JP2010153821A - Conductive film, transducer having the same, and flexible wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive film that is expandable and contractible and whose electrical resistance is hard to increase during expansion, a flexible transducer, and a flexible wiring board. <P>SOLUTION: The conductive film 100 is constituted by a conductive layer 101 having an elastomer and a conductive material that is filled in the elastomer, and a protection layer 102 made of the elastomer that is disposed so as to cover the conductive layer 101. At least either of an electrode or wiring of a transducer is formed by the conductive film. At least part of the wiring of a flexible wiring board is formed by the conductive film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrode that can be expanded and contracted, a conductive film suitable for wiring and the like, a transducer including the conductive film, and a flexible wiring board.

  For example, as a means for detecting the deformation of a member, the magnitude of a load acting on the member, etc., development of a flexible sensor using a conductive resin or an elastomer has been advanced. In addition, actuators using polymer materials such as dielectric elastomers are highly flexible, lightweight, and easy to miniaturize, so their use in various fields such as artificial muscles, medical instruments, and fluid control is being studied. . For example, an actuator can be configured by sandwiching a dielectric film made of a dielectric elastomer between a pair of electrodes (see, for example, Patent Documents 1 and 2).

  These flexible sensors and actuators are required to be able to follow the deformation of a base material made of an elastomer or the like, a dielectric film, and the like of electrodes and wiring. That is, for example, in an actuator, the dielectric film expands and contracts depending on the applied voltage. For this reason, it is desirable that the electrodes arranged on the front and back of the dielectric film can be expanded and contracted according to the expansion and contraction of the dielectric film so as not to hinder the movement of the dielectric film. For these reasons, a conductive material in which conductive carbon or metal powder is mixed with a binder such as an elastomer is currently used for electrodes and wiring.

JP 2008-070327 A Special table 2003-506858 JP-A-9-289361 JP 2008-124425 A

  The specific resistance of conductive carbon is relatively large, about 0.1 to 1 Ωcm. For this reason, when a conductive material in which conductive carbon is blended in a binder such as an elastomer is used, there is a problem that the electrical resistance of the electrode or the like increases. If the electrical resistance of the electrode or the like is large, the element is likely to deteriorate due to heat generated by the internal resistance. In addition, the responsiveness of the actuator may be reduced due to the generation of reactance components in the high frequency region. Also, if the internal resistance is too high for the detection signal, the resolution of the sensor may be reduced.

  In this respect, the specific resistance of the metal powder such as silver is as small as 0.001 Ωcm or less. However, generally, the metal powder has a larger particle size than the conductive carbon. Moreover, since it is hard to aggregate, a conduction path | route is hard to be formed. Therefore, in order to obtain desired conductivity, it is necessary to highly fill the binder with metal powder. A conductive material in which a metal powder is highly filled in a binder has high elastic modulus and poor flexibility. For this reason, for example, when used for an electrode of an actuator, it cannot follow the expansion and contraction of the dielectric film, and the movement of the dielectric film is likely to be hindered. Further, in addition to being able to expand and contract, electrodes and wirings such as flexible sensors and actuators are required to have a small change in electrical resistance when expanded. However, according to the conductive material in which the binder is highly filled with the metal powder, when the elongation is large, stress concentrates on the interface between the binder and the metal powder, and cracks are generated. As a result, the electrical resistance of the electrodes and the like increases significantly. Further, once a crack is generated, stress is more likely to be concentrated around the crack. Therefore, there is a possibility that the electrode or the like may be broken by the extension. In addition, as a method of reducing the stress concentration at the interface between the binder and the metal powder, a method of improving the adhesion with the binder by subjecting the metal powder to a surface treatment can be considered. However, the surface treatment increases the contact resistance between the metal powders, resulting in an increase in electrical resistance.

  On the other hand, in various wiring boards, by covering the wiring with a protective film, migration is suppressed and insulation between adjacent wirings is ensured. For example, according to Patent Document 3, the wiring is covered with carbon. According to Patent Document 4, the wiring is covered with a thermosetting resin paste. However, both protective films of carbon and thermosetting resins are hard and poor in flexibility. Therefore, it is unsuitable for an expandable electrode and wiring. For example, if the electrode of the actuator is covered with a protective film made of a thermosetting resin, the electrode cannot follow the expansion and contraction of the dielectric film, which may hinder the movement of the dielectric film.

  This invention is made | formed in view of such a situation, and makes it a subject to provide the electrically conductive film which can be expanded-contracted and an electrical resistance does not increase easily at the time of expansion | extension. Another object of the present invention is to provide a flexible transducer and a flexible wiring board by using such a conductive film.

  (1) In order to solve the above-described problems, the conductive film of the present invention is disposed so as to cover the conductive layer having an elastomer and a conductive material filled in the elastomer, and the conductive layer. And a protective layer made of an elastomer.

  Both the conductive layer and the protective layer constituting the conductive film of the present invention have an elastomer as a base material. Therefore, the conductive film of the present invention is flexible and can be expanded and contracted. Therefore, the followability with respect to deformation of the base material, the dielectric film, etc. is excellent. Moreover, the protective layer is arrange | positioned so that a conductive layer may be coat | covered. The protective layer serves to protect and reinforce the conductive layer. That is, when the conductive film of the present invention is stretched, the generated stress is dispersed in the protective layer and the conductive layer. For this reason, stress concentration at the interface between the elastomer and the conductive material at the time of stretching can be reduced as compared with that of the conductive layer alone. Thereby, generation | occurrence | production of the crack in the surface of a conductive layer is suppressed. Therefore, even if the electrically conductive film of this invention is extended | stretched, an electrical resistance does not increase easily. In addition, there is little risk of breakage.

  (2) Moreover, the transducer of this invention is equipped with the electrically conductive film of the said invention as at least one of an electrode and wiring, It is characterized by the above-mentioned.

  A transducer is a device that converts one type of energy into another type of energy. The transducer includes, for example, an actuator and a sensor that perform conversion between electric energy and mechanical energy. According to the transducer of the present invention, at least one of the electrode and the wiring (hereinafter referred to as “electrode etc.” as appropriate) is made of the conductive film of the present invention. Therefore, even when the member on which the electrode or the wiring is formed is deformed, the electrode or the like expands and contracts following the deformation. For this reason, the movement of the transducer is difficult to be hindered by the electrode or the like. Moreover, even if it extends | stretches, the electrical resistance of an electrode etc. does not increase easily. Therefore, the responsiveness is good. Furthermore, even when the expansion and contraction is repeated, there is little possibility that the electrode or the like breaks. In addition, since the heat generated by the internal resistance is small, the electrodes and the like are hardly deteriorated. Therefore, the transducer of the present invention is excellent in durability.

  (3) The flexible wiring board of the present invention is characterized in that at least a part of the wiring is made of the conductive film according to any one of claims 1 to 9.

  According to the flexible wiring board of the present invention, the wiring expands and contracts following the deformation of the base material. Even if the wiring is extended, there is little decrease in conductivity, and even when the expansion and contraction are repeated, heat generation due to internal resistance is small. Therefore, the flexible wiring board of the present invention is excellent in durability.

It is a cross-sectional schematic diagram of an example of the electrically conductive film of this invention. It is a cross-sectional schematic diagram of another example of the electrically conductive film of this invention. It is a top view of the capacitive type sensor which is one Embodiment of the transducer of this invention. It is IV-IV sectional drawing of FIG. It is a cross-sectional schematic diagram of the actuator which is one Embodiment of the transducer of this invention, Comprising: (a) shows an OFF state, (b) shows an ON state, respectively. It is a cross-sectional schematic diagram of the electric power generation transducer which is one Embodiment of the transducer of this invention, Comprising: (a) shows at the time of expansion | extension, (b) shows the time of contraction, respectively. It is an upper surface transmission figure of the flexible wiring board which is one Embodiment of this invention.

  Hereinafter, embodiments of the conductive film, the transducer including the conductive film, and the flexible wiring board of the present invention will be described in order.

<Conductive film>
The conductive film of the present invention comprises a conductive layer and a protective layer. The conductive layer has an elastomer and a conductive material filled in the elastomer. In this specification, “elastomer” includes rubber and thermoplastic elastomer. The type of elastomer is not particularly limited, but from the viewpoint of being flexible at room temperature, for example, those having a glass transition temperature (Tg) of −20 ° C. or lower are suitable. Examples of such an elastomer include acrylic rubber, urethane rubber, hydrin rubber, and the like. For example, the acrylic rubber desirably contains 50 mol% or more of an acrylate monomer unit having an alkyl group having 4 or more carbon atoms. When the alkyl group is large (the number of carbon atoms is large), the crystallinity is lowered, so that the elastic modulus of the acrylic rubber becomes lower.

  Further, the elastomer may contain additives such as a plasticizer, a processing aid, a crosslinking agent, a vulcanization accelerator, a vulcanization aid, an antiaging agent, a softening agent, and a colorant. For example, when a plasticizer is added, the processability of the elastomer is improved and the flexibility can be further improved. As the plasticizer, known organic acid derivatives such as phthalic acid diester, phosphoric acid derivatives such as tricresyl phosphate, adipic acid diester, chlorinated paraffin, polyether ester and the like may be used.

  The conductive material may be appropriately selected from carbon materials such as carbon black and carbon nanotubes, and metal materials such as silver, gold, copper, and nickel. For example, one or more metal powders selected from silver, gold, and copper having a small specific resistance may be employed. Further, a mixture of silver powder and carbon black may be used. Carbon black has high adhesion to the elastomer. Moreover, since it is easy to aggregate, a conduction | electrical_connection path | route is easy to be formed. Therefore, when carbon black is mixed with silver powder, even when the silver powder is separated during stretching, the carbon black enters the gap between the silver powder, and a conduction path is easily secured. Therefore, an increase in electrical resistance during expansion can be suppressed. In this case, from the viewpoint of reducing the electric resistance, it is desirable that the filling amount of the silver powder is 30% by volume or more when the entire conductive material is 100% by volume.

  What is necessary is just to determine the filling amount of a electrically conductive material so that desired electroconductivity may be obtained. For example, it is desirable to set it as 300 to 1500 mass parts with respect to 100 mass parts of an elastomer. More preferably, it is 400 parts by mass or more and 1000 parts by mass or less.

  The protective layer is made of an elastomer and is disposed so as to cover the conductive layer. The protective layer may cover the entire surface of the conductive layer, but may cover a part of the surface of the conductive layer, for example, an embodiment in which only one surface of the conductive layer is covered.

  The kind of elastomer which comprises a protective layer is not specifically limited. It may be the same as or different from the elastomer constituting the conductive layer. For example, as the flexible elastomer, one or more selected from polyurethane, acrylic, polyvinyl chloride, polyester, and polyether ester are preferable. Similarly to the above, the elastomer may contain additives such as a plasticizer, a processing aid, a crosslinking agent, a vulcanization accelerator, a vulcanization aid, an anti-aging agent, a softening agent, and a colorant.

  Moreover, if carbon black is blended in the elastomer and predetermined conductivity is imparted to the protective layer, it is effective in suppressing migration. For example, a potential difference is likely to occur between adjacent wirings. When moisture intervenes there, the metal component elutes from the wiring (anode) on the high potential side to generate metal ions. The generated metal ions move toward the wiring (cathode) on the low potential side. When such migration (migration) of metal ions occurs, metal is deposited on the wiring on the cathode side, and it becomes difficult to maintain insulation between the wirings. When the conductive film of the present invention is used as a wiring, if the protective layer contains carbon black and imparts conductivity, the voltage gradient between the conductive layer and the protective layer becomes gentle. Therefore, the movement of metal ions can be suppressed.

In order to relieve stress of the conductive layer due to stretching, it is desirable that the protective layer is harder than the conductive layer and difficult to stretch. The hardness of the conductive layer and the protective layer depends on the elastic modulus of the material constituting each layer and the thickness of the layer. Thus, for example, the elastic modulus of the conductive layer E _e, the cross-sectional area as S _e, E the modulus of the protective layer _c, and the cross-sectional area in the case of the S _c, it is desirable to satisfy the following formula (I).
E _{e Se} / E _{c Sc} <1 (I)
Here, the “cross-sectional area” of the conductive layer and the protective layer means a cross-sectional area when each layer is cut perpendicularly to the stretching direction. Hereinafter, the “cross-sectional area” of each layer will be specifically described with reference to schematic cross-sectional views of the conductive film of the present invention.

  In FIG. 1, the cross-sectional schematic diagram of an example of the electrically conductive film of this invention is shown. FIG. 1 is a schematic diagram for explaining the cross-sectional areas of the conductive layer and the protective layer, and the conductive film of the present invention is not limited at all in terms of the arrangement of the protective layer relative to the conductive layer, the thickness of each layer, and the like. Not what you want.

As shown in FIG. 1, the conductive film 100 includes a conductive layer 101 and a protective layer 102. The conductive film 100 has a strip shape extending in the front-back direction. The upper surface, the lower surface, and the left and right side surfaces of the conductive layer 101 are all covered with the protective layer 102. The conductive film 100 expands and contracts in the front-back side direction. Therefore, the cross-sectional area of the conductive layer 101 is indicated by a vertical cross-sectional area S _e relative expansion and contraction direction of the conductive film 100. Further, the cross-sectional area of the protective layer 102 is indicated by a vertical cross-sectional area S _c with respect to expansion and contraction direction of the conductive film 100.

  The conductive film of the present invention can be formed on the surface of a substrate, a dielectric film or the like depending on the application. Examples of the base material include a flexible resin film made of polyimide, polyethylene, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and an elastomer sheet. When the conductive film of the present invention is formed on the surface of an elastic member that can be elastically deformed by pulling, bending, etc., it is possible to exhibit the effect that the flexibility is high and the electrical resistance hardly increases even when stretched. it can. Here, the elastic member includes a dielectric film in an actuator or the like. The thin-film elastic member can be manufactured, for example, by coating a paint for forming the elastic member on a substrate having releasability, and then cutting it into a desired shape and peeling it off.

When the conductive film of the present invention is formed on the surface of the elastic member, it is desirable that one surface of the conductive layer is in contact with the elastic member and the other surface of the conductive layer is covered with a protective layer. According to this aspect, the elastic member in contact with one surface of the conductive layer plays the same role as the protective layer. In this case, the elastic modulus of the conductive layer is E _e , the cross-sectional area is S _e , the elastic modulus of the protective layer is E _c , the cross-sectional area is S _c , the elastic modulus of the elastic member is E _s , and the elastic member in the conductive film formation portion cross-sectional area of the when the S _s, it is desirable to satisfy the following formula (II). Furthermore, it is desirable to satisfy the following formula (III).
_{E e S e / (E c} S c + E s S s) <1.2 ··· (II)
_{E e S e / (E c} S c + E s S s) <1 ··· (III)
Here, the “cross-sectional area” of the conductive layer, the protective layer, and the elastic member means the area of a cross section when each is cut perpendicularly to the expansion / contraction direction, as described above. Hereinafter, each “cross-sectional area” will be specifically described with reference to a schematic cross-sectional view of the conductive film of this embodiment.

  In FIG. 2, the cross-sectional schematic diagram of an example of the electrically conductive film of this aspect is shown. FIG. 2 is a schematic diagram for explaining the cross-sectional areas of the conductive layer, the protective layer, and the elastic member. Regarding the arrangement of the protective layer with respect to the conductive layer, the thickness of the conductive layer, the protective layer, the elastic member, etc. The conductive film of the present invention is not limited at all.

As shown in FIG. 2, the conductive film 100 is formed on the upper surface of the elastic member 103. The conductive film 100 has a strip shape extending in the front-back direction. The conductive film 100 includes a conductive layer 101 and a protective layer 102. The upper surface and the left and right side surfaces of the conductive layer 101 are covered with a protective layer 102. The lower surface of the conductive layer 101 and the lower surface of the protective layer 102 are in contact with the elastic member 103. The conductive film 100 expands and contracts in the front-back side direction. Therefore, the cross-sectional area of the conductive layer 101 is indicated by a vertical cross-sectional area S _e relative expansion and contraction direction of the conductive film 100. Further, the cross-sectional area of the protective layer 102 is indicated by a cross-sectional area S _c (C-shape opened downward) in a direction perpendicular to the expansion / contraction direction of the conductive film 100. Further, the cross-sectional area of the elastic member 103, among the cross-sectional area in the direction perpendicular to the stretching direction of the conductive film 100, as shown in partial S _s corresponding to the formation portion of the conductive film 100 (in FIG. 2, the dashed line (Indicated by hatching). That is, the cross-sectional area S _s of the elastic member 103 is a region surrounded by the contact interface between the elastic member 103 and the conductive film 100 and the thickness (the length in the stacking direction of the conductive film 100 and the elastic member 103). .

  The electrically conductive film of this invention can be manufactured as follows, for example. First, paints for forming the conductive layer and the protective layer are prepared. For example, the conductive layer coating material may be prepared by adding a conductive material to a solution obtained by dissolving a polymer for an elastomer in a solvent together with a predetermined additive, followed by stirring and mixing. Next, the prepared coating material for a conductive layer is applied to a substrate or the like and dried by heating. Next, a protective layer coating is applied so as to cover the surface of the formed conductive layer, and dried by heating. In this case, the crosslinking reaction for the elastomer may be allowed to proceed at the time of drying the paint.

  Here, various known methods can be adopted as the coating method of the paint. For example, in addition to printing methods such as inkjet printing, flexographic printing, gravure printing, screen printing, pad printing, and lithography, dipping, spraying, bar coating, and the like can be given. For example, when a printing method is employed, it is possible to easily separate the applied part and the non-applied part. Also, printing of large areas, thin lines, and complicated shapes is easy. Among the printing methods, a screen printing method is preferable because a conductive paint having a high viscosity can be used and the coating thickness can be easily adjusted.

  In addition, an elastomer composition obtained by kneading a polymer for an elastomer (including appropriate additives) and a conductive material using a pressure kneader such as a kneader or a Banbury mixer, two rolls, etc., is molded or extruded. By doing so, you may manufacture a conductive layer. In this case, the surface of the manufactured conductive layer may be appropriately covered with a protective layer to form a conductive film.

  The conductive film of the present invention is suitable for transducer electrodes and wiring, flexible wiring board wiring, and the like. Hereinafter, first, embodiments of an elastomer sensor, an actuator, and a power generation transducer will be described as examples of a transducer including the conductive film of the present invention, and then an embodiment of a flexible wiring board will be described. In the transducer and flexible wiring board of the present invention, it is desirable to employ the preferred embodiment of the conductive film of the present invention described above.

<Elastomer sensor>
An embodiment of a capacitive sensor will be described as an example of an elastomer sensor using the conductive film of the present invention for electrodes and wiring. First, the configuration of the capacitive sensor of this embodiment will be described. FIG. 3 shows a top view of the capacitive sensor. FIG. 4 is a sectional view taken along the line IV-IV in FIG. As shown in FIGS. 3 and 4, the capacitive sensor 1 includes a dielectric film 10, a pair of electrodes 11a and 11b, and wirings 12a and 12b.

  The dielectric film 10 is made of urethane rubber and has a strip shape extending in the left-right direction. The thickness of the dielectric film 10 is about 300 μm.

  The electrode 11a has a rectangular shape. Three electrodes 11 a are formed on the upper surface of the dielectric film 10. Similarly, the electrode 11b has a rectangular shape. Three electrodes 11b are formed on the lower surface of the dielectric film 10 so as to face the electrode 11a with the dielectric film 10 interposed therebetween. Thus, three pairs of electrodes 11a and 11b are arranged with the dielectric film 10 in between. The electrodes 11a and 11b are made of the conductive film of the present invention.

  That is, the electrode 11a includes a conductive layer 110a and a protective layer 111a. The upper surface and the left and right side surfaces of the conductive layer 110a are covered with a protective layer 111a. The lower surface of the conductive layer 110 a and the lower surface of the protective layer 111 a are in contact with the dielectric film 10. Similarly, the electrode 11b includes a conductive layer 110b and a protective layer 111b. The lower surface and the left and right side surfaces of the conductive layer 110b are covered with a protective layer 111b. The upper surface of the conductive layer 110 b and the upper surface of the protective layer 111 b are in contact with the dielectric film 10.

  The wiring 12a is connected to each of the electrodes 11a formed on the upper surface of the dielectric film 10. The electrode 11a and the connector 14 are connected by the wiring 12a. The wiring 12 a is formed on the upper surface of the dielectric film 10. Similarly, the wiring 12b is connected to each of the electrodes 11b formed on the lower surface of the dielectric film 10 (indicated by a dotted line in FIG. 3). The electrode 11b and the connector (not shown) are connected by the wiring 12b. The wiring 12 b is formed on the lower surface of the dielectric film 10. The wirings 12a and 12b are made of the conductive film of the present invention.

  That is, the wiring 12a includes the conductive layer 120a and the protective layer 121a. The upper surface and the left and right side surfaces of the conductive layer 120a are covered with a protective layer 121a. The lower surface of the conductive layer 120a and the lower surface of the protective layer 121a are in contact with the dielectric film 10. Although not shown, the wiring 12b has the same configuration as the wiring 12a.

  Next, the movement of the capacitive sensor 1 will be described. For example, when the capacitive sensor 1 is pressed from above, the dielectric film 10 and the electrode 11a are united and curved downward. The thickness of the dielectric film 10 is reduced by the compression. As a result, the capacitance between the electrodes 11a and 11b increases. By this capacitance change, deformation due to compression is detected.

  Next, the function and effect of the capacitive sensor 1 of the present embodiment will be described. According to the capacitive sensor 1 of the present embodiment, the dielectric film 10, the electrodes 11a and 11b, and the wirings 12a and 12b are all made of an elastomer material. For this reason, the entire capacitive sensor 1 is flexible and can be expanded and contracted. Moreover, since the electrodes 11a and 11b can be expanded and contracted, they can be deformed following the deformation of the dielectric film 10. Furthermore, even if the electrodes 11a and 11b and the wirings 12a and 12b are expanded, the increase in electric resistance is small. For this reason, the responsiveness of the capacitive sensor 1 is good. In the capacitive sensor 1 of the present embodiment, three pairs of electrodes 11a and 11b facing each other with the dielectric film 10 narrowed are formed. However, the number, size, arrangement, etc. of the electrodes may be appropriately determined according to the application.

<Actuator>
An embodiment of an actuator using the conductive film of the present invention as an electrode will be described. FIG. 5 is a schematic cross-sectional view of the actuator of this embodiment. (A) shows an OFF state, and (b) shows an ON state. As shown in FIG. 5, the actuator 2 includes a dielectric film 20 and electrodes 21a and 21b. The dielectric film 20 is made of urethane rubber. The electrodes 21a and 21b are arranged on the front and back of the dielectric film 20, respectively. The electrodes 21a and 21b are connected to the power source 22 through wiring. When switching from the off state to the on state, a voltage is applied between the pair of electrodes 21a and 21b. The thickness of the dielectric film 20 is reduced by applying a voltage. Accordingly, the dielectric film 20 extends in a direction parallel to the surfaces of the electrodes 21a and 21b as indicated by white arrows in FIG. Thereby, the actuator 2 outputs the driving force in the horizontal and vertical directions in FIG.

  Here, the electrodes 21a and 21b are made of the conductive film of the present invention. Since the electrodes 21 a and 21 b can expand and contract, they can be deformed following the deformation of the dielectric film 20. That is, since the movement of the dielectric film 20 is not easily disturbed by the electrodes 21a and 21b, a larger amount of displacement can be obtained. Furthermore, even if the electrodes 21a and 21b are stretched, the increase in electrical resistance is small. Further, since the heat generated by the internal resistance is small, the electrodes 21a and 21b are not easily deteriorated. That is, the actuator 2 is excellent in durability. Note that a greater force can be generated when a laminated structure in which a plurality of dielectric films and electrodes are alternately laminated. As a result, the output of the actuator is increased, and the driven member can be driven with a greater force.

<Power generation transducer>
An embodiment of a power generation transducer using the conductive film of the present invention as an electrode will be described. In FIG. 6, the cross-sectional schematic diagram of the electric power generation transducer in this embodiment is shown. (A) shows the time of expansion, and (b) shows the time of contraction. As shown in FIG. 6, the power generation transducer 3 includes a dielectric film 30 and electrodes 31a and 31b. The dielectric film 30 is made of urethane rubber. The electrodes 31a and 31b are fixed to the front and back of the dielectric film 30, respectively. Conductive wires are connected to the electrodes 31a and 31b, and the electrode 31b is grounded.

  As shown in FIG. 6A, when the power generation transducer 3 is compressed and the dielectric film 30 is expanded in a direction parallel to the surfaces of the electrodes 31a and 31b, the film thickness of the dielectric film 30 is reduced, and the distance between the electrodes 31a and 31b is reduced. The charge is stored in Thereafter, when the compressive force is removed, the dielectric film 30 contracts due to the elastic restoring force of the dielectric film 30 as shown in FIG. At that time, electric charges are released and electric power is generated.

  Here, the electrodes 31a and 31b are made of the conductive film of the present invention. That is, the electrodes 31a and 31b can be expanded and contracted. For this reason, the movement of the dielectric film 30 is not easily disturbed by the electrodes 31a and 31b. In addition, in the electrodes 31a and 31b, there is little decrease in conductivity when stretched, and even when repeatedly deformed, heat generation due to internal resistance is small. Therefore, the transducer 3 is excellent in durability.

<Flexible wiring board>
An embodiment of a flexible wiring board using the conductive film of the present invention for wiring will be described. In FIG. 7, the upper surface transparent view of the flexible wiring board of this embodiment is shown. In FIG. 7, the wiring on the back side is indicated by a thin line. As shown in FIG. 7, the flexible wiring board 4 includes a base material 40, front side electrodes 01X to 16X, front side electrodes 01X to 16X, front side wirings 01x to 16x, back side wirings 01y to 16y, and front side wiring connectors. 41 and a backside wiring connector 42.

  The base material 40 is made of urethane rubber and has a sheet shape. A total of 16 front side electrodes 01 </ b> X to 16 </ b> X are arranged on the upper surface of the base material 40. The front side electrodes 01X to 16X each have a strip shape. The front side electrodes 01X to 16X each extend in the X direction (left-right direction). The front-side electrodes 01X to 16X are arranged in the Y direction (front-rear direction) so as to be substantially parallel to each other at a predetermined interval. Front side connection portions 01X1 to 16X1 are arranged at the left ends of the front side electrodes 01X to 16X, respectively. Similarly, a total of 16 back-side electrodes 01Y to 16Y are arranged on the lower surface of the base material 40. The back side electrodes 01Y to 16Y each have a strip shape. The back-side electrodes 01Y to 16Y each extend in the Y direction. The back-side electrodes 01Y to 16Y are arranged in the X direction so as to be substantially parallel to each other at a predetermined interval. Back side connection portions 01Y1 to 16Y1 are arranged at the front ends of the back side electrodes 01Y to 16Y, respectively. As shown by hatching in FIG. 7, a detection unit that detects a load or the like is formed by a portion (overlapping portion) where the front side electrodes 01X to 16X intersect with the back side connection portions 01Y1 to 16Y1 with the base material 40 interposed therebetween. ing.

  A total of 16 front side wirings 01x to 16x are arranged on the upper surface of the substrate 40. The front side wirings 01x to 16x each have a linear shape. The front wiring connector 41 is disposed at the left rear corner of the base member 40. The front side wirings 01x to 16x connect the front side connection portions 01X1 to 16X1 and the front side wiring connector 41, respectively. Moreover, the upper surface of the base material 40, the front side electrodes 01X to 16X, and the front side wirings 01x to 16x are covered with a front side cover film (not shown) from above.

  A total of 16 back-side wirings 01y to 16y are arranged on the lower surface of the substrate 40. The back side wirings 01y to 16y each have a linear shape. The backside wiring connector 42 is disposed at the left front corner of the base material 40. The back side wirings 01y to 16y connect the back side connection portions 01Y1 to 16Y1 and the back side wiring connector 42, respectively. Moreover, the lower surface of the base material 40, the back side electrodes 01Y to 16Y, and the back side wirings 01y to 16y are covered with a back side cover film (not shown) from below.

  Each of the front side wiring connector 41 and the back side wiring connector 42 is electrically connected to a calculation unit (not shown). The impedance in the detection unit is input from the front side wirings 01x to 16x and the back side wirings 01y to 16y to the arithmetic unit. Based on this, the surface pressure distribution is measured.

  Here, the front-side wirings 01x to 16x and the back-side wirings 01y to 16y are each made of the conductive film of the present invention. That is, the front side wirings 01x to 16x and the back side wirings 01y to 16y can be expanded and contracted, respectively. For this reason, it can be deformed following the deformation of the substrate 40. Further, in the front-side wirings 01x to 16x and the back-side wirings 01y to 16y, there is little decrease in conductivity during expansion, and even when repeatedly deformed, heat generation due to internal resistance is small. Therefore, the flexible wiring board 4 is excellent in durability.

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

<Manufacture of conductive film>
[Example 1]
First, a conductive layer was formed on the surface of the substrate. A urethane rubber sheet (elastic member) having a thickness of 0.1 mm was used as the substrate. 100 parts by mass of an acrylic rubber polymer (“Nipol (registered trademark) AR42W” manufactured by Nippon Zeon Co., Ltd.), 1 part by mass of a processing aid stearic acid (“Lunac (registered trademark) S30” manufactured by Kao), and vulcanization 2.5 parts by mass of an accelerator zinc dimethyldithiocarbamate (“Noxeller (registered trademark) PZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.) and ferric dimethyldithiocarbamate (“Noxeller TTFE” manufactured by Ouchi Shinsei Chemical Co., Ltd.) 5 parts by mass was mixed with a roll kneader to prepare an elastomer composition. Subsequently, the prepared elastomer composition was dissolved in 312 parts by mass of a solvent, ethylene glycol monobutyl ether acetate, to prepare an elastomer solution. To this elastomer solution, 720 parts by mass of silver powder A (silver coated glass beads, “ES6000-S7” manufactured by Potters Ballotini Co., Ltd.), which is a conductive material, is added and kneaded with three rolls for a conductive layer. A paint was obtained. This conductive layer coating was applied to the surface of the substrate by a bar coating method. Thereafter, the substrate on which the coating film was formed was allowed to stand in a drying furnace at about 150 ° C. for about 30 minutes. And while drying the coating film, the crosslinking reaction was advanced and the conductive layer was formed. The conductive layer was formed to have a width of 10 mm, a length of 25 mm, and a thickness of 30 to 50 μm (the same applies to the following examples and comparative examples).

  Next, a protective layer was formed so as to cover the upper surface and the left and right side surfaces of the conductive layer. The same elastomer solution that formed the conductive layer was used as the protective layer coating. This protective layer coating was applied by a bar coating method so as to cover the conductive layer. Thereafter, the substrate on which the coating film was formed was allowed to stand in a drying furnace at about 150 ° C. for about 30 minutes. And while drying the coating film, the crosslinking reaction was advanced and the protective layer was formed. The conductive film thus obtained was named Example 1.

Table 1 below shows the elastic modulus and cross-sectional area of the conductive layer, protective layer, and substrate. Further, above-mentioned formula (II), are also shown the values of the left side _{[E e S e / (E} c S c + E s S s)] of (III). Each elastic modulus was calculated by a tensile test according to JIS K7127 (1999). The shape of the test piece was set to test piece type 2 (the same applies to the following examples and comparative examples).

[Example 2]
A conductive film was produced in the same manner as in Example 1 except for the type of conductive material in the conductive layer and the type of elastomer in the protective layer. Specifically, silver powder B (manufactured by DOWA Electronics Co., Ltd., product “FA-D-4”) and silver powder C (manufactured by the company, product “AG2-1C”) were used as the conductive material. Moreover, urethane rubber was used for the protective layer. That is, 100 parts by mass of a urethane rubber polymer (“Nipporan (registered trademark) 5230” manufactured by Nippon Polyurethane Industry Co., Ltd.) was dissolved in 150 parts by mass of butyl carbitol as a solvent to prepare a coating material for a protective layer. This protective layer coating was applied by a bar coating method so as to cover the conductive layer. Thereafter, the substrate on which the coating film was formed was allowed to stand in a drying furnace at about 150 ° C. for about 30 minutes. And while drying the coating film, the crosslinking reaction was advanced and the protective layer was formed. The obtained conductive film was named Example 2.

[Example 3]
A conductive film was produced in the same manner as in Example 1 except for the type of elastomer for the conductive layer and the protective layer. That is, urethane rubber was used for the conductive layer and the protective layer. First, 720 parts by mass of silver powder A were added to 100 parts by mass of the same urethane rubber polymer used in the protective layer of Example 2. Subsequently, 150 parts by mass of a solvent butyl carbitol was added and stirred to obtain a conductive layer coating material. This conductive layer coating was applied to the surface of the substrate by a bar coating method. Thereafter, the substrate on which the coating film was formed was allowed to stand in a drying furnace at about 150 ° C. for about 30 minutes. And while drying the coating film, the crosslinking reaction was advanced and the conductive layer was formed. Next, a protective layer was formed in the same manner as in Example 2 using the same urethane rubber polymer as that of the conductive layer. The obtained conductive film was named Example 3.

[Example 4]
A conductive film was produced in the same manner as in Example 2 except that it did not have a base material (elastic member) and the type of conductive material in the conductive layer. First, 20 parts by mass of conductive material carbon black (“Ketjen Black (registered trademark) EC-600JD” manufactured by Lion Corporation) was added to the elastomer solution used in the conductive layers of Examples 1 and 2, and three A conductive layer coating was obtained by kneading with a roll. This conductive layer coating was applied to the surface of a PET substrate that had been subjected to a release treatment by a bar coating method. Thereafter, the substrate on which the coating film was formed was allowed to stand in a drying furnace at about 150 ° C. for about 30 minutes. And while drying the coating film, the crosslinking reaction was advanced and the conductive layer was formed. Next, a protective layer was formed in the same manner as in Example 2 using the protective layer coating material used in the protective layer of Example 2. The conductive film thus obtained was peeled from the base material to give Example 4.

[Comparative Example 1]
A conductive film was produced in the same manner as in Example 1 except that the protective layer was not formed. That is, the formed conductive film consists only of a conductive layer. The obtained conductive film was referred to as Comparative Example 1.

[Comparative Example 2]
A conductive film was produced in the same manner as in Example 2 except for the type of elastomer for the protective layer. That is, the same acrylic rubber as the protective layer of Example 1 was used for the protective layer. The obtained conductive film was referred to as Comparative Example 2.

[Comparative Example 3]
A conductive film was produced in the same manner as in Example 2 except that the protective layer was not formed. That is, the formed conductive film consists only of a conductive layer. The obtained conductive film was referred to as Comparative Example 3.

[Comparative Example 4]
A conductive film was produced in the same manner as in Example 4 except that the protective layer was not formed. That is, the formed electrically conductive film consists only of an electrically conductive layer, and does not have a base material (elastic member). The obtained conductive film was referred to as Comparative Example 4.

<Evaluation method>
About the manufactured electrically conductive film, the volume resistivity at the time of changing an expansion rate, durability, and migration were evaluated. Hereinafter, each evaluation method will be described.

[Volume resistivity]
The volume resistivity of the conductive film was measured according to JIS K6271 (2008). The initial inter-electrode distance (before stretching) was 10 mm. The volume resistivity was measured by changing the stretching ratio from 0% (no stretching) to 500%. Here, the expansion rate is a value calculated by the following formula (IV) (the same applies to the following expansion rates).
Elongation rate (%) = (ΔL ₀ / L ₀ ) × 100 (IV)
[L ₀ : Distance between marked lines of test piece, ΔL ₀ : Increase due to extension of distance between marked lines of test piece]
[durability]
The manufactured conductive film was used as a test piece together with the base material to conduct a durability test. First, both ends of the test piece were sandwiched between a pair of jigs. Next, the test piece was expanded and contracted by fixing one of the jigs and reciprocating the other at a speed of 50 mm / min. The maximum elongation of the test piece was 50%, and the jig was reciprocated 100 times. After the durability test, the volume resistivity of the conductive film was measured in the same manner as described above. When the volume resistivity is 0.01 Ωcm or less, good (circle mark in Table 1 below), and when it exceeds 0.01 Ωcm and slightly less than 10 Ωcm (symbol Δ in Table 1), it exceeds 10 Ωcm. The case was determined to be defective (x in Table 1).

[migration]
A migration test was performed on the conductive films having the same composition as the conductive films of the above Examples and Comparative Examples. First, a pair of conductive films having a width of about 1 mm and a length of about 15 mm were formed on the surface of a base material made of polyethylene terephthalate (PET) so as to be adjacent to each other with a spacing of about 0.5 mm. Next, 30 μl of ion-exchanged water was dropped between the conductive films so that the water drops were in contact with each other. In this state, a voltage of DC 10V was applied between the conductive films for 300 seconds. Thereafter, both conductive films were observed with a microscope, and the case where no silver deposition was observed on the conductive film was good (marked with a circle in Table 1 below), and the case where silver deposition was observed was poor (Table 1). Middle x).

<Evaluation results>
The evaluation results of the conductive films of Examples and Comparative Examples are shown in Table 1 together with the composition, elastic modulus, cross-sectional area and the like of each layer.

As shown in Table 1, the conductive films of Examples 1 to 4 had a small increase in volume resistivity even when the expansion ratio increased, that is, greatly expanded. On the other hand, for the conductive films of Comparative Examples 1, 3, and 4 without a protective layer, the volume resistivity increased as the elongation rate increased. That is, the conductivity decreased due to stretching. Further, the conductive film of Comparative Example 2 has a protective layer, above-mentioned formula (II), the value of the left side _{[E e S e / (E} c S c + E s S s)] of (III) 1 .26 and large. For this reason, when the elongation ratio was 200% or more, the volume resistivity increased.

  Moreover, the electrically conductive film of Examples 1-4 was excellent in durability. That is, even when the expansion and contraction was repeated, the increase in electrical resistance was small. Furthermore, it was confirmed that migration was also suppressed. On the other hand, the durability of the conductive films of Comparative Examples 1, 3, and 4 without the protective layer was low. Moreover, about the electrically conductive film of the comparative examples 1 and 3, precipitation of silver was recognized by migration.

  From the above, it was confirmed that the conductive film of the present invention was flexible and highly conductive, and the electrical resistance hardly increased even when stretched. Moreover, it was confirmed that even when the expansion and contraction was repeated, the change in electric resistance was small and the durability was excellent.

  Flexible actuators are used in, for example, artificial muscles for industrial, medical, and welfare robots, small pumps for cooling electronic parts, medical use, and medical instruments. The conductive film of the present invention is suitable for such flexible actuator electrodes and wiring. It is also suitable for electrodes and wiring of elastomer sensors such as capacitance type sensors. Furthermore, in addition to the power generation transducer, it is also suitable for flexible transducer electrodes, wiring, and the like that emit light, generate heat, and color. Moreover, the electrically conductive film of this invention is useful also for the flexible wiring board etc. which are used for a wearable device etc.

1: Capacitance type sensor (elastomer sensor) 10: Dielectric films 11a, 11b: Electrodes 12a, 12b: Wiring 14: Connectors 110a, 110b: Conductive layers 111a, 111b: Protective layers 120a: Conductive layers 121a: Protective layers 2: Actuator 20: Dielectric film 21a, 21b: Electrode 22: Power supply 3: Power generation transducer 30: Dielectric film 31a, 31b: Electrode 4: Flexible wiring board 40: Base material 41: Front side wiring connector 42: Back side wiring connector 01X-16X : Front side electrode 01X1 to 16X1: Front side connection part 01Y to 16Y: Back side electrode 01Y1 to 16Y1: Back side connection part 01x to 16x: Front side wiring 01y to 16y: Back side wiring 100: Conductive layer 101: Conductive layer 102: Protective layer 103: Elasticity Member S _e : sectional area of conductive layer S _c : sectional area of protective layer S _s : conductive Cross-sectional area of elastic member at the formation part of the electromembrane

Claims (15)

A conductive layer having an elastomer and a conductive material filled in the elastomer;
An elastomeric protective layer arranged to cover the conductive layer;
A conductive film comprising: The conductive film according to claim 1, wherein the elastic modulus and the cross-sectional area of each of the conductive layer and the protective layer satisfy the following formula (I).
E _{e Se} / E _{c Sc} <1 (I)
[E _e : Elastic modulus of conductive layer, S _e : Cross sectional area of conductive layer, E _c : Elastic modulus of protective layer, S _c : Cross sectional area of protective layer]   The conductive film according to claim 1, wherein the conductive film is formed on a surface of the elastic member. One surface of the conductive layer is in contact with the elastic member,
The conductive film according to claim 3, wherein the other surface of the conductive layer is covered with the protective layer. 5. The conductive film according to claim 3, wherein an elastic modulus and a cross-sectional area of each of the conductive layer, the protective layer, and the elastic member satisfy the following formula (II).
_{E e S e / (E c} S c + E s S s) <1.2 ··· (II)
[E _e : Elastic modulus of conductive layer, S _e : Cross sectional area of conductive layer, E _c : Elastic modulus of protective layer, S _c : Cross sectional area of protective layer, E _s : Elastic modulus of elastic member, S _s : Conductive Cross-sectional area of elastic member at film forming portion] The electrically conductive film of Claim 3 or Claim 4 with which the elasticity modulus and sectional area of each of the said conductive layer, the said protective layer, and the said elastic member satisfy | fill following Formula (III).
_{E e S e / (E c} S c + E s S s) <1 ··· (III)
[E _e : Elastic modulus of conductive layer, S _e : Cross sectional area of conductive layer, E _c : Elastic modulus of protective layer, S _c : Cross sectional area of protective layer, E _s : Elastic modulus of elastic member, S _s : Conductive Cross-sectional area of elastic member at film forming portion]   The conductive film according to claim 1, wherein the conductive material includes one or more metal powders selected from silver, gold, and copper.   The conductive film according to claim 1, wherein the conductive material includes carbon black. The conductive material includes silver powder and carbon black,
The conductive film according to any one of claims 1 to 8, wherein a filling amount of the silver powder is 30% by volume or more when the whole of the conductive material is 100% by volume.   The conductive film according to any one of claims 1 to 9, wherein the elastomer constituting the protective layer is at least one selected from polyurethane, acrylic, polyvinyl chloride, polyester, and polyetherester.   The conductive film according to any one of claims 1 to 10, wherein the elastomer constituting the protective layer contains carbon black.   12. A transducer comprising the conductive film according to claim 1 as at least one of an electrode and a wiring.   A dielectric film made of an elastomer, a plurality of electrodes arranged via the dielectric film, and a wiring connected to each of the plurality of electrodes, according to a voltage applied between the plurality of electrodes The transducer according to claim 12, wherein the dielectric film is an actuator that expands and contracts.   A dielectric film made of an elastomer, a plurality of electrodes arranged through the dielectric film, and a wiring connected to each of the plurality of electrodes, and based on a change in capacitance between the plurality of electrodes The transducer according to claim 12, wherein the transducer is an elastomer sensor that detects deformation.   A flexible wiring board, wherein at least a part of the wiring is made of the conductive film according to any one of claims 1 to 11.

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