| 摘要 |
PROBLEM TO BE SOLVED: To prevent sticking of toner to an optical material surface without impairing light transmissivity and performance of a liquid developer in a toner concentration detecting sensor. SOLUTION: This toner concentration detecting sensor excellent in an antifouling property is provided by arranging an extremely thin and excellently light transmissive chemical adsorption film 17 of a nanometer or angstrom unit via a siloxane bond by using an organosilane compound (most suitably, a silane compound having a long chain alkyl group or an organic functional group including fluorine) on a surface of an optical material 12 contacting with a liquid developer and being arranged in an optical path. |
