How is the transfer of charge?

Question

Physics

Good afternoon, I have a question about the device of a laser printer. Consider Fig. 1 we have a drum that is charged with a negative charge from a rubber roller. An alternating-direct current is supplied to the roller.

Rice. one

1. What is AC bias and DC bias (like AC-DC bias)? Why are they needed at all, and what do they do?
   
2. How is the roller charged with electrons?
   

Let's say we answered the previous questions. Now let's take a closer look at the surface of the primary charge roller. On Fig. 2, the electron tries to fly out from the surface, but the resulting hole does not give it and pulls it back.
Question:
Why does the electron manage to fly to the photoreceptor drum?

Rice. 2

Answer 1

Let's approach this question from the other side, why do holes prevent electrons from flying away during the photoelectric effect?
ZSE - there must be additional energy that helps them fly away.