JPH05230142A - Adjustment of ph of polyvinyl pyrrolidone and polyvinyl pyrrolidone having ph adjusted with same and screen printing electrolyte composition containing the same and oxygen electrode using the composition and its production - Google Patents

Abstract

PURPOSE:To stably adjust the pH of polyvinyl pyrrolidone by dissolving the polyvinyl pyrrolidone in a buffer solution having a prescribed pH value and subsequently removing the buffer solution component from the solution. CONSTITUTION:Polyvinyl pyrrolidone is dissolved in a buffer solution having a prescribed pH value, and the buffer solution component is removed from the obtained solution preferably by a gel filtration method or by a dialysis method. The buffer solution may be that usually used as a pH buffer solution such as a phosphoric acid buffer solution, acetic acid buffer solution or a citric acid buffer solution. An electrolytic composition for screen printing is obtained by dispersing a fine powdery inorganic salt capable of passing through a mesh for screen printing in a polyvinyl pyrrolidine organic solvent solution controlled to the above-mentioned pH.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting pH of polyvinylpyrrolidone, polyvinylpyrrolidone having a pH adjusted by the method, an electrolyte composition for screen printing containing the same, an oxygen electrode using the composition, and the same. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Polyvinylpyrrolidone (PVP) is soluble in water and organic solvents, and imparts a viscosity suitable for use in various solutions and slurries (for example, paints, inks, ceramics, etc.) or in solvents during use. It is used for various purposes such as containing and holding a specific component in a solid state until it is administered to (for example, a tablet of a pharmaceutical product).

In general, many commercially available PVPs show acidity when made into an aqueous solution, and the pH value at that time is allowed in a considerably wide range. For example, Kanto Chemical Co., Ltd.
The manufactured PVP exhibits a pH of 4 to 5 as an aqueous solution. In addition, according to the standard of PVP used for pharmaceuticals, pH 3 to 7 has a wide pH range.
The H range is allowed. Therefore, when the commercially available PVP is used as it is, the pH value of the aqueous solution varies depending on the product lot.

However, depending on the application, it is desirable to adjust the pH of PVP so that it always becomes a constant value. For example, the inventors of the present invention, in an organic solvent solution of polyvinylpyrrolidone, a fine powdery inorganic salt that can pass through a screen-printing mesh is dispersed as an electrolyte component to obtain a screen-printing electrolyte composition, which is then screen-printed. We have proposed a method of manufacturing a small oxygen electrode that fills the oxygen sensitive part. (Note: Your company No.91-15091, specification manuscript 1 /
14 sent. Apply before this case and enter the application number here. This method makes it possible to mass-produce a diaphragm type oxygen electrode having a simpler structure and a smaller size than the conventional one with uniform quality by applying a semiconductor process technology.

The oxygen electrode is very useful for measuring the dissolved oxygen concentration in various fields. For example, an oxygen electrode is used to measure the biochemical oxygen demand (BOD) for water quality conservation, and to adjust the dissolved oxygen concentration in the fermenter to make alcohol fermentation and the like efficient in the fermentation and brewing industries. Furthermore, the oxygen electrode can also be used as an enzyme electrode by combining it with an enzyme.

The oxygen electrode is also very useful for controlling the oxygen concentration in the gas phase in addition to the dissolved oxygen in the solution. For example, an oxygen electrode is used for measuring the oxygen concentration in the atmosphere for the purpose of preventing oxygen deficiency in various working environments, and for strictly controlling the oxygen concentration of gas used for treatment such as oxygen cylinder suction and gas anesthesia. As described above, the oxygen electrode has high utility value in various fields such as environmental measurement, fermentation industry, clinical medicine, and occupational safety.

The electrolyte composition used in the production of the small oxygen electrode is a fine powder of an inorganic salt such as potassium chloride dispersed in PVP dissolved in an organic solvent. PVP has a role as a thickener for obtaining a viscosity suitable for screen printing and a role for fixing printed potassium chloride on a substrate (usually a silicon wafer). Since PVP is soluble in both water and organic solvents as described above, when water is introduced into the electrolyte composition of the oxygen sensitive part through the gas permeable membrane to activate the electrode when a small oxygen electrode is used, the electrode is activated together with potassium chloride. It dissolves in water to form an aqueous solution.

Since the electrochemical reaction in the oxygen sensitive part depends on the pH of the aqueous solution, it is important to keep the pH constant in order to stabilize the characteristics of the small oxygen electrode.
Also, it is desirable to maintain the neutral to alkaline side rather than the acidic side. As described above, commercially available PVPs generally have large variations depending on product lots and often show acidity, so that it is difficult to control the pH value of the oxygen sensitive part to a desired constant value.

Since PVP itself does not include a structure showing acidity, it is considered that the cause of acidity is impurities. PVP
Can be purified to remove acidic impurities, but this is difficult in practice. As a method for purifying a polymer resin, a method of dissolving the polymer resin in a good solvent and then dropping it into a poor solvent for precipitation is generally used. Impurities in PVP should have the property of dissolving in water since they show acidity. Here, since many of the usual polymer substances are not soluble in water, it should be easy to separate and remove impurities that are soluble in water. But PV
In the case of P, since it also dissolves in water, it behaves similarly to water-soluble impurities, so that separation is extremely difficult.

Further, there is a solubilizing agent as a use of PVP for pharmaceuticals. Although many pharmaceuticals are difficult to dissolve in water or the like, they can be made soluble by adding PVP. At that time, the impurities in PVP are also dissolved in the solvent, which should not be dissolved, by the action of PVP, which makes removal difficult.

[0011]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and a method of stably adjusting the pH of polyvinylpyrrolidone to a predetermined value, polyvinylpyrrolidone having a predetermined pH value by this method, and the predetermined method. It is an object of the present invention to provide an electrolyte composition for screen printing using polyvinylpyrrolidone having a pH, a small oxygen electrode with improved stability of operating characteristics using the same, and a method for producing the same.

[0012]

In order to achieve the above object, in the present invention, polyvinylpyrrolidone is dissolved in a buffer solution having a predetermined pH value, and then the above-mentioned buffer solution component is removed from the obtained solution. Thereby adjusting the pH of polyvinylpyrrolidone. Desirably, removal of buffer components is accomplished by gel filtration or dialysis. The polyvinylpyrrolidone thus obtained is freeze-dried to obtain polyvinylpyrrolidone in powder form.

The buffer used in the present invention is a phosphate buffer,
Acetate buffer, borate buffer, citrate buffer, phthalate buffer, tetraborate buffer, glycinate buffer, tris (hydroxymethyl) aminomethane buffer, etc., usually pH
What is used as a buffer may be used. The electrolyte composition for screen printing of the present invention is obtained by dispersing, as an electrolyte component, a fine powdery inorganic salt capable of passing through a screen printing mesh in an organic solvent solution of polyvinylpyrrolidone having the above-mentioned predetermined pH.

The small oxygen electrode of the present invention is produced by filling the oxygen sensitive portion with the above-mentioned screen printing electrolyte composition by screen printing.

[0015]

In the present invention, polyvinylpyrrolidone (P
VP) is neutralized by dissolving it in a buffer solution and placed in an environment of a predetermined pH. The buffer component is removed by gel filtration or dialysis of this. At that time, the pH of the PVP maintains the pH of the buffer solution even after the components of the buffer solution are removed. By removing the water content by freeze-drying PVP in this state, PVP powder is obtained.

[0016]

【Example】

[Example 1] PVP (K = 30, Kanto Chemical Co., Inc.) was dissolved in a phosphate buffer to prepare a 10% solution (pH 7.1). This is the Fast Desalting Column (φ10 × 10
Gel filtration was carried out at a flow rate of 1 ml / min using a water of 0 mm, Pharmacia Co., Ltd. as a solvent. The PVP fraction was collected, monitored by light absorption at 254 nm. This was freeze-dried to obtain a powder having the same pH 7.1 as the buffer solution.
On the other hand, the untreated PVP had a pH of 3.8.

For dialysis, a 10% PVP solution injected into a dialysis membrane is immersed in a large excess of water in which water is gently stirred. Replace the water 2-3 times overnight (8-1
When left for 2 hours or more), the buffer component is removed.
The PVP solution was taken out from the dialysis membrane and freeze-dried to obtain PVP powder having a pH similar to that in the case of gel filtration.

An electrolyte paste for an oxygen electrode was prepared using the PVP powder thus obtained. The composition of the electrolyte paste was as follows. Potassium chloride 1 g PVP 1 g Pentanol 5 g Here, in consideration of the mesh diameter of screen printing performed later, potassium chloride used is pulverized to have a particle diameter of 10 μm or less.

Example 2 The electrolytic paste prepared in Example 1 was screen-printed on the sensitive part of a small oxygen electrode,
Further, a gas permeable film is formed on it to complete the oxygen electrode. The small oxygen electrode of the present invention is basically manufactured by the following steps. (A) Formation of grooves in oxygen-sensitive portion by anisotropic etching (b) Formation of metal thin film by vacuum deposition (c) Formation of electrode pattern by etching of metal thin film (d) Negative resist pattern for determining oxygen-sensitive portion (E) Filling the oxygen sensitive part with an electrolyte by screen printing (f) Forming a gas permeable film covering the oxygen sensitive part filled with the electrolyte With reference to FIGS. explain. Each drawing number corresponds to the following procedure number. In the figure, a region of one small oxygen electrode on the substrate is shown in a plan view from above, but in reality, a large number of small oxygen electrodes are collectively formed on one substrate.

Step 1: Wafer cleaning A 250-500 μm thick (100) surface 3-inch silicon wafer 1 was prepared and thoroughly washed with a mixed solution of hydrogen peroxide and ammonia and concentrated nitric acid.

[0021]Step 2: SiO ₂ film formation By wet thermal oxidation of wafer 1,
0.8 μm thick SiO ₂The film 2 was formed.

Step 3: Photoresist for etching mask
Formation of a photoresist pattern A photoresist pattern 3 for an etching mask was formed on the wafer using a negative photoresist (OMR-83 manufactured by Tokyo Ohka Co., Ltd., viscosity 60 cP). Apply the same photoresist to the backside of wafer 1 and apply the same photoresist at 130 ° C for 3
Bake for 0 minutes.

Step 4: Etching of SiO ₂ film (anisotropic
Formation of Etching Mask ) The wafer is dipped in a 50% hydrofluoric acid + 40% ammonium fluoride aqueous solution (mixing ratio 1: 6) to remove the exposed portion of the SiO ₂ film 2 (electrolyte filling groove formation planned position) 4A. did. Further, the photoresist 3 was removed with concentrated nitric acid + 30% hydrogen peroxide aqueous solution (mixing ratio 2: 1).

Step 5: Anisotropic Etching of Wafer Silicon
(The above-mentioned basic step (a)) Using the SiO ₂ film 2 patterned in the previous step 4 as a mask, the wafer silicon 1 is anisotropically etched with a 35% potassium hydroxide aqueous solution at 80 ° C. to fill the electrolyte. Two electrolyte-filling grooves 4 having a V-shaped cross section having a depth of 300 μm were dug at the planned groove formation position 4A. After the anisotropic etching was completed, the SiO ₂ film 2 used as a mask was removed with the same aqueous solution as in the previous procedure 4.

Step 6: Formation of SiO ₂ film serving as an insulating film After cleaning the wafer by the same method as in step 1, wet thermal oxidation is performed under the same conditions as in step 2 to obtain a thickness of 0.
An SiO ₂ insulating film 5 having a thickness of 8 μm was formed.

Step 7: Formation of chromium thin film and gold thin film
(Basic step (b)) A chromium thin film 6 (thickness 400 Å) and a gold thin film 7 (thickness 4000 Å) thereon were formed on the entire surface of the wafer by vacuum evaporation. The gold thin film 7 is later patterned to become a substantial part of the electrode, and the chromium thin film 6 is for adhering the gold thin film 7 to the substrate.

Step 8: Photoresist for electrode patterning
Doo positive photo on the application wafer 1 of the resist 8 (Tokyo Ohka Kogyo Co., Ltd. OF
PR-800, 20cP or OFPR-5000, 5
0 cP) was dripped and spread evenly over the wafer 1. The amount of the photoresist 8 is preferably such that the photoresist 8 reaches the periphery of the wafer 1. This was post-baked at 80 ° C. for 1 day.

Step 9: Photoresist for electrode patterning
After forming a pattern with a glass mask using an aligner, a photoresist 8 was patterned by exposure and development. When the positive type photoresist is applied thickly as in this example, the exposure / development cycle was repeated several times because it was not exposed once.

Step 10: Etching of gold thin film (basic process
( First half of (c)) The wafer 1 was immersed in a gold etching solution having the following composition, and the exposed portion of the gold thin film 7 was removed by etching. After this,
The positive photoresist 8 was removed with acetone. Etching solution composition for gold: 4 g potassium iodide + 1 g iodine + 40 ml water

Step 11: Etching of chromium thin film (basic
The latter half of the step (c))) The wafer 1 is dipped in an etching solution for chromium having the following composition,
The exposed portion of the chromium thin film 6 was removed by etching. Chromium etching liquid composition: 0.5 g sodium hydroxide + 1 g potassium ferricyanide + 4 ml water By the steps 10 and 11, the lower layer for adhesion of the chromium thin film 6 and the gold thin film 7 are formed on the SiO ₂ insulating film 5 covering the surface of the silicon wafer 1. An electrode pattern (anode 9A, cathode 9B) consisting of the upper layer for the electrode substantial part of (3) was formed. In the figure, the anode has two right ends separated into the two electrolyte filling grooves 4, and the left end serves as a pad 9Ap for electrical connection with the outside. Also, the cathode 9
B has a right end reaching a flat portion between the two grooves 4 and a left end serving as a pad 9Bp for electrical connection with the outside. In a later procedure, the electrolyte composition is arranged in a range extending over the two grooves 4 and the flat portion between them to form the oxygen sensitive portion.

Step 12: Photoresist for confirming oxygen sensitive part
Pattern formation (basic step (d)) The substrate surface excluding the oxygen sensitive portion formation-scheduled region 10 (two trenches 4 and the flat portion between them) and the region 11 of the pad portions 9Ap and 9Bp is processed with a negative photo Resist 12
(Tokyo Ohka OMR-83, 60 cP). This coating process applies a photoresist 12 to the surface of the substrate,
It was performed by exposing and developing after prebaking.

Step 13: Screen marking of electrolyte paste
Printing (basic step (e)) The electrolyte paste prepared in Example 1 was screen-printed on the oxygen sensitive portion formation scheduled region 10. In the printed electrolyte paste 13, the portion filled in the groove 4 is the anode 9
The part where the flat part between the grooves 4 is in contact with A is the cathode 9B.
To form an oxygen sensitive part together with these electrodes.

Step 14: Formation of Pad Area Covering Film A thermosetting release coating (Fujikura Kasei XB-8) is formed on the pad area 11.
01) was screen-printed and then heated and cured at 150 ° C. for 10 minutes to form a pad region coating film 14.

Step 15: Formation of gas permeable membrane (basic process
(F)) The gas permeable film 15 was coated on the entire surface of the substrate. Gas permeable membrane 15
Is a negative photoresist (Tokyo Ohka OMR-83, 6
0 cP) as a lower layer by spin coating, and a silicone resin (Toray Dow Corning Silicone SE9
176) is spin coated to form an upper layer having a two-layer structure.

Step 16: Exposed pad area The pad area coating film 14 was peeled off with tweezers to expose the pad area 11 including the pads 9Ap and 9Bp. By the above procedures 1 to 16, a large number of small oxygen electrodes were collectively and uniformly produced on one silicon wafer 1. From this, each small oxygen electrode was cut out as a chip with a dicing saw.

The characteristics of the small-sized oxygen electrode manufactured according to this example are shown in FIG. This is a response curve when the dissolved oxygen concentration is instantly zeroed by adding sodium sulfite powder to the state where the dissolved oxygen in water is saturated. A small oxygen electrode using PVP whose pH is not adjusted has an oxygen concentration of 0.
However, the output current does not become zero. On the other hand, in the present embodiment, the output current approaches 0. This is p
It is considered that this is because the operation of the small oxygen electrode was stabilized by adjusting H.

[0037]

As described above, according to the present invention,
The pH of polyvinylpyrrolidone can be stably adjusted to a predetermined value. By applying the electrolyte composition for screen printing using polyvinylpyrrolidone having a regulated predetermined pH to the oxygen sensitive part of the small oxygen electrode, the stability of the operating characteristics of the small oxygen electrode can be improved.

[Brief description of drawings]

FIG. 1 shows an example of a procedure for collectively producing a large number of small oxygen electrodes on a single silicon wafer using polyvinylpyrrolidone whose pH is adjusted according to the present invention. FIG. 3 is a plan view showing the above, showing a stage where a silicon wafer to be used is cleaned and prepared.

2 is a schematic diagram of S on the wafer surface of FIG. 1 in accordance with the present invention.
FIG. 6 is a plan view showing a stage where an iO ₂ film is formed.

FIG. 3 is a plan view showing a step of forming a photoresist pattern for an etching mask according to the present invention.

FIG. 4 is a plan view showing a step of etching a SiO ₂ film according to the present invention.

FIG. 5 is a plan view showing a step in which wafer silicon is anisotropically etched according to the present invention.

FIG. 6 is a plan view showing a stage in which an insulating film SiO ₂ film is formed according to the present invention.

FIG. 7 is a plan view showing a step of forming a chromium thin film and a gold thin film according to the present invention.

FIG. 8 is a plan view showing a step of applying a photoresist for electrode patterning according to the present invention.

FIG. 9 is a plan view showing a step of forming a photoresist pattern for electrode patterning by exposing and developing the photoresist of FIG. 8 according to the present invention.

FIG. 10 is a plan view showing a step of etching a gold thin film according to the present invention.

FIG. 11 is a plan view showing a step of etching a chromium thin film according to the present invention.

FIG. 12 is a plan view showing a step of forming a photoresist pattern for defining an oxygen sensitive portion according to the present invention.

FIG. 13 is a plan view showing a stage in which an electrolyte paste is screen-printed according to the present invention.

FIG. 14 is a plan view showing a step of forming a pad region coating film according to the present invention.

FIG. 15 is a plan view showing a step of forming a gas permeable film according to the present invention.

FIG. 16 is a plan view showing a step of exposing a pad region according to the present invention.

FIG. 17 is a graph showing characteristics of a small enzyme electrode produced according to the present invention in comparison with a conventional example.

[Explanation of symbols]

1 ... Silicon wafer 2 ... SiO ₂ film 3 ... Etching mask photoresist pattern 4 ... Electrolyte filling groove 5 ... Insulating film SiO ₂ film 6 ... Chromium thin film 7 ... Gold thin film 8 ... Electrode patterning photoresist pattern 9A ... Anode 9B ... Cathode 9Ap ... Anode 9A pad 9Bp ... Cathode 9B pad 10 ... Oxygen sensitive part formation planned region 11 ... Pad region 12 ... Oxygen sensitive part defining photoresist pattern 13 ... Screen-printed electrolyte paste 14 ... Pad region covered Covering film 15 ... Gas permeable film

 ─────────────────────────────────────────────────── ───Continued from the front page (54) Title of the invention: Method for adjusting pH of polyvinylpyrrolidone, polyvinylpyrrolidone having pH adjusted by the method, electrolyte composition for screen printing containing the same and use of this composition Oxygen electrode and manufacturing method thereof

Claims (6)

[Claims] 1. A polyvinylpyrrolidone p which comprises dissolving polyvinylpyrrolidone in a buffer solution having a predetermined pH value and then removing the above-mentioned buffer solution components from the solution.
H adjustment method. 2. The method for adjusting pH of polyvinylpyrrolidone according to claim 1, wherein the buffer solution is removed by gel filtration or dialysis. 3. A polyvinylpyrrolidone having a predetermined pH value adjusted by the method according to claim 1. 4. A screen printing, characterized in that a fine powdery inorganic salt capable of passing through a screen printing mesh is dispersed as an electrolyte component in the organic solvent solution of polyvinylpyrrolidone having a predetermined pH according to claim 3. Electrolyte composition. 5. A method for producing a small-sized oxygen electrode, which comprises filling the oxygen-sensitive portion with the electrolyte composition for screen printing according to claim 4 by screen printing. 6. A small-sized oxygen electrode, comprising an oxygen-sensitive part formed by filling the electrolytic composition for screen printing according to claim 4 by screen printing.