KR102050753B1 - Manufaturing method of flexible Piezoelectric Element without heat treatment and Piezoelectric Element using it - Google Patents

Abstract

The present invention relates to a manufacturing method of a flexible piezoelectric element, comprising: a step of forming a coating by coating a sol including a ferroelectric material on a substrate; a pattern forming step of forming a pattern by using a nano imprint method on the coating layer; and a hardening step of manufacturing a crystalline ferroelectric material layer by irradiating an ultraviolet ray onto the pattern. The manufacturing method of a flexible piezoelectric element according to the present invention has an advantage of having excellent reliability by including the crystalline ferroelectric material having a constant arrangement without heat treatment.

Description

Manufacturing method of flexible piezoelectric element and flexible piezoelectric element manufactured therefrom {Manufaturing method of flexible Piezoelectric Element without heat treatment and Piezoelectric Element using it}

The present invention relates to a method for manufacturing a flexible piezoelectric device including a crystalline ferroelectric material without a high temperature heat treatment and having a uniform arrangement, and having excellent reliability, and a flexible piezoelectric device manufactured therefrom.

It is the most widely used energy source in everyday life and industrial sites, and the electric energy is produced by using hydro, thermal or nuclear materials as energy sources. However, these energy sources have a limited amount of storage, generate pollutants that are difficult to purify, and require a large-scale facility.

Accordingly, attention has been focused on the development of alternative energy to produce energy by replacing it, and researches for converting energy sources such as solar light, wind power, heat, etc. into electric energy have been actively conducted.

Furthermore, energy harvesting technology has recently attracted attention as a power source for small electronic devices. Specifically, the energy harvesting material is a device that collects and discards energy discarded by various principles such as piezoelectric, photovolataic, and thermoelectric and converts it into electrical energy.

In particular, the piezoelectric energy harvesting device converts and stores mechanical energy, such as human movement, into electrical energy, and has no particular limitation because it is not limited to the surrounding climate or the terrain and can be implemented as a micro device. Furthermore, piezoelectric energy harvesting elements (hereinafter referred to as piezoelectric elements) can be manufactured in a small size and used as a power source for portable devices. Further, attempts have been made to expand the applications by forming piezoelectric elements into flexible elements.

In order to realize a high performance flexible piezoelectric element, the method includes forming a crystalline piezoelectric material into a nanostructure. However, when the flexible substrate is to be used, there is a limit in the heat treatment temperature of the piezoelectric element. In order to overcome this limitation, a technique for manufacturing a flexible piezoelectric element by mixing a crystallized ferroelectric material with a polymer has been developed. In this case, as the crystallized ferroelectric material is randomly disposed inside the flexible piezoelectric element, the alignment of the piezoelectric polarization is changed. It is difficult and there is a problem that the reliability of the piezoelectric element manufactured is poor.

Republic of Korea Patent Registration 10-1738983

The present invention forms a pattern by applying a sol containing a ferroelectric material, and after the pattern is formed to form a crystal through ultraviolet irradiation, to form a layer of crystalline ferroelectric material, including a constant array of crystalline ferroelectric material of low temperature An object of the present invention is to provide a flexible piezoelectric element manufacturing method having excellent reliability even by heat treatment.

Flexible piezoelectric device manufacturing method according to the present invention comprises the steps of coating a sol containing a ferroelectric material on the substrate to form a coating layer;

A pattern forming step of forming a pattern on the coating layer using a nano imprint method; And

And a curing step of manufacturing a crystalline ferroelectric material layer by irradiating ultraviolet rays on the pattern.

In the flexible piezoelectric device manufacturing method according to an embodiment of the present invention, the pattern may be characterized in that all or part of the sol containing the ferroelectric material protrudes.

In the flexible piezoelectric device manufacturing method according to an embodiment of the present invention, the thickness of the coating layer may be 30 to 800 nm.

In the flexible piezoelectric device manufacturing method according to an embodiment of the present invention, the sol including the ferroelectric material may include 2 to 20% by weight of the ferroelectric material.

In the method of manufacturing a flexible piezoelectric device according to an embodiment of the present invention, the crystalline ferroelectric material layer may exhibit peaks at 22.2 ± 0.3 ° and 31.5 ± 0.3 ° by 2θ values by X-ray rotation measurement.

In the method of manufacturing a flexible piezoelectric element according to an embodiment of the present invention, in the crystalline ferroelectric material layer, a peak appearing at 22.2 ± 0.3 ° may be 1.2 to 4 times the intensity of the peak at 31.5 ± 0.3 °.

In the flexible piezoelectric device manufacturing method according to an embodiment of the present invention, the crystals included in the crystalline ferroelectric material layer may include crystals arranged in the same direction.

In the flexible piezoelectric device manufacturing method according to an embodiment of the present invention, the sol including the ferroelectric material is barium titanate, lead titanate, lead zirconate titanate (PZT), zinc oxide, aluminum nitride, cadmium sulfide, bismuth iron oxide, and carbonization. It may include one or two or more selected from silicon.

The present invention provides a flexible piezoelectric element manufactured by a method of manufacturing a flexible piezoelectric element according to an embodiment of the present invention.

The present invention provides a piezoelectric nanogenerator including electrodes formed on both sides of the flexible piezoelectric element.

The present invention coats a sol containing a ferroelectric material and forms a pattern in the shape of a piezoelectric element, and then crystallizes by ultraviolet irradiation, thereby forming a layer of crystalline ferroelectric material in a certain arrangement, very excellent reliability, and the manufacturing step Since it is significantly simplified and does not require heat treatment, there is an advantage in that the dielectric material layer can be directly formed on the flexible substrate without additional transfer.

1 is a view schematically showing an implementation step of a method of manufacturing a flexible piezoelectric element according to an embodiment of the present invention.
Figure 2 is a flexible piezoelectric element according to an embodiment of the present invention is photographed and shown by a scanning electron microscope.
3 is photographed through a transmission electron microscope to confirm the crystallinity of the flexible piezoelectric element according to an embodiment of the present invention and shows this.
4 illustrates the output of the piezoelectric nanogenerator with or without UV treatment in the piezoelectric nanogenerator according to the embodiment of the present invention through voltage and current.
Figure 5 measures the output of each part of the piezoelectric nanogenerator manufactured by the embodiment of the present invention and shows it.

Hereinafter, a method of manufacturing a flexible piezoelectric element according to the present invention will be described in detail. In this case, unless there is another definition in the technical terms and scientific terms used, it has the meaning that is commonly understood by those of ordinary skill in the art, unnecessarily obscure the subject matter of the present invention in the following description Description of known functions and configurations that may be omitted.

The present invention comprises the steps of coating a sol comprising a ferroelectric material on the substrate to form a coating layer;

A pattern shape step of forming a pattern on the coating layer using a nano imprint method; And

It relates to a flexible piezoelectric device manufacturing method comprising a; curing step of manufacturing a crystalline ferroelectric material layer by irradiating ultraviolet rays on the pattern.

The method for manufacturing a flexible piezoelectric element according to the present invention eliminates a heat treatment step for use of a flexible substrate which is essential for a flexible piezoelectric element, and forms a shape of the piezoelectric element and then cures it by irradiating ultraviolet rays to form a crystalline ferroelectric material layer having a predetermined arrangement. There is an advantage that can be obtained.

Specifically, the method for manufacturing a flexible piezoelectric element according to the present invention uses a sol containing a ferroelectric material and hardens it, thereby easily forming and forming a pattern having a uniform shape and arrangement using a nanoimprint method. There is an advantage. That is, the crystals included in the crystalline ferroelectric material layer according to an embodiment of the present invention may be arranged in the same direction. Accordingly, since it is not necessary to add a separate material to improve the orientation, there is an advantage that can significantly improve the piezoelectric properties of the flexible piezoelectric element manufactured by minimizing the additives.

In addition, by including a ferroelectric material having a uniform distribution in the sol containing a ferroelectric material, there is an advantage that can be fundamentally prevented from pulling or disproportionation of the particle material that may occur when mixing the conventional particle material and the binder. Therefore, there is an advantage that can manufacture a flexible flexible piezoelectric element.

In the flexible piezoelectric device manufacturing method according to an embodiment of the present invention, the pattern may have a shape in which all or part of the sol including the ferroelectric material protrudes. By this projecting shape, the pressure applied from the outside can be efficiently converted into electrical energy. Preferably, the protruding shape may be a pillar shape including a cylinder or a polygonal cross section, but the present invention is not limited thereto. Further, the mold used in the nano imprint method to form the above-described protruding pattern may be formed in an intaglio, but the present invention is not limited thereto.

Furthermore, when the pattern is cut in the horizontal direction with the substrate, that is, the area formed by the pattern may be 10 to 60%, more specifically 15 to 50% of the area of the entire coating layer. It prevents unnecessary interaction between the pillars due to excessive closeness, and enables power generation in a large area through the uniform distribution of applied pressures, thereby increasing power generation efficiency. have. In addition, the cross section of a single pattern formed when the pattern is cut in the horizontal direction with the substrate may have a diameter of 30 to 500 nm, specifically, 50 to 400 nm, while forming a pillar having a uniform shape in such a range. There is an advantage that can maximize the effect of improving the power production efficiency by forming the pillar shape.

In the method of manufacturing a flexible piezoelectric element according to an embodiment of the present invention, the height of the crystalline ferroelectric material layer may be 30 to 800 nm, specifically, 100 to 700 nm, thereby reducing the flexibility of the flexible piezoelectric element manufactured in this range. There is an advantage that can exhibit high power production efficiency while preventing. Further, the height of the pattern may be 80% or more, specifically, 85 to 99% of the total height of the crystalline ferroelectric material layer, and since most of the applied ferroelectric material layers are included in the pattern, power of the thickness of the ferroelectric material layer The problem of a decrease in production efficiency can be prevented.

Furthermore, the ferroelectric material contained in the sol containing the ferroelectric material may be used without limitation in the case of a material generally used in an energy harvesting device, specifically, a piezoelectric device. As a specific and non-limiting example, the sol containing the ferroelectric material is one or two selected from barium titanate, lead titanate, lead zirconate titanate (PZT), zinc oxide, aluminum nitride, cadmium sulfide, bismuth iron oxide, and silicon carbide. It may include the above, and more preferably may include barium titanate, but the present invention is not limited thereto.

Specifically, in the flexible piezoelectric device manufacturing method according to an embodiment of the present invention, when the sol containing ferroelectric material includes barium titanate (BaTiO ₃ ), the crystalline ferroelectric material layer has a 2θ value by X-ray diffraction measurement. Peaks at 22.2 ± 0.3 ° and 31.5 ± 0.3 ° simultaneously. Furthermore, in the method of manufacturing a flexible piezoelectric element according to an embodiment of the present invention, the peak appearing at 22.2 ± 0.3 ° by X-ray diffraction measurement of the crystalline ferroelectric material layer has a peak contrast intensity at 31.5 ± 0.3 °. 1.2 to 4 times, specifically 2 to 3.5 times.

In the flexible piezoelectric device manufacturing method according to an embodiment of the present invention, the sol including the ferroelectric material is 30 to 60% by weight of the ferroelectric material, 10 to 20% by weight of the doped metal compound, 20 to 40% by weight of the solvent and the initiator 2 To 10% by weight.

In this range, the pattern formed when the pattern is formed by the nanoimprint method can be maintained until the curing step, and by the excessively high viscosity, it is possible to prevent a problem in which bubbles are included in the formation of the coating layer or when the pattern is formed or excessive energy is required for the pattern formation. have.

In this case, the doping metal compound may be a compound including a transition metal such as titanium or iron, and the inclusion of the doping metal may further improve the output of the flexible piezoelectric element. In addition, the solvent may include one or two or more selected from alcohols having 1 to 7 carbon atoms and ketones having 2 to 8 carbon atoms, and preferably a mixed solvent thereof may be used, but the present invention is not limited thereto.

In addition, an initiator may be used without limitation in the case of a compound known as an initiator, and specifically, a photoinitiator may be used, and more specifically, may include an aniline-based initiator or a hydroxyl-based initiator, and the present invention is limited thereto. It is not.

In the method of manufacturing a flexible piezoelectric element according to an embodiment of the present invention, the curing step may be applied without limitation in the case where the crystallization of the ferroelectric material is performed by irradiating ultraviolet rays. As a specific and non-limiting example, crystallization may be performed by irradiating ultraviolet rays in a wavelength range of 200 to 600 nm, specifically, 250 to 500 nm for 0.2 to 20 minutes. In this case, the energy density of the applied ultraviolet light may be 10 to 500 mW / cm ² , specifically 20 to 100 mW / cm ² , but may be appropriately selected according to the type of ferroelectric material and the thickness of the ferroelectric material layer. . In addition, the irradiation amount of ultraviolet light may vary depending on the type and thickness of the ferroelectric material to be crystallized, but as a specific and non-limiting example may be 10 to 500 W.sec / ㎡, and the contact with the substrate in the above range Crystallization to ferroelectric materials is possible, but damage or degeneration of the piezoelectric element manufactured by excessively strong energy can be prevented, and problems of consuming unnecessary energy for the production of the piezoelectric element can be prevented.

The method of manufacturing a flexible piezoelectric element according to an embodiment of the present invention may further include a heat treatment step of heat treating a sol including a ferroelectric material having a pattern formed thereon after the pattern forming step and before the curing step. Through this heat treatment it is possible to gel the sol containing the ferroelectric material, it is possible to maintain the formed pattern until curing through this. Furthermore, by including a step of heat-treating the sol containing the ferroelectric material in a method of forming a pattern, and curing the sol, the ferroelectric material is evenly distributed, there is an advantage that the formation of a ferroelectric material layer having a constant arrangement.

At this time, the heat treatment step is not limited in the range in which the sol including the ferroelectric material can be gelled in a temperature range in which the flexible substrate is not damaged, as a specific and non-limiting example 70 to 150 ℃, more specifically 90 to 140 It may be ℃, but the present invention is not limited thereto.

The flexible piezoelectric device manufacturing method according to an embodiment of the present invention may further include a polling step of treating the cured ferroelectric material layer in an electric field after the curing step. The growth of the crystals formed by including the polling step, there is an advantage that can produce a flexible piezoelectric element of a higher output. Specifically, the electric field applied in the polling step may be from 50 to 500 kV / cm, more specifically from 80 to 200 kV / cm, while promoting the growth of the crystal in this range and at the same time excessive production of the flexible piezoelectric element This can prevent problems that require a lot of energy. Furthermore, the polling step may be performed for 3 to 50 hours, more specifically, 5 to 30 hours, but this may vary depending on the type of ferroelectric material included in the flexible piezoelectric element.

The present invention also provides a flexible piezoelectric element manufactured by the manufacturing method according to an embodiment of the present invention and a piezoelectric nanogenerator including the same. The flexible piezoelectric element according to the present invention has the advantage that the crystalline ferroelectric material layer can be formed directly on the flexible substrate without heat treatment, thereby preventing the problems that may occur due to the transfer of the ferroelectric material layer. Furthermore, since there is no need for an additive for forming an array of ferroelectric materials in a predetermined direction, there is an advantage of further improving the output of the resulting piezoelectric nanogenerator.

Hereinafter, an Example demonstrates this invention concretely. The embodiments described below are merely to aid the understanding of the present invention, and the present invention is not limited to the embodiments described below.

Example 1

A 100 nm thick ITO thin film was formed on a 5 × 5 cm polyethylene terephthalate (PET) substrate by sputtering, and a BaTiO ₃ sol was spin-coated at 4,000 rpm for 30 seconds on the formed ITO thin film to obtain a coating layer having a thickness of about 1500 nm. Formed.

The BaTiO ₃ sol barium hydroxy octa hydrate _{(Ba (OH) 2 · 8H} 2 O, 95.0%): titanium (IV) butoxide _{(Ti (OCH 2 CH 2 CH} 2 CH 3) 4, 97%): iron (III) Nitrate nonahydrate (FeNO ₃ · 9H ₂ O, 98.5%) was prepared in a molar ratio of 1: 0.98: 0.02, and a mixed solvent in which acetone and ethanol were mixed at a ratio of 1: 1 was mixed. After that, the gelled through aging was used. At this time, the mixed metal: mixed solvent was mixed 1: 1 by volume.

The pattern is formed on the coating layer by using a PDMS (polydimethylsiloxane, Sylgard, 184 Silicon elastomer) mold patterned in a cylindrical shape on the formed coating layer. At this time, the pattern is 300 nm in height, 150 nm in diameter in the cross section of a single pattern, and was formed such that the pattern is uniformly distributed on a 50 mm x 50 mm substrate. The patterned barium titanate sol was heat-treated at 130 ° C. for 5 hours to conduct gelation.

Crystallization was performed by irradiating the gelled pattern with ultraviolet light having an energy density of 40 mW / cm ² and a wavelength of 365 nm for 2 minutes, and a flexible piezoelectric device was manufactured by applying an electric field of 100 kV / cm for 10 hours.

Subsequently, a piezoelectric nanogenerator was manufactured by attaching a PET electrode coated with ITO (100 nm) using an adhesive PDMS polymer liquid solution on the manufactured flexible piezoelectric element.

Comparative Example 1

In the manufacturing process of Example 1, except for the crystallization process through ultraviolet irradiation to dry at room temperature to produce a piezoelectric device, and then attached to the electrode as in Example 1 to prepare a piezoelectric nanogenerator.

Comparative Example 2

BaTiO ₃ sol of Example 1 was applied to a PET substrate with a thickness of 300 nm and dried at room temperature to prepare a piezoelectric device. Then, the electrode was attached as in Example 1 to prepare a piezoelectric nanogenerator.

Check shape and crystal formation of flexible piezoelectric element

The flexible piezoelectric element manufactured according to Example 1 was photographed through a scanning electron microscope, and this is illustrated in FIG. 2. The flexible piezoelectric element according to Comparative Example 1 (left) and the flexible piezoelectric element according to Example 1 (right) were photographed. It was taken through a transmission electron microscope and shown in FIG.

Referring to Figure 2, it can be seen that the flexible piezoelectric element manufactured according to the embodiment of the present invention includes a nano-pillar of uniformly arranged uniformly.

Referring to FIG. 3, it can be confirmed that the amorphous form before the ultraviolet treatment (Comparative Example 1), but the crystal form appears after the ultraviolet treatment (Example 1), and further includes crystals arranged in a uniform direction. Can be confirmed.

Confirmation of output improvement of piezoelectric element generator by UV treatment

Voltage and current density were measured when the same pressure of 0.3 MPa was applied to the piezoelectric nanogenerators manufactured by Examples and Comparative Examples using a push machine. In Figure 4, non-poled means Comparative Example 2, poled means Comparative Example 1, and UV-treated & Poled Example 1.

Referring to FIG. 4, it can be seen that in Comparative Example 2, there is almost no output in terms of current and voltage, and in Comparative Example 1, although a certain level of output is shown, it shows a significantly lower voltage and current density than the example. You can check it.

Check output uniformity of manufactured piezoelectric nanogenerator

In the piezoelectric nanogenerator manufactured in Example 1, an area of 1 × 1 cm was arbitrarily selected at 4 places, and pressure was applied thereto.

Referring to FIG. 5, even when a pressure is arbitrarily selected, a uniform output may be obtained.

Claims (10)

Coating a sol comprising a ferroelectric material on the substrate to form a coating layer;
A pattern forming step of forming a pattern on the coating layer using a nano imprint method; And
And a curing step of manufacturing a crystalline ferroelectric material layer by irradiating ultraviolet rays on the pattern.
Crystals contained in the crystalline ferroelectric material layer is a flexible piezoelectric device manufacturing method comprising a crystal arranged in the same direction. The method of claim 1,
The pattern is a flexible piezoelectric device manufacturing method characterized in that the protruding shape of all or part of the sol containing the ferroelectric material. The method of claim 1,
The height of the crystalline ferroelectric material layer is 30 to 800 nm flexible piezoelectric device manufacturing method. The method of claim 1,
The sol containing the ferroelectric material is a flexible piezoelectric device manufacturing method comprising 2 to 20% by weight of the ferroelectric material. The method of claim 1,
The crystalline ferroelectric material layer is a flexible piezoelectric element manufacturing method showing a peak at 22.2 ± 0.3 ° and 31.5 ± 0.3 ° by X-ray rotation measurement at the same time. The method of claim 5,
In the crystalline ferroelectric material layer, the peak appearing at 22.2 ± 0.3 ° is 1.2 to 4 times the intensity (intensity) relative to the peak appearing at 31.5 ± 0.3 °. delete The method of claim 1,
The sol containing the ferroelectric material is a flexible piezoelectric element including one or more selected from barium titanate, lead titanate, lead zirconate titanate (PZT), zinc oxide, aluminum nitride, cadmium sulfide, bismuth iron oxide, and silicon carbide. Manufacturing method. A flexible piezoelectric element manufactured by the flexible piezoelectric element manufacturing method of any one of claims 1 to 6 and 8. The piezoelectric nanogenerator comprising electrodes formed on both sides of the flexible piezoelectric element of claim 9.

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