KR20210050254A - Conductive substrate and thermoacoustic loudspeaker comprising the same - Google Patents

Abstract

Provided is a conductive substrate that comprises: a resin substrate; and a conductive layer coated on the resin substrate. The resin substrate includes a poly (urethane-urea) resin. The conductive layer includes a silver nano-wire (AgNW, Ag nano-wire). In addition, provided is a thermoacoustic loudspeaker that comprises: the conductive substrate; and an electrode on the conductive substrate. The conductive substrate has high transparency and can simultaneously implement flexibility and self-healing performance, so it has the advantage of being applicable to a next-generation wearable small electronic device. In addition, the thermoacoustic loudspeaker to which the conductive substrate is applied can be thinned and miniaturized, and has excellent sound wave generation performance, so that it can be applied as a new acoustic application for a flexible or wearable device.

Description

Conductive substrate and hot acoustic loudspeaker including the same {CONDUCTIVE SUBSTRATE AND THERMOACOUSTIC LOUDSPEAKER COMPRISING THE SAME}

The present invention relates to a conductive substrate, for example, to a conductive substrate applicable to a hot acoustic loudspeaker.

Recently, various electronic devices that simulate human sense organs, such as artificial electronic skin and artificial voice, have been developed. These electronic devices are key technologies in the robotics, flexible electronic devices, healthcare monitoring, and sensor industries, and their utilization is very high.

As flexible electronic devices are actively developed, portability, flexibility, and miniaturization are required even in acoustic devices capable of inputting and outputting sound. In order to escape the limitations of the existing rigid microphone or speaker, various research teams are developing flexible acoustic devices that are very thin and can be driven using characteristics such as piezoelectricity and triboelectricity. However, despite technological advances such as self-driving, high-performance, and multifunctional audio equipment, there are still external limitations in terms of portability, miniaturization, and flexibility to be used as a next-generation wearable or body-attached electronic device. to be.

The concept introduced to utilize as an acoustic device of such an electronic device is thermoacoustic. Hot sound waves are a phenomenon that generates sound by expanding and contracting the surrounding air through thermal changes that occur when metal is rapidly heated and cooled using alternating current. The concept of a thermoacoustic (TA) loudspeaker was first proposed a century ago. The first hot sonic loudspeakers were implemented with a platinum (Pt) strip fixed to a lead (Pb) electrode, but their use was limited due to their very high heat capacity. In this way, when the heat capacity is high, the efficiency is significantly lowered in the process of vibrating the surrounding air. Accordingly, in recent years, in order to reduce the heat capacity per unit area, a technology of applying nanomaterials such as carbon nanotubes (CNTs) and graphene as a conductive filler is being actively studied. However, in the case of applying carbon nanotubes or the like as a conductive filler, it is common to use a silicon (Si) wafer or the like as a substrate, which has a disadvantage in that it is vulnerable to mechanical impact.

An embodiment of the present invention is to provide a conductive substrate that is transparent and flexible and has excellent mechanical durability based on self-healing performance.

Another embodiment of the present invention is to provide the conductive substrate to provide a hot sonic loudspeaker having excellent durability, flexibility and transparency at the same time.

In one embodiment of the present invention, a resin substrate; And a conductive layer coated on the resin substrate, wherein the resin substrate includes a poly(urethane-urea) resin, and the conductive layer includes a silver nano-wire (AgNW, Ag Nano-Wire). Provides.

In another embodiment of the present invention, a conductive substrate; And an electrode on the conductive substrate, wherein the conductive substrate includes a resin substrate; And a conductive layer coated on the resin substrate, wherein the resin substrate includes a poly(urethane-urea) resin, and the conductive layer includes a silver nano-wire (AgNW).

The conductive substrate has an advantage of being able to implement flexibility and self-healing performance at the same time while having high transparency, so that it can be applied to a next-generation wearable small electronic device.

In addition, the hot-sound loudspeaker to which the conductive substrate is applied can be made thinner and downsized, and has excellent sound wave generation performance, so that it can be applied as a new acoustic application for a flexible or wearable device.

1 shows a SEM photograph of a conductive layer of a conductive substrate according to an embodiment.
2 is a graph showing light transmittance of a conductive substrate according to an embodiment.
3 is a schematic diagram of a self-healing process of a conductive substrate according to an embodiment.
4 is a view showing an optical microscope (OM) photograph before and after self-healing according to Experimental Example 2 with respect to a conductive substrate according to an embodiment.
5 and 6 show graphs of results according to Experimental Example 2.
7 is a diagram illustrating a photograph indirectly showing a self-healing process after scratch processing on a conductive substrate according to an embodiment through lighting of an LED lamp.
8 is a SEM photograph showing a surface change of a conductive substrate before and after tapping according to Experimental Example 3. FIG.
9 is a graph showing a change in resistance value as the number of tappings increases according to Experimental Example 3;
10 shows a graph of the results according to (1) of Experimental Example 4.
11 shows a graph of the results according to (2) of Experimental Example 4.
FIG. 12 is a photograph showing a photo that can confirm the conductive network after (a) bending test according to Experimental Example 4, (b) bending with a radius of curvature of 5 mm, and (c) completing 10,000 bending tests with a radius of curvature of 5 mm I did it.
13 is a photograph showing a sample of the hot-sound loudspeaker prepared in Example 2. FIG.
14 schematically shows the principle of amplifying the hot sound wave of FIG. 13.
15 shows a photograph of an experiment setup for measuring a sound pressure level (SPL) of sound emitted from a hot-sound loudspeaker in Experimental Example 5. FIG.
16 is a graph of the results of Experimental Example 5, showing an SPL graph for each state of the conductive substrate in each frequency range of 1 kHz to 20 kHz.
FIG. 17 is a photograph showing the resistance measurement values after (a) scratch processing, (b) immediately after scratch processing, and (c) self-healing of the conductive substrates of the hot sonic loudspeaker sequentially from above.
18 is a graph showing the scratch shape of Experimental Example 2.
19 shows XPS data for the conductive substrates of Example 1 and Comparative Example 1.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments to be described later. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, However, these embodiments are provided to complete the disclosure of the present invention, and to fully inform the scope of the invention to a person skilled in the art to which the present invention pertains, and the present invention is defined by the scope of the claims. It just becomes.

In at least some of the drawings, the thickness is enlarged to clearly express various layers and regions. In addition, in the drawings, for convenience of description, the thicknesses of some layers and regions are exaggerated.

In addition, in the present specification, when a portion such as a layer, film, region, plate, etc. is said to be'on','on' or'top' of another portion, this Includes cases where there are parts. Conversely, when one part is said to be'right above' another part, it means that there is no other part in the middle. In addition, when a part such as a layer, film, region, or plate is said to be'below','below' or'lower' another part, it is not only the case that the other part is'directly below', but also another part in the middle. This includes cases where there is. Conversely, when one part is said to be'right below' another part, it means that there is no other part in the middle.

In one embodiment of the present invention, a resin substrate; And a conductive layer coated on the resin substrate, wherein the resin substrate includes a poly(urethane-urea) resin, and the conductive layer includes a silver nano-wire (AgNW, Ag Nano-Wire). Provide a substrate.

The conductive substrate has the advantage of implementing excellent thermal properties, transparency, and flexibility suitable for application to a hot sonic loudspeaker, and at the same time implementing self-healing performance against damage. This may be possible by applying a poly(urethane-urea) resin as the resin substrate and at the same time applying a silver nanowire as the conductive layer. In the case of applying graphene, carbon nanotubes (CNT), or the like as a conductive material, or applying other types of resins as a resin, these advantages cannot be obtained.

In one embodiment, the poly(urethane-urea) resin may have a structure represented by Formula 1 below.

[Formula 1]

In Formula 1, R ¹ and R ² are each independently a linear or branched alkylene group having 1 to 20 carbon atoms, a linear or branched heteroalkylene group having 1 to 20 carbon atoms, or substituted or unsubstituted with 5 to 30 carbon atoms. It may be one selected from a cyclic cycloalkylene group, a substituted or unsubstituted arylene group having 5 to 30 carbon atoms.

For example, the R ¹ and R ² may each independently be one selected from methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, sec-butylene, pentylene, and hexylene have. In one embodiment, R ¹ and R ² may each independently be one selected from pentylene or hexylene. For example, R ¹ may be pentylene, and R ² may be hexylene.

In Formula 1, R ³ , R ⁴ and R ⁵ are each independently hydrogen, a linear or branched alkyl group having 1 to 20 carbon atoms, a linear or branched heteroalkyl group having 1 to 20 carbon atoms, and a carbon number of 5 to 30 It may be one selected from a substituted or unsubstituted cycloalkyl group and a substituted or unsubstituted aryl group having 5 to 30 carbon atoms. For example, the R ³ , R ⁴ and R ⁵ are each independently hydrogen, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, pentyl group, It may be one selected from hexyl groups. In one embodiment, R ³ , R ⁴ and R ⁵ may be a methyl group.

In Formula 1, R ⁶ may be a branched alkyl group having 3 to 10 carbon atoms. When R ⁶ is a branched alkyl group having 3 to 10 carbon atoms, compared to a linear alkyl group having 1 to 2 carbon atoms or a linear alkaline group having 3 to 10 carbon atoms, a stereoscopic effect suitable for the poly(urethane-urea) resin (Steric effect) Can improve self-healing performance. For example, R ⁶ may be one selected from isopropyl group, sec-butyl group, and tert-butyl group. In one embodiment, R ⁶ may be a tert-butyl group.

In Formula 1, n may be 1 to 10. For example, n may be 1 to 9, for example, 1 to 8, for example, 1 to 5, for example, 1.5 to 4.5, for example , It may be 2.5 to 4.5, for example, it may be 3.5 to 4.5.

A thermoacoustic (TA) loudspeaker is a new type of speaker that produces sound without relying on speaker vibration, and has recently received great interest. Hot acoustic loudspeakers can generate sound by applying an alternating current (AC) voltage to a conductive network. The application of the AC voltage generates heat by Joule-heating of the conductive network and vibration of the surrounding air to generate sound waves. In order to manufacture a high-efficiency hot sonic loudspeaker, a material with a low heat capacity that facilitates heat conduction to the surrounding air is required.

Among various materials, silver nanowire (AgNW, Ag-Nano-Wire) applied to the conductive layer is an advantageous material for manufacturing a hot acoustic loudspeaker with low heat capacity, and the conductive substrate is advantageous to be applied to a hot acoustic loudspeaker through the conductive layer to which it is applied. It can have an advantage.

1 shows a SEM photograph of a conductive layer of a conductive substrate according to an embodiment. Referring to FIG. 1, in one embodiment, the conductive layer may include a three-dimensional network structure of the silver nanowire. The silver nanowires form a dense three-dimensional network structure, thereby constructing a dense conductive network, and as a result, network recovery may be possible within a predetermined time even after the silver nanowires are disconnected due to surface damage or the like.

In one embodiment, the silver nanowires in the conductive layer may have an average diameter of about 20 nm to about 100 nm in a cross section perpendicular to the length direction, for example, about 20 nm to about 80 nm, for example, about It may be 20 nm to about 60 nm, for example, it may be about 20 nm to about 45 nm.

In one embodiment, the silver nanowire in the conductive layer may have a length of about 7 μm to about 100 μm, for example, about 7 μm to about 80 μm, for example, about 7 μm to about It may be 60 μm, for example, from about 7 μm to about 40 μm, for example, from about 7 μm to about 35 μm, for example, from about 7 μm to about 30 μm, , For example, it may be about 7 μm to about 28 μm.

As the silver nanowire satisfies the above-described length and has a thickness corresponding to the average diameter of the cross section, the poly(urethane-urea) resin penetrates between the three-dimensional network structures of the silver nanowire to form a dense structure as a whole. It can be done, and suitable thermal conductivity, electrical conductivity, and self-healing performance can be realized at the same time.

In one embodiment, the silver nanowire (AgNW) may include a coating layer on its surface. For example, the coating layer may be a resin layer surrounding the surface of the silver nanowire (AgNW) strand. In one embodiment, the coating layer may include a resin having a weight average molecular weight of about 10 kg/mol to about 100 kg/mol. For example, the coating layer may include a polyvinylpyrrolidone (PVP) resin, and the weight average molecular weight of the polyvinylpyrrolidone resin may be about 10 kg/mol to about 100 kg/mol. . Through the coating layer, adhesion between the silver nanowire (AgNW) and the substrate including the poly(urethane-urea) resin may be improved, so that the conductive substrate may have excellent durability.

In another embodiment, a conductive substrate; And an electrode on the conductive substrate, wherein the conductive substrate includes a resin substrate; And a conductive layer coated on the resin substrate, wherein the resin substrate includes a poly(urethane-urea) resin, and the conductive layer includes a silver nanowire (AgNW, Ag Nano-Wire). Can provide.

All of the conductive substrate, the resin substrate, and the conductive layer are as described above. That is, the hot sonic loudspeaker includes a conductive substrate including a resin substrate to which the poly(urethane-urea) resin is applied and a conductive layer to which the silver nanowire is applied as a component, thereby implementing excellent durability based on self-healing performance, and at the same time The sound efficiency can be maximized.

A conventional speaker requires a separate accessory component called a diaphragm, and generates sound by relying on its vibration. In contrast, a speaker using a thermoacoustic (TA) loudspeaker can generate sound by heat generated by vibrating the surrounding air without a diaphragm. The hot-sound loudspeaker can implement a performance optimized for a hot-sound speaker through a simple structure in which an electrode thin film is applied to the above-described conductive substrate.

The conductive substrate may vary depending on the use of the hot-sound loudspeaker, but considering the importance of thinning and flexibility of an acoustic device in recent years, the minimum possible thickness on the premise of performance implementation may be about 40 μm or less, for example. For example, it may be about 30 μm or less, for example, about 30 μm or less, and for example, it may be about 15 μm to about 25 μm. Since the minimum thickness for implementing the performance of the conductive substrate satisfies the above range, the hot-sound loudspeaker can be applied to various small devices requiring flexibility and thinness, such as a wearable device.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only intended to specifically illustrate or describe the present invention, and thus the present invention is not limited.

<Examples and Comparative Examples>

Example 1: Preparation of conductive substrate

(1) Synthesis of poly(urethane-urea) resin

A solution of 3.00 g (17.4 mmol) of N,N'-di-tert-butyl ethylene diamine (N,N'-di-tert-butyl ethylene diamine) in 20 mL of 2-butanone was added to 2-butanone. A solution of 7.74 g (34.8 mmol) of isophorone diisocyanate (IPDI) in 10 mL was added dropwise using a dropping funnel, followed by stirring at 35° C. for 2 hours. Then, the stirred solution was added to a solution of 27.8 g of polycarbonate diol (PCD-diol) in 50 mL of 2-butanone, followed by stirring at 70° C. for 1 hour and 150° C. for 30 minutes. Then, the reaction mixture was concentrated using a rotary evaporator under reduced pressure conditions, as a result of which a colorless viscous poly(urethane-urea) resin was obtained. The poly(urethane-urea) resin in Formula 1, R ¹ is pentylene, R ² is hexylene, R ³ , R ⁴ and R ⁵ are methyl groups, R ⁶ is tert-butyl group, n It was a compound of =4.3.

(2) Preparation of resin substrate

The poly(urethane-urea) resin obtained in (1) is poured onto a 130 µm-thick polyethylene naphthalate (PEN) film base material having a size of 2.5 cm 2 x 2.5 cm 2 prepared in advance. The poured poly(urethane-urea) resin is well spread out and stored at room temperature for 20 minutes. Then, it is stored in an oven at 50° C. for 20 minutes. Subsequently, heat treatment was performed at 70° C., 100° C., and 150° C. for 40 minutes (20 minutes temperature rise and 20 minutes temperature maintenance) to prepare a substrate having a thickness of 80 μm including a poly(urethane-urea) resin.

(3) Preparation of conductive layer

The surface of the poly(urethane-urea) resin substrate prepared in (2) was surface-treated for 10 minutes using oxygen plasma having an RF power of 18 W. An average length of 23㎛, an average diameter of 23nm, a solution containing 0.5wt% silver nanowire (AgNW) having a polyvinylpyrrolidone (PVP) coating layer on the surface (nandb Corporation) 200 µl for 60 seconds at 2000 rpm. A conductive layer was prepared by spin coating twice at a spin speed.

Example 2: Preparation of a hot sonic loudspeaker

The surface of the poly(urethane-urea) resin substrate prepared in Example 1 (2) was surface-treated for 10 minutes using oxygen plasma having an RF power of 18 W. A polyimide (PI) tape is applied to the surface of the substrate and divided into 10 zones with an area of 0.1 cm 2 x 2.5 cm 2. A conductive layer was prepared by spin coating 200 µl of a solution containing 0.5 wt% of silver nanowires (AgNW) having an average length of 23 μm and an average diameter of 23 nm (nandb Corporation) for 60 seconds at a spin speed of 2000 rpm. Then, a copper (Cu) electrode having a size of 0.5 cm 2 X 7.5 cm 2 was attached to both ends using an aqueous silver conductive coating agent (SUPER SHIELD, MG Chemicals), and dried for 2 hours. This produced a hot sonic loudspeaker.

Comparative Example 1

In Example 1, a solution containing 0.5 wt% of silver nanowires (AgNW) having an average length of 23 μm and an average diameter of 23 nm on the polyethylene naphthalate (PEN) substrate without a substrate containing a poly(urethane-urea) resin (nandb Coporation) 200 µl was spin-coated twice at a spin speed of 2000 rpm for 60 seconds to prepare a conductive layer.

<Evaluation>

Experimental Example 1: Light transmittance evaluation

For the 210 μm-thick conductive substrate and the resin substrate itself prepared as in Example 1, the light transmittance of 550 nm was measured using a measurement equipment (Technologies, Cary 5000 UV-Vis-NIR spectroscopy). 2 is a graph showing the results. 2, it was confirmed that the resin substrate (Polymer) had a light transmittance of about 85% or more, for example, about 90% or more, for example, about 95% or more at a wavelength of 550 nm. In addition, it was confirmed that the conductive substrate (Polymer/AgNW) of the entire laminated structure formed on the resin substrate to the conductive layer had a light transmittance of about 70% or more, for example, about 75% or more at a wavelength of 550 nm.

Experimental Example 2: Self-healing performance evaluation

With respect to the conductive substrate prepared in Example 1, the surface was scratched with a force of 100 mN or less using a razor blade (ST-300, DORCO), and as shown in FIG. 18, a scratch having a width of 0.75 μm and a depth of 1.00 μm was obtained. gave. Then, it was placed under conditions of a temperature of 95° C. and a relative humidity of 80% to check whether or not self-healing.

3 is a schematic diagram of the self-healing process of the conductive substrate. 3, the substrate including the poly(urethane-urea) resin of the conductive substrate and the conductive layer including silver nanowires (AgNW) through the scratch processing are partially cut and then under a predetermined environment. After being placed for a predetermined period of time, it can be confirmed that it is recombined and self-healing.

4 shows an optical microscope (OM) photograph of the conductive substrate of Example 1 after the scratch processing was placed for 20 minutes at a temperature of 95° C. and a relative humidity of 80%. 4A and 4B, it can be seen that the resin substrate and silver nanowire (AgNW) in the conductive substrate of Example 1 were broken by scratch processing and then recovered again.

FIG. 5 is a graph showing the results of measuring resistance values over time after the scratch processing was placed under conditions of a temperature of 95° C. and a relative humidity of 80%. 5A and 5B, since the silver nanowire (AgNW) is broken by the scratch processing, the resistance is greatly increased, but after that, it is placed under conditions of a temperature of 95°C and a relative humidity of 80%. It can be seen that the self-healing process proceeds over time, and the resistance value gradually recovers to a value approximating the initial resistance value before the scratch process. Referring to FIG. 5, the Rf/Ri value, which is the ratio of the initial resistance value Ri before scratch processing and the resistance value Rf after self-healing for 20 minutes at 95°C temperature and 80% relative humidity condition after the surface scratch processing is It can be confirmed that it is 2.0 or less.

6 is a graph showing a result of self-healing through the recovery of resistance values even after repeatedly performing the scratch processing. Referring to FIG. 6, it was confirmed that the increased resistance value of the conductive substrate of Example 1 was recovered through the self-healing process for all cases where the scratch processing was continuously repeated 5 times.

FIG. 7 is a photograph showing a self-healing process after scratch processing on the conductive substrate of Example 1 through lighting of an LED lamp. The photo of FIG. 7 shows that electricity flowed enough to turn on the LED lamp before scratch processing on the conductive substrate, and after the scratch processing, the silver nanowire (AgNW) was cut off and the resistance value increased and the LED lamp failed to light, but at 95°C. And it is shown sequentially from above that after self-healing for 20 minutes under 80% relative humidity condition, the LED lamps succeeded in lighting again.

3 to 7, the conductive substrate of Example 1 is a poly(urethane-urea) resin substrate and a conductive layer including silver nanowires (AgNW), and thus not only the resin substrate itself, but also silver nanowires (AgNW). ) It was found that the excellent self-healing performance was realized up to the conductive network.

Experimental Example 3: Evaluation of adhesion

With respect to the conductive substrate of Example 1, a resistance value was measured in the process of taping an adhesive tape (3M, Scotch Tape) 1,000 times on its surface, and the substrate containing the poly(urethane-urea) resin and the The interfacial durability between the conductive layers including silver nanowires (AgNW) was confirmed.

8 is an SEM photograph showing a change in the surface of the conductive substrate before and after taping. Referring to FIG. 8, it was confirmed that the silver nanowires (AgNW) on the surface of the conductive substrate were slightly peeled off after taping (b) compared to before (a) taping 1,000 times.

9 is a graph showing a change in resistance value as the number of taping increases. Referring to FIG. 8, as the number of taping on the surface of the conductive substrate increased from 200 to 1,000 times, it was confirmed that the resistance value gradually increased little by little. As a result, it was confirmed that Rx/Ri, which is the ratio of the initial resistance value Ri before taping and the resistance value Rx after 1,000 taping, was less than 3.0, which confirmed that the adhesion durability of silver nanowires (AgNW) to the resin substrate was excellent. It was a possible result.

Experimental Example 4: Evaluation of mechanical properties

The conductive substrate of Example 1 was subjected to a bending test.

(1) Results of bending tests according to the radius of curvature

A first sample having a total thickness of 210 µm and a second sample having a total thickness of 150 µm were prepared and prepared as in Example 1 above. For each sample, a bending test was performed while changing a bending radius from 8mm to 1.4mm, and the result is as shown in the graph shown in FIG. 10. Referring to FIG. 10, for both the first sample and the second sample, the Rm/Ri value, which is the ratio of the initial resistance value Ri before bending and the resistance value Rm after bending with a radius of curvature of 1.4mm, is less than 1.5, for example. For example, it was confirmed that it was 1.3 or less, for example, 1.2 or less.

(2) Results of bending test according to repeated bending

A bending test was performed 10,000 times with a radius of curvature of 5 mm on the conductive substrate having a total thickness of 210 μm prepared as in Example 1. The result is the same as the graph shown in FIG. 11. Referring to FIG. 11, the resistance value was measured by increasing the bending cycles from 2,000 to 10,000 times, and Rt, which is the ratio of the initial resistance value Ri before bending and the resistance value Rt after bending 10,000 times with a radius of curvature of 5 mm. It was confirmed that the /Ri value was less than 2.0, for example, 1.8 or less.

Figure 12 shows that (a) before the bending test, (b) after bending with a radius of curvature of 5 mm, (c) after completing the bending test 10,000 times with a radius of curvature of 5 mm, all the conductive networks of silver nanowires (AgNW) are robust. As a photograph, it was confirmed that the LED lamps can be turned on in all cases (a), (b) and (c) above.

Experimental Example 5: Evaluation of hot sonic amplification performance

With respect to the hot-sound loudspeaker manufactured as in Example 2, the hot-sound loudspeaker performance was evaluated. 13 is a photograph of a sample of the hot-sound loudspeaker prepared in Example 2. FIG. The principle of amplifying the hot sound wave of the sample is as shown in FIG. 14. Referring to FIG. 14, when direct current (DC) and alternating current (AC) voltages are applied at a predetermined frequency, the hot acoustic loudspeaker generates heat by Joule heating. The generated temperature wave vibrates surrounding gas molecules to generate sound waves of a predetermined frequency. 15 is a photograph of an experiment setup for measuring the sound pressure level (SPL) of sound emitted from a hot-sound loudspeaker, and FIG. 16 is a SPL graph for each state of the conductive substrate in each frequency range from 1 kHz to 20 kHz. I did it. The SPL was evaluated at the points of before scratching, after scratching, and after self-healing of the conductive substrate in the hot sonic loudspeaker. The scratch processing and self-healing environmental conditions are as described above with respect to Test Example 2.

This test was conducted in an anechoic room where the ambient noise signal could be neglected. The hot-sound loudspeaker is connected to a function generator and a voltage is applied in a sin waveform. The microphone was placed 2 cm away from the hot sonic loudspeaker to collect sound. Referring to FIG. 16, considering that the noise level is in the range of 28dB to 33dB in a generally quiet room, it can be seen that there is substantially no sound generated immediately after scratch processing. On the other hand, after going through the self-healing process, it showed almost the same SPL as before scratch processing.

FIG. 17 is a photograph showing the resistance measurement values after (a) scratch processing, (b) immediately after scratch processing, and (c) self-healing of the conductive substrates of the hot sonic loudspeaker sequentially from above. As can be seen in FIG. 17, the conductivity disappeared immediately after the scratch processing, but it was confirmed that the resistance value was less than 2.0 times compared to the resistance value (Ri) before the scratch processing after undergoing the self-healing process. That is, in the case of a hot-sound loudspeaker manufactured using the conductive substrate, it can be clearly seen that the ability to restore a conductive network through a self-healing process is realized.

Experimental Example 6: XPS measurement

19A and 19B show XPS data for the conductive substrates of Example 1 and Comparative Example 1, respectively. Referring to FIG. 19, it was confirmed that, unlike Comparative Example 1, in Example 1, a peak corresponding to C-O-(C=0) derived from poly(urethane-urea) appeared in the C 1s peak. In Experimental Examples 1 to 5 described above, it was confirmed that the conductive substrate of Example 1, in which the peak appears, implements excellent performance.

As can be seen from the experimental example, the conductive substrate according to one embodiment includes a conductive layer of silver nanowire (AgNW) on a poly(urethane-urea) resin substrate, thereby implementing a robust conductive network with transparency and flexibility. I can. In this way, when the coated electrode of silver nanowire (AgNW) is damaged by repetitive bending applied to a flexible device or a wearable device, the resistance can be healed up to twice the initial resistance value, and all can be recovered even from continuous damage. Can have.

Further, in the case of the hot acoustic loudspeaker to which the conductive substrate is applied, sound from 1 kHz to 20 kHz can be generated with an SPL of 50 dB or more before and after damage. In addition, the hot-sound loudspeaker can simplify an existing complex structure and maximize the performance of thinning and miniaturization to provide an advanced type of speaker application.

Claims (8)

Resin substrate; And a conductive layer coated on the resin substrate,
The resin substrate comprises a poly (urethane-urea) resin,
The conductive layer comprises a silver nanowire (AgNW, Ag Nano Wire),
Conductive substrate.
The method of claim 1,
The poly(urethane-urea) resin has the structure of the following formula (1),
Conductive substrate.
[Formula 1]

In Chemical Formula 1,
The R ¹ and R ² are each independently a linear or branched alkylene group having 1 to 20 carbon atoms, a linear or branched heteroalkylene group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkylene group having 5 to 30 carbon atoms , Is one selected from a substituted or unsubstituted arylene group having 5 to 30 carbon atoms,
The R ³ , R ⁴ and R ⁵ are each independently hydrogen, a linear or branched alkyl group having 1 to 20 carbon atoms, a linear or branched heteroalkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted group having 5 to 30 carbon atoms Is one selected from a cycloalkyl group, a substituted or unsubstituted aryl group having 5 to 30 carbon atoms,
R ⁶ is a branched alkyl group having 3 to 10 carbon atoms,
Wherein n is 1 to 10,
Conductive substrate.
The method of claim 1,
The conductive layer is a three-dimensional network structure of the silver nanowire,
Conductive substrate.
The method of claim 1,
The resin substrate has a light transmittance of 85% or more at a wavelength of 550 nm,
Light transmittance of 70% or more at 550nm wavelength of the entire stacked structure,
Conductive substrate.
The method of claim 1,
With the initial resistance value Ri,
The ratio of the resistance value Rf after self-healing for 20 minutes at 95°C temperature and 80% relative humidity condition after surface scratch processing with a width of 0.75 μm and a depth of 1.00 μm,
Rf/Ri value is 2.0 or less,
Conductive substrate.
The method of claim 1,
With the initial resistance value Ri,
The ratio of the resistance value Rt after 10,000 bending tests with a radius of curvature of 5 mm,
Rt/Ri value is 2.0 or less,
Conductive substrate.
A conductive substrate; And an electrode on the conductive substrate,
The conductive substrate is a resin substrate; And a conductive layer coated on the resin substrate,
The resin substrate comprises a poly (urethane-urea) resin,
The conductive layer comprises a silver nano-wire (AgNW, Ag Nano-Wire),
Hot sonic loudspeaker.
The method of claim 7,
The sound pressure level (SPL, Sound Pressure Level) generated after self-healing for 20 minutes at 95°C temperature and 80% relative humidity conditions after surface scratch processing with a width of 0.75 μm and a depth of 1.00 μm of the conductive substrate ranges from 1 kHz to 20 kHz. More than 50dB at,
Hot sonic loudspeaker.

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