JP5945469B2 - Pressure sensor - Google Patents

Description

  The present invention relates to a pressure-sensitive sensor having a characteristic that an electric resistance value is changed by applying pressure.

  Conventionally, as a means of measuring the magnitude of pressure acting on a member and the distribution of pressure, a conductive material in which a polymer material such as rubber, elastomer or resin material is used as a base material and conductive particles are dispersed in this base material It is known to use members.

  The pressure-sensitive characteristics due to the conductive member are roughly classified into the following two types. One of them is that the state of the conductive path formed by the conductive particles in the conductive member changes that the electric resistance value changes depending on whether the pressure is applied or not. The resistance value change type. In addition, since the change of the electrical resistance value greatly affects the dispersion state of the conductive particles in the base material, the reproducibility of the change in the electrical resistance value due to repeated compression deformation is a problem. In particular, as the pressing is repeated, the conductive member undergoes permanent deformation due to fatigue, and the state of formation of the conductive path by the conductive particles remains changed, which makes it difficult to detect the pressure.

  The other type is a type in which a conductive coating film is formed using the conductive member, and the conductive coating films are arranged opposite to each other, or the conductive coating film and, for example, a comb-type electrode are arranged to face each other. In the case of this type of pressure-sensitive 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-type electrode changes, thereby changing the conduction state. Therefore, it is possible to detect a change in pressure as a change in electric resistance value, which can be said to be a contact area change type.

  Such a pressure-sensitive sensor is composed of at least a conductive member that receives pressure and an electrode substrate that serves as an output path for a change in electrical resistance value. Furthermore, the pressure-sensitive conductive member and the electrode substrate are fixed or the pressure-sensitive conductive member is pressed against the electrode substrate so that stable pressure-sensitive performance can be maintained during use.

  For example, in a pressure-sensitive sensor in which a pressure-sensitive conductive elastic body is provided on a comb-shaped electrode, the pressure-sensitive conductive elastic body is covered with a thin skin (film or the like) having pressure. A sensor has been proposed (Patent Document 1). When the pressure sensor is released after pressure is applied by the pusher, the shape recovery property of the thin skin itself acts in addition to the shape recovery property of the pressure-sensitive conductive elastic body. It becomes a structure and it becomes a pressure-sensitive sensor with small hysteresis of a resistance value-load curve.

  In addition, the first and second insulating films formed in a desired shape by continuously forming a circuit pattern having a conductive layer are opposed to the circuit pattern, and a spacer made of a third insulating film having a plurality of openings. A film sensor having a detection unit sandwiched between the two insulating films and facing the circuit pattern at each opening, wherein each circuit pattern has a second conductive property in a region corresponding to the plurality of openings. A film sensor is proposed in which a layer is formed and formed only on the periphery of the second conductive layer, and the inner side of the second conductive layer is omitted (Patent Document 2). . In this film sensor, the conductive layer is opposed to the spacer with a space corresponding to the thickness of the spacer in the opening, and a pressure detection unit is formed in the opening. In the film sensor configured as described above, when pressure is applied to the detection unit, one or both of the film substrates are elastically deformed to connect the conductive layers, and when the pressure is released, the connection between the conductive layers is released. .

JP 2001-195945 A JP 2001-21423 A

The pressure-sensitive sensor of Patent Document 1 has problems in the following points.
(1) Since pressure is constantly applied to the pressure-sensitive conductive elastic body, an electrical signal is output before external pressure is applied, which may cause erroneous detection.

Moreover, the film sensor of Patent Document 2 has problems in the following points.
(1) The detection unit is limited to the opening portion, and pressure is not detected unless pressure is applied only to the detection unit while avoiding the spacer portion.
(2) Further, for the structural reason of (1), it is not suitable for downsizing.

  Therefore, the problem of the present invention is that it is difficult to detect erroneously, the pressure-sensitive conductive rubber member is hard to be permanently deformed, shows a load-output characteristic that is highly reliable over a long period of time, and the pressure load shape on the detection unit is The present invention provides a pressure-sensitive sensor that can be downsized without being limited thereto.

The present invention provides a pressure-sensitive sensor in which an electrode substrate and a conductive rubber member are arranged to face each other in a close and non-contact state, and the electrode substrate and the conductive rubber member are provided with at least a fixing agent layer. And is covered with an insulating coating member made of a conductive film and fixed to the insulating coating member via the fixing agent layer, and the electrode substrate and the conductive rubber member in the proximity non-contact state, The flexible film has a Young's modulus of 2 GPa or more and 10 GPa or less and a thickness of 10 μm or more and 60 μm or less. .

  According to the present invention, electrical insulation at no load is ensured, it is difficult to detect erroneously, the conductive rubber member is hard to be permanently deformed, load hysteresis at load-unloading is small, and durability against repeated use Provides a highly reproducible load-output characteristic over a long period of time, and provides a pressure-sensitive sensor that can be miniaturized with little variation in load position, without limiting the load shape of the pressure on the detector Is done.

It is sectional drawing of the pressure-sensitive sensor which concerns on this invention. It is a figure which shows the relationship between the magnitude | size of a load and the magnitude | size of an electroconductive rubber member. It is a figure which shows the amount of clearance gaps between an electrode substrate and a conductive rubber member. It is sectional drawing which shows the state which coat | covers an electrode substrate and a conductive rubber member with an insulating coating member. It is the figure seen from the direction from which the projected area of the insulating coating | coated member of the pressure sensor which concerns on this invention becomes the maximum value. It is a figure which shows a comb-type electrode substrate. It is a figure which shows the evaluation apparatus of a pressure-sensitive characteristic. It is a figure which shows the position of the pusher with respect to a detection part.

  Hereinafter, the pressure sensor of the present invention will be described with reference to the drawings. In the following description, the surface of the conductive rubber member that faces the electrode substrate and the opposite surface may be referred to as “A surface” and “B surface”, respectively. In addition, the surface of the electrode substrate having the electrode and the surface on the opposite side may be referred to as “a surface” and “b surface”, respectively.

  FIG. 1 is an example of a cross-sectional view of a pressure-sensitive sensor according to the present invention. The A surface of the conductive rubber member (110) is disposed so as to face the surface of the electrode substrate (120) having the electrodes (that is, the a surface) in a proximity non-contact state. These electrode substrate and conductive rubber member are covered with an insulating covering member (130). This insulating covering member has a flexible film (131) and an adhesive fixing agent layer (132) formed over the entire one surface (inner surface). The conductive rubber member and the electrode substrate are fixed to the insulating covering member via this adhesive fixing agent layer.

  The insulating covering member is bent as shown in the figure, and the A surface of the conductive rubber member and the a surface of the electrode substrate are in close proximity and non-contact state due to the waist of the film when in an unloaded state. When a load is applied, as shown in FIG. 1B, the insulating covering member bends, the electrode on the a-side of the electrode substrate contacts the A-side of the conductive rubber member, and the conduction resistance changes.

  The pressure-sensitive sensor of the present embodiment is not only when the size (area) of the pressure application surface of the applied load is smaller than the area of the conductive rubber member of the pressure-sensitive sensor (FIG. 2-a), but also when it is large ( Also in FIG. 2B, since there is no inclusion such as a spacer between the electrode and the conductive rubber member, the electrode and the conductive rubber member can be in contact with each other and can function as a pressure-sensitive sensor.

  In an environment where a pressure sensor is mounted and used, the conductive resistance may change due to contact between the electrode and the conductive rubber member due to noise caused by high-speed movement or vibration, causing false detection. There is. In the pressure-sensitive sensor of the present invention, the conductive rubber member and the electrode are fixed in proximity and non-contact by the insulating coating member, and the Young's modulus and thickness of the conductive coating member, and the gap amount between the conductive rubber member and the electrode By adjusting the value, the minimum detection load can be adjusted effectively, so that such erroneous detection can be prevented.

  In the proximity non-contact state, the gap amount (141 in FIG. 3) between the A surface of the conductive rubber member and the a surface having the electrode of the electrode substrate is preferably 10 μm or more and 300 μm or less. When the gap amount is 10 μm or more, it can be stably restored to the separated state when repeated load-unloading is performed, and the reproduction accuracy of the minimum detection load is excellent, and the occurrence of erroneous detection is prevented. When the gap amount is 300 μm or less, the contact state between the conductive rubber member and the facing electrode is kept uniform even when the pressure position, angle, and the like change, and variations in output characteristics hardly occur.

<Insulating coating member>
The insulating covering member according to the present invention is a member having at least a flexible film and a fixing agent layer, and is a member for covering and fixing the conductive rubber member and the electrode substrate. By using such an insulating covering member, the conductive rubber member and the electrode substrate can be arranged to face each other in a close proximity and non-contact state, and the gap amount can be easily adjusted.

  FIG. 4 shows a state in which the separation forming jig (140) is used when the conductive rubber member (110) and the electrode substrate (120) according to the present invention are covered with the insulating covering member (130). It is an example of sectional drawing shown. First, the conductive rubber member and the electrode substrate are covered with an insulating covering member in a state where a gap forming jig is sandwiched between the conductive rubber member and the electrode substrate. At that time, the conductive rubber member and the electrode substrate are fixed to the insulating covering member by an adhesive fixing agent layer present on the inner surface of the insulating covering member. Thereafter, by removing the separation forming jig, as shown in FIG. 1A, the electrode substrate and the conductive rubber member can be arranged to face each other in the proximity non-contact state. The proximity non-contact state can be formed with high precision by forming the thickness and width of the separation forming jig to predetermined dimensions, and the gap amount can be adjusted by adjusting the dimensions of the separation forming jig. is there.

[Flexible film]
The flexible film according to the present invention is a main component of the insulating covering member. When the conductive rubber member and the electrode substrate are fixed in the proximity non-contact state by the insulating coating member, the bent portion of the flexible film acts as a waist, and the electrode and the conductive rubber in the no-load state Maintains a separated state from the member and prevents false detection. Further, when a load is applied, the flexible film is bent and deformed so that the conductive rubber member and the electrode can be brought into contact with each other. Furthermore, when the load is removed, the conductive rubber member and the electrode can be restored to the separated state by the waist force of the film, and the output hysteresis in the load-unloading can be made difficult to occur. . Furthermore, even when used repeatedly over a long period of time, a stable separation state can be maintained and erroneous detection can be prevented.

  The thickness of the flexible film is 10 μm or more and 60 μm or less. If the thickness of the flexible film is within the above range, the film is moderately stretched, and in a no-load state, the separated state between the electrode and the conductive rubber member can be maintained to prevent erroneous detection. Furthermore, a stable separation state can be maintained even during long-term use, and erroneous detection can be prevented.

The waist of the film is proportional to the product of the Young's modulus E of the film, the width b, and the cube of the thickness d. That is, the following relational expression is established. Therefore, the influence of the film thickness is particularly important.
Formula (1) The waist strength of the film ∝E · b · d ³ .

  When the thickness of the flexible film is less than 10 μm, the flexibility of the flexible film is too weak to follow the load-unloading of the load, and the output hysteresis may increase. In addition, even when the conductive rubber member and the electrode substrate are not in close contact with each other when there is no load, it is difficult to restore a stable separation state when repeated loading and unloading, and the minimum detected load is reproduced. Inaccurate and may cause false detection. In addition, the minimum detection load becomes almost no load, making it difficult to distinguish from noise, and there is a risk of erroneous detection.

  On the other hand, when the thickness of the flexible film exceeds 60 μm, the flexibility of the flexible film is too strong, making it difficult to maintain and fix the conductive rubber member, and the conductive rubber member may be peeled off from the insulating covering member. There is. Alternatively, even if not peeled off, the conductive member bends following the flexible film, and when a load is applied, the contact state between the opposing electrode and the conductive rubber member is not good depending on the position where the load is applied. In some cases, the output characteristics of the pressure-sensitive sensor may vary.

  The Young's modulus of the flexible film is 2 GPa or more and 10 GPa or less. If the Young's modulus is within the above range, variations in pressure-sensitive characteristics due to various pressure forms are suppressed, and highly reproducible pressure-sensitive characteristics are exhibited even when the pressure-sensitive sensor is repeatedly used. When pressure is applied from the outside to the pressure sensitive sensor, the pressure is transmitted to the conductive rubber member via the flexible film. When using a pressure-sensitive conductive member that changes the contact area, in order to obtain stable pressure-sensitive characteristics, the contact state between the conductive rubber member and the electrode substrate when the conductive rubber member receives a certain pressure. It is important to ensure that is constant. By using an insulating covering member having a certain Young's modulus within a specific range as in the present invention, various forms of pressure, that is, even if the shape of the presser and the angle of the applied pressure change depending on the application. Since a stable contact area can be ensured by dispersing pressure over the entire surface of the pressure-sensitive conductive member, stable pressure-sensitive characteristics that are not affected by the form of pressure can be obtained.

  When the Young's modulus of the flexible film is less than 2 GPa, pressure dispersion to the entire conductive rubber member when a load is applied becomes insufficient, and therefore the conductive rubber member faces the conductive rubber member depending on the position where the load is applied. In some cases, the contact state with the electrode becomes non-uniform, resulting in variations in output characteristics. On the other hand, when the Young's modulus of the flexible film exceeds 10 GPa, the durability against repeated bending is inferior, so that the output gradually changes and the reproducibility may be inferior.

  The material of the flexible film is not particularly limited as long as it is insulating and satisfies the above Young's modulus and thickness, and examples thereof include the following. Biaxially stretched nylon film, polyimide film, polyethylene terephthalate film, polyphenylene sulfide film, polysulfene sulfide film, polyester film, polystyrene film and the like. Among them, a polyimide film having high heat resistance and high moisture absorption resistance is preferable.

[Maximum projected area]
In the state where the electrode substrate and the conductive rubber member are covered with the insulating coating member, the projected area of the insulating coating member as viewed from the direction in which the area becomes maximum is 3 mm ² or more and 80 mm ² or less. Is preferred. FIG. 5 is an example of a view seen from the direction in which the projected area of the insulating covering member of the pressure-sensitive sensor according to the present invention is maximized. The insulating covering member (130) encloses and fixes the electrode substrate (120) and a conductive rubber member (not shown). The maximum projected area S is represented by the product (S = b × c) of the lateral width b of the insulating covering member and the length (vertical length) c in the longitudinal direction. If the maximum projected area is within the above range, the conductive rubber member and the electrode can be fixed by the insulating covering member, and variations in output characteristics can be suppressed. When the maximum projected area is 3 mm ² or more, the insulating covering member can secure a sufficient margin for fixing with the conductive rubber member and the electrode substrate, so that the conductive rubber member and the electrode substrate are not short of fixing force. Hard to peel. When the maximum projected area is 80 mm ² or less, when a load is applied, the contact state between the opposing electrode and the conductive rubber member is unlikely to be uneven depending on the position where the load is applied, resulting in variations in output characteristics. hard.

  Further, the lateral width of the insulating covering member is not particularly limited, but is preferably 1.5 mm or more and 20 mm or less. When the width of the film is 1.5 mm or more, a sufficient margin for securing the conductive rubber member and the electrode substrate can be secured, so that the conductive rubber member and the electrode substrate are not easily peeled without insufficient fixing force. When the width of the film is 20 mm or less, when a load is applied, the contact state between the conductive rubber member and the facing electrode is less likely to be uneven depending on the position where the load is applied, and variations in output characteristics are unlikely to occur. .

  The longitudinal length of the insulating covering member is not particularly limited, but is preferably 1.5 mm or more and 20 mm or less. When the length of the film is 1.5 mm or more, it is difficult to peel off the conductive rubber member and the electrode substrate without a shortage of fixing force because a sufficient margin can be secured between the conductive rubber member and the electrode substrate. . When the length of the film is 20 mm or less, when a load is applied, the contact state between the conductive rubber member and the opposing electrode is less likely to be uneven depending on the position where the load is applied, resulting in variations in output characteristics. hard.

[Fixing agent layer]
In the flexible film which comprises the insulating coating member of this invention, the fixing agent layer is provided at least. The fixing agent layer can be formed, for example, by applying an adhesive to at least one surface of the flexible film. In the pressure-sensitive sensor of FIGS. 1 to 4, the fixing agent layer is formed over the entire one surface (inner surface) of the flexible film. The fixing agent layer is preferably formed in at least a region corresponding to the B surface of the conductive rubber member and the b surface of the electrode substrate, and a region where the flexible films overlap each other.

  The fixing agent applied to the surface of the flexible film may be an adhesive or an adhesive, but an acrylic adhesive is preferred. Also, rubber-based or silicone rubber-based adhesives can be used. However, in the rubber-based adhesive, a tackifier or the like is blended in order to obtain adhesiveness. For this reason, the tackifier oozes out in a specific use environment or for a long period of time, causing electric contact failure, or depending on the type of rubber used, due to curing, deterioration, etc., the tackiness itself Concern about being lost. In addition, the silicone rubber-based pressure-sensitive adhesive may cause an electrical contact failure due to the leakage of the low molecular siloxane component contained. On the other hand, an acrylic adhesive is more suitable because the acrylic ester copolymer itself, which is a main component, has adhesiveness and has higher adhesive strength than rubber-based and silicone-based adhesives. Although the thickness in particular of an adhesive layer is not restrict | limited, Generally it uses in the range of 10-50 micrometers.

<Electrode substrate>
In the pressure-sensitive sensor of the present invention, a known electrode substrate can be used as the electrode substrate. For example, a pattern formed by printing a copper foil or the like on an insulating substrate such as a glass epoxy substrate, or a combination of an insulating film such as polyamide and a conductor such as copper foil as in a flexible printed substrate It is done. Also, in order to reduce the size and flexibility of the pressure sensor, use a screen paste of conductive paste containing silver or carbon black on an insulating film made of polyamide or polyethylene terephthalate (PET) in an arbitrary pattern. You can also.

<Conductive rubber member>
In the pressure-sensitive sensor of the present invention, the conductive rubber member is a rubber member that is elastically deformed with compression and has a function of significantly changing the conduction resistance with the electrode disposed facing the conductive rubber member. . The conductive rubber member may be a conductive rubber base material obtained by cross-linking a rubber composition containing a conductivity-imparting agent, or a conductive rubber base material obtained by cross-linking a rubber composition made of ionic conductive rubber. Also good. Moreover, you may have a structure of two or more layers in which the electroconductive coating layer was formed on the surface of these rubber base materials. Those having a conductive coating layer formed on the surface are preferably used because hysteresis loss derived from the adhesiveness of the conductive rubber member can be suppressed as compared with those having no conductive coating layer. It is preferable that at least one conductive coating layer is formed on the A surface of the conductive rubber member (the surface facing the electrode substrate).

  Specific examples of the rubber component of the rubber composition constituting the rubber substrate include the following. Natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), ethylene propylene rubber (EPM, EPDM), chloroprene rubber (CR), isoprene rubber (IR), epichlorohydrin rubber ( CO, ECO), silicone rubber, urethane rubber (U) and the like. These can be used alone or in admixture of two or more. Among these, in consideration of hysteresis loss, NR, BR, low styrene SBR, and low nitrile NBR (AN amount 18%) are preferably used.

  The rubber composition usually contains various compounding agents in addition to the rubber component. For example, those conventionally used as rubber compounding agents such as conductivity imparting agents, vulcanizing agents, vulcanization accelerators, fillers, anti-aging agents, anti-scorching agents, softeners, plasticizers, dispersants, etc. It mix | blends suitably.

  The unvulcanized product of the rubber composition can be mixed using, for example, a kneader such as a pressure kneader or an open roll. The method for molding and crosslinking the unvulcanized rubber composition is not particularly limited. Examples of the molding method include extrusion molding and press molding. 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 to be continuously molded. Press molding is a method in which a mold is filled with the above unvulcanized product and pressure molded. 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.

  Although the elasticity modulus of a rubber base material is not specifically limited, 0.5 MPa or more and 30 MPa or less are preferable. If it is in the said range, the elastic rubber base material which has the effect | action which elastically deforms with compression and the conduction resistance with the electrode arrange | positioned facing a conductive rubber member will change significantly will be obtained. When the elastic modulus is 0.5 MPa or more, the rubber base material is deformed little by little without being immediately deformed with compression, and a sensor having a wide detection load range can be obtained. When the elastic modulus is 30 MPa or less, the rubber base material is elastically deformed following the increase and decrease of the load, and the detection resistance value becomes a smooth curve.

  The thickness (d) of the rubber base material is not particularly limited, but is preferably 0.1 mm or more and 5 mm or less. When the thickness of the rubber substrate is 0.1 mm or more, there is an amount of elastic deformation accompanying compression as the conductive rubber member, and there is a change in conduction resistance with the electrode disposed facing the conductive rubber member. can get. When the thickness of the rubber substrate is 5 mm or less, it is preferable because it is suitable for small size and shape freedom as a conductive rubber member.

  As the conductive rubber member, the rubber base material obtained as described above can be used, or a structure in which a conductive coating layer is further formed on the surface of the rubber base material can be used.

[Conductive coating layer]
The conductive rubber member in which the conductive coating layer is formed on the surface of the rubber base material has a hysteresis loss derived from the adhesiveness of the conductive rubber member, compared to the conductive rubber member in which the conductive coating layer is not formed. Can be suppressed. The conductive coating layer may be one in which the surface of the rubber base material is irradiated with ultraviolet rays or electron beams and a modified layer is provided on the surface, or a resin coating layer is formed by applying a resin to the surface of the rubber base material. May be provided. In order to more effectively suppress the hysteresis loss derived from adhesiveness, a resin coating layer is preferably used.

  Specific examples of the resin component constituting the coating composition that is a raw material for the resin coating layer include the following. Fluorine resin, polyamide resin, acrylic resin, polyurethane resin, polyester resin, epoxy resin, silicone resin, butyral resin, styrene-ethylene-butylene-olefin copolymer (SEBC) and olefin-ethylene-butylene-olefin copolymer (CEBC) )etc. These resins may be used alone or in combination of two or more. Further, the resin may be a cross-linked resin, and as a curing agent therefor, for example, an isocyanate compound and an amine compound can be appropriately blended.

In order to obtain a desired electric 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 in the coating composition. Can be blended. These may be used alone or in combination of two or more. The electric resistance value of the resin coating layer is not particularly limited, but it is preferably 10 ⁻¹ Ω · cm or more and 10 ³ Ω · cm or less under a pressure of 500 kPa or more. If this value is 10 ⁻¹ Ω · cm or more, insulation under no load is maintained, and a smooth conduction change characteristic is obtained with a change in contact area according to the load during load. Moreover, if this value is 10 ³ Ω · cm or less, there is no such thing that an output cannot be obtained even when a load is applied, and an output corresponding to the load can be obtained.

  In addition to the resin and the conductive agent, other components can be blended, and examples thereof include organic elastic fillers, inorganic oxide fillers, and dispersants.

  The resin coating layer can be formed, for example, by the following method. First, a coating liquid composed of a material constituting the resin coating film and an organic solvent is prepared by dispersion using a dispersion apparatus using beads such as a sand mill, a paint shaker, a dyno mill, and a pearl mill. Next, the obtained coating solution is applied to the surface of the rubber substrate by dipping or spray coating. In consideration of the utilization efficiency of the coating composition, the dipping method is preferable. Further, the solvent is removed using a hot air circulating dryer or an infrared drying furnace to form a resin coating on the surface of the rubber substrate.

  If the wettability between the rubber base material and the coating liquid is not good, the surface free energy is increased by irradiating the rubber base material with ultraviolet rays or a primer is applied to the rubber base material before coating. Thus, a uniform coating film can be formed by improving the wettability. The resin coating film may be formed on at least one surface of the elastic rubber substrate, and the conductive rubber member may be disposed so that the resin coating film faces the electrode.

  The elastic modulus of the conductive rubber member on the surface on which the resin coating film of the present invention is formed is not particularly limited, but is preferably 10 MPa or more and 700 MPa or less. When the elastic modulus is 10 MPa or more, the amount of deformation does not gradually increase when a certain force is applied to the sensor, and the change in output with time can be suppressed. When the elastic modulus is 700 MPa or less, the flexibility as a member is not impaired, the contact state with the electrode is excellent, and the reproducibility when the load-unloading test is repeated is good.

  The film thickness (d) of the resin coating film is not particularly limited, but is preferably 5 μm or more and 100 μm or less. When the film thickness of the resin coating film is 100 μm or less, a change in contact area corresponding to a change in load can be obtained without impairing the flexibility as the conductive rubber member. When the film thickness of the resin coating is 5 μm or more, a desired elastic modulus is obtained as the conductive rubber member, and the amount of deformation does not gradually increase when a certain force is applied to the sensor. It can suppress that an output changes with time.

  Further, the ratio of the elastic modulus (E1) of the rubber base material constituting the conductive rubber member of the present invention and the elastic modulus (E2) of the conductive rubber member on the surface on which the resin coating film is formed is not particularly limited. It is preferable that 1 <E2 / E1 <1,000. When E2 / E1 is larger than 1, the elastic modulus (E2) of the conductive rubber member is larger than the elastic modulus (E1), and the amount of deformation gradually increases when a certain force is applied to the sensor. It is possible to suppress the output from changing with time without increasing. Further, the conductive rubber member does not have adhesiveness and the like, and hysteresis loss of the detection resistance value hardly occurs. When E2 / E1 is smaller than 1,000, the elastic modulus of the conductive rubber member is not too high, the contact state with the electrode is excellent, and the reproducibility when the load-unloading test is repeated Excellent. Further, the contact state when a constant force is applied to the sensor is kept uniform, and the problem that the output changes with time hardly occurs.

  As the conductive rubber member used in the present invention, one that detects a change in the contact area between the conductive rubber member and the electrode substrate, which occurs when pressure is applied, as a change in electric resistance value is preferably used. In order to control the contact area, the contact surface can be appropriately provided with an uneven shape or roughened. Examples of the method for providing the surface uneven shape include a method of adding spherical particles made of a resin such as silicone, urethane, acrylic, styrene, or polyamide as rough particles in the conductive paint.

  Hereinafter, the pressure sensor of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. “Part” means “part by mass”.

Example 1
<1. Creation of conductive rubber member>
[1-1. Creation of rubber base]
Seven types of materials shown in Table 1 were mixed with two rolls for 20 minutes to produce an unvulcanized rubber compound. Next, this unvulcanized rubber compound is filled in a mold having a length of 50 mm, a width of 50 mm, and a depth of 0.5 mm previously heated to 170 ° C., and press vulcanized at 170 ° C. and 100 kgf for 15 minutes, A rubber base material to be a base material for the conductive rubber member was obtained.

[1-2. Preparation of coating composition]
Subsequently, six materials shown in Table 2 were blended to obtain a resin solution having an index (NCO / OH ratio) of 1.0 and a solid content of 30% 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 12 hours using a paint shaker. Finally, the solution was filtered through a 200 mesh screen to prepare a coating composition.

[1-3. Formation of conductive coating layer]
The coating composition is placed in a bath, the rubber base material is immersed, a coating film is formed on the surface of the rubber base material at a lifting speed of 10 mm / sec, air-dried for 30 minutes, and then heated at 160 ° C. for 1 hour using an oven. The coating was cured by heating to form a conductive coating layer having a thickness of 13 μm. Thus, the conductive rubber member 1 was created.

<2. Creation of insulating covering member>
A polyimide film (trade name “Kapton 100H (Young's modulus 3.4 GPa, thickness 25 μm)” manufactured by Toray DuPont Co., Ltd.) was used as the flexible film. An acrylic pressure-sensitive adhesive (trade name “Olivein BPS-5127” manufactured by Toyo Ink Co., Ltd.) was applied to one side of this film by a gravure roll method, and a coating film was formed. An insulating covering member 1 having an agent layer (fixing agent layer) was obtained.

<3. Creation of pressure-sensitive sensor>
From the conductive rubber member 1, a small-piece-shaped conductive rubber member 1 ′ (length 3.5 mm, width 4 mm, thickness 0.5 mm) was obtained. In addition, an insulating covering member 1 ′ cut to a width of 4 mm was obtained from the insulating covering member 1.

  The conductive rubber member 1 ′ and the comb-shaped electrode substrate (length 3.5 mm, width 4 mm, thickness 0.5 mm) shown in FIG. 6 were laminated via a separation forming jig (width 3.8 mm, thickness 130 μm). . Next, this laminate was covered with an insulating covering member 1 'to obtain a pressure-sensitive sensor 1 in which the electrode substrate and the conductive rubber member shown in FIG.

<4. Evaluation of pressure-sensitive sensor>
The following evaluations were performed on the pressure-sensitive sensor thus obtained. Table 9 shows the evaluation results.

[4-1. Maximum projected area measurement]
For measurement of the maximum projected area, “Microscope” VHX-900 manufactured by Keyence Corporation was used. The measurement condition is 50 times magnification. The created pressure-sensitive sensor is projected from the direction shown in FIG. 5 (perpendicular to the paper surface), the horizontal width (b) and the vertical length (c) of the insulating coating member in the projection are measured, and the projection of the insulating coating member is measured. The area of the figure (S = b × c) was determined.

[4-2. Measurement of gap amount]
For measurement of the gap amount, “Microscope” VHX-900 manufactured by Keyence Corporation was used. The measurement condition is 50 times magnification. The created pressure-sensitive sensor was observed from the direction shown in FIG. 1 (direction perpendicular to the paper surface), and the gap amount (141) between the conductive rubber member and the electrode substrate was determined.

[4-3. Measurement of elastic modulus]
For the measurement of the elastic modulus, “Shimadzu Dynamic Ultra Hardness Tester” DUH-W 201S manufactured by Shimadzu Corporation was used. The measurement conditions are: test mode: load-unload test, load speed: 0.28 mN / sec, holding time: 5 sec, indenter type: triangular pan indenter 115. The test force was adjusted so that the indentation depth of the indenter was 1/10 or less of the thickness of the measurement object. That is, for example, when the thickness of the rubber base material is 0.5 mm, the test force is adjusted so that the indentation depth is 50 μm or less. For example, when the thickness of the resin coating layer is 13 μm, the test force is adjusted so that the indentation depth is 1.3 μm or less.

  In addition, about the elasticity modulus of a rubber base material, said [1-1. The elastic modulus was obtained by pushing a triangular pan indenter into the surface of the flat rubber base material prepared in [Production of rubber base material]. About the elasticity modulus of the conductive rubber member of the surface in which the resin coating film was formed, [1-3. The elastic modulus was determined by pushing a triangular pan indenter into the surface of the resin coating layer formed on the surface of the flat rubber substrate prepared in [Formation of conductive coating layer].

  The obtained rubber base material had an elastic modulus E1 of 3.5 MPa, a surface on which the conductive coating layer was formed, an elastic modulus E2 of 226 MPa, and a ratio of the elastic modulus, E2 / E1 was 64.6.

[4-4. Load detection performance as a pressure sensor]
After the pressure sensor is left in an environment (N / N environment) at a temperature of 23 ° C. and a relative humidity of 60% for 24 hours or more, the pressure sensor is fixed using an evaluation device for pressure sensitivity as shown in FIG. A load was applied to the detection unit (101) by a cubic pusher (410) having an area of a pressing part of 1 mm ² from above. In this state, a DC voltage of 5 V is applied to the comb-shaped electrode, and a load-unloading test is performed in the range of 0 to 1 MPa at a speed of 5 mm / min in the thickness direction of the pressure sensor with a load measuring instrument. The voltage applied to a 1 kΩ resistor connected in series with the electrode was measured.

1) Minimum Detected Load Stability As shown in FIG. 8, a load is applied by installing a pusher at the center of the detection unit (location indicated by “1”). At the time of the load at this time, the load (N detection) when a voltage of 50 mV or higher starts to be detected was used as an indicator of the minimum detection load. This load-unloading test is repeated 1000 times to obtain the maximum value (N detection max) and minimum value (N detection min) of the minimum detection load, and the stability of the minimum detection load is determined by the values shown in Table 3. evaluated.

2) Hysteresis loss As shown in FIG. 8, a load was applied by installing a pusher at a position in the center of the detection portion (location of reference numeral “1”). The absolute value of the difference between the resistance value at the time of loading (LogR load) and the resistance value at the time of unloading (LogR unloading) under a load from 200 kPa to 1 MPa was determined, and the maximum value was used as an index of hysteresis loss. Also, the ranking was based on the criteria shown in Table 4.

3) Reproducibility As shown in FIG. 8, a pusher was installed at a position in the center of the detection unit (location of reference numeral “1”) so that a load was applied. The load-unloading test was repeated 1000 times, and the reproducibility of the detected resistance value under a load from 200 kPa to 1 MPa was evaluated. Standard deviation (3σ) of the value measured 1000 times at each load of the resistance value at the time of loading (LogR load), and standard deviation of the value measured 1000 times at each load of the resistance value at the time of unloading (LogR unloading) (3σ) was determined, and the maximum value (3σmax) was used as an index of reproducibility. Also, the ranking was based on the criteria shown in Table 5.

4) Variation due to position As shown in FIG. 8, the pushers are sequentially installed at five locations “reference numerals 1 to 5” so that a load of 500 kPa is applied, and from the variation in the electric resistance value of the pressure sensor at that time evaluated. That is, first, the electrical resistance values R1, R2, R3, R4, and R5 at each measurement location 1, 2, 3, 4, and 5 are measured, and then the respective logarithmic values logR1, logR2, logR3, logR4, and logR5 was determined. Ranking was based on the criteria shown in Table 6.

5) Comprehensive evaluation of load detection performance Comprehensive evaluation of the load detection performance of the pressure sensor was performed according to the criteria shown in Table 7.

(Examples 2 and 3)
A pressure-sensitive sensor was obtained in the same manner as in Example 1 except that a separation forming jig having the size shown in Table 8 was used when the pressure-sensitive sensor was created. Table 9 shows the evaluation results.

(Examples 4 to 7)
A pressure-sensitive sensor was obtained in the same manner as in Example 1 except that the flexible film shown in Table 9 was used as the flexible film. Table 9 shows the evaluation results.

(Examples 8 to 12)
A pressure-sensitive sensor was obtained in the same manner as in Example 1 except that a conductive rubber member, a comb-shaped electrode substrate, and a separation forming jig having the sizes shown in Table 8 were used in the production of the pressure-sensitive sensor. Table 9 shows the evaluation results.

(Comparative Example 1)
A pressure-sensitive sensor in which the electrode substrate and the conductive rubber member were in contact with each other was obtained in the same manner as in Example 1 except that the separation forming jig was not used when creating the pressure-sensitive sensor. Table 10 shows the evaluation results.

(Comparative Examples 2 to 5)
A pressure-sensitive sensor was obtained in the same manner as in Example 1 except that the flexible film shown in Table 10 was used as the flexible film. In addition, the thickness of the flexible film in Comparative Examples 2 and 3 is 5.7 μm and 75 μm, respectively. Moreover, the Young's modulus of the flexible film in Comparative Examples 4 and 5 is 0.71 GPa and 15 GPa, respectively. Table 10 shows the evaluation results.

(Summary of evaluation results)
In Example 1, the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and minimum detection load stability, hysteresis loss, reproducibility, and variation due to position are all excellent, and the conductive property of the present invention is excellent. It can be seen that a suitable pressure-sensitive sensor can be provided by applying a conductive rubber member.

  In Example 2, the variation in the minimum detection load (N detection max-N detection min) when repeatedly used due to the small amount of the gap between the conductive rubber member and the electrode substrate in the non-contact state is small. Since it tends to be a little larger and the minimum value (N detection min) is also small, the minimum detected load stability tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and hysteresis loss, reproducibility, and variation due to position are excellent, and the pressure sensor is good.

  In Example 3, the contact state between the conductive rubber member and the electrode facing the electrode is uniform depending on the position where the load is applied due to the large gap amount in the proximity non-contact state between the conductive rubber member and the electrode substrate. The characteristics tend to be slightly inferior, and the variation in output characteristics depending on the position tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and the minimum detection load stability, hysteresis loss, and reproducibility are excellent, and the pressure sensor is good.

  In Example 4, due to the small thickness of the flexible film, the variation in the minimum detection load when repeatedly used (N detection max-N detection min) tends to be slightly large, and the minimum value ( Since N detection min) is also small, the minimum detected load stability tends to be slightly inferior and the reproducibility tends to be slightly inferior. In addition, the film is weak, the load following-unloading performance is slightly inferior, and the output hysteresis loss tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and the variation due to the position is excellent, and the pressure sensor is good.

  In Example 5, due to the large thickness of the flexible film, the flexible film is strong and the conductive member bends following the flexible film. Therefore, when a load is applied, the contact state between the conductive rubber member and the electrode facing the conductive rubber member becomes non-uniform depending on the position where the load is applied, and the variation due to the position of the output characteristics tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and the minimum detection load stability, hysteresis loss, and reproducibility are excellent, and the pressure sensor is good.

  In Example 6, due to the small Young's modulus of the flexible film, the pressure distribution to the entire conductive rubber member when a load is applied becomes insufficient. Therefore, depending on the position where the load is applied, the contact state between the conductive rubber member and the opposing electrode becomes non-uniform, and variations in output characteristics depending on the position tend to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and the minimum detection load stability, hysteresis loss, and reproducibility are excellent, and the pressure sensor is good.

  In Example 7, due to the large Young's modulus of the flexible film, the durability against repeated bending is poor, the output gradually changes, and the reproducibility tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close contact and non-contact state, and the minimum detection load stability, hysteresis loss, and variation due to position are excellent, and the pressure sensor is good. .

  In Example 8, due to the fact that the maximum projected area and the lateral width of the insulating covering member are small, the film is weak, the load-following performance with respect to unloading is inferior, and the output hysteresis loss tends to be slightly inferior. It is in. However, it can be seen that the conductive rubber member and the electrode substrate are in close contact and non-contact state, and the minimum detection load stability, reproducibility, and variation due to position are excellent, and the pressure sensor is good. .

  In Example 9, due to the large maximum projected area, width, and length of the insulating covering member, when a load is applied, depending on the position where the load is applied, the electrode facing the conductive rubber member The contact state is non-uniform, and the variation due to the position of the output characteristics tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and the minimum detection load stability, hysteresis loss, and reproducibility are excellent, and the pressure sensor is good.

  In Example 10, the variation in the minimum detection load when repeatedly used (N detection max-N detection min) due to the small gap amount in the non-contact state between the conductive rubber member and the electrode substrate. Since it tends to be a little larger and the minimum value (N detection min) is also small, the minimum detected load stability tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and hysteresis loss, reproducibility, and variation due to position are excellent, and can be used as a pressure-sensitive sensor.

  In Example 11, the contact state between the conductive rubber member and the electrode facing the electrode is uniform depending on the position where the load is applied due to the large gap amount in the non-contact state between the conductive rubber member and the electrode substrate. The characteristics tend to be slightly inferior, and the variation in output characteristics depending on the position tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and the minimum detection load stability, hysteresis loss, and reproducibility are excellent, and can be used as a pressure-sensitive sensor.

  In Example 12, due to the large maximum projected area, width, and length of the insulating covering member, when a load is applied, depending on the position where the load is applied, the electrode facing the conductive rubber member The contact state is non-uniform, and the variation due to the position of the output characteristics tends to be slightly inferior. However, it can be seen that the conductive rubber member and the electrode substrate are in close proximity and non-contact state, and the minimum detection load stability, hysteresis loss, and reproducibility are excellent, and can be used as a pressure-sensitive sensor.

  In Comparative Example 1, an electrical signal was output when there was no load due to the fact that the gap between the conductive rubber member and the electrode substrate was zero and both were in contact, and a load was applied. There is a risk of misdetection because it cannot be distinguished from the time. It can also be seen that permanent deformation occurs due to the constant pressure applied to the conductive rubber member by tightening the insulating covering member, resulting in poor reproducibility, and is not suitable as a pressure-sensitive sensor.

  In Comparative Example 2, due to the small thickness of the flexible film, the minimum detection load gradually changes when repeatedly used, the minimum value (N detection min) indicates 0, and the output value of the sensor Therefore, the presence or absence of a load cannot be determined, and there is a risk of erroneous detection, and the reproducibility is poor. Further, it can be seen that the film is weak, the followability to load-unloading is poor, the output hysteresis loss is poor, and it is not suitable as a pressure-sensitive sensor.

  In Comparative Example 3, due to the large thickness of the flexible film, the flexibility of the flexible film becomes strong, and the conductive rubber member bends following the flexible film. Therefore, when a load is applied, depending on the position where the load is applied, the contact state between the conductive rubber member and the opposing electrode becomes non-uniform, resulting in poor variation in the position of the output characteristics, making it suitable as a pressure-sensitive sensor. I understand that there is no.

  In Comparative Example 4, due to the small Young's modulus of the flexible film, the pressure dispersion to the entire conductive rubber member when a load is applied becomes insufficient. Accordingly, it can be understood that the contact state between the conductive rubber member and the electrode facing the conductive rubber member becomes non-uniform depending on the position where the load is applied, and the variation in the position of the output characteristic is inferior, making it unsuitable as a pressure sensor.

  In Comparative Example 5, the durability against repeated bending is inferior due to the large Young's modulus of the flexible film. Accordingly, it can be seen that the output gradually changes over time, the reproducibility is poor, and it is not suitable as a pressure-sensitive sensor.

DESCRIPTION OF SYMBOLS 100 Pressure-sensitive sensor 101 Detection part 110 Conductive rubber member 120 Electrode board | substrate 111 The surface (A surface) facing an electrode board | substrate of a conductive rubber member
112 Surface (B surface) opposite to the surface facing the electrode substrate of the conductive rubber member
121 surface having electrode of electrode substrate (a surface)
122 surface (b surface) opposite to the surface having electrodes of the electrode substrate
130 Insulating Cover Member 131 Flexible Film 132 Fixing Agent Layer 140 Spacing Forming Tool 140a Spacing Forming Tool Width 140b Spacing Forming Tool Thickness 141 Gap Amount Between Conductive Rubber Member and Electrode Substrate b Insulating Covering Member Projects Maximum Width c when showing the area c Vertical length when the insulating covering member shows the maximum projected area 410 Pusher 420 DC voltage generator 430 Resistor 440 Voltage measuring instrument 450 Load measuring instrument

Claims (3)

In the pressure-sensitive sensor in which the electrode substrate and the conductive rubber member are arranged to face each other in the close proximity non-contact state, the electrode substrate and the conductive rubber member are made of a flexible film provided with at least a fixing agent layer. It is covered with an insulating covering member and is fixed to the insulating covering member via the fixing agent layer, and the gap amount between the electrode substrate in the proximity non-contact state and the conductive rubber member is small. The pressure-sensitive sensor , wherein the flexible film has a Young's modulus of 2 GPa or more and 10 GPa or less and a thickness of 10 μm or more and 60 μm or less. In a state where the electrode substrate and the conductive rubber member are covered with the insulating coating member, the projected area of the insulating coating member as viewed from the direction in which the area is maximized is 3 mm ² or more and 80 mm ² or less. The pressure-sensitive sensor according to claim 1. The pressure-sensitive sensor according to claim 1, wherein at least one conductive coating layer is formed on a surface of the conductive rubber member facing the electrode substrate.