FR2825504A1 - Method of resetting a plasma display, involves holding voltage on first display lines at first voltage while second voltage on second electrode lines is reduced - Google Patents

Abstract

A method of resetting a plasma display with a front substrate and a rear substrate involves gradually increasing a voltage present on the first display conductors to a first voltage in a first resetting step, followed by similarly increasing a voltage on the second display electrodes gradually to a second voltage and increasing the voltage on the first display electrodes gradually to a third voltage in a second resetting step. The voltage of the first display electrode conductors is held at the first voltage while that on the second electrode lines is gradually reduced to a fourth voltage in a third resetting step. The second voltage is higher than the first and the third voltages, and the fourth voltage is lower than the third voltage. An Independent claim is given for a plasma display driver device.

Description

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METHOD FOR RESETTING A DISPLAY SCREEN
PLASMA TO IMPROVE CONTRAST
The present invention relates to a method for resetting a plasma display screen and more specifically, to a method for resetting a plasma display screen, this reset being first carried out in an elementary secondary field which constitutes a minimum driving period. for a plasma display screen of the three-electrode surface discharge type, so that the wall charges in all the display cells are uniformly distributed and made suitable for the addressing to be carried out in the next step.

 FIG. 1 represents a typical example of a plasma display screen of the surface discharge type with three electrodes. FIG. 2 illustrates an example of a display cell for the screen in FIG. 1. As illustrated in FIGS. 1 and 2, a typical example of a plasma display screen 1 with surface discharge, comprises between front and rear glass substrates 10 and 13, lines of address electrodes Ai, As, ..., Am-1 and Am, front and rear dielectric layers 11 and 15, lines Y of electrodes Yi , ..., Yn, X lines of electrodes Xi, ..., Xn, a fluorescent substance 16, a plurality of partition walls 17, and a protective layer 12 which consists of a monoxide layer of magnesium (MgO).

 The rows of address electrodes A1, A2, ..., Am1 and An, are formed in a predetermined pattern on the front surface of the rear glass substrate 13. The rear dielectric layer 15 is applied to the front surface of the rear glass substrate 13 at the location where the lines of address electrodes Ai, A2, ..., Am-1 and Am are formed. The partitions 17 are formed on the front surface of the rear dielectric layer 15,

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 parallel to the lines of address electrodes Ai, A2 '..., Am-1 and Am. The partitions 17 delimit a discharge zone of each display cell and prevent interference between the neighboring display cells. The fluorescent substance 16 is applied to the surface between the partitions 17.

 The lines X of electrodes Xi, ..., Xn and the lines Y of electrodes Yi, ..., Yn are formed on the rear surface of the front glass substrate 10 perpendicularly to the lines of address electrodes Ai, As, ..., Am-l and Am. Each intersection point defines a corresponding display cell. Each of the lines X of electrodes Xi, ..., Xn is formed of a line of transparent electrode Xna of FIG. 2, which is formed of a transparent conductive material such as ITO (indium oxide and tin), and a metal electrode line Xnb in Figure 2, to increase the conductivity. Each of the lines Y of electrodes Yi, ..., Yn is formed of a line of transparent electrode Yna of FIG. 2, which is formed of a transparent conductive material such as ITO (indium oxide and of tin) and a line of metallic electrode Ynb in FIG. 2, to increase the conductivity. The front dielectric layer 11 is applied to the rear surface of the front glass substrate 10 where the lines X of electrodes Xi, ..., Xn and the lines Y of electrodes Yi, ... are formed. yn. A protective layer 12, for example consisting of a layer of MgO, to protect the screen 1 from an intense electric field, is applied to the rear surface of the front dielectric layer 11. A plasma generating gas is hermetically contained in the discharge space 14.

 FIG. 3 represents a typical example of a device for controlling the plasma display screen 1 of FIG. 1. Referring to FIG. 3, a conventional device for controlling the plasma display screen 1 includes an image processor 66, a device 62 for

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 logic control, an address control circuit 63, an X control circuit 64, and a Y control circuit 65. The image processor 66 converts an external analog image signal into a digital signal and generates a signal d internal image, for example 8-bit red image data (R), 8-bit green image data (G), 8-bit blue image data (B), a clock signal and vertical and horizontal synchronization signals. The logic control device 62 generates control control signals SA, Sy and Sx as a function of the internal image signal output by the image processor 66. The address control circuit 63 processes the address signal SA, among the control control signals SA, Sy and Sx output by the logic control device 62, to generate a display data signal. The display data signal produced is applied to the lines of address electrodes Ai, As, ..., Am-1 and Am. The piloting circuit 64 X processes the piloting command signal Sx X, among the control command signals SA, Sy and Sx output by the logic control device 62, to apply the processed signal to the lines X of electrodes Xi, ..., Xn. The piloting circuit 65 Y processes the piloting control signal Sy among the piloting control signals SA, Sy and Sx output by the logic control circuit 62, in order to apply the processed signal to the lines Y of electrodes Yi, ..., Yn.

des périodes d'adressage Al,... A8 et des périodes de décharge de maintenance SI,..., S8. FIG. 4 represents a typical example of a piloting method by display separation and addressing relating to the lines y of electrodes of the plasma display screen of FIG. 1. Referring to FIG. 4, an elementary frame is divided into 8 secondary fields SF1, ..., SF8 to produce a grayscale display by time distribution. In addition, each of the secondary fields SF1, ..., SF8 is divided into

addressing periods A1, ... A8 and maintenance discharge periods SI, ..., S8.

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 During each of the addressing periods A1, ..., A8, scanning pulses corresponding to each of the lines Y of electrodes Y, Yi, ..., Yn of FIG. 1, are sequentially applied at the moment when the display data signal is applied to the address electrode lines Ai, A2, ..., Am-1 and Am of Figure 1. Therefore, if a high display data signal is applied while scanning pulses are applied, it produces address line discharges and forms wall charges in selected discharge cells.

 During each of the maintenance discharge periods Sil, ..., S8, maintenance discharge pulses are applied alternately to all the lines Y of electrodes Yi, ..., Yn and to all the lines X d ' electrodes Xi, ..., Xn. A display discharge is then produced in the discharge cells at the place where the wall charges formed during the addressing periods Ai, ..., Ag. As a result, the brightness of the screen d plasma display is proportional to the length of the maintenance discharge periods Sil, ..., S8 in the elementary frame. The length of the maintenance discharge periods 81, m, S8 in the elementary frame is 255 T, where T is a unit of time. As a result, it is possible to display 256 levels of gray, including the case of never performing display in the elementary frame.

 In the present case, a time of 1T corresponding to 20 is fixed for the maintenance discharge period 81 of the first secondary field SF1. A time of 2T corresponding to 21 is fixed for the maintenance discharge period S2 of the second secondary field SF2. A time of 4T corresponding to 22 is fixed for the maintenance discharge period S3 of the third secondary field SF3. A time of 8T corresponding to 23 is fixed for the maintenance discharge period S4 of the fourth secondary field SF4. A time of 16T

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 corresponding to 24 is fixed for the maintenance discharge period S5 of the fifth secondary field SFS. A time of 32T corresponding to 25 is fixed for the maintenance discharge period S6 of the sixth secondary field SF6. A time of 64T corresponding to 26 is fixed for the maintenance discharge period S7 of the seventh secondary field SF7. A time of 128T corresponding to 27 is fixed for the maintenance discharge period S8 of the eighth secondary field SF8.

 Therefore, by appropriately selecting a secondary field from the eight secondary fields to be displayed, a total of 256 gradations can be displayed, including the case where no display is made in any of the secondary fields.

 In the above-mentioned plasma display screen driving method, during each of the addressing periods A1, ..., A8, a reset is carried out in such a way that the wall charges of all the cells display are uniformly distributed and are made suitable for addressing to be performed in the next step.

 FIG. 5 shows waveforms of signals applied to the electrode lines of a plasma display screen in accordance with a conventional reset method. Figure 6 shows the distribution of wall loads in a display cell at time t3 in Figure 5. Figure 7 shows the distribution of wall loads in a display cell at time t4 in Figure 5. FIG. 8 represents the level of illumination SL of the light produced by a plasma display screen corresponding to control signals of FIG. 5.

 The conventional reset process shown in Figure 5 is described in Japanese patent publications NO 2000-214.823 and 2000-242.224. In FIG. 5, the reference Spy designates a control signal applied to all the lines Y of electrodes Y1, ..., yin of

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la figure 1, la référence Spx désigne un signal de pilotage appliqué à toutes les lignes X d'électrodes Xi, ..., Xn de la figure 1, et la référence SRA désigne un signal de pilotage appliqué à toutes les lignes d'électrodes d'adresses Al,..., Am de la figure 1.

FIG. 1, the reference Spx designates a control signal applied to all the lines X of electrodes Xi, ..., Xn in FIG. 1, and the reference SRA designates a control signal applied to all the lines of electrodes Al, ..., Am of Figure 1.

 Referring to FIGS. 5 to 8, during the first reinitialization step (tl-t2), the voltages applied to the lines X of electrodes Xl, ..., Xn are gradually increased until a first voltage VBx, for example of 190 V, starting from the voltage of the ground VG as the fourth voltage. The voltage of the ground VG is here applied to the lines Y of electrodes Yi, ..., Yn and to the lines of address electrodes Ai, ..., Am.

Consequently, small discharges occur between the lines X of electrodes X1, ..., Xn and the lines Y of electrodes Yi, ..., Yn, and between the lines X of electrodes Xi, ... , Xn and the address electrode lines Ai, .... Am. Wall charges having the second polarity, that is to say the negative polarity, are then formed in the vicinity of the electrode lines X X1, ... Xn.

 During the second reset step (t2t3), a voltage applied to the lines Y of electrodes Yi, ..., Yn is gradually increased to a second voltage VByp, for example 400 V, starting from a fifth VBYM voltage, for example 180 V. The second voltage VByp is much higher than the first voltage VBX and the fifth voltage VsvM is slightly lower than the first voltage VBX. The voltage of the ground VG is here applied to the lines X of electrodes X1, ..., Xn and to the lines of address electrodes Ai, ..., Am. Consequently, a weak discharge is produced between the lines Y of electrodes Yi, ..., Yn and lines X of electrodes Xi, ..., Xn while a weaker discharge is produced between the lines Y of electrodes Yi, ..., Yn and the lines of electrodes of addresses Ai, ..., Am. The discharge between the lines Y of electrodes and the lines X of electrodes is here more intense than that which occurs between the

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 electrode lines Y and address electrode lines due to the fact that many wall charges of negative polarity form in the vicinity of the electrode lines X when the first reset step (tl-t2) is performed . Consequently, many wall charges of negative polarity form in the vicinity of the lines Y of electrodes Yi, ..., Yn.

Wall charges having the first polarity, namely the positive polarity, form in the vicinity of the lines X of electrodes Xi, ..., Xn. Wall charges of positive polarity are formed in smaller quantities in the vicinity of the lines of address electrodes Ai, ..., Am (refer to FIG. 6).

During the third reinitialization step (t3t4), while the voltage applied to the lines X of electrodes Xi, ..., Xn is maintained at the first voltage Vox, the voltage applied to the lines Y of electrodes Y, .. ., yin is gradually reduced to the voltage of the VG ground. The voltage of the ground VG is here applied to the lines of address electrodes Ai, ..., Am. Consequently, a small discharge is produced between the lines X of electrodes Xi, ..., Xn and the lines Y of electrodes Yi, ..., Yn, so that some of the wall charges of negative polarity in the vicinity of the lines Y of electrodes Yi, .... Yn move towards the lines of electrode of addresses Xi , ..., Xm (refer to figure 7). As the voltage of the ground VG is here applied to the rows of address electrodes Ai, ..., Am, the number of wall charges of positive polarity in the vicinity of the rows of address electrodes Ai, ... Am increases slightly.

 Therefore, in the next addressing step, a positive polarity display data signal is applied to the selected electrode lines Ai, ..., Am and a negative polarity scan signal is sequentially applied to the lines Y of electrodes Yi, ..., Yn, so that regular addressing can be carried out.

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 However, in the case of the conventional reset method, despite the fact that wall charges of negative polarity are formed in the vicinity of the lines X of electrodes Xl, ..., Xn during the first reset step tl-t2, the same ground voltage VG is applied to the lines X of electrodes Xi, ..., Xn and to the lines of address electrodes Ai, ..., Am during the second reset step (t2-t3). This therefore poses the following problems.

 First, an unnecessarily intense discharge is produced between the lines Y of electrodes Yi, ..., Yn and the lines X of electrodes Xl, ..., Xn during the second reinitialization step (t2-t3) . This reduces the contrast of the plasma display screen. In addition, an unnecessarily high number of positive polarity wall charges formed in the vicinity of the electrode lines X produce an excessively intense discharge between the electrode lines Y and the electrode lines during the third reset step ( t3-t4). This further reduces the contrast of a plasma display screen, as shown in Figure 8.

 Second, a relatively small discharge between the electrode lines Y and the address electrode lines during the second reset step (t2-t3) forms insufficient wall charges of positive polarity in the vicinity of the lines d 'address electrodes (refer to figure 6). Therefore, the positive polarity wall charges formed in the vicinity of the address electrode lines Ai, ..., Am are insufficient, as shown in Figure 7, and are not sufficient for the selected display cells during subsequent addressing.

 To solve the problems described above, the present invention aims to provide a method for resetting a plasma display screen aimed at increasing the contrast of the display screen at

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 plasma and to form a sufficient quantity of wall charges in display cells selected by addressing.

 To achieve the above-mentioned objective, a method is proposed for resetting a plasma display screen comprising front and rear substrates, separated from each other and opposite one of the another, wherein first and second lines of display electrodes are formed parallel to each other between the front and rear substrates and lines of address electrodes are formed perpendicular to the first and second lines of electrode display, the method consisting in gradually increasing the voltage applied to the first lines of display electrodes up to a first voltage (first reset step), in gradually increasing a voltage applied to the second lines of display electrodes up to at a second voltage higher than the first voltage and to gradually increase the voltage applied to the first lines of display electrodes up to a third sth voltage lower than the first voltage (second reset step), and to maintain the voltage applied to the first lines of display electrodes at the first voltage and to gradually reduce the voltage applied to the second lines of display electrodes until 'at a fourth voltage lower than the third voltage (third reset step).

 According to the reset method of the present invention, the voltage applied to the first lines of display electrodes during the second reset step gradually increases to the third voltage which is lower than the first voltage. Therefore, the following effects can be obtained.

 First, the present invention does not produce an unnecessarily intense discharge between the first

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 and second electrode lines during the second reset step. This prevents the plasma display screen from having a lower contrast. Furthermore, the present invention does not unnecessarily form numerous wall charges having the first polarity in the vicinity of the first lines of display electrodes. This does not lead to the production of an unnecessarily intense discharge between the first and second electrode lines during the third reset step, which increases the contrast of the plasma display screen.

 Second, during the second reset step, the present invention relatively intensifies the discharge between the second rows of display electrodes. This forms a sufficient amount of wall charges having the first polarity in the vicinity of the address electrode lines. Therefore, a sufficient amount of positively polarity wall charges formed in the vicinity of the address electrode lines can form a sufficient amount of wall charges in display cells selected by the subsequent addressing.

 It is preferable, in accordance with the present invention, that during the second reset step, when the first lines of display electrodes are in an electrically floating state, the voltage applied to the first lines of display electrodes is gradually increased up to the third voltage under the effect of wall charges having the first polarity formed in the vicinity of the first lines of display electrodes during the first reset step.

 The above-mentioned objective and the advantages of the present invention will emerge more clearly from the detailed description of one of its preferred embodiments with reference to the accompanying drawings.

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 FIG. 1 is a perspective view showing the structure of a typical example plasma display screen of the 3-electrode surface discharge type.

 FIG. 2 is a sectional view showing an example of a display cell for the screen in FIG. 1.

 FIG. 3 is a block diagram representing a typical example of a device for controlling the plasma display screen of FIG. 1.

 FIG. 4 is a timing diagram representing a typical example of a display separation and addressing control method relating to lines Y of electrodes of the plasma display screen of FIG. 1.

 Fig. 5 is a perspective view showing the waveform of signals applied to electrode lines of the plasma display screen in the case of a conventional reset method.

 FIG. 6 is a sectional view showing the distribution of the wall loads of a display cell at point t3 of FIG. 5.

 FIG. 7 is a sectional view showing the distribution of the wall charges of a display cell at point t4 of FIG. 5.

 FIG. 8 is a graph representing the level of brightness provided by the light produced by the plasma display screen corresponding to the control signals of FIG. 5.

 Fig. 9 is a view showing the waveform of signals applied to electrode lines of the plasma display screen in the case of a reset method according to a preferred embodiment of the present invention .

 FIG. 10 is a sectional view showing the distribution of the wall loads of a display cell at point t3 in FIG. 9.

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 FIG. 11 is a sectional view showing the distribution of the wall loads of a display cell at point t4 of FIG. 9.

 FIG. 12 is a graph representing the level of brightness provided by the plasma display screen as a function of time (tF-t3) of FIG. 9.

 FIG. 13 is a graph representing the level of luminosity of the light produced by the plasma display screen corresponding to the control signals of FIG. 9.

 In FIG. 9, the reference SRY designates a control signal applied to all of the lines Y of electrodes (Yl, ... Yn in FIG. 1), the reference SRX designates a control signal applied to all of the lines X of electrodes (Xi, ..., Xn in FIG. 1), and the reference SRA designates a control signal applied to all of the rows of address electrodes (Ai, ..., Am of FIG. 1).

 Referring to FIGS. 9 to 13, during the first reinitialization step (tl-t2), a voltage Srx applied to the lines X of electrodes Xi, ..., Xn gradually increases until a first voltage VBx, for example 190 V, starting from a ground voltage VG.

At the same time, the voltage of the ground VG is applied to the lines Y of electrode Y ,, ... Y. and to the lines of electrodes of addresses Ai, ..., Am. Consequently, a weak discharge occurs. produced between the electrode X lines and the electrode Y lines, and between the electrode X lines and the address electrode lines. This forms wall charges of negative polarity in the vicinity of the electrode lines X.

 During the second reinitialization step (t2-t3), a voltage SRy applied to the lines Y of electrodes gradually increases by a fifth voltage VsvM up to a second voltage VByp, for example by 400 V.

This is much higher than the first voltage VBx.

 VBYM, which is here for example 180 V, is slightly lower than the first voltage VBx. Voltage

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où C est la capacité totale de l'écran d'affichage à plasma et est proportionnelle au rapport de charge et i est la quantité totale de courant. applied to the electrode lines Y increases here up to the second voltage VByp. It then varies inversely proportional to the ratio of the number of discharge cells to be displayed to the total number of discharge cells ("charge ratio") in each secondary field. More precisely, at the end point tByp, the voltage increases more rapidly inversely proportional to the charge ratio in each secondary field. This is due to the fact that a voltage V applied to the capacitor C is preferably defined by equation 1 below: [Equation 1]

where C is the total capacity of the plasma display screen and is proportional to the charge ratio and i is the total amount of current.

 However, during the time (tF-t3), starting from a certain point tF and going to an end point t3 during the second reset step (t2-t3), the voltage applied to the lines X d ' electrodes gradually increase to a third VBF voltage. The third voltage VBF is lower than the fifth voltage VBYM.

 The control circuit 64 X in FIG. 3 can directly increase the voltage. However, if the voltages of the control circuit 64 X are in an electrically floating state, that is to say in a state of high impedance, an identical effect can be obtained. In fact, by making the upper and lower transistors of all the output terminals of the control circuit X X not passable, the voltage applied to the lines X of electrodes gradually increases until the third voltage VBF. This saves electrical energy for the control performed

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 during the second reset step (t2-t3). The voltage of the ground VG is applied to all the rows of address electrodes Ai, ..., Am. The third voltage VBF is here determined by equation 2 below.

[Equation 2]

In Equation 2, VF designates a voltage applied to the Y lines of electrodes at a floating start point.

progressivement jusqu'à la troisième tension VBF, un point de départ tF de l'état flottant doit ici être inférieur au temps de montée (tBYM-tBYp) de la tension appliquée aux lignes Y d'électrodes. Dans le cas présent, le point où la tension appliquée aux lignes Y d'électrodes atteint la seconde tension VBYP, c'est-àdire le point final du temps de montée (typ) diminue de façon inversement proportionnelle au rapport de charge dans le champ secondaire. De ce fait, le point de départ tF de l'état flottant doit également être antérieur d'un temps inversement proportionnel au rapport de charge. A cet effet, il est nécessaire de faire en sorte que le point de départ tF de l'état flottant soit fixé en un point où la tension appliquée aux lignes Y d'électrodes atteint la tension VF fixée. Dans le cas présent, la tension appliquée aux lignes X d'électrodes jusqu'à la troisième tension VBF croît à la même vitesse que celle avec laquelle la tension appliquée aux lignes Y d'électrodes augmente progressivement jusqu'à la seconde

tension VByp. To cause the voltage applied to the electrode lines X by electrical float to increase

gradually until the third voltage VBF, a starting point tF of the floating state must here be less than the rise time (tBYM-tBYp) of the voltage applied to the lines Y of electrodes. In this case, the point where the voltage applied to the electrode lines Y reaches the second voltage VBYP, i.e. the end point of the rise time (typ) decreases inversely proportional to the charge ratio in the field secondary. Therefore, the starting point tF of the floating state must also be earlier than a time inversely proportional to the charge ratio. For this purpose, it is necessary to ensure that the starting point tF of the floating state is fixed at a point where the voltage applied to the lines Y of electrodes reaches the fixed voltage VF. In the present case, the voltage applied to the electrode lines X up to the third voltage VBF increases at the same speed as that with which the voltage applied to the electrode lines Y gradually increases until the second

VByp voltage.

 During the second reset step (t2t3) under the driving conditions mentioned above, a relatively small discharge is produced between the lines Y of electrodes and the lines X

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 electrode. Furthermore, a relatively intense discharge is produced between the electrode lines Y and the address electrode lines. As a result, many wall charges of negative polarity form in the vicinity of the electrode lines Y and a relatively smaller number of wall charges of positive polarity form in the vicinity of the electrode lines X. As a result, a relatively higher number of wall charges of positive polarity are formed in the vicinity of the electrode lines of address Al, ..., Am, as shown in FIG. 10.

t4), alors que la tension appliquée aux lignes X d'électrodes est maintenue à la première tension Vox, la tension appliquée aux lignes Y d'électrodes diminue progressivement jusqu'à la tension de la masse VG en partant de la cinquième tension VBYM. La tension de la masse VG est ici appliquée aux lignes d'électrodes d'adresses. Par conséquent, une décharge relativement faible est produite entre les lignes X d'électrodes et les lignes Y d'électrodes, de sorte qu'une partie des charges de paroi de polarité négative au voisinage des lignes Y d'électrodes se déplacent vers les lignes X d'électrodes (se référer à la figure 11). Comme la tension de la masse VG est ici appliquée aux lignes d'électrodes d'adresses, le nombre de charges de paroi de polarité positive au voisinage des lignes d'électrodes d'adresses augmente légèrement. During the third reset step (t3-

t4), while the voltage applied to the lines X of electrodes is maintained at the first voltage Vox, the voltage applied to the lines Y of electrodes decreases progressively until the voltage of the ground VG from the fifth voltage VBYM. The VG ground voltage is applied here to the address electrode lines. Consequently, a relatively small discharge is produced between the electrode lines X and the electrode lines Y, so that part of the wall charges of negative polarity in the vicinity of the electrode lines Y move towards the lines X of electrodes (refer to figure 11). As the voltage of the ground VG is applied here to the address electrode lines, the number of wall charges of positive polarity in the vicinity of the address electrode lines increases slightly.

 Therefore, in the next addressing step, a positive polarity display data signal is applied to the electrode lines of selected addresses and sequentially, a scanning signal is applied to the electrode lines Y in such a way that addressing can be carried out regularly.

 According to the reset method described above of the present invention, as an increasing voltage is applied to the X lines of electrodes in

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 the second half of the second reset step (t2-t3), the following effects can be obtained.

 Firstly, this can increase the contrast of the plasma display screen due to the fact that an unnecessarily intense discharge is prevented between the X lines of electrodes and the Y lines of electrodes during the second reset step (t2-t3). This therefore prevents the formation of an excessive amount of wall charges of positive polarities in the vicinity of the X lines of electrodes. Therefore, during the third step (t3-t4), an unnecessarily intense discharge is not produced between the lines X of electrodes and the lines Y of electrodes. This can further increase the contrast of a plasma display screen, as illustrated in FIGS. 12 and 13. In FIG. 12, the upper curve corresponds to a case where the first voltage VBx is relatively high, and the lower curve corresponds to a case where the first voltage VBx is relatively low.

 Second, during the second reset step (t2-t3), as the discharge between the electrode lines Y and the address electrode lines is relatively intensified, the wall charges of positive polarity are formed in sufficient quantity in the vicinity of the address electrode lines shown in FIG. 10. Consequently, a sufficient quantity of positively polarity wall charges formed in the vicinity of the address electrode lines, as illustrated in FIG. 11, can produce a sufficient amount of wall charge in each display cell selected by subsequent addressing.

 As described above, the slope of the voltage increase applied to the electrode lines Y and to the electrode lines X during the second reset step (t2-t3) varies inversely.

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 proportional to the load ratio in each secondary field. As a result, the reset speed and efficiency are further improved.

 The method of resetting a display screen in accordance with the present invention increases the contrast of the plasma display screen and forms a sufficient amount of wall charges in each display cell selected by addressing.

 Although the present invention has been illustrated and described in a particular way with reference to its preferred embodiments, those skilled in the art will note that various modifications of the form and details can be made without departing from the scope. of the invention as defined by the appended claims.

Claims (14)

1. Method for resetting a plasma display screen comprising a front substrate and a rear substrate separated from one another and opposite one another, in which first lines of electrodes of display and second lines of display electrodes are formed parallel to each other on the front substrate and lines of address electrodes are formed perpendicular to the first lines of display electrodes and to the second lines of display electrodes, said method comprising the steps of: gradually increasing a voltage applied to the first lines of display electrodes to a first voltage (first reset step); gradually increasing a voltage applied to the second lines of display electrodes to a second voltage and gradually increasing the voltage applied to the first lines of display electrodes to a third voltage (second reset step); and maintain the voltage applied to the first lines of display electrodes at the first voltage and gradually decrease the voltage applied to the second lines of display electrodes to a fourth voltage (third reset step), characterized in that the second voltage is greater than the first voltage, the third voltage is less than the first voltage, and the fourth voltage is less than the third voltage.  2. Method according to claim 1, in which, during the second reinitialization step, when the first display electrode lines are in an electrically floating state, the voltage applied to the first display electrode lines <Desc / Clms Page number 19>  is gradually increased until the third tension.  3. Method according to claim 1, in which, during the second reinitialization step, the gradient of progressive increase in the voltage applied to the second lines of display electrodes up to the second voltage varies inversely proportional to the ratio of the number of discharge cells to be displayed to the total number of discharge cells in each secondary field.  4. Method according to claim 3, in which, during the second reinitialization step, when the first lines of display electrodes are in an electrically floating state, the voltage applied to the first lines of display electrodes gradually increases until the third voltage.  5. Method according to claim 4, in which, during the second reinitialization step, when the first lines of display electrodes are in an electrically floating state and when the voltage applied to the second lines of display electrodes reaches a predetermined voltage, the slope of progressive increase in the voltage applied to the first lines of display electrodes up to the third voltage varies so as to become identical to the slope of progressive increase in the voltage applied to the second lines d 'display electrodes up to the second voltage which is higher than the first voltage.  Method for resetting a plasma display screen having a first electrode, a second electrode and an address electrode, wherein the first electrode and the second electrode are parallel to each other and the address electrode <Desc / Clms Page number 20>  is perpendicular to the first electrode and the second electrode, the method comprising the steps of: during a first step, discharging between the first electrode and the second electrode as well as between the first electrode and the electrode d 'address ; in a second step, discharge between the second electrode and the first electrode as well as between the second electrode and the address electrode, in which the discharge carried out between the second electrode and the first electrode is weaker than the discharge carried out between the second electrode and the address electrode; in a third step, discharge between the first electrode and the second electrode as well as between the first electrode and the address electrode, in which the discharge carried out between the first electrode and the second electrode is weaker than the discharge carried out between the first electrode and the address electrode.  7. The method of claim 6, wherein the first electrode receives voltages gradually increasing to a first voltage in the first step, wherein the second electrode receives voltages gradually increasing to a second voltage in the second step and the first electrode receives gradually increasing voltages up to a third voltage starting some time after the second electrode has received gradually increasing voltages in the second step, wherein the first electrode constantly receives the first voltage and the second electrode receives voltages decreasing by a fifth <Desc / Clms Page number 21>  voltage at a fourth voltage in the third step, and wherein the address electrode receives the fourth voltage throughout the first step, the second step and the third step.  8. The method of claim 7, wherein the second voltage is greater than the first voltage, the fifth voltage is less than the first voltage, the third voltage is less than the fifth voltage and the fourth voltage is the ground voltage.  9. The method of claim 8, wherein the voltages increase inversely proportional to a charge ratio.  10. The method of claim 9, wherein, in the second step, the voltage that the first electrode receives gradually increases leaving the first electrode line in an electronically floating state.  11. A plasma display screen control device, comprising: a plasma display screen which displays

 pictures; an image processor which receives external image signals and produces internal image signals; a logic controller which receives the internal image signals and produces address drive signals, first electrode drive signals and second electrode drive signals; an address control circuit which receives the address control signals; <Desc / Clms Page number 22>  a first electrode driving circuit which receives the first electrode signals; a second electrode driving circuit which receives the second electrode signals; wherein, during the first reset period, in a first step, the first electrode signals gradually increase to a first voltage and the second electrode signals remain at ground voltage; in a second step, the second electrode signals gradually increase to a second voltage and the first electrode signals gradually increase to a third voltage some time after the second electrode signals have increased; in a third step, the first electrode signals remain at the first voltage and the second electrode signals decrease from a fifth voltage to a fourth voltage, and in which, during the reset period, the signals addresses remain at the fourth voltage.  12. A plasma display screen control device according to claim 11, in which the second voltage is greater than the first voltage, the fifth voltage is less than the first voltage, the third voltage is less than the fifth voltage and the fourth tension is the tension of the mass.  13. A plasma display screen control device according to claim 12, in which, during the second step, the second electrode signals increase inversely proportional to a charge ratio. <Desc / Clms Page number 23>  14. A plasma display screen control device according to claim 13, in which the first electrode signals gradually increase leaving the first electrode line in an electronically floating state.