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MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
NSF CRCD Project LectureNovember 29, 2004
Fa-Gung FanWilson Center for Research & Technology
Xerox CorporationWebster, NY
http://chester.xerox.com/innovation/wcrt.html
Particle Transport, Deposition, and Removal in Xerography
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Outline of the Lecture
General Overview of Xerography
Transport, Adhesion/Cohesion and Removal of Fine Particles (Toner) in XerographyMeasuring Toner Charge --- Cage Blowoff, Charge SpectrographElectrostatic Adhesion, Detachment of Toner ParticlesMeasuring Toner Adhesion --- Atomic Force Microscopy (AFM), Centrifuge Detachment, Electric Field DetachmentMeasuring Cohesion --- Fluidized Bed
Modeling of Electrostatics in SubsystemsModeling of Electrostatics in Subsystems(in MAE Seminar 4:00(in MAE Seminar 4:00--5:00pm today)5:00pm today)
Q&AQ&A
Acknowledgements:S. Chang, C. Duke, D. HaysN. Goodman, H. Mizes
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Xerographic Process
Charging Cleaning
Exposure
Paper
Fusing
TransferPhotoreceptor
SubstrateS NS N
SN
SNN
Development
4
5
62
1
3C. Duke, J. Noolandi, T. Thieret, “The surface science of xerography,” Surface Science, 500, p. 1005, (2002)
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
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.
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
DocuColor 40 Pro Color Office Multifunction Machine
40 prints/min, full-color
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
DocuTech 6180 Production Publisher
180 prints/min Black-and-White
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
DocuColor iGen3 Digital Production Color Press
100 prints/min, full-color
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
iGen3Xerographic Unit
Finisher/Binder
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
A semiconductor whose conductivity is a strong function of light exposure.
Exposure (ergs/cm2)
Vol
tage
on
Surf
ace
(V)
Electron/hole pairs
_ _ _ _
+ + + + ++ +
_ _ _+_ +_
_ _ _ __ _ _ _
+ + + + ++ ++ + + + ++ + + + ++ +
_ _ __ _ _+_ +_ +_ +_
_ _ _ _
+ + ++ ++ +
_ _ _ __ _ _ _
+ + ++ ++ +
0
-1000
0 5
• Requirements– Insulator in the dark.– Conductor when exposed to light– Builds up enough voltage.– Uniform properties
Photoreceptor
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Charging Subsystem
ElectronsPositive IonsElectronsPositive Ions
Free ions are attractedto wire; Free electrons are repelled. Counter-charges build up on grounded surfaces.
Rapidly moving electronsand ions collide with airmolecules, ionizing them and creating a corona.
Electrons continue tofollow Electric Field linesto Photoreceptor until uniform charge builds up
HV PowerSupply (-)HV PowerSupply (-)
HV PowerSupply (-)HV PowerSupply (-)
HV PowerSupply (-)HV PowerSupply (-)
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Imaging/Exposure
Traditional Analog Copier Laser Printer
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Development
Charge particlestriboelectrically Electric field moves particles from developer roll to photoreceptor
Apply EField
Development roll
Photoreceptor Photoreceptor
Development roll
Toner
Phot
orec
epto
r DevelopmentRoll
MixingCharging
Toner
Phot
orec
epto
r DevelopmentRoll
MixingCharging
Triboelectrification of toner particles and carrier beads
E
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
5-10 microns5-10 microns
• Charging• Adhesion/cohesion• Powder flow• Rheology• Color - hue and density• Pigment dispersion
Toner
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
q ≅ 2 x 104 em ≅ 2 x 10-10 gm
q/m ≅ 16 µC/gm
20 µm
Toned Carrier Bead
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Transfer
Apply EField & Separate
Paper
Photoreceptor
Paper
Photoreceptor
Paper
Photoreceptor
Paper
Photoreceptor
Electric field moves particles from photoreceptor to paper or transparencyDetachment field must overcome toner adhesion to photoreceptor
Photoreceptor
Paper
E
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Fusing Subsystem
Permanently affix the image to the final substratepaper of various roughnesses and surface treatmenttransparency (plastic)
Apply heat and/or pressure
Hot Roll Fuser: Pressure Roll
Heat Roll
Paper
Pressure Roll
Heat Roll
Paper
Elastomer
Unfused toner Fused toner
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
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
Residual toner
Charge
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Transport, Adhesion/Cohesion and Removal of Fine Particles (Toner) in Xerography
paper
Toner must transfer fromroll to paper
Toner must flow smoothlydown dispenser
Toner must developonto roll uniformly
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Toner Charge Measurements
Blowoff Tribo
Blow toner from toned beads in cageMeasure charge & mass differenceCalculate average Q/M
0
10
20
30
40
50
0 1 2 3 4Toner Concentration (%)
Q/M
(µC
/gm
)
Air
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Toner Charge Measurements
Charge Spectrograph
-0.5
0
0.5
1
1.5
0 5 10 15 20 25 30 35
Air Flow
E Field
Diameter (µm)
q/D
(fC
/µm
)
Inject tonerDisplacement ∝ q/D Measure position & size of particles
Lycopodium50%80%
90%95%
99%
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Particle adhesion depends on:
Size, shape, & roughnessMaterialsFlow agentsChargeSurface charge distribution on particle
Toner Adhesion Forces
++++
++++ +
+++++
+
++++
++++ +
+++++
+
++++
++++ +
+++++
+
Fad
Fa
Detachment when Fa > Fad
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
σπ
=QR4 2R
FiQ
oR= − α
πε
2
16 2
Fi
Fa QE oR E= −β γ π ε 2 2
EEFa
EdQ
o R≅ ≈
α
β π εµ
16 2 1 V / m
Image Force Applied Force
Electrostatic Image Force Model
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Q At= σ
f AcAt
=AcFa
Charge Patch Adhesion Model
cco
ad AWAF −−=ε
σ2
2
Fad
+−=
σεσ WQfo2
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Additives Control Adhesion
Changing type of additive modifies adhesionChanging type of additive modifies adhesionAtomic Force Microscopy results
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Atomic Force Microscopy (AFM)
Bring toner near surface
Push toner against surface
Retract toner until probe releases
200 µm20 µm
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Measure Single Particle Adhesion
Laser
Cantilever
Photodetector
Particle
Piezoelectric:moves upand down
AFM
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
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
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Electric Field Detachment
VVDonor ReceiverV
transparent conductiveelectrodes
Measure Many Particle Adhesion
E. Eklund, W. Wayman, L. Brillson, D. Hays, 1994 IS&T Proc., 10th Int. Cong. on Non-Impact Printing, 142-146
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Electrical Field Detachment of Charged Toner
Detachment Cell
0
0.2
0.4
0.6
0.8
1
0 2 4 6 8 10 12 14 16 18
Detachment Field (V/µm)
Tran
sfer
red
Frac
tion
Adhesion of Triboelectrically Charged Toner
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
-
-
--
FE
FAD
Toner Transferred When FE > FAD
Donor Surface-
-
--
FE
FAD
Toner Transferred When FE > FAD
Donor Surface
E. Eklund, W. Wayman, L. Brillson, D. Hays, 1994 IS&T Proc., 10th Int. Cong. on Non-Impact Printing, 142-146
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Fluidized Bed
Measure Powder Cohesion
P.K. Watson, “Yield Locus of Cohesive Granular Materials”, Workshop on Dynamics of Granular Materials: Understanding & Control, Univ. of Chicago, 5/11/95
α
∆ P
hα
τ σ
σ
Stresses on the toner bed
σ = ρ (1−ε) gh cos α − ∆ P
τ = ρ (1−ε) gh sin α
Tension \ Compression
Shear
α
∆ P
hα
τ σ
σ
Stresses on the toner bed
σ = ρ (1−ε) gh cos α − ∆ P
τ = ρ (1−ε) gh sin α
Tension \ Compression
Shear
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
0
10
20
30
40
50
60
70
τ ,Sh
ear
S tre
ss(N
/m2 )
Tension
Compression
-30 -20 -10 0 10 20 30 40 50 60 70
σ , Compre ss ive Stress (N/m2)
Less Additives
More Additives
0
10
20
30
40
50
60
70
τ ,Sh
ear
S tre
ss(N
/m2 )
Tension
Compression
-30 -20 -10 0 10 20 30 40 50 60 70
σ , Compre ss ive Stress (N/m2)
Less Additives
More Additives
MAE Dept., Clarkson University, 4/14/2003Fa-Gung Fan, Xerox Corporation
Q&AQ&A
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