The substrate layer (20) is formed by pressurized knife coating the above composition to a thickness of 0.38 to 0.50 millimeters (mm) on a substrate such as glass fiber, vellum paper, etc., and then by heating to gel for one to two minutes in an oven at a temperature of 130??? to 200??? C. at a line speed of 40 to 50 meters/minute (m/min).