CA1261911A - Display unit by cathodoluminescence excited by field emission - Google Patents
Display unit by cathodoluminescence excited by field emissionInfo
- Publication number
- CA1261911A CA1261911A CA000487389A CA487389A CA1261911A CA 1261911 A CA1261911 A CA 1261911A CA 000487389 A CA000487389 A CA 000487389A CA 487389 A CA487389 A CA 487389A CA 1261911 A CA1261911 A CA 1261911A
- Authority
- CA
- Canada
- Prior art keywords
- anode
- unit according
- cathode
- grid
- rows
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J31/00—Cathode ray tubes; Electron beam tubes
- H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
- H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
- H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
- H01J31/15—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen with ray or beam selectively directed to luminescent anode segments
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J31/00—Cathode ray tubes; Electron beam tubes
- H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
- H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
- H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
- H01J31/123—Flat display tubes
- H01J31/125—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection
- H01J31/127—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection using large area or array sources, i.e. essentially a source for each pixel group
Abstract
ABSTRACT OF THE DISCLOSURE
Display unit by cathodoluminescence excited by field emission.
It comprises a plurality of elimentary patterns, each having a cathodoluminescent anode and a cathode able to emit electrons.
Each cathode comprises a plurality of electrically interconnected micropoints subject to electron emission by field effect when the cathode is negatively polarized compared with the corresponding anode, the electrons striking the latter, which is then subject to a light emission. Each anode is integrated to the corresponding cathode.
Application to the display of stationary or moving pictures.
Display unit by cathodoluminescence excited by field emission.
It comprises a plurality of elimentary patterns, each having a cathodoluminescent anode and a cathode able to emit electrons.
Each cathode comprises a plurality of electrically interconnected micropoints subject to electron emission by field effect when the cathode is negatively polarized compared with the corresponding anode, the electrons striking the latter, which is then subject to a light emission. Each anode is integrated to the corresponding cathode.
Application to the display of stationary or moving pictures.
Description
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BACKGRO~ND OF THE INVENTION
The present invention relates to a display unit by cathodoluminescence excited by field emission.
It more particularly applies to the production of simple displays, permitting the display of fixed images or pictures, and to the production of complex multiplexed screens, making it possible to display moving pictures, such as television pictures.
Cathodoluminescence display units are already known, which use a thermoelectronic emission. Such display units suffer from the disadvantages of the definition of the images which they make it possible to obtain not being of a high quality, devices or units are complicated to produce and they have a high electric power consumption, in view of the fact that the filaments have to be heated.
The principle of electronic emission-by field effect is also known, which is also called "field emission" or "cold emission". This principle has already been used for applications unlinked with visual display.
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SUMMARY OF THE INVENTION
_ ~ he ob3ect of the present invention $8 to obvl~te th~ ~forementl~ned dlsadvantagas by propo~lng a display unit utlll~ing field eml~sion, whose p~lnciple has been gl~en herelnbefore.
Specific~lly, the pre~ent lnvention relates to a di2pln~ unlt co~prising a plur~lity of element~y p~teern~, e~ch h~vlng ~ c~thodo-lu~inescent node ~nd n cethode able to ~it electron~, ~bereln each c~thode comp~lses a plur~lity of electric~lly lnterconne~ted ~loropolnts ~nd ~ub~ect to ~n electron emla~on by fleld effect wh~n the t~thode i8 negn~lvely pol~rlzed rel~tlve to ebe cor~esponding ~node, ~aid electrDn~
~triking the latter1 which i~ then subje~t t~ ghe emls~ion. ~sch ~node tan be lntegrated to the corresponding cathode And electrle~lly lnsul~ted therefro~. ~
~ In fact~ ~leot~on em~0~ion i~ onl~ high ~boYe a certaln pDlsrlz-tlon thre~hold ~nd belo~ it~e~ on 1~ lo~ ~nd then onl~ le~d~ to ~ small amount o~ llght bein8 produced.
In tbis ~ay lt is pos~4ble to obt~in ~n over~ll ll~ht l~age by pprGpri~tely polAri~lng the olement~ry pattern~. ~he~ tbe different - .~;"
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pol~rlzation~ ~re maintained const~t over A period of time, the lmage obtalned i8 flxed, but it is al~o pos~ible to obtain moving lm~gea or pictures, by varying in an appropri~te msnner the polarlzationR during period of time.
The pre~nt invention makes it po~sible to obt~in flat acreens operating under a low voltage, ln the same way aa the known units referred to hereinbefore. However, the plctures obtalned by means of the unlt accordlng to the invention have a much better deflnition.
Thus, it i9 possible to produce very 6mall micropolnt0, ~t a rate of ~ few tens of thousands of micropoints per ~quare millimet~e, which makes it pos~ible to produce element~ry cathode~ h~ving a very small surface and consequently it is po3Rible to excite very ~m~ll c~thodo-luminescent ~nodes.
In addition, the unit sccording to the invention h~6 8 much lower electris power cons~mption than the ~forementloned Prlor Art unlts, in view of the fcct that it u~e~ cold cathodes.
The ~urf~ce of the cathode corresponding to an elementary p~ttern can elther be ~quRl to or le~s than the ~urfece of the anode of ~ald pattern. As it i8 possible to produce ~ l~rge number of micropoints per ~qu~re ~illimetre, lt is pos~ible to excite each anode by 3 very l~rge nu~ber of micropoint~. The light emisslsn of an elemen~ry pattern corresponds to the me n e~lssion characteri~tic of all the correaponding mlcropoint~. If a small nu~ber of micropoints do not f~nction, this mean char~cteristic re~ains 0ub~tantially unchanged, ~hlch con~titute~
~n important adv~ntage of the inventlon.
Accordlng to ~ special embodiment of the unit according to the inventlon, the laeter al~o comprise~ a plurallty of electrlcally con^
ductlve gr1d~, ~hlch sre respectively ~ocisted ~ith the patterns, 8216.3 Py - 4 ~
e~ch grid is positloned between the ~node and the corre~pondLng cathode, i~ electrlcally in~ul~ted from s~ld cathode snd i8 lntended to be poYitlvely polarlzed comp~red w$eh ehe latter~and negatively polarized compared with the anode or r~lHed to the potenti~l of the latter.
In cert~in constructlons, ~he ~node~ are formPd in such a w~y that they can ~180 function a~ grids.
According to ~nother embodiment of the unit a~cording to the invention, each ~node i~ placed on ~ tranaparent support f~clng the correspondlng cathode.
According to another embodiment, eech anode iR integr~ted to ~he corresponding cathote snd i8 electric~lly 1nsulated therefrom, the micropoint~ of each c~thode coverin~ the complete ~urf~ce of the corresponding snode. In o~her word~, the pro~ection of the ~urface occupied by the~e micropoints on to the ~urface occupied by the anode substanti~lly coincide~ wi~h the latter.
According to another special embodiment, each anode 18 integrated to the corr2~pondin~ c~thode ~nd i8 electrlcally in~ulnted therefrom, the mlcropoints of each p~ttern being grouped in the ~ame area sepAr~te from the active portion Df the anode. In other worda, seen from ~he anode, ~he area occ~pied by the ~icropointd and ~he cathodo-lumine~cent zone of the snode ~re oeparate.
In the~e two latter embodiments snd ~hen the unit according to the invention h~s the afore~entioned grid~, e~ch grid can also be lntegrsted ~ o the correspondin~ csthode ~nd electrically lnsuL~ed from the corresponding ~node.
In thi~ ca~e, or in the ca~e where ~ach anode is pl~ced on a tran3parent ~upport f~clng ehe correspondlng cathode, each anode can c~mpr~se a lay~r of~c3thodolumine~cent oubstance and ~n electrically , ~ 8216~3 PV
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conductive fllm pl~ced on the latter, f~cln~ th~ corre~pondlng c~thode, or an electric~lly conductive snd transp~rent co~ting and ~ coating of c~thodolumin~scen~ aub~t~nce placed on the latter~f~cing the corre~pondlng cathode.
In a special embodiment of the lnvention, e~ch anode c~n compri~e co~tlng of an electrically conductive, cathodoluminescent ~ub~tance.
In th~ two embodiments referred to hereintobefore, c~rresponding to the case where each ~node i8 inte8rated -to the corresponding cathode~and when the aforementioned grids ~re used, each grid can al80 be integrated .to the correspondlng cathode, each ~node then having 2 c~thodolumine~cent sub~t~nce l~yer r~ised to the potential of the corresponding grid or to a potentiQl higher th~n th~t of the grid, the 13tter being positive.
In the two special embodi~ent~ in question, the unit according to the inYention cAn ~l~o comprise a thin, transparent electrod~ f~cing the anode~ on ~ tr~nspArent support.
According to ~n embodl~ent of the inventlon using the aforamentioned gr$d~, the c~thode~ ~re grouped ~long rowc parallel ~o one another 3 ~h~
c~thode~ of the same ro~ being electrlcally in~erconnected, the grida bein~ grouped ~lon~ par~llel columns and whlch are perpendicular to the~
rows, the 8rid~ of one colu~n bein8 electric~lly int~rconnected and the unlt al~o co~prl~ing el~c~ronic control mean~ for carrying ou~ a matrix addre~in~ of the ~ow~ ~nd columna. When ~ch ~node and each ~rid corre~pondlng thereto are ~p~r~ted by ~n electric~lly in~ul~ing coatlng, all the ~node~ can be electrically interconnected~
Finally~ ~ccording to ano~her speci~l embodiment corr~spondin~ to one or other of the ~o ~forem~ntioned embodim~nts, in which e~ch ~node 1~ int~grated .to the Porresponding c~thode, e~ch ~node al~o belng boeh B 8216.3 PV
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c~thodolumlnescent and conductlve in o~der to f~lfll the function of the grid, or the ~rids beinq present and respectively electrlcally connected to the corresponding anodes, the cAthodes are grouped ~long parAllel row~, the c~thode~ of one row being electricAlly interconnected, the anodea ~8 well aa the grid~ optionally a~sociated therewith ~re grouped along par~llel column~ and ~hich are perpendicular to ~he rows, ~he 8rids of the ~ame column being electric~lly interconnected~ the anodes of ~
~ame column being a1R0 electrically connected to one another, the unit then ~180 comprising electronic control mean~ for carrying out ~ m~trix addre~ing of the row~ and columns.
The possibility of obtaining the cathode~ and grlds by an integrated technology makeæ it pos~ible to produce ehe unit accordlng to the invention in a fiimpler way than with the aforementioned known dlsplay units.
Moreover, it ha~ been ~een that the latter sre controlled by u~ing m~trix addre~sing of ~he snode- grid By8tem. ~3 st~ted, in certaln con~tructiona, ~he unit according to the lnvention c~n be con~rolled by c~rrylng out a matrix ~ddre6~ing of the cathodea and grids~ bec~u3e the respon~e time of the cathodes in ~he inYention i8 very f~t. Thi~
further facilitates the constructlsn of the ~nit according to the lnven~ion as comp~red ~ith the ~fore~entioned known dlspl~y unlt~.
BRIEF DESGRIPTION OF THE DRAWINGS
Flg. 1 - a diagrammatic vi~w of a known unlt for di~pl~y by cathodolumine~cence excited by thermoelectron$c emission and already descrlbed.
Fig. 2 - a dlagram ll~u~tr~ting the ~forementioned field eml~lon principle~
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Fl~. 3 - 5 d~r3mn~tlc vlew of an 2mbodlment of An rl~m~nts~y p~ttern provided Dn the dlspl~y unlt ~ccordlng to the lnventlon.
Flg3. 4 and 5 - d~agr~mmatic vlew~ of ~pecl~l embodiment~ of cathodolumlnescent an~dea ~sed ln th~ lnY~ntlon.
Flg~O 6, 7, 8 ~nd 9 - dl~r~atic Vi~W8 of other ~peclal ~mb~d1me~t~ ~f elem~ntary p~e~r~ ua~d on ~h~ ~nl~ ~coY~lng Lv lnventlon, ln whlch th~ ~uthode, the grld And the ~nod~ of the 8am~
element~ry p~tter~ are lntegr~ted ~n to the ~ame subatr~te, the ~node also ~erYln~ th~ function of a ~rid in the constructlon ~ccording to Fi8. g.
Fig. lO - ~ dlagr~mm~tic v12w ~f ~n~ther 8pecl~1 embodiment of the ~nvent~on u~lng ~ thln, t~n~p~r~nt electro~e f~clng the c~thodo-luminesc~nt ~node~.
~ dlAgr~mm~tlc vlew of ~ ~peci81 emb~d~ment of the unlt ~ccording to the ln~n~lon, in vhlch the mlcrop~nt~ of the 8~me ~lement~ry p~ttern ~re grouped ln the s~me field or ~gi~n.
~ 1~. 12 - a dlagramm~tlc ~iew of anDth~r ~pecl~l embodlment, ln ~hlch the mlcropolnt~ ~f h ~ pattern l'coverl' the complete ~urfAc~
of the corr~p~nd1ng Mnode.
DESCRIPTION OF THE PRIOR ART
-Cathodoluminescence display units are already known, wnich use a thermoelectronic emission. A particular construction of such units is diagrammatically represented in Fig. 1 and comprises a pluxality of anodes coated with a cathodoluminescent substance or phosphor 2 and arranged in parallel lines on an insulating support 4, together with a plurality of filaments 6 able to emi~ electrons when heated and which act as cathodes, said filaments being arranged along lines parallel to the anodes. A plurality of grids 8 are placed between the anodes and the filaments, being arranged in parallel columns and the latter are perpendicular to the lines or rows. The assembly constituted by the anodes, ,. . . .
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- 7a -the filaments and the grids are exposed or bared in a transparent box or casing 10, which is sealingly connected to support 4. When heated, the filaments 6 emit elec-trons and an appropriate polarization of a filament, grid and anode enable the electrons emitted by said filament to strike the anode, which is then subject to light emission.
By matrix addressing of the rows of anodes and columns of grids, it is in this way possible to produce images or pictures, which are visible through the transparent casing 10 .
The principle of electronic emission by field effect is also known, which is also called "field emission" or "cold emission". This principle has already been used for application unlinked with visual display. It is diagramma-tically illustrated in Fig. 2 where, in a vacuum, metal points 12 serving as cathodes and placed on a support 14, are able to emit electrons when an appropriate voltage is established between them and an anode16 positioned facing said points.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 3 diagrammatically shows a special embodiment of the elementary patterns provided on the unit according to the invention. In this embodiment, each elementary pattern comprises a low voltage-excitable cathodoluminescent phosphor coating facing the corresponding cathode, the phosphor coating being observed from the side opposite to its excitation.
More speci~ically, in the embodiment diagrammatically shown in Fig. 3, each elementary pattern comprises a cathode 18 and a cathodo-__ /
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lu~inescent anode 20. Cnthode 18 comprlsea ~ plursllty of electrlc~llyconductive mlcropoint~ 22, formed on an electrically conductive coatlng 24, which i~ Itself pl~ced on sn electrically insulating substrAte 26.
Coating 24 could be semiconducting insee~d of being conducting.
~ he micropoints 22 are sep~r~ted from one enother by electric~lly insulatlng coatlngs 28. Each elemcnt~ry pattern al~o comprises A 8rid 30. The lAtter i~ constltuted by a plurallty of electrically conductlve coatinga 32 depo3ited on insulAting co~tings Z8, the latt~r hsving Yubstanti~lly the same thickness, ~ld thickness being choaen in such a way that the spex of aach micropolnt i8 sub~tsntially level wlth the electrlcally conductlv~ co~tings 32 fonmlng grid 30.
Anode 20 comprises a lo~ voltsge~excitable csthodolumins~cent phosphor coating 34, deposlted on ~ transparent planar support 36, posltloned facing grid 30 parallel thereto, the pho6phor coating 34 being deposlted on the face of a support directly facing ~aid grid.
Anode 2n al80 compri~e~ ~n electrically conductive film 38 depo~ited on the cathodolumine~cent phosphor coating 34 ~nd ~hich dlrectl~ faces grid 30~ The la~ter can be in the form of ~ continuous coating perforsted by holes faclng the micropolnts. In the ~eme way9 the insulatlng co~tlngo 28 can form a single continuou~ coating perforated by hole~ traver~ed by micropoints.
In ~ purely lndlc~tive ~nd in no w~y l~mlt~tlve manner, subatr~tP
26 i8 m~de from glaas and coating 24 i~ m~de from aluminlum or 611i~on.
Micropoints 22 are =~d~ irom lanthanum hex~borlde or from one of the metals taken from th~ group including niobium, h~fnium, ~irconlum ~nd molybdenum, or B carblde or nltride of sald met~l~, The pho~phorous costlng 34 1~ o ~lnc sulphlde or c~dmlum sulphide. Tran~parent ~upport 36 i~
made from 81~8~, conductive coatlng 38 ia m~de from aluminium or gold, in~ulatlng coaeing~ 28 are m~de rom sllica, grid 30 i~ mad~ from niobium ,.
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or molybdenum, the mlcropolnts are ln the form of cone~, whose bAse diAmeter i8 ~pproxlmately 2~ and whose height i~ appr~xlmately 1.7~m.
The thicknes6 of e~ch insulsting coatin~ 28 i8 ~pproxlmately 1~5~m.
The thicknea~ of the grid 18 approximately 0~4~m and the hole~ therein have ~ diameter of ~pproxlmfitely 2~m. Finally, the conductlve film 38 has a thickness of approximately 50 to lOO R.
In practice, a single glas~ substr~te 26 and a 3ingle transparent ~l~#a ~upport 36 are u~ed for All the elementary pnttern~ ~nd when the latter ~re produced in the w~y ahown hereinafter, a v~cuum i~ formed between the anodes and cathodes, the substrate 26 and trsnspsrent aupport 36 being interconnected in a ~ealing manner.
An element~ry p~tte~n i~ exclted by simult~neou~ly polarizing ~he anode, the gsid and the cathode~ One of ~he~e, e.g. the grid, 18 used a~ the reference potentlal and i8 earthed. The anode can be rai~ed to the potentl~l of the 8rid or can be po~itively polarized relative thereto with the aid of a voltsge ~upply 40. The ca~hode 18 negat~vely polArized compared with the 8rid uaing a voltage ~upply 42.
E~ch polnt of the elementary pattern then e~it~ electrons which will excite the pho~phor coating, the conductive c~attng 38 having been made a~ thin a8 possible ~o a~ not to stop the electron3, the thu~
e~cited pho~phor coatlng emittin8 light which c~n be ob~erved through the trsnsp~rent suppore 36. A low volt~ge o~ approximately lOO volts between the grid and the cathode makes it pos~lble ~o obtaln an electronlc c~rrent of ~ fe~ micro&mpere~ per mlcrop~int and con~equently an electronic current density of ~everal milliamperes per aquare ~illimetre for the co~plete p&ttern ~hich h~ very large number of micropoin~R ~ever~l tens of eho~ nd~) per QqUare u~ metre.
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In the variant of FiB. 4, th~ conductlve coatlng no longer fAc~
the mlcropoints and i8 ln~eead located between the transpar~nt aupport 36 and the pho~phor costlng 34, the latter then dlrectly facing the micropolnts 22. In thi~ c~se, conductlve fllm 38 i~ cho3en ~o a~ to be tran~parent to the llght emls~ion of the phosphor. For thi~ purpose, fllm 38 i8 e.~. ~ tin- doped indlum oxld~ coating.
In a further variant according to Fig. 5, conductive fllm 38 i~
elimln~ted ~nd the phosphor coating 34, deposited on the tr~nsparent ~upport 36, i8 then cho~en in ~uch a way that it i8 alao electric&lly conductive. To thls end, u~e i8 e.g. made of a zlnc- doped ~inc oxide coating.
In another speciAl embodiment, the pho~phor i8 depo~ited on th~
grid (with the po6~ible exception of the lnterposing of coating~), the ~aembly formed by the caehode, the grid and the anode then belng ineegrated on to the ~ame sub~trat~ and ~he phospho~ belng observed from the 6ide where it i8 exclted, which m~keff lt possible to ellminste the llght lo~a due to the pasa~ge through the phosphor and which occurs in th~ embodlments of Fi8. 3, 4 and 5.
More spe~lfically, ln the other smbodlment of the elementary patterns di~gr~mmatlcslly repre~ented ln Fig. 6, cathode 18 compri~es micropoints 22 on ~he conductive co~ting 24, the l~tter bein~ depo~lted on the ln~ulating sub~tr~te 26, the micropoint~ being ~eparat~d b~
electrically lnsulsting coatings 28 sn ~h$ch the grld 30 1~ deposited.
An electrlrally $nsul~ting coating 44, e.~. of d I lica 18 depo~lted on the 8rit co~t~ng 30 ~nd al~o ha~ holes corr~sponding to the hole~ made in the ~rid coAtlng ~ 80 that the micropoints 22 appear.
Anode 20 compri~es an electrically conductive coating 39, e.g. of gold or aluminium, deposited on the insulating coating 44 ~nd ~ pho~phor co~ting 34 d~po~it2d on the conductiv~ costlng 39. Obviously these B 8216.3 PV
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coatings 34 and 39 have holes 37 enabling the mlcropolnts 22 to appe~r, flO that the composite coating re~ultlng from the stacking of coatlngs 30, 44, 39 nnd 34 constitute0 a co~tlng perforated by holes permittlng the appesrance of mlcropoint~ 22.
Moreover, the mlcropoin~s are preferably regularly dlstributed ln such a way that the surface occupied by them substantially coincidea wlth the surfsce occupled by the phosphor coating and on observing the latter, it appears to be covered by micropoints.
The transparent support 36 la positioned faclng the phosphor coating 34, parallel to the latter and is sealingly connected to substrate 26, once the vacuum has been e~tabli6hed between them.
As hereinbefore, the anode can be raised to the same potential as the grid, or to a positive potentlal compared with the latter, by ~eans oi a voltage supply 40, whilst the cathode 18 raised to a negative potential compared with the 8rid with the aid of a voltage supply 42, the grid being taken AS the reference potential and connected to earth.
Under these conditions, each micropoint 22 emits electrons, which pass through the hole corresponding to the mlcropoint in question and whose path is then curved ln the direction of the phosphor coating 34, 80 that the electrons strike the phosphor coating, whlch then emits light whlch can be observed through the transparent support 360 In a not shown varlant, the phosphor coating 34 i5 directly deposited on the insulating coating 44 and the conductive coating 39 is then deposited on the phosphor coating 34 and is cho6en 80 as to be transparent to the light emitted by said phosphor coating. In another variant dlagra~matically ~hown in Fig. 7, the electrically conductive coating 39 is eliminated snd the phosphor coating 34 is directly depo ited on the insulating coating 44, the phosphor coating then being chosen ~o as to be electrically conductive.
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In another vsriAnt diagrammatically ~hown in Fig. 8, the lnsulating coating 44 i8 eliminated Ind the phosphor coating 34 is directly deposited on grid coating 30 and i8 rsi~ed to the potential of th0 grid, the e~citntion of the elementary pattern then being carried out by raising the cathode to a negative potential compared with the grid by means of a voltage supply 46, the grld then being earthed.
In another variant diagrammatically shown in Fig. 9, the grid i~
eliminated and the phosphor coating 34, chosen 80 as to be electrically conductive, al80 serYes as the grid~ The cathode i8 then rsised to a negative potential compared with the phosphor costing, which i9 earthed.
In a special embodiment corresponding to the case where the snode and cathode are integrated on to the s~me 3ubstrate, an electrically conductive,transparent coating 48 (Fig. 7) i8 deposited on the face of the trAnsparent support 36 directly facing anode 20. This conductive, transparent support 48 can be left floating or can be rai~ed to a repulsive potential with respect to the electrons emitted by micropoints 22 by mean~ of a voltage supply 50 (Fig. 10).
Fig. 11 diagrammatically shows another embodiment of an elementary pattern, the only difference compared with the aforementioned embodiments and corresponding to the case where the anode, grid and cathode are integrated on to the same substrate is thaS the mlcropoints 22, observed from above the phosphor coating 34, do not appear to cover the complete coating 34. In the preaent case, they are brought together in the same region. More speclfically, in the embodiment of Fig. 11, the micropoints are locsted in the same region 64 on conductive coating 24, which is itself deposited on the insulating sub~trate 26. The in~ulatlng coating 28 i3 deposised on conductive coating 24, whilst aeparating the micro-point~ fro~ one another, a grid coating 30 having holes corresponding to the micropoinSs belng deposited on the in~ulating coating 28 and a phosphor coating 34 i8 depo~ited on the grid coating, except above the region in ~ ~216.3 PV
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which the micropoint~ are concentr~ted and 1~ rsi0ed to the 3ame potenti~l RS the grld (~9 explained ln the descrlptlon of Flg. 8).
A3 a vsrlant, it would be po~slble to deposit a perforated grid coating on the insulating coatlng 28, followed by another inaulating coating on the grid coating, except above said region 64 and finally an optionally composlte coating serving a~ the anode on said other insulatlng coating, the anode coating being con6tituted by an electrically conductive coating associated with a phosphor coating (as explained relative to Fig. 6), or simply an electrlcally conductive phosphor coating (as explained relative to Fig. 7).
According to another variant, it would be possible to deposlt on insulating coating 28 an electrically conductive pho6phor coating serving both as the snode ~nd the grid and perforated with holes corre~ponding to the micropolnts.
Obviously,the transparent support 36 is still positioned facing the anode and i3 optionally provided with a conductive coating, left floating or rai~ed to an 2ppropriate potential, as explained hereinbefore.
Fig. ~ diagra~matically ~hows 8 special embodiment of ~ dL6play unlt according to the invention in which case the elementary patterns ~re produced $n accordance wi~-h the description of Fig. 3, with possible variants de6cribed with reference to Figs. 4 and 5. Furthermore, the cathode~ are grouped in accordance with parallel rows 52 and ehey are formed on the same electrically insulAting substrate 26. MoreoYer, in each row, the cathodes are continuous, i.e. there ia no interruption on passing from one cathoda to another.
The grids are grouped along paraIlel columns 54, which are perpendicular to the rows 52. In each cGlumn, the grids are continuous, i.e. there ii3 no interruption between adjscent grids. The micropoints serve no useful ~ ' B 8216.3 PV
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in any zone corresponding to a gap separating two column~.
Moreover, the anodes form a continuou~ sy~tem constltuted by a ~ingle phosphor coating 34 as~oclated, when lt 19 not electrically conducting, with a single electricfllly conducting coating 38, said two coatlngs being deposited on a single transparent support 36. The characteristic~ of costing 38 were explained in ehe description of Figs.
3 and 4, as a function of the sltuAtion of said coating. Thus, each elementary pattern 56 corresponds to the crossing of one row and one column.
The display unit shown in Fig. 12 al80 comprises electronic control means for effecting a matrix addressing of the rows and column~.
Such electronic means are known in the art, both in the case where it i~
wished to obtain stationary pictures and in the case where it i8 wi~hed to obtain moving pictures.
For each elementary pattern, field emission mainly occurs when a potential difference exceeding a positiYe threshold voltage Vs, is applied between the grid and the cathode of the pattern in question, the anode of the latter being raised to a potential at least equal to that of the grid.
In order to form stationary or moving pictures, the following operations are csrried out for the first row, then for the second and 90 on up to the final row. The row in question ls raised to potential -V/2,potential V
being equal to or higher thsn Vs and lower than 2Vs, whilst all the other rows are lPft iloating or are raised to a zero potential, which is carried out with the aid of fir~t means 58 forming part of the electronic means and in a simultaneous manner, all the columns corresponding to the elementary patterns to be excLted on the row in question are rai~ed to potential V/2, whil~t the other columns are left floating or raised to a ~ero potentisl, this being carried out with the aid of second means 60 fo~ning part of the electronic means, the anodes being con3tantly maintained :.~
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at a potential at least equal to V/2 with the aid of ~n appropriate voltage 8upply 62.
It i~ also possible to produce a unit according to the invention by forming the elementary patterns in the manner described relative to Figs.
6 to 10. In this case, the rows are formed in the manner explained hereinbefore and the anodes, when they are electrically connected to the associated grids or when they act a~ grids, are arranged along the columns, the anodes of the same column not being separated.
When the anodes and grids are sepArated by insulatin~ coatings, all the anodes of the unit can be electrically interconnected.
It is then possible to use the same electronic matrix addressing means a8 those described hereinbefore. In this ca~e, when in eAch column the anodes have to be electrically insulated from the corresponding grids, said Anodes are constantly maintained and a potential at lesst equal to V/2.
Another special embodiment of the unit according to the invention is also shown in Fig. 11. This other embodiment comprises elementary patterns 61, in each of which the micropoints are grouped in the same region 64, as explained hereinbefore with reference to Fig. 11. The cathodes are grouped in parallel rows 52 and the anodes, when they are electrically connected to the associated grids or when they serve as grids, are thus grouped to~ether with any possible grids along columns 54 which are parallel to one another and perpendlcular to the rows, as explained ; hereinbefore. The crossing of a row and a column corresponds to ar.
elementary pattern, in the centre of which said region 64 is located. The display unit of Fig. 11 can be co~trolled in the same way as the unit described relati~e to Fi8. 12. Obviously, the insulating sub3trate 26 and the tran~parent support 36 are common to all the elementary patterns.
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When the anodes and the grids are seperated by insulAting coAtings, all the anode6 of the unit can be electrically interconnected.
The formation of micropoints 22 on a conductive coatlng 24 and separated by insulating coatings 28 is known in the Art and has been studied by Spindt at the Stanford Research In~titute (for applica~ions unrelated with visual di3plays). For producing the uni~s represented in Figs. ll and 12, known microelectronics procedures are used.
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BACKGRO~ND OF THE INVENTION
The present invention relates to a display unit by cathodoluminescence excited by field emission.
It more particularly applies to the production of simple displays, permitting the display of fixed images or pictures, and to the production of complex multiplexed screens, making it possible to display moving pictures, such as television pictures.
Cathodoluminescence display units are already known, which use a thermoelectronic emission. Such display units suffer from the disadvantages of the definition of the images which they make it possible to obtain not being of a high quality, devices or units are complicated to produce and they have a high electric power consumption, in view of the fact that the filaments have to be heated.
The principle of electronic emission-by field effect is also known, which is also called "field emission" or "cold emission". This principle has already been used for applications unlinked with visual display.
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SUMMARY OF THE INVENTION
_ ~ he ob3ect of the present invention $8 to obvl~te th~ ~forementl~ned dlsadvantagas by propo~lng a display unit utlll~ing field eml~sion, whose p~lnciple has been gl~en herelnbefore.
Specific~lly, the pre~ent lnvention relates to a di2pln~ unlt co~prising a plur~lity of element~y p~teern~, e~ch h~vlng ~ c~thodo-lu~inescent node ~nd n cethode able to ~it electron~, ~bereln each c~thode comp~lses a plur~lity of electric~lly lnterconne~ted ~loropolnts ~nd ~ub~ect to ~n electron emla~on by fleld effect wh~n the t~thode i8 negn~lvely pol~rlzed rel~tlve to ebe cor~esponding ~node, ~aid electrDn~
~triking the latter1 which i~ then subje~t t~ ghe emls~ion. ~sch ~node tan be lntegrated to the corresponding cathode And electrle~lly lnsul~ted therefro~. ~
~ In fact~ ~leot~on em~0~ion i~ onl~ high ~boYe a certaln pDlsrlz-tlon thre~hold ~nd belo~ it~e~ on 1~ lo~ ~nd then onl~ le~d~ to ~ small amount o~ llght bein8 produced.
In tbis ~ay lt is pos~4ble to obt~in ~n over~ll ll~ht l~age by pprGpri~tely polAri~lng the olement~ry pattern~. ~he~ tbe different - .~;"
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pol~rlzation~ ~re maintained const~t over A period of time, the lmage obtalned i8 flxed, but it is al~o pos~ible to obtain moving lm~gea or pictures, by varying in an appropri~te msnner the polarlzationR during period of time.
The pre~nt invention makes it po~sible to obt~in flat acreens operating under a low voltage, ln the same way aa the known units referred to hereinbefore. However, the plctures obtalned by means of the unlt accordlng to the invention have a much better deflnition.
Thus, it i9 possible to produce very 6mall micropolnt0, ~t a rate of ~ few tens of thousands of micropoints per ~quare millimet~e, which makes it pos~ible to produce element~ry cathode~ h~ving a very small surface and consequently it is po3Rible to excite very ~m~ll c~thodo-luminescent ~nodes.
In addition, the unit sccording to the invention h~6 8 much lower electris power cons~mption than the ~forementloned Prlor Art unlts, in view of the fcct that it u~e~ cold cathodes.
The ~urf~ce of the cathode corresponding to an elementary p~ttern can elther be ~quRl to or le~s than the ~urfece of the anode of ~ald pattern. As it i8 possible to produce ~ l~rge number of micropoints per ~qu~re ~illimetre, lt is pos~ible to excite each anode by 3 very l~rge nu~ber of micropoint~. The light emisslsn of an elemen~ry pattern corresponds to the me n e~lssion characteri~tic of all the correaponding mlcropoint~. If a small nu~ber of micropoints do not f~nction, this mean char~cteristic re~ains 0ub~tantially unchanged, ~hlch con~titute~
~n important adv~ntage of the inventlon.
Accordlng to ~ special embodiment of the unit according to the inventlon, the laeter al~o comprise~ a plurallty of electrlcally con^
ductlve gr1d~, ~hlch sre respectively ~ocisted ~ith the patterns, 8216.3 Py - 4 ~
e~ch grid is positloned between the ~node and the corre~pondLng cathode, i~ electrlcally in~ul~ted from s~ld cathode snd i8 lntended to be poYitlvely polarlzed comp~red w$eh ehe latter~and negatively polarized compared with the anode or r~lHed to the potenti~l of the latter.
In cert~in constructlons, ~he ~node~ are formPd in such a w~y that they can ~180 function a~ grids.
According to ~nother embodiment of the unit a~cording to the invention, each ~node i~ placed on ~ tranaparent support f~clng the correspondlng cathode.
According to another embodiment, eech anode iR integr~ted to ~he corresponding cathote snd i8 electric~lly 1nsulated therefrom, the micropoint~ of each c~thode coverin~ the complete ~urf~ce of the corresponding snode. In o~her word~, the pro~ection of the ~urface occupied by the~e micropoints on to the ~urface occupied by the anode substanti~lly coincide~ wi~h the latter.
According to another special embodiment, each anode 18 integrated to the corr2~pondin~ c~thode ~nd i8 electrlcally in~ulnted therefrom, the mlcropoints of each p~ttern being grouped in the ~ame area sepAr~te from the active portion Df the anode. In other worda, seen from ~he anode, ~he area occ~pied by the ~icropointd and ~he cathodo-lumine~cent zone of the snode ~re oeparate.
In the~e two latter embodiments snd ~hen the unit according to the invention h~s the afore~entioned grid~, e~ch grid can also be lntegrsted ~ o the correspondin~ csthode ~nd electrically lnsuL~ed from the corresponding ~node.
In thi~ ca~e, or in the ca~e where ~ach anode is pl~ced on a tran3parent ~upport f~clng ehe correspondlng cathode, each anode can c~mpr~se a lay~r of~c3thodolumine~cent oubstance and ~n electrically , ~ 8216~3 PV
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conductive fllm pl~ced on the latter, f~cln~ th~ corre~pondlng c~thode, or an electric~lly conductive snd transp~rent co~ting and ~ coating of c~thodolumin~scen~ aub~t~nce placed on the latter~f~cing the corre~pondlng cathode.
In a special embodiment of the lnvention, e~ch anode c~n compri~e co~tlng of an electrically conductive, cathodoluminescent ~ub~tance.
In th~ two embodiments referred to hereintobefore, c~rresponding to the case where each ~node i8 inte8rated -to the corresponding cathode~and when the aforementioned grids ~re used, each grid can al80 be integrated .to the correspondlng cathode, each ~node then having 2 c~thodolumine~cent sub~t~nce l~yer r~ised to the potential of the corresponding grid or to a potentiQl higher th~n th~t of the grid, the 13tter being positive.
In the two special embodi~ent~ in question, the unit according to the inYention cAn ~l~o comprise a thin, transparent electrod~ f~cing the anode~ on ~ tr~nspArent support.
According to ~n embodl~ent of the inventlon using the aforamentioned gr$d~, the c~thode~ ~re grouped ~long rowc parallel ~o one another 3 ~h~
c~thode~ of the same ro~ being electrlcally in~erconnected, the grida bein~ grouped ~lon~ par~llel columns and whlch are perpendicular to the~
rows, the 8rid~ of one colu~n bein8 electric~lly int~rconnected and the unlt al~o co~prl~ing el~c~ronic control mean~ for carrying ou~ a matrix addre~in~ of the ~ow~ ~nd columna. When ~ch ~node and each ~rid corre~pondlng thereto are ~p~r~ted by ~n electric~lly in~ul~ing coatlng, all the ~node~ can be electrically interconnected~
Finally~ ~ccording to ano~her speci~l embodiment corr~spondin~ to one or other of the ~o ~forem~ntioned embodim~nts, in which e~ch ~node 1~ int~grated .to the Porresponding c~thode, e~ch ~node al~o belng boeh B 8216.3 PV
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c~thodolumlnescent and conductlve in o~der to f~lfll the function of the grid, or the ~rids beinq present and respectively electrlcally connected to the corresponding anodes, the cAthodes are grouped ~long parAllel row~, the c~thode~ of one row being electricAlly interconnected, the anodea ~8 well aa the grid~ optionally a~sociated therewith ~re grouped along par~llel column~ and ~hich are perpendicular to ~he rows, ~he 8rids of the ~ame column being electric~lly interconnected~ the anodes of ~
~ame column being a1R0 electrically connected to one another, the unit then ~180 comprising electronic control mean~ for carrying out ~ m~trix addre~ing of the row~ and columns.
The possibility of obtaining the cathode~ and grlds by an integrated technology makeæ it pos~ible to produce ehe unit accordlng to the invention in a fiimpler way than with the aforementioned known dlsplay units.
Moreover, it ha~ been ~een that the latter sre controlled by u~ing m~trix addre~sing of ~he snode- grid By8tem. ~3 st~ted, in certaln con~tructiona, ~he unit according to the lnvention c~n be con~rolled by c~rrylng out a matrix ~ddre6~ing of the cathodea and grids~ bec~u3e the respon~e time of the cathodes in ~he inYention i8 very f~t. Thi~
further facilitates the constructlsn of the ~nit according to the lnven~ion as comp~red ~ith the ~fore~entioned known dlspl~y unlt~.
BRIEF DESGRIPTION OF THE DRAWINGS
Flg. 1 - a diagrammatic vi~w of a known unlt for di~pl~y by cathodolumine~cence excited by thermoelectron$c emission and already descrlbed.
Fig. 2 - a dlagram ll~u~tr~ting the ~forementioned field eml~lon principle~
~ 8216~3 PV
Fl~. 3 - 5 d~r3mn~tlc vlew of an 2mbodlment of An rl~m~nts~y p~ttern provided Dn the dlspl~y unlt ~ccordlng to the lnventlon.
Flg3. 4 and 5 - d~agr~mmatic vlew~ of ~pecl~l embodiment~ of cathodolumlnescent an~dea ~sed ln th~ lnY~ntlon.
Flg~O 6, 7, 8 ~nd 9 - dl~r~atic Vi~W8 of other ~peclal ~mb~d1me~t~ ~f elem~ntary p~e~r~ ua~d on ~h~ ~nl~ ~coY~lng Lv lnventlon, ln whlch th~ ~uthode, the grld And the ~nod~ of the 8am~
element~ry p~tter~ are lntegr~ted ~n to the ~ame subatr~te, the ~node also ~erYln~ th~ function of a ~rid in the constructlon ~ccording to Fi8. g.
Fig. lO - ~ dlagr~mm~tic v12w ~f ~n~ther 8pecl~1 embodiment of the ~nvent~on u~lng ~ thln, t~n~p~r~nt electro~e f~clng the c~thodo-luminesc~nt ~node~.
~ dlAgr~mm~tlc vlew of ~ ~peci81 emb~d~ment of the unlt ~ccording to the ln~n~lon, in vhlch the mlcrop~nt~ of the 8~me ~lement~ry p~ttern ~re grouped ln the s~me field or ~gi~n.
~ 1~. 12 - a dlagramm~tlc ~iew of anDth~r ~pecl~l embodlment, ln ~hlch the mlcropolnt~ ~f h ~ pattern l'coverl' the complete ~urfAc~
of the corr~p~nd1ng Mnode.
DESCRIPTION OF THE PRIOR ART
-Cathodoluminescence display units are already known, wnich use a thermoelectronic emission. A particular construction of such units is diagrammatically represented in Fig. 1 and comprises a pluxality of anodes coated with a cathodoluminescent substance or phosphor 2 and arranged in parallel lines on an insulating support 4, together with a plurality of filaments 6 able to emi~ electrons when heated and which act as cathodes, said filaments being arranged along lines parallel to the anodes. A plurality of grids 8 are placed between the anodes and the filaments, being arranged in parallel columns and the latter are perpendicular to the lines or rows. The assembly constituted by the anodes, ,. . . .
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- 7a -the filaments and the grids are exposed or bared in a transparent box or casing 10, which is sealingly connected to support 4. When heated, the filaments 6 emit elec-trons and an appropriate polarization of a filament, grid and anode enable the electrons emitted by said filament to strike the anode, which is then subject to light emission.
By matrix addressing of the rows of anodes and columns of grids, it is in this way possible to produce images or pictures, which are visible through the transparent casing 10 .
The principle of electronic emission by field effect is also known, which is also called "field emission" or "cold emission". This principle has already been used for application unlinked with visual display. It is diagramma-tically illustrated in Fig. 2 where, in a vacuum, metal points 12 serving as cathodes and placed on a support 14, are able to emit electrons when an appropriate voltage is established between them and an anode16 positioned facing said points.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 3 diagrammatically shows a special embodiment of the elementary patterns provided on the unit according to the invention. In this embodiment, each elementary pattern comprises a low voltage-excitable cathodoluminescent phosphor coating facing the corresponding cathode, the phosphor coating being observed from the side opposite to its excitation.
More speci~ically, in the embodiment diagrammatically shown in Fig. 3, each elementary pattern comprises a cathode 18 and a cathodo-__ /
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lu~inescent anode 20. Cnthode 18 comprlsea ~ plursllty of electrlc~llyconductive mlcropoint~ 22, formed on an electrically conductive coatlng 24, which i~ Itself pl~ced on sn electrically insulating substrAte 26.
Coating 24 could be semiconducting insee~d of being conducting.
~ he micropoints 22 are sep~r~ted from one enother by electric~lly insulatlng coatlngs 28. Each elemcnt~ry pattern al~o comprises A 8rid 30. The lAtter i~ constltuted by a plurallty of electrically conductlve coatinga 32 depo3ited on insulAting co~tings Z8, the latt~r hsving Yubstanti~lly the same thickness, ~ld thickness being choaen in such a way that the spex of aach micropolnt i8 sub~tsntially level wlth the electrlcally conductlv~ co~tings 32 fonmlng grid 30.
Anode 20 comprises a lo~ voltsge~excitable csthodolumins~cent phosphor coating 34, deposlted on ~ transparent planar support 36, posltloned facing grid 30 parallel thereto, the pho6phor coating 34 being deposlted on the face of a support directly facing ~aid grid.
Anode 2n al80 compri~e~ ~n electrically conductive film 38 depo~ited on the cathodolumine~cent phosphor coating 34 ~nd ~hich dlrectl~ faces grid 30~ The la~ter can be in the form of ~ continuous coating perforsted by holes faclng the micropolnts. In the ~eme way9 the insulatlng co~tlngo 28 can form a single continuou~ coating perforated by hole~ traver~ed by micropoints.
In ~ purely lndlc~tive ~nd in no w~y l~mlt~tlve manner, subatr~tP
26 i8 m~de from glaas and coating 24 i~ m~de from aluminlum or 611i~on.
Micropoints 22 are =~d~ irom lanthanum hex~borlde or from one of the metals taken from th~ group including niobium, h~fnium, ~irconlum ~nd molybdenum, or B carblde or nltride of sald met~l~, The pho~phorous costlng 34 1~ o ~lnc sulphlde or c~dmlum sulphide. Tran~parent ~upport 36 i~
made from 81~8~, conductive coatlng 38 ia m~de from aluminium or gold, in~ulatlng coaeing~ 28 are m~de rom sllica, grid 30 i~ mad~ from niobium ,.
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or molybdenum, the mlcropolnts are ln the form of cone~, whose bAse diAmeter i8 ~pproxlmately 2~ and whose height i~ appr~xlmately 1.7~m.
The thicknes6 of e~ch insulsting coatin~ 28 i8 ~pproxlmately 1~5~m.
The thicknea~ of the grid 18 approximately 0~4~m and the hole~ therein have ~ diameter of ~pproxlmfitely 2~m. Finally, the conductlve film 38 has a thickness of approximately 50 to lOO R.
In practice, a single glas~ substr~te 26 and a 3ingle transparent ~l~#a ~upport 36 are u~ed for All the elementary pnttern~ ~nd when the latter ~re produced in the w~y ahown hereinafter, a v~cuum i~ formed between the anodes and cathodes, the substrate 26 and trsnspsrent aupport 36 being interconnected in a ~ealing manner.
An element~ry p~tte~n i~ exclted by simult~neou~ly polarizing ~he anode, the gsid and the cathode~ One of ~he~e, e.g. the grid, 18 used a~ the reference potentlal and i8 earthed. The anode can be rai~ed to the potentl~l of the 8rid or can be po~itively polarized relative thereto with the aid of a voltsge ~upply 40. The ca~hode 18 negat~vely polArized compared with the 8rid uaing a voltage ~upply 42.
E~ch polnt of the elementary pattern then e~it~ electrons which will excite the pho~phor coating, the conductive c~attng 38 having been made a~ thin a8 possible ~o a~ not to stop the electron3, the thu~
e~cited pho~phor coatlng emittin8 light which c~n be ob~erved through the trsnsp~rent suppore 36. A low volt~ge o~ approximately lOO volts between the grid and the cathode makes it pos~lble ~o obtaln an electronlc c~rrent of ~ fe~ micro&mpere~ per mlcrop~int and con~equently an electronic current density of ~everal milliamperes per aquare ~illimetre for the co~plete p&ttern ~hich h~ very large number of micropoin~R ~ever~l tens of eho~ nd~) per QqUare u~ metre.
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In the variant of FiB. 4, th~ conductlve coatlng no longer fAc~
the mlcropoints and i8 ln~eead located between the transpar~nt aupport 36 and the pho~phor costlng 34, the latter then dlrectly facing the micropolnts 22. In thi~ c~se, conductlve fllm 38 i~ cho3en ~o a~ to be tran~parent to the llght emls~ion of the phosphor. For thi~ purpose, fllm 38 i8 e.~. ~ tin- doped indlum oxld~ coating.
In a further variant according to Fig. 5, conductive fllm 38 i~
elimln~ted ~nd the phosphor coating 34, deposited on the tr~nsparent ~upport 36, i8 then cho~en in ~uch a way that it i8 alao electric&lly conductive. To thls end, u~e i8 e.g. made of a zlnc- doped ~inc oxide coating.
In another speciAl embodiment, the pho~phor i8 depo~ited on th~
grid (with the po6~ible exception of the lnterposing of coating~), the ~aembly formed by the caehode, the grid and the anode then belng ineegrated on to the ~ame sub~trat~ and ~he phospho~ belng observed from the 6ide where it i8 exclted, which m~keff lt possible to ellminste the llght lo~a due to the pasa~ge through the phosphor and which occurs in th~ embodlments of Fi8. 3, 4 and 5.
More spe~lfically, ln the other smbodlment of the elementary patterns di~gr~mmatlcslly repre~ented ln Fig. 6, cathode 18 compri~es micropoints 22 on ~he conductive co~ting 24, the l~tter bein~ depo~lted on the ln~ulating sub~tr~te 26, the micropoint~ being ~eparat~d b~
electrically lnsulsting coatings 28 sn ~h$ch the grld 30 1~ deposited.
An electrlrally $nsul~ting coating 44, e.~. of d I lica 18 depo~lted on the 8rit co~t~ng 30 ~nd al~o ha~ holes corr~sponding to the hole~ made in the ~rid coAtlng ~ 80 that the micropoints 22 appear.
Anode 20 compri~es an electrically conductive coating 39, e.g. of gold or aluminium, deposited on the insulating coating 44 ~nd ~ pho~phor co~ting 34 d~po~it2d on the conductiv~ costlng 39. Obviously these B 8216.3 PV
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coatings 34 and 39 have holes 37 enabling the mlcropolnts 22 to appe~r, flO that the composite coating re~ultlng from the stacking of coatlngs 30, 44, 39 nnd 34 constitute0 a co~tlng perforated by holes permittlng the appesrance of mlcropoint~ 22.
Moreover, the mlcropoin~s are preferably regularly dlstributed ln such a way that the surface occupied by them substantially coincidea wlth the surfsce occupled by the phosphor coating and on observing the latter, it appears to be covered by micropoints.
The transparent support 36 la positioned faclng the phosphor coating 34, parallel to the latter and is sealingly connected to substrate 26, once the vacuum has been e~tabli6hed between them.
As hereinbefore, the anode can be raised to the same potential as the grid, or to a positive potentlal compared with the latter, by ~eans oi a voltage supply 40, whilst the cathode 18 raised to a negative potential compared with the 8rid with the aid of a voltage supply 42, the grid being taken AS the reference potential and connected to earth.
Under these conditions, each micropoint 22 emits electrons, which pass through the hole corresponding to the mlcropoint in question and whose path is then curved ln the direction of the phosphor coating 34, 80 that the electrons strike the phosphor coating, whlch then emits light whlch can be observed through the transparent support 360 In a not shown varlant, the phosphor coating 34 i5 directly deposited on the insulating coating 44 and the conductive coating 39 is then deposited on the phosphor coating 34 and is cho6en 80 as to be transparent to the light emitted by said phosphor coating. In another variant dlagra~matically ~hown in Fig. 7, the electrically conductive coating 39 is eliminated snd the phosphor coating 34 is directly depo ited on the insulating coating 44, the phosphor coating then being chosen ~o as to be electrically conductive.
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In another vsriAnt diagrammatically ~hown in Fig. 8, the lnsulating coating 44 i8 eliminated Ind the phosphor coating 34 is directly deposited on grid coating 30 and i8 rsi~ed to the potential of th0 grid, the e~citntion of the elementary pattern then being carried out by raising the cathode to a negative potential compared with the grid by means of a voltage supply 46, the grld then being earthed.
In another variant diagrammatically shown in Fig. 9, the grid i~
eliminated and the phosphor coating 34, chosen 80 as to be electrically conductive, al80 serYes as the grid~ The cathode i8 then rsised to a negative potential compared with the phosphor costing, which i9 earthed.
In a special embodiment corresponding to the case where the snode and cathode are integrated on to the s~me 3ubstrate, an electrically conductive,transparent coating 48 (Fig. 7) i8 deposited on the face of the trAnsparent support 36 directly facing anode 20. This conductive, transparent support 48 can be left floating or can be rai~ed to a repulsive potential with respect to the electrons emitted by micropoints 22 by mean~ of a voltage supply 50 (Fig. 10).
Fig. 11 diagrammatically shows another embodiment of an elementary pattern, the only difference compared with the aforementioned embodiments and corresponding to the case where the anode, grid and cathode are integrated on to the same substrate is thaS the mlcropoints 22, observed from above the phosphor coating 34, do not appear to cover the complete coating 34. In the preaent case, they are brought together in the same region. More speclfically, in the embodiment of Fig. 11, the micropoints are locsted in the same region 64 on conductive coating 24, which is itself deposited on the insulating sub~trate 26. The in~ulatlng coating 28 i3 deposised on conductive coating 24, whilst aeparating the micro-point~ fro~ one another, a grid coating 30 having holes corresponding to the micropoinSs belng deposited on the in~ulating coating 28 and a phosphor coating 34 i8 depo~ited on the grid coating, except above the region in ~ ~216.3 PV
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which the micropoint~ are concentr~ted and 1~ rsi0ed to the 3ame potenti~l RS the grld (~9 explained ln the descrlptlon of Flg. 8).
A3 a vsrlant, it would be po~slble to deposit a perforated grid coating on the insulating coatlng 28, followed by another inaulating coating on the grid coating, except above said region 64 and finally an optionally composlte coating serving a~ the anode on said other insulatlng coating, the anode coating being con6tituted by an electrically conductive coating associated with a phosphor coating (as explained relative to Fig. 6), or simply an electrlcally conductive phosphor coating (as explained relative to Fig. 7).
According to another variant, it would be possible to deposlt on insulating coating 28 an electrically conductive pho6phor coating serving both as the snode ~nd the grid and perforated with holes corre~ponding to the micropolnts.
Obviously,the transparent support 36 is still positioned facing the anode and i3 optionally provided with a conductive coating, left floating or rai~ed to an 2ppropriate potential, as explained hereinbefore.
Fig. ~ diagra~matically ~hows 8 special embodiment of ~ dL6play unlt according to the invention in which case the elementary patterns ~re produced $n accordance wi~-h the description of Fig. 3, with possible variants de6cribed with reference to Figs. 4 and 5. Furthermore, the cathode~ are grouped in accordance with parallel rows 52 and ehey are formed on the same electrically insulAting substrate 26. MoreoYer, in each row, the cathodes are continuous, i.e. there ia no interruption on passing from one cathoda to another.
The grids are grouped along paraIlel columns 54, which are perpendicular to the rows 52. In each cGlumn, the grids are continuous, i.e. there ii3 no interruption between adjscent grids. The micropoints serve no useful ~ ' B 8216.3 PV
' ~: ' `-J.~2~9~
in any zone corresponding to a gap separating two column~.
Moreover, the anodes form a continuou~ sy~tem constltuted by a ~ingle phosphor coating 34 as~oclated, when lt 19 not electrically conducting, with a single electricfllly conducting coating 38, said two coatlngs being deposited on a single transparent support 36. The characteristic~ of costing 38 were explained in ehe description of Figs.
3 and 4, as a function of the sltuAtion of said coating. Thus, each elementary pattern 56 corresponds to the crossing of one row and one column.
The display unit shown in Fig. 12 al80 comprises electronic control means for effecting a matrix addressing of the rows and column~.
Such electronic means are known in the art, both in the case where it i~
wished to obtain stationary pictures and in the case where it i8 wi~hed to obtain moving pictures.
For each elementary pattern, field emission mainly occurs when a potential difference exceeding a positiYe threshold voltage Vs, is applied between the grid and the cathode of the pattern in question, the anode of the latter being raised to a potential at least equal to that of the grid.
In order to form stationary or moving pictures, the following operations are csrried out for the first row, then for the second and 90 on up to the final row. The row in question ls raised to potential -V/2,potential V
being equal to or higher thsn Vs and lower than 2Vs, whilst all the other rows are lPft iloating or are raised to a zero potential, which is carried out with the aid of fir~t means 58 forming part of the electronic means and in a simultaneous manner, all the columns corresponding to the elementary patterns to be excLted on the row in question are rai~ed to potential V/2, whil~t the other columns are left floating or raised to a ~ero potentisl, this being carried out with the aid of second means 60 fo~ning part of the electronic means, the anodes being con3tantly maintained :.~
B 8216.3 PV
`: :
, - 15 ~
at a potential at least equal to V/2 with the aid of ~n appropriate voltage 8upply 62.
It i~ also possible to produce a unit according to the invention by forming the elementary patterns in the manner described relative to Figs.
6 to 10. In this case, the rows are formed in the manner explained hereinbefore and the anodes, when they are electrically connected to the associated grids or when they act a~ grids, are arranged along the columns, the anodes of the same column not being separated.
When the anodes and grids are sepArated by insulatin~ coatings, all the anodes of the unit can be electrically interconnected.
It is then possible to use the same electronic matrix addressing means a8 those described hereinbefore. In this ca~e, when in eAch column the anodes have to be electrically insulated from the corresponding grids, said Anodes are constantly maintained and a potential at lesst equal to V/2.
Another special embodiment of the unit according to the invention is also shown in Fig. 11. This other embodiment comprises elementary patterns 61, in each of which the micropoints are grouped in the same region 64, as explained hereinbefore with reference to Fig. 11. The cathodes are grouped in parallel rows 52 and the anodes, when they are electrically connected to the associated grids or when they serve as grids, are thus grouped to~ether with any possible grids along columns 54 which are parallel to one another and perpendlcular to the rows, as explained ; hereinbefore. The crossing of a row and a column corresponds to ar.
elementary pattern, in the centre of which said region 64 is located. The display unit of Fig. 11 can be co~trolled in the same way as the unit described relati~e to Fi8. 12. Obviously, the insulating sub3trate 26 and the tran~parent support 36 are common to all the elementary patterns.
.::
~ 8216.3 PV
,~ :
~' .
'`'``' '.
- 16 _ ~ ~ 6 ~
When the anodes and the grids are seperated by insulAting coAtings, all the anode6 of the unit can be electrically interconnected.
The formation of micropoints 22 on a conductive coatlng 24 and separated by insulating coatings 28 is known in the Art and has been studied by Spindt at the Stanford Research In~titute (for applica~ions unrelated with visual di3plays). For producing the uni~s represented in Figs. ll and 12, known microelectronics procedures are used.
B 8216.3 PV
Claims (16)
1. A display unit comprising a plurality of elementary patterns, each pattern having an anode comprising a cathodoluminescent layer and a cathode able to emit electrons, each cathode comprising a plurality of electrically interconnected micropoints subject to an electron emission by field effect when the cathode is negatively polarized relative to the corresponding anode, each anode being integrated onto the corresponding cathode and being electrically insulated therefrom, said anode having openings opposite said micropoints, whereby electrons emitted by said micropoints first pass through said openings and thereafter return towards said cathodoluminescent layer and strike the latter around said openings.
2. A unit according to claim 1 further comprising a plurality of electrically conductive grids, respectively associated with the patterns, each grid being integrated onto the corresponding cathode, disposed between the latter and the corresponding anode, electrically insulated from said cathode and positively polarized with respect to the latter, and negatively polarized with respect to the anode or raised to the potential of the latter, and having holes opposite the micropoints.
3. A unit according to claim 1, wherein the projection of the surface occupied by the micropoints of each cathode on the surface occupied by the corresponding anode substantially coincides with the latter.
4. A unit according to claim 1, wherein the micropoints of each pattern are grouped into the same region separate from the active part of the anode.
5. A unit according to claim 2, wherein each grid is also electrically insulated from the corresponding anode, by an electrically insulating layer.
6. A unit according to claim 5, wherein each anode comprises an electrically conductive layer placed on the insulating layer and wherein said cathodoluminescent layer is placed on the conductive layer.
7. A unit according to claim 5, wherein said cathodoluminescent layer is placed on the insulating layer and wherein each anode also comprises an electrically conductive transparent layer placed on the cathodoluminescent layer.
8. A unit according to claim 1, wherein the said cathodoluminescent layer is also electrically conductive.
9. A unit according to claim 2, wherein each cathodoluminescent layer is brought to the potential of the corresponding grid or to a potential higher than that of said grid, the latter being positive.
10. A unit according to claim 1, wherein it also comprises a thin, transparent electrode, positioned facing the anodes on a transparent support.
11. A unit according to claim 2, wherein said cathodoluminescent layer is directly deposited on the corresponding grid and is raised to the potential of the grid, the excitation of the elementary pattern then being carried out by raising the cathode to a negative potential with respect to the grid, the grid being earthed.
12. A unit according to claim 1, wherein said cathodoluminescent layer is also electrically conductive, and also serves as a grid, the cathode being raised to a negative potential with respect to the cathodoluminescent layer which is earthed.
13. A unit according to claim 2, wherein the cathodes are grouped along parallel rows, the cathodes of the same row being electrically interconnected, wherein the grids are grouped along parallel columns and which are perpendicular to the rows, the grids of the same column being electrically interconnected and wherein the unit also comprises electronic control means for effecting a matrix addressing of the rows and columns.
14. A unit according to claim 8, wherein the cathodes are grouped along parallel rows, the cathodes of the same row being electrically interconnected, wherein the anodes are grouped along columns parallel to one another and perpendicular to the rows, the anodes of the same column also being electrically interconnected and wherein the unit also comprises electronic control means for effecting a matrix addressing of the rows and columns.
15. A unit according to claim 9, wherein the cathodes are grouped along parallel rows, the cathodes of the same row being electrically interconnected, wherein the anodes and the grids are grouped along parallel columns, which are perpendicular to the rows, the grids of the same column being electrically interconnected, the anodes of the same column also being electrically interconnected and wherein the unit also comprises electronic control means for effecting matrix addressing of the rows and columns.
16. A unit according to claim 2, wherein each anode comprises a coating of an electrically conductive, cathodoluminescent substance, wherein the cathodes are grouped along parallel rows, the cathodes of the same row being electrically connected, wherein the anodes and grids are grouped along columns parallel to one another and perpendicular to the rows, the grids of the same column being electrically interconnected, the anodes of the same column also being electrically interconnected, and wherein the unit also comprises electronic control means for effecting a matrix addressing of the rows and columns.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8411986A FR2568394B1 (en) | 1984-07-27 | 1984-07-27 | DEVICE FOR VIEWING BY CATHODOLUMINESCENCE EXCITED BY FIELD EMISSION |
| FR8411986 | 1984-07-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1261911A true CA1261911A (en) | 1989-09-26 |
Family
ID=9306574
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000487389A Expired CA1261911A (en) | 1984-07-27 | 1985-07-24 | Display unit by cathodoluminescence excited by field emission |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4908539A (en) |
| EP (1) | EP0172089B1 (en) |
| JP (1) | JPH0614263B2 (en) |
| CA (1) | CA1261911A (en) |
| DE (1) | DE3577774D1 (en) |
| FR (1) | FR2568394B1 (en) |
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-
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-
1985
- 1985-07-23 EP EP85401521A patent/EP0172089B1/en not_active Expired - Lifetime
- 1985-07-23 DE DE8585401521T patent/DE3577774D1/en not_active Expired - Lifetime
- 1985-07-24 CA CA000487389A patent/CA1261911A/en not_active Expired
- 1985-07-26 JP JP60165606A patent/JPH0614263B2/en not_active Expired - Fee Related
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1988
- 1988-03-24 US US07/177,880 patent/US4908539A/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5176557A (en) * | 1987-02-06 | 1993-01-05 | Canon Kabushiki Kaisha | Electron emission element and method of manufacturing the same |
| US5201681A (en) * | 1987-02-06 | 1993-04-13 | Canon Kabushiki Kaisha | Method of emitting electrons |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2568394A1 (en) | 1986-01-31 |
| DE3577774D1 (en) | 1990-06-21 |
| EP0172089A1 (en) | 1986-02-19 |
| JPH0614263B2 (en) | 1994-02-23 |
| EP0172089B1 (en) | 1990-05-16 |
| US4908539A (en) | 1990-03-13 |
| JPS61221783A (en) | 1986-10-02 |
| FR2568394B1 (en) | 1988-02-12 |
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