A process for manufacturing a mask having submillimetric openings, in which: for a masking layer, a first solution of colloidal nanoparticles in a first solvent is deposited, the particles having a given glass transition temperature Tg, the drying of the masking layer, known as the first masking layer, is carried out at a temperature below said temperature Tg until a mask having a two-dimensional network of substantially straight-edged submillimetric openings, that defines a mask zone known as a network mask zone is obtained, a solid mask zone is formed by a liquid deposition, on the face, of a second masking zone, the solid mask zone being adjacent to and in contact with the network mask zone, and/or at least one cover zone is formed, the cover zone being in contact with the network mask zone, and/or after the drying of the first masking layer, a filled mask zone is formed by filling, via a liquid route, openings of a portion of the network mask zone. The invention also relates to the mask and the electroconductive grid obtained.