XEROGRAPHIC RESPONSE OF AN AGING CONDUCTIVE DEVELOPER

From a materials viewpoint, the xerographic developability of a conduc tive developer is governed by a balancing of opposing controlling para meters, namely toner concentration, toner triboelectric charge-to-mass ratio, and developer conductivity. For an age-induced decline in deve loper conductivity, the resultant decline in developability can be off set through an increase in toner concentration/decrease in toner charg e-to-mass ratio. However, because an increasing toner concentration de presses developer conductivity, a critical loss in conductivity will t rigger repeated increases in toner concentration and will hence provok e an accelerating trend to failure. In certain cases, however, a toner concentration-runaway failure can occur, even though the developer re mains highly conductive, and for such cases the developability failure appears to be driven by physical factors such as the increased textur e and reduced fluidity of a development brush having enhanced carrier- to-carrier contacts.