JP7827099B2 - Method for manufacturing a sensitive film of an odor sensor element, a sensitive film of an odor sensor element, an odor sensor element, and an odor sensor - Google Patents

Description

The present invention relates to a method for manufacturing a sensitive film of an odor sensor element, a sensitive film of an odor sensor element, an odor sensor element, and an odor sensor.

One known method for manufacturing a sensitive film for an odor sensor element is shown in Patent Document 1. The manufacturing method described in Patent Document 1 uses a syringe-type dispenser.

Japanese Patent Application Laid-Open No. 2020-165971

When forming a coating film on a substrate, the resin composition solution that has risen to the tip of the nozzle evaporates and solidifies, changing the wettability of the nozzle tip. Continuing to manufacture the sensitive film while the wettability of the nozzle tip has changed results in an unstable amount of resin composition solution being applied, reducing the manufacturing stability of the sensitive film and reducing the smoothness (smoothness) of the surface of the sensitive film, resulting in a decrease in the sensitivity of the odor sensor element.

Therefore, one aspect of the present invention aims to provide a method for manufacturing a sensitive membrane of an odor sensor element that can improve the sensitivity of the odor sensor element while increasing the manufacturing stability of the sensitive membrane.

The inventors of the present application conducted repeated trial and error to solve the above-mentioned problems, and as a result discovered the novel fact that by using a pipette-type dispenser equipped with a detachable nozzle at the tip and setting the amount of resin composition solution dispensed from the nozzle to a predetermined amount, it is possible to prevent the resin composition solution from creeping up onto the tip of the nozzle while increasing the smoothness (smoothness) of the surface of the sensitive film, leading to the completion of the present invention. Here, the predetermined amount is 0.1 μL to 5.0 μL.

A manufacturing method according to aspect 1 of the present invention is a method for manufacturing a sensitive film of an odor sensor element on a substrate, and includes the following steps: a suction step in which a resin composition solution containing an organic solvent is drawn into a container storing the resin composition solution using a pipette-type dispenser equipped with a detachable nozzle at the tip; a coating step in which, after the suction step is completed, the resin composition solution is discharged from the nozzle and applied onto the substrate to form a coating film on the substrate; and a drying step in which, after the coating step is completed, the coating film is dried to form the sensitive film. The amount of the resin composition solution discharged from the nozzle is 0.1 μL to 5.0 μL.

The sensitive film of the odor sensor element according to aspect 2 of the present invention is manufactured by the method for manufacturing the sensitive film of the odor sensor element according to aspect 1 of the present invention.

An odor sensor element according to aspect 3 of the present invention comprises a substrate and a sensitive film manufactured on the substrate by the method for manufacturing a sensitive film of an odor sensor element according to aspect 1 of the present invention.

An odor sensor according to aspect 4 of the present invention includes an odor sensor element according to aspect 3 of the present invention.

One aspect of the present invention makes it possible to improve the manufacturing stability of the sensitive membrane while also improving the sensitivity of the odor sensor element.

FIG. 1 is a schematic plan view of an odor sensor element according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 is an SEM image of a cross section of an odor sensor element. 3A to 3C are schematic diagrams illustrating an inhalation step in a first manufacturing method for the sensitive film of the odor sensor element according to the present embodiment. 3A to 3C are schematic diagrams illustrating a coating step in a first manufacturing method for the sensitive film of the odor sensor element according to the present embodiment. 3A to 3C are schematic diagrams illustrating a coating step in a first manufacturing method for the sensitive film of the odor sensor element according to the present embodiment. 3A to 3C are schematic diagrams illustrating a drying step in a first manufacturing method for the sensitive film of the odor sensor element according to the present embodiment. 10A and 10B are schematic diagrams illustrating an inhalation step in a second manufacturing method of the sensitive film of the odor sensor element according to the present embodiment. 10A and 10B are schematic diagrams illustrating a coating step in a second manufacturing method for the sensitive film of the odor sensor element according to the present embodiment. 10A and 10B are schematic diagrams illustrating a coating step in a second manufacturing method for the sensitive film of the odor sensor element according to the present embodiment. 10A and 10B are schematic diagrams illustrating a drying step in a second manufacturing method for the sensitive film of the odor sensor element according to the present embodiment. 1 is a schematic diagram illustrating an odor sensor according to an embodiment of the present invention. FIG. 1 is a top view showing an example of the configuration of an odor sensor element according to an embodiment of the present invention. FIG. FIG. 2 is a top view showing another example of the configuration of the odor sensor element according to the present embodiment. 1 is a perspective view showing an example of the configuration of an odor sensor element according to an embodiment of the present invention. 1A to 1C are schematic diagrams illustrating a method for manufacturing a sensor substrate used in the examples. 1A to 1C are schematic diagrams illustrating a method for manufacturing a sensor substrate used in the examples. FIG. 2 is a schematic diagram showing the configuration of the surface of a sensor substrate used in the examples. FIG. 2 is a schematic diagram showing the configuration of the back surface of a sensor substrate used in the examples.

One embodiment of the present invention is described below, but the present invention is not limited to this. Furthermore, unless otherwise specified in this specification, the numerical range "A to B" means "greater than or equal to A and less than or equal to B."

[Odor sensor element 10]
First, an example of an odor sensor element having a sensitive membrane manufactured using a manufacturing method according to one aspect of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a schematic plan view of an odor sensor element 10 according to this embodiment. Figure 2 is a cross-sectional view taken along line II-II in Figure 1.

(Outline of odor sensor element 10, odor substances)
As shown in Figures 1 and 2, the odor sensor element 10 according to this embodiment is an odor sensor element for detecting odorants. The odor sensor element 10 includes a substrate 12, an odorant receiving layer 14, metal wiring 16, and an odorant permeation layer 20. While the present invention will be described by way of example with reference to the manufacture of an odor sensor element having an odorant permeation layer and an odorant receiving layer, it is not limited to this. For example, the present invention can also be applied to the manufacture of an odor sensor element having only an odorant receiving layer, or an odor sensor element in which the arrangement of the metal wiring 16 differs from that shown in the figure.

Here, "odor substances" are not particularly limited, but examples include hexane, ethyl acetate, methanol, diethyl carbonate, toluene, d-limonene, bornan-2-one, cis-3-hexenol, β-phenylethyl alcohol, citral, L-carvone, γ-undecalactone, eugenol, linalyl acetate, menthol, benzaldehyde, vanillin, hexanal, ethanol, pentyl valerate, linalool, and 2-propanol. "Odor substances" also include substances that are not generally considered to cause odors. "Odor substances" include not only individual odor substances, but also multiple odor substances.

[Substrate 12]
As shown in FIGS. 1 and 2 , the odor sensor element 10 includes a substrate 12, which is made of, for example, a glass epoxy plate. The substrate 12 may be made of paper phenol, glass composite, polyimide, PET (polyethylene terephthalate), glass ceramic, alumina, or aluminum. The substrate 12 also has a structure that restricts the wetting and spreading of the resin composition solutions L1 and L2 described below. For example, as shown in FIG. 2 , when the substrate 12 is viewed from the side, the region (coating region) to which the resin composition solution (described below) is applied may be recessed compared to other regions of the substrate 12. The recessed coating region may be formed by, for example, applying solder resist to regions other than the coating region during the process of fabricating the substrate 12. Alternatively, tape or the like may be attached to the outside of the coating region of the substrate 12. These configurations result in the coating region being lower than other regions of the substrate 12. Therefore, even if the resin composition solution is applied to the substrate 12, the wetting and spreading of the resin composition solution is regulated, and the resin composition solution can be prevented from wetting and spreading beyond the applied area.

[Odorant Receptive Layer 14]
As shown in Figures 1 and 2, the odor sensor element 10 includes an odorant receiving layer 14 as a sensitive membrane provided on a substrate 12, and the odorant receiving layer 14 is capable of adsorbing odorants. The odorant receiving layer 14 is manufactured on the substrate 12 by the first manufacturing method (M1) of the sensitive membrane of the odor sensor element described below. The odorant receiving layer 14 is composed of a resin composition containing a resin and a conductive material as a filler. The electrical resistance value (electrical conductivity) of the odorant receiving layer 14 changes depending on the adsorption state of the odorant. The odor sensor element 10 is a chemiresistor-type odor sensor element that uses changes in the electrical resistance value of the odorant receiving layer 14 as a sensitive membrane as an indicator of odor detection.

The thickness of the odorant receiving layer 14 is 0.1 μm to 250 μm. Preferably, it is 0.1 μm to 200 μm, more preferably 0.1 μm to 120 μm, even more preferably 0.1 μm to 50 μm, and even more preferably 1 μm to 25 μm. The thickness of the odorant receiving layer 14 may vary between the center and edge portions. For example, as shown in FIG. 2, if the substrate 12 has a recessed coating area compared to other areas, the edge portions of the odorant receiving layer 14 formed by coating the coating area will adhere to the substrate 12 and rise compared to the center. As a result, the edge portions tend to be thicker than the center portion. For example, the thickness of the center of the odorant receiving layer 14 may be approximately 1 to 6 μm, and the edge portions may be approximately 20 μm. The thickness of the odorant receiving layer 14 may be determined as long as the average thickness of multiple locations, including the center and edge portions, falls within the above-mentioned range. Furthermore, it is preferable that the thickness of the odorant receiving layer 14 be within the above-mentioned range throughout the entire layer, including the center and edge portions. By setting the thickness of the odorant receiving layer 14 within this range, changes in the electrical conductivity of the odorant receiving layer 14 due to the adsorption of odorants into the odorant receiving layer 14 can be accurately detected as an electrical signal. Furthermore, when creating the odorant receiving layer 14, the thickness of the odorant receiving layer 14 can be controlled by regulating the area of the coated film using the electrode shape, etc., and by controlling the evaporation residue and dispensed amount of the odor permeation layer solution to be dispensed.

[Metal wiring 16]
As shown in FIGS. 1 and 2, the odor sensor element 10 includes a pair of metal wires 16 disposed on a substrate 12. The pair of metal wires 16 are arranged parallel to each other and covered with an odorant receiving layer 14. The pair of metal wires 16 function as electrodes for measuring changes in the electrical conductivity of the odorant receiving layer 14. Lead wires 18 are connected to the pair of metal wires 16. The width of each metal wire 16 is preferably 10 μm to 2 mm, more preferably 10 μm to 1 mm. The thickness of each metal wire 16 is preferably 1 μm to 100 μm, more preferably 10 μm to 50 μm. The length of each metal wire 16 is preferably 100 μm to 50 mm, more preferably 500 μm to 30 mm. The spacing between the pair of metal wires 16 is preferably 1 μm to 3 mm, more preferably 1 μm to 1.5 mm.

[Odor-permeable layer 20]
As shown in FIGS. 1 and 2 , the odor sensor element 10 may include an odorant-permeable layer 20 as another sensitive membrane provided to cover the odorant receiving layer 14. The odorant-permeable layer 20 is manufactured on the substrate 12 via the odorant receiving layer 14 by the second manufacturing method (M2) of the sensitive membrane of the odor sensor element described below. The odorant-permeable layer 20 has the function of selectively allowing odorants to reach the odorant receiving layer 14. The odorant-permeable layer 20 also functions as a protective layer that reduces the rate of deterioration of the odorant receiving layer 14 due to factors such as humidity in the measurement environment. The odorant-permeable layer 20 is composed of a resin composition containing a resin and zeolite (a general term for crystalline silicates) as a filler. The odorant-permeable layer 20 may also be composed of a resin composition containing a resin and a filler other than zeolite. The odorant-permeable layer 20 may also be composed of a resin composition that does not contain a filler. The following explanation will be given using a resin composition containing a filler as an example.

The thickness of the odorant permeation layer 20 is 0.1 μm to 200 μm, preferably 1 μm to 20 μm. The reason why the odorant permeation layer 20 is set to a thickness of 0.1 μm or more is that if it is less than 0.1 μm, it will not be able to fully perform its function of selectively allowing odorants to reach the odorant reception layer 14, and it will not be able to fully protect the odorant reception layer 14. The reason why the odorant permeation layer 20 is set to a thickness of 200 μm or less is that if it exceeds 200 μm, fewer odorants will reach the odorant reception layer 14, and the measurement sensitivity of the odor sensor element 10 will decrease.

The odorant-permeable layer 20, which serves as another sensitive membrane, may be omitted from the configuration of the odor sensor element 10.

<Method for measuring the thickness of the odorant-permeable layer 20>
The method for measuring the thickness of the odorant permeation layer 20 will be explained below with reference to FIG. 3. FIG. 3 is a scanning electron microscope (SEM) image of a cross section of an odor sensor element 10 including an odorant receiving layer 14 and an odorant permeation layer 20, observed at 25,000 magnification. The cross section of the odor sensor element 10 including an odorant receiving layer 14 and an odorant permeation layer 20 is formed using, for example, a cross-section polisher, specifically, an IB-19530CP (product name, manufactured by JEOL Ltd.). The lines indicated by symbols X1 to X20 in FIG. 3 indicate the length from the boundary between the odorant receiving layer 14 and the odorant permeation layer 20 to the surface of the odorant permeation layer 20 at each location. Hereinafter, the length from the boundary between the odorant receiving layer 14 and the odorant permeation layer 20 to the surface of the odorant permeation layer 20 will be referred to as the cross-sectional length of the odorant permeation layer 20. The boundary between the odorant receiving layer 14 and the odorant permeable layer 20 can be determined using, for example, SEM reflection observation, electron image SEM-EDX, or STEM.

The thickness of the odorant-permeable layer 20 may be the average value of the cross-sectional lengths at multiple locations on the odorant-permeable layer 20. The measurement locations for the cross-sectional length that serve as the basis for calculating the thickness of the odorant-permeable layer 20 may be the two locations, the thickest and thinnest locations, or ten locations arbitrarily selected within the odorant-permeable layer 20, or even more. As an example, the average value of the cross-sectional lengths at 20 locations indicated by symbols X1 to X20 in the example shown in Figure 3 may be used as the thickness of the odorant-permeable layer 20. The thickness of the odorant-permeable layer 20 may be determined as long as the average value of the cross-sectional lengths at multiple locations falls within the above-mentioned numerical range.

<Method for measuring the thickness of the odorant receiving layer 14>
The thickness of the odorant receiving layer 14 may also be measured using a method similar to that used to measure the thickness of the odorant permeation layer 20. When measuring the thickness of the odorant receiving layer 14, the length from the boundary between the odorant receiving layer 14 and the odorant permeation layer 20 to the surface of the substrate 12 is taken as the cross-sectional length of the odorant receiving layer 14.

[First manufacturing method (M1) of the sensitive film of the odor sensor element]
A first manufacturing method (M1) for the sensitive membrane of the odor sensor element according to this embodiment will be described with reference to FIGS. 4 to 7. FIG. 4 is a schematic diagram illustrating the inhalation step (M1-2) in the first manufacturing method (M1) for the sensitive membrane of the odor sensor element according to this embodiment. FIGS. 5 and 6 are schematic diagrams illustrating the application step (M1-3) in the first manufacturing method (M1) for the sensitive membrane of the odor sensor element according to this embodiment. FIG. 7 is a schematic diagram illustrating the drying step (M1-4) in the first manufacturing method (M1) for the sensitive membrane of the odor sensor element according to this embodiment.

(Outline of the first manufacturing method (M1) of the sensitive film of the odor sensor element)
As shown in FIGS. 4 to 7 , the first manufacturing method (M1) for the sensitive membrane of the odor sensor element according to this embodiment is a method for manufacturing an odorant-receiving layer 14 as a sensitive membrane on a substrate 12. The first manufacturing method (M1) for the sensitive membrane of the odor sensor element according to this embodiment includes a preparation step (M1-1), an inhalation step (M1-2), an application step (M1-3), a drying step (M1-4), and a replacement step (M1-5). The specific details of each step in the first manufacturing method (M1) for the sensitive membrane of the odor sensor element according to this embodiment are as follows: Before starting the first manufacturing method (M1), a step of preparing a substrate 12 on which metal wiring 16 is previously arranged is performed. Furthermore, the substrate 12 thus prepared is provided with a structure that restricts the wetting and spreading of the resin composition solution L1 or L2, which will be described later.

(Preparation process (M1-1))
An organic solvent is added to a resin composition containing a resin and a conductive material as a filler, and the mixture is uniformly kneaded with a stirrer to produce a slurry-like resin composition solution L1 (see FIG. 4), which is then placed in a container 22 (see FIG. 4). The resin composition solution L1 may contain a surfactant. For example, when preparing about 10 ml of resin composition solution L1, the container 22 may be a screw tube with a capacity of about 20 ml.

Here, the resin contained in the resin composition solution L1 is not particularly limited, but may be, for example, a urethane resin, a polyalkylene oxide, an acrylic resin, a fluorine-containing resin, a vinyl resin (e.g., polyvinylpyrrolidone, polyvinyl butyral, etc.), a silicone resin, a polyamide resin, or a polyester resin.

The resin composition solution L1 may contain a filler. The conductive material contained as a filler in the resin composition solution L1 is a conductive carbon material, more specifically, a carbon material having a volume resistivity of 0.25 Ω·cm or less. Examples of conductive carbon materials include carbon black, carbon nanotubes, and graphene. The conductive carbon material is preferably fibrous or spherical in shape. If the conductive carbon material is fibrous, the fiber diameter is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 5 μm. The fiber length is preferably 0.1 μm to 10 μm, more preferably 1 μm to 10 μm. If the conductive carbon material is spherical, the primary particle diameter is preferably 10 nm to 200 nm, more preferably 20 nm to 150 nm.

The conductive materials dispersed in the resin come into contact with each other to form conductive paths, making the resin composition conductive. Furthermore, from the perspective of achieving sufficient conductivity and sensitivity in the odor sensor element 10, the content of the conductive material is preferably 10% to 70% by weight, assuming the total amount of the resin composition to be 100% by weight.

The surfactant contained in resin composition solution L1 acts as a dispersant for the conductive material. The surfactant can be appropriately selected from known surfactants, such as ionic surfactants. Examples of ionic surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants.

The organic solvent contained in resin composition solution L1 is not particularly limited, but examples include N-methyl-2-pyrrolidone, propylene glycol monomethyl ether acetate, ethyl butyrate, diethylene glycol monobutyl ether, butyl butyrate, ethyl acetate, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, xylene, diethylene glycol monobutyl ether acetate, and dibenzyl ether.

The viscosity of the resin composition solution L1 measured using an E-type viscometer (not shown) is 1 mPa·s to 500 mPa·s, preferably 1 mPa·s to 300 mPa·s. The viscosity of the resin composition solution L1 is set to 1 mPa·s or greater because if the viscosity is less than 1 mPa·s, the resin composition solution L1 is likely to leak from the tip of the nozzle 28 (see FIG. 4) after being sucked up. The viscosity of the resin composition solution L1 is set to 500 mPa·s or less because if the viscosity exceeds 500 mPa·s, the resin composition solution L1 will not wet and spread after being applied to the substrate 12. The viscosity is measured using an E-type viscometer [Model "TV-22" manufactured by Toki Sangyo Co., Ltd.] with a cone rotor of 1°34' x R24, a measurement temperature of 25°C, and a rotor rotation speed of 2 rpm, and the value is read 60 seconds after the start of measurement.

The boiling point of the organic solvent contained in resin composition solution L1 is 150°C to 250°C. The boiling point of the organic solvent is set to 150°C or higher because, if the boiling point is lower than 150°C, the organic solvent will volatilize during storage of resin composition solution L1, causing a change in the solid content. Here, the solid content of resin composition solution L1 refers to the proportion of solids relative to the total resin composition solution L1, and may be, for example, the ratio of the weight of a given amount of resin composition solution L1 before drying to the weight after drying. The boiling point of the organic solvent is set to 250°C or lower because, if the temperature exceeds 250°C, the organic solvent cannot be completely removed in the drying step (M1-4). The boiling point refers to the boiling point at 1 atmosphere (101,325 Pa). The boiling point is a value measured using a boiling point meter, such as a DosaTherm 300 manufactured by Titan Technologies, Inc.

The solid content of the resin composition solution L1 is 2% to 20%. The reason for setting the solid content of the resin composition solution at 2% or more is that if it is less than 2%, the coating thickness after drying will be thin, reducing the surface smoothness of the odorant receiving layer 14 as a sensitive film. The reason for setting the solid content of the resin composition solution L1 at 20% or more is that if it exceeds 20%, the viscosity of the resin composition solution L1 will increase, making it difficult to suck up the resin composition solution L1 with the nozzle 28. The solid content of the resin composition solution L1 is a value indicating the proportion of solids in the resin composition solution L1, and is the non-volatile content measured in accordance with JIS K0067:1992. However, the resin composition solution L1 was dried using a vacuum dryer at a drying temperature of 100°C for a drying time of 2 hours.

The thixotropic index of resin composition solution L1, measured with a rheometer (not shown), is 1.05 to 5.00. The thixotropic index of resin composition solution L1 is set to 1.05 or higher because if it is less than 1.05, it will be difficult to suck up resin composition solution L1 with nozzle 28 and to apply it. The thixotropic index of resin composition solution L1 is set to 5.00 or lower because if it exceeds 5.00, the structure of resin composition solution L1 will be easily destroyed by the shear force applied during sucking up and application.

Thixotropy refers to the phenomenon in which viscosity decreases as the shear rate increases. The thixotropic index (TI value) is commonly used as an index of thixotropy. The TI value is the viscosity at low shear rate divided by the viscosity at high shear rate, and a value greater than 1 is said to be thixotropic. Using an E-type viscometer [Model "TV-22", manufactured by Toki Sangyo Co., Ltd.] with a cone rotor of 1°34' x R24, measurement temperature of 25°C, and rotor rotation speed of 2 rpm, the value (viscosity at 2 rpm) is read 60 seconds after the start of measurement. Another value (viscosity at 20 rpm) is then read 60 seconds after the start of measurement at 20 rpm. The viscosity at 2 rpm divided by the viscosity at 20 rpm is the thixotropic index.

(Inhalation process (M1-2))
During or after the preparation step (M1-1), a pipette-type dispenser 24 shown in FIG. 4 is prepared. Here, the pipette-type dispenser 24 includes a pipette 26 capable of sucking and ejecting air, and a nozzle 28 detachably attached to the tip of the pipette 26. The nozzle 28 is sometimes referred to as a pipette tip, and a nozzle 28 of a size suited to the amount of resin composition solution L1 to be applied is used. In this embodiment, for example, a 10 μL nozzle 28 is used. As the shape of the nozzle 28, a standard type is used, but a long type or a tapered type may also be used. As the nozzle 28, a generally commercially available resin nozzle may be used, and the resin constituting the nozzle 28 is, for example, polypropylene.

After the preparation step (M1-1) is completed, as shown in FIG. 4, a pipette-type dispenser 24 is used to immerse a nozzle 28 in the resin composition solution L1 stored in a container 22. Then, the resin composition solution L1 is sucked into the nozzle 28 from the container 22 by the suction action of the pipette 26.

(Coating process (M1-3))
After the suction step (M1-2) is completed, the tip of the nozzle 28 is brought close to a predetermined portion on the substrate 12 while facing the predetermined portion, as shown in Fig. 5. Then, the resin composition solution L1 is discharged from the nozzle 28 by the discharging operation of the pipette 26 and applied to the predetermined portion on the substrate 12. This allows a coating film F1 to be formed at the predetermined portion on the substrate 12, as shown in Fig. 6. The distance between the tip of the nozzle 28 and the substrate 12 may be, for example, 0.3 mm.

Here, the amount of resin composition solution L1 ejected from nozzle 28 is 0.1 μL to 5.0 μL, preferably 0.1 μL to 1 μL. The reason why the amount of resin composition solution L1 ejected is 0.1 μL or more is that if it is less than 0.1 μL, it becomes difficult to stably form coating film F1 on substrate 12. The reason why the amount of resin composition solution L1 ejected is 5.0 μL or less is that if it exceeds 5.0 μL, it becomes difficult to improve the smoothness and uniformity of the surface of coating film F1, i.e., the smoothness and uniformity of the surface of odorant receiving layer 14 as a sensitive film.

In the first manufacturing method (M1) of the sensitive film of the odor sensor element according to this embodiment, the coating step (M1-3) may be repeated multiple times. Note that the coating step (M1-3) is a step performed to form coating films F1 at different locations, and is not a step of repeatedly coating the resin composition solution L1 in a single location. For example, the coating step (M1-3) may be performed once at each of multiple locations on a single substrate 12, or once on each of multiple substrates 12. By repeating the coating step (M1-3) multiple times, it is possible to create a single substrate 12 on which coating films F1 are formed at multiple predetermined locations, or to create multiple substrates 12 on which coating films F1 are formed at predetermined locations on the substrate 12. Furthermore, when the coating step (M1-3) is repeated multiple times using the same nozzle 28, it is not necessary to replace the nozzle 28 for each coating step (M1-3). This allows application without wasting the resin composition solution L1 remaining in the nozzle 28 after one application step (M1-3). Furthermore, the time required to replace the nozzle 28 can be eliminated, improving the production speed of the odor sensor element 10.

(Drying process (M1-4))
After the coating process (M1-3) is completed, the coating film F1 is dried to form the odorant receiving layer 14 as a dried solid, as shown in Figure 7. This allows the odorant receiving layer 14 to be produced as a sensitive film on the substrate 12.

The drying method for the coating film F1 is not particularly limited, but for example, it may be heated at 100°C under normal pressure for 1 hour, followed by heating at 100°C for 1 hour while reducing the pressure in a vacuum dryer. Note that the temperature and reduced pressure conditions in the drying step (M1-3) are not limited to those described above, as long as the coating film F1 can be dried. For example, the temperature when drying the coating film F1 in the drying step (M1-3) may be 40°C to 160°C. The temperature during drying may also vary, such as by gradually increasing. Furthermore, the time during which the reduced pressure is applied in the drying step (M1-3) may be 0.5 hours to 3 hours, for example, 2 hours. Furthermore, reducing the pressure in the drying step (M1-3) is not essential and may be omitted.

(Replacement process (M1-5))
The nozzle 28 is replaced every time the application step (M1-3) is performed a predetermined number of times. Specifically, after the application step (M1-3) is performed a predetermined number of times, the used nozzle 28 is detached from the tip of the pipette 26, and an unused nozzle 28 is attached to the tip of the pipette 26. Here, the predetermined number of times can be set arbitrarily depending on the extent to which the resin composition solution L1 creeps up to the tip of the resin composition in the nozzle 28, and may be 1 time, 10 times, or 30 times.

According to the configuration of the first manufacturing method for the sensitive film of the odor sensor element 10 of this embodiment, as described above, a pipette-type dispenser 24 equipped with a detachable nozzle 28 at its tip is used to eject resin composition solution L1 from the nozzle 28 and apply it to a predetermined portion of the substrate 12, thereby forming a coating film F1 at the predetermined portion of the substrate 12. The amount of resin composition solution L1 ejected from the nozzle 28 is 0.1 μL to 5.0 μL. This prevents the resin composition solution L1 from creeping up to the tip of the nozzle 28, while increasing the smoothness of the surface of the coating film F1, thereby enhancing the smoothness of the surface of the odorant receiving layer 14 serving as the sensitive film. As a result, the first manufacturing method for the sensitive film of the odor sensor element 10 of this embodiment can improve the manufacturing stability of the odorant receiving layer 14 while improving the sensitivity of the odor sensor element 10.

When the resin composition solution L1 is sucked using a nozzle 28 that has sucked the resin composition solution L1 a predetermined number of times or more, the effect of the resin composition solution L1 creeping up to the tip of the nozzle 28 becomes significant. Therefore, the nozzle 28 is replaced every time the application process (M1-3) is performed a predetermined number of times. This prevents the resin composition solution L1 from creeping up to the tip of the nozzle 28, while further increasing the smoothness of the surface of the odorant receiving layer 14 and further improving the sensitivity of the odor sensor element 10.

When the resin composition solution L1 contains a conductive material (conductive carbon material) as a filler, the nozzle 28 drains the liquid better, further improving the manufacturing stability of the odorant receiving layer 14, and the resin ratio in the odorant receiving layer 14 can be reduced to further improve the sensitivity of the odor sensor element 10.

[Second Manufacturing Method (M2) of the Sensitive Film of the Odor Sensor Element 10]
A second manufacturing method (M2) for the sensitive membrane of the odor sensor element 10 according to this embodiment will be described with reference to FIGS. 8 to 11. FIG. 8 is a schematic diagram illustrating the inhalation step (M2-2) in the second manufacturing method (M2) for the sensitive membrane of the odor sensor element 10 according to this embodiment. FIGS. 9 and 10 are schematic diagrams illustrating the application step (M2-3) in the second manufacturing method (M2) for the sensitive membrane of the odor sensor element 10 according to this embodiment. FIG. 11 is a schematic diagram illustrating the drying step (M2-4) in the second manufacturing method for the sensitive membrane of the odor sensor element 10 according to this embodiment.

(Outline of the second manufacturing method (M2) of the sensitive film of the odor sensor element 10)
As shown in Figures 8 to 11, the second manufacturing method (M2) for the sensitive membrane of the odor sensor element 10 according to this embodiment is a method for manufacturing an odorant-permeable layer 20 as a sensitive membrane on a substrate 12 via an odorant-receiving layer 14. The second manufacturing method (M2) for the sensitive membrane of the odor sensor element 10 according to this embodiment includes a preparation step (M2-1), an inhalation step (M2-2), an application step (M2-3), a drying step (M2-4), and a replacement step (M2-5). The specific details of each step in the second manufacturing method (M2) for the sensitive membrane of the odor sensor element 10 according to this embodiment are as follows. If the odor sensor element 10 does not have an odorant-permeable layer 20, the respective steps in the second manufacturing method (M2) are omitted.

(Preparation process (M2-1))
An organic solvent is added to a resin composition containing a resin and a filler, and the mixture is uniformly kneaded with a stirrer to produce a resin composition. The resin composition may or may not contain a filler. The resin composition is then dissolved to produce a resin composition solution L2 (see FIG. 8), which is then placed in a container 30 (see FIG. 8). The resin composition solution L2 may contain a surfactant. The container 30 may have the same shape as the container 22.

Here, the resin contained in the resin composition solution L2 is not particularly limited, but may be, for example, a vinyl resin (e.g., polyvinylpyrrolidone, polyvinyl butyral, etc.), a silicone resin, a urethane resin, a polyalkylene oxide, an acrylic resin, a fluorine-containing resin, a vinyl resin (e.g., polyvinylpyrrolidone, polyvinyl butyral, etc.), a silicone resin, a polyamide resin, or a polyester resin.

The organic solvent contained in resin composition solution L2 is not particularly limited, but may be the same organic solvent as the organic solvent contained in resin composition solution L1 (see Figure 4).

The viscosity of resin composition solution L2 measured using an E-type viscometer is 1 mPa·s to 500 mPa·s, preferably 1 mPa·s to 300 mPa·s, for the same reasons as for setting the viscosity of resin composition solution L1. Furthermore, the boiling point of the organic solvent contained in resin composition solution L2 is 150°C to 250°C, for the same reasons as for setting the boiling point of the organic solvent contained in resin composition solution L1.

The solids content of resin composition solution L2 is 2% to 20% for the same reasons as those for setting the solids content of resin composition solution L1. Furthermore, the thixotropic index of resin composition solution L2, measured with a rheometer (not shown), is 1.05 to 5.00 for the same reasons as those for setting the thixotropic index of resin composition solution L1.

(Inhalation process (M2-2))
8, a pipette-type dispenser 24 is used to immerse a nozzle 28 in the resin composition solution L2 stored in a container 30. Then, the resin composition solution L2 is sucked into the nozzle 28 from the container 30 by a suction operation of the pipette 26.

(Coating process (M2-3))
After the suction step (M2-2) is completed, as shown in Figure 9, the tip of the nozzle 28 is brought close to the application surface to a distance of approximately 0.3 mm while facing a predetermined portion on the substrate 12. Then, by discharging the pipette 26, the resin composition solution L2 is discharged from the nozzle 28 and applied to the predetermined portion on the substrate 12 so as to cover the odorant receiving layer 14. This allows a coating film F2 to be formed on the predetermined portion on the substrate 12 via the odorant receiving layer 14, as shown in Figure 10.

Here, the amount of resin composition solution L2 discharged from nozzle 28 is 0.1 μL to 5.0 μL, preferably 0.1 μL to 1 μL, for the same reasons as for setting the amount of resin composition solution L1 discharged from nozzle 28.

In the second manufacturing method (M2) of the sensitive film of the odor sensor element 10 according to this embodiment, the coating step (M2-3) may be repeated multiple times. By repeating the coating step (M2-3) multiple times, it is possible to form a coating film F2 via an odorant receiving layer 14 at predetermined locations on multiple substrates 12, or to form a coating film F2 via an odorant receiving layer 14 at multiple predetermined locations on the substrate 12.

(Drying process (M2-4))
After the coating process (M2-3) is completed, the coating film F2 is dried to form a dried odorant-permeable layer 20, as shown in Figure 11. This allows the odorant-permeable layer 20 as a sensitive membrane to be produced on the substrate 12 via the odorant-receiving layer 14.

The drying method for coating film F2 is not particularly limited, but the same method as the drying method for coating film F1 may be used. The drying conditions, such as the drying temperature and time, in the drying step (M2-3) for coating film F2 may be the same as or different from the drying conditions, such as the drying temperature and time, in the drying step (M1-3) for coating film F1.

(Replacement process (M2-5))
After the application step (M2-3) has been performed a predetermined number of times (including once), the nozzle 28 is replaced. Specifically, after the application step (M2-3) has been performed a predetermined number of times, the used nozzle 28 is detached from the tip of the pipette 26, and an unused nozzle 28 is attached to the tip of the pipette 26.

According to the second manufacturing method of the sensitive film of the odor sensor element of this embodiment, as described above, a pipette-type dispenser 24 equipped with a detachable nozzle 28 at its tip is used to eject a resin composition solution L2 from the nozzle 28 and apply it to a predetermined portion of the substrate 12 so as to cover the odorant receiving layer 14, thereby forming a coating film F2 on the predetermined portion of the substrate 12 via the odorant receiving layer 14. The amount of resin composition solution L2 ejected from the nozzle 28 is 0.1 μL to 5.0 μL. This prevents the resin composition solution L2 from creeping up to the tip of the nozzle 28, while increasing the smoothness of the surface of the coating film F2, thereby enhancing the smoothness of the surface of the odorant permeation layer 20 serving as the sensitive film. As a result, the second manufacturing method of the sensitive film of the odor sensor element of this embodiment improves the manufacturing stability of the odorant permeation layer 20 and improves the sensitivity of the odor sensor element 10.

When replacing the nozzle 28 after performing the application process (M2-3) a predetermined number of times, the nozzle 28 that has already sucked in the resin composition solution L2 is not used to suck in the resin composition solution L2 again. This more sufficiently prevents the resin composition solution L2 from creeping up to the tip of the nozzle 28, further increasing the smoothness of the surface of the odorant-permeable layer 20 and further improving the sensitivity of the odor sensor element 10.

When the resin composition solution L2 contains zeolite as a filler, the nozzle 28 drains better, further improving the manufacturing stability of the odorant-permeable layer 20, and the resin ratio in the odorant-permeable layer 20 can be reduced to further improve the sensitivity of the odor sensor element 10. Note that the substance contained as a filler in the resin composition solution L2 is not limited to zeolite, and may be inorganic particles or resin particles other than zeolite.

[Odor sensor 32]
An example of the configuration of an odor sensor including an odor sensor element 10 will be described with reference to Fig. 12. Fig. 11 is a schematic diagram illustrating an odor sensor 32 according to this embodiment. Fig. 12 shows the odor sensor 32 including one odor sensor element 10, but the configuration is not limited to this. For example, the odor sensor 32 may be configured to include multiple odor sensor elements 10 made of different resin compositions.

(Outline of odor sensor 32, housing 34, target sample receiving section 36)
As shown in FIG. 12 , the odor sensor 32 according to this embodiment is a sensor for detecting odorous substances and includes an odor sensor element 10. The odor sensor 32 includes a housing 34 for housing the odor sensor element 10. The housing 34 is formed with an inlet 34i for introducing odorous substance-containing air into the housing 34, and an outlet 34e for discharging odorous substance-containing air from the housing 34 at a position spaced apart from the inlet 34i. The inlet 34i of the housing 34 is connected to a target sample receiving section 36, which serves as a front chamber for containing odorous substance-containing gas generated from the target sample. The odorous substance-containing gas generated from the target sample and contained in the target sample receiving section 36 is introduced into the housing 34 by sending, for example, nitrogen and air to the target sample receiving section 36.

(Constant voltage power supply 38, voltmeter 40)
The odor sensor 32 includes a constant-voltage power supply 38 as a power source for supplying power to the odor sensor element 10, and the constant-voltage power supply 38 is connected to the pair of metal wires 16 via the lead wires 18. The constant-voltage power supply 38 supplies a constant voltage to the odor sensor element 10 via the lead wires 18. The voltage value supplied by the constant-voltage power supply 38 is 0.5 V to 10 V, for example, 2.5 V or 5.0 V. The odor sensor 32 also includes a voltmeter 40 as a measuring device that measures the potential difference between the pair of metal wires 16 when a constant voltage is supplied from the constant-voltage power supply 38 to the odorant receiving layer 14. The voltmeter 40 is connected to the pair of metal wires 16 via the lead wires 18. The voltmeter 40 is connected to an analyzer (not shown), and the analyzer calculates a value indicating the electrical conductivity of the odor sensor element 10 (e.g., electrical resistance, impedance, etc.) based on the measurement value output from the voltmeter 40.

The odor sensor 32 includes an amplifier (not shown) in front of the voltmeter 40 in the odor substance measurement circuit, which amplifies the acquired signal and supplies it to the voltmeter 40. In addition to the odor substance measurement circuit, the odor sensor 32 also includes a reference circuit (not shown), and the voltmeter 40 acquires the difference (potential difference) between the value acquired in the odor substance measurement circuit and the value acquired in the reference circuit as a voltage value.

The odor sensor 32 may be equipped with a constant current source (power supply) (not shown) instead of the constant voltage power supply 38, and an ammeter (measuring device) (not shown) instead of the voltmeter 40. In this case, the constant current source functions as a power source for supplying power to the odor sensor element 10, applying a constant current to the odor sensor element 10 via the lead wires 18. Meanwhile, the ammeter measures the value of the current flowing between the pair of metal wirings 16 when a constant current is applied to the odorant receiving layer 14.

<Configuration example of odor sensor element 10>
FIG. 13 is a top view showing an example of the configuration of an odor sensor element 10A, which is an example of one odor sensor element 10 included in the odor sensor 32. The odor sensor element 10A includes a pair of metal wirings 16 arranged on a substrate 12 and a circular odorant receiving layer 14A formed on the metal wirings 16. Although not shown in FIG. 13, the odor sensor element 10A may also include an odorant permeation layer 20. The pair of metal wirings 16 includes a first metal wiring 16A and a second metal wiring 16B. The first metal wiring 16A and the second metal wiring 16B are metal wirings that function as electrodes for measuring changes in the electrical conductivity of the odorant receiving layer 14A. The diameter R of the odorant receiving layer 14A is 0.2 mm or more and 5 mm or less. In FIG. 13, the shape of the odorant receiving layer 14A included in the odor sensor element 10A is elliptical, by way of example, but is not limited thereto. When the odorant receiving layer 14A has an elliptical shape, the average of the minor axis and the major axis may be 0.2 mm or more and 5 mm or less. The odorant receiving layer 14A may also have a circular shape.

Figure 14 is a top view showing odor sensor element 10B, another example of an odor sensor element 10. Odor sensor element 10B comprises metal wiring 16 (first metal wiring 16A, second metal wiring 16B) arranged on substrate 12, and a strip-shaped odorant receiving layer 14B formed on metal wiring 16. The length W of the width in the short direction of odorant receiving layer 14B is 0.2 mm or more and 5 mm or less. In the following description, when there is no need to distinguish between odorant receiving layers 14A and 14B, they will be collectively referred to as "odorant receiving layer 14."

The metal wiring 16 of the odor sensor element 10 included in the odor sensor 32 each has a first metal wiring and a second metal wiring, and the first metal wiring and the second metal wiring may be arranged in the form of parallel lines, parallel curves, a comb shape, or concentric circles. Regardless of which of the above shapes is adopted, the first metal wiring and the second metal wiring are preferably arranged in line symmetry or point symmetry with each other. By arranging the first metal wiring and the second metal wiring in this manner, the odor sensor 32 can measure odor substances contained in gas with high accuracy.

The odor sensor element 10A in Figure 13 has a first metal wiring 16A and a second metal wiring 16B. As an example, the first metal wiring 16A is an electrode composed of metal wiring 161A and metal wiring 161B, with the two metal wirings arranged in a T-shape so that they are perpendicular to each other. The second metal wiring 16B is an electrode composed of two metal wirings 161C and 161D, similar to the first metal wiring 16A, and is configured so that the two metal wirings are arranged in a T-shape so that they are perpendicular to each other. The first metal wiring 16A and the second metal wiring 16B are arranged in parallel lines so that the metal wiring 161A and the metal wiring 161C face each other.

For example, if the metal wiring 16 were arranged in a comb shape, the distance between the first metal wiring 16A and the second metal wiring 16B would be too short, potentially resulting in an excessively low resistance value of the metal wiring 16. In contrast, by arranging the first metal wiring 16A and the second metal wiring 16B in a T-shape, the first metal wiring 16A and the second metal wiring 16B can be positioned at an appropriate distance, stabilizing the resistance value of the metal wiring 16 (electrode). Furthermore, by arranging the first metal wiring 16A and the second metal wiring 16B in a T-shape, the resin composition can be more easily spread during the coating process of the odor sensor element 10 described above, since there are no uneven portions of the metal wiring 16 that could hinder the spreading of the resin composition at the edges of the region where the resin composition spreads. Furthermore, the ease with which the resin composition spreads also contributes to the consistent thickness of the odorant receiving layer 14 and the odorant permeation layer 20 after drying.

Figure 15 is a perspective view showing an example of the configuration of one odor sensor element 10A. As shown in Figure 15, in the odor sensor element 10A, the first metal wiring 16A and the second metal wiring 16B are each connected to a pin 22 at the end where the first metal wiring 16A and the second metal wiring 16B do not face each other. The pin 22 is a conductive member for electrically connecting the first metal wiring 16A and the second metal wiring 16B to other components of the odor sensor 32. Although not shown, the odor sensor element 10B shown in Figure 14 also has the pin 22 shown in Figure 15.

〔summary〕
A method for manufacturing a sensitive film of an odor sensor element according to a first aspect of the present invention is a method for manufacturing a sensitive film of an odor sensor element on a substrate, the method comprising the steps of: using a pipette-type dispenser equipped with a detachable nozzle at its tip to draw a resin composition solution containing an organic solvent from a container storing the resin composition solution into the nozzle; after the step is completed, discharging the resin composition solution from the nozzle and applying it onto the substrate to form a coating film on the substrate; and after the step is completed, drying the coating film to form the sensitive film. The amount of the resin composition solution discharged from the nozzle is 0.1 μL to 5.0 μL.

A method for manufacturing a sensitive film of an odor sensor element according to Aspect 2 of the present invention may be the same as Aspect 1, except that the viscosity of the resin composition solution may be 1 mPa·s to 500 mPa·s, and the boiling point of the organic solvent may be 150°C to 250°C.

In the method for manufacturing a sensitive film of an odor sensor element according to aspect 3 of the present invention, in the above-described aspect 1 or 2, the solids content of the resin composition solution may be 2% to 20%.

In the method for manufacturing a sensitive film of an odor sensor element according to aspect 4 of the present invention, in any one of aspects 1 to 3, the thixotropic index of the resin composition solution measured with a rheometer may be 1.05 to 5.00.

A method for manufacturing a sensitive film of an odor sensor element according to aspect 5 of the present invention is the same as that according to any one of aspects 1 to 4, wherein the resin composition solution may contain a filler.

A method for manufacturing a sensitive film of an odor sensor element according to aspect 6 of the present invention may be the same as that according to aspect 5, except that the filler may be a conductive material.

A method for manufacturing a sensitive film of an odor sensor element according to aspect 7 of the present invention may be the same as that according to aspect 6, except that the conductive material is a conductive carbon material.

A method for manufacturing a sensitive film of an odor sensor element according to aspect 8 of the present invention may be the same as that according to aspect 5, except that the filler may be zeolite.

The method for manufacturing a sensitive film of an odor sensor element according to aspect 9 of the present invention may further include, in any of aspects 1 to 8, a replacement step of replacing the nozzle every time the application step is performed a predetermined number of times.

A method for manufacturing a sensitive film of an odor sensor element according to aspect 10 of the present invention is any one of aspects 1 to 9, wherein the odor sensor element is a chemiresistor-type odor sensor element that uses changes in the electrical resistance value of the sensitive film as an indicator for detecting odors.

The sensitive film of the odor sensor element according to aspect 11 of the present invention is manufactured by the method for manufacturing the sensitive film of the odor sensor element according to any one of aspects 1 to 10.

An odor sensor element according to aspect 12 of the present invention comprises a substrate and a sensitive film manufactured on the substrate by the method for manufacturing a sensitive film of an odor sensor element according to any one of aspects 1 to 10.

In the odor sensor element according to aspect 13 of the present invention, in the odor sensor element according to aspect 12, the sensitive film may be an odorant-receiving layer.

In the odor sensor element according to aspect 14 of the present invention, in accordance with aspect 12, the sensitive film may be an odorant-permeable layer.

An odor sensor according to aspect 15 of the present invention includes an odor sensor element according to any one of aspects 12 to 14.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in the embodiments.

The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to these. Unless otherwise specified, % means % by weight and parts means parts by weight.

The various materials used in the examples and comparative examples are described below.

<Resin (A)>
A1: Polyamide resin (produced based on the method described below in <Polyamide resin A1>)
A2: Butyral resin ("Mobital B75H" manufactured by Kuraray Co., Ltd.)
A3: Silicone resin (DOWSIL RSN-0255 Flake Reain, manufactured by Dow Toray Industries, Inc.)
<Filler (B)>
B1: Carbon black (manufactured by Denka Co., Ltd., "Denka Black", primary particle diameter: 48 nm, DBP oil absorption: 177 cm ³ /100 g)
B2: Carbon black (manufactured by MTI Corporation, "Super C65", primary particle size: 50 nm, DBP oil absorption: 254 cm ³ /100 g)
B3: Carbon nanotubes (manufactured by Showa Denko K.K., "VGCF-H")
B4: High-silica zeolite (manufactured by Tosoh Corporation, "HSZ-690HOA")
<Surfactant (C)>
C1: Amine salt of polyether phosphate ester (Disparlon DA-325, manufactured by Kusumoto Chemicals Co., Ltd.)
<Solvent (D)>
D1: N-methyl-2-pyrrolidone (boiling point: 202°C)
D2: Butyl butyrate (boiling point: 165°C)
D3: Diethylene glycol monobutyl ether (boiling point: 230°C)
D4: N,N-dimethylformamide (boiling point: 153°C)
D5: Diethylene glycol monobutyl ether acetate (boiling point: 247°C)
D6: Methyl ethyl ketone (boiling point: 80°C)
D7: Dibenzyl ether (boiling point: 297°C)
D8: 1-decanol (boiling point: 232°C)
<Additive (E)>
E1: Silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "KBE-13")
Production Example 1 of Resin (A) is shown below.

Production Example 1-1 (Production of Polyester Resin P1)
A reaction vessel equipped with a stirrer, thermometer, heating/cooling device, nitrogen inlet tube, reflux condenser, dehydration tube with a stopcock, and pressure reducing device was charged with 58.2 parts of 12-hydroxystearic acid and 441.8 parts of ε-caprolactone, and the temperature was raised to 140°C over 4 hours under a nitrogen atmosphere, followed by a 2-hour reaction. The resin was then removed when the remaining amount of ε-caprolactone was 1% or less. The removed resin was cooled to room temperature and then pulverized into particles to obtain polyester resin P1. The number average molecular weight (Mn) of polyester resin P1 was 2600, and the acid value was 21.7 mg KOH/g.

<Method for measuring number average molecular weight (Mn) and weight average molecular weight (Mv)>
The number average molecular weight (Mn) and weight average molecular weight (Mv) were measured using gel permeation chromatography (GPC) (HLC-802A (manufactured by Tosoh Corporation)) under the following conditions.
Columns: G4000PWXL (manufactured by Tosoh Corporation) and G5000PWXL (manufactured by Tosoh Corporation), two of which were arranged in series.
Mobile phase: 20% acetonitrile (containing 50 mM lithium chloride)
Flow rate: 0.8 mL/min Column temperature: 40°C
Pump: L-6200 (Hitachi, Ltd.)
Detector: L-3300 (RI: differential refractometer, manufactured by Hitachi, Ltd.) and L-4200 (UV-VIS: ultraviolet-visible spectrophotometer, manufactured by Hitachi, Ltd.)
Sample solution: 0.5 wt % acetonitrile solution. Sample injection volume: 200 μL.

<Method for measuring acid value>
The acid value was measured by the method specified in JIS K0070 (1992 edition).

Production Example 1-2 (Production of Polyamide Resin A1)
Into a reaction vessel having the same configuration as the reaction vessel described in Production Example 1-1, 120 parts of xylene and 82.3 parts of a 20% aqueous solution of polyallylamine (manufactured by Nittobo Medical Co., Ltd., trade name "PAA-03", weight average molecular weight) were charged, and the temperature was raised to 160 ° C. with stirring under a sealed condition, and the distilled water was removed using a dehydrator with a cock. During this time, the xylene in the distillate separated from the water and was returned to the reaction vessel. Thereafter, 83.5 parts of the xylene solution of polyester resin P1 obtained in Production Example 1-1 was added, and stirring was continued at 160 ° C. for 3 hours. After 3 hours, the xylene was removed using a pressure reducing device, and polyamide resin A1 having an acid value of 14.9 mg KOH / g and a weight average molecular weight of 10,200 was obtained.

An example of how to prepare a resin composition solution is shown below.

Production Example 2 <Resin composition solution (S-1)>
The following components were weighed in the following amounts into a sample bottle to obtain a mixture.

Resin A1 (polyamide resin) 30 parts by weight Filler B1 20 parts by weight Solvent D1 450 parts by weight This mixture was stirred at 2000 rpm for 20 minutes using a planetary centrifugal mixer (ARE-310, manufactured by Thinky Corporation) to obtain a slurry. In this way, a resin composition solution (S-1) was obtained as the slurry.

Production Examples 3 to 19 <Resin composition solutions (S-2) to (S-18)>
Resin compositions (S-2) to (S-18) were prepared in the same manner as for the resin composition solution (S-1), by weighing out the components into sample bottles based on the blending amounts shown in Table 1. When surfactant (C1) or additive (E1) was used, it was weighed out into a sample bottle in the same manner as the other components.

The compositions and physical properties of each resin composition solution are shown in Table 1.

<Production of Sensor Substrate K-1>
[Substrate manufacturing]
16 and 17 are schematic diagrams illustrating a manufacturing method for sensor substrate K-1 used in the examples. In this example, a glass cloth-based epoxy resin copper-clad laminate FR-4.0 (manufactured by Panasonic Electric Works Co., Ltd.) measuring 150 mm in length, 100 mm in width, and 1.0 mm in thickness was used, and sensor substrates (corresponding to substrate 12 in the embodiment) designed on the laminate were manufactured in 16 rows vertically and 16 columns horizontally (a total of 256 substrates) by the method described below, as shown in FIGS. 16 and 17. At this time, margins of 11 mm were secured on the top and bottom, and 10 mm on the left and right.

[Wiring pattern design]
18 and 19 are schematic diagrams showing the configuration of the sensor substrate K-1 used as an example. Fig. 18 shows the front surface (the surface on which the metal wiring 16 and odorant receiving layer 14 are arranged in Fig. 14 ) of the sensor element (corresponding to the odor sensor element 10 in the embodiment), and Fig. 19 shows the back surface (the surface opposite the front surface) of the sensor element. As shown in Fig. 16 , a total of 256 wiring patterns were designed on the laminated plate, with the T-shaped metal wirings (first metal wiring 16A and second metal wiring 16B) shown in Fig. 14 facing each other, the lengths of metal wiring 161A and metal wiring 161C being 2.5 mm, the lengths of metal wiring 161B and metal wiring 161D being 2 mm, the spacing between metal wiring 161A and metal wiring 161C being 1.5 mm, and the width of each metal wiring being 0.3 mm. Furthermore, as shown in Figures 18 and 19, a circular conductive portion with a diameter of 1 mm was provided at the end of the first metal wiring 16A and the second metal wiring 16B that do not face each other, as a portion into which a pin, which is a conductive member for electrically connecting to other components of the odor sensor, is inserted, and a similar circular conductive portion with a diameter of 1 mm was designed at the same position on the back surface.

[Through-hole manufacturing process]
In order to mount pins (corresponding to pin 22 in the embodiment) on each sensor substrate, holes for through holes were drilled in the circular conductive portions with a diameter of 1 mm using an NC drill machine, and first electroless copper plating and then copper sulfate plating were applied to create through holes with a copper plating layer of 25 μm in thickness.

[Pattern Forming Process]
Photosensitive dry film resist (trade name "Photec RD-3025", film thickness 25 μm, manufactured by Showa Denko Materials Co., Ltd.) was attached to both sides of the sensor substrate using a roll laminator (pressure 0.4 MPa, temperature 110 ° C, lamination speed 0.4 m/min). Then, using a UV exposure machine, the photosensitive dry film resist side was irradiated with UV light (wavelength 355 nm) ^at 85 mJ/cm2 through a front negative photomask and a back negative photomask, and the unexposed photosensitive dry film resist was removed with a 5 wt% aqueous sodium carbonate solution at 35 ° C. The copper foil in the exposed areas where the photosensitive dry film resist had been removed was then etched using a ferric chloride aqueous solution, and the exposed photosensitive dry film resist was removed using a 10 wt% aqueous sodium hydroxide solution at 35 ° C.

The negative photomask for the front surface used had a pattern in which the designed sensor substrate was arranged in 16 rows at 8 mm intervals vertically and 16 columns at 5 mm intervals horizontally, while the negative photomask for the back surface had a pattern in which circles with a diameter of 1 mm were arranged in positions that coincided with the circular portions of the negative photomask for the front surface.

[Solder resist process]
A two-component alkaline development solder resist ink (manufactured by Taiyo Ink Mfg. Co., Ltd., product name "PSR-4000 AUS320/CA-40 AUS320") was pattern-printed on the front side, excluding the copper foil, through-hole, and strip-shaped odorant receiving layer 14 (shown with diagonal lines in Figure 18), and on the back side, excluding the copper foil and through-hole. The pattern was then heated at 80°C for 30 minutes to dry, after which it was irradiated with ultraviolet light (wavelength 355 nm) ^at 600 mJ/cm², and the unexposed portions were removed with a 1 wt% aqueous sodium carbonate solution at 35°C. The solder resist ink was then cured by heating at 150°C for 60 minutes. The solder resist formed on the sensor substrate can regulate the wetting and spreading of the resin composition solution applied in a subsequent process.

[Surface treatment process]
The sensor substrate was degreased, soft etched, and acid washed, then immersed in a catalyst application solution (manufactured by Okuno Chemical Industries Co., Ltd., product name "ICP Accela COA") at 25°C for 5 minutes, rinsed with water, and immersed in an electroless Ni plating solution (manufactured by Okuno Chemical Industries Co., Ltd., product name "Top Nicoron SA-98-MLF" 100 ml and "Top Nicoron SA-98-1LF" 55 ml) at 90°C for 6 minutes to form a Ni coating with a thickness of 3 μm, and then washed with pure water.

Next, the sensor substrate was immersed in a displacement gold plating solution (manufactured by Kojima Chemical Co., Ltd., product name "OL 2300") at 85°C for 5 minutes, forming a 0.05 μm thick displacement gold coating on the Ni coating, resulting in a substrate with the copper foil portion coated with nickel and gold plating.

[V-cut on the circuit board]
Using a V-cutting machine, V-cuts were made at intervals of 8 mm in length and 5 mm in width so that the substrate could be separated into individual sensor substrates.

[Pin implementation]
An IC terminal (manufactured by Mac Eight Corporation, product name "Hybrid IC Terminal", φ0.6 mm, length 5 mm) was soldered to the fabricated through-hole. In this way, a total of 256 sensor substrates K-1 shown in Figures 18 and 19 were fabricated.

<Sensor element>
Example 1
Using a 1μ PIPETMASTER manufactured by Musashi Engineering Co., Ltd., a Violamo Sakura tip (10μL capacity, polypropylene, stored in a dedicated rack) manufactured by Violamo was attached, and 10μL of the resin composition solution (S-1) was aspirated from a container storing the prepared resin composition solution (S-1). After aspirating, the pipette tip was attached to the edge of the container to drain the liquid, and then 0.1μL of the resin composition solution (S-1) was dispensed onto the prepared sensor substrate K-1, thereby applying it to the metal wiring portion. After application, the substrate was dried for 3 hours in a circulating air dryer heated to 100°C, and then cooled to room temperature to prepare a sensor element (E1-1). The above-mentioned dispensing process and subsequent operations were performed 10 times consecutively to prepare 10 sensor elements (E1-1).

Examples 2 to 27, Comparative Examples 2 and 3
Ten sensor elements (E1-2) to (E1-27) and (E'1-2) to (E'1-3) were prepared in the same manner as in Example 1, based on the discharge amounts and number of continuous discharges shown in Table 2. For those with fewer than 10 continuous discharges, the Viola Sakura chip was discarded after the number of continuous discharges, and a new Viola Sakura chip was attached, followed by the inhalation, discharge, and drying steps described in Example 1.

Examples 28 to 54, Comparative Examples 6 and 7
Ten sensor elements each having an odorant receiving layer were prepared by the same procedure as in Example 1, based on the resin composition solution, discharge amount, and number of continuous discharges listed in the odorant receiving layer column in Table 3. The used Viola Sakura chip was then discarded, a new Viola Sakura chip was attached, and ten sensor elements each having an odorant permeation layer (E2-1) to (E2-27), (E'2-3) to (E'2-4) were prepared by the same procedure as in Example 1, based on the resin composition solution, discharge amount, and number of continuous discharges listed in the odorant permeation layer column in Table 3.

Comparative Example 1
The resin composition solution (S-1) was poured into a syringe equipped with a SUS metal needle nozzle (inner diameter 0.1 mmΦ, outer diameter 0.23 mm), and the trapped air was removed by pushing the plunger. The syringe was then attached to an IMAGE MASTER 350PCSmart manufactured by Musashi Engineering Co., Ltd. Using this, 0.1 μL of the resin composition solution (S-1) was dispensed onto the prepared sensor substrate K-1, thereby applying it to the metal wiring portion. After application, the substrate was dried for 3 hours in a circulating air dryer heated to 100 ° C. After drying, the substrate was cooled to room temperature to prepare a sensor element (E'1-1). The same operation was repeated 10 times to prepare 10 sensor elements (E'1-1).

Comparative Examples 4 and 5
Based on the resin composition solution, discharge amount, and number of continuous discharges listed in the odorant receiving layer column of Table 3, the same operation as in Comparative Example 1 was performed to prepare 10 sensor elements each having an odorant receiving layer. Then, using a syringe different from the syringe used, based on the resin composition solution, discharge amount, and number of continuous discharges listed in the odorant permeation layer column of Table 2, the same operation as in Comparative Example 1 was performed to prepare 10 sensor elements each having an odorant permeation layer (E'2-1) to (E'2-2).

<Construction of an odor sensor>
A housing was fabricated that included a target sample receiving section with an inlet for introducing the sample (odor substance) and an aluminum block thermostatic bath for temperature control, a nitrogen gas cylinder for gas supply, a mass flow controller, and a sensor chamber. The volume of the target sample receiving section was designed to be five times the volume of the sensor chamber.

Lead wires for connecting the sensor terminals to the outside were soldered to each of the sensor elements (E1-1) to (E1-27), (E2-1) to (E2-27), (E'1-1) to (E'1-3), and (E'2-1) to (E'2-4) under evaluation, and the elements were placed inside the sensor chamber. A 5V constant-voltage power supply and a 300Ω fixed resistor were connected in series to the ends of the lead wires connected to the outside of the sensor chamber for each of the sensor elements (E1-1) to (E1-27), (E2-1) to (E2-27), (E'1-1) to (E'1-3), and (E'2-1) to (E'2-4), and a voltmeter was connected to measure the voltage across both terminals of the sensor element. In this way, multiple odor sensors were constructed, each having one of the sensor elements (E1-1) to (E1-27), (E2-1) to (E2-27) and the comparative sensor elements (E'1-1) to (E'1-3), (E'2-1) to (E'2-4). The correspondence between the odor sensor numbers and the sensor element numbers of the odor sensors is as shown in Tables 2 and 3.

〔evaluation〕
<Measurement of voltage change (ΔV) when measuring ion-exchanged water>
Each of odor sensors 1-54 and c1-c7 was installed in a laboratory (temperature 25°C, humidity 50%). The temperature inside the target sample receiving section was adjusted to 30°C using an aluminum block thermostatic chamber. 5 mL of ion-exchanged water was then placed in the target sample receiving section as a specimen. Nitrogen carrier gas was then introduced from the carrier gas inlet into the chamber containing the sensor element at a flow rate of 1 L/min using a gas flow regulator and discharged to the outside. During this time, the measurements of the voltmeter connected to the sensor element were recorded by a computer. Thus, the voltage values of each of the 10 sensor elements in the odor sensor were measured. For each sensor element of each odor sensor, the maximum difference ΔV (water) between the output voltage V0 before sample introduction and the voltage V after sample introduction was calculated. The average value μ (water) of the 10 maximum ΔV data obtained for each odor sensor was then calculated.

<Measurement of voltage change (ΔV) and ΔV variation coefficient in ethanol measurement>
The ΔV (ethanol) and average value μ (ethanol) were calculated under the same conditions except that ethanol was used instead of ion-exchanged water as the sample. Furthermore, the standard deviation σ (ethanol) of ΔV (ethanol) was calculated, and the coefficient of variation of ΔV (=σ/μ) for each sensor element was determined.

<Measurement of voltage change (ΔV) in hexane measurement>
The same procedure was followed except that hexane was used as the sample instead of ion-exchanged water, and ΔV (hexane) and the average value μ (hexane) were calculated.

<Ratio of voltage change amount (ΔV)>
The voltage change (ΔV) when ion-exchanged water, ethanol, and hexane were measured as samples was divided by the voltage change (ΔV) for ion-exchanged water for each sensor element to calculate the ratio of voltage changes (ΔV).

Table 2 shows the shape of the dispenser, type of resin composition solution, and discharge amount used for odor sensors 1 to 27 of Examples 1 to 27 and odor sensors c1 to c3 of Comparative Examples 1 to 3.

Table 3 shows the shape of the dispenser, type of resin composition solution, and discharge amount used for odor sensors 28-54 of Examples 28-54 and odor sensors c4-c7 of Comparative Examples 4-7.

In Tables 2 and 3, the ratio of ΔV for each sample is preferably as large as the difference between the three values, from the perspective of the sensitivity of the odor sensor. On the other hand, the smaller the ΔV coefficient of variation, the more preferable it is, from the perspective of reducing the variability.

<Consideration>
As shown in Tables 2 and 3, odor sensors 1 to 54 all exhibit larger differences in ΔV ratios and lower ΔV coefficients of variation than odor sensors c1 to c7, which are comparative examples.

Comparing Examples 1 to 54 with Comparative Examples 1, 4, and 5, it was found that odor sensors c1, c4, and c5, which have odorant receptive layers or odorant permeable layers manufactured using methods that do not use pipette-type dispensers, have small differences in the ΔV ratio and large ΔV coefficients of variation.

Comparing Examples 1 to 54 with Comparative Examples 2, 3, 6, and 7, it was found that odor sensors c2, c3, c6, and c7, which have odorant receiving layers or odorant permeation layers manufactured using methods with discharge volumes of less than 0.1 μL or more than 5.0 μL, had small differences in the ΔV ratios and large ΔV coefficients of variation.

Comparing Examples 5, 9-19, 28, and 32-42, practically acceptable ΔV ratios and ΔV variation coefficients were obtained regardless of the viscosity of the resin composition solution or the boiling point of the organic solvent. In particular, odor sensor 5, which was equipped with a sensor element manufactured using a resin composition solution with a viscosity of 8 mPa·s and an organic solvent boiling point of 202°C, had the largest difference in ΔV ratio and the smallest ΔV variation coefficient.

Comparing Examples 5, 11, 12, 19, 28, 34, 35, and 42, it was found that practically acceptable ΔV ratios and ΔV coefficients of variation were obtained regardless of the solid content of the resin composition solution. In particular, odor sensor 5, which was equipped with a sensor element manufactured using a resin composition solution with a solid content of 10%, had the largest difference in ΔV ratio and the smallest ΔV coefficient of variation.

Comparing Examples 5, 11, 12, 19, 28, 34, 35, and 42, it was found that practically acceptable ΔV ratios and ΔV variation coefficients were obtained regardless of the thixotropic index of the resin composition solution. In particular, odor sensor 5, which was equipped with a sensor element manufactured using a resin composition solution with a thixotropic index of 1.1, had the largest difference in ΔV ratio and the smallest ΔV variation coefficient.

Comparing Examples 5 and 25, or 28 and 48, and Examples 12, 20, and 21, it was found that even when filler was present or the type of filler was different, ΔV ratios and ΔV variation coefficients that were practically acceptable were obtained.

Accordingly, it was found that odor sensor elements manufactured by a manufacturing method including: an inhalation process in which a resin composition solution containing an organic solvent is drawn into a container containing the resin composition solution using a pipette-type dispenser equipped with a detachable nozzle at the tip; an application process in which, after the inhalation process, the resin composition solution is discharged from the nozzle and applied onto the substrate to form a coating film on the substrate; and a drying process in which, after the application process, the coating film is dried to form the sensitive film, wherein the amount of resin composition solution discharged from the nozzle is 0.1 μL to 5.0 μL, exhibit a ΔV ratio and ΔV coefficient of variation that are acceptable for practical use. In other words, an odor measurement device equipped with such an odor sensor has high odor detection sensitivity and can output stable measurement results, and therefore can be said to have high odor identification performance.

10 odor sensor element 12 substrate 14 odorant receiving layer (sensitive film)
16 Metal wiring 18 Lead wire 20 Odorant permeable layer (sensitive membrane)
22 Container 24 Pipette-type dispenser 26 Pipette 28 Nozzle 30 Container 32 Odor sensor 34 Housing 34i Inlet 34e Outlet 36 Target material receiving section (front chamber)
38 Constant voltage power supply (power supply)
40 Voltmeter L1 Resin composition solution F1 Coating film L2 Resin composition solution F2 Coating film

Claims (9)

A method for manufacturing a sensitive film of an odor sensor element on a substrate, comprising:
a suction step of using a pipette-type dispenser having a detachable nozzle at its tip to suck a resin composition solution containing an organic solvent from a container storing the resin composition solution into the nozzle;
a coating step of discharging the resin composition solution from the nozzle and coating it on the substrate after the suction step is completed, thereby forming a coating film on the substrate;
a drying step of drying the coating film to form the sensitive film after the coating step is completed,
The method for manufacturing a sensitive film of an odor sensor element, wherein the amount of the resin composition solution discharged from the nozzle is 0.1 μL to 5.0 μL. The method for manufacturing a sensitive film of an odor sensor element according to claim 1, wherein the viscosity of the resin composition solution is 1 mPa·s to 500 mPa·s, and the boiling point of the organic solvent is 150°C to 250°C. The method for manufacturing a sensitive film of an odor sensor element according to claim 1, wherein the solids content of the resin composition solution is 2% to 20%. The method for manufacturing a sensitive film of an odor sensor element according to claim 1, wherein the thixotropic index of the resin composition solution measured with a rheometer is 1.05 to 5.00. The method for manufacturing a sensitive film of an odor sensor element according to claim 1, wherein the resin composition solution contains a filler. The method for manufacturing a sensitive film of an odor sensor element described in claim 5, wherein the filler is a conductive material. The method for manufacturing a sensitive film of an odor sensor element described in claim 6, wherein the conductive material is a conductive carbon material. The method for manufacturing a sensitive film of an odor sensor element described in claim 1 further includes a replacement process for replacing the nozzle every time the application process is performed a predetermined number of times. The method for manufacturing a sensitive film of an odor sensor element described in claim 1, wherein the odor sensor element is a chemiresistor-type odor sensor element that uses changes in the electrical resistance value of the sensitive film as an indicator for detecting odor.