.screenrc.key

escape ^Bb

#   Set  the  command character to x and the character generating a literal
#   command character (by triggering the "meta" command) to y (similar to the -e
#   option).  Each argument is either a single character, a two-character
#   sequence of the form "^x" (meaning "C-x"), a backslash followed by an octal
#   number (specifying the ASCII code of the character),  or a backslash
#   followed by a second character, such as "\^" or "\\".  The default is "^Aa".