The most probable cause is a broken power connection. A bad connection between the graphics card and screen could cause symptoms as well. A problem with the card's driver is a possible, but unlikely, cause of the problem.
Laptop screens require a constant source of power, and any interruption will cause the screen to go black. While the problem could reside in the power supply itself, the cable that connects the power supply to the screen is the most likely culprit. Replacing the cable may fix the problem.
In most laptops, the screen is connected to the graphics card by a robust cable that is unlikely to wear down over time. However, the connection can still become damaged. If this is the reason why the screen goes black, fixing it may require purchasing a new screen. Laptop screens contain complex wiring to ensure that all parts are working correctly, and any faults in this wiring can cause the screen to turn off. Fixing this problem is impractical, and it may require purchasing a new screen and installing it.
It is possible that the graphics driver has become corrupted, but these problems do not usually result in the screen turning off completely. Reinstalling the driver is easy, so it may be worth trying before opening up the laptop.