How do I return records based on which records only exist during a certain time period?

I've got a table of invoices and customer codes. I'd like to pull only the customers that have not done any business with us since 2009.

My regular select statement is simple

SELECT INVOICE.CUSTOMER_CODE FROM INVOICES

WHERE INVOICES.ORDER_DATE <= '01-01-2010'

But, this statement also pulls customer codes of customers who have done business before and after 2010. I want only those customers that have not done business before 2010. It seems so simple, but I can't grasp how to do this and my google searches only bring up how to do a range of dates.