WO2008007526A1

WO2008007526A1 - Wiring connection structure in polymer actuator or polymer sensor

Info

Publication number: WO2008007526A1
Application number: PCT/JP2007/062417
Authority: WO
Inventors: Ryo Yoshitomi
Original assignee: Eamex Corporation
Priority date: 2006-07-14
Filing date: 2007-06-20
Publication date: 2008-01-17
Also published as: JP2008022655A

Abstract

This invention provides a wiring connection structure which can increase the degree of freedom in the attachment of a polymer actuator and a polymer sensor and, at the same time, has no large protrusions and can stably maintain a precompressed state. The wiring connection structure is adapted for use in a polymer actuator (1) or a polymer sensor, in which a metal electrode layer (11) is formed on a surface of an ion exchange resin layer (10), and is characterized in that a wiring connection region (1a) set on the metal electrode layer (11), a metal electrode plate (2) for wiring, and a flexible sheet (3) are stacked on top of each other in that order followed by joining by joining means in such a state that the stacked part has been compressed to impart precompression in the stacked direction. The joining means is a resin rivet (4). Regarding the joining, a method is preferably adopted in which the rivet (4) is extended through the stacked part, and the joining is carried out by thermal caulking. The metal electrode plate (2) for wiring is preferably formed of a metal foil. The flexible sheet (3) is preferably a resin sheet. An alternative method may also be used in which an electrically nonconductive string (5) is used as the joining means and the stacked part is sewed with the string (5).

Description

Specification

Wiring connection structure in polymer actuator or polymer sensor

The present invention relates to a wiring connection structure in a polymer actuator or polymer sensor in which a metal electrode layer is formed on the surface of an ion exchange resin layer.

Background art

Conventionally, as one of polymer actuators, there has been known an ion conduction actuator comprising an ion exchange resin layer and a metal electrode layer formed in an insulating state on the surface of the ion exchange resin layer. (For example, Patent Document 1 below). This polymer activator

In addition, a potential difference is applied between the metal electrode layers to cause the ion exchange resin layer to bend and deform, thereby functioning as an activator. Polymer actuators are also used as polymer sensors because an electromotive force is generated when an external force is applied to the ion exchange resin layer, and impedance changes when moisture contained in the outside air is absorbed. Hereinafter, the polymer actuator and the polymer sensor are collectively referred to as a polymer actuator or the like.

[0003] It is necessary to provide a wiring connection structure in order to apply a voltage to this polymer actuator or the like or to perform electrical detection. As an example of this wiring connection structure, a wiring connection region set on a metal electrode layer is sandwiched by hard bracket parts with a metal electrode plate for wiring interposed therebetween, and screw connection is performed. As another example, there is a structure in which the surface of a sheet metal member having a panel property is plated with gold to sandwich the wiring connection region. In particular, a high molecular weight actuator or the like swells or contracts depending on the environment, and therefore it is necessary to perform wiring connection in a state where a pressure is applied.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-172635

Disclosure of the invention

Problems to be solved by the invention

[0005] The conventional wiring connection structure described above has the following problems. In other words, the above structure is relatively large even though the polymer activator is formed in a thin sheet. It has a large thickness and a relatively large protrusion. The presence of such protrusions has a problem in that the installation location of the polymer actuator or the like is limited or the size of the apparatus used is increased. In addition, when attaching a polymer actuator or the like, there is a demand to attach to a curved surface instead of a flat surface. In such a case, if a hard bracket part is used, the degree of freedom with respect to the mounting surface is lost. Furthermore, although it is necessary to perform wiring connection in a state where a pressurized pressure is applied, a wiring connection structure that can stably maintain the pressurized pressure against environmental changes such as temperature and humidity is also required.

[0006] The present invention has been made in view of the above circumstances, and the problem is that the degree of freedom in attaching a polymer actuator or the like can be increased and a large protruding portion can be eliminated to stably maintain a pressurized pressure. Is to provide a simple wiring connection structure.

Means for solving the problem

[0007] In order to solve the above problems, a wiring connection structure of a polymer actuator or the like according to the present invention is a wiring connection structure in a polymer actuator or a high molecular sensor in which a metal electrode layer is formed on the surface of an ion exchange resin layer. And

A wiring connection region set on the metal electrode layer, a metal electrode plate for wiring, and a flexible sheet are laminated in this order, and the laminated portion is compressed in the laminating direction to apply pressure. In this state, they are combined by the connecting means.

[0008] According to this wiring connection structure, a wiring connection region for wiring connection is set on a metal electrode layer such as a polymer actuator. The location and size of this area can be determined appropriately according to the purpose of use. This wiring connection region, a wiring metal electrode plate, and a flexible sheet are laminated in this order, and are coupled by a coupling means. The metal electrode plate for wiring can be connected to the circuit portion by, for example, soldering a lead wire. In addition, a flexible sheet is interposed between them, and a compressive force can be easily applied. Further, the metal electrode plate and the flexible sheet can be easily deformed together, and can be easily attached to the curved surface. Therefore, a flexible wiring connection structure can be obtained.

[0009] The coupling means according to the present invention is a resin rivet, and the laminated portion is penetrated by the rivet. It is preferable to bind by caulking.

[0010] By passing through the laminated portion with rivets and caulking and joining, a large protruding portion can be eliminated and the thickness can be reduced. The rivet is made of resin so that ions in the polymer activator do not react. Resin rivets can be joined by, for example, heat caulking. Bonding with resin rivets is performed in a state where the laminated portion is compressed in advance, and after the bonding is completed, a state where a pressurized pressure is applied is maintained.

In the present invention, the metal electrode plate for wiring is preferably formed of a metal foil. By forming the metal foil, the thickness of the laminated portion can be reduced and the flexibility can be further increased.

[0012] The flexible sheet according to the present invention is preferably a resin sheet. By using a resin sheet, the thickness of the laminated portion can be reduced, and a pressure can be easily applied.

[0013] As the coupling means according to the present invention, a thread having no electrical conductivity can be used, and a structure in which the stacked portion is sewn with a thread is also preferable. By performing sewing with a thread, it is possible to provide a connection structure with almost no protrusions. In addition, it is easy to sew in a state where a pressure is applied, and the pressure can be maintained regardless of environmental changes. In addition, sewing with a thread has the advantage that flexibility can be secured while firmly connecting the members.

[0014] The flexible sheet according to the present invention is preferably a leather or sponge-like resin sheet. By using a sheet of strong material, it is possible to facilitate sewing with thread.

Brief Description of Drawings

[0015] [Fig. 1] Schematic diagram showing the structure of a polymer activator

FIG. 2 is a diagram showing a wiring connection structure that works according to the first embodiment.

[FIG. 3] A diagram showing a wiring connection structure that works according to the second embodiment.

Explanation of symbols

[0016] 1 Polymer Actuator la Wiring connection area

2 Metal electrode plate

3 Resin sheet

4 Resin rivets

5 Yarn

10 Ion exchange resin layer

11 Metal electrode layer

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of a wiring connection structure such as a polymer actuator according to the present invention will be described with reference to the drawings. First, the structure of the polymer actuator will be described.

[0018] <Structure of polymer actuator>

An ion conducting actuator, which is one of polymer actuators, has a structure in which a metal electrode layer is formed on the surface of an ion exchange resin layer. More specifically, an ion conducting actuator is formed between ion metal layers facing each other. An exchange resin and a polar organic solvent containing a salt or a liquid organic compound that is an ionic liquid are included. In principle, when a potential difference is applied to the ion exchange resin through a metal electrode, the ionic substance in the liquid organic compound contained in the ion exchange resin is V It utilizes the phenomenon in which deformation occurs due to movement in the electrode direction.

[0019] (Ion exchange resin)

The ion exchange resin of the polymer actuator element used in the present invention is not particularly limited, and a known ion exchange resin can be used. In fact, the effectiveness of the ion exchange resin of the actuator is that of a cation exchange resin. However, the same effect can be expected by changing how the potential difference is applied regardless of whether the ion exchange resin is a cation type or an anion type. In the case of using a cation exchange resin, it is possible to use a product obtained by introducing a hydrophilic functional group such as a sulfonic acid group or a carboxyl group into polyethylene, polystyrene, fluororesin or the like. Examples of such resins include perfluorosulfonic acid resin (trade name “Nafion”, manufactured by DuPont), perfluorocarboxylic acid resin (trade name “Flemion”, manufactured by Asahi Glass), ACIPLEX ( Asahi Kasei Kogyo), NEOSEPTA (Tokuyama) Can be used.

[0020] In order to increase the bending / displacement amount of the polymer actuator used in the present invention, the ion exchange resin preferably has flexibility. In order to impart flexibility to the ion exchange resin, the ion exchange resin is swollen with a liquid organic compound. The ion exchange resin can become a gel electrolyte by being swollen. The degree of swelling is not particularly limited, but the degree of swelling of the polymer activator, that is, the thickness of the polymer electrolyte in a dry state, is not limited. The rate of increase in thickness in the swollen state is preferably 3 to 200%, more preferably 5 to 60%. When the degree of swelling is less than 3%, the displacement bending performance is inferior, and when the degree of swelling is greater than ¾00%, the displacement bending performance is also inferior and the tensile strength is further greatly reduced. End up. When the force metal electrode contained in the ion exchange resin is porous, a part of the solvent may be contained in the metal electrode together with a salt.

[0021] (Liquid organic compound)

As the liquid organic compound used in the present invention, a polar organic solvent containing a salt or an ion liquid is used. The ionic liquid can be used alone, but in the case of a polarizable organic solvent, a salt containing ions serving as charge carriers is required. However, the ionic liquid may be used as the salt. This is because these liquid organic compounds easily move in the ion exchange resin when a potential difference is given to the ion exchange resin. The liquid organic compound is an organic compound that is liquid at normal temperature and pressure, and particularly preferably has a boiling point of 180 ° C. or higher or a decomposition temperature. In this case, the solvent is less likely to vaporize.

[0022] (Polarizable organic solvent)

The polarizable organic solvent is preferably an organic compound having a boiling point or decomposition temperature of 180 ° C. or higher, but is particularly preferably a polarizable organic solvent having a boiling point of 245 ° C. or higher. Specific examples of preferred polarizable organic solvents include diethylene glycol, glycerin, sulfolane, propylene carbonate, butyrolatathone or mixtures thereof. Among them, diethylene glycol, glycerin, sulfolane or a mixture of these Especially preferred to be a compound.

[0023] The salt contained in the polarizable organic solvent is not particularly limited as long as it is a salt that can be dissolved in the polarizable organic solvent. In particular, the ion exchange resin forms a counter ion with a cation. Can be used:: ~ A salt of a trivalent cation can be used, and the use of a monovalent cation such as Na ⁺ K ⁺ Li ⁺ is preferable because it can be bent or displaced greatly. It is more preferable to use a larger alkylammonium ion because it can be bent or displaced more greatly. Examples of the alkyl ammonium include CH N + HCH N + H (CH) N + H (CH) N + H (CH) N + H (CH)

N + H (CH) N ⁺ (CH) N ⁺ (CH) N ⁺ (CH) N ⁺ HN ⁺ (CH) N ⁺ HHC = CH

CH N + HCH HN ⁺ (CH) N + H (CH) N + H HC≡CCH N + H CH CH (OH) C

H N + HHN ⁺ (CH) OH HN ⁺ CH (CH OH) (HOCH) C (CH N ⁺ H) CH〇

Ammonium ions having CH CH N ⁺ H and aliphatic hydrocarbons as substituents, or ammonium ions having alicyclic cyclic hydrocarbons in addition to hydrocarbons as functional groups can be used. At this time, the concentration of the salt is 0.0 :! 1 Omol / 1 in order to obtain sufficient bending or displacement if it is contained as a concentration equal to or higher than the functional group of the ion exchange resin. Preferably, 0.:! 1. Omol / 1 is more preferred.

[0024] (Ionic liquid)

Preferred examples of the ionic liquid include, but are not limited to, tetraalkyl ammonium ions, imidazolium ions, alkyl pyridinium ions, virazolium ions, pyrrolium ions, pyrrolium ions, pyrrolidinium ions, and piberyl ions. At least one cation selected from the group consisting of genium ions,

PF BF A1C1 CIO and sulfonium imide anion represented by the following formula (1)

6 4 4 4

Mention may be made of salts composed of combinations with at least one anion selected from the group of forces. In the following formula (1), n and m are arbitrary integers.

(C F SO) (C F SO) N— (1)

n (2n + l) 2 m (2m + l) 2

The tetraalkylammonium cation is not particularly limited.

, Trimethylpropylammonium, trimethylhexylammonium, and tetrapentylammonium can be used. As the imidazolium cation, a dialkyl imidazolium ion and / or a trialkylimidazolium ion can be used. For example, the imidazolium cation is not particularly limited, but includes 1-ethyl-3-methylimidazolium ion, 1-hexyl_3-methylimidazolium ion, 1-butyl_3-methylimidazolium ion, 1 , 3 _dimethyl imidazolium ion, 1 _methyl _ 3 -ethyl imidazolium ion, 1, 2, 3 _trimethyl imidazolium ion, 1,2-dimethyl _ 3 -ethyl imidazolium ion, 1, 2— Examples thereof include dimethyl-3-propyl imidazolium ion and 1-butyl-1,2,3-dimethylimidazolium ion.

[0026] The alkylpyridinium cation is not particularly limited, but N-butyl pyridinium ion, N-methylpyridinium ion, N-ethylpyridinium ion, N — Examples include propylpyridinium ion, 1-ethyl1-2-methylpyridinium, 1-butyl-1, 4-methylpyridinium, 1_butyl-1,2,4-dimethylpyridinium. .

[0027] The pyrazolium cation is not particularly limited, but 1, 2 dimethylpyrazolium ion, 1-ethyl-2-methyl virazolium ion, 1 propyl 2-methyl virazolium ion, 1 petitru 2-methyl Examples of virazolium ions

[0028] The pyrrolium cation is not particularly limited, and examples thereof include 1,1-dimethylpyrrolium ion, 1-ethyl-1 methylpyrrolium ion, 1-methyl-1 propylpyrrolium ion, and 1-butyl-1 methylpyrrolium ion. can do.

[0029] The pyrrolinium cation is not particularly limited, but 1,2-dimethylpyrrolium ion, 1_ethyl_2_methylpyrrolonium ion, 1_propyl-1-2_methylpyrrolonium ion 1_butyl_2_methylpyrrolonium ion can be exemplified

[0030] The pyrrolidinium cation is not particularly limited, but may be 1,1-dimethylpyrrolidinium ion, 1_ethyl_i_methylpyrrolidinium ion, 1_methyl_1_propyl pill. The ability to illustrate the pyrrolidinium ion, 1-butyl-1- 1-methylpyrrolidinium ion. [0031] The piperidinium cation is not particularly limited, but 1, 1 dimethylbiperidinium ion, 1-ethyl-1-methylbiperidinium ion, 1-methyl-1 propylpiperidinium ion, 1 The ability to illustrate -butyl- 1-methylbiperidinium ion.

[0032] The ionic liquid is not particularly limited to a combination of the anion and the cation. For example, 1_methyl_3-ethylimidazolium trifluoromethane sulfoimide (EMITFSI), 1_ Methyl _ 3 _ imidazolium tetrafluoroborate (EM IBF), 1 _ Methyl _ 3_ imidazolium hexafluorophosphate (EMIPF), Trimethyl

4 6-neck pyrammonium trifluoromethanesulfoimide, 1 _hexyl _ 3—methylimidazole tetrafluoroborate, 1 _hexyl _ 3 methyl imidazolium hexafluorophosphate, 1 _hexyl _ 3-Methylimidazolium trifluoromethanesulfonimide can be used.

[0033] (Metal electrode)

In the present invention, the surface of the ion exchange resin is provided with one or more sets of metal electrodes at opposing positions so that a force S can be applied to the ion exchange resin. The metal used for the metal electrode can be used without limitation as long as it is a solid metal with good conductivity, excluding liquid metals such as mercury, and may be an alloy. An appropriate metal can be selected depending on the type of ion exchange resin or liquid organic compound used.

[0034] The phrase "a pair of metal electrodes" is an ideal state where a pair of metal electrodes exist in parallel. However, it is not necessary for both electrodes to be completely parallel, so long as the actuator element can be displaced by applying a voltage to both metal electrodes, it may be slightly deviated from parallel. However, as the deviation from parallel occurs, the bending and deformation efficiency per Coulomb amount changes.

[0035] In order to make a pair of metal electrodes exist in parallel, the shape of the ion exchange resin is changed to a plate shape or a bar shape having parallel flat side walls, and the surfaces of the flat side walls facing in parallel are arranged. In addition, it is preferable to provide a metal electrode to be paired by a plating method, particularly an electroless plating method. As described later, when a metal film that can be a metal electrode is formed on the surface of the ion exchange resin by an electroless plating method, the contact area between the ion exchange resin and the metal electrode is increased. This is because the amount of bending and displacement as the feature actuator can be increased.

[0036] (Coating resin)

The polymer actuator used in the present invention can be driven for a long time without being coated, but may be further coated with a flexible resin. The resin is not particularly limited, but polyurethane resin and / or silicon resin can be used. The polyurethane resin is not particularly limited, but it is particularly preferable to use a flexible thermoplastic polyurethane because of its high flexibility and good adhesion. As flexible thermoplastic polyurethanes, the product name “Asaflex 825” (flexibility 200%, manufactured by Asahi Kasei Co., Ltd.), the product name “Pelecene 2363 _80A” (flexibility 550%), “Pelecene 2363_ 80AE” (flexible) 650%), “Pelecene 2363-90A” (flexibility: 500%), “Pelecene 236 3_90AE” (flexibility: 550%), (manufactured by Dow Chemical Co., Ltd.). The silicone resin is not particularly limited, but a resin having a flexibility of 50% or more is particularly preferable because of its high flexibility and good adhesion. As the silicone resin, for example, “Sila Seal 3FW”, “Sila Seal DC738RTV”, “DC3145”, and “DC3140” (above, manufactured by Dow Co., Ltd.) can be used. In the present application, the flexibility refers to the tensile elongation at break (Ultimate Elongation%) in accordance with ASTM D412.

[0037] <Wiring connection structure of polymer actuator>

Next, the wiring connection structure of the polymer actuator will be described. First, the structure of the polymer actuator 1 is shown as a schematic diagram in Fig. 1. In the polymer actuator 1, a metal electrode layer 11 is formed on the surface of the ion exchange resin layer 10. In the illustrated example, metal electrode layers 11 are formed on both the front and back surfaces of the ion exchange resin layer 10. When no voltage is applied, it is a straight state as shown in FIG. 1 (a). However, when a voltage is applied, it bends as shown in (b) or (c) depending on the direction of application. This is because ions (cations or anions) in the ion exchange resin layer 10 move in the direction of the metal electrode layer 11 by applying a voltage, and a difference in swelling occurs between the front and back surfaces.

[0038] Such displacement characteristics are determined by changing conditions when the polymer actuator 1 is driven. For example, the geometry, size, Displacement characteristics can be controlled by the type of voltage and applied voltage waveform.

[0039] The polymer actuator 1 may have various shapes such as a sheet shape, a prismatic shape, and a cylindrical shape, but the present invention is not limited to a specific shape. Further, the thickness of the ion exchange resin layer 10 and the metal electrode layer 11 is not limited to a specific size.

FIG. 2 is a diagram showing a wiring connection structure according to the first embodiment. A wiring connection region la is set on the metal electrode layer 11 of the polymer actuator 1. The wiring connection area la is set on both the front and back sides of the high-molecular-weight actuator 1. A pair of metal electrode plates 2 for wiring are disposed on both the front and back sides of the polymer actuator 1, and a pair of sheets 3 are disposed on the surface side thereof.

[0041] The metal electrode plate 2 for wiring is preferably formed of a metal foil (such as gold) or a copper foil plated with gold, so that the thickness can be reduced. Moreover, by forming it with foil, it has flexibility and can be easily deformed. Alternatively, a thin metal electrode plate 2 that has been subjected to sheet metal pressing may be used. The thickness of the metal electrode plate 2 is preferably about 10 / im to 0.1 mm. By soldering the lead wire to the strong metal electrode plate 2, it can be connected to the circuit section.

[0042] As the sheet 3, a resin sheet having flexibility can be used. The material of the resin sheet is not particularly limited, and for example, a material such as polyethylene terephthalate, polycarbonate, or acrylic can be used. In consideration of providing flexibility, the thickness is preferably set to about 0.05 mm to 0.5 mm.

[0043] As described above, the laminated portion is formed by sandwiching the front and back surfaces of the polymer actuator 1 between the metal electrode plate 2 and the resin sheet 3, and this laminated portion is joined by the resin rivet 4 (corresponding to the joining means). To do. In order to penetrate the resin rivet 4, holes are formed at predetermined positions of the polymer actuator 1, the metal electrode plate 2, and the resin sheet 3. In the illustrated example, the number of holes is two, but the number, size, arrangement, etc. of the holes are not limited to a specific form.

[0044] The resin rivet 4 includes a head 4a having a large diameter. The reason for using resin rivets is that if they are made of metal, ions of the ion exchange resin layer 10 may react. The material of the resin rivet 4 is not particularly limited. Resins such as bonate, polyacetal, and polybutylene terephthalate can be used.

[0045] When bonding with the resin rivet 4, the stacked portions are bonded in a state in which a pressure is applied by compressing the stacked portion in the stacking direction (vertical direction in FIG. 2). By applying pressure, it is possible to ensure a good contact state between the metal electrode layer 11 of the polymer actuator 1 and the metal electrode plate 2 for wiring. The completed state is shown in Figure 2 (b). By using the thin metal electrode plate 2 and the resin sheet 3, it is easy to apply a pressure to the polymer actuator 1. After the resin sheet 4 is inserted into the laminated portion, the end opposite to the head 4a is crushed with caulking to complete the coupling. As a method of force squeezing, it is preferable to carry out by thermal staking.

[0046] According to the force and the connection structure, the thickness of the laminated portion can be reduced. Further, the protruding portion in the laminated portion is only the portion crushed with the head 4a of the resin rivet 4 and heat caulking, and the protruding height can be suppressed. Moreover, the laminated portion has flexibility as a whole, and can be attached not only to a flat surface but also to a curved surface. Accordingly, the degree of freedom of attachment of the polymer actuator 1 is increased, and the application range is expanded. In addition, a pressurized state can be maintained regardless of changes in environmental conditions (temperature and humidity).

Next, the wiring connection structure according to the second embodiment will be described with reference to FIG. In this connection structure, sewing is performed using thread 5 as a coupling means. The stacking mode in the stacking part is the same as in FIG. Fig. 3 (a) shows the state before sewing, and (b) shows the state after sewing. The yarn 5 as the coupling means may be made of a material such as cotton, silk, or resin that does not have conductivity. The thickness of the thread 5 can be used as appropriate in consideration of the bond strength.

[0048] With respect to the sheet 3, it is possible to use a resin sheet made of leather or sponge in consideration of sewing with the thread 5. Both are flexible materials and are easy to compress. Therefore, it is possible to perform the sewing with the thread 5 in a state where a pressure is applied, and the pressure can be maintained even after the coupling is completed. Sewing with thread 5 increases the degree of freedom in the attachment method where the protruding part of the laminated part is connected. In addition, since the entire laminated portion has flexibility, it can be easily attached to a curved surface as in the first embodiment. If the polymer actuator 1 is attached to leather or cloth, directly onto the thread 5 It is possible to perform sewing by force S.

The force that has been described as a polymer actuator in the above description. This actuator can also be used as a polymer sensor. In other words, the structure of the polymer actuator 1 shown in FIG. 1 is that an electromotive force is generated when an external force is applied to the ion exchange resin layer 10, and the impedance changes when water contained in the external air is absorbed. For example, it is also used as a humidity sensor. Even when used as a polymer sensor, the above wiring connection structure can be applied as it is.

Claims

The scope of the claims

[1] A wiring connection structure in a polymer actuator or a high molecular sensor in which a metal electrode layer is formed on the surface of an ion exchange resin layer,

A wiring connection region set on the metal electrode layer, a metal electrode plate for wiring, and a flexible sheet are laminated in this order,

A wiring connection structure characterized in that these laminated portions are joined together by a joining means in a state where compression is applied in the laminating direction.

[2] The wiring connection structure according to [1], wherein the coupling means is a resin rivet, and the laminated portion is coupled by caulking through the stacked portion.

[3] The wiring connection structure according to claim 1 or 2, wherein the metal electrode plate for wiring is formed of a metal foil.

[4] The wiring connection structure according to any one of claims 1 to 3, wherein the flexible sheet is a resin sheet.

5. The wiring connection structure according to claim 1, wherein the coupling means is a thread that does not have conductivity, and the laminated portion is sewn with a thread.

6. The wiring connection structure according to claim 5, wherein the flexible sheet is a leather or sponge-like resin sheet.