JPH0675535A - Plasma address electrooptical device - Google Patents

Abstract

PURPOSE:To uniformalize and stabilize a plasma discharge over the entire length of row scanning units of the plasma address electrooptical device. CONSTITUTION:This plasma address electrooptical device has a flat panel structure integrally laminated with an electrooptical cell and a plasma cell. The electrooptical cell has plural signal electrodes D1, D2,..., DM constituting column signal units and the plasma cell has plural discharge electrode pairs constituting row scanning lines. These discharge electrode pairs consist of sets of cathodes K1, K2,..., Kn and corresponding anode electrodes A1, A2,..., An. A horizontal signal circuit 1 for supplying electric signals is connected to the signal electrodes D1 to Dm and a vertical scanning circuit 2 is connected to the cathode electrodes K1 to Kn successively line sequentially scan the respective discharge electrode pairs and to impress driving voltages thereto during the prescribed selection period. This vertical scanning circuit 2 has a discharge uniformalizing means for switching the driving voltages at a high speed during the selection period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma addressed electro-optical device having a two-layer structure of an electro-optical cell such as a liquid crystal cell and a plasma cell. More specifically, the present invention relates to a discharge uniformization driving method for a plasma cell.

[0002]

2. Description of the Related Art Conventionally, a switching element such as a thin film transistor is provided for each pixel as a means for improving resolution and contrast of a matrix type electro-optical device using a liquid crystal cell as an electro-optical cell, for example, a liquid crystal display device. Is generally known, and an active matrix addressing method of driving this line-sequentially is generally known. However, in this case, it is necessary to provide a large number of semiconductor elements such as thin film transistors on the substrate, and there is a disadvantage that the manufacturing yield deteriorates especially when the area is increased.

As a means for solving this disadvantage, Japanese Patent Laid-Open No. 1-217396 proposes a method of using a plasma switch instead of a switching element such as a thin film transistor. Hereinafter, the configuration of the plasma addressed display device that drives the liquid crystal cell using the switch based on the plasma discharge will be briefly described. As shown in FIG. 4, this device has a liquid crystal cell 101 and a plasma cell 1.
02 and a common intermediate plate 103 interposed between the two, and has a laminated flat panel structure. The plasma cell 102 is formed using a glass substrate 104, and a plurality of parallel grooves 105 are provided on the surface thereof. The grooves 105 extend, for example, in the row direction of the matrix. Each groove 105 is sealed by an intermediate plate 103 and constitutes a plasma chamber 106 which is individually separated. The hermetically sealed plasma chamber 106 is filled with an ionizable gas. Convex portion 10 separating adjacent grooves 105
Numeral 7 serves as a partition wall for partitioning the individual plasma chambers 106, and also serves as a gap spacer for each plasma chamber 106. A pair of discharge electrodes 108 and 109 which are parallel to each other are provided at the bottom of each groove 105. This discharge electrode pair functions as an anode A and a cathode K and ionizes the gas in the plasma chamber 106 to generate discharge plasma. The discharge area is a row scanning unit.

On the other hand, the liquid crystal cell 101 is composed of a transparent substrate 110. The transparent substrate 110 is the intermediate plate 10.
3 are opposed to each other through a predetermined gap, and a liquid crystal layer 111 is filled in the gap. A signal electrode 112 made of a transparent conductive material is formed on the inner surface of the transparent substrate 110. The signal electrode 112 is orthogonal to the plasma chamber 106 and serves as a column signal unit. Matrix-like pixels are defined at the intersections of column signal units and row scanning units.

A vertical scanning circuit is connected to each row scanning unit, and each discharge electrode pair is line-sequentially scanned to apply a driving voltage for a predetermined selection period. On the other hand, a horizontal signal circuit is connected to each column signal unit, and an image signal is supplied to a plurality of signal electrodes in synchronization with the above-described line sequential scanning. By line-sequential scanning,
When a plasma discharge is generated in the plasma chamber 106, the inside becomes substantially uniformly at the anode potential, and pixel selection is performed for each row. That is, the plasma chamber 106 functions as a sampling switch. When an image signal is applied to each pixel while the plasma sampling switch is in a conducting state, sampling and holding is performed to control lighting or extinction of the pixel. Even after the plasma sampling switch is turned off, the image signal is held in the pixel as it is.

[0006]

By the way, unlike the usual plasma display panel in which a dot-shaped discharge region is formed for each pixel, in the above-mentioned display device in which the liquid crystal cell is addressed by the plasma sampling switch,
A linear discharge region is formed between the anode and the cathode adjacent to each other for each row scanning unit. When the screen is enlarged, the span of each discharge area becomes considerably long. In this case, there arises a problem that the discharge is concentrated only in a part due to the voltage drop due to the resistance component of the discharge electrode itself, the variation in the distance between the electrodes, etc. and becomes non-uniform along the row scanning unit.
When it becomes non-uniform, the conduction resistance of the plasma sampling switch corresponding to each pixel varies. Conventionally, an external load resistor has been connected to each cathode electrode. However, this load resistance is for equalizing the variation of the plasma discharge between the row scanning units and cannot suppress the concentration of the plasma discharge in each row scanning unit. Therefore, in order to generate stable plasma discharge over one scanning unit, it is necessary to supply a discharge current with a sufficient margin. As a result, display contrast is reduced due to unnecessary plasma emission, power consumption is increased,
Various problems such as deterioration of life due to electrode sputtering have occurred. As described above, in the conventional discharge current compensation method for each scanning unit, when the discharge electrode span is extended, the plasma discharge distribution becomes delicate due to local non-uniformity of the electrode shape, voltage drop, or disturbance in the discharge space. There is a problem that it is liable to fluctuate, and adverse effects such as uneven brightness of each pixel cannot be avoided.

In order to facilitate understanding of the present invention, the above-mentioned problems of the conventional technique will be described more specifically. FIG. 5 shows the waveform of the drive voltage supplied by the vertical scanning circuit when line-sequential scanning is performed on each discharge electrode pair. In this conventional example,
An anode electrode A1, which constitutes one of the individual discharge electrode pairs
A2, A3, ... Are always held at a predetermined ground potential (for example, 0 V). On the other hand, cathode electrodes K1, K2, K
A constant negative potential -V is applied to 3, 3, ... During the sequentially assigned selection period.

FIG. 6 shows an equivalent circuit for one scanning unit.
The plasma chamber provided along the discharge electrode pair of the anode A and the cathode K has many discharge cells T1, T2, T3, T.
4, ..., can be regarded as a set of Tm. A load resistance R is inserted between the anode A and each discharge cell, and a constant drive voltage V is supplied between the anode A and the cathode K for a predetermined selection period. At the start of discharge, the drive voltage V is applied as a trigger to all the discharge cells T1, T2, ..., Tm. However, if there is a cell T1 whose discharge start voltage is lower than that of other cells, this discharge cell T1 is first detected.
Starts to discharge, and the discharge sustaining voltage drops. As a result, the discharge concentration in the discharge cell T1 is further accelerated, and the sustain voltage is further lowered. Then, the electrode surface of the discharge cell T1 is activated by sputtering and the discharge concentration increases. On the other hand, when the cell T1 starts to discharge first, the effective voltage VT decreases, so that the discharge of the remaining discharge cells T2, T3, T4, ..., Tm is hindered. As a result, a plurality of cells T1 to T
The non-uniformity of discharge at m increases and the display quality is adversely affected, and the service life is shortened due to local concentration of electrode spatter.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned problems or problems of the conventional technique, the present invention is a row scanning unit.
An object of the present invention is to provide a driving method capable of ensuring the uniformity and stability of discharge over the entire plasma chamber of a book. INDUSTRIAL APPLICABILITY The present invention is generally applied to a plasma-addressed electro-optical device and has, as basic components, an electro-optical cell having a plurality of signal electrodes that are column signal units and a plurality of discharge electrode pairs that are a row scanning unit. It has a plasma cell laminated on the optical cell, a horizontal signal circuit for supplying an electric signal to the signal electrode, and a vertical scanning circuit for line-sequentially scanning the discharge electrode pair and applying a drive voltage during a predetermined selection period. ing. In such a structure, the vertical scanning circuit is provided with discharge equalizing means for switching the drive voltage at high speed during the selection period. According to one aspect of the present invention, the discharge equalizing means holds one of the discharge electrode pairs at a constant potential and applies a high-speed oscillating potential to the other to perform DC on / off drive. According to another aspect, the discharge uniformizing means applies a high-speed oscillating potential to one of the discharge electrode pairs and an inversion high-speed oscillating potential to the other to perform AC driving. The discharge uniformization driving method is applicable not only to the plasma address electro-optical device but also to driving a discharge element having a plurality of discharge electrode pairs arranged in stripes.

[0010]

According to the present invention, the ON / OFF switching of the driving voltage is repeated at high speed during each selection period assigned to each row scanning unit, and local concentration of discharge is prevented from proceeding. There is. Further, the discharge can be spread over the entire length of the plasma chamber by repeatedly applying the trigger. This improves the uniformity of discharge, improves the display quality, and
The purpose of this is to prevent local electrode sputtering and prolong the service life.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. 1 is a schematic circuit diagram showing a first embodiment of a plasma addressed electro-optical device according to the present invention. As shown in (A), this device includes an electro-optical cell having a plurality of signal electrodes D1, D2, ..., Dm which are column signal units, and a plasma cell having a plurality of discharge electrode pairs which are row scanning units. It has a laminated structure. Each discharge electrode pair comprises a set of cathode electrodes K1, K2, K3, ..., Kn and corresponding anode electrodes A1, A2, A3 ,. This apparatus further includes a horizontal signal circuit 1, a vertical scanning circuit 2, and a control circuit 3. Horizontal signal circuit 1
To the signal electrodes D1 to Dm are connected via a buffer. On the other hand, cathode electrodes K1 to Kn are also connected to the vertical scanning circuit 2 via a buffer.
The anode electrodes A1 to An are commonly grounded.
The cathode is line-sequentially scanned by the scanning circuit 2, and the signal circuit 1 supplies an analog electric signal to each signal electrode in synchronization with this. The control circuit 3 controls synchronization between the signal circuit 1 and the scanning circuit 2. A discharge region is formed along each cathode to form the row scanning unit described above. On the other hand, each signal electrode serves as a column signal unit. A pixel 4 is defined between both units.

As a feature of the present invention, the vertical scanning circuit 2 is provided with discharge equalizing means, and the driving voltage applied to the corresponding discharge electrode pair during the selection period assigned to each row scanning unit is made high speed. I am trying to switch with. This drive voltage waveform is shown in (B). In this embodiment,
As mentioned above, the anode A is always at ground potential (for example, 0V).
Held in. On the other hand, to the cathode K, a potential that oscillates at high speed between the ground potential and -V is applied during the selection period, and DC on / off drive is performed. By this driving, on / off of the discharge is repeated at high speed in the selected plasma chamber. Therefore, it is possible to prevent local concentration of discharge from proceeding. Further, high-speed switching of the driving voltage can repeatedly provide a discharge trigger, can spread the discharge over the entire length of the plasma chamber, and can improve uniformity and stability.

FIG. 2 is a schematic circuit diagram showing a second embodiment of the plasma addressed electro-optical device according to the present invention. The first embodiment employs DC on / off drive, whereas this embodiment employs AC drive. Basically, it has the same structure as the first embodiment, and corresponding reference numerals are given to corresponding parts for easy understanding. The difference is that, as shown in (A), the discharge electrode pairs X1, X2, X3, ..., Xn forming each row scanning unit are composed of two functionally equivalent plasma electrodes, both of which are connected to the scanning circuit 2. It is that. Further, the discharge equalizing means incorporated in the scanning circuit 2 includes the discharge electrode pairs X1,
AC driving is performed by applying a high-speed oscillating potential to one of the plasma electrodes X2, X3, ..., Xn and applying a reverse high-speed oscillating potential to the other plasma electrode.

(B) shows a drive voltage waveform applied to the discharge electrode pair X. A high-speed oscillating potential that repeats switching between + V and -V during the selection period is applied to the first electrode. A high-speed oscillating potential with inverted phase is applied to the second electrode. By doing so, the voltage V required to maintain the plasma discharge can be continuously supplied to the discharge electrode pair X. By performing such AC driving, it is possible to successively provide triggers while maintaining the discharge state to the maximum. In this case, since the discharge electrode coated with the dielectric can be used as in the general AC drive type plasma display panel, electrode spattering can be effectively prevented and the life can be further extended. On the other hand, in the DC on / off drive shown in the first embodiment, the sum of the actual on times becomes short during the selection period, and the duty decreases.

Finally, FIG. 3 is a schematic sectional view showing a specific example of the plasma addressed electro-optical panel which operates according to the driving method of the present invention. This panel has a structure in which a liquid crystal cell 11, a plasma cell 12 and an intermediate plate 13 made of thin glass interposed therebetween are laminated. Liquid crystal cell 1
Reference numeral 1 denotes a glass substrate 14, and a plurality of signal electrodes D made of a transparent conductive film are formed on the inner main surface of the glass substrate 14 in parallel to each other in the column direction. The substrate 14 is bonded to the intermediate plate 13 by using a spacer 15 with a predetermined gap. A liquid crystal layer 16 which is an electro-optical material layer is provided in the gap.
Is filled. In this embodiment, liquid crystal is used as the electro-optical material, but it is not limited to this, and other fluid materials can be used. Further, although the present embodiment relates to a plasma addressed display panel, the present invention is not limited to this and can be widely applied to plasma addressed electro-optical panels such as optical modulators.

On the other hand, the plasma cell 12 is constructed by using the lower glass substrate 17. Discharge electrodes 18 are formed in stripes on the inner main surface of the glass substrate 17. The discharge electrodes 18 alternately function as an anode A and a cathode K to generate plasma discharge. The discharge electrodes 18 are arranged along the row direction so as to intersect the signal electrodes D. A partition 19 is formed along the discharge electrode 18, and its top surface is in contact with the back surface side of the intermediate plate 13. A low melting point glass 20 is arranged along the peripheral edge of the glass substrate 17, and the intermediate plate 13 and the glass substrate 17 are bonded to each other. An airtightly sealed plasma chamber 21 is formed between the two. An ionizable gas is enclosed in the plasma chamber 21. The gas species can be selected from, for example, helium, neon, argon, xenon or a mixed gas thereof. The plasma chamber 21 is divided by the partition wall 19 and constitutes a row scanning unit.

In the present invention, the pair of anodes A and cathodes K are selected according to the line-sequential scanning, and the drive voltage is switched at high speed through the discharge equalizing means.
It should be noted that instead of line-sequentially selecting the row scanning units one by one, line-sequentially selecting two line scanning units may be selected and driven. That is, one row scanning unit simultaneously drives two row scanning units each including a specific cathode K and anodes A located on both sides thereof. Thereafter, two lines are sequentially driven.
In this case, one row scanning unit overlaps between the previous selection period and the next selection period, but there is no problem in operation because writing of the electric signal is always performed in the next selection period.
It is needless to say that the discharge uniformizing drive according to the present invention can be implemented even in such an operation.

[0018]

As described above, according to the present invention, when line-sequential scanning is performed in the plasma addressed electro-optical device, the frequency of the drive voltage pulse applied to each row scanning unit is increased to turn it on / off. By repeating the operation or repeating the polarity inversion by AC driving, high-speed switching is performed during the selection period. This has the effect that local concentration of discharge can be prevented and uniform and stable operation can be achieved, which in turn leads to a longer life.

[Brief description of drawings]

FIG. 1 is a circuit diagram and a waveform diagram showing a first embodiment of a plasma addressed electro-optical device according to the invention.

FIG. 2 is a circuit diagram and a waveform diagram showing a second embodiment of the plasma address electro-optical device according to the invention.

FIG. 3 is a schematic cross-sectional view showing the structure of a plasma address electro-optical device according to the present invention.

FIG. 4 is a schematic perspective view showing an example of a conventional plasma address electro-optical device.

FIG. 5 is a waveform diagram of a drive voltage used in a conventional plasma address electro-optical device.

FIG. 6 is an equivalent circuit diagram for explaining a problem of a conventional plasma address electro-optical device.

[Explanation of symbols]

 1 Signal Circuit 2 Scanning Circuit 3 Control Circuit 4 Pixel 11 Liquid Crystal Cell 12 Plasma Cell 13 Intermediate Plate 14 Glass Substrate 16 Liquid Crystal Layer 17 Glass Substrate 18 Discharge Electrode 19 Partition Wall 21 Plasma Chamber D Signal Electrode A Anode K Cathode

Claims (4)

[Claims] 1. An electro-optical cell having a plurality of signal electrodes as a column signal unit, a plasma cell having a plurality of discharge electrode pairs as a row scanning unit and stacked on the electro-optical cell, and a signal electrode A plasma address electro-optical device having a horizontal signal circuit for supplying an electric signal and a vertical scanning circuit for line-sequentially scanning each discharge electrode pair and applying a driving voltage for a predetermined selection period, wherein the vertical scanning circuit is selected. A plasma addressed electro-optical device comprising a discharge uniformizing means for switching the drive voltage at high speed during a period. 2. The discharge equalizing means holds one of the discharge electrode pairs at a constant potential and applies a high-speed oscillating potential to the other to perform DC on / off drive. Plasma address electro-optical device. 3. The plasma according to claim 1, wherein the discharge uniformizing means applies a high-speed oscillating potential to one of the discharge electrode pairs and an inversion high-speed oscillating potential to the other to perform AC driving. Address electro-optical device. 4. When performing line-sequential scanning of a discharge element having a plurality of discharge electrode pairs arranged in stripes, a drive voltage is applied to each discharge electrode pair while switching at high speed during an assigned selection period. A method for driving uniform discharge of a discharge element, which comprises: