1C: Flat Panel Displays
1C0102: Diagnostics of Dynamic Behaviors
of Excited Atoms in Microplasmas for Plasma Display Panels Kunihide Tachibana, Department of Electronic Science and
Engineering, Kyoto University, Yoshida, Sakyo, Kyoto 606-8501, Japan.
1C0304: Electrical Breakdown Properties of High-Pressure Discharge in the
Plasma Display Panel Han Sup
Uhm and Eun H. Choi* Department of
Molecular Science and Technology, Ajou University, San 5 Wonchon-Dong,
Paldal-Gu, Suwon 442-749, Korea.
1C05: Cell Geometry Designs for Efficient Plasma Display Panels G. Veronis and U.S. Inan, Space, Telecommunications, and Radioscience
Laboratory, Stanford University, Stanford, California 94305.
1C06: Improvement of Luminous Efficiency and Radiation Transport in PDP S.W. Shin, S.S. Yang, H.C. Kim, H.J. Lee, and J.K. Lee, Department of Electronic and Electrical
Engineering, Pohang University of Science and Technology, Pohang, 790-784, S.
Korea.
1C07: Mechanism of High Efficiency
Discharge in PDP Cell Under High Pressure Conditions W.J. Chung, T.J.
Kim, H.S. Bae,
and K.-W. Whang, Plasma Laboratory, School of
Electrical Engineering, Seoul National University San 56-1, Shinrim-dong, Kwanak-gu, Seoul
151-742, KOREA.
1C08: Influence of
Ne-Xe Gas Mixture Ratio on Vacuum Ultraviolet and Infrared Line in AC-PDPs J.C. Ahn,
P.Y. Oh, Y. Jung, E.H. Choi, Charged
Particle Beam and Plasma Laboratory, Department of Electrophysics PDP Research Center, Kwangwoon University, Seoul 139-701, Korea.
******************************************
Diagnostics of Dynamic Behaviors of Excited
Atoms in Microplasmas
for Plasma Display Panels
Kunihide
Tachibana
Department of Electronic Science and
Engineering, Kyoto University, Yoshida, Sakyo, Kyoto 606-8501, Japan
Improvement of luminous efficiency from a current typical value of 1-2 m/W to 5 lm/W is the most crucial issue for PDPs to be of practical home use. Although variety of cell structures and operating conditions have been tested up to now, it is still difficult to get firm guiding principles towards the goal. Much effort to understand the basic physics of the microdischerge in a PDP cell has been done mostly by computer simulations, but the validity of the results should be checked by proper diagnostics.
We
developed a microscopic laser-absorption method for the absolute measurement of
excited Xe(1s4, 1s5) atoms, which lead to VUV emissions
for the excitation of RGB phosphors, with a spatial and temporal resolution of
20 mm and 5 ns, respectively.
For the measurement of higher lying excited Xe(2p) atoms and Ne(2p) atoms, the
corresponding near IR and visible emissions were observed by a gated CCD camera
equipped with appropriate optical band pass filters.
For
the simultaneous front and side view observations, we constructed a special
panel, which had a realistic AC-type cell structure and sizes. The essential
point to realize this panel was the use of transparent glass prisms as barrier
ribs. Those prisms were assembled with other rectangular glass spacers to fit
into the supporting ceramic ribs print-formed on the front glass plate. The
panel has a pair of transparent ITO sustain electrodes on the front glass plate
and an address electrode on the back glass plate. A mixture of Xe and Ne was
filled in the panel at a pressure of 500 Torr. Two different contents of Xe (5%
and 10%) were tested.
At a
normal operating condition with a pulse voltage of about 200 V, both the
behaviors of Xe(1s) and Xe(2p) atoms showed a similar characteristic feature;
there appeared several sharp density peaks on the temporal anode side and a broader
peak at the cathode side. The decay of Xe(1s4) atoms was governed
mostly by the effective lifetime of the imprisoned resonant radiation, while
that of Xe(1s5) atoms was determined by the three-body collisions to
form Xe2* excimers. With increase of the pulse voltage to 250 V, a
different feature appeared; the distribution bowed to the counter address
electrode side. This suggests that the accumulated charge on the address
electrode in the preceding pulse influences the discharge to trigger a sort of
self-erasing discharge at the tailing edge of the pulsed voltage.
From
the measured density of Xe(1s4, 1s5) atoms, the VUV
emission intensity was estimated. Those results are compared with simulations,
and the dependence of the luminous efficiency on the operating parameters will
be discussed.
Electrical Breakdown Properties of High-Pressure Discharge
in the Plasma Display Panel
Han Sup Uhm and Eun H. Choi*
Department of Molecular Science and Technology, Ajou University
San 5 Wonchon-Dong, Paldal-Gu, Suwon 442-749, Korea
One of the most important
issues in the PDP study is the reduction of the electrical breakdown voltage,
which is the key element in enhancing the electrical efficiency of PDP
operation. The electrical efficiency enhancement in turn prolongs panel life.
The plasma display panel is operated with high-pressure gas, for which the
breakdown voltage reduction may be accomplished by mixing a small amount of
xenon with neon gas. The UV light emitted from xenon discharge plasma is
converted into fluorescent light, providing TV images. A recent theoretical
calculation indicates that the breakdown voltage is significantly reduced for
the mixed gas due to a collisional frequency decrease. It is easy to ionize
xenon atoms with low ionization energy. The electrons can also easily get their
kinetic energy in neon gas mixed with xenon atoms, thereby reducing their
collisional cross-section and ionizing xenon atoms. However, previous
literature indicates that the breakdown voltage can be reduced further by the
Penning effects, which have been studied mostly in low-pressure discharge. We
therefore investigate the influence of the Penning effects on the electrical
discharge properties in a mixed gas in connection with applications to the
plasma display panel, where the pressure is almost one atmosphere. A
theoretical model of the breakdown voltage in a mixed gas is developed, based
on the Townsend criteria. The breakdown temperature Tb and voltage Vb
are obtained in terms of the gas mixture ratio. As an example, electrical
breakdown properties in neon gas mixed with xenon are investigated. It is shown
that the electron breakdown-temperature Tb
decreases monotonically as the xenon mole fraction c increases. The Penning effects modify the
electron temperature significantly, particularly in the range of a small mole
fraction. A preliminary experiment using the plasma display panel is carried
out to verify some of the theoretical models. The Paschen curves of the
breakdown voltage are experimentally obtained in terms of the pressure
parameter (pd) and the xenon mole
fraction. It is shown that the breakdown voltage is reduced significantly at
the xenon mole fraction of 0.015, which agrees remarkably well with
experimental data.
*Address:
Department of Electrophysics, Kwangwoon University, Seoul, Korea
G. Veronis and U.S. Inan
Space, Telecommunications, and Radioscience Laboratory,
Stanford University, Stanford, California 94305
Plasma display panels (PDPs) are one of the leading candidates in the competition for large-size, high-brightness flat panel displays, suitable for high definition television (HDTV) wall-mounted monitors. Recent progress of PDP technology development and manufacturing has been remarkable. One of the most critical issues in ongoing PDP research is the improvement of the luminous efficiency, which is still low compared to conventional cathode ray tube displays (CRTs). Another important problem is the relatively high operating voltages.
We use a two-dimensional self-consistent simulation model to study the effect of the geometric parameters on the operating voltages and the efficiency of a coplanar-electrode plasma display panel cell. For the standard coplanar-electrode geometry it is found that there is a trade-off between high efficiency and low operating voltages as the electrode gap, or other parameters of the upper dielectric are varied, while variation of the sustain electrode width has no significant effect on either the operating voltages or efficiency. We also investigate the performance of several non-standard cell geometry designs involving two-dimensional variations of the coplanar-electrode PDP cell. A PDP cell with modified shape of sustain electrodes is found to have ~20% larger luminous efficiency without substantial increase of the operating voltages. Similar performance improvement is achieved by designs with different shapes of the upper dielectric, or by those involving two different dielectric layers. The dependence of PDP performance on the design parameters of these structures is also investigated.
Improvement of
Luminous Efficiency and Radiation Transport in PDP
S.W. Shin, S.S. Yang, H.C.
Kim, H.J. Lee , and J.K. Lee
Department of Electronic and Electrical Engineering
Pohang University of Science and Technology, Pohang, 790-784, S. Korea
Plasma display panel (PDP)
has been the brightest prospective candidate for the next generation
high-definition (HD) display device. However low luminous efficiency and high
power consumption are still important research issues of present PDP. There are
two essential factors to increase the luminous efficiency. One is to improve
the discharge efficiency and the other is to increase the phosphor utilization. Low
electric field induces high discharge efficiency and long path and
downsweeeping discharge has not only high discharge efficiency but also
luminous efficiency [1]. Using two- and three-dimensional fluid simulation codes (FL2P, FL3P),
we have suggested several new PDP cell structures that have higher efficiency
than conventional PDP cell. Varying electrodes and pulse shapes, arch-shaped
long discharge path can be formed in the plasma region. Arch-shaped long
discharge path reduces the power consumption and increases the discharge
efficiency in cathode. Because the proximity between generated Xe* and
phosphor layer is also improved, we have obtained high luminance and luminous
efficiency. Furthermore, effective cutting of central region in large area
sustain electrodes makes two discharge regions near the barrier ribs, on which
phosphor layer is deposited. Using these kinds of new structures, we have
achieved 80~100% improvement in luminous efficiency in simulation. For the accurate radiation
trapping simulation of xenon (Xe) excited species in PDP cell, we have calculated
full radiation transport using Holstein’s equation instead of effective decay
time approximation. From the simulation with full radiation transport, there
are differences in space distribution of Xe*(3P1) and
photon flux compared with conventional calculation.
[1]
C.H. Shon, J.K. Lee, S. Dastgeer, S.S. Yang, and S.W. Shin, “Striation
Phenomenon of Plasma Display Panel(PDP) Cell and Its Application to Efficiency
Improvement”, SID’01(2001)
Mechanism of High Efficiency Discharge in PDP
Cell
Under High Pressure Conditions
W.J.
Chung, T.J.
Kim, H.S. Bae,
and K.-W. Whang
Plasma
Laboratory, School of Electrical Engineering, Seoul National University
Plasma
display panel (PDP) is one of the promising flat panel display devices with the
size lager than 40-inch diagonal. One of the main and urgent issues in PDP research is the improve-ment
of the luminous
efficiency. Because the PDP uses the micro-discharges in the Xe
mixed gas to generate VUV to excite phosphor for visible light emission, the
gas condition is one of the main factors which determine the luminous
efficiency of PDP. Recent experimental studies reported that high efficiency could
be obtained under the gas condition of high pressure (>400Torr) and high Xe
concentration (>10%). Especially interest thing is that under those high-pressure
condition, the efficiency increases as the sustain voltage increases unlike the
low-pressure condition where the efficiency decreases as the sustain voltage
increases. Using 2D fluid PDP cell simulation, we investigated the mechanism of
different efficiency dependence on the sustain voltage under low and high-pressure
gas condition.
The
VUV generation efficiency is determined mainly by two partial efficiencies. The
first is the electron heating efficiency by electric field, and the second is
the Xe excitation efficiency by electron. We found that these two partial
efficiencies have different dependencies on the sustain voltage. As the sustain
voltage increases, the Xe excitation efficiency by electron decreases because
more electron power is used for ionization than excitation. We found that under
low-pressure, this mechanism is dominant, which results in that the total VUV
efficiency decreases as the sustain voltage increases. On the other hand, we
found that under high-pressure condition, the electron heating efficiency determines
the VUV efficiency. The mechanism is as follows. At high pressure, the cathode
sheath is formed locally and strongly due to low ion mobility. Thus, as the
sustain voltage increases, the electric field intensity in the cathode sheath
increases, which results in the more generation of Ne+ than Xe+.
Because the Ne+ has much higher secondary electron emission
coefficient than that of Xe+, much more secondary electrons are
emitted from cathode surface, and these secondary electrons experience all the
cathode sheath potential, which results in higher electron heating efficiency
in the discharge volume. Thus, the total VUV efficiency increases as the
sustain voltage increases. Consequently, it can be said that there exist two
kinds of discharge mode from the viewpoint of efficiency dependence on the
sustain voltage. Under the low ion mobility condition resulted from high
pressure and high Xe concentration, the VUV generation efficiency is determined
by electron heating efficiency.
Influence of Ne-Xe Gas Mixture Ratio on
Vacuum Ultraviolet and Infrared Line in AC-PDPs
J.C. Ahn,
P.Y. Oh, Y. Jung, E.H. Choi
Charged Particle Beam and Plasma Laboratory,
Department of Electrophysics
/ PDP Research Center, Kwangwoon
University
Seoul 139-701, Korea
The surface discharge AC-PDPs (alternating current plasma
display panels) utilizes the photoluminescence phenomena of phosphors excited
by VUV(Vacuum Ultra Violet) rays from xenon in the Penning mixture gas. The
luminous efficiency improvement is one of the most important parts to make PDP
into leader of large flat panel display device. The present AC-PDPs showed very
little change, for example, cells structure, pressure and mixing condition of
rare gas, phosphor, and MgO, and driving scheme, with its panel luminance
efficiency staying at 1.5 lm/W level in 40" class. In order to improve the
discharge luminous efficiency for AC-PDP, the emission characteristics of VUV
rays from xenon is important for color AC-PDPs. The influence of Ne-Xe
gas-mixture ratio on resonance state Xe*(3p1) and exited state Xe*
(3p2) has been investigated. At first, we observed xenon 823 and
828nm infrared light which relates to VUV 173nm and 147nm emission,
respectively, and we measured the 147nm from Xe(3p1) resonance
emission and the 173 nm from molecular dimer Xe2*(3p2)
for Ne-Xe mixture gas using an vacuum monochromator. It is found that the
intensity of VUV 147nm emission is proportional to that of the IR 828 nm
emission, and the VUV 173nm emission is roughly proportional to that of the IR
823nm emission. It is noted that for high Xe gas mixture ratio greater
than 7 % the increase of the luminous efficiency is found to be saturate. This
saturation characteristic with increasing Xe gas mixture ratio associates with
the plasma saturation. For increasing Xe gas mixture the ratio of molecular dimmer
emission to resonance emission increases, due to the increasing emission
probability for molecular dimmer formation in three-body collision. The electron temperature and
plasma density have been experimentally measured from the center of sustaining
electrode gap by a micro Langmuir probe and high-speed ICCD (intensified
charged couple device)camera methods in AC-PDPs. The plasma density from the center of sustaining
electrode gap is shown to be maximum value of 9×1011
cm-3, while the electron temperature is about 1 eV in this
experiment.