It seems like that the built in LCD display is faulty. Please do try these troubleshooting steps that may help.
- Do a hard reboot for starters, remove the battery and unplug the AC adapter then press and hold the power button for 20 seconds then test it again.
- First, connect an external monitor while the laptop is on and see if you'll get a display from it.
- If it does display normally that means you may need to open the laptop and check if the ribbon cable is properly connected to both the motherboard and the display itself.
- But if there's still no display on the external monitor that means it's the graphics card that is faulty.