The circuit board 1, wherein said {TAIL ~ halogen compound} is {HEAD ~ at least one compound} selected from the group consisting of YF3, YOF, LaF3 and CaF2 
The circuit board 1 , wherein said { TAIL ~ halogen compound } is { HEAD ~ at least one compound } selected from the group consisting of YF3 , YOF , LaF3 and CaF2
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH