A B737 CREW; TAXIING FOR TKOF AT LAX; TAXIED PAST A HOLD SHORT LINE.

Narrative

AFTER PUSHBACK WE WERE CLRED TO TXWYS D; S; AND B TO RWY 25R. AFTER PASSING 'CHKPOINT 2' WE WERE RECLRED TO TXWYS S; AND B TO RWY 25R. ON TXWY B THERE WERE STEEL PLATES; IF YOU TAXIED SLOWER YOU COULD DRIVE AROUND MOST OF THEM. THIS IS WHAT I WAS DOING. IT WAS DARK AND THE TAXI LIGHT DID NOT ILLUMINATE THEM VERY WELL. AFTER WE PASSED TXWY F; TWR ASKED US WHY WE DID NOT HOLD SHORT OF TXWY F. WE TOLD HIM WE WERE NOT INSTRUCTED TO. HE TOLD US THAT WE WERE NOT INSTRUCTED TO BY HIM; BUT THERE WAS A SIGN THERE. WE ASKED HIM WHAT HE WANTED US TO DO AND HE CLRED US INTO POS AND HOLD. IT IS NOT STANDARD PROC FOR US TO GO TO RWY 25R. BEFORE WE PUSHED I THOUGHT WE WOULD BE GIVEN RWY 25R AT THAT TIME OF THE MORNING. I LOOKED AT THE ARPT DIAGRAM AND THOUGHT I READ THE SIGNS AS WE WERE TAXIING. I MUST HAVE ISSUED AT LEAST ONE. SUPPLEMENTAL INFO FROM ACN 537193: I CHANGED TO TWR FREQ APCHING TXWY F. SHORTLY THEREAFTER; TWR ASKED US WHY WE DIDN'T STOP AT TXWY F. NEITHER THE CAPT NOR MYSELF HEARD ANY INSTRUCTIONS TO DO SO. TWR SAID THERE WAS A SIGN ON THE TXWY. WE DID NOT SEE THAT EITHER (NIGHTTIME).