Patent Grant
12237095
The present disclosure relates to a conductor and a manufacturing method of the conductor.
There has been known a conductive film in which chloroauric acid as a dopant is brought into contact with a surface of a carbon nanotube (CNT)-containing film that is a film containing CNT. In this conductive film, the dopant reduces a sheet resistance of the CNT-containing film and improves conductivity. The sheet resistance is also called a surface resistivity.
The present disclosure provides a conductor and a manufacturing method of the conductor. The conductor includes a conductive structure and a dopant. The conductive structure has a predetermined shape and includes a carbon material having conductivity. The dopant causes the carbon material to generate an electric charge. The dopant includes a trifluoromethanesulfonate that is composed of a trivalent ion of a lanthanide and triflate anions.
Objects, features and advantages of the present disclosure will become apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:
The present inventors have found that a conductive film in which chloroauric acid as a dopant is brought into contact with a surface of a CNT-containing film deteriorates in performance in a high-temperature and high-humidity environment and loses its effect of improving conductivity. Note that this is not limited to the conductive film containing the CNT-containing film and chloroauric acid. It is conceivable that the performance deteriorates in a high-temperature and high-humidity environment in a conductive structure containing a carbon material and a conductor containing chloroauric acid.
According to one aspect of the present disclosure, a conductor includes a conductive structure having a predetermined shape and including a carbon material having conductivity, and a dopant that causes the carbon material to generate an electric charge. The dopant includes a trifluoromethanesulfonate that is composed of a trivalent ion of a lanthanide and triflate anions.
According to this configuration, the conductivity of the conductive structure can be improved by the dopant, and deterioration of performance in a high-temperature and high-humidity environment can be restricted.
According to another aspect of the present disclosure, a manufacturing method of a conductor includes: preparing a conductive structure having a predetermined shape and including a carbon material having conductivity; preparing a solution including a solute and a solvent, the solute serving as a dopant that causes the carbon material to generate an electric charge; attaching the solution to the conductive structure; and removing the solvent from the conductive structure after attaching the solution to the conductive structure. The preparing of the solution includes preparing the solute including a trifluoromethanesulfonate that is composed of a trivalent ion of a lanthanide and triflate anions.
According to this manufacturing method, the conductivity of the conductive structure can be improved by the dopant, and deterioration of performance in a high-temperature and high-humidity environment can be restricted.
Hereinafter, an embodiment of the present disclosure will be described. A conductor of the present embodiment includes a conductive structure containing a conductive carbon material and a dopant that causes the carbon material to generate electric charges.
As the conductive carbon material, a nanocarbon material is used. The nanocarbon material is a carbon material whose structure is controlled at a nano-size level. The nano-size is a size of 1000 nm or less, including 1 nm or less. The nanocarbon material includes a carbon material whose smallest dimension among its own dimensions is in a range from 1 nm to 1000 nm inclusive. Examples of the nanocarbon material include CNT, carbon nanobud (CNB), graphene, and the like. CNT, CNB, graphene, and the like mainly have a six-membered ring structure. As the conductive carbon material, a carbon material having conductivity other than the nanocarbon material may also be used.
The conductive structure is an object having conductivity and having a predetermined shape. An example of the conductive structure is a transparent conductive film 10 shown in
The transparent conductive film 10 is supported by a substrate 20 that is transparent. As the substrate 20, a substrate made of a synthetic resin material (for example, PET and the like) or an inorganic material (for example, quartz glass and the like) is used. Note that the transparent conductive film 10 does not have to be supported by the substrate 20.
The transparent conductive film 10 is used as a transparent heater. The transparent heater is used as a heater for securing the function of an in-vehicle sensor or a windshield of a vehicle. The transparent heater heats the sensor or the windshield when icing, fogging and or like occurs on the sensor or the windshield. Accordingly, the icing, the fogging, or the like is eliminated.
The conductive structure may be an opaque conductive film. The shape of the conductive structure may also be a wire shape instead of the film shape.
The dopant is interspersed with respect to the conductive structure. The dopant is a substance that increases charges present in the carbon material. In the present embodiment, the dopant is a positive charge imparting dopant (that is, p-type dopant) that imparts positive charges to the carbon material.
In the present embodiment, the dopant includes a trifluoromethane-sulfonate composed of a trivalent ion of a lanthanide and triflate anions. The dopant may include other compounds as long as the dopant mainly includes trifluoromethanesulfonate. Lanthanides are elements with atomic numbers from 57 to 71. Lanthanides include cerium (Ce). The chemical formula of the triflate anion is CF3SO3−.
Next, a manufacturing method of the conductor having the above-described structure will be described. As shown in
In the structure preparation process S1, the conductive structure including the conductive carbon material is prepared.
In the solution preparation process S2, a solution containing a solute that serves as the dopant and a solvent is prepared. In the solution, the solute is dissolved in the solvent. As the solute, a solute that includes a trifluoromethanesulfonate composed of a trivalent ion of a lanthanide and triflate anions is used. As the solvent, an organic solvent such as isopropyl alcohol, ethanol, THF, hexane, dichloroethane, diethylene glycol diethyl ether, acetone, NMP, or ethyl acetate is used. The concentration of the solution prepared at this time may be any concentration that allows the dopant to come into contact with the carbon material.
Either the structure preparation process S1 or the solution preparation process S2 may be performed first, or they may be performed at the same time.
After the structure preparation process S1 and the solution preparation process S2 are performed, the solution attachment process S3 is performed. In the solution attachment process S3, the solution is attached to the conductive structure.
As a method of attaching the solution, a method of applying the solution, a method of spraying the solution, a method of immersing the conductive structure in the solution, or the like can be employed. In a case where a membrane is used as the conductive structure, the solution is attached to a surface of the membrane. Alternatively, the solution may be attached inside the membrane by penetrating inside the membrane.
After the solution is attached in the solution attachment process S3, the solvent removal process S4 is performed. In the solvent removal process S4, the conductive structure attached with the solution is dried. At this time, the conductive structure is heated to a temperature equal to or higher than a boiling point of the solvent. Accordingly, the solvent in the solution is removed from the conductive structure to which the solution is attached. The conductor is manufactured as described above.
Here, dopants according to comparative examples will be described.
As shown in
As will be described later in Examples, a conductor using chloroauric acid, which is a dopant that imparts a positive charge, has an effect of improving conductivity due to the dopant. However, the present inventors found that when the conductor is exposed to a high-temperature and high-humidity environment, the performance of the conductor deteriorates and the effect of improving the conductivity disappears. It is considered that the reason why the performance of the conductor deteriorated is that the water reacted with the chloroauric acid in which surplus electric charges are present in the high-temperature and high-humidity environment.
In contrast, the dopant of the present embodiment includes the trifluoromethanesulfonate composed of the trivalent ion of the lanthanide and the triflate anions. As shown in
Therefore, according to the conductor of the present embodiment, since the electric charge is generated in the carbon material by the dopant, the conductivity of the conductive structure is improved. Furthermore, since the generation of surplus electric charges is restricted, it is possible to restrict deterioration of the performance of the conductor in a high-temperature and high-humidity environment, and to maintain the effect of improving conductivity.
The lanthanide of the dopant described above is preferably cerium as described in the examples described below. The trifluoromethanesulfonate composed of the trivalent ion of cerium and the triflate anions has a strong dopant polarization and a high electron-attracting property, and is therefore considered to be capable of generating charges in the carbon material.
However, the electron density of an element that becomes a cation can be cited as a factor of the high electron-attracting property of the dopant. Similar to Ce, a trifluoromethanesulfonate of an element in which electrons are arranged in f-orbitals and d-orbitals is considered to have a high electron-attracting property. Thus, trifluoromethanesulfonates of lanthanides other than Ce, which have similar electronic states to Ce, also have high electron-attracting properties, and are considered to have the same effect as Ce.
The present disclosure is not limited to the foregoing description of the embodiment and can be modified. The present disclosure may also be varied in many ways. Such variations are not to be regarded as departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. Individual components or features of the above-described embodiment are not necessarily essential unless it is specifically stated that the components or the features are essential in the foregoing description, or unless the components or the features are obviously essential in principle.
The numerical value such as the number, the numerical value, the quantity, the range, or the like of components mentioned in the above-described embodiment is not limited to a specific number unless specified as being required, clearly limited to such a specific number in principle, or the like. The material, the shape, the positional relationship, and the like of a component or the like mentioned in the above embodiment are not limited to those being mentioned unless otherwise specified, or limited to specific material, shape, positional relationship, and the like in principle.
<Dopant Treatment>
As shown in
The present inventors performed a dopant treatment on the prepared specimen 22. For the dopant treatment, a solution in which anhydrous Ce(III) triflate as a solute is dissolved in IPA (that is, isopropyl alcohol) as a solvent was prepared. The IPA used is 19516 IPA manufactured by Sigma-Aldrich Co. LLC. The anhydrous Ce(III) triflate used is Ce triflate abcr GmbH, PubChem SID: 316470470, Purchasable Chemical: AB255546. The concentration of the prepared solution is 10 mM.
Then, the present inventors dropped the prepared solution onto the surface of the CNT film 12 with a pipette. As a result, a droplet 31 of the solution was attached to the surface of the CNT film 12, as shown in
<Evaluation of Conductivity Improvement>
The present inventors measured the sheet resistance of the CNT film 12 before the dopant treatment and the CNT film 12 after the dopant treatment using an eddy current type sheet resistance measuring instrument. The unit of sheet resistance is Ω square. Then, the present inventors calculated the sheet resistance change rate with respect to the sheet resistance before the dopant treatment using the sheet resistance value before the dopant treatment, the sheet resistance value after the dopant treatment, and the following equation.
Sheet resistance change rate (%)=(Rs2−Rs1)/Rs1×100
In this equation, Rs1 is the sheet resistance value before the dopant treatment. Rs2 is the sheet resistance value after the dopant treatment.
<Durability Evaluation Test>
The present inventors held the specimen after the dopant treatment for 1000 hours inside a thermo-hygrostat maintained in a high-temperature and high-humidity environment. The setting of the thermo-hygrostat is 85° C. and RH 85%. The present inventors measured the sheet resistance of the CNT film using the eddy current type sheet resistance measuring instrument every elapsed time. Then, the present inventors calculated the sheet resistance change rate with respect to the sheet resistance before the dopant treatment in the same manner as described above.
The present inventor performed a dopant treatment in the same manner as in Example 1 using AuCl4H·3H2O (that is, chloroauric acid) as a solute. The chloroauric acid used is Tetrachloroauric (III) acid trihydrate 99.5% for analysis EMSURE (R), CAS 16961-25-4, EC 240-948-4, chemical formula AuCl4H·3H2O manufactured by Sigma-Aldrich Co. LLC. The concentration of the solution used is 20 mM.
The present inventors measured the sheet resistance before and after the dopant treatment in the same manner as in Example 1. The sheet resistance change rate was calculated from the results. Furthermore, the present inventors conducted the durability evaluation test in the same manner as in Example 1. The present inventors measured the sheet resistance of the CNT film at each elapsed time. The present inventors calculated the sheet resistance change rate from these results.
In addition, the present inventors analyzed the chemical state of the dopant before and after the durability evaluation test using X-ray photoelectron spectroscopy. “After the durability evaluation test” means after holding for 1000 hours in the thermo-hygrostat.
As shown in
As shown in
It was confirmed that the performance of a specimen using chloroauric acid as a dopant, as Comparative Example 1, deteriorates in a high temperature environment of 120° C. and the effect of improving conductivity disappears. On the other hand, it was confirmed that the performance of a specimen using anhydrous Ce(III) triflate, as in Example 1, did not deteriorate in a high temperature environment of 120° C.
In Example 2, the present inventors used the same anhydrous Ce(III) triflate as in Example 1 as the solute. Using a specimen different from that of Example 1, the present inventors performed a dopant treatment, sheet resistance measurements before and after the dopant treatment, and sheet resistance measurements at each elapsed time in the durability evaluation test in the same manner as in Example 1. Then, the present inventors calculated the sheet resistance change rate with respect to the sheet resistance before the dopant treatment. However, in Example 2, the specimen was held inside the thermo-hygrostat for 216 hours.
In addition, the present inventors analyzed the chemical state of the dopant before and after the durability evaluation test using X-ray photoelectron spectroscopy. “After the durability evaluation test” means after holding for 216 hours in the thermo-hygrostat.
In Comparative Example 2, the present inventors used anhydrous Ce(IV) triflate as shown in
As in Example 2, the present inventors performed a dopant treatment, sheet resistance measurements before and after the dopant treatment, and sheet resistance measurements for each elapsed time in the durability evaluation test. Then, the present inventors calculated the sheet resistance change rate with respect to the sheet resistance before the dopant treatment. Moreover, the present inventors conducted chemical state analysis of the dopant before and after the durability evaluation test in the same manner as in Example 2.
In Comparative Example 3, the present inventors used, as a solute, a compound whose reagent name is hydrous Ce(III) triflate. Hydrous Ce(III) triflate is a trifluoromethanesulfonate salt of the trivalent ion of cerium containing water molecules, and is represented as hydrous Ce(III)TfO, as shown in
As in Example 2, the present inventors performed a dopant treatment, sheet resistance measurements before and after the dopant treatment, and sheet resistance measurements for each elapsed time in the durability evaluation test. Then, the present inventors calculated the sheet resistance change rate with respect to the sheet resistance before the dopant treatment. Moreover, the present inventors conducted chemical state analysis of the dopant before and after the durability evaluation test in the same manner as in Example 2.
As shown in
In both Comparative Examples 2 and 3, the sheet resistance change rate at 0 hours is less than −40%. From these results, it can be seen that the effect of improving conductivity is high. However, in both Comparative Examples 2 and 3, the sheet resistance change rate increased significantly in the initial stage within 24 hours after the start of the durability evaluation test compared to Example 2. The increase in the sheet resistance change rate means that the sheet resistance increased and the conductivity decreased. Thus, in Comparative Examples 2 and 3, performance deterioration occurs in the initial stage.
Table 1 shows the results of chemical state analysis of the dopants before and after the durability evaluation test of Example 2, Comparative Example 2 and Comparative Example 3. In the dopant of Comparative Example 2, after the test, the presence ratio of Ce(IV) decreased and the presence ratio of Ce(III) increased compared to before the test.
The name of a reagent used as a dopant in Comparative Example 3 was hydrous Ce(III) triflate. However, there was significantly more Ce(IV) than Ce(III) in the dopant before the test. Therefore, the dopant used in Comparative Example 3 includes a trifluoromethanesulfonate composed of tetravalent ion of cerium and triflate anions more than a trifluoromethanesulfonate composed of a trivalent ion of cerium and triflate anions. In the dopant after the test, the presence ratio of Ce(IV) decreased and the presence ratio of Ce(III) increased compared to before the test. However, even after the test, more Ce(IV) than Ce(III) was present in the dopant.
As described above, both Ce(III) and Ce(IV) function as dopants. However, in terms of redox potential, Ce(III) is more stable than Ce(IV). Therefore, in the dopants of Comparative Examples 2 and 3, Ce(IV) changes to Ce(III) in the initial stage. This is considered to be the cause of the initial deterioration in Comparative Examples 2 and 3.
On the other hand, in the dopant of Example 2, the presence ratio of Ce(III) did not change before and after the test. Therefore, initial deterioration does not occur in the dopant of Example 2. The performance of the dopant is stable even when exposed to the high-temperature and high-humidity environment.
It is generally known that Ce(IV) is more stable than Ce(III) in Ce oxides. However, as described above, in trifluoromethanesulfonates of Ce, Ce(III) is more stable than Ce(IV). Therefore, when using a trifluoromethanesulfonate of Ce as a dopant, it is preferable that Ce is a trivalent ion.
From the results of
In Example 3, the present inventors prepared three solutions in which the solute and the solvent were same as those in Example 1, and solute concentrations were 1, 5 and 10 mM. Then, the present inventors performed the dopant treatment on specimens in the same manner as in Example 1 using these three kinds of solutions. In addition, the present inventors measured the sheet resistance before and after the dopant treatment. Using these results, the present inventors calculated the sheet resistance change rate with respect to the sheet resistance before the dopant treatment.
In Comparative Example 4, the present inventors prepared three solutions in which the solute was anhydrous K(III) triflate (that is, potassium trifluoromethanesulfonate) and the solute concentrations were 1, 5, and 10 mM. The anhydrous K(III) triflate used is 422843 manufactured by Sigma-Aldrich Co. LLC. Then, the present inventors performed the dopant treatment on specimens in the same manner as in Example 1 using these three kinds of solutions. In addition, the present inventors measured the sheet resistance before and after the dopant treatment. Using these results, the present inventors calculated the sheet resistance change rate with respect to the sheet resistance before the dopant treatment.
Thus, it was confirmed that in a case where a cation of the trifluoromethanesulfonate is Ce of a lanthanide, an effect as a dopant is high compared to a case where the cation of the trifluoromethanesulfonate is K of an alkali metal.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-113133 | Jun 2020 | JP | national |
The present application is a continuation application of International Patent Application No. PCT/JP2021/020415 filed on May 28, 2021, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No. 2020-113133 filed on Jun. 30, 2020. The entire disclosures of all of the above applications are incorporated herein by reference.
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| Number | Date | Country | |
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| 20230120391 A1 | Apr 2023 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2021/020415 | May 2021 | WO |
| Child | 18068563 | US |
