JP2003031093A - Electrode structure of electrostatic capacity type proximity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detection performance as well as achieving thin size. SOLUTION: Electrode plates 30, 30 are overlapped on both the top and bottom faces of a spacer 10 having a ring-shape frame 11, and an insulation film 40 is overlapped on those surfaces, and a holding member 50 is formed integrally on the outer circumference of these through injection molding. Since the gap between the electrodes is hollow, the electrostatic capacity is small, and as the electrode plate 30 covered by the insulation film 40 constitutes the outer wall of the electrode structure, the switch becomes thin as a whole.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrode structure of a capacitance type proximity switch.

[0002]

2. Description of the Related Art A capacitance type proximity switch is used, for example, as a wafer detection sensor in a semiconductor manufacturing process.
For example, as disclosed in Japanese Patent Application Laid-Open No. 11-288999, this is attached to a hand on which a wafer is placed, and when the hand enters a cassette containing the wafer and scoops up the wafer, the capacitance of the wafer is changed. The presence or absence of a wafer is detected based on the change.

The specific configuration is, for example, Japanese Patent Laid-Open No. 62-1.
It is disclosed in Japanese Patent Laid-Open No. 00919 and has a structure as shown in FIG. Here, 1 is a flat case made of plastic, 2 is a printed circuit board housed in the case 1, and 3 and 4 are detection electrodes and shielding electrodes formed so as to face both surfaces of the printed circuit board 2.

[0004]

According to the operating principle of this type of proximity switch, the reference capacitance C1 between the detection electrode 3 and the shield electrode 4 is constant, while the ground capacitance C of the detection electrode 3 is fixed.
2 is based on the fact that it greatly changes depending on the distance between the detection electrode 3 and the wafer 5 (see FIG. 11B). Because of this principle, it is desirable that the reference capacitance C1 be as small as possible and the permittivity ε of the space forming the ground capacitance C2 be as small as possible in view of detection distance and S / N ratio.

To reduce the reference capacitance C1, this is C
It is well known that 1 = εS / d, so
It is necessary to make the distance d between the detection electrode 3 and the shield electrode 4 as large as possible and the dielectric constant ε between them as small as possible. However, in the conventional structure shown in FIG. 11, since the electrodes 3 and 4 are formed on both sides of the printed circuit board 2, the distance d between the electrodes becomes small, and at the same time, the dielectric constant ε (ε> of the insulating plate of the printed circuit board). Since 1) is added, the reference capacitance C1 cannot be made sufficiently small.

On the other hand, this type of apparatus requires a thin hand because the wafers are accommodated in the cassette with a small space in the vertical direction, and accordingly, the electrode structure of the wafer detection sensor is also required. Further thinning is demanded. In recent years, for example, it is sometimes desired that the thickness of the electrode structure be 1.5 mm. Since such a request for thinning is in the direction of reducing the distance between the electrodes 3 and 4, there is a contradiction between improvement in detection performance and thinning. Moreover, on the outside of the electrodes 3 and 4, the outer wall 1A of the case 1
Under the circumstances where 1A is located, there is a limit to thinning.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an electrode structure of a capacitance type proximity switch which can be made thinner while improving detection performance.

[0008]

As a means for achieving the above object, in the electrode structure of a capacitance type proximity switch according to the invention of claim 1, a pair of electrode plates are provided on the outer peripheral portion thereof. It is characterized in that it is held in a facing state by the holding member and that an insulating film is laminated on the surface of each electrode plate opposite to the surface facing the other side.

The invention of claim 2 is characterized in that, in the invention of claim 1, the holding member is provided on an outer periphery of a spacer having a hollow annular frame portion sandwiched by an outer peripheral edge portion of the electrode plate. Have.

The invention of claim 3 is characterized in that, in the invention of claim 2, a spacer is integrally formed in the annular frame part with a holding frame part sandwiched between both electrode plates.

A fourth aspect of the invention is characterized in that, in the second or third aspect of the invention, the holding member is formed with an air passage for communicating a space surrounded by both the electrode plates and the holding member to the outside.

A fifth aspect of the invention is characterized in that, in the first to fourth aspects of the invention, a foamed resin body containing closed cells is arranged in the holding member so as to be sandwiched between both electrode plates. .

According to a sixth aspect of the present invention, in any one of the second to fifth aspects, a film supporting ridge having a thickness smaller than a thickness of the spacer is provided on the outer circumference of the spacer so as to project toward the outer circumference. The holding member is formed by injection molding so as to fill the outer circumference of the spacer in a state where the insulating film overlaps both sides of the film supporting ridge.

According to a seventh aspect of the present invention, in any one of the second to sixth aspects, the holding member is provided on the outer peripheral side of the electrode plate in order to secure a connection space for pulling in the cable and connecting to the electrode plate. It is characterized in that a bulging portion that bulges out is formed, an engaging portion is intermittently formed on the outer periphery of the spacer, and the engaging portion is injection-molded in a form of engaging with the holding member.

The invention of claim 8 is characterized in that, in any one of claims 1 to 7, the electrode plate and the insulating film are laminated and adhered by an adhesive.

[0016]

According to the invention of claim 1, since the electrode plate itself is located in a portion corresponding to the outer wall 1A of the conventional flat type case 1 to form a wall surface of the case, both electrode plates are provided. The facing distance can be maximized in the thickness dimension of the electrode structure. As a result, the reference capacitance C1 generated between both electrode plates can be reduced, so that the detection distance becomes long and the S / N ratio becomes large, so that the detection performance can be improved.

Further, even if the outer wall is constituted by the electrode plate as described above, since the insulating film is located on the surface of the electrode plate, the electrode plate may come into contact with other conductors and become undetectable. Absent. Moreover, since the insulating film does not generate structural stress unlike the outer wall of the case, the required strength may be low, and the insulating film can be made sufficiently thin within a range where insulation can be secured. This means that not only can the overall thickness of the electrode structure be reduced, but the dielectric constant ε of the space between the electrode plate and the object to be detected can be made sufficiently smaller than in the case where a thick case outer wall is present. Therefore, the detection performance can be further improved.

According to the second aspect of the present invention, the air having the smallest dielectric constant ε is positioned between the two electrode plates next to the vacuum, so that the capacitance between the two electrodes can be further reduced and the detection performance can be improved. More effective.

According to the third aspect of the invention, since the holding frame portion is located between the two electrode plates, the distance between the two electrode plates can be made constant, and the detection accuracy is improved by making the capacitance between them constant. In addition, in the case of this configuration, if the electrode plate is bonded to the holding frame portion, the electrode plate is less likely to be deformed, so that it is more effective in making the inter-electrode capacitance constant. In this case, a material having a dielectric constant ε larger than air is partially located between the electrode plates, but the increase in the capacitance C1 between the electrode plates due to the frame shape is suppressed to a small level. be able to.

In the invention of claim 4, the space surrounded by both the electrode plates and the holding member is communicated with the outside through the ventilation passage. Therefore, even if there is a change in temperature or pressure around the electrode structure, the electrode plates are not deformed by the expansion and contraction of the air inside, and it is possible to prevent the distance variation between the electrode plates.

Further, in the invention of claim 5, since the foamed resin body is located between the two electrode plates, the distance between the two electrode plates can be kept constant, and the detection accuracy is further improved. In addition, by making this foamed resin body contain closed cells, even if there is a change in temperature and pressure around the electrode structure, it is possible to keep the pressure change in the closed cells, so that the deformation of the foamed resin body itself Is less likely to occur and is effective in maintaining the distance between the electrode plates.
In this case as well, it is more preferable to bond the electrode plate to the foamed resin body.

According to the sixth aspect of the present invention, when the holding member is molded by injection molding so as to fill the outer peripheral portion of the spacer, the insulating film is softened by the heat of the injected resin and both sides of the film supporting ridge of the spacer are softened. It is pressed against and sticks. Then, when the resin is cooled, it solidifies and shrinks during molding, so that the insulating member is pressed against the film supporting ridges of the spacer by the shrinking holding member, and the adhesiveness is further enhanced. Further, since the insulating film also undergoes thermal shrinkage as a whole after molding, the adhesion with the electrode plate is improved and the slack of the flat portion is eliminated.

In this case, if the resin constituting the holding member is made to have a melting temperature higher than that of the insulating film, the peripheral edge of the insulating film is melted during injection molding and integrated with the holding member, so that the adhesiveness is improved. Can be increased. For this purpose, as a combination of resins, an ABS (acrylonitrile butadiene styrene) resin sheet is used as the insulating film, and PES is used as the resin for the holding member.
(Polyether suffphone) can be used. Since these resins are non-crystalline resins, there is no clear melting point.
The injection molding resin temperature of S is about 220 ° C, and the injection molding resin temperature of PES is about 340 ° C. Therefore, the heat of the PES flowing in the mold melts the portions of the tip of the insulating film that are likely to receive and transfer heat, and can fuse them together. If the tip of the peripheral edge of the insulating film is formed thin, the amount of heat required for melting will be small and fusion will be easier to achieve. In addition, various combinations of materials can be selected depending on the shape and thickness.

Further, in the invention of claim 7, the holding member is formed with a bulging portion bulging toward the outer peripheral side of the electrode plate, and a connection space for connecting the cable by drawing the cable therein is secured. With such a structure, the holding member cannot be made into a simple shape such as a circle, so that the holding member is separated from the spacer at the root part of the bulging portion during cooling contraction after injection molding the holding member. May become. However, as in the present invention, peeling can be prevented in advance by intermittently forming the engaging portion on the outer periphery of the spacer and molding the engaging portion so as to engage with the holding member.

Further, in the invention of claim 8, since the electrode plate and the insulating film are adhered to each other by the adhesive, the rigidity of the electrode plate is enhanced and the deterioration of the detection performance due to the deformation of the electrode plate can be prevented. .

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. <First Embodiment> A first embodiment of the present invention will be described with reference to FIGS. 10 is a flat spacer,
A bulging frame portion 12 that is a bulging portion that radially projects from one side portion of the annular frame portion 11 is provided. The bulging frame portion 12 is in a divided state at the center, and is elastically deformed so that the dividing portion of the bulging frame portion 12 opens and closes with the annular frame portion 11 side as a fulcrum.

On the inner peripheral side of the annular frame portion 11, an electrode supporting ridge 13 having a thickness dimension slightly smaller than the thickness dimension of the annular frame portion 11 projects inwardly over substantially the entire circumference. On the other hand, on the outer peripheral side of the annular frame portion 11, the film supporting ridges 14 having a thickness dimension slightly smaller than the thickness dimension of the annular frame portion 11 are also outside along the entire periphery including the outer periphery of the bulging frame portion 12. Is projected toward. Further, on the outer peripheral side of the annular frame portion 11, for example, engaging protrusions 15 corresponding to a total of four engaging portions are intermittently projected, and particularly two of them are the bulging frame portion 12. It is located at the root part near the connecting part.

The bulging frame portion 12 is designed to form a connection space for the cable 20 by closing the dividing portion. Here, the bulging frame portion 12 is divided into two parts at the end opposite to the annular frame portion 11. A tubular cable introduction tubular portion 16 is integrally formed. As shown in FIG. 6, a ventilation groove 16A is formed along the insertion direction of the cable 20 on the inner peripheral surface of the cable introducing tubular portion 16, and the ventilation groove 16A ( It is possible to communicate with the outside through a ventilation path.

Two electrode plates 30 and 30 having a circular shape are provided on the annular frame portion 11 above and below, respectively.
The inner electrode support projections 13 are sandwiched by 30 from above and below. Each electrode plate 30 is made of metal and has the same shape, and a connecting piece portion 31 is projectingly provided on the outer peripheral edge thereof.
The core wire 21 of the cable 20 is soldered to the connection piece portion 31 of the one electrode plate 30, and the connection piece portion 3 of the other electrode plate 30 is soldered.
The shield braided wire 22 of the cable 20 is soldered to the wire 1. In addition, these electrode plates 30 are connected to each connecting piece 3
1 is located in the bulging frame portion 12, and each connecting piece portion 3
1 are arranged at different angles so that they point in different directions (see FIG. 2).

The insulating film 40 is formed on the surface of each electrode plate 30 (the surface opposite to the spacer 10).
Are stacked from above and below. The insulating film 40 is made of ABS resin, for example, and has a shape that exactly covers the region surrounded by the annular frame portion 11 and the bulging frame portion 12 of the spacer 10 as shown in FIGS. 3 and 7. The outer peripheral edge of the insulating film 40 not only completely covers the outer peripheral edge of the spacer 10 but also covers the side surface of the film supporting protrusion 14 on the outer peripheral side of the spacer 10. The outermost peripheral edge of the film is preliminarily molded to be thin, and as shown in FIG. In addition, this insulating film 40
The outer peripheral edge portion of FIG.
As shown in FIG. 5, the film is preliminarily molded in such a shape that a gap G is left between the film supporting ridge 14 and the root of the film supporting ridge 14 when the spacer 10 is overlaid, and is set in the molding die 70 in that state (see FIG. 8)), after the molding, as shown in FIG.

A holding member 50 is located on the outer peripheral side of the spacer 10 so as to surround the entire circumference. This is spacer 1
Electrode plates 30, 30 with cables 20 connected to both sides of 0
The insulating film 40 and the insulating film 40 are placed in a mold 70 for injection molding, and are formed by injection molding of PES resin, for example. When molding the holding member 50, the injection molding temperature of the PES resin is about 340 ° C.
Since the temperature is higher than about 220 ° C., which is the injection molding temperature of the ABS resin forming the insulating film 40, the insulating film 40 not only softens but also melts at the tip,
Will be mixed with PES resin. As a result, it comes into close contact with the holding member 50. Further, when the PES resin is cooled, molding shrinkage occurs. Therefore, as shown in FIG. 7, the portions 51 of the holding member 50 located on both sides of the film supporting ridge 14 of the spacer 10 cause the insulating film 40 to move to the film supporting ridge 14. Then, the insulating film 40 comes into close contact with the spacer 10.

Since the holding member 50 has a shape that integrally surrounds the annular frame portion 11 of the spacer 10 and the bulging frame portion 12 that bulges from this, the arrow in FIG. As shown by, the force of the holding member 50 tending to separate from the spacer 10 may act on the root portion of the bulging frame portion 12. In view of this, in the present embodiment, the engaging projection 15 is intermittently formed on the spacer 10, and the engaging projection 15 engages with the holding member 50. Therefore, the force as described above acts. However, the holding member 50 is not separated.

During the injection molding of the holding member 50, the annular frame portion 1 of the spacer 10 is pressed by the pressure of the injected resin.
A force that crushes 1 from the outside to the inside acts, but this force is applied to the annular frame portion 11 supported from the inside by the electrode plate 30.
Accepted by. Here, since the electrode plate 30 is made of metal, it can sufficiently receive pressure and has excellent thermal conductivity, so that the temperature increase of the annular frame portion 11 is suppressed and the hardness thereof is maintained high. There is an effect of surely preventing the deformation of the portion 11.

According to the present embodiment having the above-described structure, the electrode plates 30 and 30 themselves are located in a portion corresponding to the outer wall 1A of the conventional flat type case 1 shown in FIG. 11 to form a case wall surface. Therefore, the facing distance between the two electrode plates 30 and 30 can be maximized in the thickness dimension D of the electrode structure. Moreover, since air having a small dielectric constant is only present in the space between the two electrode plates 30, 30,
The capacitance generated between zero can be made extremely small. As a result, the detection distance when configured as a capacitance type proximity sensor becomes long, and the S / N ratio becomes large, so that the detection performance can be improved.

Even if the outer wall is constituted by the electrode plate 30 as described above, the insulating film 40 is located on the surface of the electrode plate 30, so that the electrode plate 30 comes into contact with another conductor and cannot be detected. Never be. Moreover, insulating film 4
Since 0 is not a structural member, the required strength may be low, and it can be made sufficiently thin within the range where insulation can be secured. This not only makes it possible to reduce the overall thickness dimension D of the electrode structure, but also makes the permittivity ε of the space between the electrode plate 30 and the object to be detected (wafer) larger than the conventional case outer wall 1A. This means that the detection performance can be further improved because it can be made sufficiently smaller than when it exists.

When used as a capacitance type proximity sensor, a high voltage may be applied between the electrode plate 30 and the object to be detected (wafer). In such a case, the insulating film 40 does not cover the electrode plate 30 exactly,
If there is a slight gap between the electrode plate 30 and the holding member 50, discharge may occur through the gap. In view of this point, in the present embodiment, the holding member 50 is formed by injection molding so as to fill the outer periphery of the spacer 10.
At that time, the insulating film 40 was simultaneously pressed against both sides of the film supporting protrusion 14 of the spacer 10.
As a result, when the holding member 50 is molded, the insulating film 40 is pressed against both sides of the film supporting ridge 14 of the spacer 10 while being softened by the heat of the injected resin. When the resin is cooled, the resin solidifies and shrinks, so that the insulating member 40 is pressed against the film supporting ridges 14 of the spacer 10 by the shrinking holding member 50, and the adhesiveness is further enhanced. In addition, since the insulating film 40 also undergoes thermal contraction as a whole after molding, the adhesiveness with the electrode plate 30 is improved and the slack of the flat portion is eliminated.
As a result, since the electrode plate 30 is covered with the insulating film 40 without any gap, it is possible to reliably prevent the occurrence of discharge between the electrode plate 30 and the detection target (wafer).

On the other hand, if the space surrounded by the spacer 10 and the electrode plates 30 and 30 is sealed from the outside air by being sealed with the insulating film 40 as described above, the following problems may occur. There is also. That is, if there is a change in temperature or pressure around the electrode structure, the electrode plate 30 may be deformed due to the expansion or contraction of air inside the electrode structure, and the distance between the two electrode plates 30, 30 may fluctuate. Since it is preferable that the capacitance formed between the two electrode plates 30 and 30 is always constant from the viewpoint of detection accuracy, the deformation of the electrode plate 30 as described above causes a decrease in accuracy.

On the other hand, in this embodiment, the spacer 1
Since the ventilation groove 16A is formed in the bulging frame portion 12 of 0, the space surrounded by both electrode plates 30 and the spacer 10 is communicated to the outside through the ventilation groove 16A, and no pressure difference between the inside and the outside is generated. Therefore, the distance between the electrode plates 30, 30 is kept constant, and the detection accuracy can be kept sufficiently high. Moreover, while forming such a ventilation groove 16A, it is formed at the tip portion of the swelling frame portion 12 and is at the farthest position from the electrode plate 30, so this ventilation groove 1
There is no risk of discharge occurring through 6A.

<Second Embodiment> FIG. 9 shows a second embodiment of the present invention. The difference from the first embodiment lies in the structure of the spacer 10, and other configurations are the same as those of the first embodiment, so only the different parts will be described. Spacer 10
In the annular frame portion 11, here, a holding frame portion 17 is integrally formed in the upper half portion and the upper half portion so as to have an inverted T shape and a T shape, respectively. The holding frame portion 17 has the same thickness dimension as the electrode supporting ridges 13, and when the electrode plates 30 are directed vertically, the holding frame portion 17 is sandwiched between the electrode supporting ridges 13 together with the electrode supporting ridges 13.

With this structure, since the electrode plate 30 is supported by the holding frame portion 17, it is possible to prevent the two electrode plates 30 from bending and deforming toward each other. In addition, when it is necessary to prevent the bending deformation in the direction away from each other, the electrode plate 30 is attached to the holding frame portion 1.
It may be bonded to 7 by an adhesive. In addition, in order to prevent such deformation, the distance between the electrode plates 30 is made constant and the electrode plates 3 are prevented.
This is preferable for making the electrostatic capacitance between 0 constant and for improving the detection accuracy.

If the holding frame portion 17 is provided on the spacer 10 in this manner, the pressure acting on the spacer 10 can be dispersed and received when the holding member 50 is injection-molded later, so that the annular frame is provided. It is effective in preventing deformation of the portion 11.

The shape of the holding frame portion 17 is not limited to that shown in this embodiment, but may be a lattice shape, a honeycomb shape, or any density.

<Third Embodiment> FIG. 10 shows a third embodiment of the present invention. The difference from the first embodiment is that the foamed resin body 60 is inserted into the spacer 10, and other configurations are the same as in the first embodiment.

The foamed resin body 60 is punched out in a circular shape by pressing from a foamed resin plate containing a large number of closed cells, and the thickness dimension thereof is the same as that of the electrode supporting protrusion 13. When the foamed resin body 60 is thus arranged in the annular frame portion 11 of the spacer 10, the holding frame portion 1 of the second embodiment is arranged.
7 is effective in preventing deformation of the electrode plate 30. Also in this case, it is more effective to bond the electrode plate 30 to the foamed resin body 60.

Further, since the dielectric constant of the resin is generally larger than that of air, the foamed resin body 60 made of the foamed resin has a smaller dielectric constant than a plate of the same resin which is not foamed, so that the static electricity between the electrode plates 30 is reduced. The capacitance (reference capacitance C1) is made smaller to contribute to the improvement of detection performance. Moreover, at that time,
Since it includes closed cells, even if there is a change in temperature and pressure around the foamed resin body 60, it can be kept to the pressure change in the closed cells, and the foamed resin body 60 itself is less likely to be deformed. This is effective in maintaining the distance between the plates 30.

<Other Embodiments> The present invention is not limited to the embodiments described above and the drawings. For example, the following embodiments are also included in the technical scope of the present invention. In addition to the above, various modifications can be made without departing from the scope of the invention.

(1) In each of the above-mentioned embodiments, the electrode plate 30 and the insulating film 40 are handled as separate parts, but the invention is not limited to this, and both are integrated in advance in a laminated state with an adhesive. Alternatively, the electrode plate and the insulating film may be combined together by a flexible printed board in which a copper foil is laminated and integrated on a flexible insulating film.

(2) In each of the above embodiments, the spacer 10
Although the engaging protrusion 15 is provided on the outer peripheral portion of the above, this is not limited to the protrusion, and may be a recess, a notch, a through hole, or the like.
In short, when the holding member 50 is injection-molded on the outer periphery of the spacer 10, the resin may be entangled with each other to enhance the adhesiveness. In addition, as in the above-described respective embodiments, the engaging protrusion 15
In that case, there is an advantage that the positioning function of the spacer 10 at the time of molding the holding member 50 can be exerted together.

(3) In each of the above embodiments, the spacer 10
Although the outer periphery of the electrode plate 30 is held by the holding member 50 and the holding member 50, the spacer 10 in each embodiment is omitted, and the outer peripheral edge portions of the pair of electrode plates are embedded in the holding member by, for example, insert molding. You may make it hold | maintain both electrode plates in the opposing state.

[Brief description of drawings]

FIG. 1 is an overall exploded perspective view showing a first embodiment of the present invention.

FIG. 2 is a plan view of the same, partially broken away.

[FIG. 3] Similarly, a vertical sectional view

FIG. 4 is a plan view of a spacer.

FIG. 5 is a side view of the spacer.

FIG. 6 is a sectional view taken along line VI-VI in FIG.

FIG. 7 is a partially enlarged vertical sectional view of an electrode structure.

FIG. 8 is a partially enlarged vertical sectional view showing a state during injection molding of a holding member.

FIG. 9 is a plan view of a spacer showing a second embodiment of the present invention.

FIG. 10 is a partially enlarged vertical sectional view of an electrode structure showing a third embodiment of the present invention.

FIG. 11 is a sectional view and an equivalent circuit diagram showing a conventional example.

[Explanation of symbols]

10 ... Spacer 11 ... Ring frame 12 ... Bulging frame portion (bulging portion) 14 ... Film support ridge (support ridge) 15 ... Engagement protrusion (engagement portion) 16A ... Ventilation groove (ventilation path) 20 ... Cable 30 ... Electrode plate 31 ... Connection piece 40 ... Insulating film 50 ... Holding member 60 ... Foamed resin body

Claims (8)

[Claims] 1. A pair of electrode plates are held in a facing state by a holding member provided on the outer periphery of the pair of electrode plates, and an insulating film is laminated on a surface opposite to a facing surface of each electrode plate. The electrode structure of the capacitance type proximity switch, which is characterized in that 2. The capacitance type according to claim 1, wherein the holding member is provided on an outer periphery of a spacer having a hollow annular frame portion sandwiched by an outer peripheral edge portion of the electrode plate. Proximity switch electrode structure. 3. The electrode structure of the capacitance type proximity switch according to claim 2, wherein the spacer has a holding frame portion which is sandwiched between the electrode plates and is integrally formed in an annular frame portion. . 4. The capacitance type according to claim 2, wherein the holding member is formed with an air passage for communicating a space surrounded by both the electrode plates and the holding member to the outside. Proximity switch electrode structure. 5. The capacitance according to claim 1, wherein a foamed resin body containing closed cells is arranged in the holding member so as to be sandwiched between the electrode plates. Type proximity switch electrode structure. 6. A film supporting ridge having a thickness smaller than that of the spacer is provided on the outer periphery of the spacer so as to project outward, and the insulating film overlaps both sides of the film supporting ridge. The electrode structure of the capacitance type proximity switch according to claim 2, wherein the holding member is formed by injection molding so as to fill the outer peripheral portion of the spacer. . 7. The spacer is formed with a bulging portion that bulges out on the outer peripheral side of the electrode plate in order to secure a connection space for drawing in a cable and connecting to the electrode plate. The statically engaging member according to any one of claims 2 to 6, wherein an engaging portion is formed intermittently, and the engaging portion is injection-molded so as to engage with the holding member. Electrode structure of capacitive proximity switch. 8. The electrode structure of a capacitance type proximity switch according to claim 1, wherein the electrode plate and the insulating film are bonded to each other with an adhesive.