First of all make sure this is not just a button issue like having the BRIGHTNESS turned down too low. If you are unable to see anything including the menu screen items then the problem is probably not just a wrong display setting.
Turn on your monitor and then turn off all the lights in the room to check if your screen is completely black or if there is still a glow coming from it even though there is no video signal.
If your monitor screen stays completely black, then you most likely have a problem with the power supply to your backlight inverter circuit. This is normally caused by some failed electrolytic capacitors.
If you disassemble the unit and look on the power supply circuit board, you will probably see some scorched or bulging / leaking capacitors there. These components (usually around 6 of them) will need to be removed and replaced with new ones.
The repair procedure is not extremely difficult if you have some basic electrical safety knowledge, and some decent electronics repair / soldering skills.
You will need to unplug the power cord from the unit, and then remove the rear access panel or the entire rear cover as required in order to access the circuit boards inside.
Disconnect and remove the faulty circuit board. Desolder and remove the faulty capacitors and replace with new ones from your local or online electronic parts supplier. Then just reinstall / reconnect the board and test.
Here is a link to another Expert's solution to a similar problem which includes links to his excellent and informative set of LCD TV / MONITOR TROUBLESHOOTING GUIDES:
http://www.fixya.com/support/t10008425-when_turn_tv_picture_flicks_off
These guides will give you some idea of the various problems with LCD monitors and the associated repair procedures.
If you choose to rate BUDMRTN's troubleshooting tips by clicking on the YES THIS WAS HELPFUL icon on his solution page at the above link, then I thank you very much for your time and consideration.
Please comment back here to this page if you have any details to add, have any questions, have difficulty with the links, or just require further general assistance and I will respond as soon as I see it.
I hope that was helpful to you, good luck.
Joe.