Emission of a Macroscopic Plasma Display Panel Cell (Xe-Ne Mixtures), and

Role of Photoemission

R. Ganter, J. Ouyang, Th. Callegari, Ph. Guillot, J. Galy, and J.P. Boeuf

Centre de Physique des Plasmas et Applications de Toulouse, CNRS

Université P. Sabatier, 118 Route de Narbonne, 31062 Toulouse France

http://cpat.ups-tlse.fr

Address electrode

ViewerDielectric layers

MgOVisible

Discharge

LuminophoresU.V.Glass

Dalle de verre

Gas

Electrode XElectrode Y

BarrierZOOM

Visible

Glass

XY

Adress el.

One pixel of the Plasma display panel has three subpixels: Red, Green and Blue (R.G.B).Each subpixel include an address electrode on one substrate and two sustain electrodes on an opposed substrate.Electrodes are covered by dielectric layers (pulsed discharge).The purpose of the discharge (Xe-Ne) is to produce U.V. photons which will be convert into visible light by the phosphors (R,G,B).

One pixel of the Plasma display panel has three subpixels: Red, Green and Blue (R.G.B).Each subpixel include an address electrode on one substrate and two sustain electrodes on an opposed substrate.Electrodes are covered by dielectric layers (pulsed discharge).The purpose of the discharge (Xe-Ne) is to produce U.V. photons which will be convert into visible light by the phosphors (R,G,B).

Ne-Xe(2-10%), Gap 100µm, 300-500torr, 200V AC, 100kHz

Principle of plasma display panel

X

Y

X

Y

Addresspulse

Addresselectrode

1. A voltage pulse is applied to the address electrode which creates a discharge between a sustain electrode (X or Y) and the address electrode.

2. This first address discharge induce a wall voltage at the coplanar sustain electrode. 3. The sustain signal (square wave voltage) applied to both coplanar electrodes (X, Y) creates a « ping

pong » action of the wall charge states.

1. A voltage pulse is applied to the address electrode which creates a discharge between a sustain electrode (X or Y) and the address electrode.

2. This first address discharge induce a wall voltage at the coplanar sustain electrode. 3. The sustain signal (square wave voltage) applied to both coplanar electrodes (X, Y) creates a « ping

pong » action of the wall charge states.

AddressDischarge

SustainDischarge

Adress and sustain discharge in a cell

Stainless steel

chamber

20 c

m

12 c

m

20 c

m

ICCD quartzviewport

20 c

m

Stainless steel

chamber

20 c

m

12 c

m

Ne-XeNe-Xe

20 c

melectrodes

quartzviewport

ICCD

22 cm

quartzviewport

Discharge gap

Glass + MgO

20 c

m

MgF2 window

Macro-cell and UV source

Xe-Ne mixturesP~5.6torr

Xe-Ne mixturesP~5.6torr

Use of scaling laws: dimensions x 62.5, pressure /62.5 with respect to real PDP cell

2cm

ICCD on the side view

Front viewport

Side view front view

Side viewport

CCD : >25ns gated, integrated on ~3000 period of the sustain voltage of the cell

Conditions in Macrocell: Ne-Xe:10%, 5.6torr , dielectric barrier of 1mm, =4

covered with 500 nm of MgO

Conditions in Macrocell: Ne-Xe:10%, 5.6torr , dielectric barrier of 1mm, =4

covered with 500 nm of MgO

CCD Imaging of the Macro-Cell discharge

With a CCD camera we made movies of the discharge in the gas gap (side view) and also trough transparent electrodes (front view).

1 cm

1 mm

9 cm

2 cm

SustainElectrodes

Ceramic

Glass

0.5

cm

Macrocell(microcell)

AddressElectrodes

Front view

Side view

Spatio-temporal evolution of a discharge through a filter : 815-825nm (Xenon emission)

Ne-Xe:10%, 5.6torr, coplanar gap 0.5cm, 190V, 100Hz, CCD: 200ns gated on 3000 cycles

Spatio-temporal evolution of a discharge through a filter : 635-645nm (Neon emission)

Front view

Side view

Ne-Xe:10%, 5.6torr, coplanar gap 0.5cm, 190V, 100Hz, CCD: 200ns gated on 3000 cycles

Time evolution of discharge emission along an axis

Xe Emission

815-825 nm

Xe Emission

815-825 nmNe Emission

635-645 nm

Ne Emission

635-645 nm

Ne-Xe:10%, 5.6torr, 0.5cm coplanar gap, 190V, 100Hz, CCD: 200ns gated on 3000 cycles

Anode striations

There are no emission of neon above the anode, the anode field is more efficient for xenon excitation!

12km/s

Photoemission and scaling laws

Discharge of plasma display panel cell and macrocell discharge are similar (same dimension multiplied by pressure)!

However, there are processes which do not follow the scaling law, for example the photoémission by resonant photons at 147nm from xenon on the cathode surface:

Apparent lifetime of resonant photons (Holstein’s theory): app. proportional to d1/2 (d dimension of the cell)

Time for ions to reach the cathode:

ions proportional to d (for similar discharges)(vions= p.d / p.t)

Apparent lifetime of resonant photons (Holstein’s theory): app. proportional to d1/2 (d dimension of the cell)

Time for ions to reach the cathode:

ions proportional to d (for similar discharges)(vions= p.d / p.t)

In microcell: 147nm~330ns and current rise time ~ 50nsIn macrocell: 147nm~2.6µs and current rise time ~ 3µs

(scaling factor 62.5)Photoemission is less probable in real plasma display panel cell!

Comparisons with models: current

-1 0 1 2 30

1

2

3

4

5

Cur

rent

(m

A)

Time (s)

MacrocellMacrocell

2D Model with photoemission2D Model with photoemission

2D Model without photoemission

2D Model without photoemission

Displacement current peak:

tEj cathode

D .0 tEj cathode

D .0

Ne-Xe:10%, 5.6torr, 0.5cm coplanar gap, 240V, 100Hz

Apparition of a displacement current peak in the macrocell, because plasma expansion is very fast with photoemission!

Charge current peak

anod

eca

thod

e

0.5 128.04.02.01.0

1.9 s 2.1 s 2.3 s 2.7 s

anod

eca

thod

e

823 nm828 nm

640 nm

anod

eca

thod

e

0.5 128.04.02.01.00.5 128.04.02.01.0

1.9 s 2.1 s 2.3 s 2.7 s1.9 s 2.1 s 2.3 s 2.7 s

anod

eca

thod

ean

ode

cath

ode

823 nm828 nm

640 nm

1 . 2 s 2 . 7 s 4 . 2 s 7 . 7 s

0 . 3 1 . 0 3 . 0 1 0 .0 . 1

anod

eca

thod

e

N e

anod

eca

thod

e

X e

1 . 2 s 2 . 7 s 4 . 2 s 7 . 7 s

0 . 3 1 . 0 3 . 0 1 0 .0 . 1

anod

eca

thod

e

N e

anod

eca

thod

e

X e

1 . 2 s 2 . 7 s 4 . 2 s 7 . 7 s1 . 2 s 2 . 7 s 4 . 2 s 7 . 7 s

0 . 3 1 . 0 3 . 0 1 0 .0 . 1 0 . 3 1 . 0 3 . 0 1 0 .0 . 1

anod

eca

thod

e

N e

anod

eca

thod

e

X e

anod

eca

thod

e

1 . 1 0 s 1 . 3 1 s 1 . 5 6 s 2 . 0 s

anod

eca

thod

e

0 . 3 1 . 3 . 0 1 0 .0 . 1

N e

X e

anod

eca

thod

e

1 . 1 0 s 1 . 3 1 s 1 . 5 6 s 2 . 0 s1 . 1 0 s 1 . 3 1 s 1 . 5 6 s 2 . 0 s

anod

eca

thod

e

0 . 3 1 . 3 . 0 1 0 .0 . 1 0 . 3 1 . 3 . 0 1 0 .0 . 1

N e

X e

MacrocellMacrocell Model 2D with photoemissionModel 2D with photoemission Model 2D without photoemissionModel 2D without photoemission

Comparisons with models: negative glow

Ne-Xe:10%, 5.6torr, 0.5cm coplanar gap, 190V, 100Hz

Photoelectrons are produce over all the cathode surface (in contrary of ions they don’t follow the electric field), that’s why negative glow is more larger with photoemission.

Comparisons with models: plasma expansion velocity

Ne-Xe:10%, 5.6torr, 0.5cm coplanar gap, 190V, 100Hz (model and experiment)

Time evolution of the positions of the maximum infrared xenon emission above intensity above cathode and anode from the measurements and the simulations (with and without photoemission included in the model)

Photons at 147nm increase the plasma expansion velocity (sheath contraction)!

~2km/s

~12km/s~15km/s

Conclusion

One problem for Plasma Display Panel is the low efficiency of the discharge in producing VUV photons (less than 10% of the electrical power is converted in VUV)

ICCD imaging shows that the anode region is more efficient than the cathode region for Xe excitation (electron energy too large in the cathode sheath -> neon excitation)

• Look for conditions (geometry, discharge excitation) where electrons spreading over the anode can be increased and optimized

Comparisons with a 2D model help us to understand these differences: The faster plasma expansion in the macrocell is due to photoemission of resonant photons at 147nm of xenon on MgO surface. The photoemission effect is less important in real PDP cell because resonant photon transport does not follow the similarity laws.

The macrocell reproduce well qualitatively the discharge of real cell (striations, no neon emission above anode, …) however there are some differences (two current peaks, high plasma expansion velocity, …)