Black lines on display (laptop)?

I would like to know why black lines sometimes appear on my laptop (Acer Aspire 7750g).

I find it very funny that no black lines appear when I connect my laptop to an external monitor (on external monitor and laptop monitor not).

The lines are only for a fraction of a second on the display then disappear again (therefore no pictures).

Could you ever try to make a picture or video of it and something else happens as a distortion or a freeze?

Could be on the screen

Or Aktualliesiere Maybe your graphics driver

No, nothing else happens. Unfortunately, I can't send you a vid because I can't upload videos here.

Possibly the monitor, questionable but then why it only happens sometimes happens when gaming or surfing, etc?

It always happens when something moves on the monitor. I think it's just funny that only black stripes come if I did not connect the external monitor.

I've already tried that. The drivers are up to date