Antireflection glazing unit equipped with a porous coating and method of making

A glazing unit including a transparent substrate equipped with an antireflection coating, which coating includes at least one film of a porous material essentially including silicon, oxygen, carbon and possibly hydrogen, in which the atomic proportion PC of carbon, relative to the sum of the atomic contributions of silicon, oxygen and carbon, varies locally in the thickness direction of the film, from a first surface to a second surface thereof: increasing between a first minimum value PCmin1 and a maximum value PCmax, the ratio of the maximum value PCmax to the first minimum value PCmin1 being at least 1.2; and the proportion of carbon then decreasing, between the maximum value PCmax and a second minimum value PCmin2, the ratio of the maximum value PCmax to the second minimum value PCmin2 being at least 1.2.