In a very simple display there are often three or four layers of glass and plastics, and a more complex display may have seven or eight layers. As light passes through each layer, there will be changes in the refractive index, resulting in some form of reflection.
This is made much worse by displays that have air gaps in their glass stack- up. The best solution is to select a display that optically bonds each layer of glass, directly connecting them to greatly reduce the change in the refractive index between layers. Ideally, a circular polarizer should be employed within the glass stack-up to polarize the light on the way into the screen. It rotates the polarization so that when light reflects off the LCD or the inner layers of glass, the light is out of phase with the polarizer and cannot escape.