Patent Application
20210038154
The present invention relates to an attachment pad that is used in a state of being attached to attachment target substances utilizing an electrical attachment force, and more specifically relates to an attachment pad that can be attached to and held on attachment target substances including not only conductors but also substances such as animals, plants, and processed products thereof, which are soft and have a certain level of moisture and oil, particularly human skin.
In recent years, so-called wearable electric products that can be worn on the body and the like have been newly introduced, and motivation for collecting biological data using, for example, various sensors has been increasing. Utilizing a pad having an adhesive means such as an adhesive or a pressure-sensitive adhesive is assumed in such usage applications, but the use of an adhesive, a pressure-sensitive adhesive, or the like takes time and effort for attachment and detachment, and it is disadvantageous in that adhesives cannot be used repeatedly.
Meanwhile, an electrostatic chuck has been conventionally used as means for attaching an attachment target substance by an electrical attachment force. Electrostatic chucks are mainly used for industrial purposes for attaching and holding a semiconductor substrate or a glass substrate when they are treated. An electrostatic chuck generally has a structure in which electrodes are vertically sandwiched by dielectrics, and can attach an attachment target substance with a surface of one of the dielectrics as an attachment surface by application of a voltage to the electrodes according to the attachment principle. In some cases, an electrostatic chuck has heating means, or has a structure in which it is integrally bonded to a metal base having a conduit through which a coolant flows. Furthermore, in addition to such an electrostatic chuck for treating a semiconductor substrate and the like, the inventors of the present application have proposed an electrostatic attachment structure to which the structure and principle of electric attachment of an electrostatic chuck is applied.
For example, PTL 1 proposes an electrostatic attachment structure which is highly convenient in changing its configuration. In the electrostatic attachment structure, multiple sheet members in which two dielectrics are sandwiched between electrodes are laminated. When a voltage is applied between the electrodes, the members can be attached and fixed to each other and exhibited objects and posters such as paper and resin sheets can be attached on the other attachment surface. When application of voltage is cut off after use, sheet members can be easily separated from each other, and attachment target substances can be easily separated. For example, PTL 2 proposes a power generation device which shows good selectivity of installation locations and attachment/detachment properties. The power generation device has attachment and detachment means constituted by surfaces of an electrostatic chuck in which attachment electrodes are sandwiched between two insulating layers and a film-shaped solar cell is attached thereto. The electrostatic attachment structure of PTL 1 and the power generation device of PTL 2 have favorable attachment/detachment properties because the attachment principle of the electrostatic chuck is used. The electrostatic attachment structure and the power generation device are thin and devised considering handleability, However, they are only intended to be attached and fixed to artificial materials that are relatively large and have an even surface such as the above-mentioned industrial products or daily necessities, and their application to attachment target substances such as human skin that is soft and has a certain level of moisture and oil has not yet been studied. In fact, a polyimide film or a polyethylene terephthalate (PET) film is preferably used as a specific dielectric layer (insulator) in the electrostatic attachment structure described in PTL 1 and the power generation device described in PTL 2. However, according to preliminary examinations of the inventors of the present invention, although the detailed cause is not clear, it is presumed that a surface of an electrostatic chuck is reversely charged and an attachment force is thereby decreased in the case of attaching the electrostatic attachment structure (power generation device) to a living body (for example, human skin and the like). Because the occurrence of reverse charging and the decrease in attachment force are more remarkable than in the case of using a semiconductor substrate and the like, it is presumed that moisture and oil in human skin cause the reverse charging and decrease more strongly.
In addition, another reason is that the conventional electrostatic chuck requires a sufficient contact area between a target object and the chuck to obtain a sufficient attachment force, and when both the attachment target side and the chuck side are made flat for increasing the contact area. In this respect, since a surface of a living body (for example, human skin and the like) is generally soft and curved to some extent, it was found that only a part of an attachment surface came into contact with the conventional electrostatic chuck, and therefore a sufficient attachment force could not be obtained.
Furthermore, problems are not limited only to the reverse charging and the contact area. So-called Coulomb force, which is the attachment principle of the conventional electrostatic chuck, is fundamentally weak (several grams per square centimeter), and therefore an effective force that can be used for attachment to a living body cannot be obtained. Accordingly, another stronger force generated at an interface between the chuck surface and the living body, such as the Johnsen-Rahbek effect, is required. As an electrostatic chuck using the Johnsen-Rahbek effect, many chucks formed of a ceramic have been conventionally used, but there are few reports particularly on chucks formed of resins in which followability for securing a contact area with an attachment target object is expected.
Meanwhile, for example, an electrode pad for electrocardiographic measurement as described in PTL 3, or a medical instrument such as a patch for measuring an amount of sweat as described in PTL 4 has been conventionally known as a means used by being attached to human skin, but they are both means in which a pressure sensitive adhesive is used on an attachment surface, and are not means utilizing an electrical attachment force.
Under such circumstances of a conventional technique, the inventors of the present application have made diligent studies on means that can be attached to substances that are soft and have a certain level of moisture and oil, particularly human skin, by utilizing an electrical attachment force. As a result, the inventors of the present application have found for the first time that an attachment pad can be attached to and held particularly on human skin by an electrical attachment force without using such a conventional pressure sensitive adhesive by configuring a simple attachment pad used together with a power supply device that can receive application of a voltage to an electrode layer, in which a resin film having a specific tensile elastic modulus and a specific volume resistance value is adopted for at least an attachment surface to an attachment target substance, and a laminate sheet in which the resin film and another resin film are sandwiched together between the electrode layer and laminated is obtained, and thus completed the present invention.
Accordingly, an object of the present invention is to provide an attachment pad that can be attached to and held particularly on human skin with favorable followability by utilizing an electrical attachment force.
That is, the gist of the present invention is as follows.
using an electrode layer that comprises a bipolar electrode having a first electrode and a second electrode as an electrode layer, applying a voltage to the electrode layer to attach an attachment pad to an attachment target substance while making a potential of the attachment target substance approximately 0 V by applying a positive or negative symmetrical voltage to each of the first electrode and the second electrode.
using an electrode layer that includes a unipolar electrode as an electrode layer, applying a voltage to the electrode layer to attach an attachment pad to an attachment target substance while making a potential of the attachment target substance approximately 0 V by earth-connecting (grounding) a ground of a voltage generation source in the power supply device with the attachment target substance.
According to the present invention, it is possible to provide an attachment pad that can be attached to and held on attachment target substances that are soft and have a certain level of moisture and oil, particularly human skin, with favorable followability by utilizing an electrical attachment force. As described above, since the attachment pad can be attached and fixed by an electrical attachment force, it can be used repeatedly without using a chemical adhesive means such as an adhesive or a pressure sensitive adhesive. Furthermore, the attachment pad is simple and cost effective because a release film used therefor becomes unnecessary. In addition, by utilizing the technique of the present invention, it is possible to attach wearable electric products (for example, various sensors that read biometric information, medical devices, ornaments) and the like to surfaces of a living body including human skin and an attachment target substance equivalent to the living body. The technique is expected to expand into fields and industries such as medical care, beauty, sports, clothing, and wearable devices.
Hereinafter, the present invention will be described in detail.
As shown in
<Resin Film>
Regarding the first and second resin films used in the attachment pad of the present invention, the second resin film is on an attachment surface for an attachment target substance in the present invention, and a volume resistivity of at least the second resin film serving as the attachment surface is required to be 1×1010 to 1013 Ω·cm. As shown in Examples to be described later, when a volume resistivity of the second resin film on the attachment surface exceeds 1×1013 Ω·cm, an attachment force for an attachment target substance (human skin and the like) decreases, and, for example, the attachment pad may fall off even due to its own weight. In contrast, when a volume resistivity is less than 1×1010 Ω·cm, it is presumed that an attachment force acting on an attachment target substance increases, but this is not preferable because there may be cases in which a small discharge continuously occurs between the attachment pad and the attachment target substance, and itching and pain may be caused especially when the pad is used on a human body, and there may be damage to the skin. A volume resistivity is preferably 1×1010 to 1012 Ω·cm in view of both realization of attachment force and safety.
In the present invention, a volume resistivity can be appropriately set regarding the first resin film used on the side opposite to the attachment surface of an attachment target substance, but since there is a probability that an electric current that should flow between the second resin film and an attachment target substance may flow to the first resin film side, a volume resistivity of the first resin film is preferably the same as or higher than a volume resistivity of the second resin film.
In addition, the second resin film serving as the attachment surface is required to have a tensile elastic modulus (Young's modulus) of 1 MPa or more and less than 100 MPa. In particular, in the case of targeting a relatively soft attachment target substance such as human skin, the detailed principle is not clearly identified, but it is required to attach the attachment pad while following the shape of the attachment target substance and to maintain the attached state by suppressing repulsive force (stress) generated inside the attachment pad as much as possible while it is attached to the attachment target substance. Therefore, regarding the resin film, a tensile elastic modulus (Young's modulus) of at least the second resin film serving as the attachment surface is set within the above-mentioned range. A tensile elastic modulus (Young's modulus) of the first resin film used on the side opposite to the attachment surface of the attachment target substance can be appropriately set, but a tensile elastic modulus (Young's modulus) of the first resin film is preferably the same as or smaller than a tensile elastic modulus (Young's modulus) of the second resin film so that flexibility of the entire attachment pad (laminate sheet) is not impaired.
In addition, regarding the resin films, each of the first resin film and the second resin film is required to have a thickness of 20 to 200 μm to ensure insulation properties, followability of attachment to an attachment target substance, and attachment force, where a thickness is preferably 50 to 100 μm. When a thickness is less than 20 μm, dielectric breakdown easily occurs, and the attachment pad may not function as an attachment pad due to pinholes formed in the resin film due to the dielectric breakdown. In contrast, when a thickness exceeds 200 μm, it is not preferable because followability of attachment to an attachment target substance is poor, and a distance to the attachment target substance is large, which may reduce an attachment force.
In addition, the first and second resin films may be the same as or different from each other, and specific examples of such resin films described above include polyimide, polyethylene terephthalate (PET), nylon, polypropylene, polyurethane, soft polyvinyl chloride, polyvinylidene chloride, and the like. Examples thereof further include films processed (by mixing a filler thereinto, and the like) to adjust conductivity thereof. In particular, the second resin film is preferably polyurethane or soft polyvinyl chloride and is more preferably soft polyvinyl chloride so that a volume resistivity and a tensile elastic modulus thereof are set within the above-mentioned predetermined ranges.
<Electrode Layer>
A material, a shape, and the like of the electrode layer used in the present invention are not particularly limited, but a thickness thereof is required to be 1 to 20 μm. When a thickness is less than 1 μm, the electrode layer may be disconnected or conductivity may be reduced due to deformation of the attachment pad. In contrast, when a thickness exceeds 20 μm, hardness of the electrode layer tends to increase, and therefore, flexibility of the entire attachment pad deteriorates, and followability for an attachment target substance may deteriorate. Regarding a material and a production method, for example, a metal foil may be used as it is; an electrode layer obtained by etching a metal film formed by a sputtering method, an ion plating method, or the like into a predetermined shape may be used; or an electrode layer formed into a predetermined shape by spraying a metal material or printing a conductive ink may be used. The shape can be appropriately selected from, for example, a flat plate shape, a semicircular shape, a pattern shape such as a comb shape or a mesh, and the like.
<Laminate Sheet>
In addition, the first and second resin films and the electrode layer described above are used and laminated to form a laminate sheet. The electrode layer is required to be sandwiched between the resin films so that the electrode layer is not exposed. As a specific method, there is a method in which these resin films and electrode layer are sequentially laminated, heat and pressure are applied thereto, and thermoplasticity of the resin films themselves is utilized to fuse the laminate. Alternatively, if necessary, bonding may be performed using a bonding sheet, an adhesive, or a pressure-sensitive adhesive. However, when another material is inserted into an adhesive layer when the attachment pad is deformed or expanded or contracted, because deformation or expansion or contraction may be hindered or peeling of the adhesive surface may occur, the method of fusion welding using thermoplasticity of the films is preferable.
<Power Supply Device>
After forming the laminate sheet as described above, a power supply device for applying a voltage to the electrode layers to generate an electrical attachment force is required. The power supply device can be connected to the electrode layer of the laminate sheet via a connection terminal and a switch (both not shown). A power supply device similar to that used for a general electrostatic attachment structure may be used, and any power supply device may be used as long as it can generate a high DC voltage. A potential difference to be generated can be set up to about 500 to 5,000 V, and if necessary, a booster circuit (high voltage generator circuit) capable of boosting to a required voltage may be provided. In particular, it is preferable to design in consideration of the following (a) to (c) to apply the attachment pad of the present invention to the human skin. That is, (a) Apply as high voltage as possible to generate sufficient attachment force;
(b) Make a potential of a human body as low as 0 V. This is because static electricity will be accumulated inside the human body and the body will be impacted during discharge when a potential applied to the human body is biased to either positive or negative; and
(c) No current flows under any circumstances which may endanger the human body.
Under such design concepts of (a) to (c), it is preferable to determine a voltage applied to the attachment pad in consideration of (b) and (c). In addition, in order to achieve (b), in a case of using a unipolar electrode layer, it is preferable to perform earth-connecting (grounding) connection between an attachment target substance (human skin) and ground of a voltage generation source (for example, a high voltage generator circuit) in a power supply device; whereas in a case of using a bipolar electrode layer, it is preferable to apply positive and negative symmetrical voltages to each of the first electrode and the second electrode in the electrode layer, and as a result, it is preferable that the human body be as low as 0 V. Furthermore, in order to achieve (c), it is preferable to suppress an output current from the power supply to 0.5 mA or less. This is because the human body cannot generally perceive current when it is 0.5 mA or less. However, since a large current may be generated when an electric current is accumulated in the attachment pad or the human body and is discharged at once, an electrostatic capacity of the attachment pad is preferably set to 1,000 pF or less, which is the same level as the human body, specifically to about 10 pF to 100 pF, and a voltage is preferably set within ±5,000 V so that current will be 5 pC or less even when it is accumulated in the human body.
The above-mentioned laminate sheet and power supply device are provided to form the attachment pad of the present invention. If necessary, a sensor or the like may be separately provided to the attachment pad of the present invention. Furthermore, appropriate change or addition of the configuration may be performed within the scope of the object of the present invention such as changing the pattern of the electrode layer.
Regarding an attachment target substance, not only a conductor but also paper or cloth having poor electric conductivity can be adapted. Substances, typically the human skin, that are soft and have a certain level of moisture and oil equivalent to human skin, which are substances having a certain surface to which the attachment pad can be connected and attached (for example, organs, animal skin, plants, foods such as meat and processed meat products/vegetables and processed vegetable products/fruits and processed fruit products, or a combination thereof) can be particularly targeted. In addition, although the principle of attachment is not clear, it is presumed that a minute current is generated between an attachment surface of the attachment pad (laminate sheet) and an attachment target substance, and it is presumed that an attachment force by the Johnsen-Rahbek effect acts between an attachment surface of the attachment pad (laminate sheet) and an attachment target substance.
Hereinafter, preferable embodiments of the present invention will be specifically described based on examples and comparative examples, but the present invention is not construed as being limited thereto.
As a bipolar attachment pad, the following was prepared. Two aluminum foils b (thickness: 0.012 mm) as electrode layers having a predetermined shape with dimensions (unit: mm) as shown in
The produced laminate sheet a was provided with a power supply device as shown in
As a unipolar attachment pad, the following was prepared. One aluminum foil b (thickness: 0.012 mm) having a predetermined shape with a dimension (unit: mm) as shown in
The laminate sheet a′ thus produced was provided with a power supply device as shown in
<Evaluation of Attachment Properties of Attachment Pad>
As shown in
A volume resistivity of the soft polyvinyl chloride film in Example 1 was measured by a double ring electrode method (IEC 60093, ASTM D257, JIS K 6911, JIS K 6271), and a volume resistivity of each resin film used in Examples 2 to 6 and Comparative Examples 1 to 3 to be described later was also measured by the same method.
An attachment pad according to Example 2 was produced in the same manner as in Example 1 except that a soft polyvinyl chloride film (thickness: 100 μm) having a volume resistivity of 1×1012 Ω·cm (measured by the method described above) and a tensile elastic modulus (Young's modulus) of 20 to 30 MPa was used as the second resin film c′ that served as an attachment surface of an attachment target substance. Furthermore, attachment properties of the attachment pad were evaluated in the same manner as in Example 1. The results are as shown in Table 1.
An attachment pad according to Example 3 was produced in the same manner as in Example 1 except that a soft polyvinyl chloride film (thickness: 100 μm) having a volume resistivity of 1×1013 Ω·cm (measured by the method described above) was used as the second resin film c′ that served as an attachment surface of an attachment target substance. Furthermore, attachment properties of the attachment pad were evaluated in the same manner as in Example 1. The results are as shown in Table 1.
Attachment properties were evaluated in the same manner as in Example 1 except that the attachment pad h′ used in Example 1 was used, the leaf of the foliage plant (plant name: Ficus umbellata) was used as the attachment target substance g′ instead of the human skin, and the pad was attached to a surface of the leaf. The results are as shown in Table 1.
Attachment properties were evaluated in the same manner as in Example 1 except that the attachment pad h′ used in Example 1 was used, processed pork meat (manufactured by Foodlier Co., Ltd., product name: loin ham) was used instead of the human skin as the attachment target substance g′, and the pad was attached to a surface of the meat after removing some oil on the surface. The results are as shown in Table 1.
Attachment properties were evaluated in the same manner as in Example 1 except that the attachment pad h′ used in Example 1 was used, vegetable eggplant was used as the attachment target substance g′ instead of the human skin, and the pad was attached to a surface of the skin without processing such as cutting. The results are as shown in Table 1.
An attachment pad h′ according to Comparative Example 1 was produced in the same manner as in Example 1 except that a soft polyvinyl chloride film (trade name: 711M, manufactured by Nakagawa Chemical Inc., thickness: 100 μm) having a volume resistivity of 1×1015 Ω·cm (measured by the method described above) was used as the second resin film c′ that served as an attachment surface of an attachment target substance. Furthermore, attachment properties of the attachment pad with respect to human skin were evaluated in the same manner as in Example 1. The results are as shown in Table 1.
An attachment pad h′ according to Comparative Example 2 was produced in the same manner as in Example 1 except that a polyimide film [manufactured by DU PONT-TORAY CO., LTD., product name: Kapton (registered trademark) H, volume resistivity: 1×1017 Ω·cm (measured by the method described above), tensile elastic modulus (Young's modulus): 3×103 MPa, thickness 50 μm] was used as the second resin film c′ that served as an attachment surface of an attachment target substance. Furthermore, attachment properties of the attachment pad with respect to human skin were evaluated in the same manner as in Example 1. The results are as shown in Table 1.
An attachment pad h′ according to Comparative Example 3 was produced in the same manner as in Example 1 except that a polyethylene terephthalate (PET) film [manufactured by Toray Industries, Inc., product name: Lumirror (registered trademark) S10, volume resistivity: 1×1017 Ω·cm (measured by the method described above), tensile elastic modulus (Young's modulus): 4×103 MPa, thickness 50 μm] was used as the second resin film c′ that served as an attachment surface of an attachment target substance. Furthermore, attachment properties of the attachment pad with respect to human skin were evaluated in the same manner as in Example 1. The results are as shown in Table 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-065085 | Mar 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/010533 | 3/14/2019 | WO | 00 |
