Abstract:
A method of treating paper to have a photo-feel backcoating includes preparing a mixture of a binder and polyethylene particles wherein the polyethylene particles have first and second sizes, and coating the mixture onto a surface of a sheet of paper which is opposite the surface of the sheet which is configured to receive printing thereon.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of co-pending U.S. patent application Ser. No. 11/062,482, filed on Feb. 23, 2005, which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to a paper which is provided with a coating on a surface opposite to that which receives printing thereon and which provides a photobase feel to the paper. 
         [0003]    Paper which exhibits a photobase feeling is inherently expensive due to the procedures/materials required to produce the same. For example, the process of extruding polyethylene onto paper sheet requires specialized equipment which is not widely available and normally not available in the mills in which the paper is initially produced. Thus, the cost of such paper is increased not only the need for specialized extrusion equipment but the need to move the paper from the point of manufacture to another site for the coating operation. 
         [0004]    A simpler, less expensive technique for producing such paper is therefore necessary. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The various aspects and features of this disclosure will become more clearly appreciated as a detailed description of the preferred embodiments is given with reference to the appended drawings wherein: 
           [0006]      FIG. 1  is a schematic side view of an embodiment of the disclosure. 
           [0007]      FIG. 2  is an enlarged view of the portion of the coated sheet enclosed in circle  11  of  FIG. 1  wherein the sheet comprises untreated basestock. 
           [0008]      FIG. 3  is an enlarged view of the portion of the coated sheet enclosed in circle  11  of  FIG. 1  wherein the sheet comprises treated basestock. 
           [0009]      FIG. 4  is a flow chart depicting the steps which are carried out in accordance with one embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    In an embodiment of the disclosure, a sheet of paper or basestock  100 , which can be either untreated or treated, is coated with a “photo feel” layer  200  comprising one or more binders and polyethylene particles. This photo feel coating  200  is provided on a surface  102  of the paper which is opposite the printing surface  101  on which printing is carried out. 
         [0011]    In the case of untreated basestock, the photo feel coating  200  is applied directly to the basestock in the manner shown in  FIG. 2 . In the case of treated basestock, wherein both sides are treated via the application of a print enhancing offset coating comprised of, but not limited to clays, grounded calcium carbonate, precipitated calcium carbonate, barium sulfate, titanium dioxide, silica, aluminum trihydrate, aluminum oxide, boehmite, and combinations thereof, the photo feel coating  200  is applied to the print enhancing offset coating  102 A in the manner shown in  FIG. 3 . 
         [0012]    The coating technique via which the photo feel coating is applied can, with the exception of extrusion, be selected from any suitable commercially available technique such as curtain coating, rod coating or slot coating. However, embodiments of the disclosure are not limited to these arrangements and gravure coating, reverse roll coating, knife over roll coating, for example, are not excluded. 
         [0013]    The thickness of the coating can be varied between about 3 and about 50 gsm (grams per square meter). Usually coatings of about 5-25 gsm would be adequate, however this thickness can be varied depending upon the application and the paper that is used. 
         [0014]    The paper or basestock to which the coating can be applied can be selected from commercially available stock such as “Galerie one gloss” and “Galerie one silk” produced by M-real of Kangus Finland, and # Savvy and # Influence by International Paper. The embodiments of the disclosure are, of course not limited to these selections and can be applied to different substrates (paper) as appropriate. 
         [0015]    In  FIG. 1  a printing arrangement  300  is schematically depicted printing onto the printing surface  101 . This printing arrangement may take the form of an inkjet printer, but is not limited thereto. For example, the printing arrangement can take the form of electrographic print, gravure, etc. 
         [0016]    In one embodiment of the disclosure, the paper  100  can have the printing surface  101  coated with a layer or layers of material which facilitate ink jet printing. However, the embodiments of the disclosure are not limited to this type of treatment and can include treatment with calcium carbonate or silica, clay, aluminum oxide, aluminum trihydrates, titanium dioxide, aluminum silicates, etc. or the like. 
         [0017]    The coating or layer  200  can comprise a single binder such as latex acrylic in which polyethylene particles are dispersed. In accordance with one embodiment of the disclosure, these polyethylene particles have at least two different sizes. A first group of particles can have a diameter in the range of about 25-200 nanometers while a second group can have a diameter in the range of about 1-6 microns. In accordance with one embodiment, a more preferred particle sizes range for the first particles is about 30-70 nm and a more preferred particle size for the second particle is about 3-5 microns. 
         [0018]    The above mentioned binder can be selected from but not limited to styrene, styrene-acrylic, styrene-butadiene, acrylic, polyvinyl acetate, etc. It is also within the scope of the present disclosure to use a mixture of the just mentioned binders. 
         [0019]    In a further embodiment of the disclosure an anti-curl agent can be introduced into the coating. This anti-curl agent can be a binder which can be selected from, but is not limited to polyvinyl alcohol, gelatin, starches, cellulose, modified cellulose, etc. 
         [0020]    The combination of the large and small particles contributes to the smooth photo feel of the backchat which provides the photobase characteristics. The use of similar sized particles does not provide the desired feel, and, while it has not been positively determined, it is suspected that the smaller particles tend to fill in the gaps between the larger particles and provide a smoothing effect which leads to the desired feel of the backcoat. 
         [0021]    To further illustrate embodiment(s) of the present disclosure, various examples are given herein. It is to be understood that these examples are provided for illustrative purposes and are not to be construed as limiting the scope of the disclosed embodiment(s). 
       EXAMPLE 1 
       [0022]      
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 100 parts of binder #1 
                 Acrylic Latex (Rhoplex GL618) 
               
               
                   
                  10 parts of binder #2 
                 Polyvinyl Alcohol (Mowiol 20-98) 
               
               
                   
                  40 parts of particle #1 
                 Polyethylene particles 4 μm 
               
               
                   
                   
                 (Michem Guard 20) 
               
               
                   
                  60 parts of particle #2 
                 Polyethylene particles 50 nm 
               
               
                   
                   
                 (Michem Shield 251) 
               
               
                   
                 Paper: 
                 coated basestock 
               
               
                   
                 Coat thickness: 
                 8gsm 
               
               
                   
                 Feel 
                 preferred 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 2 
       [0023]      
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 100 parts of binder #1 
                 Acrylic Latex (Rhoplex R-253) 
               
               
                   
                  40 parts of particle #1 
                 Polyethylene particles 7 μm 
               
               
                   
                   
                 (Michem Guard 60) 
               
               
                   
                  60 parts of particle #2 
                 Polyethylene particles 35 nm 
               
               
                   
                   
                 (Michem Emulsion 39235) 
               
               
                   
                 Paper: 
                 uncoated basestock 
               
               
                   
                 Coat thickness: 
                 20 gsm 
               
               
                   
                 Feel 
                 acceptable 
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 3 
       [0024]      
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 50 parts of binder #1 
                 Styren/butadiene Latex (Rovene 4021) 
               
               
                 40 parts of particle #1 
                 Teflon particles 4 μm (Michem Glide 5) 
               
               
                 60 parts of particle #2 
                 Polypropylene particles 45 nm 
               
               
                   
                 (Michem emulsion 43040) 
               
               
                 Paper: 
                 coated basestock 
               
               
                 Coat thickness: 
                 3-5 gsm 
               
               
                 Feel 
                 acceptable 
               
               
                   
               
             
          
         
       
     
         [0025]    It will be appreciated that, although the disclosure has been described with reference to only a limited number of embodiments, the various modifications and changes that can be implemented without departing from the scope of appended claims, will be, given the preceding disclosure, readily apparent to those skilled in the art to which the present disclosure pertains or mostly pertains.