particle transport, deposition, and removal in xerography · 2016. 11. 29. · Ñgeneral overview...

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


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


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)


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.


DocuColor 40 Pro Color Office Multifunction Machine



DocuTech 6180 Production Publisher

180 prints/min Black-and-White


DocuColor iGen3 Digital Production Color Press



iGen3Xerographic Unit

Finisher/Binder


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


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 (-)




Imaging/Exposure

Traditional Analog Copier Laser Printer


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


5-10 microns5-10 microns

• Charging• Adhesion/cohesion• Powder flow• Rheology• Color - hue and density• Pigment dispersion

Toner


q ≅ 2 x 104 em ≅ 2 x 10-10 gm

q/m ≅ 16 µC/gm

20 µm

Toned Carrier Bead


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


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


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


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


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


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%


Particle adhesion depends on:

Size, shape, & roughnessMaterialsFlow agentsChargeSurface charge distribution on particle

Toner Adhesion Forces

++++

++++ +

+++++

+

++++

++++ +

+++++

+

++++

++++ +

+++++

+

Fad

Fa

Detachment when Fa > Fad


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


Q At= σ

f AcAt

=AcFa

Charge Patch Adhesion Model

cco

ad AWAF −−=ε

σ2

2

Fad

+−=

σεσ WQfo2


Additives Control Adhesion

Changing type of additive modifies adhesionChanging type of additive modifies adhesionAtomic Force Microscopy results


Atomic Force Microscopy (AFM)

Bring toner near surface

Push toner against surface

Retract toner until probe releases

200 µm20 µm


Measure Single Particle Adhesion

Laser

Cantilever

Photodetector

Particle

Piezoelectric:moves upand down

AFM


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


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


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


-

-

--

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


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


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


Q&AQ&A

particle transport, deposition, and removal in xerography · 2016. 11. 29. · Ñgeneral overview...

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