question about hpunix display wm log with Chinese Characters

hello, all
We are using IS6.1 chinese version on HPUNIX.
In server log in IE was fine to read chinese characters.
And if I download the serveryyyyymmdd.log file , i have to convert unicode to utf8 in UltraEdit, then I can read Chinese charactors.
But, when i vi serveryyyyymmdd.log or tail -f serveryyyyymmdd.log , chinese charactors will be a mess. And the unix env parameter is : LANG=zh_CN.hp15CN.
So could anybody help me about this?
Thanks a lot.