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Why losing charges under light?

  1. Oct 31, 2011 #1
    Does anyone have any suggestions on what charge of static electricity is being applied into the material?
    When this material is exposed to light the areas exposed lose the charge, Does anyone know what kind of process it is for losing the charge under light?
    Thanks in advance for any suggestions

    "For xerographic copier, a special type of material is used, which is non-conducting in darkness but conductive when exposed to light. While in the dark the materials is charged with static electricity. When it is exposed to light the areas exposed lose the charge, while most not exposed retain the charge. After exposure to light the plate is sprayed with a fine powder of oppositely charged dry ink (toner), which adheres to the areas of the plate, which retained a charge by electrostatic attraction. Finally, a sheet of paper, which is also charged is placed on the plate, and the toner is transferred to the paper. The paper is then heated briefly to make the toner adhere permanently. The excess toner is scraped off the plate, and the entire plate is exposed to light to remove any remaining charge."
  2. jcsd
  3. Oct 31, 2011 #2

    Simon Bridge

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    Photo-electric effect.

    The exact charge applied depends on the xerox machine.
  4. Oct 31, 2011 #3
    Usually, we can smell ozone gas near the copy machine,
    Do you have any suggestions whether the materials is charged with negative or positive static electricity before photo-electric effect?
    Thanks you very much for any suggestions
  5. Oct 31, 2011 #4


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    It is negative charge. The ozone smell happens to be noticed at older machines. Newer ones have a charge roller which is in direct contact with the image drum. Lower voltage too. The laser or the LEDs is lit on the image drum. The charge changes and the negative charged toner will "jump" towards these lit areas.

  6. Oct 31, 2011 #5
    Thanks everyone very much for your suggestions
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