Article coated with a low refractive index layer based on organic silsesquioxane compounds

An article comprising a substrate having at least one main surface coated with a layer A having a refractive index lower than or equal to 1.55, wherein said layer A was obtained by deposition of activated species issued from at least one compound C in gaseous form having the following formula:

• wherein R1, R2, R3, R4, R5, R6, R7, R8 are independently selected from the group consisting of alkyl, aryl, vinyl, acrylic, methacrylic, alkyl substituted with one or more heteroatoms, and —OSiRaRbRc in which Ra, Rb and Rc independently represent H, alkyl, vinyl, aryl, hydroxyl or a hydrolyzable group, with the proviso that Ra, Rb and Rc are not all selected from H or a hydrolyzable group, and
• wherein the deposition of said layer A is carried out by applying a bombardment with an ion beam to layer A while layer A is being formed.