JP5636302B2 - Conductive member for pressure sensor, pressure sensor using the same - Google Patents

Description

  The present invention relates to a pressure-sensitive sensor conductive member that measures the magnitude and distribution of pressure acting on a member. The present invention also relates to a pressure sensor using this conductive member.

  Conventionally, a method using piezoelectric ceramics such as lead zirconate titanate or a method using a strain gauge has been used as means for measuring the magnitude and distribution of pressure acting on a member. However, since the method using piezoelectric ceramics is generally formed of a highly rigid material, the degree of freedom in shape is limited, and the method using a strain gauge is similarly low in shape design freedom. Have a problem.

  In response to these problems, a pressure-sensitive sensor having a high degree of freedom in shape can be obtained by using a conductive member in which conductive materials are dispersed using a polymer material such as rubber, elastomer, or resin material as a base material. It has been known.

  In addition, the following two are mentioned as a pressure detection mechanism using the said electroconductive member.

  One shows a high electrical resistance value when no pressure is applied, but due to compression deformation accompanying an increase in pressure, the distance between the conductive particles in the substrate is narrowed, and a conductive path is formed by the conductive particles. For this reason, the resistance value is reduced, and the resistance value is changed. In addition, since the dispersion state of the conductive particles in the base material greatly affects this resistance change, the reproducibility of the electrical resistance value change due to repeated compression deformation is a problem. In particular, during repeated pressing, the conductive member undergoes permanent deformation due to fatigue, and there is a problem that it becomes difficult to detect pressure because the conductive particles are in contact with each other and are in contact with each other.

  On the other hand, the other uses the change in conduction caused by the contact state between the conductive member and the detection electrode. For example, there is one in which a conductive coating film is formed using the conductive member, and the conductive coating films, or the conductive coating film and a detection electrode such as a comb electrode are arranged to face each other. In the case of this type of pressure sensor, as the pressure increases, the contact area between the conductive coating films or the contact area between the conductive coating film and the comb electrode changes, thereby changing the conduction state. Therefore, it is possible to detect a change in pressure as a change in electrical resistance value, which can be said to be a contact area change type.

  Patent Document 1 discloses a pressure-sensitive type in which the resistance between the application-side and receive-side electrodes varies depending on the contact area between the conductive coating films formed of pressure-sensitive conductive ink containing conductive carbon black. Sensors have been reported. In this pressure-sensitive sensor, the pressure-sensitive conductive ink increases the strength as a resin and adds conductive carbon black by adding 30 to 70 parts by weight of silicon dioxide to 100 parts by weight of the silicone elastomer component as a binder. Increases the dispersion effect. In the case of this pressure sensor, unlike the resistance value change type pressure sensor, the change in the interparticle distance between the conductive particles is not used, and the pressure is detected while the conductive particles are in contact with each other. It does not cause problems that become difficult to do.

  In addition, as a pressure-sensitive sensor using a rubber, an elastomer, a resin material, or the like as a base material, a capacitance change type using a dielectric constant of the base material is known. For example, Patent Document 2 includes a pair of electrode layers, and a dielectric layer made of a rubber elastic body that is interposed between the pair of electrode layers and separates each of the pair of electrode layers. Pressure sensitive sensors have been reported. In this pressure-sensitive sensor, the dielectric layer has a tan δ at 1 to 30 Hz at 10 ° C. to 30 ° C. of 0.03 or less and rubber at A scale in accordance with JIS-K-6301 at 10 ° C. to 30 ° C. The hardness is 20 to 80 degrees. This pressure sensor utilizes the fact that the dielectric layer made of a rubber elastic body is elastically deformed by pressure to change the capacitance. Therefore, unlike the resistance value change type pressure-sensitive sensor, the change in the interparticle distance of the conductive particles is not used, and there is no problem that it is difficult to detect the pressure due to the contact state of the conductive particles. .

Japanese Patent No. 3882172 Japanese Patent No. 3593184

  The pressure sensor disclosed in the cited document 1 has the following problems. Depending on the type of the substrate on which the pressure-sensitive conductive ink layer is formed, there are cases where the method of bending the substrate varies or is permanently deformed by repeated compression and release. As a result, the reproducibility of the change in the contact area between the detection electrode and the pressure-sensitive conductive ink layer at the time of compression release may be lacking, and the reproducibility of the electrical resistance value obtained as a detection signal may not be good.

  Further, the pressure sensor disclosed in the cited document 2 has the following problems.

  (1) When a rubber elastic body having a small hysteresis against compressive deformation is used as a dielectric layer in a capacitive sensor, a chattering phenomenon (a phenomenon in which ON / OFF is repeated in a short time) occurs during sensor detection, and the reproducibility of the detection signal May not be good. In some cases, the control itself as a sensor may be difficult.

  (2) Depending on the main chain structure of the polymer used for the rubber elastic body, which is a dielectric layer, the dielectric constant is too low, and the amount of change in capacitance due to repeated compression deformation is not sufficient, which may not be practical as a sensor. is there.

  (3) Depending on the main chain structure of the polymer used for the rubber elastic body that is the dielectric layer, the remaining low-molecular-weight volatile components may become an insulating material due to sparks in electrical contact parts such as connectors, causing contact failure. There is.

  As described above, there is a demand for a member for a pressure-sensitive sensor that has good reproducibility of a detection signal for repeated compression deformation and that does not contaminate a contact object.

  Accordingly, an object of the present invention is to provide a conductive member for a pressure-sensitive sensor that has excellent reproducibility with respect to a change in electric resistance value, which is a detection signal for repeated compressive deformation, and is free from contamination of a contact object. is there.

As a result of intensive studies to achieve the above object, the present inventor has a small hysteresis loss due to repeated compression deformation, and has excellent reproducibility with respect to electrical resistance value change which is a detection signal due to compression deformation, The present inventors have found a pressure-sensitive sensor conductive member that is free from contamination of a contact object. This is a pressure sensitive sensor conductive member having an elastic body as a base material and a conductive coating film formed on the surface of the elastic body. The specific polymer is a main component of rubber, and the ratio of all rubber components is a certain amount or more. It is obtained by using the rubber composition part as a base material. That is, the pressure-sensitive sensor conductive member of the present invention, an elastic member as a substrate, possess the formed elastic surface conductive coating film, due to contact of the conductive coating film and the detecting electrode A conductive member for a pressure-sensitive sensor that detects pressure by a change in electrical resistance value , wherein the elastic body is made of a rubber composition containing 70% by volume or more of a rubber component, and the rubber composition has a total amount of rubber component of 100. In the case of mass parts, 60 parts by mass or more of polybutadiene rubber and 40 parts by mass or less of diene rubber excluding polybutadiene rubber are included.

  The conductive member for a pressure sensitive sensor of the present invention uses a rubber composition in which a ratio of a rubber component mainly composed of polybutadiene rubber is a predetermined amount or more as a base material for forming a conductive coating film, thereby preventing repeated compression deformation. Excellent reproducibility was realized with respect to the change in electrical resistance, which is the detection signal.

  Further, the conductive member for a pressure sensitive sensor of the present invention is composed of a rubber composition containing a polybutadiene rubber and a diene rubber excluding polybutadiene rubber as a base material, for example, a low molecular weight siloxane component generated in the case of silicone rubber. Does not cause electrode contamination. In addition, a conductive coating film is formed on the outer layer, and contact member contamination due to a vulcanizing agent residue remaining in the base material does not occur.

It is a schematic diagram which shows a measurement of the pressure and electrical resistance value in repeated compression. 3 is a graph showing the relationship between pressure and resistance LogR during repeated compression in Example 1. FIG. It is a graph which shows the relationship between the pressure at the time of repeated compression in Example 2, and resistance LogR. It is a graph which shows the relationship between the pressure at the time of repeated compression in Comparative Example 1, and resistance LogR. It is a graph which shows the relationship between the pressure at the time of repeated compression in Comparative Example 2, and resistance LogR.

  In the conductive member for a pressure-sensitive sensor in which a conductive coating film is formed on the surface of the substrate, the present inventors have determined the influence of the substrate on the reproducibility of the change in electrical resistance value with respect to repeated compression deformation, The research was inspired by the influence of structure and impact resilience. As a result, a conductive member having a rubber composition mainly composed of polybutadiene rubber, which has high impact resilience, and a conductive coating film formed on the surface can improve the reproducibility of the change in electrical resistance value against compression deformation. The present invention has been completed and the present invention has been completed.

  The conductive member for a pressure sensitive sensor of the present invention has an elastic body made of a rubber composition as a base material, and a conductive coating film is formed on the elastic body surface. The rubber composition contains 60 parts by mass or more of polybutadiene rubber and 40 parts by mass or less of diene rubber excluding polybutadiene rubber when the total amount of rubber components is 100 parts by mass. Contains 70% by volume or more of components.

  The following reasons can be considered as the reason why the conductive member for a pressure-sensitive sensor of the present invention has excellent reproducibility in electrical resistance value change due to repeated compression deformation. In general, when an elastic body made of a rubber composition is repeatedly compressed and deformed, energy loss occurs between a polymer and a polymer, between a polymer and a filler, or between a filler and a filler. The magnitude of this energy loss affects the hysteresis with respect to repeated compression deformation of the rubber composition. Therefore, the rubber composition with small energy loss has good hysteresis against repeated compression deformation, and in the case of a conductive member having a conductive coating film formed on the surface of the rubber composition, the electrical resistance value change due to repeated compression deformation is reproduced. The property is good.

  As for the reproducibility of the change in the electric resistance value due to repeated compression deformation, it is desirable that the resistance difference at the time of releasing the compression is 0.3 digits or less, more preferably 0.1 digits or less, in the region where the pressure is 100 kPa or less. . Such a resistance difference can be suitably used, for example, for a sensor that abuts against a comb-shaped electrode and measures the magnitude and distribution of the applied pressure acting on the member.

  In the present invention, the polymer-derived energy loss is reduced by using polybutadiene rubber having a small intermolecular force and less steric hindrance during molecular rotation as a main rubber component. Furthermore, by setting the blending ratio of the rubber component in the rubber composition to a certain amount or more, the blending ratio of other additives is relatively reduced, and the energy loss caused by the filler which is one of the additives is reduced. A rubber composition having good hysteresis against repeated compression deformation is realized.

  In addition, the compounding quantity of polybutadiene rubber is 60 mass parts or more when all the rubber components are 100 mass parts. If it is more than the above blending amount, the hysteresis with respect to repeated compression deformation will be good due to the characteristics of the polybutadiene rubber having a small intermolecular force and little steric hindrance during molecular rotation. Moreover, as other rubber components, 40 mass parts or less of diene rubbers excluding polybutadiene rubber are contained.

  Examples of the diene rubber include natural rubber, isoprene rubber, acrylonitrile butadiene rubber, styrene butadiene rubber, and chloroprene rubber.

  Among these, since the polybutadiene rubber is a nonpolar diene rubber, a nonpolar diene rubber is preferable in consideration of affinity. Examples of such rubber include isoprene rubber, natural rubber, and styrene butadiene rubber.

  Among these, in view of the influence of the molecular structure on the steric hindrance during molecular rotation, isoprene rubber or natural rubber having an isoprene structure is more preferable. By containing at least one of isoprene rubber and natural rubber in a range of 5 parts by mass (5% by mass or more) and 40 parts by mass (40% by mass or less) when the total amount of rubber components is 100 parts by mass. The properties of the polybutadiene rubber are not impaired, kneading workability is improved, and the mechanical strength of the pressure-sensitive sensor conductive member can be increased. In the case of containing at least one of isoprene rubber and natural rubber, the polybutadiene rubber is 60 parts by mass (60% by mass or more), 95 parts by mass or less (95% by mass or less) when the total amount of rubber components is 100 parts by mass. Range. Even if the polybutadiene rubber is 100 parts by mass (100% by mass) without containing other rubber components, no inconvenience occurs.

  In the rubber composition containing polybutadiene as a main rubber component, the ratio of the rubber component is 70% by volume or more. The rubber composition usually contains various compounding agents in addition to the rubber component. Examples thereof include those conventionally used as rubber compounding agents such as conductivity imparting agents, vulcanizing agents, vulcanization accelerators, fillers, anti-aging agents, softening agents, plasticizers and the like.

  Any conventionally known sulfur vulcanization or organic peroxide vulcanization can be used as the vulcanization system for the pressure sensitive sensor conductive member of the present invention. In the case of a vulcanization system using sulfur, a polysulfide bond is included as a crosslinked form, whereas organic peroxide vulcanization is a bond between carbon atoms in a polymer chain. For this reason, rubber peroxide chains become dense vulcanizates with excellent compression set and good resistance to repeated compression deformation, and therefore organic peroxide vulcanization is preferred. In addition, there is no restriction | limiting in particular as an organic peroxide to be used, A conventionally well-known diacyl peroxide, peroxyester, dialkyl peroxide, a perketal, etc. can be used. Among these, dialkyl peroxide is more preferable, and dicumyl peroxide is preferable. The blending amount of dicumyl peroxide is 0.3 parts by mass or more and 3 parts by mass or less when the total amount of the rubber component is 100 parts by mass, so that the reproducibility of the change in electric resistance value due to repeated compression deformation can be achieved. A good conductive member for a pressure sensitive sensor can be obtained. More preferably, it is 1 part by mass or more and 2 parts by mass or less.

  As the conductivity-imparting agent, any conventionally known one can be used without particular limitation, and examples thereof include the following. Metal particles such as copper powder and silver powder, surface-treated products in which metal particles are surface-treated with inorganic substances, or zinc oxide powder or carbon black, spherical graphite, organic, which are made N-type semiconductors by doping zinc oxide or the like with a different element Resin carbides.

  In view of the affinity with the rubber component, carbon-based particles such as carbon black, spherical graphite, and organic resin carbide are preferable. As the anti-aging agent, 2-mercaptobenzimidazole, polymerized 2,2,4-trimethyl 1,2-bihydroquinoline and the like are preferable. In the case of organic peroxide vulcanization, improvement in heat aging resistance can be expected by adding zinc oxide. As the plasticizer and softener, for example, a paraffinic oil having a small unsaturated bond is suitable.

  In the present invention, the above compounding agent can be appropriately blended as necessary, but considering the effect of the other compounding agents on the energy loss, the ratio of the rubber component in the rubber composition is 70% by volume. It is necessary to do it above. When the ratio of the rubber component in the rubber composition is 70% by volume or more, it is possible to obtain a rubber composition having good hysteresis against repeated compression deformation. The ratio of the rubber component in the rubber composition is 100% by volume, which is an ideal state for hysteresis against compression deformation. For example, it is most ideal when the raw rubber is compounded with only an organic peroxide and vulcanized. A thing close to the state is obtained.

  The polybutadiene rubber used in the present invention is preferably a high cis type polybutadiene rubber containing 90% by mass or more, more preferably 95% by mass or more of cis 1,4-butadiene bonds. The cis 1,4-butadiene rubber bond serves as an index of the linearity of the molecular chain, and when it is 90% by mass or more, the linearity of the molecular chain of the polybutadiene rubber is good. Therefore, a rubber composition having small steric hindrance during molecular rotation and good hysteresis against repeated compression deformation can be obtained.

  The polybutadiene rubber preferably has a ratio (Tcp / ML) of 5 mass% toluene solution viscosity (Tcp) at 25 ° C. to Mooney viscosity (ML) at 100 ° C. of 2 to 5.

  Tcp indicates the degree of entanglement of molecules in a concentrated solution. In the case of polybutadiene having the same molecular weight distribution, if the molecular weight is the same (that is, if ML1 + 4 is the same), the index of branching degree. (The greater the Tcp, the smaller the branching degree). As a method for measuring the toluene solution viscosity (Tcp), after dissolving the polymer in toluene at a concentration of 5% by mass, a standard solution for calibrating viscometer (JIS Z8809) is used as a standard solution, and Canon Fenceke viscometer NO . Measure using 400. The Mooney viscosity is measured by the method described in JIS K6300.

  Further, Tcp / ML is used as an index (when Tcp / ML is larger, the degree of branching is smaller) when comparing the degree of branching of polybutadienes having different MLs. When the ratio (Tcp / ML) of the toluene solution viscosity (Tcp) to the Mooney viscosity (ML) is in the above range, the degree of branching of the molecular chain is small, and the steric hindrance at the time of molecular rotation is small. A composition is obtained. In addition, when Tcp / ML ratio is larger than the said range, the cold flow property of a natural rubber will become large, and when it is smaller than the said range, impact resilience will become low.

  Moreover, it is preferable that the 5 mass% toluene solution viscosity (Tcp) in 25 degreeC of polybutadiene rubber is the range of 50-150 cp. Moreover, it is preferable that the Mooney viscosity (ML) in 100 degreeC of polybutadiene rubber is the range of 30-100. Within these numerical ranges, a rubber composition having good kneadability and excellent resilience can be obtained.

  The substrate hardness of the pressure-sensitive sensor conductive member of the present invention is not particularly limited. In the test method for determining the hardness of vulcanized rubber according to JIS K6253, the hardness of the A type is from 30 degrees to 80 degrees. Degrees, more preferably 40 degrees to 70 degrees. If it is in the said range, a rubber composition with favorable hysteresis will be obtained with respect to repeated compression deformation.

  The unvulcanized rubber composition used as the base material for the pressure-sensitive sensor conductive member is added with other compounding agents such as the above-mentioned rubber component and other polymers, conductivity-imparting agents, and fillers, if necessary. , Can be prepared by mixing. Mixing can be performed using, for example, a closed kneader such as a Banbury mixer, an intermix or a pressure kneader, or an open kneader such as an open roll. As a mixing condition, for example, a condition that allows other compounding agents to be uniformly dispersed in the base rubber, such as 30 to 150 ° C. and 3 to 30 minutes, may be selected.

  The method for molding and vulcanizing the rubber composition is not particularly limited, and examples of the molding method include extrusion molding, injection molding, and press molding. Injection molding is a method in which an injection pressure is applied to the unvulcanized product and the resulting product is pushed into a mold, filled in the mold, and molded into a mold shape. Extrusion molding is a method in which the unvulcanized product is kneaded with a screw and passed through an extrusion die (die) at the tip for continuous molding. Moreover, you may shape | mold in flat form with an open roll etc. other than the said method.

  The vulcanization method for the unvulcanized rubber mixture after molding is not particularly limited as long as the vulcanization is performed by temperature control such as heating and cooling.

  Peroxide vulcanization compounds are hot air vulcanization or direct steam vulcanization involving air, and the surface of the vulcanizate is formed by molecular cutting that occurs in order to bond oxygen in the air to the free radicals of the polymer produced. A method that does not involve air is suitable because it exhibits extremely high tackiness. For example, a vulcanizing can degassed by in-mold vulcanization or purging, a hot molten salt tank (LCM), or the like can be used. Specifically, for example, it can be carried out by heating at 150 to 180 ° C. under pressure for 5 to 50 minutes while being filled in a mold.

  Moreover, when removing unreacted residues, such as a vulcanizing agent, the method of carrying out the secondary vulcanization | cure of the pressure-sensitive conductive material after the said vulcanization | cure with a hot air oven etc. is mentioned, What is necessary is just to implement. For example, as the conditions for secondary vulcanization, heating can be performed in a hot air oven at 120 to 200 ° C. for 15 to 100 minutes.

  The conductive member for a pressure-sensitive sensor of the present invention is obtained by forming a conductive coating film on the surface of a base material made of the rubber composition. The role of the conductive coating film functions as an element that detects the action of external force on the conductive member for the pressure sensitive sensor of the present invention as an electric resistance value, and also contaminates the contact member due to undecomposed residue remaining in the base material. It is to prevent.

  Examples of the base resin for the conductive coating film include the following. Fluorine resin, polyamide resin, acrylic resin, polyurethane resin, silicone resin, butyral resin, styrene-ethylene / butylene-olefin copolymer (SEBC) and olefin-ethylene / butylene / olefin copolymer (CEBC). These resins may be used alone or in combination of two or more. Further, the base resin may be a cross-linked resin, and as a curing agent for this purpose, for example, an isocyanate compound and an amine compound can be appropriately blended.

  Moreover, in order to obtain a desired electrical resistance value, conductive carbon, graphite, copper, aluminum, nickel, iron powder, and conductive agents such as conductive tin oxide and conductive titanium oxide which are metal oxides are contained. These may be used alone or in combination of two or more.

  The blending ratio of the conductive particles with respect to 100 parts by weight of the base resin of the conductive coating film may be appropriately adjusted according to the desired electric resistance value, and is in the range of 2 to 200 parts by weight, preferably 5 to 100 parts by weight. The

  In addition to the base resin and conductive particles, other components can be blended, and examples thereof include organic elastic fillers and inorganic oxide fillers. Examples of the organic elastic filler include spherical particles made of an elastomer such as silicone or urethane, or a resin such as acrylic, styrene, or polyamide. Examples of the inorganic oxide filler include silica, alumina, titanium oxide, zinc oxide, and magnesium oxide.

  The conductive coating film has one or more layers, and preferably has a thickness of 10 to 50 μm as a whole, more preferably 10 to 30 μm. When the thickness of the conductive coating film is 50 μm or less, the flexibility is not impaired, and it can be suitably used as a conductive member for a pressure sensitive sensor. Moreover, if thickness is 10 micrometers or more, the contamination resulting from base rubber can be suppressed.

  As a method for producing a conductive coating film, a coating liquid composed of the above-mentioned conductive coating film and an organic solvent is prepared, and after the coating liquid is applied to the base rubber surface, the solvent is removed. This can be done. The coating liquid is prepared by dispersing using a dispersing device using beads such as a sand mill, paint shaker, dyno mill, pearl mill and the like. The solvent may be any solvent that can dissolve or disperse a material necessary for the conductive coating film. For example, the following are mentioned. Alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran , Ethers such as dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, ethylene chloride, dichloroethylene, carbon tetrachloride and trichloroethylene, benzene and toluene , Aromatic compounds such as xylene, ligroin, chlorobenzene and dichlorobenzene.

  Examples of the method for applying the coating liquid to the base rubber surface include conventionally known dip coating, spray coating, roll coating, and the like. Particularly preferred.

  Further, the solvent is removed using a hot air circulating dryer or an infrared drying furnace to form a conductive coating film on the surface of the base rubber.

  The conductive coating film may be formed on at least one surface of the elastic body serving as a base material. When the conductive member of the present invention is used as a pressure-sensitive sensor, an electrode is formed on a substrate on which at least a pair of electrode layers are formed. What is necessary is just to arrange | position a conductive member so that a conductive coating film may oppose a layer. A pressure-sensitive sensor having a substrate, at least a pair of electrode layers provided on the substrate, and a conductor layer provided to face the electrode layer, the conductive member for a pressure-sensitive sensor of the present invention being a conductor. It is used as a layer. In this pressure-sensitive sensor, a change in pressure applied to at least one of the electrode layer and the conductor layer can be detected as a change in electric resistance value.

  The conductive member for a pressure sensor of the present invention will be specifically described.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited only to these examples.

  The raw materials of the base materials used in each example and comparative example are as shown in Table 1 below.

  The raw materials other than the vulcanizing agent were kneaded at a ratio shown in Tables 3 and 4 using a 3 L pressure kneader (D3-10: manufactured by Moriyama Corporation).

  First, only the raw rubber was masticated for 1 minute at a rotor rotational speed of 30 rpm, and then zinc oxide, zinc stearate and carbon black were added and kneaded for 10 minutes. The filling amount of the material with respect to the kneader capacity was 65 vol%. After the obtained rubber composition was cooled at room temperature (25 ° C.) for 1 hour, a vulcanizing agent was further kneaded using an open roll machine (12-inch test roll machine: manufactured by Kansai Roll Co., Ltd.). After kneading for 15 minutes at a front roll of 15 rpm and a back roll of 18 rpm as appropriate, after passing through a roll gap of 0.6 mm, it is cut into 15 mm × 15 mm, and then unvulcanized rubber composition that becomes a base material Got. Next, the unvulcanized product is filled in a 15 mm × 15 mm × 0.5 mm mold preheated to 170 ° C., press vulcanized at 170 ° C. and 100 kgf for 15 minutes, and a pressure sensitive sensor conductive member An elastic body serving as a base material was obtained.

  Subsequently, in order to prepare a conductive paint, each component shown in Table 2 below and its composition were blended to obtain a solution having a solid content of 30.0% by mass.

  To 200 parts by mass of this resin solution, 200 parts by mass of glass beads having a diameter of 0.8 mm were added, placed in a 450 ml mayonnaise bottle, and dispersed for 6 hours using a paint shaker. Finally, the solution was filtered through a 200 mesh screen to prepare a resin paint.

  The conductive paint is applied to the surface of the elastic body by a dipping method at a pulling rate of 10 mm / sec, air-dried for 30 minutes, and then cured by heating at 160 ° C. for 1 hour using an oven. A conductive member for a pressure-sensitive sensor having a conductive coating film was obtained.

[Reproducibility of electrical resistance change due to repeated compression deformation]
The obtained rectangular sheet of the pressure-sensitive sensor conductive member was left in a 23 ° C./60% RH (N / N) environment for 24 hours or more, and then the reproducibility of the change in electric resistance value with respect to repeated compression deformation was evaluated.

  As shown in FIG. 1, the test piece for evaluation was placed on the comb-shaped electrode 1 (electrode width 1 mm, electrode interval 0.5 mm), and pressure was applied to the entire top surface of the square sheet. In this state, DC voltage 5V6 is applied to the comb-shaped electrode, and the load measuring device 7 repeatedly compresses the pressure-sensitive conductive material 2 in the thickness direction in the range of 0 to 100 kPa 1000 times and is connected in series to the comb-shaped electrode. The voltage applied to the 1 kΩ resistor 5 was measured by the voltage measuring device 4. The resistance value (R) of the pressure-sensitive conductive material was determined from the average value Vave (V) of the measured voltage values.

In the evaluation of reproducibility, logR _A1 , LogR _A3 , and LogR _A5 are values obtained by logarithmically changing resistance values (R) at 10 kPa, 20 kPa, and 40 kPa at the first pressurization of repeated compression, respectively.

Further, LogR _B1 , LogR _B3 , and LogR _B5 are values obtained by logarithmically converting resistance values (R) at 10 kPa, 20 kPa, and 40 kPa at the time of decompression for the 1000th repetitive compression.

The absolute value of the difference was obtained from the above LogR _A and LogR _B, and used as an index of reproducibility of the change in electric resistance value with respect to repeated compression deformation.
_A : | Δ (LogR _A -LogR _B ) | ≦ 0.1 Best reproducibility ○: 0.1 <| Δ (LogR _A -LogR _B ) | ≦ 0.3 Good reproducibility ×: 0.3 <| Δ (LogR _A -LogR _B ) | Low reproducibility Further, in the above evaluation criteria, comprehensive judgment in reproducibility evaluation at pressures of 10 kPa, 20 kPa, and 40 kPa was performed according to the following criteria.
◎: Reproducibility evaluation at pressures of 10 kPa, 20 kPa, and 40 kPa ◎ Two, ○ One or more (x not included)
○: Reproducibility evaluation at pressures of 10 kPa, 20 kPa, and 40 kPa: ◎ 1, ○: 2 or less (x not included)
X: In any of the reproducibility evaluations at pressures of 10 kPa, 20 kPa, and 40 kPa, x is included.

  The relationship between the pressure and resistance LogR in the repeated compression release of Examples 1 and 2 and Comparative Examples 1 and 2 is shown in FIGS. From the results of Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4, it can be seen that the rubber component of the rubber composition is suitable to contain polybutadiene rubber within the scope of the present invention. That is, Comparative Example 1, which is outside the scope of the present invention, and Comparative Examples 2, 3, and 4 in which no polybutadiene rubber is used as the rubber component, are inferior in reproducibility of change in electrical resistance value due to repeated compression deformation.

  Further, Example 4 and Comparative Example 5 show that it is suitable that polybutadiene rubber is contained as a rubber component within the scope of the present invention, and the ratio of the rubber component in the rubber composition is within the scope of the present invention. That is, Comparative Example 5 in which the ratio of the rubber component is outside the range of the present invention is inferior in reproducibility of the change in electric resistance value with respect to repeated compression deformation.

  Examples 1, 6, and 7 show that the polybutadiene rubber of the present invention is more preferably a polybutadiene rubber having a ratio of toluene solution viscosity (Tcp) to Mooney viscosity (ML) within the range of the present invention. That is, in Examples 5 and 6 in which the ratio of the toluene solution viscosity (Tcp) to the Mooney viscosity (ML) is smaller than 2, the difference in the electric resistance value change at 10 kPa and 20 kPa tends to increase.

  Further, Examples 2, 5, 8, and 9 show that isoprene rubber and natural rubber are more preferable when polybutadiene rubber is used by blending with other rubber. That is, as compared with Examples 2 and 9 using styrene butadiene rubber or acrylonitrile butadiene rubber as a blend rubber of polybutadiene rubber, Examples 5 and 8 using isoprene rubber and natural rubber are more different in electric resistance value change. Small and good.

  The conductive member for a pressure-sensitive sensor of the present invention can be suitably used as a sensor for measuring the magnitude and distribution state of a pressure applied to a member by forming the conductive member into a desired shape and bringing it into contact with a comb-shaped electrode, for example. .

1 Single-sided electrode (comb type)
2 Pressure-sensitive conductive material 3 Insulating sheet 4 Voltage measuring instrument 5 1 kΩ resistor 6 DC voltage 5V
7 Load measuring device

Claims (6)

An elastic member as a substrate, possess the formed elastic surface conductive coating film, for pressure-sensitive sensor for detecting the pressure by the electric resistance change due to contact of the conductive coating film and the detecting electrode A conductive member,
The elastic body is composed of a rubber composition containing 70% by volume or more of a rubber component,
The rubber composition contains 60 parts by mass or more of polybutadiene rubber and 40 parts by mass or less of diene rubber excluding polybutadiene rubber when the total amount of rubber components is 100 parts by mass. Conductive member for sensor.   The conductive member for a pressure-sensitive sensor according to claim 1, wherein the polybutadiene rubber contains 90% by mass or more of cis 1,4-butadiene bonds.   The pressure-sensitive sensor according to claim 1 or 2, wherein the polybutadiene rubber has a 5 mass% toluene solution viscosity (Tcp) at 25 ° C of 50 to 150 cp and a Mooney viscosity (ML) at 100 ° C of 30 to 100. Conductive member.   4. The ratio (Tcp / ML) of 5 mass% toluene solution viscosity (Tcp) at 25 ° C. to Mooney viscosity (ML) at 100 ° C. is 2 to 5 in the polybutadiene rubber. Conductive member for pressure sensitive sensor.   When the rubber composition has a total amount of rubber components of 100 parts by mass, it contains polybutadiene rubber in a range of 60 parts by mass or more and 95 parts by mass or less, and at least one kind of isoprene rubber and natural rubber is 5 parts by mass or more. The conductive member for pressure-sensitive sensors according to any one of claims 1 to 4, which is contained in a range of 40 parts by mass or less. A pressure change with respect to at least one of the electrode layer and the conductor layer, comprising: a substrate; at least a pair of electrode layers provided on the substrate; and a conductor layer provided to face the electrode layer In the pressure sensor which detects this as an electrical resistance value change, this conductor layer is the conductive member for pressure sensors in any one of Claims 1-5, The pressure sensor characterized by the above-mentioned.

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