JP2000146890A - Regulating method of electrode area - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an electrode at a low cost with a simple facility and perform a precise measurement by sticking a tape having an adhesive having a specified thickness adhered to a base material in the regulation of the area of an electrode using an electrode film formed on the whole one-side surface of an insulating substrate. SOLUTION: A conductive ink containing a resin binder is applied or sprayed to the whole one-side surface of an insulating substrate of polyethylene terephthalate or the like to form an electrode film. The electrode film may be formed by means of various depositions such as resistance heating deposition, high frequency induction heating deposition. As the material to be deposited, a chemically stable metal as electrode, for example, noble metal such as gold, palladium, platinum, silver or the like is preferably used. As the tape used for regulating the electrode area, a single-sided tape or single-sided heat seal having a pressure sensitive or heat fusible adhesive adhered to one side of a base material is used. The thickness of the adhesive is important for the regulation of electrode area, and it must be set to 1-50 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for analyzing a liquid sample and a method for regulating the area of the electrode. The present invention also relates to a biosensor using an oxidoreductase or the like as a reagent and an electrode in combination as a detector.

[0002]

2. Description of the Related Art As a conventional biosensor, for example, one described in Japanese Patent No. 2548147 is known. This has an electrode system mainly composed of carbon formed by screen printing on an insulating substrate, and a reaction layer composed of an enzyme and an electron acceptor. Methods of forming an electrode system mainly composed of carbon by screen printing include fine powders such as carbon black, polyester resin,
By printing a carbon ink composed of resins such as polyvinyl chloride and polyurethane resin and a binder containing a volatile component such as an organic solvent, and heating and drying the carbon ink.
From above, an insulating layer is formed by screen printing in order to regulate the area of the electrode. The formation of this insulating layer can be obtained by using a thermosetting insulating ink to remove volatile components contained in the ink by heating and drying after screen printing, and using an ultraviolet curable insulating ink. If so, it is obtained by irradiating ultraviolet rays after screen printing. The insulating layer formed in this way covers a part of the electrode system mainly composed of carbon, and by exposing a part thereof, only the exposed part comes into contact with the liquid to work as an electrode. is there. That is, the electrode area is regulated using screen printing.

When the above biosensor is applied to, for example, the measurement of glucose concentration in a liquid sample, glucose oxidase (GOD) is used as an enzyme and potassium ferricyanide is used as an electron acceptor. The reaction between these and glucose in the liquid sample produces potassium ferrocyanide. The generated potassium ferrocyanide can be electrochemically oxidized by applying a voltage to the electrode, and the concentration of glucose in the liquid can be measured from the current obtained at this time. At this time, the obtained current is proportional to the electrode area even if the concentration of the generated potassium ferrocyanide is the same, so that the electrode area needs to be accurately and precisely regulated for accurate measurement.

[0004] In the formation of an insulating layer by screen printing, there is a problem in that the electrode area varies due to ink bleeding. Generally, in screen printing, it is said that there is a bleed of about ± 10 μm.
When it is necessary to form a small electrode of about 1 mm × 1 mm, an error of about ± 4% occurs at the maximum in consideration of bleeding on all four sides of the square.

Further, when an insulating ink for forming an insulating layer is applied on an electrode formed by screen printing of carbon, there is a problem that the electric resistance increases because the insulating ink permeates the carbon. Was.

As a biosensor using means other than screen printing as means for regulating the electrode area,
The one described in JP-A-9-189675 is known. In this method, an electrode system is produced by forming a metal film on the entire surface by vapor deposition or bonding a metal layer to an insulating substrate, dividing by a slit formed using a laser, and then disposing a cover. . In this case, the method of regulating the electrode area is a combination of two means, that is, the formation of a slit by a laser and the regulation of the exposed area of the metal film by disposing a cover. A reaction layer made of oxidoreductase or the like is formed on the electrode system thus formed to construct a biosensor.

However, when a slit is formed by using a laser, there is a problem that the boundary area between the slit and the electrode is blurred, thereby causing variations in the electrode area. The mechanism in which a slit is formed in a metal film by a laser is that a portion irradiated with a laser beam is locally heated, and the metal is locally evaporated and removed. For this reason, in order to minimize the blur, it is necessary to strictly control the area of the portion irradiated with the laser light. That is, the focusing accuracy of the laser must be strict. However, in order to improve the focusing accuracy, it is necessary to control the incident angle when irradiating the metal film with laser light, and to create a metal surface without irregularities for that purpose.
Such as technical difficulty is high. Further, since metals generally have high thermal conductivity, when locally heated and locally evaporated, the temperature at the end of the local region is lower than that at the center, and the blur is reduced. Cause.

In addition, equipment for forming a slit using a laser is considerably expensive, and there is a problem that it is difficult to produce an inexpensive electrode.

The method of regulating the electrode area by arranging the cover can be manufactured with simple equipment. However, depending on the material and structure of the cover, the electrode area may not be regulated with accuracy. .

For example, when a tape made of a base material and an adhesive material is used as the cover, if the adhesive material is thick, the pressure-sensitive adhesive material is crushed when the tape is pressure-bonded. In some cases, the adhesive material was distorted at the boundary.

[0011]

SUMMARY OF THE INVENTION In view of the problems involved in the prior art as described above, the problem to be solved by the present invention can be implemented with simple equipment, can manufacture an inexpensive electrode, and has an accurate and accurate method. An object of the present invention is to provide an electrode capable of performing accurate measurement, and to provide an accurate and accurate electrode area control method for that purpose.

[0012]

Means for Solving the Problems In order to solve this problem, the method for regulating the electrode area according to the present invention is a method for regulating the area of an electrode using an electrode film formed on the entire surface of an insulating substrate. A method of attaching a tape made of a material and an adhesive material glued thereto, wherein the thickness of the adhesive material of the tape is
This is a method for regulating an electrode area of 1 to 50 μm. The tape is preferably cut with a blade.
The tape may be a double-sided tape having a pressure-sensitive adhesive adhered to both sides of the substrate, or a double-sided heat tape having a heat-adhesive adhesive adhered to both sides of the substrate. Is also good.
The base material is preferably an insulating plastic, and among them, polyethylene terephthalate is more preferable. In addition, it is also possible to use an area regulating method of providing a groove in the electrode film and dividing the electrode film, and it is preferable that the means for providing the groove is a half cut by a blade.
Preferably, the electrode film is made of one selected from gold, palladium, platinum, silver, and carbon.

The present inventors have also solved the problem by providing an electrode prepared by the above-described method for regulating the electrode area, and a biosensor in which the electrode is covered with a reagent layer containing at least an oxidoreductase. Can be provided.

[0014]

Embodiments of the present invention will be described below. As the insulating substrate in the present invention, polyesters such as polyethylene terephthalate, polybutylene terephthalate and copolymer polyesters containing these units as main components, 6-nylon, 6,6-nylon and these units as main components Substrates made of copolymerized polyamide, polyethylene or polypropylene, copolymerized polyolefins containing these units as main components, aromatic polyamides, polyimides, polyvinyl alcohol-based polymers and the like can be exemplified. Among them, polyethylene terephthalate, a polyester having 85% by weight or more of polyethylene terephthalate units, a substrate made of polyethylene, polypropylene, or a copolymerized polyolefin containing these units as a main component is preferred because of its physical properties, economical efficiency, environmental compatibility and the like. More preferred. The thickness of the substrate is not particularly limited, but is preferably about 100 to 300 μm in consideration of handleability, physical strength, and the like. However, when you want to make a curved electrode,
If desired, a substrate having a thickness of 100 μm or less can be used.

An electrode film is formed on the entire surface of the insulating substrate. The electrode film can be formed by applying or spraying a conductive ink containing a resin binder, but is not limited thereto, and may be formed by vapor deposition or the like.

The term “vapor deposition” in the present invention means various known vapor deposition methods. For example, resistance heating deposition, high-frequency induction heating deposition, electron beam heating deposition, ion plating deposition, sputtering, resistance heating reactive deposition, high-frequency induction heating reactive deposition, electron beam heating reactive deposition , An ion plating reactive vapor deposition method, a reactive sputtering method, and the like. The thickness of the electrode film formed by vapor deposition is usually 5 to 50 nm.
Although it is within the range, it is preferably 20 nm or more from the viewpoint of electric conductivity. In order to improve the adhesion between the electrode film formed by vapor deposition and the substrate, the substrate may be subjected to a known pretreatment. Examples of the pretreatment include a resin undercoating treatment, a corona discharge treatment, a glow discharge treatment, an ultraviolet irradiation treatment, an ozone treatment, and the like. As the resin used for the undercoating treatment of the resin, any of various resins such as a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin can be used, if desired. For example,
Acrylic resin, nitrocellulose resin, urethane resin, melamine resin, melamine-acryl resin, urea melamine resin, epoxy resin, epoxy-isocyanate resin, amino alkyd resin and the like can be used alone or in combination. . The material to be deposited is preferably a chemically stable metal from the viewpoint of use as an electrode. It is preferable to use a noble metal such as gold, palladium, platinum, or silver having good electrode characteristics, and gold is particularly preferable.

The electrode film can be divided by providing grooves. By providing the groove, the electrode film on one side of the groove and the electrode film on the other side can be substantially insulated. As a means for providing a groove, a half cut using a blade is particularly preferable from the viewpoint of minimizing blurring and distortion at a boundary portion between the groove portion and the electrode film portion. The half-cut referred to here does not mean cutting the entire substrate on which the electrode film is formed, but rather cutting the electrode film to a depth at least such that the electrode film is cut but not to the substrate itself. Means to put The depth at which the blade is inserted is not particularly limited as long as one side and the other side of the groove are substantially insulated, but it is not necessary to insert the blade deep enough to impair the physical strength of the substrate. However, this does not apply particularly when the purpose is to insert the blade deeply.

The tape used for regulating the electrode area may be a single-sided tape in which a pressure-sensitive or heat-adhesive adhesive is adhered to one side of a substrate, or a single-sided heat seal, A double-sided tape or a double-sided heat seal to which a pressure-sensitive or heat-adhesive adhesive is glued may be used. As the base material of the tape, known materials such as nonwoven fabric, polyester, polyethylene terephthalate, and polystyrene can be used, but hard plastics, which are easy to cut accurately with a blade or the like, particularly polyethylene terephthalate are preferable. The thickness of the substrate is not particularly limited, but is preferably 10 μm or more in consideration of handleability and the like in relation to the preferable thickness of the pressure-sensitive adhesive described later. As the adhesive, a known adhesive such as an acrylic adhesive or a rubber adhesive can be used.

The thickness of the adhesive is important in regulating the electrode area, and must be 1 to 50 μm. Particularly preferred is 25 μm or less. However, there is no particular limitation on the thickness of the adhesive material on the side not in contact with the metal film surface when using a double-sided tape or a double-sided heat seal.

The tape cut by a blade is pressure-bonded or heat-bonded to the electrode film. Thereby, the electrode area is regulated together with the installation of the groove.

A biosensor can be constructed by forming a reagent layer containing at least an oxidoreductase on the electrode thus produced. The oxidoreductase is, depending on the substance to be measured, for example, GOD when measuring glucose, lactate oxidase when measuring lactic acid, cholesterol oxidase when measuring cholesterol, and so on. Can be selected and used. If desired, it is easy to form a reagent layer containing a metallocene compound such as potassium ferricyanide or ferrocene, or an electron donor such as quinones.
If necessary, a reagent layer containing a coenzyme such as nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate, or pyrroloquinoline quinone can be used. In addition, it is easy for those skilled in the art to construct a known reaction system as a reagent layer when constructing a biosensor.

Example 1 Gold was vapor-deposited on one entire surface of polyethylene terephthalate (hereinafter abbreviated as PET) having a thickness of 100 μm to prepare a gold-deposited substrate. This gold-deposited substrate is
As shown in FIG. 1, half cutting was performed at 1.5 mm intervals. For the half cut, a Thomson blade with a thickness of 0.75 mm was used. Next, the base material is a PET having a thickness of 150 μm, and the adhesive is cut off a double-sided tape, which is an acrylic adhesive having a thickness of 25 μm, while leaving a backing sheet, and peeling off unnecessary portions, as shown in FIG. A double-sided tape pattern having a width of 2.25 mm, a gap of 1.5 mm and 4 mm was prepared. The release paper on the side opposite to the backing of the double-sided tape pattern thus produced was peeled off, and the adhesive was exposed, and then pressure-bonded to a half-cut gold-deposited substrate as shown in FIG. 4.5mm x 10m using scissors along the half cut
Thus, the electrode as shown in FIG. 4 was obtained.

The measurement was performed using the electrode thus manufactured. An aqueous solution prepared by adjusting potassium ferricyanide and potassium ferrocyanide to a concentration of 10 mM each was dropped to cover the entire area of the working electrode (41) and the counter electrode (42), and the current when a constant voltage (500 mV) was applied was measured. The measurement was performed for 5 seconds. The measurement was performed using a potentiostat.
Electrical conduction was obtained by pressing metal probe pins against the leads (43, 44), and voltage application and current measurement were performed.
The coefficient of variation of the current value 5 seconds after the application of the voltage was calculated to be 0.91%. The number of measurements (n) was 30. It was found that the electrode area could be regulated accurately.

Example 2 A carbon ink was applied to the entire surface of a 100 μm-thick polyethylene terephthalate (hereinafter abbreviated as PET) to prepare a carbon-coated substrate. As shown in FIG. 1, a 1.5 m
Half-cut at m intervals. For the half cut, a Thomson blade with a thickness of 0.75 mm was used. Next, the base material is a 150 μm-thick PET, and the adhesive is cut off a double-sided tape that is an acrylic adhesive having a thickness of 25 μm, leaving the backing paper,
By removing unnecessary portions, the width as shown in FIG.
A double-sided tape pattern of 25 mm, a gap of 1.5 mm and 4 mm was prepared. The release paper on the side opposite to the backing paper of the double-sided tape pattern thus produced was peeled off to expose the adhesive, and then pressure-bonded to a half-cut carbon-coated substrate as shown in FIG. This was cut into 4.5 mm × 10 mm using scissors along the half cut to obtain an electrode as shown in FIG.

The measurement was performed using the electrode thus manufactured. An aqueous solution prepared by adjusting potassium ferricyanide and potassium ferrocyanide to a concentration of 10 mM each was dropped to cover the entire area of the working electrode (41) and the counter electrode (42), and the current when a constant voltage (500 mV) was applied was measured. The measurement was performed for 5 seconds. The measurement was performed using a potentiostat.
Electrical conduction was obtained by pressing metal probe pins against the leads (43, 44), and voltage application and current measurement were performed.
The coefficient of variation of the current value 5 seconds after the application of the voltage was calculated to be 1.01%. The number of measurements (n) was 30. It was found that the electrode area could be regulated accurately.

Comparative Example 1 A silver ink, a carbon ink, and a resist ink were screen-printed in this order on a PET substrate to produce an electrode as shown in FIG. Silver printing was performed as a lead, carbon printing was performed as an electrode, and resist printing was performed to regulate the area of the carbon printed electrode and cover the silver printed lead. In the same manner as in Example 1 using the electrode thus manufactured, potassium ferricyanide,
When potassium ferrocyanide and a 10 mM aqueous solution were measured, the coefficient of variation of the current value after 5 seconds from the application of the voltage was 1.65%. The number of measurements (n) was 30.

Comparative Example 2 In the same manner as in Example 1, a gold-deposited substrate was produced. Next, the thickness of the adhesive material without the base material is 2
By cutting the double-sided tape, which is an acrylic adhesive material of 00 μm, leaving the backing sheet, and peeling off unnecessary portions, a width of 2.25 mm, a gap of 1.5 mm and 4 mm as shown in FIG.
Was prepared. In this way, the release paper on the side opposite to the backing of the double-sided tape pattern was peeled off to expose the adhesive, and then pressure-bonded to a half-cut gold-deposited substrate as shown in FIG. This was cut into 4.5 mm × 10 mm using scissors along the half cut to obtain an electrode as shown in FIG. In the same manner as in Example 1 using the electrode thus manufactured, potassium ferricyanide, potassium ferrocyanide,
When a 0 mM aqueous solution was measured, the coefficient of variation of the current value after 5 seconds from the application of the voltage was 4.71%. The number of measurements (n) was 30.

Example 3 A gold vapor-deposited substrate was produced in the same manner as in Example 1. Next, the base material is a PET having a thickness of 150 μm, and the adhesive is cut off a double-sided tape, which is an acrylic adhesive having a thickness of 25 μm, while leaving a backing sheet, and peeling off unnecessary portions, as shown in FIG. 2.25 mm width, gap 1.
5 mm and 4 mm double sided tape patterns were made.
In this way, the release paper on the side opposite to the backing of the double-sided tape pattern was peeled off to expose the adhesive, and then pressure-bonded to a half-cut gold-deposited substrate as shown in FIG. 3. Use scissors along the half cut.
By cutting into 5 mm × 10 mm, an electrode as shown in FIG. 4 was obtained.

An aqueous solution comprising a water-soluble polymer (carboxymethylcellulose), potassium ferricyanide, and GOD was dropped on the electrode thus prepared, and dried to form a reagent layer, thereby producing a glucose sensor.

On the electrode on which the reagent layer is formed, peel off the release paper on the side opposite to the electrode of the double-sided tape, and attach a PET sheet having a thickness of 75 μm and 4.5 mm × 6 mm to the capillary. Formed. This allows the liquid sample to be guided into the capillary by capillary action only by touching the end of the capillary. Further, since the volume inside the capillary is regulated to be constant using the double-sided tape as a spacer, it is possible to collect a fixed amount of liquid sample.

When the glucose concentration is 0,100,300,5
An aqueous glucose solution was prepared so that the concentration of sodium chloride was 00 mg / dl and the concentration of sodium chloride was 0.9%. Using this as a sample, measurement was performed using the produced glucose sensor.
The glucose aqueous solution was brought into contact with the end of the glucose sensor, and 50 seconds after being introduced into the capillary.
A constant voltage of 0 mV was applied, and the current was measured 5 seconds after the voltage was applied. FIG. 6 shows the relationship between the obtained current value and the concentration of the aqueous glucose solution. Good linear response to glucose concentration was obtained.

[0032]

As described above, according to the present invention, the electrode area can be regulated with high accuracy, and therefore, an electrode having good response accuracy can be easily manufactured at low cost. Also,
By providing a reagent layer such as an oxidoreductase, a biosensor capable of specifically measuring a specific substance can be manufactured.

[0033]

[Brief description of the drawings]

FIG. 1 is a plan view of a half-cut gold deposition substrate.

FIG. 2 is a plan view of a double-sided tape pattern.

FIG. 3 is a plan view when a double-sided tape pattern is attached to a half-cut gold vapor deposition substrate.

FIG. 4 is a plan view of an electrode cut out from a half-cut gold vapor-deposited substrate having a double-sided tape pattern attached thereto.

FIG. 5 is a plan view of an electrode manufactured by screen printing.

FIG. 6 is a graph showing a relationship between a current value and a glucose concentration.

[0034]

[Description of sign]

 DESCRIPTION OF SYMBOLS 11 Gold vapor deposition board 12 Half cut 21 Double-sided tape 22 Mount 41 Working electrode 42 Counter electrode 43,44 Lead 51 Silver printing 52 Carbon printing 53 Resist printing

Claims (11)

[Claims] In a method for regulating an area of an electrode using an electrode film formed on an entire surface of an insulating substrate, a tape made of a substrate and an adhesive adhered to the substrate is attached to the electrode film. The thickness of the adhesive of the tape is 1 to 50.
μm, wherein the electrode area is regulated. 2. The method according to claim 1, wherein the tape is cut by a blade. 3. The method for regulating an electrode area according to claim 1, wherein the tape is a double-sided tape in which a pressure-sensitive adhesive is adhered to both sides of a base material. 4. The method for regulating an electrode area according to claim 1, wherein the tape is a double-sided heat tape in which a heat-adhesive adhesive is adhered to both surfaces of a base material. 5. The method according to claim 1, wherein the base material is a hard plastic. 6. The method according to claim 5, wherein the hard plastic is polyethylene terephthalate. 7. The method according to claim 1, wherein an area regulating method of dividing the electrode film by providing a groove is used.
The method for regulating an electrode area according to any one of the above. 8. The method according to claim 7, wherein the means for providing the groove is a half cut by a cutting tool. 9. The method according to claim 9, wherein the electrode film is made of gold, palladium, platinum,
9. The method for regulating an electrode area according to claim 1, wherein the electrode area is made of one selected from silver and carbon. 10. An electrode manufactured by using the electrode area regulating method according to claim 1. 11. A biosensor comprising the electrode according to claim 10 covered with a reagent layer containing at least an oxidoreductase.