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