Optical security component with reflective effect, production of such a component and secure document provided with such a component

A method for manufacturing an optical security component intended to be observed in a spectral band lying between 380 and 780 nm and in direct reflection, the method comprising:

• the deposition on a support film of a first layer of a material of refractive index n0;
• the formation on the first layer of at least one engraved structure,
• the structure exhibiting a first pattern modulated by a second pattern in such a way that:
• in at least one first region, the first pattern comprises a bas-relief with a first set of facets whose shapes are determined so as to generate one or more cylindrical reflective elements concave seen from the observation face, arranged according to a first line, exhibiting a first principal direction, and the second pattern forms a first sub wavelength grating acting, after deposition of the thin layer and encapsulation of the structure, as a first wavelength-subtractive filter, exhibiting a first color;
• in at least one second region, the first pattern comprises a bas-relief with a second set of facets whose shapes are determined so as to generate one or more cylindrical reflective elements convex seen from the observation face, exhibiting a second principal direction, and the second pattern forms a second sub wavelength grating acting, after deposition of the thin layer and encapsulation of the structure, as a second wavelength-subtractive filter, different from the first wavelength-subtractive filter, exhibiting a second color different from the first color,
• wherein the first and second sub wavelength gratings are defined from the projections on each of the first and second sets of facets of two, unidimensional, plane gratings arranged in a plane parallel to the plane of the component and exhibiting respectively first and second grating vectors of perpendicular directions, the direction of one of the grating vectors being parallel to said first and second principal directions;
• the method furthermore comprising:
• the deposition on the engraved structure of a thin layer of a dielectric material exhibiting a refractive index n1 different from n0;
• the encapsulation of the structure overlaid with the thin layer by a layer of a material exhibiting a refractive index n2 different from n1.