Anti-reflection optical member

An anti-reflection optical member, used in a medium, that prevents incident light with a predetermined wavelength from being reflected, the anti-reflection optical member comprising a laminated structure in which the following are laminated in this order:

• a transparent substrate that has a first refractive index greater than that of the medium;
• a metal-microparticle-containing layer that contains a plurality of metal microparticles;
• and
• a dielectric layer that has a second refractive index greater than that of the medium,
• wherein at least 60% of all the plurality of metal microparticles are flat metal particles each of which has a ratio of diameter to thickness of equal to or greater than 3,
• wherein main flat surfaces of the flat metal particles are oriented in a plane at in a range of 0° to 30° to a surface of the metal-microparticle-containing layer,
• wherein in the metal-microparticle-containing layer, the plurality of metal microparticles is disposed without forming a conductive path,
• wherein a thickness of the dielectric layer is a thickness at which light reflected on a surface of the dielectric layer in a case where the incident light enters the laminated structure from the surface of the dielectric layer interferes with and is canceled out by light reflected on an interface between the dielectric layer and the metal-microparticle-containing layer,
• wherein said incident light with the predetermined wavelength is visible light, and
• wherein a wavelength bandwidth, at which a reflectance of the incident light is equal to or less than 0.5%, is equal to or greater than 100 nm.