CA1117177A - Electrographic printing head - Google Patents
Electrographic printing headInfo
- Publication number
- CA1117177A CA1117177A CA000307429A CA307429A CA1117177A CA 1117177 A CA1117177 A CA 1117177A CA 000307429 A CA000307429 A CA 000307429A CA 307429 A CA307429 A CA 307429A CA 1117177 A CA1117177 A CA 1117177A
- Authority
- CA
- Canada
- Prior art keywords
- styli
- printing head
- electrographic printing
- electrographic
- head according
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/385—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material
- B41J2/39—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material using multi-stylus heads
- B41J2/395—Structure of multi-stylus heads
Landscapes
- Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
- Dot-Matrix Printers And Others (AREA)
- Electrophotography Using Other Than Carlson'S Method (AREA)
Abstract
ELECTROGRAPHIC PRINTING HEAD
Abstract of the Disclosure An electrographic printing head includes a plurality of stylii. Each stylus has a resistive and capacitive coupling for connection to two different drive circuits. A conductive plate is mounted at one or both sides of the stylii and contacts the recording medium. A circuit is provided to maintain the plate or plates at or near datum potential. The head at least in the region of the tips of the stylii preferably is formed of flexible material.
Abstract of the Disclosure An electrographic printing head includes a plurality of stylii. Each stylus has a resistive and capacitive coupling for connection to two different drive circuits. A conductive plate is mounted at one or both sides of the stylii and contacts the recording medium. A circuit is provided to maintain the plate or plates at or near datum potential. The head at least in the region of the tips of the stylii preferably is formed of flexible material.
Description
7~77 The :inventiotl relates to electrograr,hic prin-t:ing heads, in elec-trographic prin-ting heads i-t is usual to have a plurality of exposed styli and -to move a recor~ing medium past the exosed styli. 'rhe record medium is conventionally a conduc-tive material having a dielectrically coated sur~ce which is presentecl to the s-tyli as the record medium moves pastthe head. The head is responsive to input signals and arranged to select individual or groups O:e styli so as to form a sur~ace charge image on the recording medium, which image is later developed elsewhere in the printing system.
Considerable electrical energy is of-ten required to ensure that the relative potential between styli and record msdium is achieved to enable wri-ting by causing ionisation of the gap between -the styli and the medium so that the sur:Eace charge image can be formed.
, ' , In USA 3859960 for example, selected styli and a backing plate behlnd the record medium are energised simultaneously with signals of opposite polarity to enable writing. The backing plate and styli are energised by signals of opposite polarity, on the styli and plate, and a capacitlve coupling is formed witn the record medium to enable writing. It normally re~uired in practice, to avoid false writing, to energise groups of styli separated by groups oi non-energlsed styli, achieved by making sure adjacent backing pla-tes are not energised simultaneously.
:;
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In USA Patent 4,030,107 it is proposed to provide a stylus head in which each stylus is energised through a respective res:Lstive and capacitive coupling. The present invention relates to such a stylus head.
An electrographic printing heacl comprising an insulating substrate, a plurality of spaced apart conductive strips on the substrate, the tips of the conductive strips constitu-ting an array of electrographic styli, a resistive coupling section in each strip, for resistively coupling the styli to a first set of drive circuits, a dielectric layer over said strips adjacent their tips, a conductor over said dielectric layer for capacit-ively coupling the styli to a second set of drive circuits, a conductive plate mounted on the head on one or both sides of the stylus array for contacting a recording medium in use adjacent to the styli, and circuit means for maintaining the plate or plates at or near a datum potential.
.
~nbo~ n-ts of t'se :inrent:i.on ~/11'L no~/ oe de3c~i,0ed b~ ~/a,1~ o~ exe~le with ~s-~er~ncs i;o thr3 acco-Q~)an,rirlC~ ~ra~rinC~r~ :in uhicn:- , Fig~e 1 S'QOWS schema-tically the electrica:L co~r^.i~lratLon OI th~ head;
Figure 2 sho~s di~grr~m~atica~1~ a pl m vieYI of the head;
~igure 3 sho~rs a-side view of the head ta'~en throuO~h III-III of ~ig~re
Considerable electrical energy is of-ten required to ensure that the relative potential between styli and record msdium is achieved to enable wri-ting by causing ionisation of the gap between -the styli and the medium so that the sur:Eace charge image can be formed.
, ' , In USA 3859960 for example, selected styli and a backing plate behlnd the record medium are energised simultaneously with signals of opposite polarity to enable writing. The backing plate and styli are energised by signals of opposite polarity, on the styli and plate, and a capacitlve coupling is formed witn the record medium to enable writing. It normally re~uired in practice, to avoid false writing, to energise groups of styli separated by groups oi non-energlsed styli, achieved by making sure adjacent backing pla-tes are not energised simultaneously.
:;
~ .
In USA Patent 4,030,107 it is proposed to provide a stylus head in which each stylus is energised through a respective res:Lstive and capacitive coupling. The present invention relates to such a stylus head.
An electrographic printing heacl comprising an insulating substrate, a plurality of spaced apart conductive strips on the substrate, the tips of the conductive strips constitu-ting an array of electrographic styli, a resistive coupling section in each strip, for resistively coupling the styli to a first set of drive circuits, a dielectric layer over said strips adjacent their tips, a conductor over said dielectric layer for capacit-ively coupling the styli to a second set of drive circuits, a conductive plate mounted on the head on one or both sides of the stylus array for contacting a recording medium in use adjacent to the styli, and circuit means for maintaining the plate or plates at or near a datum potential.
.
~nbo~ n-ts of t'se :inrent:i.on ~/11'L no~/ oe de3c~i,0ed b~ ~/a,1~ o~ exe~le with ~s-~er~ncs i;o thr3 acco-Q~)an,rirlC~ ~ra~rinC~r~ :in uhicn:- , Fig~e 1 S'QOWS schema-tically the electrica:L co~r^.i~lratLon OI th~ head;
Figure 2 sho~s di~grr~m~atica~1~ a pl m vieYI of the head;
~igure 3 sho~rs a-side view of the head ta'~en throuO~h III-III of ~ig~re
2; and Figure ~ shows isometrically a bloc~ of material from 7~Thich the hs~d cc~ be formed.
, .
Refe~ring to the dra~ings, in Figure 1 a part o~ a styl~s arra~ iY sho~n~
Ihe styli 10 to 13 are each connected -tnrough raspective ~asisto~s 14 to 17 to di~ferent drive pulse supplies in 18 to 21. ~ne styli 10 is capacitively coupled by capacitor 22 to drive pulse sup~ly 2~ a~d the st~li 11 to 13 are all cap,~citively coupled by common capacitor 24 to drive p~llse supply 25. ~hus, each st~lus i9 conueclod to receive driva pulses from two rlifferent drive pulsc? supplies via a resistor a~d a capacitor respectively.
In use9 to.enable a stylus to write in one configuratio~ it is supplied in sequence with a first drive signal through its r~sisto~ and a . .
second drive signal of the same pol æ~lty throuO~h its capacitor. ~
-,the first signal is prsse-nt9 then on application of the secoud dxiv2 signal the voltage at the stylus is raised above the,Pasc~en brea'~dawn voltage so than an electrostatio char~e can be applied to,a rscord .
medium opposite that st~lus. One earthing plate 2~ is sho~.~ i~
gur2 2 ~hich contacts the record ~edium 27 (see FigQre 1) movin~
past the end Or the styli in use -to prevent the record mediu~ de~elop.~g an overall charge potential. In pr2ctice, in the configuration sho~.~n, e apply a negative potential o~ around 300 volts as ~he fir3-t drive ~-L7~1L77 SiC~nal. ~r~e SL'COn~l d~ e .r-,i~ aLso at a rL~r!;3.ti~re potsn~ial of c~o~md 300 ~rol-ts. I-t ~J.i.ll be appreciated. tha-t i~ onl~ s~i~2ar a firs-t; or seco~cl dri~e s,:irrnal is ap~lied alone to any st~lus, tha s-tylus voltage ~1111 not ~o belol.r about 300 volts in this ca~e, ~"hich is lress than the PaschQn bre~kdown ~roltage f'or the o~le con~iO~uratlo~, ~he "Pasahen breakdol~n volt~ge" is -the volta~e at which -ths insul~,io~
of` -the air brea~s do~n and an avalanche condition ensues allo~ g ions to flow from the st~lus to -ths recora madium. ~he breakdo7.~n voltzg3 varies with the sepA~ation of' s-ty1u3 and record medium and ambie~t oonditionQ but in the con~iguration of ~igura 1, i-t can be expaoted to .
be ~rou~d 450 volts.
' In the configuration above, writin~r is achieved by the applicatio~ o~
both drive signals. In another confic~lration ~7ri-tinO is ~rev2ntea by ~ach co~ditions a~d wri-ting ac~ieved by the a~sence of *he firs~
drive si~nal. In this other configuration the threshold is set ~cr example at around -200 volts for the s-tyli and the first dri~e signal arrr~nged to be at +250 vGlts, say. ~hus; on the applicatlon o~ the first drive signal the potential o~ the stylus rises to around +~50 volts so that the result of applyi~g the second drive signal is to reduce ths potsntial of the stylus to near zero volts^ ~o~ever, in the absence o~ the first drive signal, tke second drive signal cause~ the potential of ths stylus to drop -to -250 volts, so that as the Paschen voltage level is -200 volts~in this case writing occurs It will be noted that this latter Paschen voltage level can be achieved by movi~
the record medium closer to the stylus than before if possible ~ ~Qr ma~ntaininO~ the surfaoe of the record medium at a hon-zero da~u~ voltage level, of around say +200 volts in thls case.
' .
. .
' , .
,' ' ' ' ' ' . . .
1~17~77 It ~'/i1.1 be ~Ipp:L~ecLatod that o'~her d-r.ive slgTIal co~m'bination~ Cer~ ~e used to con-tro'L the ~ite a~La non-~rrite condit;:ion~ o the styli and that the datum voltage of the r~cord M~dium adju~ted ac req~ ed~
'Ho-,reve~, in.each case ;the st~li a~:e driven by the a~plicati~n or no~
application of a first sig~l~l ap~lied to -tho resistive couplin~ 1r'nich is th~x iollo~2d by ths application of' a second drive sig~al to ~he capacitor couplingr. m e sequence oP a.pplication of fl~st and second drive signal~ is controlled by conven-tional logic circuit Laans.
It will be noted that the choices of the ~alues of the resi~ti7re (~) and capaciti7re couplings (C) represe~t a compromise. 0~ applicatio~
o.f the first si~nal a ~i~ite t.ume rise (or fall as the'case ma7~ be) cal 7~e reduced if the -time constant OL the ~C cil~cuit is kept low enabling the second signal to be applied very soon after the application - of the first signal. Hotre~er, if the -tiDe cons-t-~nt is low, on ap~lioation of -the seco~d signal, the voltage pulse at the end of the S~ylU9 ca-lsed by the second signal will then be ver~ narrow thus causLn~ a ve~y brief . '-voltage excursion through -the Paschen b~eakdot~l le~el. ~y contra3t, if the time constant is higher, this Pasche~ voltage eXcux3ion is - longer but the seco~d dri-~e sigr~l must be dela~ed somel~hat after ' -the applicatio~s o~ th9 first signal to allo~ the stylus poténtial '-caused thereby to rise or fall to the first sig~al level. In pr2ctice in one arrangeme~t, we usa a resistance value of 200~ ohms approxi3a-tely ' . and a capacitive value of 15 picofarads approximately. ~ -' ' , ' : ~
In Figure 2 ~na 3, the st~li 10 to 14 are foxmed of copper plating '~-mounted on a substrate 30. ~ne resistors 14 to 17 are formed o~
resistance ~atexial doped resin mo~nted on the substrate 309 ~he capacitors 22 and 24 are provided by a thin epo~y re3in shaet fi~ced on co t,h~ t~-Lu~ cld and d.ic:~:cete OOppf3~ p'l~,ts~ o:c p1.a-tir~-0 mount~3d on thf~ ~esin shee-t.
A second ro~r of' st~li c~e shown Pi~ed to a second su'osGrats ~-l cu~d ~orfn :Ln e~Iec-t z mirror im~e o~' the first ro~,r of st~li. Tha seco~a row o~ st~li are ho~.~ever stag~ered wlth re~pect -to the firs-t row of st~li to increase -the lines per inch of ~lriti~Or, as is kno~Q in o~'~r styli hezd proposal~ ana to fill in g.~ps bet~.~een styli o~' th~ previous rows -to improve print quali-ty. End pla-tes 26 are provided a-t eao~
side o~ the pai~ of st~lus array~. In practi,ca these end platas are , , '-u~ually',,~earthed and e~g~ the surface o~ -the record IQsdium du~ing printing.
.
Tha method of makinO~ each stylus array of the electro~raphic pri~ti~æ
head is a~ follo~,rs:-:, ~ ' . - ' , :
A substrate of Kap-ton (trada ma~) which is clad l~ith 18 micron coppsr plate is dippsd into Koaik (trade mark) printed circuit liquid resist. .
ne~ative is placad against t,he coppsr pla-ting ~or exposur.e and '' .
- developm~nt. .~tchinO~ llquid is then usad to etch awa~ the copper ,, .
. ~rhere the lio~ht did;not fall to produce the co~'ig~raGlo~ shown in ure-4.
.
:: : ' , : ' . , .
The Capa~GorS are the~ fo~med~by twice dippinO~ in pol~amide~imide eg, - X~ODEFTAL 200 (trade mark), d~ between tha dippmO~ to for~ c~ -dielectric ooating. ~ne~ coatinO~ is cured `ib~ hea-Gin~ to.arou~d 250C.
~ ~ copper coa~in~ is then added to the dialectric by alectroless platin2 . and inall~ Sepa~aGiOn to form discrete plate~ (such as 22 and 24 ': Fig 2) is achieved by pho-to etchin~
:: - .
,,, , , , , ,,, ,, _ . . . . .. .. . . . . .. . . . . . . .
' ' ' ' 7~77 !
~rO fo~n tne res~;tc~:r~;, cL O.O~r)1" I;hi.ck l.aLIinat.i.or~ of RIS'COiT ~trQde m~r~ prsssHcl on to thr t;urfacr~ of thr~ st~ s ~rr,~ ~tl31~irlg 5~t~9 -to li~.a up ~r-t ~lo:rl.~ orl-the la~lnate to for~L tfLe s-t~Li and ths supply lines. 'I'he arr~fLgemr~n t i5 then e~pos~3d and de~elop~d to r or~t cha~Lels in the lamina-te extending be-t~tearl xesp~c-t:~vs st~li &nd su~ply lines. 'The chc~rLtsl3 are thc-?n filled wi-th colloidr~l graphil.e a~.td the surir-ces of the chrn~els mackLined to remoJ2 rmy surplus ~rz~hite.
~ additional step oan be provide~ to increase ths size of the 3t-jli tips whic~ user~ a further RISrrON lc~miQate. qrnis addi-tional s-teD, wh~c~
could be c~rrled ou-t simul-t3nsou~1y wl-th the ~or~in~.o the re~i~tors, involves lami~atinO~ a RIST0~ sheet over the styli tips, zlig~in~ the art wor~ ~ith styl~ -tips. ~h~nels which are fo~mod over the styli by exposure and develop~ent, ~re then fillea with coppsr. ~ this ~ay the styli ends can be increasea rom 18 microns to arolm d 125 micro~s, say.
. . . .
~ereas copper platin~ and styli tips ar~ used the above ma~hod ca~
. be carried out using other conductive materials such as nic~el~
It will be appreciated that the styli arrays described herein are ` ~ re~uirea to be joined together and aligned into subst2ntia7 a ~ ay~
.
generally extendinO~ the ~ridth of a page or document. ~s such several . . , tech~iques whick m~y i~clude ~urther coa-tinO~ and etchinO~ of the substra-tes are required to enable group~ and selections of O~roups and individual styii -to be ener~ised during printinO~ operatio of tha electrographic head. lhe present invention ls not concernaa wit~ the formulation of the o~erall styli array connections and reS~scti~e commoni~g and logic control of various group~ of drive circuit arr3~sman~s for electroO~raphic heads.
~73~77 'l`he me thod Or f'Or~ (J tile eloctrog~ar~t~ head may :Lnclude encapsula-~:ion in ~po.~y res:i.rl o.E at l~a~t part of t~le head described. In one arrangemen-t, ho-~,ever, -the head in the reuion of -the s-tyli -tips at least is dellbera-tel.y Made ~le~Yible ancl in use the heacl is arranged to pres~ agains-t the record medium. In the arrangement -the plane o:~ -the head is positioned at an angle to the normal to the medium, say around 45 -to the normal, but other angles between 0 and 60 can also be used.
For example, we iabrica-te copper stylus electrodes, possibly plated with a harder material, eg nickel, on a ~lexible substrate eg, polyimide, with an additional layer o~ resilient mat~rial, - eg, beryllium copper on the back to provide an even ~ressure .
and to overcome any tendency oi the substra-te ma-terial to creep or retain a s~t.
.:
: , :
.
:: .
: :
' .
~,
, .
Refe~ring to the dra~ings, in Figure 1 a part o~ a styl~s arra~ iY sho~n~
Ihe styli 10 to 13 are each connected -tnrough raspective ~asisto~s 14 to 17 to di~ferent drive pulse supplies in 18 to 21. ~ne styli 10 is capacitively coupled by capacitor 22 to drive pulse sup~ly 2~ a~d the st~li 11 to 13 are all cap,~citively coupled by common capacitor 24 to drive p~llse supply 25. ~hus, each st~lus i9 conueclod to receive driva pulses from two rlifferent drive pulsc? supplies via a resistor a~d a capacitor respectively.
In use9 to.enable a stylus to write in one configuratio~ it is supplied in sequence with a first drive signal through its r~sisto~ and a . .
second drive signal of the same pol æ~lty throuO~h its capacitor. ~
-,the first signal is prsse-nt9 then on application of the secoud dxiv2 signal the voltage at the stylus is raised above the,Pasc~en brea'~dawn voltage so than an electrostatio char~e can be applied to,a rscord .
medium opposite that st~lus. One earthing plate 2~ is sho~.~ i~
gur2 2 ~hich contacts the record ~edium 27 (see FigQre 1) movin~
past the end Or the styli in use -to prevent the record mediu~ de~elop.~g an overall charge potential. In pr2ctice, in the configuration sho~.~n, e apply a negative potential o~ around 300 volts as ~he fir3-t drive ~-L7~1L77 SiC~nal. ~r~e SL'COn~l d~ e .r-,i~ aLso at a rL~r!;3.ti~re potsn~ial of c~o~md 300 ~rol-ts. I-t ~J.i.ll be appreciated. tha-t i~ onl~ s~i~2ar a firs-t; or seco~cl dri~e s,:irrnal is ap~lied alone to any st~lus, tha s-tylus voltage ~1111 not ~o belol.r about 300 volts in this ca~e, ~"hich is lress than the PaschQn bre~kdown ~roltage f'or the o~le con~iO~uratlo~, ~he "Pasahen breakdol~n volt~ge" is -the volta~e at which -ths insul~,io~
of` -the air brea~s do~n and an avalanche condition ensues allo~ g ions to flow from the st~lus to -ths recora madium. ~he breakdo7.~n voltzg3 varies with the sepA~ation of' s-ty1u3 and record medium and ambie~t oonditionQ but in the con~iguration of ~igura 1, i-t can be expaoted to .
be ~rou~d 450 volts.
' In the configuration above, writin~r is achieved by the applicatio~ o~
both drive signals. In another confic~lration ~7ri-tinO is ~rev2ntea by ~ach co~ditions a~d wri-ting ac~ieved by the a~sence of *he firs~
drive si~nal. In this other configuration the threshold is set ~cr example at around -200 volts for the s-tyli and the first dri~e signal arrr~nged to be at +250 vGlts, say. ~hus; on the applicatlon o~ the first drive signal the potential o~ the stylus rises to around +~50 volts so that the result of applyi~g the second drive signal is to reduce ths potsntial of the stylus to near zero volts^ ~o~ever, in the absence o~ the first drive signal, tke second drive signal cause~ the potential of ths stylus to drop -to -250 volts, so that as the Paschen voltage level is -200 volts~in this case writing occurs It will be noted that this latter Paschen voltage level can be achieved by movi~
the record medium closer to the stylus than before if possible ~ ~Qr ma~ntaininO~ the surfaoe of the record medium at a hon-zero da~u~ voltage level, of around say +200 volts in thls case.
' .
. .
' , .
,' ' ' ' ' ' . . .
1~17~77 It ~'/i1.1 be ~Ipp:L~ecLatod that o'~her d-r.ive slgTIal co~m'bination~ Cer~ ~e used to con-tro'L the ~ite a~La non-~rrite condit;:ion~ o the styli and that the datum voltage of the r~cord M~dium adju~ted ac req~ ed~
'Ho-,reve~, in.each case ;the st~li a~:e driven by the a~plicati~n or no~
application of a first sig~l~l ap~lied to -tho resistive couplin~ 1r'nich is th~x iollo~2d by ths application of' a second drive sig~al to ~he capacitor couplingr. m e sequence oP a.pplication of fl~st and second drive signal~ is controlled by conven-tional logic circuit Laans.
It will be noted that the choices of the ~alues of the resi~ti7re (~) and capaciti7re couplings (C) represe~t a compromise. 0~ applicatio~
o.f the first si~nal a ~i~ite t.ume rise (or fall as the'case ma7~ be) cal 7~e reduced if the -time constant OL the ~C cil~cuit is kept low enabling the second signal to be applied very soon after the application - of the first signal. Hotre~er, if the -tiDe cons-t-~nt is low, on ap~lioation of -the seco~d signal, the voltage pulse at the end of the S~ylU9 ca-lsed by the second signal will then be ver~ narrow thus causLn~ a ve~y brief . '-voltage excursion through -the Paschen b~eakdot~l le~el. ~y contra3t, if the time constant is higher, this Pasche~ voltage eXcux3ion is - longer but the seco~d dri-~e sigr~l must be dela~ed somel~hat after ' -the applicatio~s o~ th9 first signal to allo~ the stylus poténtial '-caused thereby to rise or fall to the first sig~al level. In pr2ctice in one arrangeme~t, we usa a resistance value of 200~ ohms approxi3a-tely ' . and a capacitive value of 15 picofarads approximately. ~ -' ' , ' : ~
In Figure 2 ~na 3, the st~li 10 to 14 are foxmed of copper plating '~-mounted on a substrate 30. ~ne resistors 14 to 17 are formed o~
resistance ~atexial doped resin mo~nted on the substrate 309 ~he capacitors 22 and 24 are provided by a thin epo~y re3in shaet fi~ced on co t,h~ t~-Lu~ cld and d.ic:~:cete OOppf3~ p'l~,ts~ o:c p1.a-tir~-0 mount~3d on thf~ ~esin shee-t.
A second ro~r of' st~li c~e shown Pi~ed to a second su'osGrats ~-l cu~d ~orfn :Ln e~Iec-t z mirror im~e o~' the first ro~,r of st~li. Tha seco~a row o~ st~li are ho~.~ever stag~ered wlth re~pect -to the firs-t row of st~li to increase -the lines per inch of ~lriti~Or, as is kno~Q in o~'~r styli hezd proposal~ ana to fill in g.~ps bet~.~een styli o~' th~ previous rows -to improve print quali-ty. End pla-tes 26 are provided a-t eao~
side o~ the pai~ of st~lus array~. In practi,ca these end platas are , , '-u~ually',,~earthed and e~g~ the surface o~ -the record IQsdium du~ing printing.
.
Tha method of makinO~ each stylus array of the electro~raphic pri~ti~æ
head is a~ follo~,rs:-:, ~ ' . - ' , :
A substrate of Kap-ton (trada ma~) which is clad l~ith 18 micron coppsr plate is dippsd into Koaik (trade mark) printed circuit liquid resist. .
ne~ative is placad against t,he coppsr pla-ting ~or exposur.e and '' .
- developm~nt. .~tchinO~ llquid is then usad to etch awa~ the copper ,, .
. ~rhere the lio~ht did;not fall to produce the co~'ig~raGlo~ shown in ure-4.
.
:: : ' , : ' . , .
The Capa~GorS are the~ fo~med~by twice dippinO~ in pol~amide~imide eg, - X~ODEFTAL 200 (trade mark), d~ between tha dippmO~ to for~ c~ -dielectric ooating. ~ne~ coatinO~ is cured `ib~ hea-Gin~ to.arou~d 250C.
~ ~ copper coa~in~ is then added to the dialectric by alectroless platin2 . and inall~ Sepa~aGiOn to form discrete plate~ (such as 22 and 24 ': Fig 2) is achieved by pho-to etchin~
:: - .
,,, , , , , ,,, ,, _ . . . . .. .. . . . . .. . . . . . . .
' ' ' ' 7~77 !
~rO fo~n tne res~;tc~:r~;, cL O.O~r)1" I;hi.ck l.aLIinat.i.or~ of RIS'COiT ~trQde m~r~ prsssHcl on to thr t;urfacr~ of thr~ st~ s ~rr,~ ~tl31~irlg 5~t~9 -to li~.a up ~r-t ~lo:rl.~ orl-the la~lnate to for~L tfLe s-t~Li and ths supply lines. 'I'he arr~fLgemr~n t i5 then e~pos~3d and de~elop~d to r or~t cha~Lels in the lamina-te extending be-t~tearl xesp~c-t:~vs st~li &nd su~ply lines. 'The chc~rLtsl3 are thc-?n filled wi-th colloidr~l graphil.e a~.td the surir-ces of the chrn~els mackLined to remoJ2 rmy surplus ~rz~hite.
~ additional step oan be provide~ to increase ths size of the 3t-jli tips whic~ user~ a further RISrrON lc~miQate. qrnis addi-tional s-teD, wh~c~
could be c~rrled ou-t simul-t3nsou~1y wl-th the ~or~in~.o the re~i~tors, involves lami~atinO~ a RIST0~ sheet over the styli tips, zlig~in~ the art wor~ ~ith styl~ -tips. ~h~nels which are fo~mod over the styli by exposure and develop~ent, ~re then fillea with coppsr. ~ this ~ay the styli ends can be increasea rom 18 microns to arolm d 125 micro~s, say.
. . . .
~ereas copper platin~ and styli tips ar~ used the above ma~hod ca~
. be carried out using other conductive materials such as nic~el~
It will be appreciated that the styli arrays described herein are ` ~ re~uirea to be joined together and aligned into subst2ntia7 a ~ ay~
.
generally extendinO~ the ~ridth of a page or document. ~s such several . . , tech~iques whick m~y i~clude ~urther coa-tinO~ and etchinO~ of the substra-tes are required to enable group~ and selections of O~roups and individual styii -to be ener~ised during printinO~ operatio of tha electrographic head. lhe present invention ls not concernaa wit~ the formulation of the o~erall styli array connections and reS~scti~e commoni~g and logic control of various group~ of drive circuit arr3~sman~s for electroO~raphic heads.
~73~77 'l`he me thod Or f'Or~ (J tile eloctrog~ar~t~ head may :Lnclude encapsula-~:ion in ~po.~y res:i.rl o.E at l~a~t part of t~le head described. In one arrangemen-t, ho-~,ever, -the head in the reuion of -the s-tyli -tips at least is dellbera-tel.y Made ~le~Yible ancl in use the heacl is arranged to pres~ agains-t the record medium. In the arrangement -the plane o:~ -the head is positioned at an angle to the normal to the medium, say around 45 -to the normal, but other angles between 0 and 60 can also be used.
For example, we iabrica-te copper stylus electrodes, possibly plated with a harder material, eg nickel, on a ~lexible substrate eg, polyimide, with an additional layer o~ resilient mat~rial, - eg, beryllium copper on the back to provide an even ~ressure .
and to overcome any tendency oi the substra-te ma-terial to creep or retain a s~t.
.:
: , :
.
:: .
: :
' .
~,
Claims (5)
1. An electrographic printing head comprising an insulating substrate, a plurality of spaced apart conductive strips on the substrate, the tips of the conductive strips constituting an array of electrographic styli, a resistive coupling section in each strip, for resistively coupling the styli to a first set of drive circuits, a dielectric layer over said strips ajacent their tips, a conductor over said dielectric layer for capacitively coupling the styli to a second set of drive circuits, a conductive plate mounted on the head on one or both sides of the stylus array for contacting a recording medium in use adjacent to the styli, and circuit means for maintaining the plate or plates at or near a datum potential.
2. An electrographic printing head according to claim 1 wherein the head in at least the region of the styli is formed of flexible materials.
3. An electrographic printing head according to claim 1, in which said styli arearranged in mutually spaced rows of styli, successive styli within each row being spaced from one another, and the styli of successive rows being staggered with respect to one another.
4. An electrographic printing head according to any one of claims 1 to 3 in which said resistive coupling comprises resin impregnated with conductive material.
5. An electrographic printing apparatus including a printing head according to any one of claims 1 to 3, and logic circuit means arranged to connect the respective drive circuits such that the resistive couplings are connected before the capacitive couplings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB30819 | 1977-07-22 | ||
| GB3081977A GB1559641A (en) | 1977-07-22 | 1977-07-22 | Electrographic printing head |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117177A true CA1117177A (en) | 1982-01-26 |
Family
ID=10313646
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000307429A Expired CA1117177A (en) | 1977-07-22 | 1978-07-14 | Electrographic printing head |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5423532A (en) |
| CA (1) | CA1117177A (en) |
| DE (1) | DE2831389A1 (en) |
| GB (1) | GB1559641A (en) |
| NL (1) | NL7807681A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4766450A (en) * | 1987-07-17 | 1988-08-23 | Xerox Corporation | Charging deposition control in electrographic thin film writting head |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3611419A (en) * | 1969-04-02 | 1971-10-05 | Clevite Corp | Electrographic imaging system and heads therefor |
| US3626422A (en) * | 1969-07-28 | 1971-12-07 | Varian Associates | Electrographic-writing head having a preponderance of conductive portions engaging the recording medium |
| JPS5415414B2 (en) * | 1974-11-15 | 1979-06-14 |
-
1977
- 1977-07-22 GB GB3081977A patent/GB1559641A/en not_active Expired
-
1978
- 1978-07-14 JP JP8597378A patent/JPS5423532A/en active Pending
- 1978-07-14 CA CA000307429A patent/CA1117177A/en not_active Expired
- 1978-07-17 DE DE19782831389 patent/DE2831389A1/en not_active Ceased
- 1978-07-18 NL NL7807681A patent/NL7807681A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| GB1559641A (en) | 1980-01-23 |
| DE2831389A1 (en) | 1979-02-08 |
| JPS5423532A (en) | 1979-02-22 |
| NL7807681A (en) | 1979-01-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |