Plasma display driving method and device

Technology that enables writing in a PDP to be conducted effectively, even when a time period of the writing is shortened. In a PDP driven by a method in which a write discharge is selectively generated in a plurality of cells by applying a scan pulse sequentially to a plurality of first electrodes and a data pulse selectively to a plurality of third electrodes in a write period, the technology provides for a write auxiliary discharge to be generated at least in a cell selected for writing or in a vicinity of the selected cell when the scan pulse is applied in the write period, the write auxiliary discharge being smaller in magnitude than the write discharge. The write auxiliary discharge results in the generation of priming particles in or in a vicinity of the selected cell, and these priming particles facilitate the generation of a write discharge in the selected cell. Consequently, the occurrence of defective writing is reduced and effective writing can be conducted, even when a width of the scan pulse is shortened.

TECHNICAL FIELD

The present invention relates to a flat-panel plasma display panel and a drive method that are used in display devices of information terminals, personal computers and the like, as well as in image display devices of televisions and the like.

BACKGROUND ART

Plasma display panels (PDPs) can be broadly divided into direct current (DC) and alternating current (AC) types. However, AC PDPs are currently the major focus of attention due to their suitability for large-screen application.

Conventional AC-type surface discharge PDPs that conduct RGB color image display, as well as related drive methods are disclosed, for example, in Japanese publication of unexamined applications No. 6-186927 and No. 5-307935. The disclosed technology is basically as follows.

A conventional PDP is structured from a front cover plate and a back plate that are disposed parallel to each other and with a gap therebetween. On the front cover plate, display electrodes (i.e. scan electrodes and sustain electrodes) are arranged in a stripe pattern, and a dielectric layer is provided so as to cover these electrodes. On the back panel, data electrodes and barrier ribs are arranged in a stripe pattern that is orthogonal to the display electrodes, and between the barrier ribs are arranged ultraviolet light excitation phosphor layers corresponding to the colors red, green and blue. Between the two plates, cells are formed where the electrodes extend across each other orthogonally, and a discharge space within each cell is filled with a discharge gas.

According to a conventional drive method, firstly, in an initialization period, an initialization discharge is generated in all of the cells within the panel by applying an initialization pulse to the scan electrodes. The initialization discharge serves to equilibrize the space charge throughout the panel, and to accumulate wall charge (i.e. effective when a write discharge is subsequently generated) in a vicinity of the data electrodes.

Next, in a write period, a write discharge is generated in cells to be turned on (hereafter, “on-cells”) by applying a positive data pulse selectively to the scan electrodes at the same time that a negative scan pulse is applied sequentially to the scan electrodes. Here, the write discharge generally induces a write sustain discharge to generate between the scan electrode and the sustain electrode in the on-cells, thus completing the writing.

Next, in a sustain period, a high voltage sustain pulse is applied alternately to the scan electrode and the sustain electrode in the on-cells. In this way a discharge is selectively repeated in the written cells, and image display is achieved as a result of the luminescence that arises from this sustain discharge. Then, in an erase period, the wall charge stored on the dielectric as a result of the sustain discharge is erased by erase pulses applied to the sustain electrodes.

With respect to PDP design, the present task is to improve the luminescence brightness in a PDP having the above structure.

However, in order to improve luminescence brightness, it is desirable to lengthen the sustain period as much as possible by shortening the initialization, write and erase periods, since the sustain period is the only period that actually contributes to luminescence in the cells.

To shorten the write period, a pulse width of the scan pulse applied to the scan electrodes and the data pulse applied to the data electrodes is preferably shortened as much as possible. Currently, there is an increasing demand for display devices capable of high definition image display, and attempts are being made to keep the aforementioned pulse widths to around 1.0 μsecs or less in order to conduct effective writing without having to extend the length of the write period.

However, a certain amount of dispersion occurs from the time that application of the scan and data pulses is commenced until the time that a discharge is generated, and thus shortening the pulse widths of the scan and data pulses increases the possibility that defective writing will occur.

Since the occurrence of defective writing results in the on-cells not being turned on, the quality of the displayed image is consequently reduced.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide technology that allows for writing to be conducted effectively in a PDP, even when a time period of the writing is shortened.

A drive method provided to achieve this object drives a PDP by applying a scan pulse sequentially to first electrodes and a data pulse selectively to third electrodes in a write period, in order to selectively generate a write discharge in a plurality of cell, and illuminating a written cell in a sustain period that succeeds the write period. Here, when the scan pulse is applied to the first electrodes in the write period, a write auxiliary discharge of smaller magnitude than the write discharge is generated at least in a cell selected for writing or in a vicinity of the selected cell.

According to this structure, priming particles resulting from the write auxiliary discharge are generated at least in cells selected for writing or in a vicinity of the selected cells, and thus a state within these cells becomes conducive to the generation of a write discharge. Consequently, it is possible to achieve a significant reduction in the time required to generate a discharge after application of the scan and data pulses has been commenced. The chance of defective writing occurring is thus reduced and writing can be conducted effectively, even if the pulse width of the scan and data pulses is shortened.

Furthermore, since the discharge magnitude of the write auxiliary discharge is less than that of the write discharge, the write auxiliary discharge does not expand to become a write discharge. Moreover, since the luminescence levels resulting from the write auxiliary discharge are low, the write auxiliary discharge has almost no detrimental effect on contrast.

The methods given below in (1) to (4) may be used to generate the write auxiliary discharge in the write period as described above.(1) In the write period, an auxiliary pulse may be applied to third electrodes in cells other than the selected cells (i.e. the off-cells), at the same time that the scan pulse is applied to the first electrodes, the auxiliary pulse having the same polarity as the data pulse.

According to this structure, a write discharge is generated in on-cells corresponding to the first electrode to which the scan pulse is being applied, and a write auxiliary discharge is generated in the off-cells. Priming particles generated from the write discharge or the write auxiliary discharge flow into cells corresponding to the first electrode to which the scan pulse is next applied (i.e. the first electrode next in the sequence of first electrodes), and thus a state within these cells becomes conducive to the generation of a discharge.(2) In the write period, the voltage between a first electrode to which the scan pulse is being applied and a third electrode to which the data pulse is not being applied may be adjusted such that the voltage exceeds a discharge sparking voltage between the first electrode and the third electrode.

As with (1) above, according to this structure a write discharge is generated in on-cells corresponding to the first electrode to which the scan pulse is being applied, and a write auxiliary discharge is generated in the off-cells. The priming particles generated as a result of the write discharge or the write auxiliary discharge flow into the cells corresponding to the first electrode to which the scan pulse is next applied, and thus a state within these cells becomes conducive to the generation of a discharge.(3) An auxiliary discharge electrode may be provided adjacent to each first electrode in the plasma display panel, and in the write period a write auxiliary discharge may be generated between a first electrode to which the scan pulse is being applied and an auxiliary discharge electrode positioned adjacent to the first electrode.

According to this structure, in cells corresponding to the first electrode to which the scan pulse is being applied, priming particles are generated from the write auxiliary discharge occurring between the first electrode and the auxiliary discharge electrode positioned adjacent thereto, and thus a state within these cells becomes conducive to the generation of a discharge.(4) In the plasma display panel, a first auxiliary discharge electrode may be provided adjacent to each first electrode, and a second auxiliary discharge electrode may be provided adjacent to each first auxiliary discharge electrode, and in the write period the write auxiliary discharge may be generated between the first auxiliary discharge electrodes and the second auxiliary discharge electrodes.

According to this structure, a write auxiliary discharge can be generated in cells corresponding to a first electrode to which the scan pulse is being applied, and/or a write auxiliary discharge can be generated in cells corresponding to the first electrode to which the scan pulse is next applied. In either case, priming particles are generated from the write auxiliary discharge that occurs between the first and second auxiliary discharge electrodes, and thus a state within these cells becomes conducive to the generation of a discharge.

In (1) and (2) above, the generation of the write auxiliary discharge may cause a surplus or a deficiency in the amount of wall charge that accumulates on the dielectric layer over the scan electrodes. However, in (3) and (4) above, because auxiliary discharge electrodes for use in generating the write auxiliary discharge are provided in addition to the scan and data electrodes, any detrimental effect the write auxiliary discharge may have on the formation of wall charge by the write discharge is reduced. Particularly in (4), because the write auxiliary discharge is generated between the first and second auxiliary discharge electrodes, the write auxiliary discharge has very little effect on the formation of wall charge by the write discharge.

The luminescence level of the write auxiliary discharge is preferably in a range of 1/10 to 1/100 of the discharge generated during the write period in cells to be written.

Although described in detail in embodiments 1-1 to 1-5, according to a drive method and a drive circuit relating to (1) above, an auxiliary pulse is preferably applied in the write period to third electrodes in cells other than selected cells, at the same time that the scan pulse is applied to the first electrodes, the auxiliary pulse having the same polarity as the data pulse.

The auxiliary pulse may be set such that a pulse width is shorter than that of the data pulse, or such that an absolute value of the average voltage is lower than that of the data pulse. Moreover, a wave height of the auxiliary pulse may be set to be lower than that of the data pulse, or a shape of a waveform of the auxiliary pulse may be set to be one of a triangular wave and a pulse train.

When the auxiliary pulse is applied, a cell in a vicinity of the selected cell may be detected, and the auxiliary pulse may be applied selectively in the detected cell.

When the PDP is driven using a time-division gray scale display method according to which a single field has a plurality of subfields, an auxiliary write discharge may be generated in the write period of a subfield having a specific brightness weight, or it may be judged for each field whether the number of cells for illuminating within a period of the field satisfies a predetermined reference value, and the write auxiliary discharge may be selectively generated in fields judged to satisfy the predetermined reference value.

Although described in detail in embodiments 2-1 to 2-3, according to a drive method and a drive circuit relating to (2) above, a write auxiliary discharge can be generated by adjusting a voltage between a first electrode to which the scan pulse is being applied and a third electrode to which the data pulse is not being applied to exceed the discharge sparking voltage between the first electrode and the third electrode.

Here, in the write period, a first base pulse having the same polarity as the data pulse may be applied to all of the third electrodes, and the data pulse may then be applied over the first base pulse, or a second base pulse having the same polarity as the scan pulse may be applied to all of the first electrodes, and the scan pulse may then be applied over the second base pulse. Alternatively, in the write period, a wave height of the scan pulse applied to the first electrodes may be such that a voltage between a first electrode to which the scan pulse is being applied and a third electrode to which the data pulse is not being applied exceeds a discharge sparking voltage between the first electrode and the third electrode.

A voltage of the second electrodes in the write period is preferably maintained in a range that (i) allows for a write sustain discharge to be induced by the write discharge and generated between the first and second electrodes in cells in which the write discharge is generated, and (ii) prevents a write sustain discharge from being generated between first and second electrodes in cells in which the write auxiliary discharge is generated.

Although described in detail in embodiments 3-1 to 3-6, according to a drive method and a drive circuit relating to (3) above, when the scan pulse is being applied to a first electrode in the write period, a voltage applied to an auxiliary discharge electrode positioned adjacent to the first electrode is adjusted such that a voltage between the first electrode and the auxiliary discharge electrode exceeds a discharge sparking voltage.

The drive circuit may be structured by a sustain pulse generation circuit for generating a sustain pulse to be applied to the first electrodes in the sustain period; an initialization pulse generation circuit that operates using an output voltage of the sustain pulse generation circuit as a reference potential, and applies an initialization pulse to the first electrodes in an initialization period that precedes the write period; a scan pulse generation circuit that operates using an output voltage of the initialization pulse generation circuit as a reference potential, and applies a scan pulse sequentially to the first electrodes; and a discharge inducing pulse generation circuit that operates using an output voltage of one of the initialization pulse generation circuit and the sustain pulse generation circuit as a reference potential, and applies a discharge inducing pulse to the auxiliary discharge electrodes so as to generate an auxiliary discharge between the first electrodes and the auxiliary discharge electrodes.

Alternatively, the drive circuit may be structured by a sustain pulse generation circuit for generating a sustain pulse to be applied to the first electrodes in the sustain period; an initialization pulse generation circuit that operates using an output voltage of the sustain pulse generation circuit as a reference potential, and applies an initialization pulse to the first electrodes in the initialization period preceding the write period; a scan pulse generation circuit that operates using an output voltage of the initialization pulse generation circuit as a reference potential, and applies a scan pulse sequentially to the first electrodes; a second initialization pulse generation circuit that operates using the output voltage of the sustain pulse generation circuit as a reference potential, and applies to the auxiliary discharge electrodes a second initialization pulse that has a lower voltage than the initialization pulse applied to the first electrodes; and a discharge inducing pulse generation circuit that operates using an output voltage of the second initialization pulse generation circuit as a reference potential, and applies a discharge inducing pulse to the auxiliary discharge electrodes so as to generate an auxiliary discharge between the first electrodes and the auxiliary discharge electrodes.

Alternatively, the drive circuit may be structured from a sustain pulse generation circuit for generating a sustain pulse to be applied to the first electrodes in the sustain period; an initialization pulse generation circuit that operates using an output voltage of the sustain pulse generation circuit as a reference potential, and applies an initialization pulse to the first electrodes in the initialization period preceding the write period; a scan pulse generation circuit that operates using an output voltage of the initialization pulse generation circuit as a reference potential, and applies a scan pulse sequentially to the first electrodes; a discharge inducing pulse generation circuit that operates using an output voltage of the sustain pulse generation circuit as a reference potential, and applies a discharge inducing pulse to the auxiliary discharge electrodes so as to generate an auxiliary discharge between the first electrodes and the auxiliary discharge electrodes; and a second initialization pulse generation circuit that operates using the output voltage of the discharge inducing pulse generation circuit as a reference potential, and applies to the auxiliary discharge electrodes a second initialization pulse that has a lower voltage than the initialization pulse applied to the first electrodes.

In the sustain period, sustain pulses having the same waveform may be applied to the first electrodes and the auxiliary discharge electrodes, or in the initialization period preceding the write period, initialization pulses having the same waveform may be applied to the first electrodes and the auxiliary discharge electrodes.

In the initialization period preceding the write period, a potential of the auxiliary discharge electrodes may be adjusted to be lower than a potential of the first electrodes. In this case, a positive initialization pulse may be applied to the first electrodes in the initialization period and the auxiliary discharge electrodes may be maintained at a ground potential, or alternatively a positive initialization pulse may be applied to the first electrodes in the initialization period and a negative pulse may be applied to the auxiliary discharge electrodes.

In the sustain period, the auxiliary discharge electrodes may be maintained in a high impedance state, or a potential of the auxiliary discharge electrodes may be maintained in a range within which a potential of the first electrodes and second electrodes fluctuates.

In order to achieve this, the discharge inducing pulse generation circuit or the second initialization pulse generation circuit may be set such that the auxiliary discharge electrodes are maintained in a high impedance state, or such that a potential of the auxiliary discharge electrodes is maintained in a range within which a potential of the first electrodes and second electrodes fluctuates.

In the write period, the write auxiliary discharge may be generated at the same time or prior to application of the data pulse to the third electrodes being commenced. Here, application of the data pulse to the third electrodes may be commenced approximately 500 ns or less after application of the scan pulse to the first electrodes is commenced.

With respect to the panel structure, a width of a gap between a first electrode and an auxiliary discharge electrode positioned adjacent thereto may be set such that when a voltage equivalent to half or more of an amplitude of the scan pulse is applied between the first electrode and the auxiliary discharge electrode, a discharge is generated between the first electrode and the auxiliary discharge electrode.

Furthermore, the width of this gap may be such that when a voltage equivalent to an amplitude of the scan pulse is applied between the first electrode and the auxiliary discharge electrode, the voltage exceeds a discharge sparking voltage between the first electrode and the auxiliary discharge electrode.

Furthermore, the width of this gap is preferably in a range of 10 μm to 50 μm inclusive.

Furthermore, the width of this gap may be less than a width of a gap between the first electrode and a second electrode positioned adjacent thereto. A width of a gap in an electrode extension area between a first electrode and an auxiliary discharge electrode positioned adjacent thereto may be set so that a discharge is not generated in the electrode extension area when a voltage equivalent to an amplitude of the scan pulse is applied between the first electrode and the auxiliary discharge electrode. Here, the width of this gap is preferably in a range of 10 μm to 300 μm inclusive.

In a vicinity of the auxiliary discharge electrodes, a shading film is preferably formed that prevents light generating from the auxiliary discharge from reaching a panel surface.

In each cell, at least one of the first electrode and the auxiliary discharge electrode may have a projection that extends toward the other electrode.

Although described in detail in embodiments 4-1 to 4-6, according to a drive method and a drive circuit relating to (4) above, when the scan pulse is being applied to a first electrode in the write period, a volt-age between a first auxiliary discharge electrode positioned adjacent to the first electrode and a second auxiliary discharge electrode positioned adjacent to the first auxiliary discharge electrode is adjusted to exceed a discharge sparking voltage between the first and second auxiliary discharge electrodes.

The drive circuit may be structured by a sustain pulse generation circuit for generating a sustain pulse to be applied to the first electrodes in the sustain period; an initialization pulse generation circuit that operates using an output voltage of the sustain pulse generation circuit as a reference potential, and applies an initialization pulse to the first electrodes and the first auxiliary discharge electrodes in the initialization period preceding the write period; a scan pulse generation circuit that operates using an output voltage of the initialization pulse generation circuit as a reference potential, and applies a scan pulse sequentially to the first electrodes; and a discharge inducing pulse generation circuit that operates using the output voltage of one of the initialization pulse generation circuit and the sustain pulse generation circuit as a reference potential, and applies a discharge inducing pulse to the second auxiliary discharge electrodes so as to generate an auxiliary discharge between the first and second auxiliary discharge electrodes.

Alternatively, the drive circuit may be structured by a sustain pulse generation circuit for generating a sustain pulse to be applied to the first electrodes in the sustain period; an initialization pulse generation circuit that operates using an output voltage of the sustain pulse generation circuit as a reference potential, and applies an initialization pulse to the first electrodes and the first auxiliary discharge electrodes in the initialization period preceding the write period; a scan pulse generation circuit that operates using an output voltage of the initialization pulse generation circuit as a reference potential, and applies a scan pulse sequentially to the first electrodes; a second initialization pulse generation circuit that operates using the output voltage of the sustain pulse generation circuit as a reference potential, and applies to the second auxiliary discharge electrodes a second initialization pulse that has a lower voltage than the initialization pulse applied to the first electrodes; and a discharge inducing pulse generation circuit that operates using an output voltage of the second initialization pulse generation circuit as a reference potential, and applies a discharge inducing pulse to the second auxiliary discharge electrodes so as to generate an auxiliary discharge between the first and second auxiliary discharge electrodes.

Alternatively, the drive circuit may be structured by a sustain pulse generation circuit for generating a sustain pulse to be applied to the first electrodes in the sustain period; an initialization pulse generation circuit that operates using an output voltage of the sustain pulse generation circuit as a reference potential, and applies an initialization pulse to the first electrodes and the first auxiliary discharge electrodes in the initialization period preceding the write period; a scan pulse generation circuit that operates using an output voltage of the initialization pulse generation circuit as a reference potential, and applies a scan pulse sequentially to the first electrodes; a discharge inducing pulse generation circuit that operates using an output voltage of the sustain pulse generation circuit as a reference potential, and applies a discharge inducing pulse to the second auxiliary discharge electrodes so as to generate an auxiliary discharge between the first auxiliary discharge electrodes and the second auxiliary discharge electrodes; and a second initialization pulse generation circuit that operates using the output voltage of the discharge inducing pulse generation circuit as a reference potential, and applies to the second auxiliary discharge electrodes a second initialization pulse that has a lower voltage than the initialization pulse applied to the first electrodes.

Each first electrode may be connected to a first auxiliary discharge electrode positioned adjacent thereto, and sustain pulses having the same waveform may be applied to the first electrodes, the first auxiliary discharge electrodes and the second auxiliary discharge electrodes.

In the sustain period, sustain pulses having the same waveform may be applied to the first electrodes, the first auxiliary discharge electrode, and the second auxiliary discharge electrode.

In the initialization period preceding the write period, a potential of the second auxiliary discharge electrodes may be adjusted to be lower than a potential of the first auxiliary discharge electrodes.

To achieve this, in the initialization period, a positive initialization pulse may be applied to the first auxiliary discharge electrodes, and the second auxiliary discharge electrodes maybe maintained at a ground potential, or alternatively a positive initialization pulse may be applied to the first auxiliary discharge electrodes, and a negative pulse may be applied to the second auxiliary discharge electrodes.

In the sustain period, the second auxiliary discharge electrodes may be maintained in a high impedance state, or a potential of the second auxiliary discharge electrodes may be maintained in a range within which a potential of the first electrodes and second electrodes fluctuates.

To achieve this, the discharge inducing pulse generation circuit or the second initialization pulse generation circuit may be set such that the second auxiliary discharge electrodes are maintained in a high impedance state, or such that the potential of the second auxiliary discharge electrodes is maintained in a range within which a potential of the first electrodes and second electrodes fluctuates.

In the write period, the write auxiliary discharge may be generated at the same time or prior to application of the data pulse to the third electrodes being commenced, or alternatively, application of the data pulse to the third electrodes may be commenced approximately 500 ns or less after application of the scan pulse to the first electrodes is commenced.

Here, in the write period, the write auxiliary discharge may be generated between (i) a first auxiliary discharge electrode positioned adjacent to a first electrode to which the scan pulse will next be applied and (ii) a second auxiliary discharge electrode positioned adjacent to the first auxiliary discharge electrode.

In this case, each first electrode may be connected to a first auxiliary discharge electrode positioned adjacent to a first electrode to which the scan pulse is next applied, and in the write period, the same voltage waveform may be applied to (i) the first electrode to which the scan pulse is being applied and (ii) the first auxiliary discharge electrode positioned adjacent to the first electrode to which the scan pulse is next applied.

With respect to the panel structure, a width of a gap between a first auxiliary discharge electrode and a second auxiliary discharge electrode positioned adjacent thereto is set such that when a voltage equivalent to half or more of an amplitude of the scan pulse is applied between the first auxiliary discharge electrode and the second auxiliary discharge electrode, a discharge is generated between the first electrode and the auxiliary discharge electrode. Here, the preferable width of the gap is in a range of 10 μm to 50 μm inclusive.

Furthermore, a width of a gap in an electrode extension area between a first auxiliary discharge electrode and a second auxiliary discharge electrode positioned adjacent thereto may be set so that a discharge is not generated in the electrode extension area when a voltage equivalent to an amplitude of the scan pulse is applied between the first auxiliary discharge electrode and the second auxiliary discharge electrode. Here, the width of this gap is preferably in a range of 10 μm to 300 μm inclusive.

In a vicinity of the auxiliary discharge electrodes, a shading film is preferably formed that prevents light generating from the auxiliary discharge from reaching a panel surface.

In each cell, at least one of the first auxiliary discharge electrode and the second auxiliary discharge electrode may have a projection that extends toward the other electrode.

BEST MODE FOR CARRYING OUT THE INVENTION

Structure of PDP Display Device

FIG. 1shows a structure of a PDP display device according to embodiment 1-1.

The structure of the PDP display device is described below, and is substantially the same as a conventional surface discharge PDP.

As with a conventional PDP, a PDP1in the PDP display device includes a plurality of scan electrodes11extending in a horizontal direction, a plurality of sustain electrodes12extending parallel to the scan electrodes, and a plurality of data electrodes21extending orthogonally to the scan electrodes.

Although not depicted inFIG. 1, PDP1is structured by a front glass substrate and a back glass substrate that are arranged with a gap therebetween, and the gap is filled with a discharge gas so as to form a discharge space. Scan electrodes11and sustain electrodes12are provided on the facing surface of the front glass substrate, and data electrodes21are provided on the facing surface of the back glass substrate. A dielectric layer and protective layer are provided over the scan and sustain electrodes on the front glass substrate, and phosphor layers corresponding to the colors red (R), green (G), and blue (B) are provided over the data electrodes on the back glass substrate.

Furthermore, a plurality of discharge cells are formed in a matrix pattern where scan electrodes11extend across data electrodes21, and image display is achieved is achieved by varying the combination of on-states and off-states of each discharge cell.

In a method (i.e. field time-division gray scale display method) used to drive the PDP, intermediate gray scales are expressed by time dividing a single frame (i.e. TV field) into a plurality of subframes (i.e. subfields) and varying the combination of subframes.

For example, since a television image according to the NTSC standard is composed of sixty fields per second, a single TV field is set at 16.7 ms.FIG. 2shows the division of a single field to express 256 gray scales, with time represented in the lengthwise direction. As shown inFIG. 2, a single TV field is structured by eight subfields, and the ratio of luminescence periods of the subfields is 1, 2, 4, 8, 16, 32, 64, and 128, respectively. Here, by using the subfields to vary the combination of on-states and off-states of each cell, it is possible to control the luminescence periods within a single TV field of the cells using 256 gray scales.

FIG. 3shows drive waveforms generated by the above drive circuit with respect to a single subfield.

Basically, the drive method of the present embodiment is the same as a conventional method for driving a surface discharge PDP. Firstly, in an initialization period, an initialization pulse100is applied to scan electrodes11to generate an initialization discharge in all of the cells within the panel. A space charge within the entire panel is equilibrized by the initialization discharge, and wall charge, which is effective in the generation of the write discharge, is stored in a vicinity of data electrodes21.

Next, in a write period, a negative scan pulse110is applied sequentially to the scan electrodes, and at the same time a positive data pulse130is applied to the data electrodes in accordance with the display data, and as a result a write discharge is generated (i.e. writing is conducted) in cells positioned at an intersection of the scan electrodes and data electrodes to which the respective pulses are applied.

Next, in a sustain period, high voltage sustain pulses401and402are applied alternately to scan electrodes11and sustain electrodes12. This results in a discharge being repeatedly generated only in the cells in which the write discharge occurred, and image display is achieved by using the luminescence generated from this sustain discharge. Then, in an erase period that follows the sustain period, the wall charge stored on the dielectric layer as a result of the sustain discharge is erased by applying an erase pulse403to sustain electrodes12.

Drive Waveforms and Drive Circuits

A drive circuit for realizing the above waveforms will now be described.

As shown inFIG. 1, The PDP display device includes a scan pulse generation circuit50for applying a scan pulse sequentially to the plurality of scan electrodes11, an initialization/sustain pulse generation circuit60for applying an initialization pulse and a sustain pulse collectively to the plurality of scan electrodes11, a sustain/erase pulse generation circuit70for applying a sustain pulse and an erase pulse collectively to the plurality of sustain electrodes12, a data pulse generation circuit80for applying a data pulse to data electrodes21in accordance with the display data, and a pulse control circuit90for controlling the above pulse generation circuits as well as for processing the image data.

In addition to extracting image data for each field from inputted image data, producing image data for each subfield from the extracted field image data (i.e. subfield image data), and storing the produced subfield image data in frame memory, pulse control circuit90outputs data one line at a time to data pulse generation circuit80from the current subfield image data stored in frame memory. Furthermore, based, for example, on the horizontal synchronizing signal, vertical synchronizing signal and the like of the inputted image data, pulse control circuit90produces a trigger signal that indicates an application timing of the various pulses, and sends the generated trigger signal to the pulse generation circuits.

Pulse generation circuits50,60,70and80apply the various pulses to electrodes11,12and21based on the trigger signal sent from pulse control circuit90.

Scan pulse generation circuit50and initialization/sustain pulse generation circuit60are connected in a manner that allows circuit50to operate using the output of circuit60as a provisional ground level Vg, Furthermore, a power supply51, a capacitor52, a FET53and a FET54of circuit50are provided in a vicinity of circuit50.

In the write period FET53is “on” and FET54is “off”, and in the other periods FET53is “off” and FET54is “on”. Thus, power is only supplied to circuit50from power supply51during the write period.

Also, in the write period, the reference potential of scan electrodes11(i.e the reference potential at point P inFIG. 1) is maintained at a potential Vt by capacitor52, and a negative scan pulse of amplitude (Vt−Vg) is applied by circuit50with respect to this reference potential (seeFIG. 3).

Data pulse generation circuit80will be described in detail in a later section, although basically, circuit80includes a line memory81(seeFIG. 6) for temporarily storing data showing subfield image data inputted one line at a time (i.e. data that shows for each data electrode21, whether the data electrode is “on” or “off”), and functions to output a data pulse in parallel to a plurality of data electrodes21in the write period.

Operation in the Write Period

FIG. 4shows a positioning of scan electrodes11and data electrodes21in PDP1. InFIG. 4, areas marked by squares where electrodes11and21extend across each other show the discharge cells. These cells are the smallest unit of luminescence in the panel.

The plurality of scan electrodes11extending in the horizontal direction are provided in the order X0, X1, . . . , Xn−1, Xn, Xn+1 . . . from top to bottom. The plurality of data electrodes21extending in the vertical direction are provided in the order Z0, Z1, . . . , Zm−1, Zm, Zm+1 . . . from left to right.

Here, when X0, X1, . . . , Xn−1, Xn, Xn+1 . . . , and Z0, Z1, Zm−1, Zm, Zm+1 . . . are used in the description of present invention, the cell positioned where scan electrode Xn extends across data electrode Zm (i.e. the shaded cell inFIG. 4) is designated as an “on” cell, and the other cells are designated as “off” cells.

FIG. 5shows exemplary drive waveforms applied to the scan and data electrodes inFIG. 4.

As shown inFIG. 5, when a scan pulse110cis being applied to scan electrode Xn, a data pulse130is applied to data electrode Xm corresponding to the on-cell, and when scan pulses110a,110band110dare being applied respectively to scan electrodes Xn−2, Xn−1, Xn+1, a data pulse130is applied to data electrode Xm corresponding to the off-cells.

As shown inFIG. 3, sustain/erase pulse generation circuit70applies a positive sustain write pulse120of amplitude Ve to sustain electrodes12in the write period. Sustain write pulse120is applied so as to generate a write sustain discharge when the write discharge occurs, and thus to store negative wall charge on the dielectric layer over sustain electrodes12.

Here, with-respect to cells corresponding to the scan electrode to which scan pulse110is being applied, a write discharge is generated in the on-cell and a write auxiliary discharge (hereafter “auxiliary discharge”) is generated in the off-cells, the magnitude of the auxiliary discharge being insufficient for writing to occur. The write discharge induces a write sustain discharge to be generated in the on-cell, and writing is thus completed. On the other hand, even though an auxiliary discharge is generated in the off-cells, the magnitude of the auxiliary discharge is insufficient to generate a write sustain discharge.

Priming particles generated by the write discharge or the auxiliary discharge also flow into cells corresponding to scan electrode to which the scan pulse will next be applied (i.e the cells adjacent to and below the cells corresponding to a scan electrode to which the scan pulse is currently being applied).

Consequently, when the scan pulse is applied to the next scan electrode, a state of the cells corresponding to this scan electrode becomes conducive to the generation of a discharge (i.e. the priming particles that flow into these cells help to generate a write discharge), and thus a write discharge can be generated in the on-cell only a very short period after application of the scan and data pulses is commenced (i.e. this structure allows for write discharge delay to be reduced).

Thus, according to this structure, the scan and data pulses can be set to have a short pulse width (i.e. approx. 1.0 μsec), the length of the write period can be shortened in comparison to a conventional write period, and the occurrence of defective writing can be suppressed.

The following description relates to a structure of a drive circuit that conducts the driving described above by applying the data pulse and auxiliary pulse selectively to data electrodes21.

As shown inFIG. 6, in addition to a data pulse generator82for generating the data pulse, data pulse generation circuit80includes, for each data electrode, an auxiliary pulse generator83for generating an auxiliary pulse, and a switcher84for selectively operating the two pulse generators82and83(FIG. 6shows only the structure of the data electrode positioned on the far left-hand side of the panel, and the other data electrode structures have been omitted).

When corresponding data stored in a line memory81shows “on”, switcher84drives data pulse generator82in order to applied a data pulse to data electrodes21, and when corresponding data stored in line memory81shows “off”, switcher84drives auxiliary pulse generator83so as to apply an auxiliary pulse to data electrodes21.

According to the present embodiment as described above, a panel structure and basic drive method that are the same as conventional technology can be used to achieve a high quality of image display while at the same time reducing the length of the write period.

A structure of the PDP display device according to the present embodiment is the same as in embodiment 1-1.

Furthermore, the application in the write period of the auxiliary pulse to the data electrodes corresponding to the off-cells and the data pulse to the data electrodes corresponding to the on-cells is also the same as in embodiment 1-1.

In embodiment 1-1, the pulse width of the auxiliary pulse was set to be shorter than that of the data pulse. However, in the present embodiment, the average voltage absolute value of the auxiliary pulse is set to be lower than that of the data pulse. Here, the fact that the auxiliary pulse and the data pulse both have a positive polarity means that the average voltage absolute value of the auxiliary pulse is described as being set to a “lower” value than that of the data pulse.

Since the auxiliary discharge generated in off-cells corresponding to the scan electrode to which the scan pulse is being applied is smaller in magnitude than the write discharge, the same effects as in embodiment 1-1 can be achieved, even when the waveforms are regulated as described above.

Specific examples of the auxiliary pulse waveforms are shown inFIGS. 7A to 7C.

In the example shown inFIG. 7A, although the pulse width of auxiliary pulses150a,150b, . . . , is not substantially different from that of data pulse130, the wave height of the auxiliary pulses has been set so as to be shorter than that of data pulse130.

In the example shown inFIG. 7B, the waveforms of the auxiliary pulses are in the shape of triangular waves.

Having waveforms in the shape of triangular waves allows the auxiliary discharge to be generated gradually, and thus the slight luminescence that follows the auxiliary discharge can be suppressed. Any deterioration in contrast can thus be minimized.

In the example shown inFIG. 7C, the waveforms of the auxiliary pulses are in the shape of a pulse train.

Here also, having waveforms in the shape of a pulse train allows the auxiliary discharge to be generated gradually, and thus the slight luminescence that follows the auxiliary discharge can be suppressed, and any deterioration in contrast can be minimized.

In embodiment 1-1, the auxiliary pulse is applied to data electrodes corresponding to off-cells in all of the eight subfields (SF1˜SF8) structuring a single field. However, in the present embodiment, the auxiliary pulse is applied to data electrodes corresponding to the off-cells in subfields having a comparatively high brightness weight (i.e. SF1˜SF5), whereas in the write period of subfields having a comparatively low brightness weight (i.e. SF6˜SF8) only a write pulse is applied to data electrodes corresponding to off-cells (i.e. the auxiliary pulse is not applied to these data electrodes).

In other words, as shown inFIG. 8, when scan pulse110cis applied to scan electrode Xn, data pulse130is applied to data electrode Zm corresponding to the on-cell in any of subfields SF1to SF8so as to write the cell, although with respect to the off-cells, auxiliary pulses150a,150b, are only applied to data electrode Zm in subfields SF1to SF5, whereas in subfields SF6to SF8, auxiliary pulses are not applied to data electrode Zm.

According to this method of driving the panel, writing can be conducted effectively in subfields having higher brightness weights (i.e. those most visible to the human eye) even when the write period is shortened as a result of conducting the auxiliary discharge, and thus a high quality of image display without defective writing can be achieved.

On the other hand, although writing may not always be conducted effectively in subfields having a lower brightness weight due to an auxiliary discharge not being generated in these subfields, the low brightness weight of these subfields means that even if defective writing does occur, visually there will be little detrimental effect.

Furthermore, this structure allows the number of auxiliary discharges generated per field to be reduced in comparison to embodiment 1-1. Consequently, it is possible to suppress the occurrence of detrimental effects such as reductions in contrast due to auxiliary discharges, or increases in power consumption due to the increases in the frequency with which charging and discharging is conducted between the scan electrodes and data electrodes functioning as a capacitive load.

In order to realize the above drive method, data pulse generation circuit80may include a switch for turning auxiliary pulse generator83on and off. Here, the switch may be set to “on” in subfields SF1to SF5, and “off” in subfields SF6to SF8.

According to the present embodiment, when the image data of each field is comparatively bright, the auxiliary pulse is applied in the off-cells as described in embodiment 1-1 (FIG. 5), although when the image is dark, the auxiliary pulse is not applied.

Whether or not the image data in each field is bright can be judged, for example, by determining whether the total number of cells illuminated in a single field exceeds 10% of the total number of cells in PDP1. Here, the “cells illuminated in a single field” refers to the cells in all of the subfields in a single field, with the exception of the off-cells. That is, the existence of an on-cell in even one of the subfields in a field is here defined as “cells illuminated in a single field”.

The effects described below can be achieved by only generating an auxiliary discharge when the image data of the field is comparatively bright.

The effect of defective writing on an image is comparatively greater for a bright image than a dark image. Consequently, an acceptably high quality of image display can be achieved if, as in the present embodiment, defective writing is suppressed by generating an auxiliary discharge only when the image is bright.

On the other hand, generating an auxiliary discharge in the off-cells results in a faint luminescence, and this can reduce contrast. The reduction in contrast due to this faint luminescence is comparatively greater with respect to dark images. Consequently, contrast can be maintained, as in the present embodiment, by not generating an auxiliary discharge when the image is dark.

Thus, in the present embodiment, improvements in image quality can be achieved by preventing defective writing while at the same time maintaining contrast.

Furthermore, because the number of auxiliary discharges is reduced in comparison to embodiment 1-1, the present embodiment allows for power consumption to be suppressed.

A circuit for realizing the above drive method may be provided as follows.

A switch may be provided in data pulse generation circuit80for turning data pulse generator83“on” and “off”, and an on-cell counter may be provided in pulse control circuit90for counting the number of on-cells in a single field.

Here, when the total number of on-cells counted by the on-cell counter exceeds a predetermined reference value (e.g. 10% of the total number of cells in PDP1) the switch may be set to “on”, and when the number of on-cells counted by the on-cell counter is less than or equal to 10% of the total number of cells in PDP1the switch may be set to “off”.

Whereas in embodiment 1-1 an auxiliary discharge is generated in all of the off-cells in the write period, in the present embodiment an auxiliary discharge is only generated in off-cells positioned in a vicinity of the on-cells.

FIG. 9shows drive waveforms applied to each of the electrodes according to the present embodiment.

As shown inFIG. 9, scan pulses110a,10b,110cand110dare applied in order to scan electrodes Xn−2 to Xn+1, respectively.

Also, at the same time that scan pulse110cis applied, data pulse130is applied to data electrode Zm corresponding to the on-cell.

In the off-cells, on the other hand, at the same time that the scan pulse is applied, auxiliary pulse150is applied to data electrodes Zm−1, Zm and Zm+1 corresponding to off-cells positioned in a vicinity of the on-cell. However, auxiliary pulse150is not applied to data electrodes corresponding to off-cells that are not in a vicinity of the on-cell (i.e. although not depicted inFIG. 9, these are all other data electrodes apart from Zm−1, Zm and Zm+1).

Thus, even when application of the auxiliary pulse is restricted to those off-cells positioned in a vicinity of the on-cell as described above, generation of a write discharge in the on-cell is aided by the priming particles that are generated by at least one of a write discharge and an auxiliary discharge generated in cells in a vicinity of the on-cell prior to the on-cell being written. Consequently, the capacity to achieve a high quality of image display without the occurrence of defective writing is the same as in embodiment 1-1 above.

On the other hand, because an auxiliary discharge is not generated in off-cells that are not in a vicinity of on-cells due to the auxiliary pulse not being applied in these cells according to the present embodiment, the effect on contrast of the slight luminescence following the auxiliary discharge can be restricted to those cells in a vicinity of the on-cells.

Furthermore, in comparison with embodiment 1-1 in which the auxiliary discharge is generated in all of the cells, the number of cells in which the auxiliary discharge is generated is reduced in the present embodiment, and thus reductions in power consumption can also be realized.

Consideration will now be given to the method of distinguishing between “off-cells positioned in a vicinity of the on-cell” and “off-cells not positioned in a vicinity of the on-cell”.

With respect to the generation of priming particles that will assist the write discharge in the on-cell (i.e. the cell at an intersection of electrodes Xn and Zm) when the on-cell is written, the most important cell is the adjacent cell to which the scan pulse is applied immediately before the on-cell (i.e. the cell at an intersection of electrodes Xn−1 and Zm).

Thus, reference herein to “off-cells positioned in a vicinity of the on-cell” may be understood as indicating at least an off-cell positioned adjacent to and directly above an on-cell in the sequence of cells.

To give a specific example, if only the off-cell positioned adjacent to and directly above the on-cell is designated as the “off-cells positioned in a vicinity of the on-cell”, then all other off-cells may be understood as being the “off-cells not positioned in a vicinity of the on-cell”. Alternatively, if, as shown in the example inFIG. 8, the off-cells positioned around the on-cell are designated as the “off-cells positioned in a vicinity of the on-cell”, then all other off-cells may be understood as being the “off-cells not positioned in a vicinity of the on-cell”.

A circuit for realizing the above drive method may be provided as follows.

Data pulse generation circuit80as shown inFIG. 6is structured such that line memory81stores, in addition to a scan line to which the scan pulse is currently being applied, subfield information relating to a number of scan lines adjacent to the aforementioned scan line.

Furthermore, a judging unit is provided in data pulse generation circuit80for referring to line memory81in order to judge for each cell corresponding to the scan line currently being written, whether the cell is in a vicinity of an on-cell.

When the corresponding data stored in line memory81shows “on”, switcher84corresponding to each data electrode21drives data pulse generator82and a data pulse is applied to the data electrodes. On the other hand, when the corresponding data stored in line memory81shows “off”, switcher84firstly refers to the judgment conducted by the judging unit. If judged that the “cell is in a vicinity of the on-cell”, the switcher operates to drive data pulse generator82to apply an auxiliary pulse to the data electrodes, and if judged that the “cell is not in a vicinity of the on-cell”, the auxiliary pulse is not applied.

A structure of the PDP display device according to the present embodiment is the same as that shown inFIG. 1relating to embodiment 1-1.

FIG. 10Ashows drive waveforms applied to the electrodes in PDP1according to the present embodiment.

As shown inFIG. 10A, a data base pulse131is applied collectively to all of the data electrodes in the write period according to the present embodiment.

Also, scan pulse110a,110b,110cand110dare sequentially applied to scan electrodes Xn−2 to Xn+1, respectively, although when scan pulse110cis applied to scan electrode Xn, a data pulse132is applied over data base pulse131to data electrode Zm corresponding to the on-cell.

Here, a voltage of the sustain electrodes is maintained at an even rate for the duration of the write period.

FIG. 10Bshows a comparative example of the drive waveforms. Here, only data pulse130is applied to the data electrodes in the write period (i.e. data base pulse131is not applied).

FIG. 11shows the relationship of potential differences generated between the electrodes in the write period according to a drive method of present embodiment.

The setting of an amplitude of data base pulse131and a data pulse132will now be described with reference toFIG. 11.

An amplitude occurring when data pulse132is applied over data base pulse131(i.e. the combined amplitude of pulses131and132) is set such that (i) a potential difference203between a scan electrode to which scan pulse110is being applied and a data electrode to which both data base pulse131and data pulse132are being applied is high enough to generate a write discharge (i.e. much higher than a discharge sparking voltage201between the scan electrode and the data electrode), and (ii) a potential difference204between a scan electrode to which scan pulse110is being applied and a data electrode to which only data base pulse131is being applied is only slightly above discharge sparking voltage201between the scan electrode and data electrode (i.e. lower than a voltage required to generate a write discharge).

A potential difference205between the scan electrodes and sustain electrodes is set so as not to exceed a discharge sparking voltage202between the scan electrodes and sustain electrodes.

By conducting the setting as described above, the voltage applied to the data electrodes is, as shown inFIG. 10A, higher than in the comparative example inFIG. 10B. This allows the following effects to be achieved in the write period.

Since a data pulse is applied in the on-cell corresponding to the scan electrode to which the scan pulse is currently being applied, potential difference203between the scan electrode and data electrode greatly exceeds discharge sparking voltage201between the scan and data electrodes, and a write discharge is generated as a result. A write sustain discharge is then induced by the write discharge and generated, and writing is thus conducted.

On the other hand, although only the scan pulse is applied in off-cells of the cells corresponding to the scan electrode to which the scan pulse is currently being applied (i.e. the data pulse is not applied), potential difference203between the scan electrode and data electrode slightly exceeds discharge sparking voltage201between the scan and data electrodes, and an auxiliary discharge is generated as a result. Since this auxiliary discharge is weaker than the write discharge, writing does not occur, and a write sustain discharge is not induced.

Priming particles, generated by either the auxiliary discharge or the write discharge occurring in cells corresponding to the scan electrode to which the scan pulse is currently being applied, also flow into cells corresponding to the scan electrode to which the scan pulse will next be applied (i.e. cells adjacent to and sequentially below the cells corresponding to the scan electrode to which the scan pulse is currently being applied), and thus the space within these cells becomes conducive to the generation of a discharge.

Consequently, a write discharge can be generated in the on-cells only a short period after application of the scan pulse and data pulse to these cells has been commenced. Thus the occurrence of defective writing can be suppressed, even when the scan and data pulses are set to have short pulse widths (i.e. approx. 1.0 μsec). That is, a high quality of image display can be achieved while at the same time shortening the length of the write period.

To achieve a circuit structure for applying data pulse132over data base pulse131, data pulse generation circuit80shown inFIG. 1may include, in addition to a data pulse generator, a data base pulse generator for generating a data base pulse, and the data pulse and data base pulse may both be applied to the data electrodes. By applying the data pulse over the data base pulse as described above, it becomes comparatively easy to apply a high voltage to the data electrodes.

Consideration will now be given to the magnitude of the auxiliary discharge.

Whenever a scan pulse is applied to a scan electrode, luminescence results from the write discharge or auxiliary discharge that is generated. A graph210inFIG. 10Ashows the luminescence intensity when a photodiode, for example, is used to measure, through an oscilloscope, the luminescence of the discharge generated by data electrode Zm, while moving the oscilloscope down the scan electrodes sequentially.

Graph210shows slight luminescence peaks211resulting from the auxiliary discharges generated in the off-cells, and a comparatively large luminescence peak212resulting from the write discharge and write sustain discharge generated in the on-cell. Here, luminescence peaks211and212are marked inFIG. 11using the same numbering.

Although the size of luminescence peaks211and212changes with variations in the waveforms, the luminescence level ratio of peaks211to peak212is preferably set equal to or greater than 1/100 given that the sufficient generation of priming particles is effective in suppressing the occurrence of defective writing. On the other hand, if this ratio is to large, misaddressing and reductions in contrast can occur, and thus the ratio is preferably maintained at no greater than 1/10.

Here, in a graph210inFIG. 10B, which shows the luminescence intensity in the comparative example, the existence of luminescence peak212resulting from the write discharge and write sustain discharge generated in the on-cell can be observed, although because auxiliary discharges were not generated in the off-cells, no luminescence peaks211can be observed.

A structure of the PDP display device according to the present embodiment is the same as that shown inFIG. 1relating to embodiment 1-1.

FIG. 12shows drive waveforms applied to the electrodes in PDP1according to the present embodiment.

According to the present embodiment, as shown inFIG. 12, a scan base pulse111is applied continuously to all of scan electrodes11in the write period, and scan pulses122ato122dare applied sequentially to scan electrodes Xn−2, Xn−1, Xn and Xn+1 over scan base pulse111.

Here, when scan pulse112cis applied to scan electrode Xn, data pulse130is applied at the same time to data electrode Zm corresponding to the on-cell.

Furthermore, a sustain base pulse121having the same polarity as scan base pulse111is applied continuously to sustain electrodes12for the duration of the write period.

In the drive method of the present embodiment, the relationship of potential differences occurring between the various electrodes in the write period is the same as that shown inFIG. 11.

In other words, an amplitude occurring when scan pulse112is applied over scan base pulse111is set such that (i) potential difference203between a scan electrode to which both scan base pulse111and scan pulse112are being applied and a data electrode to which data base pulse130is being applied is high enough to generate a write discharge, and (ii) potential difference204between a scan electrode to which both scan base pulse111and scan pulse112are being applied and a data electrode to which data pulse130is not being applied is only slightly above the discharge sparking voltage between the scan electrode and data electrode (i.e. lower than the voltage required to generate a write discharge).

Furthermore, an amplitude of sustain base pulse121is set such that a potential difference between the sustain electrodes to which sustain base pulse121is being applied is lower than the discharge sparking voltage between scan electrodes11and sustain electrodes12.

By conducting the setting as described above, the absolute value of the voltage applied to the scan electrodes is, as shown inFIG. 12, higher than of the comparative example shown inFIG. 10B. This allows for the same effects as in embodiment 2-1 to be achieved in the write period.

In other words, since a data pulse is applied in the on-cell corresponding to the scan electrode to which the scan pulse112is currently being applied, the potential difference between the scan electrode and data electrode greatly exceeds the discharge sparking voltage between the scan and sustain electrodes, and a write discharge is generated as a result. A write sustain discharge is then induced by the write discharge and generated, and writing is thus conducted.

On the other hand, although only the scan pulse is applied in the off-cells (i.e. the data pulse is not applied), the potential difference between the scan electrode and data electrode slightly exceeds the discharge sparking voltage between the scan and sustain electrodes, and thus an auxiliary discharge is generated. This auxiliary discharge is not sufficient to induce a write sustain discharge.

Priming particles generated by either the auxiliary discharge or the write discharge occurring in cells corresponding to the scan electrode to which the scan pulse is currently being applied also flow into cells corresponding to the scan electrode to which the scan pulse will next be applied, and as a result the space within these cells becomes conducive to the generation of a discharge. Thus, the occurrence of defective writing can be suppressed, even when the scan and data pulses are set to have short pulse widths (i.e. approx. 1.0 μsec).

In order to apply scan pulse112over scan base pulse111as described above, a scan base pulse generator may be provided in initialization/sustain pulse generation circuit60(seeFIG. 1) for applying scan base pulse111, and circuit60may be structured so as to apply scan pulse112over scan base pulse111. Furthermore, in order to apply sustain base pulse121to the sustain electrodes, a sustain base pulse generator may be included in sustain/erase pulse generation circuit70.

Also, by applying the scan pulse over the scan base pulse as described above, it becomes comparatively easy to apply a high voltage to the scan electrodes.

In the present embodiment, as with embodiment 2-1, a graph210inFIG. 12shows slight luminescence peaks211resulting from the auxiliary discharges generated in the off-cells, and a comparatively large luminescence peak212resulting from the write discharge and write sustain discharge generated in the on-cell. Here again, the luminescence level ratio of peaks211to peak212is preferably set in a range of 1/100 to 1/10 inclusive.

A structure of the PDP display device according to the present embodiment is the same as that shown inFIG. 1relating to embodiment 1-1.

FIG. 13shows drive waveforms applied to the electrodes in PDP1according to the present embodiment.

A drive method in the present embodiment is basically the same as a conventional drive method, and as shown inFIG. 13, scan pulses113ato113dare applied sequentially to the scan electrodes, although when scan pulse113cis applied to scan electrode Xn, data pulse130is applied at the same time to data electrode Zm corresponding to the on-cell.

Furthermore, sustain base pulse121having the same polarity as scan base pulse111is applied to sustain electrodes12for the duration of the write period.

In the present embodiment, the amplitude of scan pulses113ato113dis, as described below, set considerably higher than that of the scan pulses in the comparative example given inFIG. 10B.

The amplitude of scan pulses113is set such that the potential difference between a scan electrode to which scan pulse113is being applied and a data electrode to which the data pulse is not being applied is higher than the discharge sparking voltage between the scan and data electrodes, and yet lower than the voltage required to generate a write sustain discharge.

The amplitude of data pulse130is set such that the potential difference between a scan electrode to which scan pulse113is being applied and a data electrode to which the data pulse is being applied allows for a write sustain discharge to be generated.

Furthermore, the amplitude of sustain base pulse121is set such that the potential difference between a scan electrode to which scan pulse113is being applied and a sustain data electrode to which the sustain base pulse is being applied is lower than the discharge sparking voltage between the scan and sustain electrodes.

By conducting the setting as described above, the relationship of potential differences occurring between the various electrodes in the write period is the same as that shown inFIG. 11.

In other words, since a data pulse is applied in the on-cell corresponding to the scan electrode to which the scan pulse113is currently being applied, the potential difference between the scan electrode and data electrode greatly exceeds the discharge sparking voltage between the scan and sustain electrodes, resulting in the generation of a write discharge, which in turn induces a write sustain discharge to be generated to conduct the writing.

On the other hand, although only the scan pulse is applied in the off-cells (i.e. data pulse not applied), the potential difference between the scan electrode and data electrode slightly exceeds the discharge sparking voltage between the scan and data electrodes, and an auxiliary discharge is generated as a result. This auxiliary discharge is not sufficient to induce a write sustain discharge.

Because a write discharge is generated in the on-cell and an auxiliary discharge that is insufficient to conduct writing is generated in the off-cells, priming particles also flow into cells corresponding to the scan electrode to which the scan pulse will next be applied. Thus, the occurrence of defective writing can be suppressed, even when the scan and data pulses are set to have short pulse widths (i.e. approx. 1.0 μsec)

In the present embodiment, as with embodiment 2-1, a graph210inFIG. 13shows slight luminescence peaks211resulting from the auxiliary discharges generated in the off-cells, and a comparatively large luminescence peak212resulting from the write discharge and write sustain discharge generated in the on-cell. Here again, the luminescence level ratio of peaks211to peak212is preferably set in a range of 1/100 to 1/10 inclusive.

Structure of the PDP Display Device

A structure of the PDP display device according to the present embodiment is substantially the same as that shown inFIG. 1relating to embodiment 1-1.

FIG. 14shows the structure of a PDP display device according to the present embodiment.

Although the structure of a PDP2in the PDP display device is the substantially the same as that of PDP1shown inFIG. 1relating to embodiment 1-1, auxiliary discharge electrodes31are provided so as to be adjacent to and parallel with scan electrodes11.

In PDP2, a front glass substrate10and back glass substrate are provided to face each other with a discharge space30existing therebetween.

On the facing surface of front glass substrate10, scan electrodes11, sustain electrodes12and auxiliary discharge electrodes31are arranged parallel to each other, and a dielectric layer14and a protective layer15are provided to cover to electrodes. Scan electrodes11are each formed from a transparent electrode layer11b, and a bus electrode layer11athat is layered over the transparent electrode layer. Sustain electrodes12are each formed from a transparent electrode layer12b, and a bus electrode layer12athat is layered over the transparent electrode layer. Auxiliary discharge electrodes31are each provided so as to be over a shading film32and adjacent to a bus electrode layer11aof a scan electrode.

The gap between each auxiliary discharge electrode31and scan electrode11is narrower than the gap between each scan electrode and sustain electrode, and is set so as to allow an auxiliary discharge to be generated when a potential difference occurs that approximates the amplitude of the scan pulse (Vt−Vg).

On the other hand, on the facing surface of the back glass substrate, data electrodes21are arranged so as to extend orthogonally across scan electrodes11, and a dielectric layer23and phosphor layers24are provided so as to cover data electrodes21.

Drive Method and Drive Circuit

FIG. 16shows drive waveforms applied to the electrodes in PDP2.

The waveforms applied to scan electrodes11, sustain electrodes12and data electrodes21are as described in embodiment 1-1, and the operation of the electrodes is the same as for the drive waveforms in a conventional three electrode AC-type surface discharge PDP.

As shown inFIG. 14, a drive circuit in the PDP display device of the present embodiment is the same as that shown inFIG. 1relating to embodiment 1-1, and auxiliary discharge electrodes31are connected to the drive circuit at point P inFIG. 14.

As described in embodiment 1-1, in the drive circuit of the present embodiment, FET53is “on” and FET54is “off” in the write period, whereas in all other periods FET53is “off” and FET54is “on”.

Consequently, an initialization pulse and a sustain pulse are applied to auxiliary discharge electrodes31from initialization/sustain pulse generation circuit60in the initialization period and sustain period, respectively, whereas in the write period a scan pulse is not applied to the auxiliary discharge electrodes.

In other words, except for the scan pulse not being applied in the write period, the waveforms applied to auxiliary discharge electrodes31are the same as the waveforms applied to scan electrodes11, with both an initialization pulse100and a sustain pulse141being applied to scan electrodes11and auxiliary discharge electrodes31.

The generation of discharges and the like within the panel during the write period will now be described with reference toFIGS. 17A to 17C.

As described in embodiment 1-1, the scan pulse has a negative polarity and an amplitude (Vt−Vg), and thus a potential difference (Vt−Vg) occurs between a scan electrode and an adjacent auxiliary discharge electrode when the scan pulse is applied to the scan electrode.

Consequently, as shown inFIG. 17A, an auxiliary discharge is generated between the scan electrode and the adjacent auxiliary discharge electrode, and as shown inFIG. 17B, space charge is generated in the discharge space of the cell in which the auxiliary discharge has occurred.

Here, the data pulse is applied to the data electrode corresponding to the on-cell at the same time that the scan pulse is applied to the scan electrode in the on-cell. Here, because of the large quantity of charged particles generated in the on-cell as a result of the auxiliary discharge described above, a write discharge is, as shown inFIG. 7C, effectively generated in the on-cell only a very short time after application of the scan and data pulses has been commenced.

On the other hand, only the scan pulse is applied in the off-cells, with the data pulse not being applied to data electrodes corresponding to the off-cells. Consequently, the potential difference between scan electrodes11and data electrodes21in the off-cells does not exceed the discharge sparking voltage between the scan and data electrodes, and thus a write discharge is not generated.

According to the drive method of the present embodiment, it is possible to generated a write discharge effectively, even when the scan pulse and data pulse are set to have a short pulse width (approx. i.e. 1.0 sec), and thus the occurrence of defective writing can be suppressed.

The gap between each auxiliary discharge electrode31and scan electrode11is preferably of a width that allows for a discharge to be generated when the potential difference between the auxiliary discharge electrode31and scan electrode11is equal to or greater than (Vt−Vg)/2. Here, the gap is preferably set in a range of 10 μm to 50 μm.

Generally, when a discharge is generated between electrodes that are positioned close together, deterioration of the film in a vicinity of the electrodes can occur as a result of ion sputtering. However, because only a small number of auxiliary discharges are generated in a single field ( 1/60 sec) according to the present embodiment, there is virtually no deterioration in the properties of protective layer15due to ion sputtering.

Furthermore, because a faint luminescence occurs as a result of the auxiliary discharge, and because the auxiliary discharge is conducted at least a few times during the display of black levels in a field, a reduction in contrast can easily occur as a result of the increased brightness of the black levels that generally occur when an auxiliary discharge is generated. However, because shading film32is formed beneath each auxiliary discharge electrode31according to the present embodiment, it is possible to suppress the reduction in contrast caused by luminescence from the auxiliary discharge.

Furthermore, because the same waveforms are applied to scan electrodes11and auxiliary discharge electrodes31in the initialization period and sustain period, initialization/sustain pulse generation circuit60can be used to apply these waveforms to both electrodes11and31. Moreover, because auxiliary discharge electrodes31are maintained at a potential Vt during the write period, there is no particular need to provide an additional drive circuit, and thus the device can be provided at a relatively low cost.

Configurations within Electrode Extension Area

The configuration of electrodes within an electrode extension area at an edge of the panel will now be described with reference toFIGS. 18A and 18B.

FIG. 18Ashows a section of PDP2that includes front glass substrate10, back glass substrate20, a sealing unit16, scan electrodes11, sustain electrodes12and auxiliary discharge electrodes31.

In the present embodiment, as shown inFIG. 18A, a gap D1between each auxiliary discharge electrode31and scan electrode11in a display area of the panel (i.e. the area within the boundary marked by sealing unit16) is set narrowly so as to facilitate the auxiliary discharge. However, this gap widens in a section of the display area near sealing unit16(i.e. the circled section inFIG. 18A), and a gap d1between the auxiliary discharge electrodes and scan electrodes in the electrode extension area (i.e. the area outside the boundary marked by sealing unit16) is set to be wider than gap D1.

Gap d1is wide enough to prevent a discharge from occurring, even when the potential difference between auxiliary discharge electrodes31and scan electrodes11approximates (Vt−Vg). Here, gap d1is preferably set to be in a range of 50 μm to 300 μm.

Consequently, it is possible to realize a structure of the panel in which an auxiliary discharge is only generated within the display area, and not between adjacent electrodes in the electrode extension area.

Furthermore, on a front glass substrate310of a conventional prior art PDP300as shown inFIG. 18B, a gap d between adjacent scan electrodes311outside of the area marked by a sealing unit316(i.e. within the electrode extension area) is made narrower than a gap D between adjacent scan electrodes311within an area marked by sealing unit316. The advantage of this structure is that a width of the flexible printed circuitry (FPC) that contacts with the electrode extension area can also be set narrowly for connecting with an external circuit.

In contrast, according to the present embodiment as shown inFIG. 18A, a gap d2between adjacent scan electrodes11in the electrode extension area is set to be equal to or greater than a gap D2between adjacent scan electrodes11within the display area. This structure has the following advantages.

In PDP2of the present embodiment, the number of auxiliary discharge electrodes31formed on the front glass substrate10is equal to the number of scan electrodes11, and as a result there are twice as many electrodes in the electrode extension area than is the case with a conventional PDP. Consequently, if the gap between scan electrodes11in the electrode extension area was set narrowly, the gap between adjacent electrodes in the electrode extension area would be considerably narrow, and thus a discharge could possibly be generated in the electrode extension area. However, by setting the gap between scan electrodes11in the electrode extension area to be equal to or greater than that in the display area, the possibility of a discharge generating in the electrode extension area can be suppressed.

FIG. 19shows a structure of a PDP display device according to the present embodiment.

The structure of a PDP2in the PDP display device is substantially the same as that shown inFIG. 14relating to embodiment 3-1.

As drive circuits, the panel includes scan pulse generation circuit50for applying a scan pulse (i.e. a negative pulse of amplitude Vt referenced on a potential Vt), a sustain pulse generation circuit61for applying a sustain pulse301, and an initialization pulse generation circuit62for applying an initialization pulse, and as a circuit for applying a pulse to auxiliary discharge electrodes31, the panel includes a discharge inducing pulse generation circuit55for generating, in the write period, a discharge inducing pulse having a regular voltage Vp.

Initialization pulse generation circuit62operates using the output of sustain pulse generation circuit61as a provisional ground level, and scan pulse generation circuit50and discharge inducing pulse generation circuit55operate using the output of initialization pulse generation circuit62as a provisional ground level.

Furthermore, as circuits for applying pulses to sustain electrodes12, the panel includes a sustain pulse generation circuit71for applying a sustain pulse, a sustain write pulse generation circuit72for applying a positive sustain write pulse120(amplitude Ve) to sustain electrodes12, and an erase pulse generation circuit73for applying an erase pulse.

Here, sustain pulse generation circuit61and initialization pulse generation circuit62are structure so as to apply sustain and initialization pulses to auxiliary discharge electrodes31as well as scan electrodes11. The use of circuits61and62to apply pulse to electrodes11and31allows costs relating to the circuitry of the panel to be reduced.

Sustain write pulse generation circuit72operates using the output of sustain pulse generation circuit71as a provisional ground level, and erase pulse generation circuit73operates using the output of sustain write pulse generation circuit72as a provisional ground level.

Here, the sustain write pulse is applied so as to generate a write sustain discharge between a scan electrode and a sustain electrode when a write discharge is generated, and thus allow for the accumulation of negative charge on the dielectric layer over the sustain electrode.

Furthermore, the panel includes a data pulse generation circuit80for applying a data pulse to data electrodes in accordance with the display data.

As with embodiment 1-1 above, these circuits are controlled by panel control circuit90.

FIG. 20shows drive waveforms applied to the electrodes in PDP2according to the present embodiment.

The drive waveforms according to the present embodiment are the same as those inFIG. 16relating to embodiment 3-1, although in comparison to embodiment 3-1 in which a voltage Vt equal to a reference voltage level of scan electrodes11is applied to auxiliary discharge electrodes31in the write period, in the present embodiment a voltage Vp applied to auxiliary discharge electrodes31in the write period is determined by the wave height of a discharge inducing pulse160generated by discharge inducing pulse generation circuit55.

Consequently, voltage Vp can be set freely by discharge inducing pulse generation circuit55, and thus it is possible to set voltage Vp to a higher value than voltage Vt.

Here, the gap between scan electrodes11and auxiliary discharge electrodes31must be set so that a potential difference Vd2(=Vp) between an auxiliary discharge electrode and a scan electrode to which the scan pulse is being applied is slightly greater than the discharge sparking voltage between the auxiliary discharge electrode and scan electrode. As such, being able to set voltage Vp to a high value allows a certain degree of freedom in the setting of the gap between the auxiliary discharge electrodes and scan electrodes.

In other words, the gap between scan electrodes11and auxiliary discharge electrodes31is set so that when the potential difference between a scan electrode and an auxiliary discharge electrode is (Vp−Vt), a discharge does not occur between the two electrodes, and when the potential difference between the scan electrode and auxiliary discharge electrode is Vd2(=Vp), a discharge does occur between the two electrodes. Consequently, setting voltage Vp to higher values allows scan electrodes11and auxiliary discharge electrodes31to be set further apart.

The generation of discharges and the like in the panel during the write period when the waveforms shown inFIG. 20are applied in PDP2is as described above in embodiment 3-1 with reference toFIG. 17. That is, an auxiliary discharge is generated between a scan electrode and auxiliary discharge electrode whenever a scan pulse is applied to the scan electrode. And as a result of the large quantity of charged particles generated by the auxiliary discharge, the time required for a write discharge to occur after the application of a data pulse has been commenced is extremely short, and the write discharge can be generated effectively.

Here, because auxiliary discharge electrodes31are provided closer to scan electrodes11than sustain electrodes12, a discharge only occurs between auxiliary discharge electrodes31and scan electrodes11, and not between auxiliary discharge electrodes31and sustain electrodes12.

Furthermore, as shown in the example inFIG. 19, although auxiliary discharge electrodes31are shown in the example inFIG. 19to be connected to each other so that the same waveforms can be applied to all of the auxiliary discharge electrodes, the same effects can be achieved by applying the same waveforms to each of the auxiliary discharge electrodes, even if the auxiliary discharge electrodes are not connected to each other.

A structure of the PDP according to the present embodiment is the same as PDP2shown in embodiment 3-2 above. The drive method is also the same as in embodiment 3-2, although in the sustain period according to the present embodiment, auxiliary discharge electrodes31may be set to a high impedance state as shown inFIG. 21or maintained at a medium potential as shown inFIG. 22.

In order to set auxiliary discharge electrodes31to a high impedance state in the sustain period as shown inFIG. 21, a switch may be provided for turning “on” and “off” the connection between discharge inducing pulse generation circuit55(see drive circuit block inFIG. 19) and the auxiliary discharge electrodes, and the switch may be set to “off” in the sustain period, and “on” in all other periods.

In embodiment 3-2, because of the large potential difference between each auxiliary discharge electrode and an adjacent sustain electrode, unnecessary discharge is generated between the auxiliary discharge electrodes and sustain electrodes in the sustain period, and this unnecessary discharge can weaken or terminate a discharge generated between scan electrodes11and sustain electrodes12. However, in the present embodiment, the occurrence of unnecessary discharge is prevented by maintaining auxiliary discharge electrodes31in a high impedance state in the sustain period.

Here, the high impedance state may be maintained with the auxiliary discharge electrodes being connected to each other, although to improve the prevention of unnecessary discharge it is preferable to disconnect auxiliary discharge electrodes in the sustain period and separately maintain each auxiliary discharge electrode in a high impedance state.

As shown inFIG. 22, on the other hand, in order to maintain auxiliary discharge electrodes31at a medium potential in the sustain period, the output of discharge inducing pulse generation circuit55may be kept at a regular level that is of the same polarity as the sustain pulse but lower in value (i.e. approx. ½ the amplitude of the sustain pulse).

In this case, the potential of all of the auxiliary discharge electrodes in the sustain period is maintained as at a level approximating the middle of the range over which the potential of scan electrodes11and sustain electrodes12fluctuates (i.e. a “medium potential”), and as result no great voltage occurs between auxiliary discharge electrodes31and adjacent sustain electrodes12. As in the high impedance example above, it is thus possible to prevent the occurrence of unnecessary discharge.

Here, the circuit structure is, as shown inFIG. 19, relatively simple, since auxiliary discharge electrodes31in PDP2are connected to one another so that they can be driven collectively by discharge inducing pulse generation circuit55.

FIG. 23shows a structure of a PDP display device according to the present embodiment.

The structure of a PDP2in the PDP display device is the same as that shown inFIG. 14relating to embodiment 3-1 above.

A structure of the drive circuits is the same as that shown inFIG. 19, although included in the structure is a second initialization pulse generation circuit63for applying a second initialization pulse101having a regular amplitude (Vs) to auxiliary discharge electrodes31in the initialization period.

The circuits are connected such that discharge inducing pulse generation circuit55operates using the output of sustain pulse generation circuit61as a provisional ground level, and second initialization pulse generation circuit63operates using the output of discharge inducing pulse generation circuit55as a provisional ground level.

FIG. 24shows drive waveforms applied to the electrodes in PDP2according to the present embodiment. The application of these waveforms will now be described with reference toFIG. 24.

The drive waveforms applied to scan electrodes11, sustain electrodes12and data electrodes21are the same as those shown inFIG. 20relating to embodiment 3-2.

On the other hand, a positive second initialization pulse101(voltage Vs) having an amplitude Vs is applied to auxiliary discharge electrodes31by second initialization pulse generation circuit63in the initialization period, and a positive sustain pulse161(voltage Vp2) having an amplitude Vp2is applied to the auxiliary discharge electrodes by discharge inducing pulse generation circuit55in the sustain period. Here, amplitude Vs of the second initialization pulse is set lower than an amplitude of the initialization pulse applied to scan electrodes11.

Consideration will now be given to the setting of voltage Vp2and the gap between scan electrodes11and auxiliary discharge electrodes31.

When, in the write period, a discharge inducing pulse is applied to auxiliary discharge electrodes31without a scan pulse being applied to scan electrodes11, a potential difference of Vd3=(potential difference resulting from charge stored in the initialization period)+(Vp2−Vt) occurs between the scan electrodes and auxiliary discharge electrodes. Furthermore, when, in the write period, a scan pulse is applied to scan electrodes11in addition to the discharge inducing pulse applied to auxiliary discharge electrodes31, a potential difference of Vd4=(potential difference resulting from charge stored in the initialization period)+Vp2occurs between the scan electrodes and auxiliary discharge electrodes.

Consequently, the value of voltage Vp2and the width of the gap between scan electrodes11and auxiliary discharge electrodes31is set so that a discharge is not generated between scan electrodes11and auxiliary discharge electrodes31at a potential difference between these electrodes of Vd3, whereas a discharge is generated between scan electrodes11and auxiliary discharge electrodes31at a potential difference between these electrodes of Vd4.

The following description relates to the generation of discharges and the like in the panel during the initialization and write periods when the drive waveforms shown inFIG. 24are applied.

In the present embodiment, the amplitude Vs of second initialization pulse101applied to auxiliary discharge electrodes31is of lower amplitude than initialization pulse100, and thus a preliminary discharge is generated between auxiliary discharge electrodes31and scan electrodes11in the initialization period (seeFIG. 25A).

As a result of this preliminary discharge, positive charge is stored on the dielectric layer above auxiliary discharge electrodes31, and negative charge is stored on the dielectric layer above scan electrodes11(seeFIG. 25B).

Next, an auxiliary discharge is generated between scan electrodes11and auxiliary discharge electrodes31in the write period when the scan pulse is applied to scan electrodes11(seeFIG. 25C), and space charge is generated in the discharge space (seeFIG. 25D).

The basic operations and effects according to this structure are the same as those in embodiment 3-2, and thus the occurrence of defective writing can be suppressed, even when the scan pulse and data pulse are set to have a short pulse width (approx. 1.0 μsec). In the present embodiment, however, it is possible to set amplitude Vp2of the discharge inducing pulse to a lower value than amplitude Vp of the discharge inducing pulse in embodiment 3-2.

In other words, a comparison of potential difference Vd4of the present embodiment with potential difference Vd2(=Vp) of embodiment 3-2 shows that both Vd4and Vd2can be viewed similarly, since both potential differences result in a voltage that only slightly exceeds the discharge sparking voltage between the scan electrodes and the auxiliary discharge electrodes. Consequently, it is possible to set amplitude Vp2of the discharge inducing pulse to a lower value than amplitude Vp of the discharge inducing pulse applied to auxiliary discharge electrodes31in embodiment 3-2.

Costs related to the circuitry can thus be reduced as a result of being able to lower the voltage resistance of the circuit elements in discharge inducing pulse generation circuit55.

Furthermore, the voltage resulting from the discharge inducing pulse applied in the write period is supplemented by the voltage generated by the charge stored in the initialization period, and thus an auxiliary discharge can be generated, even when amplitude Vp2of the discharge inducing pulse is set lower than the discharge sparking voltage between scan electrodes11and auxiliary discharge electrodes31.

Moreover, because sustain pulse generation circuit61is used to apply pulses to both scan electrodes11and auxiliary discharge electrodes31according to the present embodiment, circuitry costs can be reduced below those involved in providing separate circuits.

Variations of the Present Embodiment

As shown by the drive waveforms inFIG. 26, by setting auxiliary discharge electrodes31to a ground potential instead of applying the second initialization pulse, the same effects as described for the present embodiment can be achieved, even when the an amplitude Vp3of the discharge inducing pulse is set to a lower value than amplitude Vp2. Moreover, according to this variation, it is possible to omit second initialization pulse generation circuit63, and thus further reduce circuitry costs.

Also, the second initialization pulse applied to auxiliary discharge electrodes31need not have a positive polarity, and may be set to have a negative polarity. In this case, the amount of positive charge stored over auxiliary discharge electrodes31is further increased, and thus the same effects of the present embodiment can be achieved, even if the amplitude of the discharge inducing pulse applied to auxiliary discharge electrodes31is set still lower.

Furthermore, as described above in embodiment 3-3, by maintaining the output of second initialization pulse generation circuit63or discharge inducing pulse generation circuit55(see drive circuit block inFIG. 23) to be either (i) in a high impedance state in the sustain period, or (ii) ½ the amplitude of the sustain pulse in the sustain period, it is possible to prevent the weakening or terminating of a sustain discharge between the scan electrodes11and sustain electrodes12required for display, and it is further possible to prevent a discharge from occurring between auxiliary discharge electrodes31and sustain electrodes12.

Again, the same effects as described above for the present embodiment can be achieved, even if the positioning of second initialization pulse generation circuit63and discharge inducing pulse generation circuit55is switched so that circuit63is operated using the output of sustain pulse generation circuit61as a reference potential, and circuit55is operated using the output of circuit63as a reference potential.

FIG. 27shows drive waveforms of a PDP according to the present embodiment. These drive waveforms are substantially the same as those shown inFIG. 16, although in the present embodiment, a short delay period Td is set between the time at which application of the scan pulse is commenced and the time at which application of the data pulse is commenced.

The setting of delay period Td may be conducted by adjusting the timing at which the trigger signal is sent from panel control circuit90to data pulse generation circuit80.

Delay period Td may be set to be greater than Ons and less than or equal to 500 ns, although preferably below 300 ns. The reasons for this are as follows.

According to this structure, the auxiliary discharge is generated after a short delay from when application of the scan pulse is commenced, and the space charge resulting from this discharge recombines over time and is eliminated. Furthermore, in order to generate a fast and effective write discharge, the data pulse must be applied while there is space charge in the discharge space. Consequently, application of the data pulse is preferably conducted after the generation of space charge from the auxiliary discharge and before the space charge is eliminated. This period is in a range of 0 ns to 500 ns.

Consequently, by delaying application of the data pulse by 0 ns to 500 ns after application of the scan pulse is commenced, it is possible to further shorten the time period required for the write discharge to generate from the auxiliary discharge.

Here, the drive waveforms shown inFIG. 16relate to when delay period Td=0.

Furthermore, the same effects as described for the present embodiment can be achieved by setting delay period Td in not only embodiment 3-1 but also in embodiments 3-2 to 3-4.

In embodiments 3-1 to 3-4 relating to PDP2, an auxiliary discharge is generated between a scan electrode11and an auxiliary discharge electrode31whenever a scan pulse is applied to the scan electrode. However, in the present embodiment, as described below, it is possible to further enhance the generation of this auxiliary discharge by making some adjustments to the electrode structure of PDP2.

In the example shown inFIG. 28A, one or a plurality of ctenoid-shaped small protrusions33ais formed on auxiliary discharge electrodes31in the cells, so as to protrude toward scan electrodes11. According to this structure, the gap between auxiliary discharge electrodes31and scan electrodes11is narrowed, and this facilitates the generation of the auxiliary discharge.

In the example shown inFIG. 28B, a wide protrusion33bis formed on auxiliary discharge electrodes31in the cells, so as to protrude toward scan electrodes11. According to this structure, in addition to the gap between auxiliary discharge electrodes31and scan electrodes11being narrowed, the resistance value of auxiliary discharge electrodes31is reduced, and this prevents a reduction in voltage when a discharge is generated, in addition to facilitating the generation of an auxiliary discharge.

In the example shown inFIG. 28C, one or a plurality of T-shaped protrusions33cis formed on auxiliary discharge electrodes31in the cells, so as to protrude toward scan electrodes11.

And in the example shown inFIG. 28D, one or a plurality of L-shaped protrusions33cis formed on auxiliary discharge electrodes31in the cells, so as to protrude toward scan electrodes11. According to these structures, in addition to the auxiliary discharge being facilitated by the narrowing of the gap between auxiliary discharge electrodes31and scan electrodes11, it is possible to prevent the electrodes from burning out due to the flow of excess voltage current.

In comparison with the T-shaped protrusions33cinFIG. 28C, which each have two end parts (i.e. the circled parts inFIG. 28C), the L-shaped protrusions33dinFIG. 28Deach have only one end part. Here, it is relatively easy for the end parts of electrodes formed on a substrate to become detached from the substrate. As such, there is less chance of the end parts of the L-shaped protrusions from becoming detached.

Here, in the examples shownFIGS. 28A to 28D, protrusions33ato33dare formed on auxiliary discharge electrodes31. However, the same effects can be achieved, even if protrusions33ato33dare formed on scan electrodes11as shown inFIGS. 28E to 28H.

Structure of PDP Display Device

FIG. 29shows a structure of a PDP display device according to the present embodiment.FIG. 30is a structural cross-sectional diagram along a B˜B axis of a PDP3shown inFIG. 29.

The structure of PDP3in the PDP display device is the same as PDP2shown inFIG. 14, although in comparison with PDP2in which auxiliary discharge electrodes31are provided adjacent to scan electrodes11so that an auxiliary discharge may be generated between scan electrodes and adjacent auxiliary discharge electrodes, in PDP3of the present embodiment, a pair of auxiliary discharge electrodes (i.e. a first auxiliary discharge electrode41and a second auxiliary discharge electrode42) are arranged adjacent to each scan electrode11, the auxiliary discharge electrodes are provided over a shading film43, and the auxiliary discharge is generated between the auxiliary discharge electrodes41and42in each pair.

In order to generate an auxiliary discharge between first and second auxiliary discharge electrodes41and42, the gap between electrodes41and42is set so that a small discharge is generated at a potential difference of approximately (Vt−Vg). Here, this gap is preferably set at a width that allows a discharge to be generated when the aforementioned potential difference is greater than or equal to (Vt−Vg)/2. In numerical terms this equates to a gap in a range of 10 μm to 50 μm.

Furthermore, as shown inFIG. 29, each first auxiliary discharge electrode41is connected to an adjacent scan electrode11, and second auxiliary discharge electrodes42are connected to each other at point P inFIG. 29.

The drive circuit structure according to the present embodiment is identical to that described in embodiment 3-1 with reference toFIG. 14, and thus there is no increase in circuitry related costs according to the present embodiment.

Drive Waveforms and Drive Circuits

FIG. 31shows drive waveforms applied to the electrodes in PDP3.

The drive waveforms applied to scan electrodes11, sustain electrodes12and data electrodes21are the same as those shown inFIG. 16relating to embodiment 3-1, and the operation of PDP3is basically the same as for drive waveforms in a conventional three electrode AC-type surface discharge PDP. Also, the drive waveforms applied to second auxiliary discharge electrodes42are the same as those applied to auxiliary discharge electrodes31as described in embodiment 3-1 with reference toFIG. 16.

Furthermore, the drive waveforms applied to each first auxiliary discharge electrode41are the same as those applied to scan electrodes11positioned adjacent thereto. Here, with respect to first auxiliary discharge electrodes41,FIG. 31only shows the drive waveform applied to the first auxiliary discharge electrode positioned adjacent to scan electrode Xn.

The generation of discharges and the like in the panel during the write period will now be described with reference toFIGS. 32A to 32C.

Since the scan pulse has a negative polarity and an amplitude (Vt−Vg), a potential difference (Vt−Vg) occurs between first auxiliary discharge electrodes41and second auxiliary discharge electrodes42when the scan pulse is applied to scan electrodes11. Consequently, as shown inFIG. 32A, an auxiliary discharge is generated between the first and second auxiliary discharge electrodes whenever the scan pulse is applied to the scan electrodes. And as shown inFIG. 32B, space charge is generated in the discharge space as a result of the auxiliary discharge.

On the other hand, a data pulse is applied to the data electrode corresponding to the on-cell whenever the scan pulse is applied to the scan electrode in the on-cell. Because of the large amount of space charge existing in the on-cell as a result of the auxiliary discharge, a write discharge is generated quickly and effectively. Thus, it is possible to generate a write discharge effectively, even when the scan pulse is set to have a short pulse width (i.e. approx. 1.0 μsec).

Furthermore, as described above in embodiment 3-1, because the number of auxiliary discharges that are generated is not great, there is no deterioration in the properties of protective layer15caused by ion sputtering. Moreover, because a shading film is formed beneath each pair of first and second auxiliary discharge electrodes41and42, it is possible to suppress reductions in contrast caused by the auxiliary discharge.

In addition to the effect achievable by embodiment 3-1 above, the present embodiment can achieve the following.

In embodiment 3-1, because an auxiliary discharge is generated between auxiliary discharge electrodes31and scan electrodes11, either excess or insufficient amounts of wall charge may be stored on the surface of the dielectric layer over scan electrodes11, and this may result in defective illumination, such as off-cells being illuminated or on-cells not being illuminated in the sustain period.

However, in the present embodiment, because the auxiliary discharge is generated between the first and second auxiliary discharge electrodes41and42(i.e. electrodes other than scan electrodes11), the auxiliary discharge has virtually no effect on the formation of wall charge on the dielectric layer over scan electrodes11. This means that prior art drive technology for a conventional three electrode AC-type surface discharge PDP can be used without modification to conduct the basic driving of scan electrodes11, sustain electrodes12and data electrodes21.

Here, as shown in the example inFIG. 30, first and second auxiliary discharge electrodes41and42in PDP3are formed directly over shading film43, and these electrodes are covered with dielectric layer14and protective layer15. However, as shown inFIG. 33, dielectric layer14and protective layer15may be formed over shading film43, and first and second auxiliary discharge electrodes41and42may then be formed on top of layers14and15. In this case, the auxiliary discharge can still be generated as described above, even though first and second auxiliary discharge electrodes41and42face directly into the discharge space.

Furthermore, because the number of auxiliary discharges that are generated is not great, there is no deterioration of the properties of first and second auxiliary discharge electrodes41and42due to ion sputtering. Moreover, because a shading layer is formed beneath electrodes41and42, it is possible to suppress the reductions in contrast caused by the auxiliary discharge.

Configurations within Electrode Extension Area

The configuration of electrodes within the electrode extension area will now be described with reference toFIG. 34.

In PDP3of the present embodiment, the number of first auxiliary discharge electrodes41and second auxiliary discharge electrodes42formed on the front glass substrate10is each equal to the number of scan electrodes11, and thus the number of electrodes increases two-fold over the number of scan electrodes in a conventional PDP.

If, for example, scan electrodes11and first and second auxiliary discharge electrodes41and42were extended to an area outside of sealing unit16, the number of electrodes in the electrode extension area would be 1.5 times that of embodiment 3-1 (or 3 times that of a conventional PDP), and connecting each of the electrodes in the electrode extension area to the FPC would be difficult.

However, in the present embodiment, first auxiliary discharge electrodes41are connected to adjacent scan electrodes11within the area marked by sealing unit16(i.e. electrodes41are not extended), and thus the number of electrodes that are extended beyond the area marked by sealing unit16is restricted to the same as that in embodiment 3-1.

Consequently, by setting the gap between scan electrodes11in the electrode extension area to be greater than or equal to the equivalent gap in the display area (i.e. the same as in embodiment 3-1), it is possible to prevent a discharge from being generated in the electrode extension area.

Furthermore, as in embodiment 3-1, the gap between the first and second auxiliary discharge electrodes in each pair widens in a section of the display area near sealing unit16(i.e. the circled section inFIG. 34), and the gap between these electrodes in the electrode extension area is set to be wide.

Specifically, by setting the gap between first and second auxiliary discharge electrodes41and42in the electrode extension area at a width (preferably in a range of approx. 50 μm to 300 μm) that does not allow a discharge to generate even at a potential difference of approximately (Vt−Vg), it is possible to prevent a discharge from occur-ring between the first and second auxiliary discharge electrodes in the electrode extension area.

FIG. 35shows a PDP display device according to the present embodiment. The structure of a PDP3in the PDP display device is the same as that shown inFIG. 29relating to embodiment 4-1.

Since the drive circuitry is the same as that in embodiment 3-2, a detailed description will not be given here, although to apply pulses to scan electrodes11and first auxiliary discharge electrodes41, the panel includes scan pulse generation circuit50for applying a scan pulse (i.e. a negative pulse of amplitude Vt referenced on a potential Vt), sustain pulse generation circuit61for applying a sustain pulse, and initialization pulse generation circuit62for applying an initialization pulse. Furthermore, to apply pulses to second auxiliary discharge electrodes41, the panel includes discharge inducing pulse generation circuit55for generating, in the write period, a discharge inducing pulse having a regular voltage Vp, and to apply pulses to sustain electrodes12, the panel includes a sustain pulse generation circuit71for applying a sustain pulse, a sustain write pulse generation circuit72for applying a positive sustain write pulse120(amplitude Ve) to sustain electrodes12, and an erase pulse generation circuit73for applying an erase pulse to sustain electrodes12.

FIG. 36shows drive waveforms applied to the electrodes in PDP3. Although these drive waveforms are substantially the same as those shown inFIG. 31relating to embodiment 4-1, in the present embodiment it is possible for discharge inducing pulse generation circuit55to adjust voltage Vp applied to second auxiliary discharge electrodes42in the write period independently of voltage Vt, and thus voltage Vp can be set to a high value.

The value of voltage Vp and the width of the gap between first and second auxiliary discharge electrodes41and42are set so that (i) a potential difference between a first and second auxiliary discharge electrode positioned adjacent to a scan electrode to which a scan pulse is being applied only slightly exceeds the discharge sparking voltage between electrodes41and42, (ii) a discharge is not generated between electrodes41and42when the potential difference between these electrodes is (Vp−Vt), and (iii) a discharge is generated between electrodes41and42at a potential difference Vp.

Here, because voltage Vp is set at a high value in the present embodiment, it is possible to set the gap between the first and second auxiliary discharge electrodes in each pair to be wider than was possible in embodiment 4-1.

The generation of discharges and the like when the waveforms shown inFIG. 36are applied in PDP3is the same as described in embodiment 4-1 with reference toFIG. 32, and thus an auxiliary discharge is generated between first and second auxiliary discharge electrodes41and42whenever a scan pulse is applied. Consequently, due to the large quantity of charged particles generated from the auxiliary discharge, a write discharge occurs only an extremely short period after application of the data pulse has been commenced, and the write discharge can be generated effectively.

Furthermore, because the auxiliary discharge is generated between the first and second auxiliary discharge electrodes, there is virtually no effect on the formation of wall charge on the dielectric layer over scan electrodes11. There is also no deterioration of the properties of dielectric layer15due to ion sputtering, and reductions in contrast caused by the auxiliary discharge are suppressed by shading film43. Moreover, because the sustain pulse generation circuit is used to apply pulses to both the scan electrodes and the first auxiliary discharge electrodes, costs related to the circuitry can be reduced. These effects are the same as those described in embodiment 4-1.

The present embodiment is basically the same as embodiment 4-2, although the present embodiment differs in that, as shown inFIG. 37, the second auxiliary discharge electrodes are maintained in a high impedance state in the sustain period, or as shown inFIG. 38, the output of discharge inducing pulse generation circuit55is maintained at approximately½ the sustain pulse amplitude in order to maintain the second auxiliary discharge electrodes at a potential that is intermediate with respect to the potential of scan electrodes 11 and sustain electrodes 12.

The method of maintaining second auxiliary discharge electrodes42in a high impedance state is the same as that described in embodiment 3-3 above.

The effects are also the same as those described in embodiment 3-3. Thus, in comparison to embodiment 4-1 in which the large potential difference between second auxiliary discharge electrodes42and sustain electrodes12in the sustain period may cause an unnecessary discharge between these electrodes and thus a weakening or terminating of the sustain discharge between scan electrodes11and sustain electrodes12, in the present embodiment these detrimental effects can be prevented.

Here, the structure of the circuits when second auxiliary discharge electrodes42are kept at a medium potential may be simplified by connecting electrodes42to one another and driving them collectively.

FIG. 39shows a structure of a PDP display device according to the present embodiment. The structure of a PDP3in the PDP display device is the same as that described in embodiment 4-1.

The circuitry structure of PDP3is the same as that shown inFIG. 23relating to embodiment 3-4. That is, a drive circuit of the present embodiment is the same as that shown inFIG. 35, although a second initialization pulse generation circuit is included for applying a pulse having a regular voltage Vs to second auxiliary discharge electrodes42in the initialization period.

The drive waveforms applied to the electrodes are the same as those shown inFIG. 40, and thus the drive waveforms applied to scan electrodes11, sustain electrodes12and data electrodes21are the same as the drive waveforms for a prior art three electrode AC-type surface discharge PDP.

In the initialization period, a second initialization pulse (voltage Vs) having an amplitude Vs (i.e. having an amplitude set lower than an amplitude of the initialization pulse applied to scan electrodes11) is applied to second auxiliary discharge electrodes42, and in the write period a discharge inducing pulse (voltage Vp2) having an amplitude Vp2is applied to electrodes42.

The generation of discharges and the like when the drive waveforms shown inFIG. 40are applied in the panel will now be described.

The drive waveforms applied to scan electrodes11, sustain electrodes12and data electrodes21are the same as those shown inFIG. 36, and the basic operation is also the same as that of embodiment 4-2. However, in the present embodiment, a second initialization pulse having an amplitude Vs (i.e. lower than an amplitude of initialization pulse) is applied to second auxiliary discharge electrodes42in the initialization period, and this results in a discharge903being generated between the second auxiliary discharge electrodes and the first auxiliary discharge electrodes (FIG. 41A).

As a result of this discharge, positive charge is stored on the dielectric layer above second auxiliary discharge electrodes42, and negative charge is stored on the dielectric layer above first auxiliary discharge electrodes41(FIG. 41B).

Next, when in the write period a discharge inducing pulse is applied to second auxiliary discharge electrodes42without a scan pulse being applied to scan electrodes11, a potential difference Vd3=(potential difference resulting from charge stored in initialization period)+(Vp2−Vt) occurs between the first and second auxiliary discharge electrodes.

Furthermore, when in the write period a scan pulse is applied to scan electrodes11together with the application of the discharge inducing pulse to second auxiliary discharge electrodes42, a potential difference Vd4=(potential difference resulting from charge stored in initialization period)+Vp2occurs between the first and second auxiliary discharge electrodes.

Here, an auxiliary discharge is generated between the first and second auxiliary discharge electrodes whenever the scan pulse is applied. Space charge is generated in the discharge space following this auxiliary discharge (FIG. 41D) Consequently, the time required for a write discharge to generate (FIG. 41E) in the on-cell after application of the data pulse is commenced can be greatly reduced in comparison to the prior art, and the write discharge can be generated effectively.

In the present embodiment, the value of voltage Vp2and the width of the gap between a first and second auxiliary discharge electrodes in each pair is set so that a discharge is not generated between the first and second auxiliary discharge electrodes when the potential difference between these electrodes is Vd3, and so that a discharge is generated between the first and second auxiliary discharge electrodes when the potential difference between these electrodes is Vd4.

Here, a comparison of potential difference Vd4in the present embodiment with potential difference Vd2in embodiment 4-2 shows that because both Vd2and Vd4result in a voltage that slightly exceeds the discharge sparking voltage between the first and second auxiliary discharge electrodes, it is possible to set voltage Vp2to a lower value than voltage Vp. Thus circuitry costs can be reduced as a result of being able to lower the resistance voltage of circuit elements in discharge inducing pulse generation circuit55.

Variations of the Present Embodiment

Even if the second initialization pulse is not applied to second auxiliary discharge electrodes42, the same effects can be achieved by setting second auxiliary discharge electrodes42to a ground potential in the initialization period. This structure allows for second initialization pulse generation circuit63to be omitted, and thus for circuitry costs to be further reduced.

Also, the second initialization pulse (amplitude Vs) applied to second auxiliary discharge electrodes42need not be of positive polarity. For example, if the second initialization pulse is of negative polarity, then the amount of positive charge stored over second auxiliary discharge electrodes42is further increased, and this allows for further reductions in amplitude Vp2of the discharge inducing pulse applied to second auxiliary discharge electrodes42.

As described in embodiment 4-3 above, by maintaining the output of second initialization pulse generation circuit63or discharge inducing pulse generation circuit55(see drive circuit block inFIG. 39) either in a high impedance state in the sustain period or at approximately ½ the sustain pulse amplitude in the sustain period, it is possible to prevent the weakening or terminating of the sustain discharge generated between the scan electrodes and sustain electrodes required for image display.

Here, in the example shown inFIG. 39, all of the second auxiliary discharge electrodes are connected to one another, although even if they are not all connected, the same effects can be achieved by applying the same drive waveforms to all of the second auxiliary discharge electrodes.

FIG. 42shows a structure of a PDP display device according to the present embodiment.

The structure of a PDP4in the PDP display device is the same as that of PDP3in embodiment 4-2 above, although in comparison to PDP3of embodiment 4-2 in which each first auxiliary discharge electrode41is connected to an adjacent scan electrode11, in PDP4of the present embodiment as shown inFIG. 42, each first auxiliary discharge electrode is connected to the scan electrode positioned in the next line.

Furthermore, the structure of the drive circuits is as described in embodiment 4-2, and the drive waveforms applied to electrodes11,12,21and41are the same as those shown inFIG. 36.

In the present embodiment, when a scan pulse is applied to scan electrode Xn, the same pulse is applied to a first auxiliary discharge electrode positioned adjacent to scan electrode Xn+1 (i.e. the scan electrode subsequent to scan electrode Xn), and an auxiliary discharge is generated between this first auxiliary discharge electrode and a second auxiliary discharge electrode positioned adjacent thereto. In other words, at the same time that the scan pulse is applied to scan electrode Xn, an auxiliary discharge is generated in the on-cell during a period equivalent to one line of writing prior to the data pulse being applied to data electrode Zm in the on-cell.

Consequently, the application of scan and data pulses in order to write the on-cell is conducted with space charge from the auxiliary discharge (i.e. generated one line of writing earlier) having been sufficiently dispersed throughout the discharge space of the on-cell. Thus it is possible to further enhance the reductions in time required for a discharge to be sparked from the auxiliary discharge.

Here, the descriptions given in embodiment 4-3 in relation to maintaining a high impedance state (FIG. 37) and a medium potential (FIG. 38), and the description given in embodiment 4-4 in relation to a potential of the pulse applied to second auxiliary discharge electrodes42in the initialization period (FIG. 40, etc) can be applied equally to the PDP display device of the present embodiment.

As shown inFIGS. 43A to 43H, the generation of the auxiliary discharge can be facilitated by providing protrusions44ato44don first auxiliary discharge electrodes41or by providing protrusions45ato45don second auxiliary discharge electrodes42in the PDP display devices described in embodiments 4-1 to 4-5 above.

Here, the shape of protrusions44ato44dand protrusions45ato45dshown inFIGS. 43A to 43Hhave the same characteristics as protrusions33ato33dand protrusions13ato13dshown inFIGS. 28A to 43H, respectively, and the effects of these configurations is also respectively the same.

Related Matters

The setting of delay period Td as described in embodiment 3-5 can be applied equally to embodiments 4-1, 4-2, 4-3 and 4-4, and as described above, it is possible to further enhance the reductions in time required for a discharge to be sparked from the auxiliary discharge.

Although the above embodiments are described in terms of each subfield being provided with an initialization period in which an initialization pulse is applied, it is not necessary to provide an initialization period in each subfield. For example, the present invention may be realized by only providing an initialization period at the head of each field.

Furthermore, the initialization period is not always required, and the present invention may be realized by structuring each subfield from only a write period and a sustain period.

Furthermore, although the erase pulse is applied to sustain electrodes12in the above embodiments, the erase pulse may be applied to scan electrodes11.

INDUSTRIAL APPLICABILITY

The PDP of the present invention is applicable in display devices of computers, televisions, and the like, and is particularly applicable in large-screen display devices that conduct high definition image display.