Just enclose all dates in a TRUNC function if you are not bothered with the time as you say.
and TRUNC(pl.work_time) >= TRUNC(to_date('2014-04-12 11:22:06', 'YYYY-MM-DD HH24:MI:SS'))
and TRUNC(pl.work_time) <= TRUNC(to_date('2014-04-12 11:30:00', 'YYYY-MM-DD HH24:MI:SS'))
or depending on your situation
and TRUNC(pl.work_time) <= TRUNC(:your_date_parameter)
Beware though, if you have an index on the work_time column then you will need to create a new index (function-based) as follows
CREATE INDEX my_index ON person_log (TRUNC(work_time))