JP2876688B2 - Driving method of plasma display panel - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color plasma display panel used for an information display terminal, a flat-panel television, and the like. The present invention relates to a driving method for realizing driving.

[Conventional technology]

In a color plasma display panel, a phosphor formed on the inner surface of the panel is excited by vacuum ultraviolet rays generated by gas discharge to obtain a desired luminescent color. However, the conventional method has a very low efficiency of generating vacuum ultraviolet rays, The luminous efficiency of the display panel is low. In particular, a large-screen high-definition display panel causes a problem such as heat generation, which is an obstacle to practical use. Therefore, a driving method using short pulses was devised. This short pulse driving method for a plasma display panel is applied to an AC type color plasma display panel in which electrodes are covered with an insulating layer, and can be applied to both a counter discharge type and a surface discharge type. This is explained using an example.

FIG. 6 shows an example of a cross-sectional view of an AC surface discharge type plasma display panel. A glass substrate 10 on which an electrode 9 is formed and covered with an insulating layer 11 and a glass substrate 18 on which a phosphor 14 is formed are sealed with a partition 15 interposed therebetween. Gas 16 is sealed. Discharge is generated between the electrodes 9 to emit plasma 12, and the ultraviolet light 13 is used to excite the phosphor 14 to obtain visible light 17. Normally, a mixed gas containing several percent of Xe with He as the base gas is enclosed in the panel for several hundred torr and 147n of Xe excited by discharge
The phosphor is excited and emits light by vacuum ultraviolet light of m.

FIG. 2A shows the waveform of the potential difference between the electrodes in the driving method using a short pulse. The current waveform at this time is shown in FIG. Displacement current 6 flows with the rise of the pulse, and discharge current 7 flows with a delay of usually several hundred nsec.
If the pulse width is sufficiently wide, the wall charges are gradually formed by the discharge, and the effective electric field applied to the discharge cells is weakened by the reverse electric field due to the wall charges. The discharge stops before self-stop because the pulse falls before the start.

If the width of the pulse voltage is sufficiently large, the effective electric field applied to the discharge cell is weakening during the latter half of the discharge when wall charges are gradually being formed, and the electron temperature in the discharge cell is low. Excitation cannot be performed efficiently, and saturation of Xe excitation also occurs, so that the luminous efficiency of vacuum ultraviolet rays is low. On the other hand, the short pulse driving method in which the discharge in the latter half of the discharge current is forcibly stopped has a high luminous efficiency of vacuum ultraviolet light, but the discharge stops halfway, so that wall charges are not sufficiently formed and the next pulse When the polarity of the applied voltage is reversed in step (b), the electric field due to the wall charges is not superimposed, and the discharge starting voltage is increased.

FIG. 4 is a graph showing the relationship between the pulse width, the luminous efficiency, and the discharge starting voltage. The display panel used was a surface discharge type, with a discharge gap of 0.2 mm, a gas composition of He gas 96% and Xe 4% mixed gas of 250 torr. The driving frequency is 200 kHz. Since the delay of the discharge current is about 500 nsec., When the pulse width is 500 nsec., The effect of short pulse driving with high luminous efficiency is obtained, but the sustain voltage is greatly increased.

[Problems to be solved by the invention]

In order to greatly improve the luminous efficiency, which is the biggest problem in large-screen, high-definition color plasma display panels, we devised a short-pulse driving method for AC-type plasma display panels. Although the driving voltage is greatly improved, the driving voltage increases. If the drive voltage is high, the breakdown voltage of the IC in the drive circuit will occur, and the voltage applied to the discharge cells will increase, and the protective layer of the insulating layer that covers the electrodes will deteriorate due to spattering due to discharge and shorten the life. Occurs.

The present invention provides a driving method for drastically reducing the driving voltage while maintaining high luminous efficiency of short pulse driving.

[Means for solving the problem]

The driving method of the plasma display panel according to the present invention includes:
In the short pulse driving method in which the pulse falls to stop the discharge before the discharge self-stops, the pulse-like voltage waveform applied to the AC type plasma display panel remains in space after the pulse falls and the discharge stops. A voltage pulse is applied to cause the accumulated charges to be adsorbed on the insulating layer to form wall charges, and the driving voltage is reduced while taking advantage of the high luminous efficiency of the short pulse driving method.

[Action]

The conventional short pulse drive forcibly stops the discharge before the discharge self-stops due to the wall charge, so that the wall charge is not sufficiently formed, and the discharge pulse is applied to the discharge cell when the polarity of the applied voltage is reversed by the next pulse Although the discharge voltage rises because the electric field of the wall charge is not superimposed on the electric field, the driving method of the present invention has a period in which the electric field is applied to the discharge cells even after the pulse is dropped by short pulse driving. Since the formed space charges are attracted to the insulating layer covering the electrodes to form wall charges, the driving voltage can be reduced.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1A shows a waveform of the potential difference between the electrodes in the driving method of the present invention. FIG. 1B shows a current waveform at this time. The same effect can be obtained by using a facing discharge type or a surface discharge type as long as the panel used is an AC type plasma display.

A pulse voltage as shown in FIG. 1A is applied to the electrodes of the display panel. With the rise of the pulse, the potential current 1 flows and the discharge current 2 flows with a delay of several hundred nsec., And the discharge starts, and before the discharge stops, the applied voltage decreases and the discharge stops. When the applied voltage is reduced, the absolute value of the potential difference between the electrodes is not immediately reduced to zero, and the applied voltage is maintained at, for example, several tens of volts for a short period of time. A few microseconds is sufficient for maintaining. At this time, since the discharge also stops, the discharge current 2 is cut off halfway, and the displacement current 3 flows in the opposite direction. During this period of maintaining several tens of volts, space charges formed by the discharge are attracted to the insulating layer covering the electrodes with an electric field of several tens of volts to form wall charges. Flows to Thereafter, the applied voltage is reduced to zero, and then a pulse voltage of the opposite polarity is applied. As a result, the drive voltage (sustain voltage) is significantly reduced.

Next, a graph showing the relationship between the pulse width, the luminous efficiency, and the drive voltage (sustain voltage) is shown. The panel used was a surface discharge type with a discharge gap of 0.2 mm, a gas composition of 96% He and a mixed gas of 250% Xe 4%.
orr. The driving frequency is 20 kHz. FIG. 3 shows data of the driving method of the present invention. The pulse width on the horizontal axis indicates the time from the rise to the fall of a pulse having a narrow width for causing a discharge, and the sustain period of the subsequent voltage pulse for forming wall charges was constant at 100 volts and 5 μsec. Although the luminous efficiency is greatly increased at 0.5 μsec as in the conventional short pulse drive, the sustain voltage changes in the same manner as the luminous efficiency, but the pulse width is 0.5 μmsec compared to the conventional short pulse drive.
At this time, the maintenance voltage has dropped about 80V. Note that the luminous efficiency is slightly lower than that of the conventional short pulse driving because a current flows due to the movement of space charges.

FIG. 5 shows a graph of the relationship between the sustain voltage and the second voltage pulse, that is, the pulse for forming the wall charges after the discharge is stopped. When the second voltage pulse is 0 V, the sustaining voltage is 280 V, which is the same as that of the conventional short pulse driving. However, as the second voltage pulse is raised, the sustaining voltage decreases because wall charges are formed correspondingly. When the second voltage pulse reaches 130 V, the discharge does not stop even at the stage of the second voltage pulse, so that more wall charges can be generated and the sustain voltage is lowered. The second voltage pulse has a low effect at a very low voltage and is practically 10 pulses.
It is desirable to multiply by about V or more. The upper limit of the second voltage pulse is the maximum value of the voltage at which the discharge is stopped by the second voltage pulse, but it is several volts lower than this in view of a margin in practical use.

In the above-described driving waveform, a pulse having a narrow width for generating a discharge and a pulse for forming a wall charge have been described as being applied continuously. However, there may be a pause between the two pulses. However, if the idle period is too long, the space charges will recombine, so the upper limit is about 50 μsec.

As described above, the driving method of the plasma display panel according to the present invention has made it possible to substantially maintain the high luminous efficiency of the conventional short pulse driving and to drive at a low voltage.

Note that all the driving waveforms indicate the potential difference between the electrodes.

〔The invention's effect〕

According to the driving method of the plasma display panel of the present invention, low-voltage driving can be realized while almost maintaining high luminous efficiency of short pulse driving. Low-voltage drive is now possible, so the drive circuit IC can be an IC developed for existing monochrome plasma display panels, and the spattering of the protective layer of the insulating layer that covers the electrodes caused by high voltage is greatly reduced, and the lifespan is reduced. Has increased dramatically. Of course, it is needless to say that electric characteristics required for a large-screen high-definition color plasma display panel can be obtained because of high luminous efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a drive waveform and a current waveform according to the present invention.
FIG. 2 shows a conventional drive waveform and current waveform. FIG. 3 is a diagram showing the relationship between the pulse width, the luminous efficiency, and the discharge starting voltage according to the present invention. FIG. 4 is a diagram showing the relationship between a conventional pulse width, luminous efficiency, and discharge starting voltage. FIG. 5 is a graph showing the relationship between the voltage of the second voltage pulse and the sustain voltage. FIG. 6 is a sectional view of an AC discharge type plasma display panel. Note that all the driving waveforms indicate the potential difference between the electrodes. 1 ... potential current, 2 ... discharge current, 3 ... potential current, 4 ... current due to movement of space charge, 5 ... displacement current, 6 ... displacement current,
7 discharge current, 8 displacement current, 9 electrode, 10 glass substrate, 11 insulating layer, 12 plasma, 13 ultraviolet light, 14 phosphor, 15 partition, 16 rare gas, 17 visible Light, 18 ... glass substrate.

Claims (1)

(57) [Claims] 1. A method of driving a plasma display panel, in which a pulse-like voltage is applied to a plasma display panel having an electrode group covered with an insulating layer to perform AC driving, the waveform of a voltage applied between the electrodes is a discharge. And a first voltage pulse having a pulse width narrower than the time during which the generated discharge is self-suspended due to the generation of a reverse electric field due to wall charge formation and the like, and a voltage generated by the first voltage pulse. The second voltage is lower than the voltage at which the discharge can be continued and at least a part of the space charge generated by the discharge by the first voltage pulse forms the wall charge.
A method for driving a plasma display panel, comprising: