Patent ID: 7850886

Claim:
A method for the manufacturing of tablets with an optical security feature from a powder mixture, using a tablet press comprising a die and two punches, wherein the surface of at least one of said die or at least one of said two punches faces said powder mixture and is provided with an embossing relief in the form of a diffractive micro-structure that is smaller than 5 μm and having a grating relief, said diffractive micro-structure that produces recognizable diffraction effects in the optical spectral range, said method comprising the steps: compressing the powder mixture to a tablet by employing said die and said two punches to obtain a compressed tablet; reproducing said diffractive micro-structure on at least a part of the surface of said compressed tablet, wherein said diffractive micro-structure is reproduced on the surface of said particles of said powder mixture, wherein the temperature of said tablet and of the ambient during the step of compressing is in the range of 15° C. to 50° C.; and ejecting said compressed tablet from said two punches.