JP7421164B2 - heat flow switching element - Google Patents

Description

The present invention relates to a heat flow switching element whose heat conduction can be actively controlled by a bias voltage.

Conventionally, as a thermal switch that changes thermal conductivity, for example, Patent Document 1 describes a thermal diode in which two thermal conductors having different coefficients of thermal expansion are brought into light contact and heat flows in different ways depending on the direction of the temperature gradient. ing. Further, Patent Document 2 also describes a heat dissipation device that is a thermal switch using physical thermal contact due to thermal expansion.

Further, Patent Document 3 describes a variable heat conduction device whose thermal conductivity changes due to a reversible redox reaction that occurs when a voltage is applied to a compound.
Furthermore, Non-Patent Document 1 proposes a heat flow switching element that changes thermal conductivity by sandwiching a polyimide tape between two sheets of Ag ₂ S _0.6 Se _0.4 and applying an electric field.

Patent No. 2781892 Patent No. 5402346 JP2016-216688A

Takuya Matsunaga, 4 others, "Fabrication of heat flow switching device operated by bias voltage", 15th Academic Conference of the Thermoelectrics Society of Japan, September 13, 2018

The above conventional techniques still have the following problems.
In other words, the techniques described in Patent Documents 1 and 2 use physical thermal contact due to thermal expansion, so reproducibility is not achieved, size design is particularly difficult due to minute changes, and plasticity due to mechanical contact pressure is not achieved. Deformation cannot be avoided. Additionally, there was a problem in that the influence of convective heat transfer between materials was too large.
Further, the technique described in Patent Document 3 uses an oxidation-reduction reaction, which is a chemical reaction, and has disadvantages such as poor thermal responsiveness and unstable thermal conduction.
In contrast, in the technology described in Non-Patent Document 1, by applying a voltage, a charge capable of thermal conduction is generated at the material interface, and heat can be carried by the charge, so that a state in which heat conduction has changed is generated. It is possible to immediately transfer to the temperature range, and relatively good thermal response can be obtained. However, since the amount of charge generated is small, a heat flow switching element is desired that can increase the amount of charge generated and has a larger change in thermal conductivity.
Furthermore, with conventional elements, it is difficult to install them on any curved surface and change the thermal conductivity over a wide range of the curved surface.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a heat flow switching element that has a larger change in thermal conductivity, has excellent thermal response, and can be installed on any curved surface. do.

The present invention employs the following configuration to solve the above problems. That is, the heat flow switching element according to the first invention includes a flexible insulating film, an N-type semiconductor layer, an insulator layer, and a P-type semiconductor layer, and the N-type semiconductor layer is provided on the insulating film. one of the type semiconductor layer and the P-type semiconductor layer is stacked, the insulator layer is stacked on the one semiconductor layer, and the N-type semiconductor layer and the P-type semiconductor layer are stacked on the insulator layer. It is characterized in that the other semiconductor layer among the layers is stacked.

That is, in this heat flow switching element, one of an N-type semiconductor layer and a P-type semiconductor layer is laminated on an insulating film, an insulating layer is laminated on one of the semiconductor layers, and an insulating layer is laminated on one of the semiconductor layers. Since the other semiconductor layer of the N-type semiconductor layer and the P-type semiconductor layer is stacked, when a voltage is applied to the P-type semiconductor layer and the N-type semiconductor layer, the P-type semiconductor layer and the N-type semiconductor layer and the insulator are stacked. Charge is induced mainly at the interface with the layer, and this charge transports heat, changing the thermal conductivity. In particular, since charges are generated both at and near the interface between the N-type semiconductor layer and the insulator layer and at and near the interface between the P-type semiconductor layer and the insulator layer, the amount of charge generated is large. , a large change in thermal conductivity and high thermal responsiveness can be obtained. In addition, since the amount of charge induced at the interface changes by multiplying by the magnitude of the external voltage, it is possible to adjust the thermal conductivity by adjusting the external voltage. Heat flow can be actively controlled.
In addition, since the N-type semiconductor layer, the insulator layer, and the P-type semiconductor layer are stacked, the interface with the insulator layer can be set wide, and the distance between the N-type semiconductor layer and the P-type semiconductor layer can be set as wide as the insulator layer. It is determined by the thickness of the layer, and it becomes easier to design the distance between PNs to be small.
Note that since the insulator layer is an insulator, no current is generated due to voltage application, so Joule heat is not generated. Therefore, heat flow can be actively controlled without self-heating.
In addition, since the N-type semiconductor layer and the P-type semiconductor layer sandwich the insulator layer on the flexible insulating film, it can be flexibly bent and can be pasted along the curved surface. This allows the thermal conductivity to be changed over a wide range of curved surfaces even when installed on any curved surface.

A heat flow switching element according to a second invention is characterized in that, in the first invention, the insulator layer is an insulating film.
That is, in this heat flow switching element, since the insulating layer between the N-type semiconductor layer and the P-type semiconductor layer is also a flexible insulating film, it becomes possible to bend the device more flexibly.

A heat flow switching element according to a third invention is characterized in that, in the first or second invention, the insulating film is made of resin.

A heat flow switching element according to a fourth invention is characterized in that, in any one of the first to third inventions, the strip-shaped insulating film is curved into a cylindrical shape.
In other words, in this heat flow switching element, the strip-shaped insulating film is curved into a cylindrical shape, so by installing it so as to cover the outer peripheral surface of the object to be attached, such as a cylinder or cylinder, it is possible to remove heat. It becomes possible to adjust the amount of heat released from the pipes through which the medium flows. Moreover, by attaching this heat flow switching element so as to cover the outer peripheral surface of the cylindrical container, it is also possible to use the cylindrical container as a temperature-adjustable heat storage container.

A heat flow switching element according to a fourth invention is characterized in that, in any one of the first to third inventions, the strip-shaped insulating film is spirally wound into a columnar shape.
In other words, in this heat flow switching element, the strip-shaped insulating film is spirally wound into a columnar shape, so that by inserting it into the inside of the cylindrical object, the inner circumferential surface of the object is exposed. It becomes easy to adjust the amount of heat dissipated from the inside of the object to be attached by thermally contacting the entire circumferential direction of the object.
Further, a heat flow switching element having characteristics equivalent to a laminate can be manufactured without stacking an N-type semiconductor layer and a P-type semiconductor layer multiple times during manufacturing.

According to the present invention, the following effects are achieved.
That is, according to the heat flow switching element according to the present invention, one of the N-type semiconductor layer and the P-type semiconductor layer is laminated on the insulating film, and the insulating layer is laminated on one of the semiconductor layers, Since the other semiconductor layer of the N-type semiconductor layer and the P-type semiconductor layer is laminated on the insulator layer, the interface between the N-type semiconductor layer and the insulator layer and its vicinity, and the P-type semiconductor layer and the insulator layer are stacked. Since charges are generated by applying an external voltage at the interface with the layer and in the vicinity thereof, a large amount of charges are generated, and a large change in thermal conductivity and high thermal responsiveness can be obtained.
In addition, since the N-type semiconductor layer and the P-type semiconductor layer sandwich the insulator layer on the flexible insulating film, it can be flexibly bent and can be pasted along the curved surface. This allows the thermal conductivity to be changed over a wide range of curved surfaces even when installed on any curved surface. Since the area in thermal contact with the curved heat source or cooling source is large, heat flow switching with extremely high thermal responsiveness is possible.

FIG. 2 is a perspective view showing a state in which the heat flow switching element is attached to a cylindrical object in the first embodiment of the heat flow switching element according to the present invention. FIG. 2 is a perspective view showing a heat flow switching element in the first embodiment. FIG. 2 is a conceptual diagram for explaining the principle in the first embodiment. It is a top view (a) and a perspective view (b) which show 2nd Embodiment of the heat flow switching element based on this invention. FIG. 7 is a perspective view showing a state in which a heat flow switching element is attached to a cylindrical object in a second embodiment. FIG. 7 is an exploded perspective view showing a heat flow switching element in a second embodiment.

Hereinafter, a first embodiment of a heat flow switching element according to the present invention will be described with reference to FIGS. 1 to 3. In the drawings used in the following explanation, the scale is changed as necessary to make each part recognizable or easily recognizable. In particular, in FIGS. 2 and 6, each layer is illustrated to be much thicker than it actually is.

As shown in FIGS. 1 to 3, the heat flow switching element 1 of this embodiment includes a flexible insulating film 2, an N-type semiconductor layer 3, an insulator layer 4, and a P-type semiconductor layer 5. It is equipped with
On the insulating film 2 that is the base material, one of the N-type semiconductor layer 3 and the P-type semiconductor layer 5 is laminated, and the insulator layer 4 is laminated on one of the semiconductor layers. The other semiconductor layer of the N-type semiconductor layer 3 and the P-type semiconductor layer 5 is laminated on the layer 4 .

Furthermore, as shown in FIG. 2, the heat flow switching element 1 of this embodiment insulates the N-side electrode 6 connected to the N-type semiconductor layer 3 and the P-side electrode 7 connected to the P-type semiconductor layer 5. It is provided on the sex film 2.
That is, in this embodiment, the N-side electrode 6, the N-type semiconductor layer 3, the insulating layer 4, the P-type semiconductor layer 5, and the P-side electrode 7 are laminated in this order on the insulating film 2.
Note that the layers may be laminated on the insulating film 2 in the reverse order to the above.

An external power supply V is connected to the N-side electrode 6 and the P-side electrode 7, and a voltage is applied thereto. Note that the arrow in FIG. 2 indicates the direction in which the voltage (electric field) is applied.
Note that if a voltage can be applied directly to the N-type semiconductor layer 3 and the P-type semiconductor layer 5, the N-side electrode 6 and the P-side electrode 7 are unnecessary. That is, the N-type semiconductor layer 3 and the P-type semiconductor layer 5 may be directly wire-bonded or connected with lead wires.

In this embodiment, the strip-shaped insulating film 2 is curved into a cylindrical shape. In this embodiment, the strip-shaped insulating film 2 has both ends connected to form a cylindrical shape. As shown in FIG. 1, the heat flow switching element 1 of this embodiment is attached to the outer circumferential surface of, for example, a cylindrical attachment target M in a wound state.
The cylindrical attachment object M is, for example, a pipe through which a heat medium flows.

The N-type semiconductor layer 3 and the P-type semiconductor layer 5 are formed of thin films with a thickness of less than 1 μm. In particular, since the charge e generated at and near the interface with the insulating layer 4 is mainly accumulated in the thickness range of 5 to 10 nm, the N-type semiconductor layer 3 and the P-type semiconductor layer 5 are formed with a thickness of 100 nm or less. More preferably, it is formed thick. Note that the N-type semiconductor layer 3 and the P-type semiconductor layer 5 preferably have a thickness of 5 nm or more.
Note that the type of charge e generated at and near the interface between the N-type semiconductor layer 3 and the insulator layer 4 in FIG. 1 is an electron, and is indicated by a white circle. Furthermore, the type of charge e generated at and near the interface between the P-type semiconductor layer 5 and the insulator layer 4 is a hole, which is indicated by a black circle. (A hole is a hole created by a lack of electrons in the valence band of a semiconductor, and appears to have a relatively positive charge.)
Further, the insulator layer 4 preferably has a thickness of 40 nm or more, and is set to a thickness that does not cause dielectric breakdown. Note that if the insulator layer 4 is too thick, it becomes difficult to carry the charge e, so it is preferable to have a thickness of less than 1 μm.

The N-type semiconductor layer 3 and the P-type semiconductor layer 5 are preferably made of a degenerate semiconductor material with low lattice thermal conductivity; for example, thermoelectric materials such as SiGe, nitride semiconductors such as CrN, oxide semiconductors such as _VO2, etc. can be used. It is. Note that the N-type and P-type conductivities are set by adding N-type and P-type dopants to the semiconductor material.

The insulator layer 4 is preferably made of an insulating material with low thermal conductivity, and may be an insulator such as SiO ₂ , a dielectric such as HfO ₂ or BiFeO ₃ , or an organic material. In particular, a dielectric material with a high dielectric constant is preferred.
The insulating film 2 is also preferably made of an insulating material with low thermal conductivity. The insulating film 2 is made of resin, and for example, a polyimide resin sheet can be used as the resin. As the insulating film 2, it is also possible to use PET: polyethylene terephthalate, PEN: polyethylene naphthalate, LCP: liquid crystal polymer, etc.
The N-side electrode 6 and the P-side electrode 7 are made of a metal such as Mo or Al, for example.

As shown in FIG. 3, the heat flow switching element 1 of this embodiment generates thermally conductive charges e at and near the interface between the N-type semiconductor layer 3 and the insulator layer 4 by applying an electric field (voltage). As a result, the generated charge e carries heat and the thermal conductivity changes.
Note that the thermal conductivity is obtained by the following formula.
Thermal conductivity = lattice thermal conductivity + electronic thermal conductivity Of these two types of thermal conductivity, the electronic thermal conductivity changes depending on the amount of charge generated by applying an electric field (voltage). Therefore, in this embodiment, a material with a small lattice thermal conductivity is suitable for obtaining a larger change in thermal conductivity. Therefore, for each of the N-type semiconductor layer 3, the insulator layer 4, and the P-type semiconductor layer 5, a material with a low lattice thermal conductivity, that is, a material with a low thermal conductivity is selected.

The thermal conductivity of the materials constituting each layer of the present embodiment is preferably as low as 5 W/mK or less, more preferably 1 W/mK or less, and the above-mentioned materials can be used.
Moreover, the electronic thermal conductivity increases according to the amount of charge e generated according to the applied external electric field (voltage).
Note that since charges e are generated at the interfaces between the N-type semiconductor layer 3 and the P-type semiconductor layer 5 and the insulator layer 4, the amount of generated charges e can be increased by increasing the total area of the interfaces. can.

The above method for measuring thermal conductivity involves, for example, instantaneously heating a thin film sample formed on a substrate with a pulsed laser, and measuring the rate of decrease in surface temperature or rate of increase in surface temperature due to heat diffusion into the thin film. The pulsed light heating thermoreflectance method is used to determine the thermal diffusivity or thermal effusivity in the film thickness direction of a thin film. Among the above-mentioned pulsed light heating thermoreflectance methods, the method of directly measuring thermal diffusion (backside heating/frontside thermometry (RF) method) requires the use of a transparent substrate through which the pulsed laser can pass. If it is not a substrate, the thermal conductivity is measured using a surface heating/temperature measurement (FF) method, which is a method of measuring the thermal effusivity and converting it into thermal conductivity. Note that this measurement requires a metal film, and Mo, Al, etc. are used.

In this way, in the heat flow switching element 1 of this embodiment, one of the N-type semiconductor layer 3 and the P-type semiconductor layer 5 is laminated on the insulating film 2, and the insulating layer 4 is laminated on one of the semiconductor layers. are stacked, and the other semiconductor layer of the N-type semiconductor layer 3 and the P-type semiconductor layer 5 is stacked on the insulator layer 4, so a voltage is applied to the P-type semiconductor layer 5 and the N-type semiconductor layer 3. Then, charges e are induced mainly at the interfaces between the P-type semiconductor layer 5 and the N-type semiconductor layer 3 and the insulator layer 4, and this charge e carries heat, thereby changing the thermal conductivity.

In particular, since charges e are generated both at the interface between the N-type semiconductor layer 3 and the insulator layer 4 and in the vicinity thereof, and at the interface and the vicinity thereof between the P-type semiconductor layer 5 and the insulator layer 4, It has a large amount of charge, and can achieve large changes in thermal conductivity and high thermal responsiveness. Furthermore, since the mechanism does not use a chemical reaction mechanism and physically changes the thermal conductivity, it is possible to immediately shift to a state where the thermal conductivity has changed, and to obtain good thermal responsiveness.

Further, one of the N-type semiconductor layer 3 and the P-type semiconductor layer 5 is laminated on the insulating film 2, the insulator layer 4 is laminated on one of the semiconductor layers, and the N-type semiconductor layer 4 is laminated on the insulator layer 4. Since the other of the type semiconductor layer 3 and the P type semiconductor layer 5 is laminated, the interface with the insulator layer 4 can be set wide, and the distance between the N type semiconductor layer 3 and the P type semiconductor layer 5 can be set wide. is determined by the thickness of the insulator layer 4, making it easier to design a small PN distance. In addition, the amount of charge induced at the interface changes by multiplying by the magnitude of the external voltage, so by adjusting the external voltage, it is possible to adjust the thermal conductivity. Active control becomes possible.
Note that since the insulator layer 4 is an insulator, no current is generated due to voltage application, and therefore no Joule heat is generated. Therefore, heat flow can be actively controlled without self-heating.

In addition, since the N-type semiconductor layer 3 and the P-type semiconductor layer 5 sandwich the insulator layer 4 on the flexible insulating film 2, it can be flexibly bent and curved on a curved surface. By pasting along the curved surface, the thermal conductivity can be changed over a wide range of curved surfaces even if it is installed on any curved surface. Since the area in thermal contact with the curved heat source or cooling source is large, heat flow switching with extremely high thermal responsiveness is possible.

In particular, since the strip-shaped insulating film 2 is curved into a cylindrical shape, by installing it so as to cover the outer circumferential surface of the object M to be attached, such as a cylinder or cylinder, the heat medium can flow. It becomes possible to adjust the amount of heat released from the pipes etc. Moreover, by attaching this heat flow switching element 1 so as to cover the outer peripheral surface of the cylindrical container, it is also possible to use the cylindrical container as a temperature-adjustable heat storage container.
Although the strip-shaped insulating film 2 is installed around the cylindrical or cylindrical mounting object M, the insulating film 2 may be wound multiple times, and may be wound around the mounting object M in a spiral shape. You can also wrap it around it.
Furthermore, the attachment target M does not have to be cylindrical or cylindrical, but may be columnar or elliptical with a substantially polygonal cross section.

Next, a second embodiment of the heat flow switching element according to the present invention will be described below with reference to FIGS. 4 to 6. In addition, in the following description of the embodiment, the same components described in the above embodiment are given the same reference numerals, and the description thereof will be omitted.

The difference between the second embodiment and the first embodiment is that in the first embodiment, the strip-shaped insulating film 2 is curved into a cylindrical shape, and the heat flow switching element 1 is attached to the cylindrical mounting object M. In contrast, in the heat flow switching element 21 of the second embodiment, as shown in FIGS. 4 and 5, the N-type semiconductor layer 23, the insulator layer, and the P-type semiconductor layer 25 The strip-shaped insulating film 22, which is laminated with , is spirally wound into a columnar shape, and is inserted into the cylindrical object M in close contact with the inner circumferential surface thereof.

That is, in the second embodiment, by spirally winding the strip-shaped insulating film 22 to form a cylindrical shape, the N on the insulating film 22 is reduced as shown in FIGS. The type semiconductor layer 23 and the P type semiconductor layer 25 are spirally wound with an insulating layer sandwiched therebetween.
Further, in the first embodiment, an insulator layer 4 such as SiO ₂ is interposed between the N-type semiconductor layer 3 and the P-type semiconductor layer 5, whereas in the second embodiment, the insulator layer 4 is interposed between the N-type semiconductor layer 3 and the P-type semiconductor layer 5. The difference is that the insulating film 22 is made of resin such as a polyimide resin sheet.

That is, as shown in FIG. 6, the heat flow switching element 21 of the second embodiment includes an N-type semiconductor layer 23 on an insulating film 22 and an N-side electrode 26 patterned on the end of the N-type semiconductor layer 23. An N-side film 22N in which a P-type semiconductor layer 25 and a P-side electrode 27 patterned on the end of the P-type semiconductor layer 25 are formed on an insulating film 22. , an N-type semiconductor layer 23 and a P-type semiconductor layer 25 are stacked on top of each other with an insulating film 22 in between, and are wound into a columnar shape.

In this way, in the heat flow switching element 21 of the second embodiment, the strip-shaped insulating film 22 is spirally wound to form a columnar shape, so that the cylindrical attachment target M By inserting it into the inside of the attachment target M, it becomes easy to make thermal contact with the entire circumferential direction of the inner circumferential surface of the attachment target M, and adjust the amount of heat dissipation of the attachment target M from the inside.
Furthermore, since the insulating layer between the N-type semiconductor layer 23 and the P-type semiconductor layer 25 is also a flexible insulating film 22, it becomes possible to bend the film more flexibly.
In the second embodiment, a cylindrical heat flow switching element is formed using two insulating films, the N-side film 22N and the P-side film 22P. A cylindrical heat flow switching element may be obtained by spirally winding a layered structure of an N-type semiconductor layer 3, an insulating layer 4, and a P-type semiconductor layer 5 around an insulating film 2.

Note that the technical scope of the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1, 21... Heat flow switching element, 2, 22... Insulating film, 3, 23... N-type semiconductor layer, 4... Insulator layer, 5, 25... P-type semiconductor layer, 6, 26... N-side electrode, 7, 27...P side electrode

Claims (6)

a flexible insulating film base material ;
an N-type semiconductor layer;
an insulator layer;
a P-type semiconductor layer ;
an N-side electrode connected to the N-type semiconductor layer;
and a P-side electrode connected to the P-type semiconductor layer,
One of the N-type semiconductor layer and the P-type semiconductor layer is laminated on the insulating film, the insulator layer is laminated on the one semiconductor layer, and the N-type semiconductor layer is laminated on the insulator layer. type semiconductor layer and the other semiconductor layer of the P-type semiconductor layer are stacked,
The N-type semiconductor layer and the P-type semiconductor layer are in an insulating state with the insulator layer disposed therebetween,
Thermal conductivity changes by applying an external voltage to the N-side electrode and the P-side electrode,
A heat flow switching element , wherein the base material is in a curved state . The heat flow switching element according to claim 1,
A heat flow switching element, wherein the insulator layer is an insulating film. The heat flow switching element according to claim 2 ,
A heat flow switching element , wherein the base material and the insulating film of the insulator layer are made of resin. The heat flow switching element according to any one of claims 1 to 3,
A heat flow switching element characterized in that the base material is strip-shaped and curved into a cylindrical shape. The heat flow switching element according to any one of claims 1 to 3,
A heat flow switching element characterized in that the base material is strip-shaped and spirally wound to form a columnar shape. The heat flow switching element according to any one of claims 1 to 5,
The N-type semiconductor layer and the P-type semiconductor layer are formed of thin films with a thickness of 5 nm or more and less than 1 μm,
A heat flow switching element characterized in that the insulator layer has a thickness of less than 1 μm.

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