KR102446078B1 - Variable resistance film and sensor device comprising the same - Google Patents

Abstract

A variable resistive film comprising thermosetting polymer and dendritic silver particles, and a pressure sensor and a temperature sensor comprising the variable resistive film are provided.

Description

Variable resistance film and sensor device comprising the same

The present invention relates to a variable resistance film whose resistance is changed from an external stimulus, and a sensor device including the same.

A sensor means a device that detects a physical quantity or change of an external stimulus, for example, heat, light, temperature, pressure, sound, etc. There are sensors, magnetic sensors, light sensors, acoustic sensors, taste sensors, olfactory sensors, and the like.

Considering the purpose of detecting the amount or change of an external stimulus, it is very important to improve the sensitivity of the sensor to the external stimulus, and research on this is being made steadily.

Recently, research has been made on the fabrication of a sensor using a material whose resistance value is sensitively changed in response to an external stimulus, but there is still a demand for a material having superior sensing properties compared to the conventional sensor.

Korean Registration Publication, No. 101412623, "Carbon nanotube composite with improved piezoresistive sensing sensitivity and manufacturing method therefor, and pressure sensitive sensor having this carbon nanotube composite"

An object of the present invention is to provide a variable resistance film whose resistance is changed from an external stimulus, and a sensor device including the same.

The inventor of the present invention has confirmed that the resistance value of the film made using the dendritic grown silver particles and the curable polymer is sensitive to external stimuli, and in this respect, the variable resistance film of the present invention and the sensor device including the same succeeded in

According to one aspect, a variable resistance film comprising a thermosetting polymer and dendritic silver particles is provided.

According to another aspect, the first substrate; a first electrode disposed on the first substrate; a second electrode facing the first electrode; a second substrate disposed on the second electrode; and the variable resistance film interposed between the first electrode and the second electrode.

According to another aspect, the substrate; the variable resistance film; and a first electrode and a second electrode interposed between the substrate and the variable resistance layer.

A sensor device including a variable resistance film according to one aspect, for example, a pressure sensor and a temperature sensor, shows a rapid and large change in resistance in response to a physical amount or change of pressure and heat applied from the outside, thereby increasing the resistance of the sensor device. A sensing characteristic, which is an essential function, may be improved.

1 is a field emission scanning electron microscope (FESEM) photograph of primary silver dendritic particles.
2 is a field emission scanning electron microscope (FESEM) photograph of secondary silver dendritic particles.
3 is a field emission scanning electron microscope (FESEM) photograph of tertiary dendritic silver particles.
4 is a diagram schematically showing the structure of a pressure sensor.
5 is a graph showing the piezoresistive characteristics of the pressure sensor.
6A-6C are graphs showing the response time of the pressure sensor.
7 is a graph showing the light transmittance of the pressure sensor.
8 is a pressure versus resistance graph of a pressure sensor including spherical gold nanoparticles.
9 is a diagram schematically showing the structure of a temperature sensor.
10 is a graph of measuring heat flow according to the temperature of the thermosetting polymer and the variable resistance film used in the temperature sensor.
11 is a graph showing a change in a resistance value according to a temperature of a temperature sensor.
12 is a graph showing a change in resistance according to the content of dendritic silver nanoparticles and spherical silver nanoparticles.
13 is a graph showing transmittance according to the content of dendritic silver nanoparticles.

The present inventive concept described below can apply various transformations and can have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present inventive concept to a specific embodiment, and should be understood to include all transformations, equivalents or substitutes included in the technical scope of the present inventive concept.

Terms used below are only used to describe specific embodiments, and are not intended to limit the present inventive concept. The singular expression includes the plural expression unless the context clearly dictates otherwise. Hereinafter, terms such as “comprising” or “having” are intended to indicate that a feature, number, step, action, component, part, component, material, or combination thereof described in the specification exists, but one or the It should be understood that the above does not preclude the existence or addition of other features, numbers, steps, operations, components, parts, components, materials, or combinations thereof, or additions thereof. "/" used below may be interpreted as "and" or "or" depending on the situation.

In the drawings, in order to clearly express various components, layers, and regions, diameters, lengths, and thicknesses are enlarged or reduced. Throughout the specification, like reference numerals are assigned to similar parts. Throughout the specification, when a part, such as a layer, film, region, plate, etc., is referred to as “on” or “on” another part, it includes not only the case where it is directly on the other part, but also the case where there is another part in the middle. .

Throughout the specification, terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. Some of the components may be omitted from the drawings, but this is for helping understanding of the features of the invention and is not intended to exclude the omitted components.

According to one aspect, a variable resistance film comprising a thermosetting polymer and dendritic silver particles is provided.

According to an embodiment, the dendritic silver particles may include a core particle including silver (Ag) particles; It may include one or more branch portions grown in a radial direction from the core particle, and an end of the branch portion may have a needle shape. When the ends of the one or more branch portions have needle-like shapes, electrical characteristics due to quantum tunneling effect may be improved. Specifically, since the end of the branch has a needle-like shape, current is easily concentrated at the end of the branch, and thus electrons are ejected from the end of the branch to the outside. In addition, the improvement of the electrical characteristics results in improving the sensitivity according to the external stimulus, and thus can be applied to a device for detecting the amount of change in the external stimulus, such as a sensor.

According to an exemplary embodiment, among the dendritic silver particles, the branch portion may include a main branch portion and one or more sub-branch portions grown two-dimensionally and/or three-dimensionally from the main branch portion.

The main branch has a larger cross-sectional diameter than other sub-branches, and a length (hereinafter, referred to as a “growth length”) in the growth direction of the main branch is longer than the length of the sub-branch. For example, the growth length ratio of the main branch portion and the sub branch portion may be in a range of 1:0.5 to 1:0.0001, but is not limited thereto, and may have any ratio range falling within the range.

The sub-branch may include one or more two-dimensionally grown sub-branches. In the present specification, the two-dimensionally grown sub-branch includes a branch that grows radially from the main branch. An end of the sub-branch may have a needle shape.

Similarly, the sub-branch may include one or more three-dimensionally grown sub-branches. In the present specification, the three-dimensionally grown sub-branch includes a branch grown from the surface of the branch grown in a radial direction from the main branch. An end of the sub-branch may have a needle shape.

Since both the ends of the main branch and the sub-branch have needle-shaped ends, the quantum tunneling effect may be maximized, thereby remarkably improving electrical characteristics.

The thermosetting polymer may include at least one selected from the group consisting of acrylate-based, acrylic urethane-based, epoxy-based, silicone-based, unsaturated polyester-based, and polyurethane-based polymers.

The thermosetting polymer may be selected according to the purpose of use of the variable resistance film. For example, among the thermosetting polymers, as will be described later, a thermosetting polymer having elasticity may be used in a variable resistance film for a pressure sensor, and a polymer having a positive temperature coefficient effect may be used in a variable resistance film for a temperature sensor. can be used

The thermosetting polymer serves as a matrix enclosing the silver dendritic particles after curing, thereby preventing the silver dendritic particles from being detached, and receiving external stimuli and delivering them to the silver dendritic particles.

According to an embodiment, the variable resistance layer may further include an additive. For example, it may further include an antioxidant, an adhesive, a plasticizer, an ultraviolet absorber, an antifoaming agent, a filler, a curing agent, and the like.

According to one aspect, a pressure sensor and a temperature sensor including the variable resistance film are provided.

First, a pressure sensor will be described with reference to FIG. 4 below.

Referring to Figure 4, the first substrate (1); a first electrode (2) disposed on the first substrate; a second electrode (4) facing the first electrode; a second substrate 5 disposed on the second electrode; and the variable resistance film 3 interposed between the first electrode and the second electrode.

According to one embodiment, between the first electrode 2 and the variable resistance film 3 and/or between the second electrode 4 and the variable resistance film 3, one or more conductive layers (not shown) city) may be further arranged.

According to another embodiment, between the first electrode 2 and the variable resistance film 3 , and/or the second electrode 4 and the variable resistance film 3 may be disposed to contact each other. .

The variable resistance film 4 may be prepared by applying a slurry in which one or more types of thermosetting polymer and silver dendritic particles are mixed on the first electrode 2 and then thermosetting the slurry.

The thermosetting polymer may include at least one selected from the group consisting of acrylate-based, acrylic urethane-based, epoxy-based, silicone-based, unsaturated polyester-based, and polyurethane-based polymers. For example, polydimethylsiloxane (PDMS), polydiethylsiloxane, polyurethane, etc. may be used as the thermosetting polymer, but is not limited thereto, and any elastic polymer may be used.

The thermosetting polymer may be included in an amount of 50 to 99.9 parts by weight in the variable resistance film 4 . When the content of the thermosetting polymer is within the above range, it is possible to function as a matrix of silver dendritic particles to prevent separation of the silver dendritic particles, and to maximize resistance change according to pressure.

According to one embodiment, the thickness of the variable resistance layer 3 may be 20 μm to 1 mm. When the thickness of the variable resistance film 3 falls within the above range, the dendritic silver particles may be included in the variable resistance film without being exposed to the outside. In addition, when the thickness of the film 3 is too thick, the stress applied in the variable resistance film may not be sufficiently transmitted to the silver dendritic particles, so that the reaction speed of the pressure sensor may be reduced.

According to an exemplary embodiment, the content ratio of the silver dendritic particles in the variable resistance film 3 may be 0.1 parts by weight to 50 parts by weight based on 100 parts by weight of the total weight of the variable resistance film. For example, the content ratio of silver dendritic particles in the variable resistive film 3 is 0.1 to 50 parts by weight, 0.5 to 50 parts by weight, 1 to 50 parts by weight based on 100 parts by weight of the total variable resistive film. parts, 5 parts by weight to 50 parts by weight, 10 parts by weight to 50 parts by weight, 15 parts by weight to 50 parts by weight, 20 parts by weight to 50 parts by weight, 25 parts by weight to 50 parts by weight, 30 parts by weight to 50 parts by weight; 35 parts by weight to 50 parts by weight, 40 parts by weight to 50 parts by weight, 0.1 parts by weight to 45 parts by weight, 0.1 parts by weight to 40 parts by weight, 0.1 parts by weight to 35 parts by weight, 0.1 parts by weight to 30 parts by weight, 0.1 parts by weight parts by weight to 25 parts by weight, 0.1 parts by weight to 20 parts by weight, 0.1 parts by weight to 15 parts by weight, 0.1 parts by weight to 10 parts by weight, or 0.1 parts by weight to 5 parts by weight. When the content of the silver dendritic particles falls within the above range, the change in resistance to external pressure of the variable resistance film may be maximized. When the content of the silver dendritic particles is less than 0.1 parts by weight, the variable resistance film 3 and the silver dendritic particles are far apart, and it is difficult to expect a quantum tunneling effect between the silver dendritic particles, so that a sufficient reaction rate according to pressure is obtained. becomes difficult to obtain In addition, when the content of the silver dendritic particles exceeds 50 parts by weight, since the silver dendritic particles are dispersed very closely, they already function as a conductive layer before pressure is applied, making it difficult to detect a change in resistance according to pressure.

According to one embodiment, the density of the silver dendritic particles in the variable resistance film 3 employed in the pressure sensor may be 0.1 mg/mL to 1 g/mL. When the density of the dendritic silver particles falls within the above range, excellent resistance change characteristics according to pressure can be achieved.

According to one embodiment, the substrate 1, 5 is a flexible material, for example, polydimethylsiloxane (PDMS), polyethylene-terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyy It may include at least one polymer selected from the group consisting of imide (PI), polymethylmethacrylate, and polycarbonate (PC). Therefore, by employing such a base material, it is easy to manufacture a flexible pressure sensor.

According to one embodiment, the electrodes 2 and 4 may be a conductor or a non-conductor coated with a conductive film. For example, the electrode may be a transparent conductor. The transparent conductor may include, for example, a transparent conductive material such as ITO, IZO, or ZnO. The electrodes 2 and 4 may be formed by depositing a transparent conductive material by sputtering.

According to one embodiment, when the pressure sensor measures the resistance by a digital source meter using a 1V DC bias as a source-drain voltage, 10000 times More resistance changes may be observed.

Next, a temperature sensor will be described with reference to FIG. 9 .

Referring to FIG. 9 , a first substrate 21; the variable resistance film 23; and

A temperature sensor 20 including a first electrode 22 and a second electrode 24 interposed between the first substrate 21 and the variable resistance layer 23 is provided.

According to one embodiment, the first electrode 22 and the second electrode 24 may be disposed to be spaced apart from each other on the same plane.

According to an exemplary embodiment, a portion of the variable resistance layer 23 may be in contact with the first electrode 22 , and the remaining portion may be disposed to contact the second electrode 24 , but is not limited thereto. , the second electrode and the first electrode 22 may be in contact with the upper and lower surfaces of the variable resistance layer 23 , respectively.

The variable resistance film 23 may be manufactured by applying a slurry in which one or more types of thermosetting polymer and silver dendritic particles are mixed on the first electrode 22 and the second electrode 24 and then thermosetting.

The thermosetting polymer may include at least one selected from the group consisting of acrylate-based, acrylic urethane-based, epoxy-based, silicone-based, unsaturated polyester-based, and polyurethane-based polymers. For example, as the thermosetting polymer, acrylate copolymer, polyethylene (PE), polysulfone (PS), polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), polyamide (PA), etc. may be used. , but is not limited thereto, and any polymer having a positive temperature coefficient (PTC) characteristic may be used.

The thermosetting polymer may be included in the variable resistance film 23 in an amount of 25 to 99.5 parts by weight. When the content of the thermosetting polymer falls within the above range, the thermosetting polymer functions as a matrix of silver dendritic particles to prevent separation of the silver dendritic particles and exhibit excellent temperature sensing properties.

According to one embodiment, the thickness of the variable resistance layer 23 may be 10 μm to 5 mm. When the thickness of the variable resistance film 23 is within the above range, the dendritic silver particles may be included in the variable resistance film without being exposed to the outside. In addition, when the thickness of the film 23 is too thick, the sensing characteristic for external temperature change may be deteriorated.

According to one embodiment, the content ratio of the silver dendritic particles in the variable resistance film 23 may be 0.5 parts by weight to 75 parts by weight based on 100 parts by weight of the total weight of the variable resistance film. For example, the content ratio of silver dendritic particles in the variable resistive film 23 is 0.5 to 70 parts by weight, 0.5 to 65 parts by weight, 0.5 to 50 parts by weight based on 100 parts by weight of the total variable resistive film. parts, 0.5 parts by weight to 45 parts by weight, 0.5 parts by weight to 40 parts by weight, 0.5 parts by weight to 35 parts by weight, 0.5 parts by weight to 30 parts by weight, 0.5 parts by weight to 25 parts by weight, 0.5 parts by weight to 20 parts by weight; 0.5 parts by weight to 15 parts by weight, 0.5 parts by weight to 10 parts by weight, 0.5 parts by weight to 9.5 parts by weight, 0.5 parts by weight to 9 parts by weight, 0.5 parts by weight to 8.5 parts by weight, 0.5 parts by weight to 8 parts by weight, 0.5 parts by weight parts by weight to 7.5 parts by weight, 0.5 parts by weight to 7 parts by weight, 0.5 parts by weight to 6.5 parts by weight, 0.5 parts by weight to 6 parts by weight, 0.5 parts by weight to 5.5 parts by weight, 0.5 parts by weight to 5 parts by weight, 0.5 parts by weight to 4.5 parts by weight, 0.5 parts by weight to 4 parts by weight, 0.5 parts by weight to 3.5 parts by weight, 0.5 parts by weight to 3 parts by weight, 0.5 parts by weight to 2.5 parts by weight, 0.5 parts by weight to 2 parts by weight, 0.5 parts by weight to 1.5 parts by weight parts, 0.5 parts by weight to 1 parts by weight, or 0.5 parts by weight to 0.6 parts by weight. When the content of the dendritic silver particles falls within the above range, it may have excellent resistance change characteristics according to temperature change.

According to one embodiment, the content of the silver dendritic particles may be less than 7.5 parts by weight. Since the dendritic silver particles have needle-shaped ends, even if a small amount is included in the variable resistance film, excellent conductivity may be exhibited due to the quantum tunneling effect. Therefore, it is possible to exhibit the same or higher conductivity in a small amount compared to silver particles having a general spherical, cylindrical, rod-shaped, or the like end. As a result, it has an advantage in application as a variable resistance film of a temperature sensor that detects a region in which resistance changes rapidly due to expansion of a polymer having a positive temperature coefficient characteristic.

In addition, since the content of the silver dendrite particles can be reduced from the excellent electrical properties due to the structural characteristics of the silver dendrite particles, the transparency of the temperature sensor can be secured.

In other words, from the combination of a polymer having excellent electrical properties and positive temperature coefficient properties of silver dendritic particles, it has an advantage in that it has excellent temperature sensing properties with only a small amount of silver dendrite particles, and at the same time, transparency can be secured.

According to one embodiment, the density of the silver dendritic particles in the variable resistance film 23 employed in the temperature sensor may be 5 mg/mL to 1.2 g/mL. In the above range, the resistance change characteristic according to the temperature is excellent.

According to another embodiment, one or more conductive layers (not shown) may be further disposed between the variable resistance layer 23 and the first electrode 22 and the second electrode 24 .

According to one embodiment, the substrate 21 is a flexible material, for example, polydimethylsiloxane (PDMS), polyethylene-terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyimide ( PI), polymethylmethacrylate, and polycarbonate (PC) may include one or more polymers selected from the group consisting of. For example, the substrate may be polyethylene-terephthalate (PET).

According to an exemplary embodiment, the variable resistance layer 23 may include a thermosetting polymer and dendritic silver particles in a weight ratio of 2:1. When the thermosetting polymer and the silver dendritic particles are included in the above weight ratio, the melting point of the variable resistance film is about 40° C., so that a positive temperature coefficient effect may be exhibited near body temperature. As a result, a change in resistance may occur abruptly near body temperature. Accordingly, it is easy to manufacture a temperature sensor with improved temperature sensing function in the vicinity of body temperature.

According to an embodiment, the melting point of the variable resistance layer may be about 38°C to about 40°C. Since the melting point of the variable resistance film is within the above range, the temperature sensor may be used in a device requiring sensing of the temperature, for example, a thermometer.

According to one embodiment, when the temperature sensor measures the resistance by a digital source meter using a 1V DC bias as a source-drain voltage, 35° C. Compared to that, the resistance value at 38°C can be increased by more than 10 ⁸ times. That is, by showing a dramatic change in resistance value near the body temperature, the temperature sensing characteristic is excellent near the body temperature.

Example

(Synthesis of dendritic silver particles)

<Synthesis of primary particles>

25mL of 0.06M AgNO3 _{and 25mL of 0.06M NH2OH were injected into a 125mL Erlenmeyer flask pre-packed with 5mL of 0.06M NH 2 OH using} a peristaltic pump at a rate of 2.5mL/min, respectively. While injecting the solution, the solution in the Erlenmeyer flask was stirred using a magnetic bar. After the injection was completed, the reaction proceeded completely for about 5 minutes, and it was confirmed that a precipitate was formed, and a gray precipitate was obtained through filtration under reduced pressure. To remove residual ligands and ions, the filtered precipitate was dried in a vacuum desiccator for about 3 hours to obtain a gray powdery material.

After dispersing the obtained material in ethanol using an ultrasonic disperser, drop casting on a silicon wafer and drying, the obtained powder was photographed with a FESEM (Field Emission Scanning Electron Microscope) (S-4800, Hitachi), It was confirmed that the branches of the obtained powder particles are dendritic particles that exist only in the first order.

The dendritic silver particles confirmed by FESEM are shown in FIG. 1 .

<Synthesis of secondary particles>

25 mL of 0.06M AgNO ₃ and 25 mL of 0.12M NH ₂ OH were injected into a 125 mL Erlenmeyer flask using a peristaltic pump at a rate of 5 mL/min, respectively. While injecting the solution, the solution in the Erlenmeyer flask was stirred using a magnetic bar. After the injection was completed, the reaction proceeded completely for about 5 minutes, and it was confirmed that a precipitate was formed, and a gray precipitate was obtained through filtration under reduced pressure. To remove residual ligands and ions, the filtered precipitate was dried in a vacuum desiccator for about 3 hours to obtain a gray powdery material.

After dispersing the obtained material in ethanol using an ultrasonic disperser, dropwise casting on a silicon wafer and drying the obtained powder was photographed with FESEM (S-4800, Hitachi). It was confirmed that the dendritic silver particles were.

Fig. 2 shows dendritic silver particles identified by FESEM.

<Synthesis of tertiary particles>

25 mL of 0.06M AgNO ₃ and 25 mL of 0.24M NH ₂ OH were injected into a 125 mL Erlenmeyer flask using a peristaltic pump at a rate of 15 mL/min, respectively. While injecting the solution, the solution in the Erlenmeyer flask was stirred using a magnetic bar. After the injection was completed, the reaction proceeded completely for about 5 minutes, and it was confirmed that a precipitate was formed, and a gray precipitate was obtained through filtration under reduced pressure. To remove residual ligands and ions, the filtered precipitate was dried in a vacuum desiccator for about 3 hours to obtain a gray powdery material.

After dispersing the obtained material in ethanol using an ultrasonic disperser, dropwise casting on a silicon wafer, and then drying the obtained powder was photographed with FESEM (S-4800, Hitachi). It was confirmed that it was a silver particle.

The silver dendritic particles confirmed by FESEM are shown in FIG. 3 .

(Manufacture of pressure sensor)

Example 1

36 mg of secondary silver dendritic particles were placed in a 25 mL vial containing an appropriate amount of ethanol and dispersed using an ultrasonic disperser. 2 mL of polyurethane resin (Robnor Resins Ltd., EL227CL) was put into the solution in which the dendritic particles were dispersed and mixed using a vortex mixer and an ultrasonic disperser. Thereafter, the ethanol solvent was evaporated at room temperature using a rotary evaporator. After the solvent was all evaporated, 0.5 mL of a polyurethane curing agent (Robnor Resins Ltd., HL227CL) was added and mixed for 5 minutes as above to induce a polyurethane polymerization reaction. Before all polymerization was completed, the mixture was coated on a PET/ITO substrate to a thickness of about 50 μm using a doctor blade. The mixture was cured in an oven at 50° C. for about 18 hours to induce a rapid polymerization reaction of the coated film. Another PET/ITO substrate was attached to the cured film to finally prepare a transparent piezoresistive pressure sensor having a PET/ITO/AgFDs-PU/ITO/PET structure.

Comparative Example 1

A pressure sensor was manufactured in the same manner as in Example 1, except that 9 mg of 100 nm spherical gold nanoparticles were used instead of the secondary silver dendritic particles.

Evaluation Example 1: Characteristic evaluation of pressure sensor

Connect the wires to the ITO electrodes above and below the pressure sensor prepared in Example 1 and use a digital source meter (2636A, Keithley) in a state where the source-drain voltage is 1V DC voltage. The resistance was measured. The resistance measurement results are shown in FIG. 5 . Referring to FIG. 5 , when the sensor was touched with a hand, a stable and large resistance change of about 10000 times from to was confirmed.

In addition, referring to FIGS. 6A to 6C , as a result of analyzing the response speed of the sensor, a fast response speed of about 30 ms was shown. In particular, since the response time limit of the measuring equipment is 30 ms, the actual sensor response speed may be faster.

Furthermore, referring to FIG. 7 , the prepared silver dendritic particles ?? To determine the transmittance of the PU film, it was measured using a UV-vis-NIR spectrophotometer (CARY 5000 spectrophotometer, Agilent). It was confirmed that the transmittance of the film was 73.56% at a wavelength of 550 nm and had transparency.

In addition, with respect to the pressure element manufactured in Comparative Example 1, the magnitude of the resistance was measured while increasing the pressure. As a result, as shown in FIG. 8 , a resistance value of 10 ⁸ or more was maintained even when the pressure exceeded 10000 Pa. That is, it is considered that the spherical silver nanoparticles are difficult to operate as a pressure sensor because it is difficult for electrons to smoothly move between the silver nanoparticles even when a high pressure is applied.

(Production of temperature sensor)

<Preparation of acrylate copolymer>

2.53 g (78 mol%) octadecyl acrylate and 0.31 mL (22 mol%) butyl acrylate were placed in a 100 mL beaker. Then, add 3.2mL (about 100wt%) of tetrahydrofuran and 28mg (about 1wt%) of 2,2-dimethoxy-2-2-phenylacetophenone (about 1wt%) to a beaker and shake to dissolve. gave. The completely stirred and transparent solution was irradiated with 365 nm UV light for 24 hours to proceed with polymerization. To prevent contact with oxygen while irradiating UV light, the upper part was blocked with a glass plate, and it was carried out in a dark room to block light of other wavelengths. After the reaction was completed, the synthesized polymer was scraped from the beaker to remove the solvent and dried in a vacuum desiccator for about 24 hours to obtain a polymer material in the form of white powder.

<Production of temperature sensor>

Example 2

Secondary dendritic silver particles (2.5 wt%) and acrylate copolymer were placed in a 25 mL vial in a mass ratio of 1 g: 2 g. Heat at 50°C to melt the copolymer and stir it for about 24 hours using a magnetic bar to create dendritic silver particles. An acrylate copolymer composite was obtained. After that, the obtained material is placed on the PET/ITO substrate where ITO is cut at a distance of about 40 μm, heat is applied at 50°C, and uniform pressure is applied downward using PI tape and a glass plate to coat both ITO electrodes. , a temperature sensor was fabricated.

(Evaluation of temperature sensor)

Evaluation Example 2: Positive temperature coefficient evaluation

The composite of the acrylate copolymer and the acrylate copolymer-dendritic silver particle was measured by DSC (DISCOVERY, TA instruments), and temperature-related information is shown in FIG. 10 . It was confirmed that the melting point of the copolymer and the silver dendritic particle-copolymer composite was around 40°C, and a positive temperature coefficient effect was exhibited near body temperature, thereby inducing a dramatic change in resistance.

Evaluation Example 3: Resistance Change Evaluation (1)

Connect the wires to the ITO electrodes on both sides of the temperature sensor manufactured in Example 2 and use a digital source meter (2636A, Keithley) in a state where the source-drain voltage is 1V DC voltage. The change in resistance according to the change in was measured. The results are shown in FIG. 11 . Referring to FIG. 11 , the measured resistance showed a large change from about 10 ³ Ω to a maximum of 5×10 ¹¹ Ω, and it was confirmed that a dramatic change occurred especially after 35° C., which is near the body temperature.

Evaluation Example 4: Resistance Change Evaluation (2)

A temperature sensor was manufactured in the same manner as in Example 2, but containing secondary silver dendritic nanoparticles in an amount of 0.6 wt%, 2.5 wt%, 5.0 wt%, 7.5 wt%, 10.0 wt%, 12.5 wt%, 15.0 wt% Each temperature sensor was fabricated,

A temperature sensor was fabricated in the same manner as in Example 2, except that, instead of dendritic silver nanoparticles, 0.6 wt%, 2.5 wt%, 5.0 wt%, 7.5 wt%, 10.0 wt%, 12.5 wt% of spherical silver nanoparticles having a diameter of about 2 μm were used. Each temperature sensor was prepared to contain 15.0% by weight and 15.0% by weight.

Thereafter, the resistance was measured at a temperature of around 35° C. for each of them, and the results are shown in FIG. 12, and when the secondary silver dendritic nanoparticles are included in an amount of less than 7.5 wt %, low resistance is shown. Able to know.

Evaluation Example 5: Transparency Evaluation

A temperature sensor was fabricated in the same manner as in Example 2, but the temperature sensor was manufactured to contain secondary silver dendritic nanoparticles in an amount of 0 wt%, 2.5 wt%, 5 wt%, and 10 wt%, and each of 300 nm to 800 nm of light transmittance was measured. In addition, as a control, the transmittance of the PET/ITO substrate was also measured.

The results are shown in FIG. 13, and when the secondary silver dendritic nanoparticles were included in 2.5 wt%, the transmittance was 85% or more at 550 nm.

Comprehensively examining the results of Evaluation Example 4 and Evaluation Example 5, it is possible to manufacture a temperature sensor including a small amount of silver dendritic nanoparticles due to the excellent electrical properties of the secondary silver dendritic nanoparticles. can be obtained

Claims (20)

thermosetting polymers and dendritic silver particles,
The dendritic silver particles,
a core particle comprising silver (Ag); and
Comprising one or more branches grown in a radial direction from the core particles,
The end of the branch has a needle shape,
The branch includes a main branch and one or more sub-branches grown two-dimensionally and/or three-dimensionally from the main branch,
and a growth length ratio of the main branch portion and the sub branch portion is in a range of 1:0.5 to 1:0.0001. delete delete According to claim 1,
The thermosetting polymer is a variable resistance film comprising at least one selected from the group consisting of acrylate-based, acrylic urethane-based, epoxy-based, silicone-based, unsaturated polyester-based, and polyurethane-based polymers. According to claim 1,
The variable resistance film further comprises an antioxidant, an adhesive, a plasticizer, an ultraviolet absorber, an antifoaming agent, a filler, and a curing agent. the first substrate;
a first electrode disposed on the first substrate;
a second electrode facing the first electrode;
a second substrate disposed on the second electrode; and
A variable resistance film according to any one of claims 1, 4, and 5 interposed between the first electrode and the second electrode;
comprising, a pressure sensor. 7. The method of claim 6,
and 0.1 to 50 parts by weight of silver dendritic particles in 100 parts by weight of the variable resistance film. 7. The method of claim 6,
The variable resistance film includes dendritic silver particles,
The pressure sensor, wherein the density of the silver dendritic particles in the variable resistance film is 0.1 mg/mL to 1 g/mL. 7. The method of claim 6,
The thickness of the variable resistance film is 20㎛ to 1mm, the pressure sensor. 7. The method of claim 6,
The variable resistance film includes a thermosetting polymer,
wherein the thermosetting polymer is an elastomeric polymer. 7. The method of claim 6
The thermosetting polymer is included in an amount of 50 parts by weight to 99.9 parts by weight in 100 parts by weight of the variable resistance film. 7. The method of claim 6,
The first and second substrates are polydimethylsiloxane (PDMS), polyethylene-terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyimide (PI), polymethylmethacrylate ( A pressure sensor comprising at least one polymer selected from the group consisting of polymethylmethacrylate), and polycarbonate (PC). 7. The method of claim 6,
When the pressure sensor measures the resistance by a digital source meter using a 1V DC voltage as a source-drain voltage, the pressure sensor shows a resistance change of 10,000 times or more, pressure sensor. the first substrate;
A variable resistance film according to any one of claims 1, 4 and 5; and
a first electrode and a second electrode interposed between the first substrate and the variable resistance layer;
A temperature sensor comprising a. 15. The method of claim 14,
The first electrode and the second electrode are disposed spaced apart from each other on the same plane, the temperature sensor. 15. The method of claim 14,
A portion of the variable resistance film is in contact with the first electrode, and the remaining portion is in contact with the second electrode. 15. The method of claim 14,
The variable resistance film includes dendritic silver particles,
and 0.5 to 75 parts by weight of silver dendritic particles in 100 parts by weight of the variable resistance film. 15. The method of claim 14,
The variable resistance film includes dendritic silver particles,
The temperature sensor, wherein the density of the silver dendritic particles in the variable resistance film is 5 mg/mL to 1.2 g/mL. 15. The method of claim 14,
The variable resistance film includes a thermosetting polymer and dendritic silver particles,
wherein the weight ratio of the thermosetting polymer and the dendritic silver particles is 2:1. 18. The method of claim 17,
The variable resistance film includes a thermosetting polymer,
The thermosetting polymer comprises a polymer having a positive temperature coefficient property.

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