Optical functional film for head-up display, optical laminate, functional glass, and head-up display system

An optical functional film for a head-up display according to the present disclosure includes (A) two or more phase difference layers and (B) an adhesive layer. The adhesive layer is adjacent to at least one phase difference layer, and an absolute value of difference between a refractive index of the adhesive layer and a refractive index of the phase difference layer adjacent to the adhesive layer in a direction of a fast axis is less than 0.060.