I think e-ink requires a side-light rather than backlight, as the little spheres are opaque, with a dark side and a light side that physically reorient, meaning

I think e-ink requires a side-light rather than backlight, as the little spheres are opaque, with a dark side and a light side that physically reorient, meaning illumination from a backlight would have to somehow shine through the dark side, when the dark side faced the backlight, but be blocked by the dark side when it faced outward. Maybe someone can up with a UV transparent dark side and a fluorescing light side or something.