The invention relates to a substrate (30) coated on one face (31) with a multilayer of thin films (34) comprising at least one metal functional layer (140) based on silver or made of silver and two antireflective coatings (120, 160), the said antireflective coatings each comprising at least one antireflective layer (124, 164), the said functional layer (140) being disposed between the two antireflective coatings (120, 160), characterized in that the said metal functional layer (140) is a discontinuous layer having a surface area occupation factor in the range between 50% and 98%, or even between 53% and 83%.