Doctor process of toner layer in non-magnetic single-component development system in electrophotography

In a non-magnetic single-component development system in electrophotography, formation of a thin and uniform toner layer on the development roller is important for obtaining high image quality. We conducted experimental and numerical investigations to clarify the dynamics of toner particles in this process. Two approaches were adopted for the investigation. One is experimental and the other is numerical simulation using the distinct element method. We manufactured a mock-up apparatus consisting of a supply roller, a development roller, and a doctor blade for forming a thin toner layer on the development roller. The thickness, surface roughness, and charge density of the formed toner layer were measured after the doctoring process. It was clarified that the thickness of the toner layer was increased, but the charge density was decreased, by increasing the applied voltage and rotational speed. These findings were confirmed by direct observation of the toner motion in the doctoring area with a high-speed microscope camera. Numerical calculations performed using an improved distinct element method revealed that the elastic energy applied to the toner particles, which is an index of toner degradation, was increased by increasing the stiffness and pressing force of the doctor blade, but decreased when the curvature of the blade tip was large. The present experimental and numerical results can be used to improve non-magnetic single-component development system in electrophotography.