Multilayer body and method for producing same

A multilayer body comprising:

• a substrate film;
• a replication layer applied to a surface of the substrate film, into the surface of which facing away from the substrate film a first surface relief appearing to the observer in the form of a three-dimensional free-form surface is introduced which comprises a Fresnel lens structure comprising a diffractive free-form element with a grating structure, the Fresnel lens structure generating a magnifying, demagnifying or distorting effect, the first surface relief being defined by a series of peaks and depressions extending along a plane defined by the surface of the replication layer;
• a first metal layer or a first high-refractive-index dielectric layer, which is arranged on the surface of the replication layer forming the surface relief;
• a wet-chemically applied, at least partially transparent spacer layer, which is applied to a surface of the metal layer or of the high-refractive-index layer facing away from the replication layer, and which forms a second surface relief on a surface of the spacer layer opposite the first relief structure, the second relief structure being defined by a series of peaks and depressions extending along a plane defined by the surface of the replication layer, wherein the peaks and depressions of the second relief structure at least partially correlate with the peaks and depressions of the first relief structure such that the depressions of the second relief structure fall within the depressions of the first relief structure and have a structure depth of at most 90% of a structure depth of the depressions of the first relief structure;
• and
• a second metal layer or a second high-refractive-index dielectric layer, which is applied to a surface of the spacer layer facing away from the first metal layer or the first high-refractive-index dielectric layer,
• wherein, due to the smaller structure depth of the second relief structure as compared to the first relief structure, the thickness of the spacer layer varies between the peaks of the first and second relief structures and the depressions of the first and second relief structures resulting in a shape leveling of the surface of the spacer layer having the second relief structure as compared to the surface of the replication layer having the first relief structure, and
• wherein, the thickness of the dried spacer layer is greater in the center, or in areas with a coarse period Δx, than at the edge, or in areas with a smaller period Δx of the relief structures.

A method for producing a multilayer body, with the steps of:

• a) providing a substrate film with a replication layer;
• b) molding a first surface relief into a surface of the replication layer, the first surface relief appearing to the observer in the form of a three-dimensional free-form surface, which is formed by a Fresnel lens structure comprising a diffractive free-form element with a grating structure, the Fresnel lens structure generating a magnifying, demagnifying or distorting effect, the first surface relief being defined by a series of peaks and depressions extending along a plane defined by the surface of the replication layer;
• c) applying a first high-refractive-index dielectric layer to the surface of the replication layer forming the surface relief;
• d) wet-chemically applying an at least partially transparent spacer layer to the entire surface of the first dielectric layer, wherein, upon drying of the spacer layer, a second relief structure is formed on a surface of the spacer layer opposite the first relief structure, the second relief structure being defined by a series of peaks and depressions extending along a plane defined by the surface of the replication layer, wherein the peaks and depressions of the second relief structure at least partially correlate with the peaks and depressions of the first relief structure such that the depressions of the second relief structure fall within the depressions of the first relief structure and have a structure depth of at most 90% of a structure depth of the depressions of the first relief structure;
• and
• e) applying a second high-refractive-index dielectric layer to the spacer layer, wherein the spacer layer has a lower refractive index than the first and the second high-refractive-index layers,
• wherein, due to the smaller structure depth of the second relief structure as compared to the first relief structure, the thickness of the spacer layer varies between the peaks of the first and second relief structures and the depressions of the first and second relief structures resulting in a shape leveling of the surface of the spacer layer having the second relief structure as compared to the surface of the replication layer having the first relief structure, and
• wherein, the thickness of the dried spacer layer is greater in the center, or in areas with a coarse period Δx, than at the edge, or in areas with a smaller period Δx of the relief structures.