How photocopier works

R.B.Chavan Department of Textile Technology

Indian Institute of TechnologyHauz-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 particlereleased 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.