Release coatings for dielectric substrates

Claim 1

An image release sheet comprising: (a) a substrate on which one major surface thereof is a dielectric-layer; and (b) a silicone-urea block polymer coating on top of said dielectric layer, said coating being sufficiently thin so as to not substantially affect the dielectric properties of said substrate, said block polymer having a weight percent of 1-65 weight percent of silicone, and represented by the formula: ##STR6## wherein: Z is a divalent radical selected from the group consisting of phenylene, alkylene, aralkylene and cycloalkylene; Y is an alkylene radical of 1 to 10 carbon atoms; R is at least 50% methyl with the balance of the 100% of all R radicals being selected from the group consisting of methyl and a monovalent alkyl radical having from 2 to 12 carbon atoms, a vinyl radical, a phenyl radical, and a substituted phenyl radical; D is selected from the group consisting of hydrogen, and an alkyl radical of 1 to 10 carbon atoms; B is selected from the group consisting of alkylene, aralkylene, cycloalkylene, azaalkylene, cycloazaalkylene, phenylene, polyalkylene oxides, polyethylene adipate, polycaprolactone, polybutadiene, a radical completing a ring structure including A to form a heterocycle and mixtures thereof; A is selected from the group consisting of ##STR7## where G is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, phenyl, a radical which completes a ring structure including B to form a heterocycle and mixtures thereof; n is an integer which is 4 or larger; and m is an integer which is zero to 25.