Photoconductor Drum - Oki LP-1040 Maintenance Manual

12.5.2

Photoconductor Drum

This Printer uses OPC (organic photoconductor) materials for its electrophotographic
photoconductor materials.
(1) Photoconductor Drum Functions
(a) Charge holding function
(b) Electrostatic latent image holding function
(c) Toner transport function
(2) Outline of the OPC Photoconductor Drum
(a) Basis
Carrier generation (photoexcitons)
Excitons are emitted by optical illumination within organic molecular crystals. These
excitons proliferate to the crystal surface and lattice defects, pushing out electrons and
holes by interacting with the electrostatic potential there.
Excitons excite the entire crystal in the same phase by bouncing around the crystal as an
excitation wave made up of specific excited molecules within the organic molecular crystal.
An exciton is merely this excitation wave when it is quantized.
Now the ion pair that was separated into an electron and a hole will evade coming back
together and thermally separate creating an electron-hole carrier. If the surface of the
photoconductor does not have any charge, the Coulomb force required to separate the
carrier will not act on the particles and so they will re-join.
Carrier transport
In the amorphous carrier transport layer, carriers move by hopping through carrier transport
particles.
If neighboring particles take on a special orientation at close range causing a structural
defect, a carrier trap is created.
(b) Structure
Most OPC photoconductors in use today are of a stacked type, where the basic
photoconductor processes of carrier creation and carrier transport are separated.
(c) Photoconductor surface potential
- Charge: -420 to - 390V -> -400 to -370V (dark decay)
- Exposure: -20 to -60V
- Development: -230 to -300V (for developer toner)
- Transfer: -40 to -80V
- AC Separation: 0 ± AC -> 0V -> ± unstable surface potential and unstable charge toner
will remain.
12-14