在使用expdp导出数据表时，在query中用to_date指定具体的时间，但导出过程出错，情形如下：

请问正确的书写方式是怎样的？

$ expdp GROUP_TEST/oracle directory=recover_dir dumpfile=test1.dmp logfile=exp_test1.log tables=t_rqf_log query=t_rqf_log:'"where ctime > to_date(''2021-09-30'',''yyyy-mm-dd'')"'
......
ORA-31693: Table data object "GROUP_TEST"."T_RQF_LOG" failed to load/unload and is being skipped due to error:
ORA-00904: "DD": invalid identifier


$ expdp GROUP_TEST/oracle directory=recover_dir dumpfile=test1.dmp logfile=exp_test1.log tables=t_rqf_log query=t_rqf_log:'"where ctime > to_date(''''2021-09-30''','''yyyy-mm-dd'''')"'
......
ORA-31693: Table data object "GROUP_TEST"."T_RQF_LOG" failed to load/unload and is being skipped due to error:
ORA-00904: "DD": invalid identifier