sql: "LIKE" problem

I am using "postgresql-7.3.2-1" now!

I met a problem when using "LIKE" in "WHERE" clause.
For example, a table named "t_test", and its data looks like below:

# SELECT * FROM t_test;id | c_name 
----+-------- 1 | abc\ 2 | abc\de
(2 rows)

The thing I want to do is searching in above table and restricting  
the results to those that begin with string "abc\". The search result is:

# SELECT * FROM t_test WHERE c_name LIKE 'abc\%';id | c_name 
----+-------- 1 | abc\ 2 | abc\de
(2 rows)

I want to go a step further, and  restrict the results to those 
that begin with string "abc\d". The search result is:

# SELECT * FROM t_test WHERE c_name LIKE 'abc\d%';id | c_name 
----+--------
(0 rows)

I don't know why the result is "0 rows"(why not is "1 rows"), 
And I have trid "LIKE 'abc\\d%'", the result is also "0 rows".

Is this a bug for "postgresql-7.3.2-1" ? 
Or how can I search a field when it contains a backslash('\') ?

Thanks!!!