1 On Counter-Charges in Development Rollers for Electrophotography Inan Chen and Ming-Kai Tse Quality Engineering Associates (QEA), Inc. Burlington, MA, USA www.qea.com NIP22 NIP-22 Denver, September. 2006
Mar 26, 2015
1
On Counter-Charges in
Development Rollers for
Electrophotography
Inan Chen and Ming-Kai Tse
Quality Engineering Associates (QEA), Inc.
Burlington, MA, USA
www.qea.com
NIP22NIP-22 Denver, September. 2006
2
Counter-Charges in Development Rollersfor Electrophotography
Latent images developed by moving Charged Toners
- Extensively studied.
Counter-charges : Little attention
- Reside in carrier beads (2-component development),
or development rollers (Single-Component Dev.)
Objectives:
• Quantitative analyses of roles of counter-charges
in Toner-charging and Toner-deposition in SCD
• Requirements for ideal roller coating materials,
and characterization method for SCD rollers
NIP22
3
Single-Component Development (SCD)
2. Toner Charging at
Metering Blade (MB):
Charges supplied to toner,
Counter-charges to Roll coating
3. Toner deposition:
Charged toners move to PR,
Counter charges impede toner motion,
must be removed (neutralized)
to improve deposition efficiency
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1. Development Rolls:
Conductive elastomer core
Semi-insulator Coating
MB
Dev.Roll
PR
VB
VB
4
Single-component Development
Induction at charging, and
Neutralization at deposition of Counter Charges
Charge injection and transport
in Semi-insulator Coating layer
Charge-Transport Model
Non-Ohmic nature
Applied and reported :
Roller charging of PR (NIP21)
Electrostatic toner transfer (NIP16, 20, ICIS’06)
Liquid development (J. App. Phy. 80, 6796)
Counter-charges in SCD (This talk)
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MB
Dev.Roll
PR
VB
VB
MB
Dev.Roll
PR
VBVB
VB
5
Charge Transport Model
Semi-insulators characterized by 3 parameters
1. Densities of mobile charges, qp(y, t), qn(y, t),
Initial (intrinsic) value: qi = qp(y, 0) = –qn(y, 0)
2. Charge mobility: (E) - field dependent
3. Charge injection strength s
Injection currents from boundary at y
Ji = sE(y), E(y) = field at y ( = 0 or L)
Continuity eq. q(y, t)/t = – (qE)/y
Poisson’s eq. E(y, t)/y = (qp + qn)/
Results for SCD charging and deposition
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+ + + + + +sp, sn
– – – – – –
y
L
0
6
Bias voltage VB
Toner charge density:
QT(t) = [VB – QR(t)DR – UR(t)]/(DT/2 + DR) (D = L/ = 1/C)
• QR(t) = Interface charge density
• UR(t) = 0LR dy0
y’(qP + qN)dy’/R
• Transport equations, calculate QR(t), UR(t) QT(t)
NIP22 Toner Charging in SCD (1)
Toner Coating
Thickness: LT LR
Permittivity: T R
} Counter-charges
–VB
Metering Blade
– – Toner – – QT
Roll-Coating
QR + + + + + + + +
yR
yT
0
0
LR
s
7
Toner Charging in SCD (2)
Growth of toner charge QT(t)
with time
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Dependence on Injection Strength s very significant at t 100to
High speed printing -- short charging time: high s important
0
1
2
3
4
5
1 10 100 1000Time
-To
ner
Ch
arg
e D
ensi
ty
Vb = 0.2qi = 0.1up= un= 1 Lr = 1Lt = 0.3 r = 1 t = 1
SCDC060107/1
s = 1
0.3
0.1 0.03
0.01
Units: to = LR
2/oVB 10 msec so = oqo = o/to 3x10–11 S/cm qo= oVB/LR
2 3x10–6 C/cm3
–VB
Metering Blade
– – Toner – – QT
Roll-Coating
QR + + + + + + + +
yR
yT
0
0
LR
s
–VB
Metering Blade
– – Toner – – QT
Roll-Coating
QR + + + + + + + +
yR
yT
0
0
LR
s
8
Toner Charging in SCD (3)
Dependence on mobility p, n
in RC
For QT< 0
• Smaller pos mobility p
has significant effect (A, B, C)
• Insensitive to neg n (A, D)
• Build-up of counter-charge
mostly from injection of
pos charge from VB,
not from depletion of
neg charge in coating layer
Units
Mobility: o 10–5 cm2/ Vs
Time: to = LR2/oVB 10–2 sec
Chg density: qo= oVB/LR2
3x10–6 C/cm3
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0
1
2
3
4
5
1 10 100 1000Time
-To
ner
Ch
arg
e D
ensi
ty
Vb = 0.2qi = 0.1s = 0.1
SCDC060107/1
A
B
D
C
up un A: 1.0 1.0B: 0.1 1.0C: 0.01 1.0D: 1.0 0.0 –VB
Metering Blade
– – Toner – – QT
Roll-Coating
QR + + + + + + + +
yR
yT
0
0
LR
s
–VB
Metering Blade
– – Toner – – QT
Roll-Coating
QR + + + + + + + +
yR
yT
0
0
LR
s
9
Toner Deposition in SCD (1)
Fields and Voltages in layers
• Photoreceptor: EP, VP
• Toner-layer: ET(y), VT
• Roller coating: ER(y), VR
Bias voltage: -VB = VP + VT + VR
Gauss’ theorem relates charges QP, QR, QT to E’s
Field in toner layer:
ET(y, t) = ET0 + (QT/)(y/LT(detail in Proc.
paper)
= func.[VB, QP, QT, QR(t), UR(t), L’s, ’s]
Injection & transport of Counter-charges in RC
contribute to QR(t), UR(t)
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–LPPR
Roll Coating (RC)
–VB
– – Toner – –
QP
LT
0
y
+ + + + QR
–LPPR
Roll Coating (RC)
–VB
– – Toner – –
QP
LT
0
y
+ + + + QR
QT
10
Toner Deposition in SCD (2)
Negative toner deposition: ET(y, t) > 0
Demarcation line at y = YD
ET > 0 for y < YD
ET < 0 for y > YD
ET(YD) = ET0 + (QT/T)(YD/LT) = 0
Deposition efficiency:
YD/LT = – TET0/QT
= func.[VB, QP, QT, QR(t), UR(t), L’s, ’s] (in proc. paper)
QR(t), UR(t) from Transport Eqs.
Time evolution of Deposition efficiency YD/LT
–LP
PR
Roll Coating (RC)
–VB
– – Toner – QT QP
LT
0
y
+ + + +QR
YD
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11
Toner Deposition in SCD (3)
Deposition efficiency YD/LT vs. time
Dependence on strength s
of injection into RC from VB
Significant effects
due to small s,
in time 10 < t <100
Time unit:
to = LR2/oVB 10 msec
0.5
0.6
0.7
0.8
0.9
1.0
0.1 1 10 100 1000Time
Yd
/Lt
Vd =1qt = 5qi = 0.1Lt =0.2up=un=1
0.01
SCD060227/1
s = 1
0.3
0.1
0.03
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–LPPR
Roll Coating (RC)
–VB
– – Toner – QT
QP
LT
0
y
+ + + + QR
YD
–LPPR
Roll Coating (RC)
–VB
– – Toner – QT
QP
LT
0
y
+ + + + QR
YD
12
0.5
0.6
0.7
0.8
0.9
1.0
0.1 1 10 100 1000Time
Yd
/Lt
Vd =1qt = -5qi = 0.1s = 0.1Lt =0.2
up un A: 1 1B: 1 0.1 C: 1 0.01D: 0 1
A
B
C
D
SCD060227/2
Toner Deposition in SCD (4)
Charge mobility (P, N) dependence of YD/LT (QT< 0)
Neg. n reduced (A B C)
Significant decrease Pos. p reduced (A D)
No effects Neutralize Counter-charge
requires negative charge
injection and transport
opposite to polarity
required at chargingFor efficient charging & deposition, it requires
good injection (s) and transport () for bothpos and neg charges in SCD roller-coating
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13
Summary and Conclusions (1)
In SCD, Counter Charges in semi-insulator coating
Induced at toner Charging, and
Neutralized at toner Deposition steps Analyses: Charge-Transport model Good bi-polar charge injection and transport
e.g., for negative toners,
Pos. charge inject. & transport for Charging
Neg. charge inject. & transport for Deposition
Process time > 100 to (to = LR2/VB)
High speed printing requires high mobility (+ and –) Dev. Roller performance can’t be evaluated properly
with closed-circuit resistance measurements
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14
Summary and Conclusions (2)
Alternative evaluation method:
Electrostatic Charge Decay (ECD) technique
(NIP-11, 15, 16, 17; ICIS’02; JHC-00, 02, 05)
Open-circuit voltage decay
- simulating actual process in Electrophotography
Field applied by Corona charging
- Scan and map large area,
efficient, non-destructive
Applied to transfer belts, paper,
charge rolls, dev- rolls, PR
Consistently predict device performance
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Voltageprobe
-------
Corona
sample
15
ECD Data for Intermediate Transfer Belt
© 2005 Quality Engineering Associates (QEA), Inc. All Rights Reserved
(a) Voltage
0
100
200
300
0 50 100 150 200 250
Position (mm)
Vo
ltag
e (V
)Voltage *
Rolls and Belts Testing Fixture
Exhibit Booth #210
NIP22
16
Thank you for your attention
Please visit
Exhibition Booth #210
Inan Chen and Ming-Kai Tse
Quality Engineering Associates (QEA), Inc.
Burlington, MA, USA
www.qea.com
NIP22
NIP-22 Denver, September. 2006