Abstract: A method of forming a film of photonic crystal material. A first process is performed upon a material capable of having a photonic crystal structure, this process causing deformation of the material so as to form a film in which incident light received by the material is selectively reflected or transmitted to generate a first optical effect in the film. A second process is performed upon substantially all of the film which applies a shear stress to the film. This causes a change in the material structure so as to generate a second optical effect in the film, different from the first optical effect, in response to incident light. Security films, devices, articles and documents formed using the method are also discussed.

Abstract: The invention relates to a membrane-electrode assembly (MEA) for electrochemical devices, in particular for membrane fuel cells. The membrane-electrode assembly has a semi-coextensive design and comprises an ion-conducting membrane, two catalyst layers and gas diffusion layers of differing sizes on the front side and rear side. The first gas diffusion layer has smaller planar dimensions than the ion-conducting membrane, while the second gas diffusion layer has essentially the same planar dimensions as the ion-conducting membrane. As a result, the ion-conducting membrane has a surface which is not supported by a gas diffusion layer on the front side. The membrane-electrode assembly has, owing to the particular construction, a stable structure which can be handled readily and displays advantages in the sealing of the reactive gases from one another and also in terms of the electrical properties. In particular, the hydrogen penetration current is significantly reduced.

Abstract: A method of forming a film of photonic crystal material. A first process is performed upon a material capable of having a photonic crystal structure, this process causing deformation of the material so as to form a film in which incident light received by the material is selectively reflected or transmitted to generate a first optical effect in the film. A second process is performed upon substantially all of the film which applies a shear stress to the film. This causes a change in the material structure so as to generate a second optical effect in the film, different from the first optical effect, in response to incident light. Security films, devices, articles and documents formed using the method are also discussed.

Abstract: The invention relates to composite materials having an optical effect, comprising at least one moulding which essentially consists of core/shell particles whose shell forms a matrix and whose core is essentially solid and has an essentially monodisperse size distribution, where a difference exists between the refractive indices of the core material and of the shell material, and at least one further material which determines the mechanical properties of the composite, and to a process for the production of the composite materials. The materials according to the invention exhibit a viewing angle-dependent colour effect with freely adjustable mechanical properties.

Abstract: The invention relates to mouldings having an optical effect which essentially consist of core/shell particles whose shell forms a matrix and whose core is essentially solid and has an essentially monodisperse size distribution, where a difference exists between the refractive indices of the core material and of the shell material. The mouldings are characterized in that they are obtainable by a process in which the core/shell particles are heated to a temperature at which the shell is flowable, and the flowable core/shell particles are subjected to the action of a mechanical force.

Abstract: The invention relates to composite materials having an optical effect, comprising at least one moulding which essentially consists of core/shell particles whose shell forms a matrix and whose core is essentially solid and has an essentially monodisperse size distribution, where a difference exists between the refractive indices of the core material and of the shell material, and at least one further material which determines the mechanical properties of the composite, and to a process for the production of the composite materials. The materials according to the invention exhibit a viewing angle-dependent colour effect with freely adjustable mechanical properties.