Patent Description:
In recent years, a polymer actuator that converts electrical energy into mechanical energy is widely known. One of the polymer actuators is a multilayer actuator in which an electrode and an elastomer layer are arranged in a layered formation (for example, refer to Patent Literature <NUM>).

Patent Literature <NUM>: <CIT> <CIT> is directed to a polymeric actuator which can switch its illumination state by utilizing the flexural action of the body of an actuator. <CIT> relates to a transducer for converting electric energy into mechanical energy and an electronic device including the transducer.

However, when the multilayer actuator described above is applied to, for example, a drive apparatus or an electronic apparatus, there may be a decrease in strain caused when voltage is applied.

It is an object of the present disclosure to provide an actuator that makes it possible to reduce a decrease in strain caused when voltage is applied, a drive apparatus that includes the actuator, and an electronic apparatus that includes the actuator. Solution to Problem.

In order to achieve the object described above, the invention relates to an actuator according to claim <NUM>.

A Preferred embodiment relates to a drive apparatus according to claim <NUM>.

A further preferred embodiment relates to an electronic apparatus according to claim <NUM>.

Embodiments and application examples of the present disclosure will be described in the following order. Note that, in all of the figures for the following embodiments and the following application examples, identical or corresponding portions are denoted by the same reference numeral.

A of <FIG> is a cross-sectional view illustrating an example of a configuration of an actuator <NUM> including a first surface S101 and a second surface S102 that face each other are entirely constrained. B of <FIG> is a graph illustrating stress-strain characteristics of the actuator <NUM> illustrated in A of <FIG> (hereinafter referred to as "S-S characteristics") when the actuator <NUM> is driven. The actuator <NUM> includes a plurality of elastomer layers <NUM>, a plurality of electrodes <NUM>, and a plurality of electrodes <NUM>. The electrode <NUM> and the electrode <NUM> are alternately arranged in a layered formation such that the elastomer layer <NUM> is situated between the electrode <NUM> and the electrode <NUM>. An extraction electrode <NUM> that is connected to the plurality of electrodes <NUM>, and an extraction electrode <NUM> that is connected to the plurality of electrodes <NUM> are provided on the periphery of the actuator <NUM>.

When the actuator <NUM> having the configuration described above is applied to, for example, a drive apparatus or an electronic apparatus, the first surface S101 is entirely constrained by a driven body <NUM> since the first surface S101 is bonded to the driven body <NUM>. On the other hand, a base material <NUM> is bonded to the second surface S102, and the second surface S102 is entirely constrained by the base material <NUM>. When the first surface S101 and the second surface S102 are entirely constrained, as described above, there will be a significant decrease in strain, compared to when the first surface S101 and the second surface S102 are unconstrained, as illustrated in B of <FIG>. In other words, there is a significant decrease in an amount of displacement of the actuator <NUM>. The actuator <NUM>, which is a dielectric elastomer actuator, has a low rigidity and is not compressed. Thus, the actuator <NUM> is easily affected by the first surface S101 and the second surface S102 being constrained. In particular, when the actuator <NUM> is made thinner, an amount of displacement is significantly reduced by the first surface S101 and the second surface S102 being constrained.

A of <FIG> is a cross-sectional view illustrating an example of a configuration of an arrayed actuator <NUM>. B of <FIG> is a graph illustrating S-S characteristics of the actuator <NUM> illustrated in A of <FIG> when the actuator <NUM> is driven. According to findings of the inventors, the arrayed actuator <NUM> makes it possible to reduce a decrease in strain, compared with the actuator <NUM> (refer to A of <FIG>) of which the first surface S101 and the second surface S102 are entirely constrained, as illustrated in A of <FIG>. In other words, it is possible to reduce a decrease in an amount of displacement of the actuator <NUM>. However, with respect to the arrayed actuator <NUM>, the configuration of the actuator <NUM> and the process of producing the actuator <NUM> are complicated.

Thus, the inventors have made every effort to discuss an actuator that makes it possible to reduce a decrease in strain caused when voltage is applied, while preventing the configuration of the actuator and the process of producing the actuator from being made complicated. Consequently, the inventors have found a configuration in which constraining members <NUM> and <NUM> that correspond to the electrode <NUM> are respectively provided to the first surface S1 and the second surface S2 of an actuator body 10A, as illustrated in A of <FIG>. The actuator <NUM> having such a configuration is described below.

A of <FIG> is a cross-sectional view illustrating an example of a configuration of the actuator <NUM> according to a first embodiment of the present disclosure. B of <FIG> is a graph illustrating S-S characteristics of the actuator <NUM> when the actuator <NUM> is driven. <FIG> is a perspective view illustrating an example of the configuration of the actuator <NUM>. <FIG> is an exploded perspective view illustrating an example of the configuration of the actuator <NUM>. The actuator <NUM> is a multilayer dielectric elastomer actuator (DEA). The actuator <NUM> is in the form of a rectangular film. Note that, in the present disclosure, a film is defined as including a sheet.

As illustrated in A of <FIG> and <FIG>, the actuator <NUM> includes the actuator body 10A, the constraining member (a first constraining member) <NUM>, the constraining member (a second constraining member) <NUM>, an extraction electrode (a first extraction electrode) <NUM>, and an extraction electrode (a second extraction electrode) <NUM>. The extraction electrodes <NUM> and <NUM> are electrically connected to a voltage source (not illustrated) through wiring (not illustrated). Due to voltage being applied, the actuator <NUM> can expand and contract in an in-plane direction of the actuator <NUM>. In other words, the actuator <NUM> can be displaced in a direction of the thickness of the actuator <NUM>.

As illustrated in B of <FIG>, the actuator <NUM> makes it possible to reduce a decrease in strain, compared with the actuator <NUM> of which the first surface S101 and the second surface S102 are entirely constrained (refer to A of <FIG>). In other words, it is possible to reduce a decrease in an amount of displacement of the actuator <NUM>.

The actuator <NUM> can be applied to various drive apparatuses or various electronic apparatuses. In this case, the actuator <NUM> is fixed on the base material <NUM> included in a drive apparatus or an electronic apparatus. Further, the driven body <NUM> included in the drive apparatus or the electronic apparatus is fixed on the actuator <NUM>. The actuator <NUM> and the base member <NUM> are bonded to each other using an adhesive (not illustrated), and the actuator <NUM> and the driven body <NUM> are bonded to each other using an adhesive (not illustrated). Note that, in the present disclosure, a pressure-sensitive adhesion is defined as a type of adhesion.

Specific examples of a drive apparatus to which the actuator <NUM> can be applied include a lens drive apparatus, an apparatus that corrects for a hand induced-shake, and an oscillation device (a tactile display, a vibrator, and an acoustic transducer (such as a speaker)), but the drive apparatus to which the actuator <NUM> can be applied is not limited thereto. Examples of an electronic apparatus to which the actuator <NUM> can be applied include a personal computer, a mobile apparatus, a cellular phone, a tablet computer, a display apparatus, an image-capturing apparatus, an audio apparatus, a game machine, industrial equipment, and a robot, but the electronic apparatus to which the actuator <NUM> can be applied is not limited thereto.

The actuator body 10A is in the form of a rectangular film. The actuator body 10A includes the first and second surfaces S1 and S2 facing each other. The actuator body 10A includes a constraint portion 10B in which the first and second surfaces S1 and S2 are respectively constrained by the constraining members <NUM> and <NUM>, and an unconstraint portion 10C in which the first and second surfaces S1 and S2 are respectively not constrained by the constraining members <NUM> and <NUM>. Here, the constraint portion 10B refers to a portion, in the actuator body 10A, that is situated between the constraining members <NUM> and <NUM>, and the unconstraint portion 10C refers to a portion, in the actuator body 10A, that is provided between the constraint portions 10B being adjacent to each other and is not situated between the constraining members <NUM> and <NUM>.

As illustrated in A of <FIG> and <FIG>, the actuator body 10A is a multilayer body, and includes a plurality of elastomer layers <NUM>, a plurality of electrodes (first electrodes) <NUM>, and a plurality of electrodes (second electrodes) <NUM>. From the viewpoint of insulating properties, it is favorable that the first and second surfaces S1 and S2 of the actuator body 10A be covered with the elastomer layer <NUM>.

The elastomer layer <NUM> is elastic in an in-plane direction of the actuator body 10A. The elastomer layer <NUM> is provided between the electrodes <NUM> and <NUM>. The elastomer layer <NUM> is a rectangular film. The elastomer layer <NUM> is a so-called dielectric elastomer layer. The elastomer layer <NUM> includes, for example, an insulating elastomer as an insulating elastic material. The insulating elastomer includes, for example, at least one of acrylic rubber, silicone rubber, ethylenepropylene-diene terpolymer (EPDM), natural rubber (NR), butyl rubber (IIR), isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (H-NBR), hydrin rubber, chloroprene rubber (CR), fluororubber, urethane rubber, or the like.

The elastomer layer <NUM> may include an additive as necessary. For example, the additive is at least one of a crosslinker, a plasticizer, an antioxidant, a surfactant, a viscosity modifier, a reinforcement, a colorant, or the like.

The electrodes <NUM> and <NUM> are elastic in the in-plane direction of the actuator body 10A. This enables the electrodes <NUM> and <NUM> to expand and contract in response to the expansion and contraction of the elastomer layer <NUM>. There are a gap between the electrodes <NUM> and a gap between the electrodes <NUM> in the in-plane direction of the actuator body 10A. Specifically, each of the electrodes <NUM> and <NUM> is a pattern electrode having a stripe pattern. The electrode <NUM> faces the electrode <NUM>. The electrode <NUM> and the electrode <NUM> are alternately arranged in a layered formation such that the elastomer layer <NUM> is situated between the electrode <NUM> and the electrode <NUM>. The electrodes <NUM> and <NUM> overlap each other, with the elastomer layer <NUM> being situated between the electrodes <NUM> and <NUM>. The electrode <NUM> extends to a first long side of the elastomer layer <NUM>. The electrode <NUM> extends to a second long side of the elastomer layer <NUM>. Thus, an end of the electrode <NUM> is exposed from a side surface on the side of a first long side of the actuator body 10A, and an end of the electrode <NUM> is exposed from a side surface on the side of a second long side of the actuator body 10A.

It is favorable that the electrodes <NUM> and <NUM> each have a Young's modulus not greater than ten times the Young's modulus of the elastomer layer <NUM>. When the electrodes <NUM> and <NUM> each have a Young's modulus not greater than ten times the Young's modulus of the elastomer layer <NUM>, this makes it possible to reduce a decrease in amounts of deformation of the electrodes <NUM> and <NUM> due to the degree of rigidity of the electrodes <NUM> and <NUM>. The Young's modulus described above is measured on the basis of JIS K <NUM>:<NUM>.

The electrodes <NUM> and <NUM> include a conductive material. For example, the conductive material is at least one of a conductive filler or a conductive polymer. Examples of the form of a conductive filler include forms of a sphere, an ellipse, a needle, a plate, a scale, a tube, a wire, a rod, and a fiber; an unfixed form; and the like, but the form of a conductive filler is not particularly limited thereto. Note that only a conductive filler of one type may be used, or conductive fillers of two or more types may be used in combination.

For example, the conductive filler includes at least one of a carbon-based filler, a metal-based filler, a metallic-oxide-based filler, or a metal-coated filler. Here, the metal is defined as including a semimetal.

For example, the carbon-based filler includes at least one of carbon black (such as keitjen black and acetylene black), porous carbon, a carbon fiber (such as a PAN-based carbon fiber and a pitch-based carbon fiber), a carbon nanofiber, fullerene, graphene, a vapor-grown carbon fiber (VGCF), a carbon nanotube (such as SWCNT and MWCNT), a carbon microcoil, or a carbon nanohorn.

For example, the metal-based filler includes at least one of copper, silver, gold, platinum, palladium, nickel, tin, cobalt, rhodium, iridium, iron, ruthenium, osmium, manganese, molybdenum, tungsten, niobium, tantalum, titanium, bismuth, antimony, or lead.

For example, the metallic-oxide-based filler includes indium tin oxide (ITO), zinc oxide, indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, silicon-doped zinc oxide, zinc oxide-tin oxide, indium oxide-tin oxide, or zinc oxide-indium oxidemagnesium oxide.

The metal-coated filler is obtained by coating a base filler with metal. For example, the base filler is mica, a glass bead, a glass fiber, a carbon fiber, calcium carbonate, zinc oxide, or titanium oxide. For example, the metal used to cover the base filler includes at least one of Ni or Al.

For example, the conductive polymer includes at least one of polyethylenedioxythiophene/polystyrene sulfonate (PEDOT/PSS), polyaniline, polyacetylene, or polypyrrole.

The electrodes <NUM> and <NUM> may further include at least one of a binder, a gel, a suspension, or an oil as necessary. The binder is elastic. It is favorable that the binder be an elastomer. Examples of the elastomer may include an elastomer similar to an elastomer included in the elastomer layer <NUM>.

The electrodes <NUM> and <NUM> may further include an additive as necessary. Examples of the additive may include an additive similar to an additive included in the elastomer layer <NUM>.

The electrodes <NUM> and <NUM> may include a composite material. For example, the composite material includes at least one of a composite material of at least one of a conductive polymer or a conductive filler and an elastomer, a composite material of an elastic ion conductive material and an electrolyte, a composite material of at least one of a conductive polymer or a conductive filler and a suspension of a polymer (such as an acrylic emulsion), a composite material of at least one of a conductive polymer or a conductive filler and a block copolymer, or a composite material of a polymer gel and an ion conductor.

The constraining member <NUM> constrains the first surface S1 from expanding and contracting in the in-plane direction of the actuator body 10A. The constraining member <NUM> constrains the second surface S2 from expanding and contracting in the in-plane direction of the actuator body 10A.

The constraining member <NUM> is provided on the first surface S1 of the actuator body 10A. The constraining member <NUM> is provided on the second surface S2 of the actuator body 10A. The constraining members <NUM> and <NUM> are situated across the actuator body 10A from each other. The constraining members <NUM> and <NUM> are provided correspondingly to the electrodes <NUM> and <NUM>. Specifically, the constraining members <NUM> and <NUM> are provided to overlap the electrodes <NUM> and <NUM> in a direction of the thickness of the actuator body 10A. A of <FIG>, and <FIG> and <FIG> illustrate an example in which the constraining members <NUM> and <NUM> and the electrodes <NUM> and <NUM> entirely overlap, but the constraining members <NUM> and <NUM> and the electrodes <NUM> and <NUM> may partially overlap.

The constraining members <NUM> and <NUM> have a pattern similar to the pattern of the electrodes <NUM> and <NUM>, that is, a stripe pattern.

It is favorable that the constraining members <NUM> and <NUM> be harder than the constraint portion 10B of the actuator body 10A. When the constraining members <NUM> and <NUM> are harder than the constraint portion 10B, this makes it possible to stabilize driving of the driven body <NUM> during driving of the actuator <NUM>. A material of the constraining members <NUM> and <NUM> is not particularly limited. The constraining members <NUM> and <NUM> may be made of an organic material or an inorganic material.

It is favorable that the constraining members <NUM> and <NUM> each have a Young's modulus not less than three times the Young's modulus of the actuator body 10A. When the constraining members <NUM> and <NUM> each have a Young's modulus not less than three times the Young's modulus of the actuator body 10A, this makes it possible to stabilize driving of the driven body <NUM> during driving of the actuator <NUM>. The Young's modulus described above is measured on the basis of JIS K <NUM>:<NUM>.

When a width w<NUM> of a drive portion of the actuator body 10A satisfies w<NUM>=<NUM>, a width w<NUM> of a non-drive portion of the actuator body 10A is favorably satisfies <NUM>≤w<NUM>≤<NUM>. When the width w<NUM> of the non-drive portion of the actuator body 10A satisfies w<NUM><<NUM>, an amount of displacement is decreased due to the influence of the constraining members <NUM> and <NUM>. On the other hand, when the width w<NUM> of the drive portion of the actuator body 10A satisfies <NUM><w<NUM>, there is a decrease in the proportion of the drive portion in a cross section that is orthogonal to a drive direction. This results in a decrease in generated force. when the width w<NUM> of the drive portion of the actuator body 10A satisfies w<NUM>=<NUM>, a thickness h of the actuator body 10A favorably satisfies <NUM>≤h≤<NUM>. When the thickness h of the actuator body 10A satisfies h<<NUM>, the amount of displacement is decreased due to the influence of the constraining members <NUM> and <NUM>. On the other hand, when the thickness h of the actuator body 10A satisfies <NUM><h, the aspect ratio determined by w<NUM>/h is made smaller, and a generated force escapes in a direction orthogonal to a drive direction. This results in a decrease in the generated force.

As used herein, the width w<NUM> of the drive portion, the width w<NUM> of the non-drive portion, and the thickness h of the actuator body 10A refer to those when the actuator <NUM> is not driven. As used herein, the drive portion refers to a portion that is included in the actuator body 10A and in which all of the elastomer layer <NUM> and the electrodes <NUM> and <NUM> overlap each other. A of <FIG> illustrates an example in which the constraint portion 10B corresponds to the drive portion. On the other hand, the non-drive portion refers to a portion situated between the drive portions being adjacent to each other. A of <FIG> illustrates an example in which the unconstraint portion 10C corresponds to the non-drive portion.

It is favorable that the extraction electrodes <NUM> and <NUM> be elastic. This enables the extraction electrodes <NUM> and <NUM> to expand and contract in response to the expansion and contraction of the actuator body 10A. This results in being able to prevent the extraction electrodes <NUM> and <NUM> from respectively unsticking from the side surface on the side of the first long side of the actuator body 10A and from the side surface on the side of the second long side of the actuator body 10A.

The extraction electrode <NUM> is provided on the side surface on the side of the first long side of the actuator body 10A. The extraction electrode <NUM> is in contact with the end of the electrode <NUM> exposed from the side surface on the side of the first long side of the actuator body 10A. The extraction electrode <NUM> is provided on the side surface on the side of the second long side of the actuator body 10A. The extraction electrode <NUM> is in contact with the end of the electrode <NUM> exposed from the side surface on the side of the second long side of the actuator body 10A.

The extraction electrodes <NUM> and <NUM> include a conductive material. Examples of the conductive material may include a conductive material similar to a conductive material included in the electrodes <NUM> and <NUM>. The extraction electrodes <NUM> and <NUM> may include an elastic binder as necessary. The binder is favorably an elastomer. Examples of the elastomer may include an elastomer similar to an elastomer included in the elastomer layer <NUM>.

Next, an example of an operation of the actuator <NUM> according to the first embodiment of the present disclosure is described with reference to <FIG>.

When a drive voltage is applied between the electrodes <NUM> and <NUM>, an attractive force due to the Coulomb force acts between the electrodes <NUM> and <NUM>. For this reason, a portion, in the elastomer layer <NUM>, that is situated between the electrodes <NUM> and <NUM> is compressed in a direction of the thickness of the elastomer layer <NUM> to expand in the in-plane direction of the actuator body 10A. This results in making the portion thinner. Consequently, forces F1 and F2 from the constraint portions 10B respectively situated on two sides of the unconstraint portion 10C act on the unconstraint portion 10C, and the unconstraint portion 10C is compressed in the in-plane direction of the actuator body 10A. In response to the compression, the unconstraint portion 10C expands toward a gap 14A of the constraining member <NUM> and a gap 15A of the constraining member <NUM>.

Consequently, the constraint portion 10B of the actuator body 10A is made thinner, and the second surface S2, that is, the driven body <NUM> is displaced downward. As used herein, "downward" refers to a direction of the thickness of the actuator body 10A from the first surface S1 to the second surface S2.

On the other hand, when a drive voltage applied between the electrodes <NUM> and <NUM> is turned off, the attractive force due to the Coulomb force does not act between the electrodes <NUM> and <NUM>. Thus, the portion, in the elastomer layer <NUM>, that is situated between the electrodes <NUM> and <NUM> contracts in the in-plane direction of the actuator body 10A, and the thickness of the portion is returned to its original thickness. Consequently, the acting of F1 and F2 on the unconstraint portion 10C is released, and the unconstraint portion 10C in the expanding state is returned to its original state.

Consequently, the thickness of the constraint portion 10B of the actuator body 10A is returned to its original thickness, and the second surface S2, that is, the driven body <NUM> is displaced upward to be returned to its original position. As used herein, "upward" refers to a direction of the thickness of the actuator body 10A from the second surface S2 to the first surface S1.

Note that, when the actuator <NUM> is applied to various drive apparatuses or various electronic apparatuses, a default state (an initial state) of the actuator <NUM> may be a state in which a prescribed voltage is applied to the actuator <NUM>, or may be a state in which voltage is not applied to the actuator <NUM>.

Next, an example of a method for producing the actuator <NUM> according to the first embodiment of the present disclosure is described.

An elastomer is added to be dispersed in a solvent to prepare a coating used to form an elastomer layer. An additive may be further added to the solvent as necessary. The solvent may be any solvent in which an elastomer or the like can be dispersed, and is not particularly limited.

A conductive material is added to be dispersed in a solvent to prepare a conductive coating that corresponds to a coating used to form an electrode. At least one of a binder or an additive may be further added to the solvent as necessary. The solvent may be any solvent in which a conductive material or the like can be dispersed, and is not particularly limited.

The actuator body 10A is produced as indicated below. First, a plate base material is prepared, and a removal treatment is performed on a surface of the base material as necessary. The base material may be an inorganic base material or a plastic base material.

Next, the coating used to form an elastomer layer is applied to one of surfaces of the base material, and is dried. This results in forming the elastomer layer <NUM> on the one of the surfaces of the base material. Here, the applying includes printing. Next, a treatment of improving adhesion may be performed on the one of the surfaces corresponding to the elastomer layer <NUM> as necessary.

Next, the conductive coating is applied to the one of the surfaces corresponding to the elastomer layer <NUM> in stripes, and is dried. This results in forming the electrode <NUM> on the one of the surfaces corresponding to the elastomer layer <NUM>. Next, a treatment of improving adhesion may be performed, as necessary, on the one of the surfaces corresponding to the elastomer layer <NUM> on which the electrode <NUM> has been formed.

Next, the coating used to form an elastomer layer is applied to the one of the surfaces corresponding to the elastomer layer <NUM> on which the electrode <NUM> has been formed, and is dried. This results in forming the elastomer layer <NUM> on the electrode <NUM>. Next, a treatment of improving adhesion may be performed on the one of the surfaces corresponding to the elastomer layer <NUM> as necessary.

Next, the process of forming the electrode <NUM>, the process of forming the elastomer layer <NUM>, and the process of forming the electrode <NUM> are repeatedly performed to form a multilayer object on the one of the surfaces of the base material. Next, the entirety of, or a portion of the multilayer object is removed from the base material. This results in obtaining the actuator body 10A in the form of a multilayer body.

Subsequently, a coating used to form a constraining member is applied to the first and second surfaces S1 and S2 of the actuator body 10A, and is hardened to form the constraining members <NUM> and <NUM>. Note that the method for forming the constraining members <NUM> and <NUM> is not limited thereto, and, for example, the constraining members <NUM> and <NUM> being formed in advance may be respectively bonded to the first and second surfaces S1 and S2 of the actuator body 10A. Alternatively, a thin film may be formed on the first and second surfaces S1 and S2 of the actuator body 10A, and then the thin film may be patterned using, for example, a photolithography technique or an etching technique to form the constraining members <NUM> and <NUM>. As described above, the target actuator <NUM> is obtained.

In the actuator <NUM> according to the first embodiment, the constraining members <NUM> and <NUM> are provided correspondingly to the electrodes <NUM> and <NUM>. This makes it possible to reduce a decrease in strain caused when voltage is applied, without the actuator body 10A being arrayed (refer to A of <FIG>). This results in being able to reduce a decrease in an amount of displacement of the actuator <NUM>, while preventing the configuration of the actuator <NUM> from being made complicated.

Further, the constraining members <NUM> and <NUM> can be respectively easily formed on the first and second surfaces S1 and S2 of the actuator body 10A using, for example, applying or bonding. This makes it possible to prevent the production process from being made complicated.

The example in which the actuator <NUM> includes the constraining members <NUM> and <NUM> has been described in the first embodiment above. However, the driven body <NUM> may include the constraining member <NUM>. In this case, the constraining member <NUM> is a convex portion that protrudes toward the first surface S1 of the actuator body 10A. The base member <NUM> may include the constraining member <NUM>. In this case, the constraining member <NUM> is a convex portion that protrudes toward the second surface S2 of the actuator body 10A.

The example in which the actuator <NUM> includes a plurality of electrodes <NUM> each being a pattern electrode has been described in the first embodiment above. However, the actuator <NUM> may include a non-pattern electrode <NUM> that has no pattern, instead of the plurality of electrodes <NUM>, as illustrated in <FIG> and <FIG>. The non-pattern electrode <NUM> is a layer obtained by continuously forming the plurality of electrodes <NUM> in the entirety of a facing region. <FIG> and <FIG> illustrate an example in which the non-pattern electrode <NUM> is rectangular. However, the shape of the non-pattern electrode <NUM> is not limited thereto.

The electrode <NUM> extends to first and second short sides of the elastomer layer <NUM>. Thus, ends of the electrode <NUM> are respectively exposed from a side surface on the side of the first short side of the actuator body 10A and a side surface on the side of the second short side of the actuator body 10A. The extraction electrode <NUM> is provided on one of the side surface on the side of the first short side and the side surface on the side of the second short side.

The above-described inclusion of the non-pattern electrode <NUM> in the actuator <NUM> makes it possible to make the process of producing the actuator <NUM> simple.

The actuator <NUM> may further include a plurality of dummy electrodes <NUM>, as illustrated in <FIG> and <FIG>. The dummy electrode <NUM> is elastic in the in-plane direction of the actuator body 10A. The dummy electrode <NUM> is provided in a gap between the electrodes <NUM> being adjacent to each other. The dummy electrode <NUM> is a stripe pattern electrode. The dummy electrode <NUM> may be made of a material similar to a material of the electrode <NUM>, or a material different from the material of the electrode <NUM>. However, it is favorable that the dummy electrode <NUM> be made of a material similar to the material of the electrode <NUM>. In this case, the electrode <NUM> and the dummy electrode <NUM> can be formed at the same time, and this results in making the process of producing the actuator <NUM> simple.

The above-described inclusion of the dummy electrode <NUM> in the actuator <NUM> makes it possible to prevent a difference in level from being caused in the gap between the electrodes <NUM>. This results in being able to keep the flatness of the elastomer layer <NUM>. Consequently, the actuator <NUM> of high quality can be provided.

The example in which the electrodes <NUM> and <NUM> each have a stripe pattern has been described in the first embodiment above. However, the patterns of the electrodes <NUM> and <NUM> are not limited thereto, and various patterns having at least one of a gap or a hole can be used. For example, a mesh pattern (refer to A of <FIG>), a grid pattern (refer to B of <FIG>), a dot pattern (refer to A of <FIG>), a meander pattern, a radial pattern, a geometric pattern, a meander pattern, a concentric pattern (such as a concentric-circle pattern), a spiral pattern, a cobweb pattern, a tree pattern, a fishbone pattern, or a net pattern can be used. Further, the electrodes <NUM> and <NUM> each do not necessarily have to have a pattern when the electrodes <NUM> and <NUM> each have at least one of a gap or a hole. For example, the electrodes <NUM> and <NUM> may have a ring-shape (refer to B of <FIG>). The constraining members <NUM> and <NUM> may respectively have shapes similar to the shapes of the electrodes <NUM> and <NUM> described above.

As illustrated in <FIG>, a thickness d1 of the elastomer layer <NUM> in the constraint portion 10B may be thinner than a thickness d2 of the elastomer layer <NUM> in the unconstraint portion 10C. In this case, a drive voltage of the actuator <NUM> can be reduced.

For example, the actuator <NUM> having the configuration described above is produced as indicated below. First, the actuator body 10A is produced as in the case of the first embodiment described above. Next, the actuator body 10A is expanded in the in-plane direction of actuator body 10A, as illustrated in A of <FIG>. The expansion direction is, for example, at least one of a longitudinal direction or a lateral direction of the actuator body 10A having a rectangular shape.

Next, as illustrated in B of <FIG>, the constraining members <NUM> and <NUM> are respectively formed on the first and second surfaces S1 and S2 of the actuator body 10A, with the actuator body 10A remaining expanded. Next, the expansion of the actuator body 10A is released, as illustrated in C of <FIG>. Consequently, the constraint portion 10B remains expanded using the constraining members <NUM> and <NUM>, whereas the unconstraint portion 10C is returned to its original state. Accordingly, the actuator <NUM> having the configuration illustrated in <FIG> is obtained.

The actuator <NUM> may further include leaf springs <NUM> and <NUM> and holding members <NUM> and <NUM>, as illustrated in <FIG>. The leaf springs <NUM> and <NUM> are sandwiching members between which the actuator body 10A is sandwiched from the side of the first surface S1 through the constraining member <NUM> and from the side of the second surface S2 through the constraining member <NUM>. The leaf springs <NUM> and <NUM> are elongated. The leaf spring <NUM> is provided to face the first surface S1 of the actuator body 10A. The leaf spring <NUM> presses the constraining member <NUM>. The leaf spring <NUM> is provided to face the second surface S2 of the actuator body 10A. The leaf spring <NUM> presses the constraining member <NUM>. The holding member <NUM> holds one of two ends of the leaf spring <NUM> and one of two ends of the leaf spring <NUM>, and the holding member <NUM> holds another of the two ends of the leaf spring <NUM> and another of the two ends of the leaf spring <NUM>, such that biasing is performed by the leaf springs <NUM> and <NUM> respectively toward the first and second surfaces S1 and S2. The holding members <NUM> and <NUM> are ring-shaped elastic members.

In the actuator <NUM> having the configuration described above, the leaf springs <NUM> and <NUM> respectively press the constraining members <NUM> and <NUM>. Thus, a compressive force is applied to the constraint portion 10B from both of the sides of the first surface S1 and the second surface S2 of the actuator body 10A. Consequently, the thickness d1 of the elastomer layer <NUM> in the constraint portion 10B is made thinner than the thickness d2 of the elastomer layer <NUM> in the unconstraint portion 10C (refer to <FIG>). This makes it possible to reduce a drive voltage of the actuator <NUM>. Further, this results in being able to improve adhesion between the elastomer layer <NUM> and each of the electrodes <NUM> and <NUM>. Furthermore, it is also possible to prevent the respective layers forming the actuator body 10A from unsticking from each other, since the actuator body 10A is sandwiched between the leaf springs <NUM> and <NUM>, and.

As illustrated in <FIG>, the actuator <NUM> may further include magnets <NUM> and <NUM>. The magnets <NUM> and <NUM> are sandwiching members between which the actuator body 10A is sandwiched from the side of the first surface S1 through the constraining member <NUM> and from the side of the second surface S2 through the constraining member <NUM>. The magnets <NUM> and <NUM> attract each other. The magnet <NUM> is provided to face the first surface S1 of the actuator body 10A. The magnet <NUM> presses the constraining member <NUM>. The magnet <NUM> is provided to face the second surface S2 of the actuator body 10A. The magnet <NUM> presses the constraining member <NUM>.

In the actuator <NUM> having the configuration described above, the magnets <NUM> and <NUM> respectively press the constraining members <NUM> and <NUM>. Thus, effects similar to the effects provided by the sixth modification can be provided.

The example in which the actuator body 10A includes a plurality of rectangular elastomer layers <NUM> has been described in the first embodiment above. However, the actuator body 10A may include a plurality of looped elastomer layers 11A, as illustrated in <FIG>. The elastomer layers 11A of the plurality of elastomer layers 11A are concentrically arranged in a layered formation. A semi-circumferential portion of the innermost elastomer layer 11A is folded such that fold portions of the semi-circumferential portion overlap, with a plurality of electrodes <NUM> being situated between the fold portions. The electrodes <NUM> and <NUM> are alternately arranged in a layered formation such that the elastomer layer 11A is situated between the electrodes <NUM> and <NUM>. The constraining member <NUM> is provided on an outer peripheral surface of one of semi-circumferential portions of the outermost elastomer layer 11A, and the constraining member <NUM> is provided on an outer peripheral surface of another of the semi-circumferential portions of the outermost elastomer layer 11A.

An example of a method for producing the actuator body 10A having the configuration described above is described below with reference to <FIG>. First, a cylindrical base material <NUM> is prepared, and a removal treatment is performed on a peripheral surface (a cylindrical surface) of the base material <NUM> as necessary. Next, a conductive coating is applied to the peripheral surface of the base material <NUM> to form a stripe coating film parallel to a central axis of the base material <NUM>. Subsequently, the coating film formed on the peripheral surface of the base material <NUM> is dried. This results in forming the electrode <NUM> on the peripheral surface of the base material <NUM>. Next, a treatment of improving adhesion may be performed on the surface of the electrode <NUM> as necessary.

Next, a coating used to form an elastomer layer is applied to the peripheral surface of the base material <NUM> to form a cylindrical coating film. Subsequently, the coating film formed on the peripheral surface of the base material <NUM> is dried. This results in forming the elastomer layer <NUM> on the electrode <NUM>. Next, a treatment of improving adhesion may be performed on one of the surfaces of the elastomer layer <NUM> as necessary.

Next, the electrode <NUM> is formed on a peripheral surface of the elastomer layer <NUM> as in the case of the process of forming the electrode <NUM> described above.

Next, the process of forming the electrode <NUM>, the process of forming the elastomer layer <NUM>, and the process of forming the electrode <NUM> are repeatedly performed to form a multilayer object on the peripheral surface of the base material <NUM>. Thereafter, the entirety of, or a portion of the multilayer object is removed from the base material <NUM>. This results in obtaining the looped actuator body 10A.

The example in which the rectangular elastomer layer <NUM> and the stripe electrode <NUM>, <NUM> are alternately arranged in a layered formation to form the rectangular actuator body 10A has been described in the first embodiment above. However, the method for producing the actuator body 10A is not limited thereto.

For example, a looped multilayer object (the actuator body 10A) may be produced, as described in the eighth modification, and then, the produced multilayer object may be cut and spread to produce the rectangular actuator body 10A.

The example in which the actuator <NUM> includes a plurality of elastomer layers <NUM> has been described in the first embodiment above. However, instead of the plurality of elastomer layers <NUM>, a plurality of elastomer layers <NUM> and a plurality of elastomer layers <NUM> may be included, as illustrated in <FIG>.

The elastomer layer <NUM> is similar to the elastomer layer <NUM> in the first embodiment, except that the elastomer layer <NUM> has the same size or substantially the same size as the electrode <NUM>, <NUM>. The constraint portion 10B is a multilayer object that includes a plurality of electrodes <NUM>, a plurality of electrodes <NUM>, and a plurality of elastomer layers <NUM>.

The elastomer layer <NUM> is provided between the constraint portions 10B being adjacent to each other in the in-plane direction of the actuator body 10A. The elastomer layer <NUM> may have a single layer structure or a multilayer structure. The unconstraint portion 10C includes the elastomer layer <NUM>.

The actuator <NUM> having the configuration described above is produced as indicated below. First, a multilayer object that includes the elastomer layer <NUM> and the electrodes <NUM> and <NUM> of the same size is formed such that the elastomer layer <NUM> is situated between the electrodes <NUM> and <NUM>, as illustrated in A of <FIG>.

Next, as illustrated in B of <FIG>, a plurality of multilayer objects each forming the constraint portion 10B is cut out and placed on a base material (not illustrated) in a line at regular intervals. Next, as illustrated in C of <FIG>, a space between the adjacent constraint portions 10B is filled with a coating used to form an elastomer layer, and then, the coating used to form an elastomer layer is hardened. This results in forming a plurality of unconstraint portions 10C. Next, the integrated plurality of constraint portions 10B and plurality of unconstraint portions 10C are removed from the base material (not illustrated). Accordingly, the target actuator body 10A is obtained.

<FIG> is a cross-sectional view illustrating an example of a configuration of an actuator <NUM> according to a second embodiment of the present disclosure. <FIG> is an exploded perspective view illustrating the example of the configuration of the actuator <NUM>. The actuator <NUM> includes an actuator body 210A instead of the actuator body 10A of the first embodiment (refer to A of <FIG>, and <FIG>). The actuator body 210A is different from the actuator body 10A of the first embodiment in further including a plurality of electrodes (third electrodes) <NUM>, and in including an electrode <NUM> instead of a plurality of electrodes <NUM> (refer to A of <FIG>, and <FIG>). Note that a portion of the second embodiment that is similar to a portion of the first embodiment is denoted by the same reference numeral as the first embodiment, and the description thereof is omitted.

The electrode <NUM> is elastic in the in-plane direction of the actuator body 10A. Specifically, the electrode <NUM> is a pattern electrode having a stripe pattern. The electrode <NUM> is provided in a gap between the electrodes <NUM> being adjacent to each other, and is situated across the elastomer layer <NUM> from the electrode <NUM>. The electrode <NUM> extends to the second long side of the elastomer layer <NUM>. Thus, an end of the electrode <NUM> is exposed from a side surface on the side of a second long side of the actuator body 10A. In the second embodiment, the extraction electrode <NUM> is an extraction electrode of the plurality of electrodes <NUM>. A material of the electrode <NUM> is similar to the material of the electrodes <NUM> and <NUM> of the first embodiment.

The electrode <NUM> is similar to the non-pattern electrode <NUM> of the second modification of the first embodiment (refer to <FIG> and <FIG>).

Next, an example of an operation of the actuator <NUM> according to the second embodiment of the present disclosure is described.

When a drive voltage is not applied between the electrodes <NUM> and <NUM> and when a drive voltage is applied between the electrodes <NUM> and <NUM>, an attractive force due to the Coulomb force only acts between the electrodes <NUM> and <NUM> from among a space between the electrodes <NUM> and <NUM> and a space between the electrodes <NUM> and <NUM>. For this reason, a portion, in the elastomer layer <NUM>, that is situated between the electrodes <NUM> and <NUM> expands in an in-plane direction of the actuator body 210A. This results in making the portion thinner. Due to the expansion, forces F1 and F2 from the constraint portions 10B respectively situated on two sides of an unconstraint portion 10D act on the unconstraint portion 10D, as illustrated in A of <FIG>. Due to the action of the forces F1 and F2, the unconstraint portion 10D is compressed in the in-plane direction of the actuator body 10A. In response to the compression, the unconstraint portion 10D expands toward the gaps 14A and 15A, and this results in an increase in the thickness of the unconstraint portion 10D. Thus, a first surface S1 of the actuator body 210A is displaced downward from its initial position, and the driven body <NUM> moves downward from its initial position. Here, the initial position refers to a position when no drive voltage is applied between the electrodes <NUM> and <NUM> and between the electrodes <NUM> and <NUM>.

On the other hand, when a drive voltage applied between the electrodes <NUM> and <NUM> is turned off and when a drive voltage is applied between the electrodes <NUM> and <NUM>, an attractive force due to the Coulomb force only acts between the electrodes <NUM> and <NUM> from among the space between the electrodes <NUM> and <NUM> and the space between the electrodes <NUM> and <NUM>. For this reason, a portion, in the elastomer layer <NUM>, that is situated between the electrodes <NUM> and <NUM> expands in the in-plane direction of the actuator body 210A. This results in making the portion thinner. Due to the expansion, forces F3 and F4 from the constraint portions 10D respectively situated on two sides of the unconstraint portion 10B act on the unconstraint portion 10B, as illustrated in B of <FIG>. Due to the action of the forces F3 and F4, the unconstraint portion 10B is compressed in the in-plane direction of the actuator body 10A. In response to the compression, the thickness of the unconstraint portion 10B is increased. Accordingly, the thickness of the unconstraint portion 10B of the actuator body 10A is increased, and the first surface S1 is displaced upward from its initial position, and the driven body <NUM> moves upward from its initial position.

As described above, the actuator <NUM> according to the second embodiment further includes a plurality of electrodes <NUM>, and the electrode <NUM> is provided in a gap between the electrodes <NUM> being adjacent to each other. Consequently, when a drive voltage is not applied between the electrodes <NUM> and <NUM> and when a drive voltage is applied between the electrodes <NUM> and <NUM>, the thickness of the constraint portion 10B is reduced, and the constraint portion 10B is displaced downward from its initial position. When a drive voltage applied between the electrodes <NUM> and <NUM> is turned off and when a drive voltage is applied between the electrodes <NUM> and <NUM>, the thickness of the constraint portion 10B is increased, and the constraint portion 10B is displaced upward from its initial position. Consequently, the actuator <NUM> according to the second embodiment makes it possible to increase an amount of displacement of the driven body <NUM>, compared with the actuator <NUM> according to the first embodiment.

Instead of the electrode <NUM> being a non-pattern electrode, a plurality of first electrodes each having a stripe pattern and a plurality of second electrodes each having a stripe pattern may be included, the plurality of first electrodes respectively facing a plurality of electrodes <NUM>, the plurality of second electrodes respectively facing a plurality of electrodes <NUM>. In this case, the constraint portion 10B is driven by voltage being applied between the electrode <NUM> and the first electrode, and the unconstraint portion 10D is driven by voltage being applied between the electrode <NUM> and the second electrode.

<FIG> is a cross-sectional view illustrating an example of a configuration of an image-capturing apparatus <NUM> as an application example. The image-capturing apparatus <NUM> is a so-called single-lens reflex camera, and includes a camera body <NUM> and an image-capturing lens <NUM> that is removable from the camera body. The image-capturing apparatus <NUM> is an example of an electronic apparatus.

The camera body <NUM> includes, for example, an imaging device <NUM>, a monitor <NUM>, and an electronic viewfinder <NUM>. The imaging device <NUM> performs a photoelectric conversion on an optical image of a subject to generate a captured-image signal, the optical image of a subject being formed by light L that passes through the image-capturing lens <NUM> to enter the imaging device <NUM>. The imaging device <NUM> is, for example, a CCD image sensor or a CMOS image sensor.

Image processing such as a resolution conversion is performed by an image processor (of which an illustration is omitted) on the captured-image signal output by the imaging device <NUM>, and display on the monitor <NUM> and the electronic viewfinder <NUM> is performed with respect to the captured-image signal. Further, when a shutter button is pressed, compression processing and record-and-encode processing are performed on the captured-image signal, and then, the captured-image signal is stored in a recording medium (not illustrated).

The monitor <NUM> and the electronic viewfinder <NUM> are display apparatuses such as an organic electroluminescence (EL) display or a liquid crystal display.

The image-capturing lens <NUM> includes, for example, a lens optical system <NUM> and a lens controller (not illustrated). The lens optical system <NUM> includes, for example, a plurality of lens 321A, 321B, and 321C, and a plurality of holders (support members) 322A, 322B, and 322C respectively supporting the lenses 321A, 321B, and 321C. The holder 322A includes a plurality of actuators <NUM> according to the first embodiment or one of the modifications of the first embodiment, and supports the lens 321A through the plurality of actuators <NUM>. However, the holder 322A may include the actuator <NUM> according to the second embodiment or the modification of the second embodiment instead of the actuator <NUM> according to the first embodiment or one of the modifications of the first embodiment.

A of <FIG> is a plan view illustrating an example of a configuration of the lens 321A and the holder 322A that holds the lens 321A. B of <FIG> is a cross-sectional view along the line XXVB-XXVB in A of <FIG>. <FIG> is an enlarged cross-sectional view of a region R in B of <FIG>. The lens 321A is a lens for autofocus purpose. The holder 322A includes a lens support <NUM>, a plurality of actuators <NUM>, and a holder body <NUM>.

The lens support <NUM> has a ring shape. The lens support <NUM> supports the lens 321A with its inner peripheral surface. A driven body is formed by the lens support <NUM> and the lens 321A. The holder body <NUM> has a ring shape. The holder body <NUM> supports the lens support <NUM> through the plurality of actuators <NUM>. The holder body <NUM> is an example of a base material that supports the driven body formed by the lens support <NUM> and the lens 321A.

The actuator <NUM> is an actuator for autofocus purpose. The actuator <NUM> moves the lens 321A in a direction of an optical axis corresponding to incident light L. The first surface S1 of the actuator <NUM> is fixed to the lens support <NUM> through a plurality of constraining members <NUM>. The second surface S2 of the actuator <NUM> is fixed to the holder body <NUM> through a plurality of constraining members <NUM>.

The lens 321C is a lens used to correct for a hand induced-shake. The holder 322C includes an actuator that corrects for a hand induced-shake (not illustrated). The actuator that corrects for a hand induced-shake moves the lens 321C in a plane orthogonal to the optical axis corresponding to the incident light L.

The lens controller controls the actuator <NUM> for autofocus purpose and the actuator that corrects for a hand induced-shake.

The example in which the actuator <NUM> includes the constraining member <NUM> on the first surface S1 has been described in the application example above. However, the lens support <NUM> may include the constraining member <NUM> on a surface of the lens support <NUM> that faces the first surface S1 of the actuator <NUM>. The example in which the actuator <NUM> includes the constraining member <NUM> on the second surface S2 has been described in the application example above. However, the holder body <NUM> may include the constraining member <NUM> on a surface of the holder body <NUM> that faces the second surface S2 of the actuator <NUM>.

<FIG> is a cross-sectional view illustrating an example of a configuration of a display apparatus <NUM> as an application example. The display apparatus <NUM> is a so-called flat speaker, and includes, for example, a back chassis <NUM>, a display panel <NUM>, the actuator <NUM> according to the first embodiment or one of the modifications of the first embodiment, and a controller (not illustrated). Although the display apparatus <NUM> includes a single actuator <NUM> in <FIG>, the display apparatus <NUM> may include a plurality of actuators <NUM>. The display apparatus <NUM> may include the actuator <NUM> according to the second embodiment or the modification of the second embodiment instead of the actuator <NUM> according to the first embodiment or one of the modifications of the first embodiment. The display apparatus <NUM> is an example of an electronic apparatus or a drive apparatus.

The back chassis <NUM> is an example of a base material that supports the actuator <NUM>, and forms a back surface of the display apparatus <NUM>. The back chassis <NUM> is provided on the second surface S2 of the actuator <NUM>. The back chassis <NUM> includes a support surface <NUM> that faces the display panel <NUM>.

The display panel <NUM> is an example of a driven body driven by the actuator <NUM>, and is, for example, an organic EL panel or a liquid crystal panel. The display panel <NUM> is provided on the first surface S1 of the actuator <NUM>. The display panel <NUM> includes a back surface <NUM> that faces the back chassis <NUM>.

The second surface S2 of the actuator <NUM> is fixed to the support surface <NUM> through a plurality of constraining members <NUM>. The first surface S1 of the actuator <NUM> is fixed to the back surface <NUM> through a plurality of constraining members <NUM>. The actuator <NUM> drives the display panel <NUM> to emit a plane wave (a sound wave). The controller controls driving of the display panel <NUM> and the actuator <NUM>.

The example in which the actuator <NUM> includes the constraining member <NUM> on the first surface S1 has been described in the application example above. However, the display panel <NUM> may include the constraining member <NUM> on the back surface <NUM> facing the first surface S1 of the actuator <NUM>. The example in which the actuator <NUM> includes the constraining member <NUM> on the second surface S2 has been described in the application example above. However, the back chassis <NUM> may include the constraining member <NUM> on the support surface <NUM> facing the second surface S2 of the actuator <NUM>.

<FIG> is a cross-sectional view illustrating an example of a configuration of a multipoint tactile display <NUM> as an application example. The multipoint tactile display <NUM> is similar to the actuator <NUM> according to the first embodiment or one of the modifications of the first embodiment, or the actuator <NUM> according to the second embodiment or the modification of the second embodiment, except that the multipoint tactile display <NUM> has a cylindrical shape. The multipoint tactile display <NUM> is an example of a drive apparatus.

The multipoint tactile display <NUM> includes a plurality of constraining members <NUM> on its inner peripheral surface S1, and includes a plurality of constraining members <NUM> on its outer peripheral surface S2. In the multipoint tactile display <NUM>, the inner peripheral surface S1 is attached to a body part <NUM> through the plurality of constraining members <NUM>. Example of the body part <NUM> to which the multipoint tactile display <NUM> is attached include an arm, a leg, and a finger, but the body part <NUM> is not limited thereto.

The present disclosure is specifically described below using experimental examples, but the present disclosure is not limited to these experimental examples.

A of <FIG> schematically illustrates a model of a Finite Element Method (FEM) simulation of a first experimental example. In the first experimental example, the actuator body 10A in the form of a square film (DEA: a Young's modulus of <NUM> MPa, a Poisson's ratio of <NUM>) was used as a model of the FEM simulation. The S-S characteristics when the actuator was driven were analyzed using the FEM simulation. B of <FIG> illustrates a result of it.

A of <FIG> schematically illustrates a model of an FEM simulation of a second experimental example. In the second experimental example, a square rigid body in the form of a thin plate was formed on a primary surface of the actuator of the first experimental example, and the obtained actuator was used as a model of the FEM simulation. The S-S characteristics when the actuator was driven were analyzed using the FEM simulation. B of <FIG> illustrates a result of it.

A of <FIG> schematically illustrates a model of an FEM simulation of a third experimental example. In the third experimental example, a stripe rigid body was formed on the primary surface of the actuator of the first experimental example, and the obtained actuator was used as a model of the FEM simulation. The S-S characteristics when the actuator was driven were analyzed using the FEM simulation. B of <FIG> illustrates a result of it.

The results of the FEM simulations described above show that the actuator including the stripe rigid body on its primary surface exhibits an amount of displacement about ten times greater than the amount of displacement exhibited by the actuator including, on its primary surface, the square rigid body in the film of a thin plate.

A of <FIG> schematically illustrates a model of FEM simulations of fourth to twelfth experimental examples. Note that a portion of this model that corresponds to a portion of the first embodiment is denoted by the same reference numeral as the portion of the first embodiment. A strain maintaining rate and a stress maintaining rate of the model were analyzed using the FEM simulations. The strain maintaining rate is a rate of strain caused under each condition, with a certain value being used as a reference, the certain value being obtained by dividing an amount of displacement by the length of a device in a drive direction in which the device is driven, the displacement being caused upon driving performed when w<NUM>=<NUM> and in a no-load state in which the primary surface of the actuator <NUM> is unconstrained. The stress maintaining rate is a rate of stress caused under each condition, with a certain value being used as a reference, the certain value being obtained by dividing a generated force by the area of a cross section that is orthogonal to the direction in which the device is driven, the generated force being generated upon driving performed when w<NUM>=<NUM> and when the primary surface of the actuator <NUM> is fully constrained. In the FEM simulations of the fourth to twelfth experimental examples, the width w<NUM> of the constraint portion 10B was fixed to <NUM>, and the width w<NUM> of the unconstraint portion 10C and the thickness h of the actuator 10A were changed, as shown in Table <NUM>. Results of them are shown in Table <NUM> and B of <FIG>.

Conditions for and the results of the FEM simulations of the fourth to twelfth experimental examples are given in Table <NUM>.

The results of the FEM simulations described above show that, under the condition that the width w<NUM> of the constraint portion 10B is <NUM>, a satisfactory strain maintaining rate and a satisfactory stress maintaining rate are obtained when the width w<NUM> of the unconstraint portion 10C is not less than <NUM> or is not greater than <NUM>/<NUM>, and the thickness h of the actuator body 10A is not less than <NUM> or is <NUM>/<NUM>.

Further, the results show that, under the condition that the width w<NUM> of the constraint portion 10B is <NUM>, a favorable balance between stress and strain is achieved when the width w<NUM> of the unconstraint portion 10C is about <NUM>, and the thickness h of the actuator body 10A is about <NUM>.

<FIG> schematically illustrates a model of an FEM simulation of a thirteenth experimental example. Note that a portion of this model that corresponds to a portion of the second embodiment is denoted by the same reference numeral as the portion of the second embodiment. The width W of the constraint portion 10B was set such that w<NUM>=<NUM>, the width w<NUM> of the unconstraint portion 10D was set to <NUM>, and the thickness h of the actuator body 210A was set to <NUM>. In this model, a state and a strain maintaining rate of the constraint portion 10B when voltage was applied to the constraint portion 10B and the constraint portion 10B was driven were analyzed using the FEM simulation. As a result, the constraint portion 10B contracted in a direction of the thickness of the actuator body 210A, and the strain maintaining rate of the constraint portion 10B was <NUM>%. Note that the strain maintaining rate refers to a strain maintaining rate similar to the strain maintaining rate in the fourth to twelfth experimental examples described above.

In a model similar to the model of the thirteenth experimental example, the state and the strain maintaining rate of the constraint portion 10B when voltage was applied to the unconstraint portion 10C and the unconstraint portion 10C was driven were analyzed using the FEM simulation. As a result, the constraint portion 10B expanded in the direction of the thickness of the actuator body 210A, and the strain maintaining rate of the constraint portion 10B was <NUM>%. Note that the strain maintaining rate refers to a strain maintaining rate similar to the strain maintaining rate in the fourth to twelfth experimental examples described above.

Claim 1:
An actuator (<NUM>, <NUM>, <NUM>), comprising:
an actuator body (10A, 210A) that includes a first surface and a second surface that face each other;
a first constraining member (<NUM>) that is provided on the first surface, and constrains the first surface from expanding and contracting; and
a second constraining member (<NUM>) that is provided on the second surface, and constrains the second surface from expanding and contracting,
the actuator body including
a first electrode (<NUM>),
a second electrode (<NUM>) that faces the first electrode, wherein there is a gap (14A, 15A) between the first electrode and the second electrode in an in-plane direction of the actuator body,
an elastomer layer (<NUM>, 11A) that is provided between the first electrode and the second electrode, and
a dummy electrode (<NUM>) that is provided in the gap,
the first electrode being a pattern electrode,
the first constraining member and the second constraining member being provided to overlap the first electrode and the second electrode in a direction of the thickness of the actuator body.