1. Field of the Invention
The present invention relates to a plasma display panel (PDP) and a driving method thereof, and more particularly, to a PDP and a driving method thereof that can improve luminous efficiency.
2. Discussion of the Related Art
A PDP is a display device using visible rays generated from a phosphor when vacuum ultraviolet rays generated by gas discharge excite the phosphor. The PDP is thinner and lighter in weight than a cathode ray tube (CRT) that has been mainly used as a display device. The PDP also enables a large sized screen with high definition.
Such a PDP includes a plurality of discharge cells, each cell having one pixel on a screen.
FIG. 1 is a perspective view illustrating a discharge cell of a related art three-electrode alternating current area discharge type PDP.
Referring to FIG. 1, the discharge cell of the related art three-electrode alternating current area discharge type PDP includes a scan/sustain electrode 12Y, a common sustain electrode 12Z, and an address electrode 20X. The scan/sustain electrode 12Y and the common sustain electrode 12Z are formed on an upper substrate 10, and the address electrode 20X is formed on a lower substrate 18.
On the upper substrate 10 on which the scan/sustain electrode 12Y and the common sustain electrode 12Z are formed in parallel, an upper dielectric layer 14 and a passivation film 16 are layered. Wall charges generated by a plasma discharge are accumulated in the upper dielectric layer 14. The passivation film 16 prevents the upper dielectric layer 14 from being damaged due to sputtering generated by the plasma discharge and increases secondary electron emission. MgO is generally used as the passivation film 16.
A lower dielectric layer 22 and a sidewall 24 are formed on the lower substrate 18 on which the address electrode 20X is formed. A phosphor layer 26 is deposited on surfaces of the lower dielectric layer 22 and the sidewall 24.
The address electrode 20X is formed to cross the scan/sustain electrode 12Y and the common sustain electrode 12Z. The sidewall 24 is formed in parallel with the address electrode 20X, so that ultraviolet rays and visible rays generated by a discharge are prevented from leaking out to an adjacent discharge cell. The phosphor layer 26 is excited by the ultraviolet rays generated by the plasma discharge and generates one of red, green, or blue visible rays.
Also, an inert gas for a gas discharge is injected into a discharge space between the upper substrate 10 or the lower substrate 18 and the sidewall 24.
The aforementioned alternating current area discharge type PDP divides one frame into a plurality of sub-fields having different discharge number of times to display gray level of a picture image. Each sub-field includes a reset period for uniformly generating a discharge, an address period for selecting a discharge cell, and a sustain period for displaying gray level in accordance with discharge number of times. For example, if a picture image is displayed in 256 gray levels, a frame period (16.67 ms) corresponding to 1/60 sec. is divided into eight sub-fields. Each of the eight sub-fields is divided into a reset period, an address period, and a sustain period. The reset period has the same value in each sub-field. Likewise, the address period has the same value in each sub-field. However, the sustain period is increased at a rate of 2n (n=0,1,2,3,4,5,6,7) in each sub-field. Since the sustain period is varied in each sub-field, gray level of the picture image can be displayed.
A reset pulse is supplied to the scan/sustain electrode 12Y during the reset period, so that a reset discharge occurs. During the address period, a scan pulse is supplied to the scan/sustain electrode 12Y and a data pulse is supplied to the address electrode 20X so that an address discharge occurs between the electrodes 12Y and 20X. Wall charges are generated in the upper and lower dielectric layers 14 and 22 during the address discharge. During the sustain period, an alternating current signal is alternately supplied to the scan/sustain electrode 12Y and the common sustain electrode 12Z so that a sustain discharge occurs between the electrodes 12Y and 12Z.
However, in the related art alternating current area discharge type PDP, a sustain discharge space is concentrated on the center of the upper substrate 10, thereby reducing applicability of the discharge space. That is, as shown in FIG. 2, since the sustain discharge occurs between the scan/sustain electrode 12Y and the common sustain electrode 12Z formed on the upper substrate 10 at a narrow distance, a discharge area is reduced, thereby reducing luminous efficiency. At this time, if the scan/sustain electrode 12Y and the common sustain electrode 12Z are formed at a wider distance to increase the discharge area, a high driving voltage should be applied to the scan/sustain electrode 12Y and the common sustain electrode 12Z. That is, power consumption is increased for the sustain discharge, thereby reducing driving efficiency of the PDP.
To solve such a problem, a five-electrode alternating current area discharge type PDP as shown in FIG. 3 has been proposed.
FIG. 3 is a perspective view illustrating a discharge cell of another related art five-electrode alternating current area discharge type PDP.
Referring to FIG. 3, the related art five-electrode alternating current area discharge type PDP includes first and second trigger electrodes 34Y and 34Z formed at the center of a discharge cell on an upper substrate 30, a scan/sustain electrode 32Y and a common sustain electrode 32Z formed at a peripheral portion of the discharge cell on the upper substrate 30, and an address electrode 42X formed at the center of the lower substrate 40 to be orthogonal to the trigger electrodes 34Y and 34Z, the scan/sustain electrodes 32Y, and the common sustain electrode 32Z. On the upper substrate 30 on which the scan/sustain electrode 32Y, the first trigger electrode 34Y, the second trigger electrode 34Z, and the common sustain electrode 32Z are formed in parallel, an upper dielectric layer 36 and a passivation film 38 are layered. On the lower substrate 40 on which the address electrode 42X is formed, a lower dielectric layer 44 and a sidewall 46 are formed. A phosphor layer 48 is deposited on surfaces of the lower dielectric layer 44 and the sidewall 46.
An alternating current pulse is supplied to the trigger electrodes 34Y and 34Z formed at the center of the discharge cell at a narrow distance during the sustain period. The trigger electrodes 34Y and 34Z are used to start a sustain discharge. The alternating current pulse is also supplied to the scan/sustain electrode 32Y and the common sustain electrode 32Z formed at a wider distance at the peripheral portion of the discharge cell during the sustain period. The scan/sustain electrode 32Y and the common sustain electrode 32Z are used to start a plasma discharge between the trigger electrodes 34Y and 34Z and to maintain the plasma discharge. To drive the five-electrode alternating current area discharge type PDP, a waveform shown in FIG. 4 is applied.
Referring to FIG. 4, in the related art five-electrode alternating current area discharge type PDP, one frame is divided into various sub-field having different discharge number of times to display gray level of a picture image. Each sub-field includes a reset period for uniformly generating a discharge, an address period for selecting a discharge cell, and a sustain period for displaying gray level in accordance with discharge number of times.
During the reset period, a reset pulse is supplied to the second trigger electrode Tz so that a reset discharge for initiating the discharge cell occurs. At this time, a direct current voltage is supplied to the address electrode X to prevent an error discharge from occurring.
During the address period, scan pulses C are sequentially supplied to the first trigger electrode Ty and data pulses Va synchronized with the scan pulses C are supplied to the address electrode X. At this time, an address discharge occurs in the discharge cell to which the data pulses Va are supplied.
During the sustain period, sustain pulses are alternately applied between the first trigger electrode Ty and the scan/sustain electrode Sy and between the second trigger electrode Tz and the common sustain electrode Sz. At this time, a voltage Vt applied to the trigger electrodes Ty and Tz has a lower level than a voltage Vs applied to the scan/sustain electrode Sy and the common sustain electrode Sz. During the sustain period, a direct current voltage is supplied to the address electrode X to prevent an error discharge from occurring.
A sustain discharge step will be described in more detail with reference to FIG. 5.
First, if the sustain pulse is applied to the first trigger electrode Ty, the scan/sustain electrode Sy, the second trigger electrode Tz, and the common sustain electrode Sz, a trigger discharge occurs between the first trigger electrode Ty and the second trigger electrode Tz. Then, a transition discharge occurs between the second trigger electrode Tz and the common sustain electrode Sz or between the first trigger electrode Ty and the scan/sustain electrode Sy. As a result, the trigger discharge generated between the first trigger electrode Ty and the second trigger electrode Tz is transited to the sustain discharge between the scan/sustain electrode Sy and the common sustain electrode Sz. In other words, the sustain discharge occurs between the scan/sustain electrode Sy and the common sustain electrode Sz after the transition discharge occurs. At this time, even if the distance between the scan/sustain electrode Sy and the common sustain electrode Sz is great, a discharge can occur by means of a sustain pulse having a relatively low voltage level due to priming charged particles generated by the transition discharge. Thus, the sustain discharge having a long discharge path can occur while reducing increase of a sustain voltage.
However, a transition discharge path in the five-electrode alternating current area discharge type PDP is almost half of a sustain discharge path. That is, to generate the transition discharge corresponding to half of the sustain discharge path, a high voltage should be applied to the trigger electrodes Ty and Tz. A strong transition discharge occurs due to the high voltage applied to the trigger electrodes Ty and Tz. Wall charges are generated by the transition discharge and accumulated in a surface of the scan/sustain electrode 12Y or the common sustain electrode 12Z. The wall charges accumulated in the scan/sustain electrode 12Y or the common sustain electrode 12Z cause the sustain discharge contributed to luminance to be weakened, thereby reducing luminous efficiency of the PDP.