Coloured film

Abstract

A polyester film can be dyed by coating the film with a layer of a dye mixture which is a suspension of at least one disperse dyestuff in a solution of a thickener in water and which has a viscosity of no more than 500 centipoise, preferably 5-50 centipoise, at ambient temperature, followed by heating to cause the dyestuff to migrate from the layer into the film. The coating process is preferably reverse gravure printing. The process can be used to prepare films which contain one or more dyestuffs in one surface region of the film and one or more different dyestuffs, for example an ultraviolet absorber, in the other surface region of the film. The dyed films show good resistance to fading when exposed to light and are useful for example as automobile window films.

1 . A process for producing a coloured polyester film including the steps of: 
 (1) providing a dye mixture which has a viscosity of no more than 500 centipoise at ambient temperature and which is a suspension of at least one disperse dyestuff in a solution of a thickener in water;    (2) coating said dye mixture onto a polyester film to form a layer; and    (3) heating said film to cause said at least one dyestuff to migrate from said layer into said film.    
     
     
         2 . A process according to    claim 1   , wherein said dye mixture has a viscosity of no more than 100 centipoise.  
     
     
         3 . A process according to    claim 1   , wherein said dye mixture has a viscosity of at least 2 centipoise.  
     
     
         4 . A process according to    claim 1   , wherein said dye mixture has a viscosity in the range 5 to 50 centipoise.  
     
     
         5 . A process according to    claim 1   , wherein a 1 percent solution of said thickener in water exhibits a viscosity in the range 5 to 50 centipoise at ambient temperature.  
     
     
         6 . A process according to    claim 1   , wherein the amount of said thickener in said dye mixture is in the range 0.2 to 5 percent by weight.  
     
     
         7 . A process according to    claim 1   , wherein the amount of said at least one dyestuff in said dye mixture is in the range 2 to 10 percent by weight.  
     
     
         8 . A process according to    claim 1   , wherein the total solids content of said dye mixture is in the range 2 to 10 percent by weight.  
     
     
         9 . A process according to    claim 1   , wherein said thickener is a water-soluble cellulose ether.  
     
     
         10 . A process according to    claim 9   , wherein said thickener is sodium carboxymethylcellulose.  
     
     
         11 . A process according to    claim 1   , wherein said thickener is poly(vinyl alcohol).  
     
     
         12 . A process according to    claim 1   , wherein the thickness of said film is in the range 10 to 50 micron.  
     
     
         13 . A process according to    claim 1   , wherein said dye mixture additionally comprises an organic liquid which is at least partially miscible with water and which is miscible with water in the proportion used.  
     
     
         14 . A process according to    claim 13   , wherein the boiling point of said organic liquid is in the range 70 to 120° C.  
     
     
         15 . A process according to    claim 13   , wherein the proportion of said organic liquid in said dye mixture is in the range 10 to 25 percent by weight.  
     
     
         16 . A process according to    claim 13   , wherein said organic liquor is isopropyl alcohol.  
     
     
         17 . A process according to    claim 1   , further including the step of filtering said dye mixture to remove essentially all particles larger than 10 micron in size from said dye mixture prior to coating said dye mixture onto said film.  
     
     
         18 . A process according to    claim 1   , wherein the average particle size of said at least one disperse dyestuff is less than about 1 micron.  
     
     
         19 . A process according to    claim 1   , wherein said dye mixture is coated onto said film by means of a gravure printing roll in a gravure printing process.  
     
     
         20 . A process according to    claim 19   , wherein said gravure printing process is reverse gravure printing.  
     
     
         21 . A process according to    claim 19   , wherein the speed of said film is in the range 100 to 200 feet per minute relative to the outside world.  
     
     
         22 . A process according to    claim 1   , wherein said dye mixture is coated onto said film at ambient temperature.  
     
     
         23 . A process according to    claim 1   , wherein the thickness of said layer in the wet state is in the range 1 to 10 micron.  
     
     
         24 . A process according to    claim 1   , additionally including the step of drying said layer to form a dried layer prior to the step of heating said film to cause said dyestuff to migrate from said layer into said film.  
     
     
         25 . A process according to    claim 24   , wherein the weight of said dried layer is in the range 0.1 to 2.0 grams per square meter.  
     
     
         26 . A process according to    claim 1   , wherein said heating is carried out in an oven at a temperature in the range 160 to 180° C.  
     
     
         27 . A process according to    claim 1   , wherein said heating is carried out for a time in the range 5 to 60 seconds.  
     
     
         28 . A process according to    claim 1   , additionally including the step of washing said film with water subsequent to said heating.  
     
     
         29 . A process according to    claim 28   , additionally including the step of washing said film with a water-miscible organic solvent subsequent to said heating and prior to said washing with water.  
     
     
         30 . A coloured polyester film having a first and a second surface, said film being dyed with at least two disperse dyestuffs, at least a first dyestuff of said dyestuffs being substantially all present in a surface region adjacent said first surface, and at least a second dyestuff of said dyestuffs being substantially all present in a surface region adjacent said second surface.  
     
     
         31 . A coloured polyester film according to    claim 30   , wherein at least one of said dyestuffs is an ultraviolet absorber.  
     
     
         32 . A coloured polyester film according to    claim 30   , wherein said first dyestuff is an ultraviolet absorber and said second dyestuff comprises one or more coloured dyestuffs.  
     
     
         33 . A coloured polyester film containing an ultraviolet absorber substantially uniformly dispersed therethrough, said film being dyed with at least one disperse dyestuff, said at least one dyestuff being substantially all present in a surface region of said film.  
     
     
         34 . A polyester film having a first and a second surface, said film being dyed with at least one disperse dyestuff, said at least one disperse dyestuff being substantially all present in a surface region adjacent said first surface, and said film being metallised on said first or said second surface.  
     
     
         35 . A film according to    claim 34   , wherein said film is metallised on said second surface.  
     
     
         36 . A film according to    claim 34   , wherein said film is additionally dyed with a ultraviolet absorber, said ultraviolet absorber being substantially all present in a surface region adjacent said second surface, and said film being metallised on said first surface.  
     
     
         37 . A process for producing a coloured polyester film, said film having a first and a second surface, including the steps of: 
 (1) providing a dye mixture which has a viscosity of no more than 500 centipoise at ambient temperature and which is a suspension of at least one disperse dyestuff in a solution of a thickener in water;    (2) coating said dye mixture onto said polyester film to form a layer on said first surface;    (3) heating said film to cause said dyestuff to migrate from said layer into said film; and    (4) metallising said first or said second surface.    
     
     
         38 . A film laminate, said laminate containing at least one polyester film having a first and a second surface, said film being dyed with at least one disperse dyestuff, said dyestuff being substantially all present in a surface region adjacent said first surface, said film being laminated to a metallised polyester film.  
     
     
         39 . A film laminate according to    claim 38   , wherein said second surface of said film is laminated to the unmetallised surface of said metallised film.  
     
     
         40 . A window having a polyester film adhered thereto, said film having a first and a second surface, said film being dyed with at least one disperse dyestuff, said dyestuff being substantially all present in a surface region adjacent said first surface.  
     
     
         41 . A window according to    claim 40   , said window having an inside surface and an outside surface, wherein said film is adhered to said inside surface of said window.  
     
     
         42 . A window according to    claim 41   , wherein said second surface of said film is adhered to said inside surface of said window.