Do Kindle and Rakuten Kobo Emit Blue Light?

Backlight Models Emit Blue Light

E-readers with built-in light functions, such as Kindle Paperwhite and Rakuten Kobo Glo, use LED lights, so they do emit blue light.
On the other hand, older generation e-readers without lights, such as the basic Kindle, do not emit blue light because they do not have LED lights.

Structurally Less Blue Light

Kindle and Rakuten Kobo models with light functions also emit blue light, but structurally, the amount is less compared to LCD displays.
This is because e-readers that use E-ink displays project light from the front of the screen toward the top and bottom, so the blue light is not directly projected toward the user’s face. Of course, some blue light does come from the screen, but it is considered minimal.

Meanwhile, smartphone and PC displays, as their name "backlight" suggests, project light from behind the screen directly toward the user’s face, causing blue light to continuously hit the eyes while in use.

Best Practice: Lower the Brightness

E-readers tend to be set with high brightness for easier reading, but it is best to keep brightness low and let room lighting illuminate the screen. This reduces the amount of blue light exposure.

Especially during the daytime with sunlight, it is surprisingly easy to read even when brightness is set to 0. At brightness level 0, the e-reader does not use LED lights, so it does not emit blue light.

At night, this is not fully possible, but by ensuring external light falls onto the screen, similar to reading a paper book, you can still keep the brightness relatively low while reading comfortably.