Xerography/Electrophotography:
         The Technology of Photocopiers
               and Laser Printers
                 ...
Outline of the Talk

           Part I. General Overview of Xerography
              Xerographic Process
              Bri...
Part I.
            General Overview of Xerography




Fa-Gung Fan, Xerox Corporation   MAE Dept. Seminar, Clarkson Univer...
Xerographic Process
                                                                                      5
              ...
Xerox Phaser 7700 Color Desktop Laser
          Printer
               22 prints/min, full-color




            Xerograph...
DocuColor 40 Pro Color Office
           Multifunction Machine
    40 prints/min, full-color




Fa-Gung Fan, Xerox Corpor...
DocuTech 6180 Production Publisher

       180 prints/min
       Black-and-White




Fa-Gung Fan, Xerox Corporation       ...
DocuColor iGen3 Digital Production Color
          Press
            100 prints/min, full-color




Fa-Gung Fan, Xerox Cor...
iGen3
                                 Xerographic Unit



                                                    Finisher/Bi...
Photoreceptor
               A semiconductor whose
               conductivity is a strong                                ...
Charging Subsystem



                        HV Power                   HV Power                                   HV Pow...
Imaging/Exposure




           Traditional Analog Copier   Laser Printer

Fa-Gung Fan, Xerox Corporation         MAE Dept...
Development

                                                    Photoreceptor                       Photoreceptor
       ...
Toner

                • Charging
                • Adhesion/cohesion
                • Powder flow
                • Rheo...
Toned Carrier Bead


            q ≅ 2 x 104 e
            m ≅ 2 x 10-10 gm

            q/m ≅ 16 µC/gm




              ...
Transfer


                                       Paper

                                                                 ...
Fusing Subsystem


           Permanently affix the image to the final substrate
                 paper of various roughne...
Cleaning and Erase

          Removes unwanted residual toner and charge
          from photoreceptor before next imaging ...
Particle Transport, Deposition and
          Removal in Xerography

                                       Toner must flow...
Toner Adhesion Forces

                                   Fa         Particle adhesion
                                   ...
Electrostatic Image Force Model
                                                                Q
                        ...
Charge Patch Adhesion Model
                                                             Q = σ At
                        ...
Electric Field Detachment of Fine Particles

                                    Measure Many Particle Adhesion



       ...
Toner Transferred
          When FE > FAD
                                     FE



                                 -
  ...
Adhesion Control Additives

         Changing type of additive modifies adhesion
                                 Atomic F...
Part II.
                      Modeling of Electrostatics




Fa-Gung Fan, Xerox Corporation            MAE Dept. Seminar,...
Xerographic Machine Using Drum
           Photoreceptor and Biased Rolls

                                             Bia...
Biased Charging/Transfer Rolls
           (BCR/BTR)

            pre-nip              nip        post-nip            Appli...
Basic Equations

                                           2    ρ
 Electrical Potential                    ∇ φ =−        ...
KEY Requirements for the Integrated
          Model:
          1. Allows Implementation volume and surface
            cha...
Flowchart of the Integrated Model
                          Start


                        Input/Pre
                    ...
Modeling of Biased Charging Roll (BCR) &
          Comparison with Field Probe Measurement
C. DiRubio, G. Fletcher, “Field...
σ probe
      Eair    =                   (6)
                  ε0                                      30

              ...
The computational mesh used. (yellow mesh --- elastomer; white mesh --- air gap;
          blue mesh --- insulator on the ...
Potential map for T=32. The color scale is from 0V (dark blue) to 400V (red).


Fa-Gung Fan, Xerox Corporation            ...
Potential map for T=1. The color scale in this figure is from 0V (dark blue) to
             697V (red).

Fa-Gung Fan, Xer...
Nip


         The blow-up of the nip region shown in previous slide. The contours represent equal
         electrical pot...
Potential map for T=0.13. The color scale in this figure is from 0V (dark blue) to
             822V (red).

Fa-Gung Fan, ...
Pre-Nip        Nip            Post-Nip




         The model predictions of field profile for various values of T as eval...
30

                                                                                               Τ=32
                  ...
Transfer Subsystem Using A Biased
            Transfer Roll


                                                         Pho...
Air Breakdown & Paschen Curve


                                     50
                                     45
          ...
The region that is included in the model and the computational mesh used. (yellow
      mesh --- BTR elastomer; magenta me...
The steady-state potential map of the modeled domain. The contours displayed in this
      figure are the equi-potential c...
Post-Nip        Nip        Pre-Nip




                    Field profile in the ITB-PR air gap. The Paschen breakdown limi...
Post-Nip       Nip       Pre-Nip




                                 The field profile in the BTR-ITB air gap.

Fa-Gung F...
Nip




         The variations of charge densities on different surfaces. The relevant surfaces shown
         here are t...
Transfer Subsystem I-V Curves
                                                                          increase in
      ...
Transfer Subsystem I-V Curves




                                 I-V curves for four different field-dependent BTR
     ...
Summary:

               We discussed:

           Part I. General Overview of Xerography
                Xerographic Proc...
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Xerography/Electrophotography: The Technology of Photocopiers and Laser Printers

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Xerography/Electrophotography: The Technology of Photocopiers and Laser Printers

  1. 1. Xerography/Electrophotography: The Technology of Photocopiers and Laser Printers MAE Seminar April 14, 2003 Fa-Gung Fan Wilson Center for Research & Technology Xerox Corporation Webster, NY Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  2. 2. Outline of the Talk Part I. General Overview of Xerography Xerographic Process Brief Description of Subsystems Transport, Deposition and Removal of Fine Particles (Toner) in Xerography Part II. Modeling of Electrostatics Charging & Transfer Subsystems Using Biased Rolls Modeling the Electrostatics of a Biased Rolls Modeling a Transfer Subsystem Using A Biased Transfer Roll Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  3. 3. Part I. General Overview of Xerography Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  4. 4. 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. Seminar, Clarkson University, 4/14/2003
  5. 5. 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. Seminar, Clarkson University, 4/14/2003
  6. 6. DocuColor 40 Pro Color Office Multifunction Machine 40 prints/min, full-color Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  7. 7. DocuTech 6180 Production Publisher 180 prints/min Black-and-White Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  8. 8. DocuColor iGen3 Digital Production Color Press 100 prints/min, full-color Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  9. 9. iGen3 Xerographic Unit Finisher/Binder Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  10. 10. 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. Seminar, Clarkson University, 4/14/2003
  11. 11. 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. Seminar, Clarkson University, 4/14/2003
  12. 12. Imaging/Exposure Traditional Analog Copier Laser Printer Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  13. 13. 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. Seminar, Clarkson University, 4/14/2003
  14. 14. Toner • Charging • Adhesion/cohesion • Powder flow • Rheology 5-10 microns • Color - hue and density • Pigment dispersion Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  15. 15. 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. Seminar, Clarkson University, 4/14/2003
  16. 16. 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. Seminar, Clarkson University, 4/14/2003
  17. 17. 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. Seminar, Clarkson University, 4/14/2003
  18. 18. 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. Seminar, Clarkson University, 4/14/2003
  19. 19. Particle Transport, Deposition and Removal 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. Seminar, Clarkson University, 4/14/2003
  20. 20. 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. Seminar, Clarkson University, 4/14/2003
  21. 21. 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. Seminar, Clarkson University, 4/14/2003
  22. 22. 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. Seminar, Clarkson University, 4/14/2003
  23. 23. Electric Field Detachment of Fine Particles 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. Seminar, Clarkson University, 4/14/2003
  24. 24. 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. Seminar, Clarkson University, 4/14/2003
  25. 25. Adhesion Control Additives Changing type of additive modifies adhesion Atomic Force Microscopy results Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  26. 26. Part II. Modeling of Electrostatics Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  27. 27. Xerographic Machine Using Drum Photoreceptor and Biased Rolls Biased Charging Roll 1 6 1) Charge 2) Expose 2 3) Develop 3 4) Transfer 5 5) Clean 6) Erase 4 Paper or Intermediate Belt Biased Transfer Roll J. Swift and S. Badesha, Surface Science, 500, p.1024, (2002) Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  28. 28. Biased Charging/Transfer Rolls (BCR/BTR) pre-nip nip post-nip Applications of Biased Rolls: VA Charging Transfer Roller Drum Shaft Insulator Elastomer Ground plane Field probe C. DiRubio, G. Fletcher, Proceedings of IS&T NIP 12: International Conference on Digital Printing Technologies, p.334, 1996. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  29. 29. Basic Equations 2 ρ Electrical Potential ∇ φ =− (1) ε Interface Condition  ∂φ   ∂φ  σ − k  = − k  + (2)  ∂n matl 2  ∂n  matl1 ε 0 Electric Conduction j = γ (| E |) E where E = −∇φ (3) Conservation of ∂σ ∂σ ∂ 2φ +v = γ s 2 + j matl1 ⋅ n − j matl 2 ⋅ n (4) Surface Charge ∂t ∂s ∂s Ref. P. Ramesh, private communication Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  30. 30. KEY Requirements for the Integrated Model: 1. Allows Implementation volume and surface charge density 2. Solves Poisson equation for composite domain, and obtain electric field 3. Calculates current density 4. Solves surface charge transport 5. Handles air breakdown In our integrated model, 1 and 2 are done in ABAQUS/Standard (version 5.7), and 3 to 5 are implemented as an in-house C program. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  31. 31. Flowchart of the Integrated Model Start Input/Pre child process ABAQUS check to see if ABAQUS job is completed UNIX fork() parent process UNIX shell script Check if air breakdown occurs Handling air breakdown σ brk = ε 0 (Eairgap − EPaschen ) (5) Update & solve surface charge Y t < tmax N Stop/Post Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  32. 32. Modeling of Biased Charging Roll (BCR) & Comparison with Field Probe Measurement C. DiRubio, G. Fletcher, “Field profile Parameters used in the field probe measurements in biased charging experiment: systems,” Proceedings of Image Science &Technology NIP 12, p.334, Elastomer: 1996 outer diameter = 37.83 mm inner diameter = 25.24 mm pre-nip nip post-nip dielectric constant = 4.4 resistivity = 5.0E+9 ohm-cm VA Insulator (kapton tape): thickness = 33 microns dielectric constant = 2.7 Roller Drum Field Probe (magnet wire): Shaft Insulator diameter = 1.72 mm Elastomer Ground plane Field probe Nip Width (contact) = 2.7 mm Schematic of the nip region of the experimental Charge Relaxation Time = 0.22 sec apparatus. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  33. 33. σ probe Eair = (6) ε0 30 Τ=32 25 Τ=1 where σ probe = Q / Aprobe 20 Eair (V/µ m) 15 Τ=0.35 dwell time based on effective nip width 10 T= Τ=0.13 charge relaxation time 5 0 T roll surface -3 -2 -1 0 x (mm) 1 2 3 speed, v (mm/sec) 32 0.656 The field profiles for different values of T. 1 23.65 (DiRubio and Fletcher) 0.35 65.8 0.13 251.6 (data from C. DiRubio) Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  34. 34. The computational mesh used. (yellow mesh --- elastomer; white mesh --- air gap; blue mesh --- insulator on the drum). Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  35. 35. Potential map for T=32. The color scale is from 0V (dark blue) to 400V (red). Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  36. 36. Potential map for T=1. The color scale in this figure is from 0V (dark blue) to 697V (red). Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  37. 37. Nip The blow-up of the nip region shown in previous slide. The contours represent equal electrical potentials (for T=1). The field lines are orthogonal to these equi-potential lines. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  38. 38. Potential map for T=0.13. The color scale in this figure is from 0V (dark blue) to 822V (red). Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  39. 39. Pre-Nip Nip Post-Nip The model predictions of field profile for various values of T as evaluated from Eq.(6). Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  40. 40. 30 Τ=32 25 Τ=1 20 Eair (V/µ m) 15 Τ=0.35 10 Τ=0.13 5 0 -3 -2 -1 0 1 2 3 x (mm) The field profiles for different values of T as measured with 1.72mm probe. The field profiles seen by a 1.72mm probe as (DiRubio and Fletcher) predicted by the model. (The high-resolution field profiles from the model were first averaged with a circular area of 1.72mm diameter, and then shifted so that the position of the peak field for each curve is at x=0.) The profiles on this figure should be compared with the measured ones (at the right). Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  41. 41. Transfer Subsystem Using A Biased Transfer Roll Photoreceptor (PR) Photoreceptor: ITB: BTR Elastomer: Nip Post-Nip Pre-Nip Intermediate Transfer Belt (ITB) v = Belt speed Bias Transfer Roll (BTR) Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  42. 42. Air Breakdown & Paschen Curve 50 45 Paschen Curve 40 Eair (V= -200) 35 Eair (V= -400) Eair (V/µ m) 30 Eair (V= -600) Eair (V= -800) 25 20 15 10 5 0 0 50 100 150 200 dair (µm) µ Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  43. 43. The region that is included in the model and the computational mesh used. (yellow mesh --- BTR elastomer; magenta mesh --- ITB; cyan mesh --- PR material coated on the drum; white mesh --- air gap) Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  44. 44. The steady-state potential map of the modeled domain. The contours displayed in this figure are the equi-potential contours. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  45. 45. Post-Nip Nip Pre-Nip Field profile in the ITB-PR air gap. The Paschen breakdown limit for the air gap is also plotted. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  46. 46. Post-Nip Nip Pre-Nip The field profile in the BTR-ITB air gap. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  47. 47. Nip The variations of charge densities on different surfaces. The relevant surfaces shown here are the photoreceptor surface, the upper surface of ITB, the lower surface of ITB, and the BTR surface. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  48. 48. Transfer Subsystem I-V Curves increase in resistivity I-V curves for different values of BTR resistivities. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  49. 49. Transfer Subsystem I-V Curves I-V curves for four different field-dependent BTR resistivities. Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003
  50. 50. Summary: We discussed: Part I. General Overview of Xerography Xerographic Process Brief Description of Subsystems Transport, Deposition and Removal of Fine Particles (Toner) in Xerography Part II. Modeling of Electrostatics Charging & Transfer Subsystems Using Biased Rolls Modeling the Electrostatics of Biased Rolls Modeling a Transfer Subsystem Using A Biased Transfer Roll Fa-Gung Fan, Xerox Corporation MAE Dept. Seminar, Clarkson University, 4/14/2003

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