JP5186160B2 - Flexible electrode and actuator using the same - Google Patents

Description

  The present invention relates to a flexible electrode that has high conductivity and can be expanded and contracted, and an actuator using the same.

In recent years, actuators using polymer materials such as a conductive polymer, an ion conductive polymer (ICPF), and a dielectric elastomer have been proposed. Since this type of actuator is highly flexible, lightweight, and easy to downsize, its use in various fields such as artificial muscles, medical instruments, and fluid control has been studied. For example, Patent Documents 1 and 2 introduce electrostrictive actuators in which a dielectric film made of a dielectric elastomer is held between a pair of electrodes.
Special table 2003-506858 Japanese Patent Laying-Open No. 2003-230288

  In the electrostrictive actuator, when the voltage applied between the electrodes is increased, the electrostatic attractive force between the electrodes is increased. For this reason, the dielectric film sandwiched between the electrodes is compressed from the film thickness direction, and the film thickness of the dielectric film is reduced. As the film thickness decreases, the dielectric film extends in a direction parallel to the electrode surface. On the other hand, when the applied voltage between the electrodes is reduced, the electrostatic attractive force between the electrodes is reduced. For this reason, the compressive force from the film thickness direction to the dielectric film is reduced, and the film thickness is increased by the elastic restoring force of the dielectric film. As the film thickness increases, the dielectric film shrinks in the direction parallel to the electrode surface. As described above, the electrostrictive actuator drives the drive target member by extending and contracting the dielectric film.

  Here, when the electrode is difficult to expand and contract together with the dielectric film, deformation of the dielectric film is hindered by the electrode, and it is difficult to obtain a desired amount of displacement. Therefore, it is desirable that the electrode can be deformed integrally with the dielectric film so as not to prevent the deformation of the dielectric film. The electrode capable of following the deformation of the dielectric film can be configured by filling a base material such as an elastomer with a conductive material, for example. In this case, in order to ensure conductivity as an electrode, it is necessary to disperse the conductive material throughout the base material. For this reason, the filling amount of the conductive material increases. When the filling amount of the conductive material is increased, the conductivity is improved, but since the hardness is increased, the conductive material is not easily deformed. On the other hand, if the filling amount of the conductive material is decreased in order to ensure the flexibility of the electrode, the conductivity is lowered and sufficient electric charge cannot be supplied to the dielectric film. In addition, when the electrode is greatly extended together with the dielectric film, the distance between the conductive materials is increased, so that the conductive path is cut and the electric resistance is increased. Thus, an electrode that satisfies the desired conductivity and flexibility at the same time has not yet been realized.

  Further, not only the electrostrictive actuator but also a sensor using a conductive resin or the like requires an electrode having conductivity and flexibility. That is, the sensor detects deformation such as bending based on a change in electrical resistance due to deformation of the conductive resin or the like. In this case, unless the electrode is deformed following the conductive resin or the like, a change in electrical resistance based on the deformation of the conductive resin or the like cannot be accurately detected.

  The present invention has been made in view of such circumstances, and provides a flexible electrode that is disposed on the surface of an elastic body and has high conductivity and can be deformed integrally with the elastic body. The task is to do. It is another object of the present invention to provide an actuator that uses such a flexible electrode and has good responsiveness and a large amount of displacement.

  (1) In order to solve the above-mentioned problem, the flexible electrode of the present invention has a base material and a conductive material dispersed in the base material, which is disposed on the surface of the elastic body. The concentration is changed in the thickness direction from the bonding interface with the elastic body, and can be expanded and contracted according to elastic deformation of the elastic body (corresponding to claim 1).

  According to the flexible electrode of the present invention, the concentration of the conductive material changes in the thickness direction from the joint interface with the elastic body. The concentration of the conductive material may gradually and smoothly change in the thickness direction, or may change stepwise. Further, the concentration of the conductive material may be changed singly such as high concentration → low concentration, or may be changed variously such as high concentration → low concentration → high concentration.

  In a portion where the concentration of the conductive material is high, the conductivity is high. For example, when the concentration of the conductive material near the bonding interface with the elastic body is increased, the conductivity near the bonding interface is increased. For this reason, it becomes easy to apply a voltage to an elastic body. Moreover, in the part where the density | concentration of a electrically conductive material is low, hardness becomes relatively low and a softness | flexibility improves. Therefore, it can be deformed following the deformation of the elastic body. That is, there is little risk of restraining deformation of the elastic body. Further, even when the elastic body is largely deformed, it is possible to ensure conductivity at a portion where the concentration of the conductive material is high while following the deformation mainly at a flexible portion where the concentration of the conductive material is low. Therefore, according to the flexible electrode of the present invention, both desired conductivity and flexibility can be satisfied.

  (2) Preferably, in the configuration of (1) above, the concentration of the conductive material may be the highest in the vicinity of the bonding interface (corresponding to claim 2). As described above, the conductivity is high in the portion where the concentration of the conductive material is high. Therefore, by making the concentration of the conductive material the highest near the joint interface with the elastic body, the conductivity near the joint interface can be made the highest. Therefore, according to this configuration, the conductive material can be evenly distributed in the vicinity of the bonding interface, and a voltage can be applied to the elastic body from substantially the entire surface of the bonding interface.

  (3) Preferably, in the configuration of (1) or (2), the base material may include an elastomer (corresponding to claim 3). Elastomers include rubber and thermoplastic elastomers. Since the base material contains an elastomer, it is easily elastically deformed and has excellent followability to deformation of the elastic body.

  (4) Preferably, in any one of the constitutions (1) to (3), a highly conductive layer having a high concentration of the conductive material, and a flexible layer having a low concentration of the conductive material compared to the highly conductive layer And the highly conductive layer is preferably joined to the elastic body (corresponding to claim 4).

  The flexible electrode having this configuration is formed by laminating a highly conductive layer and a flexible layer. Here, the highly conductive layer is joined to the elastic body. That is, the concentration of the conductive material is high near the joint interface with the elastic body. Therefore, a voltage can be applied to the elastic body from substantially the entire surface of the bonding interface. On the other hand, the flexible layer is disposed on the surface of the elastic body via the highly conductive layer. The flexible layer is soft because the concentration of the conductive material is low. Therefore, the followability to the elastic body is ensured by the flexible layer. That is, according to this configuration, the highly conductive layer mainly plays the role of improving the conductivity, and the flexible layer mainly plays the role of improving the followability to the elastic body. Thus, according to this structure, the flexible electrode of this invention can be simply produced by laminating | stacking two layers, the highly conductive layer from which the density | concentration of a electrically conductive material differs, and a flexible layer.

  (5) Preferably, in any one of the constitutions (1) to (4), the elastic body is an elastomer dielectric film that expands and contracts due to a change in applied voltage. Corresponding). For example, if the concentration of the conductive material near the junction interface with the dielectric film is increased, the conductivity near the junction interface is increased. Thereby, sufficient electric charge can be supplied to the dielectric film. Moreover, since the hardness is relatively low in the portion where the concentration of the conductive material is low, the flexibility is improved. Therefore, the followability to the dielectric film is improved. Therefore, for example, if the flexible electrodes of the present invention are arranged on both sides of the dielectric film so as to sandwich the dielectric film made of elastomer, an actuator with good response and large displacement can be configured.

  (6) Preferably, in any one of the configurations (1) to (5), the conductive material may be made of a carbon material (corresponding to claim 6). The carbon material has good conductivity and is relatively inexpensive. For this reason, if a carbon material is used, the manufacturing cost of a flexible electrode can be reduced.

  (7) Further, the actuator of the present invention includes an elastomeric dielectric film and a pair of electrodes disposed via the dielectric film, and at least one of the pair of electrodes is defined in claim 1. The flexible electrode according to any one of claims 6 to 6 (corresponding to claim 7).

  The actuator of the present invention drives a member to be driven by applying a voltage between a pair of electrodes to expand and contract (deform) the dielectric film. Here, at least one of the pair of electrodes is a flexible electrode having any one of the constitutions (1) to (6), that is, a flexible electrode having high conductivity and excellent followability to the dielectric film. Since sufficient charge is supplied to the dielectric film, the response of the actuator of the present invention is fast. Further, since it can expand and contract together with the dielectric film, it is difficult to inhibit the deformation of the dielectric film. Furthermore, even if the dielectric film is greatly deformed, the conductive path is maintained and the electric resistance is unlikely to increase. Therefore, a large amount of displacement can be obtained, and the responsiveness is good even when the amount of deformation of the dielectric film is large.

  Hereinafter, embodiments of the flexible electrode and the actuator of the present invention will be described.

<First embodiment>
[Configuration of actuator]
First, the configuration of the actuator of this embodiment will be described. In addition, the structure of the flexible electrode of this embodiment is also demonstrated collectively. FIG. 1 shows a cross-sectional view of the actuator of this embodiment. As shown in FIG. 1, the actuator 1 of this embodiment includes a pair of flexible electrodes 2 and a dielectric film 3.

  The dielectric film 3 is made of acrylic rubber and has a thin film shape. The pair of flexible electrodes 2 are fixed to both the front and back surfaces of the dielectric film 3. The configuration of the pair of flexible electrodes 2 is the same. Hereinafter, the flexible electrode 2 on the front side of the dielectric film 3 will be described, and it will also serve as an explanation for the flexible electrode 2 on the back side.

  The flexible electrode 2 has a thin film shape. FIG. 2 shows an enlarged view in a circle II in FIG. As shown in FIGS. 1 and 2, the flexible electrode 2 includes a highly conductive layer 20 and a flexible layer 21. Among these, the highly conductive layer 20 is fixed to the surface of the dielectric film 3. The highly conductive layer 20 includes a base material 200 and a large number of conductive materials 201. Base material 200 is made of acrylic rubber. The conductive material 201 is made of carbon black. A large number of conductive materials 201 are distributed in the base material 200.

  The flexible layer 21 is vulcanized and bonded to the surface of the highly conductive layer 20. That is, the flexible layer 21 and the highly conductive layer 20 are placed in the mold cavity in a state where the unvulcanized flexible layer 21 and the highly conductive layer 20 are in contact with each other and vulcanized in this state. It is joined. A terminal (not shown) is connected to the flexible layer 21. The terminal is connected to the positive side of the power supply V via the switch S. A terminal (not shown) connected to the flexible layer 21 of the flexible electrode 2 on the back side is connected to the negative side of the power source V. The flexible layer 21 includes a base material 210 and a large number of conductive materials 211. The base material 210 is made of acrylic rubber, like the base material 200 of the highly conductive layer 20. The conductive material 211 is made of carbon black, like the conductive material 201 of the highly conductive layer 20. A large number of conductive materials 211 are distributed in the base material 210.

  When comparing the high conductive layer 20 and the flexible layer 21, the concentration of the conductive material 201 in the high conductive layer 20 is higher than the concentration of the conductive material 211 in the flexible layer 21. For this reason, the electrical resistance of the highly conductive layer 20 is small. On the other hand, the flexible layer 21 is flexible and easily elastically deformed because the concentration of the base material 210 is high. The highly conductive layer 20 is thinner than the flexible layer 21. As described above, in the flexible electrode 2, in the direction from the surface toward the bonding interface F (thickness direction), the concentration of the conductive materials 211 and 201 changes in a step shape from the low concentration to the high concentration.

[Actuator movement]
Next, the movement of the actuator 1 of this embodiment will be described. The movement of the flexible electrode of this embodiment will also be described. FIG. 3 shows a cross-sectional view of the actuator of this embodiment in the on state. FIG. 4 shows an enlarged view in a circle IV in FIG.

  First, the case where the actuator 1 is switched from the off state to the on state will be described. In the off state, the switch S is opened as shown in FIGS. For this reason, no voltage is applied to the dielectric film 3. Therefore, the dielectric film 3 is not deformed. When the switch S is closed in the off state, the switch is switched to the on state. When switched to the ON state, as shown in FIG. 2, the conductive path P of the flexible electrode 2 (shown by a thick line in FIGS. 2 and 4 to 10) is energized. The conductive path P is formed by the conductive material 211 dispersed in the base material 210 in the flexible layer 21 and the conductive material 201 dispersed in the base material 200 in the high conductive layer 20.

  As described above, in the flexible layer 21, the conductive material 211 is dispersed at a low concentration. For this reason, the number of conductive paths P is reduced. On the other hand, in the high conductive layer 20, the conductive material 201 is dispersed at a high concentration. For this reason, the number of the conductive paths P is increased, and the conductive paths P are spread over almost the entire high conductive layer 20.

  A pair of highly conductive layers 20 are arranged on both the front and back sides of the dielectric film 3. For this reason, in the ON state, a voltage is applied between the high conductive layers 20 by the conductive paths P of the pair of front and back high conductive layers 20. As the applied voltage between the pair of high conductive layers 20 increases, the electrostatic attractive force applied to the dielectric film 3 increases. Therefore, as shown in FIG. 3, the dielectric film 3 contracts in the film thickness direction and expands in the surface development direction. The pair of flexible electrodes 2 deforms following the deformation of the dielectric film 3. That is, the flexible electrode 2 contracts in the thickness direction and expands in the surface development direction. In this way, switching from the off state to the on state is performed.

  Next, a case where the actuator 1 is switched from the on state to the off state will be described. When switching from the on state to the off state, the switch S is opened again. When the switch S is opened, the voltage between the pair of highly conductive layers 20 becomes zero. For this reason, the electrostatic attraction applied to the dielectric film 3 is removed. When the electrostatic attractive force is removed, the dielectric film 3 is restored to its original shape by its own elastic restoring force. In addition, the pair of flexible electrodes 2 is also restored to the original shape. In this way, the actuator 1 moves the drive target member by deforming the dielectric film 3 by switching between the off state and the on state.

[Function and effect]
Next, the effect of the flexible electrode 2 and the actuator 1 of this embodiment is demonstrated. According to the flexible electrode 2 of the present embodiment, the concentration of the conductive material 201 of the high conductive layer 20 is high. For this reason, even when the flexible electrode 2 extends following the dielectric film 3 when switching from the off state to the on state, as shown in FIG. 4, the bonding interface F between the high conductive layer 20 and the dielectric film 3. In addition, the conductive material 201 is evenly distributed. For this reason, charges can be supplied to the entire surface of the bonding interface F. Therefore, the dielectric film 3 can be quickly extended over the entire surface.

  Moreover, the flexible layer 21 of the flexible electrode 2 of this embodiment is soft. For this reason, there is little possibility that the flexible layer 21 restrains the deformation of the dielectric film 3 when switching between the off state and the on state. Therefore, the actuator 1 of this embodiment has a good response and a large amount of displacement.

  In addition, the conductive material 211 concentration of the flexible layer 21 is low. For this reason, when deform | transforming, it is also considered that the conductive path P of the flexible layer 21 is cut. However, on the other hand, another conductive path P is formed by a new contact of the conductive material 211. Therefore, even when the dielectric film 3 is greatly deformed, there is little possibility that the conduction to the highly conductive layer 20 is interrupted.

  In addition, the conductive material 211 is made of carbon black and is less likely to be deformed than the base material 210. For this reason, the deformation | transformation function of the flexible layer 21 is mainly carried by the base material 210. Therefore, when the flexible layer 21 contracts in the layer thickness direction, in other words, when the base material 210 contracts in the layer thickness direction, the concentration of the conductive material 211 in the layer thickness direction becomes relatively high. Therefore, the conductive material 211 tends to be continuous in the layer thickness direction. That is, a new conductive path P is easily formed.

  Moreover, the flexible electrode 2 of this embodiment is formed by bonding a highly conductive layer 20 and a flexible layer 21. That is, the flexible electrode 2 of this embodiment is easily produced by vulcanizing and bonding the highly conductive layer 20 and the flexible layer 21. The carbon black used as the conductive materials 201 and 211 has good conductivity and is relatively inexpensive. For this reason, the flexible electrode 2 can be produced at low cost.

<Second embodiment>
The difference between the flexible electrode and actuator of the present embodiment and the flexible electrode and actuator of the first embodiment is that the flexible electrode has a single-layer structure instead of a two-layer structure. Therefore, only the differences will be described here.

  In FIG. 5, the enlarged view of the flexible electrode in the OFF state of the actuator of this embodiment is shown. FIG. 6 shows an enlarged view of the flexible electrode in the ON state of the actuator. 5 and FIG. 6 are enlarged views corresponding to FIG. 2 and FIG. 4, respectively. In FIG. 5, the parts corresponding to FIG. 2 and the parts corresponding to FIG. 4 in FIG.

  As shown in FIGS. 5 and 6, the flexible electrode 2 includes a base material 22 and a conductive material 23. The base material 22 is made of acrylic rubber. The conductive material 23 is made of carbon black. A large number of conductive materials 23 are distributed on the base material 22.

  The concentration distribution of the conductive material 23 in the thickness direction of the flexible electrode 2 will be described. The concentration of the conductive material in the region from the surface to the vicinity of the bonding interface F is almost uniform and low. On the other hand, the concentration of the conductive material 23 in the vicinity of the bonding interface F is substantially uniform and high. As described above, the concentration distribution of the conductive material 23 in the thickness direction of the flexible electrode 2 changes stepwise from the low concentration to the high concentration from the surface toward the bonding interface F.

  The flexible electrode 2 and the actuator of the present embodiment have the same effects as the flexible electrode and the actuator of the first embodiment with respect to the parts having the same configuration. Further, the flexible electrode 2 of the present embodiment has a single layer structure. For this reason, compared with the case where the multilayer structure is exhibited, it is not necessary to join layers. Moreover, compared with the case where the multilayer structure is exhibited, there is no possibility that adjacent layers may be separated from each other. In addition, since there is no interlayer interface generated in the case of the multilayer structure, the entire flexible electrode 2 is integrated, and the followability to the dielectric film 3 is further improved.

<Third embodiment>
The difference between the flexible electrode and actuator of this embodiment and the flexible electrode and actuator of the second embodiment is that a conductive film is further disposed on the surface of the flexible electrode. Therefore, only the differences will be described here.

  In FIG. 7, the enlarged view of the flexible electrode in the OFF state of the actuator of this embodiment is shown. FIG. 8 shows an enlarged view of the flexible electrode in the ON state of the actuator. 7 is an enlarged view corresponding to FIG. 5 and FIG. 8 is corresponding to FIG. In FIG. 7, the parts corresponding to FIG. 5 and the parts corresponding to FIG. 6 in FIG.

  As shown in FIGS. 7 and 8, a conductive film 24 is fixed on the surface of the flexible electrode 2. The conductive film 24 is formed by applying a paste in which carbon black and oil are mixed to the surface of the flexible electrode 2. A terminal (not shown) is connected to the conductive film 24. The terminal is electrically connected to an actuator driving power source (not shown).

  The flexible electrode 2 and the actuator of the present embodiment have the same effects as the flexible electrode and the actuator of the second embodiment with respect to the parts having the same configuration. Further, the flexible electrode 2 of this embodiment includes a conductive film 24. For this reason, even if the density | concentration of the electrically conductive material 23 is low in the vicinity of the surface of the flexible electrode 2 to which the terminal is connected, the conduction with the terminal can be ensured by the conductive film 24. Thereby, the conductive path P to the dielectric film 3 can be reliably formed. Further, in the ON state, charges can be supplied to the dielectric film 3 through more conductive paths P. Therefore, the responsiveness is further improved.

<Fourth embodiment>
The difference between the flexible electrode and actuator of the present embodiment and the flexible electrode and actuator of the second embodiment is that a region having a high concentration of conductive material exists also on the surface side of the flexible electrode. Therefore, only the differences will be described here.

  In FIG. 9, the enlarged view of the flexible electrode in the OFF state of the actuator of this embodiment is shown. FIG. 10 shows an enlarged view of the flexible electrode in the ON state of the actuator. 9 is an enlarged view corresponding to FIG. 5, and FIG. 10 is an enlarged view corresponding to FIG. 9, parts corresponding to FIG. 5 and parts corresponding to FIG. 6 in FIG. 10 are denoted by the same reference numerals. As shown in FIGS. 9 and 10, a region having a high concentration of the conductive material 23 is arranged not only near the bonding interface F of the flexible electrode 2 but also near the surface. That is, the concentration distribution of the conductive material 23 in the thickness direction of the flexible electrode 2 changes from the surface toward the bonding interface F in a step-like manner from high concentration → low concentration → high concentration.

  The flexible electrode 2 and the actuator of the present embodiment have the same effects as the flexible electrode and the actuator of the second embodiment with respect to the parts having the same configuration. Further, the flexible electrode 2 of the present embodiment has a region where the conductive material 23 is highly concentrated near the surface. For this reason, it is easy to ensure conduction with the terminal in the vicinity of the surface of the flexible electrode 2. Thereby, the conductive path P to the dielectric film 3 can be reliably formed. Further, in the ON state, charges can be supplied to the dielectric film 3 through more conductive paths P. Therefore, the responsiveness is further improved. Further, it is not necessary to separately provide the conductive film 24 (see FIGS. 7 and 8) as compared with the flexible electrode of the third embodiment. For this reason, an electrode structure can be simplified. Further, there is no possibility that the conductive film 24 is peeled off.

<Others>
The embodiments of the flexible electrode and the actuator of the present invention have been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

(1) Dielectric film For example, in the above-described embodiments, a dielectric film made of acrylic rubber is used, but the material of the dielectric film is not particularly limited. For example, it may be appropriately selected from elastomers (including rubber and thermoplastic elastomers). Of these, silicone rubber, urethane rubber, acrylonitrile-butadiene copolymer rubber (NBR) and the like are preferably used in addition to the acrylic rubber from the viewpoint of high relative dielectric constant and dielectric breakdown. Further, the shape and thickness of the dielectric film are not particularly limited, and may be appropriately determined according to the use of the actuator. For example, the thickness of the dielectric film is desirably thinner from the viewpoints of downsizing the actuator, driving at a low potential, and increasing the amount of displacement. In this case, the thickness of the dielectric film is preferably set to 1 μm or more and 500 μm or less in consideration of dielectric breakdown properties and the like. More preferably, the thickness is 10 μm or more and 200 μm or less.

(2) Base material Moreover, the base material which comprises a flexible electrode will not be specifically limited if the electrically conductive material can be disperse | distributed and hold | maintained. The base material may be the same as or different from the material of the dielectric film (elastic body). The same material as the elastic body is preferable because the adhesion between the flexible electrode and the elastic body is improved and the followability to the elastic body is improved. A glass transition temperature (Tg) of 0 ° C. or lower is suitable as a base material because it has rubber-like elasticity at room temperature and high flexibility. Specifically, natural rubber, silicone rubber, acrylic rubber, ethylene-propylene-diene terpolymer (EPDM), butyl rubber, isoprene rubber, NBR, hydrogenated nitrile rubber (H-NBR), hydrin rubber, Known synthetic rubbers such as styrene butadiene rubber (SBR), butadiene rubber, chloroprene rubber, urethane rubber, and thermoplastic polyurethane elastomer (TPU), styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer Well-known thermoplastic elastomers such as coalescence (SIS) and styrene-ethylene-butylene-styrene copolymer (SEBS) can be mentioned.

(3) Conductive material In addition to the carbon black used in the above embodiment, the conductive material includes carbon materials such as carbon nanotubes, metal particles such as silver, copper, and nickel, indium oxide, tin oxide, zinc oxide, and oxidation. Metal oxide particles such as titanium and conductive polymer particles such as polythiophene, polyaniline, and polypyrrole may be used. When carbon black is used, one having a large structure is desirable from the viewpoint of dispersibility in the base material and conductivity. For example, a DBP (dibutyl phthalate) oil absorption of 300 ml / g or more may be used.

  The method for dispersing the conductive material in the base material is not particularly limited. For example, a conductive material can be mixed in a solution obtained by dissolving a base material in a predetermined solution. Further, the base material and the conductive material may be kneaded by a pressure kneader such as a kneader or a Banbury mixer, a two-roller or the like.

In the said embodiment, although the density | concentration of the electrically conductive material showed the aspect changed in step shape, the density | concentration of an electrically conductive material may be changing smoothly gradually in the thickness direction of a flexible electrode. For example, in a region where the concentration of the conductive material is high, the volume resistivity is preferably 100 Ωcm or less and the elastic modulus is less than 10 MPa in order to mainly exhibit high conductivity. On the other hand, in a region where the concentration of the conductive material is low, the volume resistivity is preferably 10,000 Ωcm or less and the elastic modulus is less than 2 MPa in order to mainly exhibit flexibility. When the concentration of the conductive material is changed stepwise, the thickness (T _h ) of the region where the concentration of the conductive material is high is changed to the thickness of the region where the concentration is low in order to improve followability to the elastic body. _Or less (T _l ). Specifically, the ratio between the thicknesses (T _h / T _l ) of the two is preferably in the range of 1 to 1/100.

  Note that the conductive materials forming the conductive path do not have to be in contact with each other. That is, adjacent conductive materials may be close to each other through the base material. Even in this case, a conductive path may be formed depending on the magnitude of the applied voltage.

(4) Structure of flexible electrode The flexible electrode may have a single-layer structure as in the second to fourth embodiments or a multilayer structure as in the first embodiment. For example, in the case of a single layer structure, the concentration distribution can be formed by allowing the conductive material in the base material to settle to one end in the thickness direction by gravity. Further, the concentration distribution may be formed by orienting the conductive material using a magnetic field or an electric field. In the case of a multilayer structure, two or more layers having different conductive material concentrations may be stacked. Here, the base material of each layer may be the same or different.

  When laminating a plurality of layers whose base material is an elastomer, the layers may be cross-linked in a state where the layers are brought into contact with each other in an uncrosslinked state, and the layers may be joined to each other as in the first embodiment. Alternatively, the layers to be laminated may be previously cross-linked and the cross-linked layers may be joined together. Note that the base material of the layer that mainly exhibits high conductivity may be uncrosslinked rubber. However, it is desirable that the base material of the layer that mainly exhibits flexibility is a crosslinked rubber (elastomer). The crosslinking agent is not particularly limited as long as it is a compound capable of crosslinking the polymer, such as an isocyanate group, a hydrosilyl group, an epoxy group, and an amine group, in addition to sulfur and peroxide.

When a highly conductive layer having a high concentration of a conductive material and a flexible layer having a low concentration are stacked, the volume resistivity of the highly conductive layer is preferably 100 Ωcm or less and the elastic modulus is less than 10 MPa. The volume resistivity of the flexible layer is preferably 10,000 Ωcm or less and the elastic modulus is less than 2 MPa. Further, in order to improve the followability to the elastic body, the thickness (T _h ) of the highly conductive layer is preferably equal to or less than the thickness (T _l ) of the flexible layer. Specifically, the ratio between the thicknesses (T _h / T _l ) of the two is preferably in the range of 1 to 1/100.

(5) Conductive film The flexible electrode may be an aspect in which a conductive material is further disposed on the surface to which a terminal conducting with an external power source is connected. As an example of this aspect, in the third embodiment, a conductive film is further disposed on the surface of the flexible electrode. Here, the configuration of the conductive film is not limited to the third embodiment. For example, conductive fine powders such as carbon black and carbon nanotubes may be directly attached to the surface of the dielectric film.

(6) Applicable object of flexible electrode In the said embodiment, the flexible electrode was applied to the electrostrictive actuator using electrostatic attraction. However, the flexible electrode of the present invention is electrically conductive to an electrode such as an actuator using an ionic electroactive polymer that operates by moving ions or molecules electrically, or a sensor using a conductive resin or conductive rubber. The present invention can be applied to various devices that are required to have both flexibility and flexibility. Therefore, the elastic body is not limited to the dielectric film described in the above (1), and a suitable one may be adopted according to the application target of the flexible electrode. For example, for ionic electroactive polymers (polyelectrolytes and ionic polymers that are electrically activated by ions and molecules), results satisfying both conductivity and flexibility have been obtained. .

  Next, the present invention will be described more specifically with reference to examples.

<Production of electrode>
(1) Production of electrode of example As the flexible electrode of the present invention, two types of electrodes in which a highly conductive layer and a flexible layer were laminated were produced. First, an unvulcanized thin film for a highly conductive layer was produced as follows. Carbon black as a conductive material is added to a solution in which 100 parts by weight (hereinafter abbreviated as “part”) of acrylic rubber as a base material (“NIPOL (registered trademark) AR54” manufactured by Nippon Zeon Co., Ltd.) is dissolved in methyl ethyl ketone (MEK). (Lion's "Ketjen Black EC-600JD") 30 parts, processing aid stearic acid (Kao "Lunac (registered trademark) S30") and vulcanization accelerator zinc dimethylcarbamate 2.5 parts of “Noxeller (registered trademark) PZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.) and 0.5 parts of iron dimethylcarbamate (“Noxeller TTFE” manufactured by Ouchi Shinsei Chemical Co., Ltd.) were added to Were mixed and dispersed to obtain a paint. This paint was applied to a polyethylene terephthalate (PET) substrate by a bar coating method and dried to obtain an unvulcanized thin film. The thickness of the obtained unvulcanized thin film was about 5 μm.

  Next, an unvulcanized thin film for a flexible layer was produced. That is, in the production of the unvulcanized thin film for the highly conductive layer, the blending amount of carbon black was changed to 5 parts, and the rest was the same as above to obtain an unvulcanized thin film. The thickness of the obtained unvulcanized thin film was about 25 μm.

  The unvulcanized thin film for the high conductive layer and the unvulcanized thin film for the flexible layer were each press vulcanized at 170 ° C. for about 30 minutes to obtain a thin film for the high conductive layer and a thin film for the flexible layer. . Both obtained thin films were bonded together to obtain a two-layered electrode composed of a highly conductive layer and a flexible layer. The obtained electrode was used as the electrode of Example 1. Separately, the uncured thin film for the highly conductive layer and the unvulcanized thin film for the flexible layer are overlapped and pressed at 170 ° C. for about 30 minutes to vulcanize and bond both thin films. An electrode having a two-layer structure composed of a conductive layer and a flexible layer was obtained. The obtained electrode was used as the electrode of Example 2. Here, in the electrodes of Examples 1 and 2, the concentration of the conductive material in the high conductive layer was about 23.1%, and the concentration of the conductive material in the flexible layer was about 4.8%. In addition, when it is assumed that the conductive material in both layers is uniformly dispersed throughout the electrode, the concentration of the conductive material (hereinafter referred to as “average conductive material concentration” as appropriate) was about 7.8%. .

(2) Production of Electrode of Comparative Example Three types of electrodes in which conductive materials were uniformly dispersed were produced as the electrodes of the comparative example. First, a paint was prepared by blending the same raw materials as described above. Here, the blending amount of carbon black (same as above) of the conductive material was three types of 5 parts, 30 parts, and 7.8 parts. Each of the prepared paints was applied on a PET substrate by a bar coating method, dried, and then press vulcanized at 170 ° C. for about 30 minutes to obtain a thin film electrode. The obtained electrode was compared with the electrode of Comparative Example 1 (5 parts), the electrode of Comparative Example 2 (30 parts), the electrode of Comparative Example 3 (7.8 parts), and the electrode of Comparative Example 4 (6.5 parts). (The amount of conductive material is in parentheses). Here, the thicknesses of the electrodes of Comparative Examples 1 to 4 were all about 30 μm.

<Measurement of electrical resistance>
(1) Relationship between elastic modulus and volume resistivity For each of the electrodes of Examples and Comparative Examples produced, a tensile test was performed in accordance with JIS K6251 (test piece: No. 5 type dumbbell), and from each stress-elongation curve The elastic modulus was determined. In this tensile test, a silver paste (Dotite 0550) was applied to the marked line portion, and a voltage of 1 V was applied between the marked lines, thereby measuring the volume resistivity of each electrode. FIG. 11 shows the relationship between the elastic modulus and the volume resistivity when not stretched. In FIG. 11, as shown by the alternate long and short dash line connecting the results of the electrode of Comparative Example 1 → the electrode of Comparative Example 4 → the electrode of Comparative Example 3 → the electrode of Comparative Example 2, the volume resistivity increases as the amount of the conductive material increases. Although it becomes small, it turns out that an elasticity modulus becomes large (it becomes hard).

  Here, the electrodes of Examples 1 and 2 and the electrode of Comparative Example 3 are compared. The concentration of the conductive material in the electrode of Comparative Example 3 is the same as the average conductive material concentration of the electrodes in Examples 1 and 2. For this reason, the elastic modulus of the electrodes of Examples 1 and 2 and the elastic modulus of the electrode of Comparative Example 3 were substantially the same value. However, the volume resistivity of the electrodes of Examples 1 and 2 was an order of magnitude smaller than the volume resistivity of the electrode of Comparative Example 3. That is, it can be seen that the electric resistance is small in the electrodes of Examples 1 and 2 having the concentration distribution of the conductive material even with the same elastic modulus. On the other hand, in the electrode of the comparative example having no conductive material concentration distribution, it is necessary to increase the blending amount of the conductive material in order to realize the volume resistivity equivalent to the volume resistivity of the electrodes of Examples 1 and 2. As a result, it can be seen that the elastic modulus increases. Thus, according to the electrodes of Examples 1 and 2 having the concentration distribution of the conductive material, it was confirmed that high conductivity can be realized without increasing the blending amount of the conductive material.

(2) Relationship between elongation and volume resistivity In the tensile test, the volume resistivity of each electrode in the stretched state was measured. FIG. 12 shows the change in volume resistivity with respect to the elongation of each electrode. In FIG. 12, “1E + 02” on the vertical axis means “1 × 10 ² ”. “1E-02” means “1 × 10 ⁻² ”. As shown in FIG. 12, in any of the electrodes, the elongation increased and the volume resistivity increased. Here, the electrodes of Examples 1 and 2 and the electrode of Comparative Example 3 are compared. As described above, the concentration of the conductive material in the electrode of Comparative Example 3 is the same as the average conductive material concentration of the electrodes of Examples 1 and 2. From FIG. 12, the volume resistivity of the electrodes of Examples 1 and 2 was smaller than that of the electrode of Comparative Example 3 even at the time of extension. Moreover, when the electrode of Example 1 and the electrode of Example 2 were compared, the increase in volume resistivity accompanying elongation was smaller in the electrode of Example 2 in which the two layers were joined by vulcanization adhesion. Thus, in the case of an electrode having a two-layer structure, it can be seen that when the two layers are integrated by vulcanization adhesion, it is easy to maintain high conductivity even during elongation.

<Measurement of actuator displacement>
(1) Manufacture of Actuator Using the electrodes of Examples 1 and 2 and Comparative Examples 1 to 3, an actuator for measuring displacement was manufactured. First, a dielectric film was produced as follows. 100 parts of acrylic rubber (“Nippol AR51” manufactured by Nippon Zeon Co., Ltd.) and 1 part of stearic acid (“Lunac S30” manufactured by Kao Corporation) as a processing aid were kneaded with a roll kneader. Subsequently, 2.5 parts of vulcanization accelerator zinc dimethylcarbamate ("Noxeller PZ" manufactured by Ouchi Shinsei Chemical) and 0.5 parts of iron dimethylcarbamate ("Noxeller TTFE" manufactured by Ouchi Shinsei Chemical) Was mixed with a roll kneader and dispersed to prepare an acrylic rubber composition. The prepared acrylic rubber composition was formed into a thin sheet, filled in a mold, and press vulcanized at 170 ° C. for about 30 minutes to obtain a thin dielectric film having a thickness of 50 μm.

  A pair of the electrodes of Examples 1 and 2 and Comparative Examples 1 to 3 was attached to the upper and lower surfaces of the produced dielectric film to produce an actuator for measuring displacement. At this time, for the electrodes of Examples 1 and 2, the high conductive layer was bonded to the dielectric film. Hereinafter, the produced actuators are referred to as actuators of Examples 1 and 2 or Comparative Examples 1 to 3 corresponding to the types of electrodes. FIG. 13 shows a top view of the manufactured actuator. FIG. 14 is a sectional view taken along line XIV-XIV in FIG. Although details are not shown in FIGS. 13 and 14, the electrode configurations of Examples 1 and 2 are the same as those in the first embodiment (see FIGS. 1 to 4).

As shown in FIGS. 13 and 14, the actuator 5 includes a dielectric film 50 and a pair of electrodes 51a and 51b. The dielectric film 50 has a circular thin film shape with a diameter of 70 mm. The dielectric film 50 is disposed in a state of being stretched in the biaxial direction at a stretch rate of 100%. Here, the stretching ratio is a value calculated by the following equation (1).
Stretch rate (%) = {√ (S ₂ / S ₁ ) −1} × 100 (1)
[S ₁ : Dielectric film area before stretching (natural state), S ₂ : Dielectric film area after biaxial stretching]

  The pair of electrodes 51a and 51b are arranged to face each other in the vertical direction with the dielectric film 50 interposed therebetween. The electrodes 51a and 51b have a circular thin film shape with a diameter of about 27 mm, and are arranged substantially concentrically with the dielectric film 50, respectively. A terminal portion 510a protruding in the diameter increasing direction is formed on the outer peripheral edge of the electrode 51a. The terminal portion 510a has a rectangular plate shape. Similarly, a terminal portion 510b protruding in the diameter increasing direction is formed on the outer peripheral edge of the electrode 51b. The terminal portion 510b has a rectangular plate shape. The terminal portion 510b is disposed at a position facing the terminal portion 510a by 180 °. The terminal portions 510a and 510b are each connected to the power source 6 via a conducting wire.

  When a voltage is applied between the electrodes 51a and 51b, an electrostatic attractive force is generated between the electrodes 51a and 51b, and the dielectric film 50 is compressed. Thereby, the thickness of the dielectric film 50 becomes thin and extends in the diameter expansion direction. At this time, the electrodes 51a and 51b are also integrated with the dielectric film 50 and extend in the diameter increasing direction. A marker 70 is attached to the electrode 51a in advance. The displacement of the marker 70 was measured by the displacement meter 7 and used as the displacement amount of the actuator 5.

(2) Measurement result of displacement of actuator For each of the actuators of Examples 1 and 2 and Comparative Examples 1 to 3, the displacement with respect to the applied voltage was measured (frequency 1 Hz). FIG. 15 shows the displacement rate with respect to the applied voltage of each actuator. Here, the “displacement rate (%)” on the vertical axis is the ratio of the displacement amount to the state where no voltage is applied (initial state), and is a value calculated by the following equation (2).
Displacement rate (%) = (displacement amount / radius of electrode) × 100 (2)

  As shown in FIG. 15, according to the actuators of Examples 1 and 2, a larger displacement amount was obtained when the same voltage was applied as compared with the actuators of Comparative Examples 1 to 3. That is, according to the actuators of Examples 1 and 2, it is understood that the applied voltage can be further reduced when a desired displacement amount is obtained. As described above, according to the electrodes of Examples 1 and 2 having the concentration distribution of the conductive material, it was confirmed that an actuator having a large displacement can be configured because both the conductivity and the followability to the dielectric film are excellent. In particular, according to the electrode of Example 2, since the conductivity is not easily lowered even when extended (see FIG. 12 above), a larger amount of displacement can be obtained. As shown in FIG. 11, the electrode of Comparative Example 2 is considered to be inferior in followability to the dielectric film because it has high conductivity but high elasticity (hard) and is brittle. Further, the electrode of Comparative Example 1 has a low elastic modulus (soft) and a good followability to the dielectric film, but is considered to have insufficient conductivity.

  FIG. 16 shows the frequency characteristics of the displacement amount in each actuator. In FIG. 16, the “decrease rate (%)” on the vertical axis is the ratio of each displacement when the displacement at the frequency of 1 Hz is 100%. As shown in FIG. 16, in any of the actuators, the amount of displacement decreased as the frequency increased. However, in the actuators of Examples 1 and 2, the decrease in the amount of displacement was smaller than in the actuators of Comparative Examples 1 to 3. In particular, the actuator of Example 2 has a large effect of suppressing a decrease in displacement at a high frequency because the conductivity of the electrode is not easily lowered even when extended (see FIG. 12 and Example 2). In the actuator of Comparative Example 2, the decrease in the amount of displacement was small because the conductivity of the electrode was high. However, since the original displacement is small (see FIG. 15 above), it cannot be said that it is excellent. Further, in the actuator of Comparative Example 1, since the electrode conductivity is low, the amount of displacement is greatly reduced, and the high frequency region cannot be handled.

  The flexible electrode of the present invention is suitable for various elements that require both conductivity and flexibility in an electrode, such as an actuator and a sensor using a polymer material. The actuator of the present invention can be used as a substitute for all actuators such as mechanical actuators such as motors and piezoelectric element actuators. For example, it is suitable for artificial muscles for industrial, medical and welfare robots, small pumps for cooling electronic parts and medical use, medical instruments and the like.

It is sectional drawing of the actuator of 1st embodiment of this invention. It is an enlarged view in the circle | round | yen II of FIG. It is sectional drawing in the ON state of the actuator. FIG. 4 is an enlarged view in a circle IV in FIG. 3. It is an enlarged view of the flexible electrode in the OFF state of the actuator of the second embodiment of the present invention. It is an enlarged view of the flexible electrode in the ON state of the actuator. It is an enlarged view of the flexible electrode in the OFF state of the actuator of 3rd embodiment. It is an enlarged view of the flexible electrode in the ON state of the actuator. It is an enlarged view of the flexible electrode in the OFF state of the actuator of the fourth embodiment. It is an enlarged view of the flexible electrode in the ON state of the actuator. It is a graph which shows the relationship between an elasticity modulus and volume resistivity about each electrode of an Example and a comparative example. It is a graph which shows the change of the volume resistivity with respect to elongation of each electrode of an Example and a comparative example. It is a top view of the actuator for displacement amount measurement. It is XIV-XIV sectional drawing in FIG. It is a graph which shows the displacement rate with respect to the applied voltage of each actuator of an Example and a comparative example. It is a graph which shows the frequency characteristic of the displacement amount in each actuator of an Example and a comparative example.

Explanation of symbols

1: Actuator 2: Flexible electrode 3: Dielectric film 20: High conductive layer 200: Base material 201: Conductive material 21: Flexible layer 210: Base material 211: Conductive material 22: Base material 23: Conductive material 24: Conductive material 5: Actuator 50: Dielectric film 51a, 51b: Electrode 510a, 510b: Terminal part 6: Power supply 7: Displacement meter 70: Marker F: Bonding interface P: Conductive path S: Switch V: Power supply

Claims (5)

An elastomeric dielectric film;
Disposed on the surface of the dielectric film, the base material having a conductive material dispersed in the base material, the concentration of the conductor material is highest in the vicinity of the bonding interface between said dielectric layer, said dielectric layer changes along the thickness direction from the bonding interface between a stretchable flexible electrodes in accordance with the elastic deformation of the dielectric film,
A flexible electrode structure comprising: The flexible electrode structure according to claim 1, wherein the base material of the flexible electrode includes an elastomer. The flexible electrode is formed by laminating a high conductive layer having a high concentration of the conductive material and a flexible layer having a low concentration of the conductive material compared to the high conductive layer,
The flexible electrode structure according to claim 1, wherein the highly conductive layer is bonded to the dielectric film . The flexible electrode structure according to claim 1, wherein the conductive material of the flexible electrode is made of a carbon material. Comprising a dielectric film made of an elastomer and a pair of electrodes disposed via the dielectric film,
At least one of the pair of electrodes includes a base material and a conductive material dispersed in the base material, and the concentration of the conductive material is highest near the junction interface with the dielectric film, An actuator characterized by being a flexible electrode that changes in a thickness direction from a bonding interface with a dielectric film and can expand and contract in accordance with elastic deformation of the dielectric film .

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