Optical information carrier having diffractive features and diffraction modulation layers

An information carrier in the form of a composite laminate having at least a first, a second and a third layer, said first layer having a surface which faces towards said second and third layers and which has diffraction structures which are in the form of microscopically fine relief structures, wherein:

• a) said first, second and third layers have optical refractive indices n3, n4 and n5 respectively,
• b) said refractive indices n3, n4 and n5 are substantially real over large parts of the visible range .GAMMA. of the electromagnetic spectrum whereby said first, second and third layers are transparent,
• c) said refractive indices n3 and n4 are approximately equal in the visible range .GAMMA. so that no diffraction occurs at a common interface of said first and second layers,
• d) said second layer only partially covers said first layer to form layer structures,
• e) said third layer (5) covers over said layer structures in direct contact with said first and second layers,
• f) the absolute differences .vertline.n5-n3.vertline. and .vertline.n5-n4.vertline. of said refractive indices in said visible range .GAMMA. are at most 0.2 so that said diffraction structures remain as far as possible concealed from the human eye,
• g) at least parts of said diffraction structures are oriented in the same manner, and
• h) the absolute difference .vertline.n5-n3.vertline. in a second predetermined spectral range .LAMBDA. is at least 0.1 so that, in an operation of reading the information carrier by means of a reading light beam in the spectral range .LAMBDA., said layer structures, according to the presence or absence of said second layer, produce no diffraction or diffraction respectively at said diffraction structures.

An information carrier in the form of a composite laminate having a first layer and at least one further layer, said first layer having a surface which faces towards said further layer and which has first diffraction structures which are in the form of microscopically fine relief structures and which, by diffraction of incident light, produce a visually verifiable authenticity feature, wherein:

• a. said first and further layers have optical refractive indices n3 and n5 respectively,
• b. said further layer is approximately transparent,
• c. the absolute difference .vertline.n5-n3.vertline. over a large part of the visible range .GAMMA. of the electromagnetic spectrum is greater than 0.2 so that said first diffraction structures produce visible diffraction effects,
• d. said surface of said first layer has first surface elements with said first diffraction structures, said first surface elements being separated by second surface elements with a second diffraction structure, and
• e. said further layer is configured to be provided with layer structures by a procedure whereby the refractive index n5, in a predetermined spectral range .LAMBDA., is locally altered by local doping with a foreign substance without said layer structures formed by the pattern of the unaltered and the altered locations being perceptible by the naked human eye and so that said layer structures, in an operation of reading the information contained therein by means of a reading light beam operating in the spectral range .LAMBDA., produce a measurable intensity modulation of the reading light beam which is diffracted at said second surface elements with said second diffraction structure.

An information carrier in the form of a composite laminate having a first layer and at least one further layer, said first layer having a surface which faces towards said further layer and which has a first diffraction structures which are in the form of microscopically fine relief structures and which, by diffraction of incident light, produce a visually verifiable authenticity feature, wherein:

• a. said first and further layers have optical refractive indices n3 and n5 respectively,
• b. one of said first and further layers is doped with a dye,
• c. said further layer is approximately transparent,
• d. the absolute difference .vertline.n5-n3.vertline. over a large part of the visible range .GAMMA. of the electromagnetic spectrum is greater and 0.2 so that said first diffraction structures produce visible diffraction effects,
• e. said surface of said first layer has first surface elements with said first diffraction structures, said first surface elements being separated by second surface elements with a second diffraction structure, and
• f. said layer doped with a dye is configured to be irreversibly provided with layer structures by local heating above a limit temperature specific to said dye, wherein the refractive index of said doped layer is locally altered at the heated locations in a predetermined spectral range .GAMMA. without said layer structures formed by the pattern of the unaltered and the altered locations being perceptible by the naked human eye and so that said layer structures, in an operation of reading the information contained therein by means of a reading light beam operating in said predetermined spectral range .LAMBDA., produce a measurable intensity modulation of the reading light beam which is diffracted at said second surface elements with said second diffraction structure.