Optical article including an antireflecting coating having antifog properties and process for making same

An optical article comprising a substrate and on at least one face of the substrate a multilayered antireflecting coating functioning in an interferential manner having antifog properties, said antireflecting coating providing to said face of the substrate a reflectance Rv less than 2.5%, said antireflecting coating including a last layer with a refractive index n≦1.55 and a physical thickness of 120 nm or less directly deposited on a high refractive index layer (HI layer) having a refractive index n>1.55, and a thickness of less than 500 nm, wherein:

• (a) the last layer comprises a layer-by-layer (LbL) coating exposed to the environment;
• (b) the LbL coating consists in multiple bilayers with at least two bilayers, each bilayer being formed by successively:
• (i) applying a first layer composition comprising at least one compound A having a first electrical charge;
• (ii) applying a second layer composition directly on the first layer resulting from step (i), said second layer composition comprising at least one compound B having a second electric charge which is opposite to said first electric charge, said compounds A and B being independently a superabsorbent polyelectrolyte, a colloid of nanoparticles of a metal oxide or a silicon oxide, or mixtures thereof, said nanoparticles comprising ionic groups;
• and said compounds A and B being functionalized by either —NH2 or —COOH functional groups, with the first proviso that at least one of compounds A or B is a superabsorbent polyelectrolyte, and with the second proviso that the layers of the antireflecting coating other than the last layer do not comprise any bilayer formed from compositions having opposite electrical charges;
• and
• (c) the LbL coating is cross-linked through chemical linkages between said NH2 and COOH groups and has a refractive index at 643 nm of from 1.40 to 1.50.