Abstract: A high optical quality transparent plastic sheet having a polyurethane layer formed by reactive pouring or reactive pulverization onto a flat horizontal support of a reaction mixture containing a polyol component and an isocyanate component, with the surface of the polyurethane layer which was facing the support during the formation of the layer containing an acrylic polymer resulting from the contact, during deposition of the reaction mixture, of the reaction mixture with a thin acrylic layer previously deposited on the support. The acrylic layer and the polyurethane layer are interpenetrated.