Don't use a function against the column, that can make performance worse, potentially much worse.
WHERE CREATE_DATE = (DATEADD(DAY, DATEDIFF(DAY, 0, GETDATE()) - 1, 0) AND CREATE_TIME >= '18:00:00') OR
(CREATE_DATE = DATEADD(DAY, DATEDIFF(DAY, 0, GETDATE()), 0) AND CREATE_TIME < '18:00:00')
SQL DBA,SQL Server MVP(07, 08, 09) "Money can't buy you happiness." Maybe so, but it can make your unhappiness a LOT more comfortable!