Developer and developing method

Claim 1

A developer comprising a binder resin, a colorant and a positive charge controller, said positive charge controller comprising fumed silica particles treated with a coupling agent having a hydrolyzable group and a non-hydrolyzable organic group bonded to a tetravalent center atom of Si or Ti, said positive charge controller having a hydrophobicity within the range of from 30 to 80 as measured by the methanol titration test, in which said coupling agent is a silane or titanate coupling agent selected from the group consistng of formula compounds (1), (2) or (3), wherein formula (1) compounds have the formula: R.sub.m SiY.sub.n ( 1) wherein R is an alkoxy group or a chlorine atom; m and n are integers satisfying the relation of m+n=4; Y is an organic group containing at least one of amino, vinyl, glycidoxy, mercapto, methacryl, and ureido groups; wherein formula 2 compounds are cation type unsaturated amino-functional silanes selected from the compounds represented by formula 2 as follows: ##STR64## wherein X is a hydroxyl group or a hydrolyzable group; R is an alkyl having 1 to 6 carbon atoms; n is an integer of 1 to 3; Q is a divalent hydrocarbon group or an organic group containing oxygen in the form of ##STR65## or nitrogen in the form of R 2 N=group; R 1 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a heterocyclic organic group having a nitrogen in the ring; m is 2; Z is a divalent organic group having a conjugated double bond with ##STR66## and bonded through C--N bonding to the nitrogen atom; R 2 is hydrogen atom or an alkyl having 1 to 6 carbon atoms; and Y is an acid anion or a hydrolyzed product of said cation type unsaturated amino-functional silane; and wherein formula 3 compounds are titanium compounds represented by the formula (3) as follows: R.sub.m --Ti--X.sub.n ( 3) wherein m and n are 1 and 2, respectively, or 4 and 2, respectively; R is an alkoxy group, ##STR67## wherein in the above formulae, R 1 is a saturated or unsaturated divalent aliphatic group having 1 to 31 carbon atoms or a divalent aromatic hydrocarbylene group; Y is a hydrogen atom or an amino group; and a plurality of X, R 1 and Y existing in the same compound being the same or different, respectively.