Method for manufacturing flow-type ion-selective electrode, and flow-type ion-selective electrode

Abstract

Provided is a technology which makes it possible to easily control film thickness when forming a thermosetting resin-type ion-sensitive film during manufacturing of a flow-type ion-selective electrode. The present disclosure is a method for manufacturing a flow-type ion-selective electrode having a flow path (12) that penetrates an electrode housing (11), the method being characterized by comprising: inserting a flow-path protection jig (101) into the flow path (12); holding a thermosetting resin liquid (104) in a gap between a film-thickness control jig (100) and a film formation part (14) of the electrode housing (11) including a portion of the flow-path protection jig (101); forming an ion-sensitive film (17) by curing the thermosetting resin liquid (104) in a state held in the gap; and removing the film-thickness control jig (100) and the flow-path protection jig (101) after curing.

Description

Method for manufacturing a flow-type ion-selective electrode and flow-type ion-selective electrode

[0001] The present disclosure relates to a method for manufacturing a flow-type ion-selective electrode and a flow-type ion-selective electrode.

[0002] Potentiometric measurements using ion-selective electrodes are used in a wide range of fields, including water quality analysis and medicine, because they allow for quick and easy quantification of specific ion concentrations in liquids. In particular, in the medical field, where metabolic reactions in living organisms are closely related to ion concentrations, quantifying specific ions in biological samples such as serum and urine is used to diagnose conditions such as hypertension, kidney disease, and neurological disorders. Because clinical testing requires the continuous analysis of multiple samples, high-throughput automated analyzers and electrolyte concentration measuring devices equipped with ion-selective electrodes are routinely used.

[0003] The measurement parameters of electrolyte concentration measuring devices mainly include cations such as sodium ions and potassium ions, and anions such as chloride ions. Regarding cations, compounds (ionophores) that selectively capture specific cations, such as crown ethers and valinomycin, have been identified. Therefore, membranes containing these ionophores are generally used in ion-sensitive electrodes for cations such as sodium and potassium, demonstrating high ion selectivity. On the other hand, regarding anions, there are no ionophores suitable for the ion-selective electrodes of automated analyzers, which require high throughput, fast response, and long-term stability. Therefore, various types of sensitive membranes have been used. Among these, sensitive membranes based on curable resins are known. For example, Patent Document 1 describes an anion-sensitive membrane whose main components are an epoxy resin base, a curing agent, and a curing accelerator. Furthermore, Non-Patent Document 1 describes how adding a plasticizer to an epoxy resin ion-sensitive membrane reduces the membrane's electrical resistance and facilitates its water absorption, thereby shortening the preconditioning time (the time until electrode performance stabilizes). As a method for forming such a sensitive film of a curable resin, Patent Document 1 describes a method in which a flat plate is formed, then hollowed out and attached to the tip of an electrode cell. Patent Document 2 describes a method in which a tube is inserted into the flow path of an electrode cell, an epoxy resin mixture is applied, and the tube is pulled out after heat curing.

[0004] JP 2003-215087 A JP 2022-060778 A

[0005] Anal. Chem. 2004, 76 (14), 4217-4222. DOI: 10.1021 / ac049973y

[0006] As described in Non-Patent Document 1, epoxy resins inherently have high electrical resistance, and it takes time for the electrode performance to stabilize. While this can be improved to some extent by adding plasticizers, variations in the thickness of the sensitive film will also lead to variations in the above-mentioned electrode characteristics. Therefore, accurately controlling the film thickness is important for stabilizing electrode quality. One method for controlling the film thickness, as described in Patent Document 1, is to adhere a pre-formed sensitive film to the electrode cell, such as a flat plate. This method has the potential to reliably control the film thickness. However, it requires many steps and limits the shape of the film adhesion surface of the electrode cell.

[0007] The method of forming a sensitive membrane directly on a flow-type electrode housing described in Patent Document 2 is simple, but it is difficult to precisely control the film thickness. Reasons for the difficulty in controlling the film thickness include the fact that the thermosetting resin undergoes a gradual curing reaction immediately after mixing the base resin and curing agent, and the viscosity at the time of application varies depending on the time and temperature until application; heating during curing temporarily reduces the viscosity of the membrane material, causing it to spread; and if there are areas with low wettability, such as fluororesin tubing, at the film formation location, the membrane material is likely to repel those areas, and the membrane material tends to rise up the wall of the electrode housing. Thus, it has been difficult to directly form a thermosetting resin-type ion-sensitive membrane on an electrode housing while controlling the film thickness.

[0008] Therefore, the present disclosure provides a technique that allows for easy film thickness control when forming a thermosetting resin-type ion-sensitive membrane in the manufacture of a flow-type ion-selective electrode.

[0009] In order to solve the above problems, the manufacturing method of a flow-type ion-selective electrode disclosed herein is a manufacturing method of a flow-type ion-selective electrode having a flow path penetrating an electrode housing, and is characterized by including the steps of inserting a flow path protection jig into the flow path, holding a thermosetting resin liquid in a gap between a film-forming portion of the electrode housing including a part of the flow path protection jig and a film thickness control jig, forming an ion-sensitive membrane by hardening the thermosetting resin liquid while held in the gap, and removing the film thickness control jig and the flow path protection jig after hardening.

[0010] Further features related to the present disclosure will become apparent from the description of this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the aspects of the following detailed description and the appended claims. The description of this specification is merely exemplary and does not limit the scope or application of the claims of the present disclosure in any way.

[0011] According to the technology of the present disclosure, in the manufacture of a flow-type ion-selective electrode, it is possible to easily control the thickness of the ion-sensitive membrane when forming a thermosetting resin membrane. Other problems, configurations, and effects will become clear from the description of the following embodiments.

[0012] 8A is a schematic front view of a flow-type ion-selective electrode according to the first embodiment. FIG. 8B is a schematic side view of a flow-type ion-selective electrode. FIG. 8C is a schematic cross-sectional view taken along the line B-B' in FIG. 2. FIG. 8D is a schematic cross-sectional view taken along the line A-A' in FIG. 1. FIG. 8E is a schematic enlarged view of the portion enclosed by the dotted frame C in FIG. 3 for explaining a conventional method for forming an ion-sensitive membrane. FIG. 8F is a schematic cross-sectional view showing another example of the configuration of a flow-type ion-selective electrode in which an ion-sensitive membrane has been formed by a conventional method for forming an ion-sensitive membrane. FIG. 8G is a schematic enlarged view of the portion enclosed by the dotted frame C in FIG. 3 for explaining a method for forming an ion-sensitive membrane according to the first embodiment. FIG. 8H is a perspective view showing an example of the configuration of a film thickness control jig according to the first embodiment. FIG. 8I is a schematic cross-sectional view showing a state in which the film thickness control jig is mounted on an electrode housing. FIG. 8I is a schematic cross-sectional view showing another example of the configuration of a film thickness control jig. FIG. 8I is a diagram showing measurement results of the film thickness of an ion-sensitive membrane formed using the film thickness control jig shown in FIG. 8A is a schematic cross-sectional view parallel to the longitudinal direction of a flow channel of a flow-type ion-selective electrode fabricated by a film formation method using a film thickness control jig. 10B is an enlarged view of the vicinity of the ion-sensitive membrane in FIG. 10A. It is a cross-sectional schematic diagram for explaining the relationship between the width of the membrane forming portion of the electrode housing and the width of the portion of the film thickness control jig that comes into contact with the membrane material. It is a photograph of the ion-sensitive membrane formed by changing the mounting speed of the film thickness control jig.

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the accompanying drawings show specific embodiments in accordance with the principles of the present disclosure, but these drawings are for understanding the present disclosure and are not to be used to interpret the present disclosure in a limiting manner. In the following embodiments and drawings, components having similar functions are designated by the same reference numerals, and repeated descriptions thereof will be omitted in the specification.

[0014] [First embodiment] <Configuration example of a flow-type ion-selective electrode> Fig. 1 is a schematic front view of a flow-type ion-selective electrode 1 according to a first embodiment. Fig. 2 is a schematic side view of the flow-type ion-selective electrode 1. As shown in Figs. 1 and 2 , the flow-type ion-selective electrode 1 of this embodiment includes an electrode housing 11, a flow path 12, an internal electrode 13, a packing 15, and a lid 18. The flow path 12 penetrates the electrode housing 11. A sample liquid to be measured passes through the flow path 12. The packing 15 is provided near the inlet / outlet of the flow path 12, thereby connecting the flow path 12 to the device or the flow path of another electrode. The internal electrode 13 is inserted into the electrode housing 11. The lid 18 is adhered to the top surface of the electrode housing 11.

[0015] FIG. 3 is a schematic cross-sectional view taken along line B-B' in FIG. 2. FIG. 4 is a schematic cross-sectional view taken along line A-A' in FIG. 1. As shown in FIGS. 3 and 4, the flow-type ion-selective electrode 1 of this embodiment includes a membrane-forming portion 14, an internal gel 16, and an ion-sensitive membrane 17. The membrane-forming portion 14 is formed so as to protrude upward from the inner bottom surface of the electrode housing 11. A groove that forms part of the flow path 12 is formed in the upper portion of the membrane-forming portion 14. The ion-sensitive membrane 17 is provided on the upper surface of the membrane-forming portion 14, and a portion of the lower surface (first surface) of the ion-sensitive membrane 17 forms part of the flow path 12. The ion-sensitive membrane 17 is formed from a thermosetting resin. When the sample liquid passes through the flow path 12, the sample liquid comes into contact with the ion-sensitive membrane 17. The internal gel 16 contains an electrolyte and fills the inside of the electrode housing 11. The upper surface (second surface) of the ion-sensitive membrane 17 comes into contact with the internal gel 16. The internal electrode 13 comes into contact with the internal gel 16. Instead of the internal gel 16, a liquid containing an electrolyte may be used.

[0016] The flow-type ion-selective electrode 1 can be mounted on, for example, an automatic analyzer or an electrolyte concentration measuring device. The flow-type ion-selective electrode 1 is mounted on such a device, and the internal electrode 13 is connected to wiring on the device side. This allows the potential generated in response to the concentration of the ions to be measured contained in the sample solution to be measured, and the concentration of the ions to be measured to be analyzed.

[0017] <Conventional Film Forming Method> A conventional film forming method for a thermosetting resin-type sensitive film will be described. The configuration of a flow-type ion-selective electrode to which the conventional film forming method is applied is the same as that described with reference to Figures 1 to 4, so a description thereof will be omitted here.

[0018] 5 is a schematic diagram illustrating an enlarged view of the area surrounded by the dotted line frame C in FIG. 3 for explaining a conventional method for forming an ion-sensitive film. As shown in FIG. 5, the conventional film formation method includes the following steps (0) to (5).

[0019] (0) An electrode housing 11 of a flow-type ion-selective electrode on which an ion-sensitive membrane is to be formed is prepared. (1) To prevent the membrane material from entering the flow path 12 provided in the membrane formation section 14 in the electrode housing 11, a tube 102 with a diameter slightly larger than the diameter of the flow path 12 is stretched and inserted into the groove of the membrane formation section 14. (2) Predetermined amounts of thermosetting resin materials are measured and mixed in a container 103 to prepare the membrane material 104. (3) The membrane material 104 is applied to the membrane formation section 14 on the electrode housing 11 so as to cover the exposed portion of the tube 102. (4) The applied membrane material 104 is heated to harden it, thereby forming an ion-sensitive membrane 107. (5) The tube 102 is removed, completing the ion-sensitive membrane 107. Thereafter, the inner gel 16 is filled into the electrode housing 11, and the lid 18 provided with the inner electrode 13 is adhered to the electrode housing 11, thereby completing the flow-type ion-selective electrode.

[0020] Here, the distance from the apex of the flow channel in step (4) to the film surface directly above it is defined as the film thickness. In this case, controlling the film thickness using the conventional method described above was difficult. If both the spreading range of the applied film material 104 and the volume of the applied film material 104 could be kept constant, the possibility of controlling the film thickness would be increased. However, the curing reaction of the thermosetting material proceeds gradually even at room temperature immediately after preparation in step (2). During mass production, the time from preparation to application varies between the start and end of processing, so the viscosity of the film material is low at the start of processing and high immediately before the end of processing. This can easily lead to variations in the amount of coating and the spreading area of ​​the film material 104 applied to the electrode housing 11. Furthermore, as shown in step (3'), depending on the shape of the electrode housing 11, a cliff-like structure from which the film material 104 flows down may exist. In this case, the spread film material 104 may flow down the cliff, leaving no film material 104 at the top of the tube 102, even resulting in areas where no film can be formed. Even if the volume and spread of the film material 104 could be kept constant at the time of application, when it is heated for curing in step (4), the temperature of the film material 104 rises and the viscosity temporarily decreases. The curing reaction then progresses, causing the viscosity to increase and eventually the film to harden. Because the viscosity of the film material 104 thus varies significantly depending on the time and temperature between steps, it is difficult to precisely control the film thickness using conventional methods.

[0021] FIG. 6 is a cross-sectional schematic diagram showing another example of the configuration of a flow-type ion-selective electrode in which an ion-sensitive membrane 107 is formed by a conventional ion-sensitive membrane formation method. As shown in FIG. 6, the portion of the electrode housing 11 where the membrane material is applied (the membrane formation portion) can be recessed to prevent the membrane material from flowing off even if the viscosity of the membrane material changes slightly. However, even in this case, there is a possibility that the membrane material 104 may rise to the wall of the recess, or that the membrane material 104 may retreat from the top of the tube 102 due to the high liquid repellency of the tube 102, exposing the tube 102. Therefore, it is necessary to apply the membrane material 104 with a certain amount of thickness margin, and precise control of the membrane thickness has been difficult.

[0022] Here, we explain why thickness control is important for thermosetting resin-type ion-sensitive membranes. Ion-selective electrodes with lower electrical resistance are less susceptible to external disturbances and enable measurements with less noise. However, epoxy resins typically have high electrical resistance, and it takes time for their performance to stabilize due to water absorption. For this reason, Non-Patent Document 1 proposes incorporating plasticizers into the membrane to reduce electrical resistance and the membrane's water absorption time. Variations in the thickness of the sensitive membrane lead to variations in the above-mentioned characteristics, so thickness control is important. Furthermore, if the desired thickness can be achieved, reducing the thickness can also reduce electrical resistance and the membrane's water absorption time. On the other hand, if the thickness is too thin, the membrane's physical strength cannot be maintained. Accurately forming a sensitive membrane with the desired thickness is important not only for stabilizing performance but also for improving it.

[0023] <Film formation method of the present disclosure> Fig. 7 is a schematic enlarged view of the area surrounded by the dotted line frame C in Fig. 3, for explaining the film formation method of the ion-sensitive film according to the first embodiment. As shown in Fig. 7, the film formation method according to this embodiment includes the following steps (10) to (17).

[0024] (10) An electrode housing 11 for a flow-type ion-selective electrode on which an ion-sensitive membrane is to be formed is prepared. (11) To prevent the membrane material from penetrating into the flow path 12 provided in the electrode housing 11, a tube 101 (flow path protection jig) having an outer diameter 1% to 10% smaller than the inner diameter of the flow path 12 is inserted. (12) A predetermined amount of a material containing an epoxy group-containing base agent and an amino group-containing curing agent is measured and mixed in a container 103 to prepare a membrane material 104. (13) The membrane material 104 is applied to the membrane formation portion 14 in the electrode housing 11 so as to cover the exposed portion of the tube 101. (14) A film thickness control jig 100 is placed on the membrane material 104, and the applied membrane material 104 is sandwiched between the jig 100, so that the distance between the top of the tube 101 and the membrane surface is the same as the desired film thickness. (15) While maintaining the state of step (14), heating is performed to harden the membrane material 104, thereby forming the ion-sensitive membrane 17. (16) Remove the film thickness control jig 100. (17) Remove the tube 101 to complete the ion-sensitive membrane 17. The subsequent assembly process for the flow-type ion-selective electrode is the same as in the conventional method.

[0025] The shape of the film thickness control jig 100 may be, for example, a rectangular parallelepiped or a cube, as shown in step (14). As will be described later, the film thickness control jig 100 may also be provided with a positioning member. The film thickness control jig 100 and the tube 101 may be made of a material that is non-adhesive to thermosetting resins. The film thickness control jig 100 and the tube 101 may be made of, for example, a fluorine-based resin such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or a silicone-based resin such as silicone rubber.

[0026] For example, the film thickness control jig 100 can be held by an operator's hand and placed on the film material 104. Alternatively, the film thickness control jig 100 can be placed on the film material 104 using a support member (e.g., a stage) that supports the film thickness control jig 100, a drive device that drives the support member at least in the vertical direction, and a control device that controls the drive device.

[0027] In the film formation method of this embodiment, the film material 104 is sandwiched in the gap between the electrode housing 11 and the film thickness control jig 100 while the film thickness control jig 100 is placed. Therefore, even if the viscosity changes, the film material 104 is held in this gap by surface tension. Furthermore, the desired film thickness can be achieved by controlling the distance of the film thickness control jig 100 from the top of the tube 101. Thus, the film formation method of the present disclosure does not require a wall or other element to prevent the film material 104 from spreading in the film formation section 14 of the electrode housing 11. This ensures a high degree of freedom in the design of the electrode housing 11. Furthermore, the film thickness can be precisely controlled without being affected by changes in the viscosity of the film material 104. Furthermore, even if there is variation in the amount of film material 104 applied, as long as a minimum amount is ensured, this does not affect the accuracy of the film thickness.

[0028] In the step (14) of placing the film thickness control jig 100, it is important that the height of the film material 104 applied to the electrode housing 11 immediately before placing the film thickness control jig 100 is thicker than the set film thickness. Therefore, if the viscosity of the film material 104 is low, it is necessary to place the film thickness control jig 100 before the applied film material 104 spreads.

[0029] In this embodiment, the film thickness control jig 100 is placed on the electrode housing 11 after the film material 104 has been applied thereto as described above. Alternatively, the film material 104 may be applied to the film thickness control jig 100, and the electrode housing 11 may then be placed thereon. In addition, in either case, the side on which the film material 104 has not been applied is placed on the side on which the film material 104 has been applied, but this is not limitative. The side on which the film material 104 has been applied may be turned upside down and the film material 104 may be placed on the side on which the film material 104 has not been applied. Furthermore, the film thickness control jig 100 may be placed on the electrode housing 11 in advance, and then the film material 104 may be injected into the gap.

[0030] As shown in step (17), the ion-sensitive membrane 17 produced by the film-forming method of the present disclosure has a surface 171 that was in contact with the film thickness control jig 100, which has a shape that conforms to the surface shape of the film thickness control jig 100, that is, a flat shape in this embodiment. The surfaces of portions 172 and 173 that were not in contact with the film thickness control jig 100 have a characteristic that they conform to the surface tension of the membrane material 104.

[0031] In this embodiment, the membrane material 104 is described as being a mixture of a base material having an epoxy group and a curing agent having an amino group. However, the technology of the present disclosure is not limited to this and can be applied to any thermosetting resin. It is particularly effective for thermosetting membrane materials that require more than one minute to cure and require heating for curing. In the case of a liquid membrane-type ion-sensitive membrane made of a base material such as flexible PVC, the membrane is formed directly on the electrode housing 11 by applying a solution of the membrane material dissolved in a solvent to the electrode housing 11 and then evaporating the solvent. While the technology of the present disclosure can be applied to such membrane materials, the evaporation of the solvent from the liquid membrane material sandwiched between the membrane thickness control jig 200 and the electrode housing 11 makes it difficult to control the location of the final solid (membrane material) within the gap. In this respect, thermosetting resins cure with little change in volume. In particular, epoxy resins undergo little volume change upon curing, making it easy to control the thickness of the ion-sensitive membrane.

[0032] In this embodiment, the outer diameter of the tube 101, which is the flow path protection jig, is described as being 1% to 10% smaller than the inner diameter of the flow path 12 in the electrode housing 11. As in the conventional method, by extending the tip of the tube 102, which has an outer diameter slightly larger than the diameter of the flow path 12, and inserting it into the flow path 12, the gap between the inner wall of the flow path 12 and the tube 102 is smaller, making it difficult for the membrane material 104 to penetrate into the flow path 12. On the other hand, as in this embodiment, when the outer diameter of the tube 101 is smaller than the inner diameter of the flow path 12, the tube 101 is easier to insert into the flow path, resulting in better mass production efficiency. However, in this case, the gap between the flow path 12 and the tube 101 is relatively wide, which usually makes it easier for the membrane material 104 to flow into the flow path 12. However, in this embodiment, the membrane material 104 is sandwiched between the film thickness control jig 200 and the electrode housing 11, and the surface tension makes it difficult for the membrane material 104 to penetrate into the flow path 12. Furthermore, even if a small amount of membrane material gets in, the cross-sectional area of ​​the flow path 12 can be secured to be at least the outer diameter of the tube 101, and therefore the flow of the sample flowing through the flow path 12 during measurement is unlikely to be disturbed. Furthermore, if a small amount of membrane material gets in the flow path 12, the contact area between the ion-sensitive membrane 17 and the electrode housing 11 increases, which has the advantage of increasing the adhesive strength between the electrode housing 11 and the ion-sensitive membrane 17. However, it is not necessarily necessary to reduce the outer diameter of the tube 101 as in this embodiment, and even if a conventional method of inserting the tube 102 is used, the film thickness control of the present disclosure can be achieved without any problems.

[0033] <Configuration Example of Film Thickness Control Jig> Fig. 8A is a perspective view showing a configuration example of a film thickness control jig 200 according to the first embodiment. As shown in Fig. 8A, the film thickness control jig 200 is composed of a base 206 and three pillars 201, 202, and 203. The pillar 203 has the same function as the film thickness control jig 100 shown in step (14) of Fig. 7.

[0034] 8B is a schematic cross-sectional view of the film thickness control jig 200 mounted on the electrode housing 11. As shown in FIG. 8B, by placing the film thickness control jig 200 on the electrode housing 11, a desired gap (film thickness) can be created between the surface 204 of the central pillar 203 and the film formation section 14 inside the electrode housing 11. The film thickness can be changed by changing the height 205 of the central pillar 203. In addition, the horizontal position relative to the electrode housing 11 is determined by the pillars 201 and 202 (positioning members) on both sides. The surface of the base 206 (positioning member) comes into contact with the upper surface of the wall of the electrode housing 11, thereby providing a reference position in the vertical direction.

[0035] 8A and 8B, the height of the pillars 201 and 202 on both sides of the film thickness control jig 200 is higher than the height of the central pillar 203. This design facilitates positioning of the film thickness control jig 200 and the electrode housing 11 when the base 206 is placed downward as shown in FIG. 8A and the film material 104 is applied to the surface 204 of the pillars 203, and the electrode housing 11 is then placed on the film thickness control jig 200. However, the design is not limited to this, and the height of the pillars 201 and 202 may be lower than the height of the pillar 203, or the pillars 201 and 202 may not be provided.

[0036] 8C is a cross-sectional schematic diagram showing another example of the configuration of the film thickness control jig 200. In this embodiment, the film thickness control jig 200 is made of a non-adhesive material, but it is sufficient if only the portion that comes into contact with the film material 104 is made of a non-adhesive material. As shown in FIG. 8C , most of the film thickness control jig 200 may be made of a different material, and only the contact portion 207 with the film material 104 (the upper portion of the pillar 203) may be made of a non-adhesive material.

[0037] When a fluororesin is used for the tube 101 (flow path protection jig) inserted into the flow path 12 and the film thickness control jig 200, components derived from the fluororesin are transferred to the surface of the formed ion-sensitive membrane 17 where the film thickness control jig 200 and the tube 101 were in contact. Therefore, when the ion-sensitive membrane 17 is subjected to surface analysis, a high proportion of F element is detected only on the surface where the film thickness control jig 200 and the tube 101 were in contact. Note that even when other materials are used as the material for the film thickness control jig 200 and the tube 101, the components of the material are transferred to the ion-sensitive membrane. For example, when a film thickness control jig 200 made of a silicone-based resin is used, Si element derived from the silicone-based resin is detected at a higher proportion on the surface of the ion-sensitive membrane 17 where the film thickness control jig 200 was in contact than inside the ion-sensitive membrane 17.

[0038] The above description has been given of a configuration in which the surface (surface 204) of the film thickness control jig facing the film forming unit 14 is flat. Alternatively, the surface (facing surface) of the film thickness control jig facing the film forming unit 14 may be curved (not shown). In this case, the facing surface may be, for example, a cylindrical surface or a spherical surface. The radius of curvature of such a facing surface is greater than the radius of curvature of the tube 101.

[0039] <Ion-Sensitive Film Formation Results> Figure 9 shows the measurement results of the thickness of ion-sensitive films formed using the film thickness control jig 200 shown in Figure 8A. First, seven types of jigs, A through G, were fabricated, each with a different height for the central pillar 203. The second column in Figure 9 shows the estimated film thickness calculated based on the height of the central pillar 203 of each jig and the shape of the electrode housing 11. Three ion-sensitive films were fabricated using each jig, and the film thickness at the center of each ion-sensitive film was measured. Each column in Figure 9 shows the film thickness measurement results, the average film thickness, and the value obtained by subtracting the minimum from the maximum. The deviation of the average film thickness from the estimated film thickness was within 0.03 mm, and the film thickness variation under each condition was also within 0.03 mm. This demonstrates that the film thickness can be precisely controlled according to the height of the pillar 203 of the film thickness control jig 200. Note that in the case of ion-sensitive films fabricated using jig A with a film thickness of approximately 0.03 mm, the strength of the ion-sensitive film was low, resulting in some tears. Therefore, by setting the film thickness to, for example, 0.05 mm or more, it is possible to prevent the ion-sensitive film from breaking. Furthermore, by setting the film thickness to 1 mm or less, or 0.5 mm or less, it is easy to achieve film formation utilizing surface tension, which is the principle of the film formation method of the present disclosure.

[0040] <Regarding the shape of the formed ion-sensitive membrane> Fig. 10A is a schematic diagram showing a cross section parallel to the longitudinal direction of the flow path 12 of a flow-type ion-selective electrode fabricated by a film formation method using a film thickness control jig 200. As shown in Fig. 10A, the upper surface of the membrane formation part 14 of the electrode housing 11 has both ends inclined upward in a direction parallel to the flow path 12. An ion-sensitive membrane 17 is formed on such a membrane formation part 14.

[0041] 10B is an enlarged view of the ion-sensitive membrane 17 and its vicinity in FIG. 10A. As shown in FIG. 10B, the surface of a portion 173 of the ion-sensitive membrane 17 that was in contact with the film thickness control jig 200 conforms to the surface shape of the film thickness control jig 200, i.e., is flat. The surface of a portion 174 that was not in contact with the film thickness control jig 200 conforms to the surface tension of the membrane material. Thus, the ion-sensitive membrane 17 fabricated using the film formation method of the present disclosure is characterized in that its surface shape is a mixture of a shape that conforms to the film thickness control jig 200 and a shape determined by the surface tension of the membrane material. A sudden change in the surface shape occurs at the boundary between these shapes. From this, in mathematical terms, it can be said that the line on the surface of the ion-sensitive membrane 17 in the section connecting the boundary 111 (first boundary) between the electrode housing 11 and the ion-sensitive membrane 17, passing through the thinnest part of the membrane thickness from the upper end of the flow channel 12, to the boundary 112 (second boundary) between the electrode housing 11 and the ion-sensitive membrane 17 on the opposite side (the surface shape in the membrane cross section shown in FIG. 10B ) has a non-differentiable point. Similarly, for the line on the surface of the ion-sensitive membrane 17 in the cross section perpendicular to the longitudinal direction of the flow channel 12 shown in FIG. 7 , the boundary between the portion 171 and the portion 172 and the boundary between the portion 171 and the portion 173 shown in step (17) in FIG. 7 can be said to be the above-mentioned non-differentiable point. Furthermore, at the top (thinnest part) of the flow channel 12, the lower surface (first surface) of the ion-sensitive membrane 17 is curved so as to be convex upward in a shape that follows the upper surface of the tube 101, and the upper surface (second surface) is flat.

[0042] As described above, the outer diameter of the tube 101, which is the flow path protection jig, is 1% to 10% smaller than the inner diameter of the flow path 12 in the electrode housing 11. For this reason, although not shown in the figure, an ion-sensitive membrane 17 is formed on part of the inner wall of the flow path 12 in a shape that follows the outer shape of the tube 101.

[0043] The shape of the upper surface (second surface) of the ion-sensitive membrane 17 will be a curved surface if the surfaces 204 (surfaces facing the film formation unit 14) of the pillars 203 of the film thickness control jig 200 have a curvature. In this case, the radius of curvature of the upper surface (second surface) is larger than the radius of curvature of the lower surface (first surface) of the ion-sensitive membrane 17.

[0044] <Regarding the Width of the Film Thickness Control Jig> FIG. 11 is a schematic cross-sectional view illustrating the relationship between the width of the film formation portion 14 of the electrode housing 11 and the width of the portion of the film thickness control jig 200 that contacts the film material 104. FIG. 11 illustrates a state in which the film thickness control jig 200 and the electrode housing 11 are fitted together. In the film thickness control jig 200 shown in FIG. 11 , the width 208 of the portion of the film thickness control jig 200 that contacts the film material 104 is larger than the width 141 of the film formation portion 14 of the electrode housing 11. In addition, if the amount of film material 104 applied is large and the ion-sensitive film 17 is formed in a manner that overhangs the film formation portion 14, when the film thickness control jig 200 is removed after curing, the force is not applied evenly. For example, if a strong upward force is applied to the left side as indicated by arrow 301, a downward force is applied from the film thickness control jig 200 to the end of the ion-sensitive film 17 that protrudes from the electrode housing 11 as indicated by arrow 302. In such a situation, the ion-sensitive membrane 17 is likely to crack or peel off from the electrode housing 11. Therefore, by forming the width of the film thickness control jig 200 smaller than the width of the film formation portion 14 of the electrode housing 11 as shown in Figure 8B, it is possible to prevent the ion-sensitive membrane 17 from cracking or peeling off.

[0045] <Regarding the Mounting Speed ​​of the Film Thickness Control Jig> The speed at which the film thickness control jig is mounted on the electrode housing 11 in step (14) of Figure 7 will be described. The film thickness control jig was fixed to a stage, and the mounting speed of the film thickness control jig on the electrode housing was controlled by controlling the driving speed of the stage. The film thickness control jig was moved and mounted (approached) to the film forming section 14 of the electrode housing 11, to which the film material had been applied, at a mounting speed of 20 mm / s, 5 mm / s, or 1 mm / s. Note that the speed at the moment the film thickness control jig contacted the film material was set to the above-mentioned mounting speed (20 mm / s, 5 mm / s, or 1 mm / s), and at other times, the film forming section and the film thickness control jig were approached at a speed faster than the above-mentioned mounting speed to shorten the process time.

[0046] Figure 12 shows photographs of ion-sensitive membranes formed by varying the mounting speed of the film thickness control jig. The horizontal lines in the center of the photograph of the ion-sensitive membrane represent the flow path. The white lines on the top, bottom, left, and right sides of the photograph of the ion-sensitive membrane in Figure 12 correspond to the non-differentiable points mentioned above. When the mounting speed of the film thickness control jig was 20 mm / s and 5 mm / s, air bubbles were observed in the membrane at the areas indicated by the arrows in Figure 12. This is thought to be because air bubbles are more likely to be trapped in the membrane when the film thickness control jig comes into contact with the membrane material at higher speeds. On the other hand, no air bubbles were observed when the mounting speed was 1 mm / s. If the ion-sensitive membrane hardens while air bubbles are still present, the ion-sensitive membrane will become locally thin, losing its physical strength, or holes will form in the ion-sensitive membrane, connecting the flow path 12 to the internal space of the electrode housing 11. Therefore, by setting the speed at which the film thickness control jig 200 is placed to less than 5 mm / s, damage to the ion-sensitive membrane can be prevented. This also applies when the membrane material is applied to the film thickness control jig and the electrode housing 11 is placed on it. Therefore, it is desirable to set the relative speed when the membrane material is sandwiched (approached) between the opposing film thickness control jig and the film forming portion 14 of the electrode housing 11 to less than 5 mm / s, at least at the moment when the membrane material comes into contact with either the film thickness control jig or the film forming portion (the side where the membrane material is not applied).

[0047] Summary of First Embodiment As described above, the method for manufacturing a flow-type ion-selective electrode having a flow path 12 penetrating an electrode housing 11 according to the first embodiment includes inserting a tube 101 (a flow path protection jig) into the flow path 12, holding a membrane material 104 (a thermosetting resin liquid) in a gap between the membrane forming portion 14 of the electrode housing 11, which includes a portion of the tube 101, and the membrane thickness control jig 100 or 200, curing the membrane material 104 while it is held in the gap to form an ion-sensitive membrane, and removing the membrane thickness control jig and the tube 101 after curing. This allows the thickness of the ion-sensitive membrane to be easily controlled.

[0048] [Modifications] The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and it is not necessary to include all of the described configurations. Furthermore, a part of one embodiment can be replaced with a configuration of another embodiment. Furthermore, a configuration of another embodiment can be added to a configuration of one embodiment. Furthermore, a part of the configuration of each embodiment can be added to, deleted from, or substituted for a part of the configuration of another embodiment.

[0049] DESCRIPTION OF SYMBOLS 1... Flow-type ion-selective electrode 11... Electrode housing 12... Flow path 13... Internal electrode 14... Membrane forming section 15... Packing 16... Internal liquid 17, 107... Ion-sensitive membrane 18... Lid 100, 200... Membrane thickness control jig 101, 102... Tube 103... Container 104... Membrane material

Claims

1. A method for manufacturing a flow-type ion-selective electrode having a flow path penetrating an electrode casing, comprising: inserting a flow path protection jig into the flow path; retaining a thermosetting resin liquid in a gap between a film thickness control jig and a film formation portion of the electrode casing including a part of the flow path protection jig; hardening the thermosetting resin liquid while held in the gap to form an ion-sensitive membrane; and removing the film thickness control jig and the flow path protection jig after hardening.

2. The method for manufacturing a flow-type ion-selective electrode according to claim 1, wherein the thermosetting resin liquid is a material containing a base agent having an epoxy group and a curing agent having an amino group.

3. A method for manufacturing a flow-type ion-selective electrode as described in claim 1, characterized in that the surfaces of the flow path protection jig and the film thickness control jig that come into contact with the thermosetting resin liquid are made of a material that is non-adhesive to the thermosetting resin liquid.

4. The method for manufacturing a flow-type ion-selective electrode according to claim 3, wherein the non-adhesive material is a fluorine-based resin or a silicone-based resin.

5. The method for manufacturing a flow-type ion-selective electrode according to claim 1, wherein the film thickness control jig has a positioning member for positioning the film forming portion of the electrode casing.

6. The method for manufacturing a flow-type ion-selective electrode according to claim 1, characterized in that the narrowest gap between the flow path protection jig and the film thickness control jig is 0.05 mm or more and 1 mm or less.

7. The method for manufacturing a flow-type ion-selective electrode according to claim 1, wherein the width of the film thickness control jig is smaller than the width of the film formation portion of the electrode casing.

8. The method for manufacturing a flow-type ion-selective electrode according to claim 1, wherein the outer diameter of the flow path protection jig is 1% to 10% smaller than the inner diameter of the flow path in the electrode casing.

9. The method for manufacturing a flow-type ion-selective electrode according to claim 1, characterized in that retaining the thermosetting resin liquid in the gap between the film forming portion of the electrode casing and the film thickness control jig includes: applying the thermosetting resin liquid to the surface of either the film forming portion of the electrode casing or the film thickness control jig to a thickness greater than a set film thickness; and bringing the film forming portion and the film thickness control jig closer together within a time period during which the thickness of the applied thermosetting resin liquid remains greater than the set film thickness.

10. A method for manufacturing a flow-type ion-selective electrode as described in claim 9, characterized in that the relative speed when the membrane forming section and the membrane thickness control jig are brought closer together is less than 5 mm / s at least at the moment when the thermosetting resin liquid comes into contact with the membrane forming section or the membrane thickness control jig.

11. A flow-type ion-selective electrode for measuring target ions contained in a sample liquid, comprising: an electrode housing for accommodating an internal liquid; a flow path penetrating the electrode housing and through which the sample liquid flows; an internal electrode having a portion in contact with the internal liquid; and an ion-sensitive membrane made of a thermosetting resin that separates the sample liquid from the internal liquid, wherein at least a portion of a first surface of the ion-sensitive membrane forms the inner wall surface of the flow path, and at least a portion of a second surface different from the first surface contacts the internal liquid, and at the thinnest portion between the second surface and the first surface at the upper part of the flow path, the first surface is curved so as to be convex upward, and the second surface is flat or has a radius of curvature greater than that of the first surface.

12. A flow-type ion-selective electrode according to claim 11, wherein the thickness of the thinnest part of the ion-sensitive membrane is 0.05 mm or more and 1 mm or less.

13. A flow-type ion-selective electrode as described in claim 11, characterized in that a line on the second surface of the ion-sensitive membrane in a section connecting a first boundary between the electrode housing and the ion-sensitive membrane, passing through the thinnest part, to a second boundary between the electrode housing and the ion-sensitive membrane on the opposite side has a non-differentiable point.

14. A flow-type ion-selective electrode according to claim 11, wherein the thermosetting resin is formed on a part of the inner wall of the flow channel.

15. The flow-type ion-selective electrode according to claim 11, wherein the thermosetting resin is a resin formed from a material containing a base agent having an epoxy group and a curing agent having an amino group.

16. A flow-type ion-selective electrode according to claim 11, wherein a component of a material that is non-adhesive to the material of said ion-sensitive membrane is transferred onto the surface of said ion-sensitive membrane.

17. The flow-type ion-selective electrode according to claim 16, wherein the non-adhesive material is a fluorine-based resin or a silicone-based resin.

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