A positively chargeable toner suitable to be carried on a cylindrical developer-carrying member having a resinous surface for developing an electrostatic latent image is formed from a composition including a binder resin, an imidazole compound and a colorant. The binder resin comprises at least one member selected from the group consisting of (i) a mixture of vinyl resin having a carboxyl group and a vinyl resin having a glycidyl group, (ii) a vinyl resin having both a carboxyl group and a glycidyl group, and (iii) a vinyl resin having a carboxyl group and a glycidyl group in a form reacted with each other. The imidazole compound is a compound having an imidazo unit represented by formula (1) below: ##STR1## wherein R.sub.1 -R.sub.4 independently denote hydrogen or a substituent as specified. In some cases, two or more such imidazole units can be included in a combined form to provide the imidazole compound. The imidazole compound is effective for promoting a crosslinking reaction between the carboxyl group and the glycidyl group to provide the toner with improved fixability and anti-offset property in combination.

An apparatus and a method for optimizing an image transfer environment in an electrophotographic developing device is provided. The apparatus includes at least one or more discharging parts disposed on a printing path, contacting with a printing paper as it is fed, for discharging electrostatic electricity formed on the printing paper; a feeder roller made of a conductive material, for electrically detecting an amount of humidity contained in the printing paper and for feeding the printing paper between the transfer roller and the photosensitive drum; and a ground controller for selectively controlling connection or disconnection of the at least one or more grounds based upon the humidity amount input from the feeder roller to the ground controller.