KR20220135069A - Transparent heating element having high flexibility and heating heater including the same - Google Patents

Abstract

The present invention relates to a transparent heating element having high flexibility and a heater including the same, which can be operated as a heating element even in a low voltage state, can be heated uniformly to provide heat, and has excellent transparency. In addition, since the transparent heating element is stacked on a flexible transparent polymer substrate, to be easily attached to an object having a complex shape, and can exhibit characteristics of durability, robustness, high conductivity, and fast thermal response time, to be used not only for applications to which existing heaters are applied, but also can be applied to wearable electronic products including biomedical devices.

Description

Transparent heating element having high flexibility and heating heater including the same

The present invention relates to a transparent heating element having high flexibility and a heating heater including the same, and specifically to a transparent heating element having high flexibility that exhibits high flexibility and can exhibit uniform heating characteristics, durability and robustness, and a heating heater including the same is about

In general, a side mirror defrosting device for automobiles is a device that removes water drops or frost generated on the side mirror in rainy weather and winter, and has the purpose of securing the driver's rear view and driving safely.

However, in the early days, the cost of the side mirror defrosting device is increased because imported hot wire materials are used, and even if the side mirror defrosting device is operated, it takes a long time to generate heat and takes a certain period of time to be effective. There was a problem in that the driver had to drive or had to stand still while receiving a visual impairment.

In the case of a conventional planar heating element using a conductive paste using a carbon material, the resistance value of the heating layer is not uniform and the heating temperature deviation is large. there was.

It is difficult to realize a low resistance value only with carbon materials such as carbon black or graphite powder, which are commonly used, so there is a limit to the application of a low voltage DC and a large area with a large inter-electrode distance.

In addition, when it becomes higher than the proper use temperature of the planar heating element, the designed resistance value changes due to external factors such as insulation, heat storage and overvoltage, and the performance of the product changes, and the durability is easily deteriorated. .

In order to solve this problem, a high-purity carbon material with high thermal conductivity is recently selected, a ceramic binder resin with high temperature stability, a heat-resistant resin, or new materials such as carbon nanofibers and carbon nanotubes are applied. Conductivity for a planar heating element Although the ink composition has been introduced, it is difficult to actually apply it because the price of the material is very high.

Conventional transparent heating elements are manufactured by connecting electrodes after forming a heating layer through a sputtering process using a transparent conductive material such as ITO (Indium Tin Oxide) or Ag thin film on top of glass. Due to the high sheet resistance of the transparent heating element, there was a problem in that it was difficult to drive at a low voltage of 40V or less.

Previously, the planar heating element can be applied to wearable electronic products including biomedical devices in addition to the side mirrors for automobiles, and the need for application is emerging. However, as described above, in the case of conventional products, there is a problem in that it is difficult to drive at a low voltage, and while it can be easily attached to objects of complex shape, it has excellent characteristics such as durability, and development of a transparent planar heating element that can be used for a long time need.

KR 10-2018-0095227 A1

An object of the present invention is to provide a transparent heating element having high flexibility and a heating heater including the same.

Another object of the present invention is to provide a transparent heating element that can operate as a heating element even in a low voltage state, can be heated uniformly to provide heat, and has excellent transparency and high flexibility.

Another object of the present invention is a transparent heating element with high flexibility that is laminated on a flexible transparent polymer substrate, can be easily attached to a complex shape object, and exhibits characteristics of durability, rigidity, high conductivity, and fast thermal response time, and the same It is to provide a heating heater comprising.

Another object of the present invention is to provide a transparent heating element having high flexibility applicable to wearable electronic products including biomedical devices and a heating heater including the same.

In order to achieve the above object, a transparent heating element having high flexibility according to an embodiment of the present invention includes a transparent polymer substrate; a heating layer formed by depositing on one surface of the transparent polymer substrate; and an electrode, wherein the electrode is disposed on both sides of the heating layer, the heating layer comprising: a first metal oxide layer; metal layer; And the second metal oxide layer is laminated on the transparent polymer substrate in this order.

The transparent polymer substrate is a flexible substrate.

The metal layer may be selected from the group consisting of Ag, Au, Pt, Al, Cu, Cr, V, Mg, Ti, Sn, Pb, Pd, W, and alloys thereof.

The metal oxide layer may be selected from the group consisting of zinc tin oxide (ZTO), indium gallium zinc oxide (IGZO), zinc aluminum oxide (ZAO), indium zinc oxide (IZO), and zinc oxide (ZnO).

The first metal oxide layer has a thickness of 10 to 30 nm.

The second metal oxide layer has a thickness of 30 to 50 nm.

The metal layer may be included as an ultra-thin metal layer having a thickness of 5 to 20 nm.

A method of manufacturing a transparent heating element having high flexibility according to another embodiment of the present invention includes the steps of: 1) preparing a transparent substrate; 2) a first metal oxide layer on one surface of the transparent substrate; metal layer; and forming a heating layer stacked in the order of the second metal oxide layer; and 3) forming electrodes on both sides of the heating layer.

The heating heater according to another embodiment of the present invention may include the transparent heating element having the high flexibility.

The present invention can be operated as a heating element even in a low voltage state, can be heated uniformly to provide heat, and has excellent transparency.

In addition, it is laminated on a flexible transparent polymer substrate, so it can be easily attached to complex shaped objects, and it can exhibit the characteristics of durability, robustness, high conductivity, and fast thermal response time. It can be applied to wearable electronic products including medical devices.

1 is a conceptual diagram of a transparent heating element according to an embodiment of the present invention.
2 is an evaluation result of transmittance of a transparent heating element according to an embodiment of the present invention.
3 is an SEM measurement result for each thickness of an ultra-thin Ag layer according to an embodiment of the present invention.
4 is a result of sheet resistance value, transmittance measurement result, current-voltage relationship and thermal uniformity as a function of Ag layer thickness of the heating element according to an embodiment of the present invention.
5 is an experimental result for the general voltage-dependent Joule heating characteristics of the heating element according to an embodiment of the present invention.
6 is a durability test result of a heating element according to an embodiment of the present invention.
7 is a heating performance evaluation result according to the bending radius of the heating element according to an embodiment of the present invention.
8 is an experimental result for a heating state in a bent state of the heating element according to an embodiment of the present invention.
9 is an evaluation result of the area dependence of the electrical parameter of the heating element according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

Because the planar heating element generates radiant heat by electricity passing through, there is no air pollution, it is hygienic, and there is no electromagnetic wave and noise. It is used in various forms in various industries, such as heating devices in various industries, plastic houses, livestock houses, agricultural equipment, side mirrors for automobiles, surface of refrigerated display cases, window systems, bathroom mirrors, and home appliances.

Currently, the most widely used commercial material for transparent heating elements is an indium tin oxide (ITO) thin film due to the material's relatively high transmittance (> 80 %) and low resistivity (10 to 100 Ω/sq.).

The ITO layer is usually deposited by sputtering directly on the glass surface at high temperature (~300° C.) for optimized heater performance. However, this manufacturing method, which requires a heat-sensitive polymer substrate, has a problem incompatible with the commercial roll-to-roll sputtering process.

In addition, the ITO layer prepared at room temperature has a significantly lowered conductivity, and for a low sheet resistance value, when formed with a significant film thickness, it can be within the range of the corresponding resistance value, increasing the manufacturing cost, and is suitable for a flexible substrate. Even during deposition, brittle properties appear. Due to this problem, it is not easy to attach the ITO heating element to an object having a complex shape, and thus it is not easy to apply it to a wearable device.

In order to overcome the disadvantages of the ITO heating element, various materials combining two or more types such as carbon nanotubes, graphene, Ag nanowire mesh, metal mesh, and hybrid are used, which are widely used to achieve high transmittance and high conductivity at the same time. is being studied extensively.

For application to mobile devices, the transparent heating element must exhibit excellent thermal uniformity, long-term stability, and sufficient flexibility, and an important requirement is whether it can be operated even in a low voltage state. This is because the voltage provided in the operating environment of a mobile device is usually fixed and relatively low. For example, in the case of a portable rechargeable lithium-ion battery, it can provide dc 12V, which is a relatively low voltage state.

In consideration of this point, for the application of the transparent heating element to various uses, a decisive factor is the high conductivity of the heating element, which is generally expressed as sheet resistance. However, in order to replace the ITO heating element, a plurality of materials under study did not achieve sufficiently low sheet resistance at the same time as the other requirements mentioned above.

For example, the carbon-based heating element has a transmittance of more than 80%, which satisfies transparency, but has a sheet resistance of several hundred Ohm/sq.

The Ag nanowire-based heater has a high transmittance of 90% or more and a sheet resistance of 10 Ohm/sq. That is, the Joule heating capability and long-term stability are significantly limited in terms of thermal response (tens of seconds to reach the target temperature) due to the higher current density and temperature in individual Ag nanowires than in the whole Ag nanowire network.

A transparent heating element having high flexibility according to an embodiment of the present invention includes a transparent polymer substrate; a heating layer formed by depositing on one surface of the transparent polymer substrate; and an electrode, wherein the electrode is disposed on both sides of the heating layer, the heating layer comprising: a first metal oxide layer; metal layer; And the second metal oxide layer is laminated on the transparent polymer substrate in this order.

Specifically, the metal layer is selected from the group consisting of Ag, Au, Pt, Al, Cu, Cr, V, Mg, Ti, Sn, Pb, Pd, W, and alloys thereof, preferably Ag.

In addition, the metal oxide layer is selected from the group consisting of Zinc Tin Oxide (ZTO), Indium Gallium Zinc Oxide (IGZO), Zinc Aluminum Oxide (ZAO), Indium Zinc Oxide (IZO), and Zinc Oxide (ZnO), preferably The first metal oxide layer and the second metal oxide layer are ZnO.

: 400 내지 800 nm) 및 투과율 90.8 %) 및 전도성(면저항 6.2 Ohm/sq.)을 나타내는 투명 발열체에 관한 것이다. The present invention is a very transparent (average visible light (

: 400 to 800 nm), transmittance 90.8%), and conductivity (sheet resistance 6.2 Ohm/sq.) to a transparent heating element.

The transparent heating element of the present invention, for being utilized as a transparent heating element, shows all necessary properties. In particular, the transparent heating element of the present invention can exhibit not only complete reversibility of the heating function when external stress is removed, but also a temperature drop of less than 15% at a bending radius of 5 mm, so that it can be applied to the medical field.

The thermo-electric parameters were extracted for a square-shaped heating element with an area ranging from 25 to 2,025 mm ² , which was obtained by direct connection of a transparent heating element with an area of 200 mm x 200 mm with a portable rechargeable Li-ion battery with DC 12V output. It can be predicted that the temperature can rise to 50 °C.

The transparent polymer substrate is polyimide (PI), but is not limited thereto, and the transparent polymer substrate may be used without limitation. However, the transparent polymer substrate is a sheet using a transparent polymer, and even when the product for attaching the heating element of the present invention has a flat shape as well as a three-dimensional shape, a transparent polymer sheet that is easily attached can be used.

The first metal oxide layer may have a thickness of 10 to 30 nm, and the second metal oxide layer may have a thickness of 30 to 50 nm. Differently limiting the thicknesses of the first metal oxide layer and the second metal oxide layer as described above prevents the problem of lowering transmittance due to the difference in refractive index between the metal oxide layer and the metal layer, as well as exhibiting low sheet resistance. It is intended to limit the scope of That is, if the above range is not satisfied or when the thicknesses of the first metal oxide layer and the second metal oxide layer are formed oppositely, there may be problems in that the transmittance is lowered or the sheet resistance value is increased.

The metal layer is included as an ultra-thin metal layer having a thickness of 5 to 20 nm, preferably 7 to 16 nm, and more preferably 10 nm. When the metal layer has a thickness of 10 nm, it has the highest visible light transmittance, can exhibit high transparency, and can reach a low sheet resistance, within an applied voltage, with a high current and a high heating element temperature.

The transparent heating element of the present invention is characterized in that the heating coating layer is formed on one surface of the second metal oxide layer. The heating coating layer is a transparent coating layer, and the heating coating layer may exhibit an even heating effect on the entire transparent heating element. Conventional transparent heating elements have a problem in that there is a difference in the degree of heat generation with respect to the center and the edge portion. That is, there is a problem that the temperature difference appears between the central portion and the edge portion because it is not evenly heated to the edge portion.

On the other hand, the transparent heating element of the present invention has almost no temperature difference between the central portion and the edge portion, thereby exhibiting an even heating effect. However, when a transparent heating element is applied to the glass part of a vehicle or a heating element having a larger area is manufactured, there is a problem in that a temperature difference may appear partly between the central part and the outermost edge part inevitably.

In addition, due to the enlargement of the area, problems such as a lower maximum temperature at which heat can be generated due to the transparent heating element or a longer time to reach the maximum temperature may occur.

In order to prevent the above problems, the present invention is characterized in that by forming a heating coating layer on one surface of the second metal oxide layer of the transparent heating element, a high level of heating effect can be exhibited.

More specifically, the exothermic coating layer may include chlorogenic acid, a benzotriazole-based compound represented by the following Chemical Formula 1, a solvent, and a binder resin:

[Formula 1]

The chlorogenic acid and the benzotriazole-based compound have excellent light absorption effect and excellent transfer effect of heat energy by the transparent heating element, so that the heating effect on the transparent heating element of the present invention can be increased by its own heating effect and heat transfer effect. .

In addition, the heating coating layer is a transparent coating layer, suitable for use as a transparent heating element.

More specifically, the exothermic coating layer may include 5 to 10 parts by weight of chlorogenic acid, 5 to 10 parts by weight of a benzotriazole-based compound, and 50 to 60 parts by weight of a binder resin based on 100 parts by weight of the solvent. When used by mixing within the above range, excellent heat-generating effect, heat-conducting effect and adhesive effect can be exhibited, so that it can be used as a coating layer.

The solvent is not particularly limited to the type, and those that can be used as the solvent may be appropriately selected. Specifically, ethanol, distilled water, butanol, ethyl acetate, ethyl cellosolve, butyl cellosolve, polypropylene glycol monomethyl ether, dimethyl sulfoxide, etc. may be mentioned, and these may be used alone or in combination of two or more, Preferably it is distilled water, but is not limited to the above example.

The type of the binder resin is not particularly limited as long as it is commonly used in the art, and specifically, it may be selected from the group consisting of polyacrylic resins, polyurethane resins, polyvinylpyrrolidone resins, polyester resins and silicone resins. However, it is not limited to the above example.

A method of manufacturing a transparent heating element having high flexibility according to another embodiment of the present invention includes the steps of: 1) preparing a transparent substrate; 2) a first metal oxide layer on one surface of the transparent substrate; metal layer; and forming a heating layer stacked in the order of the second metal oxide layer; and 3) forming electrodes on both sides of the heating layer.

More specifically, the transparent substrate uses a transparent PI film, and the first metal oxide layer and the second metal oxide layer are deposited by sputtering ZnO, and in the case of the metal layer, it can be formed by sputtering Ag.

After forming the heating layer in step 2), a heating coating layer may be formed on the second metal oxide layer. In the method of forming the exothermic coating layer, the exothermic coating layer may be formed by uniformly applying and drying the exothermic coating composition. A method of forming the coating layer may use a method such as dip coating or spray coating, and any method capable of uniformly applying the coating layer may be used without limitation.

The step of forming the electrode is to be formed on both sides of the heating layer, and may be formed on both sides of the transparent substrate in addition to the heating layer without limitation. The electrode may be formed using Ag, a transparent metal such as nanowires/paste, an oxide transparent electrode such as ITO, ZnO, SnO ₂ , or a non-oxide transparent electrode such as carbon nanotubes or graphene, However, the present invention is not limited thereto.

The heating heater according to another embodiment of the present invention may include a transparent heating element having high flexibility.

The heating heater may be attached for purposes such as defrosting, such as a side mirror of a car, and may be attached to a wearable device and used as a heating material, and the field of application of the heating heater is not limited to the above example , it can be used without limitation within the field to which the transparent heating heater can be applied.

In particular, considering that it is used by connection with a portable rechargeable battery having a DC 12V output, it can be used without any limitation in applications requiring heat generation under an environment of providing a fixed voltage and a low voltage.

Hereinafter, the present invention will be described in more detail by way of Examples, but the scope of the present invention is not limited by the Examples.

Preparation Example 1

An ultra-thin Ag (UT Ag)-based ZnO/Ag/ZnO heating element was deposited on a transparent polyimide (PI) substrate by sputtering Ag (99.99 wt %) and ZnO (99.999 wt %) in a multi-target magnetron sputtering system. Before deposition, the chamber was evacuated to a basic pressure of 4×10 ^-5 Pa, and then Ar gas having a purity of 99.9999% was introduced to maintain a deposition pressure of 0.8 Pa. Ag and ZnO were sputtered under the supply of 30 W dc power and 50 W radio frequency power. The substrate was rotated at 15 rpm during deposition to improve spatial uniformity, and the substrate was not intentionally cooled or heated during deposition. The deposition rates of Ag and ZnO were determined to be 0.37 nm/sec and 0.046 nm/sec, respectively.

Preparation 2

Preparation of exothermic coating layer

50 parts by weight of a polyacrylic resin was added to 100 parts by weight of distilled water and stirred to prepare a binder mixture, and 10 parts by weight of chlorogenic acid and 10 parts by weight of a benzotriazole-based compound represented by the following Chemical Formula 1 were added. Thereafter, the mixture was stirred for 60 minutes using a high-speed stirrer to prepare a uniformly mixed exothermic coating composition.

With respect to the heating element of the first ZnO layer / Ag layer / second ZnO layer of Preparation Example 1, dip coating the heating coating composition on one surface of the second ZnO layer and drying it at room temperature for 24 hours to prepare a heating coating layer did.

Experimental method

Film thickness was measured using a Surface Profiler (D-100, KLA). The thickness of the Ag layer was adjusted to 7 to 16 nm, and the first metal oxide layer and the second metal oxide layer were fixed to 20 and 40 nm, respectively. After the heating element of the first ZnO layer/Ag layer/second ZnO layer was fabricated, Ag electrodes having a width of 5 mm and a thickness of 100 nm were deposited on both sides of the heating element. The sheet resistance of the Ag layer was measured using a four-point probing method, and the light transmittance according to wavelength was measured using a spectrophotometric method (Agilent CARY-100). The surface morphology of the Ag layer was observed using a sample on which the second ZnO layer was not deposited, using a super-resolution field emission scanning electron microscope (SEM) (Hitachi S-5500) operated at 5 kV. To induce Joule heating, a DC power supply (EPS-3305, EZT) was used and the temperature was measured with an infrared (IR) camera (PTI120, Fluke).

Experiment result

1 relates to the schematic structure of a flexible transparent heating element composed of an ultra-thin (~ 10 nm) Ag layer sandwiched between a second ZnO layer (40 nm) and a first ZnO layer (20 nm). An external DC voltage applied between two 100 nm thick electrodes induces a current flow through the Ag layer, causing Joule heating by planar resistivity. The result of comparing the visible transparency of the transparent PI substrate and the transparent heating element is the same as that of FIG. 2, and it can be seen that there is no significant difference with the naked eye.

SEM micrographs of 5, 7, and 10 nm thick Ag layers are shown in FIG. 3 . Ag has granular and discontinuous layers observed in the initial deposition stage due to the strong Volmer-Weber 3D growth mode commonly observed in low-melting metals, forming continuous Ag layers at a thickness of ~10 nm.

The sheet resistance value as a function of the Ag layer thickness is shown in Fig. 4(b). Due to the decreased pore density and decreased severity, as the Ag layer thickness increased, surface scattering occurred, resulting in a sharp decrease in electrode resistance. After heating to 120°C, the room temperature heating element sheet resistance value decreased, and a decrease in the higher resistance value was observed for the thinner Ag layer. This is because, due to the increase in temperature, the diffusion of Ag atoms is improved and the total pore volume of the ultra-thin Ag layer is reduced in addition to the expected grain growth and defect disappearance.

FIG. 4(c) relates to the wavelength-dependent transmittance of the heating element of the PI layer/first ZnO layer (20 nm)/Ag layer (7 to 16 nm)/second ZnO layer (40 nm) structure. As a result of the measurement, in the Ag layer with a thickness of 10 nm, the transmittance of visible light (400 to 800 nm) is the highest, and even compared to the PI substrate, the average decrease rate is only 9.2%, so as shown in FIG. 2, the transmittance is relatively insignificant showed

The current-voltage relationship (Fig. 4(d)) shows a higher current and higher heating element associated with a lower sheet resistance at a given applied voltage because the electrically driven Joule heating capability for a given area is proportional to the relationship P=IV. It shows the temperature clearly. where P, I and V mean power, current and voltage, respectively.

A slight deviation in the linearity of the current-voltage relationship at elevated temperature is considered to be due to the increase in resistivity due to a higher degree of lattice scattering. The spatial thermal uniformity of the heating element is as shown in Fig. 4(e), where the maximum-minimum temperature difference of the average heating element is less than 2 °C at 100 °C, except for the position less than 5 mm of the edge where severe heat release to the air occurs.

As described above, the transparent heating element of the present invention exhibits excellent thermal uniformity, which may be attributed to the properties of a true planar heating element in contrast to a network-type heating element in which the local temperature of the conductive network is significantly higher than the average heating element temperature.

5 relates to typical voltage-dependent Joule heating characteristics for a UT-Ag (10 nm) heating element until failure at ~140°C. It can be seen that the UT-Ag heating element exhibits very fast thermal response characteristics. That is, it can be confirmed that it reaches the level of 90% of the final temperature within 2 seconds. This characteristic is due to the very uniform current density of the planar heating element. On the other hand, in the case of a network-type heating element, thermal non-uniformity between the conductive element (e.g., nanowire) and the background appears, which is resolved with the lapse of time, and it takes a relatively long time (20 to 30 seconds) to reach the target temperature. need.

6 is a result of a durability test by continuously applying a DC voltage to maintain the temperature of the heating element close to 100° C. for 10,000 minutes.

As shown in FIG. 6 , it was confirmed that the UT-Ag heating element of the present invention exhibits very stable heating performance without deterioration in performance in terms of heating performance. On the durability test for 5,000 minutes and 10,000 minutes in FIG. 3( c ), it was observed that the transmittance spectra measured additionally for the heating element were also almost identical, so that the possibility of application to actual products would be very high.

For application to wearable electronic devices, it is important to maintain the heating function under repeated mechanical stress.

7 relates to the heating performance as the bending radius gradually decreases to 5 mm and then increases back to the original state while a constant DC voltage is applied to the heating element. The heating element temperature was lowered by about 5% and 15% at the bending radii of 8 mm and 5 mm, respectively, and it was shown that the current slightly increased as the bending radius decreased, which reduced phonon scattering according to the reduced temperature. is related to It was shown that the reduced temperature and current fully recovered to the initial state with increasing curvature, completing a symmetric temperature/current profile. These excellent mechanical properties and reversibility upon unloading are very suitable properties for wearables and flexible applications.

In addition, a repeated bending test was performed to change the bending radius in the range of 14 to 5 nm, and the change in sheet resistance was measured after 200 repeated bending operations. The increase in sheet resistance by the bending test was less than 2%, which means that it can be used in flexible devices. The excellent heating ability in the bent state can be confirmed in Fig. 8(a). 7(a) shows two vials with a radius of 12 mm containing deionized water, and only one of them was wrapped with a UT-Ag heating element. The vial to which the heating element is attached maintains optical transparency, and the heat (100°C) generated by the transparent heating element is efficiently transferred to the water in the vial, raising room temperature water to 70°C. In order to confirm the performance of the UT-Ag heating element, a DC voltage of 4V was applied to only one of the heating elements, and the removal rate of artificially generated frost on two transparent heaters was compared. When the voltage was turned on, a significant amount of the frost on the top of the heating element was removed and dried within 3 minutes, whereas the heating element without DC voltage still had a significant amount of frost left.

The fast defrosting effect as described above is due to the uniform heating ability and low response time, which are the main characteristics of the UT-Ag heater. The uniform heating performance on a non-flat surface such as a human wrist is also shown in FIG. 8( c ).

7 will show that it can be applied to wearable electronic devices, such as biomedical devices, in addition to excellent heating ability in current physical disorders.

The low-voltage operation due to the low sheet resistance of the heating element is necessary for the application of portable applications because the method capable of providing a high voltage is generally limited. For example, a portable lithium-ion battery applied to a mobile electronic device such as a cell phone exhibits an output voltage of 12V. The above is more stringent in the case of a large-scale heating element in which the current density is greatly reduced due to the inverse characteristic of the electric field with respect to the distance between the electrodes. To evaluate the area dependence of electrical parameters, the current-voltage characteristics, voltages, currents, and power ratings (power/area) required to reach various temperatures can be represented as area functions of a square-shaped UT-Ag heater. In Fig. 9(a), the current linearly increased as the voltage increased, and in the case of a square conductor, it was almost independent of the expected area, and the resistance of the heating element extracted from the linearity was 5.7Ω.

On the other hand, a smaller heating element at a given voltage as a result of the increased current density heated to a significantly higher temperature. The current-voltage relationship deviates from linearity because phonon scattering increases at a temperature above 80 °C, resulting in an increase in the resistance of the heating element.

9(b) to 9(d) show the voltage and resulting current required for the calculated rated power (power/area) to reach various temperatures as a function of the heating element area shown in the figure, respectively. The power rating value is a significantly lower temperature near the edge of the heating element in Fig. 4(e), which results in heat loss to the air at the edge of the heating element, which is confirmed to be much higher for a small heating element. On the other hand, the rated power value is saturated for an area of 1300 mm ² or more, which greatly reduces the heat loss part of the edge due to the increase of the heating element area. The rated power to reach 50 °C and 100 °C based on the saturation value is 0.67mW/mm ² (0.43W/inch ² ) and 2.2mW/mm ² (1.40W/inch ² ), respectively.

For the same experiment, it was carried out for the transparent planar heating element having a coating layer formed in Preparation Example 2, and the rated power reaching 50 ℃ and 100 ℃ based on the saturation value was 0.52mW/mm ² (0.33W/inch ² ) and It was confirmed as 1.7mW/mm ² (1.08W/inch ² ), and it was confirmed that it reached 50 ℃ and 100 ℃ even under a lower rated power.

Using this rated power and the linear current-voltage characteristic of Fig. 4(d), a heating element having an area of 200 mm Х 200 mm and 100 mm Х 100 mm can reach 50 ℃ and 100 ℃ with a DC voltage of 12V, respectively. This means portable rechargeable lithium-ion batteries are available. In addition, in the case of the planar heating element of Preparation Example 2, it can reach 50 ℃ and 100 ℃ with a DC voltage of 12V up to 150mm Х 150mm, respectively. Through this power rating, in addition to excellent heating element properties including thermal uniformity, thermal response time, durability, and robustness to mechanical bending, the UT-Ag transparent heating element of the present invention can be used in various wearable electronic devices including biomedical applications.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

100: transparent polymer substrate
200: first metal oxide layer
300: metal layer
400: second metal oxide layer
500: electrode
600: coating layer

Claims (9)

transparent polymer substrate;
a heating layer formed by depositing on one surface of the transparent polymer substrate; and
comprising an electrode;
The electrodes are disposed on both sides of the heating layer,
The heating layer may include a first metal oxide layer; metal layer; and a second metal oxide layer that is laminated on the transparent polymer substrate in the order of
Transparent heating element with high flexibility. According to claim 1,
The transparent polymer substrate is a flexible substrate
Transparent heating element with high flexibility. According to claim 1,
The metal layer is selected from the group consisting of Ag, Au, Pt, Al, Cu, Cr, V, Mg, Ti, Sn, Pb, Pd, W, and alloys thereof.
Transparent heating element with high flexibility. According to claim 1,
The metal oxide layer is selected from the group consisting of Zinc Tin Oxide (ZTO), Indium Gallium Zinc Oxide (IGZO), Zinc Aluminum Oxide (ZAO), Indium Zinc Oxide (IZO), and Zinc Oxide (ZnO).
Transparent heating element with high flexibility. According to claim 1,
The first metal oxide layer has a thickness of 10 to 30 nm
Transparent heating element with high flexibility. According to claim 1,
The second metal oxide layer has a thickness of 30 to 50 nm
Transparent heating element with high flexibility. According to claim 1,
The metal layer is included as an ultra-thin metal layer with a thickness of 5 to 20 nm.
Transparent heating element with high flexibility. 1) preparing a transparent substrate;
2) a first metal oxide layer on one surface of the transparent substrate; metal layer; and forming a heating layer stacked in the order of the second metal oxide layer; and
3) comprising the step of forming electrodes on both sides of the heating layer
A method of manufacturing a transparent heating element having high flexibility. Including a transparent heating element having high flexibility according to claim 1
heat heater.

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