JP2002181779A - Residual chlorine sensor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a residual chlorine sensor that is hardly subjected to influences from the outside, can be mass-produced, has a small size, and can readily measure the concentration of residual chlorine without requiring any agitating mechanism and the performance of which can be improved due to its little varying characteristics. SOLUTION: This residual chlorine sensor is provided with a pair of electrodes formed on an insulating substrate 30, pads 38 for external terminal which are respectively connected to the electrodes in lead sections 36, an electrolyte-containing body 44 arranged to connect the electrodes to each other. The sensor is also provided with a gas permeating film 46 provided to cover the other portion than the pads 38. Of the paired electrodes, the cathode 32 is composed of a gold electrode and the anode 34 is composed of a silver electrode. The pH value of the electrolyte is set on the acidic side. The electrolyte- containing body 44 is a screen-printed film composed, for example, of polyvinyl pyrrolidone, a sodium chloride or potassium chloride, and a buffering agent. The buffering agent is one or more kinds selected from among borates, acetates, phthalates, citrates, and phosphates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diaphragm type residual chlorine sensor and a method for manufacturing the same.
Using a gold electrode as the cathode and a silver electrode as the anode of the pair of electrodes, the residual chlorine concentration (hypochlorous acid concentration) in the aqueous solution can be measured stably by setting the electrolyte pH to the acidic side. The present invention relates to a sensor and a method for manufacturing the sensor.

[0002]

2. Description of the Related Art In waterworks, pools, septic tanks, etc., chlorine is used for the purpose of sterilization. Therefore, these facilities are required to measure the residual chlorine concentration, and it is necessary to appropriately measure and monitor the residual chlorine amount.

[0003] A dedicated test paper is generally used for measuring the residual chlorine concentration. However, there is a problem that the cost for one measurement is high and the accuracy is low due to visual confirmation.

One of the methods for measuring the residual chlorine with relatively high accuracy is a polarographic electrode type measuring method. FIG. 3 shows an example of the measurement situation. In this method, a detection electrode 12 is provided at the tip of a cylindrical insulator 10, and an electrode device 16 having a structure in which a counter electrode 14 is wound around the outer periphery of the cylindrical insulator 10 is immersed in a sample solution 18. 14 is a method of applying a constant voltage between the first and second electrodes. A current is generated due to the oxidation-reduction reaction occurring on the electrode surface, and since this current has a correlation with the residual chlorine concentration in the sample solution, the residual chlorine concentration can be obtained by measuring the output current value. .

In order to obtain a stable output in this apparatus, a rotor 22 is put together with a sample liquid 18 in a beaker 20, and these are placed on a stirrer 24 to stir the sample liquid. . Instead of using a stirrer, a mechanism for vibrating or rotating the sample liquid may be incorporated in the electrode device itself.

[0006]

However, in the conventional polarographic electrode type measuring method as described above, since both electrodes are in direct contact with the sample solution, a stable sensitivity is obtained due to the influence of the external environment and the adhesion of reactants. Is difficult to obtain. For this reason, maintenance such as periodically polishing the electrode with an abrasive or the like is required. Furthermore, in order to obtain a stable output, it is necessary to add a stirring mechanism. If the device is incorporated in an electrode device, the size of the device is increased and the cost is increased. If a stirrer or the like is used, the measurement is troublesome.

[0007] As a diaphragm type sensor, a small-sized oxygen sensor for measuring the concentration of dissolved oxygen such as a solution has been developed. This is a configuration having a pair of silver electrodes formed on an insulating substrate, arranging an electrolyte-containing body so as to connect the pair of electrodes and between them, and providing a gas permeable membrane so as to cover them. However, such an oxygen sensor cannot stably detect residual chlorine (hypochlorous acid) as it is.

[0008] The object of the present invention is to be less susceptible to external influences,
Small variations in characteristics, high performance, suitable for mass production,
In addition, an object of the present invention is to provide a residual chlorine sensor which is small in size and can be easily measured without requiring a stirring mechanism, and a method for producing the same. Another object of the present invention is to provide a low-cost residual chlorine sensor and a method for manufacturing the same, which are less likely to cause peeling of the gas permeable membrane even when used repeatedly and therefore have a long service life.

[0009]

According to the present invention, a pair of electrodes formed on an insulating substrate, a pad for an external terminal connected to each electrode by a lead portion, and a connection between the pair of electrodes and the electrodes are provided. And a gas permeable membrane provided so as to cover portions other than the pad, the cathode of the pair of electrodes is a gold electrode, the anode is a silver electrode, and the electrolyte pH is on the acidic side. It is a residual chlorine sensor set in.

Here, the electrolyte-containing material is, for example, a screen-printed film comprising polyvinylpyrrolidone, sodium chloride or potassium chloride, and a buffer, wherein the buffer is N 2
H ₂ groups shall not be present, for example borates, acetates,
Any one or more of phthalates, citrates, and phosphates. The pH of the electrolyte is desirably 5.0 to 7.0.

As the gas permeable membrane, a dealcoholized silicone resin or a deoxime type silicone resin in which low molecular siloxane is reduced is desirable. By using these resins, adhesion to the sensor substrate surface is improved, and peeling of the gas permeable film does not occur.

According to the present invention, a cathode gold electrode and an anode silver electrode serving as a pair of electrodes, a pad for an external terminal, and a lead portion connecting between each electrode and the pad for an external terminal are provided on an insulating substrate. And contains polyvinylpyrrolidone, sodium chloride or potassium chloride, and any one or more of borate, acetate, phthalate, citrate, and phosphate as a buffer, and has a screen printable viscosity. The dispersion electrolyte composition is screen-printed in the range connecting the pair of electrodes and the electrodes to form an electrolyte-containing body, and a resin is applied so as to cover portions other than the pads to form a gas permeable membrane. This is a method for manufacturing a residual chlorine sensor.

According to the present invention, a cathode gold electrode and an anode silver electrode serving as a pair of electrodes, a pad for an external terminal, and a lead portion connecting between each electrode and the pad for an external terminal are provided on an insulating substrate. And contains polyvinylpyrrolidone, sodium chloride or potassium chloride, and at least one of borate, acetate, phthalate, citrate, and phosphate as a buffer, and has a screen-printable viscosity. The dispersion electrolyte composition is screen-printed in a range connecting the pair of electrodes and the electrodes to form an electrolyte-containing body, and a pad protective film is formed by screen-printing a peelable coating agent on the pad portion. Then, a resin is spin-coated on the entire substrate to form a gas permeable film, and then the pad protective film is peeled off to remove the gas permeable film thereover, thereby exposing the pad to a residual chlorine film. It is a manufacturing method of support.

In these, it is preferable to use a silicon substrate having a surface oxidized as the insulating substrate. Silicone resin is used as the resin that becomes the gas permeable membrane.
In that case, it is preferable to perform HMDS (hexamethyldisilazane) treatment on the sensor substrate before forming the gas permeable film. For example, before the gas permeable membrane is formed, HMDS
(Hexamethyldisilazane) and the sensor substrate are placed in a vacuum desiccator for about 3 to 10 minutes, more preferably for about 5 to 10 minutes to deposit evaporates and form a thin and uniform HM.
A DS layer is formed. By performing the HMDS treatment as described above, the adhesion between the sensor substrate surface and the gas permeable film can be chemically improved.

When forming the pad protective film, it is preferable to use a thermosetting resin as the coating agent. Electrodes, leads, and pads for external terminals can be easily formed by photolithography and thin film deposition techniques.

[0016]

FIG. 1 is an explanatory view showing one embodiment of a residual chlorine sensor according to the present invention, wherein A shows the internal structure (without electrolyte containing material and gas permeable membrane), and B shows its x-. It shows a cross section at the x position. On the insulating substrate 30, a pair of electrodes consisting of a cathode 32 and an anode 34, and a pad 38 for an external terminal connected to each electrode by a lead portion 36,
It is formed by photolithography technology and thin film deposition technology. As the insulating substrate 30, a silicon substrate 40
Having an oxide film 42 formed on the surface thereof. Here, the cathode 32 is made of a gold electrode, and the anode 34 is made of a silver electrode. Note that the lead portion 36 is covered with an electric insulating film.

An electrolyte-containing member 44 is arranged on the cathode 32 and the anode 34 and so as to connect between them. The electrolyte containing body 44 is a screen-printed film made of polyvinylpyrrolidone, sodium chloride or potassium chloride, and a buffer, and the buffer includes borate, acetate,
One or more of phthalate, citrate, and phosphate are used. This electrolyte pH is on the acidic side (5.0-7.0).
Is set to Then, a gas permeable film 46 is provided so as to cover portions other than the pads. As the gas permeable film 46, a dealcohol-type silicone resin in which low molecular siloxane is reduced or a deoxime-type silicone resin is preferable.

When such a residual chlorine sensor is immersed in a hypochlorous acid solution and a voltage of +0.05 V is applied between the electrodes, the hypochlorous acid that has passed through the gas permeable membrane 46 is converted to the cathode 3.
Reduction on 2 (HClO + e ⁻ → 1 / 2H ₂ + ClO ⁻ )
Is, oxidized on the anode ^{34 (Ag → Ag + + e} -)
A reaction occurs. At this time, a current having a magnitude corresponding to the reaction is generated. By measuring this with the pad 38, the hypochlorous acid concentration (residual chlorine concentration) can be obtained.

In the case of a residual chlorine sensor, silver (Ag) such as an oxygen sensor cannot be used as a cathode material. The reason is that the Ag surface is oxidized by HClO passing through the gas permeable membrane to be changed to AgCl, and the electrode reaction becomes unstable. Therefore, gold (A
u). On the other hand, Ag is used because the anode is a side that originally causes an oxidation reaction.

In this residual chlorine sensor, the electrolyte p
H is set on the acidic side (5.0-7.0). HClO
Since the form changes depending on the pH of the solution, the above setting must be maintained for stable detection. By the way,
In the case of an oxygen sensor, the electrolyte pH is set on the alkaline side. This is because when the electrode is brought to the acidic side, a smooth electrode reaction does not occur and the output current value becomes unstable.

[0021] Since the thus further HClO changes in combined chlorine by substances with NH ₂ groups, a buffer to fix the pH must also be selected from materials such as the not having a NH ₂ group.

In the oxygen sensor, a current is generated when a negative voltage is applied, and a stable output current can be obtained by applying a voltage of -0.9 V. On the other hand, in the residual chlorine sensor, a voltage of about +0.05 V is applied between the electrodes. Therefore, O
_The reduction current is generated only by HClO without being affected by ₂ , and a stable output is obtained.

Next, an example of a procedure for manufacturing the residual chlorine sensor will be described below. (1) Preparation of insulating substrate A silicon wafer is thermally oxidized, and an oxide film (Si
O ₂ ) is formed to form an insulating substrate. (2) Formation of electrode base pattern Chromium (40 nm) is deposited on an insulating substrate by a thin film deposition method.
Films are formed in the order of gold (200 nm). A positive photoresist is applied to the deposition surface, and baked at 80 ° C. Using an exposure apparatus, exposure, development, and cleaning are performed using an electrode pattern mask to form a photoresist pattern. Using the photoresist pattern as a mask, the exposed gold is removed using a gold etchant, and then immersed in acetone to remove the photoresist. Subsequently, the exposed chromium is removed using a chromium etching solution using the gold pattern as a mask, and the chromium is washed, and an electrode base pattern of an electrode portion, a lead portion, and a pad portion is formed. (3) Formation of Lead Insulation Film A photosensitive polyimide resist is applied, and after baking, exposure, development, and cleaning are performed so that the resist remains only in the lead. Subsequently, curing is performed at 280 ° C. for 1 hour in a dryer. (4) Formation of silver thin film Apply a photoresist, and cover it except the anode.
Performs exposure, development, and cleaning. Silver (400
nm) and then immersed in acetone to lift off the silver and form a silver film on the anode only. (5) Formation of Electrolyte-Containing Body An electrolyte pattern is formed by screen-printing an electrolyte paste on the cathode, the anode, and the passage connecting them. The electrolyte paste used here was obtained by dispersing a mixture of powdered potassium chloride, disodium hydrogen phosphate, and potassium dihydrogen phosphate in an alcohol solution of polyvinylpyrrolidone. (6) Formation of gas permeable film A pad protective film is formed by screen-printing a thermosetting release coating on the pad. Next, a predetermined silicone resin is applied by a spin coat method, and dried by a drier.
Cure at 0 ° C. to form a gas permeable membrane. Subsequently, the pad protective film is peeled off from the pad, and the silicone resin on the pad protective film and the pad protective film thereover are also removed, exposing the pad. (7) Chip cutting In this way, a large number of residual chlorine sensors can be simultaneously formed on one silicon wafer. Therefore, the silicon wafer is diced vertically and horizontally, and individual residual chlorine sensors are cut out.

The prepared residual chlorine sensor was immersed in an aqueous solution.
Immerse for more than an hour or introduce water in an autoclave to form an electrolyte. Thereafter, the sample was immersed in a sample solution, a voltage of +0.05 V was applied between the electrodes, and the output current value with respect to the hypochlorous acid concentration in the sample solution was measured. FIG. 2 shows an example of the measurement result. As shown in FIG. 2, a good correlation was obtained with respect to the concentration of hypochlorous acid.

To improve the adhesion strength of the gas permeable membrane, H
MDS (hexamethyldimirazane) treatment is also effective.
Before applying the silicone resin to be a gas permeable membrane, place a beaker containing about 1 ml of HMDS and a wafer (sensor substrate) in a vacuum desiccator and maintain the vacuum state for about 5 minutes, and apply a thin and uniform surface on the wafer. Deposit the HMDS layer. Thereafter, a silicone resin to be a gas permeable film is applied. Since an electrolyte-containing material that has been screen-printed and dried is formed on the wafer surface during the HMDS process, if it is directly immersed in an HMDS solution, they will be peeled off. Therefore, as described above, the method of vaporizing and adhering HMDS is particularly preferable because it does not damage the formed electrolyte-containing body.

The shape, arrangement, size, and the like of each electrode in the residual chlorine sensor according to the present invention are not limited to those in the above-described embodiment, and it goes without saying that they can be appropriately changed according to the application and use conditions.

[0027]

As described above, the present invention makes it possible to measure the hypochlorous acid concentration with a small structure by devising the materials and properties of the electrode and the electrolyte-containing body. Further, since the residual chlorine sensor according to the present invention is basically a diaphragm type structure, it is hardly affected by outside, can stabilize the output, does not require maintenance, and is easy to handle.

According to the present invention, lithography, thin film deposition, and screen printing techniques can be used to collectively manufacture an insulating substrate, so that fine processing can be performed with high accuracy and variations in individual characteristics can be achieved. Small and mass production is possible. In addition, since the size can be reduced, a stirring mechanism is not required, and in that respect, the cost can be significantly reduced and the measurement can be easily performed.

Further, by using an appropriate silicone resin as the gas permeable film or performing HMDS treatment on the sensor substrate before the formation of the gas permeable film, the adhesion strength between the gas permeable film and the sensor substrate is improved. As a result, peeling hardly occurs, and the life can be extended.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a residual chlorine sensor according to the present invention.

FIG. 2 is a graph showing an example of the measurement result.

FIG. 3 is an explanatory diagram of a measurement situation by a conventional residual chlorine sensor device.

[Explanation of symbols]

 Reference Signs List 30 Insulating substrate 32 Cathode 34 Anode 36 Lead part 38 Pad 44 Electrolyte-containing material 46 Gas permeable membrane

Claims (12)

[Claims] 1. A pair of electrodes formed on an insulating substrate, a pad for an external terminal connected to each electrode by a lead, and an electrolyte-containing body disposed so as to connect the pair of electrodes to each other. A gas permeable membrane provided so as to cover portions other than the pad, wherein the cathode of the pair of electrodes is a gold electrode, the anode is a silver electrode, and the electrolyte pH is set to an acidic side. And residual chlorine sensor. 2. The electrolyte-containing material is a membrane comprising polyvinylpyrrolidone, sodium chloride and a buffer, wherein the buffer is any one of borate, acetate, phthalate, citrate and phosphate. 2. The residual chlorine sensor according to claim 1, wherein the sensor is at least one. 3. The electrolyte-containing material is a membrane comprising polyvinylpyrrolidone, potassium chloride and a buffer, wherein the buffer is any one of borate, acetate, phthalate, citrate and phosphate. 2. The residual chlorine sensor according to claim 1, wherein the sensor is at least one. 4. The residual chlorine sensor according to claim 1, wherein the electrolyte has a pH of 5.0 to 7.0. 5. The residual chlorine sensor according to claim 1, wherein the gas permeable membrane is made of a dealcoholized silicone resin in which low molecular siloxane is reduced. 6. The residual chlorine sensor according to claim 1, wherein the gas permeable membrane is made of a deoxime type silicone resin. 7. A cathode gold electrode and an anode silver electrode serving as a pair of electrodes, a pad for an external terminal, and a lead portion connecting between each electrode and the pad for an external terminal are formed on an insulating substrate. And polyvinylpyrrolidone, sodium chloride or potassium chloride, and borate, acetate, phthalate, citrate, a dispersion having a viscosity capable of screen printing and containing at least one of phosphates as a buffering agent. An electrolyte composition is screen-printed in a range connecting the pair of electrodes and the electrodes to form an electrolyte-containing body, and a resin is applied so as to cover portions other than the pads to form a gas permeable membrane. Characteristic method for manufacturing residual chlorine sensor. 8. A cathode gold electrode and an anode silver electrode serving as a pair of electrodes, a pad for an external terminal, and a lead portion connecting between each electrode and the pad for an external terminal are formed on an insulating substrate. And polyvinylpyrrolidone, sodium chloride or potassium chloride, and borate, acetate, phthalate, citrate, a dispersion having a viscosity capable of screen printing and containing at least one of phosphates as a buffering agent. An electrolyte composition is screen-printed in the range between the pair of electrodes and the electrode to form an electrolyte-containing body, and a pad protective film is formed by screen-printing a peelable coating agent on the pad portion, Resin salt characterized by spin-coating a resin to form a gas permeable film, and then removing the pad protective film to remove the gas permeable film on the pad to expose the pad. Element sensor manufacturing method. 9. The method for producing a residual chlorine sensor according to claim 8, wherein a thermosetting resin is used as a coating material for forming a pad protective film. 10. The method for manufacturing a residual chlorine sensor according to claim 7, wherein a silicon substrate having a surface oxidized is used as the insulating substrate. 11. The sensor according to claim 7, wherein a silicone resin is used as a resin to be a gas permeable film, and the sensor substrate is subjected to HMDS (hexamethyldisilazane) treatment before the gas permeable film is formed. Manufacturing method of residual chlorine sensor. 12. The method according to claim 1, further comprising the step of:
The method for manufacturing a residual chlorine sensor according to claim 11, wherein the HMDS treatment is performed by placing DS (hexamethyldisilazane) and the sensor substrate in a vacuum desiccator for 3 to 10 minutes.