LCD display reverse engineering
As some of you as pointed out, at last I resolved myself the issues I had.
It wasn't that easy for me to find where my problem was, and since this question seemed not to be so popular I assumed nobody cared about the solution. 
Sorry if some of you, trying to give me an hint, spent their time in the pursuit of find info for me.
Problem was mainly in the negative voltage this display needed to work.
Here a blog post I made about the argument, if somebody really care about it.

http://carminatialessandro.blogspot.it/2014/05/recently-i-got-into-my-hand-this-old.html

I want to express my gratitude to anyone trying to help me spent his/her time answering this question.