Blue light blocking film and light source

A light source comprising:

• a light emitting element and a blue light blocking film,
• the blue light blocking film comprising
• a selective reflection layer,
• wherein the selective reflection layer exhibits selective reflection having a center wavelength in a wavelength range of 450 nm to 500 nm, and a half-width of the selective reflection is 20 nm to 45 nm,
• a light transmittance of the selective reflection layer at the center wavelength is 50% or less,
• the selective reflection layer includes a cholesteric liquid crystal layer formed by curing a cholesteric liquid crystalline phase,
• the selective reflection layer includes the cholesteric liquid crystal layer which selectively reflects right circularly polarized light and the cholesteric liquid crystal layer which selectively reflects left circularly polarized light,
• a light transmittance of the blue light blocking film at any wavelength in a wavelength range of more than 500 nm and 780 nm or less is 60% or more, and
• the selective reflection layer is arranged on the light emission side of the light source with respect to the light emitting element.