Gas Discharge Panel

Abstract

A gas discharge panel which has a shift layer for shifting a priming fire with a surface discharge and a display layer for memory and display when a discharge is produced between opposing electrodes. An equivalent electrostatic capacitance provided by a dielectric layer coated on the shift layer is made larger than that by a dielectric layer on the display layer to increase thereby a wall charge on the shift layer resulting from the surface discharge and decrease that resulting from the discharge between the opposing electrodes, thereby eliminating the possibility that an unnecessary priming fire for shifting is generated at the position of the discharge produced between the opposing electrodes.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a gas discharge panel in which a priming fire is shifted with a surface discharge and a display is produced with a discharge caused between opposing electrodes (hereinafter referred to as an opposite electrode discharge).

2. Description of the Prior Art

Hitherto, there has been employed a display panel commonly referred to as a plasma display panel which utilizes a gas discharge. This display panel is characterized in that electrodes for selecting unit discharge regions are isolated by a dielectric layer from a gas discharge space and it has a unique function of storing written information. However, this conventional display panel requires the same number of drivers as row and column electrodes disposed in a matrix form within the panel, for addressing the unit discharge regions by selecting the electrodes individually, so that peripheral circuits become extremely complicated and expensive.

To avoid this defect, it has been proposed to omit the drivers for either row or column electrodes of the display panel be effecting the selection of the row or column electrodes with an operation of shifting a fire priming discharge spot.

This will be described with regard to FIGS. 1 and 2. On a base plate 1 as of glass are arranged electrodes a1, b1, c1, d1, a2, . . . cyclically connected to four-phase buses A to D, a start electrode w connected to a bus W, keep-alive electrodes k1 and k2 connected to buses K1 and K2, and a dielectric layer 2 of a low-melting-point material is coated on the base plate 1 to cover the above-described electrodes. Further, electrodes y1 to y 4 are disposed on the other base plate 3, which is covered with a dielectric layer 4. These base plates 1 and 3 are disposed opposite to each other with a discharge space 5, in which space is sealed a discharge gas such as neon or the like. A discharge is always produced between the keep-alive electrodes k1 and k2 to provide a priming fire and, at the time of starting the shift of the priming fire, a voltage is impressed to the bus W to cause a discharge between the electrodes k2 and w. Thereafter, by sequential impression of a voltage to the buses A to D, the priming fire is sequentially shifted between the electrodes a1 and b1, between b 1 and c1, between c1 and d1, . . . due to the so-called primary current effect. Namely, the discharge is shifted in the form of a surface discharge. Upon application of a write signal voltage to the electrodes y1 to y 4 in accordance with the timing for shifting the fire priming discharge, a discharge is produced between the electrodes y1 to y4 and a1, b1, . . . and the written signal is stored in the form of a wall charge at the position corresponding to the priming fire. After completion of such writing to all the columns in accordance with shifting of the fire priming discharge, a sustain voltage is applied between all the electrodes, thereby to provide a display by discharges produced between the opposing electrodes in accordance with the written wall voltage pattern. Since the display is produced by the opposite electrode discharge, the side of the base plate 3 will hereinafter be referred to as a display layer and the side of the base plate 1 on which the fire priming discharge is shifted will hereinafter be referred to as a shift layer. With this type of driving method, it is sufficient to connect drivers to only the electrodes y1 to y4 for writing information, as will be seen from FIGS. 1 and 2.

However, such a gas discharge panel has the following defect. For example, where a priming fire is produced between the electrodes b2 and c2, a discharge is caused by written information between the opposing electrodes y1 and c1 and the priming fire is shifted between c2 and d2, there is the possibility that, under the influence of the wall charge resulting from the discharge produced between the opposing electrodes y1 and c1, a lateral discharge is also produced between the electrodes c1 and d1 where no fire priming discharge should be produced, since a voltage is being impressed between the electrodes c1 and d1 through the common buses, too.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a novel gas discharge panel which is free from the above described defect.

It is a further object of this invention to establish a large wall charge on the shift layer resulting from the surface discharge and a small wall charge resulting from the opposite electrode discharge, thereby to avoid unnecessary generation of a priming fire at the position of the opposite electrode discharge in accordance with written information.

The gas discharge panel of this invention comprises a first base plate, which has electrodes arranged thereon and covered with a dielectric layer and is energized to cause a surface discharge between adjacent ones of the electrodes, and a second base plate, which has electrodes arranged thereon and covered with a dielectric layer and is diposed opposite to the first base plate with a discharge gas space being defined therebetween. An ionizable gas is sealed in the discharge gas space. The gas discharge panel is characterized in that an equivalent electrostatic capacitance produced by the one dielectric layer is made larger than that by the other dielectric layer.

Other objects, features and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an electrode arrangement of a conventional gas discharge panel;

FIG. 2 is a cross-sectional view of the principal part of the panel of FIG. 1;

FIG. 3 is a diagram, for explaining the principles of this invention;

FIGS. 4A and 4B show equivalent circuits in the cases of an opposite electrode discharge and a surface discharge respectively;

FIGS. 5A to J show a series of impression voltage waveforms in the case of low-speed shifting of a priming fire; and

FIGS. 6A to H show a series of impression voltage waveforms in the case of high-speed shifting of the priming fire.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3 is a diagram for explaining the principles of this invention, in which the same reference numerals and characters as those in FIG. 2 indicate the same parts. In the present invention, an equivalent electrostatic capacitance on the side of a shift layer SL is made larger than that on the side of a display layer DL and this can be achieved by selecting the thicknesses and/or dielectric constants of the dielectric layers 2 and 4 different from each other. In FIG. 3, if the thickness of the dielectric layer 4 of the display layer DL, is taken as dg 1, if its dielectric constant is taken as .epsilon.1, if the thickness of the dielectric layer 2 of the shift layer SL, is taken as dg 2, if its dielectric constant is taken as .epsilon.2 and if the width of the discharge gas space 5 is taken as dc, an equivalent circuit in the case of an opposite electrode discharge becomes such as shown in FIG. 4A. Namely, reference characters C.sub.c, C.sub.g1 and C.sub.g2 indicate electrostatic capacitances between opposing electrodes and they correspond to the discharge gas space 5 and the dielectric layers 4 and 2, respectively. Reference character DC identifies a discharge and, at the time of discharging, the capacitance C.sub.c of the discharge space becomes shorted and wall charges +Q and -Q produced by the discharge are stored in the dielectric layers 2 and 4. Accordingly, if the overall effective area of the electrodes is taken as S, the electrostatic capacitances are as follows:

C.sub.c = .epsilon..sub.o S/dc , (1)

where .epsilon..sub.o is the dielectric constant of the gas within the discharge gas space 5.

C.sub.g1 = .epsilon..sub.o .epsilon..sub.1 S/d.sub.g1 (2) C.sub.g2 = .epsilon..sub .o .epsilon..sub .2 S/d.sub.g2 (3)

Since Q = Q1 + Q2, ##SPC1##

A voltage V.sub.w equals V.sub.w1 + V.sub.w2 and is given as follows: ##SPC2##

From the relationship that Q2 = C.sub.g1 .sup.. V.sub.w1 = C.sub.g2 .sup.. V.sub.w2, it follows that

V.sub.w2 /V.sub.w1 = C.sub.g2 /C.sub. g1 (7) V.sub.w1 = V.sub.w C.sub.g2 /C.sub.g1 + (8) ub.g2

V.sub.w2 = V.sub.w C.sub.g1 /C.sub.g1 + C.sub.g2

An equivalent circuit in the case of the surface discharge is such as depicted in FIG. 4B. In this case, the effective distance between adjacent ones of the electrodes on the shift layer SL is taken as dc'. The electrostatic capacitances are given by the following equations with primes corresponding to the foregoing equations.

C.sub.c ' = .epsilon.S'/odc' (10) C.sub.g2 ' = .epsilon..sub .o.sup.. .epsilon..sub. 2 S'/d.sub.g1 (11) ##SPC3##

V.sub.w2 ' = V.sub.w '/2 (13)

Accordingly, unnecessary fire priming discharge due to the opposite electrode discharge can be avoided by establishing the following condition:

V.sub.w2 << V.sub.w2 ' (14)

Substituting the terms of the equations (9) and (13) into the equation (14), it follows that

V.sub.w C.sub.g1 /C.sub.g1 + C.sub.g2 << V.sub.w '/2 (15)

The wall voltages V.sub.w and V.sub.w ' produced by the opposite electrode discharge and the surface discharge are dependent upon the kind of a discharge gas used, the coefficient of secondary emission of the dielectric layer, the construction of each discharge cell and so on. The wall voltages are difficult to express definitively, but if the distances between the electrodes in the cases of the opposite electrode discharge and the surface discharge are equal to each other, it may be considered that V.sub.w .congruent. V.sub.w '. Consequently, the equation (15) becomes as follows: ##SPC4##

and it follows that

C.sub.g2 /C.sub. g1 >> 1 (17)

Therefore,

C.sub.g2 >> C.sub.g1 (18)

thus obtaining the condition of this invention. Since the dielectric layers 2 and 4 are usually formed of the same material, thickness of the dielectric layers dg1 and dg2 are as follows:

d.sub.g2 << d.sub.g1 (19)

Namely, the purpose can be attained by selecting the thickness d.sub.g1 of the dielectric layer 4 of the display layer DL greater than that d.sub.g2 of the dielectric layer 2 of the shift layer SL. The difference between them is sufficient if d.sub.g2 .ltoreq. 0.2d.sub.g1. Of course, it is possible to form the dielectric layers of the same thickness and select their dielectric constants different from each other and it is also possible to satisfy the condition of the equation (18) by the combination of the relationships of the dielectric constants and thicknesses of the layers.

FIGS. 5A to J show a series of impression voltage waveforms in the case of low-speed shifting of the priming fire. This is the case of employing four-phase buses. Namely, in the case of the electrode arrangement of FIG. 1, a fire priming discharge is always produced between the keep-alive electrodes k1 and k2 by supplying the buses K1 and K2 with a voltage V1 shown in FIGS. 5A and B. A pulse V2 is impressed to the bus W only at the time of initiation of shifting the priming fire shown in FIG. 5C. A pulse train including pulses V2 and V4/2 are sequentially impressed to the buses A to D as shown in FIGS. 5D to G. Addressing may be achieved by a single pulse and a double pulse method. With the single pulse method, a voltage shown in FIG. 5H is selectively applied to the electrodes y1 to y 4. With the double pulse method, a voltage shown in FIG. 5H is selectively impressed to the electrodes y1 to y4. The voltages in the cases of the opposite electrode discharge and the surface discharge bear the following relationships, the voltages in the latter case being identified with primes. Namely, in FIG. 5, usual firing voltages V.sub.f and V.sub.f ', discharge voltages V.sub.f2 and V.sub.f2 ' lowered by the primary current effect of adjoining discharge spot, discharge voltages V.sub.f1 and V.sub.f1 ' lowered under the influences of the primary current effect and the wall voltage and minimum sustain voltages Vsm and Vsm' are selected as follows:

V1 > V.sub.f '

V1 + V2>V.sub.f '

V.sub.f2 '<V2 + V4/2 <V.sub.f '

Vsm'<V4<V.sub.f1 '

Vsm<V5<V.sub.f1

V5 + V6>V.sub.f1

V7 = V5 + V6

Those pulses in voltage pulse trains VYS and VYD in FIGS. 5I and J which are marked with small circles, that is, pulses V6 and V7, are impressed only at the time of writing. Reference characters a1, b1, . . . in the voltage VYS indicate the timing for writing to those positions corresponding to the electrodes a1, b1, . . . in FIG. 1. Positive and negative pulses marked with * in the voltage VYD may be omitted and when these pulses are not omitted, the brightness of a display is increased.

FIGS. 6A to H show a series of impression voltage waveforms in the case of high-speed shifting of the priming fire. This is the case of employing three-phase buses. In this case, the voltages are selected as follows:

V1<V.sub.f '

V2 + V3>V.sub.f '

V.sub.f2 '<V3<V.sub.f '

Vsm<V5<V.sub.f

V5 + V6>V.sub.f2

V7 = V5 + V6

Those pulses of the voltages VYS and VYD which are marked with small circles are impressed only at the time of writing as in the foregoing. The high-speed priming fire shift operation is different from the low-speed one in that the voltage impressed to the buses A to C is composed of a single pulse and the shift operation is carried out at every impression of the pulse.

As compared with the high-speed shift, the low-speed operation is slow in shifting the priming fire but has an advantage that the margin of the shift operation is large because the wall voltage can be utilized. Both shift operations have a large margin of the display operation by the opposite electrode discharge. Further, as compared with the single pulse method, the double pulse method has an advantage that since the polarity of a write pulse is the same as that of a preceding one, no discharge is produced again in a cell having once discharged to avoid abuse of the cells, but a write logic circuit is complicated in construction. As will be seen from FIGS. 5 and 6, the voltages impressed to the electrodes of the shift layer and the display layer are not at the same timing. These voltages may be impressed at the same timing but the impression of the voltages at the same timing has an advantage that no opposite electrode discharge is caused in the case of no write pulse being impressed.

With the present invention, the electrodes are covered with the dielectric layers, and hence are not directly exposed to discharge, and this allows ease in the selection of the electrode material. Since the dielectric layers are selected so that the wall voltage on the shift layer produced by the surface discharge may be high and that the wall voltage by the opposite electrode discharge for display may be low, there is no possibility of unnecessary generation of a priming fire that is, a surface discharge due to the opposite electrode discharge for display. Further, even if the wall voltage produced by the surface discharge is high, the wall voltage is neutralized during the shift operation and further neutralized by the opposite electrode discharge for display. This provides an advantage that an erasing pulse need not be inserted in the voltage for the shift.

It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concepts of this invention.

Claims

1. Display apparatus comprising:

a first base plate having a first set of electrodes disposed thereon and a first dielectric layer covering said first set of electrodes;

means coupled to said first set of electrodes for establishing a surface discharge between adjacent ones of said first set of electrodes; and

a second base plate having a second set of electrodes disposed thereon and a second dielectric layer covering said second set of electrodes, said second base plate disposed opposite said first base plate for defining a discharge region therebetween for receiving an ionizable gas;

said first dielectric layer having an equivalent electrostatic capacity

2. Display apparatus as claimed in claim 1, wherein said first dielectric

3. Display apparatus as claimed in claim 1, wherein said first dielectric layer has a first dielectric constant greater than that of said second

4. Display apparatus as claimed in claim 1, wherein said first dielectric layer has a dielectric constant and thickness selected with regard to the dielectric constant and thickness of said second dielectric layer, such that the electrostatic capacitance of said first dielectric layer is greater than that of said second dielectric layer.