Patent Description:
Low-voltage driving of actuators is known to need thin-film stacking techniques. Patent Literature <NUM> proposes a technique for depositing thin films while the elastomer is subjected to a pre-strain to control the elastomer motion direction. Patent Literature <NUM> proposes a technique for producing a stack by rolling a dielectric elastomer sheet having a thickness of several tens of µm formed by an applying process. Patent literature <NUM> discloses transducers and their fabrication. Patent Literature <NUM> and <NUM> disclose transducers, their use and fabrication. Electroactive polymer devices are known from the US patent application publication <CIT>.

An object of the present technique is to provide an actuator with low driving voltage and a method for manufacturing the actuator.

According to a first aspect, the present invention provides an actuator in accordance with independent claim <NUM>. According to a second aspect, the present invention provides a method for manufacturing an actuator in accordance with independent claim <NUM>. Further aspects of the present invention are set forth in the dependent claims, the drawings and the following description.

A first technology to achieve the above object relates to an actuator including: a stack including: an elastomer layer; and an elastic electrode disposed on each surface of the elastomer layer, in which the stack is subjected to a pre-strain of <NUM>% or more at least in one direction.

A second technology relates to a method for manufacturing an actuator, the method including: alternately stacking an electrode and an elastomer to form a stack; and stretching the formed stack in one direction.

The present technique can reduce the driving voltage of actuators. It should be noted that the advantageous effects described herein are not necessarily limited, and any of the advantageous effects described in the present disclosure or any advantageous effect different from the advantageous effects may be obtained.

<FIG> and <FIG> are showing embodiments of the present invention and <FIG> and <FIG> are embodiments not part of the present invention but useful to understand the present invention.

In the present technique, the stack is subjected to a pre-strain of <NUM>% or more at least in one direction. More specifically, the stack is subjected to a pre-strain of <NUM>% or more in one direction or two directions. In a case where the stack is subjected to a pre-strain in two directions, the pre-strain in one direction may be the same as or different from the pre-strain in the other direction. In a case where the stack is subjected to a pre-strain in two directions, one of the directions may be or may not be orthogonal to the other direction.

Examples of the shape of the stack include, but are not limited to, a flat shape, a tubular shape such as a round tubular shape, a spiral shape, a spherical shape, a curved shape, and the like. Examples of the curved shape include, but are not limited to, a partially spherical shape, a partially cylindrical shape, and the like.

Examples of the shape of the main surface of the stack include, but are not limited to, circle, ellipse, polygons (e.g., quadrilaterals, hexagon, octagon, and the like), and irregular shapes.

Embodiments of the present technique will be described in the following order.

An actuator <NUM> according to a first embodiment of the present technique in accordance with the present invention is a so-called dielectric elastomer actuator. As illustrated in <FIG>, the actuator <NUM> includes a stack <NUM>, which has a rectangular sheet shape. The stack <NUM> includes a plurality of elastic electrodes 11a and a plurality of elastic elastomer layers (dielectric layers) 11b. The electrodes 11a and the elastomer layers 11b are alternately stacked on top of one another in the thickness direction of the stack <NUM>. The first embodiment illustrates a case where the main surface of the stack <NUM> is rectangular, but the shape of the main surface of the stack <NUM> is not limited to this shape. In the following description, the direction parallel to one pair of two pairs of the opposite sides of the main surface of the stack <NUM> is referred to as an x-axis direction (first direction), and the direction parallel to the other pair as a y-axis direction (second direction).

The actuator <NUM> according to the first embodiment is installed in, for example, medical devices, such as artificial muscles and endoscopes, industrial devices, artificial chromatophores, antennas, electronic devices, acoustic transducers (speakers and the like), rehabilitation devices, robots, robot suits, microdevices, vibration devices (haptic presentation devices or the like), image stabilization modules, or vibrators. Examples of electronic devices include, but are not limited to, personal computers, mobile devices, mobile phones, tablet computers, displays, imaging devices, audio devices, game devices, and the like.

The actuator <NUM> can preferably be driven with a driving voltage of <NUM> V or more and <NUM> kV or less. As described below, the elastomer layers 11b can be thinned in the method for manufacturing the actuator according to the first embodiment because the stack <NUM> is stretched in the x-axis direction and the y-axis direction after formed. Therefore, the actuator <NUM> can be driven with the low voltage as described above.

The stack <NUM> is subjected to a pre-strain of <NUM>% or more in each of the x-axis direction and the y-axis direction (see <FIG>). The pre-strain in the x-axis direction may be the same as or different from the pre-strain in the y-axis direction. The pre-strain in each of the x- and y-axis directions is preferably <NUM>% or more, more preferably <NUM>% or more, and still more preferably <NUM>% or more. The upper limit of the pre-strain in each of the x- and y-axis directions is preferably <NUM>% or less, and more preferably <NUM>% or less.

The pre-strain is obtained from the following formulas. <MAT> <MAT>.

In the formulas, Lx, L0x, Ly, and L0y denote the values of the following physical properties.

It is noted that Lx, L0x, Ly, and L0y are all values measured at room temperature (<NUM>).

The elastomer layers 11b are elastic sheets. To lower the driving voltage, the mean thickness of the elastomer layers 11b in the pre-strained state is preferably <NUM> or less, more preferably <NUM> or less, and still more preferably <NUM> or less. It is noted that, in a known method for forming elastomer layers by only applying and drying processes, it is difficult to form elastomer layers with a mean thickness of <NUM> or less. The lower limit of the mean thickness of the elastomer layers 11b in the pre-strained state is not limited but, for example, <NUM> or more.

To lower the driving voltage, the mean thickness of the elastomer layers 11b in the pre-strain-released state is preferably <NUM> or less, more preferably <NUM> or less, and still more preferably <NUM> or less. The lower limit of the mean thickness of the elastomer layers 11b in the pre-strain-released state is not limited but, for example, <NUM> or more.

The mean thickness of the elastomer layers 11b is obtained as described below. First, the stack <NUM> is processed by using a focused ion beam (FIB) method or the like to create a cross section, and the cross-sectional image (hereinafter referred to as a "cross-sectional SEM image") is captured with a scanning electron microscope (SEM). Next, the thickness of one of the elastomer layers 11b in the cross-sectional SEM image is measured at each of randomly selected ten points, and the measurements are simply averaged to obtain the mean thickness (arithmetic mean) of the elastomer layer 11b.

The Young's modulus of the elastomer layers 11b is preferably <NUM> MPa or less, more preferably <NUM> MPa or more and <NUM> MPa or less, and still more preferably <NUM> MPa or more and <NUM> MPa or less. The Young's modulus is a value determined in accordance with JIS K <NUM>:<NUM>. A Young's modulus of <NUM> MPa or less makes it easy to stretch the elastomer layers 11b. In addition, a Young's modulus of <NUM> MPa or more makes it easy to handle the elastomer layers 11b. The strain at break of the elastomer layers 11b is preferably <NUM>% or more, and more preferably <NUM>% or more and <NUM>% or less. A strain at break of <NUM>% or more enables a large amount of stretching. The strain at break is measured in accordance with, for example, JIS K <NUM>:<NUM>.

The elastomer layers 11b contain, for example, an insulating elastomer as an insulating elastic material. The elastomer layers 11b may contain an additive as needed. The additive is, for example, at least one of a cross-linker, a plasticizer, an anti-aging agent, a surfactant, a viscosity modifier, a reinforcing agent, a colorant, or the like. The insulating elastomer contains at least one of acrylic rubber, silicone rubber, ethylene-propylene-diene terpolymer (EPDM), natural rubber (NR), butyl rubber (IIR), isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), hydrogenated acrylonitrile-butadiene copolymer rubber (H-NBR), hydrin-based rubber, chloroprene rubber (CR), fluorocarbon rubber, urethane rubber, or the like. To express good conductivity, the insulating elastomer is preferably free of an additive such as titanium oxide or silicon oxide.

The electrodes 11a have elasticity. The electrodes 11a having elasticity can be deformed in conformity with deformation of the elastomer layers 11b when the actuator <NUM> is driven. Furthermore, as described below, the electrodes 11a can be deformed in conformity with deformation of the elastomer layers 11b when the stack <NUM> is stretched.

The electrodes 11a are, for example, solid, gel, or liquid. The electrode 11a may be formed of a thin film, or a conductive material carried on the surface of the elastomer layer 11b without a binder. The electrode 11a may be disposed on the entire surface or substantially the entire surface of the elastomer layer 11b, or may be disposed on part of the surface of the elastomer layer 11b so as to form a predetermined pattern. <FIG> illustrates the latter example. Examples of the predetermined pattern include, but are not limited to, stripe, lattice, spiral, concentric, mesh, geometric patterns, and the like.

The mean thickness of the electrodes 11a in the pre-strain-released state is preferably <NUM> or less, more preferably <NUM> or less, and still more preferably <NUM> or less. The lower limit of the mean thickness of the electrodes 11a in the pre-strain-released state is not limited but, for example, <NUM> or more. The mean thickness of the electrodes 11a is obtained in the same manner as that for the mean thickness of the elastomer layers 11b.

The Young's modulus of the electrodes 11a is preferably <NUM> MPa or less, more preferably <NUM> MPa or more and <NUM> MPa or less, and still more preferably <NUM> MPa or more and <NUM> MPa or less. The Young's modulus is a value determined in accordance with JIS K <NUM>:<NUM>. A Young's modulus of <NUM> MPa or less makes it easy to stretch the electrodes 11a. In addition, a Young's modulus of <NUM> MPa or more makes it easy to handle the electrodes 11a. The strain at break of the electrodes 11a is preferably <NUM>% or more, and more preferably <NUM>% or more and <NUM>% or less. A strain at break of <NUM>% or more enables a large amount of stretching. The strain at break is measured in accordance with, for example, JIS K <NUM>:<NUM>.

The volume resistivity of the electrodes 11a with the stack <NUM> subjected to a strain of <NUM>% or more is preferably <NUM> MΩ ·cm or less. Accordingly, even in a case where the stack <NUM> is subjected to a strain of <NUM>% or more, the electrodes 11a can function as electrodes having good conductivity. The upper limit of the strain is not limited, but preferably <NUM>% or less, and more preferably <NUM>% or less. The volume resistivity of the electrodes 11a is a value obtained by the four-terminal method in accordance with JIS K <NUM>-<NUM>. In the cross-cut test in accordance with JIS K <NUM>-<NUM>-<NUM>:<NUM>, the adhesion between the electrode 11a and the elastomer layer 11b is preferably rated as any one of scales <NUM> to <NUM>. In a case where the adhesion is rated as any one of scales <NUM> to <NUM>, peeling between the elastomer layer 11b and the electrode 11a due to the difference in rigidity between the elastomer layer 11b and the electrode 11a is unlikely to occur after the stack <NUM> is greatly stretched so as to be subjected to a pre-strain of <NUM>% or more.

The electrodes 11a contain a conductive material. The electrodes 11a may further contain, as needed, at least one of an elastic binder, a gel, a suspension, or an oil. In addition, the electrodes 11a may further contain an additive as needed.

The conductive material is, for example, at least one of a conductive filler or a conductive polymer. Examples of the shape of the conductive filler include, but are not limited to, sphere, ellipse, needle, plate, scale, tube, wire, bar (rod), fiber, irregular shapes, and the like. It is noted that a conductive filler with one shape may be used alone or conductive fillers with two or more shapes may be used in combination.

The conductive filler contains, for example, at least one of a carbon-based filler, a metal-based filler, a metal oxide-based filler, or a metal-coated filler. Here, metals include semimetals.

The carbon-based filler contains, for example, at least one of carbon black (e.g., Ketjenblack, acetylene black, or the like), porous carbon, carbon fiber (e.g., PAN-based carbon fiber, pitch-based carbon fiber, or the like), carbon nanofiber, fullerene, graphene, vapor-grown carbon fiber (VGCF), carbon nanotube (e.g., SWCNT, MWCNT, and the like), carbon microcoil, or carbon nanohorn.

The metal-based filler contains, for example, 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.

The metal oxide-based filler contains, for example, 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 oxide-magnesium oxide.

The metal-coated filler is a filler including a base filler coated with a metal. Examples of the based filler include mica, glass beads, glass fiber, carbon fiber, calcium carbonate, zinc oxide, and titanium oxide. The metal that covers the base filler contains, for example, at least one of Ni or Al.

The mean size of the conductive filler is preferably <NUM> or more and <NUM> or less. This is because the electrodes 11a having excellent conductivity are obtained. Here, the mean size is obtained in the following manner. First, a scanning electron microscope (SEM) is used to capture a SEM image of the conductive filler. Subsequently, the size of each of <NUM> pieces of the conductive filler, which are randomly selected in the SEM image, is measured by using image analysis software. Here, the size of the conductive filler means the so-called maximum Feret diameter and, specifically, means the maximum distance between two parallel lines that are drawn at given angles and tangential to the contour of the conductive filler.

The conductive polymer is, for example, at least one of polyethylene dioxythiophene/polystyrene sulfonate (PEDOT/PSS), polyaniline, polyacethylene, or polypyrrole.

The binder is preferably an elastomer. Examples of the elastomer include the same elastomers as those in the elastomer layers 11b. Examples of the additive include the same additives as those in the elastomer layers.

The electrodes 11a may contain a composite material (complex material). The composite material contains, for example, at least one of a composite material containing an elastomer and at least one of a conductive polymer or a conductive filler, a composite material containing an elastic ion-conductive material and an electrolyte, a composite material containing a polymer suspension (acrylic emulsion or the like) and at least one of a conductive polymer or a conductive filler, a composite material containing a block copolymer and at least one of a conductive polymer or a conductive filler, or a composite material containing a polymer gel and an ion conductor.

The interface between the elastomer layer 11b and the electrode 11a undergoes an adhesion improving treatment. With improved adhesion, peeling between the elastomer layer 11b and the electrode 11a due to the difference in rigidity between the elastomer layer 11b and the electrode 11a is unlikely to occur after the stack <NUM> is greatly stretched so as to be subjected to a pre-strain of <NUM>% or more.

To improve the adhesion of the interface, the stack <NUM> includes at least (<NUM>) a silane coupling agent disposed between the elastomer layer 11b and the electrode 11a, and optionally further includes at least one of (<NUM>) a primer layer disposed between the elastomer layer 11b and the electrode 11a, (<NUM>) the physically pretreated surface of at least one of the elastomer layer 11b or the electrode 11a, or (<NUM>) the fine uneven surface of at least one of the elastomer layer 11b or the electrode 11a. It is noted that the physical pretreatment is, for example, at least one of excimer light irradiation treatment, ultraviolet irradiation treatment, plasma treatment, or corona treatment.

Types of the silane coupling agent are not specifically limited, allowing any of known silane coupling agents to be used. Specific examples of the silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, <NUM>-(<NUM>,<NUM>-epoxycyclohexyl)ethyltrimethoxysilane, <NUM>-glycidoxypropyltrimethoxysilane, <NUM>-glycidoxypropylmethyldiethoxysilane, <NUM>-glycidoxypropyltriethoxysilane, p-styryl trimethoxysilane, <NUM>-methacryloxypropylmethyldimethoxysilane, <NUM>-methacryloxypropyltrimethoxysilane, <NUM>-methacryloxypropylmethyldiethoxysilane, <NUM>-methacryloxypropyltriethoxysilane, <NUM>-acryloxypropyltrimethoxysilane, N-<NUM>-(aminoethyl)-<NUM>-aminopropylmethyldimethoxysilane, N-<NUM>-(aminoethyl)-<NUM>-aminopropyltrimethoxysilane, N-<NUM>-(aminoethyl)-<NUM>-aminopropyltriethoxysilane, <NUM>-aminopropyltrimethoxysilane, <NUM>-aminopropyltriethoxysilane, <NUM>-triethoxysilyl-N-(<NUM>,<NUM>-dimethyl-butylidene)propylamine, N-phenyl-<NUM>-aminopropyltrimethoxysilane, hydrochloride of N-(vinylbenzyl)-<NUM>-aminoethyl-<NUM>-aminopropyltrimethoxysilane, <NUM>-ureidopropyltriethoxysilane, <NUM>-chloropropyltrimethoxysilane, <NUM>-mercaptopropylmethyldimethoxysilane, <NUM>-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl) tetrasulfide, and <NUM>-isocyanotopropyltriethoxysilane.

Next, an example operation of the actuator <NUM> according to the first embodiment of the present technique will be described.

When a driving voltage is applied across the electrodes 11a and 11a facing each other with the elastomer layer 11b therebetween, an attractive force due to the Coulomb force is generated between the electrodes 11a and 11a. Thus, the elastomer layer 11b disposed between the electrodes 11a and 11a is pressed in the thickness direction so as to be thinned and elongated.

On the other hand, when the driving voltage applied across the electrodes 11a and 11a facing each other with the elastomer layer 11b therebetween is released, an attractive force due to the Coulomb force is not generated between the electrodes 11a and 11a. Thus, the elastomer layer 11b returns to its original thickness and contracts to its original size because of the resilience of the elastomer layer 11b.

Next, an example method for manufacturing the actuator <NUM> according to the first embodiment of the present technique will be described.

A conductive coating material, which is a coating material for electrode formation, is prepared by dispersing a conductive material in a solvent. As needed, at least one of binders or additives may be further added to the solvent. For example, additives such as a surfactant, a viscosity modifier, and a dispersant, may be added as needed in order to improve the coatability of the conductive coating material on the elastomer layer 11b and the pot life. The conductive coating material may be a conductive ink or may be a conductive paste. The dispersion method preferably involves, for example, stirring, ultrasonic dispersion, bead dispersion, kneading, or homogenizer treatment.

The solvent may be either a polar solvent or a non-polar solvent, but preferably a non-polar solvent. The solvent is any solvent that can disperse the conductive material. Examples of the solvent include water, toluene, ethyl acetate, ethanol, methyl ethyl ketone, isopropanol alcohol, acetone, anones (cyclohexanone, cyclopentanone), hydrocarbon (hexane), amide (DMF), sulfide (DMSO), butyl cellosolve, butyl triglycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol isopropyl ether, dipropylene glycol isopropyl ether, tripropylene glycol isopropyl ether, methyl glycol, terpineol, and butyl carbitol acetate. Specifically, the conductive coating material preferably contains a carbon-based filler, silicone, and a non-polar solvent.

A coating material for elastomer-layer formation is prepared by dispersing an elastomer in a solvent. As needed, at least one of additives or resin materials other than elastomers may be further added to the solvent. For example, additives such as a surfactant, a viscosity modifier, and a dispersant may be added as needed in order to improve the coatability of the coating material for elastomer-layer formation on the electrode 11a and the pot life. Examples of the dispersion process include the same processes as those described in the step of preparing the conductive coating material. The solvent is any solvent that can disperse the elastomer. Examples of the solvent include the same solvents as those described in the step of preparing the conductive coating material.

The stack <NUM> is produced in the following manner. First, a substrate is provided, and the surface of the substrate undergoes a peel treatment as needed. The substrate may be either an inorganic substrate or a plastic substrate. The substrate has, for example, a plate shape or a sheet shape.

Next, a conductive coating material is applied to one surface of the substrate to form a coating film. Here, applying includes printing. Examples of the applying method include, but are not limited to, microgravure coating method, wire-bar coating method, direct gravure coating method, die coating method, dipping method, spray coating method, reverse roll coating method, curtain coating method, comma coating method, knife coating method, spin coating method, ink jet printing method, relief printing method, offset printing method, gravure printing method, intaglio printing method, rubber plate printing method, screen printing method, and flexographic printing method.

Subsequently, the coating film formed on one surface of the substrate is dried. The drying conditions are not limited and may be either natural drying or heat drying. The electrode 11a is accordingly formed on one surface of the substrate. Next, one surface of the electrode 11a may undergo the adhesion improving treatment as needed.

Next, a coating material for elastomer-layer formation is applied to one surface of the electrode 11a to form a coating film. Examples of the applying method include the same applying methods as those for the conductive coating material. Subsequently, the coating film formed on one surface of the substrate is dried. The drying conditions are not limited and may be either natural drying or heat drying. Accordingly, the elastomer layer 11b is formed on one surface of the electrode 11a. Next, one surface of the elastomer layer 11b may undergo the adhesion improving treatment as needed.

Thereafter, the step of forming the electrode 11a and the step of placing the elastomer layer 11b are alternately repeated to form a layered product on one surface of the substrate. The layered product is then entirely peeled from the substrate, or the layered product is partially peeled from the substrate. The stack <NUM> is obtained accordingly.

Subsequently, the obtained stack <NUM> is stretched (biaxially stretched) in the x- and y-axis directions. The stack is thus subjected to a pre-strain of <NUM>% or more in the x- and y-axis directions. In this stretched state, the periphery of the stack <NUM> may be holed by a holder. The intended actuator <NUM> is obtained accordingly.

The actuator <NUM> according to the first embodiment includes the stack <NUM> including a plurality of the elastic elastomer layers 11b and a plurality of the elastic electrodes 11a. The elastic elastomer layers 11b and the elastic electrodes 11a are alternately stacked on top of one another. The stack <NUM> is subjected to a pre-strain of <NUM>% or more in the x- and y-axis directions. The elastomer layer 11b can be thus thinned to lower the driving voltage.

In addition, since the electrodes 11a in the actuator <NUM> according to the first embodiment are capable of functioning as electrodes even when greatly elongated, the stack <NUM> can be greatly stretched after formed and subjected to a pre-strain of <NUM>% or more in the x- and y-axis directions. On the other hand, in a typical actuator, the conformability of the electrodes is as low as about several tens of percent with respect to the initial length, and the electrodes may thus lose their function as electrodes when greatly elongated. It is thus difficult to greatly stretch the stack and subject the stack to a pre-strain of <NUM>% or more in the x- and y-axis directions.

In addition, in the method for manufacturing the actuator according to the first embodiment, the electrodes 11a and the elastomer layers 11b are repeatedly stacked on top of one another by an applying process to form the stack <NUM>, and the stack is stretched to provide the stack <NUM>. This method makes it possible to form the stack <NUM> including the elastomer layers 11b and the electrodes 11a each having a film thickness that is difficult to obtain by a typical applying process.

In addition, since elastomer layers are handled in the form of single layer in a typical method for manufacturing an actuator, the handling ability of the elastomer layers may be poor, or the actuator may be manufactured at low efficiency. On the other hand, in the method for manufacturing the actuator according to the first embodiment, the elastomer layers 11b are handled in the form of the stack <NUM> instead of single layer, and thus the handling ability of the elastomer layers 11b can be improved, and the actuator <NUM> can be manufactured at high efficiency. In addition, in a case where the elastomer layers 11b, which are difficult to handle in the form of single layer, are stacked, it is easy to handle the elastomer layers 11b, for example, cut out or superimpose the elastomer layers 11b. Also, the influence of unevenness of the surface can be reduced.

As illustrated in <FIG>, the actuator <NUM> further includes a holding unit <NUM>, which holds the stack <NUM> in the pre-strained state. The holding unit <NUM> holds the entire periphery of the stack <NUM>. The holding unit <NUM> is stretchable in the x- and y-axis directions as indicated by the arrows in <FIG>. In other words, the holding unit <NUM> is capable of changing the stack <NUM> in size. The pre-strain on the stack <NUM> can be adjusted by changing the stack <NUM> in size.

It is noted that the holding unit <NUM> has any structure as long as the holding unit <NUM> can hold the stack <NUM> subjected to a pre-strain in the x- and y-axis directions. For example, the holding unit <NUM> may partially hold the periphery of the stack <NUM> at discontinuous positions. In addition, the holding unit <NUM> may be disposed in advance on a housing, flame, or the like of an electronic device. Alternatively, the stack <NUM> may be held in the pre-strained state by attaching the periphery or the like of the stack <NUM> to a housing, frame, or the like of an electronic device.

The sheet-like elastomer layer 11b may be placed on one surface of the electrode 11a instead of applying and drying a coating material for elastomer-layer formation on one surface of the electrode 11a to form the elastomer layer 11b. Here, before the elastomer layer 11b is placed, at least one of the surface of the electrode 11a on which the elastomer layer 11b is to be placed or the surface of the elastomer layer 11b to be placed on the electrode 11a undergoes the adhesion improving treatment.

The elastomer layer 11b may have a multilayer structure. In this case, the layer forming the surface in contact with the electrode 11a may be made of a material having high adhesion to the electrode 11a.

The stretching and strain properties of the elastomer layer 11b may be such that the Young's modulus of the elastomer layer 11b after stretching is preferably <NUM> MPa or more and <NUM> MPa or less, and more preferably <NUM> MPa or more and <NUM> MPa or less, and the Young's modulus after further stretching from the stretched state rapidly increases to <NUM> MPa or more or about <NUM> MPa.

At least part of the electrode 11a may be made of a hard material having a Young's modulus exceeding <NUM> MPa. For example, the electrode 11a may have a flexible portion having elasticity and a hard portion having lower elasticity than the flexible portion. The hard portion is preferably located at an easily breakable part of the drive section. The hard portion is made of, for example, metal or the like.

The electrode 11a may have elastic anisotropy. Specifically, the electrode may have different elasticity in the first direction and the second direction. For example, the electrode may have elasticity in the first direction, but may have almost no elasticity in the second direction.

The first embodiment illustrates an example where the entire stack <NUM> is subjected to a pre-strain, but part of the stack <NUM> may be subjected to a pre-strain. In this case, the pre-strain is obtained from the following formulas. <MAT> <MAT>.

In the formulas, Mx, M0x, My, and M0y denote the values of the following physical properties.

It is noted that Mx, M0x, My, and M0y are all values measured at room temperature (<NUM>).

As illustrated in <FIG>, an actuator <NUM> according to a second embodiment of the present technique in accordance with the present invention includes a round tubular, sheet-like stack <NUM>, a round tubular coil spring <NUM>, which supports the inner circumferential surface of the stack <NUM>, and sealing members <NUM> and <NUM>, which close the openings at the opposite ends of the stack <NUM>. The actuator <NUM> may further include a round tubular protective layer (not illustrated) that covers the outer circumferential surface of the stack <NUM>. The stack <NUM> may be formed in a round tubular shape in advance, or may be wound around the coil spring <NUM> to form a round tubular shape.

The actuator <NUM> is installed in, for example, medical devices such as endoscopes, industrial devices, electronic devices, artificial muscles, robots, robot suits, and the like. The actuator <NUM> may be continuously usable or may be disposable. In a case where the actuator <NUM> is used in medical devices, such as endoscopes, the actuator <NUM> is preferably disposable from a hygienic point of view.

The actuator <NUM> has a sealed cylindrical internal space and has the coil spring <NUM> in the internal space. The internal space is filled with gas serving as fluid. The gas is, for example, at least one of air, noble gas, carbon dioxide, or the like.

The stack <NUM>, the coil spring <NUM>, the sealing members <NUM> and <NUM>, and the protective layer in the actuator <NUM> will be sequentially described below.

As indicated by the arrows in <FIG>, the stack <NUM> is subjected to a pre-strain of <NUM>% or more in each of the height direction and the circumferential direction of the stack <NUM>. When the opposite ends of the stack <NUM> are held by the opposite ends of the sealing members <NUM> and <NUM> or the coil spring <NUM>, the stack <NUM> is held in the pre-strained state. The pre-strain in the height direction may be the same as or different from the pre-strain in the circumferential direction. The pre-strain in the height direction and the circumferential direction is preferably <NUM>% or more, more preferably <NUM>% or more, and still more preferably <NUM>% or more. The upper limit of the pre-strain in the height direction and the circumferential direction is preferably <NUM>% or less, and more preferably <NUM>% or less.

It is noted that H, H0, C, and C0 are all values measured at room temperature (<NUM>).

As illustrated in <FIG>, the stack <NUM> includes a plurality of elastic electrodes 21a and a plurality of elastic elastomer layers 21b. The electrodes 21a and the elastomer layers 21b are alternately stacked on top of one another in the radial direction of the stack <NUM>.

The elastomer layers 21b are round tubular sheets. The elastomer layers 21b are stacked on top of one another concentrically about the coil spring <NUM>. Alternatively, the elastomer layers 21b having a strip shape may be spirally wound around the circumferential surface of the coil spring <NUM>. The elastomer layers 21b may be formed in a round tubular shape in advance, or may be wound around the coil spring <NUM> to form a round tubular shape. Except for these points, the elastomer layers 21b are the same as the elastomer layers 11b in the first embodiment.

The electrodes 21a extend in the height direction of the stack <NUM> and are spaced from each other at regular intervals in the circumferential direction. In addition, the electrodes 21a overlap one another in the radial direction of the stack <NUM>. In other words, the electrodes 21a on both sides of the elastomer layer 11b face each other with the elastomer layer 11b therebetween. Except for these points, the electrodes 21a are the same as the electrodes 11a in the first embodiment.

The coil spring <NUM> is an example support that can be bent in any direction and can be elastically deformed. The coil spring <NUM> is a coil spring formed by winding a linear member, such as a metal wire, into a round tubular, spiral shape. A space is formed between turns of the linear member. Therefore, the coil spring <NUM> discretely supports the inner circumferential surface of the stack <NUM> in the height direction of the stack <NUM>. Supporting the inner circumferential surface of the stack <NUM> in this manner facilitates deformation of the stack <NUM> and facilitates expansion/contraction and bending of the actuator <NUM>. Here, the "discretely supporting the inner circumferential surface of the stack <NUM> in the height direction of the stack <NUM>" means supporting the inner circumferential surface of the stack <NUM> at discontinuous positions in the height direction of the stack <NUM>. Here, the intervals between discontinuous positions may be regular or irregular.

The sealing members <NUM> and <NUM> have a disk shape. The sealing members <NUM> and <NUM> contain a metal or a polymer resin. The sealing members <NUM> and <NUM> may contain an elastomer or the like and may be elastically deformable. The sealing members <NUM> and <NUM> may be a device (e.g., an electronic device, such as a camera) provided at an end portion of the actuator <NUM>, or may be an operation section of the actuator <NUM>.

The protective layer is intended to protect the electrode 11a and is an elastic sheet. The protective layer contains an insulating polymer resin. Examples of the polymer resin include vinyl chloride.

Next, an example operation of the actuator <NUM> according to the second embodiment of the present technique will be described.

When a driving voltage is applied across one pair of the electrodes 21a and 21a among a plurality of pairs of the electrodes 21a and 21a facing each other with the elastomer layer 21b therebetween, the elastomer layer 11b disposed between the pair of the electrodes 21a and 21a elongates, so that the actuator <NUM> bends. When the driving voltage applied to the one pair of the electrodes 21a and 21a is released, the actuator <NUM> returns to its original cylindrical shape.

Next, an example method for manufacturing the actuator according to the second embodiment of the present technique will be described.

First, the conductive coating material and the coating material for elastomer-layer formation are alternately applied and dried on the cylindrical surface of a round tubular substrate. Thereafter, the stack is entirely peeled from the substrate, or the stack is partially peeled from the substrate to obtain the stack <NUM>.

Next, the stack <NUM> is stretched (biaxially stretched) in the height direction and the circumferential direction of the stack <NUM>. The stack <NUM> is thus subjected to a pre-strain of <NUM>% or more in the height direction and the circumferential direction. The coil spring <NUM> is inserted into the inner side of the pre-strained stack <NUM>. Alternatively, the coil spring <NUM> may be inserted into the inner side of the stack <NUM> while the stack <NUM> is stretched in the height direction and the circumferential direction. Next, the sealing members <NUM> and <NUM> are fitted to the respective openings at the opposite ends of the stack <NUM> to close the openings at the opposite ends of the stack <NUM>. Next, the opposite ends of the stack <NUM> are held by the sealing members <NUM> and <NUM> or the opposite ends of the coil spring <NUM>. The actuator <NUM> illustrated in <FIG> is obtained accordingly.

The actuator <NUM> according to the second embodiment and the method for manufacturing the actuator <NUM> offer the same advantageous effects as those offered by the actuator <NUM> according to the first embodiment and the method for manufacturing the actuator <NUM>.

The first embodiment illustrates a case where the electrodes 21a are disposed on part of the circumferential surface of the elastomer layer 21b so as to form a predetermined pattern. However, the electrode 21a may be formed in the entire circumferential surface of the elastomer layer 21b.

The actuator <NUM> may be manufactured in the following manner. First, a strip-shaped stack <NUM> is obtained in the same manner as in the first embodiment except that the conductive coating material is applied in the form of stripes. It is noted that, in the case of using a sheet as a substrate, the stack <NUM> may be produced by the roll-to-roll process. Next, the stack <NUM> is wound around the circumferential surface of the coil spring <NUM> while the stack <NUM> is stretched in the height direction and the circumferential direction. The subsequent steps are the same as those in the second embodiment.

The pre-strain in the circumferential direction of the stack <NUM> may be larger than the pre-strain in the height direction of the stack <NUM>. In this case, the resistance of the stack <NUM> to dielectric breakdown can be improved while the displacement in the height direction of the stack <NUM> is maintained satisfactory.

The stack <NUM> may be subjected to a pre-strain in the circumferential direction and no pre-strain in the height direction. In this case, the resistance of the stack <NUM> to dielectric breakdown can also be improved while the displacement in the height direction of the stack <NUM> is maintained satisfactory.

As illustrated in <FIG>, a speaker <NUM> according to a third embodiment of the present technique in accordance with the present invention includes a rectangular actuator <NUM>, and a holding unit <NUM>, which holds the peripheral portion of the actuator <NUM>. The actuator <NUM> is the same as the actuator <NUM> according to the first embodiment.

The holding unit <NUM> holds the actuator <NUM> in such a manner that the actuator <NUM> (i.e., stack) is curved in an arch shape and subjected to a pre-strain of <NUM>% or more in each of the curving direction and the width direction of the actuator <NUM> (the directions denoted by the arrow in <FIG>).

In the speaker <NUM> according to the third embodiment, the actuator <NUM> (i.e., stack) is subjected to a pre-strain of <NUM>% or more in each of the curving direction and the width direction. This configuration can lower the driving voltage of the speaker <NUM>.

As illustrated in <FIG>, a speaker <NUM> according to a fourth embodiment of the present technique in accordance with the present invention includes a round tubular, sheet-like actuator <NUM>, and a holding unit <NUM>, which holds the opposite end portions of the actuator <NUM>. The actuator <NUM> is the same as the actuator according to the first embodiment except that the elastomer layers and the electrodes have a round tubular shape.

The holding unit <NUM> includes a shaft 212a and holding members 212b and 212c, which have a disk shape and are provided at the opposite ends of the shaft 212a. The holding members 212b and 212c hold the actuator <NUM> in a round tubular shape in such a manner that the actuator <NUM> is subjected to a pre-strain of <NUM>% or more in each of two directions, that is, the height direction and the circumferential direction.

In the speaker <NUM> according to the fourth embodiment, the actuator <NUM> is subjected to a pre-strain of <NUM>% or more in each of the height direction and the circumferential direction. This configuration can lower the driving voltage of the speaker <NUM>.

The actuator <NUM> may have a polygonal tubular shape such as quadrangular tubular shape, and the holding members 212b and 212c may have a polygonal shape such as a quadrangular shape.

As illustrated in <FIG>, an endoscope module according to a fifth embodiment of the present technique not being part of the present invention includes an endoscope <NUM> and a controller <NUM>. The controller <NUM> is connected to a power source <NUM>. It is noted that, in the fifth embodiment, the same parts as those in the second embodiment are denoted by the same characters, and the description thereof is omitted.

The endoscope <NUM> includes an operation section <NUM>, an actuator <NUM> in accordance with the present invention, which is a bendable section, and a distal end section <NUM>. The operation section <NUM> has a button, a knob, or the like used to operate the endoscope.

The actuator <NUM> includes a stack <NUM> and a coil spring <NUM>. The internal space of the actuator <NUM> is sealed. One opening of the actuator <NUM> is closed by the distal end section <NUM>, and the other opening at the other end is closed by the operation section <NUM>. The distal end surface of the distal end section <NUM> has an illumination lens and an objective lens (not illustrated). A portion of the surface of the distal end section <NUM> other than the illumination lens and the objective lens is made of, for example, stainless steel or the like. The illumination lens and the objective lens are, for example, glass lenses. An illumination device is provided on the inner side of the illumination lens. An imaging device, such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), is provided on the inner side of the objective lens. The imaging device is connected to a display (not illustrated) via an image processor (not illustrated).

The distal end section <NUM> and the operation section <NUM> are connected to each other by means of a cable located in the internal space of the actuator <NUM>. An operation signal is sent to the distal end section <NUM> from the operation section <NUM> through the cable. In addition, the distal end section <NUM> and the image processor are connected to each other by means of a cable located in the internal space of the actuator <NUM>. A video signal is sent to the image processor from the distal end section <NUM> via the cable. However, the operation section <NUM> may wirelessly send an operation signal to the distal end section <NUM>, and the distal end section <NUM> may wirelessly send a video signal to the image processor.

The controller <NUM> controls a bending drive circuit <NUM> on the basis of the control signal sent from the operation section <NUM>. The bending drive circuit <NUM> causes the actuator <NUM> to bend on the basis of the control signal sent from the controller <NUM>. The bending drive circuit <NUM> may be disposed in the operation section <NUM>.

In the endoscope module according to the fifth embodiment, the actuator <NUM> includes the round tubular stack <NUM>, which is subjected to a pre-strain of <NUM>% or more in the height direction and the circumferential direction. This configuration can lower the driving voltage of the endoscope module.

As illustrated in <FIG>, an actuator <NUM> according to a sixth embodiment of the present technique in accordance with the present invention includes a round tubular stack <NUM>, a round tubular coil spring <NUM>, which supports the inner circumferential surface of the stack <NUM>, sealing members <NUM> and <NUM>, which close the openings at the opposite ends of the stack <NUM>. It is noted that, in the sixth embodiment, the same parts as those in the second embodiment are denoted by the same characters, and the description thereof is omitted.

The stack <NUM> is subjected to a pre-strain in the circumferential direction and no pre-strain in the height direction. Here, the height direction of the stack <NUM> corresponds to the driving direction of the actuator <NUM>, and the circumferential direction of the stack <NUM> corresponds to the direction orthogonal to the driving direction of the actuator <NUM>.

The pre-strain in the circumferential direction of the stack <NUM> is <NUM>% or more, preferably <NUM>% or more, more preferably <NUM>% or more, and still more preferably <NUM>% or more. The upper limit of the pre-strain in the circumferential direction of the stack <NUM> is preferably <NUM>% or less, and more preferably <NUM>% or less.

The stack <NUM> is a main body of the actuator <NUM>. As illustrated in <FIG>, which shows an embodiment in accordance with the present invention, the stack <NUM> includes an elongated electrode sheet <NUM> and an elongated electrode sheet <NUM>. The electrode sheets <NUM> and <NUM> are spirally wound around the circumferential surface of the coil spring <NUM>, which serves as a support, in such a manner that one end of each of the electrode sheets <NUM> and <NUM> in the longitudinal direction is located on the inner circumferential side, and the other end in the longitudinal direction is located on the outer circumferential side.

The electrode sheet <NUM> includes an elastomer layer (dielectric layer) 32a, which is uniaxially stretched in the circumferential direction and has elasticity, and an electrode 32b, which is disposed on one surface of the elastomer layer 32a and has elasticity. The elastomer layer 32a and the electrode 32b both have an elongated rectangular shape. The electrode 32b is disposed on one surface of the elastomer layer 32a in such a manner that the longitudinal direction of the elastomer layer 32a corresponds to the longitudinal direction of the electrode 32b.

The electrode sheet <NUM> includes an elastomer layer (dielectric layer) 33a, which is uniaxially stretched in the circumferential direction and has elasticity, and an electrode 33b, which is disposed on one surface of the elastomer layer 33a and has elasticity. The elastomer layer 33a and the electrode 33b both have an elongated rectangular shape. The electrode 33b is disposed on one surface of the elastomer layer 33a in such a manner that the longitudinal direction of the elastomer layer 33a corresponds to the longitudinal direction of the electrode 33b.

The electrode sheets <NUM> and <NUM> are spirally wound in the longitudinal direction of the electrode sheets <NUM> and <NUM> in such a manner that the sides of the electrode sheet <NUM> overlap the respective sides of the electrode sheet <NUM>. The elastomer layer 32a or the elastomer layer 33a is sandwiched between the wound electrodes 32b and 33b. Specifically, the electrode sheets <NUM> and <NUM> are wound in the longitudinal direction of the electrode sheets <NUM> and <NUM> in such a manner that the electrode 32b, the elastomer layer 32a, the electrode 33b, and the elastomer layer 33a are repeated in this order from the center to the outer circumference of the stack <NUM>.

Except for the above-described points, the elastomer layer 32a and the elastomer layer 33a are the same as the elastomer layer 11b in the first embodiment. In addition, except for the above-described points, the electrodes 32b and 33b are the same as the electrode 11a in the first embodiment.

Next, an example operation of the actuator <NUM> according to the sixth embodiment of the present technique will be described.

When a driving voltage is applied across the electrodes 32b and 33b facing each other with the elastomer layer 32a or the elastomer layer 33a therebetween, an attractive force due to the Coulomb force is generated between the electrodes 32b and 33b. Thus, the elastomer layer 32a or 33a disposed between the electrodes 32b and 33b is pressed in the thickness direction so as to be thinned. The stack <NUM> is elongated in the height direction (driving direction).

On the other hand, when the driving voltage applied across the electrodes 32b and 33b facing each other with the elastomer layer 32a or the elastomer layer 33a therebetween is released, an attractive force due to the Coulomb force is not generated between the electrodes 32b and 33b. Thus, the elastomer layers 32a and 33a return to their original thickness and contract to their original size because of the resilience of the elastomer layers 32a and 33a.

Next, an example method for manufacturing the actuator according to the sixth embodiment of the present technique will be described.

The electrode sheet <NUM> is produced in the following manner. First, a substrate is provided, and one surface of the substrate undergoes a peel treatment as needed. The substrate may be an inorganic substrate or may be a plastic substrate. In addition, the substrate may be a plate-like substrate or may be a sheet-like substrate.

Next, the coating material for elastomer-layer formation is applied to one surface of the substrate to form a coating film having an elongated rectangular shape. Here, applying includes printing. Subsequently, the coating film formed on one surface of the substrate is dried. The drying conditions are not limited and may be either natural drying or heat drying. Accordingly, the elastomer layer 32a is formed on one surface of the substrate. Subsequently, one surface of the elastomer layer 32a undergoes an adhesion improving treatment.

Next, the conductive coating material is applied to one surface of the elastomer layer 32a to form a coating film having an elongated rectangular shape. Subsequently, the coating film formed on one surface of the elastomer layer 32a is dried to form the electrode 32b. The drying conditions are not limited and may be either natural drying or heat drying. The electrode sheet <NUM> is produced accordingly.

The electrode sheet <NUM> is produced in the same manner as that for the electrode sheet <NUM>.

The stack <NUM> having an elongated rectangular shape is obtained by placing the electrode sheet <NUM> on the electrode sheet <NUM> in such a manner that the sides of the electrode sheet <NUM> overlap the respective sides of the electrode sheet <NUM> and the electrode 33b faces the elastomer layer 32a.

While the obtained stack <NUM> is uniaxially stretched in the longitudinal direction (circumferential direction), the stack <NUM> is spirally wound around the circumferential surface of the coil spring <NUM> in such a manner that one end of the stack <NUM> in the longitudinal direction is located on the inner circumferential side and the other end of the stack <NUM> is located on the outer circumferential side.

First, the sealing members <NUM> and <NUM> are fitted to the respective openings at the opposite ends of the stack <NUM> to close the openings at the opposite ends of the stack <NUM>. Next, the opposite ends of the stack <NUM> are held by the sealing members <NUM> and <NUM> or the opposite ends of the coil spring <NUM>. The actuator <NUM> illustrated in <FIG> and <FIG> is obtained accordingly.

In the actuator <NUM> according to the sixth embodiment, the stack <NUM> is subjected to a pre-strain in the circumferential direction (direction orthogonal to the driving direction) and no pre-strain in the height direction (driving direction). This configuration can improve the resistance dielectric breakdown while maintaining the displacement in the driving direction satisfactory. In addition, the pre-strain in the circumferential direction of the stack <NUM> makes thin the elastomer layer 32a and the elastomer layer 33a and thus can lower the driving voltage.

The stack <NUM> may be subjected to a pre-strain in each of the circumferential direction and the height direction. In this case, the pre-strain in the circumferential direction of the stack <NUM> is preferably larger than the pre-strain in the height direction of the stack <NUM>. More specifically, the pre-strain in the circumferential direction of the stack <NUM> is <NUM>% or more, preferably <NUM>% or more, more preferably <NUM>% or more, and still more preferably <NUM>% or more. The upper limit of the pre-strain in the circumferential direction of the stack <NUM> is preferably <NUM>% or less, and more preferably <NUM>% or less. Meanwhile, the pre-strain in the height direction of the stack <NUM> is less than <NUM>%, preferably <NUM>% or less, more preferably <NUM>% or less, still more preferably <NUM>% or less, and yet still more preferably <NUM>% or less.

The electrode sheets <NUM> and <NUM> may have a round tubular shape, and the electrode sheets <NUM> and <NUM> may be stacked on top of each other concentrically about the coil spring <NUM> to form the stack <NUM>.

As illustrated in <FIG>, an actuator <NUM> according to a seventh embodiment of the present technique which is not part of the present invention but useful for understanding the present invention includes a fiber-shaped roll <NUM>, a terminal 42A, which is drawn from one end portion of the roll <NUM>, and a terminal 42B, which is drawn from the other end portion of the roll <NUM>. It is noted that, in the seventh embodiment, the same parts as those in the sixth embodiment are denoted by the same characters, and the description thereof is omitted.

The roll <NUM> is subjected to a pre-strain in the circumferential direction and no pre-strain in the longitudinal direction. Here, the longitudinal direction of the roll <NUM> corresponds to the driving direction of the actuator <NUM>, and the circumferential direction of the roll <NUM> corresponds to the direction orthogonal to the driving direction of the actuator <NUM>.

The roll <NUM> is an example stack. The roll <NUM> is the same as the stack <NUM> in the sixth embodiment except that the roll <NUM> has no coil spring <NUM> in a central portion and has a fiber shape. The roll <NUM> may have or may not have a cavity at the center.

The terminals 42A and 42B have an elongated shape. As illustrated in <FIG>, one end of the terminal 42A is connected to the electrode 32b, and the other end is drawn from one end portion of the roll <NUM>. Furthermore, one end of the terminal 42B is connected to the electrode 33b, and the other end is drawn from the other end portion of the roll <NUM>.

In the actuator <NUM> according to the seventh embodiment, the roll <NUM>, which is an example stack, is subjected to a pre-strain in the circumferential direction (direction orthogonal to the driving direction) and no pre-strain in the longitudinal direction (driving direction). This configuration can improve the resistance to dielectric breakdown while maintaining the displacement in the driving direction satisfactory. In addition, the pre-strain in the circumferential direction of the roll <NUM> makes thin the elastomer layer 32a and the elastomer layer 33a and thus can lower the driving voltage.

The roll <NUM> may be subjected to a pre-strain in each of the circumferential direction and the longitudinal direction. In this case, the pre-strain in the circumferential direction of the roll <NUM> is preferably larger than the pre-strain in the longitudinal direction of the roll <NUM>. More specifically, the pre-strain in the circumferential direction and the pre-strain in the longitudinal direction of the roll <NUM> are preferably set at the same values as the pre-strain in the circumferential direction and the pre-strain in the longitudinal direction of the stack <NUM> in Modification <NUM> of the sixth embodiment, respectively.

The electrode sheets <NUM> and <NUM> may have a round tubular shape, and the electrode sheets <NUM> and <NUM> may be stacked on top of one another to form a fiber-shaped stack.

Referring to <FIG>, an example which is not part of the present invention but where the present technique useful for understanding the present invention is applied to a tactile presentation device will be described. The tactile presentation device is an example driving device and includes an actuator array <NUM>, a voltage source <NUM>, and a controller (not illustrated). It is noted that, in the eighth embodiment, the same parts as those in the seventh embodiment are denoted by the same characters, and the description thereof is omitted.

The actuator array <NUM> is an example driving member and includes a plurality of fiber-shaped actuators <NUM>. The actuators <NUM> are aligned such that the actuators <NUM> each have the same longitudinal direction and the circumferential surfaces of the adjacent actuators <NUM> face each other. A terminal 42A is connected to the voltage source <NUM> through a wire 413A, whereas a terminal 42B is connected to the voltage source <NUM> through a wire 413B. The voltage source <NUM> supplies a driving voltage at a predetermined frequency to each actuator <NUM> on the basis of a control signal from the controller (not illustrated). Here, the actuators <NUM> may be the same as that in the modifications of the seventh embodiment.

Referring to <FIG>, which are not part of the present invention but useful for understanding the present invention, an example operation of the tactile presentation device having the above-described structure will be described. Here, as illustrated in <FIG>, the case where the opposite ends of the actuator array <NUM> included in the actuator array <NUM> are supported by the respective supports <NUM> will be described.

As illustrated in <FIG>, the application of a driving voltage to the actuator <NUM> causes the actuator <NUM> to elongate and curve. As illustrated in <FIG>, the release of the driving voltage applied to the actuator <NUM> causes the actuator <NUM> to contract, return to its original length, and become straight.

In the tactile presentation device according to the eighth embodiment, the actuator array <NUM> includes a plurality of the actuators <NUM> according to the seventh embodiment. This configuration can improve the resistance of the tactile presentation device to dielectric breakdown and can lower power consumption.

Referring to <FIG>, another example which is not part of the present invention but where the present technique useful for understanding the present invention is applied to a tactile presentation device will be described. The tactile presentation device includes an actuator array <NUM>, a voltage source <NUM>, and a controller (not illustrated). It is noted that, in this modification, the same parts as those in the eighth embodiment are denoted by the same characters, and the description thereof is omitted.

The actuator array <NUM> includes a plurality of actuators <NUM>, which is two-dimensionally arranged in a grid-like pattern. More specifically, the actuator array <NUM> includes a first actuator group <NUM><NUM> and a second actuator group <NUM><NUM>, which is disposed on the first actuator group <NUM><NUM>. The first actuator group <NUM><NUM> includes a plurality of actuators <NUM> that is oriented in a first direction. In addition, the second actuator group <NUM><NUM> includes a plurality of actuators <NUM> that is oriented in a second direction orthogonal to the first direction. Here, the first direction and the second direction are not necessarily orthogonal to each other.

Referring to <FIG>, an example which is not part of the present invention but where the present technique useful for understanding the present invention is applied to a robot will be described. The robot includes a joint driving device <NUM> in the arm.

The joint driving device <NUM> is an example driving device and includes a columnar member <NUM>; a pair of fiber-shaped actuators 512A and 512B; a support <NUM>, which supports one end of the columnar member <NUM>, one end of the actuator 512A, and one end of the actuator 512B; a rotary member <NUM>, which is rotatably supported at the other end of the columnar member <NUM>; and a drive shaft <NUM>, which is supported by the rotary member <NUM>.

The columnar member <NUM>, the actuators 512A and 512B, and the support <NUM> are disposed in an upper arm part of the robot arm, and the support <NUM> is supported in the upper section of the upper arm part. The drive shaft <NUM> is disposed in a front arm part of the robot arm, and the front arm part moves with driving of the drive shaft <NUM>. The rotary member <NUM> is disposed in a joint section between the upper arm part and the front arm part of the robot arm and functions as a joint.

A linear member <NUM>, such as a wire, is stretched around the circumferential surface of the rotary member <NUM>. One end of the linear member <NUM> is connected to the other end of the actuator 512A, and the other end of the linear member <NUM> is connected to the other end of the actuator 512B. The rotary member <NUM> can rotate as a result of the expansion/contraction of the actuators 512A and 512B through the linear member.

The actuators 512A and 512B are the same as the actuator <NUM> according to the seventh embodiment or the modifications thereof.

The robot further includes a voltage source (not illustrated) and a controller (not illustrated). The voltage source is electrically connected to the actuators 512A and 512B through wires. The voltage source supplies a driving voltage to the actuators 512A and 512B on the basis of a control signal from the controller.

The robot having the above-described structure operates in the following manner. Specifically, the rotary member <NUM> rotates counterclockwise in <FIG> through the linear member <NUM> when the driving voltage is controlled so as to expand the actuator 512A and contract the actuator 512B by the length corresponding to the expansion of the actuator 512A. This drives the drive shaft <NUM> in the direction denoted by an arrow 517A. On the other hand, the rotary member <NUM> rotates clockwise in <FIG> through the linear member <NUM> when the driving voltage is controlled so as to contract the actuator 512A and expand the actuator 512B by the length corresponding to the contraction of the actuator 512A. This drives the drive shaft <NUM> in the direction denoted by an arrow 517B.

The robot according to the ninth embodiment which is not part of the present invention but useful for understanding the present invention includes the actuator <NUM> according to the seventh embodiment or the modifications thereof as the actuators 512A and 512B in the joint driving device <NUM>. This configuration can improve robot durability and can lower power consumption.

The seventh embodiment illustrates the structure of the robot including the joint driving device <NUM> in the arm. However, the robot may include the joint driving device <NUM> in the leg.

The present technique will be specifically described below by way of Examples, but the present technique is not limited only to these Examples.

The Samples <NUM> to <NUM> are not part of the present invention but useful for understanding the present invention.

The following materials are used for Samples <NUM> to <NUM> described below.

First, a first solution of <NUM>/L SEBS in toluene and a second solution of <NUM>/L SEBS-g-MA in toluene were prepared. It is noted that, since SEBS-g-MA takes a long time to dissolve, a mixture of SEBS-g-MA and toluene was subjected to ultrasonic agitation for <NUM> hour in the sealed state.

Next, a polymer solution was prepared by mixing the first solution and the second solution such that the first solution:the second solution = <NUM>:<NUM> in terms of mass ratio. Subsequently, a solution of <NUM> mass% polyaniline in toluene was prepared, and this solution was mixed with the polymer solution. At this time, the amount of polyaniline was adjusted to <NUM> mass% relative to the entire solution. After mixing, the mixture was subjected to ultrasonic agitation for about <NUM> minutes to provide a coating material for electrode formation. To use the coating material as an electrode for dielectric elastomer actuators (DEAs), <NUM> mass% or more of polyaniline is preferably added in terms of weight ratio.

Subsequently, a rectangular acrylic elastomer sheet subjected to no initial strain was provided, and the coating material for electrode formation was applied to the acrylic elastomer sheet by using a nylon brush and naturally dried. The intended rectangular sheet-like stack was obtained accordingly.

A stack was obtained in the same manner as that for Sample <NUM> except that the stack was stretched so as to be subjected to a pre-strain of <NUM>% (amount of stretching λ = <NUM>) per side.

The stacks of Samples <NUM> to <NUM> obtained as described above were evaluated in the following manner.

The film thickness of the elastomer layer was obtained from the cross-sectional SEM image.

The volume resistivity of the electrode on the stack surface was determined by the four-terminal method in accordance with JIS K <NUM>-<NUM>.

<FIG>, which is not part of the present invention but useful for understanding the present invention, shows the evaluation results of the film thickness of the elastomer layer and the volume resistivity for the stacks of Samples <NUM> to <NUM>. Since the elastomer is an incompressible material, the thickness of the elastomer layer decreases in inverse proportion to the square of the amount λ of biaxial stretching. The resistance of the conformable electrode increases with increasing amount of stretching. This is considered to be because the electrode becomes thinner when stretched. It is noted that actual application of a driving voltage to the stacks of Samples <NUM> to <NUM> produced by stretching showed that the stacks of Samples <NUM> to <NUM> operated as actuators.

The Sample <NUM> is in accordance with the present invention.

First, silicone was applied by the bar coating method to form a silicone elastomer sheet having a thickness of <NUM>. Next, the surface of the sheet was subjected to excimer cleaning for <NUM> minutes, and a silane coupling agent was then applied to the sheet to form a coating film. Subsequently, the same coating material (aniline/SEBS/SEBS-g-MA mixture) for electrode formation as that in Sample <NUM> was applied onto the coating film and dried to form an electrode. The intended stack was obtained accordingly.

First, the electrode was subjected to the cross-cut test in accordance with JIS K <NUM>-<NUM>-<NUM>:<NUM>. Next, the condition of the cross-cut section after the test was evaluated on the basis of scales <NUM> to <NUM> described above in JIS K <NUM>-<NUM>-<NUM>:<NUM>, and the adhesion was graded on the basis of the evaluation results in accordance with the following criteria. As a result, the adhesion was determined to be "good".

It is noted that, in the case of scales <NUM> to <NUM>, the electrode may be peeled when stretched.

The above-described test results indicate that the adhesion between the elastomer sheet and the electrode can be improved by applying a silane coupling agent to the surface of the silicon sheet after pretreating the surface of the silicon sheet by means of excimer cleaning or the like. It is noted that the adhesion can also be improved by subjecting the surface of the elastomer sheet to only excimer cleansing or UV cleansing.

In Sample <NUM> described above, a trialkoxysilane coupling agent was used as a silane coupling agent. However, the same adhesion improving effect is also obtained by using a dialkoxysilane coupling agent, a mono-alkoxy silane coupling agent, or the like other than a trialkoxysilane coupling agent. Moreover, an acrylic group, a methacrylic group, an epoxy group, a vinyl group, a styryl group, an isocyanate group, a mercapto group, or the like can be used as a terminal functional group according to the type of polymer.

The following embodiments are not part of the present invention but useful for understanding the present invention.

First, as illustrated in <FIG>, a circular silicone elastomer sheet (elastomer layer) 611a having a thickness of <NUM> was provided, and the elastomer sheet 611a was biaxially stretched in the X- and Y-axis directions. In this case, as shown in Table <NUM>, the stretching ratio in the X- and Y-axis directions was changed for each sample, and the amount of stretching (stretching ratio) was adjusted to <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. Next, as illustrated in <FIG>, the peripheral portion of the biaxially stretched elastomer sheet 611a was fixed to a ring-shaped fixing jig <NUM> having an inner diameter of <NUM>. Subsequently, as illustrated in <FIG>, a coating material containing carbon black powder was applied to a central portion of each of both surfaces of the elastomer sheet 611a to form circular electrodes 611b having a diameter of <NUM>. The intended actuators were obtained accordingly.

First, as illustrated in <FIG>, an elliptical silicone elastomer sheet (elastomer layer) 611a having a thickness of <NUM> was provided, and the elastomer sheet 611a was uniaxially stretched in the Y-axis direction (minor axis direction). In this case, as shown in Table <NUM>, the stretching ratio in the Y-axis directions was changed for each sample, and the amount of stretching (stretching ratio) was adjusted to <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. The subsequent steps were performed in the same manner as those for Samples <NUM>-<NUM> to <NUM>-<NUM>. The intended actuators were obtained accordingly.

The actuators of Samples <NUM>-<NUM> to <NUM>-<NUM> and <NUM>-<NUM> to <NUM>-<NUM> obtained as described above were evaluated for their rigidity and dielectric breakdown strength. First, as illustrated in <FIG>, the voltage applied to the electrodes 611b and 611b was gradually increased, and the voltage (hereinafter referred to as "dielectric withstanding voltage") V and the electrode widths x and y immediately before dielectric breakdown were measured. Next, the dielectric breakdown strength E, the rigidity EX in the X-axis direction, and the rigidity EY in the Y-axis direction were calculated from the results on the basis of the following formula.

It is noted that, in the formula, V: dielectric withstanding voltage, t<NUM>: initial thickness, x: electrode width in X-axis direction, y: electrode width in Y-axis direction, x<NUM>: electrode width in X-axis direction in initial state, and y<NUM>: electrode width in Y-axis direction in initial state. Here, the initial state means the state before voltage application. <MAT> <MAT>.

It is noted that, in the formula, σ: Maxwell stress, εX: strain in X-axis direction, and εY: strain in Y-axis direction, which are obtained from the following respective formulas. <MAT> <MAT> <MAT>.

Table <NUM> shows the evaluation results of the actuators of Samples <NUM>-<NUM> to <NUM>-<NUM>.

It is noted that the expression "AE-B" in the section of "permittivity" in Tables <NUM> and <NUM> means A × <NUM>-B.

<FIG> shows the relationship between the biaxial stretching ratio and the rigidity. <FIG> shows the relationship between the biaxial stretching ratio and the dielectric breakdown strength. <FIG> shows the relationship between the uniaxial stretching ratio and the rigidity. <FIG> shows the relationship between the uniaxial stretching ratio and the dielectric breakdown strength.

<FIG> reveal the following facts. Specifically, in a case where the elastomer sheet 611a is biaxially stretched in the X- and Y-axis directions, the rigidity increases with increasing biaxial stretching ratio. In addition, the dielectric breakdown strength increases with increasing biaxial stretching ratio.

<FIG> reveal the following facts. Specifically, in a case where the elastomer sheet 611a is uniaxially stretched in the y-axis direction, the rigidity in the X-axis direction is substantially constant with increasing uniaxial stretching ratio. However, the rigidity in the Y-axis direction increases with increasing uniaxial stretching ratio. In addition, the dielectric breakdown strength increases with increasing uniaxial stretching ratio.

Therefore, uniaxial stretching of the actuator in the direction perpendicular to the driving direction can improve the resistance to dielectric breakdown while maintaining the displacement in the driving direction satisfactory.

First, as illustrated in <FIG>, a square silicone elastomer sheet 621a having a size of <NUM> × <NUM> was provided. Next, as illustrated in <FIG>, a rectangular electrode 621b having a size of <NUM> × <NUM> was formed on a central portion of the elastomer sheet 621a by means of spray coating.

The process for forming the electrode 621b will be described below in detail.

Nanocarbon and isopropanol were mixed at a mass ratio of <NUM>:<NUM> (nanocarbon:isopropanol). The mixture was placed in a polypropylene case, <NUM> capacity, (AS ONE Corporation, Aiboy, wide mouth, PP) together with <NUM> zirconia beads, <NUM> in diameter, and agitated by shaking for <NUM> minutes. It is noted that DENKA BLACK Li (Li-<NUM>, mean particle size: <NUM>) available from Denka Company Limited was used as nanocarbon. In addition, Vortex was used for shaking.

A solution of <NUM> mass% (in terms of mass ratio) elastomer (binder) in toluene was prepared. A silicone resin (available from Dow Corning Toray Co. , MS1003) was used as an elastomer.

First, the carbon filler solution and the elastomer solution were mixed such that the mass ratio (carbon filler:elastomer) of the carbon filler to the elastomer was <NUM>:<NUM>, and zirconia beads were added to the mixture, followed by agitation for <NUM> minutes. Subsequently, zirconia beads were removed. A carbon-silicone solution was obtained accordingly.

The carbon-silicone solution obtained as described above was sprayed onto the elastomer sheet 621a from a distance of about <NUM> by using an air spray gun (FS110 round pattern type) available from Meiji Air Compressor Mfg. so as to form a uniform coating as visually observed. The air flow rate was set to the conditions obtained as follows: connecting a houseline of about <NUM> MPa to the air spray gun; and releasing the gas flow control nozzle of FS110 by one and half turns. Accordingly, the electrode 621b having a surface roughness (peak to peak distance) of about <NUM> and a thickness of about <NUM> was formed. The intended actuator is obtained accordingly.

An actuator was obtained in the same manner as that for Sample <NUM>-<NUM> except that DENKA BLACK Li (Li-<NUM>, mean particle size: <NUM>) available from Denka Company Limited was used as nanocarbon.

First, the end portions of the actuator were fixed so as to prevent buckling, and a four-terminal probe was then brought into contact with the upper surface (the surface of the electrode 621b) of the actuator in the non-stretched state (the stretching ratio in the X-axis direction: <NUM>, the stretching ratio in the Y-axis direction: <NUM>) to measure the resistance. Next, the film thickness of the electrode 621b was measured with a profilometer to determine the cross-sectional area of the electrode 621b. The resistivity of the electrode 621b was then calculated by using the resistance and the cross-sectional area of the electrode 621b obtained as described above.

<FIG> shows the relationship between the type of nanocarbon used in Samples <NUM>-<NUM> to <NUM>-<NUM> and the resistivity. <FIG> indicates that the electrode has excellent conductivity when the mean particle size of nanocarbon is <NUM> or more and <NUM> or less.

Actuators were obtained in the same manner as that for Sample <NUM>-<NUM> except that, in the step of preparing the solution, the carbon filler solution and the elastomer solution were mixed such that the mass ratio (carbon filler:elastomer) of a carbon filler (available from Denka Company Limited, DENKA BLACK Li (Li-<NUM>)) to an elastomer (available from Dow Corning Toray Co. , MS1003) was <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, and <NUM>:<NUM>.

First, a pair of elastomer sheets <NUM> was prepared by cutting a double-sided adhesive acrylic elastomer sheet (available from <NUM>, VHB4905J) into a hollow rectangular shape. Subsequently, as illustrated in <FIG>, a portion of the elastomer sheet 621a on which no electrodes 621b were formed was sandwiched between the pair of elastomer sheets <NUM> to form a section to be fixed to a jig. Next, as illustrated in <FIG>, the four sides of the elastomer sheet <NUM> were fixed to a biaxial stretching jig <NUM> and, as illustrated in <FIG>, the elastomer sheet <NUM> was then biaxially stretched (the stretching ratio in the X-axis direction: <NUM> to <NUM>, the stretching ratio in the Y-axis direction: <NUM> to <NUM>).

Next, a digital multimeter (<NUM> Digital Multi-mater available from Keithley Instruments) equipped with a four-terminal probe <NUM> in accordance with JIS K <NUM> standard was provided and, as illustrated in <FIG>, the four-terminal probe <NUM> was brought into contact with the upper surface (the surface of the electrode 621b) of the actuator in the stretched state to measure the resistance. Next, the film thickness of the electrode 621b was measured with a profilometer to determine the cross-sectional area of the electrode 621b. The resistivity of the electrode 621b was then calculated by using the resistance and the cross-sectional area of the electrode 621b obtained as described above. It is noted that the resistivity was calculated in each <NUM>-times increment of the stretching ratio.

The resistivity was measured in the same manner as that in the evaluation of the conductivity in biaxial stretching described above except that the stretching was uniaxial stretching and the stretching ratio was in the range from <NUM> to <NUM>.

<FIG> showns the relationship between the stretching ratio and the resistivity. <FIG> shows the relationship between the area change caused by stretching and the resistivity. <FIG> indicate that the resistance change corresponding to stretching does not depend on the magnitude of stretching in one axial direction, but depends on the area change of the entire sheet.

In Samples <NUM>-<NUM> to <NUM>-<NUM> and <NUM>-<NUM> to <NUM>-<NUM> described below, the parts corresponding to those in Sample <NUM>-<NUM> are denoted by the same characters.

Electrodes 611b and silicone elastomer sheets 611a having a thickness of <NUM> were alternately stacked on top of one another to form a stack. In addition, as shown in Table <NUM>, the biaxial stretching ratio in the X-axis direction and the Y-axis direction was set to <NUM>, <NUM>, and <NUM>. It is noted that, in stacking, the elastomer sheet 611a was sandwiched between the electrodes 611b, and the number of the elastomer sheets 611a was <NUM>. Moreover, the electrodes 611b were produced so as to contain nanocarbon (available from Denka Company Limited, DENKA BLACK Li (Li-<NUM>)) and a silicone elastomer (available from Dow Corning Toray Co. , MS1003) at a mass ratio (nanocarbon:silicone elastomer) of <NUM>:<NUM>. Actuators were obtained in the same manner as that for Sample <NUM>-<NUM> except for the above-described points.

Actuators were obtained in the same manner as that for Samples <NUM>-<NUM> to <NUM>-<NUM> except that the number of the elastomer sheets 611a was <NUM>.

The dielectric breakdown strength of the actuators of Samples <NUM>-<NUM> to <NUM>-<NUM> and <NUM>-<NUM> to <NUM>-<NUM> obtained as described above was calculated in the same manner as that in the evaluation of the dielectric breakdown strength of Sample <NUM>-<NUM>.

<FIG> shows the relationship between the biaxial stretching ratio and the dielectric breakdown strength. <FIG> indicates that the dielectric breakdown strength of the actuators including <NUM> stacked elastomer sheets 611a increases with increasing amount of stretching like the dielectric breakdown strength of the actuators including a single elastomer sheet 611a.

The area change of Samples <NUM>-<NUM> and <NUM>-<NUM> (stretched samples including <NUM> stacked elastomer sheets 611a) upon application of a <NUM> MV/m electric field was obtained.

Table <NUM> shows the evaluation results of the actuators of Samples <NUM>-<NUM> and <NUM>-<NUM>.

Claim 1:
An actuator (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising:
a holding unit (<NUM>, (<NUM>, <NUM>, <NUM>), <NUM>, <NUM>) configured to hold a stack (<NUM>, <NUM>, <NUM>), wherein the holding unit (<NUM>, (<NUM>, <NUM>, <NUM>), <NUM>, <NUM>) holds the stack (<NUM>, <NUM>, <NUM>) in a pre-strained state in which the stack (<NUM>, <NUM>, <NUM>) is subjected to a pre-strain of <NUM>% or more at least in one direction; and
the stack (<NUM>, <NUM>, <NUM>) including:
an elastomer layer (11b, 21b, 32a, 33a),
an elastic electrode (11a, 21a, 32b, 33b) disposed on each surface of the elastomer layer (11b, 21b, 32a, 33a),
wherein the electrodes (11a, 21a, 32b, 33b) and the elastomer layer (11b, 21b, 32a, 33a) are stacked alternately and repeatedly, characterized in that
a silane coupling agent is disposed between the elastomer layer (11b, 21b, 32a, 33a) and the electrode (11a, 21a, 32b, 33b) for improving an adhesion of an interface between the elastomer layer (11b, 21b, 32a, 33a) and the electrode (11a, 21a, 32b, 33b).