Microporous film and image accepting member

Abstract

A method for manufacturing a microporous film comprising the steps of: (a) providing a first polymer which is a hydrophobic thermoplastic polymer and a second polymer which is a hydrophilic polymer or copolymer of N-vinylpyrrolidone; (b) dissolving said first and second polymers in a solvent system which is compatible with both polymers, said solvent system comprising a blend of an aprotic organic solvent and an alcohol; (c) coating the resulting solution on a support; (d) effecting at least a partial drying of the resulting coating; and (e) washing the coating in an aqueous medium so as to extract at least 50% by weight of the said second polymer. Image accepting members comprising a microporous film made by the above method, and preferably comprising a support which is also microporous.

What is claim d is:  
     
         1 . A method for manufacturing a microporous film comprising the steps of: 
 (a) providing a first polymer which is a hydrophobic thermoplastic polymer and a second polymer which is a hydrophilic polymer or copolymer of N-vinylpyrrolidone;    (b) dissolving said first and second polymers in a solvent system which is compatible with both polymers, said solvent system comprising a blend of an aprotic organic solvent and an alcohol;    (c) coating the resulting solution on a support;    (d) effecting at least a partial drying of the resulting coating; and    (e) washing the coating in an aqueous medium so as to extract at least 50% by weight of the said second polymer.    
     
     
         2 . The method of  claim 1  wherein said first polymer is selected from the group consisting of vinyl polymers; acrylate and methacrylate polymers; cellulose esters; polyethers; polyesters; and polycarbonates.  
     
     
         3 . The method of  claim 1  wherein said first polymer comprises pendant hydroxyl groups and has a hydroxyl number of at least 300.  
     
     
         4 . The method of  claim 1  wherein said second polymer is selected from the group consisting of homopolymers of N-vinylpyrrolidone and copolymers of N-vinylpyrrolidone and vinyl acetate comprising up to 50% by weight vinyl acetate.  
     
     
         5 . The method of  claim 1  wherein the weight ratio of said first and second polymers is in the range 2:1-1:3.  
     
     
         6 . The method of  claim 1  wherein said aprofic organic solvent has a boiling point of less than 120° C. at normal atmospheric pressure.  
     
     
         7 . The method of  claim 1  wherein said aprotic organic solvent is selected from th group consisting of ketones; thers; sters; and hydrocarbons and wherein said alcohol is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol and mixtures of these.  
     
     
         8 . The method of  claim 1  wherein the weight ratio of aprotic solvent to alcohol is in the range 30:1 to 1:2.  
     
     
         9 . The method of  claim 1  wherein the aqueous medium of step (e) contains one or more functional materials selected from the group consisting of surfactants, mordents, UV absorbers and antioxidants.  
     
     
         10 . The method of  claim 1  wherein one or more ingredients selected from the group consisting of particulate fillers, chemical modifiers, crosslinking agents, hardeners, levelling agents, surfactants, UV absorbers, antioxidants, free radical scavengers and mordents is added to the solution formed in step (b) prior to the coating thereof.  
     
     
         11 . An image receiving element comprising a microporous film made by the method of any one of  claims 1  to  10 .  
     
     
         12 . An ink accepting member comprising a support which is a sheet-form microporous material which on a coating-free, printing ink-free and impregnant-free basis comprises: (a) a matrix consisting essentially of substantially water-insoluble thermoplastic organic polymer, (b) finely divided substantially water-insoluble filler partides, of which at least 50% by weight are siliceous partides, the filler partides being distributed throughout the matrix and constituting from 40 to 90% by weight of the microporous material, and (c) a network of interconnecting pores communicating substantially throughout the microporous material, the pores constituting from 35 to 95% by volume of the microporous material, said support bearing on at least one side thereof a microporous organic polymer film comprising a network of pores which communicate with the pores in said support.  
     
     
         13 . The ink accepting member of  claim 12  wherein said microporous organic polymer film has a thickness in the range 5 to 100 μm and has a porosity in the range 30 to 80% by volume.  
     
     
         14 . The ink accepting member of  claim 12  wherein said microporous organic polymer film compris s 10 4 -10 7  pores/mm 2  with an average pore size in the range 0.2-2.0 μm.  
     
     
         15 . The ink accepting member of  claim 12  wherein said microporous organic polymer film comprises a polymer selected from the list consisting of poly(methyl methacrylate), cellulose acetate butyrate, poly(vinyl acetal)s and vinyl chloride/vinyl acetate copolymers.  
     
     
         16 . The ink accepting member of  claim 12  wherein said support bears on both sides thereof a microporous organic polymer film comprising a network of pores which communicate with the pores in said support.  
     
     
         17 . The ink accepting member of  claim 12  wherein said support is adhered to an auxiliary support.  
     
     
         18 . The ink accepting member of  claim 12  wherein the microporous organic polymeric film is made according to the method of claims  1 - 10 .  
     
     
         19 . An imaging method wherein an ink comprising a colorant in a carrier fluid is imagewise deposited on any one of the members of claims  11 - 18 .  
     
     
         20 . The imaging method of  claim 19  wherein said image is deposited by ink jet printing.  
     
     
         21 . The imaging method of  claim 20  wherein said ink jet printing uses oil-based inks.  
     
     
         22 . The imaging method of  claim 20  wherein said ink jet printing is multilevel ink jet printing, employing the technique of jetting a normal density ink and a lower density ink of the same color from separate printheads, or the technique of delivering multiple droplets of ink per pixel, or a combination of both of these techniques.  
     
     
         23 . The imaging method of  claim 22  wherein said ink jet printing is carried out by means of a piezoelectric shared-wall printhead.  
     
     
         24 . The imaging method of  claim 20  wherein the microporous organic polymer film swells or distorts as a result of contact with said carrier liquid.