on demand black screen screensaver - black screen without switching off monitor
Solution 1:
Create a batch file containing the Screen Saver command. The command should look like %systemroot%\system32\scrnsave.scr /s. This command starts the screen saver program which defaults to a black screen.
If you want something more complex I would advise you to take a look at NirCmd. This utility gives you the ability to do random miscellaneous stuff in Windows from the command line and therefore also from scripts. The monitor command might be of interest to you but I am not sure how it will behave on your laptop.