Measurement method

Abstract

Provided is a measurement method that is performed by a measurement device, wherein the measurement device performs: a first step (S2) for deriving surface resistivities of a composite material including a material with a high resistance value and a material with a low resistance value at a respective plurality of surface positions; and a second step (S6) for calculating a representative value of the surface resistivities of the composite material using a plurality of surface resistivities derived until the convergence of a surface resistivity-related value.

Description

Measurement method

[0001] The present disclosure relates to a measurement method.

[0002] Electrostatic charge can be prevented by mixing a material with a high resistance value with a material with a low resistance value (see Patent Document 1). Therefore, there is a need for a technique to evaluate the antistatic properties of a composite material that is a mixture of these two types of materials.

[0003] The antistatic properties of a material can be evaluated by the surface resistance value of the material per unit area (see Non-Patent Documents 1 and 2). Hereinafter, the surface resistance value will be referred to as the surface resistivity.

[0004] The surface resistivity of a material can be measured by applying a current or voltage to the surface of the material, contacting a pair of electrodes with the surface of the material, measuring the resistance of the surface of the material from the voltage or current generated between the two electrodes, and multiplying the measured resistance by the value obtained by dividing the electrode width by the distance between the electrodes.

[0005] Then, by using a correspondence table in which the relationship between the surface resistivity and the antistatic property is previously correlated, the antistatic property corresponding to the measured surface resistivity can be evaluated. For example, when the surface resistivity is 10 to 10 ４ If it is not charged but dielectric, 10 ４ ~10 １０ If it is, it will not be charged at all, 10 １０ ~10 １４ If it is almost charged, it will decay. １４ It can be evaluated that if ~, it will become charged.

[0006] Patent No. 4082149

[0007] “Principles of Resistivity and Sheet Resistance Measurement,” [online], [Retrieved June 3, 2024], <URL: https: / / www.napson.co.jp / technique / > “C2139:2008,” [online], [Retrieved June 3, 2024], <URL: https: / / kikakurui.com / c2 / C2139-2008-01.html>

[0008] If the resistance value of the material surface is uniform and constant across the material surface, the measured surface resistivity will be constant regardless of how the electrode pairs are arranged, and the evaluation result of the antistatic property will be the same.

[0009] However, in the case of composite materials, the resistance value of the material surface is not necessarily uniform. If the resistance value of the material surface is uniform across the material surface, the distance through which the current flows and the type of material through which the current flows will change depending on the position of the electrode pair and the distance between the two electrodes, and the measured surface resistivity will also change. Therefore, even if the surface resistivity measurement results at one position indicate that the material is "almost free from charging," this may not be possible at another position.

[0010] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a technique capable of evaluating the antistatic properties of a composite material containing a material with a high resistance value and a material with a low resistance value.

[0011] A measurement method according to one aspect of the present disclosure is a measurement method performed using a measurement device, which includes a first step of deriving each surface resistivity at a plurality of surface positions for a composite material containing a material with a high resistance value and a material with a low resistance value, and a second step of calculating a representative value of the surface resistivity of the composite material using the plurality of surface resistivities derived until convergence is reached.

[0012] According to the present disclosure, it is possible to provide a technique capable of evaluating the antistatic properties of a composite material containing a material with a high resistance value and a material with a low resistance value.

[0013] FIG. 1 is a diagram showing an example of the configuration of a measurement device. FIG. 2 is a diagram showing an example of an electrode arrangement pattern. FIG. 3 is a diagram showing a method for measuring the surface resistivity of a composite material. FIG. 4 is a diagram showing an example of a measurement. FIG. 5 is a graph showing the relative standard deviation for each measurement count. FIG. 6 is a diagram showing examples of a composite material with no material bias and a composite material with material bias. FIG. 7 is a diagram showing an example of the distribution of surface resistivity when measured at a short inter-electrode distance. FIG. 8 is a diagram showing an example of the distribution of surface resistivity when measured at a long inter-electrode distance. FIG. 9 is a diagram showing an example of the distribution of surface resistivity when measured with different inter-electrode distances. FIG. 10 is a diagram showing an example of the distribution of surface resistivity when measured with different electrode widths. FIG. 11 is a diagram showing an example of an electrode arrangement method. FIG. 12 is a diagram showing an example of an electrode arrangement method. FIG. 13 is a diagram showing an example of an electrode arrangement method. FIG. 14 is a diagram showing an example of an electrode arrangement method and an electrode shape. FIG. 15 is a diagram showing an example of an electrode arrangement method and an electrode shape. FIG. 16 is a diagram showing an example of the application of an electrode arrangement pattern to the first embodiment. Fig. 17 is a diagram showing an example of application of an electrode arrangement pattern to the second embodiment. Fig. 18 is a diagram showing an example of application of an electrode arrangement pattern to the second embodiment.

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same parts are designated by the same reference numerals and the description thereof will be omitted.

[0015] [First embodiment] In the first embodiment, for a composite material in which a material with a high resistance value is mixed with a material with a low resistance value, the surface resistivity is measured at each of a plurality of surface positions, and a representative value of the surface resistivity is calculated by performing statistical processing on the measured surface resistivities.

[0016] For example, the average value, median value, mode value, standard deviation, relative standard deviation, x-th largest value, y-th smallest value, etc. of the surface resistivity are used for the statistical processing. x and y are natural numbers. Statistical processing other than these various types may also be used. These various types of statistical processing may also be used in any combination.

[0017] FIG. 1 is a diagram showing an example of the configuration of a measurement device 1.

[0018] The measuring device 1 includes an electrode pair 11 consisting of a pair of electrodes 11a and 11b, an application unit 12 that applies a voltage or current to the composite material 100, a calculation unit 13 that determines the surface resistance value of the composite material 100 to measure (derive) the surface resistivity and evaluate the antistatic property of the composite material 100 from the measured surface resistivity, a display unit 14 that displays the measurement results of the surface resistivity and the evaluation results of the antistatic property, and a memory unit 15 that stores various data handled by the measuring device 1.

[0019] The electrode pair 11 may be a probe-type electrode pair 11 as illustrated in Fig. 1, or may be formed on the surface of the composite material 100 using conductive paint as illustrated in Fig. 2(a). Furthermore, multiple points may be measured using the electrodes 11 of the electrode arrangement pattern P1 shown in Fig. 2(a). In this case, it is desirable to set the electrodes 11 so that the areas of the electrode arrangement pattern P1 do not overlap at each measurement point.

[0020] Alternatively, a four-probe or four-prong measurement device may be used, which includes both the electrode pair 11 and the application unit 12. In a four-probe measurement device, as shown in Fig. 2(b), a voltage or current is applied to the outer electrode pair 12a, 12b of four electrodes arranged in a row, and the surface resistivity is measured by the inner electrode pair 11a, 11b. In this case, too, when measuring multiple points, it is desirable to set the four electrode arrangement patterns P2 so that they do not overlap at each measurement point.

[0021] It is sufficient that the surface resistivity of the composite material 100 can be measured by the calculation unit 13 using the electrode pair 11, and it is optional whether the application unit 12 applies a voltage or a current.

[0022] FIG. 3 is a diagram showing a method for measuring the surface resistivity of the composite material 100.

[0023] Step S1: The measurer forms a pair of electrodes 11a, 11b having a certain electrode width W on the surface of the composite material 100, spaced apart by a certain inter-electrode distance L. Although the probe-type electrode pair 11 illustrated in FIG. 1 may be pressed against the surface of the composite material 100, in this example, the electrode pair 11 was formed on the surface of the composite material 100 using conductive paint.

[0024] Step S2: The application unit 12 applies a constant voltage or a constant current to the composite material 100. The calculation unit 13 measures the resistance value R of the surface of the composite material 100 from the current or voltage generated between the two electrodes 11 a and 11 b, and measures (derives) the surface resistivity of the composite material 100 by integrating the measured resistance value R with the value obtained by dividing the electrode width W by the inter-electrode distance L.

[0025] Step S3: The measurer and the measuring device 1 change the position of the measurement point and perform steps S1 and S2 n times, as shown in Figure 4. n is a natural number. The surface resistivities of measurement points 1 to 14 (n = 14) shown in Figure 4 are shown in Table 1.

[0026]

[0027] Step S4: The calculation unit 13 calculates the average value, median value, standard deviation, relative standard deviation, etc. of the surface resistivity, and plots the relative standard deviation for each measurement point (=number of measurements) on a graph, as shown in FIG.

[0028] Step S5: The calculation unit 13 determines whether the average value, median value, standard deviation, relative standard deviation, etc. of the surface resistivity calculated during the n-th measurement have sufficiently converged. If they have not sufficiently converged, the process returns to step S1, and the (n+1)-th measurement is performed.

[0029] For example, the calculation unit 13 calculates the difference between the average value, standard deviation, or relative standard deviation of the surface resistivity calculated during the nth measurement and the same value calculated during the (n-1)th measurement, and determines whether the difference is sufficiently small.

[0030] For example, the calculation unit 13 determines whether sufficient convergence has occurred by determining whether the value obtained by dividing the nth standard deviation by the (n-1)th standard deviation is within the range of "1±0.05."

[0031] The convergence condition can be set arbitrarily.

[0032] Step S6: The calculation unit 13 calculates a representative value of the surface resistivity using all the surface resistivities measured until the average value of the surface resistivity (i.e., the surface resistivity of the composite material 100) sufficiently converges, and sets this representative value as the surface resistivity of the composite material 100.

[0033] For example, the calculation unit 13 sets the average value of the surface resistivity as the representative value of the surface resistivity of the composite material 100. Instead of the average value of the surface resistivity, the average value + standard deviation, the average value - standard deviation, or the like may be set as the representative value of the surface resistivity.

[0034] This concludes the method for measuring the surface resistivity of the composite material 100.

[0035] Thereafter, the calculation unit 13 evaluates (judges) the antistatic property corresponding to the representative value of the surface resistivity calculated in step S6 by using a correspondence table in which the relationship between the surface resistivity and the antistatic property is previously associated. Then, the display unit 14 displays the representative value of the surface resistivity and the evaluation result (judgement result) of the antistatic property on the screen.

[0036] As described above, according to this embodiment, the surface resistivity of the composite material 100 is measured (derived) at each of multiple surface positions, and a representative value of the surface resistivity of the composite material 100 is calculated using the multiple surface resistivities measured (derived) until convergence occurs, thereby making it possible to appropriately evaluate the antistatic properties of the composite material.

[0037] So far, we have described the method for measuring the surface resistivity and the method for evaluating the antistatic property of the composite material 100. In the following embodiment, we will describe a method for evaluating the bias of two types of materials contained in the composite material 100.

[0038] As shown in Fig. 6(a), composite material 100 includes composite material 100α, which is balanced between high-resistivity materials and low-resistivity materials, and composite material 100β, which is balanced between these two types of materials, as shown in Fig. 6(b). In this case, composite material 100α, which is balanced, should be evaluated as having high antistatic properties.

[0039] However, in the first embodiment, the surface resistivity is measured with the electrode width W and the inter-electrode distance L kept constant, so there is a possibility that the measurement results for composite materials 100α and 100β will be similar to each other. Therefore, in the second and third embodiments, methods for evaluating the bias of the two types of materials will be described.

[0040] Second Embodiment In a second embodiment, a method for evaluating the bias of the material by changing the inter-electrode distance L will be described.

[0041] First, the concept of the evaluation method will be explained.

[0042] When the inter-electrode distance L is short, the surface resistivity varies greatly depending on whether or not there are locally low resistance values, resulting in a large variation in the distribution of surface resistivity. For example, the distribution will have two peaks, one at low surface resistivity and one at high surface resistivity. The standard deviation will also increase. Figure 7 shows an example of the distribution of surface resistivity when measured with a short inter-electrode distance L for a uniform composite material 100α.

[0043] When the inter-electrode distance L is long, the surface resistivity distribution tends to include both locally low and locally high resistance values, resulting in a smaller variation in the surface resistivity distribution. For example, the surface resistivity distribution will have a single peak. The standard deviation will also be smaller. Figure 8 shows an example of the surface resistivity distribution when measured with a long inter-electrode distance L for a uniform composite material 100α.

[0044] That is, in the case of the unbiased composite material 100α, as the inter-electrode distance L increases, the variation in the distribution of surface resistivity gradually decreases. That is, the number of peaks appearing in the surface resistivity decreases, for example, from two to one, and the standard deviation, etc., decreases from large to small. A similar trend may also be observed in the biased composite material 100β. In such cases, the bias in the material is evaluated based on, for example, the change in the number of peaks in the surface resistivity, the difference in the average value, median, standard deviation, and relative standard deviation of the surface resistivity, the difference in the degree of change in surface resistivity due to the change in the inter-electrode distance L, etc.

[0045] Therefore, in the second embodiment, the bias between high-resistivity materials and low-resistivity materials is evaluated by utilizing the fact that the variation in the distribution of surface resistivity changes depending on the length of the inter-electrode distance L, that is, by utilizing the fact that the representative value of the surface resistivity changes. This evaluation is performed, for example, after step S6 shown in FIG.

[0046] Note that evaluating the bias means, for example, determining which of two or more composite materials 100 has a higher degree of bias, determining the order of highest degree of bias among three or more composite materials 100, or determining whether one composite material has bias by utilizing a threshold value, etc. In addition to determining whether or not there is bias, the quantified degree of bias may be roughly calculated.

[0047] The method will be specifically described below.

[0048] 9(a-1), the surface resistivity was measured at three points on the composite material 100α, with the inter-electrode distance L being d, and a representative value of the surface resistivity was calculated. As a result, two peaks appeared in the surface resistivity, and the relative standard deviation was 150%.

[0049] 9(a-2), the surface resistivity was measured at three points on the composite material 100α with the inter-electrode distance L set to 2d (=d×2), and a representative value of the surface resistivity was calculated. As a result, one peak appeared in the surface resistivity, and the relative standard deviation was 70%.

[0050] 9(a-3), the surface resistivity was measured at three points on the composite material 100α with the inter-electrode distance L set to 3d (=d × 3), and a representative value of the surface resistivity was calculated. As a result, one peak appeared in the surface resistivity, and the relative standard deviation was 70%.

[0051] Similarly, for composite material 100β, the surface resistivity was measured at three locations on composite material 100β with inter-electrode distances L of d, 2d, and 3d, and a representative value of the surface resistivity was calculated. As a result, when the inter-electrode distances L were d and 2d, two peaks appeared in the surface resistivity, with a relative standard deviation of 150%, as shown in Figures 9(b-1) and 9(b-2). When the inter-electrode distance L was 3d, one peak appeared in the surface resistivity, with a relative standard deviation of 70%, as shown in Figure 9(b-3).

[0052] (Evaluation Method 1) In the case of composite material 100α, a relatively uniform distribution of surface resistivity was obtained for two of the three different inter-electrode distances L due to the small number of peaks or the small relative standard deviation. On the other hand, in the case of composite material 100β, a relatively uniform distribution of surface resistivity was obtained for only one of the three different inter-electrode distances L, which is fewer than that of composite material 100α.

[0053] Therefore, composite material 100α can be evaluated as a composite material having a relatively more uniform surface resistivity than composite material 100β.

[0054] (Evaluation Method 2) For composite material 100α, the boundary between when a relatively uniform distribution of surface resistivity is obtained and when it is not is determined by the magnitude of the number of peaks or the magnitude of the relative standard deviation, when the inter-electrode distance L is between d and 2d. On the other hand, for composite material 100β, the boundary is determined between 2d and 3d, and the inter-electrode distance at which this boundary occurs is larger than that for composite material 100α.

[0055] Therefore, composite material 100α can be evaluated as a composite material having a relatively more uniform surface resistivity than composite material 100β.

[0056] (Other Evaluation Methods) In order to determine whether the desired uniformity has been obtained, a threshold value for the number of peaks or a threshold value for the relative standard deviation may be determined in advance, and whether a uniform distribution of surface resistivity has been obtained may be determined based on the threshold value.

[0057] If the average value of the surface resistivity does not change significantly when the inter-electrode distance L is changed, the standard deviation may be used instead of the relative standard deviation. If the average value of the surface resistivity changes significantly when the inter-electrode distance L is changed, the average value may be used instead of the relative standard deviation.

[0058] Third Embodiment In a third embodiment, a method for evaluating the material bias by changing the electrode width W will be described.

[0059] The concept of the evaluation method in this case is similar to the method of evaluating the bias of the material by changing the inter-electrode distance L. That is, in the case of the unbiased composite material 100α, the variation in the distribution of the surface resistivity gradually decreases as the electrode width W increases. A similar tendency may also be observed in the biased composite material 100β, in which case the bias of the material is evaluated based on, for example, the change in the number of peaks of the surface resistivity, the difference in the average value, median, standard deviation, and relative standard deviation of the surface resistivity, the difference in the degree of change in the surface resistivity due to the change in the electrode width W, etc.

[0060] Therefore, in the third embodiment, the difference between materials with high resistance and materials with low resistance is evaluated by utilizing the fact that the variation in the distribution of surface resistivity changes depending on the length of the electrode width W, that is, by utilizing the fact that the representative value of the surface resistivity changes.

[0061] 10(a-1), the surface resistivity was measured at three points on the composite material 100α with the electrode width W set to D, and a representative value of the surface resistivity was calculated. As a result, one peak appeared in the surface resistivity.

[0062] 10(a-2), the electrode width W was set to 2D (=D×2), and the surface resistivity was measured at three points on the composite material 100α, and a representative value of the surface resistivity was calculated. As a result, one peak appeared in the surface resistivity.

[0063] 10(a-3), the electrode width W was set to 3D (=D × 3), and the surface resistivity was measured at three points on the composite material 100α, and a representative value of the surface resistivity was calculated. As a result, one peak appeared in the surface resistivity.

[0064] Similarly, for composite material 100β, the surface resistivity was measured at three locations on composite material 100β with electrode widths W of D, 2D, and 3D, and a representative value of the surface resistivity was calculated. As a result, when the electrode widths W were D and 2D, two peaks appeared in the surface resistivity, as shown in Figure 10(b-1) and Figure 10(b-2). When the electrode width W was 3D, one peak appeared in the surface resistivity, as shown in Figure 10(b-3).

[0065] (Evaluation Method 1) For two types of composite materials 100α and 100β, the average value and standard deviation of the surface resistivity are calculated for each of three different electrode widths W. The more uniform the material, the smaller the difference in the average value and standard deviation when the electrode width W is changed. Therefore, a material with a smaller rate of change in the average value and standard deviation is considered to be a composite material with higher antistatic properties.

[0066] Since the rate of change between Figure 10(a-2) and Figure 10(a-3) is smaller than the rate of change between Figure 10(b-2) and Figure 10(b-3), composite material 100α can be evaluated as a composite material with a relatively more uniform surface resistivity than composite material 100β.

[0067] (Evaluation Method 2) Even when the electrode width W is changed, the variation in the distribution of surface resistivity changes depending on the length of the electrode width W, just as when the inter-electrode distance L is changed. Therefore, similar to the second embodiment, the bias in the material is evaluated based on the magnitude of the number of peaks or the magnitude of the relative standard deviation.

[0068] (Other Evaluation Methods) The material bias may be evaluated by changing both the inter-electrode distance L and the electrode width W. This allows for more accurate evaluation of the material bias. The material bias may also be evaluated by any combination of the evaluation methods described in the second and third embodiments.

[0069] [Electrode Arrangement Method and Electrode Shape] Hereinafter, the electrode arrangement method and electrode shape will be described.

[0070] (Electrode Arrangement Method 1) The two electrodes 11a and 11b constituting the electrode pair 11 are arranged so that their sides (the sides closest to each other) face each other, and the lengths of the facing sides are made the same.

[0071] 11(a), the sides (the sides closest to each other) of the two electrodes 11a and 11b do not face each other, making it difficult to define the inter-electrode distance L and the electrode width W. On the other hand, in the case of Fig. 11(b), the electrode width W can be defined as the length of the electrode side, and the inter-electrode distance L can be defined as the distance between the opposing sides of the electrodes, making it possible to accurately measure the surface resistivity.

[0072] (Electrode Arrangement Method 2) In order to efficiently measure a plurality of surface resistivities, two or more pairs of electrodes are used.

[0073] In this case, multiple electrode pairs may be fabricated (formed) on the surface of the composite material using conductive paint or the like, or multiple pre-fabricated electrode probes may be pressed against the composite material, or both may be used. Pre-fabricating electrodes on the surface of the composite material allows for stable evaluation because they are less susceptible to the influence of contact resistance between the electrodes and the composite material.

[0074] When using two or more pairs of electrodes, it is preferable to arrange each pair of electrodes so that measurements do not interfere with each other. Figures 12(a) and 12(b) both use two pairs of electrodes 11, 11', but in the case of Figure 12(a), when measuring current with one pair of electrodes 11, the electrode 11a' of the other pair of electrodes 11' interferes with the flow of the current. The arrangement of Figure 12(b) allows accurate measurement of surface resistivity. When using four pairs of electrodes 11, 11', an arrangement such as that shown in Figure 12(c) is possible.

[0075] (Electrode Arrangement Method 3) A central electrode is prepared, and multiple electrodes are arranged around it.

[0076] For example, one electrode 11b is placed at the center, and four electrodes 11a are placed at four locations, above, below, left and right, as shown in Fig. 13. This allows many surface resistivities to be measured even in a small area.

[0077] (Electrode Arrangement Method 4 and Electrode Shape) The shape of the electrode is not limited to a rectangle, but may be any other polygon such as a hexagon, a circle, an ellipse, or any other shape. When the electrode shape is a polygon, the length of one side of the electrode is defined as the electrode width W.

[0078] For example, as shown in Fig. 14(a), a hexagonal electrode 11b is placed at the center, and six square electrodes 11a are placed around it. As shown in Fig. 14(b), a hexagonal electrode 11b is placed at the center, and six hexagonal electrodes 11a are placed around it. In either arrangement method, the electrodes 11a and 11b are placed so that their sides (the sides closest to each other) face each other.

[0079] (Others) The above electrode arrangement methods 1 to 4 and the above electrode shapes may be combined in any desired manner.

[0080] For example, as shown in Figure 15, multiple electrode arrangement patterns shown in Figure 14(b) are arranged in a row. At this time, a portion of the electrode 11a is shared between adjacent electrode arrangement patterns. The surface resistivity is measured between the electrode 11b at the center of the regular hexagonal area R1 and the electrodes 11a at each vertex, and then measured sequentially in the regular hexagonal areas R2 and R3. This allows multiple surface resistivities to be measured more efficiently.

[0081] [Application Example of Electrode Arrangement Method and Electrode Shape] (Application Example to First Embodiment) In the case of the first embodiment, one type of electrode arrangement pattern is used to measure the surface resistivity at each of a plurality of positions on the composite material 100 .

[0082] For example, as shown in Fig. 16, the electrode arrangement pattern of Fig. 14(b) is sequentially applied to each surface position of the composite material 100 for measurement. This makes it possible to measure the surface resistivity while reducing the position dependency of the electrode arrangement pattern.

[0083] (Example of Application to Second Embodiment) In the case of the second embodiment, a plurality of electrode arrangement patterns with different inter-electrode distances L are prepared in advance, and the surface resistivity is measured.

[0084] For example, as shown in Fig. 17, three electrode arrangement patterns are prepared in advance, each with a different inter-electrode distance L from the electrode arrangement pattern shown in Fig. 14(b), and the surface resistivity is measured. At this time, the surface resistivity may be measured sequentially using each of the three electrode arrangement patterns, or may be measured simultaneously using the three electrode arrangement patterns. This allows for more efficient measurement of multiple surface resistivities. Alternatively, an electrode arrangement pattern such as that shown in Fig. 18 may also be used.

[0085] Finally, the arrow between the two electrodes 11a and 11b shown in the drawing represents a current flowing from the electrode 11a to the electrode 11b, but the current may also flow in the opposite direction.

[0086] REFERENCE SIGNS LIST 1 Measuring device 11 Electrode pair 11a, 11b Electrode 12 Application unit 13 Calculation unit 14 Display unit 15 Storage unit 100 Composite material 100α Composite material with no material bias 100β Composite material with material bias

Claims

1. A measurement method using a measurement device, comprising: a first step of deriving each surface resistivity at a plurality of surface positions for a composite material containing a material with a high resistance value and a material with a low resistance value; and a second step of calculating a representative value of the surface resistivity of the composite material using the plurality of surface resistivities derived until convergence is reached.

2. The measurement method according to claim 1, further comprising a third step of evaluating the bias between materials with high resistance values ​​and materials with low resistance values, utilizing the fact that in the case of composite materials, the representative value of surface resistivity changes when the inter-electrode distance or electrode width of the electrode pair used for measuring surface resistivity is changed.

3. The measurement method of claim 2, wherein in the third step, the bias between the high resistance material and the low resistance material is evaluated based on one or more of the change in the number of peaks of the surface resistivity, the change in the average value of the surface resistivity, the change in the median value of the surface resistivity, the change in the standard deviation of the surface resistivity, and the change in the relative standard deviation of the surface resistivity caused by changing the inter-electrode distance or the electrode width of the electrode pair.

4. The measurement method according to claim 1, wherein in the first step, a central electrode and a plurality of electrodes positioned around the central electrode are used to derive the surface resistivity at each of the plurality of surface positions.

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