JP2004234963A - Switching element and switching circuit using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching element with a new construction, and a switching circuit using the same. <P>SOLUTION: The switching element comprises a first electrode 10, a second electrode 21 and a third electrode 22, a structural body 20 having an insulation body 23 insulating the second electrode 21 from the third electrode 22, facing the first electrode 10, electrophoretic media 40 arranged between the first electrode and the structural body 20, and numerous conductive electrophoretic particles 50 included in the electrophoretic media having electric charge, which move electrophoretically in compliance with an electric field and precipitate in a state in which the electric field is not charged. When the voltage impressed between the first electrode 10 and the second electrode 21 or the third electrode 22 is less than a threshold voltage, the electrophoretic particles 50 precipitate in the electrophoretic media 40 and deposit on the structural body 20 by gravity, and the second electrode 21 is electrically connected with the third electrode 22. On the other hand, when the voltage exceeds the threshold voltage, the electrophoretic particles 50 move up toward a first electrode side by the electrophoresis and the second electrode 21 is electrically insulated from the third electrode 22. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a switching element for switching between conduction and interruption of a circuit, and a switching circuit using the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, switching elements, such as varistors, fuses, and Zener diodes, capable of switching on / off of a circuit are known. For example, the varistor performs a switching operation by a tunnel effect of electrons at a grain boundary. Further, the fuse performs a switching operation when a wire is cut by Joule heat. The Zener diode performs a switching operation by the Zener effect, which is a tunnel phenomenon of electrons at a PN junction.
[0003]
By using these switching elements, for example, when an overvoltage is supplied, the electronic device can be protected. For example, by connecting a varistor or a zener diode in parallel with the electronic device to be protected, when an overvoltage is applied to the electronic device, the current is bypassed and the electronic device is protected. In addition, by connecting a fuse in series with the electronic device, when an overvoltage is applied to the electronic device, a circuit to the electronic device is cut off and the electronic device is protected.
[Patent Document 1]
JP-A-46-7371
[Patent Document 2]
JP-A-50-350
[Patent Document 3]
JP-A-5-6806
[Patent Document 4]
JP-A-5-227738
[Patent Document 5]
JP-A-8-204127
[Patent Document 6]
JP-A-11-103145
[0004]
[Problems to be solved by the invention]
However, in order to enable further cost reduction and higher performance, there is a demand for the development of a switching element having a configuration different from the conventional one.
[0005]
The present invention has been made in view of the above problems, and has as its object to provide a switching element having a novel configuration and a switching circuit using the same.
[0006]
[Means for Solving the Problems]
The switching element according to the present invention has a first electrode, a second electrode, a third electrode, and an insulator that electrically insulates the second electrode and the third electrode. The electrode and the insulator each have a structure facing the first electrode, an electrically insulating electrophoretic medium interposed between the first electrode and the structure, and are present in the electrophoretic medium, A plurality of electrophoretic particles that are electrically charged and electrophoresed in response to an electric field, can conduct electricity, and float or sink in the electrophoretic medium when no electric field is applied.
[0007]
According to the switching element according to the present invention, when the electrophoretic particles settle in the electrophoretic medium when no electric field is applied, and the switching element is arranged such that the first electrode is located above the structure, the following: Such an operation becomes possible. That is, the magnitude of the voltage between the first electrode and the second electrode or the third electrode is less than a predetermined threshold, and the migrating particles are caused by the electric field between the first electrode and the second electrode or the third electrode. If not migrated upwards against the gravity, the migrating particles settle down in the electrophoresis medium by gravity and are spread on the structure from the second electrode through the insulator to the third electrode, and the second electrode And the third electrode are electrically connected by the group of migrating particles. On the other hand, the magnitude of the voltage applied between the first electrode, the second electrode and the third electrode exceeds a predetermined threshold, and the electrophoresis occurs due to the electric field between the first electrode and the second electrode or the third electrode. When the particles are electrophoresed upward against gravity, the migrating particles move from the second structure to the first electrode side, so that the migrating particles do not contact the second or third electrode and the second electrode And the third electrode are electrically insulated.
[0008]
When the switching element is arranged such that the migrating particles float in the migrating medium when no electric field is applied and the first electrode is located below the structure, the following operation can be performed. That is, the magnitude of the voltage between the first electrode and the second electrode or the third electrode is less than a predetermined threshold, and the migrating particles are caused by the electric field between the first electrode and the second electrode or the third electrode. When not migrated downward against gravity, the migrating particles float on the electrophoresis medium by gravity and are spread on the lower surface of the structure from the second electrode through the insulator to the third electrode, The group of the migrating particles electrically connects the electrode and the third electrode. On the other hand, the first electrode, the magnitude of the voltage applied between the second electrode and the third electrode exceeds a predetermined threshold, by the electric field between the first electrode and the second electrode or the third electrode, When the migrating particles move downward due to the electrostatic force against the gravity, the migrating particles move from the second structure side to the first electrode side, and the migrating particles do not contact the second electrode or the third electrode. The second electrode and the third electrode are electrically insulated.
[0009]
For this reason, a switching element having a novel configuration capable of repeatedly switching conduction / interruption between the second electrode and the third electrode according to the voltage between the first electrode and the second electrode or the third electrode. Is achieved.
[0010]
Here, the portion of the structure facing the first electrode is preferably flat.
[0011]
According to this, the electrophoretic particles can be easily spread evenly, so that the conduction / interruption can be reliably switched by the voltage.
[0012]
An insulating spacer sandwiched between the first electrode and the structure and defining a predetermined closed space between the first electrode and the structure; The particles are preferably introduced into the closed space.
[0013]
According to this, a switching element having a suitable structure is realized, and manufacturing is also facilitated.
[0014]
Further, it is preferable that the electrophoretic particles have been subjected to a surface treatment with a nonionic surface treating agent.
[0015]
According to this, the electrophoretic particles are hardly aggregated in the electrophoresis medium, and the switching is performed more reliably.
[0016]
Further, the electrophoretic particles have a specific resistance of 10 ² It is preferably Ω · cm or less.
[0017]
According to this, the resistance when conducting between the second electrode and the third electrode is reduced, and heat generation is suppressed.
[0018]
The electrophoretic particles have a specific surface area of 10 to 100 m. ² / G.
[0019]
According to this, electrophoresis of the migrating particles is suitably performed.
[0020]
The electrophoresis medium has a kinematic viscosity at 40 ° C. of 1 × 10 ^-6 ~ 100 × 10 ^-6 m ² / S.
[0021]
According to this, the electrophoretic particles are suitably electrophoresed, and the repetition performance is enhanced.
[0022]
The electrophoresis medium has a density at 5 ° C. of 0.7 to 2.0 g / cm. ³ It is preferable that
[0023]
According to this, electrophoresis is suitably performed, sedimentation and floating by gravity are also suitably performed, and the repetition performance is enhanced.
[0024]
When the weight of the electrophoretic particles is A and the weight of the electrophoretic medium is B, A / B is preferably 0.01 to 0.05.
[0025]
According to this, when the voltage is less than the predetermined threshold, the connection between the second electrode and the third electrode is suitably conducted by the migrating particles, and when the voltage exceeds the predetermined threshold, the electrophoresis occurs in the electrophoresis medium. The particles migrate favorably.
[0026]
A switching circuit according to the present invention is a circuit that is connected to a DC power supply that generates a predetermined DC voltage between a first output terminal and a second output terminal. One output terminal and a load connected between one of the second electrode and the third electrode of the switching element, wherein the first electrode of the switching element is connected to the first output terminal of the DC power supply. The other of the second electrode and the third electrode of the switching element is a circuit connected to the second output terminal of the DC power supply.
[0027]
According to the switching circuit of the present invention, the following effects can be obtained by using the above-described switching element. That is, when a DC voltage smaller than the magnitude of the threshold voltage at which the switching element switches is applied between the first electrode and the second or third electrode, the voltage between the second electrode and the third electrode is reduced. The conduction is ensured, and a predetermined voltage is applied to the load. On the other hand, when a voltage having a magnitude exceeding the threshold voltage is applied between the first electrode and the second or third electrode, the migrating particles migrate upward or downward, and the second electrode and the second electrode move. The three electrodes are insulated from each other to prevent a voltage exceeding a threshold voltage from being applied to the load. Thus, an overvoltage protection circuit for the load is suitably provided.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a switching element according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements have the same reference characters allotted, and overlapping description will be omitted.
[0029]
FIG. 1 is a partially cutaway perspective view of a switching element according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view of the switching element according to the embodiment of the present invention. The switching element 100 according to the present embodiment mainly includes the first electrode 10, the structure 20, the spacer 30 interposed between the first electrode 10 and the structure 20, the first electrode 10 and the structure 20. And an electrophoretic medium 40 and electrophoretic particles 50 enclosed in a space 35 defined by the spacer 30 and the spacer 30.
[0030]
The first electrode 10 is a rectangular plate formed of a conductor, and is arranged horizontally.
In addition, the structure body 20 faces the first electrode 10 at a predetermined interval below the first electrode 10, and has a rectangular plate shape similar to the first electrode 10.
[0031]
This structure 20 has an insulator 23 formed of an electrically insulating material. Further, the structure 20 is formed of a conductor and has a pair of second electrodes 21 and third electrodes 22 that sandwich the insulator 23 from both sides in the horizontal direction. The second electrode 21 and the third electrode 22 are electrically insulated from each other by an insulator 23. In addition, a portion extending from the second electrode 21 to the insulator 23 through the third electrode 22 on the upper surface of the structure 20 is a horizontal surface, and faces the lower surface of the first electrode 10.
[0032]
The second electrode 21, the third electrode 22, and the insulator 23 are connected to each other and integrated by a joining member 24 that joins them from the lower surface side.
[0033]
The material of the first electrode 10, the second electrode 21, and the third electrode 22 is not particularly limited as long as it is a conductor, and may be a metal such as aluminum, copper, nickel, or a material obtained by coating glass or plastic with a conductive film. Available.
[0034]
The spacer 30 has a rectangular horizontal frame shape made of an insulating material, has an insulating adhesive layer 31 on the upper surface side, and has an insulating adhesive layer 32 on the lower surface side. And the structure 20 are vertically sandwiched and fixed. The lower surface of the first electrode 10, the upper surfaces of the second electrode 21, the third electrode 22, and the insulator 23 of the structure 20, and the inner peripheral surfaces of the spacer 30, the adhesive layer 31, and the adhesive layer 32, A predetermined space (closed space) 35 is defined.
[0035]
In the space 35, a migration medium 40 and a large number of migration particles 50 are sealed. The electrophoresis medium 40 is a fluid having an insulating property. The electrophoresis medium 40 enables the electrophoresis and sedimentation of the electrophoresis particles 50 in the electrophoresis medium 40 by dispersing the electrophoresis particles 50. It is preferable that the electrophoretic medium 40 is chemically stable, has high electric breakdown strength, and can stably disperse the electrophoretic particles 50. The electrophoretic medium 40 preferably does not contain ions, and does not generate ions even when an electric field is applied. Examples thereof include liquid paraffin, silicone oil, various hydrocarbons, various aromatic hydrocarbons, and organic chlorides.
[0036]
Further, the electrophoresis medium 40 has a kinematic viscosity at 40 ° C. of 1 × 10 ^-6 ~ 100 × 10 ^-6 m ² / S (1 to 100 cSt). If the kinematic viscosity is out of this range, the migrating particles 50 tend not to migrate or the repetition performance described later tends to decrease.
[0037]
The electrophoresis medium 40 has a density at 25 ° C. of 0.7 to 2.0 g / cm. ³ It is preferable that If the density of the electrophoresis medium 40 is out of this range, electrophoresis tends to hardly occur or sedimentation tends to hardly occur, and the repetition performance tends to decrease.
[0038]
On the other hand, the electrophoretic particles 50 placed in the electrophoretic medium 40 in the space 35 exhibit a charge in the electrophoretic medium 40, that is, have a positive or negative net charge. Electrophoresis in the electrophoresis medium 40.
[0039]
The charging mode of the migrating particles 50 may be variously considered. For example, the entire migrating particles 50 may be charged, and when the migrating particles 50 have a multiple structure having a nucleus and a coating layer, the nucleus is charged. Alternatively, the coating layer may be charged, and when the electrophoretic medium 40 has been surface-modified, the interface may be charged by a surface-modifying substance.
[0040]
Further, the density of the migrating particles 50 is higher than that of the migrating medium 40, and when no electric field is applied in the space, the migrating particles 50 sediment by gravity. Further, the migrating particles 50 can have a semiconductor or a conductor on at least the surface thereof to conduct electricity.
[0041]
In addition, the amount of the migrating particles 50 is such that it can be spread from the surface of the second electrode 21 to the surface of the third electrode 22 through the surface of the insulator 23 on the upper surface of the structure 20. When the migrating particles 50 are spread over the upper surface of the structure 20 from the second electrode 21 through the insulator 23 to the third electrode 22, contact between the migrating particles 50 and a part of the migrating particles 50 are performed. By contact between the second electrode 21 and the third electrode 22 or the like, an electric conduction path from the second electrode 21 to the third electrode is formed, and electric conduction is enabled.
[0042]
Here, the electrophoretic particles 50 preferably have a low specific resistance, and specifically, have a specific resistance of 10 ² It is preferably Ωcm or less. The specific resistance of the migrating particles 50 is 10 ² If it exceeds Ωcm, the resistance of the electric conduction path formed by the migrating particles 50 tends to increase, and the amount of heat generated tends to increase.
[0043]
Further, the electrophoretic particles 50 preferably have a small particle diameter. Specifically, the specific surface area of the migrating particles 50 is 10 to 100 m ² / G. If the specific surface area of the migrating particles 50 is out of this range, electrophoresis is unlikely to occur, and the migration speed tends to decrease. Further, the electrophoretic particles 50 preferably have a narrow particle size range.
[0044]
The migrating particles 50 are preferably surface-treated with a nonionic surface treating agent. When the surface treatment is performed, the aggregation of the migrating particles 50 in the migrating medium 40 does not easily occur, and the adhesion to the first electrode 10, the structure 20, or the like does not easily occur. This results in higher repetition performance and faster response.
Here, when the electrophoresis solvent 40 is other than a fluorine solvent, it is preferable to use a nonionic surfactant, a nonionic ether-based surface treatment agent, or the like. On the other hand, when the electrophoresis solvent 40 is a fluorinated solvent, it is preferable to use a nonionic fluorinating agent. When electrophoretic particles that have been surface-treated with a non-fluorinated solvent other than a nonionic fluorinated solvent are used, the processing agent tends to separate from the electrophoretic particles in the electrophoretic solvent.
[0045]
As a specific example of such migrating particles 50, for example, a semiconductor can be suitably used. Specifically, there is a semiconductor in which a surface of Si, Ge, or the like is doped with a donor or an acceptor to form a semiconductor. As an oxide semiconductor, for example, TiO ₂ , SnO ₂ , ZnO, Fe ₂ O ₃ , BaTiO ₃ , SrTiO ₃ And those obtained by doping the surface of these particles with a donor or an acceptor to form a semiconductor. Further, nitrides such as TiN, TaN, NbN, etc., carbides such as SiC, TiC, WC, TaC, etc., and carbon can also be used.
[0046]
A metal can also be used as the migrating particles 50. For example, a noble metal such as Au, Pt, or Ag, a base metal such as Ni or Cu, an alloy of a noble metal and a base metal, or a semiconductor or a conductive polymer. Coated ones are available.
[0047]
The ratio between the electrophoretic medium 40 and the electrophoretic particles 50 existing in the space 35 is such that when the weight of the electrophoretic particles 50 is A and the weight of the electrophoretic medium 40 is B, A / B is 0.01 to 0.05. Preferably. When the A / B is less than 0.01, the amount of the migrating particles 50 is small, so that even if the migrating particles 50 are laid on the structure 20, electrical continuity between the second electrode 21 and the third electrode 22 is maintained. It tends to be difficult to establish. On the other hand, when the A / B is 0.05 or more, the electrophoresis of the migrating particles tends to be easily inhibited because the proportion of the migrating particles in the space 35 increases.
[0048]
Next, the operation of the switching element 100 will be described. In the present switching element, conduction / interruption between the second electrode 21 and the third electrode 22 is determined by the magnitude of the voltage applied between the first electrode 10 and the second electrode 21 or the third electrode 22. Is switched.
[0049]
This will be described in detail below. An upward or downward electric field E is generated in the space 35 by the voltage V applied between the first electrode 10 and the second electrode 21 or the third electrode 22. Therefore, an upward or downward electrostatic force S is generated on the migrating particles 50 in the migrating medium 40. Further, a force W due to gravity and buoyancy, that is, a force generated according to a difference between the density of the electrophoretic medium 40 and the density of the electrophoretic particles 50 acts on the electrophoretic particles 50. Then, the net force F acting on the migrating particles 50 is F = S + W with the upward direction being positive.
[0050]
Here, first, for simplicity, a case where the migrating particles 50 are positively charged will be described. When the magnitude of the voltage V applied between the first electrode 10 and the second electrode 21 or the third electrode 22 becomes lower than a predetermined threshold voltage VS, the strength of the upward electric field in the electrophoresis medium 40 becomes predetermined. When F <0, the migrating particles 50 settle down due to gravity and are spread over the surfaces of the second electrode 21, the insulator 23, and the third electrode 22, as shown in FIG. Thus, the second electrode 21 and the third electrode 22 are electrically connected.
[0051]
On the other hand, when the magnitude of the voltage V applied between the first electrode 10 and the second electrode 21 or the third electrode 22 exceeds a predetermined threshold voltage VS, the strength of the upward electric field in the electrophoresis medium 40 becomes When F> 0, the electrophoretic particles 50 rise by electrophoresis and come out of contact with the second electrode 21 or the third electrode 22, as shown in FIG. And the third electrode 22 are insulated.
[0052]
On the other hand, when the migrating particles 50 are negatively charged, the following occurs. That is, the magnitude of the voltage V applied between the first electrode 10 and the second electrode 21 or the third electrode 22 becomes smaller than the predetermined threshold voltage VS, and the strength of the downward electric field in the electrophoresis medium 40 is reduced. Is smaller than a predetermined value, and when F <0, as shown in FIG. 2, the migrating particles 50 settle down due to gravity and fall on the respective surfaces of the second electrode 21, the insulator 23, and the third electrode 22. And the second electrode 21 and the third electrode 22 are electrically connected to each other.
[0053]
On the other hand, when the magnitude of the voltage V applied between the first electrode 10 and the second electrode 21 or the third electrode 22 exceeds a predetermined threshold voltage VS, the strength of the downward electric field in the electrophoresis medium 40 becomes When F> 0, as shown in FIG. 3, the migrating particles 50 rise by electrophoresis and stop coming into contact with the second electrode 21 or the third electrode 22. And the third electrode 22 are insulated.
[0054]
Also, in any case where the migrating particles 50 are positively charged or negatively charged, the magnitude of the voltage V between the first electrode 10 and the second electrode 21 and the third electrode 22 is predetermined. When the voltage returns to less than the threshold voltage VS, for example, zero, the migrating particles 50 settle down and are laid again on the structure 20, and the conduction between the second electrode 21 and the third electrode 22 is established. It returns and the switching operation can be repeated.
[0055]
The threshold voltage VS at which such switching occurs depends on the physical properties such as the charge amount and the density of the migrating particles 50, the physical properties such as the density of the migrating medium 40, and the first electrode 10, the second electrode 21, and the second electrode 21. The switching element changes depending on the gap length or the like, and by appropriately changing these, a switching element in which a switching operation occurs at a desired threshold voltage VS can be obtained.
[0056]
Further, in the present embodiment, since the portion facing the first electrode 10 in the structure 20 is a flat surface, migrating particles extend from the second electrode 21 through the insulator 23 to the third electrode 22. It is easy to spread, and switching between conduction and interruption is suitably performed.
[0057]
In addition, since the spacer 30 defines a predetermined closed space 35 in which the migrating particles 50 and the migrating medium are enclosed, the structure is simplified and the switching element can be suitably manufactured.
[0058]
As described above, according to the switching element according to the present embodiment, the magnitude of the voltage between the first electrode 10, the second electrode 21, and the third electrode 22 is less than the predetermined threshold, When the migrating particles 50 do not migrate upward due to the electric field between the one electrode 10 and the second electrode 21 or the third electrode 22, the migrating particles 50 settle down in the migrating medium due to gravity, and the surface of the second electrode 21 From the surface of the insulator 23 to the surface of the third electrode 22, and the group of the migrating particles 50 electrically connects between the second electrode 21 and the third electrode 22. On the other hand, the magnitude of the voltage applied between the first electrode 10 and the second electrode 21 or the third electrode 22 exceeds a predetermined threshold, and the first electrode 10 and the second electrode 21 or the third electrode 22 When the electrophoretic particles 50 overcome the gravity and are electrophoresed upward by the electric field between the electrophoretic particles, the electrophoretic particles 50 move to the first electrode 10 side, and the electrophoretic particles 50 contact the second electrode 21 or the third electrode 22. And the second electrode 21 and the third electrode 22 are electrically insulated. For this reason, according to the voltage between the first electrode 10 and the second electrode 21 or the third electrode 22, the conduction / interruption between the second electrode 21 and the third electrode 22 can be repeatedly switched. The switching element 100 having the configuration is realized.
[0059]
In the present embodiment, as the migrating particles 50, those that settle by gravity in the migrating medium 40 when no electric field is applied are used, but the migrating particles that float by gravity in the migrating medium 40 when no electric field is applied. May be used. In this case, the switching element 100 may be used upside down with the first electrode 10 positioned below the structure 20 and the same switching operation as described above is possible.
[0060]
Next, an example of a method for manufacturing such a switching element 100 will be described with reference to FIGS.
[0061]
Specifically, first, the structural body plate 70 is manufactured. Here, as shown in FIG. 4 (a), the plate material 6 as an insulator is arranged in a plate shape sandwiching the plate material 3 as a conductor and the plate material 2 as a conductor from both sides. The plate member 3, the plate member 6, and the plate member 2 are integrated by bonding the joining member 9. In addition, as shown in FIG. 4B, after applying an adhesive such as a thermosetting type to both sides of the plate member 6, the plate member 6 may be sandwiched between the plate members 2 and 3 from both sides. Thus, the flat structure plate 70 shown in FIG. 5A is completed.
[0062]
Next, as shown in FIG. 5B, a first electrode plate 74 is prepared. The first electrode plate 74 is a conductor having a predetermined thickness corresponding to the size of the structure plate 70.
[0063]
Next, a spacer plate 72 as shown in FIG. 5C is prepared. The spacer plate 72 is formed by forming a plurality of holes 7 having a predetermined size by pressing or the like on an insulating sheet having a predetermined thickness corresponding to the size of the structure plate 70.
[0064]
Next, an adhesive layer 73 having a predetermined thickness is applied to the lower surface of the spacer plate 72 by printing or the like, and the spacer plate 72 is bonded to the structural body plate 70 and then dried (see FIG. 6A). Then, the electrophoretic medium 40 and the electrophoretic particles 50 are mixed and stirred at a predetermined ratio, and then filled into the holes 7 in the spacer plate 72 with a pipette or the like.
[0065]
Next, an adhesive layer 75 having a predetermined thickness is applied by mask printing to a portion corresponding to the surface shape of the spacer plate 72 on the lower surface of the first electrode plate 70, and as shown in FIG. The first electrode plate 70 is placed on the spacer plate 72 and bonded together so as to prevent air bubbles from entering, and then dried to form the element assembly 150.
[0066]
Finally, the element assembly 150 is cut into a predetermined size to obtain the switching element 100.
[0067]
Next, an embodiment of a switching circuit using the switching element according to the present embodiment will be described with reference to FIG. 7 by taking as an example a case where the switching element 100 is used to protect the load R1 so that an overvoltage is not applied. Will be explained.
[0068]
The switching circuit 200 according to the present embodiment includes a DC power supply 80, a variable resistor RV, a load R1 to be protected, and a load R2. One end of the load R1 is connected to a negative electrode of a DC power supply 80 that generates a voltage V1 via a variable resistor RV. On the other hand, the other end of the load R1 is connected to the third electrode 22 of the switching element 100. The first electrode 10 of the switching element 100 is connected to the negative electrode of the DC power supply 80 via the load R2 and the variable resistor RV. Further, the second electrode 21 of the switching element 100 is connected to the positive electrode of the DC power supply 80 via the switch SW1. Here, in the switching element 100, migrating particles 50 that are positively charged and settle in the migrating medium 40 in a state where no electric field is applied are used.
[0069]
When SW1 is open, no voltage is applied to the switching element or load R1. At this time, the migrating particles 50 have settled down from the surface of the second electrode 21 to the surface of the insulator 23 and the surface of the third electrode 22 as a result of sedimentation due to gravity. The migrating particles 50 as a whole enable electrical conduction between the second electrode 21 and the third electrode 22.
[0070]
Next, when the switch SW1 is closed, the current flows from the positive electrode of the DC power supply 80 to the switch SW1, the second electrode 21, the migrating particles 50, and the third electrode 22 of the switching element 100 in this order by the voltage V1 from the DC power supply 80. It flows and is supplied to the load R1, and further returns to the negative electrode of the DC power supply 80 through the variable resistor RV. At this time, the first electrode 10 is connected to the negative electrode of the DC power supply 80, and the voltage V1 is applied between the first electrode 10 of the switching element 100 and the second and third electrodes 22 of the switching element 100. As a result, an upward electric field E1 is generated in the space 35. Therefore, an upward electrostatic force S1 acts on the migrating particles 50 having a positive charge. However, by setting the threshold voltage VS of the switching element 100 to be higher than V1 and by setting F = S1 + W <0 in the electric field of E1, the conduction is maintained without the migrating particles 50 migrating upward. . Then, the predetermined DC voltage V1 is continuously applied to the load R1. That is, a circuit equivalent to the circuit shown in FIG.
[0071]
On the other hand, when an overvoltage V2 exceeding the voltage V1 of the DC power supply 80 is applied to both ends of the load R1 due to a disturbance such as a surge, the first electrode 10, the second electrode 21, and the third electrode 22 , An electric field E2 higher than E1 is generated. Then, an upward electrostatic force S2 stronger than S1 acts on the migrating particles 50 having a positive charge. Then, when V2 exceeds the threshold voltage VS of the switching element 100 and F = S2 + W> 0, the migrating particles 50 start moving upward. Thereby, the second electrode 21 and the third electrode 22 are insulated from each other, and the overvoltage V2 is not applied to the load R1. That is, a circuit equivalent to the circuit shown in FIG. In this state, the migrating particles 50 come into contact with the surface of the first electrode 10.
[0072]
Then, after the migrating particles 50 move upward and come into contact with the first electrode 10 due to the overvoltage V2, the voltage between the first electrode 10 and the second electrode 21 returns to V1 or the voltage becomes zero. As a result, the migrating particles 50 settle down, the conduction between the second electrode 21 and the third electrode 22 is restored, and the voltage V1 can be applied to the load R1. That is, even if switching occurs due to disturbance or the like and the circuit to the load R1 is cut off, automatic recovery is possible if the problem is solved.
[0073]
As described above, according to the switching circuit 200 according to the present embodiment, the DC voltage lower than the threshold voltage at which the switching element 100 switches is applied between the first electrode 10 and the second electrode 21 or the third electrode 22. Is applied, the conduction between the second electrode 21 and the third electrode 22 is ensured, and a predetermined voltage is applied to the load R1. On the other hand, when a voltage exceeding the threshold voltage is applied between the first electrode 10 and the second electrode 21 or the third electrode 22, the migrating particles 50 migrate upward and the second electrode 21 The three electrodes 22 are insulated from each other, thereby preventing a voltage exceeding the threshold voltage from being applied to the load R1. Thereby, an overvoltage protection circuit for the load R1 can be provided.
[0074]
Next, the switching element according to the present embodiment was prepared and its characteristics were examined.
[0075]
(Example 1)
First, the surface layer is made of SnO doped with Sb. ₂ Particles were prepared. This SnO ₂ The specific surface area of the particles is 70 m ² / G, and the powder resistance was 1.5Ω · cm. Then, an ether-based nonionic surface treating agent (manufactured by Toho Chemical Co., Ltd.) was added to the particles as a surface treating agent, mixed, and then dried to obtain electrophoretic particles.
[0076]
Isoparaffin was prepared as a migration medium. This isoparaffin has a density of 0.78 g / cm at 25 ° C. ³ Kinematic viscosity at 40 ° C. is 85 × 10 ^-6 m ² / S (85 cSt). Here, the migrating particles are positively charged in the migrating medium, and sediment in the migrating medium when no electric field is applied.
[0077]
Next, an aluminum plate having a length of 3 mm, a width of 100 mm, and a thickness of 0.2 mm was prepared and used as a first electrode plate. Further, a PET sheet having a length of 3 mm, a width of 100 mm, and a thickness of 0.15 mm was prepared. A plurality of holes having a length of 2 mm and a width of 6 mm were formed in the sheet at intervals of 10 mm in the horizontal direction by a 2t press to form a spacer plate.
[0078]
Subsequently, a PET plate having a length of 0.5 mm, a width of 100 mm, and a thickness of 0.2 mm is prepared, and is sandwiched between two aluminum plates having a length of 1.25, a width of 1.25, and a thickness of 0.2 mm. A polyimide tape was adhered from the surface side of the above and integrated to prepare a structural board having a length of 3 mm, a width of 100 mm and a thickness of 0.2 mm.
[0079]
Next, a two-part epoxy adhesive having a thickness of 0.05 mm was applied to one surface of the spacer plate by printing, and the spacer plate was bonded to the other surface of the structural plate and dried.
[0080]
Next, the electrophoretic medium and the electrophoretic particles were mixed and stirred such that the weight A of the electrophoretic particles / the weight B of the electrophoretic medium became 0.0135, and the mixture was dropped into each hole of the spacer plate. Then, an epoxy adhesive having a thickness of 0.05 mm was applied to one surface of the first electrode plate by mask printing. At this time, an epoxy adhesive was applied to the first electrode plate by using a mask so as to remove a portion corresponding to a hole portion of the spacer plate when bonded to the spacer plate. Thereafter, the first electrode plate was attached to the spacer plate so as to prevent air bubbles from entering the holes in the spacer plate and dried to obtain a switching element assembly having a length of 3 mm, a width of 100 mm, and a thickness of 0.65 mm. Then, this assembly was cut into 10 mm in width to obtain a switching element according to the first example having a length of 3 mm, a width of 10 mm, and a thickness of 0.65 mm.
[0081]
(Example 2)
The electrophoresis medium has a density of 1.32 g / cm at 25 ° C. ³ Kinematic viscosity at 40 ° C. is 53 × 10 ^-6 m / s ² A switching element according to a second embodiment was obtained in the same manner as in the first embodiment except that silicon oil of (53 cSt) was used.
[0082]
(Example 3)
1.65 g / cm density at 25 ° C. as electrophoresis medium ³ Kinematic viscosity at 40 ° C. is 2 × 10 ^-6 m / s ² (53cSt) fluorinated solvent (Fluorinert manufactured by Sumitomo 3M Ltd.) is used, and a nonionic fluorinated treatment agent (for example, manufactured by Daikin Industries, Ltd.) is used as a surface treatment agent in preparing electrophoretic particles. A switching element according to a third embodiment was obtained in the same manner as in the first embodiment except for the difference.
[0083]
Then, the switching element thus obtained is applied as the switching element 100 in the switching circuit (see FIG. 7) in the above-described embodiment, and the power supply voltage is set to 5, 10, 20, 30, 50, 75, and 100V. The current was gradually increased, and in each case, the value of the current flowing through the load R1 was measured. Here, the switching elements were arranged such that the first electrode was above the structure. After measuring the current value at 100V, the power supply voltage was returned to 0V. Further, in order to verify the repetition performance, such a series of operations was repeated 10 times in total. The results are shown in FIGS. In addition, although illustration of each measured value in the third, fourth, and sixth to ninth voltage increase processes is omitted for simplicity, the results are all the same as the first results.
[0084]
As is clear from these results, in the switching elements of Examples 1 to 3, when a voltage equal to or more than a predetermined voltage was applied, no current flowed to the load R1, and the second electrophoresis caused by electrophoresis above the electrophoretic particles. It was shown that the electrode and the third electrode were insulated and functioned as a switching element. Further, even when the repetition operation was performed ten times, the switching operation was performed at the same switching voltage, and thus it was shown that a switching element capable of repetition operation was provided.
[0085]
The switching threshold value of the switching element of the first embodiment is between 5 and 10 V, the switching threshold value of the switching element of the second embodiment is between 10 and 20 V, and the switching threshold value of the switching element of the third embodiment. Are between 50 and 75 V and are different from each other. In Example 1, Example 2 and Example 3, the density and physical properties of the electrophoretic medium are different from each other, and this changes the buoyancy and the charge amount acting on the electrophoretic medium. Can be These have demonstrated the usefulness of the switching element according to the present embodiment.
[0086]
Note that the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above circuit, a switching element having migrating particles which settles in the electrophoretic medium in a state where no electric field is applied is used, but a switching element having migrating particles which floats in the electrophoretic medium in a state where no electric field is applied is used. You may. In the above circuit, a switching element having electrophoretic particles which are positively charged in the electrophoretic medium is used, but a circuit having a switching element having electrophoretic particles which are negatively charged in the electrophoretic medium may be used.
[0087]
【The invention's effect】
As described above, according to the present invention, conduction / interruption between the second electrode and the third electrode is repeatedly switched according to the voltage between the first electrode and the second electrode or the third electrode. A switching element having a novel configuration and a switching circuit using the same are realized.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view showing a switching element according to an embodiment.
FIG. 2 is a vertical sectional view of FIG.
FIG. 3 is a vertical sectional view showing a state in which migrating particles migrate upward in the switching element of FIG. 2;
4 (a) and 4 (b) are cross-sectional views illustrating a process for manufacturing the switching element of FIG. 1. FIG.
5 (a), 5 (b), and 5 (c) are perspective views for explaining a step following FIG. 4 (a).
FIGS. 6 (a) and 6 (b) are perspective views for explaining steps following FIGS. 5 (a), 5 (b) and 5 (c).
FIG. 7 is a circuit diagram of a switching circuit using the switching element of FIG.
8A is a circuit diagram showing a circuit equivalent to a first operation state of the circuit of FIG. 7, and FIG. 8B is a circuit diagram showing a second operation state of the circuit of FIG. FIG. 3 is a circuit diagram showing an equivalent circuit.
FIG. 9 is a diagram illustrating characteristics of the switching element according to the first embodiment.
FIG. 10 is a diagram illustrating characteristics of the switching element according to the second embodiment.
FIG. 11 is a diagram illustrating characteristics of the switching element according to the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... 1st electrode, 21 ... 2nd electrode, 22 ... 3rd electrode, 23 ... Insulator, 30 ... Spacer, 40 ... Electrophoretic medium, 50 ... Electrophoretic particle, 80 ... DC power supply, 100 ... Switching element, 200 ... Switching Circuit, R1 ... load.

Claims (10)

A first electrode;
A second electrode, a third electrode, and an insulator that electrically insulates the second electrode and the third electrode, wherein the second electrode, the third electrode, and the insulator are each A structure facing the first electrode,
An electrically insulating electrophoretic medium interposed between the first electrode and the structure,
A large number of migrating particles that are present in the electrophoresis medium, exhibit electrophoresis in response to an electric field by exhibiting charge, can conduct electricity, and float or settle in the electrophoresis medium when no electric field is applied. And a switching element comprising: The switching element according to claim 1, wherein a portion of the structure facing the first electrode is a flat surface. An insulating spacer sandwiched between the first electrode and the structure and defining a predetermined closed space between the first electrode and the structure, the electrophoretic medium and the electrophoretic particles The switching element according to claim 1, wherein the switching element is introduced into the closed space. The switching element according to claim 1, wherein the migrating particles are surface-treated with a nonionic surface treatment agent. The electrophoretic particles, the switching device according to any one of claims 1 to 5 that resistivity is less than 10 ² Ω · cm. The switching element according to claim 1, wherein the electrophoretic particles have a specific surface area of 10 to 100 m ² / g. The switching element according to claim 1, wherein the electrophoretic medium has a kinematic viscosity at 40 ° C. of 1 × 10 ^{−6 to} 100 × 10 ⁻⁶ m ² / s. The switching element according to claim 1, wherein the electrophoretic medium has a density at 5 ° C. of 0.7 to 2.0 g / cm ³ . The switching element according to any one of claims 1 to 9, wherein A / B is 0.01 to 0.05, where A represents the weight of the migrating particles and B represents the weight of the migrating medium. A circuit connected to a DC power supply that generates a predetermined DC voltage between the first output terminal and the second output terminal,
A switching element according to any one of claims 1 to 9,
A first output terminal of the DC power supply, and a load connected between one of the second electrode and the third electrode of the switching element,
A first electrode of the switching element is connected to a first output terminal of the DC power supply, and either the second electrode or the third electrode of the switching element is connected to a second output terminal of the DC power supply. .

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