JPH05303350A - Plasma address electrooptical device - Google Patents

Abstract

PURPOSE:To attain the perfect AC driving of the plasma address electrooptical device. CONSTITUTION:Plural signal electrodes 5 are formed in a stripe form on the inside surface of an upper liquid crystal cell substrate 4 and plural pairs of anodes 10/cathodes 11 intersecting orthogonally with the signal electrodes 5 are formed on the inside surface side of a lower plasma substrate 8. A dielectric sheet 3 is interposed between these two substrates and a liquid crystal layer 7 is packed between the upper substrate 4 and the dielectric sheet 3. The lower glass substrate 8 is hermetically sealed by the dielectric sheet 3 to form individual plasma chambers 12. The gases in the plasma chambers 12 are ionized by the discharge between the anodes 10/the cathodes 11 and the liquid crystal layer 7 existing in the intersected parts of the signal electrodes 5 and the discharge regions is AC driven with the discharge regions where the ionized gases exist locally as a scanning unit. Electrode means 14 for detecting the potentials of the discharge regions are provided on the surface of the dielectric sheet 3. The level of the AC driving signals is adjusted according to the offset potentials detected by such means.

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 for switching. More specifically, it relates to the drive control means.

[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. A generally known active matrix addressing system is one in which a pixel is provided and is driven line-sequentially. 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, Buzaku et al. Propose in Japanese Unexamined Patent Publication No. 1-217396 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 comprises a liquid crystal cell 101, a plasma cell 102, and an ultrathin dielectric sheet 1 interposed therebetween.
03 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 a dielectric sheet 103 and constitutes an individually separated plasma chamber 106. The hermetically sealed plasma chamber 106 is filled with an ionizable gas. The ridges 107 that separate the adjacent grooves 105 serve as partition walls that partition the individual plasma chambers 106, and also serve as gap spacers for the plasma chambers 106. Each groove 1
A pair of plasma electrodes 10 parallel to each other is provided on the bottom of 05.
8,109 are provided. The pair of electrodes function as an anode and a cathode, and ionize 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 arranged to face the dielectric sheet 103 with a predetermined gap, and a liquid crystal layer 111 is filled in the gap. Also, the transparent substrate 1
A signal electrode 112 made of a transparent conductive material is provided on the inner surface of 10.
Are formed. The signal electrode 112 is connected to the plasma chamber 1
It is orthogonal to 06 and serves as a column drive unit. Matrix-shaped pixels are defined at the intersections of the column driving units and the row scanning units.

In the display device having such a structure,
Display driving is performed by line-sequentially switching and scanning the plasma chamber 106 in which plasma discharge is performed, and applying a drive signal to the signal electrode 112 on the liquid crystal cell side in synchronization with this scanning. When plasma discharge is generated in the plasma chamber 106, the inside becomes substantially close to the anode potential, and pixel selection is performed for each row. In other words, a virtual electrode will appear on the surface of the dielectric sheet 103 that is in contact with the liquid crystal layer immediately above the discharge region. The potential of the virtual electrode is the dielectric sheet 1
It is determined by the polarization of No. 03 and corresponds to the potential of the discharge region. The plasma chamber 106 functions as a sampling switch for applying a predetermined potential to this virtual electrode. When a driving signal is applied to each pixel while the plasma sampling switch is in a conductive state, sampling and holding is performed and lighting or extinction of the pixel can be controlled. That is, the light transmittance of the liquid crystal layer changes according to the potential difference generated between the virtual electrode and the signal electrode. When the plasma sampling switch is turned off, the potential of the virtual electrode becomes floating and the drive signal written in the pixel is held as it is.

[0006]

When the liquid crystal is driven by direct current, deterioration occurs and the life is shortened, which is not preferable. Normally, the liquid crystal is driven by alternating current. In a general liquid crystal display device, the potential of the signal electrode is inverted, for example, for each frame with reference to the potential of the counter electrode. In a general liquid crystal display device, there is no problem because the potential of the counter electrode is constant. However, in the plasma addressed liquid crystal display device described above, the virtual electrode corresponds to the counter electrode. The potential of this virtual electrode is controlled by the discharge potential. The discharge potential in the plasma chamber is close to the anode potential side, but it does not always match completely and an offset is included. This offset amount is not constant and varies depending on the discharge characteristics of each plasma chamber. Therefore, even if a reference potential is set in advance in consideration of a predetermined offset amount and AC driving is performed, there is a problem or problem that a DC component is actually contained and causes deterioration of the liquid crystal. Further, there is a problem in that it is not possible to obtain a uniform display contrast over the entire image display surface because there is a variation in virtual electrode potential between individual row scanning units.

[0007]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, it is an object of the present invention to achieve complete AC drive. In addition, the purpose is to make the driving of the liquid crystal uniform. The following measures have been taken in order to achieve this object. The plasma addressed electro-optical device to which the present invention is applied has, as a basic component, a first substrate having a plurality of first electrodes or signal electrodes arranged in parallel with each other along a predetermined main surface, for example, a liquid crystal cell substrate. And a second substrate or plasma cell substrate having a plurality of second electrodes or plasma electrodes arranged orthogonal to the signal electrodes and parallel to each other, and arranged so that the plasma electrodes face the signal electrodes. An electro-optical material layer, such as a liquid crystal layer, interposed between both substrates, and a plasma chamber for enclosing an ionizable gas formed between the liquid crystal layer and the plasma cell substrate. The gas is selectively ionized by the discharge between adjacent plasma electrodes, that is, between the anode / cathode, and a liquid crystal layer located at the intersection of the signal electrode and the discharge region is set with the discharge region in which the ionized gas is localized as a scanning unit. To drive. As a feature of the present invention, means for detecting the potential of the discharge region is provided.

More specifically, a dielectric layer or a dielectric sheet is interposed so as to contact the liquid crystal layer on the side opposite to the inner surface of the liquid crystal cell substrate. A plasma chamber is provided between the dielectric layer and the lower plasma cell substrate. Electrode means for detecting the potential of the discharge region is provided on the dielectric layer so as to be aligned with the plasma chamber. In addition, a means for adjusting the level of the drive signal applied to the signal electrode according to the detected offset potential is provided.

[0009]

According to the present invention, the electrode means for detecting the discharge potential is provided through a dielectric layer or a dielectric sheet in a portion of the plasma chamber located outside a predetermined plasma chamber, preferably the effective display area. This electrode means is arranged at the position of the virtual electrode described above. By connecting a lead wire to the electrode means from the outside, the actual dielectric potential on the surface of the dielectric sheet can be monitored. Based on this monitoring result, the level of the AC drive signal applied to the signal electrode or the reference potential is adjusted. In this way, complete liquid crystal AC drive can be realized by applying feedback using the fluctuation of the discharge potential as an error signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic sectional view showing a plasma address electro-optical device according to the present invention. It shows a shape cut along the column direction, that is, the signal electrode direction.
This device has a structure in which a liquid crystal cell 1, a plasma cell 2, and an ultrathin dielectric sheet 3 interposed therebetween are laminated.
The liquid crystal cell 1 is composed of a glass substrate 4, and a plurality of signal electrodes 5 made of a transparent conductive film are formed on the inner main surface of the liquid crystal cell 1.
Are formed parallel to each other. The substrate 4 is adhered to the dielectric sheet 3 by using a spacer 6 with a predetermined gap. An electro-optical material layer such as a liquid crystal layer 7 is filled in the gap.

On the other hand, the plasma cell 2 has a lower glass substrate 8
It is configured using. A stripe-shaped groove 9 orthogonal to the signal electrode 5 is formed on the inner main surface of the glass substrate 8. At the bottom of each groove, a pair of plasma electrodes, that is, an anode 10 and a cathode 11, are extended. The substrate 8 is adhered to the dielectric sheet 3, and each of the hermetically sealed grooves 9 constitutes a plasma chamber 12 in which an ionizable gas is sealed. The gas species can be selected from, for example, helium, neon, argon or a mixed gas thereof. The ridges 13 located between the individual grooves 9 function as partition walls, and also contact the back surface side of the dielectric sheet 3 to function as spacers. The structure of the plasma cell 2 is not limited to that shown in the figure. For example,
The anode / cathode may be thick-film printed on the flat substrate surface, and the partition walls may be formed by thick-film printing.

As a feature of the present invention, the detection electrode 14 is provided on the interface of the dielectric sheet 3 which is in contact with the liquid crystal layer 7. The detection electrode 14 is arranged at the intersection of the signal electrode 5 which constitutes a column driving unit and the plasma chamber 12 which constitutes a row scanning unit. It is preferably provided outside the effective display area. Alternatively, the detection electrode 14 can be provided in the pixel portion in the effective display area by forming the detection electrode 14 with a transparent conductive material. The detection electrode 14 serves as means for detecting the potential of plasma discharge generated in the plasma chamber 12. More precisely, the potential on the interface of the dielectric sheet 3 which is controlled by the discharge potential is detected.

Next, the operation of the apparatus shown in FIG. 1 will be described. Glow discharge occurs in the plasma chamber 12 by setting the cathode 11 to a negative potential with respect to the anode 10. The generated plasma spreads over the entire stripe-shaped groove 9, and the back surface of the dielectric sheet 3 becomes close to the anode potential. On the other hand, the anode 10 located in the groove 9 where plasma discharge is not generated is separated from the dielectric sheet 3 with high impedance. Line-sequential row scanning of the liquid crystal cell 1 is performed by utilizing the switching action of this plasma discharge. The signal electrode 5 is synchronized with this scanning.
When a drive signal is applied to the liquid crystal layer 7, the drive signal can be written in the liquid crystal layer 7 via the dielectric sheet 3. By the way, liquid crystal layer 7
Degradation occurs when a DC electric field is applied to. Since the discharge potential of each plasma chamber 12 is offset from the anode potential, it is necessary to allow the signal electrode 5 to be AC-driven in consideration of this amount. For this reason, it is necessary to accurately monitor the discharge potential, and the detection electrode 14 is provided.

FIG. 2 shows a signal electrode drive circuit externally connected to the plasma addressed electro-optical device shown in FIG. 1, and includes means for adjusting the level of the drive signal. C _LC is equivalent to the capacitance formed by the liquid crystal layer 7. The capacitance C _LC is a specific signal electrode 5 and a detection electrode 1 facing the specific signal electrode 5.
And 4 are formed. A capacitance C _DI composed of the dielectric sheet 3 is connected in series with the liquid crystal capacitance C _LC . This capacitance C _DI uses both the front and back surfaces of the dielectric sheet 3 as electrodes. A plasma switch SWp is connected in series to the dielectric sheet capacitance C _DI . The plasma switch SWp represents the function of the plasma chamber 12 in an equivalent manner. As described above, the discharge potential of the plasma chamber 12 is offset from the anode 10, and the amount of the drop is equivalently represented by Vofs.

A comparator 21 is connected to the detection electrode 14. The adjusting means 22 is connected to the output terminal of the comparator 21. This adjusting means 22 is a switch 2
3, a capacitor 24 and a comparator 25, and holds the comparator output potential Vc. Adjusting means 22
A driving signal source 26 is connected between the signal electrode 5 and each of the signal electrodes 5. The signal source 26 supplies the AC signal Vs to the signal electrode 5, and the reference level thereof is set in accordance with the potential Vc held by the adjusting means 22.

Next, the operation of the circuit shown in FIG. 2 will be described in detail. First, the plasma switch SWp is made conductive by discharge, and the drive signal Vs applied to the signal electrode 5 is set to a constant voltage, for example, 0V. In this state, the interface potential Vd is detected. At this time, if the output potential of the adjusting means 22 is 0V, this potential Vd is the offset voltage Vofs.
_Is divided by a pair of capacitances C _LC and C _DI , and is given by Vd = Vofs × C _DI / (C _DI + C _LC ). That is, the interface potential Vd is the offset voltage Vo.
It is a function of fs.

When the switch 23 is turned on, the comparator 2 is caused by the voltage difference between the output potential of the adjusting means 22 and the interface potential Vd.
The output potential of 1 changes until it becomes equal to the offset voltage Vofs and is held by the adjusting means 22. After that, the normal display drive is performed, and the held offset potential Vo is held.
An AC signal Vs is applied to the signal electrode 5 centering on fs. A complete AC signal can be supplied to the liquid crystal capacitor C _LC . That is, feedback control is performed via the detection electrode 14, the comparator 21, the adjusting means 22 and the like to prevent the application of the DC component to the liquid crystal layer 7. The operation of detecting the interface potential Vd may be executed, for example, for each frame in which the drive signal is inverted. Offset voltage V due to changes in discharge state
Even if ofs changes with time, stable AC drive can be realized by superimposing the change on the liquid crystal drive signal. Although the detection electrode 14 is provided on the front surface side of the dielectric sheet in this embodiment, it may be formed on the back surface side instead of this. In this case, the detection electrode directly monitors the offset of the discharge potential.

FIG. 3 shows an application example of the present invention. The signal electrodes 5 forming a driving unit and the stripe-shaped plasma chambers 12 forming a scanning unit are orthogonal to each other, and individual pixels 31 are defined at intersections. In this application example, the plurality of detection electrodes 14 are divided and arranged outside the effective display region including the pixels 31 arranged in a matrix. Each detection electrode 14 is arranged at the intersection of the signal electrode 5 and the plasma chamber 12 along the periphery of the effective display area. The variation or distribution of the offset potential on the screen can be known based on the information output from each detection electrode 14. This distribution state is stored in, for example, the frame memory. If the reference level of the AC drive signal is corrected in synchronization with the line-sequential scanning based on the stored data, it is possible to drive all the pixels in the screen uniformly without applying the DC component.

[0019]

As described above, according to the present invention, means for detecting the potential of the plasma discharge region is provided and the reference level of the liquid crystal AC drive signal is adjusted based on the detection result. With such a configuration, it is possible to prevent application of a direct current component to the liquid crystal and suppress deterioration and deterioration in display quality. When a large screen display is performed, the discharge potential detecting means is provided in a divided manner to detect the voltage drop distribution for each scanning unit caused by the discharge current. Based on this, the liquid crystal drive current can be corrected. There is an effect that it is possible to prevent display unevenness.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of a plasma address electro-optical device according to the present invention.

FIG. 2 is a drive circuit diagram of the plasma address electro-optical device shown in FIG.

FIG. 3 is a schematic plan view showing an application example of the present invention.

FIG. 4 is a perspective view showing a conventional plasma address electro-optical device.

[Explanation of symbols]

 1 Liquid Crystal Cell 2 Plasma Cell 3 Dielectric Sheet 4 Glass Substrate 5 Signal Electrode 7 Liquid Crystal Layer 8 Glass Substrate 9 Groove 10 Anode 11 Cathode 12 Plasma Chamber 14 Detecting Electrode 22 Adjusting Means 26 Liquid Crystal Driving Signal Source

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01J 17/49 C 7354-5E

Claims (2)

[Claims] 1. A first substrate having a plurality of first electrodes arranged parallel to each other along a predetermined main surface, and a plurality of second electrodes orthogonal to the first electrodes and arranged parallel to each other. And a second substrate having the second electrode arranged so as to face the first electrode, an electro-optical material layer interposed between the first and second substrates, and the electro-optical material. A plasma chamber for enclosing an ionizable gas formed between a layer and the second substrate is provided, the gas is selectively ionized by discharge between adjacent second electrodes, and the ionized gas is localized. The first discharge area is used as a scanning unit.
A plasma address electro-optical device characterized in that means for driving an electro-optical material layer located at an intersection of an electrode and the discharge area and detecting a potential of the discharge area is provided. 2. A first substrate having a plurality of first electrodes arranged parallel to each other along a predetermined main surface, and a plurality of second electrodes orthogonal to the first electrodes and arranged parallel to each other. And a second substrate arranged so that the second electrode faces the first electrode, an electro-optical material layer provided in contact with the plurality of first electrodes, and a plurality of the plurality of first electrodes. 1
A dielectric layer disposed on the side opposite to the electrode so as to be in contact with the electro-optical material layer, and a plasma chamber for enclosing an ionizable gas formed between the dielectric layer and the second substrate. Electro-optically located at the intersection of the first electrode and the discharge region with the discharge region in which the ionized gas is localized as a scanning unit. A drive signal is applied to the material layer from the first electrode, and electrode means for detecting the potential of the discharge region is provided on the dielectric layer, and the level of the drive signal is adjusted according to the offset potential detected by the electrode means. A plasma address electro-optical device characterized in that means are provided.