| abstract |
The invention relates to a polymer film with a helically twisted molecular structure exhibiting at least two maxima of the selective reflection wavelength, to a process of such a polymer film and to the use of such a polymer film for optical data storage, photomasks, decorative pigments, cosmetics, security applications or active and passive optical elements such as polarizers, optical retarders or colour filters. The film can be obtained by A) coating a thermochromic polymerizable mesogenic composition comprising the following components a) at least one achiral polymerizable mesogenic compound, b) at least one chiral compound that is optionally also polymerizable and/or mesogenic, c) a polymerization initiator, and d) optionally a dye component, on a substrate or between two substrates in form of a layer, B) aligning the polymerizable mesogenic composition so that the axis of the molecular helix extends transversely to the layer, C) optionally heating at least part of the aligned composition to a defined temperature, D) polymerizing at least a part of the aligned composition by exposure to actinic radiation, E) optionally repeating step D) alone or together with step C) and/or steps A) and B) at least once, F) optionally removing the substrate or, if two substrates are present, one or both of the substrates from the polymerized material, characterized in that the temperature is varied in step D). |