A stretchable substrate having a self-regulating stiffness distribution, a method for manufacturing the same, and a method for varying the stiffness distribution thereof.

Abstract

In a stretchable substrate having a self-stiffness distribution, a method for manufacturing the same, and a method for varying the stiffness distribution, the stretchable substrate includes a stiffness-maintaining portion and a stiffness-variable portion, which are divided into different regions. Furthermore, the stretchable substrate maintains a predetermined stiffness only at temperatures below a predetermined temperature, with the stiffness-maintaining portion and the stiffness-variable portion maintaining a predetermined stiffness. Only the stiffness-variable portion deforms at temperatures above the predetermined temperature, becoming less stiff than the predetermined stiffness and thus stretchable.

Description

Technical Field

[0001] The present invention relates to a stretchable substrate having a self-rigidity distribution, a method for manufacturing the same, and a method for varying the rigidity distribution. More specifically, by varying the temperature, in a specific region, the rigidity is lowered and stretching is possible, but in other regions, the rigidity is maintained and deformation is minimized, so that selective stretching for each region is realized, a stable structure as a whole is maintained, and a stretchable substrate having a self-rigidity distribution with control of specific factors, a simple manufacturing process, and simple circuit wiring, a method for manufacturing the same, and a method for varying the rigidity distribution.

Background Art

[0002] As the needs for various flexible electronic devices increase, not only has the manufacturing technology for flexible display devices developed, but in addition to simply having flexibility, manufacturing technology for stretchable display devices has also been developed.

[0003] Republic of Korea Registered Patent No. 10-2340855 discloses a technology related to a stretchable display device configured to include a stretchable substrate and a variable part and capable of stretching.

[0004] However, in the case of such stretchable or flexible display devices, when the entire substrate stretches, there is a problem that the elements mounted on the substrate are either damaged due to low stretchability or removed from the substrate due to increased rigidity.

[0005] In this regard, Republic of Korea Registered Patent No. 10-1756847 discloses a technology in which the region where elements are mounted is made of a material having a relatively high elastic modulus, and other regions are made of a material having a relatively low elastic modulus.

[0006] However, when manufacturing a substrate with such different materials, it is difficult to maintain structural stability at the boundary portion, and there is a problem that the manufacturing process becomes complicated.

[0007] On the other hand, in order to locally change stiffness, in addition to varying the elastic modulus, a technique for changing local dimensions and shapes is disclosed in Registered Korean Patent No. 10-2368540. However, realizing local stiffness changes in such a structural manner requires further manufacturing processes and presents the problem of complex circuit wiring.

[0008] Furthermore, there is a growing technical need for stretchable substrates that can maintain relatively high rigidity in the region where the elements are mounted while also having structural stability at the boundary, and that can control factors such as Poisson's ratio and anisotropic elastic modulus, enabling simple manufacturing processes and circuit wiring. [Overview of the project] The problem to be solved

[0009] The present invention was made for the reasons described above, and its objective is to provide a stretchable substrate with a self-stiffness distribution that, by varying the temperature, allows for stretching in certain regions due to reduced rigidity, while maintaining rigidity and minimizing deformation in other regions, thereby enabling selective stretching in different regions. Overall, it is possible to maintain a stable structure by eliminating boundaries, and to provide a stretchable substrate with a self-stiffness distribution that allows for control of specific factors, a simple manufacturing process, and simple circuit wiring.

[0010] Another object of the present invention is to provide a method for manufacturing the stretchable substrate.

[0011] Another object of the present invention is to provide a method for varying the stiffness distribution of the stretchable substrate. [Means for solving the problem]

[0012] A stretchable substrate in one mode for achieving the objectives of the present invention is a stretchable substrate including a rigidity-maintaining portion and a rigidity-variable portion, which are divided into different regions, characterized in that the rigidity-maintaining portion and the rigidity-variable portion maintain a predetermined rigidity only below a predetermined temperature, and only the rigidity-variable portion deforms to become stretchable when its rigidity is lower than the predetermined rigidity above the predetermined temperature.

[0013] The rigidity maintenance portion is formed by multiple regions having a predetermined pattern, and the rigidity variable portion is formed in the regions other than the rigidity maintenance portion.

[0014] 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.

[0015] An element is mounted on the rigidity maintenance section.

[0016] The variable stiffness portion is formed with a predetermined pattern, and the stiffness maintenance portion is formed in the region other than the variable stiffness portion.

[0017] The aforementioned variable rigidity portion is formed along a paper-cutting pattern.

[0018] If Poisson's ratio is negative and expansion or contraction occurs in the first direction, then expansion or contraction in the second direction perpendicular to the first direction also occurs at the same rate.

[0019] The predetermined temperature is the glass transition temperature of the variable-stiffness portion.

[0020] The glass transition temperature of the variable-stiffness section is lower than that of the stiffness-maintaining section.

[0021] The rigidity-maintaining portion and the rigidity-variable portion contain PDMS (polydimethylsiloxane) or polyimide.

[0022] In a method for manufacturing a stretchable substrate according to one aspect for realizing the object of the present invention, for a stretchable substrate including a rigidity maintaining portion and a rigidity variable portion partitioned into different regions, a step of positioning a mask portion so that an opening is aligned with the rigidity maintaining portion, and a step of providing ultraviolet rays above the mask portion to provide ultraviolet rays only to the rigidity maintaining portion are included.

[0023] By providing ultraviolet rays only to the rigidity maintaining portion, the glass transition temperature of the rigidity variable portion is formed lower than the glass transition temperature of the rigidity maintaining portion.

[0024] The stretchable substrate contains glycol gel.

[0025] By providing ultraviolet rays only to the rigidity maintaining portion, the glycol gel forms a network by photo-crosslinking, and polyimide polymerizes in the space between the networks to induce a high-density polymer entanglement.

[0026] The degree of ultraviolet ray passage of the opening of the mask portion gradually decreases from the central portion to the peripheral portion of the opening.

[0027] The ultraviolet rays are modulated light whose intensity gradually decreases from the central portion to the peripheral portion of the opening.

[0028] The glass transition temperature of the rigidity maintaining portion gradually decreases from the central portion to the peripheral portion which is the boundary with the rigidity variable portion.

[0029] The rigidity maintaining portion is formed to have a larger thickness than the rigidity variable portion.

[0030] 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.

[0031] In a method for varying the stiffness distribution of a stretchable substrate in one manner to achieve the objectives of the present invention, the stretchable substrate includes a stiffness-maintaining portion and a stiffness-variable portion, which are divided into different regions from each other. The method is characterized in that the stiffness-maintaining portion maintains its temperature, while heating only the stiffness-variable portion to increase its temperature, or heating the stretchable substrate so that the stiffness-variable portion has a higher temperature than the stiffness-maintaining portion.

[0032] When heating only the variable-rigidity section to increase the temperature, a heater is attached to the lower surface of the variable-rigidity section.

[0033] When the temperature of the variable stiffness portion is maintained relatively higher than that of the stiffness-maintaining portion to heat the expandable substrate, the variable stiffness portion is formed to have a higher thermal diffusivity than the stiffness-maintaining portion.

[0034] When the temperature of the variable-stiffness portion is maintained relatively higher than that of the stiffness-maintaining portion to heat the expandable substrate, the variable-stiffness portion is formed to contain more photothermal particles than the stiffness-maintaining portion. [Effects of the Invention]

[0035] According to the present invention, in a stretchable substrate, the rigidity of only the rigidity-variable portion becomes lower above a predetermined temperature, causing it to deform and become stretchable. By controlling the temperature, the rigidity of a specific region is maintained while the rigidity of other regions is controlled to be variable, thus enabling the construction of stretchable substrates with different rigidity distributions.

[0036] In particular, by forming the rigidity-maintaining portion in a specific arrangement and mounting elements on the rigidity-maintaining portion, temperature control allows the stretchable substrate to maintain its stretchability while minimizing stretchability in the area where the elements are mounted, thereby maintaining a stable element connection state. In this case, by forming the rigidity-maintaining portion in various patterns and shapes, it becomes possible to mount elements on rigidity-maintaining portions of various shapes, thereby enabling the construction of stretchable substrates with various rigidity distributions.

[0037] Furthermore, by solving the conventional problems of contact and structural instability at the interface between the expandable and non-expandable parts, it is possible to construct an expandable substrate that maintains a stable structure at the interface while having expandability, thanks to the continuous structural characteristics of the same material.

[0038] Furthermore, the temperature control, based on information regarding the glass transition temperatures of the variable-rigidity section and the rigidity-maintaining section, allows for control of the expandability of the expandable substrate of the variable-rigidity structure by controlling it within the glass transition temperature range. Here, based on information regarding the temperature range during the manufacturing process or in use of the expandable substrate, the glass transition temperatures of the variable-rigidity section and the rigidity-maintaining section can be set to be different from each other. Therefore, during the manufacturing process, a highly rigid state can be maintained to ensure the stability of the manufacturing process, while in actual use, the rigidity can be varied to improve the various usability of the expandable substrate.

[0039] In this method of forming glass transition temperatures that differ between a variable-stiffness portion and a stiffness-maintaining portion, by applying ultraviolet light only to the stiffness-maintaining portion on the stretchable substrate, a relatively high glass transition temperature can be formed. Therefore, the stretchable substrate can be manufactured with a relatively simple process and a limited material selection for the stretchable substrate.

[0040] In particular, by providing ultraviolet light to the rigidity-maintaining portion so that the light intensity changes sequentially, or by manufacturing the mask portion so that the degree of opening changes sequentially, the structural stability of the expandable substrate during repeated expansion and contraction can be further improved by the gradual change in rigidity at the interface between the rigidity-variable portion and the rigidity-maintaining portion.

[0041] Furthermore, by forming the rigidity maintenance portion with a relatively thicker thickness, the deformation rate and expansion rate of the rigidity maintenance portion are kept lower, thereby minimizing the deformation rate of the elements mounted on the rigidity maintenance portion and maintaining a more stable element connection state, making it possible to manufacture a stretchable substrate with high electrical stability and reliability.

[0042] Furthermore, the stiffness distribution in the stretchable substrate can be varied by heating the stiffness-maintaining portion and the stiffness-variable portion at different temperatures, or by heating only the stiffness-variable portion. This allows the regions of the stiffness-maintaining portion and the stiffness-variable portion to be set to have various patterns and arrangements, and by varying the stiffness distribution in various ways using a relatively simple heating method, it becomes possible to manufacture stretchable substrates with a wider variety of self-stiffness distribution characteristics. [Brief explanation of the drawing]

[0043] [Figure 1] Figure 1 is a perspective view showing a stretchable substrate having a self-stiffness distribution according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram illustrating the state in which the stiffness distribution of the stretchable substrate shown in Figure 1 is varied by temperature variation. [Figure 3] Figures 3a and 3b are graphs illustrating the state in which the stretchable substrate of Figure 1 has a self-stiffness distribution based on the distribution of the glass transition temperature. [Figure 4] Figure 4 is a perspective view showing a stretchable substrate having a self-stiffness distribution according to another embodiment of the present invention. [Figure 5] Figure 5 is a perspective view showing a stretchable substrate having a self-stiffness distribution according to yet another embodiment of the present invention. [Figure 6] Figure 6 is a process diagram showing the manufacturing method of the stretchable substrate shown in Figure 1. [Figure 7] Figures 7a and 7b are process diagrams showing a method for manufacturing a stretchable substrate according to yet another embodiment of the present invention. [Figure 8] Figures 8a to 8d are process diagrams showing a method for manufacturing a stretchable substrate according to yet another embodiment of the present invention. [Figure 9] Figures 9a and 9b are process diagrams showing a method for varying the stiffness distribution of a stretchable substrate according to yet another embodiment of the present invention. [Figure 10] Figures 10a and 10b are graphs illustrating the stress concentration phenomenon due to temperature variation in the stretchable substrate shown in Figure 1. Specific details for implementing the invention

[0044] The present invention can be modified in various ways and may take on various forms; embodiments are described in detail below. However, this should be understood not as an attempt to limit the invention to any particular disclosure, but rather as including all modifications, equivalents, or substitutes that fall within the spirit and technical scope of the invention. In the description of each drawing, similar reference numerals are used for similar components. Terms such as "first," "second," etc., may be used to describe various components, but such components should not be limited by such terms.

[0045] The terms used herein are for the sole purpose of distinguishing one component from another. The terms used in this application are used solely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context explicitly indicates otherwise.

[0046] In this application, terms such as “including” or “consisting of” are intended to specify the existence of features, figures, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood not to preemptively exclude the existence or possibility of adding one or more other features, figures, steps, actions, components, parts, or combinations thereof.

[0047] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by a person of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted to have the meaning consistent with their meaning in the context of the relevant art, and not as ideally or excessively formal unless expressly defined herein.

[0048] Preferred embodiments of the present invention will be described in more detail below with reference to the attached drawings.

[0049] Figure 1 is a perspective view showing a stretchable substrate having a self-stiffness distribution according to one embodiment of the present invention.

[0050] As shown in Figure 1, the stretchable substrate 10 having a self-stiffness distribution according to this embodiment (hereinafter referred to as the stretchable substrate) includes a stiffness variable portion 100 and a stiffness maintenance portion 200.

[0051] The variable stiffness section 100 is defined as a region in which the stiffness changes by varying the temperature at a specific temperature, as will be described later, and the stiffness maintenance section 200 is defined as a region in which the stiffness does not change regardless of the temperature variation to the specific temperature. The range of temperature variation and the resulting stiffness variation will be described later.

[0052] The variable stiffness portion 100 is defined as a region where the stiffness maintenance portion 200 is not formed.

[0053] Furthermore, when the variable rigidity portion 100 is defined as a specific region as described above, the region corresponding to the variable rigidity portion 100 corresponds to the variable rigidity portion 100 regardless of the thickness of the stretchable substrate 10, in the thickness direction of the stretchable substrate 10. The same applies to the rigidity maintenance portion 200. In other words, the variable rigidity portion 100 or the rigidity maintenance portion 200 does not have the property of having variable rigidity or maintaining rigidity only on the surface of the stretchable substrate 10, but rather has the property of having variable rigidity or maintaining rigidity throughout the entire thickness direction of the stretchable substrate 10.

[0054] In addition, as will be described later, the stretchable substrate 10 can also be formed to have different rigidities along its thickness direction, which will be described later.

[0055] Furthermore, the rigidity maintenance section 200 does not overlap with the rigidity variable section 100, and each is defined as a distinct region. Here, for example, each of the rigidity maintenance sections 200 has a certain region, and the whole can have m*n matrix arrays (where m and n are natural numbers).

[0056] The arrangement state or arrangement pattern of the rigidity-maintaining parts 200 described above is not limited to the matrix arrangement, but can have various arrangements. That is, each of the rigidity-maintaining parts 200 can have a square shape, a circular shape, or various other shapes to form a predetermined area, and furthermore, the arrangement pattern can also have various arrangements and patterns, such as being arranged at arbitrary positions, a structure in which a long pattern extending in one direction is repeated, or a zigzag structure. Further arrangements and patterns of the rigidity-maintaining parts 200 will be explained with reference to the drawings described later.

[0057] However, each of the rigidity-maintaining parts 200 has a certain area, and multiple parts are formed spaced apart from one another.

[0058] As described above, a predetermined electronic device is mounted in the region where the rigidity maintenance portion 200 is formed. That is, at least one electronic device is mounted in each region formed by the rigidity maintenance portion 200. Here, the type, structure, function, etc., of the electronic device are not limited.

[0059] For example, the electronic element is a micro-LED (light-emitting device). Furthermore, as described above, when the electronic element is mounted on the rigidity-maintaining portion 200, a wiring structure for driving the electronic element should also be formed on the stretchable substrate 10, but further illustration of the wiring structure has been omitted.

[0060] In the case of the aforementioned wiring structure, known wiring structures can be applied as is, and they can be further formed on the lower surface of the stretchable substrate 10 or inside the stretchable substrate 10, and the formation structure is not limited. Furthermore, the wiring structure is not divided into the rigidity variable portion 100 and the rigidity maintaining portion 200, but can be formed in the necessary shape and structure over the entire area of ​​the stretchable substrate 10.

[0061] In the case of this embodiment, the configurations of the rigid variable portion 100 and the rigid maintaining portion 200 that constitute the stretchable substrate 10 are described. For components that must be further formed because the stretchable substrate 10 is used in a display device or the like, such as the wiring structure described above, components according to the prior art can be directly applied, and descriptions thereof are omitted. Similarly, it is obvious that the components that should be further provided can be configured on the upper surface, the lower surface, or inside the stretchable substrate 10.

[0062] In the stretchable substrate 10, as described above, the rigid variable portion 100 and the rigid maintaining portion 200 have the characteristics that their rigidity is variable or maintained by temperature variation to a specific temperature, and both are made of the same material. That is, by further performing specific processes and steps as described below on the stretchable substrate 10 made of the same material, the characteristics are varied so as to be partitioned into a region where the rigidity is stably maintained and a region where the rigidity is variable.

[0063] Hereinafter, the partitioning of the rigid variable portion 100 and the rigid maintaining portion 200 and the characteristics of the self-rigidity distribution of the stretchable substrate 10 due to this will be described more specifically.

[0064] FIG. 2 is a schematic diagram for explaining a state in which the rigidity distribution is variable due to temperature variation in the stretchable substrate of FIG. 1.

[0065] As shown in FIG. 2, when the stretchable substrate 10 is maintained at a temperature (T < Tc) lower than a predetermined specific temperature (Tc), it maintains the same relatively high rigidity as a whole. Therefore, in such a state, the stretchable substrate 10 maintains a highly rigid and stable structure without having another stretchability.

[0066] However, when the stretchable substrate 10 is exposed to an environment with a temperature higher than a predetermined specific temperature (Tc) (T>Tc), the rigidity maintenance portion 200 maintains a relatively high rigidity, the same as in the initial state, while the rigidity variable portion 100 has a lower rigidity than in the initial state.

[0067] Furthermore, in this state, the rigidity-maintaining portion 200 does not expand or contract due to external forces and maintains a stable structure, while the rigidity-variable portion 100 expands or contracts due to external forces and undergoes deformation. The expandable substrate 10 as a whole can be stretched or compressed depending on the direction of the external force.

[0068] In other words, in the case of the stretchable substrate 10, a deformation in which the overall length is stretched or decreased can be induced, but the rigidity maintenance portion 200 on which the aforementioned electronic elements are mounted maintains the same shape as the initial state, and its structure does not change.

[0069] Therefore, the mounting state and electrical connection state of the electronic element in the region where the electronic element is mounted can be stably maintained. In this case, if the configuration is such as wiring for driving the electronic element, a stable connection state can be maintained when it is formed in the region where the electronic element is mounted. However, if the configuration is mounted in the rigidity variable part 100, which is a region where the electronic element is not mounted, then, considering the degree of deformation of the rigidity variable part 100, the configuration must also be made of a material that can deform simultaneously with the degree of deformation.

[0070] As described above, the reason why elasticity is not induced only in the rigidity-maintaining portion 200, which is defined as a localized area, and why a stable structure with relatively high rigidity is maintained, will be explained with reference to the following drawings.

[0071] Figures 3a and 3b are graphs illustrating the state in which the stretchable substrate of Figure 1 has a self-stiffness distribution based on the distribution of the glass transition temperature.

[0072] First, as shown in Figure 3a, if the stretchable substrate 10 includes a first material and the glass transition temperature of the first material is Tg1, the rigidity of the first material may decrease rapidly at a temperature higher than the glass transition temperature Tg1.

[0073] Similarly, if the stretchable substrate 10 includes a second material and the glass transition temperature of the second material is T2, the rigidity of the second material may also decrease rapidly at a temperature higher than the glass transition temperature Tg2.

[0074] In this case, if the stretchable substrate 10 is maintained within a temperature range between Tg1, which is the glass transition temperature of the first material, and Tg2, which is the glass transition temperature of the second material, the rigidity of the stretchable substrate 10 decreases in the region containing the first material, but does not decrease in the region containing the second material, maintaining a constant level.

[0075] As a result, in the stretchable substrate 10, the rigidity decreases in the region containing the first material, resulting in high elasticity as shown in Figure 3b, and allowing for easy deformation by external force. However, in the region containing the second material, the rigidity remains the same, and no deformation occurs.

[0076] Therefore, by maintaining the stretchable substrate 10 within the temperature range of Tg1 and Tg2, the stretchable substrate 10 can be controlled to have elasticity in response to external forces and to deform easily. In other words, by considering the temperature (T) of the environment in which the stretchable substrate 10 is used, and selecting the first and second materials such that the temperature (T) falls within the temperature range of Tg1 and Tg2, or by controlling the glass transition temperatures of the first and second materials such that the temperature (T) falls within the range between the glass transition temperatures of the first and second materials, the stretchable substrate 10 can be controlled to have elasticity in a specific region and maintain rigidity in other regions.

[0077] As described above, by configuring the stretchable substrate 10 to have different glass transition temperatures, the stretchable substrate 10 can be controlled to be stretchable in a specific region while maintaining rigidity in other regions.

[0078] Herein, the control of the stretchability of the stretchable substrate 10 as described above can be applied not only when the stretchable substrate 10 contains first and second materials that are different from each other, but also when the stretchable substrate 10 contains the same material and is formed so that each region has a different glass transition temperature.

[0079] In other words, although the stretchable substrate 10 contains the same material throughout, if a specific region is formed by a predetermined processing step to have a different glass transition temperature from other regions, then, as explained in Figures 3a and 3b above, the stretchability can be controlled differently by the difference in glass transition temperatures between the specific region and other regions.

[0080] As mentioned above, if the temperature (T) in the environment in which the stretchable substrate 10 is used falls within the range between the glass transition temperature in the specific region and the other region, then the stretchable substrate 10 will ultimately have different stretchability in each region depending on the environment in which it is used.

[0081] Furthermore, if, in addition to the temperature in the operating environment of the stretchable substrate 10, the temperature (T') of the stretchable substrate 10 in the process environment is controlled to be lower than the glass transition temperature in the specific region and the other region, the stretchable substrate 10 will have a constant strength in all regions of the process environment, and its stretchability will be minimized. Similarly, if the temperature (T') of the stretchable substrate 10 in the process environment is controlled to be higher than the glass transition temperature in the specific region and the other region, the stretchable substrate 10 will also be able to be deformed and stretchable in all regions of the process environment.

[0082] Figure 4 is a perspective view showing a stretchable substrate having a self-stiffness distribution according to another embodiment of the present invention.

[0083] The stretchable substrate 11 according to this embodiment is substantially the same as the stretchable substrate 10 described in Figure 1, except for the shape and arrangement of the rigidity maintenance portion 204, so redundant explanations will be omitted.

[0084] As shown in Figure 4, in the stretchable substrate 11 according to this embodiment, the rigidity-maintaining portions 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). Here, two rigidity-maintaining portions 204 can be arranged consecutively in the second direction (Y). Alternatively, one rigidity-maintaining portion 204 can extend to a relatively long length in the second direction (Y), or three or more can be arranged consecutively.

[0085] In conclusion, in this embodiment, the rigidity-maintaining portion 204 is formed such that the length along the second direction (Y) is relatively larger than the length along the first direction (X) (i.e., width). Thus, in the expandable substrate 11, the expandability in the first direction (X), where the rigidity-maintaining portion 204 is distributed over a relatively small area, is formed to be greater than the expandability in the second direction (Y).

[0086] As previously mentioned, the rigidity-maintaining portion 204 has the same characteristics in the thickness direction of the stretchable substrate 11, and does not have the characteristics of the rigidity-maintaining portion 204 only on the surface of the stretchable substrate 11. The same applies to the variable rigidity portion 104.

[0087] As described above, by forming the rigidity maintenance portion 204 into a rectangular shape that is relatively long in a specific direction, relatively long rectangular elements can be mounted more stably. Furthermore, since the rigidity maintenance portion 204 is formed with different lengths along the first direction (X) and the second direction (Y), the stretchability along the first direction (X) and the stretchability along the second direction (Y) are different, thus enabling a variety of applications. Here, an example of such an application is a rollable display.

[0088] Figure 5 is a perspective view showing a stretchable substrate having a self-stiffness distribution according to yet another embodiment of the present invention.

[0089] The stretchable substrate 12 according to this embodiment is substantially the same as the stretchable substrate 10 described in Figure 1, except for the shape and arrangement of the rigidity maintenance portion 205 and the rigidity variable portions 105 and 106, so redundant explanations will be omitted.

[0090] As shown in Figure 5, in the stretchable substrate 12 according to this embodiment, the rigidity maintenance portion 205 occupies most of the area of ​​the stretchable substrate 12, while the rigidity variable portions 105 and 106 are formed in a shape that extends long in a specific direction.

[0091] In other words, the first variable stiffness portion 105 extends on the stretchable substrate 12 for a predetermined length along the first direction (X), and the second variable stiffness portion 106 extends in the second direction (Y) and is short-circuited in the portion facing the first variable stiffness portion 105. Here, the first variable stiffness portion 105 does not extend to the side of the stretchable substrate 12, but the second variable stiffness portion 106 is formed to extend to the side of the stretchable substrate 12.

[0092] Thus, the first and second rigidity-variable portions 105 and 106 are formed on the rigidity-maintaining portion 205 in a cross shape overall, which is the shape in which the cutting line portion of the so-called paper-cutting pattern is formed by the rigidity-variable portions 105 and 106. Here, it is sufficient that the first and second rigidity-variable portions 105 and 106 are formed substantially like the cutting line of the paper-cutting pattern, and it does not mean that they are cut along the paper-cutting pattern.

[0093] As a result, unlike in Figure 4, in the stretchable substrate 12 according to this embodiment, the length of the rigidity maintenance portion 205 along the first direction (X) is substantially the same as the length of the rigidity maintenance portion 205 along the second direction (Y).

[0094] On the other hand, as shown in Figure 5, the arrangement of the rigidity variable portion and the rigidity maintenance portion results in a negative Poisson's ratio for the entire stretchable substrate 12, close to -1. When the stretchable substrate 12 is stretched in the second direction (Y), stretching in the first direction (X) occurs at a similar rate, allowing for uniform stretching or contraction throughout the entire stretchable substrate 12.

[0095] Thus, the stretchable substrate 12 in this embodiment can significantly reduce the distortion of the aspect ratio of the display image due to unidirectional stretching.

[0096] Furthermore, in this embodiment as well, the rigidity-maintaining portion 205, as well as the rigidity-variable portions 105 and 106, can have the same characteristics in the thickness direction of the expandable substrate 12.

[0097] The following describes an embodiment of a method for treating the stretchable substrate 10, which contains the same material as described above, so that it has different glass transition temperatures in a specific region and other regions.

[0098] Figure 6 is a process diagram showing the manufacturing method of the stretchable substrate shown in Figure 1.

[0099] First, as shown in Figure 6, in the manufacture of the stretchable substrate 10, a mask portion 300 is aligned on the upper part of the stretchable substrate 10, which is made of the same material. Here, the mask portion 300 blocks ultraviolet (UV) light provided from above, and it is sufficient that it contains a material capable of blocking ultraviolet light.

[0100] Furthermore, the mask portion 300 has a plurality of openings 310 formed therein, and the positions where the openings 310 are formed must be located above the position where the rigidity maintenance portion 200 is formed on the stretchable substrate 10.

[0101] In other words, the size and pattern of the opening 310 are formed to be substantially the same as the size and pattern of the rigidity-maintaining portion 200, and as mentioned above, the size and pattern of each of the rigidity-maintaining portions 200 can be varied in design, so it is sufficient to design the size and pattern of each of the openings 310 accordingly.

[0102] Subsequently, ultraviolet (UV) light is provided above the mask portion 300, so that the ultraviolet light passes only through the opening 310 and is supplied to the stretchable substrate 10.

[0103] Thus, on the stretchable substrate 10, the properties of the area exposed to the ultraviolet light 50 are changed by exposure to the ultraviolet light 50, and the rigidity-maintaining portion 200 is formed thereon. In other words, 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 in the rigidity-variable portion 100.

[0104] Here, the stretchable substrate 10 includes PDMS or polyimide.

[0105] In particular, the stretchable substrate 10 contains glycol gel. Thus, as shown in Figure 6, in the region exposed to ultraviolet light 50, i.e., the rigidity-maintaining portion 200, the glycol gel forms a network by photocrosslinking, and polyimide polymerizes in the spaces between the networks, inducing high-density polymer entanglement.

[0106] In other words, when the glycol gel is irradiated with ultraviolet light, a crystalline / entangled phase region is formed with a locally high polymer concentration. Subsequently, when a semi-IPN structure of polyimide is formed in the space between the networks, even more polymer entanglement can be induced in the localized region with a relatively high polymer concentration. Thus, as shown in Figure 6, the glass transition temperature (Tg) increases due to the relatively high polymer concentration.

[0107] On the other hand, in the region irradiated with ultraviolet light, it is necessary to control the intensity and duration of the ultraviolet light irradiation in order to induce sufficient polymer entanglement in the thickness direction by the irradiation of ultraviolet light, thereby having the same properties in the thickness direction.

[0108] Of course, considering the characteristics of the stretchable substrate being manufactured, it may be necessary to form the rigidity maintenance portion 200 only on the surface of the stretchable substrate, that is, to maintain rigidity only on the upper side of the stretchable substrate on which the element is mounted, and to form the lower side so that its rigidity is variable. In such cases, the intensity and duration of irradiation with ultraviolet light can be controlled to induce the stretchable substrate to have different characteristics in the thickness direction as well.

[0109] In contrast, in regions not irradiated with ultraviolet light, the relatively high polymer concentration described above is not formed, and a relatively low polymer concentration is maintained, so the glass transition temperature (Tg) is kept relatively low.

[0110] Thus, in the stretchable substrate 10, the rigidity-maintaining portion 200 to which the ultraviolet light 50 is irradiated has a relatively high glass transition temperature (Tg2), while the rigidity-variable portion 100 to which the ultraviolet light 50 is blocked has a relatively low glass transition temperature (Tg1).

[0111] Therefore, as explained in Figure 3, the temperature between the glass transition temperatures (Tg2~Tg1) (T stretch In this configuration, the rigidity-maintaining portion 200 of the expandable substrate 10 maintains relatively high rigidity and does not deform, while the rigidity-variable portion 100 becomes less rigid and is expanded and contracted and deformed by external forces.

[0112] As described above, even with the same material, the stretchable substrate 10 can form regions with different rigidities, thereby minimizing deformation in specific regions while allowing other regions to stretch and deform.

[0113] In this case, when an electronic element is mounted in a specific region where the deformation is minimized, i.e., the rigidity-maintaining portion 200, even if another region, i.e., the rigidity-variable portion 100, is expanded or contracted and deformed by an external force, the region where the electronic element is mounted will have minimal deformation, and a stable electrical connection state can be maintained. Therefore, the expandable substrate 10 is expandable and can maintain electrical or mechanical stability by maintaining a stable connection state of the electronic element mounted inside.

[0114] Figures 7a and 7b are process diagrams showing a method for manufacturing a stretchable substrate according to yet another embodiment of the present invention.

[0115] In the method for manufacturing the stretchable substrate 20 according to this embodiment, except for the difference in the structure of the opening 311 formed in the mask portion 301 and the resulting structure of the rigidity maintenance portion 201, it is the same as the method for manufacturing the stretchable substrate 10 described in Figure 6. Therefore, the same reference numerals are used for the same components, and redundant explanations are omitted.

[0116] As shown in Figure 7a, in the manufacturing method of the stretchable substrate 20 according to this embodiment, the mask portion 301 is aligned on the upper part of the stretchable substrate 20 located on the base substrate 20.

[0117] The mask portion 301 blocks ultraviolet (UV) light provided from above, and it is sufficient if it includes a material capable of blocking ultraviolet light.

[0118] Furthermore, as previously mentioned, the mask portion 301 has a plurality of openings 311, and the positions where the openings 311 are formed must be above the position where the rigidity maintenance portion 201 should be formed on the stretchable substrate 20.

[0119] In this embodiment, the aperture ratio of the mask portion 301 decreases progressively from the center to the periphery, and as a result, the degree of ultraviolet light transmission decreases progressively from the center to the periphery. That is, if the degree of ultraviolet light transmission is greatest in the central portion, showing an ultraviolet light transmittance of 100%, the ultraviolet light transmittance decreases progressively from the center to the periphery, and finally, in the boundary region between the rigidity maintenance portion 201 and the rigidity variable portion 100, the ultraviolet light transmittance is 0%.

[0120] As described above, the transmittance of ultraviolet light 50 decreases as the opening 311 moves from the center to the periphery, and consequently, the degree to which the characteristics are varied by ultraviolet light 50 also decreases as the opening moves from the center to the periphery.

[0121] In other words, as described above, exposure to the ultraviolet light 50 provided by the opening 311 causes the rigidity maintenance portion 201 to experience an increase in its glass transition temperature (Tg) due to its relatively high polymer concentration. This increase in glass transition temperature (Tg) decreases progressively from the central portion 211 to the peripheral portion 212 of the rigidity maintenance portion 201.

[0122] In addition, as shown in Figure 7b, the rigidity of the rigidity maintenance portion 201 also decreases sequentially from the central portion 211 to the peripheral portion 212, and the elasticity of the peripheral portion 212 also increases.

[0123] Generally, as shown in Figure 6, when the rigidity maintenance portion 200 and the rigidity variable portion 100 have a relatively large difference in glass transition temperature, a sharp difference in rigidity exists at the interface between the rigidity maintenance portion 200 and the rigidity variable portion 100. This increases the likelihood of damage or defects occurring due to the sharp difference in elasticity or deformation at the interface. In other words, a stress concentration phenomenon can occur in the stretchable substrate 10.

[0124] Therefore, in order to minimize the stress concentration phenomenon caused by the abrupt difference in elasticity or degree of deformation at such an interface, as in this embodiment, the glass transition temperature is gradually reduced in the rigidity maintenance portion 201 from the central portion 211 to the peripheral portion 212, thereby minimizing the difference in elasticity or degree of deformation at the interface between the rigidity maintenance portion 201 and the rigidity variable portion 100 and mitigating stress concentration.

[0125] This minimizes the occurrence of damage and defects at the interface, even when the stretchable substrate 20 undergoes various and repeated deformations, thereby further improving the electrical or mechanical stability of the electronic element 400 mounted on the upper surface of the rigidity maintenance portion 201.

[0126] On the other hand, unlike in Figure 7a, where the opening 311 formed in the mask portion 301 is formed so that the aperture ratio decreases sequentially, it is also possible to control the intensity of the irradiated ultraviolet light 50 to decrease sequentially while maintaining the aperture ratio of the opening 311.

[0127] In other words, the opening 311 is formed such that both the central and peripheral portions have a transmittance of 100%, as shown in the opening 310 in Figure 6, and the ultraviolet light 50 irradiated from the top of the mask portion 301 can be composed of modulated light whose intensity decreases sequentially from the central portion to the peripheral portion.

[0128] Thus, when the ultraviolet light 50 is composed of modulated light whose intensity decreases sequentially from the center to the periphery, the intensity of the light supplied to the rigidity maintenance portion 201 of the stretchable substrate 20 is substantially the same as when the aperture ratio of the opening 311 in Figure 7a is varied.

[0129] Thus, as shown in Figure 7b, in the case of the rigidity maintenance portion 201, the glass transition temperature (Tg) decreases sequentially from the central portion 211 to the peripheral portion 212. This minimizes the difference in elasticity or deformation at the interface between the rigidity maintenance portion 201 and the rigidity variable portion 100, thereby mitigating stress concentration.

[0130] Furthermore, such differences in stretchability or degree of deformation can be induced to occur horizontally with respect to the stretchable substrate 20, or conversely, to occur vertically with respect to the stretchable substrate 20, i.e., in the thickness direction. Therefore, the upper side of the stretchable substrate 20 can be formed to have relatively high rigidity, and the lower side of the stretchable substrate 20 can be formed to have relatively low rigidity.

[0131] Figures 8a to 8d are process diagrams showing a method for manufacturing a stretchable substrate according to yet another embodiment of the present invention.

[0132] The method for manufacturing the stretchable substrate 30 according to this embodiment is the same as the method for manufacturing the stretchable substrate 10 described in Figure 6, except that the thicknesses of the rigidity variable portion 101 and the rigidity maintenance portion 202 in the stretchable substrate 30 are formed to be different from each other. Therefore, the same reference numerals are used for the same components, and redundant explanations are omitted.

[0133] First, as shown in Figure 8a, in the case of the stretchable substrate 30 in this embodiment, the rigidity maintenance portion 202 has a first thickness (t1), and the rigidity variable portion 101 has a second thickness (t2). Here, the first thickness (t1) is greater than the second thickness (t2).

[0134] Furthermore, due to these structural features, the stretchable substrate 30 includes a protruding portion 150 that protrudes downward in the region where the rigidity maintenance portion 202 is formed. Similarly, in order to perform a predetermined process on the stretchable substrate 30, if the base substrate 21 has the stretchable substrate 30 on its upper surface, it includes a recessed portion 22 that is recessed to correspond to the protruding portion 150.

[0135] In this case, the protruding portion 150 has a curved outer surface, protrudes downward, and can have, for example, a hemispherical shape. However, the shape of the protruding portion 150 is not limited, and it can be formed such that its thickness gradually decreases from the center to the periphery.

[0136] In this configuration, the first thickness (t1) of the rigidity maintenance portion 202 corresponds to the thickness in the central part of the rigidity maintenance portion 202, and the first thickness (t1) decreases sequentially from the central part towards the periphery. Thus, the interface between the rigidity maintenance portion 202 and the rigidity variable portion 101 forms the second thickness (t2).

[0137] On the other hand, although not explained in detail, the protruding portion 150 is formed in a process in which the stretchable substrate 30 is formed on the upper surface of the base substrate 21 by a transfer process such as imprinting, with the recessed portion 22 already formed on the base substrate 21. In other words, the recessed portion 22 of the base substrate 21 is transferred as is, and the protruding portion 150 is formed on the lower surface of the stretchable substrate 30.

[0138] Referring to Figure 8b, with respect to the stretchable substrate 30 including the protruding portion 150 as described above, the mask portion 300 is positioned on the upper part and ultraviolet light 50 is irradiated onto it.

[0139] Here, the mask portion 300 is the same as the mask portion 300 described in Figure 6, and includes a plurality of openings 310, the openings 310 being aligned with the positions and patterns in the stretchable substrate 30 where the rigidity maintenance portion 202 is formed.

[0140] Thus, when the ultraviolet light 50 is irradiated, the rigidity maintenance portion 202 is exposed to the ultraviolet light 50 through the opening 310, and the glass transition temperature (Tg) of the rigidity maintenance portion 202 increases relatively. Here, the internal polymer entanglement state that causes the glass transition temperature of the rigidity maintenance portion 202 to increase relatively is as described above.

[0141] Therefore, as shown in Figure 8b, the rigidity-maintaining portion 202 is formed. However, as shown in Figure 8b, polymer entanglement is not induced internally at the location where the protrusion 150 is formed.

[0142] 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 will not irradiate up to the protrusion 150, and only the upper part of the protrusion 150 will have its properties changed by the ultraviolet light.

[0143] Therefore, in the stretchable substrate 30, the rigidity maintenance portion 200 is formed only at the upper part of the protruding portion 150, and the glass transition temperature of the protruding portion 150 does not rise, maintaining the same glass transition temperature as the surrounding rigidity variable portion 101.

[0144] After this, as shown in Figures 8c and 8d, the electronic elements 400 are mounted on the upper surface of the rigidity maintenance portion 200, and then the base substrate 21 located below it is removed from the outside, completing the expandable substrate 30 having the structure shown in Figure 8d.

[0145] In the case of the stretchable substrate 30, as described above, the rigidity-maintaining portion 200 is formed in the portion where the electronic element 400 is mounted, and is formed to have a relatively high glass transition temperature. However, the portion where the electronic element 400 is not mounted has a relatively low glass transition temperature due to the rigidity-variable portion 101. Furthermore, the protruding portion 150, in a portion where the ultraviolet light 50 does not reach, also maintains a relatively low glass transition temperature, similar to the rigidity-variable portion 101.

[0146] Thus, the localized area where the electronic element 400 is mounted exhibits relatively high strength, maintaining structural stability, while the remaining area, and even the area beneath the electronic element 400, deforms to become stretchable. In other words, the stretchable substrate 30 as a whole can stretch and deform over its entire surface area while minimizing the deformation rate at the location where the electronic element 400 is mounted. As a result, the stretchable substrate 30 can maintain the electrical or mechanical stability of the electronic element 400 while further improving its stretchability.

[0147] The above describes a method for manufacturing the stretchable substrate such that different regions within the substrate have different rigidities.

[0148] However, in addition to the method of manufacturing the stretchable substrate itself so that it has different glass transition temperatures in different regions, it is also possible to vary the rigidity so that the stretchable substrate as a whole has different stretchability in different regions, even if it has the same glass transition temperature overall.

[0149] The following describes a method for varying the stiffness distribution of such a stretchable substrate.

[0150] Figures 9a and 9b are process diagrams showing a method for varying the stiffness distribution of a stretchable substrate according to yet another embodiment of the present invention.

[0151] In the case of the stretchable substrate 40 according to this embodiment, the entire substrate contains the same material, similar to the stretchable substrate described above, and furthermore, the glass transition temperature is not varied to a relatively high level in a specific region by further ultraviolet irradiation. That is, the stretchable substrate 40 has the same glass transition temperature (Tg) throughout its entire surface.

[0152] As described above, the method for varying the stiffness distribution in the stretchable substrate 40 having the same glass transition temperature (Tg) is as follows.

[0153] First, as shown in Figure 9a, the stretchable substrate 40 includes a rigidity-maintaining portion 203, which is a region with relatively high rigidity, and a rigidity-variable portion 102, which is a region with relatively low rigidity and is stretchable.

[0154] Subsequently, the stretchable substrate 40 is heated unevenly at different temperatures for the rigidity maintenance portion 203 and the rigidity variable portion 102. Here, the heating temperature of the rigidity variable portion 102 is controlled to be higher than the heating temperature of the rigidity maintenance portion 203.

[0155] Thus, by heating the rigidity maintenance section 203 and the rigidity variable section 102 unevenly at different temperatures as described above, the rigidity maintenance section 203 maintains relatively high rigidity, while the rigidity variable section 102 has relatively low rigidity, as shown in Figure 9b, and the rigidity variable section 102 deforms with elasticity.

[0156] In other words, even if the stretchable substrate 40 as a whole has the same glass transition temperature (Tg), if a localized region is heated to a temperature above the glass transition temperature, the strength of that region becomes relatively lower, and it deforms with stretchability.

[0157] In this configuration, the stretchable substrate 40 has a stiffness distribution that allows it to deform with stretchability only in specific regions.

[0158] On the other hand, as shown in Figure 9a, an example of a method for uniformly heating the rigidity maintenance portion 203 and the rigidity variable portion 102 of the stretchable substrate 40 at different temperatures is described below.

[0159] First, with respect to the stretchable substrate 40, the rigidity maintenance portion 203 is not heated separately, and only the rigidity variable portion 102 is selectively heated to increase its temperature.

[0160] For this reason, a thin-film heater is attached only to the lower part of the variable-stiffness section 102, allowing the temperature to be increased by heating only the variable-stiffness section 102. In particular, the stretchable substrate 40 in this embodiment contains PDMS or polyimide, and the thermal conductivity of the substrate as a whole is not high, so even if local heating of the variable-stiffness section 102 is performed by the thin-film heater, the heating of the stiffness maintenance section 200 by heat conduction is limited.

[0161] Here, since the thermal conductivity of the stretchable substrate 40 is not high, heating can be performed with the thin-film heater attached not only to the lower part of the stiffness variable part 102 but also to the upper part, in order to vary the stiffness so that the stretchable substrate 40 has the same stiffness in the thickness direction.

[0162] 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 maintenance portion 203.

[0163] For example, if the variable stiffness portion 102 is formed to have a higher thermal diffusivity than the stiffness maintenance portion 203, even if the stretchable substrate 40 as a whole is heated, the variable stiffness portion 102 will be heated to a higher temperature. Thus, the temperature at the variable stiffness portion 102 can be controlled to be higher than the glass transition temperature, and the stiffness of the variable stiffness portion 102 can be controlled to be relatively low, thereby making it stretchable.

[0164] Here, a possible method for heating the entire stretchable substrate 40 is to position a light source around the stretchable substrate 40 and heat it, but the method is not limited to this.

[0165] Furthermore, as a method for heating the stretchable substrate 40 such that the temperature of the variable stiffness portion 102 is relatively higher than that of the stiffness maintenance portion 203, there is a method of forming the variable stiffness portion 102 to contain more photothermal particles than the stiffness maintenance portion 203.

[0166] In other words, the stretchable substrate 40 can be manufactured by mixing in particles that induce a photothermal reaction, and the distribution or density of the photothermal particles can be made different between the rigidity maintenance section 203 and the rigidity variable section 102.

[0167] If photothermal particles are included in the rigidity variable portion 102 such that they have a higher distribution or density than those in the rigidity maintenance portion 203, the rigidity variable portion 102 can be heated to a higher temperature even when the stretchable substrate 40 is heated to the same temperature. Thus, the temperature in the rigidity variable portion 102 can be controlled to be higher than the glass transition temperature, and the rigidity of the rigidity variable portion 102 can be controlled to be relatively low, thereby making it stretchable.

[0168] As mentioned above, a possible and not limited method for heating the entire stretchable substrate 40 is to place a hot plate on the underside of the stretchable substrate 40 and heat it.

[0169] Figures 10a and 10b are graphs illustrating the stress concentration phenomenon due to temperature variation in the stretchable substrate shown in Figure 1.

[0170] As shown in Figure 10a, in the stretchable substrate 10 described in Figure 1, the temperature (T) of the stretchable substrate 10 is the stretching temperature (T) shown in Figure 3a. stretch If you keep it smaller than (T <T stretch ), the stretchable substrate 10 as a whole will maintain the same rigidity. That is, the rigidity-maintaining portion 200 and the rigidity-variable portion 100 will have the same rigidity.

[0171] Furthermore, if an external force is applied to the stretchable substrate 10 in the environment described above, the stretchable substrate 10 will be stretched, causing stress to concentrate in the area where the electronic element 400 is mounted, which will result in defects in the mounted state of the electronic element 400.

[0172] In contrast, as shown in Figure 10b, the temperature (T) of the stretchable substrate 10 is the stretching temperature (T) shown in Figure 3a. stretch If we maintain it identically to (T=T stretch ), the stretchable substrate 10 will have locally different rigidities from one another. That is, since the temperature (T) is lower than the glass transition temperature (Tg2) of the rigidity maintenance section 200 and higher than the glass transition temperature (Tg1) of the rigidity variable section 100, the rigidity maintenance section 200 will maintain relatively high rigidity, while the rigidity variable section 100 will have relatively lower rigidity.

[0173] Thus, when an external force is applied to the stretchable substrate 10 in the environment described above, the stretchable substrate 10 is stretched, causing the rigidity-maintaining portion 200, on which the electronic elements 400 are mounted, to maintain high rigidity and minimize deformation, while the rigidity-variable portion 100 is stretched by the tensile force.

[0174] Furthermore, when the variable rigidity portion 100 is extended in this manner, stress concentration does not occur in the rigidity maintenance portion 200, which is the portion on which the electronic element 400 is mounted. As a result, the mounting state of the electronic element 400 can be stably maintained.

[0175] Thus, even under repeated expansion and contraction conditions due to repeated application of external force, the electronic element 400 maintains a stable mounting state, and the electrical or mechanical stability of the expandable substrate 10 is maintained.

[0176] According to the embodiments of the present invention described above, in a stretchable substrate, the rigidity of only the rigidity variable portion decreases above a predetermined temperature, causing it to deform and become stretchable. By controlling the temperature, the rigidity of a specific region is maintained while the rigidity of other regions is controlled to be variable, thus enabling the construction of stretchable substrates with different rigidity distributions.

[0177] In particular, by forming the rigidity maintenance portion in a specific arrangement and mounting elements on the rigidity maintenance portion, the expandable substrate retains its expandability through temperature control, while the expandability is minimized in the area where the elements are mounted, thereby maintaining a stable element connection state.

[0178] Furthermore, by solving the problems of contact and structural instability at the interface between the expandable and non-expandable parts of conventional materials, it is possible to construct an expandable substrate that maintains a stable structure at the interface while possessing expandability, as a continuous structural characteristic of the same material.

[0179] Furthermore, the temperature control, based on information regarding the glass transition temperatures of the variable-rigidity section and the rigidity-maintaining section, allows for control of the expandability of the expandable substrate of the variable-rigidity structure by controlling it within the glass transition temperature range. Here, based on information regarding the temperature range during the manufacturing process or in use of the expandable substrate, the glass transition temperatures of the variable-rigidity section and the rigidity-maintaining section can be set to be different from each other. Therefore, during the manufacturing process, a state of high rigidity can be maintained to maintain the stability of the manufacturing process, while in actual use, the rigidity can be varied to improve the various usability of the expandable substrate.

[0180] By forming the glass transition temperatures of the variable-stiffness portion and the stiffness-maintaining portion in a manner that differs from each other, ultraviolet light can be applied only to the stiffness-maintaining portion on the stretchable substrate, thereby creating a relatively high glass transition temperature. This makes it possible to manufacture the stretchable substrate with a relatively simple process and a suitable material selection for the stretchable substrate.

[0181] In particular, by providing ultraviolet light to the rigidity maintenance portion so that the light intensity changes sequentially, or by manufacturing the mask portion so that the degree of opening changes sequentially, the structural stability of the stretchable substrate during repeated stretching and contraction can be further improved by the gradual variation of rigidity at the interface between the variable rigidity portion and the rigidity maintenance portion. In this case, by forming the rigidity maintenance portion in various patterns and shapes, it is possible to mount elements on a wider variety of rigidity maintenance portion configurations, thereby enabling the construction of stretchable substrates with various rigidity distributions.

[0182] Furthermore, by forming the rigidity maintenance portion with a relatively thicker thickness, the deformation rate and expansion rate of the rigidity maintenance portion are kept lower, thereby minimizing the deformation rate of the elements mounted on the rigidity maintenance portion, maintaining a more stable element connection state, and enabling the manufacture of a stretchable substrate with high electrical stability and reliability.

[0183] Furthermore, the stiffness distribution in the stretchable substrate can be varied by heating the stiffness-maintaining portion and the stiffness-variable portion at different temperatures, or by heating only the stiffness-variable portion. This allows the regions of the stiffness-maintaining portion and the stiffness-variable portion to be set to have various patterns and arrangements, and by varying the stiffness distribution in various ways using a relatively simple heating method, it becomes possible to manufacture stretchable substrates with a wider variety of self-stiffness distribution characteristics.

[0184] While preferred embodiments of the present invention have been described above with reference to those skilled in the art, a person skilled in the art will understand that the present invention can be modified and altered in various ways without departing from the spirit and scope of the invention as set forth in the following claims. [Explanation of symbols]

[0185] 10, 11, 12, 20, 30, 40: Stretchable board 20, 21: Base board 22: Recessed area 50: Ultraviolet rays 150: Protrusion 100, 101, 102, 104, 105, 106: Stiffness variable section 200, 201, 202, 203, 204, 205: Rigidity maintenance part 211: Central part 212: Peripheral area 300, 301: Mask section 310: Opening 400: Electronic elements

Claims

1. A stretchable substrate including a rigidity-maintaining portion and a rigidity-variable portion, which are divided into different regions from each other, The rigidity maintenance section and the rigidity variable section maintain a predetermined rigidity only at temperatures below a predetermined temperature. A stretchable substrate characterized in that only the stiffness-variable portion deforms to become less stiff than a predetermined stiffness at temperatures above a predetermined temperature, thereby allowing it to expand and contract.

2. The rigidity maintenance portion is formed with a plurality of regions having a predetermined pattern, The stretchable substrate according to claim 1, characterized in that the stiffness variable portion is formed in a region other than the stiffness maintenance portion.

3. The stretchable 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.

4. The stretchable substrate according to claim 2, characterized in that an element is mounted on the rigidity-maintaining portion.

5. The aforementioned variable rigidity portion is formed having a predetermined pattern, The stretchable substrate according to claim 1, characterized in that the rigidity-maintaining portion is formed in a region other than the rigidity-variable portion.

6. The stretchable substrate according to claim 5, characterized in that the rigidity variable portion is formed along a paper-cut pattern.

7. Poisson's ratio is negative, The expandable substrate according to claim 6, characterized in that when expansion or contraction occurs in the first direction, expansion or contraction in the second direction perpendicular to the first direction also occurs at the same rate.

8. The stretchable substrate according to claim 1, characterized in that the predetermined temperature is the glass transition temperature of the rigidity variable portion.

9. The stretchable 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.

10. The stretchable substrate according to claim 1, characterized in that the rigidity-maintaining portion and the rigidity-variable portion contain PDMS or polyimide.

11. For a stretchable substrate including a rigidity-maintaining portion and a rigidity-variable portion that are divided into different regions, The steps include positioning the mask portion so that the opening is aligned with the rigidity maintenance portion, A method for manufacturing a stretchable substrate, characterized by including the step of providing ultraviolet light to the upper part of the mask portion and providing ultraviolet light only to the rigidity-maintaining portion.

12. The method for manufacturing a stretchable substrate according to claim 11, characterized in that ultraviolet light is supplied only to the rigidity maintenance portion, thereby forming a glass transition temperature higher than that of the rigidity variable portion.

13. The method for manufacturing a stretchable substrate according to claim 11, characterized in that the stretchable substrate contains a glycol gel.

14. The method for manufacturing a stretchable substrate according to claim 13, characterized in that ultraviolet light is supplied only to the rigidity-maintaining portion, causing the glycol gel to form a network by photocrosslinking, polyimide to polymerize in the spaces between the networks, inducing high-density polymer entanglement, and raising the glass transition temperature.

15. The method for manufacturing a stretchable substrate according to claim 11, characterized in that the degree of ultraviolet light transmission decreases sequentially from the center to the periphery of the opening in the mask portion.

16. The method for manufacturing a stretchable substrate according to claim 11, characterized in that the ultraviolet light is modulated light whose intensity decreases sequentially from the center to the periphery of the opening.

17. The method for manufacturing a stretchable substrate according to claim 15 or 16, characterized in that the glass transition temperature of the rigidity-maintaining portion decreases progressively from the central portion to the peripheral portion which is the boundary with the rigidity-variable portion.

18. The method for manufacturing an expandable substrate according to claim 11, characterized in that the rigidity-maintaining portion is formed to have a greater thickness than the rigidity-variable portion.

19. The method for manufacturing an expandable substrate according to claim 18, characterized in that the thickness of the rigidity-maintaining portion decreases sequentially from the central portion to the peripheral portion which is the boundary with the rigidity-variable portion.

20. For a stretchable substrate including a rigidity-maintaining portion and a rigidity-variable portion that are divided into different regions, The rigidity maintenance section maintains the temperature, and heats only the rigidity variable section to increase its temperature, A method for varying the stiffness distribution of an expandable substrate, characterized by heating the expandable substrate such that the stiffness variable portion has a higher temperature than the stiffness maintenance portion.

21. The method for varying the stiffness distribution of an expandable substrate according to claim 20, characterized in that when the temperature is increased by heating only the stiffness variable portion, a heater is attached to the lower surface of the stiffness variable portion.

22. The method for varying the stiffness distribution of an expandable substrate according to claim 20, characterized in that, when the temperature of the variable stiffness portion is maintained relatively higher than that of the stiffness maintenance portion to heat the expandable substrate, the variable stiffness portion is formed to have a higher thermal diffusivity than the stiffness maintenance portion.

23. The method for varying the stiffness distribution of an expandable substrate according to claim 20, characterized in that, when the temperature of the variable stiffness portion is maintained relatively higher than that of the stiffness-maintaining portion to heat the expandable substrate, the variable stiffness portion is formed to contain more photothermal particles than the stiffness-maintaining portion.

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