operation between 2 files

Hi,
I have two files, say  file_A  and file_B

# cat file_A

0714-pippo-sia-w2k-ep
0714-pluto-reg-w2k-ep
0714-gigio-sic-sun-ep
0856-rossi-sia-w2k-ep
0564-bianchi-sil-syn-ep
....
....

# cat file_B

0714-pippo-gw
0856-rossi-gw
....
.....
I want to have an output from teh 2 precedent files like this:

0714-pluto-reg-w2k-ep
0714-gigio-sic-sun-ep
0564-bianchi-sil-syn-ep
..
...

the output file have the file_A whitout the lines that contain the name in
the file_B.....

How to acheive this?

Please help me....

thanks in advance