What was found
PARKING BRAKE NOT RELEASED EICAS MESSAGE ABOUT 5 MINUTES AFTER TAKEOFF. RAN QRH AND IT DID NOT EXTINGUISH.DECLARED EMERGENCY. IT FINALLY EXTINGUISHED ON ITS OWN ABOUT 10 MINUTES LATER BEFORE LANDING. EMERGENCY/PARKING BRAKE INDICATOR LIGHT LEFT OF EICAS WAS ALSO ILLUMINATED DURING THAT TIME AND ALSO EXTINGUISHED BEFORE LANDING. LANDED WITHOUT INCIDENT. R&R EMERGENCY/PARKING BRAKE PRESSURE SWITCH 1 AND 2 IAW AMM 32-44-09.