KR102185633B1 - Flexible substrate, manufacturing method thereof, and flexible electronic device including the same - Google Patents

Abstract

A flexible substrate is provided. The flexible substrate is a first film having a first Young's modulus, a second film disposed on the first film and having a second Young's modulus, and a second film interposed between the first film and the second film, and having a third Young's modulus. I include 3 films. The third Young's modulus is smaller than the first Young's modulus and the second Young's modulus.

Description

Flexible substrate, manufacturing method thereof, and flexible electronic device including the same TECHNICAL FIELD [Flexible substrate, manufacturing method thereof, and flexible electronic device including the same}

The present invention relates to a flexible substrate that can be applied to various electronic devices, a method of manufacturing the same, and a flexible electronic device including the same.

With recent technological advances, flexible electronic devices having flexibility have been developed. The flexible electronic device may include a display device or a memory device configured on a flexible substrate, and for example, may include a flexible display device, a mobile phone, a digital device, an information communication device, and the like. The flexible electronic device can be flexibly bent according to a user's request, thereby improving portability and convenience of the user.

As the flexible substrate, a polymer material having excellent ductility may be mainly used. When the flexible substrate is bent, a surface strain applied to the surface of the flexible substrate may be transmitted to a display device or a memory device provided on the surface. In this case, even if the flexible substrate itself has high ductility, electrical characteristics of the display device or the memory device may be degraded due to the surface strain, and thus, implementation of the entire flexible electronic device It can be difficult.

An object of the present invention is to provide a flexible substrate with reduced surface stress and a method for manufacturing the same.

Another technical problem to be achieved by the present invention is to provide a flexible electronic device capable of minimizing performance degradation due to physical bending or deformation.

The flexible substrate according to the present invention includes a first film having a first Young's modulus; A second film disposed on the first film and having a second Young's modulus; And a third film interposed between the first film and the second film and having a third Young's modulus. The third Young's modulus may be smaller than the first Young's modulus and the second Young's modulus.

According to some embodiments, the first film and the second film may include the same material.

According to some embodiments, the third film may include a material different from the first film and the second film.

According to some embodiments, the first to third films may include a polymer material.

According to some embodiments, each of the first to third films is polytetrafluoroethylene (PTFE), polyimide, polyamide, polyester, and polyethylene ( polyethylene), polypropylene, polyurethane (polyurethane), polydimethylsiloxane (PDMS), polyacrylate, polyarylate, fiber-reinforced plastic, and at least one selected from a combination thereof. Can include.

According to some embodiments, the first film and the second film may include polyimide.

According to some embodiments, the third film may include polydimethylsiloxane (PDMS).

According to some embodiments, the lower surface of the third film may directly contact the upper surface of the first film, and the upper surface of the third film may directly contact the lower surface of the second film.

A method of manufacturing a flexible substrate according to the present invention includes sequentially forming a first film and a first preliminary film on a first support substrate; Sequentially forming a second film and a second preliminary film on a second support substrate; Bonding an upper surface of the first preliminary film and an upper surface of the second preliminary film to each other; And performing a heat treatment process to cure the first preliminary film and the second preliminary film to form a third film. The third film may have a Young's modulus smaller than each of the first film and the second film.

According to some embodiments, forming the first preliminary layer may include partially curing the first composition by applying the first composition on the first film and performing a first heat treatment process. Forming the second preliminary film may include partially curing the second composition by applying a second composition on the second film and performing a second heat treatment process. The first heat treatment process and the second heat treatment process may be performed at a lower temperature than the heat treatment process.

According to some embodiments, bonding the upper surface of the first preliminary film and the upper surface of the second preliminary film to each other includes separating the second support substrate from the second film; And after the second support substrate is separated, providing the second film and the second preliminary film on the first support substrate so that the upper surface of the second preliminary film faces the upper surface of the first preliminary film. can do.

According to some embodiments, the method of manufacturing a flexible substrate according to the present invention may further include separating the first support substrate from the first film after the third film is formed.

According to some embodiments, bonding the upper surface of the first preliminary layer and the upper surface of the second preliminary layer to each other is such that the upper surface of the second preliminary layer faces the upper surface of the first preliminary layer, , It may include providing the second film and the second preliminary film on the first support substrate.

According to some embodiments, in the method of manufacturing a flexible substrate according to the present invention, after the third film is formed, the first support substrate and the second support substrate are separated from the first film and the second film, respectively. It may further include doing.

A flexible electronic device according to the present invention includes a flexible substrate; And it may include an electronic device on the flexible substrate. The flexible substrate may include a first film, a second film on the first film, and a third film interposed between the first film and the second film. The third film may have a Young's modulus smaller than each of the first film and the second film.

According to some embodiments, the first to third films may include a polymer material.

According to some embodiments, the first film and the second film may include the same polymer material.

According to some embodiments, the third film may include a polymer material different from the first film and the second film.

According to some embodiments, the first film and the second film may include polyimide, and the third film may include polydimethylsiloxane (PDMS).

According to some embodiments, the electronic device may include at least one of a memory device, a display device, a solar cell, a light emitting diode, and a sensor.

According to the concept of the present invention, the flexible substrate may include a first film, a second film, and a third film interposed therebetween, and the third film is a Young's modulus smaller than that of the first film and the second film. It may include a material having. Accordingly, when the flexible substrate is bent, a surface stress applied to the flexible substrate may be reduced, and an external force applied to an electronic device provided on the flexible substrate may be reduced. Accordingly, a stable flexible electronic device capable of minimizing performance degradation due to physical bending or deformation may be provided.

1 is a cross-sectional view of a flexible substrate according to embodiments of the present invention.
2 is a cross-sectional view showing a state in which the flexible substrate of FIG. 1 is bent.
3 and 4 are graphs showing surface stress of a flexible substrate according to embodiments of the present invention, respectively.
5 is a graph showing a change in sheet resistance according to the number of bending of a flexible substrate according to embodiments of the present invention.
6 and 7 are cross-sectional views illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention.
8 is a cross-sectional view illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention.
9 to 11 are cross-sectional views illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention.
12 and 13 are cross-sectional views illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention.
14 and 15 are cross-sectional views illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention.
16 is a cross-sectional view illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention.
17 is a cross-sectional view of a flexible electronic device including a flexible substrate according to embodiments of the present invention.

In order to fully understand the configuration and effects of the present invention, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms and various modifications may be added. However, it is provided to complete the disclosure of the present invention through the description of the present embodiments, and to fully inform the scope of the present invention to those of ordinary skill in the art.

In the present specification, when a component is referred to as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. In addition, in the drawings, the thickness of the components is exaggerated for effective description of the technical content. Parts indicated by the same reference numerals throughout the specification represent the same elements.

Embodiments described herein will be described with reference to cross-sectional views and/or plan views, which are ideal exemplary views of the present invention. In the drawings, the thicknesses of films and regions are exaggerated for effective description of technical content. Accordingly, the regions illustrated in the drawings have schematic properties, and the shapes of the regions illustrated in the drawings are intended to illustrate a specific shape of a device region and are not intended to limit the scope of the invention. In various embodiments of the present specification, terms such as first, second, and third are used to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one component from another component. The embodiments described and illustrated herein also include complementary embodiments thereof.

The terms used in the present specification are for describing exemplary embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, "comprises" and/or "comprising" does not exclude the presence or addition of one or more other elements.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a flexible substrate according to embodiments of the present invention.

Referring to FIG. 1, a flexible substrate 1000 includes a first film 10, a second film 20 on the first film 10, and the first film 10 and the second film 20. It may include a third film 30 interposed therebetween. The lower surface (30L) of the third film 30 may directly contact the upper surface of the first film 10, and the upper surface (30U) of the third film 30 is the lower surface of the second film 20 You can come in direct contact with. The first film 10 may have a first Young's modulus, and the second film 20 may have a second Young's modulus. In some embodiments, the first Young's modulus may be the same as the second Young's modulus, but according to other embodiments, the first Young's modulus may be different from the second Young's modulus. The third film 30 may have a third Young's modulus smaller than the first Young's modulus and the second Young's modulus.

The first to third films 10, 20, and 30 may include a polymer material. Each of the first film 10 and the second film 20 may include a polymer material having a Young's modulus greater than that of the third film 30, and the third film 30 is the first film. (10) and a polymer material having a Young's modulus smaller than that of the second film 20 may be included. Each of the first to third films (10, 20, 30) is polytetrafluoroethylene (PTFE), polyimide, polyamide, polyester, and polyethylene. At least one selected from (polyethylene), polypropylene, polyurethane, polydimethylsiloxane (PDMS), polyacrylate, polyarylate, fiber-reinforced plastic, and combinations thereof It may include.

The first film 10 and the second film 20 may contain the same material, and the third film 30 is different from the first film 10 and the second film 20. It may contain substances. For example, the first film 10 and the second film 20 may include the same polymer material, and the third film 30 may include the first film 10 and the second film ( 20) and other polymer materials may be included. For example, the first film 10 and the second film 20 may include polyimide, and the third film 30 may include polydimethylsiloxane (PDMS). I can.

2 is a cross-sectional view showing a state in which the flexible substrate of FIG. 1 is bent. 3 and 4 are graphs showing surface stress of a flexible substrate according to embodiments of the present invention, respectively. 5 is a graph showing a change in sheet resistance according to the number of bending of a flexible substrate according to embodiments of the present invention.

Referring to FIG. 2, when the flexible substrate 1000 is bent, a tensile stress (S _T ) may be applied to one surface of the flexible substrate 1000, and a surface opposite to the flexible substrate 1000 may be applied. Compressive strain (S _C ) may be applied. The tensile stress (S _T ) or the compressive stress (S _C ) applied to the surface of the flexible substrate 1000 may be referred to as a surface strain. According to the concept of the present invention, as the third film 30 has a Young's modulus smaller than that of the first and second films 10 and 20, a part of the surface stress applied to the flexible substrate 1000 is It may be absorbed by the third film 30. Accordingly, the surface stress of the flexible substrate 1000 may be reduced.

According to the ratio of the thickness (30T) of the third film 30 to the total thickness (T) of the flexible substrate 1000, and the change of the third Young's modulus of the third film 30, the flexible substrate The surface stress of (1000) can be controlled. In the following Experimental Examples 1 and 2, the surface stress due to the bending of the flexible substrate 1000 was calculated using a finite element method (FEM) simulation. The surface stress of the flexible substrate was calculated according to i) a ratio of the thickness (30T) of the third film 30, and ii) a change in the third Young's modulus of the third film 30.

<Experimental Example 1>

It is assumed that the total thickness T of the flexible substrate 1000 is 20 μm, and the flexible substrate 1000 is bent with a radius of curvature of 1 mm. Physical properties of polyimide are applied to the first film 10 and the second film 20, and properties of polydimethylsiloxane (PDMS) are applied to the third film 30. The ratio of the thickness (30T) of the third film 30 is changed to 0%, 20%, 40%, and 60%, and the third Young's modulus of the third film 30 is 0.1 MPa, 0.99 MPa , And 3.27 MPa.

Surface stress (%) Young's modulus of the third film (MPa) 0.1 0.99 3.27 Of the third film
Thickness ratio (%) 0 2.03 2.03 2.03 20 - 1.6922 1.7172 40 1.4378 1.6407 1.6777 60 - 1.6 1.656

3 is a graph showing the change in the surface stress of the flexible substrate 1000 according to Experimental Example 1, and shows the results of Table 1. Referring to FIG. 3, as the ratio of the thickness 30T of the third film 30 increases and the third Young's modulus of the third film 30 decreases, the flexible substrate 1000 It can be seen that the surface stress decreases.

<Experimental Example 2>

It is assumed that the total thickness T of the flexible substrate 1000 is 100 μm, and the flexible substrate 1000 is bent with a radius of curvature of 5 mm. Physical properties of polyimide are applied to the first film 10 and the second film 20, and properties of polydimethylsiloxane (PDMS) are applied to the third film 30. The ratio of the thickness (30T) of the third film 30 is changed to 0%, 20%, 40%, and 60%, and the third Young's modulus of the third film 30 is 0.1 MPa, 0.99 MPa , And 3.27 MPa.

Surface stress (%) Young's modulus of the third film (MPa) 0.1 0.99 3.27 Of the third film
Thickness ratio (%) 0 2.236 2.236 2.236 20 1.216 1.57 1.818 40 1.148 1.483 1.614 60 1.11 1.45 1.54

4 is a graph showing the change in the surface stress of the flexible substrate 1000 according to Experimental Example 2, and shows the results of Table 2. Referring to FIG. 4, as the ratio of the thickness 30T of the third film 30 increases and the third Young's modulus of the third film 30 decreases, the flexible substrate 1000 It can be seen that the surface stress decreases.

According to the present invention, the flexible substrate 1000 may be configured to minimize the surface stress applied thereto when the flexible substrate 1000 is bent. For this reason, even when bending of the flexible substrate 1000 is repeated a plurality of times, a change in sheet resistance of the flexible substrate 1000 can be minimized. In Experimental Example 3, the rate of change of the sheet resistance of the flexible substrate 1000 according to the number of bending of the flexible substrate 1000 is verified.

<Experimental Example 3>

A multilayer flexible substrate on which polyimide (thickness 20 μm)/PDMS (thickness 40 μm)/polyimide (thickness 20 μm) is laminated is prepared. A 100 nm thick ITO (Indium Tin Oxide) thin film is deposited on the multilayer flexible substrate. The multilayer flexible substrate is bent to a radius of curvature of 6 mm and then the unfolding process is repeated to apply tensile stress to the ITO thin film. The change in resistance of the ITO thin film is measured.

<Comparative Example>

A single-layer flexible substrate made of polyimide (thickness 80 μm) is prepared. A 100 nm thick ITO (Indium Tin Oxide) thin film is deposited on the single-layer flexible substrate. The single-layer flexible substrate is bent to a radius of curvature of 6 mm and then the unfolding process is repeated to apply tensile stress to the ITO thin film. The change in resistance of the ITO thin film is measured.

In the vertical axis of FIG. 5, R0 represents the initial resistance and R represents the resistance measured after repeating the process of bending and unfolding the flexible substrate of Experimental Example 3 or Comparative Example. The horizontal axis of FIG. 5 represents the number of times that the flexible substrate of Experimental Example 3 or Comparative Example was bent and unfolded. Referring to FIG. 5, when the process of bending and unfolding the single-layer flexible substrate of the comparative example is repeated about 200 or more times, it can be seen that the rate of change in sheet resistance of the single-layer flexible substrate is greatly increased. That is, it can be seen that the resistance of the ITO thin film on the single-layer flexible substrate is greatly increased. In the multilayer flexible substrate of Experimental Example 3, even if the process of bending and unfolding it exceeds about 2000 times, the rate of change of the sheet resistance of the multilayer flexible substrate may be maintained at 30% or less. That is, a change in resistance of the ITO thin film on the multilayer flexible substrate may be relatively reduced.

According to the concept of the present invention, the flexible substrate 1000 is interposed between the first film 10 and the second film 20, and a Young's modulus smaller than that of the first and second films 10 and 20 It may include the third film 30 having. For this reason, when the flexible substrate 1000 is bent, the surface stress applied to the flexible substrate 1000 may be reduced. In addition, according to the present invention, the ratio of the thickness (30T) of the third film 30 to the total thickness (T) of the flexible substrate 1000, and the third Young's modulus of the third film 30 By adjusting, when the flexible substrate 1000 is bent, the surface stress applied to the flexible substrate 1000 may be controlled to be less than a limit value. As a result, a change in electrical characteristics of an electronic device provided on the flexible substrate 1000 (for example, a change in resistance of the ITO thin film) can be minimized. Here, the limit value refers to a maximum value of the surface stress capable of maintaining the required performance of the electronic device.

6 and 7 are cross-sectional views illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention. For simplicity of explanation, descriptions overlapping with the flexible substrates according to embodiments of the present invention described with reference to FIGS. 1 to 5 may be omitted.

Referring to FIG. 6, a first film 10 may be formed on the first support substrate 101. The first support substrate 101 may be, for example, a silicon wafer or a glass wafer. The first film 10 may be formed by applying a first film composition on the first support substrate 101 and thermally curing the first film composition. The first film composition may be, for example, a polyimide solution. The application of the first film composition may be performed using, for example, spin coating, bar coating, blade coating, pouring, or the like. A first preliminary layer 32 may be formed on the first film 10. Forming the first preliminary film 32 may include applying the first composition on the first film 10, and partially curing the first composition by performing a first heat treatment process. I can. The first composition may be, for example, a polydimethyl siloxane (PDMS) solution. The application of the first composition may be performed using, for example, spin coating, bar coating, blade coating, or pouring. When the first preliminary layer 32 includes polydimethyl siloxane (PDMS), the first heat treatment process may be performed at a temperature of about 60° C. for about 30 to 40 minutes. As the first composition is partially cured, the first preliminary layer 32 may have a sticky solid form.

A second film 20 may be formed on the second support substrate 102. The second support substrate 102 may be, for example, a silicon wafer or a glass wafer. The second film 20 may be formed by applying a second film composition on the second support substrate 102 and thermally curing the second film composition. The second film composition may be, for example, a polyimide solution. The application of the second film composition may be performed using, for example, spin coating, bar coating, blade coating, or pouring. A second preliminary layer 34 may be formed on the second film 20. Forming the second preliminary film 34 may include applying a second composition on the second film 20 and partially curing the second composition by performing a second heat treatment process. I can. The second composition may be, for example, a polydimethyl siloxane (PDMS) solution. The application of the second composition may be performed using, for example, spin coating, bar coating, blade coating, or pouring. When the second preliminary layer 34 includes polydimethyl siloxane (PDMS), the second heat treatment process may be performed at a temperature of about 60° C. for about 30 to 40 minutes. As the second composition is partially cured, the second preliminary layer 34 may have a sticky solid form.

Referring to FIG. 7, the second support substrate 102 may be removed from the second film 20. Removing the second support substrate 102 may include physically separating the second support substrate 102 from the second film 20. After the second support substrate 102 is removed, the first preliminary film (32U) of the first preliminary film (32) and the upper surface (34U) of the second preliminary film (34) face each other. On 32), the second film 20 and the second preliminary film 34 may be provided. After bonding the upper surface 32U of the first preliminary layer 32 and the upper surface 34U of the second preliminary layer 34, a third heat treatment process may be performed. The third heat treatment process may be performed at a higher temperature than the first heat treatment process and the second heat treatment process. As an example, when the first and second preliminary layers 32 and 34 include polydimethyl siloxane (PDMS), the third heat treatment process may be performed at a temperature of about 120° C. for about 30 minutes. I can. The first preliminary film 32 and the second preliminary film 34 are cured by the third heat treatment process, so that the third film 30 shown in FIG. 1 may be formed. Accordingly, the flexible substrate 1000 of FIG. 1 may be manufactured.

8 is a cross-sectional view illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention. For simplicity of explanation, the method of manufacturing the flexible substrate described with reference to FIGS. 6 and 7 and the differences will be mainly described.

First, as described with reference to FIG. 6, the first film 10 and the first preliminary film 32 may be sequentially formed on the first support substrate 101, and the second support substrate ( On 102), the second film 20 and the second preliminary film 34 may be sequentially formed.

Referring to FIG. 8, on the first preliminary layer 32 so that the upper surface 32U of the first preliminary layer 32 and the upper surface 34U of the second preliminary layer 34 face each other, The second support substrate 102, the second film 20, and the second preliminary film 34 may be provided. After bonding the upper surface 32U of the first preliminary layer 32 and the upper surface 34U of the second preliminary layer 34, the third heat treatment process may be performed. The third heat treatment process may be performed at a higher temperature than the first heat treatment process and the second heat treatment process. The first preliminary film 32 and the second preliminary film 34 are cured by the third heat treatment process, so that the third film 30 shown in FIG. 1 may be formed. Thereafter, the first support substrate 101 and the second support substrate 102 may be removed from the first film 10 and the second film 20, respectively. Removing the first and second support substrates 101 and 102 physically removes the first and second support substrates 101 and 102 from the first and second films 10 and 20. It may include separating. Accordingly, the flexible substrate 1000 of FIG. 1 may be manufactured.

9 to 11 are cross-sectional views illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention. For simplicity of explanation, the method of manufacturing the flexible substrate described with reference to FIGS. 6 and 7 and the differences will be mainly described.

Referring to FIG. 9, the first film 10 may be formed on the first support substrate 101. The first film 10 may be formed by applying the first film composition on the first support substrate 101 and thermally curing the first film composition. According to the present embodiments, thermally curing the first film composition may be performed at a relatively low temperature. For example, the first film 10 may include a low-temperature curing polyimide.

Referring to FIG. 10, the third film 30 may be formed on the first film 10. The third film 30 may be formed by applying a third film composition on the first film 10 and thermally curing the third film composition. The third film composition may be, for example, a polydimethyl siloxane (PDMS) solution. Applying the third film composition may be performed using, for example, spin coating, bar coating, blade coating, or pouring.

Referring to FIG. 11, the second film 20 may be formed on the third film 30. The second film 20 may be formed by applying the second film composition on the third film 30 and thermally curing the second film composition. According to the present embodiments, thermosetting the second film composition may be performed at a relatively low temperature. For example, the second film 20 may include a low-temperature curing polyimide. According to the present embodiments, the first film 10, the third film 30, and the second film 20 may be sequentially formed on the first support substrate 101. Thereafter, the first support substrate 101 may be removed from the first film 10. Removing the first support substrate 101 may include physically separating the first support substrate 101 from the first film 10. Accordingly, the flexible substrate 1000 of FIG. 1 may be manufactured.

12 and 13 are cross-sectional views illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention. For simplicity of explanation, the method of manufacturing the flexible substrate described with reference to FIGS. 6 and 7 and the differences will be mainly described.

Referring to FIG. 12, the first film 10 and the second film 20 may be formed on the first support substrate 101 and the second support substrate 102, respectively. The first film 10 and the second film 20 may be formed in substantially the same manner as the method described with reference to FIG. 6. Thereafter, the first support substrate 101 and the second support substrate 102 may be removed from the first film 10 and the second film 20, respectively. Removing the first and second support substrates 101 and 102 physically removes the first and second support substrates 101 and 102 from the first and second films 10 and 20. It may include separating.

According to the present embodiments, the third film 30 may be formed on the third support substrate 103. The third support substrate 103 may be, for example, a silicon wafer or a glass wafer. The third film 30 may be formed by applying a third film composition on the third support substrate 103 and thermally curing the third film composition. The third film composition may be, for example, a polydimethyl siloxane (PDMS) solution. Applying the third film composition may be performed using, for example, spin coating, bar coating, blade coating, or pouring. After the third film 30 is formed, the third support substrate 103 may be removed from the third film 30. Removing the third support substrate 103 may include physically separating the third support substrate 103 from the third film 30.

Referring to FIG. 13, after the first to third support substrates 101, 102, and 103 are removed, the third film 30 is separated from the first film 10 and the second film 20. The first to third films 10, 20, and 30 may be stacked to be interposed therebetween. A pressure P may be provided on the stacked first to third films 10, 20, and 30. For example, a pressing roller may provide pressure P on the stacked first to third films 10, 20, and 30. Accordingly, the third film 30 may be recured, and as a result, the flexible substrate 1000 of FIG. 1 may be manufactured.

14 and 15 are cross-sectional views illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention. For simplicity of explanation, the method of manufacturing the flexible substrate described with reference to FIGS. 6 and 7 and the differences will be mainly described.

Referring to FIG. 14, the first film 10 may be provided on the first support substrate 101. For example, the first film 10 may be formed by substantially the same method as the method described with reference to FIG. 6. As another example, the first film 10 prepared separately from the first support substrate 101 may be attached to be fixed to the first support substrate 101. A third film composition 36 may be applied on the first film 10. The third film composition 36 may be, for example, a polydimethyl siloxane (PDMS) solution. Applying the third film composition 36 may be performed using, for example, spin coating, bar coating, blade coating, pouring, or the like.

Referring to FIG. 15, the separately prepared second film 20 may be provided on the first support substrate 101 to which the third film composition 36 is applied. The second film 20 may be provided to cover the third film composition 36. After that, a heat treatment process may be performed to cure the third film composition 36. Accordingly, the third film 30 of FIG. 1 may be formed. After the third film 30 is formed, the first support substrate 101 may be removed, and the flexible substrate 1000 of FIG. 1 may be manufactured.

16 is a cross-sectional view illustrating a method of manufacturing a flexible substrate according to some embodiments of the present invention. For simplicity of explanation, the method of manufacturing the flexible substrate described with reference to FIGS. 6 and 7 and the differences will be mainly described.

Referring to FIG. 16, a single layer flexible substrate 40 may be provided. The single layer flexible substrate 40 may include a polymer material having a predetermined Young's modulus. The single-layer flexible substrate 40 is polytetrafluoroethylene (PTFE), polyimide, polyamide, polyester, polyethylene, polypropylene , Polyurethane, Polydimethylsiloxane (PDMS), Polyacrylate, Polyarylate, Fiber-reinforced plastic, and at least one selected from a combination thereof.

According to the present embodiments, heat (H) or electric field (E) may be provided on the upper surface (40U) and the lower surface (40L) of the single-layer flexible substrate 40. By the heat (H) or the electric field (E), the Young's modulus of the upper and lower portions of the single layer flexible substrate 40 may be changed. The Young's modulus in the upper and lower portions of the single layer flexible substrate 40 may be changed to be greater than the Young's modulus in the middle portion of the single layer flexible substrate 40. Accordingly, the flexible substrate 1000 of FIG. 1 may be manufactured.

17 is a cross-sectional view of a flexible electronic device including a flexible substrate according to embodiments of the present invention.

Referring to FIG. 17, the flexible electronic device 2000 may include the flexible substrate 1000 of FIG. 1 and the electronic device 200 on the flexible substrate 1000. The electronic device 200 may include at least one of a memory device, a display device, a solar cell, a light emitting diode, and a sensor, but the concept of the present invention is not limited thereto. The electronic device 200 may be formed of an electronic material such as a conductor, a semiconductor, and/or a non-conductor. According to the concept of the present invention, when the flexible substrate 1000 is bent, the surface stress applied to the flexible substrate 1000 may be reduced. For this reason, even when the flexible substrate 1000 is bent, an external force (for example, the surface stress) applied to the electronic device 200 on the flexible substrate 1000 may be reduced. Accordingly, a change in electrical characteristics of the electronic device 200 may be minimized, and as a result, a stable flexible electronic device 2000 capable of minimizing performance degradation due to physical bending or deformation may be provided.

The above description of the embodiments of the present invention provides an example for describing the present invention. Therefore, the present invention is not limited to the above embodiments, and various modifications and changes are possible within the technical spirit of the present invention, such as by combining the above embodiments by a person having ordinary skill in the art. It is obvious.

1000: flexible substrate 10: first film
20: second film 30: third film
200: electronic element 2000: flexible electronic device

Claims (20)

A first film having a first Young's modulus;
A second film disposed on the first film and having a second Young's modulus; And
In the flexible substrate comprising a third film interposed between the first film and the second film,
The third film includes a material having a Young's modulus less than the first Young's modulus and the second Young's modulus,
The first film is in direct contact with the bottom surface of the third film, the second film is in direct contact with the upper surface of the third film,
The ratio of the thickness of the third film to the total thickness of the flexible substrate is 20% to 60% of the flexible substrate. The method according to claim 1,
The first film and the second film are flexible substrates containing the same material. The method according to claim 2,
The third film is a flexible substrate comprising a material different from the first film and the second film. The method according to claim 1,
The surface stress of the flexible substrate is controlled according to a ratio of the thickness of the third film to the total thickness of the flexible substrate, and the Young's modulus of the third film. The method of claim 4,
Each of the first to third films is polytetrafluoroethylene (PTFE), polyimide, polyamide, polyester, polyethylene, and polypropylene. ), polyurethane (polyurethane), polydimethylsiloxane (PDMS), polyacrylate (Polyacrylate), polyarylate (Polyarylate), fiber-reinforced plastic and a flexible substrate comprising at least one selected from a combination thereof. The method of claim 4,
The first film and the second film are flexible substrates containing polyimide. The method of claim 4,
The third film is a flexible substrate containing polydimethylsiloxane (PDMS). delete Sequentially forming a first film and a first preliminary film on the first support substrate;
Sequentially forming a second film and a second preliminary film on a second support substrate;
Bonding an upper surface of the first preliminary film and an upper surface of the second preliminary film to each other; And
Including forming a third film by performing a heat treatment process to cure the first pre-film and the second pre-film,
The first film, the second film, and the third film interposed therebetween constitute a flexible substrate,
The third film includes a material having a Young's modulus less than each of the first film and the second film,
A method of manufacturing a flexible substrate in which a ratio of the thickness of the third film to the total thickness of the flexible substrate is 20% to 60%. The method of claim 9,
Forming the first preliminary film includes applying a first composition on the first film and performing a first heat treatment process to partially cure the first composition,
Forming the second preliminary film includes partially curing the second composition by applying a second composition on the second film and performing a second heat treatment process,
The first heat treatment process and the second heat treatment process are performed at a lower temperature than the heat treatment process. The method of claim 9,
Bonding the upper surface of the first preliminary film and the upper surface of the second preliminary film to each other:
Separating the second support substrate from the second film; And
After the second support substrate is separated, providing the second film and the second preliminary film on the first support substrate so that the upper surface of the second preliminary film faces the upper surface of the first preliminary film. Method of manufacturing a flexible substrate. The method of claim 11,
After the third film is formed, the method of manufacturing a flexible substrate further comprising separating the first support substrate from the first film. The method of claim 9,
Bonding the upper surface of the first preliminary film and the upper surface of the second preliminary film to each other:
A flexible substrate comprising providing the second support substrate, the second film, and the second preliminary film on the first support substrate so that the upper surface of the second preliminary film faces the upper surface of the first preliminary film. Manufacturing method. The method of claim 13,
After the third film is formed, the method of manufacturing a flexible substrate further comprising separating each of the first support substrate and the second support substrate from the first film and the second film. Flexible substrate; And
Including an electronic device on the flexible substrate,
The flexible substrate includes a first film, a second film on the first film, and a third film interposed between the first film and the second film,
The third film includes a material having a Young's modulus less than each of the first film and the second film,
The first film is in direct contact with the bottom surface of the third film, the second film is in direct contact with the upper surface of the third film,
A flexible electronic device in which a ratio of the thickness of the third film to the total thickness of the flexible substrate is 20% to 60%. The method of claim 15,
The surface stress of the flexible substrate is controlled according to a ratio of the thickness of the third film to the total thickness of the flexible substrate, and the Young's modulus of the third film. The method of claim 15,
The first film and the second film are flexible electronic devices containing the same polymer material. The method of claim 17,
The third film includes a polymer material different from the first film and the second film. The method of claim 16,
The first film and the second film include polyimide,
The third film is a flexible electronic device containing polydimethylsiloxane (PDMS). The method of claim 15
The electronic device is a flexible electronic device comprising at least one of a memory device, a display device, a solar cell, a light emitting diode, and a sensor.

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