Try FN + Z

"The keyboard CAN be set to stay on all the time. On your Qosmio, just go to: >Start >Toshiba >Utilities >HWSetup >Illumination >then under "Keyboard Backlight," click the radio button "FN" then check the box "On." After you reboot, you'll be able to turn the keyboard on and off by using the "FN" + "Z" keys."