The present invention relates to cholesteric layered materials having an improved color impression, comprising at least one three-dimensionally crosslinked, aligned cholesteric layer, to a process for their production, and to their use.
Cholesteric layers, pigments prepared therefrom and compositions containing cholesteric pigments are widely used, for example in the motor vehicle or motor vehicle accessory sector, in the computer, leisure, sport and toy sector, as optical components, such as polarizers or filters, in the cosmetics area, in the textiles, leather or jewelry area, in gift articles, in writing implements, or on spectacle frames, in the construction sector, in the domestic sector, in print products of all types and in the production of paints and coatings, furthermore for the anticounterfeiting treatment of articles, for the coating of utility articles or for the painting of motor vehicles.
In these applications, the cholesteric layers and the pigments and compositions containing the latter have to satisfy a number of conditions in order to be usable for the above-mentioned purposes. Firstly, the color impression should be as bright as possible, and secondly the color impression should be substantially independent of external stimuli, in particular it should be stable over a broad temperature and pressure range and to the action of solvents. In addition, the cholesteric layers should be as thin as possible in order that the pigments prepared therefrom have the smallest possible thickness, thus reducing costs and simplifying the applications.
On use of the cholesteric layers known from the prior art, the problem of inadequate color brightness frequently arises. It is therefore an object of the present invention to provide cholesteric layered material which has improved color brightness.
We have found that, surprisingly, this object is achieved by the provision of a cholesteric layered material comprising at least one three-dimensionally crosslinked, aligned cholesteric layer, where the crosslinked, cholesteric layer(s) has (have) a homogeneous interference line pattern essentially over the entire layer thickness. Investigations by the applicant have shown that the interference line pattern which can be observed in thin sections was particularly inhomogeneous in conventional materials having inadequate brightness.
Cholesteric layered materials which satisfy this homogeneity criterion exhibit superior color brightness. The same applies to the products derived from layered materials of this type, for example pigments and films.