Method of laminating plastic film and shaped metal substrates

A method of laminating a plastic film and shaped metal substrates utilizing a pair of rollers, said pair of rollers comprising at least one heat resistant roll having a hollow, the depth of which is equal to the thickness of said substrate .+-.1.5 mm, capable of receiving at least a forward edge of the shaped metal substrates, said method comprising:

• treating the surface of the shaped metal substrates such that surface roughness of the surface is less than 100 microns;
• preheating the shaped metal substrates, the upper limit of the preheating temperature being set lower than thermal decomposition initiation temperature of the plastic film and the lower limit being set 5.degree.-100.degree. C. higher than the melting point or melt flowable temperature;
• melt bonding the plastic film on the shaped metal substrates by passing said shaped metal substrates together with said plastic film, under compression, between said pair of rolls wherein clearance at the forward edge between the hollow and the shaped metal substrates is greater than 0 mm and less than 10 mm;
• and
• contacting the shaped metal substrates, all of which are the same shape with uniformly varying widths, with the rolls whereby the plastic film is cut by the edge of the shaped metal substrates.