CA2028106C

CA2028106C - Body electrode and process for producing it

Info

Publication number: CA2028106C
Application number: CA002028106A
Authority: CA
Inventors: Walter Schmid
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-02-27
Filing date: 1990-02-26
Publication date: 1996-09-24
Anticipated expiration: 2010-02-26
Also published as: AU620701B2; AU5182290A; WO1990009758A1; EP0413802B1; EP0413802A1; ATE113453T1; CA2028106A1

Abstract

A body electrode comprises one or more galvanically active sensor(s) which is (are) combined on the body contact side with a layer (4) capable of adhering to the skin. The layer (4) comprises an electrically conductive, adherent, elastic hydrophilic material. The side of the sensor or sensors facing away from the body and the layer capable of adhering to the skin are covered with a non-adherent covering layer (5). Both the said layers each comprise a castable polymer which is cast in a mold and then hardened.
Avoiding the stamping processes, the electrode may be produced in a cost-effective manner by casting.

Description

:

Body ~lectrode and Process for its Manufacture The invention relates to a bodY electrode and a Process for its manufacture~

Such electrodes are known (see~ for examPle, U ~.
Patents No. 4,554,92~ and 47066,07~ and 4,362,16S as well as DE-AS 28 14 061~ DE-OS 35 07 301 and WO
81tO2097)~ TheY are fastened to the skin of the patient to be examined or treated and serve the purPose of transmitting electrical signals from the body to a recording instrument, or in the other direction~
signals from a device to the bodY. They are used, for example, to record electrocardiograms, as ground electrodes in oPeratiOns, or to mitigate Pain through transmission of electrical Pulses These electrodes essentiallY comPrise one or more generallY Plate-shaped galvanicallY active sensorts3 which have a Place of attachment for an electrical conductor leading to a recording device or transmitting electrical Pulses frorn a device into the body. The senson is connected on its body contact side to a laYer capable of adhering to the skin and consisting of an electrically conductive, adherent, elastic hYdroPhilic material or combinations of material. This laYer serves the PurPose of ensuring firm adhes;on of the body electrode to the skin while smoothing out unevenesses of the bodY to make certain of transmission of electrical signals from the bodY by way of the sensor to a disPlaY unit or of a signal generated in an instrument by way of the ~ensor into the bodY. Or, the side of the sensor facing away from the bodY there is a `--non-conductive elastic and non-adhesive laYer which is a covering or suPPortins layer and which covers the electrode and the laYer that adheres to the bodY (in case this laYer is larger than the electrode plate) and is connected to the electrode Plate.

~ lectrodes of this kind are thus manufactured bY
stamping Parts in the desired size and shaPe from a wide continous striP of the adhesive layer which comes in contact with the skin, a sensor then being aPPlied to the Preform obtained, and finallY a covering and supporting layer (also produced bY being stamped out) is aPPlied in alignment onto the layer that has contact with the skin if this laYer is larger in area than the sensor plate. Considerable Problems arise in stamPing out the first layer which adheres to the skin, because it is difficult to remove the stamped adhesive Parts from the stamPins tool.
Due to the adhesiveness of the strip from which the parts of the laYer which adheres to the skin are stamped, difficulties arise in the stamPing Procedure as the stamPed out Parts tend to adhere to the stamping tool, so that it is difficult to carrY out high-sPeed continuous stamping.

Hence, the invention was set the task of developing a body electrode which can be Produced bY
avoiding the stampins Processes.

Furthermore, it was set the task of develoPing a Procedure for the manufacture of bodY electrodes that can be conducted in a trouble-free and cost-effective manner.

- ~ 2028106 3 electrode and the laYer that adheres to the bodY (in case this laYer is larger than the electrode Plate) and is connected to the electrode Plate~
~:
Electrodes of this kind are thus manufactured by stamping Parts in the desired size:and shape from a wide continous~striP of the adhesive laYer which comes in contact with the skin, a sensor then being aPPlied to the Preform obtained, and finally a covering and supporting laYer (also Produced by being stamPed out) is aPPlied in alignment onto the layer that has contact with the skin if this laYer is larger in area than the sensor Plate~ Considerable Problems arise in stamPing out the first laYer which adheres to the skin, because it is difficult to remove the stamped adhesive Parts from the stamPing tool.

Due to the adhesiveness of the striP from which the parts of the layer which adheres to the skin are stamped, difficulties arise in the stamPing procedure as the stamped out parts tend to adhere to the stamPing tool, so that it is difficult to carry out high-sPeed continuous stamPing.
~ ence, the invention was set the task of develoPing a bodY electrode which can be Produced bY
avoiding the stamping Processes.

Furthermore~ it was set the task of develoPing a procedure for the manufacture of bodY electrodes that can be conducted in a trouble free and cost-effective manner~

20281:06 4 These tasks are accomPlished by means of the bodY
electrode described in Patent claim 1 and the Procedure described in Patent claim 2 The body electrode according to the present invention comPrises an electricallY conductive, elastic and hYdroPhilic first layer capable of adhering to the skin, of one or more conventional Plate-like sensors, and of a non-conducting and non-adhesive Protective coating or covering or supporting laYer over the sensor and the side facing awaY from the bodY of the laYer that adheres to the skin. ~ach of the said laYers consists of a castable PolYmer which is cast in a mold and then hardened, so that the Problems described above as arising from stamping out these laYers, especially the adhesive ones of the laYer in contact with the skin, no longer occur~

The Process according to the invention consists of manufacturing the laYer adhering to the skin and the covering or suPporting layer by using a castable PolYmer which is cast in a mold and then hardened.

As the problem of adhesion while stamPing out the parts of the laYer adherins to the skin no longer exists in the Process claimed for the invention, it can be conductd on a commercial scale continuouslY, trouble-free and at high sPeed.
It is advisable for the ratio of the area of the first layer adhering to the skin to the area of the plate-like sensor or sensors to be higher than one, and in Particular two or three. That is~ it is advisable to use the smallest Possible sensor in relation to the ~ 5 first layer that adheres to the skin. This arrangement is particularlY expedient if 7 according to a further Preferred form of the invention, both the laYer adhering to the skin and the covering laYer are transparent so that observation is possible of the skin contact surface on the Patient undergoing treatment. It can thus be determined whether skin irritations occur, especiallY when the electrode is applied for long Periods of time.

The laYer adhering to the skin exPedientlY
comprises a conductive natural and~or sYnthetic material, in Particular a Polymer material, which for example can be an elastomeric Polymer or a collagen.
Furthermore, this laYer can comprise a non-conductive natural or sYnthetic material, that contains an electrolyte to Produce conductivity~ It maY also be expedient for the laYer adhering to the skin to contain a tackifying agent, a Plasticiser (softener) and/or hYgroscoPic agent, so that in this way the adhesive proPerties~ elastic Properties and the hygroscopicitY may be customized.

The covering layer Preferably comPrises a natural or sYnthetic non-conductive material which is expedientlY a Polymer, Preference being given to elastomers or collagens.

The laYer adhering to the skin and the covering laYer maY comPrise the same material. The laYer adhering to the skin must naturally be rendered conductive by the addition of an electrolYte, as well ~202810 i as adherent. The adhesiveness can be achieved bY
addition of a tackifYing agent or, in the event that cross-linkable PolYmers are used to Produce the two laYers, bY making the laYer coming in contact with the skin less heavilY cross-linked than the covering laYer in the event that Polymers in a less heavilY cross-linked state are sufficientlY adhesive.
According to another preferred embodiment of the invention, if the laYer adhering to the skin and the covering layer are transParent, the bodY electrode of the invention maY have an intermediate transParent layer bearing symbols, for examPle, either caPtions or graphic images. In this waY it is possible to identifY
the electrode from the viewpoint of its origin.

The bodY electrodes according to the invention may contain one or more sensors and PreferablY be round or square in shaPe, but theY can also be Produced in anY other shaPes~

All known sensors are suitable for the bodY
electrode of the Present invention, for examPle, those described in DE-OS 24 59 627, U.S. Patents No.
~,55~,92~ and ~,066,078, in DE-AS 22 1~ 061 and D~-OS
29 35 238. A Plate-like sensor equipped with a push-button tYPe of connection for an electric lead has proved to be esPecially suitable. This plate-like sensor is made of Plastic and is coated with a conductive, galvanicallY active material such as a silver~silver chloride layer. The sensors maY also Preferably comprise polymers which represent a reversible redox system. Such tYPes of material are known.

~ ` -20~8106 , Generally speaking, although a Plate-like sensor which i5 mostly round is emPloyed in the body electrode of the invention, but it is also Possible to emPloY as a sensor the conductor or conductors of the electric lead or leads bY means o~ which signals are transmitted to a recording device In this Particular cost-effective embodiment, an electric lead with a silver conductor which is coated with a silver chloride laYer~
is preferablY emPloyed~

In addition, microsPheres made of sYnthetic material and coated with zinc or silver can, for example, be used as galvanicallY active sensors, such as the materials marketed under the brand name of Metalite. A suitable number of these microsPheres are positioned between the layer coming in contact with the skin and the covering layer, and are connected with an electric lead which leads to a recording device~

The sensors and~or electric ieads maY also comPrise laYers which have been aPplied to a foil, for examPle with screen Printing~
If a Plate-like sensor is used in the electrode of the invention~ the Plate element PreferablY has recesses, in particular holes, which ensure better holding for the layer having cQntact with the skin and/or the covering laYer~

It is also Possible to transmit electric signals received from the bodY to a recording device by a wireless method~ For this PurPose the electrode maY be fitted witt. an integrated circuit as transmitter characterized bY low Power consumPtion and energized bY
a power source such as a round cell~

- ~ ~ 2028106 8 If the electrode of the invention is to be aPPlied on the thorax~ for examPle~ it is advisable that the electrode should be elastic in the longitudinal direction. In this case~ an embodiment of a bodY electrode is Provided which comprises several electrode units connected by sheeting folded in an accordion-like arrangement that allows for the electrode's longitudinal expansion due, for example, to enlargement of the thorax caused bY breathing.

The invention is illustrated in detail by the accomPanYins Fi~ures 1 - ~. Identical Parts in each drawing have been given the same reference numbers.

Figure 1 shows a vertical section through an embodiment of the electrode of the invention with a sensor~
Figure 2 is a toP view of the electrode of the invention Provided with three sensors.
Figure 3 is a top view of another embodiment of such an electrode~
Figure 4 is a toP view of an embodiment of such an electrode which is fitted with a transmitter.
Figure 5 is a top view of an electrode of the invention designed as a stimulation electrode.
Figure 6 is a vertical section through an electrode of the invention which is extendible longitudinally Figure 7 is a top view of a rins-shaped electrode of the invention with a sensor Provided with holes in its plate element.

~ ~ ~ 9 ~ 2028106 The embodiment of the electrode of the invention as shown in Figure 1 comprises a Plate~ e round sensor 1 with a wiring Point for an electric lead which leads to a recording device. The sensor maY comPrise one of those described in the references cited above~
On its side facing the bodY, the sensor is Provided with a layer 4 that adheres to the skin7 and which maY
comprise anY known elastic, mild to the skin, non-toxic, hydrophilic and natural or sYnthetic material caPable of adhering to the s~in. A Prerequisite for this material is that it must be castable in anY form~
The material in question Preferably comprises a synthetic, and preferably elastomeric PolYmers or a polymer mixture and~or a collagen. This material is either conductive or rendered conductive by addition of an electrolYte. The laYer 4 is Produced by PreferablY
using synthetic organic PolYmers or polYmer mixtures which are either intrinsicallY conductive or rendered conductive bY the addition of an electrolYte. These polymers must be castable in the form of a solution, a melt, or a PrePolymer of suitable low viscositY. An abundance of Polymers meetins these requirements are available. Polymers suitable for conducting are, for examPle, those described in U.S. Patent ~o. 4,066,078 of 2-acrYl-amido-2-methYlProPane sulfonic acid, its salts, coPolYmers of the named acid, coPolYmers of the acid's salt, and mixtures thereof in mixtures of water~
alcohols and mixtures thereof; PolYmers described in DE-OS 29 35 238 with at least 5 mol % monomer units which contain a salt of a carboxylic acid~ conductive polymer compounds in question which consist of a hydroPhilic cross-linked Polymer and a hYdrophilic non~
cross-linked PolYmer and are described in ~P 85 327.

~ 2D:28106 lO

Among the Polymers which are not conductive as such and are rendered conductive bY the addition of an electrolyte, are polYvinyl alcohols7 PolYvinYl S acetates, PolYvinYl Proprionates and Polyvinyl ethers such as are described, for examPle, in Adhesion 5~81, Pages 20~-213, as well as polYacrylates and polYmethacrylates such as those described in DE-OS 31 36 366, U.S. Patent No. 4,554,924 and in DE-AS 28 14 061.

The unsaturated acrylate resin tYPes marketed by BASF under the brand name of "L~ROMER" have been found to be particularly useful, sPecial Preference being given to the resin that is marketed under the brand name LARO~ER EA-8812".

To increase or control adhesiveness, these polymers maY addition~llY contain one or more tackifYing agents such as the glYcidYl ether acrYlates and their derivatives known to be suitable for this purpose. In addition, they may contain Plasticizers (softeners) and/or hYsroscoPic agents, i.e. polyols, such as diols and triols, for example hexane triols, polyethylene slYcol etc. It is exPedient that the PolYmers contain an additive of bacteriostatics and odor absorbins asents such as eucalYptol.

As has alreadY been noted, the PolYmers emPloYed to Produce the laYer 4 comin~ in contact with the skin are cast in a castable state in a mold, either in the form of a solution~ a melt or a prePolYmer hardenable bY cross-lin~ing. The latter embodiment is Preferred.

:~ 202:8106 The hardening is preferably accomPlished bY irradiation with ultraviolet light and/or heat bY the use of known photoinitiators and~or hardening accelerators~ ~xamPles of suitable compounds include per compounds such as peroxides and~or ketone hardening accelerators~ for example 2-hYdroxY-2-methYl-l-Phenyl-propan-l-on~ which is an efficient Photoinitiator for acrYlated ePoxides~
acrylated polYurethanes~ acrYlated polYethers and acrylated unsaturated polyesters or mixtures thereof.

The adhesive, conductive and elastic properties of the laYer 4 having contact with the skin can be customized bY varYing the tYPe and amount of conductive Polymers emPloyed, either naturallY conductive ones or ones rendered conductive bY the addition of electrolytes, and also of anY tackifYing agent, plasticizer and~or hygroscopic agent emploYed, and also of the degree of cross-linking and hardening.

PreferablY alkali halides such as Potassium chloride are used as electrolYtes to render non-conductive polymers conductive for production of the layer 4 that comes in contact with the skin~

The material for the covering layer 5 maY be anY
known natural and~or sYnthetic hydrophilic material which is also casta~le in the form of a solution, a melt or a cross-linkable or hardenable prepolymer and which bonds with the material of the layer 4 on solidification~ The material for the coverin~ laYer 5 rnust of course not be conductive and also rr,ust not contain additives renderins it conductive~ ~s with the layer having contact with the skin~ the layer maY also be transparent~ The many known materials meeting the ~ 12 specified requirements include, among others~ PolYmers, especially elastomeric polymers, gelatins, especially ossein with a gelatin strength of 60 to 260 Bloom and a cast gelatin Shore hardness between 40 and 90 Shore, as well as in particular the Polyacrylates used to Produce the laYer 4~ but which are cross-linked or hardened to the extent that theY are no longer adhesive. Hence, in accordance with the invention, Preference is to be siiven in the manufacture of the covering laYer S to the use of the same Polyacrylate prepolYmers employed in the manufacture of the laYer having contact with the s~in, but which are cross-linked or hardened to a greater extent so that theY are no longer adhesive.
This results in an esPecially strong bonding of the polymers in the laYer 4 and the laYer 5.

In the embodiment shown in Figure 1, an intermediate laYer 7 Provided with sYmbols is Positioned between laYer 4 that has contact with the skin and the covering laYer 5. As with la~ers 4 and 5, the intermediate laYer 7 consists of transParent material so that the symbols can be recognized while examining the electrode. This intermediate laYer also consists of a castable natural or sYnthetic material, and the same material may be used as for Production of the laYers 4 and 5~ Howe~er, the intermediate layer 7 must not be conductive.
In addition, sYmbols may be applied to the uPper side of the covering laYer 5 facing away from the bod~f, for examPle by imprinting, Pasting on, or Painting. It is advisable, however, that anY embossed sYmbols are applied to the uPPer side of the covering laYer 5 and have been obtained bY casting the covering laYer in a ~ 202810B 13 form with aPProPriate indentations. In this case the body electrode is not produced, as described later, by casting the laYer having contact with the skin, applying the sensor and then casting the coverin~
layer. Instead the Process is carried out in the reverse order.

The layer adhering to the skin is Provided with a detachable Protective laYer 6 which maY consist of anY
material that is seParable from the laYer adhering to the skin, and which is water rePellant and/or is Provided with a releasing coating such as a silicone coating. It is Particularly expedient that the protective coating 6 consists of the mold in which the body ele~trode has been Produced bY casting the laYers 4 and 5, and if aPPPlicable, layer 7. That is7 the body electrode is not removed from the mold after casting but is marketed as a unit with this casting mold. The casting mold is then removed when the electrode is in use. The covering layer Preferably has a tab (not shown3 to assist in easier removal from the mold.

The bodY electrode according to the invention and which is shown in Fi~ure 2 is rectangular in shaPe and contains three circular sensors. But in this case, the electrical conductors with which the sensors maY be connected to a display unit~ are not connected with the sensor at a push-button tYpe wiring point as in the case of the embodiment shown in Figure 1. Instead, they are fastened to the sensors without Press-button tyPe of connectin~ device and are embedded in the horizontal plane of the bodY electrode in the coverin~ laYer 5, and ProJect from its lateral edge. These electrical conductors 11 may consist of conventional connecting leads~ but they PreferablY consist of carbon fibres and/or conductin~ plastics.

Fiyure 3 also shows a rectangular bodY electrode according to the invention with three sensors. the S electrical leads 11 connected with these sensors end at a connecting tab 17 from which Point conneection to a recording device is Possible~ In the case of this embodiment, the cast covering laYer 12 has round recesses 14 which are filled with a conductive adhesive material such as is used to Produce the laYer adhering to the skin. Sheeting 13 coated in areas 15 with a galvanically active layer is aPPlied to this structure.
The sheeting 13 has connecting leads 11 which are also aPPlied bY coating. Coating of this sheeting 13 with the galvanicallY active laYer or with the electrical leads maY~ for example, be carried out with the screen-printing Process.

Figure 4 shows an embodiment similar to that in Figure 3, but in this case the electrical leads 11 are connected to a transmitter 9 powered bY a round cell 16. The transmitter ~ forwards bY wireles~ means signals transmitted from the bodY to a recording device.
~5 Figure 5 shows an electrode according to the invention which may be used as a stimulation electrode with PolaritY selectable as required. This electrode comPrises a cast co~Jering laYer 5 with recesses in 3~ which the material for the layer 4 a~hering to the skin is cast, and galvanicallY active sensors 1 with the aPProPriate electrical leads 11 which are in contac-t with the layer 4 adhering to the skin are apPlied on the sheetin~ 13 corresPondins to the embodiMent shown in Fisure 3. An electrode such as this is used to transmit signals generated in a device, for example, to mitigate Pain.

~_ ~' 15 Figure 6 shows an eLectrode extendible in the longitudinal direction 1~ which comPrises se~er~l individual electrodes. It comPrises four individual electrodes which are connected on the sides of their covering laYer 5 bY sheeting 10 folded like an accordian~ The foil used preferably consists of a plastic, esPeciallY elastomeric Plastic~ which can be folded without causing cracks. The four sensors of this electrode maY be connected to a displaY ~nit with the leads 11. The sensor 1 in this embodiment, and also the embodiment shown in Figure 1, may comprise a striP of a galvanicallY active metal or a Plastic that is coated with a galvanicallY active metal. This strip Proiects in angled form through the center of the covering laYer 5 and may be connected to a disPlay unit bY an electric lead.

Fisure 7 shows a top view of a bodY electrode which princiPal 1Y corresponds to that shown in Figure 1. The Plate of the circular electrode is Provided with holes ~ to ensure better anchoring both in the laYer coming in contact with the skin (not shown) and the coverin~ laYer 5. When the electrode Pl~te is aPPlied to the freshlY cast layer- adhering to the skin and when the covering la~er 5 is cast1 the holes are Penetrated bY the resPective materials thereby achieving a good anchora~e. This electrode has a tab 1~ on it~ covering laYer side to facilitate removal from the mold The thic~ness of the la~er ~ having contact with the skin -for the embodiments of flat formed bodY
el~ctrodes as described above ranges Preferabl~ betwee~n 800 ~m and 2,500 ~m, and with Partic~lar Pr-ef~rence for 1,000 ~m to 2,000 ~m, where3~ th~ tl^,iclcness of the covering laYer 5 ranges preferablY between 500 ~m and 2,500 ~m, esPeciallY between 1,000 ~m and 2,000 ~m~
Circular electrodes of the embodiments shown in figure 1 and Figure 7 have diameters Preferably between 20 mm and 60 mm.

The thickness of the electrode Plate of the plate-like electrodes emploYed in these electrode units ranges PreferablY between 50 ~m and 1,500 ~m, especially between ~0 ~m and 1,000 ~m.

An additional embodiment of an electrode of the Present invention consists of a contact cap which is preferablY to be aPPlied to the head and used for EEG
recording, as shown in Figure ~.

This contact caP comPrises a cone-shaped contact body 20, open at its wider end, and is Produced hY
castins from a non-adhesive, conductive material into which a sensor 1 is fitted and holds the contact bodY
20 firm bY a clamPing force~ This contact caP is fastened on the Parts of the body that are to be monitored, preferably the head, by the use of adhesive tape or the like~

For Protection of the contact bodY 20, it maY be manufactured and mar~eted with the mold in which it was cast as a protective layer.

The laYer hav;ng contact with the skin is produced bY casting the above narned PolYmers in a castable state in a cast, that is to saY either in the forrm of a solution, a melt~ or a PrePolYrner that is hardenable bY cross~link;ng~

The material to be used for manufacturing the Protective or coverins laYer maY be anY natural and/or sYnthetic hYdroPhilic material~ esPecially Polymeric material which is also castable in the form of a solution, a melt, or a cross-linkable or hardenable prepolymer, and in manufacture cornbines with the material of the laYer having contact with the skin. The material for the covering laYer must naturally not be conductive and not contain any additives which maY
render it conductive, and as with the material of the layer having contact with the skin~ may also be transparent. The Polymers to be used in the Process of the present invention have been mentioned at the beginning.

Corresponding to a Preferred embodiment of the Process of the Present invention, in case either the laYer adhering to the skin and~or the covering or protective laYer (esPecially the latter~ comPrise a transParent material, a PreferablY transparent laYer with sYmbols may also be provided between these two laYers. The sYmbols consist, for examPle~ of captions or sraPhic images in order to identifY the electrode's origin or application.

The rr,aterial t~ be used for the po~sible manufacture of the intermediate laYer provided with symbols can also comPrise a castable, natural or s~fnthetic material. The same materials ma~f be used as are emPloYed ~or manufacturing the laYer5 ~a~ing contact with the skin and tl-,e covering laYers. However~
the intermediate laYer must not be conducti~le.

~ 18 202810~

The sensors employed for carrYing out the Process of the Present invention are essentiallY known and are S also described in the above n~med literature.

Identification of the electrodes Produced in accordance with the invention is also possible by engraving in the rnold sYmbols or caPtions ~such as comPany manufacture data or tYPe designations) with the aid of a die in reflected type~ The covering or protective layer will be cast first~ The electrodes produced in this way are then Provided with embossed formed symtols on the surface of the coverin~ or protective laYer~

In the following, the Process according to the invention will be described with reference to sYnthetic7 elastomeric, Polymer materials which will be employed for the manufacture of the layer adhering ko the skin and the covering or suPporting laYer of an electrode. The electrode comPrises: a laYer having contact with the skin 5 a Plate-like sensor with a connecting Point for an electric lead (the sensor ~5 plate's surface being smaller than the surface of the layer having contact with the s~in); and a coverin~ or protective la~er that covers the sensor Plate and the side facing away from the bodY of the laYer havins contact with the skin.
The process according to the invention maY, as alreadY mer,tioned be carried o~t in such a way that a melt i5 Produced frorn the polymer ermployed for forming a layer adherin~ to the skin~ With the aid of metering devic;e, this melt will be continuallY fed in ~uch ~uarltities into tt,e rnold, which corresponds to the :2028I06 size and design of the laYer having contact with the skin, so that the desired thickness of the laYer will ~e achieved~ After the melt has at least cooled or by and large solidified~ so that by aPplyin~ the sensor it does not Penetrate too deeP into the layer forming a skin7 the sensor is set down on the layer that has been made. The covering or supportins laYer is then cast in the desired thickness frorn a downstream metering device.

It is also possible to use a PolYmer solution in a suitable solvent for casting the layer forming a skin. In this case, the solvent is allowed to evaPorate after casting the layer7 accelerated if necessar~ bY
warmins, sufficiently at least so that the sensor which is applied does not sink undesirably deeP into the layer that is formed.
It is known that this cross-linkir,g or hardening maY be carried out bY heat~ light, ionizing radiation~
or with the use of catalYsts~ or initiators or hardenins and Polymerization accelerators~ Comb;nations of these methods may also be employed, wherebY each method also comPlies with the tYPe of polym~r materi31 that is used.

Catalysts~ initiators or harderling or acceleratins a~ents are added to the casting solution immediately before castins~ as is exPedient.

Another method i5 Possible~ according to the invention~ whereby a castable state of a cross-linkable ~5 or hardenabl.e preliminarY stage of the Pol~Ymer to be used is cast. After castin~ and before setting the sensor, it is e~Pedie~nt at least to sufficientlY cross-link or harden so that the cast laYer is no longer so soft that the sensor maY Penetrate it too deeply.

According to one of the three named methods, the covering or suPPorting laYer i5 also cast~ However, any one of the methods that is followed for this layer must not be identical with the method according to which the layer adhering to the skin has been cast.

It is esPecially expedient, however, that the same cross-linkable or hardenable PreliminarY stages of the Polymer are employed for manufacturing both the laYer adhering to the skin as well as the covering or supporting layer. The covering or suPPorting laYer~
which should no longer be tackY, is more heavilY cross-linked accordins to one or more of the named method~"
than the laYer adhering to the skin, which must remain tacky. The crosswlinkin~ maY be carried out in the described way.

The casting mold used to aPPlY the process according to the invention is PreferablY Produced by deeP-drawins sheeting in the desired shape and dePth~
Hence~ for the PurPose of industrial Production molds situated side bY side and one after the other are Produced bY deep--drawing from a strlP of material ti-at does not combine with the material of the laYer adhering to the skin, but can be detached from this layer- rather easily and without leavin~ residues. These molds are then brought in succession under metering devices at the speed corresPondir~ to that at which the devices in question oPerate~ for feedin~3 the castable ~ 21 20281:06 material for the laYer adherin~ to the skin. The irradiation and/or heatin~ devices by m~ans of which the crosslinking or hardening reactions can be carried out or accelerated maY be installed downstream frorn the metering devices~

The materials for the striP from which the rnolds for casting the bodY electrode of the invention are deep-drawn, PreferablY comprise a water-repellant PolYmer5 or a Polymer having a coating of an anti-adhesive or release agent such as a water-rePellent silicone. ~etal foils such as aluminium foils are also suitable.

It is suitable that the mold in which the body electrode has been produced by casting in accordance with the invention, maY be used as a Protective laYer in order that the laYer- adherins to the skin is Protected from damase or drying out. In this case, the electrode and the mold emPlo~fed to manufacture it i5 rnarketed as one unit.

A variant of the Process of the invention is that the laYer adherins to the skin is cast in a castin~
mold and hardened, a sensor with electric connection facilitY is -introduced, and finallY the covering or supportins laYer is cast with the sensor embedded.
3n Ar,other variant of the Process of the invention compri~es introducing into a castin~ mold sheetin~ on all or part of which a galvanicallY active laYer has t,een deposited bY a screen Printin~ Process for exarrlple~ and in sPecific configurations if necessarY.

~ 22 The laYer adherin~ to the skin is cast on this sheeting in contact with the ~alvanicallY active laYer~
and a covering sheet is Placed over it a~ter solidification.

In the event of the manufacture of such a bodY
electrode~ the galvanicallY active laYer maY be connected to a recording instrument by introducing into the mold connecting leads which Proiect Prior to castin~3 either from the side of the layer having contact with the skin or upwards from the electrode.
TheY may then be connected bY waY of leads to the recordin~3 instruments.
. However, the leads maY also be aPPlied7 similarlY
to the galvanically active laYer, in the form of a laYer on the sheetin~ to be introduced into the casting mold, PreferablY in a thickness of 30 ~m to 2nn ~m~ It is advisable for these leads to end in a tab on the electrode~ from which point theY can then be connected to the recording instrument tJy a conver-,tional electric lead.

In conclusion, reference rr,aY be made to several preferred embodimerlts in resPect of formin~ and rnanufacturin~ electrodes~

The laYer 4 adherin~3 to tt,~ skln and the coverin~3 layer ~ are transparent, the electrode itself is circular or square, the laykr 4 adhering to the skin is from ~
cor,ductive natural and/or sYnthetic PolYrner~ in particular from a non-conductive pol.ymer7 which contains ar, electrolyte~ The covering laYer ~ is from a 3~ non-conductive n~tural or s~fr-,thetic pol~fmer, the layer 4 adhering to the skin is Provided with a removal protective coating 6. This protective coatins maY
consist of the mold in which the electrode has been manufactured bY casting. The laYer adhering to the skin and the coverin~ layer 5 ~re transParent 7 and between both these layers there is a trasnParent laYer 7 which is provided with sYmbols~ The sensor or sensors 1 are provided with a connecting Point 3 for electric leads 11, and the sensor or sensors 1 may even t~e the conductor of the electric leads 11. The sensors 1 are plate-like and have recesses ~, the sensor or sensors 1 may be connected with a transmitter 9. The bodY
electrode may contain several sensors 1, and finallY
the ~odY electrode maY be extendible in a longitudinal direction.

The following examPle illustrates the invention:
A mixture of 100 g 1-vinYl-2-PYrrolidone, 10 g hYdro~en peroxide (3~ b~ weight solutiGn in water~, 7 g 4-(hYdroxyethoxy) phenYl-~(2--hydroxy-~-propyl)-ketone~

5 g polYetheracrylate, 15 g PolYvin~lPYrrolidone~ 100 g propanetriol, 20 g distilled water~ 4 g triethanolamine and 5 g ammonium h~droxide (10% in water) was Produced.
40 g of a solution of 30 g Potassium chloride and S g sodium tetraborat in 100 g water were added to this mixture.
The layers con,ins in contact with the skin were cast fro~, the mixture ot~tained to a thickness of 500 url in a deep-drawn c-ircular castins molds of silicone-Goated PolYettlYlene sheeking with a dian,eter of 50 mm 3~ ar,d a depth of 3 mm. The cast laYers were irradi~ted for a period o~ 15 seconds wikh ultraviolet light and heated to a temperature of 60C~

Then a round Plate-like sensor having a diameter of 6 mm and a sensor plate dePth of 1 mm was aPPlied to this layer.

Then a transParent mixture of 60 g ProPanediol, g glycide ethe-racrylate, 40 g tripropyleneglycol diacrylate5 60 g PolYethYlene slYcol-300, and 3 g 2-hydroxy-2-methyl-1-phenylpropane-1-one was cast as covering laYer to a thickness of 300 ~m on the structure obtained, and hardened by the action of ultraviolet light for a Period of 15 seconds at a temPeratUre of 60~C.
. The bodY electrode thereby obtained was transparent in the places not covered bY the sensor plate and adhered well to human skin without exerting any irritating effects.

Claims

1. Body electrode including an adhesive layer, a covering layer, and at least one galvanically active sensor which on the side normally facing the body is connected with the adhesive layer, the adhesive layer comprising an electrically conductive, adherent, elastic hydrophillic material, that side of the sensor and of the adhesive layer which normally faces away from the body, being covered with a non-adherent covering layer, the adhesive layer and the covering layer each comprising a castable polymer which has been cast in a mold and then hardened.

2. Body electrode of claim 1, wherein the ratio of the area of the adhesive layer to the area of the sensor is greater than 1.

3. Body electrode of claim 2, wherein the ratio is 2 to 3.

4. Body electrode of claims 1, 2 or 3, wherein the adhesive layer contains a tackifying agent, a plasticizer and/or a hydroscopic agent.

5. Body electrode of one of claims 1, 2 or 3, wherein the adhesive layer and the covering layer comprise the same cross-linkable, non-conductive polymer, and the polymer of the covering layer is more heavily cross-linked.

6. Body electrode of one of claims 1, 2 or 3, wherein the sensor and/or electrical lead associated therewith comprise layers of galvanically active material which have been applied to a sheeting, in particular by screen printing.

7. Process for manufacturing a body electrode of claim 1, wherein the adhesive layer and the covering layer are each manufactured from a castable polymer which is cast into a mold and then hardened.

8. Process of claim 7, wherein a melt, a solution or a crosslinkable or hardenable preliminary stage of the material to be cast is used in casting the adhesive layer and the covering layer.

9. Process of the claims 7 or 8, wherein the adhesive layer and the covering layer are transparent, and an intermediate layer provided with symbols, is fitted between the adhesive layer and the covering layer.

10. The process of claim 9, wherein the intermediate layer is also transparent.

11. Process of claims 7 or 8, wherein the adhesive layer is cast and hardened in a casting form, then a sensor with electric connection capability is introduced, and then the covering layer is cast with the sensor embedded in it.

12. Process of one of claims 7, 8 or 10, wherein sheeting with an applied galvanically active layer is introduced into said mold and the adhesive layer is cast over the galvanically active layer.