Outline of the Lecture General Overview of Xerography Particle - - PowerPoint PPT Presentation

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Outline of the Lecture General Overview of Xerography Particle - - PowerPoint PPT Presentation

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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,

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MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

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

Particle Transport, Deposition, and Removal in Xerography

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

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

Modeling of Electrostatics in Subsystems (in MAE Seminar 4:00 (in MAE Seminar 4:00-

  • 5:00pm today)

5:00pm today)

  • Q&A

Q&A Acknowledgements:

  • S. Chang, C. Duke, D. Hays
  • N. Goodman, H. Mizes

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Xerographic Process

Charging Cleaning Exposure Paper Fusing Transfer Photoreceptor Substrate

S N S N SN SN

Development

4 5 6 2 1 3

  • C. Duke, J. Noolandi, T. Thieret, “The surface

science of xerography,” Surface Science, 500, p. 1005, (2002)

MAE Dept., Clarkson University, 4/14/2003 Fa-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

  • ffice, to production machines; black-and-white, hightlight color,

and full color.

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MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

DocuColor 40 Pro Color Office Multifunction Machine

40 prints/min, full-color

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

DocuTech 6180 Production Publisher

180 prints/min Black-and-White

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

DocuColor iGen3 Digital Production Color Press

100 prints/min, full-color

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

iGen3

Xerographic Unit Finisher/Binder

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MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

A semiconductor whose conductivity is a strong function of light exposure.

Exposure (ergs/cm2) Voltage on Surface (V) Electron/hole pairs

_ _ _ _ + + + + + + + _ _ _

+ _ + _

_ _ _ _ _ _ _ _ + + + + + + + + + + + + + + + + + + + _ _ _ _ _ _

+ _ + _ + _ + _

_ _ _ _ + + + + + + + _ _ _ _ _ _ _ _ + + + + + + +

  • 1000

5

  • Requirements

– Insulator in the dark. – Conductor when exposed to light – Builds up enough voltage. – Uniform properties

Photoreceptor

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Charging Subsystem

Electrons Positive Ions Electrons Positive Ions Free ions are attracted to wire; Free electrons are

  • repelled. Counter-charges

build up on grounded surfaces. Rapidly moving electrons and ions collide with air molecules, ionizing them and creating a corona. Electrons continue to follow Electric Field lines to Photoreceptor until uniform charge builds up HV Power Supply (-) HV Power Supply (-) HV Power Supply (-) HV Power Supply (-) HV Power Supply (-) HV Power Supply (-)

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Imaging/Exposure

Traditional Analog Copier Laser Printer

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Development

Charge particles triboelectrically Electric field moves particles from developer roll to photoreceptor

Apply E Field

Development roll Photoreceptor Photoreceptor Development roll Toner Photoreceptor Development Roll Mixing Charging Toner Photoreceptor Development Roll Mixing Charging

Triboelectrification of toner particles and carrier beads

E

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MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

5-10 microns 5-10 microns

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

Toner

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

q ≅ 2 x 104 e m ≅ 2 x 10-10 gm q/m ≅ 16 µC/gm

20 µm

Toned Carrier Bead

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Transfer

Apply E Field & Separate

Paper Photoreceptor Paper Photoreceptor Paper Photoreceptor Paper Photoreceptor

Electric field moves particles from photoreceptor to paper or transparency Detachment field must overcome toner adhesion to photoreceptor

Photoreceptor Paper

E

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

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 Heat Roll Paper Pressure Roll Heat Roll Paper

Elastomer Unfused toner Fused toner

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MAE Dept., Clarkson University, 4/14/2003 Fa-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, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Transport, Adhesion/Cohesion and Removal

  • f Fine Particles (Toner) in Xerography

paper Toner must transfer from roll to paper Toner must flow smoothly down dispenser Toner must develop

  • nto roll uniformly

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Toner Charge Measurements

Blowoff Tribo

Blow toner

from toned beads in cage

Measure

charge & mass difference

Calculate

average Q/M

10 20 30 40 50 1 2 3 4

Toner Concentration (%) Q/M (µC/gm) Air

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Toner Charge Measurements Charge Spectrograph

  • 0.5

0.5 1 1.5 5 10 15 20 25 30 35

Air Flow E Field Diameter (µm) q/D (fC/µm)

Inject toner Displacement

∝ q/D

Measure

position & size of particles

Lycopodium

50% 80% 90% 95% 99%

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MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Particle adhesion

depends on:

Size, shape, &

roughness

Materials Flow agents Charge Surface charge

distribution on particle

Toner Adhesion Forces

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

Fad Fa Detachment when Fa > Fad

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

σ π = Q R 4 2

R

F i Q

  • R

= − α πε 2 16 2

Fi

Fa QE

  • R E

= − β γ π ε 2 2

E E

Fa

Ed Q

  • R

≅ ≈ α β πε µ 16 2 1 V / m

Image Force Applied Force

Electrostatic Image Force Model

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Q At = σ f Ac At = Ac

Fa

Charge Patch Adhesion Model

c c

  • ad

A W A F − − = ε σ 2

2

Fad

⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + − = σ ε σ W Qf

  • 2

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Additives Control Adhesion Changing type of additive modifies adhesion Changing type of additive modifies adhesion

Atomic Force Microscopy results

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MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Atomic Force Microscopy (AFM)

Bring toner near surface Push toner against surface Retract toner until probe releases 200 µm 20 µm

MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Measure Single Particle Adhesion Laser Cantilever Photodetector Particle Piezoelectric: moves up and down

AFM

MAE Dept., Clarkson University, 4/14/2003 Fa-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, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Electric Field Detachment

V

Donor Receiver

V

transparent conductive electrodes 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

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MAE Dept., Clarkson University, 4/14/2003 Fa-Gung Fan, Xerox Corporation

Electrical Field Detachment of Charged Toner

Detachment Cell

0.2 0.4 0.6 0.8 1 2 4 6 8 10 12 14 16 18

Detachment Field (V/µm) Transferred Fraction

Adhesion of Triboelectrically Charged Toner

MAE Dept., Clarkson University, 4/14/2003 Fa-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, 4/14/2003 Fa-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 h α 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 h α 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, 4/14/2003 Fa-Gung Fan, Xerox Corporation

10 20 30 40 50 60 70 τ , Shear Stress (N/m2)

Tension Compression

  • 30
  • 20
  • 10

10 20 30 40 50 60 70 σ , Compressive Stress (N/m2)

Less Additives More Additives

10 20 30 40 50 60 70 τ , Shear Stress (N/m2)

Tension Compression

  • 30
  • 20
  • 10

10 20 30 40 50 60 70 σ , Compressive Stress (N/m2)

Less Additives More Additives