Method for driving a gas discharge display device

Abstract: A plurality of scanning electrodes and a plurality of sustaining electrodes parallel to each other are located on an inner face of a first glass substrate. Each of the scanning electrodes and each of the sustaining electrodes form a pair. A dielectric layer and a protection layer are formed on the first glass substrate in this order, covering the electrodes. A plurality of data electrodes perpendicular to the scanning electrodes and the sustaining electrodes are located on an inner face of a second glass substrate which is located opposed to the first glass substrate with a discharge space interposed therebetween. In an AC-type PDP having such a structure, at least one of the plurality of scanning electrodes and the plurality of sustaining electrodes are divided into a plurality of groups, and pulses having different phases are applied to the electrodes in different groups, thereby causing sustaining discharge. The scanning electrodes and the sustaining electrodes may be comb-like with teeth. The comb-like scanning electrodes and the comb-like sustaining electrodes are opposed to each other with a small gap interposed therebetween in the manner that the teeth thereof are in engagement with each other. In such a case, the data electrodes are located opposed to and in a longitudinal direction of the teeth of the scanning electrodes.

Description: 1. Field of the Invention: The present invention relates to a method for driving a gas discharge display apparatus for displaying a character or an image by light emission utilizing gas discharge which is for use in an image display apparatus such as a television or an advertizing display panel. In particular, the present invention relates to a method for driving a gas discharge apparatus used in the form of an AC-type plasma display panel (hereinafter, referred to as a "PDP"). 2. Description of the Related Art: Gas discharge display apparatuses have a large display area despite a small depth thereof and realize color display. For such advantages, use of gas discharge display apparatuses is now being extended rapidly. Gas discharge display apparatuses are available in various types. One type of gas apparatus suitable for image display is an AC-type PDP. Gas discharge display apparatuses of this type, which are disclosed in Japanese Laid-Open Patent Publication Nos. 59-79938 and 61-39341, and Japanese Patent Publication No. 62-31775, have a memory function. Briefly referring to Figures 1A and 1B, a conventional AC-type PDP 1000 will be described. Figure 1A is a plan view of the AC-type PDP 1000, illustrating an arrangement of electrodes. Figure 1B is a cross sectional view of the AC-type PDP 1000 taken along line 1B-1B' in Figure 1A. As is shown in Figures 1B , the AC-type PDP 1000 includes a first glass substrate 3 and a second glass substrate 8 opposed to each other. The first glass substrate 3 and the second glass substrate 8 form an outer casing of the AC-type PDP 1000 together. On an inner face of the first glass substrate 3 , a first electrode group including a plurality of scanning electrodes (first discharge electrodes) 1 and a plurality of sustaining electrodes (second discharge electrodes) 2 is located. A dielectric layer 4 is located on the first glass substrate 3 , covering the first electrode group, and a protection layer 5 is located on the dielectric layer 4 . On an inner face of the second glass substrate 8 , a second electrode group including a plurality of data electrodes (third discharge electrodes; also referred to as "address electrodes") 7 is located. As is illustrated in Figure 1A, the scanning electrodes 1a through In (only 1a, 1b and 1c are shown here) and the sustaining electrodes 2a through 2n (only 2a, 2b and 2c are shown here) are provided in parallel alternately. The data electrodes 7a through 7m (only 7a and 7b are shown here) are provided in parallel so as to perpendicularly cross the scanning electrodes 1a through In and the sustaining electrodes 2a through 2n. Adjacent scanning electrode and sustaining electrode (for example, 1a and 2a ) form a pair. A projecting area of the scanning electrode and a projecting area of the sustaining electrode forming a pair are opposed to each other in an area S (Figure 1A ), where sustaining discharge occurs. The area S will be referred to as a "discharge area". The second electrode group including the data electrodes 7a through 7m is opposed to the protection layer 5 with a discharge space 6 full of discharge gas interposed therebetween. The dielectric layer 4 is formed of borosilicate glass or the like, and the protection layer 5 is formed of MgO or the like. As is illustrated in Figure 2, the scanning electrodes 1a through 1n , the sustaining electrodes 1a through 1n, and the data electrodes 1a through 1m are arranged orthogonally in a lattice. The scanning electrodes 1a through In are connected to a scanning electrode driving circuit 10, the sustaining electrodes 2a through 2n are connected to a sustaining electrode driving circuit 11 , and the data electrodes 7a through 7m are connected to a data electrode driving circuit 12 . Another conventional AC-type PDP 2000 will be described with reference to Figures 3A and 3B. Figure 3A is a plan view of the AC-type PDP 2000, illustrating an arrangement of electrodes, and Figure 3B is a cross sectional view of the AC-type PDP 2000 taken along line 3B-3B ' in Figure 3A . In Figure 3A , the letter P denotes a pixel area, and letter S denotes a discharge area. In Figures 3A and 3B , the same elements as those in Figures 1A and 1B bear the same reference numerals therewith. As is illustrated in Figure 3B , the AC-type PDP 2000 includes three types of phosphor layers R, G and B for emitting light of red, green and blue which are located on the inner face of the second glass substrate 8 in order to perform a color display. The phosphor layers R, G and B are located in positional correspondence with discharge areas S shown in Figure 1A, and are excited to emit light upon receiving ultraviolet rays generated by discharge caused in the discharge areas S. A method for driving such AC-type PDPs 1000 and 2000 is disclosed in, for example, Japanese Patent Publication No. 62-61278 and Japanese Laid-Open Patent Publication No. 4-170581. In the latter publication, the driving method is described as a method for driving a dot matrix display panel. With reference to Figure 4 , a conventional method for driving an AC-type ( 1000 or 2000 ) PDP will be described. First, in the writing operation performed in a writing period, a positive writing pulse having an amplitude of +Vw shown in waveform DATA in Figure 4 is applied to at least one data electrode selected from the data electrodes 7a through 7m (for example, the data electrode 7a ) which corresponds to a pixel for displaying an image in accordance with the scanning electrode 1a. Simultaneously, a negative scanning pulse having an amplitude of -Vs shown in waveform SCN1 is applied to the scanning electrode 1a. By such application, discharge occurs at an intersection W1 (Figure 1A ) of the data electrode 7a and the scanning electrode 1a, and thus a positive charge is stored in an area of a surface of the protection layer 5 , the area positionally corresponding to the intersection W1. In other words, such an area acts as a write cell. Next, a positive writing pulse having an amplitude of +Vw shown in waveform DATA is applied to at least one data electrode selected from the data electrodes 7a through 7m (for example, the data electrode 7a ) which corresponds to a pixel for displaying an image in accordance with the scanning electrode 1b. Simultaneously, a negative scanning pulse having an amplitude of -Vs shown in waveform SCN2 is applied to the scanning electrode 1b. By such application, discharge occurs at an intersection W2 (Figure 1A ) of the data electrode 7a and the scanning electrode 1b, and thus a positive charge is stored in an area of the surface of the protection layer 5 , the area positionally corresponding to the intersection W2 . In other words, such an area acts as a write cell. In this manner, during the process of applying negative scanning pulses having an amplitude of -Vs shown in waveforms SCN1 through SCNn to the scanning electrodes 1a through 1n respectively, a positive writing pulse having an amplitude of +Vw is applied to at least one selected data electrode which corresponds to a pixel for displaying an image in accordance with the respective scanning electrode. Thus, a positive charge is stored in a prescribed area (write cell) of the surface of the protection layer 5 . The writing operation is followed by the sustaining operation performed in a sustaining period. In the sustaining operation, a negative sustaining pulse having an amplitude of -Vs shown in waveform SUS is applied to all the sustaining electrodes 2 , and negative sustaining pulses having an amplitude of -Vs shown in waveforms SCN1 through SCNn are applied to all the scanning electrodes 1 , respectively. The pulse application to the sustaining electrodes 2 and the pulse application to the scanning electrodes 1 are performed alternately. The application of the first sustaining pulse to each sustaining electrode 2 discharges the positive charge stored on the protection layer 5 , and thus sustaining discharge occurs on the discharge area S which belongs to the same discharge cell as the respective intersection. The alternate application of the negative sustaining pulse to each sustaining electrode 2 and each scanning electrode 1 continues the sustaining discharge on the respective discharge area S . By light emission caused by such sustaining discharge, characters and images are displayed. In the erasing operation performed in an erasing period, a negative erasing pulse having an amplitude of -Ve and a small width t WE shown in waveform SUS is applied to all the sustaining electrodes 2 . (Hereinafter, a pulse having a small width will be referred to as a "narrow pulse".) By such application, erasing discharge occurs, and thus the charge stored on the protection layer 5 by sustaining discharge is completely erased. As a result, the sustaining discharge does not continue even if a sustaining pulse is applied. Thus, the sustaining operation is terminated. Conventionally, the erasing pulse applied to the sustaining electrodes has an absolute value of the amplitude which is smaller than the that of the sustaining pulse, or has a width smaller than that of the sustaining pulse. In order to enlarge the margin for the erasing operation, both of the absolute value of the amplitude and the width of the erasing pulse need to be smaller than those of the sustaining pulse. Alternatively, a plurality of erasing pulses having small but different widths may be applied. In order to stabilize the writing, sustaining and erasing operations, the rise and fall of each of the writing, scanning, sustaining and erasing pulses are applied with steep rise and fall. The time period required for the change in the voltage at the rise and fall is generally set to be as short as several hundred nanoseconds. The luminance of light obtained by performing sustaining discharge once is determined by the amplitude of the sustaining pulse, the capacitance between the scanning electrodes 1a through 1n and the surface of the protection layer 5 , the capacitance between the sustaining electrodes 2a through 2n and the surface of the protection layer 5 , and the like. However, the amplitude of each pulse is substantially determined by characteristics of the AC-type PDP and thus cannot be changed arbitrarily. The structure of the AC-type PDP, the material of the electrodes, the type of the discharge gas, the sealing pressure and the like cannot be changed after the AC-type PDP is produced. Accordingly, the luminance of light can be controlled simply by changing the number of times the sustaining discharges is repeated (namely, the number of pulses) per time unit. Next, the above-described operations will be described in detail with reference to Figures 5A through 5G. Figures 5A through 5G illustrate existing and moving states of the wall charges in a discharge cell in each step of the above-described operations. Figures 5A through 5G are cross sectional views of a conventional AC-type PDP which is similar to the AC-type PDPs shown in Figures 1B and 3B. In Figures 5A through 5G, the data electrode 7 on the inner face of the second glass substrate 8 is covered with a second dielectric layer 9, and the phosphor layers R, G and B (only R is shown in Figure 5A ) are located on the second dielectric layer 9. The AC-type PDP illustrated in Figures 5A through 5G has the same structure as the structure of the AC-type PDPs 1000 and 2000 shown in Figures 1B and 3B except for the above-described points. The same elements as in the AC-type PDPs 1000 and 2000 bear the same reference numerals therewith. Figure 5A shows an initial state before the AC-type PDP is turned on. The discharge cell of the AC-type PDP has no wall charge. As is shown in Figure 5B, in the writing period after the AC-type PDP is turned on, a writing pulse having an amplitude of +Vw (V) is applied to the data electrode 7 and a negative scanning pulse having an amplitude of -Vs (V) is applied to the scanning electrode 1 . Then, writing discharge occurs at the intersection of the data electrode 7 and the scanning electrode 1 . A negative wall charge is stored in an area of a surface of the second dielectric layer 9 corresponding to the data electrode 7 , and a positive wall charge is stored in an area of the surface of the protection layer 5 corresponding to the scanning electrode 1 . As is shown in Figure 5C, in the sustaining period, a negative sustaining pulse having an amplitude of -Vs (V) is applied to the sustaining electrode 2 . Thus, a positive wall charge is stored in an area of the surface of the protection layer 5 corresponding to the sustaining electrode 1 . The voltage generated by the positive wall charge is superimposed on the voltage of the sustaining pulse and applied between the area of the surface of the protection layer 5 corresponding to the scanning electrode 1 and the area of the protection layer 5 corresponding to the sustaining electrode 2. Accordingly, sustaining discharge occurs between the above-mentioned two areas. As a result, a negative wall charge is stored on the area of the protection layer 5 corresponding to the scanning electrode 1 , and a positive wall change stored on the area of the protection layer 5 corresponding to the sustaining electrode 2 . Further in the sustaining period, as is shown in Figure 5D, a negative sustaining pulse having an amplitude of -Vs (V) is applied to the scanning electrode 1. Then, the voltage generated by the negative wall charge stored on the area of the protection layer 5 corresponding to the scanning electrode 1 by the sustaining discharge and the voltage generated by the positive wall charge stored on the area of the protection layer 5 corresponding to the sustaining electrode 2 are superimposed on the voltage of the sustaining pulse and applied between the area of the protection layer 5 corresponding to the scanning electrode 1 and the area of the protection layer 5 corresponding to the sustaining electrode 2 . Thus, sustaining discharge occurs again between the above-mentioned two areas but in the opposite direction. As a result, a negative wall charge is stored on the area of the protection layer 5 corresponding to the sustaining electrode 2 , and a positive wall charge is stored on the area of the protection layer 5 corresponding to the scanning electrode 1 . Still further in the sustaining period, as is shown in Figure 5C again, a negative sustaining pulse having an amplitude of -Vs (V) is applied to the sustaining electrode 2 . Then, the voltage generated by the negative wall charge stored on the area of the protection layer 5 corresponding to the sustaining electrode 2 by the sustaining discharge and the voltage generated by the positive wall charge stored on the area of the protection layer 5 corresponding to the scanning electrode 1 are superimposed on the voltage of the sustaining pulse and applied between the area of the protection layer 5 corresponding to the scanning electrode 1 and the area of the protection layer 5 corresponding to the sustaining electrode 2 . Accordingly, sustaining discharge occurs again between the above-mentioned two areas. As a result, a negative wall charge is stored on the area of the protection layer corresponding to the scanning electrode 1, and a positive wall charge is stored on the area of the protection layer 5 corresponding to the sustaining electrode 2 . In this manner, sustaining discharge (movement of charges) occurs repeatedly in the sustaining period as is shown in Figures 5C and 5D, and the phosphor layers R, G and B are excited by ultraviolet rays generated by the repeated sustaining discharge, thereby performing display. As is shown in Figure 5E , in the erasing period, a negative narrow erasing pulse having an amplitude of -Vs (V) is applied to the sustaining electrode 2 . Then, the voltage generated by the negative wall charge stored on the area of the protection layer 5 corresponding to the sustaining electrode 2 by the sustaining discharge and the voltage generated by the positive wall charge stored on the area of the protection layer 5 corresponding to the scanning electrode 1 are superimposed on the voltage of the negative narrow erasing pulse and applied between the area of the protection layer 5 corresponding to the scanning electrode 1 and the area of the protection layer 5 corresponding to the sustaining electrode 2 . Accordingly, erasing discharge occurs again between the above-mentioned two areas. However, since such erasing discharge is maintained for a short period of time due to the narrow pulse, the discharge is terminated midway. Accordingly, by setting the width of the narrow erasing pulse to be optimum, the wall charge on the area of the protection layer corresponding to the sustaining electrode 1 and the wall charge on the area of the protection layer 5 corresponding to the scanning electrode 2 can be neutralized. Thereafter, sustaining discharge does not occur even if a sustaining pulse is applied unless a writing pulse is applied again. Accordingly, discharge is kept in a pause. The level of the residual wall charge in Figure 5E is less than the level of the residual wall charge in Figure 5B because the wall charge is partially extinguished during the sustaining discharge. As is shown in Figure 5F , in the writing period, a positive pulse having an amplitude of +Vw (V) is applied to the data electrode 7 and a negative scanning pulse having an amplitude of -Vs (V) is applied to the scanning electrode 1 . Then, writing discharge occurs between an area of the second dielectric layer 9 corresponding to the data electrode 7 and the area of the protection layer 5 corresponding to the scanning electrode 1 . By such writing discharge, a negative wall charge is stored on the area of the second dielectric layer 9 corresponding to the data electrode 7 , and a positive wall charge is stored on the area of the second dielectric layer 9 corresponding to the scanning electrode 1 in addition to the residual wall charge shown in Figure 5E. As a result, the level of the charge in Figure 5E becomes equal to the level of the charge in Figure 5B. By repeating the operation illustrated in Figures 5F, 5C, 5D and 5E in this manner, an image is displayed. In the above-described conventional example, a method for driving the AC-type PDP in which the date electrodes 7 are covered with the second dielectric layer 9 and phosphor layers R, G and B are provided on the second dielectric layer 9 is described. The same method can be used for driving an AC-type PDP in which display is performed directly utilizing light emitted by discharge and thus has no phosphor layer. The same method can also be used for driving an AC-type PDP in which the data electrodes 7 are directly covered with a phosphor layer without the second dielectric layer 9 . In such a case, the phosphor layer acts in the same manner as the second dielectric layer 9 . The same method can still be used for driving an AC-type PDP in which the data electrodes 7 are exposed to the discharge space 6 without the second dielectric 9 or the phosphor layer. In such a case, although no wall charge is stored on the area of the second dielectric layer 9 corresponding to the data electrodes 7 , an equivalent wall charge is stored on the area of the protection layer 5 corresponding to the scanning electrode 1 . A conventional scanning electrode driving circuit 30 will be described with reference to Figures 6 and 7 . Figure 6 is a circuit diagram of the scanning electrode driving circuit 30 . The scanning electrode driving circuit 30 includes p-channel MOSFETs 13 withstanding a high voltage and n-channel MOSFETs 14 also withstanding a high voltage. The p-channel MOSFETs 13 are respectively connected to scanning electrodes 1a through 1n through a drain electrode thereof, and the n-channel MOSFETs 14 are also respectively connected to scanning electrodes 1a through In through a drain electrode thereof. A source of each p-channel MOSFET 13 is grounded, and a source of each n-channel MOSFET 14 is connected to a high voltage power source of -200 V. Each p-channel MOSFET 13 and each n-channel MOSFET 14 form an output section of a push-pull system withstanding a high voltage. The p-channel MOSFETs 13 are connected to a scanning logic circuit 16 via a level shift (L/S) circuit 15 withstanding a high voltage, and the n-channel MOSFETs 14 are directly connected to the scanning logic circuit 16 . The scanning logic circuit 16 includes a shift register 17 , a first gate 18 , a second gate 19 and an inverter 20 . A common line which is the basis for a signal level in the scanning logic circuit 16 is connected to the high voltage power source of -200 V. Figure 7 is a timing chart illustrating operation in the scanning electrode driving circuit 30 . When a scanning data signal SI and a clock signal CLK are input to the shift register 17, the scanning data signal SI is taken in at the falling edge of the clock signal CLK . The level of outputs from the shift register 17 becomes low one by one, and a scanning signal is output. Only while the level of a blanking signal BLK is low, the scanning signal passes through the first gate 18, the second gate 19, the inverter 20, and the level shift circuit 15 and is applied to each p-channel MOSFET 13 and each n-channel MOSFET 14. Thus, a scanning pulse is applied to the scanning electrode 1a through In one by one. In the sustaining period, when a sustaining signal SU , is input to the second gate 19, a sustaining pulse is applied to all the scanning electrodes 1a through In simultaneously. Conventionally, in order to reduce the size of the scanning electrode driving circuit 30 illustrated in Figure 6 , the scanning electrode driving circuit 30 is divided into an appropriate number of blocks to form a monolithic IC. The conventional AC-type PDPs which are described above have the following problems. (1) The conditions for setting the erasing operation are stringent as is described above. If the conditions are set inappropriately, right image reproduction cannot be performed due to the influence of the residual charge. The potential in the discharge area S is dispersed easily by different discharge cells, and discharge characteristics change over time. In addition, since the width of the erasing pulse is small, the start of erasing discharge can be delayed by fluctuation in the width of the erasing pulse when the erasing pulse is applied. In such a case, the charge stored in the discharge area S cannot be erased completely.In detail, the tolerance for the fluctuation in the width t WE and the amplitude -Ve of the erasing pulse cannot be large. Accordingly, if the characteristics are dispersed in different discharge cells, erasing discharge can be performed excessively or insufficiently in some discharge cells. Since the charge stored on the protection layer 5 is not completely erased in such discharge cells, a sufficient margin for erasing operation cannot be obtained. Excessive erasing discharge means that, after the charge stored on the protection layer 5 is erased, a charge having an opposite polarity is stored. Insufficient erasing discharge means that the charge stored on the protection layer 5 cannot be reduced to zero. (2) When the positive charge stored on the area of the protection layer 5 corresponding to the intersection (for example, W1 or W2 in Figure 1A ) of a scanning electrode and a data electrode moves to the discharge area S, the level of the charge moving to sub-area S 1 is different from the level of the charge moving to sub-area S 2 because sub-area S 1 is closer to the intersection W1 than sub-area S 2 . Accordingly, the charge distribution in the discharge area S is not uniform. As a result, when an erasing pulse is applied, the level of the charge is non-uniform in the area of the protection layer 5 corresponding to the discharge area S . Thus, the erasing operation cannot be uniform in the entire discharge area S . (3) In the case of color display, if the widths of the scanning electrodes and the sustaining electrodes opposed to each other in the discharge area S are reduced in order to obtain a pixel area P which is substantially square, the discharge area S is also reduced. As a result, sufficient luminance cannot be obtained especially in a large color display apparatus. (4) Even when the discharge is set to be performed 60 times per second as is generally done in a personal computer, a television and the like, the luminance is excessively high when the efficiency of the AC-type PDP is high. Under the circumstances, images can be displayed at a high luminance but not at a low luminance. (5) Discharge current flowing during the sustaining period concentrates when the level of the sustaining pulse is changed as is shown in Figure 4 . Accordingly, the peak value Ip of the discharge current is excessively large compared with the average value Ia. As a result, the circuit for supplying a power source requires a capacitor having a large capacity for smoothing the current and a switching transistor for supplying a large peak current. Further, in order to prevent an adverse effect of noise generated by such a large peak current on the circuit operation, a noise removal circuit and a multiple-layer substrate are required. (6) In the conventional scanning electrode driving circuit 30 , an output section of a push-pull system withstanding a high voltage including the p-channel MOSFET 13 and the n-channel MOSFET 14 is required for each of the scanning electrodes 1a through 1n. The level shift circuit 15 withstanding a high voltage is also required. Accordingly, incorporation of the scanning electrode driving circuit 30 into an IC is difficult. Even if the scanning electrode driving circuit 30 is incorporated into an IC, the chip area is sufficiently large to raise production cost. If a shortcircuit occurs between the scanning electrodes 1a through 1n, the scanning electrode driving circuit 30 breaks down. (7) The writing operation shown in Figure 5F requires writing discharge caused in the state where the residual wall charge remains after the erasing period shown in Figure 5E is terminated. However, the residual wall charge acts in the direction to counteract the voltage of the writing pulse, writing discharge is more difficult to be realized when compared with the state shown in Figure 5B. Even if writing discharge occurs, the difference between the wall charge on the area of the protection layer 5 corresponding to the scanning electrode 1 and the wall charge on the area of the protection layer 5 corresponding to the sustaining electrode 2 is too small to easily start sustaining discharge. As a result, no light is emitted in some discharge cells. In the case that the AC-type PDP is turned on to start operating in the state where the wall charge has already been distributed as is shown in Figure 5G , namely, in the state where a negative wall charge is stored on the area of the second dielectric layer 9 corresponding to the data electrodes 7 and a positive wall charge is stored on the area of the protection layer 5 corresponding to the scanning electrodes 1 and the sustaining electrodes 2, the wall charges act in a direction counteracting the voltage of the writing pulse. Accordingly, writing discharge and sustaining discharge are both difficult to occur, and the discharge operation is not performed until the wall charges shown in Figure 5G are naturally extinguished. As a result, the rising time for the display after the AC-type PDP is turned on, namely, the time period which is required for the AC-type PDP to perform normal display after the AC-type PDP is turned on is extended. The document EP-A-0 549 275 describes a method and an apparatus for driving display panel having a first substrate, at least one display line involving first electrodes and second electrodes disposed in parallel with each other on the first substrate, a second substrate facing the first substrate, and third electrodes disposed on the second substrate and extending orthogonally to the first and second electrodes, in which write operation of the display data by a light emission is executed by carrying out a selective write discharge utilising a memory function, are adapted to execute a write discharge for all cells and to execute an erase discharge for all cells before the selective write discharge, to thereby accumulate wall charges over the third electrodes in advance. The present invention is defined in the appended claims. Thus, the present invention concerns a method for driving a gas discharge display apparatus includes a writing step of applying a writing pulse to the plurality of data electrodes and applying a scanning pulse having an opposite polarity to the polarity of the writing pulse to the plurality of scanning electrodes; a sustaining step of applying a sustaining pulse to the plurality of sustaining electrodes and the plurality of scanning electrodes; and an erasing step of applying an erasing pulse. Prior to the writing step, the initiating step is performed of applying an initiating pulse having a prescribed polarity to prescribed electrodes selected from the group consisting of the plurality of data electrodes, the plurality of sustaining electrodes and the plurality of scanning electrodes. In one embodiment of the invention, the initiating step includes the step of applying an initiating pulse having an opposite polarity to the polarity of the scanning pulse applied in the writing step to at least one of the plurality of scanning electrodes and the plurality of sustaining electrodes. In one embodiment of the invention, the initiating step includes the step of applying an initiating pulse having an opposite polarity to the polarity of the writing pulse applied in the writing step to the plurality of data electrodes. In one embodiment of the invention, a time period required for the instantaneous voltage of the initiating pulse to change between 10% and 90% of an amplitude thereof is set to be between 5 µs and 10 ms inclusive. In one embodiment of the invention, the initiating step includes the step of applying an assisting pulse, to the plurality of scanning electrodes and the plurality of sustaining electrodes, having an identical polarity and an identical amplitude with the polarity and the amplitude of the initiating pulse to the plurality of data electrodes. In one embodiment of the invention, the initiating step includes the step of applying an assisting pulse, to the plurality of data electrodes, having an identical polarity and an identical amplitude with the polarity and the amplitude of the initiating pulse to the plurality of scanning electrodes and the plurality of sustaining electrodes. In one embodiment of the invention, a time period required for the instantaneous voltage of the assisting pulse to change between 10% and 90% of an amplitude thereof is set between 5 µs and 10 ms inclusive. Thus, the invention described herein makes possisle the advantage of providing a method for driving a gas discharge display apparatus for shortening the rising time of the gas discharge display apparatus for display after the apparatus is turned on and preventing generation of a discharge cell where no light emission occurs. This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A is a plan view of a conventional AC-type PDP, illustrating an arrangement of electrodes. Figure 1B is a cross sectional view of the AC-type PDP in Figure 1A taken along line 1B-1B' in Figure 1A. Figure 2 is a schematic view illustrating the arrangement of the electrodes in the conventional AC-type PDP in Figure 1A . Figure 3A is a plan view of another conventional AC-type PDP, illustrating an arrangement of electrodes. Figure 3B is a cross sectional view of the AC-type PDP in Figure 3B taken along line 3B-3B' in Figure 3A. Figure 4 is a timing chart illustrating a method for driving a conventional AC-type PDP. Figures 5A through 5G are cross sectional views of a conventional AC-type PDP, illustrating the existing and moving state of charges in a discharge cell while the AC-type PDP is operating. Figure 6 is a circuit diagram for a conventional scanning electrode driving circuit. Figure 7 is a timing chart illustrating operation of the scanning electrode driving circuit shown in Figure 6 . Figure 9A is a partial plan view of an AC-type PDP in a first example not forming part of the present invention, illustrating an arrangement of electrodes. Figure 9B is a cross sectional view of the AC-type PDP in Figure 9A taken along line 9B-9B' in Figure 9A. Figure 9C is a cross sectional view of the AC-type PDP in Figure 9A taken along line 9C-9C' in Figure 9A . Figures 10A and 10B are timing charts illustrating a method for driving the AC-type PDP shown in Figure 9A. Figure 27 is a timing chart illustrating a method for driving an AC-type PDP in the example according to the present invention. Figures 28A through 28G are cross sectional views of an AC-type PDP, illustrating the existing and moving state of charges in a discharge cell while the AC-type PDP is operating in the example. Figure 29A is a timing chart illustrating a method for applying an initiating pulse in a modification of the example. Figure 29B is a cross sectional view illustrating the state of an electrode supplied with an initiating pulse shown in Figure 29A. Figures 30A and 30B are timing charts illustrating a method for applying an initiating pulse in other modifications of the example. Figure 31 is a graph illustrating discharge characteristics of the AC-type PDP in the example with respect to a time period required for the voltage of an initiating pulse to change between certain levels. Figures 32A and 32B are timing charts illustrating a method for applying an initiating pulse in other modifications of the example. Figures 33A and 33B are timing charts illustrating a method for applying an initiating pulse in still other modifications of the example. Figure 34 is a timing chart illustrating a method for driving an AC-type PDP in still another modification in the example. Figure 35 is a timing chart illustrating a method for driving an AC-type PDP in still another modification in the example. Figure 36 is a timing chart illustrating a method for driving an AC-type PDP in still another modification in the example. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described by way of illustrative examples with reference to the accompanying drawings. Example 1 An AC-type PDP in a first example not forming part of the present invention will be described with reference to Figures 9A through 9C and 10A and 10B. Figure 9A is a partial plan view of an AC-type PDP 100 in the first example, illustrating an arrangement of electrodes. Figure 9B is a cross sectional view of the AC-type PDP 100 taken along line 9B-9B' in Figure 9A, and Figure 9C is a cross sectional view of the AC-type PDP 100 taken along line 9C-9C' in Figure 9A . As is shown in Figures 9B and 9C, the AC-type PDP 100 includes a first glass substrate 103 and a second glass substrate 108 opposed to each other. The first glass substrate 103 and the second glass substrate 108 form an outer casing of the AC-type PDP 100 together. On an inner face of the first glass substrate 103, a first electrode group including a plurality of scanning electrodes (first discharge electrodes) 101 and a plurality of sustaining electrodes (second discharge electrodes) 102 is located. A dielectric layer 104 is located on the first glass substrate 103 , covering the first electrode group, and a protection layer 105 is located on the dielectric layer 104. On an inner face of the second glass substrate 108 , a second electrode group including a plurality of data electrodes (third discharge electrodes; also referred to as "address electrodes") 107 and a plurality of erasing electrodes 109 is located. As is illustrated in Figure 9A, the scanning electrodes 101a through 101n (only 101a, 101b and 101c are shown here) and the sustaining electrodes 102a through 102n (only 102a, 102b and 102c are shown here) are provided in parallel alternately. The data electrodes 107a through 107m (only 107a and 107b are shown here) and the erasing electrodes 109a through 109m (only 109a and 109b are shown here) are both provided in parallel alternately so as to perpendicularly cross the scanning electrodes 101a through 101n and the sustaining electrodes 102a through 102n. Adjacent scanning electrode and sustaining electrode (for example, 101a and 102a) form a pair, and adjacent data electrode and erasing electrode (for example, 107a and 109a ) form a pair. A projecting area of the scanning electrode and a projecting area of the sustaining electrode forming a pair are opposed to each other in an area S (Figure 9A ), where sustaining discharge occurs. The area S will be referred to as a "discharge area". The data electrodes 107a through 107m and the erasing electrodes 109a through 109m are strip-shaped, and are formed of a material having a satisfactory conductivity such as Ag, Ni, ITO or SnO 2 . The erasing electrodes 109a through 109m are each located so as to cross a middle part of the respective discharge area S . The second electrode group including the data electrodes 107a through 107m and the erasing electrodes 109a through 109m is opposed to the protection layer 105 with a discharge space 106 full of discharge gas interposed therebetween. The dielectric layer 104 is formed of borosilicate glass or the like, and the protection layer 105 is formed of MgO or the like. In the above-described example, the protection layer 105 is provided on the dielectric layer 104 , but the protection layer 105 may be eliminated if the dielectric layer 104 can sufficiently withstand the discharge. The substrates 103 and 108 may be formed of ceramic instead of glass if a sufficient strength is provided. At least one of the substrates 103 or 108 needs to be a transparent substrate in order to allow discharge light to transmit therethrough. Hereinafter, a method for driving the AC-type PDP 100 will be described with reference to Figures 10A and 10B. Figures 10A and 10B are timing charts illustrating the operation of the AC-type PDP 100. First, in the writing operation, a positive writing pulse having an amplitude of +Vw shown in waveform DATA in Figure 10A is applied to at least one data electrode selected from the data electrodes 107a through 107m (for example, the data electrode 107a ) which corresponds to a pixel for displaying an image in accordance with the scanning electrode 101a. Simultaneously, a negative scanning pulse having an amplitude of -Vs shown in waveform SCN1 is applied to the scanning electrode 101a. By such application, discharge occurs at an intersection W1 (Figure 9A ) of the data electrode 107a and the scanning electrode 101a, and thus a positive charge is stored in an area of a surface of the protection layer 105, the area positionally corresponding to the intersection W1. In other words, such an area acts as a write cell. Next, a positive writing pulse having an amplitude of +Vw shown in waveform DATA is applied to at least one data electrode selected from the data electrodes 107a through 107m (for example, the data electrode 107a ) which corresponds to a pixel for displaying an image in accordance with the scanning electrode 101b. Simultaneously, a negative scanning pulse having an amplitude of -Vs shown in waveform SCN2 is applied to the scanning electrode 101b. By such application, discharge occurs at an intersection W2 (Figure 9A ) of the data electrode 107a and the scanning electrode 101b, and thus a positive charge is stored in an area of the surface of the protection layer 105 , the area positionally corresponding to the intersection W2 . In other words, such an area acts as a write cell. In this manner, during the process of applying negative scanning pulses having an amplitude of -Vs shown in waveforms SCN1 through SCNn to the scanning electrodes 101a through 101n respectively, a positive writing pulse having an amplitude of +Vw is applied to at least one selected data electrode which corresponds to a pixel for displaying an image in accordance with the respective scanning electrode. Thus, a positive charge is stored in a prescribed area (write cell) of the surface of the protection layer 105 . The writing operation is followed by the sustaining operation. In the sustaining operation, a negative sustaining pulse having an amplitude of -Vs shown in waveform SUS is applied to all the sustaining electrodes 102 , and negative sustaining pulses having an amplitude of -Vs shown in waveforms SCN1 through SCNn are applied to all the scanning electrodes 101 , respectively. The pulse application to the sustaining electrodes 102 and the pulse application to the scanning electrodes 101 are performed alternately. The application of the first sustaining pulse to each sustaining electrode 102 discharges the positive charge stored on the protection layer 105 , and thus sustaining discharge occurs on the discharge area S which belongs to the same discharge cell as the respective intersection. The alternate application of the negative sustaining pulse to each sustaining electrode 102 and each scanning electrode 101 continues the sustaining discharge on the respective discharge area S . By light emission caused by such sustaining discharge, characters and images are displayed. In the erasing operation, a positive erasing pulse having an amplitude of +Va shown in waveform SUS is applied to all the sustaining electrodes 102. Simultaneously a negative erasing pulse having an amplitude of -Ve shown in waveform EXT is applied to all the erasing electrodes 109 . By such application, erasing discharge occurs between the sustaining electrodes 102 and the erasing electrodes 109 , and thus the charge stored on the protection layer 105 by sustaining discharge is completely erased. As a result, the sustaining discharge does not continue even if a sustaining pulse is applied. Thus, the sustaining operation is terminated. As is described above, in the erasing operation, the erasing discharge occurs between the sustaining electrodes 102 and the erasing electrodes 109 which are opposed to each other with the discharge space 106 interposed therebetween. At this point, discharge is induced also between the erasing electrodes 109 and the scanning electrodes 101 opposed thereto. Accordingly, when the discharge is finished, the protection layer 105 has a surface potential which is equal to the potential required for stopping the discharge, both in the area corresponding to a projecting area of the scanning electrode 101 and in the area corresponding to a projecting area of the sustaining electrode 102 in each discharge area S . In other words, the area of the protection layer 105 corresponding to a projecting area of the scanning electrode 101 and the area of a protection layer 105 corresponding to the projecting area of the sustaining electrode 102 have an equal potential in each discharge area S . Such a uniform potential eliminates the necessity of precise adjustment of the pulse voltage or the pulse width. Accordingly, the erasing operation can be performed accurately. The erasing electrodes 109 , which are supplied with a negative pulse, act as a cathode. If the erasing electrodes 109 are formed of a cathode material which is generally used for a cathode, a stable discharge effect can be obtained even if the pulse applied during the erasing operation is low. In other words, as is shown in Figure 10A, at least one of the negative erasing pulse having an amplitude of -Ve shown in waveform EXT and the positive scanning pulse having an amplitude of +Va may be lower. Accordingly, the erasing operation can be performed reliably at a lower power consumption. Preferable materials for the erasing electrodes 109 include metals such as Al, Ni and LaB 6 and oxides such as La (x) Sr (1-x) CoO 3 , and La (x) Sr (1-x) MnO 3 . In a driving method shown in Figure 10B, the negative erasing pulse having an amplitude of -Ve is applied to the erasing electrodes 109 , but application of the positive erasing pulse having an amplitude of +Va to the sustaining electrodes 102 is eliminated. Such a manner of application is sufficient to erase the residual charge on the protection layer 105 if the erasing electrodes 109 are formed of one of the above-mentioned materials. In such a case, the sustaining electrodes 102 are supplied with a negative pulse but not with a positive pulse. This simplifies the structure of the driving circuit for the AC-type PDP 100 and reduces power consumption. As is described above, in the AC-type PDP 100 , the scanning electrodes 101 and the sustaining electrodes 102 are covered with the dielectric layer 104 and the protection layer 105. The data electrodes 107 and the erasing electrodes 109 are provided opposed to the protection layer 105 with the discharge space 106 interposed therebetween. By such a structure, erasing pulses can be applied to the sustaining electrodes 102 and the erasing electrodes 109 during the erasing operation to cause discharge between the sustaining electrodes 102 and the erasing electrodes 109 . Thus, the residual charge on the protection layer 105 can be completely erased. As a result, the surface potential of the protection layer 105 obtained after the sustaining discharge can be uniform in each discharge area S even if the potential required for stopping the discharge is varied among different discharge cells or such a potential changes over time. Accordingly, a more highly reliable AC-type PDP can be obtained which reproduces characters and images accurately by eliminating influence of the residual charge. Since the erasing operation is performed by discharge caused between the sustaining electrodes 102 and the erasing electrodes 109 which are opposed to each other with the discharge space 106 interposed therebetween, it is not necessary to reduce the width of the erasing pulse as is in the conventional PDPs. Thus, insufficient erasing caused by fluctuation in the width of the narrow pulse can be prevented. Example A method for driving an AC-type PDP in the example according to the present invention will be described with reference to Figure 27. The method in the example includes an initiating period in addition to the writing, sustaining and erasing periods. Figure 27 is a timing chart illustrating the operation in the example. First, in an initiating period, a positive initiating pulse having an amplitude of +Vr (V) is applied to all the scanning electrodes and all the sustaining electrodes simultaneously as is shown in waveforms SCN1 through SCNn and SUS. By such application, initiating discharge occurs between the data electrodes and the scanning electrodes and between the data electrodes and the sustaining electrodes. In a writing period following the initiating period, a positive writing pulse having an amplitude of +Vw (V) shown in waveform DATA is applied to a prescribed data electrode. Simultaneously, a negative scanning pulse having an amplitude of -Vs (V) shown in waveform SCN1 is applied to a first scanning electrode (for example, the scanning electrode 102a in Figure 9A ). By such application, writing discharge occurs at the intersection of the prescribed data electrode and the first scanning electrode. Next, a positive writing pulse having an amplitude of +Vw (V) shown in waveform DATA is applied to a prescribed data electrode. Simultaneously, a negative scanning pulse having an amplitude of -Vs (V) shown in waveform SCN2 is applied to a second scanning electrode (for example, the scanning electrode 102b in Figure 9A ). By such application, writing discharge occurs at the intersection of the prescribed data electrode and the second scanning electrode. Such operation is repeated, and finally a positive writing pulse having an amplitude of +Vw (V) shown in waveform DATA is applied to a prescribed data electrode. Simultaneously, a negative scanning pulse having an amplitude of -Vs (V) shown in waveform SCNn is applied to an "n"th scanning electrode (for example, the scanning electrode 102n in Figure 9A ). By such application, writing discharge occurs at the intersection of the prescribed data electrode and the "n"th scanning electrode. In a sustaining period following the writing period, a negative sustaining pulse having an amplitude of -Vs (V) is applied to all the sustaining electrodes and all the scanning electrodes as is shown in waveforms SCN1 through SCN2 and SUS. By such application, sustaining discharge starts in a discharge cell including the intersection where the writing discharge occurred, and the sustaining discharge continues while application of the sustaining pulse is repeated. In an erasing period following the sustaining period, a negative narrow erasing pulse having an amplitude of -Vs (V) shown in waveform SUS is applied to all the sustaining electrodes. By such application, erasing discharge occurs, thereby terminating the sustaining discharge. Thus, in the method in this example, an initiating pulse having an opposite polarity to the polarity of the scanning pulse applied to the scanning electrodes is applied to the scanning electrodes and the sustaining electrodes. Hereinafter, effects obtained by the initiating pulse will be described with reference to movement of the wall charges in the discharge cell illustrated in Figures 28A through 28G. Figures 28A through 28G are cross sectional views of the AC-type PDP according to the present invention, illustrating the movement of the wall charges in each step of the operation shown in Figure 27. Figure 28A shows an initial state before the AC-type PDP is turned on. The discharge cell in the AC-type PDP has no wall charge. As is shown in Figure 28B, in the initiating period after the AC-type PDP is turned on, an initiating pulse having an amplitude of +Vr (V) is applied to the scanning electrodes 701 and the sustaining electrodes 702. Since no wall charge is stored in the discharge cell, a voltage which is sufficient to cause discharge is not applied between areas of a surface of a dielectric layer 709 corresponding to the data electrodes 707 and areas of a surface of a protection layer 705 corresponding to the scanning electrodes 701 and between the areas of the surface of the dielectric layer 709 corresponding to the data electrodes 707 and the areas of the surface of the protection layer 705 corresponding to the sustaining electrodes 702 . Accordingly, initiating discharge does not occur. As is shown in Figure 28C , in the following writing period, a writing pulse having an amplitude of +Vw (V) is applied to the data electrode 707 and a negative scanning pulse having an amplitude of -Vs (V) is applied to the scanning electrode 701 . Then, writing discharge occurs at the intersection of the data electrode 707 and the scanning electrode 701 . A negative wall charge is stored in the area of the surface of the dielectric layer 709 corresponding to the data electrode 70 7, and a positive wall charge is stored in the area of the surface of the protection layer 705 corresponding to the scanning electrode 701 . As is shown in Figure 28D , in the following sustaining period, a negative sustaining pulse having an amplitude of -Vs (V) is applied to the sustaining electrode 702 . Then, the voltage generated by the positive wall charge stored on the area of the surface of the protection layer 705 corresponding to the scanning electrode 701 is superimposed on the voltage of the sustaining pulse and applied between the area of the surface of the protection layer 705 corresponding to the scanning electrode 701 and the area of the protection layer 705 corresponding to the sustaining electrode 702 . Accordingly, sustaining discharge occurs between the above-mentioned two areas. As a result, a negative wall charge is stored on the area of the protection layer 705 corresponding to the scanning electrode 701 , and a positive wall change is stored on the area of the protection layer 570 corresponding to the sustaining electrode 702. Further in the sustaining period, as is shown in Figure 28E , a negative sustaining pulse having an amplitude of -Vs (V) is applied to the scanning electrode 701 . Then, the voltage generated by the negative wall charge stored on the area of the protection layer 705 corresponding to the scanning electrode 701 by the sustaining discharge and the voltage generated by the positive wall charge stored on the area of the protection layer 705 corresponding to the sustaining electrode 702 are superimposed on the voltage of the sustaining pulse and applied between the area of the protection layer 705 corresponding to the scanning electrode 701 and the area of the protection layer 705 corresponding to the sustaining electrode 702 . Thus, sustaining discharge occurs again between the above-mentioned two areas. As a result, a negative wall charge is stored on the area of the protection layer 705 corresponding to the sustaining electrode 702, and a positive wall charge is stored on the area of the protection layer 705 corresponding to the scanning electrode 701 . Still in the sustaining period, as is shown in Figure 28D again, a sustaining pulse having an amplitude of -Vs (V) is applied to the sustaining electrode 702 . Then, the voltage generated by the negative wall charge stored on the area of the protection layer 705 corresponding to the sustaining electrode 702 by the sustaining discharge and the voltage generated by the positive wall charge stored on the area of the protection layer 705 corresponding to the scanning electrode 701 are superimposed on the voltage of the sustaining pulse and applied between the area of the protection layer 705 corresponding to the scanning electrode 701 and the area of the protection layer 705 corresponding to the sustaining electrode 702 . Accordingly, sustaining discharge occurs again between the above-mentioned two areas. As a result, a negative wall charge is stored on the area of the protection layer 705 corresponding to the scanning electrode 701 , and a positive wall charge is stored on the area of the protection layer 705 corresponding to the sustaining electrode 702 . In this manner, a sustaining pulse having an amplitude of -Vs (V) is applied to all the sustaining electrodes 702 and all the scanning electrodes 701 alternately. By such application, sustaining discharge occurs repeatedly in the sustaining period as is shown in Figures 28D and 28E , and the phosphor layers 710 are excited by ultraviolet rays generated by the repeated sustaining discharge, thereby performing display. As is shown in Figure 28F , in the following erasing period, a negative narrow erasing pulse having an amplitude of -Vs (V) is applied to the sustaining electrode 702 . Then, the voltage generated by the negative wall charge stored on the area of the protection layer 705 corresponding to the sustaining electrode 702 by the sustaining discharge and the voltage generated by the positive wall charge stored on the area of the protection layer 705 corresponding to the scanning electrode 701 are superimposed on the voltage of the negative narrow erasing pulse and applied between the area of the protection layer 705 corresponding to the scanning electrode 701 and the area of the protection layer 705 corresponding to the sustaining electrode 702 . Accordingly, erasing discharge occurs again between the above-mentioned two areas. However, since such erasing discharge is maintained for a short period of time due to the narrow pulse, the discharge is terminated midway. Accordingly, by setting the width of the narrow erasing pulse to be optimum, the wall charge on the area of the protection layer 705 corresponding to the sustaining electrode 702 and the wall charge on the area of the protection layer 705 corresponding to the scanning electrode 701 can be neutralized. Thereafter, sustaining discharge does not occur even if a sustaining pulse is applied unless a writing pulse is applied again. Accordingly, discharge is kept in a pause. The level of the residual wall charge in Figure 28F is less than the level of the residual wall charge in Figure 28C because the wall charge is partially extinguished during the sustaining discharge. As is shown in Figure 28B, in the initiating period, a positive pulse having an amplitude of +Vr (V) is applied to the scanning electrodes 701 and the sustaining electrodes 702 . By such application, as is shown in Figure 28F , the voltage generated by the negative wall charge remaining on the area of the dielectric layer 709 corresponding to the data electrode 707 and the voltage generated by the positive wall charge remaining on the area of the protection layer 705 corresponding to the scanning electrode 701 and the area of the protection layer 705 corresponding to the sustaining electrode 702 are superimposed on the voltage of the initiating pulse and applied between the area of the dielectric layer 709 corresponding to the data electrode 707 and the area of the protection layer 705 corresponding to the scanning electrode 701 and between the area of the dielectric layer 709 corresponding to the data electrode 707 and the area of the protection layer 705 corresponding to the sustaining electrode 702. By such application, initiating discharge occurs between the above-mentioned areas. As a result, the wall charges remaining in the discharge cell after the erasing operation is neutralized completely, and the discharge cell has no wall charge. By repeating the operation illustrated in Figures 28B through 28F in this manner, an image is displayed. As is described above, even if some wall charges remain in the discharge cell after the erasing operation, such remaining wall charges are neutralized completely since initiating discharge occurs by application of an initiating pulse. As a result, the discharge cell has no wall charge again, and thus the next writing discharge occurs more easily. The voltage generated by the wall charge stored on the area of the protection layer 705 corresponding to the scanning electrode 701 and the wall charge stored on the area of the protection layer 705 corresponding to the sustaining electrode 702 , both stored by the writing discharge performed after the erasing operation, is larger than such a voltage which is obtained when no initiating pulse is applied. The larger voltage causes sustaining discharge more easily. Accordingly, the discharge is more stable, and thus the AC-type PDP shows no discharge cell in which light emission does not occur. In the case that the AC-type PDP is turned on to start operating in the state where the wall charge has already been distributed as is shown in Figure 28G , namely, in the state where a negative wall charge is stored on the area of the dielectric layer 709 corresponding to the data electrodes 707 and a positive wall charge is stored on the area of the protection layer 705 corresponding to the scanning electrodes 701 and the sustaining electrodes 702 , the wall charges act in the direction of counteracting the voltage of the writing pulse. Accordingly, writing discharge and sustaining discharge are both difficult to be realized. However, when the initiating pulse is applied, the voltage of the initiating pulse is superimposed on the voltage generated by the above-mentioned charge distribution state, due to the polarity of the initiating pulse, and applied between the area of the dielectric layer 709 corresponding to the data electrode 707 and the area of the protection layer 705 corresponding to the scanning electrode 701 and between the area of the dielectric layer 709 corresponding to the data electrode 707 and the area of the protection layer 705 corresponding to the sustaining electrode 702 . By such application, initiating discharge occurs, thereby completely neutralizing the wall charges distributed as is shown in Figure 28G. As a result, the discharge cell returns to the state shown in Figure 28B where no wall charge exists. Since the following writing discharge and sustaining discharge occur more easily, the rise time for display after the AC-type PDP is turned on, namely, the time period from the AC-type PDP is turned on until display is normally performed is shortened significantly. In the above example, the initiating pulse is applied to both of the scanning electrodes 701 and the sustaining electrodes 702. In the case where the wall charges remaining on the area of the protection layer 705 corresponding to the scanning electrodes 701 and the area of the protection layer 705 corresponding to the sustaining electrodes 702 exist unbalanced, namely, more wall charges exist on either area, the initiating pulse may be applied only to either the scanning electrodes 701 or the sustaining electrodes 702. With reference to Figures 29A and 29B, a method for driving an AC-type PDP in a modification of the seventh example will be described. Figure 29A is a timing chart illustrating application of an initiating pulse. The method in this modification is the same as the method described with reference to Figure 27 except for application of the initiating pulse. As is shown in Figure 29A , in the initiating period, an initiating pulse is applied to the data electrodes 707. Such an initiating pulse has an opposite polarity to the polarity of the writing pulse applied to the data electrode 707 in the writing period as is shown in waveform DATA. Figure 29B schematically illustrates voltages in the scanning, sustaining and data electrodes after the application of the initiating pulse. The level and the polarity of the potential in each electrode are different from those of the case shown in Figures 28A through 28G, but the polarity of the voltage applied between the data electrode 707 and the scanning electrode 701 and between the data electrode 707 and the sustaining electrode 702 caused by the initiating pulse is the same as the case shown in Figures 28A through 28G. Accordingly, the AC-type PDP operates in the same manner and achieves the same effect. Figures 30A and 30B are timing charts illustrating application of an initiating pulse in different shapes. In Figure 30A, the initiating pulse has a different shape from the pulse shown in Figure 27. In Figure 30B, the initiating pulse has a different shape from the pulse shown in Figure 29A. The operation in the other periods is the same as described above. In practice, the optimum voltage of the initiating pulse is different in each discharge cell for various factors. In the case that the waveform of the initiating pulse is square, each discharge cell is not supplied with an optimum voltage, but all the discharge cells are always supplied with a maximum voltage. By such a manner of application, the initiating discharge is performed insufficiently or excessively in some of the discharge cells. In such discharge cells, light emission does not occur or is unstable. As is appreciated from this, it is difficult to set the voltage of the initiating pulse so as to neutralize the wall charges in all the discharge cells completely thus to obtain the normal initiating operation. In the case when an initiating pulse having an amplitude which changes gradually is applied, initiating discharge occurs in each discharge cell when the voltage of the initiating pulse reaches the optimum level for the discharge cell, due to the slow increase in the voltage. Accordingly, the wall charges can be neutralized completely in all the discharge cells in the initiating period. Thus, the initiating operation is performed more reliably. Further, normal initiating operation can be performed in a wider range of voltages of the initiating pulse. An optimum value of a change time tc required for the voltage of the initiating pulse (shown in Figures 30A and 30B ) to change from 10% to 90% of the amplitude thereof will be described. Figure 31 illustrates the state of light emission with respect to the relationship between the voltage +Vr of the initiating pulse and the change time tc of the initiating pulse. As is appreciated from Figure 31 , if the amplitude of the initiating pulse is too small, light emission does not occur; and if the amplitude of the initiating pulse is too large, unstable light emission occurs, both regardless of the change time tc. Such a phenomenon provides the range of voltages of the initiating pulse for obtaining a normal initiating operation. If the change time tc is 1 µs or less, there is substantially no range of amplitude of the initiating pulse for providing the normal operation. If the change time tc is 5 µs or more, the range of amplitude of the initiating pulse for providing the normal operation is sufficiently wide. Accordingly, the change time tc is preferably 5 µs or more. The upper limit of the change time tc which is required to obtain the normal operation is not determined by Figure 31 . However, considering that the upper limit of a refreshing period of the display screen (sum of the writing, sustaining and erasing periods) is generally approximately 17 ms (1/60 seconds), the upper limit of the change time is approximately 10 ms in practical use. Accordingly, the preferable range of the change time tc which is practically usable is 5 µs to 10 ms inclusive. As is appreciated from the above description, the wall charges in all the discharge cells are neutralized completely in the initiating period to perform the initiating operation more reliably by setting the change time tc which is required for the voltage of the initiating pulse from 10% to 90% of the amplitude thereof between 5 µs and 10 ms inclusive. Such a range is wider than the case where a square pulse is applied. The effect is the same. In Figure 30A, the initiating pulse is applied to both of the scanning electrodes 701 and the sustaining electrodes 702 . In the case where the wall charges remaining on the area of the protection layer 705 corresponding to the scanning electrodes 701 and the area of the protection layer 705 corresponding to the sustaining electrodes 702 exist unbalanced, namely, more wall charges exist on either area, the initiating pulse may be applied only to either the scanning electrodes 701 or the sustaining electrodes 702. With reference to Figures 32A and 32B, methods for driving an AC-type PDP in other modifications of the seventh example will be described. Figure 32A is a timing chart illustrating application of an initiating pulse. The method in this modification is the same as the method described with reference to Figure 27 except for application of the initiating pulse and the assisting pulse. As is shown in Figure 32A, in the initiating period, a positive initiating pulse having an amplitude of +Vr (V) is applied to the data electrodes. Simultaneously, an assisting pulse having the same amplitude +Vr (V) and the same polarity is applied to the scanning electrodes and the sustaining electrodes. Before the assisting pulse is terminated, the initiating pulse is terminated. The initiating operation in this modification will be described, hereinafter. First, as is shown in Figure 32A, a positive assisting pulse and a positive initiating pulse both having an amplitude of +Vr (V) are applied to all the scanning electrodes, all the sustaining electrodes and all the data electrodes simultaneously. Then, the voltage in all the scanning electrodes, all the sustaining electrodes and all the data electrodes changes to +Vr. However, the voltage between the data electrodes and the scanning electrodes and the voltage between the data electrodes and the sustaining electrodes remains 0 V. When the initiating pulse is terminated while the assisting pulse is still applied, a voltage of +Vr is applied between the data electrodes and the scanning electrodes and between the data electrodes and the sustaining electrodes. The direction in which such a voltage is applied is the same as that of the voltage applied between the data electrodes 707 and the scanning electrodes 701 and between the data electrodes 707 and the sustaining electrodes 702 in the initiating period in Figure 28B. The operation is the same as described with reference to Figure 27, and the same effect is achieved. In Figure 32A , the assisting pulse is applied to both of the scanning electrodes 701 and the sustaining electrodes 702 . In the case where the wall charges remaining on the area of the protection layer 705 corresponding to the scanning electrodes 701 and the area of the protection layer 705 corresponding to the sustaining electrodes 702 exist unbalanced, namely, more wall charges exist on either area, the assisting pulse may be applied only to either the scanning electrodes 701 or the sustaining electrodes 702. Figure 32B is a timing chart illustrating application of an initiating pulse. The method in this modification is the same as the method described with reference to Figure 27 except for application of the initiating pulse and the assisting pulse. As is shown in Figure 32B, in the initiating period, a negative assisting pulse having an amplitude of -Vr (V) is applied to the data electrodes. Simultaneously, an initiating pulse having the same amplitude -Vr (V) and the same polarity is applied to the scanning electrodes and the sustaining electrodes. Before the assisting pulse is terminated, the initiating pulse is terminated. The initiating operation in this modification will be described, hereinafter. First, as is shown in Figure 32B, a negative initiating pulse and a negative assisting pulse both having an amplitude of -Vr (V) are applied to all the scanning electrodes, all the sustaining electrodes and all the data electrodes simultaneously. Then, the voltage in all the scanning electrodes, all the sustaining electrodes and all the data electrodes changes to -Vr. However, the voltage between the data electrodes and the scanning electrodes and the voltage between the data electrodes and the sustaining electrodes remains 0 V. When the initiating pulse is terminated while the assisting pulse is still applied, a voltage of -Vr is applied between the data electrodes and the scanning electrodes and between the data electrodes and the sustaining electrodes. The direction in which such a voltage is applied is the same as that of the voltage applied between the data electrodes 707 and the scanning electrodes 701 and between the data electrodes 707 and the sustaining electrodes 702 in the initiating period in Figure 28B. The operation is the same as described with reference to Figure 27, and the same effect is achieved. Figures 33A and 33B are timing charts illustrating application of an initiating pulse in different shapes. In Figure 33A, the initiating pulse has a different shape from the pulse shown in Figure 30A. In Figure 33B, the initiating pulse has a different shape from the pulse shown in Figure 30A. The operation in the other periods is the same as described above. In Figure 33A, the assisting pulse is applied to both of the scanning electrodes 701 and the sustaining electrodes 702 . In the case where the wall charges remaining on the area of the protection layer 705 corresponding to the scanning electrodes 701 and the area of the protection layer 705 corresponding to the sustaining electrodes 702 exist unbalanced, namely, more wall charges exist on either area, the assisting pulse may be applied only to either the scanning electrodes 701 or the sustaining electrodes 702. In Figures 32A, 32B, 33A and 33B, the assisting pulse is applied simultaneously with the initiating pulse. The initiating pulse may be applied prior to the assisting pulse. In all the above-described cases in the seventh example, the initiating operation is rendered simultaneously to the scanning, sustaining and data electrodes. The same effect is obtained by rendering a plurality of groups of the initiating operation to the same plurality of groups of the scanning, sustaining and data electrodes with a delay. In all the above-described cases in the example, in the writing period, a writing pulse is applied to a prescribed data electrode and a scanning pulse is applied to the scanning electrodes one by one. The same effect is obtained by applying a writing pulse to all the data electrodes and applying a scanning pulse to all the scanning electrodes, thereby performing the writing operation in all the discharge cells simultaneously. In all the above-described cases in the example, the writing pulse is positive and the scanning pulse is negative. The same effect is obtained even if the polarities are opposite. In the case when the writing pulse is negative and the scanning pulse is positive, the initiating pulse and the assisting pulse also have the opposite polarities. In all the above-described cases in the example, the scanning pulse and the sustaining pulse have the same polarity. The same effect is obtained even if the sustaining pulse is negative (-Vs) as is shown in Figure 34. In all the above-described examples, the erasing pulse is a narrow pulse having the same polarity as the polarity of the sustaining pulse. The same effect is obtained even if the erasing pulse has an opposite polarity to that of the sustaining electrode as is shown in Figure 35, or even if the erasing pulse has a larger width but a smaller amplitude as is shown in Figure 36. In all the above-described examples, the erasing pulse is applied to the sustaining electrodes. The same effect is obtained by applying the erasing pulse to the scanning electrodes. In all the above-described examples, one initiating period is provided in one field of operation, namely, between the writing period and the erasing period. The same effect is obtained even if one initiating period is provided every several fields. In the AC-type PDP used in the example, the data electrodes 707 are covered with the second dielectric layer 710 , and the phosphor layer 710 is provided on the second dielectric layer 709 . The same method can be used for driving an AC-type PDP in which display is performed directly utilizing light emitted by discharge and thus has no phosphor layer 710 . The same method can also be used for driving an AC-type PDP in which the data electrodes 707 are directly covered with a phosphor layer 710 without the second dielectric layer 709. In such a case, the phosphor layer acts in the same manner as the second dielectric layer 709. The same method can still be used for driving an AC-type PDP in which the data electrodes 707 are exposed to the discharge space 706 without the second dielectric layer 709, without the phosphor layer 710 , or without the second dielectric layer 709 and the phosphor layer 710 . In such a case, although no wall charge is stored on the area of the second dielectric layer 709 corresponding to the data electrodes 707, an equivalent wall charge is stored on the area of the protection layer 705 corresponding to the scanning electrode 701 . The pair of substrates on which the electrodes are located are formed of glass or ceramic. One of the substrates should be a transparent substrate in order to allow light emitted by discharge to transmit therethrough. As has been described so far, by a driving method in the example, an initiating period is provided before the writing, sustaining and erasing periods. In the initiating period, an initiating pulse having an opposite polarity to the polarity of the scanning pulse applied in the writing period is applied to at least one of the plurality of scanning electrodes and the plurality of sustaining electrodes. By the initiating pulse applied prior to the writing period, the wall charges remaining in the discharge cell after the erasing period can be neutralized completely. Since the discharge cell returns to the state of having no wall charge by the initiating discharge, defective writing discharge or defective sustaining discharge does not occur. Therefore, a series of operations in the writing, sustaining and erasing periods are performed reliably, and thus light is emitted in all the discharge cells. Even if the wall charges have already been distributed in the initial state before the AC-type PDP is turned on, such wall charges are neutralized completely by application of an initiating pulse performed in the initiating period, thereby returning the discharge cell to the state where no wall charge is stored. Accordingly, the rising time after the AC-type PDP is turned on is shortened, and thus the above-mentioned series of operations are performed reliably.

Claims: A method for driving a gas discharge display apparatus including a first substrate (703) and a second substrate (708) located opposed to each other with a discharge space interposed therebetween to form an outer casing; a first electrode group including a plurality of scanning electrodes (701) and a plurality of sustaining electrodes (702) located parallel to each other and alternately on the inner face of the first substrate (703); a dielectric layer (704) covering the first electrode group; and a second electrode group including a plurality of data electrodes (707) located parallel to one another on the inner face of the second substrate (708) in a direction perpendicular to the electrodes of the first electrode group, characterised by the method comprising the following sequential steps: a writing step of applying a writing pulse to the plurality of data electrodes (707) and applying a scanning pulse having an opposite polarity to the polarity of the writing pulse to the plurality of scanning electrodes (701); then a sustaining step of applying a sustaining pulse to the plurality of sustaining electrodes (702) and the plurality of scanning electrodes (701); and then an erasing step of applying an erasing pulse, wherein, prior to the writing step, an initiating step is performed of applying an initiating pulse having a prescribed polarity to prescribed electrodes selected from the group consisting of the plurality of data electrodes (707), the plurality of sustaining electrodes (701) and the plurality of scanning electrodes (702). A method for driving a gas discharge display apparatus according to claim 1, wherein the initiating step includes the step of applying an initiating pulse having an opposite polarity to the polarity of the scanning pulse applied in the writing step to at least one of the plurality of scanning electrodes and the plurality of sustaining electrodes. A method for driving a gas discharge display apparatus according to claim 1, wherein the initiating step includes the step of applying an initiating pulse having an opposite polarity to the polarity of the writing pulse applied in the writing step to the plurality of data electrodes. A method for driving a gas discharge display apparatus according to claim 1, wherein a time period required for the instantaneous voltage of the initiating pulse to change between 10% and 90% of an amplitude thereof is set to be between 5 µs and 10 ms inclusive. A method for driving a gas discharge display apparatus according to claim 2, wherein the initiating step includes the step of applying an assisting pulse to the plurality of scanning electrodes and the plurality of sustaining electrodes, the assisting pulse having an identical polarity and an identical amplitude with the polarity and the amplitude of the initiating pulse to the plurality of data electrodes. A method for driving a gas discharge display apparatus according to claim 3, wherein the initiating step includes the step of applying an assisting pulse to the plurality of data electrode, the assisting pulse having an identical polarity and an identical amplitude with the polarity and the amplitude of the initiating pulse to the plurality of scanning electrodes and the plurality of sustaining electrodes. A method for driving a gas discharge display apparatus according to claim 5, wherein a time period required for the instantaneous voltage of the initiating pulse to change between 10% and 90% of an amplitude thereof is set between 5 µs and 10 ms inclusive. A method for driving a gas discharge display apparatus according to claim 6, wherein a time period required for the instantaneous voltage of the initiating pulse to change between 10% and 90% of an amplitude thereof is set between 5 µs and 10 ms inclusive.

Inventors: HIRAO KAZUNORI, HIRAYAMA TORU, ITO YUKIHARU, ITSUDA KOICHI, OKAMOTO TAKIO, SHINO TAICHI, WAKITANI TAKAO, HIRAO, KAZUNORI, HIRAYAMA, TORU, ITO, YUKIHARU, ITSUDA, KOICHI, OKAMOTO, TAKIO, SHINO, TAICHI, WAKITANI, TAKAO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1995
Main classification: H01J17
IPC codes: H01J17, G09G3