EP0099430B1 - Elastische druckempfindliche leitende Platte und Verfahren zu deren Herstellung - Google Patents

Elastische druckempfindliche leitende Platte und Verfahren zu deren Herstellung Download PDF

Info

Publication number
EP0099430B1
EP0099430B1 EP82303786A EP82303786A EP0099430B1 EP 0099430 B1 EP0099430 B1 EP 0099430B1 EP 82303786 A EP82303786 A EP 82303786A EP 82303786 A EP82303786 A EP 82303786A EP 0099430 B1 EP0099430 B1 EP 0099430B1
Authority
EP
European Patent Office
Prior art keywords
particles
sheet
pressure
coarse
microns
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
Application number
EP82303786A
Other languages
English (en)
French (fr)
Other versions
EP0099430A1 (de
Inventor
Eiichi Ikeda
Masahiro Izaki
Ikuo Kayama
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oki Electric Cable Co Ltd
Original Assignee
Oki Electric Cable Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Oki Electric Cable Co Ltd filed Critical Oki Electric Cable Co Ltd
Priority to EP82303786A priority Critical patent/EP0099430B1/de
Priority to DE8282303786T priority patent/DE3273854D1/de
Publication of EP0099430A1 publication Critical patent/EP0099430A1/de
Application granted granted Critical
Publication of EP0099430B1 publication Critical patent/EP0099430B1/de
Expired legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys

Definitions

  • the present invention relates generally to a pressure-sensitive, conductive elastic sheet and particularly to a pressure-sensitive, conductive elastic sheet sandwiched between a pair of flat electrode plates, each having a group of straight strip electrodes which is used as a graphics digitizing tablet through which various letters or figures can be detected two-dimensionally by a character reader.
  • Pressure-sensitive, conductive elastic sheets are well-known. Elastic sheets of this kind are usually used in graphics digitizing tablets, which detect various letters or figures written thereon with a pen or the like. Such sheets are sandwiched between a pair of flat electrode plates provided with a group of straight strip electrodes in such a way that the strip electrodes on one flat electrode plate intersect those on the other flat electrode plate to form a matrix of points.
  • graphics digitizing tablet when pressure is applied to the pressure-sensitive conductive sheet via the upper and lower flat electrode plates, the conductive sheet makes electrical contact at points where pressure is applied by a pen and the contact points are digitized by the two perpendicular strip electrodes on the basis of co-ordinates.
  • the surface area of the tablet on which letters or figures are written is relatively large, ranging from 100 mm square to 400 mm square. Accordingly, when some letters or figures are written on the tablet with a pen held in the user's hand, the heel of user's hand or the user's forearm inevitably depresses the surface of the tablet, with the result that erroneous operation often occurs in detecting the letters or figures.
  • contact pressure under which some of the upper strip electrodes are connected electrically to some of the lower strip electrodes
  • the upper and lower strip electrodes are easily connected electrically when light pressure is applied over a large conduction area on the tablet.
  • a pen is placed onto the tablet to write some letters, since the contact area is small, a relatively great contact pressure is needed to connect the upper and lower strip electrodes; on the other hand when the heel of the user's hand or the user's forearm is placed on the tablet, since the contact area is large, a relatively small contact pressure easily connects the upper and lower strip electrodes, thus resulting in erroneous operation.
  • a pressure-sensitive conductive sheet is also known from French Patent No. 2357040.
  • the pressure-sensitive conductive sheet comprises an insulating elastomer containing from 3 to 40 percent by volume of electrically conductive magnetic particles, which particles are dispersed in the elastomer in preselected patterns so that high-sensitivity pressure sensitive conductor portions and low-sensitivity pressure sensitive conductor portions are both present therein.
  • the method of forming the sheet comprises the steps of mixing the magnetic particles with the liquid elastomer, applying a magnetic field and allowing the liquid elastomer to solidify.
  • the pressure-sensitive, conductive elastic sheet according to the present invention comprises a great number of ferromagnetic conductive particles aligned in an elastomer in a direction perpendicular to the plane of the sheet through the interior thereof, characterised in that:-
  • the invention also provides methods of forming the pressure-sensitive conductive elastic sheet.
  • the sheet is formed by:
  • the sheet is formed by:
  • pressure-sensitive, conductive elastic sheets are used for graphics digitizing tablets which can detect various letters and figures written thereon with a pen or the like on the basis of rectangular co-ordinates and input the detected signals indicative of the co-ordinates to a character reader.
  • Fig. 1 shows the structure of a typical graphic digitizing tablet.
  • reference numeral 1 denotes a tablet frame
  • reference numeral 2 denotes an outer flat electrode plate provided with a number of horizontally aligned strip electrodes
  • reference numeral 3 denotes an inner flat electrode plate provided with a number of vertically aligned strip electrodes
  • reference numeral 4 denotes a pressure-sensitive, conductive elastic sheet interposed between the outer and inner flat electrode plates.
  • the graphics digitizing tablet thus constructed is often as big as 500 mm square. Accordingly, while the user writes letters or figures on the tablet, the heel of the user's hand 6 or the user's forearm 7 inevitably applies pressure to the surface of outer flat electrode plate 2, so that an unintentional position is detected and thereby erroneous operation often occurs.
  • Fig. 2 shows the relationships between conductivity and pressure applied to the tablet of a prior-art pressure-sensitive, conductive elastic . sheet.
  • a pen when pressure applied to the sheet by a pen reaches a value PA, the conductivity of the sheet rises abruptly from insulative to conductive as designated by curve A.
  • the conductivity of the sheet rises abruptly from insulative to conductive at a value P B less than P A as designated by curve B. That is to say, the greater the contact area, the higher the pressure sensitivity of the conductive sheet.
  • the contact pressure P A is approximately 50 p/mm 2 when the contact area is 1 mm 2 ; however, the contact pressure P B is approximately 25 p/mm 2 when the contact area is 50 mm 2 . That is to say, if the area of the heel of the user's hand is 50 times larger than that of a pen, erroneous input occurs when approximately half of the pen pressure is applied to the pressure-sensitive sheet.
  • the conductive elastic sheet conventionally includes conductive metal particles uniformly dispersed in a rubber material microscopically spaced from each other. Therefore, when pressure is applied to the sheet, since the rubber material is compressed and deformed, particles are brought into contact with other particles at the point where pressure is applied. Since the conductive metal particles dispersed on the surface of the sheet are in contact with the strip electrodes of the outer and inner flat electrode plates when pressure is applied to the surface of the sheet, the two electrode plates are brought into contact with each other via the pressure-sensitive elastic sheet.
  • the increase in pressure sensitivity with respect to increasing contact area may be caused by other complicated factors in combination with the above-mentioned reasons; however, it is possible to simply consider that the greater the variations in different conduction factors, the higher the probability of contact between metal particles. In other words, the greater the variation in various conduction factors, the greater the number of points with a relatively low contact pressure.
  • Fig. 3 shows the microscopic structure of the conductive sheet.
  • reference numeral 10 denotes liquid elastomer such as silicon rubber
  • reference numeral 11 denotes coarse, ferromagnetic, conductive metal particles
  • reference numeral 12 denotes fine, ferromagnetic, conductive metal particles.
  • the material of both the coarse and fine particles is ferrite or carbonic nickel.
  • the average diameter of the coarse, ferromagnetic, metal particles 11 ranges from 30 to 150 microns (um); the average diameter of the fine, ferromagnetic, metal particles is less than 50 microns (pm).
  • the mixture ratio by weight of the coarse particles to the fine particles is from 1:1 to 1:0.1 in the case where the fine particles with a diameter of about 10 micron (pm) or less are used and is about 1:2 to 1:5 in the case where the fine particles with a diameter of about 50 micron (pm) or less are used.
  • the mixture ratio by weight of the elastomer to the combined coarse and fine particles is from 1:0.5 to 1:0.8.
  • the coarse metal particles are mixed with a liquid elastomer; secondly, the mixed material is allowed to solidify into an inner sheet within a uniform magnetic field; thirdly, the fine particles are mixed with another liquid elastomer; fourthly, the liquid elastomer including fine ferromagnetic conductive metal particles is laminated onto both of the surfaces of the inner sheet in such a way that the thickness of the outer laminated elastomer is less than that of the inner sheet.
  • the coarse particles are coated with a low-molecular-weight elastomer; secondly, the coated coarse particles are mixed with the fine particles in a liquid elastomer; thirdly, the mixed coarse and fine particles are allowed to set within a uniform magnetic field for a predetermined time period.
  • the differences in sedimentation velocity and agglutination rate between the coarse and fine particles ensure formation of a conductive sheet in which the fine particles are concentrated on one surface thereof.
  • the application of the uniform magnetic field to the particle-elastomer mixture during setting causes the coarse metal particles to align vertically through the sheet, as shown in Fig. 3.
  • the inner sheet is much more pressure-sensitive than if the coarse particles were randomly distributed. This allows suitable pressure-sensitivity without the damaging effects of excessive particle content.
  • the choices of the diameters of the coarse and fine ferromagnetic metal particles and the mixture ratios of the coarse and fine ferromagnetic metal particles and elastomer are very important in order to obtain optimal relationships between the contact pressure and contact area.
  • the mixture ratio R m of the coarse to fine ferromagnetic metal particles has a great influence upon the characteristics between contact pressure and contact area. The smaller the mixture ratio R M , the greater the contact pressure with respect to a constant contact area.
  • Fig. 4 shows exemplary relationships between contact pressure and contact area.
  • the curve A traces the characteristics obtained when the mixture ratio R m of the coarse to fine ferromagnetic metal particles is 1:0, that is, when there are no fine particles, which are almost the same as those of a prior-art pressure sensitive conductive sheet illustrated by curve D.
  • the curve B shows the characteristics obtained when the mixture ratio R m of coarse to fine ferromagnetic metal particles is 1:0.1 in the case where the fine ferromagnetic metal particles with a diameter of 10 micron (pm) or less are used or when the R. is 1:2 in the case where the fine particles of 50 micron ( ⁇ m) or less are used.
  • the curve C shows the characteristics obtained when the mixture ratio R M of coarse to fine ferromagnetic metal particles is 1:0.4 in the case where the fine ferromagnetic metal particles with a diameter of 50 micron ( ⁇ m) or less are used or when the R M is 1:4 in the case where the fine particles of 50 micron (pm) or less are used.
  • the conductive sheet according to the present invention since the variations in various conduction factors are small, a more uniform pressure is required to make the sheet conductive. Furthermore, since the hardness of the sheet surface is high, a relatively high pressure is required to make a large conduction area conductive.
  • the tablet can detect contact when a letter is written with a ballpoint pen (small contact area of 10 mm 2 or less), but cannot detect pressure due to contact with the heel of user's hand or the user's forearm (large contact area).
  • the elasticity of the sheet is almost the asme as in the prior-art rubber conductive sheet, because the fine ferromagnetic metal particles are concentrated near the surface of the sheet and the coarse ferromagnetic metal particles are arranged in the interior of the sheet.
  • the coarse ferromagnetic metal particles and the fine ferromagnetic metal particles are first mixed at a predetermined ratio and next mixed with liquid elastomer and since the elastomer including the particles is formed into a sheet within a uniform magnetic field, the coarse ferromagnetic metal particles can be aligned in the direction perpendicular to the plane of the sheet and additionally the fine ferromagnetic metal particles can be dispersed near one surface or near both surfaces of the conductive sheet. Therefore, it is possible to provide a pressure-sensitive, conductive elastic sheet in which the contact pressure is constant irrespective of the contact area or the contact pressure increases with increasing contact area.
  • the pressure-sensitive, conductive- elastic sheet is applied to a graphics digitizing tablet through which various letters or figures can be detected by a character reader, it is possible to provide a tablet which is sensitive only to, for instance, a pencil or a ballpoint pen with a small contact area and not sensitive to, for instance, the heel of the user's hand or the user's forearm, which have a large contact area.

Landscapes

  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Non-Insulated Conductors (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Claims (6)

1. Druckempfindliche leitende elastische Schicht (4), die eine große Anzahl von ferromagnetischen leitenden Teilchen (11) umfaßt, die in einem Elastomer (10) in einer Richtung senkrecht zur Ebene der Schicht durch deren Inneren ausgerichtet sind, dadurch gekennzeichnet:
daß die Teilchen (11) im Inneren der Schicht grobe Teilchen mit einem Durchmesser von 30 bis 150 um sind und daß die Schicht auch eine große Anzahl von feinen ferromagnetischen leitenden Teilchen (12) enthält, die in der Schicht in der Nähe mindestens einer ihrere Oberflächen verteilt sind, wobei die feinen Teilchen einen Durchmesser besitzen, der kleiner als der der groben Teilchen ist und 10 µm oder weniger, oder 50 um oder weniger beträgt, wobei das Gewichtsverhältnis der in der Schicht vorhandenen groben Teilchen (11) zu den feinen Teilchen (12) von 1:0,1 bis zu 1:1 ist, wenn der Durchmesser der feinen Teilchen 10 µm oder weniger ist, oder von 1:2 bis 1:5, wenn der Durchmesser der feinen Teilchen 50 um oder weniger ist, und das Gewichtsverhältnis des Elastomers zu dem kombinierten Gewicht der groben und feinen Teilchen von 1:0,5 bis zu 1:0,8 liegt,
wodurch der Druck, bei dem ein elektrisch leitender Weg durch die Schicht gebildet wird, unabhängig von der Kontaktfläche, auf die Druck angewendet wird, fast konstant ist oder mit zunehmender Kontaktfläche zunimmt.
2. Druckempfindliche leitende elastische Schicht nach Anspruch 1, bei der die groben und feinen Teilchen Ferrite sind.
3. Druckempfindliche, leitende elastische Schicht nach Anspruch 1, bei der die groben und feinen Teilchen Nickel-karbonat sind.
4. Druckempfindliche leitende elastische Schicht nach einem der vorangehenden Ansprüche, bei der das Elastomer Silikongummi ist.
5. Verfahren zum Bilden einer druckempfindlichen leitfähigen elastischen Schicht, in der der Druck, bei dem die Schicht leitfähig wird, unabhängig von der Kontaktfläche fast konstant ist oder mit zunehmender Kontaktfläche zunimmt, mit den folgenden Schritten:
(a) Mischen einer Anzahl von groben ferromagnetischen leitenden Teilchen mit einem Durchmesser von 30 bis 150 µm mit einem flüssigen Elastomer;
(b) Zulassen der Verfestigung des mit den groben Teilchen gemischten flüssigen Elastomers zu einer inneren Schicht in einem gleichförmigen Magnetfeld;
(c) Mischen einer Anzahl von feinen leitfähigen Teilchen mit einem Durchmesser von 10 µm oder weniger, oder 50 µm oder weniger, mit einem flüssigen Elastomer, wobei das Gewichtsverhältnis der groben Teilchen zu den feinen Teilchen von 1:0,1 bis 1:1 liegt, wenn der Durchmesser der feinen Teilchen 10 µm oder weniger ist, oder von 1:2 zu 1:5, wenn der Durchmesser der feinen Teilchen 50 um oder weniger ist; und
(d) schichtweises Auftragen des die feinen Teilchen enthaltenden flüssigen Elastomers auf beide Flächen der inneren Schicht, wobei das schichtweise aufgetragene Elastomer dünner als die innere Schicht ist und das Gewichtsverhältnis des Elastomers zum kombinierten Gewicht der groben und feinen Teilchen von 1:0,5 bis 1:0,8 beträgt.
6. Verfahren zum Bilden einer druckempfindlichen leitfähigen elastischen Schicht, bei der der Druck, bei dem die Schicht leitfähig wird, unabhängig von der Kontaktfläche fast konstant ist oder mit zunehmender Kontaktfläche zunimmt, mit folgenden Schritten:
(a) Beschichten einer Anzahl von groben ferromagnetischen leitenden Teilchen mit einem Durchmesser von 30 bis 150 µm mit einem Elastomer mit niedrigem Molekulargewicht;
(b) Mischen der beschichteten groben Teilchen mit einem flüssigen Elastomer, in dem eine Anzahl von feinen leitfähigen Teilchen eingemischt wurde, wobei die feinen Teilchen einen Durchmesser von 10 µm oder weniger oder 50 µm oder weniger besitzen, und das Gewichtsverhältnis der groben Teilchen zu den feinen Teilchen von 1:0,1 bis 1:1 liegt, wenn der Durchmesser der feinen Teilchen 10 um oder weniger ist, oder von 1:2 bis 1:5, wenn der Durchmesser der feinen Teilchen 50 um oder weniger ist, und
(c) Belassen des die beschichteten groben und feinen Teilchen enthaltenden Elastomers in Form einer Schicht innerhalb eines gleichförmigen Magnetfeldes während einer vorbestimmten Zeit, die genügend lang ist, um die feinen ferromagnetischen Teilchen sich an der unteren Fläche sammeln zu lassen, wobei das Gewichtsverhältnis des Elastomers in der Schicht zum kombinierten Gewicht der groben und feinen Teilchen von 1:0,5 bis 1:0,8 liegt.
EP82303786A 1982-07-19 1982-07-19 Elastische druckempfindliche leitende Platte und Verfahren zu deren Herstellung Expired EP0099430B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP82303786A EP0099430B1 (de) 1982-07-19 1982-07-19 Elastische druckempfindliche leitende Platte und Verfahren zu deren Herstellung
DE8282303786T DE3273854D1 (en) 1982-07-19 1982-07-19 Pressure-sensitive conductive elastic sheet and method of forming same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP82303786A EP0099430B1 (de) 1982-07-19 1982-07-19 Elastische druckempfindliche leitende Platte und Verfahren zu deren Herstellung

Publications (2)

Publication Number Publication Date
EP0099430A1 EP0099430A1 (de) 1984-02-01
EP0099430B1 true EP0099430B1 (de) 1986-10-15

Family

ID=8189719

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82303786A Expired EP0099430B1 (de) 1982-07-19 1982-07-19 Elastische druckempfindliche leitende Platte und Verfahren zu deren Herstellung

Country Status (2)

Country Link
EP (1) EP0099430B1 (de)
DE (1) DE3273854D1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4923739A (en) * 1987-07-30 1990-05-08 American Telephone And Telegraph Company Composite electrical interconnection medium comprising a conductive network, and article, assembly, and method
EP2224313B1 (de) * 2009-02-27 2012-12-05 Research In Motion Limited Berührungsempfindliche Anzeige mit einem Kraftsensor und tragbare elektronische Vorrichtung damit

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1579180A (de) * 1968-08-21 1969-08-22
US3624619A (en) * 1969-01-17 1971-11-30 Telautograph Corp Pressure-sensing tablet
US4292261A (en) * 1976-06-30 1981-09-29 Japan Synthetic Rubber Company Limited Pressure sensitive conductor and method of manufacturing the same
PT74026B (en) * 1980-12-15 1983-07-01 Moore Business Forms Inc Improvements in or relating to character recognition devices

Also Published As

Publication number Publication date
DE3273854D1 (en) 1986-11-20
EP0099430A1 (de) 1984-02-01

Similar Documents

Publication Publication Date Title
US4448837A (en) Pressure-sensitive conductive elastic sheet
DE60304711T2 (de) Berührungsempfindlicher widerstandssensor mit einer mikrostrukturierten leitfähigen schicht
JPH0353315Y2 (de)
US4220815A (en) Nonplanar transparent electrographic sensor
EP0194861B1 (de) Elektrographischer berührungsaktiver Sensor mit Z-Achsen-Empfindlichkeit
US5948990A (en) Pressure-sensitive resistor
JP2801512B2 (ja) 横方向移動検知センサ
EP0228829B1 (de) Druckempfindliches Gerät
US3911215A (en) Discriminating contact sensor
GB2446278A (en) Sensor sheet with capacitive or resistive detection regions at electrode intersections for determining directional components of externally applied force
GB2148011A (en) Sheet-like input device
US4628408A (en) Input device
EP0099430B1 (de) Elastische druckempfindliche leitende Platte und Verfahren zu deren Herstellung
JPH05143219A (ja) 透明入力パネル
CA1176342A (en) Pressure-sensitive conductive elastic sheet
JPH0436627A (ja) 感圧導電性エラストマー組成物とこれを利用して構成した感圧センサ
JP2666929B2 (ja) 情報入力用シート
JPH06274265A (ja) 面状の入力装置
US4504700A (en) Input device
JPWO2018221640A1 (ja) 樹脂組成物及び導通検査用部材
JPS60160432A (ja) 透明タツチ入力パネル
JPH10246605A (ja) 感圧入力パネルセンサ
JPS61279919A (ja) 手書座標検出装置用入力スイツチ
JPS59114690A (ja) 座標入力装置
JPH0348529B2 (de)

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19820727

AK Designated contracting states

Designated state(s): DE GB NL

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE GB NL

REF Corresponds to:

Ref document number: 3273854

Country of ref document: DE

Date of ref document: 19861120

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19880719

GBPC Gb: european patent ceased through non-payment of renewal fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19930726

Year of fee payment: 12

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19930731

Year of fee payment: 12

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19950201

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19950401