JPH0447659Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a cathode structure in a diaphragm-type oxygen measuring electrode suitable for measuring oxygen partial pressure in blood by polarography.

(Prior art) When measuring the oxygen partial pressure in blood by polarography, since the oxygen concentration in blood is low,
In order to suppress the reduction rate and obtain a current proportional to the oxygen concentration, an extremely thin platinum wire A with a diameter of several tens of micrometers is usually embedded in an insulating material B such as glass as shown in Figure 3. The cathode surface is formed by utilizing the extremely small cross-sectional area of the end surface A' of the wire A, and oxygen diffused from the diaphragm C is reduced between the cathode surface and the anode D.

However, embedding such thin wires in close contact with glass or polymeric materials requires extremely skilled technology, which makes mass production difficult. Therefore, if the environmental temperature suddenly changes, the platinum wire A may break, or the insulation material B may peel off from the platinum wire A, exposing the circumferential surface of the platinum wire A and causing the cathode to become damaged. There was a problem in that the area of the surface became abnormally large, making measurement impossible.

(Purpose) The present invention was made in view of the above problems, and its purpose is to provide a cathode for a diaphragm-type oxygen measuring electrode that is easy to manufacture and has high reliability.

(Summary of the invention) In other words, the present invention is characterized by forming a film of Polaro cathode material on at least the peripheral surface of the end of a rod-shaped insulating substrate, and forming an insulating coating so that only the end face of this film is exposed. That's what I did.

(Example) The details of the present invention will be explained below based on the illustrated example.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 denotes a rod-shaped insulating substrate made of glass or polymer material, with a non-through hole extending from one end to at least the vicinity of a cathode film 2, which will be described later. 1a, and a horizontal hole 1b communicating with the non-through hole 1a. Reference numeral 2 denotes a film constituting the aforementioned cathode, which is formed by coating the closed side peripheral surface of the rod-shaped insulating substrate 1 with a polaro cathode material such as gold or platinum by chemical vapor deposition, sputtering, or the like.

The film 2 constituting this cathode is manufactured by placing multiple substrates in a vacuum chamber of a film forming device such as an etching device or a sputtering device, and then depositing a Polaro cathode material such as gold or platinum to form a film with high precision. can be formed on multiple substrates at once while being controlled by

At the stage of forming this cathode film 2, the non-through hole 1a
Insert the core wire 3a of the coaxial cable 3 into the horizontal hole 1 from the open side of the
Insert the conductive adhesive 4 into the horizontal hole 1b.
is injected to conductively connect the core wire 3a and the cathode film 2. When the connection between the cathode film 2 and the cable 3 is completed in this way, an electrically insulating material such as alumina or a polymer material is attached to form an insulating film 5 on the surface of the cathode film 2 and the conductive adhesive 4. do. In the process of forming this insulating film, the end face of the base 1 is also covered with the insulating film 5.
However, by polishing the end face of the base 1, only the cross section of the cathode film 2 whose circumferential surface is surrounded by the insulating base 1 and the insulating film 5 is buried in the insulating material. By exposing it, a cathode surface 2a having an area determined only by the thickness of the cathode film 2 and the outer peripheral length of the insulating substrate 1 can be formed.

When the cathode surface 2a is formed in this way, an anode 6 made of a silver pipe is inserted from one end of the insulating base 1 to a position closer to the cable 3 than the horizontal hole 1b, and fixed to the base 1 with adhesive 7. At the same time, the outer wire 3b of the coaxial cable is electrically connected and assembled into an electrode body.

In this embodiment, an oxygen permeable membrane 10 made of water-blocking plastic is placed opposite the cathode surface 2 in an outer cylinder 11 (FIG. 2), and an aqueous solution of potassium chloride is placed so as to connect the cathode surface 2a and the anode 6. A diaphragm-type oxygen measuring electrode is assembled by accommodating an electrolytic solution 12 consisting of:

Between the cathode film 2 and anode 6 of this measurement electrode
When an oxygen reduction potential of about 600 mV is applied and the sample is immersed in a fluid state, the oxygen in the sample diffuses from the diaphragm 10 into the electrolyte 12 in proportion to its partial pressure, causing the cathode surface 2a and anode 6 to separate. Under the action of the electric field between the two, a reduction current proportional to the oxygen concentration is generated.

Even if bubbles are generated in the electrolytic solution 12 for some reason or solid matter enters and adheres to the cathode surface 2a, the cathode surface 2a will not touch the peripheral surface of the insulating substrate 1 for a long distance at the end. Since the cathode surface is distributed with , most of the cathode surface is still functioning effectively and the reduction rate is not affected.

In this example, the film is formed by chemical vapor deposition, sputtering, etc., but it is clear that it can be similarly formed by electroplating, electroless plating, etc.

Further, in this embodiment, the cathode film is formed on the circumferential surface of the insulating substrate, but it is clear that the same effect can be obtained even if the cathode film is formed only on a part of the circumferential surface near the horizontal hole 1b.

(Effects) As explained above, according to the present invention, a film is formed using a Polaro cathode material on at least the peripheral surface of the end of the rod-shaped insulating substrate, and an insulating film is formed so that only the end surface of this film is exposed. , by applying film forming technology such as vapor deposition to form the cathode surface,
Uniform products can be mass-produced without the need for skilled technology.

Furthermore, since the cathode membrane is connected to the external conductive member through the hole drilled in the base, the measurement electrode body and the cable can be arranged coaxially, improving usability.

In addition, since the cathode material is formed in the form of a film on the surface of the insulating substrate, the adhesion and extensibility of the cathode material are improved, reducing peeling and cutting accidents as much as possible, increasing the reliability of the measurement electrode. can be improved.

Furthermore, since the cathode surface is distributed around the end circumferential surface of the base, the effects of air bubbles and dirt are minimized, making highly reliable measurements possible.

[Brief explanation of the drawing]

Figures 1A and 2B are a vertical cross-sectional view and a cross-sectional view, respectively, of an apparatus showing an embodiment of the present invention, and Figure 2 is a cross-sectional view showing an embodiment of a diaphragm-type oxygen measuring electrode using the cathode of the present invention. , and FIG. 3 are cross-sectional views showing an example of a conventional diaphragm-type oxygen measuring electrode. 1...Insulating base, 1a, 1b...hole, 2...cathode film, 2a...cathode surface, 3...coaxial cable, 3
a...Core wire, 3b...External wire, 4...Conductive adhesive, 5...Insulating film, 6...Anode, 5...Connecting wire, 10...Oxygen permeable membrane, 12...Electrolyte solution.

Claims (1)

[Scope of utility model registration request] A film is formed using a Polaro cathode material only on the peripheral surface of the closed end of a rod-shaped insulating substrate, which has an axial hole open at one end and a horizontal hole communicating with the peripheral surface on the closed side. A cathode structure in a diaphragm-type oxygen measuring electrode, in which an insulating coating is formed so that only the end face of the membrane is exposed, and electrically connected to an external conductive member through the hole.