Abstract: A porous silica having a low refractive index and being stable when exposed to water, and which is configured to have a refractive index of 1.3 or lower and to have a difference of the refractive index at a wavelength 550 nm between before the immersion into water and after the immersion into water for 24 hours of 0.15 or lower.

Abstract: Disclosed is a heat ray reflective film having a single layer structure, which has high heat ray reflectivity, can relatively control visible light absorption and visible light reflection and has excellent heat stability. Also disclosed is a heat ray reflective laminate which has high environmental durability and is suitable as a window material for buildings or automobiles. A heat ray reflective laminate which is a laminate comprising a transparent substrate and a heat ray reflective layer and which has a solar reflectance of at least 15% as measured from the side containing the heat ray reflective layer, wherein the heat ray reflective layer comprises a binder resin containing a hydrophilic group other than an N-pyrrolidonyl group, and a metal, and the heat ray reflective layer has a layer thickness of at most 100 nm.

Abstract: There is provided porous silica having a low refractive index and being stable when exposed to water. The porous silica is configured to have a refractive index of 1.3 or lower and to have a difference of the refractive index at a wavelength 550 nm between before the immersion into water and after the immersion into water for 24 hours of 0.15 or lower.