Abstract: Provided are a liquid dispersion of fluoride particles having a refractive index lower than that of, for example, magnesium fluoride, the liquid dispersion being excellent in dispersibility and suitable for production of an optical film such as an antireflection film; a composition for forming an optical film; and an optical film. A liquid dispersion of fluoride particles according to the present invention contains: fluoride particles; an anionic surfactant as a dispersant for the fluoride particles; and an organic solvent, wherein the fluoride particles contain at least aluminum, an alkali metal, and an alkaline earth metal as an optional element in a composition of the fluoride particles, and the fluoride particles are dispersed in the organic solvent.

Abstract: Provided are a liquid dispersion of fluoride particles, which has low viscosity and excellent dispersibility, and is suitable for producing an optical film such as an antireflection film; a method for producing the same; and an optical film using the same. The liquid dispersion of fluoride particles according to the present invention is that in which particles of a fluoride represented by the chemical formula AxCFy (wherein A represents sodium or potassium, C represents silicon or boron, x is 1 or 2, and y is 4 or 6) are dispersed in an aprotic organic solvent having a relative permittivity of 5 to 40, and the optical film according to the present invention is produced by using the liquid dispersion of fluoride particles.

Abstract: Magnesium fluoride particles with a low refractive index excellent in film formability are provided. The magnesium fluoride particles each include at least one magnesium fluoride particulate. The at least one magnesium fluoride particulate each has pores that support a supported substance. Further, the at least one magnesium fluoride particulate includes a plurality of particulates. A grain boundary void-like pore serving as a gap that supports the supported substance is present between particulates adjacent to each other of the plurality of particulates.