JPH08314405A - Driving method for ac type pdp - Google Patents

Abstract

PURPOSE: To improve brightness without increasing the number of times of applying discharge holding voltage. CONSTITUTION: When discharge holding voltage Vs being lower than discharge start voltage Vf is alternately applied to a pair of display electrodes X and Y coated by a dielectric layer, and discharge is periodically caused by utilizing wall voltage Vwall by accumulated electric charges of the dielectric layer, immediately after of a conduction period TS1 in which discharge holding voltage Vs is applied, a conduction suspension period TS2 in which potentials of both display electrodes X and Y are made a ground potential is provided, the dielectric layer is electrified so that the wall voltage Vwall becomes more than discharge start voltage Vf in the conduction period TS1, and self-discharge is caused by wall voltage Vwall in the conduction suspension period TS2.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an AC type PDP (Plas
ma Display Panel: a method for driving a plasma display panel.

A PDP is a self-luminous display device having excellent visibility, and is attracting attention as a large screen display means for high definition. Under such circumstances, a driving method suitable for higher brightness is desired.

[0003]

2. Description of the Related Art An AC PDP is a PDP having a dielectric layer that covers a display electrode with respect to a discharge space.

As is well known, in an AC type PDP, when a discharge is generated between a pair of display electrodes that define a discharge cell, charged particles (electrons or ions) generated by ionization of discharge gas are attracted to the display electrode. Wall charges having a polarity opposite to the potential polarity of each display electrode are accumulated in the dielectric layer. Along with the charging of the dielectric layer, the voltage between the display electrodes (wall voltage) due to the wall charges increases. At this time, since the wall voltage has the opposite polarity to the drive voltage applied to the display electrode, the effective voltage (also referred to as cell voltage), which is the sum of the drive voltage and the wall voltage, becomes low and the discharge is stopped. Next, when a drive voltage having the opposite polarity to the previous one is applied, since the drive voltage and the wall voltage have the same polarity this time, the effective voltage exceeds the discharge start voltage (Vf) and the discharge is generated again.

In other words, in the AC type PDP, a drive voltage is applied to a pair of display electrodes so that their potential polarities alternate with each other, so that the wall charges are utilized to generate a discharge start voltage (for example, 200 V). Discharge can be generated with a low driving voltage (for example, 180 V). Then, if the polarity inversion cycle of the drive voltage is shortened, it is possible to obtain a visually continuous light emission state.

In a matrix display type AC PDP in which a large number of discharge cells are arranged vertically and horizontally, the display period of one screen is divided into an address period and a sustain period that follows.

The address period is a period for setting the display content, and the sustain period is a period for maintaining the display content. That is, in the address period, the wall charges are accumulated only in the discharge cells to be sequentially lighted (light emission) line by line by the write address method or the erase address method. Then, in the sustain period, FIG.
As in (A), for all lines, the first and second lines
Sustain electrodes Ps are alternately applied to the display electrodes X and Y of
Is applied. At this time, the peak value of the sustain pulse Ps (discharge sustaining voltage Vs) is selected to be lower than the discharge starting voltage Vf. Each time the sustain pulse Ps is applied, the relative potential relationship between the display electrodes X and Y is inverted, and at the rise of each sustain pulse Ps, discharge is generated only in the discharge cells in which the wall charges have been accumulated in advance.

[0008]

Conventionally, the number of times of light emission (the number of discharges) during the sustain period depends on the sustain pulse Ps.
, That is, the same as the number of times the discharge sustaining voltage Vs was applied. Therefore, if the number of times of light emission per unit time is increased in order to increase the brightness, it is necessary to increase the driving frequency accordingly.

When the driving frequency is increased and the number of times of light emission is increased, the number of times of ion bombardment due to discharge also increases, so that the life is shortened. In addition, the load on the drive circuit increases, and the amount of heat generated also increases.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the brightness without increasing the number of times the discharge sustaining voltage is applied.

[0011]

According to a first aspect of the present invention, a discharge sustaining voltage lower than a discharge starting voltage is alternately applied to a pair of display electrodes covered with a dielectric layer, and the dielectric material is used. A driving method of an AC PDP that periodically generates a discharge by using a wall voltage due to accumulated charges in a layer, wherein the potentials of both display electrodes are grounded immediately after an energization period in which the discharge sustaining voltage is applied. An energization pause period having a potential is provided, and the dielectric layer is charged so that the wall voltage becomes equal to or higher than the discharge start voltage during the energization period, and self-discharge due to the wall voltage occurs during the energization pause period. It is a method to let.

According to a second aspect of the present invention, the length of the energization period is selectively shortened, and the wall voltage at the end of the energization period is made lower than the discharge start voltage, whereby the self-discharge is completed. The energization suspension period that does not occur is selectively provided.

According to a third aspect of the present invention, the self-sustaining voltage is selectively lowered during the energization period, and the wall voltage at the end of the energization period is set lower than the discharge start voltage, whereby The energization suspension period during which no discharge occurs is selectively provided.

According to a fourth aspect of the present invention, the ratio of the total number of energization suspension periods in which the self-discharge occurs and the total number of energization suspension periods in which the self-discharge does not occur is determined according to the gradation level of display. It is something to set.

[0015]

In the energization period, a voltage (hereinafter referred to as an effective voltage), which is a combination of the discharge sustaining voltage and the wall voltage, is applied between the pair of display electrodes.

At the start of the energization period, the discharge sustaining voltage and the wall voltage have the same polarity, and the effective voltage exceeds the discharge starting voltage to cause discharge. After the wall voltage once disappears due to the discharge, the dielectric layer is immediately charged by the discharge sustaining voltage, and the wall voltage having the opposite polarity to that before is generated. The discharge is stopped when the wall voltage rises and the effective voltage drops to a predetermined value. However, even after the discharge is stopped, the discharge sustaining voltage is applied to the display electrode during the energization period, so that the floating charges in the discharge space are attracted to the display electrode and the dielectric layer is charged, and the wall voltage The rise continues.

Here, by appropriately setting the magnitude of the discharge sustaining voltage and the length of the energization period, that is, by selecting the intensity of the discharge and the charging time after the discharge, the wall voltage is changed to the discharge start voltage during the energization period. The voltage can be increased to the above voltage.

When the energization period ends and the energization stop period comes, the potentials of both display electrodes become the ground potential. That is,
During the energization suspension period, the wall voltage generated by charging during the immediately preceding energization period becomes the effective voltage. Since the wall voltage is equal to or higher than the discharge start voltage, self-discharge due to the wall voltage occurs, and a part of the charges (wall charges) accumulated in the dielectric layer are neutralized and disappear in the discharge space. The self-discharge is stopped when the wall voltage drops to a predetermined value (> 0), and charges necessary for the next discharge remain in the dielectric layer. In the self-discharge, unlike the discharge by applying the voltage from the outside, the charged particles cannot be attracted to the display electrode.
Ion bomb does not occur.

In the next energization period, the wall voltage after self-discharging is used for discharge, and a wall voltage higher than the discharge start voltage is newly generated as in the previous energization period. After that, the normal discharge and the self-discharge are alternately generated by repeating the energization period and the energization suspension period. That is, the number of discharges (the number of times of light emission) is twice the number of times the sustaining voltage is applied.

[0020]

1 is an exploded perspective view of a PDP 1 according to the present invention, showing a basic structure of a portion corresponding to one pixel (pixel) EG.

The PDP 1 is a surface discharge type PDP having a three-electrode structure in which a pair of display electrodes X and Y and an address electrode A correspond to a unit light emitting region EU of matrix display, and is classified according to the arrangement form of phosphors. It is called a reflective type.

The display electrodes X and Y for surface discharge are provided on the glass substrate 11 on the display surface H side, and cover the discharge space 30 with a dielectric layer 17 made of low melting glass and having a thickness of about 20 μm. Has been done. That is, the display electrodes X,
Y constitutes the discharge sustaining electrode pair 12 in AC driving. On the surface of the dielectric layer 17, a MgO film 18 having a thickness of about several thousand Å is provided as a protective film. Since the display electrodes X and Y are arranged on the front surface side of the discharge space 30, a wide transparent conductive film 41 such as a nesa film is provided in order to widen the surface discharge and minimize the shielding of the display light. And a narrow metal film (bus electrode) 42 for compensating for its conductivity.

The address electrode A is an electrode for selectively emitting light in the unit light emitting region (sub-pixel) EU, and has a constant pitch on the glass substrate 21 on the back side so as to be orthogonal to the display electrodes X and Y. Are arranged in.

A stripe-shaped partition 29 having a height of about 150 μm is provided between each address electrode A.
As a result, the discharge space 30 moves in the line direction (display electrodes X,
The unit light emitting area EU is partitioned in the Y extension direction), and the gap size of the discharge space 30 is defined. The size of the pixel EG is 660 μm × 660 μm, and the size of the unit light emitting region EU is 660 μm × 220 μm.

The glass substrate 21 covers R (red), G (green), and B for full-color display so as to cover the inner surface on the back side including the upper surface of the address electrode A and the side surface of the partition wall 29.
A phosphor 28 of three primary colors (blue) is provided. The phosphors 28 of the respective colors are excited by the ultraviolet rays emitted by the discharge gas in the discharge space 30 during surface discharge to emit light. In the PDP 1, a Penning gas, which is a mixture of neon and xenon (about 1 to 15% mol), is charged as a discharge gas at a pressure of about 500 Torr.

FIG. 2 is a plan view schematically showing the electrode structure of the PDP 1 shown in FIG. The PDP 1 has the display electrodes X and Y forming the discharge sustaining electrode pair 12 for each matrix display line L. The display electrodes X and Y are arranged adjacent to each other with a discharge gap (surface discharge gap) g of about 50 μm in each line L.

Of the display electrodes X and Y arranged in this way, one display electrode X is electrically shared by a plurality of lines L for the sake of simplification of the drive circuit. 2 (B), they are collectively connected to the drive circuit DX. On the other hand, the other display electrode Y is an individual electrode that is independent for each line in order to enable line-sequential screen scanning, and when used, an individual drive circuit DY is used.
Connected to.

In each line L, the surface discharge cells C are defined by the display electrodes X and Y for each unit light emitting region EU. Then, the display electrode Y and the address electrode A select (address) whether each surface discharge cell C is turned on or off.

FIG. 3 is a voltage waveform diagram showing the driving method of the present invention. Note that FIG. 3D shows the presence or absence of light emission.
In the display by the PDP 1, first, as in the conventional case, in the address period TA, wall charges are selectively accumulated by line-sequential screen scanning. At this time, a full erase discharge for uniformly erasing the wall charges of all lines L is generated prior to screen scanning so as not to be affected by the previous display. At the end of the address period TA, the surface discharge cells C to be lighted have a predetermined amount of wall charges.

Next, as shown in FIG. 3A, in all the lines L in the sustain period TS, the display electrodes X are provided.
And a sustain pulse P of the same polarity with respect to the display electrode Y
s (peak value Vs) is applied alternately and at fixed time intervals.

That is, the energization suspension period TS2 is immediately after the energization period TS1 corresponding to the pulse width of the sustain pulse Ps.
To provide. In the energization period TS1, the potential of one of the display electrodes X (or Y) is maintained at a potential higher than the ground potential by Vs, and in the energization suspension period TS2, the potentials of both the display electrodes X and Y are substantially the ground potential ( Held at 0V). The power supply suspension period TS2 may be about 1 to 1.5 μs.

By alternately applying the sustain pulse Ps to the display electrodes X and Y, the polarity of the drive voltage Vxy between the display electrodes X and Y is periodically changed as shown by the broken line in FIG. Invert.

The peak value Vs of the sustain pulse Ps is lower than the discharge start voltage Vf (strictly speaking, the discharge start voltage Vf of the energization pause period TS2 described later) and is the closest value to the discharge start voltage Vf within the range where no malfunction occurs. To be selected. For example, when the discharge start voltage Vf is 200V, it is set to about 195V.

Now, as shown in FIG. 3B, at the start of the sustain period TS, the surface discharge cell C to be lit has a wall voltage Vwa of a predetermined level lower than the discharge start voltage Vf.
11 has occurred. Therefore, the sustain pulse P
When s is applied, the effective voltage Veff is changed as shown in FIG.
Discharge exceeds the discharge start voltage Vf, and as a result, the phosphor 28 corresponding to the cell emits light L1 of a predetermined color as shown in FIG. 3D.

Due to the discharge, wall charges of the opposite polarity to those before are accumulated in the dielectric layer 17. Along with that, effective voltage V
eff drops and the discharge stops. Even after the discharge is stopped, the wall charges continue to be accumulated during the energization period TS1 and the wall voltage V
Wall gradually rises.

If the energization period TS1 is selected to be, for example, about 3 to 4 μs, the wall voltage Vwall exceeds the discharge start voltage Vf during the energization period TS1 as shown in FIG. 3B. When the sustain pulse Ps suddenly falls and the potentials of both display electrodes X and Y reach the ground potential, that is, the energization period T
When shifting from S1 to the energization suspension period TS2, the wall voltage Vwall
l becomes the effective voltage Veff as it is. At this time, since the wall voltage Vwall exceeds the discharge start voltage Vf at that time in which the priming effect is added, self-discharge occurs due to no external voltage application, and the phosphor 28 corresponding to the cell in FIG. The light emission L2 of a predetermined color is exhibited as in D). Part of the wall charge disappears due to self-discharge. However, the wall voltage Vwall required for the next discharge is secured.
In self-discharge, charged particles are not attracted to the display electrodes X and Y, so there is no concern about ion bombardment. Further, since the drive current does not flow, heat generation of the display electrodes X, Y and the drive system is reduced.

By causing the self-discharge in this way, the number of discharges (the number of times of light emission) during the sustain period TS becomes twice as many as the number of times the sustain pulse Ps is applied, so that the luminance is increased regardless of the driving frequency. You can

FIG. 4 is a diagram showing an example of gradation display according to the present invention. When full color display is performed by the PDP 1, the frame FM which is a display period of one screen is set to, for example, 7
It is divided into two subfields f1-7. Then, the relative ratio of the luminance in each of the subfields f1 to 7 is 1:
The number of times of light emission in the sustain period TS of each subfield f1 to 7 is set so as to be 2: 4: 8: 16: 32: 64. In the following description, for convenience, the intensity of the light emission L2 (see FIG. 3) during self-discharge is the same as that of the light emission L1 during normal discharge, and there is no difference in luminance between self-discharge and normal discharge. There is no difference.

When the surface discharge cell C is lit in a subfield appropriately selected according to the display color, R, G,
The gradation number of each color of B is 128 (= 2 ⁷ ), and in principle, about 200 (128 ³ ) colors can be displayed. In addition,
If the number of screens per second is “60”, the frame FM is about 16.7 ms.

Now, in the three subfields f5 to f7 among the seven subfields f1 to 7 that require a relatively large number of times of light emission, the wall voltage Vwall is set to the length of the energization period TS1 at the end thereof. The voltage is set to exceed the discharge start voltage Vf to cause self-discharge during the energization suspension period TS2. That is, one sustain pulse Ps causes light emission twice. Therefore, subfields f5 to
The number of times the sustain pulse Ps is applied in 7 is half the required number of times of light emission (number of times of discharge).

On the other hand, in the subfields f1 to f4, the length of the energization period TS1a is shortened, and the charging after the discharge is stopped is terminated early. As a result, the wall voltage Vwall at the end of the energization period TS1a is suppressed to a level lower than the discharge start voltage Vf, and the energization suspension period T later
Prevent self-discharge during S2a.

That is, in the example of FIG. 4, the presence or absence of self-discharge is set by switching the pulse widths of the sustain pulses Ps and Psa. Each subfield f1-7
The relative ratio of the number of pulses at 1: 2: 4: 8: 8:
It is 16:32.

When the energization suspension period TS2a of the subfields f1 to 4 has the same length as the energization suspension period TS2 of the subfields f5 to 7, the required time of the subfields f1 to 4 is shortened by the shorter energization period TS1a. It is possible to increase the number of gradations by increasing the number of subfields,
Alternatively, the display speed can be increased by shortening the frame FM itself. In that case, the driving frequency of the sub-fields f1 to 4 is higher than that of the sub-fields f5 to 7, but the number of discharges is relatively small, so the influence of ion bombardment, heat generation, etc. is small.

FIG. 5 is a diagram showing another example of gradation display according to the present invention. When the difference between the discharge sustaining voltage Vs2, which is the peak value of the sustain pulse Psb, and the discharge starting voltage Vf is increased, the discharge current at the time of normal discharge is reduced and the amount of accumulated wall charges is reduced. Therefore, since the wall voltage Vwall becomes lower than the discharge start voltage Vf at the end of the energization period TS1b, the energization suspension period TS2 immediately after the energization period TS1b.
No self-discharge occurs in b. That is, the discharge sustaining voltage V
By switching between s and Vs2, each subfield f1
It is possible to set the presence / absence of self-discharge in 7 to 7.

In the above-mentioned embodiments, the description has been made on the assumption that it is applied to the surface discharge type PDP 1 having the three-electrode structure.
The present invention can be applied to a surface discharge type PDP having another electrode structure and a counter discharge type PDP as long as it is an AC type PDP.

The self-discharge may be prevented by lowering the discharge sustaining voltage Vs and shortening the energization period TS1.

[0047]

According to the inventions of claims 1 to 4,
It is possible to improve the brightness without increasing the number of times the discharge sustaining voltage is applied.

According to the second and third aspects of the invention, gradation display can be easily performed. According to the invention of claim 4, multi-gradation display can be performed.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a PDP according to the present invention.

FIG. 2 is a plan view schematically showing an electrode configuration of the PDP shown in FIG.

FIG. 3 is a voltage waveform diagram showing a driving method of the present invention.

FIG. 4 is a diagram showing an example of gradation display according to the present invention.

FIG. 5 is a diagram showing another example of gradation display according to the present invention.

[Explanation of symbols]

1 PDP (AC type PDP) 17 Dielectric layer 18 MgO film (dielectric layer) X, Y Display electrode Vf Discharge start voltage Vs, Vs2 Discharge sustaining voltage Vwall wall voltage TS1 energization period TS1a, TS1b Energization period TS2 Energization rest period TS2a , TS2b de-energization period (de-energization period without self-discharge)

Claims (4)

[Claims] 1. A pair of display electrodes covered with a dielectric layer are alternately applied with a discharge sustaining voltage lower than a discharge start voltage, and the wall voltage generated by the charges accumulated in the dielectric layer is used to periodically. A method of driving an AC PDP that causes a discharge to occur immediately after a current-carrying period in which the discharge sustaining voltage is applied, and a current-supply pause period in which the potentials of both of the display electrodes are set to the ground potential is provided during the current-carrying period. A method of driving an AC PDP, wherein the dielectric layer is charged so that the wall voltage is equal to or higher than the discharge start voltage, and self-discharge is caused by the wall voltage during the energization suspension period. 2. The length of the energization period is selectively shortened, and the wall voltage at the end of the energization period is made lower than the discharge start voltage, whereby the energization pause period in which the self-discharge does not occur. The AC type P according to claim 1, which is selectively provided.
DP driving method. 3. The energization pause in which the self-discharge does not occur by selectively lowering the discharge sustaining voltage during the energization period and lowering the wall voltage at the end of the energization period below the discharge start voltage. 3. The method for driving an AC PDP according to claim 1, wherein the period is selectively provided. 4. The ratio between the total number of energization suspension periods in which the self-discharge occurs and the total number of energization suspension periods in which the self-discharge does not occur is set according to the gradation level of display. Item 4. A method for driving an AC PDP according to Item 3.