The present invention relates to a method of driving an alternating-current (AC) type plasma display panel.
A plasma display panel (hereinafter abbreviated as a PDP or a panel) is a display device having excellent visibility and featuring a large screen, thinness and light weight. The systems of discharging a PDP include an AC type and direct-current (DC) type. The electrode structures thereof include a three-electrode surface-discharge type and an opposite-discharge type. However, the current mainstream is an AC type three-electrode PDP, which is an AC surface-discharge type, because this type of PDP is suitable for higher definition and easy to manufacture.
Generally, an AC type three-electrode PDP has a large number of discharge cells formed between a front panel and rear panel faced with each other. In the front panel, a plurality of display electrodes, each made of a pair of scan electrode and sustain electrode, are formed on a front glass substrate in parallel with each other. A dielectric layer and a protective layer are formed to cover these display electrodes. In the rear panel, a plurality of parallel data electrodes is formed on a rear glass substrate. A dielectric layer is formed on the data electrodes to cover them. Further, a plurality of barrier ribs is formed on the dielectric layer in parallel with the data electrodes. Phosphor layers are formed on the surface of the dielectric layer and the side faces of the barrier ribs. Then, the front panel and the rear panel are faced with each other and sealed together so that the display electrodes and data electrodes intersect with each other. A discharge gas is filled into an inside discharge space formed therebetween. In a panel structured as above, ultraviolet light is generated by gas discharge in each discharge cell. This ultraviolet light excites respective phosphors to emit R, G, or B color, for color display.
A general method of driving a panel is a so-called sub-field method: one field period is divided into a plurality of sub-fields and combination of light-emitting sub-fields provides gradation images for display. Now, each of the sub-fields has an initializing period, writing period, and sustaining period.
In the initializing period, all the discharge cells perform initializing discharge operation at a time to erase the history of wall electric charge previously formed in respective discharge cells and form wall electric charge necessary for the subsequent writing operation. Additionally, this initializing discharge operation serves to generate priming (priming for discharge=excited particles) for causing stable writing discharge.
In the writing period, scan pulses are sequentially applied to scan electrodes, and write pulses corresponding to the signals of an image to be displayed are applied to data electrodes. Thus, selective writing discharge is caused between scan electrodes and corresponding data electrodes for selective formation of wall electric charge.
In the subsequent sustaining period, a predetermined number of sustain pulses are applied between scan electrodes and corresponding sustain electrodes. Then, the discharge cells in which wall electric charge are formed by the writing discharge are selectively discharged and light is emitted from the discharge cells.
In this manner, to properly display an image, selective writing discharge must securely be performed in the writing period. However, there are many factors in increasing discharge delay in the writing discharge: restraints of the circuitry inhibit the use of high voltage for write pulses; and phosphor layers formed on the data electrodes make discharge difficult. For these reasons, priming for generating stable writing discharge is extremely important.
However, the priming caused by discharge rapidly decreases as time elapses. This causes the following problems in the method of driving a panel described above. In writing discharge occurring long time after the initializing discharge, priming generated in the initializing discharge is insufficient. This insufficient priming causes a large discharge delay and unstable wiring operation, thus degrading the image display quality. Additionally, when long wiring period is set for stable wiring operation, the time taken for the writing period is too long.
Proposed to address these problems are a panel and method of driving the panel in which auxiliary discharge electrodes are provided and discharge delay is minimized using priming caused by auxiliary discharge (see Japanese Patent Unexamined Publication No. 2002-297091, for example).
However, such panels have the following problems. Because the discharge delay of the auxiliary discharge itself is large, the discharge delay of the writing discharge cannot sufficiently be shortened. Additionally, because the operating margin of the auxiliary discharge is small, incorrect discharge may be induced in some panels.
Further, when the number of scan electrodes is increased for higher definition without shortening the discharge delay in the writing discharge sufficiently, the time taken for the writing period is too long and the time taken for the sustaining period is insufficient. As a result, luminance decreases. Additionally, increasing the partial pressure of xenon to increase the luminance and efficiency further increases the discharge delay and makes the writing operation unstable.
The present invention addresses these problems and aims to provide a method of driving a plasma display panel capable of performing stable and high-speed writing operation.
To address these problems, the method of driving a plasma display panel of the present invention is a method of driving a plasma display panel having priming electrodes, in which priming discharge is generated prior to scanning of respective scan electrodes, in a wiring period of a sub-field.
Methods of driving plasma display panels in accordance with exemplary embodiments of the present invention are described hereinafter with reference to the accompanying drawings.
As shown in
On front substrate 1, a plurality of pairs of scan electrode 6 and sustain electrode 7 are formed in parallel with each other. Scan electrode 6 and sustain electrode 7 are made of transparent electrodes 6a and 7a, and metal buses 6b and 7b formed on transparent electrodes 6a and 7a, respectively. Now, between each scan electrode 6 and corresponding sustain electrode 7 on the side where metal buses 6b and 7b are formed, light-absorbing layer 8 made of a black material is provided. Projection 6b′ of metal bus 6b in scan electrode 6 projects onto light-absorbing layer 8. Dielectric layer 4 and protective layer 5 are formed to cover these scan electrodes 6, sustain electrodes 7, and light-absorbing layers 8.
On rear substrate 2, a plurality of data electrodes 9 is formed in parallel with each other. Dielectric layer 15 is formed to cover these data electrodes 9. Further on the dielectric layer, barrier ribs 10 for partitioning the discharge space into discharge cells 11 are formed. As shown in
When front substrate 1 is faced and sealed with rear substrate 2, each projection 6b′ of metal bus 6b in scan electrode 6 formed on front substrate 1 that projects onto light-absorbing layer 8 is positioned in parallel with corresponding priming electrode 14 on rear substrate 2 and faced therewith to sandwich priming space 13a. In other words, the panel shown in
In
Next, a driving waveform for driving the panel and timing of the driving waveform are described.
In the former half of the initializing period, each of data electrodes D1 to Dm, sustain electrode SU1 to SUn, and priming electrodes PR1 to PRn is held at 0 (V). Applied to each of scan electrodes SC1 to SCn is a ramp waveform voltage gradually increasing from a voltage of Vi1 not larger than discharge-starting voltage across the scan electrodes and sustain electrodes SU1 to SUn to a voltage of Vi2 exceeding the discharge-starting voltage. While the ramp waveform voltage increases, first weak initializing discharge occurs between scan electrodes SC1 to SCn, and sustain electrodes SU1 to SUn, data electrodes D1 to Dm, and priming electrodes PR1 to PRn. Thus, negative wall voltage accumulates on scan electrodes SC1 to SCn, and positive wall voltage accumulates on data electrodes D1 to Dn, sustain electrodes SU1 to SUn, and priming electrodes PR1 to PRn. Now, the wall voltage on the electrodes is the voltage generated by the wall charge accumulating on the dielectric layers covering the electrodes.
In the latter half of the initializing period, each of sustain electrode SU1 to SUn is held at a positive voltage of Ve. Applied to each of scan electrodes SC1 to SCn is a ramp waveform voltage gradually decreasing from a voltage of Vi3 not larger than discharge-starting voltage across the scan electrodes and sustain electrodes SU1 to SUn to a voltage of Vi4 exceeding the discharge-starting voltage. During this application of the ramp voltage, second weak initializing discharge occurs between scan electrodes SC1 to SCn, and sustain electrodes SU1 to SUn, data electrodes D1 to Dm, and priming electrodes PR1 to PRn. Then, the negative wall voltage on scan electrodes SC1 to SCn and the positive wall voltage on sustain electrodes SU1 to SUn are weakened. The positive wall voltage on data electrodes D1 to Dm is adjusted to a value appropriate for writing operation. The positive wall voltage on priming electrodes PR1 to PRn is also adjusted to a value appropriate for priming operation. Thus, the initializing operation is completed.
In the writing period, scan electrodes SC1 to SCn are once held at a voltage of Vc. Then, a voltage of Vp is applied to priming electrode PR1 of the first row. Especially in this case, voltage Vp is a high voltage sufficiently exceeding a voltage change (Vc−Vi4) in scan electrodes SC1 to SCn. This causes priming discharge between priming electrode PR1 and the projection of scan electrode SC1, and the priming diffuses inside of discharge cells C1,l to C1,m in the first row corresponding to scan electrode SC1 of the first row.
Next, scan pulse voltage Va is applied to scan electrode SC1 of the first row, and positive write pulse voltage Vd is applied to data electrode Dk (k being an integer ranging from 1 to m) corresponding to the signal of an image to be displayed in the first row among data electrodes D1 to Dk. At this time, discharge occurs at the intersection of data electrode Dk to which write pulse voltage Vd has been applied and scan electrode SC1. This discharge develops to discharge between sustain electrode SU1 and scan electrode SC1 in corresponding discharge cell C1,k. Then, positive wall voltage accumulates on scan electrode SC1, and negative wall voltage accumulates on sustain electrode SU1 in discharge cell C1,k. Now, discharge occurs in discharge cell C1,k in the first row including scan electrode SC1 of the first row with sufficient priming supplied from the priming discharge that has occurred between scan electrode SC1 and priming electrode PR1 immediately before the discharge. For this reason, discharge delay is extremely small, and thus high-speed and stable discharge occurs.
At the time of above writing operation in scan electrode SC1 of the first row, voltage Vp is applied to priming electrode PR2 corresponding to scan electrode SC2 of the second row to cause priming discharge and diffuse the priming inside of discharge cells C2,l to C2,m in the second row corresponding to scan electrode SC2 of the second row.
In a similar manner, writing discharge in the second row and priming discharge in the third row are performed. At this time, a series of writing discharge operations are performed with sufficient priming supplied from the priming discharge that has occurred immediately before the writing discharge operations. For this reason, the discharge delay is small and thus high-speed and stable discharge occurs.
Similar writing operations are performed in discharge cells including Cn,k, and the writing operation is completed.
In the sustaining period, after scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn are reset to 0 (V) once, a positive sustain pulse voltage of Vs is applied to scan electrodes SC1 to SCn. At this time, in the voltage on scan electrode SCi and sustain electrode SUi in discharge cell Ci,j in which writing discharge has occurred, the wall voltage accumulating on scan electrode SCi and sustain electrode SUi is added to sustain pulse voltage Vs. For this reason, the voltage exceeds the discharge-starting voltage and sustain discharge occurs. In a similar manner, by alternately applying sustain pulses to scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn, sustain discharge operations are successively performed in discharge cell Ci,j in which the writing discharge has occurred, the number of times of sustain pulses.
As described above, unlike the writing discharge depending only on the priming in the initializing discharge in accordance with a conventional driving method, the writing discharge of the driving method in accordance with the present invention is performed with sufficient priming supplied from the priming discharge that has occurred immediately before the writing operation in respective discharge cells. This can achieve high-speed and stable writing discharge with a small discharge delay, and display a high-quality image.
Next, a driving waveform for driving the above panel and the timing thereof are described.
Because the operation in the initializing period is the same as that of the first exemplary embodiment, description thereof is omitted.
In the writing period, like the first exemplary embodiment, scan electrodes SC1 to SCn are held at voltage Vc once, and voltage Vp is applied to priming electrode PR1 of the first row. Then, priming discharge occurs between priming electrode PR1 and the projection of scan electrode SC1. Thus, the priming diffuses inside of discharge cells C1,l to C1,m in the first row corresponding to scan electrode SC1. The priming also diffuses inside of discharge cells C2,l to C2,m in the second row corresponding to scan electrode SC2, at the same time.
Next, scan pulse voltage Va is applied to scan electrode SC1 of the first row, and write pulse voltage Vd corresponding to video signals is applied to data electrode Dk (k being an integer ranging from 1 to m), for writing operation on discharge cell C1,k in the first row.
Sequentially, scan pulse voltage Va is applied to scan electrode SC2 of the second row, and write pulse voltage Vd corresponding to video signals is applied to data electrode Dk (k being an integer ranging from 1 to m), for writing operation in discharge cell C2,k in the second row. At this time, at the same time as the above writing operation using scan electrode SC2 of the second row, voltage Vp is applied to priming electrode PR3 corresponding to scan electrode SC3 of the third row to cause priming discharge. Then the priming diffuses inside of discharge cells C3,l to C3,m in the third row corresponding to scan electrode SC3 of the third row and discharge cells C4,l to C4,m in the fourth row corresponding to scan electrode SC4 of the fourth row.
In the same manner, writing operations are sequentially performed. However, in the writing operation in odd-numbered discharge cells Cp,l to Cp,m (p=1, 3, 5, etc.), no priming discharge is caused. In contrast, in the writing operation in even-numbered discharge cells Cq,l to Cq,m (q=2, 4, 6, etc), priming discharge is caused in priming electrode PRq+1 corresponding to the (q+1)-th scan electrode SCq+1, and the priming diffuses inside of discharge cells Cq+1,l to Cq+1,m in the (q+1)-th row and discharge cells Cq+2,l to Cq+2,m in the (q+2)-th row.
The similar writing operations are performed in the discharge cells including those in the n-th row, and the writing operations are completed.
The operation in the sustaining period is the same as that of the first exemplary embodiment, and thus the description thereof is omitted.
As described above, like the first exemplary embodiment, the writing discharge in the driving method of the present invention is performed with sufficient priming supplied from the priming discharge that has occurred immediately before the writing operation in respective discharge cells. For this reason, the discharge delay is small, and thus high-speed and stable discharge is possible.
Further, in the second exemplary embodiment, electrodes in the vicinity of priming spaces 13a are priming electrodes 14 and scan electrodes 6 only. This also gives an advantage of stable action of the priming discharge itself because the priming discharge is unlikely to cause other unnecessary discharge, e.g. incorrect discharge involving sustain electrodes 7.
Incidentally, as shown in
Incidentally, because respective electrodes of an AC type PDP are surrounded by the dielectric layers and insulated from the discharge space. For this reason, direct-current components make no contribution to discharge itself. Therefore, of course, even the use of waveforms in which direct-current components are added to the driving waveforms of the first or second exemplary embodiment can provide similar effects.
Responsive to the sub-field signal and the timing control signal, data electrode driver circuit 102 applies a predetermined driving waveform to data electrodes 9 (data electrodes D1 to Dm in
The above circuit block can constitute a driver for implementing the methods of driving the panels of the exemplary embodiments of the present invention.
As described above, the present invention can provide a method of driving a plasma display panel capable of performing stable and high-speed writing operation.
The method of driving a plasma display panel of the present invention can perform stable and high-speed writing operation. Thus, the present invention is useful as a method of driving an AC type plasma display panel.
Number | Date | Country | Kind |
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2003080301 | Mar 2003 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP04/03950 | 3/23/2004 | WO | 11/24/2004 |