Particle Transport, Deposition, and Removal in Xerography (Fa-Gung Fan)

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National Science Foundation CRCD project lecture (April 14, 2003)

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Particle Transport, Deposition, and Removal in Xerography (Fa-Gung Fan)

  1. 1. Particle Transport, Deposition, and Removal in Xerography NSF CRCD Project Lecture April 14, 2003 Fa-Gung Fan Wilson Center for Research & Technology Xerox Corporation Webster, NY http://chester.xerox.com/innovation/wcrt.html Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  2. 2. Outline of the Lecture General Overview of Xerography Transport, Adhesion/Cohesion and Removal of Fine Particles (Toner) in Xerography Measuring Toner Charge --- Cage Blowoff, Charge Spectrograph Electrostatic Adhesion, Detachment of Toner Particles Measuring Toner Adhesion --- Atomic Force Microscopy (AFM), Centrifuge Detachment, Electric Field Detachment Measuring Cohesion --- Fluidized Bed Modeling of Electrostatics in Subsystems (in MAE Seminar 4:00-5:00pm today) Q&A Acknowledgements: S. Chang, C. Duke, D. Hays N. Goodman, H. Mizes Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  3. 3. Xerographic Process 5 2 Fusing Exposure 1 6 Cleaning Charging 4 Transfer Photoreceptor SN SN Substrate N S N Development Paper 3 C. Duke, J. Noolandi, T. Thieret, “The surface science of xerography,” Surface Science, 500, p. 1005, (2002) Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  4. 4. Xerox Phaser 7700 Color Desktop Laser Printer 22 prints/min, full-color Xerography is a versatile technology that scales from desktop, to office, to production machines; black-and-white, hightlight color, and full color. Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  5. 5. DocuColor 40 Pro Color Office Multifunction Machine 40 prints/min, full-color Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  6. 6. DocuTech 6180 Production Publisher 180 prints/min Black-and-White Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  7. 7. DocuColor iGen3 Digital Production Color Press 100 prints/min, full-color Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  8. 8. iGen3 Xerographic Unit Finisher/Binder Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  9. 9. Photoreceptor A semiconductor whose conductivity is a strong 0 0 5 Voltage on Surface (V) function of light exposure. _ _ _ _ _ _ _ _ _ _ _ _+_+ -1000 ++ + + + + + ++ ++ + + + Exposure (ergs/cm2) Electron/hole pairs • Requirements – Insulator in the dark. – Conductor when exposed to light – Builds up enough voltage. – Uniform properties Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  10. 10. Charging Subsystem HV Power HV Power HV Power Supply (-) Supply (-) Supply (-) Free ions are attracted Rapidly moving electrons Electrons continue to to wire; Free electrons are and ions collide with air follow Electric Field lines repelled. Counter-charges molecules, ionizing them to Photoreceptor until build up on grounded surfaces. and creating a corona. uniform charge builds up Positive Ions Electrons Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  11. 11. Imaging/Exposure Traditional Analog Copier Laser Printer Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  12. 12. Development Photoreceptor Photoreceptor Toner Apply E Field E Development roll Development roll Development Photoreceptor Roll Charge particles triboelectrically Electric field moves Mixing Charging particles from developer roll to photoreceptor Triboelectrification of toner particles and carrier beads Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  13. 13. Toner • Charging • Adhesion/cohesion • Powder flow • Rheology 5-10 microns • Color - hue and density • Pigment dispersion Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  14. 14. Toned Carrier Bead q ≅ 2 x 104 e m ≅ 2 x 10-10 gm q/m ≅ 16 µC/gm 20 µm Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  15. 15. Transfer Paper Apply E Paper Paper Field & Separate E Photoreceptor Photoreceptor Photoreceptor Electric field moves particles from photoreceptor to paper or transparency Detachment field must overcome toner adhesion to photoreceptor Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  16. 16. Fusing Subsystem Permanently affix the image to the final substrate paper of various roughnesses and surface treatment transparency (plastic) Apply heat and/or pressure Hot Roll Fuser: Pressure Roll Unfused toner Fused toner Paper Elastomer Heat Roll Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  17. 17. Cleaning and Erase Removes unwanted residual toner and charge from photoreceptor before next imaging cycle Physical agitation removes toner (blade or brush) Light neutralizes charge by making entire photoreceptor conductive Photoreceptor _ _ _ _ _ Charge Residual toner Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  18. 18. Transport, Adhesion/Cohesion and Removal of Fine Particles (Toner) in Xerography Toner must flow smoothly down dispenser Toner must develop onto roll uniformly Toner must transfer from roll to paper paper Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  19. 19. Toner Charge Measurements Blowoff Tribo Air 50 40 Q/M (µC/gm) 30 Blow toner µ from toned 20 beads in cage 10 Measure charge & mass 0 difference 0 1 2 3 4 Calculate Toner Concentration (%) average Q/M Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  20. 20. Toner Charge Measurements Charge Spectrograph 1.5 99% 95% q/D (fC/µm) 1 90% Air Flow µ 80% E Field 50% 0.5 Lycopodium 0 Inject toner 0 5 10 15 20 25 30 35 Displacement ∝ q/D -0.5 Diameter (µm) µ Measure position & size of particles Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  21. 21. Toner Adhesion Forces Fa Particle adhesion depends on: ++ + ++ + Size, shape, & roughness + Materials + + + + Flow agents ++ ++ Charge Surface charge Fad distribution on particle Detachment when Fa > Fad Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  22. 22. Electrostatic Image Force Model Q Fa σ= E R 4 π R2 Fi Image Force Applied Force Q2 Fi = − α Fa = β QE − γ π ε o R 2 E 2 16 π ε o R2 αQ Ed ≅ ≈ 1 V / µm β 16 π ε o R 2 Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  23. 23. Charge Patch Adhesion Model Q = σ At Fa Ac Ac Fad f = At 2 σ F ad = − A c − W A c 2 εo  σ W = −Qf   2ε +   o σ   Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  24. 24. Additives Control Adhesion Changing type of additive modifies adhesion Atomic Force Microscopy results Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  25. 25. Atomic Force Microscopy (AFM) Bring toner Push toner Retract toner until near surface against surface probe releases 200 µm 20 µm Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  26. 26. AFM Measure Single Particle Adhesion Laser Photodetector Particle Cantilever Piezoelectric: moves up and down Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  27. 27. Centrifuge Detachment Measure Many Particle Adhesion Putt, putt, putt,... Vroom, vroom,... Whoosh,... Observe Donor Plate after Each Spin H. Mizes, “Adhesion of Small Particle”, Electro. Soc. Amer. Univ. of Rochester, 6/23/95 Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  28. 28. Electric Field Detachment Measure Many Particle Adhesion transparent conductive electrodes Donor Receiver V E. Eklund, W. Wayman, L. Brillson, D. Hays, 1994 IS&T Proc., 10th Int. Cong. on Non-Impact Printing, 142-146 Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  29. 29. Electrical Field Detachment of Charged Toner Detachment Cell Adhesion of Triboelectrically Charged Toner 1 Transferred Fraction 0.8 0.6 0.4 0.2 0 0 2 4 6 8 10 12 14 16 18 Detachment Field (V/µm) µ Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  30. 30. Toner Transferred When FE > FAD FE - - Donor Surface - - FAD E. Eklund, W. Wayman, L. Brillson, D. Hays, 1994 IS&T Proc., 10th Int. Cong. on Non-Impact Printing, 142-146 Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  31. 31. Fluidized Bed Measure Powder Cohesion Stresses on the toner bed τ σ α α h σ ∆P Tension Compression σ = ρ (1−ε) gh cos α − ∆ P (1− Shear τ = ρ (1−ε) gh sin α (1− P.K. Watson, “Yield Locus of Cohesive Granular Materials”, Workshop on Dynamics of Granular Materials: Understanding & Control, Univ. of Chicago, 5/11/95 Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  32. 32. 70 Te nsi on 60 C ompression Less Additives τ , She ar Stre s s (N/m2 ) 50 More Additives 40 30 20 10 0 -30 -20 -10 0 10 20 30 40 50 60 70 σ , Compre s s ive Stre s s (N/m2 ) Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003
  33. 33. Q&A Fa-Gung Fan, Xerox Corporation MAE Dept., Clarkson University, 4/14/2003

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