How photocopier works
R.B.Chavan
Department of Textile Technology
Indian Institute of Technology
Hauz-Khas, New Delhi 110016
Basic steps
• Open the copier lid
• Place the document to be photocopied
face-down on the glass
• Select the options you want (number of
pages, enlargements, lighter/darker)
• Press the Start button
What happens
• Basic principle
• Electrostatic attraction
• Main component Light sensitive photoconductive drum made
coated with selemnium or photoconductive polymer.
• The surface of the drum is charged.
• An intense beam of light moves across the paper that
you have placed on the copier's glass surface. Light is
reflected from white areas of the paper and strikes the
drum below.
• Wherever of light hits, electrons are emitted from the
photoconductive atoms in the drum and neutralize the
positive charges above. Dark areas on the original
(such as pictures or text) do not reflect light onto the
drum, leaving regions of positive charges on the
drum's surface.
Toner attraction
• Toner
• It is a mixture of colour pigment and
thermoplastic polymer
• The toner is -vely charged
• -ve charged toner gets attracted to +ve
charge image on photoconductive drum
• Paper is charged +ve
• -ve charge toner in the form of image is
attracted to +ve charge paper
• The paer then heated during which
thermoplastic binder softens and help to
adhere the pigment colour on the paper
Steps
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
1. Clean platen, ready for service
2. Produce image for replication
3. Charge platen with corona wire
charge leaks off wire because of corona discharge,
with associated "ozone smell" in some cases
4. Expose platen to image
illuminated part of platen allows charge to
leak away because of photoconduction
5. Dark areas stay charged
6. "Charge image" of original
7. Expose platen to toner
toner is carried electrostatically by carrier particle
released onto the relatively stronger charge of the platen
Specks of toner can be seen clinging to the larger carrier particle.
8. "Toner image" of original
9. Introduce paper for copy
10. Charge paper w/ corona wire
11. Paper ready to receive toner
12. Toner adheres to paper
13. Toner image on paper
14. Toner fused to paper
1. -- accomplished by heated rollers and a bit of pressure,
hence the warm, sometimes "curled", paper
2. Cleaning and back to Step 1.