Kyung Cheol Choi

Improvement of luminance and luminous efficiency using address voltage pulse during sustain-period of AC-PDP

To improve the luminance and luminous efficiency of a surface-discharge alternate current plasma display panel (ac PDP), auxiliary voltage pulses were applied to the address electrode during a sustain-period. The luminance and luminous efficiency exhibited maximum values at an address voltage of 100 V and pulse width of 1 /spl mu/s. An improved luminance of 21.4% and luminous efficiency of 24% were simultaneously obtained based on the proper adjustment of the widths and amplitudes of the address voltage pulse. Accordingly, the proper control of the amplitudes and pulse widths of the auxiliary address voltage during a sustain-period can improve both the luminance and the luminous efficiency in a surface-discharge ac PDP.

Numerical analysis of the microdischarge in a DC plasma display panel by 2-dimensional multifluid equations

Abstruct-A numerical analysis of the microdischarge in a plasma display panel have been made by using 2-dimensional multifiuid equations. The discharge gas is used as Ne + Ar 0.1% in a state of non-LTE glow. The distributions of the microscopic variables such as the density, temperature, velocity of the charged particles and the density of the uncharged particles are obtained. The distributions of excited species are examined during glow and afterglow. From the simulation results, the nondischarge pulses applied to the auxiliary anode confine the plasma to the core of the microdischarge. It is found that metastable species and other excited species are locally confined around the auxiliary anode during glow and afterglow. Locally confined particles indirectly due to the nondischarge pulses play a role to improve the characteristics of the DC plasma display panel.

Improvement in the luminous efficiency using ramped-square sustain waveform in an AC surface-discharge plasma display panel

This paper proposes a new sustain waveform to improve the luminous efficiency of an AC plasma display panel (AC-PDP). The new sustain waveform is a superimposed waveform, which adds a ramp-waveform to a square-waveform, and has an increasing voltage slope between the rising and falling edge. This waveform can induce a longer-sustained discharge at the rising edge plus a self-erasing discharge at the falling edge, thereby improving the luminous efficiency, When compared with the conventional square sustain waveform, the proposed sustain waveform with a 9.3 V//spl mu/s voltage slope achieved a 65% higher luminous efficiency in a 4-in AC-PDP test panel even at a low frequency (62 kHz).

Effects of pre-reset conditions on reset discharge from ramp reset waveforms in AC plasma display panel

The basic characteristics of reset discharges related to a wall voltage and a priming effect were investigated under a conventional ramp driving scheme. The reset discharges could be minimized by controlling the wall voltage which is determined by pre-reset conditions. Accordingly, the current study presents a simple pre-reset condition for minimizing the reset discharge. Essentially, it is not only to reduce the duration of reset discharges but also to reduce the intensity of light emissions when the wall voltage polarity is opposite to the external voltage polarity.

Case studies on temperature-dependent Characteristics in AC PDPs

The temperature-dependent characteristics of ac plasma display panels (PDPs) are investigated, based on various case studies using a conventional driving scheme with reset pulses. Though the main factor of the thermal effects is caused by strong sustain discharges, it is not only caused by the panel characteristics, but also by the temperature-dependent characteristics of the driving system. One important thermal effect is a decreased breakdown voltage due to an increase in the panel temperature. Therefore, these results may be helpful in solving image-sticking and temperature-related phenomena.

The effect of the discharge aging process on the surface state of MgO film in AC PDPs

This paper reports on the change in the surface condition of the MgO thin film in an ac plasma display panel during the discharge aging process. The superficial layer on the MgO thin film was created during the discharge aging process, which was related to the minimum sustain voltage and the light intensity emitted from the Neon+Xenon gas mixture discharge. The superficial layer on the MgO thin film was observed using a transmission electron microscope. The X-ray diffractometer pattern of the MgO thin film after the discharge aging process was different from the pattern at the beginning of the discharge aging process.

Characteristics of charged and metastable species in micro-discharges of AC- plasma display panel

The temporal effects of charged and metastable particles in the micro-discharges of an AC plasma display panel (AC-PDP) were investigated under actual driving conditions. The discharge gas used in the 4-in PDP was Neon + 4% Xenon. The discharge characteristics in terms of the time scale related to the space-charge decay, wall charge decay, metastable decay, and charge accumulation were investigated using a pulse technique. For Neon + 4% Xenon gas-mixture discharges of 500 torr, 4 /spl mu/s was related to the time scale of the space-charge decay and wall-charge accumulation time. The minimum sustain voltage started to dramatically increase at 20 /spl mu/s, which was related to the time scale of the metastable particles. Whereas, after 40 /spl mu/s, the minimum sustain voltage slowly increased with a slope of 0.01581, which was related to the inverse of the time scale of the wall charge decay.

The Effect of the Auxiliary Electrode on the Microplasma Generated in a Plasma Display With a Coplanar Gap

The microplasma modes generated in a plasma display with a coplanar gap and an auxiliary electrode were investigated using the discharge current peak time (discharge delay) and discharge current. Three types of modes were classified as follows: mode 1) showed a decrease in both the discharge current and the discharge delay, mode 2) showed a decrease in the discharge current and an increase in the discharge delay, and mode 3) showed an increase in the discharge current and a decrease in the discharge delay. The infrared efficiency increased in modes 1) and 2) with an increase in the auxiliary pulse voltage. However, in mode 3), the IR efficiency started to decrease. According to the measurement results, modes 1) and 2) are suitable for microplasma generated in a coplanar gap with an auxiliary electrode to obtain high efficacy.

Characteristics of a wall voltage during sustain period in AC plasma display panels

According to the viewpoint of a driving scheme, the luminance and luminous efficiency is mainly determined during the sustain period. Therefore, it is very important to understand the characteristics of the wall voltage during the sustain period, which is essential to design the driving pulse scheme. In this study, the quantitative analysis of the wall voltage has been carried by the wall voltage measurement method during the sustain period. The initial difference of the wall voltage is sharply stabilized due to the sustain discharges and it is mainly determined by the sustain voltage. The wall voltage between the sustain electrodes is changed symmetrically for the reference voltage level, while the wall voltage between the address and sustain electrode is positively sustained which is roughly mean value of the total effective voltage.

Functional Design of Dielectric–Metal–Dielectric-Based Thin-Film Encapsulation with Heat Transfer and Flexibility for Flexible Displays

In this study, a new and efficient dielectric-metal-dielectric-based thin-film encapsulation (DMD-TFE) with an inserted Ag thin film is proposed to guarantee the reliability of flexible displays by improving the barrier properties, mechanical flexibility, and heat dissipation, which are considered to be essential requirements for organic light-emitting diode (OLED) encapsulation. The DMD-TFE, which is composed of Al2O3, Ag, and a silica nanoparticle-embedded sol-gel hybrid nanocomposite, shows a water vapor transmission rate of 8.70 × 10-6 g/m2/day and good mechanical reliability at a bending radius of 30 mm, corresponding to 0.41% strain for 1000 bending cycles. The electrical performance of a thin-film encapsulated phosphorescent organic light-emitting diode (PHOLED) was identical to that of a glass-lid encapsulated PHOLED. The operational lifetimes of the thin-film encapsulated and glass-lid encapsulated PHOLEDs are 832 and 754 h, respectively. After 80 days, the thin-film encapsulated PHOLED did not show performance degradation or dark spots on the cell image in a shelf-lifetime test. Finally, the difference in lifetime of the OLED devices in relation to the presence and thickness of a Ag film was analyzed by applying various TFE structures to fluorescent organic light-emitting diodes (FOLEDs) that could generate high amounts of heat. To demonstrate the difference in heat dissipation effect among the TFE structures, the saturated temperatures of the encapsulated FOLEDs were measured from the back side surface of the glass substrate, and were found to be 67.78, 65.12, 60.44, and 39.67 °C after all encapsulated FOLEDs were operated at an initial luminance of 10 000 cd/m2 for sufficient heat generation. Furthermore, the operational lifetime tests of the encapsulated FOLED devices showed results that were consistent with the measurements of real-time temperature profiles taken with an infrared camera. A multifunctional hybrid thin-film encapsulation based on a dielectric-metal-dielectric structure was thus effectively designed considering the transmittance, gas-permeation barrier properties, flexibility, and heat dissipation effect by exploiting the advantages of each separate layer.