Method for forming an optical element

A method for forming an optical element, comprising:

• providing a forming tool, a plurality of molding or hot-embossing portions being formed on a surface thereof for molding or hot-embossing structures having an optical effect onto a substrate;
• providing said substrate, wherein a plurality of preformed portions are present on a surface of said substrate facing said forming tool;
• heating said substrate to a temperature above a transition temperature of a material of said substrate, each of said plurality of preformed portions being opposite to a respective one of said plurality of molding or hot-embossing portions;
• and
• pressing said forming tool and said substrate against each other for forming an optical element having a plurality of structures having an optical effect, wherein the shape of the structures having an optical effect is given by the respective associated molding or hot-embossing portion;
• wherein when said forming tool and said substrate are pressed against each other, the respective preformed portion of said substrate first of all gets into contact to the associated molding or hot-embossing portion at a central area thereof so that a nip, which is formed between a surface of the respective preformed portion and a surface of the associated molding or hot-embossing portion extends and broadens from said central area towards an edge of the respective preformed portion, and
• wherein a base of the respective preformed portion is substantially identical with a base of the respectively associated molding or hot-embossing portion to thereby enable a low deformation ratio when deforming a respective preformed portion to a respective structure having an optical effect.