DRIVING A GAS DISCHARGE DISPLAY DEVICE

Abstract: In a method of driving a gas discharge display device having two parallel-electrode arrays, the respective arrays being on opposite walls separated by a gas filled space and being oriented mutually transversely to form discharge cells at the crossing points of the electrodes of the arrays, a write signal (2, 12) is applied to a selected electrode (Y j ) of one array to discharge all cells (C ij ) formed along that electrode, and then an erase signal (3, 13) is applied to that selected electrode (Y j ) and cancelling signals (6, 16) are applied coincidentally to selected electrodes (X i ) only of the other array. Thus the erase signals (3, 13) as applied to (3, 13) to cells located where the selected electrodes of the two arrays cross are cancelled to prevent erasure of discharges at those cells to selectively display information on the device.

Description: The present invention relates to a method of driving a gas discharge display device. For instance, it relates to a method of driving an AC driven plasma display panel. A typical gas discharge display device or gas discharge panel is a PDP (Plasma Display Panel) wherein arrays of parallel conductors, X-electrodes and Y-electrodes, arranged transversely of one another, are disposed on opposite sides of the gas filled panel. The electrodes are insulated from direct contact with the gas by dielectric layers. The PDP has a matrix type arrangement of individual discharge sites (cells) located at points of the PDP where X and Y-electrodes cross each other. The discharge cells are selectively fired - placed in a discharging condition - by application of write signals, to provide cell potentials exceeding a firing potential for gas discharge of a cell. Sustain pulse signals, lower than the firing potential, can sustain the discharge of a fired cell by means of the sum of the sustain signals and a wall potential induced on surfaces at the cell. Light emitted from the selectively fired cells forms a desired display. A fired cell (a cell in a discharging condition) is erased by applying an erasing signal, a narrow pulse having the same peak voltage as that of a sustain signal, and neutralising wall potential to prevent subsequent discharge of the cell. Various methods of driving PDP's have been proposed. For example, there has been proposed a method in which addressing of a cell is performed by applying simultaneously half values of a write (or erase) signal voltage to the X- and Y-electrodes associated with the cell. This "half-selection" method requires complicated drive systems for both X- and Y-electrodes and tends to induce misfirings. A previously proposed method not adopting the "half-selection" method still requires a complicated drive circuit for addressing and requires various power sources, and hence relatively expensive drive circuitry. In addition, the voltages of applied signals are rather high. For example, the peak voltages of a write signal, a sustain signal and an erase signal are respectively 140 V, 90 V and 90 V. Great efforts have been made to reduce the number of the power sources and to reduce the peak voltages of the applied signals, to reduce the cost of the drive circuitry. Particularly, sufficient reduction in the peak voltages of the applied signals will allow the use of elements such as transistors having relatively low breakdown voltages, resulting in a substantial cost reduction when semiconductor integrated circuits are used. An example of a previously proposed drive method will now be described. Waveforms of signals employed in this method are illustrated in time charts (a) to (f) of Fig.1. The signal waveforms are all basically rectangular. A diagonal line across a rectangular signal in Fig.1 indicates that the signal is selectively applied. The potential applied to a cell C ij of a PDP (hereinafter referred as a cell potential) is the potential difference between signals applied to the associated electrodes, the X i -electrode and the Y j -electrode, from external drive circuits. In this case, a write signal 52 of approximately 140 V, an erase signal 53 of approximately 90 V having a narrow pulse width, and repeating sustain signals 51 of approximately 90 V are applied with the same polarity to the Y j -electrode of the PDP. Throughout this specification referred-to voltage values of (pulse) signals are peak voltages of the signals concerned. To the X i -electrode, a cancelling pulse 55, for cancelling a write signal, of approximately 90 V, a preparatory converting signal 56 of approximately 90 V, and repeating sustain signals 54 of approximately 90 V are applied. A process for erasing an arbitrary cell, using a pair of signals consisting of a preparatory signal and a subsequent erase signal, is described in U.S. patent 3,771,016, published on Nov.6, 1973, by TOBA et al. A process for writing or non-writing of an arbitrary cell employs a combination of a write signal and the absence or presence of a cancelling signal applied to respective Y- and X-electrodes simultaneously. Operations of a cell driven by signals as mentioned above are described below with reference to Fig.1. When a cell C ij is selected to fire (to be written), a write signal 52 of 140V is applied to the Y j- electrode, as shown in Fig.1 (a) and no signal is applied to the X i -electrode, as shown in Fig.1(b), providing the cell with a cell potential 52 of 140 V as shown in Fig.1(c) to fire the cell. The cell discharge is sustained by the subsequent application of alternating sustain signals 51 and 54 until an erasing process is applied to the cell C ij . When the cell C ij is not to be fired, a cancelling pulse 55 of 90 V (shown in broken lines in Fig.1(b)), for cancelling the write signal 52, is applied to the X-electrode, reducing the applied voltage of 140 V to (a cell potential of) 50 V (as shown by a broken line in Fig.1(c) as a pulse 55 ), much lower than the firing voltage of the cell C ij . When the cell C ij has already been fired and is to be erased, a preparatory converting signal 56 of 90 V is applied in advance to the X i -electrode as shown in Fig.1(e), converting the polarity of the wall potential at the cell, and is followed by the application of an erase signal 53 to the Y j -electrode as shown in Fig.1(d), resulting in cell potential as shown in Fig.1(f) and erasure of the cell (the discharge in the cell). As described above, drive systems for driving Y-electrodes and X-electrodes are required to output selectively the voltages 90 V to 140 V and 90 V respectively. These voltages are rather high, resulting in an increase in the cost of drive circuits wherein many transistors and other elements having high breakdown voltage are required. Furthermore, there is an inherent problem related to fluctuation of gas discharge characteristics of cells of a PDP, arising from various electrical and physical conditions of the cells. Particularly, delay of initiation of a cell discharge tends to fluctuate from cell to cell. On the other hand, delay to erasure of gas discharges of cells is quite short such as 1 µ second. Utilizing these characteristics, a method of driving a PDP was disclosed in Japanese Patent SHO-49-38848, by UMEDA and TOBA, published on October 21, 1974. In this method all the cells located on a row or a column (herein an X-electrode or a Y-electrode) are first fired simultaneously and immediately afterwards, cells not to be fired are selectively erased by erase signals. This method can overcome the problem of non-uniformity of gas discharge characteristics of cells in a PDP, increasing the voltage margin of each signal. US-A-4 097 856, a write signal is applied to all cells via a vertical (V) line, and simultaneously an erasing signal is applied to a horizontal (H) line corresponding to a cell (along the V line) which is not to be written. Thus, only cells selected by not having the erasing signal applied thereto are discharged. In more detail, referring to an example given in US-A-4 097 856, cells are formed where lines V1 to V5 intersect lines H1 to H7. Lines V1 to V5 have write signals applied thereto in sequence, at successive times. At V1 time (see US-A-4 097 856, Col. 4, line 27) the write signal is applied, through V1, to all cells at the intersections of V1 and H1 to H7. H1 to H7 have only ground potential applied thereto, so all those cells are written. At V2 time the write signal is applied to all the cells at the intersections of V2 and H1 to H7. H1, H4, and H7 are not "selected" and have therefore only ground potential applied thereto, and so are written. H2, H3, H5 and H6, however, are "selected" and have a pulse equal in amplitude to the write signal applied thereto, acting as an erasing signal which effectively cancels the write signal applied to V2, so that the cells at the intersections of H2, H3, H5 and H6 with V2 are not written. According to the present invention there is provided a method of driving a gas discharge display device, which device has an array of first electrodes and an array of second electrodes, with a gas discharge space between the arrays and with the first electrodes crossing the second electrodes to form a matrix arrangement of gas discharge cells corresponding to respective crossing points of the electrodes, characterized by selecting a first electrode and applying a write signal, to the selected first electrode, capable of establishing a discharging condition in gas discharge cells formed along the selected first electrode, thereafter applying an erase signal to the selected first electrode, and simultaneously applying a cancelling signal to each selected second electrode, whereby in respect of each cell located at the crossing point of said selected first electrode and a non-selected second electrode, to which such a cancelling signal is not applied, the erase signal is effective to destroy a discharging condition previously established in the cell so that discharges no longer take place in the cell, and whereby in respect of each cell located at the crossing point of said selected first electrode and a selected second electrode the effect of the erase signal is cancelled and the cell remains in a discharging condition previously established by the application of the write signal, discharges in the cell being sustained by subsequent application of sustain signals to the cell. An embodiment of the present invention can provide a low cost drive method for a plasma display panel. An embodiment of the present invention can provide that a drive circuit for addressing cells of a PDP may employ low signal voltages, allowing the use of low voltage breakdown elements such as transistors to reduce the cost of the drive circuit. An embodiment of the present invention can provide a drive method affording more stable PDP operation, permitting a higher voltage margin. An embodiment of the present invention provides a method of driving an AC driven PDP in which selective erasure of a fired cell is achieved using a cancelling signal with a low peak voltage. In an embodiment of the present invention all the cells on a row, along a Y-electrode for example, are fired simultaneously first by applying a write signal to the Y-electrode, to prevent misfiring or failed firing. This step is followed by application of an erase signal to the same Y-electrode. In coincidence with the application of the erase signal to the Y-electrode, cancelling pulses are applied to X-electrodes associated with cells (along the Y-electrode) selected to be illuminated, reducing the effect of the erase signal on the cell potential at those cells to a value less than that of the full erase signal voltage. As the result, the erase signals loose their erasing function, failing to erase the cells concerned. In respect of non-selected cells along the Y-electrode (cells to be extinguished) no cancelling pulses for the erase signal are applied to the associated X-electrodes, causing the erase signal applied to the Y-electrode to be kept "alive" and resulting in erasing of the non-selected cells. Thus, the selected cells are illuminated to display a required pattern on the panel. Essentially, gas discharge of a cell is maintained as long as the actual discharge voltage applied to the cell exceeds the firing voltage of the gas discharge. The inventors have had the insight that an erasing signal as effective at a selected cell need not be cancelled entirely ; that is, the (effect of the erase signal on) cell potential need not be reduced to 0 V. The actual discharge voltage applied to a cell is the sum of the wall potential and the cell potential. If the peak value of an erase signal (as effective at a cell) is dropped to a certain value, the neutralization of the wall potential is not completed, leaving some discharge on the cell concerned. The remaining charges induce a residual potential thereon, which is added to the subsequent sustain signal voltage because the residual voltage and the sustain signal have the same polarity. If the sum of these voltages becomes sufficient to initiate gas discharge of the cell concerned, the cell is fired and the applied erase signal to the Y-electrode fails to erase the cell. Therefore, the peak voltage of a cancelling pulse for an erase signal can be selected to a lower value than that of the erase signal, such as 30 V. This allows the Y-electrode drive circuit to comprise low breakdown voltage transistors, resulting in a significant cost reduction. The inventors have thus had the insight that the voltage of a cancelling pulse for cancelling an erase signal can be less than a sustain voltage, and they have further had the insight that the voltage of a cancelling pulse for cancelling a write signal can be less than a sustain voltage. Reference is made, by way of example, to the accompanying drawings, in which:- Fig.1(a) to (f) are time charts showing waveforms of signals, for assistance in explanation of a previously proposed method of driving a PDP; Fig.2 is a schematic block diagram of apparatus to which methods of driving a PDP embodying the present invention can be applied; Fig.3(a) to (d) are time charts showing waveforms of signals for assistance in explaining a first embodiment of the present invention; Fig.4(a) to (e) are time charts showing waveforms of signals for assistance in explaining a second embodiment of the present invention; Fig.5(a) to (c) are time charts showing waveforms of signals for assistance in explaining a third embodiment of the present invention; Fig.6(a) to (e) are time charts showing waveforms of signals for assistance in further explanation of write operations of the third embodiment of the present invention; Fig.7(a) to (e) are time charts showing waveforms of signals for assistance in further explanation of erase operations of the third embodiment of the present invention; Fig.8(a) to (d) are time charts showing waveforms of signals for assistance in explaining a modified form of the third embodiment of the present invention Fig.9 is a graph illustrating the relationship between a voltage margin and voltage of a cancelling signal for cancelling an erase signal; and Fig.10 is a graph illustrating the relationship between a voltage margin and voltage of a cancelling signal for cancelling a write signal. Fig.2 is a schematic block diagram of apparatus which can be operated in accordance with methods of driving a gas discharge display device embodying the present invention. This apparatus has a gas discharge panel which is an AC type plasma display panel (PDP) 101, having a group of X-electrodes and Y-electrodes forming a matrix cell arrangement. Although not shown in Fig. 2, each Y-electrode extends horizontally in the Figure and each X-electrode extends vertically in the Figure. In the apparatus of Fig. 2, the Y-electrodes are driven by a Y-line driver 102, line selection operation of which is controlled by a large scale integrated (LSI) logic circuit 103, to perform a line sequential addressing of the Y-electrodes. A main controller 106 processes clock signals and display signals and supplies control signals to the LSI 103. A shift register 105 receives control signals from the main controller 106 and supplies control signals to an X-line driver 104 for driving the X-electrodes. A sustain driver 107 receives control signals from the main controller 106 and provides sustain signals to the X-electrodes. The X-line driver 104 and the shift register 105, surrounded by a chain line rectangle in Fig. 2, may be floated potentially to the output of the sustain driver 107. The time charts of Fig.3 illustrate a first embodiment of the invention. In line sequential addressing, Y-electrodes are selected sequentially from the top Y-electrode (i.e. the uppermost horizontal Y-electrode in Fig.2 (not shown)). When a Y j -electrode is selected, as shown in Fig.3(a) a write signal 2 of one polarity of approximately 140 V is applied to the Y j -electrode to fire all the cells located on the Y j -electrode simultaneously. Preferably, a sustain signal 1 having the same polarity as that of the write signal 2 precedes the write signal 2 as shown. This is because such a preceding sustain signal stabilizes the wall potential of the PDP and ensures proper functioning of the following write signal. After the write signal 2, a sustain signal 4 of 90 V of opposite polarity to the write signal (acting as a converting signal as mentioned above) maintaining the gas discharges of the fired cells, and an erase signal 3, a narrow pulse, follow in the recited order. The erase signal 3 is followed by a series of alternating sustain signals 1 and 4, which have opposite polarities to one another, to sustain the discharges of fired (non-erased) cells. When a cell C ij is to be non-illuminated, no signal is applied to the X j -electrode, as shown in Fig.3(b), providing a cell potential at the cell C ij with the same waveform as is shown in Fig.3(a). The erase cell potential (i.e. the potential effective at the cell due to the erase signal) is a full 90 V and is preceded by a sustain signal 4 of the opposite polarity which induces a suitable wall potential and the cell is thus erased. However, when the cell C ij is to be illuminated, a cancelling signal 6, for cancelling the effect of the erase signal 3, is applied to the cell through the X i -electrode at a timing coinciding with the erase signal 3, as shown in Fig.3(c). In this case the waveform of the cell potential becomes as shown in Fig.3(d). As a result, the effective erase signal 3 applied at the cell, the peak voltage of which is reduced to approximately to 60 V, loses its erasing function, and fails to erase the cell C ij . Thus, cells on the selected Y j -electrode are selectively illuminated or non-illuminated to complete a line addressing operation. The peak voltage of the cancelling pulses 6 for cancelling the effects of erase signals can be made as low as approximately 30 V. The selection of X-electrodes is performed by the X-line driver 104 shown in fig.2. Most of the selective addressing operations involved are performed by circuits associated with X-electrodes. These are the circuits requiring a complicated constitution. However, since the cancelling pulses 6 are of low level, the breakdown voltage of transistors used in the associated circuits for driving the X-electrodes are allowed to be low, resulting in a considerable cost reduction in respect of such circuits in spite of their complexity. Particularly for a rectangular type PDP having relatively small number of Y-electrodes and a large number of X-electrodes a remarkable cost reduction can be achieved. In addition, it is clear that the lack of cancelling pulses for write signals simplifies the drive circuits. Although relatively high breakdown voltages are required for associated circuits for driving Y-electrodes, these circuits are rather simple because they are required only to repeat predetermined cycles of drive signals and require no selective addressing circuits. Furthermore, with rectangular PDP's the number of Y-electrodes may be small, avoiding cost increases in respect of the circuits for driving Y-electrodes. As a result, a significant total cost reduction can be achieved by the employment of this driving method embodying the present inventiion. A second embodiment of the present invention, being a modification of the first embodiment, illustrated in the time charts of Fig. 4. Unlike the first embodiment, sustain signals 11 and 14 of the same polarity are applied respectively and separately to the Y-electrodes and X-electrodes. Other signals, i.e. write signal 12, erase signal 13 and cancelling signal 16 are applied in the same way as the corresponding write, erase and cancelling signals of the first embodiment. To a selected Y j -electrode, write signal 12, erase signal 13 and sustain signals 11 are applied as shown in Fig.4(a). In respect of a cell C ij located on the Y j -electrode and which is to be non-illuminated, sustain signals 14 only are applied to the X i -electrode as shown in Fig.4(b). The waveform of the cell potential in this case is shown in Fig.4(c). When the cell C ij is to be illuminated, a cancelling signal 16 preceded by a sustain signal 17, acting as a converting signal, is applied to the X i -electrode as shown in Fig.4(d) and resulting cell potential as shown in Fig.4(e) which is the same as that shown in Fig.3(e). To protect the X-line driver 104 and the shift register 105 from the 90V sustain signals floating connection to the sustain driver 107 is necessary for the circuits surrounded by a chain line rectangle as shown in Fig.2. The operation of a third embodiment of the present invention will now be described referring to Fig.2 and the time charts of Fig.5. This embodiment is suitable for more general use, usually employing a line sequential addressing to approach directly to a selected cell C ij . To Y-electrodes, as shown in Fig.5(a), sustain signals 11 of approximately 90 V, an erase signal 13 of approximately 90 V and having a narrow pulse width, and a write signal 12 of approximately 140 V, are applied from the Y-line driver 102. To X-electrodes, as shown in Fig.5(b), sustain signals 14 of 90 V, a cancelling signal 15 for cancelling the effect of a write signal 12, or a cancelling signal 16 for cancelling the effect of an erase signal 14 (both cancelling signals are shown by broken lines in Fig.5(b)) are applied. Cell potential provided by such signals as applied to X and Y electrodes is shown in Fig.5(c). As stated before, complete cancellation or "killing" of the write or erase signals is not necessary. The peak voltage of the cancelling signals 15 and 16 can be taken below two-thirds of that of sustain signals. As indicated in connection with the first embodiment, the peak voltage of cancelling signals 16 for erase signals can be taken below one-half of that of sustain signals (e.g. 30V). In this case, however, both cancelling signals for write and erase signals are of 50 V. When a write operation is performed in respect of cells located on a selected Y j -electrode, a write signal 12 and sustain signals 11 are applied to the Y j -electrode, as shown in Fig.6(a). Simultaneously, sustain signals 14 only are applied to the X-electrodes associated with the cells to be illuminated, as shown in Fig.6(b), providing the cells with a cell potential as shown in Fig.6(c). The cells are fired by a resultant write signal 12 of 140 V. In respect of cells to be non-illuminated, as shown in Fig.6(d), cancelling signals 15 of 50 V are applied to the associated X-electrodes in coincidence with the write signals 12 of Fig.6(a), resulting in a cell potential for those cells as shown in Fig.6(e). The write signal 12 as applied to such cells is reduced to be a substantial potential 12 of approximately 90 V and loses write function. Thus, the cancelling signal voltage 15 can be taken lower than that of the sustain signals 11 and 14. Thus, only selected cells along the selected Y j electrode are fired in this case. When a selective erase operation is required in respect of fired cells, an erase signal 13 is applied to the appropriate Y j -electrode followed by sustain signals 11 as shown in Fig.7(a). Simultaneously, only sustain signals 14 (at least one of which precedes the erase signal 13) are applied to X-electrodes associated with the cells to be erased as shown in Fig.7(b), resulting in cell potentials shown in Fig.7(c) to erase the associated cells. In respect of cells not to be erased, cancelling signals 16 of approximately 50 V are applied to the associated X-electrodes, in coincidence with the erase signal 13 applied to the Y j -electrode, as shown in Fig.7(d). Signals applied to the Y j -electrode remain the same as those shown in Fig.7(a). The resultant cell potential of the cells is shown in Fig.7(e). The resultant erase potential 13 is 40 V, whereby the ability to erase associated cells is lost. Thus fired cells on Y j -electrode are selectively erased. As described above, peak voltages of both cancelling pulses or signals for erase signals and write signals can be taken low, approximately 50 V in this case. Therefore, if a circuit for generating cancelling pulses for erase signals or write signals is floated to the sustain driver 107, the breakdown voltage required is allowed to be low. This facilitates the fabrication of the circuit and reduces the fabrication cost. A modified method of the third embodiment described above is illustrated by the time charts of Fig.8, which correspond generally to those of Fig.5. Similarly to Fig.5(a), Fig.8(a) is a time chart illustrating signals applied to a Y-electrode. In the case of Fig.8(a), there are applied a write signal 12, an erase signal 13, sustain signals 11, and sustain signals 14 of opposite polarity. Fig.8(b) is a time chart relating to a case in which writing or erasing is allowed to a cell concerned, showing that no signal is applied to the associated X-electrode. Fig.8(c) is a time chart relating to a case in which write signal 12 or erase signal 13 applied to the associated Y-electrode is to be cancelled, illustrating that cancelling signals 15 or 16 are applied to the associated X-electrode. Fig.8(d) is a time chart showing resultant cell potential. Broken lines in Fig.8(d) correspond to the application of the cancelling signals of Fig.8(c). In the embodiment, illustrated with reference to Fig.5(a) and (b), sustain signals 11 and 14 are applied respectively to Y and X electrodes, having the same polarity as that of other signals. However, in the modification shown in Fig.8, as illustrated in Fig.8(a), sustain signals 11 and 14 having opposite polarity to each other are applied to the Y-electrodes, requiring two power sources of positive and negative polarities for the sustain signals. However this disadvantage is balanced by an advantage in that only cancelling signals, 15 for a write signal and 16 for an erase signal, of low voltage are applied to X electrodes. As a result, for a complicated addressing circuit applied to the X-electrodes, transistors and other elements of low breakdown voltage can be used. This reduces the cost of the addressing circuit remarkably. Stability or reliability of operations for driving a PDP is indicated by "voltage margins". Generally, when a write signal or sustain signal is applied for driving a PDP, there is an allowable range of fluctuation of the signal voltage outside which range misfiring or failed firing of cells may occur. Such a range is referred as a "voltage margin" of the PDP driving method. Fluctuation of characteristics of the panel affects the voltage margin, but at least to some degree, the voltage margin can be improved by driving circuits. Usually, sustain signal voltage margin is a critical factor in relation to a PDP drive method. A well-designed drive circuit can cover some unstable properties of the panel. In the third embodiment illustrated above, for example, it is desirable that cancelling pulses for erase and write signals can be selected as low as possible. Taking a cancelling pulse for the erase signal as an example, too low a cancelling pulse results in a rather high resultant erase signal (effective at a cell) which might maintain the erase function, causing an unstable cancelling function. As a result, a voltage margin for the PDP driving method will drop as the erase signal cancelling pulse is taken lower. The relationship between erase signal cancelling pulse voltage and sustain signal voltage margin is plotted in Fig.9. The voltage of the erase signal cancelling pulse is taken along the abscissa and the sustain signal voltage margin is taken along the ordinate. With a combination of an erase signal and its cancelling pulse voltage, represented in the region marked A in Fig.9, erasing operation is performed reliably. On the other hand, in the region marked B, the function of the cancelling pulse is not sufficient to erase a cell. In the marked region C, operation is unstable for reasons other than the voltage of the cancelling pulse. Thus, from Fig.9, a cancelling pulse voltage for erase signal cancellation is found to be selectable as 30 V to maintain a reasonable voltage margin of the drive method. Similarly, the relationship between write signal cancelling pulse voltage and sustain signal voltage margin is shown in Fig.10, illustrating that a write signal cancelling pulse voltage of 50 V is sufficient to keep the system stable. As a result, in this embodiment, an erase signal cancelling pulse voltage of 30 V and a write signal cancelling pulse voltage of 50 V can afford sufficient voltage margin. In the above description, concrete voltage values for signals such as write signal, sustain signal, erase signal and cancelling signals are given, but it will be clear to those who are skilled in the art that these values are given only by way of example and that the present invention is not confined to those values. An embodiment of the present invention provides a drive method for a gas discharge display panel having two arrays of parallel electrodes on walls of a gas filled panel oriented transversely forming discharge cells at each intersection of the electrodes. A write signal is applied to a first electrode to discharge all the cells connected to the electrode, being followed by a coincided application of an erase signal to the first electrode and cancelling signals to selected second electrodes only, thus the erase signals applied to the cells in connection with the selected second electrodes are cancelled to keep the discharge of the cells selectively to display information on the panel. The present invention provides a method for driving a gas discharge display device which device has an array of first electrodes and an array of second electrodes, with a gas discharge space between the arrays and with the first electrodes crossing the second electrodes to form a matrix arrangement of gas discharge cells corresponding to respective crossing points of the electrodes, the method comprising selecting a first electrode and applying a write signal, to the selected first electrode, capable of establishing a discharging condition in the gas discharge cells formed along the selected first electrode, and applying sustain signals capable of maintaining such a discharging condition after its establishment, wherein a write cancelling signal, of a peak voltage less than that of the sustain signals, is applied simultaneously with the write signal, to a selected second electrode, to prevent establishment of the discharging condition at a cell formed along the selected first electrode where the selected first electrode crosses the selected second electrode. The present invention provides a method for driving a gas discharge display device which device has an array of first electrodes and an array of second electrodes, with a gas discharge space between the arrays and with the first electrodes crossing the second electrodes to form a matrix arrangement of gas discharge cells corresponding to respective crossing points of the electrodes, the method comprising selecting a first electrode and applying a write signal, to the selected first electrode, capable of establishing a discharging condition in the gas discharge cells formed along the selected first electrode, applying an erase signal to the selected first electrode, and, simultaneously with application of the erase signal, applying an erase cancelling signal to a selected second electrode, to prevent erasure of the discharging condition at the cell formed along the selected first electrode where the selected first electrode crosses the selected second electrode. The erase cancelling signal may be of a peak voltage less than that of sustain signals employed for maintaining such a discharging condition. In a method embodying the present invention, both erase cancelling signals and write cancelling signals may be selectively employed. The present invention provides a driving method for a gas discharging display panel, having an array of parallel first electrodes and another array of second electrodes oriented at a transverse angle to each other on opposite sides of a gas filled panel forming a matrix arrangement, each gas discharge cell located at each intersection of said matrix, comprising the step of: a first step of selecting at least one of said first electrodes and firing (discharging) said cells arranged at said selected first electrode by applying a write signal to said selected first electrode; a second step of applying an erase signal to said selected first electrode, and simultaneously applying a plurality of cancelling signals for said erase signal onto selected second electrodes, whereby said cells located at the intersections of said selected first electrode and said selected second electrodes remain discharged and said discharging being sustained by a plurality of subsequent sustain signals applied to said cells; and repeating said first step and subsequent said second step to a plurality of said first electrodes selectively to display a predetermined information on said gas discharge display panel. For such a method said first electrodes and said second electrodes may be oriented at a right angle to each other. The peak voltage of said cancelling signal may be lower than the peak voltage of said sustain signal. The peak voltage of said cancelling signal for said erase signal may be lower than the half (1/2) of the peak voltage of said sustain signal. The invention provides a driving method for a gas discharge display panel, having an array of parallel first electrodes and another array of second electrodes oriented at a transverse angle to each other on opposite sides of a gas filled panel forming a matrix arrangement, each gas discharge cell located at each intersection of said matrix, comprising the step of: selecting an electrode of said first electrodes; applying a write signal, an erase signal and a sustain signal selectively to said selected first electrode, said signals having the same polarity; and applying a cancelling signal for said write signal, a cancelling signal for said erase signal and a sustain signal, to said second electrodes selectively, said signals having the same polarity, differential voltage of said signals applied to said first electrode in combination with said signals applied to said second electrode, being applied across a cell located at the intersection of said selected first electrode and second electrode, said cell being driven by said combination of said signals applied to said cell to display information on said gas discharge display panel. Said combination of signals may comprise said erase signal and sustain signals applied to said first electrode and said cancelling signal for erase signal and sustain signals applied to said second electrode, said erase signal voltage being reduced by said cancelling signal coincidently applied with said erase signal to cause said erase signal to fail to erase a fired cell locating at the intersection of said first electrode and said second electrode. The peak voltage of said cancelling signal for write signal may be lower than the peak voltage of said sustain signal. The peak voltage of said cancelling signal for erase signal may be lower than the peak voltage of said sustain signal. The peak voltage of said cancelling signal for write signal may be lower than the two-thirds (2/3) of the peak voltage of said sustain signal. The peak voltage of said cancelling signal for erase signal may be lower than the half (1/2) of the peak voltage of the said sustain signal. The invention provides a driving method for a gas discharge display panel, having an array of parallel first electrodes and another array of second electrodes oriented at a transverse angle to each other on opposite sides of a gas filled panel forming a matrix arrangement, each gas discharge cell located at each intersection of said matrix, comprising the step of: selecting an electrode of said first electrodes; applying a write signal, an erase signal and a sustain signal of one polarity and a sustain signal of the opposite polarity selectively to said selected first electrode; and applying a cancelling signal for said write signal and a cancelling signal for said erase signal and a sustain signal to said second electrodes selectively, said signals having the same polarity, differential voltage of said signals applied to said first electrode in combination with said signals applied to said second electrode, being applied across a cell located at the intersection of said selected first electrode and second electrode, said cell being driven by said combination of said signals applied to said cell to display information on said gas discharge display panel.

Claims: A method of driving a gas discharge display device, which device has an array of first electrodes and an array of second electrodes, with a gas discharge space between the arrays and with the first electrodes crossing the second electrodes to form a matrix arrangement of gas discharge cells corresponding to respective crossing points of the electrodes characterized by selecting a first electrode and applying a write signal, to the selected first electrode, capable of establishing a discharging condition in gas discharge cells formed along the selected first electrode, thereafter applying an erase signal to the selected first electrode and simultaneously applying a cancelling signal to each selected second electrode, whereby in respect of each cell located at the crossing point of said selected first electrode and a non-selected second electrode, to which such a cancelling signal is not applied, the erase signal is effective to destroy a discharging condition previously established in the cell so that discharges no longer take place in the cell, and whereby in respect of each cell located at the crossing point of said selected first electrode and a selected second electrode the effect of the erase signal is cancelled and the cell remains in a discharging condition previously established by the application of the write signal, discharges in the cell being sustained by subsequent application of sustain signals to the cell. A method as claimed in claim 1, further comprising applying a further plurality of cancelling signals, simultaneously with the write signal, to each selected second electrode, which may be different from the selected second electrode or electrodes of claim 1, to prevent establishment of a discharging condition by the write signal at cells located at the crossing points of the selected first electrode and the selected second electrodes to which the further plurality of cancelling signals are applied. A method as claimed in claim 1 or 2, wherein the write signal, the erase signal and a sustain signal are applied to said selected first electrode with the same polarity; and the cancelling signals and a sustain signal are selectively applied to second electrodes with the same polarity. A method as claimed in claim 1 or 2, wherein the write signal, the erase signal and a sustain signal of one polarity and a sustain signal of the opposite polarity are applied to said selected first electrode; and the cancelling signals are applied selectively to second electrodes with the same polarity. A method as claimed in any preceding claim, wherein the peak voltage of the cancelling signals of claim 1 is lower than the peak voltage of said sustain signals. A method as claimed in claim 5, wherein the peak voltage of the cancelling signals of claim 1 is lower than one half (1/2) of the peak voltage of said sustain signals. A method as claimed in claim 2, or any one of claims 3 to 6 when read as appended to claim 2, wherein the peak voltage of the cancelling signals of claim 2 is lower than the peak voltage of said sustain signals. A method as claimed in claim 7, wherein the peak voltage of the cancelling signals of claim 2 is lower than the two-thirds (2/3) of the peak voltage of said sustain signals. A method as claimed in any preceding claim, comprising selecting each first electrode in turn, and so applying the said signals for each selection of a first electrode, to display a predetermined information on said gas discharge display panel.

Inventors: HORIO, KENJI C/O FUJITSU LIMITED, OTSUKA, AKIRA C/O FUJITSU LIMITED, SHINODA, TSUTAE C/O FUJITSU LIMITED, TANIOKA, TSUYOSHI C/O FUJITSU LIMITED
Applicants: FUJITSU LIMITED
Application year: 1985
Main classification: G09G3
IPC codes: G09G3