Surface potential distribution measuring device

Abstract

This invention provides a surface potential distribution measuring device capable of evaluating the surface potential distribution and in-plane distribution of charge capture state of a measured object. One embodiment of the surface potential distribution measuring device includes: a sensor substrate having a plurality of sensors; a vibration unit for vibrating the sensor substrate; an electrical characteristic measuring unit for measuring the potential of the measured object using each sensor; a heating unit for heating the measured object; a temperature measuring unit for measuring the temperature of the measured object; a surface shape measuring unit for measuring the displacement of the surface shape of the measured object caused by heating; a sample stage for placing the measured object; and a moving unit for moving the sample stage; the moving unit adjusts the distance between the surface of the measured object and the sensors to a predetermined range.

Description

[Technical Field]

[0001] This invention relates to a surface potential distribution measuring device. This application claims priority based on Japanese Patent Application No. 2024-082865, filed on May 21, 2024, the contents of which are incorporated herein by reference. [Previous Technology]

[0002] Filters using nonwoven fabrics made of polypropylene fibers, etc., are used in masks and air purifiers. To improve capture efficiency, the nonwoven fabric used in the filter is electretted. An electret system refers to a material that semi-permanently maintains electrical polarization and forms an electric field in its surroundings.

[0003] Electret formation is achieved through methods such as corona discharge or water flow charging. The state of the electret affects the trapping efficiency. Furthermore, the charge trapping state of the electret affects its stability. For example, during electret formation, if the charge can be trapped at a deeper energy level, a more stable electret can be obtained. In this specification, the energy level at which the charge is trapped is expressed as the charge trapping state.

[0004] As a technique for evaluating the charge state of an electret, Patent Document 1 discloses an electrostatic distribution measuring device comprising: a detection unit that moves continuously and relative to the surface of a charged object to be measured in a predetermined direction; a reference distance measuring unit that measures the distance between the surface of the object to be measured and the surface of the detection unit; a distance adjustment unit that adjusts the distance between the surface of the object to be measured and the surface of the detection unit in such a way that the distance measured by the reference distance measuring unit becomes a predetermined reference distance; and a vibration unit that causes the distance between the surface of the object to be measured and the surface of the detection unit to vibrate. The system includes: a predetermined periodic change; a measuring unit that measures at least one of the potential change, frequency, and phase angle detected by the detection unit; and a calculation unit that calculates the electrostatic charge on the surface of the object being measured based on the relative movement distance of the object being measured relative to the detection unit and the measurement result of the measuring unit; a plurality of sensors provided on the surface of the detection unit that detect the potential change caused by the change in distance between the object being measured and the surface of the object being measured; and a vibration unit that changes the width of the change in distance between the surface of the object being measured and the surface of the detection unit according to the electrostatic charge on the surface of the object being measured calculated by the calculation unit.

[0005] Furthermore, as a technique for evaluating the capture state of charge, Patent Document 2 discloses a thermally stimulated current measuring device, which includes: a data acquisition unit that uses measurement data obtained from the thermally stimulated current of the test sample to acquire correlation data displaying the relationship between activation energy and temperature; an extraction unit that extracts a flat portion of the plot when the correlation data is used to graph the relationship between activation energy and temperature; an evaluation unit that evaluates the characteristics of the sample based on the extraction results of the extraction unit; and a display unit that displays the evaluation results obtained by the evaluation unit on a screen. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent No. 6797378. [Patent Document 2] Japanese Unexamined Patent Publication No. 2015-28462. [Patent Document 3] Japanese Patent No. 5665151. [Patent Document 4] International Publication No. 2015 / 011942. [Summary of the Invention]

[0007] [Problem to be solved by the invention] Although the method of Patent Document 1 can evaluate the surface potential distribution of the object being measured, it cannot evaluate the in-plane distribution of the charge trap level. Although the method of Patent Document 2 applies heat to the object being measured and measures the emitted current to evaluate the averaged charge trapping state, it cannot evaluate the in-plane distribution of the charge trapping level of the object being measured.

[0008] The present invention was developed in view of the above-mentioned matters. The purpose of the present invention is to provide a surface potential distribution measuring device that can evaluate the surface potential distribution and in-plane distribution of charge capture state of the measuring object.

[0009] [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention proposes the following means. [1] The first embodiment of the present invention is a surface potential distribution measuring device, which includes: a sensor substrate having a plurality of sensors; a vibration unit for vibrating the sensor substrate; an electrical characteristic measuring unit for measuring the potential of the object to be measured using each of the aforementioned sensors; a heating unit for heating the object to be measured; a temperature measuring unit for measuring the temperature of the object to be measured; a surface shape measuring unit for measuring the displacement of the surface shape of the object to be measured caused by heating; a sample stage for arranging the object to be measured; and a moving unit for moving the sample stage; the moving unit adjusts the distance between the surface of the object to be measured and the aforementioned sensors to a predetermined range. [2] The second embodiment of the present invention is the surface potential distribution measuring device as described in the first embodiment, which may also include: a tension applying unit for applying tension to the object to be measured; the tension applying unit applies tension to the object to be measured in such a way that the amount of the aforementioned displacement falls below a threshold value. [3] The third embodiment of the present invention is a surface potential distribution measuring device as described in the second embodiment, wherein the aforementioned tension applying part applies tension to the aforementioned measuring object along a predetermined direction. [4] The fourth embodiment of the present invention is a surface potential distribution measuring device as described in the second embodiment, wherein the aforementioned tension applying part applies tension to the aforementioned measuring object along a predetermined direction and applies tension to the aforementioned measuring object along a second direction orthogonal to the aforementioned predetermined direction. [5] The fifth embodiment of the present invention is a surface potential distribution measuring device as described in any one of the first to fourth embodiments, wherein it may further include: a vibration measuring part that measures the amplitude of the aforementioned sensor substrate. [6] The sixth embodiment of the present invention is a surface potential distribution measuring device as described in any one of the first to fifth embodiments, wherein each of the aforementioned sensors is arranged in a straight line when viewed from above. [7] The seventh state of the present invention is a surface potential distribution measuring device as described in any one of the states one to six, wherein the aforementioned sample stage and the aforementioned moving part are isolated from each other; the aforementioned heating part and the aforementioned moving part are connected via a support part; and the aforementioned support part has a point contact structure.

[0010] [Effect of the Invention] According to the above-described embodiments of the present invention, a surface potential distribution measuring device can be provided, which is capable of evaluating the surface potential distribution and charge capture state of the measuring object.

Implementation Method

[0012] The surface potential distribution measuring device of this embodiment includes: a sensor substrate having a plurality of sensors; a vibration unit for vibrating the sensor substrate; an electrical characteristic measuring unit for measuring the potential of a measuring object using each of the sensors; a heating unit for heating the measuring object; a temperature measuring unit for measuring the temperature of the measuring object; a surface shape measuring unit for measuring the displacement of the surface shape of the measuring object caused by heating; and a tension applying unit for applying tension to the measuring object; the tension applying unit applies tension to the measuring object in such a way that the amount of displacement falls below a threshold value. Furthermore, the sensors are provided on a first surface of the sensor substrate of this embodiment; a plurality of conductive portions are exposed on a second surface, which is the opposite surface to the first surface, and the plurality of conductive portions extend from each sensor in the thickness direction of the sensor substrate; each conductive portion is insulated from the others.

[0013] The surface potential distribution measuring device 100 of an embodiment of the present invention will be described below with reference to the drawings. FIG1 is a schematic diagram of the surface potential distribution measuring device 100. The surface potential distribution measuring device 100 includes a sensor substrate 10, a holding part 20, a shaft 30, a vibration part 40, a vibration control part 45, an electrical characteristic measuring part 50, a temperature measuring part 51, a surface shape measuring part 52, a tension applying part 55, a sample stage 60, a support part 63, a moving part 65, a heating part 70, a vibration measuring part 110, a distance measuring part 120, and a control part 130.

[0014] The charge (surface potential) Q of the portion (measuring area) of the sensor substrate 10 facing the measuring object O opposite the sensor is calculated, for example, according to the following mathematical formula. In the mathematical formula, ΔV represents the difference between the maximum and minimum potentials detected by the sensor in the sensor substrate 10 (potential difference), ε represents the dielectric constant between the sensor in the sensor substrate 10 and the portion of the measuring object O facing the sensor, S represents the area of ​​the sensor, D represents the distance between the surface of the sensor and the surface of the measuring object O along the thickness direction of the sensor substrate 10, and R represents the amplitude of the vibration of the sensor substrate 10.

[0015] [Mathematical Formula 1]

[0016] While moving the object to be measured O in a predetermined direction, the surface potential of each part of the object to be measured O facing each sensor in the sensor substrate 10 is calculated using the above mathematical formula, thereby finally calculating the surface potential distribution of the surface of the object to be measured O. The method for calculating the surface potential can be, for example, the method described in Patent Documents 3 and 4.

[0017] The following describes each part. In the following description, the X direction is the direction parallel to the first surface 11a in the sensor substrate 10. The Y direction is the direction parallel to the first surface 11a in the sensor substrate 10 and intersects the X direction. For example, the Y direction is approximately orthogonal to the X direction. The Z direction is the thickness direction of the substrate 11 in the sensor substrate 10 and intersects the X and Y directions. For example, the Z direction is approximately orthogonal to the X and Y directions. The downward direction in the Z direction refers to the direction along the Z direction from the sensor substrate 10 toward the sample stage 60. The upward direction in the Z direction refers to the direction along the Z direction opposite to the direction from the sensor substrate 10 toward the sample stage 60. However, the terms "up" and "down" used in this specification are expressions for ease of explanation and do not define the direction of gravity.

[0018] [Sensor Substrate 10] FIG2 is a top view of the sensor side surface (first surface) of the sensor substrate 10. FIG3 is a cross-sectional view along line AA of the sensor substrate 10 shown in FIG2. The sensor substrate 10 includes: a substrate 11; a plurality of sensors 12 disposed on a first surface 11a belonging to a surface of the substrate 11; and a plurality of conductive portions 14 exposed on a second surface 11b belonging to a surface opposite to the first surface 11a and extending from each sensor 12 in the thickness direction of the substrate 11. In this embodiment, the thickness direction of the substrate 11 is the same as the Z direction.

[0019] The substrate 11 is not particularly limited as long as it can insulate the conductive parts 14 from each other. The material of the substrate 11 can be a resin commonly used in printed circuit boards. For example, paper or glass cloth can be used as the substrate, or epoxy resin, phenolic resin, polyimide resin, etc., can be used as the resin. A plurality of through holes 18 for the passage of the fixing part 22 can also be provided on the substrate 11. It is preferable that the number of through holes 18 is two or more. As long as the number of through holes 18 is two or more, even if the sensor substrate 10 is vibrated during measurement, deformation of the substrate 11 is unlikely, thus enabling precise measurement of potential changes.

[0020] The sensor 12 is disposed on a first surface 11a belonging to a surface of the substrate 11. The sensor 12 is a sensor that detects changes in potential caused by changes in the distance between itself and the surface of the object being measured O. The sensor 12 is used to measure, for example, the difference between the maximum and minimum potentials (potential difference). In addition, the sensor 12 can also be used to measure the periodic changes in potential (frequency of potential) caused by periodic changes in the distance between the charged part in the object being measured O and the sensor 12. Then, the sensor 12 can also be used to detect the phase shift between the period of the relative distance change between the charged part in the object being measured O and the sensor 12 and the period of the potential detected by the sensor 12 (phase shift of potential).

[0021] The sensor 12 is not particularly limited as long as it can detect changes in potential. The sensor 12 is a thin film of metal such as gold or copper. Although the shape of the sensor 12 is not particularly limited, it is square, for example, when viewed from above. The sensors 12 are arranged at predetermined intervals. The length lx of the sensor 12 in the X direction is not particularly limited. The length lx of the sensor 12 in the X direction is, for example, 0.1 mm to 10 mm. Similarly, the length ly of the sensor 12 in the Y direction is not particularly limited. The length ly of the sensor 12 in the Y direction is, for example, 0.1 mm to 10 mm. The length lx of the sensor 12 in the X direction, the length ly of the sensor 12 in the Y direction, and the interval of the sensors 12 can be appropriately set according to the calculated resolution. By appropriately setting the distance between the sensor 12 and the object being measured O (1 / 4 to 2 of the spatial resolution) and the vibration amplitude (1 / 8 to 1 of the spatial resolution), the spatial resolution can be arbitrarily determined.

[0022] A plurality of sensors 12 are arranged linearly on the substrate 11 in plan view. Here, the sensors 12 are arranged along a virtual line L1 parallel to the X direction. In this embodiment, the length ls of the arrangement of sensors 12 is preferably longer than the length of the object to be measured along the direction orthogonal to the direction in which the object to be measured moves (here, the Y direction) when measuring the potential. With this arrangement, the object to be measured can be moved in only one direction (Y direction) instead of moving in the X direction. Furthermore, if the length ls of the arrangement of sensors 12 is shorter than the length of the object to be measured along the direction orthogonal to the direction of movement of the object to be measured, the object to be measured can also be moved in the X direction, thereby enabling the measurement of the surface potential distribution on the total area of ​​the side of the object to be measured opposite to the sensors 12.

[0023] The sensor substrate 10 includes a plurality of conductive portions 14, which are exposed on a second surface 11b, which is opposite to the first surface 11a, and extend from each sensor 12 in the thickness direction of the substrate 11. The conductive portions 14 are insulated from each other by the substrate 11, which is an insulator. In this embodiment, the conductive portions 14 penetrate the substrate 11. In this embodiment, the sensor 12 is electrically connected to the conductive portions 14. The conductive portions 14 are not particularly limited as long as they are made of a material that can transmit the potential obtained by the sensor 12 to the electrical characteristic measuring unit 50. The conductive portions 14 are, for example, metals such as copper (Cu). The conductive portions 14 are electrically connected to the wiring 16.

[0024] The sensor substrate 10 preferably includes a connecting portion 15, which is electrically and detachably connected to the electrical characteristic measuring unit 50 and each conductive portion 14. The connecting portion 15 is electrically connected to the wiring 16. The connecting portion 15 is, for example, a connector terminal. By having a detachably connected connecting portion 15, the appropriate sensor substrate 10 can be changed according to the purpose.

[0025] [Holding Part 20] The holding part 20 holds the sensor substrate 10. The holding part 20 can also detachably hold the sensor substrate 10. The holding part 20 includes a holding plate 21 and a fixing part 22. The holding plate 21 is a plate used to fix the sensor substrate 10. The sensor substrate 10 is arranged with its second surface 11b facing the surface 21a of the holding plate 21, and the sensor substrate 10 is fixed to the holding plate 21 by the fixing part 22. In FIG1, the holding plate 21 is separated from the sensor substrate 10, but the holding plate 21 and the sensor substrate 10 can also be in contact. A spacer may also be present between the holding plate 21 and the sensor substrate 10. The fixing part 22 is not particularly limited as long as it can transmit vibration to the sensor substrate 10. For example, the fixing part 22 is a bolt and a nut. The fixing part 22 is fixed by passing through the through hole 18 of the substrate 11, thereby detachably fixing it.

[0026] [Shaft 30] Shaft 30 connects the holding plate 21 of the holding part 20 and the vibrating part 40. Shaft 30 is not particularly limited as long as it can hold the sensor substrate 10 and the holding part 20. Shaft 30 may also be directly connected to the sensor substrate 10. When shaft 30 is directly connected to the sensor substrate 10, the holding part 20 may not be present.

[0027] [Vibration Unit 40] The vibration unit 40 vibrates the holding portion 20 and the sensor substrate 10 in a predetermined direction (e.g., the thickness direction of the sensor substrate 10). When the holding portion 20 is absent, the vibration unit 40 vibrates the sensor substrate 10 in the predetermined direction. In this embodiment, the vibration unit 40 vibrates the shaft 30, thereby causing the holding plate 21 and the sensor substrate 10 to vibrate in the thickness direction of the sensor substrate 10. As for the vibration unit 40, it is not particularly limited as long as it can cause the sensor substrate 10 and the holding portion 20 to vibrate at a predetermined period. The vibration unit 40 is electrically connected to the vibration control unit 45, for example. The vibration unit 40 is controlled by the vibration control unit 45.

[0028] [Vibration Control Unit 45] The vibration control unit 45 controls the vibration unit 40 by vibrating the sensor substrate 10 under predetermined conditions. The period (number of vibrations) of the vibration unit 40 causing the sensor substrate 10 and the holding unit 20 to vibrate is not particularly limited. The period of the vibration unit 40 is, for example, from 10Hz to 5kHz. A preferred period is in the range of 50Hz to 1kHz. The amplitude of the vibration unit 40 causing the sensor substrate 10 and the holding unit 20 to vibrate is not particularly limited. The amplitude of the vibration unit 40 is, for example, from 0.01mm to 5mm. A preferred amplitude of the vibration unit 40 is from 0.05mm to 0.5mm. The vibration control unit 45 vibrates the sensor substrate 10 and the holding unit 20, for example, according to a signal transmitted from the control unit 130.

[0029] The amplitude of the vibration of the sensor substrate 10 is explained here. In the above mathematical formula one, when the charge Q, dielectric constant ε, sensor area S and distance D of the sensor substrate 10 are constant, the detected potential difference ΔV can be calculated by the following mathematical formula two. In mathematical formula two, a and b are predetermined constants.

[0030] [Mathematical Formula Two]

[0031] As shown in the above mathematical formula 2, the potential difference ΔV detected by the sensor 12 is expressed as a function of only the amplitude R of the sensor substrate 10. That is, as the amplitude R increases, the potential difference ΔV also increases. In the surface potential distribution measuring device 100, by adjusting (increasing) the amplitude R, the surface potential of the measuring object O can be detected with high precision.

[0032] [Electrical Characteristic Measurement Unit 50] The electrical characteristic measurement unit 50 uses each sensor 12 to measure potential. The electrical characteristic measurement unit 50 is, for example, an oscilloscope or a lock-in amplifier (not shown). Preferably, the electrical characteristic measurement unit 50 removes noise from the signal detected by the sensors 12 and can simultaneously measure small signals in multiple channels. The electrical characteristic measurement unit 50 is electrically connected to the control unit 130 and transmits the potential information obtained by each sensor 12 to the control unit 130.

[0033] [Temperature Measurement Unit 51] The temperature measurement unit 51 measures the temperature of the object to be measured, O. Known methods such as thermocouples and thermography can be used as the temperature measurement unit 51. A thermograph is preferred as the temperature measurement unit 51. Using a thermograph, the temperature distribution of the object to be measured, O, is measured, and information such as activation energy is converted from the temperature of the object to be measured, thereby enabling a more precise evaluation of the charge capture state of the object to be measured, O. The measured temperature information of the object to be measured, O, is transmitted to the control unit 130.

[0034] [Surface Shape Measurement Unit 52] The surface shape measurement unit 52 measures the displacement of the surface shape of the object being measured O. The surface shape measurement unit 52 is not particularly limited as long as it can measure the displacement of the surface shape of the object being measured O. The surface shape measurement unit 52 is, for example, a laser displacement meter. When the surface shape changes unevenly, the surface shape measurement unit 52 preferably measures the displacement distribution of the surface shape (two-dimensional distribution). By measuring the displacement distribution of the surface shape, tension can be applied more precisely to suppress the displacement of the object being measured O, and the moving part 65 can be controlled to keep the distance between the sensor 12 and the object being measured O constant (within a predetermined range), which is preferable. Alternatively, a distance measurement unit 120 can be used instead of the surface shape measurement unit 52. The information on the displacement of the surface shape measured by the surface shape measurement unit 52 is transmitted to the control unit 130.

[0035] [Tension Application Unit 55] The tension application unit 55 applies tension to the object to be measured, O. The tension application unit 55, controlled by the control unit 130, applies tension to the object to be measured in such a way that the displacement of the surface shape of the object to be measured due to heating is below a threshold value. Heating the object to be measured by the heating unit 70 sometimes causes deformation of the object to be measured. If the deformation of the object to be measured is large, the sensor 12 of the sensor substrate 10 may come into contact with the object to be measured, making it impossible to measure the potential of the object to be measured. Furthermore, the deformation of the object to be measured due to heating causes changes in the distance between the sensor 12 and the object to be measured, resulting in reduced measurement accuracy. The tension application unit 55 applies tension to the object to be measured in such a way that the displacement of the surface shape of the object to be measured is below a threshold value, thereby setting the change in the distance between the object to be measured and the sensor 12 within a predetermined range. This allows for the measurement of the surface potential of the object to be measured while it is being heated by the heating unit 70. The critical limit can be set appropriately based on the calculated resolution. For example, the critical limit is 10 μm.

[0036] The method of applying tension is not particularly limited, and known means can be used. Preferably, the tension applying part 55 applies tension to the measuring object O along a predetermined direction and applies tension to the measuring object O along a second direction (e.g., the Y direction) orthogonal to the predetermined direction (e.g., the X direction). In this way, deformation of the measuring object O caused by heating can be further suppressed.

[0037] [Sample Stage 60] The sample stage 60 is a stage capable of arranging the object to be measured O and the heating unit 70. In this embodiment, the heating unit 70 is arranged on the sample stage 60. The object to be measured O is arranged on the heating unit 70. The sample stage 60 is not particularly limited as long as it can accommodate the object to be measured O, etc.

[0038] [Moving Unit 65] The moving unit 65 moves the sample stage 60 in a direction parallel to the first surface 11a. Furthermore, the moving unit 65 adjusts the distance D between the surface of the object to be measured O and the surface of the sensor 12 to a predetermined range. When the plurality of sensors 12 are arranged linearly on the virtual line L1 in a top view, the moving unit 65 preferably moves the sample stage 60 in a direction perpendicular to the virtual line L1. By moving the sample stage 60 in this way, the surface potential distribution of the object to be measured O can be measured efficiently. The moving unit 65 can be moved in the X, Y, and Z directions by, for example, a motor. The moving unit 65 is controlled by the control unit 130.

[0039] The sample stage 60 and the moving part 65 are arranged in isolation. In this embodiment, the sample stage 60 and the moving part 65 are arranged in isolation in the Z direction. By arranging the sample stage 60 and the moving part 65 in this way, the influence of heating on the moving part 65 can be suppressed, and the accuracy of the position control of the sample stage 60 by the moving part 65 can be easily maintained. In order to reduce the influence of heat, heat-insulating materials can also be used. In this case, since the heat-insulating material may also expand due to heat, the moving part 65 controls the Z direction according to the displacement measured by the surface shape measuring unit 52.

[0040] The sample stage 60 and the moving part 65 are connected via a support part 63. The support part 63 has a point contact structure 62. The support part 63 is not particularly limited as long as it connects the sample stage 60 and the moving part 65 and has a point contact structure 62. In this embodiment, the support part 63 has: a shaft 61, which is connected to the sample stage 60; and a point contact structure 62, which is connected to the moving part 65. The point contact structure 62 only needs to be fixed to the shaft 61 at a position away from the heat source (heating part) 70. Since the position of fixing the point contact structure 62 and the shaft 61 is further away from the heat source (heating part) 70, the temperature decreases more through natural cooling, thus further suppressing heat transfer. The fixing method is not particularly limited. Examples of fixing methods include, for example, a magnet or a screw. For example, a magnet can also be placed near the lower end of the point contact structure 62 for fixing. The point contact structure 62 is, for example, a ball bushing. The point contact structure 62 makes point contact with the shaft 61. Therefore, heat transfer from the sample stage 60 to the moving part 65 can be suppressed. This makes it easier to maintain the accuracy of the position control of the moving part 65.

[0041] [Heating Unit 70] The heating unit 70 heats the object to be measured, O. In this embodiment, the heating unit 70 is disposed on the sample stage 60; however, the heating unit 70 may also be disposed within the sample stage 60. In this embodiment, the object to be measured, O, is disposed on the heating unit 70. The heating unit 70 is not particularly limited as long as it can heat the object to be measured, O. The heating unit 70 is, for example, a ceramic heater or an infrared heater. Preferably, the heating unit 70 heats the object to be measured, O, at a predetermined heating rate. The heating rate is, for example, 0.5 K / min to 5 K / min.

[0042] [Vibration Measurement Unit 110] The vibration measurement unit 110 measures the amplitude of the sensor substrate 10. The vibration measurement unit 110 is electrically connected to the control unit 130. The vibration measurement unit 110 is not particularly limited as long as it can measure the amplitude of the sensor substrate 10. For example, a laser displacement sensor can be used as the vibration measurement unit 110. The vibration measurement unit 110 transmits the measured vibration information of the sensor substrate 10 to the control unit 130.

[0043] [Distance Measurement Unit 120] The distance measurement unit 120 measures the distance D between the surface of the sensor 12 and the surface of the object being measured O. The positional relationship between the distance measurement unit 120 and the surface of the sensor 12 is pre-measured, thereby enabling the measurement of the distance D between the surface of the sensor 12 and the surface of the object being measured O. The distance measurement unit 120 is not particularly limited as long as it can measure the distance D between the surface of the sensor 12 and the surface of the object being measured O. For example, a laser displacement sensor can be used as the distance measurement unit 120. The distance measurement unit 120 transmits the measured distance D between the surface of the sensor 12 and the surface of the object being measured O to the control unit 130.

[0044] [Control Unit 130] The control unit 130 controls the vibration control unit 45 and the moving unit 65, thereby moving the measurement object O while vibrating the sensor substrate 10 and the holding unit 20. The control unit 130 uses the moving unit 65 to adjust the position of the measurement object O in the Z direction based on the distance D between the surface of the measurement object O and the surface of the sensor 12 obtained by the distance measuring unit 120. Specifically, the position of the measurement object O is adjusted so that the distance D falls within the allowable range (DS±α) of the reference distance DS.

[0045] The control unit 130 controls the heating unit 70 to heat the measuring object O at a predetermined heating rate. Based on the displacement of the measuring object O measured by the surface shape measuring unit 52, the control unit 130 controls the tension applying unit 55 to apply tension to the measuring object O such that the displacement of the measuring object O falls below a threshold value. Alternatively, based on the displacement of the measuring object O measured by the surface shape measuring unit 52, the control unit 130 controls the moving unit 65 to adjust the position in the Z direction such that the displacement of the measuring object O falls below a threshold value. Furthermore, the control unit 130 uses the electrical characteristic measuring unit 50 to measure the time change (potential information) of the potential of each sensor 12. In addition, the control unit 130 uses the temperature measuring unit 51 to measure the temperature distribution of the measuring object O.

[0046] The control unit 130 uses the vibration measurement unit 110 to obtain vibration information of the sensor substrate 10. Based on the temperature distribution, potential information, vibration information of the sensor substrate 10, and information on the amount of movement of the measured object O, the control unit 130 outputs the surface potential distribution and temperature distribution of the measured object O. The obtained surface potential distribution and temperature distribution of the measured object O are output to a memory unit (not shown) or a display unit (not shown). The surface potential distribution is depicted using varying shades of color to make the magnitude of the surface potential easily visible.

[0047] The control unit 130 may also be composed of, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and HDD (Hard Disk Drive) / SSD (Solid State Disk), etc., not shown. In this case, the memory unit not shown is an HDD or an SSD. The display unit is, for example, an LCD. The operation of the control unit 130 may also be achieved by executing, for example, a predetermined program in the CPU. The control unit 130 may also be constructed using dedicated hardware.

[0048] [Measurement Object O] The measurement object O is not particularly limited as long as there is a charge distribution on its surface. Examples of the shape of the measurement object O include rectangular, cylindrical, and film-shaped.

[0049] As explained above, the surface potential distribution measuring device 100 of this embodiment will be described in detail. Since the surface potential distribution measuring device 100 of this embodiment includes a plurality of sensors 12, it can quickly measure the surface potential distribution within the surface of the object being measured in a single measurement. Furthermore, since the tension application unit 55 applies tension to the object being measured O such that the displacement of the object being measured falls below a threshold value, the surface potential distribution can be measured while the object being measured O is being heated. This allows for the evaluation of the in-plane distribution of charge trapping states.

[0050] In the surface potential distribution measuring device 100, the sensor substrate 10 can also be detachably held in the holding portion 20. Furthermore, the sensor substrate 10 may also include a connecting portion 15, which detachably connects the electrical characteristic measuring portion 50 and each conductive portion 14. This allows the sensor substrate 10 to be easily replaced according to the purpose. Therefore, the resolution can be changed according to the application.

[0051] [Method for measuring the in-plane distribution of charge capture level] Next, a method for measuring the in-plane distribution of charge capture level of the object O using the surface potential distribution measuring device 100 will be described. Figure 4 is a flowchart of the method for measuring the in-plane distribution of charge capture level.

[0052] The distance D between the surface of the object to be measured O and the surface of the sensor 12 is set to be within the allowable range of a reference distance DS that can be measured (step S1). Specifically, as long as the distance D is within a predetermined value (allowable value) α (DS±α) relative to the reference distance DS, the change in potential of the portion of the object to be measured O facing the sensor 12 can be detected with high accuracy. The allowable value relative to the reference distance DS is, for example, less than 10% of the reference distance DS.

[0053] The distance D between the surface of the object to be measured and the surface of the sensor 12 is measured using the distance measuring unit 120. In this embodiment, the distance D between the surface of the object to be measured and the surface of the sensor 12 is adjusted by the moving unit 65 and the object to be measured is moved to a predetermined position (steps S2, S3). If the distance D is not within the predetermined range (DS±α), the moving unit 65 is used to adjust the distance D between the surface of the object to be measured and the surface of the sensor 12 so that the distance D between the surface of the object to be measured and the surface of the sensor 12 falls within the predetermined range.

[0054] Next, the vibration unit 40 is driven (started) (step S4). The amplitude R is measured by the vibration measuring unit 110, and the obtained amplitude R is transmitted to the control unit 130 (step S5).

[0055] The potential change of the portion of the object to be measured facing the sensor 12 is measured for a predetermined time. Information on the potential change of each sensor 12 is obtained in the electrical characteristic measurement unit 50. The obtained information on the potential change of each sensor 12 is transmitted to the control unit 130 (step S6). Then, the object to be measured is moved by a predetermined amount in the Y direction by the moving unit 65, and the distance moved by the object to be measured (movement distance) is transmitted to the control unit 130 (step S7). The movement distance of the object to be measured each time can be freely determined according to the size of the sensor 12 and the required resolution of the surface potential distribution. The movement distance is preferably the same as the length of the sensor 12 along the same direction as the movement direction of the object to be measured (about 0.1 mm to 10 mm). With this movement distance, the surface potential distribution of the object to be measured can be measured more accurately and quickly. If the change in potential is not measured on the total area of ​​the surface of the object being measured O facing the sensor 12 (step S8: no), the object being measured O is moved again by a predetermined amount in the X or Y direction (step S7).

[0056] If the potential change of the total area of ​​the surface of the object being measured O facing the sensor 12 has been measured (step S8: Yes), then the control unit 130 calculates the surface potential distribution of the object being measured O based on the potential change information transmitted from the electrical characteristic measurement unit 50, the movement distance of the object being measured O each time, the number of times the object being measured O moves, the amplitude R, and the reference distance DS (step S9). Then, the calculated surface potential distribution of the object being measured O is stored in a memory unit (not shown) or displayed on a display unit (not shown).

[0057] Specifically, a database is pre-calibrated and constructed, comprising a large amount of data related to the change in potential, the reference distance DS, the amplitude R, and the surface potential quantity corresponding to the change in potential, the reference distance DS, and the amplitude R. The surface potential quantity is calculated based on the change in potential, the reference distance DS, and the amplitude R obtained from each sensor 12. This surface potential quantity is the surface potential quantity of the portion of the measurement object O facing the sensor 12 when a change in potential is detected.

[0058] Therefore, as long as the relative position of each sensor 12 with respect to the object being measured is measured in advance, the surface potential distribution of the object being measured can be measured with high precision and quickly based on information related to the change in potential obtained from each sensor 12 (e.g., the amount of change in potential, frequency and phase shift), the moving distance of the object being measured at each time, the number of times the object being measured moves, the amplitude R and the reference distance DS.

[0059] After calculating the surface potential distribution, the temperature or temperature distribution of the object to be measured is measured using the temperature measuring unit 51 (step S10). At this time, if the object to be measured is not within the measurement range of the temperature measuring unit 51, the sensor substrate 10 can be removed from the object to be measured and measured. The temperature or temperature distribution of the object to be measured is recorded in a memory unit (not shown) or displayed on a display unit (not shown). The object to be measured is heated by the heating unit 70 (step S11). At this time, in the measurement of the surface potential distribution of the object to be measured, the temperature is increased and heated at a heating rate that does not change significantly. In addition, in the measurement of the potential distribution, the temperature is increased and heated at a set heating rate. If displacement control processing is performed after heating (step S12) and the measured temperature of the object to be measured does not reach the set value (step S13: no), the surface potential distribution is calculated using the same process. If the temperature of the measured object O has reached the set value (step S13: yes), the measurement ends.

[0060] [Displacement Control Process S12] Next, the displacement control process S12 performed in the measurement of the in-plane distribution of the charge capture level will be explained. Figure 5 is a flowchart of the displacement control method.

[0061] After the object to be measured, O, is heated by the heating unit 70 (step S11), the displacement of the surface shape of the object to be measured, O, is measured by the surface shape measuring unit 52 (step S21). The displacement is measured at predetermined intervals. The measurement interval is, for example, 5 seconds or less. If the displacement exceeds a threshold value (step S22: no), the tension applied to the object to be measured, O, is adjusted using the tension applying unit 55 (step S23). For example, if the displacement of the object to be measured, O, caused by heating is large, the tension applied to the object to be measured is increased, and the displacement of the surface shape of the object to be measured, O, is measured again by the surface shape measuring unit 52 (step S21). The direction of the tension is not particularly limited as long as it can suppress the displacement of the object to be measured, for example, the tension can be applied in either the X direction or the Y direction, or the tension can be applied in both the X direction and the Y direction, or the tension can be applied in the Z direction. If tension is applied in both the X and Y directions, the tension is adjusted so that the tension is applied to the area with the larger displacement. If the displacement falls below the threshold value (step S22: Yes), the tension adjustment is stopped (and the adjusted tension is applied to the measuring object O), thereby ending the displacement control.

[0062] As explained above, the method for measuring the in-plane distribution of charge capture level and the method for controlling displacement of the present embodiment are described in detail. Since the method for measuring the in-plane distribution of charge capture level of the present embodiment measures the charge capture level using multiple sensors while the object being measured is being heated, the in-plane distribution of charge capture level of the object being measured O can be measured. Furthermore, since the method for controlling displacement of the object being measured O caused by heating can set the displacement within a certain range, the surface potential distribution can be measured with high accuracy even if the object being measured O deforms due to heating.

[0063] In this embodiment, the moving part 65 performs the measurement by moving the sample stage 60 in a direction parallel to the first surface 11a. However, the vibration part 40 can also be moved in a direction parallel to the first surface 11a by the vibration part moving part (not shown) to perform the measurement.

[0064] In this embodiment, the vibration of the vibration unit 40 is started (step S4) and the vibration of the vibration unit 40 is measured (step S5) after the distance D between the surface of the measurement object O and the surface of the sensor 12 is set (step S1). However, the distance D between the surface of the measurement object O and the surface of the sensor 12 can also be set (step S1) after the vibration of the vibration unit 40 is started (step S4) and the vibration of the vibration unit 40 is measured (step S5).

[0065] In this embodiment, after adjusting the distance between the measurement object O and the sensor 12 (step S3) and measuring the potential change (step S6), the measurement object O is moved by a predetermined amount (step S7). However, the adjustment of the distance between the measurement object O and the sensor 12 (step S3) and the measurement of the potential change (step S6) can also be performed after moving the measurement object O by a predetermined amount (step S7). When the measurement object O is flat, the distance adjustment (step S3) can also be omitted.

[0066] Furthermore, since the vibration measurement unit 110 is used to directly measure the amplitude of the sensor substrate 10, the surface potential distribution of the object being measured O can be calculated with higher accuracy. In addition, since the distance measurement unit 120 is used to adjust the distance D between the surface of the object being measured O and the surface of the sensor 12, the surface potential distribution of the object being measured O can be calculated with higher accuracy.

[0067] Furthermore, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. In addition, the constituent elements in the above-described embodiments can be appropriately replaced with well-known constituent elements without departing from the spirit of the present invention.

[0068] [Example] Next, embodiments of the present invention will be described. However, the conditions in the embodiments are examples of conditions adopted to confirm the feasibility and effectiveness of the present invention, and the present invention is not limited to this single example of conditions. Various conditions can be adopted as long as the spirit of the present invention is not departed from and the purpose of the present invention is achieved.

[0069] Electret fabrication (P03050): Electretizing the nonwoven fabric by corona discharge (discharge condition +20kV).

[0070] The electret was evaluated using the surface potential distribution measuring device 100 shown in FIG. 1. The temperature was increased at a rate of 5 K / 3 min, and the surface potential distribution was measured every three minutes under the conditions of a measuring range of 90 mm × 90 mm and a spatial resolution of 1 mm. The temperature distribution of each electret was then measured using a thermogram. Furthermore, during the measurement of the surface potential distribution, a laser displacement meter was used to measure the displacement of the electret, and tension was applied to the electret in mutually orthogonal directions such that the displacement of the electret fell below 10 μm.

[0071] In addition, as a reference experiment, the same measurement was performed using the surface potential distribution measuring device 100 shown in FIG1, both without applying tension and with the two sides of the electret fixed in place of applying tension.

[0072] Figure 6 shows the temperature distribution of the electret measured by thermography at a heater temperature of 50 degrees Celsius, and Figure 7 shows the surface potential distribution measured just before the temperature distribution is measured. Furthermore, Figure 8 shows the temperature distribution of the electret measured by thermography at a heater temperature of 100 degrees Celsius, and Figure 9 shows the surface potential distribution measured just before the temperature distribution is measured. In Figures 6 and 8, the darker areas indicate lower temperatures, and the brighter areas indicate higher temperatures. The lower bars in Figures 7 and 9 represent the surface potential V. The darker portions of the surface potential distribution in Figures 7 and 9 indicate areas with higher positive (+) surface potentials. When comparing the surface potential distribution in Figure 7 at a heater temperature of 50 degrees Celsius with the surface potential distribution in Figure 9 at a heater temperature of 100 degrees Celsius, the darker areas in Figure 9, where the temperature is higher, are lighter. That is, the surface potential decreases due to the removal of charge caused by heat. Therefore, as shown in Figures 6 to 9, the surface potential distribution at each temperature can be evaluated. This confirms the ability to evaluate the surface potential distribution of a heated measurement object and the in-plane distribution of charge capture levels based on changes in the surface potential distribution. On the other hand, in the absence of applied tension and when the electret is fixed on both sides instead of under tension, as shown in Figure 10, the electret system deforms and comes into contact with the sensor, resulting in measurement failure. [Industry Applicability]

[0073] Since the surface potential distribution measuring device of this application is able to evaluate the surface potential distribution and charge capture state of the measured object, it has high industrial applicability. [Simplified Explanation of the Diagram]

[0011] [Fig. 1] is a schematic diagram of the surface potential distribution measuring device according to an embodiment of the present invention. [Fig. 2] is a top view of the sensor side surface of the sensor substrate. [Fig. 3] is a cross-sectional view along line AA of the sensor substrate shown in Fig. 2. [Fig. 4] is a flowchart of a method for measuring the in-plane distribution of charge capture level. [Fig. 5] is a flowchart of a displacement control method. [Fig. 6] shows the temperature distribution of the electret when the heater temperature is 50 degrees Celsius. [Fig. 7] shows the surface potential distribution of the electret when the heater temperature is 50 degrees Celsius. [Fig. 8] shows the temperature distribution of the electret when the heater temperature is 100 degrees Celsius. [Fig. 9] shows the surface potential distribution of the electret when the heater temperature is 100 degrees Celsius. [Fig. 10] is a photograph of an electret deformed by heating.

Claims

1. A surface potential distribution measuring device, comprising: a sensor substrate having a plurality of sensors; a vibration unit for vibrating the sensor substrate; an electrical characteristic measuring unit for measuring the potential of a measurement object using each of the aforementioned sensors; a heating unit for heating the measurement object; a temperature measuring unit for measuring the temperature of the measurement object; a surface shape measuring unit for measuring the displacement of the surface shape of the measurement object caused by heating; a sample stage for arranging the measurement object; and a moving unit for moving the sample stage; wherein the moving unit adjusts the distance between the surface of the measurement object and the aforementioned sensors to a predetermined range.

2. The surface potential distribution measuring device as described in claim 1, further comprising: a tension applying unit that applies tension to the aforementioned measuring object; wherein the tension applying unit applies tension to the aforementioned measuring object such that the amount of the aforementioned displacement falls below a threshold value.

3. The surface potential distribution measuring device as described in claim 2, wherein the aforementioned tension applying unit applies tension to the aforementioned measuring object along a predetermined direction.

4. The surface potential distribution measuring device as described in claim 2, wherein the aforementioned tension applying unit applies tension to the aforementioned measuring object along a predetermined direction and applies tension to the aforementioned measuring object along a second direction orthogonal to the aforementioned predetermined direction.

5. The surface potential distribution measuring device as described in claim 1 or 2, further comprising: a vibration measuring unit for measuring the amplitude of the aforementioned sensor substrate.

6. The surface potential distribution measuring device as described in claim 1 or 2, wherein each of the aforementioned sensors is arranged in a straight line when viewed from above.

7. The surface potential distribution measuring device as described in claim 1 or 2, wherein the aforementioned sample stage and the aforementioned moving part are disposed separately; the aforementioned heating part and the aforementioned moving part are connected via a support part; the aforementioned support part has a point contact structure.

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