FLC DEV FROM ASSIGNED HDG CLRNC DURING DEP.

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INCIDENT OCCURRED WHILE CLBING OUT OF SAN ON THE PEBBLE 2 DEP INTO A VERY BRIGHT SETTING SUN. BOTH PLTS HAD SUNGLASSES AND WINDSHIELD SUN SCREENS IN USE. EVEN WITH THESE DEVICES IN USE AND COCKPIT CRT'S IN THE FULL BRIGHT POS; SEEING THE FLT INSTS WAS VERY DIFFICULT. CAPT WAS PF; AUTOFLT WITH LNAV AND VNAV SELECTED IN USE. THE ACFT WAS SUPPOSED TO MAKE A L TURN AFTER PASSING PEBBLE. SOMEWHERE PRIOR TO MEDLEY THE LNAV HAD DISENGAGED AND THE ACFT HAD DRIFTED R OF COURSE FOR APPROX 2 MINS. ATC INQUIRED WHAT OUR HDG WAS; ABOUT THE SAME TIME WE NOTED THE DEV. I DISENGAGED THE AUTOFLT; SLOWED BOTH THE CLB AND AIRSPD; AND CORRECTED TO THE L. I INITIALLY OVERCORRECTED AND GOT OUTSIDE THE COURSE -- THIS TIME TO THE L. I WOULD ESTIMATE IT TOOK US ANOTHER 2 MINS TO REINTERCEPT THE COURSE EXACTLY AND RE-ESTABLISH OUR CLB RATE. ATC ASKED US IF WE HAD DSNDED DURING THE DEP. COPLT REPLIED WE HAD LEVELED FOR A MIN WHILE RE-ESTABLISHING CORRECT NAV. IN FACT; WE NEVER LEVELED; BUT HAD CONTINUED THE CLB THE ENTIRE PERIOD; BUT AT A REDUCED RATE OF APPROX 500 FPM. IN MY OPINION; THIS INCIDENT WAS A DIRECT RESULT OF THE DISTR/DIFFICULTIES THE SUNLIGHT/GLARE CREATED AND OUR INABILITY TO EASILY SEE THE LNAV DISENGAGEMENT ON OUR COCKPIT CRT'S.