Why won't the monitor turn off?

Question

Monitors

Asus k53 laptop, old.
When the laptop is turned off, the screen barely lights up.
When the laptop is turned on, if the screen goes out in time, then you can barely see what happened after turning it off.
If you turn off the screen separately with the fn button, then everything is the same - if in the dark, you can see the image, you can work and see everything.
Is it matrix degradation? It is clear that the laptop is old, but it is interesting to understand why.

Answer 1

Is it matrix degradation?

No, it turns off the backlight. The image is visible because it never stopped being displayed.