Electrode

Abstract

An electrode (1) comprises, sequentially in the thickness direction, a resin film (2) and a conductive carbon layer (4). The conductive carbon layer (4) has an sp3 bond. The heat shrinkage factor of the electrode (1) when heated for one hour at 150°C is -0.2% to 0.2%.

Description

electrode

[0001] The present invention relates to an electrode.

[0002] An electrode including a film substrate and a carbon thin film is known (see, for example, Patent Document 1 below). The carbon thin film described in Patent Document 1 includes diamond-like carbon. In this case, the carbon thin film is sp ３ Includes joins.

[0003] WO2016 / 013478

[0004] Electrodes may be curved depending on the application and purpose. However, when the electrode described in Patent Document 1 is curved, cracks are likely to occur in the carbon thin film because the carbon thin film is relatively brittle. This causes a problem of increased resistance in the electrode.

[0005] The present invention provides an electrode that can suppress damage to the conductive carbon layer even when bent.

[0006] The present invention (1) is an electrode having a resin film and a conductive carbon layer in this order in a thickness direction, and the conductive carbon layer is sp ３ The electrode has a bond, and when heated at 150° C. for 1 hour, the heat shrinkage rate is −0.2% or more and 0.2% or less.

[0007] The present invention (2) is characterized in that the conductive carbon layer is sp ２ Further having a bond, sp ３ Number of bonded atoms and sp ２ sp relative to the sum of the number of bonded atoms ３ The electrode according to (1), wherein the ratio of the number of bonded atoms is 0.10 or more.

[0008] In the present invention (3), the conductive carbon layer has a density of 1.8 g / cm ３ The electrode according to (1) or (2) has a density of at least 1000 kJ / cm2.

[0009] The electrode of the present invention can suppress damage to the conductive carbon layer even when bent, and can suppress the rate of increase in resistance before and after bending.

[0010] Fig. 1 is a cross-sectional view of one embodiment of an electrode of the present invention. Fig. 2 is a modified example of the electrode. Fig. 3 is a modified example of the electrode. Fig. 4 is a test A for measuring the rate of increase in resistance. Fig. 5 is a test B for measuring the rate of increase in resistance.

[0011] One embodiment of the electrode of the present invention will be described with reference to FIG.

[0012] (Electrode 1) As shown in Fig. 1, the electrode 1 has a predetermined thickness. The electrode 1 has a film shape (including a sheet shape) extending in a plane direction. The plane direction is perpendicular to the thickness direction. The electrode 1 has one surface and the other surface spaced apart from each other in the thickness direction.

[0013] (Thermal Shrinkage of Electrode 1) The thermal shrinkage of this electrode 1 when heated at 150° C. for 1 hour is −0.2% or more and 0.2% or less.

[0014] If the thermal shrinkage rate of the electrode 1 is less than −0.2% or more than 0.2%, the electrode 1 is likely to expand and contract when it is bent. As a result, damage to the conductive carbon layer 4, which will be described later, cannot be suppressed, and as a result, the rate of increase in the resistance of the conductive carbon layer 4 increases.

[0015] To measure the thermal shrinkage of the electrode 1, the electrode 1 is heated at 150° C. for 1 hour in air at atmospheric pressure. Then, the length of the electrode 1 before and after heating is measured to determine the thermal shrinkage of the electrode 1.

[0016] The thermal shrinkage rate of the electrode 1 is preferably −0.15% or more, more preferably −0.1% or more, and is preferably 0.15% or less, more preferably 0.1% or less.

[0017] The electrode 1 described above includes a resin film 2, a metal base layer 3, and a conductive carbon layer 4, arranged in this order toward one side in the thickness direction. Specifically, the electrode 1 includes a resin film 2, a metal base layer 3 disposed on one surface in the thickness direction of the resin film 2, and a conductive carbon layer 4 disposed on one surface in the thickness direction of the metal base layer 3. Preferably, the electrode 1 includes the resin film 2, the metal base layer 3, and the conductive carbon layer 4. Each layer will be described in detail below.

[0018] (Resin Film 2) The resin film 2 forms the other surface of the electrode 1 in the thickness direction. The resin film 2 has a film shape extending in the planar direction. The resin film 2 is a base film in the electrode 1. The resin film 2 is, for example, flexible. Examples of materials for the resin film 2 include polyester resins (e.g., polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate), acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyolefin resins (e.g., polyethylene, polypropylene, and polycycloolefin polymers), (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, polyarylate resins, and polyphenylene sulfide resins. From the viewpoint of thermal stability, the material for the resin film 2 is preferably polyester resin, and more preferably polyethylene terephthalate.

[0019] There are no limitations on the thickness of the resin film 2. The thickness of the resin film 2 is, for example, 2 μm or more, or preferably 20 μm or more, and for example, 1000 μm or less, or preferably 500 μm or less.

[0020] (Metallic Underlayer 3) The metallic underlayer 3 is in contact with one surface in the thickness direction of the resin film 2. The metallic underlayer 3 extends in the planar direction. The metallic underlayer 3 is an intermediate layer located between the resin film 2 and the conductive carbon layer 4.

[0021] There are no limitations on the material of the metal underlayer 3. Examples of the material of the metal underlayer 3 include metal elements classified into groups 3 to 14 in the periodic table defined by IUPAC in 2019, and preferably titanium from the viewpoint of chemical stability.

[0022] There are no limitations on the thickness of the metal underlayer 3. The thickness of the metal underlayer 3 is, for example, 1 nm or more, preferably 5 nm or more, and 100 nm or less, preferably 50 nm or less.

[0023] (Conductive Carbon Layer 4) The conductive carbon layer 4 is conductive. The conductive carbon layer 4 forms one surface in the thickness direction of the electrode 1. The conductive carbon layer 4 is in contact with one surface in the thickness direction of the metal base layer 3. The conductive carbon layer 4 extends in the planar direction.

[0024] The conductive carbon layer 4 is, for example, at least sp ３ Specifically, the conductive carbon layer 4 has at least sp ３ The conductive carbon layer 4 contains carbon having bonds. In other words, the conductive carbon layer 4 has at least a diamond structure. This allows the conductive carbon layer 4 to have high sensitivity to the measurement target.

[0025] The conductive carbon layer 4 is preferably sp ２ Bonds and sp ３ Specifically, the conductive carbon layer 4 has sp ２ Carbon with sp bonds ３ In other words, the conductive carbon layer 4 has a graphite structure and a diamond structure. This allows the conductive carbon layer 4 to have excellent conductivity and high sensitivity to the object to be measured.

[0026] Furthermore, the conductive carbon layer 4 may contain, for example, oxygen in addition to carbon. Specifically, for example, oxygen is contained on one surface in the thickness direction of the conductive carbon layer 4. The concentration ratio of oxygen to carbon (O / C) on one surface in the thickness direction of the conductive carbon layer 4 is not limited.

[0027] Furthermore, the conductive carbon layer 4 is allowed to contain trace amounts of unavoidable impurities other than oxygen.

[0028] In the conductive carbon layer 4, sp ３ Number of bonded atoms and sp ２ sp relative to the sum of the number of bonded atoms ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２) is, for example, 0.10 or more, preferably 0.20 or more, preferably 0.30 or more, and more preferably 0.35 or more. ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２ ) is equal to or greater than the above-mentioned lower limit, the potential window of the electrode 1 can be widened.

[0029] Also, sp ３ Number of bonded atoms and sp ２ sp relative to the sum of the number of bonded atoms ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２ ) is, for example, 0.9 or less, preferably 0.6 or less. ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２ ) is equal to or less than the above upper limit, the conductivity of the conductive carbon layer 4 can be ensured, and a decrease in the detection sensitivity of the electrode 1 can be suppressed.

[0030] sp ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２ ) is a spectrum obtained by measuring one surface of the conductive carbon layer 4 in the thickness direction by X-ray photoelectron spectroscopy. ２ Bond peak intensity and sp ３ Calculations are based on peak binding intensities.

[0031] The density of the conductive carbon layer 4 is, for example, 1.8 g / cm ３ More preferably, 2.0 g / cm ３ More preferably, 2.1 g / cm ３ More preferably, 2.2 g / cm ３ If the density of the conductive carbon layer 4 is equal to or greater than the above-mentioned lower limit, sp ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２The density of the conductive carbon layer 4 is, for example, 4.0 g / cm ３ The density of the conductive carbon layer 4 is determined by X-ray reflectivity.

[0032] The surface resistance of one surface of the conductive carbon layer 4 in the thickness direction is, for example, 1.0×10 ４ Ω / □ or less, preferably 1.0×10 ３ The surface resistance of the conductive carbon layer 4 is Ω / □ or less. There is no lower limit for the surface resistance of the conductive carbon layer 4.

[0033] The conductive carbon layer 4 has a thickness of, for example, 0.1 nm or more, preferably 0.2 nm or more, and 100 nm or less, preferably 50 nm or less.

[0034] The thickness of the electrode 1 is the total thickness of the resin film 2, the metal base layer 3, and the conductive carbon layer 4, and is specifically, for example, 2 μm or more, preferably 20 μm or more, and for example, 1000 μm or less, preferably 500 μm or less.

[0035] (Method for manufacturing electrode 1) Next, a method for manufacturing electrode 1 will be described. The method for manufacturing electrode 1 includes first to fourth steps. In this manufacturing method, the first to fourth steps are performed in order.

[0036] (First Step) In the first step, the resin film 2 is prepared.

[0037] (Second Step) In the second step, the resin film 2 prepared in the first step is heated.

[0038] Heating the resin film 2 is a step for adjusting the thermal shrinkage of the electrode 1 to -0.2% or more and 0.2% or less. The heating conditions are not limited. The temperature is, for example, 70°C or more, preferably 100°C or more, more preferably 130°C or more, and for example, 200°C or less, preferably 180°C or less, more preferably 160°C or less. The heating time is, for example, 5 minutes or more, preferably 15 minutes or more, more preferably 30 minutes or more, and for example, 10 hours or more, preferably 5 hours or more, more preferably 2 hours or more. The heating is carried out under normal pressure (0.1 MPa) or reduced pressure (less than 0.1 MPa). The atmosphere is air or an inert gas (including argon).

[0039] (Third Step) In the third step, the metal base layer 3 is formed on one surface in the thickness direction of the resin film 2. The method for forming the metal base layer 3 is not limited. Examples of the method for forming the metal base layer 3 include a dry method, preferably a PVD method, and more preferably a sputtering method.

[0040] (Fourth Step) In the fourth step, the conductive carbon layer 4 is formed on one surface in the thickness direction of the metal underlayer 3. Examples of the method for forming the conductive carbon layer 4 include a dry method. Examples of the dry method include a PVD method (physical vapor deposition) and a CVD method (chemical vapor deposition), and preferably, the PVD method. Examples of the PVD method include a sputtering method, a vacuum deposition method, a laser deposition method, and an ion plating method (including an arc deposition method). Preferably, the sputtering method is used.

[0041] Examples of sputtering methods include unbalanced magnetron sputtering (UBM sputtering), high-power pulse sputtering, electron cyclotron resonance sputtering, RF sputtering, DC sputtering, DC pulse sputtering, and ion beam sputtering. ３ From the viewpoint of easily setting the ratio of the number of bonded atoms within the desired range, DC sputtering is more preferred, and DC magnetron sputtering is even more preferred.

[0042] The target used in the sputtering method may be, for example, sintered carbon. The sputtering gas may be, for example, an inert gas. The inert gas may include Ar. The pressure during sputtering is, for example, 1 Pa or less. The film formation temperature is, for example, 0° C. or less, e.g., 150° C. or less.

[0043] By carrying out the first to fourth steps, the above-described electrode 1 is obtained.

[0044] (Uses of Electrode 1) Electrode 1 can be used as various electrodes, and preferably as an electrode for electrochemical measurement that performs electrochemical measurement, specifically as a working electrode (working electrode) that performs cyclic voltammetry (CV) or a working electrode (working electrode) that performs anodic stripping voltammetry (ASV).

[0045] In this case, in consideration of the effects described below, the electrode 1 can be curved for use. Specifically, the electrode 1 can be used by being fixed to a curved wall surface or by being attached to a rod-shaped substrate.

[0046] (Effects of One Embodiment) This electrode 1 has a thermal shrinkage rate of 0, that is, not less than −0.2% and not more than 0.2%, so even when bent, damage to the conductive carbon layer 4 can be suppressed and the rate of increase in resistance before and after bending can be suppressed.

[0047] In addition, in the conductive carbon layer 4 of this electrode 1, sp ３ Number of bonded atoms and sp ２ sp relative to the sum of the number of bonded atoms ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２ ) is 0.10 or more, the potential window of the electrode 1 can be widened.

[0048] In this electrode 1, the conductive carbon layer 4 has a density of 1.8 g / cm ３ If the density is greater than or equal to sp ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２ ) is high, the potential window can be widened.

[0049] (Modifications) In the modification, the same components and steps as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, the modification can achieve the same effects as those in the first embodiment, unless otherwise specified. Furthermore, the first embodiment and its modification can be combined as appropriate.

[0050] Furthermore, it is also possible to prepare in advance in the first step a resin film 2 whose heat shrinkage rate has been adjusted to be low so that the heat shrinkage rate of the electrode 1 is −0.2% or more and 0.2% or less, without performing the second step. For example, a resin having a molecular structure with a low heat shrinkage rate may be used as a raw material, or the heat shrinkage rate of the resin film 2 itself may be reduced by heating or reducing the tension during transport at the stage of molding the resin film 2 from the raw material.

[0051] As shown in Fig. 1 , in one embodiment, the electrode 1 includes one resin film 2, one metal base layer 3, and one conductive carbon layer 4. On the other hand, as shown in Fig. 2 , the electrode 1 may include one resin film 2, two metal base layers 3, and two conductive carbon layers 4. That is, the electrode 1 may include two metal base layers 3 and two conductive carbon layers 4 for one resin film 2. In this case, the conductive carbon layer 4, the metal base layer 3, the resin film 2, the metal base layer 3, and the conductive carbon layer 4 are arranged in this order toward one side in the thickness direction.

[0052] As shown in FIG. 3, the electrode 1 may not include the metal underlayer 3, but may include a resin film 2 and a conductive carbon layer 4 in this order on one side in the thickness direction.

[0053] The present invention will be described in more detail below with reference to examples and comparative examples. It should be noted that the present invention is in no way limited to these examples and comparative examples. The specific numerical values ​​of the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values ​​(numerical values ​​defined as "equal to or less than") or lower limit values ​​(numerical values ​​defined as "equal to or more than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the above "Modes for Carrying Out the Invention." Furthermore, unless otherwise specified in the following description, "parts" and "%" are based on mass.

[0054] First, the methods for measuring the physical properties of each layer will be described.

[0055] (In the conductive carbon layer 4, sp ３ In a spectrum obtained by measuring one surface of the conductive carbon layer 4 in the thickness direction by X-ray photoelectron spectroscopy, ２ Bond peak intensity and sp ３ Based on the peak intensity of the bond, sp ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２ ) was calculated.

[0056] (Thickness and Density) The thickness and density of the conductive carbon layer 4 were each determined based on an X-ray reflectance method.

[0057] (Surface Resistance) In accordance with JIS K 7194, the surface resistance of the electrode 1 on the conductive carbon layer 4 side was measured by a four-terminal method.

[0058] <Production of Electrode 1> (Example 1) A resin film 2 made of polyethylene terephthalate and having a thickness of 50 µm was prepared (first step).

[0059] Subsequently, the resin film 2 was heated in a heating oven at 120° C. for 1 hour (second step).

[0060] Next, a metal underlayer 3 made of titanium was formed on one surface of the resin film 2 in the thickness direction by DC magnetron sputtering (third step). The DC magnetron sputtering conditions were as follows:

[0061] Target material: titanium Target power: 100 W Sputtering gas: argon Pressure in sputtering chamber: 0.2 Pa

[0062] The thickness of the metal underlayer 3 was 12 nm.

[0063] A conductive carbon layer 4 was formed on one surface of the metal underlayer in the thickness direction by DC pulse magnetron sputtering (fourth step) under the following conditions: target material: sintered carbon, argon gas pressure: 0.4 Pa, target power: 2.0 W / cm. ２ Temperature: 120℃ or less

[0064] The surface resistance of the conductive carbon layer 4 is 1.0×10 ２ The sp in the conductive carbon layer 4 ３ Ratio (sp ３ / sp ３ +sp ２ ) is 0.35, and the density is 2.1 g / cm ３ The thickness of the conductive carbon layer 4 was 40 nm.

[0065] The third and fourth steps were carried out by a roll-to-roll method.

[0066] This produced the electrode 1. The electrode 1 was produced by the roll-to-roll method described above, and therefore had an MD direction and a TD direction.

[0067] Example 2 An electrode 1 was produced in the same manner as in Example 1. However, the heating temperature in the second step was changed from 120°C to 150°C.

[0068] Example 3 An electrode 1 was produced in the same manner as in Example 2. However, the conditions for the fourth step were changed as follows: Argon gas pressure: 0.2 Pa Target power: 1.7 W / cm ２

[0069] In the electrode 1 of Example 3, the surface resistance of the conductive carbon layer 4 was 140 Ω / □. ３ Ratio (sp ３ / sp ３ +sp ２ ) is 0.45, and the density is 2.3 g / cm ３ The thickness of the conductive carbon layer 4 was 40 nm.

[0070] Example 4 An electrode 1 was produced in the same manner as in Example 2. However, the conditions for the fourth step were changed as follows: Argon gas pressure: 2 Pa Target power: 1.1 W / cm

[0071] In the electrode 1 of Example 4, the surface resistance of the conductive carbon layer 4 was 160 Ω / □. ３ Ratio (sp ３ / sp ３ +sp ２ ) is 0.30, and the density is 1.8 g / cm ３ The thickness of the conductive carbon layer 4 was 40 nm.

[0072] Comparative Example 1 An electrode 1 was produced in the same manner as in Example 1, except that the second step was not carried out.

[0073] Comparative Example 2 An electrode 1 was produced in the same manner as in Example 3, except that the second step was not carried out.

[0074] Comparative Example 3 An electrode 1 was produced in the same manner as in Example 4, except that the second step was not carried out.

[0075] The conditions or presence or absence of the second step, the density of the conductive carbon layer 4, and sp ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp ２ ) are listed in Table 1.

[0076] <Evaluation> Electrode 1 was subjected to the following evaluations, the results of which are shown in Table 1.

[0077] (Thermal shrinkage rate of resin film 2) The electrode 1 was cut into a square with a side length of 30 mm to prepare a sample. Subsequently, the sample was heated in a heating oven at 150°C for 1 hour. The dimensions of the electrode 1 before and after heating were measured using an image dimension measuring instrument (IM-6020, manufactured by Keyence Corporation), and the thermal shrinkage rate was calculated using the following formula.

[0078] Heat shrinkage rate [%] = (length in MD direction after heating - length in MD direction before heating) / length in MD direction before heating × 100

[0079] Generally, the thermal shrinkage in the MD direction is higher than that in the TD direction, so in the above, the thermal shrinkage in the MD direction is evaluated. However, if the electrode 1 is manufactured by a method other than the roll-to-roll method, the evaluation can be performed in the direction with the larger absolute value of the thermal shrinkage. The above-mentioned method includes a batch method.

[0080] (Rate of Resistance Increase of Electrode 1) Sample 5 was prepared by cutting electrode 1 into a strip with a longitudinal length of 70 mm and a transverse length of 20 mm. The longitudinal direction was along the MD direction. Sample 5 was bent so that both longitudinal ends 6 of sample 5 approached each other. At this time, a longitudinal center portion 7 of sample 5 was wrapped around a metal rod 8 having a diameter of 6.5 mm. In addition, both longitudinal ends 6 of sample 5 were fixed with clips 10 to which 150 g weights 9 were attached and held for 10 seconds. The surface resistance of electrode 1 at the center portion 7 before and after bending was measured, and the rate of resistance increase was calculated using the following formula.

[0081] Resistance increase rate [%]=(surface resistance of electrode 1 at center portion 7 after bending−surface resistance of electrode 1 at center portion 7 before bending) / surface resistance of electrode 1 at center portion 7 before bending×100

[0082] Note that a test in which the resin films 2 face each other when the sample 5 is wrapped around the clip 10, as shown in Fig. 4, is referred to as Test A. In Test A, the rod 8, the resin film 2, the metal base layer 3, and the conductive carbon layer 4 are arranged in this order from top to bottom. In Test A, a tensile force acts on the conductive carbon layer 4 in the center.

[0083] On the other hand, a test in which the conductive carbon layers 4 face each other when the sample 5 is wrapped around the clip 10, as shown in Fig. 5, is designated as Test B. In Test B, the rod 8, the conductive carbon layer 4, the metal base layer 3, and the resin film 2 are arranged in this order from top to bottom. In Test B, a compressive force acts on the conductive carbon layer 4 in the center.

[0084]

[0085] The above invention is provided as an exemplary embodiment of the present invention, but it is merely an example and should not be interpreted as being limiting. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the following claims.

[0086] The electrode is used as an electrode for electrochemical measurements.

[0087] 1 Electrode 2 Resin film 4 Conductive carbon layer

Claims

1. An electrode having a resin film and a conductive carbon layer in that order in the thickness direction, wherein the conductive carbon layer is sp ３ an electrode having a bond, wherein the electrode has a thermal shrinkage rate of -0.2% or more and 0.2% or less when heated at 150°C for 1 hour.

2. The conductive carbon layer is sp ２ Further having a bond, ３ Number of bonded atoms and sp ２ sp relative to the sum of the number of bonded atoms ３ 2. The electrode of claim 1, wherein the ratio of the number of bonded atoms is 0.10 or greater.

3. The conductive carbon layer has a density of 1.8 g / cm ３ 3. The electrode according to claim 1, having a density equal to or greater than 1000 .mu.m.