KR20220089249A - Multilayer stretchable substrate, method for preparing the same, and electronic device comprising the same - Google Patents

Abstract

A substrate capable of mass production and excellent in reliability and elasticity, a method for manufacturing the same, and an electronic device including the same are provided. The multilayer stretchable substrate according to an exemplary embodiment of the present invention includes lower and upper flexible layers and a rigid layer having an oxetic structure disposed therebetween, and may be manufactured by a process using a mold. In addition, an electronic device including a multilayer stretchable substrate may include a solar cell.

Description

Multilayer stretchable substrate, method for manufacturing same, and electronic device comprising same

The present invention relates to a multilayer stretchable substrate, a method for manufacturing the same, and an electronic device including the same. More particularly, it relates to a multilayer stretchable substrate suitable for mass production and excellent in stretchability and reliability, a manufacturing method thereof, and an electronic device including the same.

Recently, flexible electronic devices have been in the spotlight. Since these electronic devices can be bent or bent more freely than conventional electronic devices, they are receiving great spotlight in the field of display and bio-engineering. Since such a flexible electronic device is formed on a flexible substrate, when the substrate is stretched or compressed, it is stretched or compressed accordingly. This is because, when a general elastic body receives a physical force such as tensile, bending, or twisting from the outside, the degree of deformation of the elastic body is uniform over the entire section and has isotropic properties.

Meanwhile, following flexible electronic devices, demand for stretchable electronic devices such as wearable devices is increasing.

A general material, that is, a non-auxetic material, stretches in a corresponding direction when a stress is applied therein, and at the same time contracts in a vertical direction. Therefore, the Poisson's ratio, which means the ratio between the transverse strain and the longitudinal strain due to the normal stress generated inside the material, has a positive number.

In particular, in the case of a stretchable display, having a positive Poisson's ratio may be undesirable because the image on the screen is distorted.

Conversely, a material having an oxetic structure may be elongated in both the corresponding direction and the perpendicular direction when a stress is applied therein, so that the Poisson's ratio may be very small or may have a negative number.

However, there are various difficulties in actually realizing a stretchable electronic device using a material having an oxetic structure having a small Poisson's ratio.

For example, if electrical wiring with low elasticity is formed on a substrate with higher elasticity than that, and tensile force is applied to the substrate, electrical wiring with low elasticity compared to the elasticity of the substrate does not stretch to the same extent as the substrate is stretched, Stress is applied to the wiring, resulting in physical damage such as cracks.

Accordingly, an electronic device or an electric device electrically connected by electrical wiring does not operate stably. Such a case may occur when not only electrical wiring but also an electronic device having a different elasticity from the substrate is formed on a stretchable substrate and an external force is applied to the substrate, and stable operation of the electronic device formed on the stretchable substrate cannot be guaranteed.

On the other hand, in the case of Patent Document 1, a flexible substrate having a different deformation rate due to an external force is manufactured by printing a curable polymer on a stretchable substrate and curing it to form a deformation rate control pattern. However, in this case, since it is not easy to form the strain control pattern with a uniform size and spacing, there is a problem that is not suitable for mass production.

In addition, since the curable polymer for forming the strain control pattern must be printable, there may be restrictions in material selection.

In the case of Patent Document 2, there is disclosed a conductive flexible device having an oxetic structure inserted into the substrate. This conductive flexible device has an effect of reducing the Poisson's ratio between the substrate material and the electrode material, but the oxetic structure is provided on the substrate. It is not easy to carry out in the case of inserting the oxetic structure, and when the oxetic structure is placed on glass and then filled with PDMS, the oxetic structure is not located in the center of the cross-section of the substrate, so that the elasticity of the substrate may vary depending on the position.

Korean Patent Publication No. 10-2015-0077899 Korean Patent Publication No. 2018-0061003

SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer stretchable substrate in which patterning of an oxetic structure is varied and high in accuracy, and anisotropically stretched even after repeated stretching and relaxation, and an electronic device including the same.

Another object of the present invention is to provide a method for manufacturing a multilayer stretchable substrate capable of mass production through a simple process.

Objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, a lower flexible layer comprising a first polymer compound;

an upper flexible layer comprising a second polymer compound; and

A multilayer stretchable substrate comprising a; a rigid layer positioned between the lower flexible layer and the upper flexible layer and having an oxetic structure, the rigid layer comprising a third polymer compound,

The substrate is provided with a multilayer stretchable substrate satisfying Equation 1 below:

<Equation 1>

In Equation 1 above,

는 상기 기판의 포아송비로서, 0.4 이하의 값이고,

is the Poisson's ratio of the substrate, and is a value of 0.4 or less,

x ₁ is the ratio of the total thickness of the lower flexible layer and the upper flexible layer to the thickness of the rigid layer,

x ₂ is the ratio of the Young's modulus of the rigid layer to the average Young's modulus of the lower flexible layer and the upper flexible layer.

According to another aspect of the present invention, preparing a mold having an oxetic pattern;

Preparing a composition for forming a rigid layer comprising a third polymer compound and a third curing agent;

preparing a rigid layer having an oxetic structure by applying the composition for forming a rigid layer on the mold;

forming a lower flexible layer by applying a composition for forming a first flexible layer including a first polymer compound and a first curing agent on the rigid layer;

separating the rigid layer on which the lower flexible layer is formed from the mold; and

forming an upper flexible layer by applying a composition for forming an upper flexible layer including a second polymer compound and a second curing agent on the opposite side of the rigid layer on which the lower flexible layer is formed;

There is provided a method of manufacturing a multilayer stretchable substrate comprising a.

According to another aspect of the present invention, the multi-layer stretchable substrate; and

An electrode part positioned on the stretchable substrate is provided.

According to one embodiment of the present invention, it is possible to manufacture a multilayer stretchable substrate having excellent durability and reliability in repeated stretching and an electronic device including the same.

In addition, according to another embodiment of the present invention, it is possible to mass-produce a multilayer stretchable substrate through a simple process.

1A is a schematic cross-sectional view of a multilayer stretchable substrate according to an embodiment of the present invention, and FIG. 1B is a schematic front view of the multilayer stretchable substrate according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a multilayer stretchable substrate according to another embodiment of the present invention.
3 is a view showing step-by-step a method of manufacturing a multilayer stretchable substrate according to an embodiment of the present invention.
4 is a diagram schematically illustrating a stretchable electronic device according to an embodiment of the present invention.
5 is a photograph of a sample prepared according to an embodiment of the present invention.
6 is a photograph of a sample for the repeated stretching durability test.
7A and 7B are photographs showing the results of the repeated stretching durability test.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and these embodiments merely allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

Hereinafter, specific contents for carrying out the present invention will be described in detail with reference to the accompanying drawings. Regardless of the drawings, like reference numbers refer to like elements.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, "comprises" or "comprising" does not exclude the presence or addition of one or more other elements in addition to the stated elements.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly defined in particular.

In this specification, terms such as “first” and “second” are for distinguishing one component from other components, and the scope of rights is not limited by these terms. Also, the first component may be referred to as a second component, and the second component may also be referred to as a first component.

As used herein, "polymer" may mean a polymer after curing or a polymer before curing, depending on the context.

The singular expression is to be understood as including the plural expression unless the context clearly dictates otherwise.

Each step may occur in a different order than the stated order unless the context clearly dictates a specific order. That is, each step may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

The drawings referenced to describe the embodiments in this specification are intentionally exaggerated in size, height, thickness, etc. for convenience of description and ease of understanding, and are not absolutely enlarged or reduced in proportion. Also, any one of the components shown in the drawings may be intentionally reduced and expressed, and other elements may be intentionally enlarged and expressed.

Spatially relative terms "below", "lower", "above", "upper", etc. may be used to easily describe the correlation between one component and other components as shown in the drawings. have. Spatially relative terms should be understood as terms including different directions of components during use or operation in addition to the directions shown in the drawings. For example, when a component illustrated in the drawings is turned over, a component described as “below” another component may be placed “above” the other component. Accordingly, the exemplary term “below” may include both directions below and above. Components may also be oriented in other orientations, and thus spatially relative terms may be interpreted according to orientation.

On the other hand, other expressions describing the relationship between the elements, that is, “between” includes that other elements may exist between the elements as well.

A multilayer stretchable substrate according to an aspect of the present invention includes a lower flexible layer including a first polymer compound; an upper flexible layer comprising a second polymer compound; and a rigid layer positioned between the lower flexible layer and the upper flexible layer and having an oxetic structure, the rigid layer including a third polymer compound, wherein the stretchable substrate satisfies Equation 1 below. This is provided:

<Equation 1>

In Equation 1 above,

는 상기 기판의 포아송비로서, 0.4 이하의 값이고,

is the Poisson's ratio of the substrate, and is a value of 0.4 or less,

x ₁ is the ratio of the total thickness of the lower flexible layer and the upper flexible layer to the thickness of the rigid layer,

x ₂ is the ratio of the Young's modulus of the rigid layer to the average Young's modulus of the lower flexible layer and the upper flexible layer.

The multilayer stretchable substrate according to an embodiment of the present invention satisfies Equation 1, so that when an external force is applied from an electric or electronic device on which an electrode or wiring is positioned on the substrate, biaxial deformation control can be smoothly performed.

1A is a schematic cross-sectional view of a multilayer stretchable substrate according to an embodiment of the present invention, and FIG. 1B is a schematic front view of the multilayer stretchable substrate according to an embodiment of the present invention.

1A and 1B , the multilayer stretchable substrates 1a and 1b may include lower flexible layers 11a and 11b; Rigid layers 13a and 13b having an oxetic structure positioned thereon; and upper flexible layers 12a and 12b positioned on the rigid layers 13a and 13b.

According to one embodiment of the present invention, the first polymer compound and the second polymer compound may be the same or different, for example, may be the same.

Also, for example, the first polymer compound is included in the upper flexible layer and the second polymer compound is included in the lower flexible layer, or the first polymer compound is included in the lower flexible layer and the second polymer compound is included in the lower flexible layer. It may be included in the upper flexible layer.

According to one embodiment of the present invention, the first polymer compound and the second polymer compound are not particularly limited as long as they are polymers having elasticity, and each independently at least one selected from porous PDMS, S3-PDMS, PDMS, and EcoFlex. can For example, it may be at least one selected from porous PDMS, S3-PDMS, EcoFlex 00-30, and EcoFlex 00-10.

In Equation 1, x ₁ may be 0.4 or more and 2 or less, 0.4 or more and 1 or less, 0.25 or more 1 or less, 0.3 or more and 1 or less, 0.3 or more and 0.9 or less, 0.4 or more and 0.9 or less, and 0.4 or more and 1 or less, and x ₂ may be 1 or more and 100 or less, 1 or more and 10 or less, 2 or more and 10 or less, and 2 or more and 8 or less.

When x ₁ and x ₂ are within the above ranges, the multilayer stretchable substrate may have a desired thickness and stretchability of a substrate suitable for manufacturing an electronic device while having a desired Poisson's ratio.

는 예를 들어 0.38 이하, 0.35 이하, 0.20 이하, 0.15 이하, 0 이하, -0.1 이하일 수 있다. 상기 범위 내에 드는 경우, 신축성 기판으로서 특히, 디스플레이 장치의 신축성 기판으로 사용하기에 적합할 수 있다.In Equation 1 above,

may be, for example, 0.38 or less, 0.35 or less, 0.20 or less, 0.15 or less, 0 or less, -0.1 or less. When it falls within the above range, the stretchable substrate may be particularly suitable for use as a stretchable substrate of a display device.

According to one embodiment of the present invention, the third polymer compound may be the same as or different from the first and second polymer compounds, for example, may be different.

The third polymer compound is not particularly limited, but may be at least one selected from a polydimethylsiloxane (PDMS) compound, a polyurethane (PU) compound, polymethyl methacrylate (PMMA), and polyimide (PI).

According to an embodiment of the present invention, the thickness of the rigid layer may be 300 μm or more and 800 μm or less, 300 μm or more and 700 μm or less, and 400 μm or more and 700 μm or less, and the thickness of the flexible layer is 200 μm or more and 500 μm, respectively. Below, 300 μm or more and 500 μm or less, 350 μm or more and 500 μm or less. When it falls within the above range, it can be suitable as a substrate for an electronic device, and the anisotropic strain can be controlled as desired.

According to one embodiment of the present invention, the upper flexible layer and the lower flexible layer may have a Young's modulus of 0.1 MPa or more and 1 MPa or less, 0.2 MPa or more and 0.9 MPa or less, and 0.3 MPa or more and 0.9 MPa or less, respectively. When it falls within the above range, it may be easy to control the anisotropic strain of the multilayer stretchable substrate due to the difference in the elastic modulus with the rigid layer.

According to one embodiment of the present invention, the Young's modulus of the rigid layer may be 1 MPa or more and 10 MPa or less.

Poisson's ratio of the rigid layer is 0.3 or more and 0.5 or less, 0.35 or more and 0.5 or less, 0.35 or more and 0.45 or less, and the Poisson's ratio of the lower flexible layer and the upper flexible layer are each independently, for example, 0.3 or more and 0.5 or less, 0.35 or more and 0.5 or less, it may be 0.35 or more and 0.45 or less.

According to one embodiment of the present invention, the rigid layer has an oxetic structure, and has a higher elastic modulus than the flexible layer, so that the anisotropic strain of the multilayer stretchable substrate can be effectively controlled.

According to one embodiment of the present invention, the oxetic structure may be a wavy bowtie structure. By controlling the pattern of the oxetic structure, the Poisson's ratio of the rigid layer may be adjusted.

According to one embodiment of the present invention, the multilayer stretchable substrate may include one or more layers of the upper flexible layer.

According to an embodiment of the present invention, the lower flexible layer may have a microstructure on the surface opposite to the rigid layer. By having such a microstructure, heat dissipation performance can be improved. In addition, a superhydrophobic polymer layer may be additionally included on the surface having the microstructure. In this case, the waterproof performance can be improved.

In addition, the multilayer stretchable substrate may further include one or more reliability layers on the upper flexible layer.

2 is a schematic cross-sectional view of a multilayer stretchable substrate according to another embodiment of the present invention.

Referring to FIG. 2 , the multilayer stretchable substrate 2 includes a lower flexible layer 21 ; a rigid layer 23 having an oxetic structure positioned thereon; an upper flexible layer 22 positioned on the rigid layer 23; and a reliability layer 24 located on the upper flexible layer 22 .

The reliability layer may have at least one of a heat dissipation function and a waterproof function.

When the reliability layer has a heat dissipation function, it may include metal nanowires, for example, silver nanowires.

When the reliability layer has a waterproof function, it may include a hydrophobic polymer. The hydrophobic polymer may be, for example, at least one selected from paraffin wax, candelilla wax, and bees wax.

The oxetic structure formed in the rigid layer according to an embodiment of the present invention can be modeled to implement an optimal Poisson's ratio through computational statistics.

According to another aspect of the present invention, there is provided a method for manufacturing a multilayer stretchable substrate, the method comprising: preparing a mold having an oxetic pattern; Preparing a composition for forming a rigid layer comprising a third polymer and a third curing agent; preparing a rigid layer having an oxetic structure by applying the composition for forming a rigid layer on the mold; forming a lower flexible layer by applying a composition for forming a first flexible layer including a first polymer and a first curing agent on the rigid layer; separating the rigid layer on which the lower flexible layer is formed from the mold; and forming an upper flexible layer by applying a composition for forming an upper flexible layer including a second polymer and a second curing agent on the opposite side of the rigid layer on which the lower flexible layer is formed.

3 is a view showing step-by-step a method of manufacturing a multilayer stretchable substrate according to an embodiment of the present invention.

Hereinafter, a method of manufacturing a multilayer stretchable substrate will be described in more detail with reference to FIG. 3 .

Referring to FIG. 3A , first, a mold having an oxetic pattern is prepared.

The mold having the oxetic pattern can be used repeatedly, and as long as the oxetic pattern can be implemented in various ways, there is no particular limitation in the manufacturing method or material thereof. For example, the mold having the oxetic pattern may be formed by cutting, and may be made of one or more materials selected from brass, aluminum, bakelite, and SU-8/silicon wafer.

The oxetic pattern may be formed in various shapes according to a desired unit pattern, spacing, height, and the like. The oxetic pattern is ultimately for forming an oxetic structure of the rigid layer of the multilayer stretchable substrate. That is, it means that the groove is formed to correspond to the oxetic structure of the rigid layer of the multilayer stretchable substrate.

Then, a composition for forming a rigid layer including a third polymer compound and a third curing agent is prepared.

As shown in (b) of FIG. 3, a rigid layer is formed by coating the composition for forming a rigid layer on the mold. The composition for forming the rigid layer may be applied so that the thickness of the rigid layer is equal to or less than the height of the oxetic pattern of the mold.

According to an embodiment of the present invention, the method may further include forming a self-assembled monolayer before applying the composition for forming a rigid layer on the mold.

By forming the self-assembled monolayer, the subsequent separation of the rigid layer and the mold can be easily achieved.

The composition for forming the self-assembled monolayer is not particularly limited, and, for example, a mixed solution of hexane and trichloro(octadecyl)silane may be used.

As shown in FIG. 3C , after the rigid layer is formed, a composition for forming a first flexible layer including a first polymer and a first curing agent is applied thereon to form a lower flexible layer.

Then, as shown in FIG. 3D , the rigid layer on which the lower flexible layer is formed is separated from the mold.

Thereafter, as shown in FIG. 3E , an upper flexible layer is formed by applying a composition for forming an upper flexible layer including a second polymer and a second curing agent on the opposite side of the rigid layer on which the lower flexible layer is formed. .

According to one embodiment of the present invention, the first to third polymer compounds mean the same as those described in the multilayer stretchable substrate, respectively.

According to one embodiment of the present invention, in the composition for forming the first flexible layer and the composition for forming the second flexible layer, the thickness of the lower flexible layer and the upper flexible layer is 200 μm or more and 500 μm or less, 300 μm or more and 500 μm, respectively. Hereinafter, it may be applied so as to be 350 μm or more and 500 μm or less.

The composition for forming the first flexible layer, the composition for forming the second flexible layer, and the composition for forming the rigid layer may further include a photoinitiator to control the polymerization degree during photocuring. The type of the photoinitiator is not particularly limited as long as it can initiate a polymerization reaction by generating a radical by irradiation with light, and for example, a benzoin-based initiator, a hydroxyketone-based initiator, an aminoketone-based initiator, and a caprolactam selected from There may be more than one type.

According to one embodiment of the present invention, in the composition for forming the first flexible layer, the composition for forming the second flexible layer, and the composition for forming the rigid layer, the first polymer to the third polymer are visible light, ultraviolet (UV, Ultra-Violet) In the case of a photocurable polymer that is cured by light, such as, it can be cured by irradiating visible light or ultraviolet rays. At this time, each composition may be completely cured immediately after application, or semi-cured after application of the composition for forming a rigid layer and the composition for forming the first flexible layer, and finally cured at once.

In addition, when the first to third polymers are thermosetting polymers cured by heat, they can be cured by applying heat. After applying the composition for forming the first flexible layer, it may be semi-cured and finally cured all at once.

Here, “semi-cured” refers to a state having an additionally curable site.

For example, the forming of the lower flexible layer may include semi-curing the composition for forming the first flexible layer. In addition, the forming of the upper flexible layer may include completely curing the composition for forming the second flexible layer.

The composition for forming the first flexible layer, the composition for forming a rigid layer, and the composition for forming the second flexible layer may each independently be cured at a temperature of 80° C. or more and 120° C. or less for 20 minutes or more and 40 minutes or less.

According to one embodiment of the present invention, the first to third curing agents may be photocuring agents or thermosetting agents depending on the type of polymer. Although not particularly limited, the first to third curing agents may each independently be at least one selected from a hexanediol diacrylate-based curing agent, a urethane acrylate-based curing agent, an epoxy-based curing agent, a metal chelate-based curing agent, and an isocyanate-based curing agent. have.

Epoxy-based curing agents include ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, N', N'-tetraglycidyl ethylenediamine and glycerin diglycidyl ether. It may be one or more selected. The isocyanate-based curing agent may be at least one selected from tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, tetramethylxylene diisocyanate, and naphthalene diisocyanate.

The composition for forming the lower flexible layer and the composition for forming the lower flexible layer may include the first polymer compound and the first curing agent, and the second polymer compound and the second curing agent in a weight ratio of 20:1 or 30:1, respectively. have.

The composition for forming the rigid layer may include the third polymer compound and the third curing agent in a weight ratio of 10:1 or 5:1.

According to one embodiment of the present invention, in order to improve the interlayer bonding strength of the upper flexible layer, the rigid layer, and the lower flexible layer, a conventional process such as UV treatment or acid treatment may be additionally included in each layer before lamination.

According to one embodiment of the present invention, the method may further include forming a reliability layer by applying a composition for forming a reliability layer on the upper flexible layer.

The composition for forming the reliability layer refers to a composition for forming the reliability layer as described in the multilayer stretchable substrate.

According to another aspect of the present invention, there is provided a stretchable electronic device comprising: the multilayer stretchable substrate; and an electrode part positioned on the stretchable substrate.

According to one embodiment of the present invention, the electrode part may include a wire-shaped one having an electrode pattern, and may be made of a metal material such as Au, Ag, Al, Cu, Ti.

According to one embodiment of the present invention, the stretchable electronic device can be mass-produced, and has excellent interfacial bonding strength, so that even when used repeatedly, durability can be excellent.

4 is a diagram schematically illustrating a stretchable electronic device according to an embodiment of the present invention.

In the multilayer stretchable substrate 4 of FIG. 4 , the rigid layer 43 is positioned between the upper flexible layer 41 and the lower flexible layer 42 . In addition, there is a layer in which silver nanowires are dispersed as a reliability layer 44 having a heat dissipation function on the upper flexible layer 41 . The lower flexible layer 42 has a microstructure on the opposite side to the side in contact with the rigid layer 43 , and the superhydrophobic polymer layer 45 is present thereon. The electrode part 48 and the device 49 are positioned on the multilayer stretchable substrate 4 to form a stretchable electronic device.

According to one embodiment of the present invention, the stretchable electronic device may be a solar cell. In the case of a solar cell, the stretchable electronic device may include a photoactive layer; and an encapsulation film.

The material of the photoactive layer and the encapsulation film is not particularly limited, and can be used as long as it is used in the field of solar cells. The electronic device according to an embodiment of the present invention includes a multi-layer stretchable substrate, so that the multi-layer stretchable substrate has excellent elasticity, and thus the electrode part, the photoactive layer and the encapsulation film positioned thereon can also be stretched and stretched according to the anisotropic stretching of the stretchable substrate. It can be used as a battery.

Hereinafter, the present invention will be described in more detail through examples.

Example 1: Preparation of a multilayer stretchable substrate

ingredient:

Composition for forming the second flexible layer and the composition for forming the first flexible layer (Purchase: Dow Chemical Company, trade name: sylgard 184, PDMS: curing agent = 10:1 mass ratio)

Composition for forming a rigid layer: EcoFlex (place of purchase: SMOOTH-ON, trade name: Ecoflex 00-30)

process:

mold manufacturing

An oxetic pattern was formed in a mold (material: aluminum, size: 200mm*100mm) to a depth of 500㎛ by cutting method.

Formation of self-assembled monolayer

The mold prepared above was immersed in a solution of n-hexane (from DAEJUNG) and trichloro (octadecyl) silane (from Sigma-Aldrich) in a volume ratio of 60mL:100uL for 2 hours. Then, the mold was taken out and washed sequentially with isopropyl alcohol and deionized water to form a self-assembled monolayer on the mold surface.

Formation of rigid layer

The composition for forming the rigid layer was poured into the mold on which the self-assembled monolayer was formed, and the surface of the composition was pushed with a flat plastic plate so that only the grooves of the mold were filled with the composition to form the rigid layer.

Formation of lower flexible layer

The composition for forming the first flexible layer was poured on the rigid layer and stacked to a desired thickness using a film coater. Then, thermosetting was performed at 100° C. for 30 minutes.

mold removal

The lower flexible layer and the rigid layer after the curing were removed from the mold, and then turned over.

Formation of upper soft layer

A composition for forming a second flexible layer was poured on the inverted rigid layer and stacked to a desired thickness using a film coater. after that. Thermal curing was performed at 100° C. for 30 minutes.

Reliability layer formation

An isopropyl alcohol dispersion (0.5 wt% silver nanowires) of silver nanowires (manufacturer name: Sigma-Aldrich, product name: Silver nanowires) was spray-coated on the upper flexible layer where the curing was completed, and then, at 200°C and 2G pressure for 10 minutes during thermal compression.

Examples 2 and 3

A multilayer stretchable substrate was manufactured in the same manner as in Example 1, except that the thickness ratio and Young's modulus ratio of the rigid layer and the flexible layer were changed as shown in Table 1 below.

Comparative Example 1 and Comparative Example 2

A multilayer stretchable substrate was manufactured in the same manner as in Example 1, except that the thickness ratio and Young's modulus ratio of the rigid layer and the flexible layer were changed as shown in Table 1 below.

For the multilayer stretchable substrates prepared in Examples 1 to 3 and Comparative Examples 1 and 2, Poisson's ratio and Young's modulus were measured as follows. 5 is a photograph of a sample of the multilayer stretchable substrate prepared in Example 1 of the present invention.

Poisson's ratio measurement

While tensile strength testing equipment (INSTRON MODEL 3343, LOAD CELL: MAX LOAD 500N) was used to tension the sample of the embodiment of the present invention, the strain rate was measured by measuring the distance between the recognition points (indicated by red dots) in the sample shown in FIG. was calculated. From this, Poisson's ratio was measured.

Young's modulus measurement

The Poisson's ratio according to the thickness ratio and Young's modulus ratio of the rigid layer and the flexible layer was calculated for the multilayer stretchable substrate prepared in the above example, and it is shown in Table 1 below.

is the ratio of the total thickness of the lower flexible layer and the upper flexible layer to the thickness of the rigid layer,

x ₂ is the ratio of the Young's modulus of the rigid layer to the average Young's modulus of the lower flexible layer and the upper flexible layer.

The ratio of the total thickness of the lower flexible layer and the upper flexible layer to the thickness of the rigid layer
(x ₁ ) The ratio of the Young's modulus of the rigid layer to the average Young's modulus of the lower and upper flexible layers
(x ₂ ) Poisson's ratio of the substrate
Example 1 400:500 (x ₁ =0.8) 10:1 (x ₂ =10) 0.175 (experimental value) Example 2 700:500 (x ₁ =1.4) 10:1 (x ₂ =10) 0.185 (experimental value) Example 3 1000:500 (x ₁ =2) 10:1 (x ₂ =10) 0.193 (calculated value) Comparative Example 1 500:500 (x ₁ =1) 1:10 (x ₂ =0.1) 0.7737 (calculated) Comparative Example 2 500:500 (x ₁ =1) 1:5 (x ₂ =0.2) 0.6252 (calculated)

As can be seen in Table 1, it can be seen that the multilayer stretchable substrate according to the embodiment of the present invention can be anisotropically deformed with a Poisson's ratio of 0.4 or less when Equation 1 is satisfied.

Repeat Stretching Durability Test

For the multilayer stretchable substrate prepared according to Example 2, a specimen was prepared as shown in FIG. 7, and a repeated stretching durability test was performed in the tensile strength test equipment according to the conditions of Table 2 below. 6 is a photograph of a sample for the repeated stretching durability test.

The results are shown in Table 2 and FIG. 7 below. 7A and 7B are photographs showing the results of the repeated stretching durability test.

Tensile rate (%) Tensile Rate (Hz) Temperature (℃) number of seals Whether peeling One 30 One room temperature 10,000 X 2 30 One room temperature 30,000 X 3 30 One room temperature 100,000 X 4 30 1/60 85 100 X

As can be seen in Table 2, in the multilayer stretchable substrate according to the exemplary embodiment of the present invention, peeling did not occur even during repeated stretching. In addition, as shown in FIGS. 7A and 7B , it can be confirmed that peeling did not occur because there was no change in the number and size of pores in the sample before and after repeated stretching.

Although embodiments of the present invention have been described with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can realize that the present invention can be embodied in other specific forms without changing its technical spirit or essential features. you will be able to understand Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

1a, 1b, 2, 3, 4: Multi-layer stretchable substrate
11a, 11b, 21, 31, 41: lower flexible layer
12a, 12b, 22, 32, 42: upper flexible layer
13a, 13b, 23, 33, 43: rigid layer
30: mold
24, 34, 44: reliability layer
36: plastic plate
37: film coater
45: superhydrophobic polymer layer
48: electrode part
49: element

Claims (33)

a lower flexible layer comprising a first polymer compound;
an upper flexible layer comprising a second polymer compound; and
A multilayer stretchable substrate comprising a; a rigid layer positioned between the lower flexible layer and the upper flexible layer, the rigid layer having an oxetic structure, and including a third polymer compound,
The substrate is a multilayer stretchable substrate satisfying Equation 1 below:
<Equation 1>

In Equation 1 above,

is the Poisson's ratio of the substrate, and is a value of 0.4 or less,
x ₁ is the ratio of the total thickness of the lower flexible layer and the upper flexible layer to the thickness of the rigid layer,
x ₂ is the ratio of the Young's modulus of the rigid layer to the average Young's modulus of the lower flexible layer and the upper flexible layer.
The method according to claim 1,
Wherein x ₁ is 0.4 or more and 2 or less of the multilayer stretchable substrate.
The method according to claim 1,
wherein x ₂ is 1 or more and 100 or less of the multilayer stretchable substrate.
The method according to claim 1,
The third polymer compound is a multilayer stretchable substrate comprising at least one selected from polydimethylsiloxane, polyurethane, polymethyl methacrylate, and polyimide.
The method according to claim 1,
The first polymer compound and the second polymer compound are each independently at least one selected from porous PDMS, S3-PDMS, PDMS, EcoFlex 00-30, and EcoFlex 00-10.
The method according to claim 1,
The oxetic structure is a multilayer stretchable substrate having a wavy bowtie structure.
The method according to claim 1,
A thickness of the lower flexible layer and a thickness of the upper flexible layer are each independently 200 μm or more and 500 μm or less.
The method according to claim 1,
A thickness of the rigid layer is 300 μm or more and 800 μm or less.
The method according to claim 1,
The Young's modulus of the upper flexible layer and the lower flexible layer are each independently 0.1 MPa or more and 1 MPa or less.
The method according to claim 1,
The Young's modulus of the rigid layer is 1 MPa or more and 10 MPa or less.
The method according to claim 1,
A Poisson's ratio of the rigid layer is 0.3 or more and 0.5 or less, and the Poisson's ratio of the lower flexible layer and the upper flexible layer are each independently 0.3 or more and 0.5 or less.
The method according to claim 1,
A multilayer stretchable substrate further comprising one or more reliability layers on the upper flexible layer.
13. The method of claim 12,
The reliability layer is a multilayer stretchable substrate having at least one of a heat dissipation function and a waterproof function.
14. The method of claim 13,
The reliability layer is a multilayer stretchable substrate including metal nanowires.
14. The method of claim 13,
The reliability layer is a multilayer stretchable substrate including a hydrophobic polymer.
16. The method of claim 15,
wherein the hydrophobic polymer is at least one selected from paraffin wax, candelilla wax, and beeswax.
Preparing a mold having an oxetic pattern;
Preparing a composition for forming a rigid layer comprising a third polymer compound and a third curing agent;
preparing a rigid layer having an oxetic structure by applying the composition for forming a rigid layer on the mold;
forming a lower flexible layer by applying a composition for forming a first flexible layer including a first polymer compound and a first curing agent on the rigid layer;
separating the rigid layer on which the lower flexible layer is formed from the mold; and
forming an upper flexible layer by applying a composition for forming an upper flexible layer including a second polymer compound and a second curing agent on the opposite side of the rigid layer on which the lower flexible layer is formed;
A method of manufacturing a multilayer stretchable substrate comprising a.
18. The method of claim 17,
The multilayer stretchable substrate is a method of manufacturing a multilayer stretchable substrate satisfying Equation 1 below:
<Equation 1>

In Equation 1 above,

is the Poisson's ratio of the substrate, and is a value of 0.4 or less,
x ₁ is the ratio of the total thickness of the flexible layer to the thickness of the rigid layer,
x ₂ is the ratio of the Young's modulus of the rigid layer to the average Young's modulus of the lower flexible layer and the upper flexible layer.
18. The method of claim 17,
A method for manufacturing a multilayer stretchable substrate wherein the mold having the oxetic pattern is formed by cutting.
18. The method of claim 17,
The method for manufacturing a multilayer stretchable substrate wherein the mold having the oxetic pattern is made of at least one material selected from brass, aluminum, bakelite and SU-8/silicon wafer.
18. The method of claim 17,
The first polymer compound and the second polymer compound are each independently selected from porous PDMS, S3-PDMS, EcoFlex 00-30, and EcoFlex 00-10.
18. The method of claim 17,
The third polymer compound is a method of manufacturing a multilayer stretchable substrate at least one selected from polydimethylsiloxane, polyurethane, polymethyl methacrylate and polyimide.
18. The method of claim 17,
The composition for forming a rigid layer is a method of manufacturing a multilayer stretchable substrate in which the thickness of the rigid layer is applied to be less than or equal to the height of the oxetic pattern of the mold.
18. The method of claim 17,
The method for manufacturing a multilayer stretchable substrate, wherein the first flexible layer-forming composition and the second flexible layer-forming composition are applied such that the thickness of the lower flexible layer and the upper flexible layer is 200 μm or more and 500 μm or less, respectively.
18. The method of claim 17,
The first to third curing agents are each independently selected from an isocyanate-based curing agent, an epoxy-based curing agent, a metal chelate-based curing agent, and an aziridine-based curing agent.
18. The method of claim 17,
The forming of the lower flexible layer may include semi-curing the composition for forming the first flexible layer.
18. The method of claim 17,
The forming of the upper flexible layer may include completely curing the composition for forming the second flexible layer.
18. The method of claim 17,
The composition for forming the first flexible layer, the composition for forming a rigid layer, and the composition for forming the second flexible layer are each independently cured at a temperature of 80°C or higher and 120°C or lower for 20 minutes or more and 40 minutes or less. manufacturing method.
18. The method of claim 17,
The method of manufacturing a multilayer stretchable substrate further comprising the step of forming a reliability layer by applying a composition for forming a reliability layer on the upper flexible layer.
18. The method of claim 17,
The method of manufacturing a multilayer stretchable substrate further comprising the step of forming a self-assembled monolayer before applying the composition for forming a rigid layer on the mold.
The multilayer stretchable substrate according to claim 1 ; and
and an electrode part positioned on the stretchable substrate.
32. The method of claim 31,
The stretchable electronic device is a solar cell.
32. The method of claim 31,
photoactive layer; and a stretchable electronic device further comprising an encapsulation film.

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