the preferred embodiments of the present invention will be described below with reference to the drawings . fig1 is a schematic perspective view illustrating a first embodiment of a biological electrode according to the invention . fig2 is a cross - sectional view of the essence of the biological electrode as shown in fig1 . fig3 is a cross - sectional view illustrating the essence of a variation of the biological electrode as shown in fig2 . fig4 and 5 are cross - sectional views illustrating a second embodiment of the biological electrode according to the invention . as shown in fig1 and 2 , the biological electrode 1 of this embodiment is disposable , and comprises an electrode element 2 capable of having electroconductivity with a living body , a sponge with electroconductive gel 4 on a flat side of the electrode element 2 or on a contact face with the living body ( a lower side in the figure ), and a pad portion 3 having an adhesive face 3 a on a clavate side of the electrode element 2 . this biological electrode 1 is placed at a predetermined position of the living body owing to adhesion of the adhesive face 3 a of the pad portion 3 . the electrode element 2 is clavate at a top end 2 a , and has a snap fastener type structure of fitting with a concave portion of a connecting part 15 for the lead wire , as shown in fig2 for example . and in this embodiment , of the constituent members of the biological electrode 1 , the electrode element 2 is formed of a biodegradable material . because this sponge with gel 4 serves to make close contact with the living body , the electrode element 2 can be disposed securely at a predetermined position by the pad portion 3 having adhesion . the sponge with gel 4 does not remain on the skin when peeled from an attached portion , and is unnecessary to wipe out , improving the usability of the biological electrode 1 . in this embodiment , a gel cover 6 having a concave portion 6 a for protecting the sponge with gel 4 and covering the adhesive face of the pad portion 3 is provided . this gel cover 6 prevents the gel from drying over the long time before the biological electrode 1 is used , and further protects the sponge with gel 4 and keeps adhesion of the pad portion 3 for the long term . a label 7 can secure the electrode element 2 firmly , and suppress the noise due to movement of the lead wire to the minimum . the electrode element 2 is formed of at least one kind of biodegradable material from among polyhydroxy carboxylic acids such as polylactic acid and polyglycolic acid , chitosan , cellulose , aliphatic polyester ( e . g ., polybutylenesuccinate ( pbs ), polybutylenesuccinate adipate ( pbsa ), polyethylenesuccinate ( pesu )), polycaprolactone ( pcl ), and starch derivatives . therefore , the electrode element 2 can attain a mechanical performance and is ultimately decomposed into water and carbon dioxide by soil microbes , with the small amount of heat generated in incineration . in particular , the use of polylactic acid can prevent the electrode element from molding . also , the electrode element 2 is molded by adding an adequate amount of electroconductive material to the biodegradable material , and provided with some electrochemical property . also , an electroconductive layer composed of an electroconductive material may be formed on the biodegradable material . the electroconductive materials may include , for example , silver , silver / silver chloride , or carbon . the biological electrode 1 thus constituted is finally decomposed into water and carbon dioxide owing to microbes , when wasted in the soil after the use . also , in the incineration process , it generates the smaller amount of heat while incinerating than the conventional biological electrode using abs resin or pet resin . as the biodegradable materials in this embodiment , polyhydroxy carboxylic acids such as polylactic acid are a generic name of the following substances . these substances may be used singly as raw materials or in mixture thereof . for example , lactide that is a cyclic ester of l - lactic acid , d - lactic acid , dl - lactic acid , or lactic acid may be used . the materials that can form a copolymer with lactic acid may include hydroxy carboxylic acids such as glycolic acid , 3 - hydroxybutyric acid , 4 - hydroxybutyric acid , 4 - hydroxy valeric acid , and 6 - hydroxy carboxylic acid . further , the cyclic ester of hydroxy carboxylic acids may be glycolide ( cyclic ester of glycolic acid ), or ε - caprolactone ( 6 - cyclic ester of hydroxy caproic acid ). by polymerizing the raw materials as above cited , polyhydroxy carboxylic acids such as high molecular polylactic acid can be obtained . in polymerization , direct dehydroxy polycondensation from hydroxy carboxylic acids or ring opening polymerization from ringular dimer of hydroxy carboxylic acids ( e . g . lactide ) can be used in accordance with the properties of raw material . a method of manufacturing a snap fastener type ( fig1 and 2 ) electrode element in this embodiment ( kneading electroconductive material ) will be described below . the biodegradable material of polyhydroxy carboxylic acid such as polylactic acid is used as the matrix of the electrode element 2 . by kneading and adding the electroconductive filler into the matrix , the biological electrode 1 is provided with electroconductivity . means for kneading the electroconductive filler into biodegradable material may include a henschel mixer , a ribbon blender , a mill roller , a bambari mixer , a super mixer , and a single or twin extruder . the additive amount of electroconductive filler is in a range of 15 to 40 percent for carbon black , and 30 to 80 percent for silver and silver / silver chloride , supposing 100 percent in total . the surface resistivity after kneading is in a range of 1 × 10 5 ( ω ) or less . the injection molding conditions ( injection temperature , mold temperature ) after kneading may be in the most suitable range of matrix . for example , when polylactic acid is used for the matrix , the injection temperature may be in a range from 100 to 300 ° c ., and the mold temperature may be in a range from 10 to 80 ° c . 3 ) coating the electroconductive paint onto the lead wire attaching portion of the electrode element 2 ; separately from or simultaneously with kneading the electroconductive filler to provide the electroconductivity , a highly electroconductive part is formed on the surface by coating an electroconductive paint on a lead wire attaching portion of the element , if necessary , thereby improving the electrical contact with the lead wire . further , a stainless cover ( e . g ., stud ) may be provided on the lead wire attaching portion of the electrode element 2 , thereby improving the electrical contact between the electrode element 2 and the connecting terminal of the electrode lead wire . 4 ) coating the non - polarized elecroconductive paint on the electrode paste contact face of the electrode element 2 ; to further enhance the performance of the biological electrode 1 , an electroconductive paint of silver / silver chloride as the electroconductive material may be coated at a portion in contact with the electrode paste or the electrode gel on the electrode element 2 having electroconductivity , if necessary . the electrode performance of the biological electrode 1 after assembly must satisfy the standard , aami / ansi - ec - 12 : pregelled ecg disposable electrodes ( 1982 ) that have standardized test items such as ac impedance , dc offset voltage , dc offset drift , defibrillation overload recovery , and bias current tolerance . ( 3 ) a manufacturing method of the snap fastener type electrode element 2 ( with the electroconductive paint coated on the surface to form an electroconductive layer ) the injection molding conditions ( injection temperature , mold temperature ) may be in the most suitable range of the matrix . for example , when polylactic acid is used for the matrix , the injection temperature may be in a range from 100 to 300 ° c ., and the mold temperature may be in a range from 10 to 80 ° c . 2 ) coating the electroconductive paint on the surface of the electrode element 2 ; the kinds of electroconductive material to be added to the electroconductive paint include carbon black , silver , and silver / silver chloride . the surface resistivity after coating is 1 × 10 5 ( ω ) or less . for coating an electroconductive paint , the suitable methods such as vapor deposition , plating , spray coating , screen printing , and hot melt can be taken in accordance with the characteristics of the paint . 3 ) coating the electroconductive paint on the lead wire attaching portion of the electrode element 2 ; simultaneously with coating the electroconductive paint to provide the electroconductivity , a highly electroconductive part is particularly formed on the surface by coating another kind of electroconductive paint on the lead wire attaching portion of the electrode element , if necessary , thereby improving the electrical contact with the lead wire . for coating an electroconductive paint , the suitable methods such as vapor deposition , plating , spray coating , screen printing , and hot melt can be taken in accordance with the characteristics of the paint . further , a stainless cover ( e . g ., stud ) may be provided on the lead wire attaching portion of the electrode element 2 , thereby improving the electrical contact between the electrode element 2 and the connecting terminal of the electrode lead wire . 4 ) coating the non - polarized elecroconductive paint on the electrode paste contact face of the electrode element 2 ; to further enhance the performance of the electrode element 2 of the biological electrode 1 , an electroconductive paint of silver / silver chloride as the electroconductive material may be coated at a part in contact with the electrode paste or the electrode gel on the electrode element 2 having electroconductivity , if necessary . for coating an electroconductive paint , the suitable methods such as vapor deposition , plating , spray coating , screen printing , and hot melt can be taken in accordance with the characteristics of the paint . the electrode performance of the biological electrode 1 after assembly must satisfy the standard , aami / ansi - ec - 12 : pregelled ecg disposable electrodes ( 1982 ). in the first embodiment , instead of the sponge with gel 4 , an electroconductive adhesive gel 4 a formed in the size equivalent to the pad portion 3 may be provided in the biological electrode 1 a as shown in fig3 . in this case , since the adhesion is provided by the electroconductive adhesive gel 4 a , the electrode can be secured adhesively to the skin by the electroconductive adhesive gel 4 a , so the adhesive property of the pad portion 3 is unnecessary . in the biological electrode 1 a as shown in fig3 like parts are indicated by the same numerals as shown in fig2 and are not described . in a biological electrode 30 as shown in fig4 an electrode element 31 is formed with an electroconductive layer 33 on the side of a film - like substrate 32 in contact with a living body ( i . e ., on the lower side in fig4 ), and can be thin with an electroconductive gel 34 on this electroconductive layer 33 . the substrate 32 in this embodiment can be also constituted of a non - woven fabric made of a biodegradable material . in this way , since the substrate 32 is constituted of the non - woven fabric , the biological electrode 30 is so flexible as to reduce uncomfortableness in attaching and have good air permeability . ( 4 ) a manufacturing method of the film - like electrode element 31 will be described below . the biodegradable materials of the film of polyhydroxy carboxylic acids such as polylactic acid , aliphatic polyester ( e . g ., polybutylenesuccinate ( pbs ), polybutylenesuccinate adipate ( pbsa ), and polyethylenesuccinate ( pesu ), or polycaprolactone ( pcl ) or the non - woven fabric of cellulose or chitosan may be used as the substrate of the electrode element 2 . 2 ) coating the electroconductive paint on the surface of the electrode element 31 ; the electroconductive paint is coated on the surface of the substrate 32 to provide the electroconductivity as the biological electrode 30 . the kinds of electroconductive material to be added to the electroconductive paint include carbon black , silver , and silver / silver chloride . when the substrate 32 is a non - woven fabric , the electroconductive paint is coated on the surface of the substrate 32 , or infiltrated into the substrate 32 to provide the electroconductivity as the biological electrode 30 . 3 ) coating the non - polarized elecroconductive paint on the electrode paste contact face of the electrode element 31 ; to further enhance the performance of the biological electrode element , an electroconductive paint of silver / silver chloride as the electroconductive material may be coated at least at a part in contact with the electrode paste or the electrode gel on the electrode element having electroconductivity , if necessary . the electrode performance of the biological electrode after assembly must satisfy the standard , aami / ansi - ec - 12 : pregelled ecg disposable electrodes ( 1982 ). in the above embodiments , the electrode element is composed of the biodegradable material . however , other constituent members in the biological electrode may be composed of the biodegradable material . the sponge 4 contains the gel in the above embodiments , but may contain the paste . in fig4 the structure of the biological electrode 30 is only illustrated in the second embodiment , but in practice , this biological electrode 30 has a lead wire 39 as shown in fig5 . this lead wire 39 is disposable , and made up of a water proof connector 36 , a conducting wire 37 and a connector 38 . instead of the water proof connector 36 , an adhesive tape or welding may be employed to secure the lead wire . to further enhance the adhesive strength , as required , an adhesive pad 35 may be provided on the biological electrode 30 and the lead wire 39 . in the biological electrode 30 as shown in fig5 like constituent members are indicated by the same numerals as shown in fig4 and are not described . as described above , since the biological electrode according to the present invention is constituted by the use of the biodegradable material for the electrode element , and therefore can be decomposed completely owing to microbes in the soil or water , when wasted after the high pressure steam sterilization , for example , as medical waste , the biological electrode can be provided that causes less load on natural environment . also , since the biological electrode generates the small amount of heat while incinerating , the incinerator is not damaged . further , since polyhydroxy carboxylic acids such as polylactic acid , cellulose , polyhydroxy carboxylic acids , chitosan , aliphatic polyester ( e . g ., polybutylenesuccinate ( pbs ), polybutylenesuccinate adipate ( pbsa ), polyethylenesuccinate ( pesu )), polycaprolactone ( pcl ), and starch derivatives contain no chlorine in the molecular structure , the biological electrode will not produce any environmental pollution substance such as dioxin through the incinerating process . since polylactic acid serves to suppress the molding , it is possible to prevent the biological electrode from molding in a moist environment in the biological electrode . therefore , since there is no need of adding fungicide to the electrode paste , the biological electrode has no possibility of causing skin irritation due to fungicide , saving cost of fungicide . in the invention , the case where a non - woven fabric of biodegradable material , particularly cellulose or chitosan , is employed for the film - like electrode element , it is so flexible as to follow deformation of the skin , and less delamination when attached . further , since it is not stiff at the edge part of electrode element , the biological electrode does not cause any skin failure . in the case of the film - like electrode element , compared with snap fastener type electrode element , the surface area is larger than in proportion to the outer shape and a large contact area with gel or paste is provided , so that the electrode element can exhibit the good performance . also , because this film - like electrode element is porous and sweat permeable , the biological electrode keeps good performance in spite of the perspiration .
a biological electrode includes an electrode element having electroconductivity with respect to a living body , the biological electrode used by disposing said electrode element at a predetermined position , and the electrode element being made of biodegradable material .