E-ink screens don't emit any blue light, actually they don't emit any light unless you turn on the backlight which is necessary only in a really dark environments. On the other side daylight uses LCD panel, well, reflective LCD. It can work without backlight, but only in a really well lit environments. In average use Daylight will emit much more light than the true e-ink display. It has fast refresh rate because, well it's LCD. Stick matte foil on top of the iPad, slide color temperature all the way to more warm and you got yourself a better Daylight.