This may seem like an over-simplyfied answer but have you checked the brightness? This is how Windows recommends you do it: Laptop displays don't have brightness or contrast buttons on the front. For a majority of laptops, there isn't a control for setting the contrast. However, you can set the brightness of many laptops by pressing and holding the Fn key, and then pressing a function key to decrease brightness () or increase brightness (). 

Hope that's helpfull.

I get that some times, what I do is turn it off, disconect the power cable & take out the battery.

Then hold down the on/off button for 30 seconds.

Put the battery & power cable back & tun it on as normal.

Its some kind of static build up if this works, if not its possibly more serious.