comprises a support carrier. 
     
     
         9 . A photosensitive stencil blank as claimed in  claim 6  and wherein the protective sheet comprises a release layer. 
     
     
         10 . A photosensitive stencil blank as claimed in  claim 1  and wherein the stencil carrier comprises a woven sheet material wherein the openings are defined by crisscrossing filaments of the woven sheet material. 
     
     
         11 . A photosensitive stencil blank as claimed in  claim 1  and wherein the stencil carrier comprises a non-woven sheet material and wherein the openings are formed by micro perforations extending through the non-woven sheet material. 
     
     
         12 . A photosensitive stencil blank as claimed in  claim 1  and wherein the photosensitive emulsion comprises a photopolymer emulsion. 
     
     
         13 . A photosensitive stencil blank as claimed in  claim 12  and wherein the photopolymer emulsion comprises a PVA SbQ emulsion. 
     
     
         14 . A photosensitive stencil blank as claimed in  claim 12  and wherein the photopolymer emulsion comprises selected dyes for enhancing the sensitivity of the photopolymer emulsion to electromagnetic radiation within the spectrum. 
     
     
         15 . A photosensitive stencil blank as claimed in  claim 12  and wherein the photopolymer emulsion comprises light initiators for enhancing the sensitivity of the photopolymer emulsion to electromagnetic radiation within the spectrum. 
     
     
         16 . A photosensitive stencil blank as claimed in  claim 1  and wherein the spectrum comprises the spectrum of visible light. 
     
     
         17 . A photosensitive stencil blank as claimed in  claim 16  and wherein the spectrum comprises wavelengths greater than about 400 nanometers. 
     
     
         18 . A photosensitive stencil blank as claimed in  claim 1  and wherein the surface is relatively free of concavities and deformities. 
     
     
         19 . A photosensitive stencil blank as claimed in  claim 18  and wherein the surface is defined by a film bonded to the photosensitive emulsion coating. 
     
     
         20 . A photosensitive stencil blank as claimed in  claim 19  and wherein the film comprises a photosensitive emulsion. 
     
     
         21 . A method of forming a stencil comprising the steps of:
 (a) obtaining a photosensitive stencil blank as claimed in  claim 1 ;   (b) creating a light mask over a selected portion of the surface of the photosensitive emulsion;   (c) exposing the stencil blank to electromagnetic radiation having a spectrum comprising wavelengths above about 370 nanometers so that the radiation is safe for human skin and eyes, the exposure rendering portions of the stencil blank outside the selected portion non-soluble in water;   (d) developing the stencil blank with water to dissolve and remove the selected portion of the photosensitive emulsion covered by the light mask to create a stencil with the stencil carrier being exposed within the selected portion; and   (e) drying the stencil.   
     
     
         22 . The method of  claim 21  and wherein step (b) comprises placing a sheet atop the stencil blank, the sheet having a substantially opaque image disposed thereon corresponding to the selected portion. 
     
     
         23 . The method of  claim 22  and wherein the sheet comprises a sheet of paper. 
     
     
         24 . The method of  claim 22  and wherein the sheet comprises a film. 
     
     
         25 . The method of  claim 21  and wherein step (b) comprises applying a substantially opaque material to the surface of the photosensitive emulsion in the selected portion. 
     
     
         26 . The method of  claim 25  and wherein the step of applying a substantially opaque material comprises printing the opaque material onto the surface of the photosensitive emulsion. 
     
     
         27 . The method of  claim 26  and wherein and wherein the step of printing comprises passing the photosensitive stencil blank through an inkjet printer and printing the substantially opaque material onto the surface of the emulsion with the inkjet printer; 
     
     
         28 . The method of  claim 27  and wherein the substantially opaque material comprises the ink of the inkjet printer. 
     
     
         29 . A method of forming a stencil comprising the steps of:
 (a) obtaining a photosensitive stencil blank as claimed in  claim 2 ;   (b) creating a light mask over a selected portion of the surface of the photosensitive emulsion;   (c) exposing the stencil blank to electromagnetic radiation having a spectrum comprising wavelengths above about 370 nanometers so that the radiation is safe for human skin and eyes, the exposure rendering portions of the stencil blank outside the selected portion insoluble in water;   (d) developing the stencil blank with water to dissolve and remove the selected portion of the photosensitive emulsion and adhesive covered by the light mask to create a stencil with the stencil carrier being exposed within the selected portion; and   (e) drying the stencil.   
     
     
         30 . The photosensitive stencil blank of  claim 2  and wherein the adhesive is photosensitive. 
     
     
         31 . The photosensitive stencil blank of  claim 18  and wherein the surface comprises a film on the photosensitive emulsion. 
     
     
         32 . The photosensitive stencil blank of  claim 31  and wherein the film is substantially smooth and flat.