KR20010020051A - Method of Driving Plasma Address Liquid Crystal Display Device - Google Patents

Abstract

PURPOSE: A method for driving a plasma address liquid crystal display device is provided to make the normal operation of the electrode possible even if a part of the electrode, which generates the plasma discharge, is damaged. CONSTITUTION: A method includes positive electrodes(A), negative electrodes(Y1, Y2, Y3, ... ,Yn). To the positive electrodes(A) of each scanning line the driving pulse with the same voltage value as the appointed period is supplied and to the first or n negative electrodes(Y1 or Yn) of each scanning line the driving pulse with the same period and voltage value as the positive electrodes(A) is supplied. To the negative electrodes(Y1, Y3, ... ,Yn) of scanning lines, electrodes of which aren't damaged, the scanning pulse with the narrow pulse width is supplied, but to the second negative electrode(Y2) of the second scanning line, the space of which became wide by the damage of the electrodes, the scanning pulse with the wide pulse width is supplied.

Description

Method of driving plasma address liquid crystal display device {Method of Driving Plasma Address Liquid Crystal Display Device}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a plasma address liquid crystal display device, and more particularly, to a method of driving a plasma address liquid crystal display device in which a normal operation is possible even if a part of an electrode causing plasma discharge is damaged.

One of the next generation flat panel display devices, the Plasma Address Liquid Crystal Display Device (hereinafter referred to as "PALC") is a complex of liquid crystal display devices (hereinafter referred to as "LCD") that accompany the semiconductor process. The manufacturing process is simplified by combining the technology of Plasma Display Panel (PDP) and the technology of LCD. PALC is easy to manufacture compared to the existing LCD and has the characteristics of high definition. In addition, LCDs can display screens up to 30 inches in size, while PALC has the advantage of scaling screen sizes up to 50 inches.

PALC constitutes the entire panel by arranging each pixel cell formed in a matrix form at each intersection point of the discharge electrode lines of the cathode and anode supplied with the discharge voltage for generating plasma discharge and the data transparent electrode lines supplied with the video signal. do. In the PALC, the liquid crystal layers controlled by plasma discharge in each pixel cell realize an image by adjusting the light transmittance of white light generated from the back light according to the video signal.

Referring to FIG. 1, a cell structure of a PALC is largely composed of a plasma channel unit 20, a liquid crystal unit 22, and a back-light 24. The plasma channel unit 20 is parallel to the lower glass substrate 26, the polarizing filter 28 bonded to the rear surface of the lower glass substrate 26, and the lower glass substrate 26 in the scanning line direction of the panel. A partition wall 34 formed vertically on the lower glass substrate 26 in the scanning line direction of the panel with the positive electrode 30 and the negative electrode 32 formed therebetween, and the pair of the positive electrode 30 and the negative electrode 32 interposed therebetween. ) And a dielectric glass thin film 36 bonded to the partition wall 34. The liquid crystal part 22 is a red, green and blue color bonded to the upper glass substrate 38, the polarizing filter 40 bonded to the front surface of the upper glass substrate 38, and the rear surface of the upper glass substrate 38. Between the filter 42 and the transparent electrode 44 formed of Indium-Tin-Oxide (ITO) on the rear surface of the color filter 42, between the transparent electrode 44 and the dielectric glass thin film 36. It has a liquid crystal layer 46 formed on. The transparent electrode 44 is formed in a direction orthogonal to the discharge electrodes of the anode 30 and the cathode 32. Discharge gases such as He and Ne are injected into the discharge space 50 formed by the lower glass substrate 26, the dielectric glass thin film 36, and the partition wall 34. Backlight 24 is a light source that emits white light.

Referring to the image realization process, first, plasma discharge occurs for each scan line to which a discharge voltage is applied between the anode 30 and the cathode 32 in the plasma channel unit 20. At this time, as the discharge gas is ionized in the discharge space 50 of each pixel cell by plasma discharge, charged particles such as electrons are generated. During the plasma discharge period, the potential in the discharge space 50 becomes almost equal to the potential of the anode 30 in almost all regions except near the cathode 32. In other words, a virtual electrode equal to the potential of the anode 30 is formed in the discharge space 50. As a result, the anode 30 and the dielectric glass thin film 36 are in an electrically shorted state. In the scan line where no plasma discharge occurs, the anode 30 and the dielectric glass thin film 36 are insulated from each pixel cell. When a video signal is applied to the transparent electrode 44 on the liquid crystal layer 46 in the pixel cell where the plasma discharge has occurred, the liquid crystal of the liquid crystal layer 46 is rotated by the voltage difference between the anode 30 and the transparent electrode 44. While controlling the light transmittance of the white light incident and transmitted from the backlight (24). White light passing through the liquid crystal layer 46 in each pixel cell is converted into red, green, and blue light while passing through the color filter 42, and then combined to realize an image.

In the PALC, unlike the PDP, the plasma discharge is not continuously maintained, but charged particles are charged in each cell by the discharge, and the liquid crystal layer 46 can be driven while the discharged cell is maintained in the charged state. Be sure to The amount of light transmitted through the liquid crystal layer 46 is controlled by the video signal applied to the transparent electrode 44. One other difference from PDPs is the structure of bulkheads. In the case of a typical PDP, the partition wall is formed in a direction perpendicular to the scan line to prevent mutual interference between adjacent pixel cells of each of red, green, and blue. However, in the case of PALC, the partition wall 34 is formed in the scan line direction because the plasma discharge is used as a switch for driving the liquid crystal layer in the PALC. In the PALC having such a feature, the electrode spacing between the anode 30 and the cathode 32 arranged side by side in each scan line acts as a very important factor. As the distance between the anode 30 and the cathode 32 becomes wider, the driving voltage required for causing plasma discharge becomes higher.

In the PALC having such a characteristic, the anode 30 and the cathode 32 which cause the plasma discharge are often damaged in the manufacturing process or during the plasma discharge. In particular, when discharge is continued for a long time, the electrode may be damaged by sputtering of charged particles generated during discharge. FIG. 2 is a plan view of a PALC illustrating an example in which a part of the anode formed in the second scan line is damaged by some factor among the discharge electrodes of the anode and cathode formed in each scan line. As shown in FIG. 2, a part of the positive electrode A is worn by sputtering so that the gap Z between the positive electrode A and the negative electrode Y2 is reduced. In this case, when the normal driving voltage is applied to the anode A and the cathode Y2, plasma discharge does not occur in the pixel cell in which the electrode is damaged (G region of the second scan line). Of course, normal discharge occurs in the pixel cells (regions R and B) where the electrodes are not damaged. FIG. 3 is a waveform diagram illustrating waveforms of driving pulses supplied to the anodes A and the cathodes Y1 to Yn for each scan line to cause plasma discharge. Referring to FIG. 3, in the conventional PALC driving method, all scan lines are driven in such a manner that one scan line is sequentially driven every one horizontal period. In detail, first, driving pulses having the same period and amplitude are continuously supplied to the anodes A and the first to nth cathodes Y1 to Yn for each scan line. Since the driving pulses supplied to the anodes A and the first to nth cathodes Y1 to Yn are supplied in phase as shown in the drawing, the first to nth cathodes Y1 to Yn used as scan electrodes. The voltage difference does not occur between the two electrodes unless a separate scan pulse is supplied to the N / A. In order to generate a discharge for each scan line, scan pulses having a voltage level that is capable of causing a discharge to the first to nth cathodes Y1 to Yn are sequentially supplied for each horizontal period. That is, as shown in FIGS. 2 and 3, the scanning pulse is supplied to the first cathode Y1 of the first scan line in the first horizontal period, and the second cathode Y2 of the second scan line in the second horizontal period. ), The scanning pulses are sequentially supplied to the nth scanning line by supplying the scanning pulses. As shown in FIG. 3, in the conventional driving method, the widths of the scan pulses sequentially supplied to each scan line are the same. In the conventional PALC driving method, the width of the scanning pulse is set to about 5 to 7 ms. 4 is a waveform diagram showing a waveform of a general scan pulse applied to the cathode 32 used as a scan electrode and a waveform of a discharge current flowing between the anode 30 and the cathode 32 when the scan pulse is applied in a normal pixel cell. to be. When a driving pulse having a normal voltage value V and a pulse width t is applied to the anode 30 and the cathode 32, the pixel cells in which the electrodes are not damaged are shown in FIG. 4 between the two electrodes 30 and 32. As shown in the figure, the plasma current is generated in the discharge space 50 while the discharge current flows to a level at which the discharge can occur. However, as shown in FIG. 2, in a pixel cell (G region of the second scan line) in which the electrode is damaged and thus the gap between the anode 30 and the cathode 32 is wider than normal, the two electrodes 30 and 32 are normally separated. Since the conductive channel is not formed even when the driving voltage is applied, the current waveform as shown in FIG. 4 does not exist. As described above, the problem of electrode damage is a factor of shortening the life of the PALC by making the discharge between the pixel cells uneven or causing a mis discharge. In the conventional PALC driving method, the voltage of the scanning pulse supplied to the cathode 32 is higher than the normal voltage as a method for driving all the pixel cells of the damaged electrode. However, in this method, the crosstalk phenomenon, in which mis-discharge occurs in adjacent cells due to the influence of a strong electric field, becomes a problem. For this reason, in the conventional PALC, when the electrode is damaged during the production or when it is used for a long time, it is difficult to disassemble the PALC and repair the damaged electrode part.

Accordingly, it is an object of the present invention to provide a method of driving a plasma address liquid crystal display device in which a normal operation is possible even if a part of an electrode that causes plasma discharge is damaged.

1 is a longitudinal sectional view showing the structure of a conventional plasma address liquid crystal display device;

Fig. 2 is a plan view of a plasma address liquid crystal display element showing an example where a part of an electrode line for causing plasma discharge is damaged.

3 is a waveform diagram showing voltage waveforms supplied to an anode and a cathode for driving a conventional plasma address liquid crystal display device.

FIG. 4 is a waveform diagram showing waveforms of a general scan pulse applied to a cathode of a plasma address liquid crystal display and a waveform of a discharge current flowing between the anode and the cathode when a scan pulse is applied in a normal pixel cell; FIG.

5 is a view illustrating a driving method according to an exemplary embodiment of the present invention for normally operating a plasma address liquid crystal display device when an electrode is damaged as shown in FIG. 2.

6 is a waveform diagram showing waveforms of a scan pulse supplied to a scan line including a damaged electrode and a waveform of a discharge current flowing between an anode and a cathode in a normal pixel cell included in the scan line in the driving method of the present invention; .

<Description of the code | symbol about the main part of drawing>

20: plasma channel portion 22: liquid crystal portion

24: Backlight 26: Lower glass substrate

28,40 polarization filter 30 anode

32: cathode 34: partition wall

36: dielectric glass thin film 38: upper glass substrate

42: color filter 44: transparent electrode

46: liquid crystal layer 50: discharge space

In order to achieve the above object, the driving method of the plasma address liquid crystal display according to the present invention is characterized in that the width of the scanning pulse supplied to each of the scanning lines is different.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 to 6.

In the PALC driving method according to the present invention, in order to ensure normal operation even when the discharge electrode of the positive electrode or the negative electrode is damaged, the pulse width of the scanning pulse instead of increasing the voltage of the scanning pulse supplied to the scan line including the damaged electrode. By adjusting, the pixel cell of the damaged electrode part is driven in a normal state. Since the structure of the PALC used in the present invention is the same as the conventional structure shown in FIG. 1, a detailed description thereof will be omitted.

5 is a view showing a driving method according to an embodiment of the present invention for operating the PALC normally when the electrode is damaged as shown in FIG. 2 and 5, first, a driving pulse having a predetermined period and a voltage value is supplied to the anodes A of each scan line, and the first to nth cathodes Y1 to Yn of each scan line are also supplied. An in-phase driving pulse having the same period and voltage value as the pulse supplied to the anodes A is supplied. In the state where the scanning pulse having a predetermined voltage level value is not supplied to each of the cathodes Y1 to Yn, discharge does not occur because the same voltage is applied to the anode and the cathode for each pixel cell. In order to cause plasma discharge in each scan line, scan pulses are sequentially supplied to the cathodes Y1 to Yn of each scan line every horizontal period. In the driving method according to the present invention, the pulse width of the scanning pulse supplied at this time is adjusted to drive the pixel cell in which the electrode is damaged. That is, as shown in FIG. 5, the cathodes Y1, Y3,..., Yn of the scan lines in which the electrodes are not damaged are supplied with scan pulses having the same short pulse width as in the conventional case. As a result, a scan pulse having a wide pulse width may be supplied to the second cathode Y2 of the second scan line having a wider gap between the anode and the cathode. At this time, the voltage of the scan pulse should be appropriately set to cause plasma discharge without crosstalk between adjacent cells in scan lines where the electrodes are not damaged. The voltage of the scan pulse supplied to the second scan line including the damaged electrode also has the same magnitude as the voltage of the scan pulse supplied to the other scan lines. In the normal pixel cells included in the other scan lines except for the second scan line, plasma discharge occurs as a normal discharge current as shown in FIG. 3 flows between the anode and the cathode as in the conventional case. In contrast, in the pixel cells positioned at the damaged electrode portions, the discharge current does not flow as shown in FIG. 3 because the distance between the electrodes is widened. However, in the present invention, even if the plasma discharge is not properly generated in the pixel cell of the damaged electrode region, the scan pulse having a long pulse width is supplied to the scan line including the damaged electrode so that it can operate like a normal cell. This will be described in detail with reference to FIG. 6.

6 is a waveform diagram showing a waveform of a scan pulse having a long pulse width supplied to a scan line including a damaged electrode and a waveform of a discharge current flowing between an anode and a cathode in a normal pixel cell included in the scan line. When a scanning pulse having a pulse width t + a longer than the conventional pulse width t is supplied to the scan line including the damaged electrode, the normal pixel cells adjacent to the pixel cell positioned at the damaged electrode portion The discharge current flowing between the anode and the cathode maintains a steady state for a period of time as shown in the figure. At this time, charged particles such as electrons generated at the time of discharge in the normal pixel cells move to the pixel cells of the electrode region damaged by the diffusion and transition of the plasma, causing a kind of priming effect. As a result, the pixel cell of the damaged electrode part may contain many charged particles, thereby being in the same state as that in which the plasma discharge occurred, and the switching operation of the liquid crystal layer may be performed like the normal cell. This results in a case where the problem of miss discharge due to electrode damage is solved without increasing the voltage of the scanning pulse. The pulse width increase amount (a) of the scanning pulse supplied to the damaged scan line of the electrode should be set so that the charged particles generated from the normal pixel cells can be sufficiently diffused into the pixel cell of the damaged electrode portion. It is preferable to appropriately increase the pulse width increase amount (a) of the scanning pulse in proportion to the degree of damage of the electrode so as to sufficiently compensate the shortage of charged particles according to the degree of damage of the electrode.

Such a driving method is a method that can easily solve the problem of electrode damage that may occur due to long driving. That is, even if the electrode damage occurs and no discharge occurs in a specific cell, only changing the driving circuit part to adjust the width of the scanning pulse applied to the scan line including the damaged electrode can operate the pixel cell of the damaged electrode part normally. As a result, the life of the PALC can be extended. In addition, when some damage occurs to the electrode during the manufacturing process of the PALC, some cells are conventionally treated as defective because they do not discharge, but according to the present invention, even the defective cells found during the inspection process can be driven normally. It also plays a big role in increasing manufacturing yield. In the present invention, whether or not the electrode is damaged can be easily visually confirmed by observing whether the display panel is discharged, and thus, when an abnormality occurs during manufacturing or use of the panel, the driving circuit can adjust the scanning pulse supplied to the identified cell part. Changing the design of is a common way. Alternatively, a control circuit may be separately configured to automatically detect damaged cells and automatically control the width of the scanning pulse during use.

As described above, in the method of driving the plasma address liquid crystal display device according to the present invention, the width of the scanning pulse supplied to the damaged scan line is increased so that the charged cells generated in the normal pixel cell during plasma discharge are damaged. Make sure that it spreads sufficiently. As a result, the pixel cells of the damaged electrode portions can be normally operated without increasing the voltage of the scanning pulse. By such a driving method, it is possible to effectively solve the problem of erroneous discharge and miss discharge of the pixel cell. In addition, in the driving method according to the present invention, the discharge uniformity is improved because the insufficient plasma state in the abnormally operating pixel cell is compensated for by using the charged particles generated in the adjacent pixel cell. In addition, the lifetime of the plasma address liquid crystal display device can be extended, and the yield in the manufacturing process can be increased.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (4)

In the driving method of the plasma address liquid crystal display device provided with a plurality of scan lines each including a first electrode and a second electrode for generating a discharge, And a width of a scanning pulse supplied to each of the scanning lines is different from each other. The method of claim 1, And a width of the scan pulse supplied to the damaged scan line by a portion of the first and second electrodes. The method of claim 1, And increasing the width of the scanning pulse supplied to the scanning line having a wider gap between the first and second electrodes. The method of claim 3, wherein And increasing the width of the scanning pulse in proportion to the distance between the first and second electrodes.