BUBBLE DISPLAY AND MEMORY DEVICE

Abstract: A memory or display device which includes a shift register having a bubble generator (M1, M2), a bubble propagator (F, P), and a bubble annihilator (A). Front and back glass plates (10, 12) are provided with dielectric-covered, transparent electrodes (M1, M2) with the plates being positioned in spaced, parallel alignment. A suitable medium having a bilaterally symmetric V-J characteristic with a current controlled negative resistance region is provided between the plates and in contact with the dielectric covering the transparent electrodes. Bubbles are moved along an asymmetric track in the propagator by modulating voltage on two electrodes on opposing sides of the asymmetric track.

Description: BUBBLE DISPLAY AND MEMORY DEVICE The U, S. Gcverr-p-T-ent has rights in this invention pursuant to National Science Foundation Grant No. EDS-8014561. This invention relates generally to display and memory devices and more particularly the invention -relates to such devices which employ plasma bubbles. Plasma displays are known which utilize small area glow discharges in a matrix-addressed or shift-addressed structure. The present invention is directed to display and --memory structures which utilize plasma bubbles. The structures have dielectric covered electrodes with a media therebetween which exhibits a current-controlled negative resistance (CCNR) characteristic. A plasma domain is established by providing a peak current density J (averaged over the electrode area) J-r in the subnormal glow or negative resistance region of the media. The device behavior is similar to that of a magnetic bubble device. Changing the applied field changes the size and shape of the plasma domain. There is a range of applied fields over which a bubble domain exhibits a corresponding range of stable diameters., and the bubble dαriains are bi-stable. The fundamental building block of the plasma bubble display is a plasma bubble ' shift register composed of a bubble generator, -Z- a bubble propagator, and a bubble annihilator. In a preferred ernbcdiirent the design of the propagator element is based on an analog to the "angelfish" magnetic bubble propagation element. Periodic cdulation of the applied voltage produces periodic πcdulation of the bubble area to thereby move the bubble along an asyiπnetric guiding track. The bubble generator can be a nucleate-tyupe or a mitosis-type which produces a new bubble from a parent bubble. The anrd-hiiator comprises the last position of the shift register which is electrically isolated from the propagation section. A bubble is a-nrilhilated when the voltage on the annihilator electride drops below the ir------ru-n-um sustaining level (V, ) . Sπ-m Accordingly, an object of the invention is a display and memory structure which utilizes plaaπa bubbles. Another object of the invention is apparatus for producing current cont-rolled egative resistance domains for memory and display applications. A feature of the invention is a medium confined between dielectric covered electrode structures and having a bilaterally symmetric voltage-current density characteristic with a current controlled negative resistance region. Another feature of the invention is asymmetric means for guiding plasma bubbles. The invention and objects and features thereof will be more readily apparent and fully understood from the following description and appended claims when taken with the drawings, in which: OMPI ^2 ~m m IPO l Figure la and Figure lb are a top view and section view, respectively, of a shift-addressed ac plasma display panel. Figures 2a-2e illustrate plasma domains, and Figure 2f is a scale therefor. Figures 3a-3c illustrate the plasma bubble mitosis process. Figure 4 is a plot of plasma sustaining voltage versus gap length for an atmospheric pressure C-discharge formed in helium based gas. Figure 5a and Figure 5b are a top view and a section view respectively of a three shift register device in accordance with the invention. Figures 6a-6c illustrate a plasma bubble propagator in accordance with the invention. Figure 7 is a top view of an alternative conductor etch pattern in a plasma bubble propagator. Figures 8a-8d illustrate a mitosis-type plasma bubble generator in accordance with the invention. Figures 9a and 9b illustrate a plasma bubble annihilator in accordance with the invention. Figures lOa-lOf illustrate operation of a device in accor¬ dance with the invention having a mitosis-type plasma bubble generator and shift register. Figure 11 is a plan view illustrating a multiple plasma shift register in accordance with the invention. OMPI Figure 12 is a plan view illustrating a one-hundred-eighty degree bubble propagator section layout in accordance with an embodiment of the invention. Conventional AC Plasma Display Technology The conventional ac plasma display panel (ACPOP) produces an image from a planar array of small area glow discharges formed in the volumes defined by the intersections of two orthogonal sets of dielectric-covered l ine electrodes. - The bistabil ity of "C-di scharges * formed between dielectric- covered electrodes gives the ac plasma display its important property of inherent memory. Currently, ACPOP 's are of two types: (1) the matrix- addressed graphics /alphanumeric display, and (2) the shift-addressed alphanumeric display. The matrix addressed display, invented at the University of Ill inois in 1964, has a number of attractive features which have made it the principal competitor to the CRT for large area graphics and alphanumeric display appl ications. However, the high cost of the drive electronics makes the matrix display expensive. Efforts are being made to reduce this cost through the use of integrated drive electronics and improved panel design. The shift-addressed alphanumeric display was developed as an alternative to the matrix-addressed display to further reduce the drive electronics cost. This design employs a gas/cathode composition , gas pressure, gap length, and sustain frequency similar to that of the matrix-addressed display. The principal difference Hes in the method of addressing the picture elements. In this design, each horizontal display l ine is a shift register composed of three elements : a write electrode, a three or four phase shift electrode structure, and an erase electrode . Figure ΪA. and Fiαure 13 are a top view and a section view, respectively, of a shift-addressed . ac plasma display panel . OMPI ---.i - , _.*_* , . j , _, ■ _„ .___, i Plas a 3ubble Properties Copendiπg application, serial number 390, 689, supra, presents results . on the discovery of plasma bubble domains (PBD's). These domains occur as regular patterns of small area glow discharges formed under ac excitation in an inert gas based, atmospheric pressure gas mixture confined between large area, closely spaced, plane parallel, dielectric covered electrodes. Plasma bubble domains have properties which are analogous to those of magnetic bubble domains (M O's). The plasma domain structure is composed of "glowing" and "non-gl wing 14 regions, while the magnetic domain structure is composed of magnetization "up" and magnetization "down" regions. Plasma domains exhibit the forowing properties: (1) Changing the applied sustain voltage V s changes the size and shape of the domain that forms (bubble, stripe, etc). (2) There is a range of applied sustain voltages V . < V < V . over which a bubble domain sbπ s sbx exhibits a corresponding range of stable diameters 0(V sbn ) *> 0 < 0 ( v S £, χ ) • (3) If V s is increased, then a bubble first grows in diameter, then is elliptically distorts, then runs out Into a stripe; if V s deceased, then a stripe domain breaks up into a series of bubble domains. (4) Domains are bistable over a range of sustain voltages V < V < V . (5) Domains smn s smx will move laterally to a position which maximizes V s - Y smn . The first and second properties, concerning the influence of pplied voltage on domain size and shape are illustrated by the results shown in Fig. 2(a)-(e). There is a range of stable bubble diameters as the applied voltage is increased /0 . m - 1.4, ~ . Λ - 175 μm) (Fig. 2(a) and Fig. 2(b)). There max mm mm 1s a transition from large bubble domains to stripe domains, as the voltage is increased further (F1g. 2(c)). There 1s a transition from stripes to hexagonally woven stripes (HWS), to a uniform glow, which occurs at even higher applied voltages (Fig. 2(d) and Fig. 2(e)). The stripe domains have a range of stable widths before they make the transition to the HWS domain pattern. The non-jlowing regions of the H S domain pattern form a hexagonal array of non-glowing bubbles which have a range of stable diameters prior to their collapse to a bright uniform glow. Figure 5(f) shows a scale photographed under the same magnification. The smallest division is 100 μa . These domains were formed using variable amplitude, 40 kHz, 0.4 usec rise time, square wave excitation. A gas discharge was formed in a 50-60 urn gap between dielectric (Corning 0211 microsheet) covered electrodes enclosed in a flow purged gas cell with electrode diameter 0 β » 1.1 cm, dielectric thickness t *. i * 76 μm, and ε - ε. * 6.4 . The gap was flow purged with helium a b a o gas at 1 atα. (Similar results were obtained with a neon purge gas.) The inert gas formed a Penning mixture with a small percentage of ambient air which was inevitably present. Domains will not form in a pure inert gas since bistability is a requirement for domain existence. The third property, concerning the bubble ♦ stripe and stripe * bubble transitions, 1s illustrated by the results shown in F1g.3A-3C. Figure 3(a) shows βπipt1cally distorted bubbles. Figure 3(b) shows short stripe domains approximately two bubble diameters long. Figure 3(c) shows two bubble domains formed from the breakup (mitosis) of a short stripe domain. The fourth property, concerning domain bistability, is illustrated by the following observations: (1) When conditions are unfavorable to domain formation, as in the case of pure neon gas or slow rising ac excitation, then only a dim uniform townsend discharge exhibiting no bistability forms. (2) When conditions are favorable for domain formation, then there is a range of applied sustain voltages over which the domains (bubble, stripe, etc.) can be sustained. , The fifth property, concerning lateral motion of domains, 1s Illustrated by the following observations: (1) the increased applied sustain voltage V. suzz- . ■ _ . - . causes an increased domain area ; a domain residing 1π an appl ied fiel d with a lateral gradient will expand its bjundary most where V s 1s largest; accordingly, a domain wi l l move laterally 1n the di rection of largest V s . (2) A domain will contract its boundary to achieve an optlmue current density and lower maintaining voltage V m and a corresponding lower V san ; accordingly, a domain will move laterally in the direction of smal lest V SJnn . (3) Domains are formed between plane electrodes separated by a nominal gap length x ^ 50 u and covered by dielectric layers with a total air equ-valeπt 9 dielectric thickness of x fc ■ 24 u . When the electrodes are adjusted to produce a lateral gradient in gap length 50 urn < x < 60 urn , the domains move in the di rection of largest gap length corresponding to smal l est V sιan (Fig. 4) . When the gap length gradient 1s increased, the speed of domain movement Increases. In Figure 4, V s , V sπm ■ f(x ) for an atmospheric pressure C-discharge formed in a hel ium based gas mixture with 40 kHz, 0.4 μsec rise time, square wave excitation (D e * 1 .11 cm, t « 24 μm) . Plasma Bubble Display Design In accordance with the present invention, plasma bubble domains form the picture elements of a plasma bubble display. Plasma bubble domains as picture elements are distinguished from conventional ac plasma di splay picture el ements . In conventional displays, the size and shape of the snail area gas discharges i s defined by the orthogonal narrow-l ine electrode structure which produces local ized regions of high field to initiate and sustain the discharge. In the proposed plasma bubble display, the size and shape of the domains formed between large area, featureless, plane parallel , diel ectric-covered electrodes, 1s determined by basic physical phenome la and not by the electrode structure. • The picture elements of the two displays are simi lar in that they both exhi bit the property of bi stabi l ity. SUBSTITUTE SHEET If plasma bubble domains are to form the picture elements of a display, then there must be a method of addressing them. An approach is sugt-asted by the fact that plasma domains and magnetic domains exhibit a number of analogous properties. One promising plasma bubble display design employs a shift- • addressing technique, exploiting this similarity, which 1s based on an analog to an early magnetic bubble field-access addressing scheme. Shift Register Elements: Design and Operation The fundamental building block of the plasma bubble display, In accordance with the invention, is a plasma bubble shift register composed of three elements: (1) a bubble generator, (2) a bubble propagator, and (3) a bubble annihilator. First discussed is the design operation of the bubble prooagator. The bubble generator and bubble annihilator designs are based on the propagator design. Figure 5a and Figure 5b are a top view and a section view, respectively, of three-shift registers. The device includes a glass face plate 10 and a glass back plate 12 in spaced parallel alignment. Transparent electrode struc¬ tures such as tin oxide are formed on adjacent surfaces of the plates 10, 12 and the electrodes are covered by a dielectric material. The generators in¬ clude a comπon electrode HI and an individual electrode H2. The propagator includes a back plate electrode, P, and the annihilator includes an electrode, A, en the back plate. The face plate electrode, F, is common to all three elements. 1. Bubble Propagator The design of the bubble propagator element is based on an analog * α the "angelfish" magnetic bubble propagation element. Periodic modulation of the sustain voltage produces periodic modulation of the bubble area to move the bubble along an asymmetric guiding track comprising two parallel confinement rails Inscribed with a sequence of isosoceles triangles ("angel ish") .Fig. 6(a)). The confinement rails restrict increases in bubble ΛΓ~Λ to increases in length along the direction of propagation; the inscribed isosceles trlangles produce a left-right asymmetry in the bubble expansion and contrac¬ tion. The angelfish-type plasma bubble propagator element is illustrated in Figures δa-6c as follows: (a) A bubble domain sustained at position n; regions A,B. and C are identified; (b) A bubble domain sustained at posl- tions n -* • n + 1; (c) A bubble domain sustained at position n + 1. The sustain voltage is modulated over a range sfan < V s < V sbχ corresponding to a range of stable diameters 0(V sbn ) < 0 < 0(V sbχ ) with V < V -. y < ϊ t U smn sbπ s sbx smx (1) where V smn and V smχ deflw the bistable operating margin. The confinement rails are separated by a distance Y c slightly less than or equal to the minimum bubble diameter 0( v S b n )» Increasing V s to V SQX causes the bubble to increase its area, not through an increase in diameter as in the case of the free unconfiπed bubbles, but through an increase in length along the direction of propagation. The bubbles are confined to region B between the rails and prevented from expanding into region C (Fig.5(a)) by insuring that v s (c) V (C) < 0 < V (B) V (B) smn smn (2) This patterned variation of V s - V smn insures that domai ns can be sustai ned in region B but cannot be sustained in region C. The isosceles traiπgle height h » Y ς ; the isoceles triangle base b 1s sl ightly less than or equal to Y c . The isoceles triangle center-to-csπter separation 1s equal to h; the bubble pitch is 3h ^ 3Y - 3D (V u > . The c sbn' inscribed isosceles triangle structure takes the form of a patterned variation of V s - v sw1 such that SUΞST27 T2 Cl- T " V (A) - V V s (B) s ' smn (A) > smn (3) According to the third 'property, domains will seek regions- with characteristics of A in preference to those with the characteristics of B. If we combine Eq. (2) and Eq. (3), then we can write a general relationship for the three regions. V S (A) V (A) > V S (B) Ϋ smn< B > > ° > C > ■ C > (4) There are four alternative embodiments of the confinement rail structure defined by Eq. (2) and four similar embodiments of the inscribed isosceles triangle structure defined by Eq. (3). In both structures, the first three alternative embodiments use no electrode patterning; accordingly, V S (A) » Y s (B) - V s (C) » V s (5) Combining Eq. (4) and Eq. (5) yields A > B > < V s < V smn( C > > * ■ The three alternative embodiments of Eq. (6) adjust the relative values of the secondary electron emission coefficient γ , the total air equivalent dielectric thickness x * » ij. , or the gap length x„ as follows: (i) T Variation: set τ(A) > γ(B) > τ(C) where V ■ f(γ) smn v OMPI „,_,--., ,.-—. < .- r WΛ, WIPO -twi— 'I.I .--I < 4.— — * ■ v rp rι - . ,.m r -. (11) Variation: set x t (A) < x t (B) < x t (C) . This embodiment is practical only if ^ - x g . If * t - * g . the changing x t produces an appreciable change in V snf ,. If t « x g , then changing x t produces a minimal change in V smn .^ 1 ' (iii) x_ Variation; set either or x g (A) < x g (B) < x g (C) when — ≡ > 0 The fourth alternative embodiment .of Eq. (δ) uses electrode patterning and no variation of T , x k , or x so that t g V (A) - V (B) » V (C) » V (7) smn ' smπ ' sπtr ' smn Combining Eq. (4) and Eq. (7) yields V S (A) > V s (B) > V smn > V s (C) (8) The embodiment of Eq. (8) uses electrode patterning (V $ variation). We will describe the embodiment of the confinement rail structure and the- embodiment of the inscribed isoceles triangle structure, separately. OMPI su B i m e SHEET ^ \ (iv) V e Variation: Confinement rail structure: The voltaqe V S (C) is reduced in region C by eliminating the faceplate (or backplate) electrode in that region. Inscribed isosceles traingle structure: If the characteristics of regions A and B are related as described by Eq. (8), then the shift direction is from base to vertex. (This will be further explained in the next stction.) If the characteristics of the two regions are reversed such that then the shift direction will be from vertex to base. We can consider an em- bodiment of Eq. (9) in which the backplate electrode is etched to remove a portion of the conductor inside region A. This will reduce V (A) relative to V S (B). The fringe field from the surrounding conductor in region B and the web conductor in region A prevents V S (A) from falling below V smn (Fig. 7). Figure δ illustrates a conductor etch pattern for the V s variation embodiment of the inscribed isosceles triange structure. There has been descibed four different embodiments for the guide rail structure and four different embodiments for the inscribed isosceles triangle structure. The two structures need not be implemented using the same variation; it will often be preferable to implement each with a different variation, e.g., the guide rail structure can be implemented with electrode patterning (V s variation) and the inscribed isoceles triangle structure can be implemented with x g variation. Shift operation is described by considering a bubble at its minimum area corresponding to V s - Y sbn (Fig. 6(a)). If V s « Y sbχ , thri the bubble will increase its area by increasing 1n length (Fig 6(b)). The bubble area 1s shown to be increased by approximately a factorof two which is equivalent to a fre-s domain diameter increase by a factor of 1.414. When V s 1s reduced to V bn , the domain returns to Its original area. ithout the Inscribed isosceles triangle variation in structural characteristics, the bubble returns to Its original position; with the Inscribed Isosceles triangle variation in structural characteristics, the bubble moves to the right. When the end boundary of a bubble domain moves to the right, off the vertex of one isosceles triangle onto the base of the next isosceles fiangle, there is an abrupt increase 1n the area of the inscribed isosceles triangle covered by the domain. If the end boundary of a bubble domain were to move to the left, off the base of one isosceles triangle onto the vertex of the previous, there would be an abrupt decrease in the area of the isosceles triangle which is covered by the domain. Domains move to a position which maximizes the area inside the isosceles triangles ' and hence maximizes the area-averaged value of V s - V sn ιn * Accordingly, the domain will increase its area by moving its right boundary to the right while holding its left boundary essentially fixed and will decrease its area by moving Its left boundary to the right while holding the right boundary essentially fixed (Fig. 6(b) and Fig. 6(c)). Periodic modulation of the sustain voltage produces an "inch-worm-like" shift motion of the domain along the asymmetric guiding track. The inscribed isosceles triangle structure produces a sawtooth variation in the area- averaged value of V s - Vstm.' Domains move easily up the Inclined side of a sawtooth (move easily from vertex to base) and do not move in the opposite direction against the vertical side of a sawtooth (don't move from base to vertex). The sawtooth variation produces a "ratchet" effect. There 1s an alternative embodiment of an asymmetric keeper structure which 1s equivalent to the angelfish structure. This structure uses the same confinement rail structure and an inscribed sawtooth variation in V s - V smn (embodied 1n a sawtooth variation in Ύ, x_, or x^). Although this structure is equivalent 1n function, 1t 1s usually much more difficult to implement in practicβ. It requi res a sawtooth shaped variation 1n the value of the particular parameter compared to just two values required for the angel fish scheme. 2. Bubble Generator The function of the plasma bubble generator 1s the same as the function of the write electrode pair of the conventional shi ft-addressed ACPOP. We propose two schemes for desi gning a plasma bubble generator: (1) the bubble mitosis scheme and (2) the bubble nucleation scheme. The bubble mitosis scheme is based on an analog to the bubble generation scheme used in magnetic bubble memory devices. Here, a new bubble is generated by "tear1ng-off" a portion of a continuously maintained "parent" bubble. In the case of the plasma bubble display, we propose to util ize the third plasma domain property. A bubble generator based on this phenomenon consists of a parent plasma bubble sustained at the mid-sustain voltage V im between two confining rai ls (which can be closed at the left end) inscribed with a sequence of isosceles triangles as shown in Fig. 8(a) . The operating voltages are appl ied between the uniform faceplate electrode and the backplate electrode. The back plate is partitioned into three electrodes: generator electrodes M^, and 2 and an adjoining propagator electrode P. The voltage on and M electrodes, spanning the first three bubble positions, is increased to the voltage for the bubble-to-stripe transition, Ϋ s b s* Tnβ o" 001 * increases 1n length, covering the three isosceles triangl es at positions one through three (Fig. 8(b) ). When the voltage on M } and f * s returned to V sb , the stripe undergoes a mitosis Into two bubble domains at positions one and three (Fig. 8(c) ) . The mitosis process begins with a local ized reduction 1n the width of the domain as shown by the dotted line in Fig. 8(b). The driving force for the mitosis Is the reduction of surface SUBSTITUTE SHE l ss. ' The newly generated bubble at position three. is then shifted into the adjoining propagation section by modulating the voltage, V s , on the M and P electrodes 1n the range Y st , n to V sl)χ . The parent domain remains at position one for the next bubble generation. The bubble nucleation scheme 1s a direct analog to the write scheme of the conventional ACPOP. A new discharge (bubble) 1s Initiated (nucleated) at the write electrode (nucleate electrode) with initial current I Q provided by an adjacent "keep-alive" electrode. 3. Bubble Annihilator The function of the plasma bubble annihilator is directly analogous to the function of the erase electrode of the conventional shift addressed display. The last position of the shift register Is isolated electrically from the adjacent propagation section (Fig.9a-9b). Once the bubble reaches positiqπ n, it is annihilated when the voltage on A falls to V sbβ < ^,. B. Shift Register: Design and Operation The nritos1s-type-generator based shift register is shown schematically „ lOa-lOf in Fig. / .The bubble generator, bubble propagator, and bubble annihilator structures and electrode boundaries are shown 1n top view. The basic panel structure has a clear uniform faceplate electrode F, and a clear backplate partitioned into several electrodes. The generator, propagate, and annihilator structures are typically fabricated on the backplate. A single mitosis-type register has an M j , Mg, P, A, and faceplate electrode. A single nucleate-type register has a K, N, P, A, and faceplate electrode. The separations between the M j , M j , P, and A electrodes are made as .-small as possible to minimize the break 1n field uniformity; the boundaries between these electrodes are located between bubbles for V « V t . The nominal s sbn SU33TJT ' . ^ ε: : . - „ Q O^MPI ... gap length x g , air equivalent dielectric thickness » as pressure p, gas/cathode composition and excitation conditions are chosen appropriate for domain existence. - One representative set 1s as follows: x * 50 um, 9 x t - 24 um, e « 6.4, p - 600 torr, Ne + ifr 5^, f - 25 * 150 kHz, 0.4 rise time, square wave excitation. The coordinated operation of the shift register is best explained In a step by step manner. The positions of the bubbles and the voltages appl ied between the backplate electrodes H^, M 2 , P, A and the faceplate electrode for each step of shift operation are summarized in Table 1. The positi ons of the bubbles at selected steps are shown in Fig. 0. The voltages for loading and "one" or "zero" are indicated 1n the table. The voltages, desi gnated by the value of i for V sb<j , are defined at the bottom of the table. The voltages are modulated after each full cycle. TxaiE l L nd sequence for -i ei tosis-type plase* buttle shift re s er: electrode voltages and buttle positions ■ v4] uβ f ar b uttle posi t ions elec t ro d e vol t age ^ bi parent newly generated previously Operation Step Fig. »« buttle buttle loaded bubble "l "> p y I a 6 ■ ■ ■ t I! 1 1/ 0 b 1 - 3/1 5 i/Λ- ./■ ■ I ll c 3 6 m ■ ■ IVa d 3 - 4 6- 7 m snt t [Vb e 4 7 a n n ι va 4- 5 7 - β m X I sftift Vb S a a n n i shift ' via S - « 8 - 9 a x - - annihi late VIb f S a n n i Legend: son ma -um operating voltage *. * -id operating voltage ~ (V^ * V s6fi }/2 'sbx NiiM-i operating voltage * s6β * erase voltage < M *jm SOS buttle - stripe vol tage > V OMPI fil :75s3 τm . Step 1 begins with the parent bubble at position one and a previously loaded bubble at position six. Once the bubble reaches the last position of the register, at Step Ylb, (position nine) it is annihilated and hence is shown with broken lines on F1g. 10(f). The nucleate- type-generator-based bubble shift register operation 1s similar and described 1n co-pending application, serial number 390,689, supra. - ' Bubble Oisplay: Design and Operation The pl asma bubble shift register is the basic bui lding block of single line and multiple Hne alphanumeric displays. A single Hne of (7 x 9) format characters with 3 dβcenders and a cursor Hne requires an (8 x 12) f*e1d and 13 parallel shift registers. If 0( s&n ) - Y c - ■ 175 um, then the horizontal bubble pitch 3Y C will be 425 ua (equivalent to - 60 pel s/in) . The rail width Y w may occupy half the distance Y p between paral lel regi sters (Y w « Y r /2) the ceπter-to-centβr separation between paral lel registers is 3Y C and the rail-to-rai separation Y r ■ 2 Y ς (see F1g. 11 ) . Accordingly, the vertical and horizontal pitch are equal . During shift operation the sustain voltage 1s modulated every cycle; each shift in position requires two sustain cycles of period T and each pel shift requires three position shifts. Accordingly , the shi ft time 1s 6T and the shift speed is 1/6T pels/sec. If f ■ 50 kHz, then T ■ 20 usec . and the shift speed is 8333 pels/se . This ts equivalent to 5 x 7 an 7 x 9 cnaractβr shift speed of 1388 and 1041 chars. /sec, respectively. (The character field widths are six and eight, respectively.) One of the principle advantages of al l shi ft-addressing schemes 1s the reduction 1n the number of external connections to the panel and the corresponding reduction 1n the number of drivers. (This 1s balanced agai nst an Increased addressing time.) The number of external el ctrode connections to single and multiple Hne alphanumeric plasma bubble displays wi l l fol low these rules: SU BSTITUTE SHE ET 1. the faceplate electrode F is common to al l regi sters, 2. all P electrodes can be tied in common for all registers, 3. all K or ^ electrodes can be t ed 1n common for all registers, 4. all A electrodes can be tied in common for all registers, and 5. the N or Mj electrodes are separate to each individual ly addressable register. The plasma bubble display can be organized in several di fferent ways. Let us consider two of the most interesting configurations. In eacn case we wil l calculate the number of external connections and the panel load time for one or more l ines of 80 7 x 9 characters with an 8 x 12 character field and a single cursor line. A panel of n individual ly addressable registers requi -es n + 4 connections; a single picture element shift requires δ/f sees where f is the sustain frequency. Accordingly, a single line of characters with cursors requires 17 connections and 76.8 msec to load at 50 kHz. Eight l ines of characters (640 chars.} with cursors requi res 108 connections and 76.8 msec to load at 50 kHz. These results are summarized in Table 2 where we' ve also considered the case of 32 lines of characters (2560 chars.) and compared the results to the matrix addressed panel with a (8 x 14) character field. It is well known that the relative reduction in the number of external connections for a shift addressed display is greatest for panels with a high aspect ratio (compare the number of connections for the bubble shift panel and the matrix panel for eight Hπes of characters to that for thr1ty-two lines of characters). This brings us to the second of the two display configurations. Here, the equivalent panel aspect ratio can be increased by addressing a Hne of characters with a single bubble generator at the input of the first register and a single bubble annihilator at the output of the twelfth register. (The cursor Hne is addressed separately.) The twel ve OMPI SUgSTITUTE SHEET Si registers are linked with 180 degree end connections (F1g.1Z); the angelflsh pattern 1s oriented for the odd numbered registers to shift right and for the even numbered to shift left. Accordingly, a Hne of characters is loaded as one long shift register. Here, 8 lines of characters (640 chars.) require 20 connections and .924 sees and .308 sees to load at 50 kHz and 150 kHz, respectively. These results, together with the results for 32 Hnes of characters are summarized in Table 2. External Connection .net Load Tim equlreaent-S for *ι. t.1 .»• Olsplars βf 30 (7 x 9) Characters n.tii ι 9 ι U Character field and Single Cursor Line Externa l Connections Addressing 3 L ne Displ y 32 L ne 01 so lay Load T .e» Configuration (640 Chars. ) (Z Chars.) SO kHz ISO -nz H-nrfx 752 loss 80 uS -S.7 u5 (3 x 14 field Including cursor) (112 x 640) (448 x 640) Bubo!* shift (Addressable registers) ιαβ 420 7S.3 «S 25.6 S 8ubb!e shift 20 68 0.924 S 0.3OS S (addressable character Hnes • 12 l inked registers ) Bubble shift 12 36 0.924 S 0.30B S (addressable character Hnes • 12 l inked registers - no cursor) SUBSTITUTE SHEET SU MARY There has been described a novel current-controlled nega¬ tive resistance (CCNR) medium bubble device such as a shift register memory or a display employing plasma bubbles. The display is similar in operation to a mag¬ netic bubble device. Front and back glass plates are provided with dielectric-covered, transparent electrodes with the plates being positioned in spaced, parallel alignment. A suitable medium having a bilaterally sym- metric V-J characteristic with a current-controlled negative resistance region is provided between the plates and in contact with the dielectric covering the trans¬ parent electrodes. The display device includes a plasma bubble generator (either mitosis-type or nucleate type) , a plasma bubble propagator, and a plasma bubble annihilator. The memory device is a closed loop shift register with a bubble detector. The propagator may comprise an asymmetric keeper structure such as an "angelfish" pattern or sequence of isosceles triangles between bubble-confining rails to propagate the bubbles in response to modulation of the plasma sustaining voltages across the front and back plate electrodes. Definition of the rails and sequence of tri¬ angles can be accomplished by variation in the dielectric material, spacing between plates, etching the electrodes for the required pattern, or dielectric thickness. Opera¬ tion of a multiple plasma shift register display is given. While the invention has been described with reference to specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention, as defined by the appended claims. OMPI sussτ J X£ i -n--^ ^*

Claims: WHAT IS CLAIMED IS: 1. A cu---r._ent-controlled negative resistance (CCNR) -medium bubble device comprising: a planar faceplate, a planar backplate, said plates being supported in parallel spaced alignment, can electrode structure on a surface of said faceplate and an electrode structure on a surface of said backplate, said surfaces being adjacent, dielectric material covering said electrode structures, a CCNR medium between said plates and in contact with said dielectric material, said edium having a bilaterally syπroetric voltage-current density characteristic with a current-controlled negative resistance region, said dielectric and medium exhibiting bistability, at least one asymtretric guide track for bubbles provided between said plates, said electrode structures including a cαπmon electrode on a face of one plate and a plurality of electrodes on a face of said other plate, said electrodes defining a bubble generator, one of said plurality of electrodes and said common electrode being cooperatively arranged with said asymmetric guide track for propagating bubbles from said bubble generator. 2. The bubble device as defined by Claim 1 wherein said bubble generator comprises said comrnon electrode on said one plate and first and second generator electrodes on said other plate. 3. The bubble device as defined by Claim 1 wherein said bubble a-nnihilator comprises said cc-mron electrode on said one plate and a first anrάhilator electrode on said other plate. OMPI 4. The bubble device as defined by Claim 1 wherein said asymmetric guide track comprises two bubble-confining rails and a sequence of asyππ-stric patterns between said two rails whereby modulation of a sustaining voltage between said elec- trodes cooperatively arranged with said track propagates bubbles along said sequence of,asymmetric patterns. 5." The bubble device as defined by Claim 4 wherein said asymmetric patterns comprise triangles. 6. The bubble device as defined by Claim 4 wherein said asymmetric pattern and is defined by thickness of said CCNR medium. 7. The bubble device as defined by Claim 1 and further including a plurality of bubble generators, bubble anni- hilators and asymmetric guide tracks therebetween. 8. The bubble device as defined by Claim 7 wherein said bubble generators have a c3mDn generator electrode on said other plate for maintaining bubbles and each generator has an individual electrode on said other plate for selective mitosis generation of a bubble for introduction to an associated asymmetric guide track. 9. The bubble device as defined by Claim 7 wherein said plurality of asymπetric guide tracks have a c rtnon propagatorelectrode on said other plate. 10. The bubble device as defined by Claim 7 wherein said plurality of bubble a ni-hilators have a common annihilatoi electrode on said other plate. -- tEA OMPI Abstract of the Disclosure Disclosed is a memory or display device (Figures 5A, 5B) which includes a shift register having a bubble generator (Ml, M2) , a bubble propagator (F,P) , and a bubble a-nnihilator (A) . ront and back glass plates (10, 12) are provided with dielectric-covered, transparent electrodes (Ml, M2) with the plates being positioned in spaced, parallel alignment. A suitable medium having a bilaterally symmetric V-J character¬ istic with a current controlled negative resistance region is provided between the plates and in contact with the dielectric covering the transparent electrodes. Bubbles are moved along an asyim-ietric track in the propagator by πo ulating voltage on two electrodes on opposing sides of the asymmetric track.

Inventors: BOYERS DAVID G, BOYERS, DAVID, G.
Applicants: UNIV LELAND STANFORD JUNIOR, THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIO
Application year: 1983
Main classification: G11C13
IPC codes: G09G3, G11C19