Display device and backlight for display device

A display device, comprising:

• a light-guiding body having a first major surface, a second major surface opposite to the first major surface, and a side face connecting the first major surface and the second major surface;
• a light source causing light to enter an inside of the light-guiding body from the side face;
• a wavelength selection transmission layer provided on the second major surface, the wavelength selection transmission layer having:
• a first region transmitting light of a first wavelength band, of visible light and reflecting light of a wavelength band excluding the first wavelength band;
• and
• a second region transmitting light of a second wavelength band different from the first wavelength band, of the visible light and reflecting light of a wavelength band excluding the second wavelength band;
• and
• a light control layer provided on the wavelength selection transmission layer and changing an intensity of light passing through the light control layer,
• the first major surface having a plurality of concave portions having inclined faces inclined relative to the first major surface,
• a ratio of a total area of areas of the plurality of the concave portions projected on the first major surface, relative to a total area of the first major surface, being 8% to 25%, and
• the plurality of the concave portions being evenly provided in the first major surface.