KR100605289B1 - Method of making vanadium dioxide film and homoiothermal temperature switch having same film - Google Patents

Abstract

Method for producing a vanadium dioxide film according to the invention, the method for forming a vanadium dioxide film on a substrate, the powder preparation step of preparing a vanadium pentoxide powder; A paste manufacturing step of mixing the vanadium pentoxide powder with an organic solvent to form a paste in order to have viscosity; Forming a vanadium pentoxide film by screen printing the paste on the substrate; Calcining the vanadium pentoxide film-coated substrate by heat-treating the nitrogen-filled nitrogen atmosphere in a heat treatment furnace to burn off the mixed organic solvent to form the paste state; And a reduction step of reducing the vanadium pentoxide to vanadium dioxide by heat-treating the vanadium pentoxide pentoxide film subjected to the calcination step in a heat treatment furnace in a nitrogen atmosphere filled with nitrogen. In addition, a constant temperature switch having a vanadium dioxide film according to the present invention includes a substrate including a vanadium dioxide film; Connecting means for connecting the vanadium dioxide film with an external circuit; And a package body molded around the substrate and the film; It is characterized in that it has a vanadium dioxide film containing.

Description

Method of making vanadium dioxide membrane and constant temperature switch having the membrane {Method of making vanadium dioxide film and homoiothermal temperature switch having same film}

1 is a manufacturing process diagram of a vanadium dioxide film according to the present invention.

2 is a photograph of a substrate coated with an vanadium pentoxide film.

3 is a photograph of a substrate in which an vanadium pentoxide film is reduced to a vanadium dioxide film.

4 is an X-ray diffraction graph of a vanadium dioxide film prepared according to the present invention.

5 is a temperature-resistance graph of a vanadium dioxide film prepared according to the present invention.

Figure 6 is a package cross-sectional view of a constant temperature switch with a vanadium dioxide film according to the present invention.

The present invention relates to a method for producing a vanadium dioxide film that can be applied as a temperature sensor suitable for fire detection or overheating prevention, and a constant temperature switch having the film.

The fire detector that detects fire in a building and operates an alarm or automatic fire extinguishing system is classified into a heat detection type and a smoke detection type. Among them, a heat detection type fire detector equipped with a bimetal switch is most used. The bimetal switch is a structure in which a contact is attached to a bimetal joined by two metals having different coefficients of thermal expansion, as is well known. To switch the signal.

Such a bimetal switch is widely used not only for a fire detector but also for the overheat prevention apparatus of the various mechanical mechanisms which need to prevent overheating, such as a heating mechanism, such as a heater, and a combustion mechanism of fuel.

In order to minimize the damage from fire or overheating, it is essential to use a reliable and durable temperature sensor. However, the above-described bimetal switch is greatly reduced in reliability since the operating temperature is largely affected by the change in temperature and humidity according to the season. For example, the fire detector is designed to operate at 70 ° C, but the deviation of the temperature at which the bimetal contact can be opened and closed is very large, ± 15 ° C. It is often causing problems that cause great damage to people and property by not detecting them.

On the other hand, the contact attached to the bimetal is easily oxidized and corroded in the air, and when oxidized and corroded, it may not be energized as a non-conductor.

Therefore, attention is focused on the development of temperature sensors using CTR (critical temperature resistor) characteristics, also known as sudden temperature sensors. Representative materials with CTR properties are vanadium oxides. Vanadium oxide is present as VO, VO ₂ , V ₂ O ₃ , V ₂ O ₅ , V ₃ O ₇ , V _n O _2n-1 (3≤n≤8), and among them, VO ₂ has a transition temperature of 68 ° C. It is close to the proper fire detection temperature and changes from semi-conductivity to good metallic property near its transition temperature. It has a large temperature coefficient, which is known for its high value for fire detection in buildings and prevention of overheating of various mechanical devices. .

Looking at the related art related to such vanadium oxide, Patent Publication No. 2002-0077022 proposes a method for producing powdered vanadium pentoxide (V ₂ O ₅ ) which is a spherical nano-size particles from vanadium ions. The vanadium pentoxide proposed here is intended to be used as an active material of a secondary battery with an emphasis on electrochemical activity.

In JP 2003-0019772 A, a method of manufacturing a vanadium dioxide (VO ₂ ) film through a heat treatment after forming an amorphous vanadium oxide (VO) film and a metal vanadium film in a multilayer is proposed. The vanadium dioxide film proposed here is intended to be used as an infrared sensor for object detection of an infrared camera, and has a transition temperature lower than the commonly known phase transition temperature of 68 ° C.

Patent No. 0166683 discloses a composition for switching temperature and substitution ring part of P ₂ O ₅ to Na ₂ O in the basic composition of V ₂ O ₅ -P ₂ O ₅ .

On the other hand, US Patent No. 5,801,383 and Japanese Patent Application Laid-open No. Hei 9-0145481 and 9-257565, etc., a method for controlling the electrical properties of the vanadium chloride film and a method for producing VOx (1.875 <x <2.0) for use as a bolometer-type infrared sensor Is proposed.

In addition, Korean Patent Laid-Open Publication No. 2005-0017028 discloses a method of dissolving vanadium pentoxide powder in distilled water or hydrogen peroxide solvent to form a film on a substrate by spin coating. However, this method is very difficult to control the concentration of the solution, and because the solution is very low viscosity, the problem that the coating and drying must be repeated multiple times (typically 5 to 10 times) without coating the substrate to a constant thickness. have.

As described above, various methods have been proposed in connection with the manufacture of vanadium oxide for use as a temperature sensor, but there are no examples of manufacturing vanadium dioxide in which resistance difference before and after phase transition is suitable for legal standards. Subsequently, there is a problem that has not yet reached practical use as a temperature switch in fire detection or in electrical, electronic and mechanical devices.

The present invention has been made to solve the problems described above, and is suitable for fire detection or overheating of mechanical devices such as electricity, electronics, computers, automobiles, and the like, and can be used as a highly reliable and durable temperature sensor. An object of the present invention is to provide a method for producing a vanadium dioxide film having excellent reproducibility and a constant temperature temperature switch having the film.

In order to achieve the above object, the method for producing a vanadium dioxide film according to the present invention, in the method for forming a vanadium dioxide film on a substrate,

A powder preparation step of preparing vanadium pentoxide powder;

A paste manufacturing step of mixing the vanadium pentoxide powder with an organic solvent to form a paste in order to have viscosity;

Forming a vanadium pentoxide film by screen printing the paste on the substrate;

A calcination step of heating the substrate coated with the vanadium pentoxide film to burn off the mixed organic solvent to form the paste state; And

And a reduction step of reducing the vanadium pentoxide to vanadium dioxide by heat-treating the vanadium pentoxide film passed through the calcining step in a heat treatment furnace of a nitrogen-filled nitrogen atmosphere.

Constant temperature switch having a vanadium dioxide membrane according to the present invention,

A substrate comprising a vanadium dioxide film prepared by the method for producing a vanadium dioxide film according to the present invention;

Connecting means for connecting the vanadium dioxide film with an external circuit; And

A package body molded around the substrate and the film; There is a feature in that it includes.

The organic solvent may include polyvinyl butyral (PVB), polyethylene glycol (PEG), alpha terpineol (a-Terpineol tech 90%) and butoxyethoxyethyl acetate.

The particle size of the vanadium pentoxide powder passed through the powder preparation step is 0.1 ㎛ to 10 ㎛,

The mesh of the screen has a mesh size of 10 μm × 10 μm,

The calcination step includes a heat treatment for 1 hour to 3 hours at 200 ℃ to 400 ℃,

The reduction step uses nitrogen gas having a purity of 95% or more, and preferably includes heat treatment for 1 hour to 3 hours at a temperature of 400 ° C. to 600 ° C. and atmospheric pressure.

Hereinafter, a preferred embodiment of the method for producing a vanadium dioxide film according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a manufacturing process diagram of a vanadium dioxide film according to the present invention, Figure 2 is a photograph of a substrate coated with a vanadium pentoxide film, Figure 3 is a photograph of a substrate reduced to a vanadium dioxide film by reducing the vanadium pentoxide film, Figure 4 X-ray diffraction graph of the vanadium dioxide film prepared according to the present invention, FIG. 5 is a temperature-resistance characteristic graph of the vanadium dioxide film prepared according to the present invention, and FIG. 6 is a constant temperature switch having a vanadium dioxide film according to the present invention. Package cross section of.

1 to 6, a method of manufacturing a vanadium dioxide film according to a preferred embodiment of the present invention uses the principle of forming a vanadium dioxide film on a substrate and then transforming the vanadium pentoxide into vanadium dioxide by reduction heat treatment. The vanadium dioxide film production method includes a powder preparation step (S11), a paste preparation step (S12), a film preparation step (S13), a calcining step (S14), and a reduction step (S15).

In the powder preparation step (S11), a granular vanadium pentoxide (V ₂ O ₅ ) is made into a powder state included in the range of 0.1 ㎛ to 10 ㎛ using a ball mill (ball-mill). In this process, the conditions for grinding with a ball mill are about 100 to 500 rpm for about 10 to 24 hours using a ball mill made of alumina (Al ₂ O ₃ ) with about 10 g of vanadium pentoxide (V ₂ O ₅ ) in the ball mill. It was ground by the dry ball milling method.

By this method, a fine powder having a size of 5 µm or less was obtained. After preparing the vanadium pentoxide powder in this way, it enters the paste manufacturing step (S12).

In the paste manufacturing step 12, a viscosity is given to the vanadium pentoxide powder to form an vanadium pentoxide film on the substrate. The paste manufacturing step (S12) includes the step of mixing the vanadium pentoxide powder with an organic solvent having a viscosity necessary for the operation. The organic solvent is to be physically mixed with the vanadium pentoxide powder to a paste state having a uniform particle distribution. The organic solvent must satisfy a condition that the combustion point is lower than the reduction temperature of the vanadium pentoxide so that all of the organic solvent may be burned and removed at a temperature lower than the temperature at which the vanadium pentoxide is reduced to vanadium dioxide. In the present embodiment, the organic solvent was used a mixed solvent called a vehicle (vehicle), the mixed component is polyvinyl butyral (PVB, Poly vinyl butyral-co-vinylalcohol-co-vinyl acetate) and polyethylene glycol (PEG, Polyethylene glycol), alpha terpineol (aT, a-Terpineol tech 90%) and butoxyethoxyethyl acetate (BEEA, 2- (2-Butoxyethoxy) ethyl acetate). The polyvinyl butyral (PVB, polyvinyl butyral-co-vinylacohol-co-vinyl acetate) and alpha terpineol (a-Terpineol tech 90%) wrap the particles forming the vanadium pentoxide powder and the vanadium pentoxide powder and the It plays a role to ensure that the oil is well mixed. The butoxyethoxyethyl acetate (BEEA, 2- (2-Butoxyethoxy) ethyl acetate) and polyethylene glycol (PEG, Polyethylene glycol) serve to dissolve the polyvinyl butyral and the alpha terpineol well. The a-T: BEEA: PEG: PVB is prepared by mixing at a weight ratio of 10: 5: 3: 2. 10 g of the vanadium pentoxide powder and 10 g of the organic solvent are mixed and stirred to make a paste mixture having a viscosity similar to toothpaste. In the organic solvent, it is preferable to add about 1.5% of low-temperature melting glass frit per 10 g of the vanadium pentoxide powder so that the paste-based vanadium pentoxide mixture is fused to each other in a reduction step described later. The glass frit serves to make the vanadium dioxide reduced vanadium dioxide powder particles adhere to the substrate in a reduction step described later.

In the film production step (S13), a film in a desired pattern is formed on the substrate made of alumina, which is resistant to thermal shock and excellent in electrical insulation, by a screen printing method. The screen used in the screen printing was used having a mesh size of 10 μm × 10 μm, which is such that vanadium pentoxide particles present in the paste state can pass well. The screen printing method is to seal the mesh of the other part except the pattern of the film to be formed on the screen and then pass the vanadium pentoxide in the paste state through the pattern formed on the screen to form a pattern in the form of a film on the alumina substrate will be.

After the film forming step (S13), the alumina substrate to which the vanadium pentoxide film is attached is dried at 60 ° C. for 10 to 24 hours. (Drying step)

In the calcination step (S14) filled with alumina substrate coated with the vanadium pentoxide film prepared in the film production step at a calcination temperature of 200 ℃ to 400 ℃ the organic solvent can be burned with nitrogen for 1 hour to 3 hours Heat treatment in the furnace In this process, the organic solvent is mostly burned, and the vanadium pentoxide film becomes pure vanadium pentoxide only. In this process, if the calcination temperature is less than 200 ℃ there is a problem that the organic solvent is not properly burned, if the calcination temperature exceeds 400 ℃ over-reduction of the vanadium pentoxide occurs in a form other than vanadium dioxide There is a problem that oxides are formed. In addition, when the calcination time is less than 1 hour, there is a problem that does not cause sufficient calcination, and when the calcination time exceeds 3 hours, there is a problem that over-reduction of the vanadium pentoxide film occurs.

In the reduction step (S15), the vanadium pentoxide membrane is subjected to a reduction reaction in a heat treatment furnace filled with nitrogen, thereby performing phase transformation into a vanadium dioxide membrane. As the nitrogen, it is preferable to use high purity nitrogen gas of 95% or more. The reduction step (S15) is preferably heat treatment at a temperature of 400 ℃ to 600 ℃ reduction temperature that is higher than the calcination step (S14). If the reduction temperature is less than 400 ℃ takes too much time to reduce to vanadium dioxide, there is a problem that the productivity is low, and if the reduction temperature exceeds 600 ℃ over-reduction occurs other oxides other than vanadium dioxide is formed have. In addition, there is a problem that the vanadium pentoxide is melted when it is 700 ℃ or more. In the reduction step (S15), the reduction pressure in the heat treatment furnace was maintained at atmospheric pressure. Maintaining the reducing pressure at atmospheric pressure is for improving productivity, and maintaining an excessively high pressure impairs the stability of the heat treatment furnace. Since there is air in the initial heat treatment furnace, nitrogen is introduced into the heat treatment furnace at a rate of 5 l / min, slowly flowed in for about 1 hour, and then enters a reduction step. When the atmospheric pressure is maintained in a heat treatment furnace of 2 L of internal volume filled with nitrogen and new nitrogen is introduced into the heat treatment furnace at a rate of 2 L / min, the pressure in the heat treatment furnace maintains the atmospheric pressure. The reduction heat treatment time in the reduction step (S15) was maintained for 1 hour to 3 hours. If the reduction heat treatment time is less than 1 hour, there is a problem that the productivity of reducing to vanadium dioxide takes too much time, and if the reduction time exceeds 3 hours, overreduction occurs to form oxides other than vanadium dioxide. have.

By the above process, the vanadium pentoxide film has a golden color as shown in FIG. 2, and after the reduction step, has a dark gray color as shown in FIG. 3 and an X-ray diffraction analysis as shown in FIG. It can be seen that it is reduced to the vanadium dioxide film having a result, and the resistance characteristics of the vanadium dioxide film made through this process are 25 in which the resistance change is normal temperature in the range of 63 ° C to 77 ° C as shown in FIG. There is an effect of showing a high value of 10 ^3.8 or more compared to ℃. In FIG. 5, the resistance characteristics at the time of temperature increase and temperature reduction were measured to be slightly different, but this is an experimental error. Therefore, it exhibits a resistance characteristic that can be used in a 70 ℃ constant temperature temperature switch having a vanadium dioxide film used for fire detection or electrical, mechanical devices described below.

A constant temperature switch having a vanadium dioxide film according to the present invention which achieves the above object is a substrate manufactured by the method for raising the vanadium dioxide film, a vanadium dioxide film coated on the substrate, and a connection for connecting the film with an external circuit. It comprises a means, characterized in that configured to switch to a contactless state by energizing an electrical signal by a very high resistance value is rapidly changed at a phase transition temperature in accordance with the change of the ambient temperature is rapidly reduced.

The constant temperature switch having the vanadium dioxide film may be provided in one package form including a body formed by molding an epoxy resin and the like around the substrate and the vanadium dioxide film.

5 is a graph measuring the temperature-resistance characteristics of the vanadium dioxide film according to the above embodiments. This measurement measures the resistance value while raising the temperature of the vanadium dioxide film on the substrate in the range of 25 ° C. to 100 ° C., and the change in the resistance value while decreasing the temperature in reverse, and shows its hysteresis characteristics. As a result of the measurement, the phase transition temperature was 70 ° C, and the variation of hysteresis characteristics at the time of temperature increase and temperature decrease was measured within ± 2 ° C, and even if repeated several times, the temperature-resistance characteristic curve showed little change.

Next, FIG. 6 shows a package structure of a constant temperature switch manufactured through a subsequent process for packaging the vanadium dioxide film prepared according to the preferred embodiment, that is, a pattern treatment, a cutting process, and a molding process. Reference numeral 61 denotes a substrate, 62 a vanadium dioxide film, 63 a package body molded from an epoxy resin, 64 'is bonded to both ends of the vanadium dioxide film 62 and is a lead wire. The lead wires 64 and 64 'are for connecting to an external circuit, for example, a circuit in a fire alarm system in a fire alarm, or a related circuit in a mechanical device such as electric, electronic, or automobile.

The vanadium dioxide film 62 is patterned to have an appropriate thickness and length to have a resistance value in consideration of the voltage and current required by the circuit to be used.

As described through the above embodiments, the present invention has the effect of providing a method of manufacturing a vanadium dioxide film that can be used as a temperature sensor from vanadium pentoxide, greatly improving the yield of the film, and providing excellent reproducibility, and produced by the method. It is effective to provide a constant temperature switch in the form of a package with a membrane. The vanadium dioxide film according to the present invention has a phase transition temperature suitable for fire detection, has a very small temperature deviation, and a change in resistance value at a phase transition temperature of about 10 ^3.8 or more, which is highly practical as a temperature sensor for fire detection or overheating prevention, By providing a reliable and stable temperature constant temperature switch in the form of a package for contactless switching while maintaining high reliability and stable characteristics even with repeated temperature changes.

Such a constant temperature switch according to the present invention may be used in a fire detector or an overheat prevention device to contribute to minimizing the damage of life and property from fire or overheating.

Claims (6)

In the method for forming a vanadium dioxide film on a substrate, A powder preparation step of preparing vanadium pentoxide powder; A paste manufacturing step of mixing the vanadium pentoxide powder with an organic solvent to form a paste in order to have viscosity; Forming a vanadium pentoxide film by screen printing the paste on the substrate; A calcination step of heating the substrate coated with the vanadium pentoxide film to remove the mixed organic solvent in a heat treatment furnace in a nitrogen atmosphere filled with nitrogen to form the paste state; And And a reduction step of reducing the vanadium pentoxide to vanadium dioxide by heat-treating the vanadium pentoxide pentoxide film subjected to the calcination step in a heat treatment furnace in a nitrogen-filled nitrogen atmosphere. The method of claim 1, The organic solvent is polyvinyl butyral (PVB), polyethylene glycol (PEG), alpha-terpineol (alpha-terpineol tech 90%) and the manufacturing method of the vanadium dioxide membrane, characterized in that the butoxyethoxy ethyl acetate . The method of claim 2, The organic solvent is a method for producing a vanadium dioxide film, characterized in that the glass is melted at a low temperature (glass frit). The method of claim 1, The particle size of the vanadium pentoxide powder passed through the powder preparation step is 0.1 ㎛ to 10 ㎛, The mesh of the screen has a mesh size of 10 μm × 10 μm, The calcination step includes a heat treatment for 1 hour to 3 hours at 200 ℃ to 400 ℃, The reduction step uses a nitrogen gas having a purity of 95% or more, and a method for producing a vanadium dioxide film, characterized in that it comprises a heat treatment for 1 hour to 3 hours at a temperature of 400 ℃ to 600 ℃ and atmospheric pressure. The method of claim 2, The substrate is a method for producing a vanadium dioxide film, characterized in that the alumina substrate. A substrate comprising a vanadium dioxide film produced by the method according to any one of claims 1 to 5; Connecting means for connecting the vanadium dioxide film with an external circuit; And A package body molded around the substrate and the film; Constant temperature switch having a vanadium dioxide film comprising a.

Images