Coated polyester films

A coated polyester film according to any one of the preceding claims, wherein the weight ratio of the polyurethane component (ii) relative to the melamine crosslinker component (i) is in the range of 1% to 160%, more preferably 1% to 150%, more preferably 1% to 140%, more preferably 1% to 130%, more preferably 1% to 120%, more preferably 1% to 110%, more preferably 1% to 100%, more preferably 5% to 100%, more preferably 10% to 90%, more preferably 15% to 75% or most preferably 20% to 50%.

A coated polyester film according to any one of the preceding claims, wherein the polyester film substrate is a polyethylene terephthalate film or a polyethylene-2,6-naphthalate film, preferably a polyethylene terephthalate film.

A coated polyester film according to any one of the preceding claims, wherein the polyester film substrate is optically clear or translucent.

A coated polyester film according to any one of the preceding claims, wherein the polyester film substrate is biaxially oriented.

A coated polyester film according to any one of the preceding claims, wherein the polyester film substrate has a thickness in the range of from about 5 μm to about 500 μm.

A coated polyester film according to any one of the preceding claims, wherein the melamine crosslinker component (i) comprises one or more monomeric derivatives of melamine in which some or all of the amino groups are functionalised with alkoxymethyl or hydroxymethyl groups and/or oligomers derived from said monomeric melamine derivatives.

A coated polyester film according to any one of the preceding claims, wherein the at least one diisocyanate is an aliphatic diisocyanate.

A coated polyester film according to any one of the preceding claims, wherein the at least one polymeric polyol has from 2 to 8 reactive hydroxyl groups, more preferably 2 to 4 reactive hydroxyl groups and most preferably 2 reactive hydroxyl groups.

A coated polyester film according to any one of the preceding claims, wherein the at least one polymeric polyol has a weight average molecular weight of from 200 to 8,000, for example from 500 to 5,000, or from 1,000 to 3,000.

A coated polyester film according to any one of the preceding claims, wherein the at least one polymeric polyol is selected from polyester polyols, polyether polyols, polyacrylate polyols and polycarbonate polyols.

A coated polyester film according to any one of the preceding claims, wherein the polyurethane is a polyurethane elastomer.

A coated polyester film according to any one of the preceding claims, wherein the coating has a dry thickness of no more than 5.0 μm, preferably no more than 2.0 μm, more preferably no more than 1.5 μm, for example no more than 1.0 μm, no more than 0.8 μm or no more than 0.5 μm.

A coated polyester film according to any one of the preceding claims, wherein the coating has a dry thickness (i.e. the thickness of the coating in the finished film) of at least 200 nm, more preferably at least 250 nm, more preferably at least 300 nm, more preferably at least 350 nm, more preferably at least 400 nm, more preferably at least 500 nm, more preferably at least 600 nm, more preferably at least 800 nm, or most preferably at least 1000 nm.

A coated polyester film according to any one of the preceding claims, wherein the coating has a dry thickness (i.e. the thickness of the coating in the finished film) of between 200 nm and 5 μm, more preferably between 250 nm and 5 μm, more preferably between 300 nm and 5 μm, more preferably between 350 nm and 5 μm, more preferably between 400 nm and 5 μm, more preferably between 500 nm and 5 μm, more preferably between 500 nm and 2 μm, more preferably between 600 nm and 2 μm, more preferably between 800 nm and 2 μm, or most preferably between 1 μm and 2 μm.

A coated polyester film according to any one of the preceding claims, wherein the coated polyester film is optically clear or translucent.

A coated polyester film according to any one of the preceding claims, which exhibits an increase in Taber haze of no more than 10%, preferably no more than 8% and most preferably no more than 5% when the coating is tested according to ASTM D-1044 wherein a loading of 500 g is used over 100 cycles.

A coated polyester film according to any one of the preceding claims, wherein the crack onset strain of the coated polyester film is about 5% or more, preferably about 10% or more, preferably about 15% or more, preferably about 20% or more, preferably about 25% preferably about 30% or more of the original dimension of the coated polyester film.

A coated polyester film according to any one of the preceding claims, wherein the number of cracks in the coating at 25% elongation is 25 or less, preferably 20 or less, preferably 15 or less, preferably 10 or less, preferably 5 or less, preferably 2 or less, and most preferably 0.

A coated polyester film according to any one of the preceding claims, wherein the coating is disposed directly on the polyester substrate.

A method of improving the flexibility of a crosslinked melamine resin coating disposed on a polyester film substrate, the method comprising incorporating a polyurethane component derivable from at least one diisocyanate and at least one polymeric polyol into the crosslinked melamine resin coating.

Use of a polyurethane component derivable from at least one diisocyanate and at least one polymeric polyol to improve the flexibility of a crosslinked melamine coating for a polyester film substrate.

Use of a coating composition comprising a melamine crosslinker component and a polyurethane component derivable from at least one diisocyanate and at least one polymeric polyol to improve the abrasion resistance of a polyester film substrate.