Stretchable substrate having autonomous strain distribution, method for manufacturing the same and method for changing strain distribution of the same

Abstract

In a stretchable substrate having a self-stiffness distribution, a method for manufacturing the same, and a method for varying the stiffness distribution of the same, the stretchable substrate comprises a stiffness maintaining portion and a stiffness varying portion divided into different regions. Furthermore, the stiffness maintaining portion and the stiffness varying portion maintain a preset stiffness only at a temperature below a preset temperature. At a temperature above the preset temperature, the stiffness varying portion becomes lower than the preset stiffness and deforms to enable stretchability.

Description

Technology Field

[0001] The present invention relates to a stretchable substrate having a self-stiffness distribution, a method for manufacturing the same, and a method for varying the stiffness distribution thereof. More specifically, the invention relates to a stretchable substrate having a self-stiffness distribution, a method for manufacturing the same, and a method for varying the stiffness distribution thereof, wherein selective elongation is achieved by varying the temperature, so that in a specific region, the stiffness is lowered to enable elongation, while in another region, the stiffness is maintained to minimize deformation, thereby maintaining an overall stable structure, and having control of specific factors, a simple manufacturing process, and simple circuit wiring. Background Technology

[0002] As the demand for various flexible electronic devices increases, manufacturing technology for flexible display devices is advancing, and manufacturing technology for stretchable display devices, in addition to simple flexibility, is also being developed.

[0003] Korean Registered Patent No. 10-2340855 discloses technology regarding a flexible display device capable of being stretchable, configured to include a flexible substrate and a variable part.

[0004] However, in the case of such stretchable or flexible display devices, when the entire substrate is stretched, there is a problem where the components mounted on the substrate are damaged due to low stretchability or detached from the substrate due to increased rigidity.

[0005] Accordingly, Korean registered patent No. 10-1756847 discloses a technology in which the region where the device is mounted is formed of a material having a relatively high elastic modulus, and another region is formed of a material having a relatively low elastic modulus.

[0006] However, when manufacturing substrates with such different materials, it is difficult to maintain structural stability at the boundaries, and there is a problem with the fabrication process becoming complex.

[0007] Meanwhile, Korean Registered Patent No. 10-2368540 discloses a technology for changing local dimensions or shapes in addition to varying the elastic modulus to locally change stiffness. However, implementing such a structural method of local stiffness change requires additional manufacturing processes and presents the problem of complex circuit wiring.

[0008] Accordingly, there is an increasing technical demand for flexible substrates that can maintain relatively high rigidity in the device mounting area while possessing structural stability at the boundaries, and that include simple manufacturing processes and circuit wiring while controlling factors such as Poisson's ratio and anisotropic elastic modulus. Prior art literature

[0009] Republic of Korea Registered Patent No. 10-2340855 Republic of Korea Registered Patent No. 10-1756847 Republic of Korea Registered Patent No. 10-2368540 The problem to be solved

[0010] Accordingly, the technical problem of the present invention is conceived from this point, and the objective of the present invention is to provide a stretchable substrate having a self-stiffness distribution that enables selective elongation by region by varying the temperature, thereby allowing elongation by lowering stiffness in specific regions while maintaining stiffness in other regions to minimize deformation, and maintains a stable structure by omitting boundaries overall, as well as allowing for the control of specific factors, a simple manufacturing process, and simple circuit wiring.

[0011] In addition, another objective of the present invention is to provide a method for manufacturing the above-mentioned expandable substrate.

[0012] In addition, another objective of the present invention is to provide a method for varying the stiffness distribution of the above-mentioned expandable substrate. means of solving the problem

[0013] An expandable substrate according to one embodiment for realizing the purpose of the present invention described above includes a rigidity maintaining portion and a rigidity variable portion divided into different regions. Furthermore, the rigidity maintaining portion and the rigidity variable portion maintain a preset rigidity only at a preset temperature or below. The rigidity variable portion may be deformed to allow expansion by lowering its rigidity below the preset rigidity at a temperature above the preset temperature.

[0014] In one embodiment, the stiffness maintaining portion is formed with a plurality of regions having a predetermined pattern, and the stiffness variable portion may be formed in a region other than the stiffness maintaining portion.

[0015] In one embodiment, the length of the stiffness retaining part along the first direction and the length of the stiffness retaining part along the second direction perpendicular to the first direction may be different from each other.

[0016] In one embodiment, an element may be mounted on the rigidity retaining part.

[0017] In one embodiment, the stiffness variable portion is formed having a predetermined pattern, and the stiffness maintaining portion may be formed in a different area excluding the stiffness variable portion.

[0018] In one embodiment, the stiffness variable portion may be formed along a kirigami pattern.

[0019] In one embodiment, when Poisson's ratio is negative and stretching occurs in a first direction, stretching in a second direction perpendicular to the first direction may also occur at the same ratio.

[0020] In one embodiment, the preset temperature may be the glass transition temperature of the stiffness variable part.

[0021] In one embodiment, the glass transition temperature of the stiffness variable part may be lower than the glass transition temperature of the stiffness maintaining part.

[0022] In one embodiment, the stiffness maintaining portion and the stiffness variable portion may include PDMS (polydimethylsiloxane) or polyimide.

[0023] A method for manufacturing a stretchable substrate according to one embodiment for realizing the purpose of the present invention described above comprises, for a stretchable substrate including a rigidity maintaining portion and a rigidity variable portion divided into different regions, a step of positioning a mask portion such that an opening is aligned with the rigidity maintaining portion, and a step of providing ultraviolet rays from above the mask portion so that ultraviolet rays are provided only to the rigidity maintaining portion.

[0024] In one embodiment, as ultraviolet light is provided only to the stiffness maintaining part, the glass transition temperature of the stiffness variable part can be formed lower than the glass transition temperature of the stiffness maintaining part.

[0025] In one embodiment, the stretchable substrate may include a glycol gel.

[0026] In one embodiment, as ultraviolet light is provided only to the rigidity-maintaining portion, the glycol gel forms a network by photocrosslinking, and polyimide is polymerized in the space between the networks to induce high-density polymer entanglement.

[0027] In one embodiment, the degree of ultraviolet light transmission in the opening of the mask portion may gradually decrease from the center of the opening to the periphery.

[0028] In one embodiment, the ultraviolet light may be a modulated light whose intensity gradually decreases from the center of the opening to the periphery.

[0029] In one embodiment, the glass transition temperature of the stiffness maintaining portion may gradually decrease from the central portion to the peripheral portion which is the boundary with the stiffness variable portion.

[0030] In one embodiment, the stiffness maintaining portion may be formed with a thickness greater than that of the stiffness variable portion.

[0031] In one embodiment, the thickness of the stiffness maintaining portion may gradually decrease from the central portion to the peripheral portion which is the boundary with the stiffness variable portion.

[0032] In a method for varying the stiffness distribution of an expandable substrate according to one embodiment for realizing the purpose of the present invention described above, for an expandable substrate comprising a stiffness maintaining portion and a stiffness varying portion divided into different regions, the stiffness maintaining portion may maintain a temperature while only the stiffness varying portion is heated to increase the temperature, or the expandable substrate may be heated such that the stiffness varying portion has a higher temperature than the stiffness maintaining portion.

[0033] In one embodiment, when the temperature is increased by heating only the variable stiffness part, a heater may be attached to the lower surface of the variable stiffness part.

[0034] In one embodiment, when heating the expandable substrate while maintaining the temperature of the stiffness variable part relatively higher than that of the stiffness maintaining part, the stiffness variable part can be formed to have a higher thermal diffusivity than the stiffness maintaining part.

[0035] In one embodiment, when heating the expandable substrate while maintaining the temperature of the stiffness variable part relatively higher than that of the stiffness maintaining part, the stiffness variable part may be formed to contain more photothermal particles than the stiffness maintaining part. Effects of the invention

[0036] According to embodiments of the present invention, in a stretchable substrate, when the temperature is above a preset temperature, only the stiffness variable portion is deformed to allow stretching, so that the stiffness in other regions is varied while the stiffness in a specific region is maintained, thereby enabling the construction of a stretchable substrate having a different stiffness distribution.

[0037] In particular, if the rigidity retaining portion is formed in a specific arrangement and a device is mounted on the rigidity retaining portion, the expandable substrate can maintain flexibility through temperature control while minimizing flexibility in the area where the device is mounted, thereby maintaining a stable device connection state. In this case, by forming the rigidity retaining portion in various patterns or shapes, and mounting devices on rigidity retaining portions of a wider variety, it is possible to configure an expandable substrate having a diverse rigidity distribution.

[0038] Furthermore, by resolving the contact problem or structural instability problem at the interface between the conventional expandable and non-expandable parts, it is possible to configure an expandable substrate that can maintain a stable structure at the interface while possessing expandability through the continuous structural characteristics of the same material.

[0039] Furthermore, the temperature control described above enables the control of the elasticity of the expandable substrate with a variable stiffness structure by controlling within the glass transition temperature range based on information regarding the glass transition temperatures of the variable stiffness part and the stiffness maintaining part. At this time, since the glass transition temperatures of the variable stiffness part and the stiffness maintaining part can be formed differently based on information regarding the temperature range during the manufacturing process or the usage state of the expandable substrate, the stability of the manufacturing process can be maintained by keeping the stiffness high during the manufacturing process, while the various usability of the expandable substrate can be improved by varying the stiffness during actual usage.

[0040] By forming the glass transition temperatures of the variable stiffness portion and the stiffness-maintaining portion differently, ultraviolet rays can be applied only to the stiffness-maintaining portion on the stretchable substrate to form a relatively high glass transition temperature; thus, the stretchable substrate can be manufactured through the selection of materials and a relatively simple process.

[0041] In particular, by providing ultraviolet light to the rigidity maintaining part where the ultraviolet light is provided so that the light intensity gradually changes, or by manufacturing it so that the degree of opening of the opening of the mask part gradually changes, the structural stability during the repeated stretching of the stretchable substrate can be further improved through the gradual variation of rigidity at the interface between the variable rigidity part and the rigidity maintaining part.

[0042] In addition, by forming the thickness of the rigidity retaining portion relatively thickly, the strain or elongation rate of the rigidity retaining portion is kept even lower, thereby minimizing the strain of the device mounted on the rigidity retaining portion and maintaining a more stable device connection state, making it possible to manufacture an elongation substrate with high electrical stability and reliability.

[0043] Furthermore, the stiffness distribution in the stretchable substrate can be varied through a process of heating the stiffness maintaining part and the stiffness variable part to different temperatures, or heating only the stiffness variable part. Through this, the regions of the stiffness maintaining part and the stiffness variable part can be set to have various patterns or arrangements, and by varying the stiffness distribution through a relatively simple heating method, it is possible to manufacture a stretchable substrate having more diverse self-stiffness distribution characteristics. Brief explanation of the drawing

[0044] FIG. 1 is a perspective view illustrating an expandable substrate having a self-stiffness distribution according to one embodiment of the present invention. Figure 2 is a schematic diagram illustrating a state in which the stiffness distribution varies according to temperature variation in the expandable substrate of Figure 1. Figures 3a and 3b are graphs illustrating the state of having a self-stiffness distribution according to the distribution of the glass transition temperature in the stretchable substrate of Figure 1. FIG. 4 is a perspective view illustrating an expandable substrate having a self-stiffness distribution according to another embodiment of the present invention. FIG. 5 is a perspective view illustrating an expandable substrate having a self-stiffness distribution according to another embodiment of the present invention. Figure 6 is a process diagram illustrating the method of manufacturing the expandable substrate of Figure 1. FIGS. 7a and 7b are process diagrams illustrating a method for manufacturing a stretchable substrate according to another embodiment of the present invention. FIGS. 8a to 8d are process diagrams illustrating a method for manufacturing a stretchable substrate according to another embodiment of the present invention. FIGS. 9a and 9b are process diagrams illustrating a method for varying the stiffness distribution of an expandable substrate according to another embodiment of the present invention. FIGS. 10a and FIGS. 10b are graphs illustrating the stress concentration phenomenon according to temperature variation in the stretchable substrate of FIG. 1. Specific details for implementing the invention

[0045] The present invention is susceptible to various modifications and may take various forms, and embodiments are to be described in detail in the text. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each figure. Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms.

[0046] The above terms are used solely for the purpose of distinguishing one component from another. The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0047] In this application, terms such as "comprising" or "consisting of" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0048] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0049] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings.

[0050] FIG. 1 is a perspective view illustrating an expandable substrate having a self-stiffness distribution according to one embodiment of the present invention.

[0051] Referring to FIG. 1, the expandable substrate (10, hereinafter referred to as the expandable substrate) having the self-rigidity distribution according to the present embodiment is divided into a rigidity variable portion (100) and a rigidity maintaining portion (200).

[0052] As described below, the stiffness variable part (100) is defined as a region where the stiffness varies as the temperature is varied to a specific temperature, and the stiffness maintaining part (200) is defined as a region where the stiffness does not vary regardless of the temperature variation to the specific temperature. At this time, the range of temperature variation and the stiffness variation resulting therefrom will be described later.

[0053] The above-mentioned stiffness variable part (100) is defined as an area where the above-mentioned stiffness maintaining part (200) is not formed.

[0054] Additionally, as illustrated, the stiffness maintaining part (200) does not overlap with the stiffness variable part (100), and each is defined as a different region. At this time, the stiffness maintaining part (200) may have, for example, an array of m*n matrices in total, with each having a certain region (m and n are natural numbers).

[0055] Of course, the arrangement state or arrangement pattern of the above-mentioned rigidity retaining members (200) is not limited to the matrix arrangement and can have various arrangements. That is, each of the above-mentioned rigidity retaining members (200) may have a circular shape or other various shapes in addition to the illustrated rectangular shape and may form a predetermined area. Furthermore, the arrangement pattern may also have various arrangements and patterns, such as a structure in which a pattern is repeated, extending long in one direction, or a zigzag structure. Additional arrangements or patterns of the above-mentioned rigidity retaining members (200) will be further exemplified and explained through the drawings described later.

[0056] However, each of the above rigidity maintaining parts (200) has a certain width and can be formed such that multiple parts are spaced apart from each other.

[0057] As described above, a predetermined electronic device may be mounted in the area where the rigidity maintaining part (200) is formed. That is, at least one electronic device may be mounted in each area formed by the rigidity maintaining part (200). At this time, the type, structure, and further function of the electronic device are not limited.

[0058] For example, the electronic device may be a micro LED. In addition, if the electronic device is mounted on the rigidity retaining part (200) as described above, a wiring structure for driving the electronic device must also be formed on the expandable substrate (10), but additional illustration of the wiring structure has been omitted.

[0059] In the case of the above wiring structure, a conventionally known wiring structure may be applied as is, and may be additionally formed on the lower surface of the expandable substrate (10) or inside the expandable substrate (10), and the formation structure thereof is not limited. Furthermore, the wiring structure may be formed in a necessary shape or structure over the entire area of ​​the expandable substrate (10) without being divided into the rigid variable part (100) and the rigid retaining part (200).

[0060] In the case of this embodiment, the configuration of the rigidity variable part (100) and the rigidity maintaining part (200) constituting the expandable substrate (10) as substrates is described. As components that must be additionally formed for the expandable substrate (10) to be used as a display device, such as the wiring structure described above, can be applied as they are according to the prior art, so a description thereof is omitted.

[0061] In the above-described expandable substrate (10), the rigidity variable portion (100) and the rigidity maintaining portion (200) have the characteristic of varying or maintaining rigidity through temperature variation to a specific temperature, as previously explained, but both can be formed of the same material. That is, regarding the expandable substrate (10) formed of the same material, by additionally performing a specific treatment or process as described below, the characteristics are varied so that the area where rigidity is stably maintained and the area where rigidity is varied are divided.

[0062] Below, the division of the above-mentioned rigidity variable part (100) and the above-mentioned rigidity maintaining part (200), and the characteristics of the self-rigidity distribution of the above-mentioned expandable substrate (10) according to this will be explained in more detail.

[0063] Figure 2 is a schematic diagram illustrating a state in which the stiffness distribution varies according to temperature variation in the expandable substrate of Figure 1.

[0064] Referring to FIG. 2, the expandable substrate (10) is at a temperature (T) lower than a predetermined specific temperature (Tc). <Tc)로 유지되는 상태에서는, 전체적으로 동일한 상대적으로 높은 강성을 유지한다. 따라서, 이러한 상태에서는 상기 신축기판(10)은 별도의 신축성을 가지지 않으며 고강성의 안정적인 구조를 유지한다.

[0065] However, if the above-mentioned flexible substrate (10) is exposed to an environment with a temperature (T > Tc) higher than a predetermined specific temperature (Tc), the stiffness maintaining part (200) maintains a relatively high stiffness, identical to the initial state, but the stiffness variable part (100) has a lower stiffness than the stiffness in the initial state.

[0066] Thus, in this state, the rigidity maintaining part (200) maintains a stable structure without being stretched or expanded by external force, etc., but the rigidity variable part (100) is stretched or deformed by external force, etc. Accordingly, as illustrated, the stretchable substrate (10) can be stretched or compressed overall according to the direction of the external force.

[0067] That is, in the case of the above-mentioned expandable substrate (10), a deformation in which the overall length is extended or shortened may be induced, but the above-mentioned rigidity maintaining part (200) on which the previously described electronic device is mounted maintains its shape identical to the initial state and its structure is not varied.

[0068] Accordingly, in the area where the electronic device is mounted, the mounting state and electrical connection state of the electronic device, etc., can be stably maintained.

[0069] As described above, the reason why elasticity is not induced only in the rigidity maintaining part (200) defined as a local area and a stable structure with relatively high rigidity is maintained is explained with reference to the following drawings.

[0070] Figures 3a and 3b are graphs illustrating the state of having a self-stiffness distribution according to the distribution of the glass transition temperature in the stretchable substrate of Figure 1.

[0071] First, referring to FIG. 3a, the stretchable substrate (10) includes a first material, and if the glass transition temperature of the first material is Tg1, the stiffness of the first material can decrease rapidly at a temperature greater than the glass transition temperature Tg1.

[0072] Likewise, if the above-mentioned flexible substrate (10) includes a second material and the glass transition temperature of the second material is T2, the rigidity of the second material can also decrease rapidly at a temperature greater than the glass transition temperature Tg2.

[0073] At this time, if the above-mentioned expandable substrate (10) is maintained within a temperature range between Tg1, the glass transition temperature of the first material, and Tg2, the glass transition temperature of the second material, the rigidity of the above-mentioned expandable substrate (10) decreases in the region containing the first material, but the rigidity does not decrease in the region containing the second material and can be maintained at a certain level.

[0074] Consequently, in the above-mentioned flexible substrate (10), the rigidity is reduced in the region containing the first material, so as shown in FIG. 3b, it has high elasticity and can be easily deformed according to external force, but in the region containing the second material, the rigidity is maintained and no deformation occurs.

[0075] Accordingly, by maintaining the above-mentioned expandable substrate (10) within the temperature range of Tg1 and Tg2, the expandable substrate (10) can be controlled to have elasticity and easily deform in response to external forces. In other words, this means that if the first and second materials are selected such that the temperature (T) falls within the temperature range of Tg1 and Tg2 by considering the temperature (T) of the environment in which the expandable substrate (10) is used, or if the glass transition temperatures of the first and second materials are controlled such that the temperature (T) falls within the range between the glass transition temperatures of the first and second materials, the expandable substrate (10) can be controlled to have elasticity in a specific area and maintain rigidity in another area.

[0076] As described above, if the stretchable substrate (10) is configured to have different glass transition temperatures, the stretchable substrate (10) can be controlled to have elasticity in a specific region while maintaining rigidity in another region.

[0077] At this time, the control of the elasticity of the above-described elastic substrate (10) can be applied in the same way not only when the elastic substrate (10) includes different first and second materials, but also when the elastic substrate (10) includes the same material and is formed to have different glass transition temperatures for each region.

[0078] That is, if the above-mentioned stretchable substrate (10) contains the same material over the entire area but is formed to have a different glass transition temperature from other areas through a specific area through a predetermined processing process, then, as explained above with reference to FIG. 3a and FIG. 3b, the stretchability can be controlled differently due to the difference in glass transition temperatures between the specific area and other areas.

[0079] At this time, as previously explained, if the temperature (T) in the environment where the stretchable substrate (10) is used falls within the range between the glass transition temperatures in the specific region and the other region, then the stretchable substrate (10) will have different stretchability in each region of the usage environment.

[0080] Furthermore, if the temperature (T') of the process environment of the stretchable substrate (10), in addition to the temperature in the usage environment of the stretchable substrate (10), is controlled to be lower than the glass transition temperatures in both the specific region and the other region, the stretchable substrate (10) has constant rigidity in all regions of the process environment while minimizing elasticity. Similarly, if the temperature (T') of the process environment of the stretchable substrate (10) is controlled to be higher than the glass transition temperatures in both the specific region and the other region, the stretchable substrate (10) may be able to deform while having elasticity in all regions of the process environment.

[0081] FIG. 4 is a perspective view illustrating an expandable substrate having a self-stiffness distribution according to another embodiment of the present invention.

[0082] The expandable substrate (11) according to the present embodiment is substantially the same as the expandable substrate (10) described with reference to FIG. 1, except for the shape and arrangement of the rigidity retaining part (204), so redundant description is omitted.

[0083] Referring to FIG. 4, in the expandable substrate (11) according to the present embodiment, the rigidity retaining members (204) are arranged in a plurality parallel to each other in the first direction (X) and are arranged to extend relatively long in the second direction (Y) perpendicular to the first direction (X). At this time, as illustrated, two rigidity retaining members (204) may be arranged continuously in the second direction (Y). Of course, one rigidity retaining member (204) may be extended relatively long in the second direction (Y), or three or more may be arranged continuously.

[0084] Ultimately, in this embodiment, the rigidity retaining portion (204) is formed such that its length along the second direction (Y) is relatively larger than its length (i.e., width) along the first direction (X). Thus, in the stretchable substrate (11), the elasticity in the first direction (X), where the rigidity retaining portion (204) is distributed over a relatively small area, is formed to be greater than the elasticity in the second direction (Y).

[0085] As described above, since the rigidity retaining part (204) is formed with a relatively long rectangular shape in a specific direction, a relatively long rectangular element can be mounted more stably. Furthermore, since the lengths of the rigidity retaining part (204) along the first direction (X) and the second direction (Y) are formed differently, the elasticity along the first direction (X) and the elasticity along the second direction (Y) are different, thus enabling various applications. In this case, an example of such an application is a rollable display.

[0086] FIG. 5 is a perspective view illustrating an expandable substrate having a self-stiffness distribution according to another embodiment of the present invention.

[0087] The expandable substrate (12) according to the present embodiment is substantially the same as the expandable substrate (10) described with reference to FIG. 1, except for the shape and arrangement of the rigidity maintaining part (205) and the rigidity variable part (105, 106), so redundant description is omitted.

[0088] Referring to FIG. 5, in the expandable substrate (12) according to the present embodiment, the rigidity retaining portion (205) relatively occupies most of the area of ​​the expandable substrate (12), and the rigidity variable portion (105, 106) is formed in a shape that extends long in a specific direction.

[0089] That is, the first rigid variable portion (105) extends along the first direction (X) for a predetermined length on the expandable substrate (12), and the second rigid variable portion (106) extends in the second direction (Y) and is short-circuited at the portion facing the first rigid variable portion (105). At this time, the first rigid variable portion (105) does not extend to the side of the expandable substrate (12), but the second variable rigid portion (106) can be formed to extend to the side of the expandable substrate (12).

[0090] Thus, the first and second rigidity variable parts (105, 106) are formed on the rigidity retaining part (205) in an overall cross (+) shape, which is such that the cutting line portion of the so-called kirigami pattern is formed as the rigidity variable parts (105, 106). At this time, it is sufficient that the first and second rigidity variable parts (105, 106) are formed substantially like the cutting line of the kirigami pattern, and it does not mean that they are cut along the kirigami pattern.

[0091] Through this, unlike in FIG. 4, in the expandable substrate (12) according to the present embodiment, the length of the rigidity retaining portion (205) along the first direction (X) can be substantially the same as the length of the rigidity retaining portion (205) along the second direction (Y).

[0092] Meanwhile, through the arrangement of the stiffness variable part and the stiffness maintaining part as in FIG. 5, the overall Poisson's ratio of the expandable substrate (12) becomes negative and approaches -1. Accordingly, when the expandable substrate (12) is expanded in the second direction (Y), expansion in the first direction (X) occurs at a similar ratio, thereby inducing uniform elongation or uniform contraction throughout the expandable substrate (12).

[0093] Thus, through the stretchable substrate (12) in this embodiment, the aspect ratio distortion of the display image caused by unidirectional stretching can be significantly reduced.

[0094] In the following, embodiments regarding a method of treating the above-described expandable substrate (10), which includes the same material as above, to have different glass transition temperatures in a specific region and a different region are described.

[0095] Figure 6 is a process diagram illustrating the method of manufacturing the expandable substrate of Figure 1.

[0096] First, referring to FIG. 6, in the manufacture of the expandable substrate (10), a mask portion (300) is aligned on the upper surface of the expandable substrate (10) formed from the same material. At this time, the mask portion (300) blocks ultraviolet (UV) light provided from above, and it is sufficient if it includes a material capable of blocking ultraviolet light.

[0097] Additionally, as illustrated, the mask portion (300) has a plurality of openings (310) formed therein, and the location where the openings (310) are formed must be located above the location where the rigidity retaining portions (200) are to be formed on the expandable substrate (10).

[0098] That is, the size or pattern of the openings (310) can be formed substantially the same as the size or pattern of the rigidity retaining parts (200) to be formed, and as previously explained, since the size and pattern of each of the rigidity retaining parts (200) can be designed to vary in various ways, it is sufficient if the size and pattern of each of the openings (310) are designed to correspond to this.

[0099] Afterwards, ultraviolet (UV) light is provided from the upper part of the mask portion (300), and thereby the ultraviolet light passes only through the openings (310) and is provided to the stretchable substrate (10).

[0100] Thus, on the above-mentioned flexible substrate (10), the characteristics are varied according to the exposure to the ultraviolet light (50) in the area where the ultraviolet light (50) is provided, and the rigidity maintaining portion (200) is formed accordingly. That is, the rigidity maintaining portion (200) is formed only in the area exposed to the ultraviolet light (50), and the area where the ultraviolet light (50) is blocked remains as the rigidity variable portion (100).

[0101] At this time, the above-mentioned expandable substrate (10) may include PDMS (polydimethylsiloxane) or polyimide.

[0102] In particular, the above-mentioned flexible substrate (10) may include a glycol gel. Thus, as shown in FIG. 6, in the area exposed to the ultraviolet rays (50), i.e., the rigidity retaining portion (200), the glycol gel forms a network by photocrosslinking, and polyimide is polymerized in the space between the networks to induce high-density polymer entanglement.

[0103] That is, when ultraviolet light is irradiated onto the glycol gel, a crystalline / entangled phase region is formed with a locally high polymer concentration. Subsequently, if a semi-IPN structure of polyimide is formed in the space between the networks, more polymer entanglement can be induced in the local region with a relatively high polymer concentration. Thus, as shown in Fig. 6, the glass transition temperature (Tg) increases due to the relatively high polymer concentration.

[0104] In contrast, in the region where the above-mentioned ultraviolet rays are not irradiated, a relatively high polymer concentration as described above is not formed, so a relatively low polymer concentration is maintained, and thus the glass transition temperature (Tg) is maintained at a relatively low level.

[0105] Thus, in the above-mentioned flexible substrate (10), the rigidity maintaining portion (200) to which the ultraviolet rays (50) are irradiated has a relatively high glass transition temperature (Tg2), and the rigidity variable portion (100) to which the ultraviolet rays (50) are blocked has a relatively low glass transition temperature (Tg1).

[0106] Accordingly, as explained with reference to FIG. 3, the temperature (T) between the glass transition temperatures (Tg2~Tg1) stretch In the above, the rigidity maintaining portion (200) of the above-mentioned flexible substrate (10) maintains relatively high rigidity and does not deform, but the above-mentioned rigidity variable portion (100) is stretched and deformed by an external force as its rigidity decreases.

[0107] As described above, even in the above-described stretchable substrate (10) containing the same material, regions with different rigidities can be formed, thereby allowing the deformation of a specific region to be minimized while other regions can be stretched and deformed.

[0108] At this time, if an electronic component is mounted in a specific area where the deformation is minimized, i.e., the rigidity maintaining part (200), then even if another area, i.e., the rigidity variable part (100), is stretched and deformed by an external force, the area where the electronic component is mounted will have minimal deformation, thereby maintaining a stable electrical connection state. Therefore, the stretchable substrate (10) can maintain electrical or mechanical stability by maintaining a stable connection state of the electronic component mounted inside while having elasticity.

[0109] FIGS. 7a and 7b are process diagrams illustrating a method for manufacturing a stretchable substrate according to another embodiment of the present invention.

[0110] In the method of manufacturing the expandable substrate (20) according to the present embodiment, except for the difference in the structure of the opening (311) formed in the mask portion (301) and the structure of the rigidity maintaining portion (201) therefrom, it is identical to the method of manufacturing the expandable substrate (10) described with reference to FIG. 6, so the same reference numbers are used for the same components and redundant descriptions are omitted.

[0111] Referring to FIG. 7a, in the method for manufacturing the expandable substrate (20) according to the present embodiment, the mask portion (301) is aligned on the upper portion of the expandable substrate (20) located on the base substrate (20).

[0112] The above mask part (301) blocks ultraviolet (UV) light provided from above, and it is sufficient if it includes a material capable of blocking ultraviolet light.

[0113] In addition, as illustrated, the mask portion (301) has a plurality of openings (311) formed therein, and as previously explained, the location where the openings (311) are formed must be above the location where the rigidity retaining portions (201) are to be formed on the expandable substrate (20).

[0114] In the case of this embodiment, as illustrated, the opening ratio of the mask portion (301) gradually decreases from the center to the periphery, and accordingly, the degree of ultraviolet light transmission gradually decreases from the center to the periphery. That is, if the degree of ultraviolet light transmission (50) is greatest at the center and shows an ultraviolet light transmittance of 100%, the ultraviolet light transmittance gradually decreases from the center to the periphery, so that finally, at the boundary region between the rigidity maintaining portion (201) and the rigidity variable portion (100), the ultraviolet light transmittance may be 0%.

[0115] As described above, as the transmittance of ultraviolet rays (50) decreases as the opening (311) moves from the center to the periphery, the degree to which the characteristics are varied by the ultraviolet rays (50) also decreases as it moves from the center to the periphery.

[0116] That is, as previously explained, as the rigidity retainer (201) is exposed to the ultraviolet rays (50) provided through the opening (311), the glass transition temperature (Tg) of the rigidity retainer (201) increases due to the relatively high polymer concentration, and the degree of increase in the glass transition temperature (Tg) gradually decreases from the central part (211) of the rigidity retainer (201) to the peripheral part (212).

[0117] Accordingly, as shown in FIG. 7b, the rigidity in the rigidity maintaining part (201) gradually decreases from the central part (211) to the peripheral part (212), and the elasticity is also increased as it goes to the peripheral part (212).

[0118] Generally, as shown in FIG. 6, if the rigidity maintaining portion (200) and the rigidity variable portion (100) have a relatively large difference in glass transition temperature, a sudden difference in rigidity exists at the boundary surface between the rigidity maintaining portion (200) and the rigidity variable portion (100), and the possibility of damage or defects occurring due to the sudden difference in elasticity or deformation at the boundary surface increases. That is, a stress concentration phenomenon may occur in the stretchable substrate (10).

[0119] Therefore, in order to minimize the stress concentration phenomenon caused by the rapid difference in elasticity or deformation at the interface, as in the present embodiment, the glass transition temperature is gradually reduced from the central part (211) to the peripheral part (212) in the rigidity maintaining part (201), thereby minimizing the difference in elasticity or deformation at the interface between the rigidity maintaining part (201) and the rigidity variable part (100) and alleviating stress concentration.

[0120] Through this, even when the above-mentioned flexible substrate (20) is subjected to various and repetitive deformations, the occurrence of damage or defects at the interface can be minimized, thereby further improving the electrical or mechanical stability of the electronic device (400) mounted on the upper surface of the rigidity retaining part (201).

[0121] Meanwhile, unlike the case where the opening (311) formed in the mask portion (301) is formed such that the opening rate gradually decreases as in FIG. 7a, the intensity of the irradiated ultraviolet light (50) may be controlled to gradually decrease while maintaining the opening rate of the opening (311).

[0122] That is, the opening (311) is formed to have 100% transmittance in both the central and peripheral parts, as in the opening (310) of FIG. 6, and the ultraviolet light (50) irradiated from the upper part of the mask part (301) can be configured as modulated light in which the intensity gradually decreases from the central part to the peripheral part.

[0123] In this way, if the ultraviolet light (50) is configured as modulated light whose intensity gradually decreases from the center to the periphery, the intensity of the light provided to the rigidity maintaining portion (201) of the stretchable substrate (20) can be substantially the same as in the case where the aperture ratio of the opening (311) in FIG. 7a is varied.

[0124] Thus, as shown in FIG. 7b, in the case of the rigidity maintaining part (201), the glass transition temperature (Tg) gradually decreases from the central part (211) to the peripheral part (212), and accordingly, the difference in elasticity or deformation at the interface between the rigidity maintaining part (201) and the rigidity variable part (100) is minimized, thereby allowing stress concentration to be relieved.

[0125] FIGS. 8a to 8d are process diagrams illustrating a method for manufacturing a stretchable substrate according to another embodiment of the present invention.

[0126] The method of manufacturing the expandable substrate (30) according to the present embodiment is identical to the method of manufacturing the expandable substrate (10) described with reference to FIG. 6, except that the thicknesses of the rigid variable portion (101) and the rigid retaining portion (202) in the expandable substrate (30) are formed differently from each other; therefore, the same reference numbers are used for identical components and redundant descriptions are omitted.

[0127] First, referring to FIG. 8a, in the case of the expandable substrate (30) in the present embodiment, the rigidity retaining portion (202) has a first thickness (t1), and the rigidity variable portion (101) has a second thickness (t2). At this time, the first thickness (t1) is greater than the second thickness (t2).

[0128] Additionally, to have these structural features, the expandable substrate (30) includes a protrusion (150) that protrudes downward in the area where the rigidity retaining portion (202) is formed. Likewise, in order to perform a predetermined process on the expandable substrate (30), the base substrate (21) on which the expandable substrate (30) is positioned includes a recess (22) that is concavely recessed to correspond to the protrusion (150).

[0129] In this case, the protrusion (150) has a curved outer surface as illustrated and protrudes downward, and may have, for example, a hemispherical shape. However, the shape of the protrusion (150) is not limited, and it may be formed so that the thickness gradually decreases from the center of the protrusion (150) toward the periphery.

[0130] Accordingly, the first thickness (t1) of the rigidity maintaining part (202) corresponds to the thickness at the central part of the rigidity maintaining part (202), and the first thickness (t1) can gradually decrease from the central part to the periphery. Thus, the boundary surface between the rigidity maintaining part (202) and the rigidity variable part (101) can have the second thickness (t2) formed.

[0131] Meanwhile, although not described in detail, the protrusion (150) can be formed by a process of forming a stretchable substrate (30) on the upper surface of the base substrate (21) through a transfer process such as an imprint, while the indentation (22) is formed on the base substrate (21) in advance. That is, the indentation (22) of the base substrate (21) can be transferred as is so that the protrusion (150) can be formed on the lower surface of the stretchable substrate (30).

[0132] With respect to the above-described, expandable substrate (30) including the above-described protrusion (150), referring to FIG. 8b, the mask portion (300) is positioned on the upper portion and ultraviolet light (50) is irradiated.

[0133] At this time, the mask portion (300) is identical to the mask portion (300) described with reference to FIG. 6 and includes a plurality of openings (310), wherein the openings (310) are aligned with the position and pattern where the rigidity retaining portion (202) is formed in the stretchable substrate (30).

[0134] Thus, when the above ultraviolet rays (50) are irradiated, the rigidity retaining part (202) is exposed to the ultraviolet rays (50) through the opening (310), and the glass transition temperature (Tg) of the rigidity retaining part (202) increases relatively. At this time, the internal polymer entanglement state in which the glass transition temperature of the rigidity retaining part (202) increases relatively is as described above.

[0135] Accordingly, as shown in FIG. 8b, the rigidity retaining portion (202) is formed. However, as shown in FIG. 8b, in the portion where the protrusion (150) is formed, a polymer entanglement state is not induced internally.

[0136] More specifically, since the protrusion (150) is formed to have a relatively thick thickness (t1), if the intensity of the irradiated ultraviolet light (50) is controlled, the ultraviolet light is not irradiated up to the protrusion (150), and the characteristics are varied by the ultraviolet light only up to the upper part of the protrusion (150).

[0137] Accordingly, in the above-mentioned flexible substrate (30), the rigidity maintaining portion (200) is formed only in the upper portion of the protrusion (150), and the protrusion (150) does not increase its glass transition temperature and maintains the same glass transition temperature as the surrounding rigidity variable portion (101).

[0138] Afterwards, referring to FIG. 8c and FIG. 8d, after mounting an electronic element (400) on the upper surface of the rigidity retaining part (200) and removing the base substrate (21) located at the bottom, a flexible substrate (30) having a structure as in FIG. 8d is completed.

[0139] At this time, in the case of the above-described expandable substrate (30), as previously explained, the rigidity maintaining portion (200) is formed in the portion where the electronic element (400) is mounted to have a relatively high glass transition temperature, but the portion where the electronic element (400) is not mounted has a relatively low glass transition temperature as the rigidity variable portion (101). Furthermore, the above-described protrusion (150) is also a portion where the ultraviolet rays (50) cannot reach, and thus maintains a relatively low glass transition temperature, similar to the rigidity variable portion (101).

[0140] Thus, only the local portion where the electronic device (400) is mounted has relatively high rigidity and maintains structural stability, while the remaining area as well as the lower portion of the electronic device (400) can be deformed to have elasticity. That is, while maintaining the deformation rate in the portion where the electronic device (400) is mounted to be minimized, the elastic substrate (30) can be stretched and deformed over its entire surface area. Accordingly, the elastic substrate (30) can maintain the electrical or mechanical stability of the electronic device (400) while having improved elasticity.

[0141] In the above, a method for manufacturing the expandable substrate such that it has different stiffnesses in different regions within the expandable substrate was described.

[0142] However, in addition to the method of manufacturing the above-mentioned expandable substrate itself to have different glass transition temperatures in different regions, it is possible to vary the stiffness so that the expandable substrate has different elasticity in different regions even while having the same glass transition temperature overall.

[0143] Accordingly, a method for varying the stiffness distribution of the above-mentioned flexible substrate is described below.

[0144] FIGS. 9a and 9b are process diagrams illustrating a method for varying the stiffness distribution of an expandable substrate according to another embodiment of the present invention.

[0145] In the case of the expandable substrate (40) according to the present embodiment, it is the same as the previous expandable substrates in that it contains the same material throughout, and furthermore, the glass transition temperature is not varied relatively high in a specific area through separate ultraviolet irradiation. That is, the expandable substrate (40) has the same glass transition temperature (Tg) over the entire area.

[0146] Accordingly, the method for varying the stiffness distribution in the above-described expandable substrate (40) having the same glass transition temperature (Tg) as described above is as follows.

[0147] First, referring to FIG. 9a, a rigidity maintaining portion (203), which is a region with relatively high rigidity in the above-mentioned flexible substrate (40), and a rigidity variable portion (102), which is a region with relatively low rigidity and is flexible, are defined.

[0148] Afterward, on the above-mentioned expandable substrate (40), the rigidity maintaining part (203) and the rigidity variable part (102) are heated unevenly to different temperatures. At this time, the heating temperature of the rigidity variable part (102) is controlled to be higher than the heating temperature of the rigidity maintaining part (203).

[0149] Thus, as described above, by heating the rigidity maintaining part (203) and the rigidity variable part (102) unevenly to different temperatures, as shown in FIG. 9b, the rigidity maintaining part (203) maintains a relatively high rigidity, while the rigidity variable part (102) has a relatively low rigidity, so that the rigidity variable part (102) can be deformed while having elasticity.

[0150] That is, even if the above-mentioned flexible substrate (40) has the same glass transition temperature (Tg) overall, if a local region is controlled to have a temperature above the glass transition temperature through heating, the rigidity in that region is relatively lowered and it can be deformed while having flexibility.

[0151] Accordingly, the above-mentioned flexible substrate (40) has a rigidity distribution that allows it to be deformed while having flexibility only in a specific area.

[0152] Meanwhile, as shown in FIG. 9a, an example of a method for heating the rigidity maintaining part (203) and the rigidity variable part (102) to different temperatures unevenly in the above-described flexible substrate (40) is described as follows.

[0153] First, regarding the above-mentioned flexible substrate (40), the rigidity maintaining part (203) is not heated separately, and only the rigidity variable part (102) can be selectively heated to increase the temperature.

[0154] To this end, a thin film heater is attached only to the lower part of the rigidity variable portion (102) so that the temperature can be increased through heating only for the rigidity variable portion (102). In particular, the expandable substrate (40) in this embodiment comprises PDMS (polydimethylsiloxane) or polyimide, and since the thermal conductivity of the substrate as a whole is not high, even if local heating is performed on the rigidity variable portion (102) through the thin film heater, heating due to heat conduction to the rigidity maintaining portion (200) is limited.

[0155] In contrast, the expandable substrate (40) can be heated such that the temperature of the rigidity variable portion (102) is relatively higher than that of the rigidity maintaining portion (203) with respect to the expandable substrate (40).

[0156] For example, if the stiffness variable part (102) is formed to have a higher thermal diffusivity than the stiffness maintaining part (203), the stiffness variable part (102) can be heated to a higher temperature even if the entire stretchable substrate (40) is heated. Thus, the temperature in the stiffness variable part (102) can be controlled to be higher than the glass transition temperature, thereby controlling the stiffness of the stiffness variable part (102) to be relatively low so that it has elasticity.

[0157] At this time, as a method for heating the entire expandable substrate (40), it is possible to heat it by placing a light source around the expandable substrate (40), but it is not limited to this method.

[0158] Furthermore, regarding the above-mentioned flexible substrate (40), there is a method of heating the flexible substrate (40) such that the temperature of the rigidity variable portion (102) is relatively higher than that of the rigidity maintaining portion (203), and forming the rigidity variable portion (102) to contain more photothermal particles than the rigidity maintaining portion (203).

[0159] That is, in manufacturing the above-mentioned flexible substrate (40), particles that induce a photothermal reaction can be mixed and manufactured, and at this time, the distribution or density of the photothermal particles can be made different in the rigidity maintaining part (203) and the rigidity variable part (102).

[0160] Accordingly, if photothermal particles are included so that they have a higher distribution or density in the rigidity variable part (102) than in the rigidity maintaining part (203), the rigidity variable part (102) can be heated to a higher temperature even if the flexible substrate (40) is heated equally. Thus, by controlling the temperature in the rigidity variable part (102) to be higher than the glass transition temperature, the rigidity of the rigidity variable part (102) can be controlled to be relatively low so that it has elasticity.

[0161] At this time, as previously explained, the overall heating method of the expandable substrate (40) may be a method of heating by placing a hot plate on the lower surface of the expandable substrate (40), but is not limited thereto.

[0162] FIGS. 10a and FIGS. 10b are graphs illustrating the stress concentration phenomenon according to temperature variation in the stretchable substrate of FIG. 1.

[0163] Referring to FIG. 10a, in the expandable substrate (10) described in FIG. 1, the temperature (T) of the expandable substrate (10) is the expandable temperature (T) exemplified in FIG. 3a. stretch If kept smaller than ) (T <T stretch), the above-mentioned flexible substrate (10) maintains the same rigidity overall. That is, the rigidity maintaining part (200) and the rigidity variable part (100) both have the same rigidity.

[0164] Accordingly, when an external force is applied to the expandable substrate (10) in the above environment, as the expandable substrate (10) is stretched, stress is concentrated in the part where the electronic device (400) is mounted, and thus a defect may be caused in the mounting state of the electronic device (400).

[0165] In contrast, referring to FIG. 10b, the temperature (T) of the expandable substrate (10) is the expandable temperature (T) exemplified in FIG. 3a. stretch If kept the same as ) (T=T stretch ), the above-mentioned flexible substrate (10) has locally different stiffness. That is, since the temperature (T) is lower than the glass transition temperature (Tg2) of the stiffness maintaining part (200) and higher than the glass transition temperature (Tg1) of the stiffness variable part (100), the stiffness maintaining part (200) maintains relatively high stiffness, but the stiffness variable part (100) becomes relatively low.

[0166] Thus, when an external force is applied to the above-mentioned expansion board (10) in the above-mentioned environment, as the expansion board (10) is stretched, the rigidity maintaining part (200), which is the part where the electronic element (400) is mounted, maintains high rigidity so that deformation is minimized, but the rigidity variable part (100) is stretched by the tensile force.

[0167] Furthermore, when the above-mentioned rigid variable part (100) is extended, stress concentration does not occur in the rigidity maintaining part (200), which is the part where the electronic element (400) is mounted, and thus the mounting state of the electronic element (400) can be stably maintained.

[0168] Thus, even in a repeated expansion state due to the application of repeated external force, the electronic device (400) maintains a stable mounting state, and the electrical or mechanical stability of the expansion substrate (10) can be maintained.

[0169] According to the embodiments of the present invention as described above, in a stretchable substrate, only the stiffness variable portion is deformed to allow stretching when the stiffness is lowered above a preset temperature. Therefore, by controlling the temperature, the stiffness in a specific region is maintained while the stiffness in another region is controlled to vary, thereby enabling the construction of a stretchable substrate having a different stiffness distribution.

[0170] In particular, if the rigidity maintaining portion is formed in a specific arrangement and a device is mounted on the rigidity maintaining portion, the expandable substrate has elasticity through temperature control, while the elasticity is minimized in the area where the device is mounted, thereby maintaining a stable device connection state.

[0171] Furthermore, by resolving the contact problem or structural instability problem at the interface between the conventional expandable and non-expandable parts, it is possible to configure an expandable substrate that can maintain a stable structure at the interface while possessing expandability through the continuous structural characteristics of the same material.

[0172] Furthermore, the temperature control described above enables the control of the elasticity of the expandable substrate with a variable stiffness structure by controlling within the glass transition temperature range based on information regarding the glass transition temperatures of the variable stiffness part and the stiffness maintaining part. At this time, since the glass transition temperatures of the variable stiffness part and the stiffness maintaining part can be formed differently based on information regarding the temperature range during the manufacturing process or the usage state of the expandable substrate, the stability of the manufacturing process can be maintained by keeping the stiffness high during the manufacturing process, while the various usability of the expandable substrate can be improved by varying the stiffness during actual usage.

[0173] By forming the glass transition temperatures of the variable stiffness portion and the stiffness-maintaining portion differently, ultraviolet rays can be applied only to the stiffness-maintaining portion on the stretchable substrate to form a relatively high glass transition temperature; thus, the stretchable substrate can be manufactured through the selection of materials and a relatively simple process.

[0174] In particular, by providing ultraviolet light to the rigidity retaining portion to gradually change the light intensity, or by fabricating it to gradually change the degree of opening of the opening of the mask portion, the structural stability during the repetitive stretching of the stretchable substrate can be further improved through the gradual variation of rigidity at the interface between the variable rigidity portion and the rigidity retaining portion. In this case, by forming the rigidity retaining portion by varying it into various patterns or shapes, and mounting devices on the rigidity retaining portion of a wider variety of shapes, it is possible to configure a stretchable substrate having a variety of rigidity distributions.

[0175] In addition, by forming the thickness of the rigidity retaining portion relatively thickly, the strain or elongation rate of the rigidity retaining portion is kept even lower, thereby minimizing the strain of the device mounted on the rigidity retaining portion and maintaining a more stable device connection state, making it possible to manufacture an elongation substrate with high electrical stability and reliability.

[0176] Furthermore, the stiffness distribution in the stretchable substrate can be varied through a process of heating the stiffness maintaining part and the stiffness variable part to different temperatures, or heating only the stiffness variable part. Through this, the regions of the stiffness maintaining part and the stiffness variable part can be set to have various patterns or arrangements, and by varying the stiffness distribution through a relatively simple heating method, it is possible to manufacture a stretchable substrate having more diverse self-stiffness distribution characteristics.

[0177] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims. Explanation of the symbols

[0178] 10, 11, 12, 20, 30, 40 : Stretchable substrate 20, 21: Base substrate 22: Recessed part 50: UV 150: Protrusion 100, 101, 102, 104, 105, 106: Variable rigidity 200, 201, 202, 203, 204, 205: Rigidity retaining parts 211 : Central part 212 : Periphery part 300, 301: Mask part 310: Opening 400 : Electronic components

Claims

Claim 1 A stretchable substrate comprising a stiffness maintaining portion and a stiffness variable portion divided into different regions, wherein the stiffness maintaining portion and the stiffness variable portion are made of the same material and have different glass transition temperatures so as to have different characteristics so as to control their elasticity differently, wherein the stiffness maintaining portion and the stiffness variable portion maintain a preset stiffness only below a preset temperature, and the stiffness variable portion deforms to allow for stretchability by having a stiffness lower than the preset stiffness above the preset temperature. Claim 2 An expandable substrate according to claim 1, wherein the rigidity maintaining portion is formed in a plurality of regions having a predetermined pattern, and the rigidity variable portion is formed in a region other than the rigidity maintaining portion. Claim 3 An expandable substrate according to claim 2, characterized in that the length of the rigidity-maintaining portion along the first direction and the length of the rigidity-maintaining portion along the second direction perpendicular to the first direction are different from each other. Claim 4 A flexible substrate characterized in that, in paragraph 2, an element is mounted on the rigidity maintaining portion. Claim 5 An expandable substrate according to claim 1, wherein the stiffness variable portion is formed having a predetermined pattern, and the stiffness maintaining portion is formed in a different area excluding the stiffness variable portion. Claim 6 In claim 5, the above-mentioned rigid variable portion is characterized by being formed along a kirigami pattern, forming an expandable substrate. Claim 7 A stretchable substrate according to claim 6, characterized in that Poisson's ratio is negative, and when stretching occurs in a first direction, stretching in a second direction perpendicular to the first direction also occurs at the same ratio. Claim 8 A stretchable substrate according to claim 1, characterized in that the above-mentioned preset temperature is the glass transition temperature of the above-mentioned rigidity variable portion. Claim 9 An expandable substrate according to claim 1, characterized in that the glass transition temperature of the stiffness variable portion is lower than the glass transition temperature of the stiffness maintaining portion. Claim 10 A stretchable substrate characterized in that, in any one of claims 1 to 9, the stiffness maintaining portion and the stiffness variable portion comprise PDMS (polydimethylsiloxane) or polyimide. Claim 11 A method for manufacturing a stretchable substrate comprising a stiffness retaining portion and a stiffness variable portion that are partitioned into different regions, wherein the properties are varied to have different glass transition temperatures while including the same material, thereby controlling the stretchability differently, and the method comprises the steps of: positioning a mask portion such that an opening is aligned with the stiffness retaining portion; and providing ultraviolet rays from above the mask portion so that only the stiffness retaining portion receives ultraviolet rays. Claim 12 A method for manufacturing a stretchable substrate according to claim 11, characterized in that, as ultraviolet light is provided only to the rigidity maintaining portion, the glass transition temperature of the rigidity maintaining portion is formed to be higher than the glass transition temperature of the rigidity variable portion. Claim 13 A method for manufacturing a stretchable substrate according to claim 11, wherein the stretchable substrate comprises a glycol gel. Claim 14 A method for manufacturing a stretchable substrate according to claim 13, characterized in that, as ultraviolet light is provided only to the rigidity-maintaining portion, the glycol gel forms a network by photocrosslinking, polyimide is polymerized in the space between the networks to induce high-density polymer entanglement, and the glass transition temperature rises. Claim 15 A method for manufacturing a stretchable substrate according to claim 11, wherein the opening of the mask portion is characterized in that the degree of ultraviolet light transmission gradually decreases from the center of the opening to the periphery. Claim 16 A method for manufacturing a stretchable substrate according to claim 11, wherein the ultraviolet light is a modulated light whose intensity gradually decreases from the center of the opening to the periphery. Claim 17 A method for manufacturing a stretchable substrate according to claim 15 or 16, characterized in that the glass transition temperature of the stiffness maintaining portion gradually decreases from the central portion to the peripheral portion which is the boundary with the stiffness variable portion. Claim 18 A method for manufacturing an expandable substrate according to claim 11, characterized in that the stiffness maintaining portion is formed with a greater thickness than the stiffness variable portion. Claim 19 A method for manufacturing a flexible substrate according to claim 18, characterized in that the thickness of the rigidity maintaining portion gradually decreases from the central portion to the peripheral portion which is the boundary with the rigidity variable portion. Claim 20 A method for varying the stiffness distribution of a stretchable substrate, wherein the stretchable substrate includes a stiffness maintaining portion and a stiffness variable portion divided into different regions, wherein the stiffness maintaining portion maintains the temperature and only the stiffness variable portion is heated to increase the temperature, or the stretchable substrate is heated such that the stiffness variable portion has a higher temperature than the stiffness maintaining portion. Claim 21 A method for varying the stiffness distribution of an expandable substrate, characterized in that, in the case of heating only the stiffness variable part to increase the temperature in claim 20, a heater is attached to the lower surface of the stiffness variable part. Claim 22 A method for varying the stiffness distribution of an expandable substrate according to claim 20, characterized in that when heating the expandable substrate while maintaining the temperature of the stiffness variable part relatively higher than that of the stiffness maintaining part, the stiffness variable part is formed to have a higher thermal diffusivity than the stiffness maintaining part. Claim 23 A method for varying the stiffness distribution of a stretchable substrate according to claim 20, characterized in that when heating the stretchable substrate while maintaining the temperature of the stiffness variable part relatively higher than that of the stiffness maintaining part, the stiffness variable part is formed to contain more photothermal particles than the stiffness maintaining part.

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