The coating is the core of OPC drums, usually adopting a three-layer structure (UC + CG + CT), each with specific functions to ensure print quality and service life.

Note that OPC drum color (HP standard, Mitsubishi green, Xerox purple, etc.) is the natural color of CG layer material and cannot judge quality. The scientific criteria are key parameters: voltage, inductance, dielectric constant, refractive index, reflectivity and film thickness.

UC Layer (base layer): Bonds coatings to aluminum substrate and determines baseline voltage/resistance, critical to avoiding drum breakdown and ghosting.

CG Layer (photoconductive layer): Determines print density, with inductance (standard range: 680–820) and light decay as key properties. Higher inductance means darker prints, lower means lighter. Domestic manufacturers currently rely on imported CG materials due to technical constraints.

CT Layer (surface layer): Made of resin, determining wear resistance. Film thickness decides lifespan: 18μ–26μ (30k–60k pages), 26μ–33μ (60k–100k pages), above 38μ (100k–120k pages). Drums with over 120k pages require special materials for stable performance.