Stretchable substrate having self-stiffness distribution, manufacturing method therefor, and stiffness distribution varying method therefor

Abstract

Provided are a stretchable substrate having a self-stiffness distribution, a manufacturing method therefor, and a stiffness distribution varying method therefor, the stretchable substrate comprising a stiffness maintaining part and a stiffness varying part that are partitioned into different areas. In addition, in the stretchable substrate, the stiffness maintaining part and the stiffness varying part maintain preset stiffness only at the preset temperature or lower. Only the stiffness varying part is modified to be stretchable since the stiffness thereof is lower than a preset stiffness at a preset temperature or higher.

Description

Stretchable substrate having self-stiffness distribution, method for manufacturing the same, and method for varying the stiffness distribution thereof

[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 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, in which, as the temperature is varied, the stiffness is lowered in a specific region to enable elongation, while the stiffness is maintained in other regions to minimize deformation, thereby implementing selective elongation in each region, maintaining an overall stable structure, and having a control of a specific factor, a simple manufacturing process, and simple circuit wiring.

[0002] As the demand for various flexible electronic devices increases, manufacturing technology for flexible display devices is advancing, and manufacturing technology for display devices that are not only flexible but also stretchable is being developed.

[0003] Korean Patent No. 10-2340855 discloses a technology for a flexible display device that is configured to include a flexible substrate and a variable portion and is capable of being stretched.

[0004] However, in the case of such elastic or flexible display devices, there is a problem that when the entire substrate is stretched, the elements mounted on the substrate may be damaged due to low elasticity or detached from the substrate due to increased rigidity.

[0005] Accordingly, through Korean Patent Registration No. 10-1756847, a technology is disclosed in which the area where the element is mounted is formed of a material having a relatively high elastic modulus, and other areas are formed of a material having a relatively low elastic modulus.

[0006] However, when manufacturing substrates with these different materials, it is difficult to maintain structural stability at the boundary, and the manufacturing process becomes complicated.

[0007] Meanwhile, a technique for locally changing stiffness by varying local dimensions or shape, in addition to varying the elastic modulus, is disclosed in Korean Patent No. 10-2368540. However, implementing this structural approach to local stiffness variation requires additional manufacturing processes and complicates the circuit wiring.

[0008] Accordingly, there is an increasing technological demand for a flexible substrate that can maintain relatively high rigidity in the area where the device is mounted while also having structural stability at the boundary, and that includes a simple manufacturing process and circuit wiring while controlling factors such as Poisson's ratio and anisotropic elastic modulus.

[0009] Accordingly, the technical problem of the present invention is conceived from this point, and the purpose of the present invention is to provide an elastic substrate having a self-stiffness distribution that can selectively elongate by region by varying the temperature, whereby the stiffness is lowered in a specific region to enable elongation, while the stiffness is maintained in other regions to minimize deformation, and whereby a stable structure is maintained by omitting the boundary portion as a whole, and whereby control of specific factors, a simple manufacturing process, and simple circuit wiring are possible.

[0010] In addition, another object of the present invention is to provide a method for manufacturing the above-mentioned flexible substrate.

[0011] In addition, another object of the present invention is to provide a method for varying the stiffness distribution of the elastic substrate.

[0012] According to one embodiment of the present invention, a flexible substrate includes a rigidity maintaining portion and a rigidity variable portion, which are divided into different regions. In addition, the flexible substrate maintains a predetermined rigidity in the rigidity maintaining portion and the rigidity variable portion only below a preset temperature. Only the rigidity variable portion can be deformed to be elastic by lowering the rigidity below the preset rigidity when the temperature is above the preset temperature.

[0013] In one embodiment, the rigid maintenance portion is formed with a plurality of regions having a predetermined pattern, and the rigid variable portion can be formed in a region other than the rigid maintenance portion.

[0014] In one embodiment, the length of the rigid retaining member along the first direction and the length of the rigid retaining member along the second direction perpendicular to the first direction may be different from each other.

[0015] In one embodiment, a component may be mounted on the rigid retaining member.

[0016] In one embodiment, the rigid variable portion is formed with a predetermined pattern, and the rigid maintenance portion can be formed in a region other than the rigid variable portion.

[0017] In one embodiment, the rigid variable portion may be formed along a kirigami pattern.

[0018] In one embodiment, if the Poisson's ratio is negative and a stretch occurs in a first direction, a stretch in a second direction perpendicular to the first direction may also occur at the same rate.

[0019] In one embodiment, the preset temperature may be the glass transition temperature of the rigid variable portion.

[0020] In one embodiment, the glass transition temperature of the rigid variable portion may be lower than the glass transition temperature of the rigid maintaining portion.

[0021] In one embodiment, the rigidity maintaining portion and the rigidity variable portion may include polydimethylsiloxane (PDMS) or polyimide.

[0022] In one embodiment of a method for manufacturing a flexible substrate for realizing the purpose of the present invention described above, the method comprises the steps of positioning a mask portion so that an opening is aligned with the rigid maintenance portion, for a flexible substrate including a rigid maintenance portion and a rigid variable portion divided into different regions, and providing ultraviolet rays from an upper portion of the mask portion so that only the rigid maintenance portion is provided with the ultraviolet rays.

[0023] In one embodiment, since only the rigid maintenance portion is provided with ultraviolet rays, the glass transition temperature of the rigid variable portion can be formed lower than the glass transition temperature of the rigid maintenance portion.

[0024] In one embodiment, the flexible substrate may include a glycol gel.

[0025] In one embodiment, when only the rigid maintenance part is provided with ultraviolet light, the glycol gel forms a network by photocrosslinking, and polyimide is polymerized in the space between the networks, thereby inducing high-density polymer entanglement.

[0026] In one embodiment, the opening of the mask portion may allow the degree of ultraviolet light passing through the opening to gradually decrease from the center to the periphery of the opening.

[0027] In one embodiment, the ultraviolet light may be modulated light whose intensity gradually decreases from the center to the periphery of the opening.

[0028] In one embodiment, the glass transition temperature of the rigidity maintaining portion may gradually decrease from the central portion to the peripheral portion, which is the boundary with the rigidity variable portion.

[0029] In one embodiment, the rigidity maintaining portion may be formed to have a greater thickness than the rigidity variable portion.

[0030] In one embodiment, the thickness of the rigid maintenance portion may gradually decrease from the central portion to the peripheral portion, which is the boundary with the rigid variable portion.

[0031] In a method for varying the rigidity distribution of a flexible substrate according to one embodiment for realizing the purpose of the present invention described above, for a flexible substrate including a rigidity maintaining portion and a rigidity variable portion divided into different regions, the rigidity maintaining portion can maintain a temperature and only the rigidity variable portion can be heated to increase the temperature, or the flexible substrate can be heated so that the rigidity variable portion has a higher temperature than the rigidity maintaining portion.

[0032] In one embodiment, when only the rigid variable portion is heated to increase the temperature, a heater may be attached to the lower surface of the rigid variable portion.

[0033] In one embodiment, when heating the flexible substrate while maintaining the temperature of the rigid variable portion relatively higher than that of the rigid maintenance portion, the rigid variable portion can be formed to have a higher thermal diffusivity than the rigid maintenance portion.

[0034] In one embodiment, when the temperature of the rigid variable portion is maintained relatively higher than that of the rigid maintenance portion and the flexible substrate is heated, the rigid variable portion can be formed to include more photothermal particles than the rigid maintenance portion.

[0035] According to embodiments of the present invention, in a flexible substrate, only the rigidity variable portion is deformed to be elastic by lowering the rigidity when the temperature is higher than a preset temperature, so that by controlling the temperature, the rigidity of a specific region is maintained as is while the rigidity of another region is controlled to be variable, so that a flexible substrate having a different rigidity distribution can be formed.

[0036] In particular, if the rigid support portion is formed in a specific arrangement and a device is mounted on the rigid support portion, the flexible substrate can be made flexible through temperature control while the flexibility is minimized in the area where the device is mounted, thereby maintaining a stable device connection state. In this case, by forming the rigid support portion in various patterns or shapes, it is possible to mount devices on rigid support portions of more diverse shapes, thereby configuring a flexible substrate having various rigidity distributions.

[0037] Moreover, by solving the contact problem or structural instability problem at the interface between the conventional elastic and non-elastic portions, it is possible to construct an elastic substrate that can have elasticity while maintaining a stable structure at the interface with the continuous structural characteristics of the same material.

[0038] Furthermore, the temperature control can control the elasticity of the flexible substrate having a variable stiffness structure through control within the glass transition temperature range based on information about the glass transition temperatures of the stiffness variable portion and the stiffness maintaining portion. At this time, since the glass transition temperatures of the stiffness variable portion and the stiffness maintaining portion can be formed differently based on information about the temperature range in the manufacturing process or use state of the flexible substrate, the stability of the manufacturing process can be maintained by maintaining a high stiffness state during the manufacturing process, while the stiffness can be varied during actual use to improve the various usability of the flexible substrate.

[0039] By forming the glass transition temperatures of the rigid variable portion and the rigid maintenance portion differently, the glass transition temperature can be formed relatively high by providing ultraviolet rays only to the rigid maintenance portion on the flexible substrate, so that the flexible substrate can be manufactured through selection of the material for the flexible substrate and a relatively simple process.

[0040] In particular, by providing ultraviolet rays so that the light intensity of the rigid maintenance portion to which the ultraviolet rays are provided gradually changes, or by manufacturing the opening degree of the opening of the mask portion so that it gradually changes, the structural stability of the flexible substrate in repeated stretching can be further improved through gradual stiffness variation at the interface between the rigid variable portion and the rigid maintenance portion.

[0041] In addition, by forming the thickness of the rigid maintenance portion relatively thick, the strain or elasticity of the rigid maintenance portion is kept lower, thereby minimizing the strain of the element mounted on the rigid maintenance portion, thereby maintaining a more stable element connection state, and thus manufacturing a flexible substrate with high electrical stability and reliability is possible.

[0042] Furthermore, the stiffness distribution in the flexible substrate can be varied through a process of heating the stiffness maintaining portion and the stiffness variable portion at different temperatures or heating only the stiffness variable portion. Through this, the areas of the stiffness maintaining portion and the stiffness variable portion can be set to have various patterns or arrangements, and by varying the stiffness distribution in various ways through a relatively simple heating method, it is possible to manufacture a flexible substrate having a more diverse self-stiffness distribution characteristic.

[0043] FIG. 1 is a perspective view illustrating a flexible substrate having a self-rigidity distribution according to one embodiment of the present invention.

[0044] Figure 2 is a schematic diagram for explaining a state in which the stiffness distribution changes according to temperature variation in the flexible substrate of Figure 1.

[0045] Figures 3a and 3b are graphs for explaining a state in which the flexible substrate of Figure 1 has a self-stiffness distribution according to the distribution of glass transition temperature.

[0046] FIG. 4 is a perspective view illustrating a flexible substrate having a self-rigidity distribution according to another embodiment of the present invention.

[0047] FIG. 5 is a perspective view illustrating a flexible substrate having a self-rigidity distribution according to another embodiment of the present invention.

[0048] Figure 6 is a process diagram illustrating a method for manufacturing the flexible substrate of Figure 1.

[0049] FIGS. 7a and 7b are process diagrams illustrating a method for manufacturing a flexible substrate according to another embodiment of the present invention.

[0050] Figures 8a to 8d are process diagrams illustrating a method for manufacturing a flexible substrate according to another embodiment of the present invention.

[0051] FIGS. 9a and 9b are process diagrams illustrating a method for varying the stiffness distribution of a flexible substrate according to another embodiment of the present invention.

[0052] Figures 10a and 10b are graphs for explaining the stress concentration phenomenon according to temperature variation in the flexible substrate of Figure 1.

[0053] <Explanation of symbols>

[0054] 10, 11, 12, 20, 30, 40: Stretchable substrate

[0055] 20, 21: Base substrate 22: Recessed portion

[0056] 50: UV 150: Protrusions

[0057] 100, 101, 102, 104, 105, 106: Variable stiffness section

[0058] 200, 201, 202, 203, 204, 205: Rigidity retaining part

[0059] 211: Central 212: Periphery

[0060] 300, 301: Mask part 310: Opening part

[0061] 400: Electronic components

[0062] The present invention is susceptible to various modifications and takes various forms, and thus embodiments are described in detail herein. However, this is not intended to limit the present invention to a specific disclosed form, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. Similar reference numerals have been used to designate similar components throughout the description of each drawing. While terms such as "first," "second," etc. may be used to describe various components, these components should not be limited by these terms.

[0063] The above terms are used solely to distinguish one component from another. The terms used in this application are used solely to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0064] In this application, it should be understood that terms such as “comprise” or “consist of” are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0065] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0066] Hereinafter, with reference to the attached drawings, a preferred embodiment of the present invention will be described in more detail.

[0067] FIG. 1 is a perspective view illustrating a flexible substrate having a self-rigidity distribution according to one embodiment of the present invention.

[0068] Referring to FIG. 1, the elastic substrate (10, hereinafter referred to as the elastic 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).

[0069] The above-described rigidity variable portion (100) is defined as a region in which the rigidity varies as the temperature varies to a specific temperature, as described below, and the above-described rigidity maintenance portion (200) is defined as a region in which the rigidity does not vary regardless of the temperature variation to the specific temperature. In this case, the range of temperature variation and the resulting rigidity variation will be described below.

[0070] The above rigid variable portion (100) is defined as an area where the above rigid maintenance portion (200) is not formed.

[0071] In addition, when the rigid variable portion (100) is defined as a specific region as described above, in the region corresponding to the rigid variable portion (100), the entire region corresponds to the rigid variable portion (100) in the thickness direction of the flexible substrate (10) regardless of the thickness of the flexible substrate (10). The same applies to the rigidity maintaining portion (200). That is, the rigidity changing portion (100) or the rigidity maintaining portion (200) does not have the property of varying or maintaining the rigidity only on the surface of the flexible substrate (10), but has the property of varying or maintaining the rigidity throughout the entire region in the thickness direction of the flexible substrate (10).

[0072] Of course, as described later, the elastic substrate (10) can also be formed to have different stiffnesses along the thickness direction, and this will be described later.

[0073] In addition, as illustrated, the rigidity maintaining portion (200) does not overlap with the rigidity variable portion (100), and each portion is defined as a different area. At this time, the rigidity maintaining portion (200) may have, for example, a matrix array of m*n in total, each portion having a constant area (m and n are natural numbers).

[0074] Of course, the arrangement state or arrangement pattern of the above rigidity maintaining portions (200) is not limited to the matrix arrangement, and may have various arrangements. That is, each of the above rigidity maintaining portions (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 the rigidity maintaining portions (200) are arranged at an arbitrary position or a structure in which a long pattern extending in one direction is repeated, a zigzag structure, etc. Additional arrangements or patterns of the above rigidity maintaining portions (200) will be further illustrated and described through the drawings described below.

[0075] However, each of the above rigidity maintenance parts (200) has a constant width and can be formed in multiple pieces spaced apart from each other.

[0076] As described above, a predetermined electronic device may be mounted in the region where the rigid maintenance member (200) is formed. That is, at least one electronic device may be mounted in each region formed by the rigid maintenance member (200). At this time, the type, structure, and further, the function of the electronic device are not limited.

[0077] For example, the electronic device may be a micro LED (light emitting device). In addition, if the electronic device is mounted on the rigid support member (200) as described above, a wiring structure for driving the electronic device must also be formed on the flexible substrate (10), but additional drawings regarding the wiring structure are omitted.

[0078] In the case of the above wiring structure, a wiring structure that is already known in the past can be applied as is, and can be additionally formed on the lower surface of the elastic substrate (10) or inside the elastic substrate (10), and the formation structure, etc. are not limited. Furthermore, the wiring structure can be formed in a necessary shape or structure on the entire area of ​​the elastic substrate (10) without being divided into the rigidity variable portion (100) and the rigidity maintaining portion (200).

[0079] In the present embodiment, the configuration of the rigid variable portion (100) and the rigid maintenance portion (200) constituting the elastic substrate (10) is described as a substrate. As for the components that must be additionally formed in order for the elastic substrate (10) to be used as a display device, such as the wiring structure described above, components according to conventional technology can be applied as they are, and thus a description thereof will be omitted. Likewise, it is also obvious that the components that must be additionally provided can be formed on the upper surface, lower surface, or inside the elastic substrate (10).

[0080] In the above-described elastic substrate (10), the rigidity variable portion (100) and the rigidity maintaining portion (200) have the characteristics of varying or maintaining the rigidity through temperature variation to a specific temperature as described above, but can be formed of the same material. That is, by additionally performing a specific treatment or process as described below on the elastic substrate (10) formed of the same material, the characteristics are varied so that it is divided into a region where the rigidity is stably maintained and a region where the rigidity is variable.

[0081] Hereinafter, the partitioning of the above-mentioned rigid variable portion (100) and the above-mentioned rigid maintenance portion (200) and the characteristics of the self-rigidity distribution of the above-mentioned elastic substrate (10) according to this will be described in more detail.

[0082] Figure 2 is a schematic diagram for explaining a state in which the stiffness distribution changes according to temperature variation in the flexible substrate of Figure 1.

[0083] Referring to Fig. 2, the elastic substrate (10) is heated to a temperature (T) lower than a preset 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.

[0084] However, if the above-mentioned flexible substrate (10) is exposed to an environment having a temperature (T>Tc) higher than a preset specific temperature (Tc), the rigidity maintaining portion (200) maintains a relatively high rigidity similar to the initial state, but the rigidity variable portion (100) has a lower rigidity than the rigidity in the initial state.

[0085] Thus, in this state, the rigidity maintaining portion (200) maintains a stable structure without being stretched by external force, etc., but the rigidity variable portion (100) is stretched by external force, etc., and deformation occurs. Accordingly, as illustrated, the elastic substrate (10) as a whole can be stretched or compressed depending on the direction of the external force.

[0086] That is, in the case of the above-mentioned flexible substrate (10), a deformation in the form of an overall length extension or reduction may be induced, but the rigid support member (200) on which the electronic component described above is mounted maintains its shape identical to the initial state and its structure does not change.

[0087] Accordingly, the mounting state and electrical connection state of the electronic component in the area where the electronic component is mounted can be stably maintained. Of course, in this case, if the components such as wiring for driving the electronic component are formed in the area where the electronic component is mounted, a stable connection state can be maintained. However, if the components are mounted in the rigid variable portion (100), which is an area where the electronic component is not mounted, it is necessary to form the components from a material that can simultaneously deform according to the degree of deformation, taking into account the degree of deformation of the rigid variable portion (100).

[0088] As described above, the reason why elasticity is not induced only in the rigidity maintenance portion (200) defined as a local area and a stable structure with relatively high rigidity is maintained is explained with reference to the subsequent drawings.

[0089] Figures 3a and 3b are graphs for explaining a state in which the flexible substrate of Figure 1 has a self-stiffness distribution according to the distribution of glass transition temperature.

[0090] First, referring to FIG. 3a, if the elastic substrate (10) includes a first material and the glass transition temperature of the first material is Tg1, the rigidity of the first material can be rapidly reduced at a temperature higher than the glass transition temperature Tg1.

[0091] 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 may also decrease rapidly at a temperature higher than the glass transition temperature Tg2.

[0092] At this time, if the elastic substrate (10) is maintained in 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 elastic substrate (10) decreases in the region where the first material is included, but the rigidity does not decrease in the region where the second material is included and can be maintained at a certain level.

[0093] As a result, in the elastic substrate (10), the rigidity is lowered in the region including the first material, so that it has high elasticity as shown in Fig. 3b and can be easily deformed according to an external force, but in the region including the second material, the rigidity is maintained as is and no deformation occurs.

[0094] Therefore, by maintaining the elastic substrate (10) within the temperature range of Tg1 and Tg2, the elastic substrate (10) can be controlled to have elasticity and be easily deformed in response to an external force. In other words, this means that if the first and second materials are selected so that the temperature (T) falls within the temperature range of Tg1 and Tg2 in consideration of the temperature (T) of the environment in which the elastic substrate (10) is used, or if the glass transition temperatures of the first and second materials are controlled so that the temperature (T) falls within a range between the glass transition temperatures of the first and second materials, the elastic substrate (10) can be controlled to have elasticity in a specific region and maintain rigidity in other regions.

[0095] As described above, if the elastic substrate (10) is configured to have different glass transition temperatures, the elastic substrate (10) can be controlled to have elasticity in a specific area while maintaining rigidity in other areas.

[0096] At this time, the control of the elasticity of the above-described elastic substrate (10) can be equally applied not only when the elastic substrate (10) includes different first and second materials, but also when the elastic substrate (10) includes the same material but is formed to have different glass transition temperatures for each region.

[0097] That is, if the above-mentioned elastic substrate (10) includes the same material in the entire area, but is formed to have a different glass transition temperature from other areas through a predetermined processing process for a specific area, the elasticity can be controlled differently due to the difference in glass transition temperature between the specific area and other areas, as described above with reference to FIGS. 3a and 3b.

[0098] At this time, as previously explained, if the temperature (T) in the environment in which the elastic substrate (10) is used falls within the range between the glass transition temperatures in the specific region and the other region, the elastic substrate (10) will eventually have different elasticities in each region in the environment in which it is used.

[0099] Furthermore, if the temperature (T') in the process 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 in addition to the temperature in the use environment of the stretchable substrate (10), the stretchable substrate (10) may have a constant stiffness in all regions in the process environment while minimizing elasticity. Similarly, if the temperature (T') in 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 be deformed while having elasticity in all regions in the process environment.

[0100] FIG. 4 is a perspective view illustrating a flexible substrate having a self-rigidity distribution according to another embodiment of the present invention.

[0101] The above-described elastic substrate (11) according to the present embodiment is substantially the same as the above-described elastic substrate (10) described with reference to FIG. 1 except for the shape and arrangement of the rigid maintenance part (204), and therefore, redundant description is omitted.

[0102] Referring to FIG. 4, in the flexible substrate (11) according to the present embodiment, the rigid maintenance portions (204) are arranged in a plurality of parallel manners 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 rigid maintenance portions (204) may be arranged continuously in the second direction (Y). Of course, one rigid maintenance portion (204) may extend relatively long in the second direction (Y), or three or more may be arranged continuously.

[0103] Ultimately, in the present embodiment, the rigidity maintaining portion (204) is formed so that the length along the second direction (Y) is relatively larger than the length (i.e., width) along the first direction (X). Thus, in the elastic substrate (11), it can be said that the elasticity in the first direction (X), where the rigidity maintaining portion (204) is distributed over a relatively small area, is formed to be larger than the elasticity in the second direction (Y).

[0104] At this time, as described above, the rigidity maintaining portion (204) has the same characteristics in the thickness direction of the elastic substrate (11), and does not have the characteristics of the rigidity maintaining portion (204) only on the surface of the elastic substrate (11). The same applies to the rigidity variable portion (104).

[0105] As described above, since the rigidity retaining member (204) is formed in a relatively long rectangular shape in a specific direction, a relatively long rectangular element can be mounted more stably. Furthermore, since the rigidity retaining member (204) is formed to have different lengths along the first direction (X) and the second direction (Y), the elasticity along the first direction (X) and the elasticity along the second direction (Y) are different, so that various applications can be possible. At this time, an example of the application is a rollable display.

[0106] FIG. 5 is a perspective view illustrating a flexible substrate having a self-rigidity distribution according to another embodiment of the present invention.

[0107] The elastic substrate (12) according to the present embodiment is substantially the same as the elastic substrate (10) described with reference to FIG. 1 except for the shape and arrangement of the rigidity maintaining portion (205) and the rigidity variable portion (105, 106), and therefore, redundant description is omitted.

[0108] Referring to FIG. 5, in the elastic substrate (12) according to the present embodiment, the rigidity maintaining portion (205) relatively occupies most of the area of ​​the elastic substrate (12), and the rigidity variable portion (105, 106) is formed in a form that extends in a specific direction.

[0109] That is, the first rigid variable portion (105) extends along the first direction (X) to a predetermined length on the elastic substrate (12), and the second rigid variable portion (106) extends in the second direction (Y) and is short-circuited at a 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 elastic substrate (12), but the second variable rigid portion (106) can be formed to extend to the side of the elastic substrate (12).

[0110] Thus, the first and second rigid variable portions (105, 106) are formed on the rigid maintenance portion (205) in an overall cross (+) shape, which is a form in which a cutting line portion of a so-called kirigami pattern is formed by the rigid variable portions (105, 106). At this time, it is sufficient if the first and second rigid variable portions (105, 106) are formed substantially like the cutting line of the kirigami pattern, and it does not mean that cutting is performed along the kirigami pattern.

[0111] Through this, unlike in FIG. 4, in the flexible substrate (12) according to the present embodiment, the length of the rigid maintenance portion (205) along the first direction (X) can be substantially equal to the length of the rigid maintenance portion (205) along the second direction (Y).

[0112] Meanwhile, through the arrangement of the rigid variable portion and the rigid maintenance portion as in Fig. 5, the overall Poisson's ratio of the elastic substrate (12) becomes negative and approaches -1. Accordingly, when the elastic substrate (12) is stretched in the second direction (Y), stretching in the first direction (X) occurs at a similar rate, thereby inducing uniform elongation or uniform contraction throughout the elastic substrate (12).

[0113] Thus, in this embodiment, the aspect ratio distortion of the display image due to one-way stretching can be significantly reduced through the elastic substrate (12).

[0114] Furthermore, in this embodiment, the rigid variable portion (105, 106) as well as the rigid maintenance portion (205) can all have the same characteristics in the thickness direction of the elastic substrate (12).

[0115] Hereinafter, embodiments of a method for processing the above-described flexible substrate (10) including the same material as described above so that it has different glass transition temperatures in a specific region and in another region will be described.

[0116] Figure 6 is a process diagram illustrating a method for manufacturing the flexible substrate of Figure 1.

[0117] First, referring to Fig. 6, in manufacturing the above flexible substrate (10), a mask portion (300) is aligned on the upper portion of the flexible substrate (10) formed of the same material. At this time, the mask portion (300) blocks ultraviolet rays (UV light) provided from the upper portion, and it is sufficient if it includes a material capable of blocking ultraviolet rays.

[0118] In addition, as shown, 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 positions where the rigid retaining portions (200) are to be formed in the flexible substrate (10).

[0119] That is, the size or pattern of the openings (310) can be formed to be substantially the same as the size or pattern of the rigidity retaining parts (200) to be formed, and as described above, the size and pattern of each of the rigidity retaining parts (200) can be designed to be variously variable, so it is sufficient if the size and pattern of each of the openings (310) are designed to match this.

[0120] After this, ultraviolet light is provided from the upper portion of the mask portion (300), and through this, the ultraviolet light passes only through the openings (310) and is provided to the flexible substrate (10).

[0121] Thus, on the elastic substrate (10), the characteristics change depending on the exposure to the ultraviolet rays (50) in the area where the ultraviolet rays (50) are 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 rays (50), and the area where the ultraviolet rays (50) are blocked remains as the rigidity variable portion (100).

[0122] At this time, the elastic substrate (10) may include PDMS (polydimethylsiloxane) or polyimide.

[0123] In particular, the elastic substrate (10) may include a glycol gel. Thus, as illustrated in FIG. 6, in the region exposed to the ultraviolet rays (50), i.e., the rigid maintenance portion (200), the glycol gel forms a network through photocrosslinking, and polyimide is polymerized in the space between the networks, thereby inducing high-density polymer entanglement.

[0124] That is, when UV light is irradiated on the glycol gel, a crystal phase / entangled phase region formed locally with a high polymer concentration is formed, and then, when the Semi-IPN structure of polyimide is formed in the space between the networks, more polymer entanglements 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.

[0125] Meanwhile, in the area where the ultraviolet rays are irradiated, it is necessary to control the intensity or time of the ultraviolet rays irradiation in order to induce sufficient polymer entanglement in the thickness direction by the irradiation of the ultraviolet rays and to have the same characteristics in the thickness direction.

[0126] Of course, if it is necessary to form the rigidity maintaining portion (200) only on the surface of the flexible substrate in consideration of the characteristics of the flexible substrate to be manufactured, that is, if it is necessary to form only the upper side of the flexible substrate on which the element is mounted to maintain rigidity and the lower side to have variable rigidity, it is also possible to control the intensity or time of the ultraviolet ray irradiation to induce different characteristics in the thickness direction of the flexible substrate.

[0127] In contrast, in the area where the above 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 relatively low.

[0128] Thus, in the above-mentioned flexible substrate (10), the rigid maintenance portion (200) to which the ultraviolet rays (50) are irradiated has a relatively high glass transition temperature (Tg2), and the rigid variable portion (100) to which the ultraviolet rays (50) are blocked has a relatively low glass transition temperature (Tg1).

[0129] Therefore, as described with reference to FIG. 3, the temperature (T) between the glass transition temperatures (Tg2~Tg1) stretch ), the rigidity maintaining portion (200) of the elastic substrate (10) maintains relatively high rigidity and is not deformed, but the rigidity variable portion (100) is deformed and stretched by an external force as the rigidity decreases.

[0130] As described above, even in the above-described elastic substrate (10) containing the same material, regions with different rigidities can be formed, thereby minimizing deformation in a specific region while forming other regions to be elastic and deformable.

[0131] At this time, if an electronic device is mounted in a specific area where the deformation is minimized, i.e., the rigidity maintaining portion (200), even if another area, i.e., the rigidity variable portion (100), is stretched and deformed by an external force, the area where the electronic device is mounted has minimal deformation, and a stable electrical connection state can be maintained. Accordingly, the elastic substrate (10) can maintain electrical or mechanical stability by maintaining a stable connection state of the electronic device mounted therein while having elasticity.

[0132] FIGS. 7a and 7b are process diagrams illustrating a method for manufacturing a flexible substrate according to another embodiment of the present invention.

[0133] In the method for manufacturing the elastic 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 retaining portion (201) according to the same, the method for manufacturing the elastic substrate (10) described with reference to FIG. 6 is the same, and therefore, the same reference numbers are used for the same components and redundant descriptions are omitted.

[0134] Referring to FIG. 7a, in the method for manufacturing the flexible substrate (20) according to the present embodiment, the mask portion (301) is aligned on the upper portion of the flexible substrate (20) positioned on the base substrate (20).

[0135] The above mask portion (301) blocks ultraviolet rays (UV light) provided from the top, and it is sufficient to include a material capable of blocking ultraviolet rays.

[0136] In addition, as shown, the mask portion (301) has a plurality of openings (311) formed therein, and as described above, the positions where the openings (311) are formed must be above the positions where the rigid retaining portions (201) are to be formed in the flexible substrate (20).

[0137] In the present embodiment, as illustrated, the mask portion (301) has an aperture ratio that gradually decreases from the center to the periphery, and accordingly, the degree of penetration of ultraviolet rays gradually decreases from the center to the periphery. That is, if the degree of penetration of ultraviolet rays (50) is the greatest in the center, indicating an ultraviolet transmittance of 100%, the ultraviolet transmittance gradually decreases from the center to the periphery, and ultimately, the ultraviolet transmittance may be 0% in the boundary region between the rigidity maintaining portion (201) and the rigidity variable portion (100).

[0138] As described above, as the transmittance of ultraviolet rays (50) decreases from the center to the periphery of the opening (311), the degree to which the characteristics are changed by the ultraviolet rays (50) also decreases from the center to the periphery.

[0139] That is, as described above, when exposed to the ultraviolet rays (50) provided through the opening (311), the glass transition temperature (Tg) of the rigid maintenance portion (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 portion (211) to the peripheral portion (212) of the rigid maintenance portion (201).

[0140] Accordingly, as shown in Fig. 7b, the rigidity of the rigidity maintenance part (201) gradually decreases from the central part (211) to the peripheral part (212), and the elasticity also increases as it goes toward the peripheral part (212).

[0141] In general, as 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 sharp difference in rigidity exists at the boundary between the rigidity maintaining portion (200) and the rigidity variable portion (100), and thus, the possibility of damage or defects occurring due to a sharp difference in elasticity or deformation at the boundary increases. In other words, a stress concentration phenomenon may occur in the elastic substrate (10).

[0142] Therefore, in order to minimize the stress concentration phenomenon due to the difference in elasticity or deformation at the interface, as in this embodiment, the glass transition temperature is gradually reduced from the central portion (211) to the peripheral portion (212) in the rigidity maintaining portion (201), thereby minimizing the difference in elasticity or deformation at the interface between the rigidity maintaining portion (201) and the rigidity variable portion (100), thereby alleviating the stress concentration.

[0143] Through this, even when the elastic substrate (20) is subjected to various and repetitive deformations, the occurrence of damage or defects at the boundary surface can be minimized, thereby further improving the electrical or mechanical stability of the electronic device (400) mounted on the upper surface of the rigid maintenance member (201).

[0144] Meanwhile, unlike the case where the opening (311) formed in the mask portion (301) is formed to have a gradually decreasing aperture ratio as shown in FIG. 7a, the intensity of the irradiated ultraviolet ray (50) can be controlled to gradually decrease while maintaining the aperture ratio of the opening (311) as is.

[0145] That is, the above opening (311) is formed to have 100% transmittance in both the central and peripheral portions, as in the opening (310) of FIG. 6, but the ultraviolet rays (50) irradiated from the upper portion of the mask portion (301) can be configured as modulated light whose intensity gradually decreases from the central portion to the peripheral portion.

[0146] In this way, if the ultraviolet ray (50) is configured as modulated light whose intensity gradually decreases from the center to the periphery, the intensity of the light provided to the rigid retaining portion (201) of the elastic substrate (20) can be substantially the same as in the case where the aperture ratio of the opening (311) in FIG. 7a is varied.

[0147] Thus, as shown in FIG. 7b, in the case of the rigidity maintaining portion (201), the glass transition temperature (Tg) gradually decreases from the central portion (211) to the peripheral portion (212), thereby minimizing the difference in elasticity or deformation at the boundary between the rigidity maintaining portion (201) and the rigidity variable portion (100), thereby alleviating stress concentration.

[0148] Furthermore, this difference in elasticity or deformation may induce a difference in the horizontal direction with respect to the elastic substrate (20), or alternatively, may induce a difference in the vertical direction, i.e., the thickness direction, with respect to the elastic substrate (20). Accordingly, the upper side of the elastic substrate (20) may be formed to have relatively high rigidity, and the lower side of the elastic substrate (20) may be formed to have relatively low rigidity.

[0149] Figures 8a to 8d are process diagrams illustrating a method for manufacturing a flexible substrate according to another embodiment of the present invention.

[0150] The method for manufacturing the elastic substrate (30) according to the present embodiment is the same as the method for manufacturing the elastic substrate (10) described with reference to FIG. 6, except that the thicknesses of the rigid variable portion (101) and the rigid maintenance portion (202) in the elastic substrate (30) are formed differently from each other. Therefore, the same reference numbers are used for the same components, and redundant descriptions are omitted.

[0151] First, referring to Fig. 8a, in the case of the elastic substrate (30) in the present embodiment, the rigidity maintaining 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).

[0152] In addition, in order to have these structural features, the flexible substrate (30) includes a protrusion (150) that protrudes downward in the region where the rigid maintenance portion (202) is formed. Similarly, in order to perform a predetermined process on the flexible substrate (30), the base substrate (21) on which the flexible substrate (30) is positioned includes a recessed portion (22) that is recessed to correspond to the protrusion (150).

[0153] In this case, the protrusion (150) has a curved outer surface as shown and protrudes downward, and may have, for example, a hemispherical shape. However, the shape of the protrusion (150) is not limited, and may be formed so that the thickness gradually decreases from the center to the periphery of the protrusion (150).

[0154] Accordingly, the first thickness (t1) of the rigidity maintaining portion (202) corresponds to the thickness at the central portion of the rigidity maintaining portion (202), and the first thickness (t1) may gradually decrease from the central portion to the peripheral portion. Thus, the boundary surface between the rigidity maintaining portion (202) and the rigidity variable portion (101) may be formed with the second thickness (t2).

[0155] Meanwhile, although not described in detail, the protrusion (150) may be formed by a process of forming a flexible substrate (30) through a transfer process such as imprinting on the upper surface of the base substrate (21) while the recessed portion (22) is formed in advance on the base substrate (21). That is, the recessed portion (22) of the base substrate (21) may be transferred as is to form the protrusion (150) on the lower surface of the flexible substrate (30).

[0156] With reference to FIG. 8b, for the above-described flexible substrate (30) including the protrusion (150), the mask portion (300) is positioned on the upper portion and ultraviolet rays (50) are irradiated.

[0157] At this time, the mask portion (300) is the same as the mask portion (300) described with reference to FIG. 6, and includes a plurality of openings (310), but the openings (310) are aligned with the position and pattern where the rigid retaining portion (202) is formed in the flexible substrate (30).

[0158] Thus, when the ultraviolet ray (50) is irradiated, the rigid maintenance portion (202) is exposed to the ultraviolet ray (50) through the opening (310), and the glass transition temperature (Tg) of the rigid maintenance portion (202) relatively increases. At this time, the internal polymer entanglement state in which the glass transition temperature of the rigid maintenance portion (202) relatively increases is as described above.

[0159] Accordingly, as illustrated in Fig. 8b, the rigidity retaining portion (202) is formed. However, as illustrated in Fig. 8b, in the portion where the protrusion (150) is formed, a polymer entanglement state is not induced internally.

[0160] More specifically, since the protrusion (150) is formed to have a relatively thick thickness (t1), if the intensity of the irradiated ultraviolet ray (50) is controlled, the ultraviolet ray is not irradiated up to the protrusion (150), and the characteristics are changed by the ultraviolet ray only up to the upper portion of the protrusion (150).

[0161] Accordingly, in the above-described flexible substrate (30), the rigidity maintaining portion (200) is formed only in the upper portion of the protrusion (150), and the glass transition temperature of the protrusion (150) does not rise, and maintains the same glass transition temperature as the surrounding rigidity variable portion (101).

[0162] After this, referring to FIGS. 8c and 8d, after mounting the electronic component (400) on the upper surface of the rigid maintenance part (200), the base substrate (21) located at the bottom is removed to the outside, thereby completing a flexible substrate (30) having a structure as in FIG. 8d.

[0163] At this time, in the case of the above-described flexible substrate (30), as described above, the rigidity maintaining portion (200) is formed in the portion where the electronic component (400) is mounted, so as to have a relatively high glass transition temperature, but the portion where the electronic component (400) is not mounted has a relatively low glass transition temperature due to the rigidity variable portion (101). Furthermore, the protrusion portion (150) is also a portion where the ultraviolet rays (50) cannot reach, and maintains a relatively low glass transition temperature, similar to the rigidity variable portion (101).

[0164] Thus, only the local portion where the electronic component (400) is mounted has relatively high rigidity and maintains structural stability, while the remaining area, as well as the lower portion of the electronic component (400), can be deformed to have elasticity. That is, the stretchable substrate (30) can be stretched and deformed over the entire area as a whole while maintaining the strain in the portion where the electronic component (400) is mounted to be minimized. Accordingly, the stretchable substrate (30) can maintain the electrical or mechanical stability of the electronic component (400) while further improving its elasticity.

[0165] In the above, a method for manufacturing the elastic substrate so that each region within the elastic substrate has different stiffness has been described.

[0166] However, in addition to the method of manufacturing the elastic substrate itself to have different glass transition temperatures in different regions, it is possible to vary the rigidity so that the elastic substrate has different elasticities in different regions even when the elastic substrate has the same glass transition temperature overall.

[0167] Hereinafter, a method for varying the stiffness distribution of the above-mentioned elastic substrate is described.

[0168] FIGS. 9a and 9b are process diagrams illustrating a method for varying the stiffness distribution of a flexible substrate according to another embodiment of the present invention.

[0169] In the case of the elastic substrate (40) according to the present embodiment, it is the same as the previous elastic substrates in that it contains the same material throughout, and furthermore, the glass transition temperature is not changed relatively high in a specific area through separate ultraviolet irradiation. In other words, the elastic substrate (40) has the same glass transition temperature (Tg) throughout the entire area.

[0170] Accordingly, a method for varying the stiffness distribution in the above-described flexible substrate (40) having the same glass transition temperature (Tg) is described as follows.

[0171] First, referring to Fig. 9a, a rigidity maintenance portion (203), which is a region having relatively high rigidity in the elastic substrate (40), and a rigidity variable portion (102), which is a region having relatively low rigidity and being elastic, are defined.

[0172] After this, in the elastic substrate (40), the rigidity maintaining portion (203) and the rigidity variable portion (102) are heated unevenly to different temperatures. At this time, the heating temperature of the rigidity variable portion (102) is controlled to be higher than the heating temperature of the rigidity maintaining portion (203).

[0173] Thus, as the rigidity maintaining portion (203) and the rigidity variable portion (102) are heated unevenly to different temperatures as described above, the rigidity maintaining portion (203) maintains relatively high rigidity, but the rigidity variable portion (102) has relatively low rigidity, as shown in FIG. 9b, so that the rigidity variable portion (102) can be deformed while having elasticity.

[0174] That is, even if the above-mentioned flexible substrate (40) has the same glass transition temperature (Tg) as a whole, if a local area is controlled to have a temperature higher than the glass transition temperature through heating, the rigidity in that area is relatively low and it can be deformed while having elasticity.

[0175] Accordingly, the elastic substrate (40) has a rigidity distribution that is deformed while being elastic only in a specific area.

[0176] Meanwhile, as shown in Fig. 9a, an example of a method of heating the rigidity maintaining portion (203) and the rigidity variable portion (102) in the flexible substrate (40) unevenly at different temperatures is described below.

[0177] First, for the above-mentioned flexible substrate (40), the rigidity maintaining portion (203) is not heated separately, and only the rigidity variable portion (102) can be selectively heated to increase the temperature.

[0178] To this end, a thin film heater is attached only to the lower portion of the rigid variable portion (102), so that the temperature can be increased through heating only for the rigid variable portion (102). In particular, the elastic substrate (40) in the present embodiment includes PDMS (polydimethylsiloxane) or polyimide, and since the thermal conductivity of the substrate as a whole is not high, even if local heating is performed for the rigid variable portion (102) through the thin film heater, heating due to heat conduction to the rigidity maintaining portion (200) is limited.

[0179] At this time, since the thermal conductivity of the elastic substrate (40) is not high, in order to vary the stiffness so that the elastic substrate (40) has the same stiffness in the thickness direction, heating can be performed while the thin film heater is attached to both the lower part and the upper part of the stiffness variable part (102).

[0180] In contrast, the flexible substrate (40) can be heated so that the temperature of the rigid variable portion (102) is relatively higher than that of the rigid maintenance portion (203).

[0181] For example, if the rigid variable portion (102) is formed to have a higher thermal diffusivity than the rigid maintenance portion (203), even if the entire flexible substrate (40) is heated, the rigid variable portion (102) can be heated to a higher temperature. Thus, by controlling the temperature in the rigid variable portion (102) to be higher than the glass transition temperature, the rigidity of the rigid variable portion (102) can be controlled to be relatively low, thereby providing elasticity.

[0182] At this time, as a method for heating the entire elastic substrate (40), a method of heating by positioning a light source around the elastic substrate (40) is possible, but is not limited to this method.

[0183] Furthermore, there is a method of forming the rigid variable portion (102) to include more photothermal particles than the rigid maintenance portion (203) by heating the flexible substrate (40) so that the temperature of the rigid variable portion (102) is relatively higher than that of the rigid maintenance portion (203).

[0184] That is, when manufacturing the above-mentioned flexible substrate (40), it can be manufactured by mixing particles that induce a photothermal reaction, and at this time, the distribution or density of the photothermal particles can be made different in the rigidity maintaining portion (203) and the rigidity variable portion (102).

[0185] Accordingly, if the photothermal particles are included in the rigid variable portion (102) to have a higher distribution or density than the rigid maintenance portion (203), even if the elastic substrate (40) is heated in the same manner, the rigid variable portion (102) can be heated to a higher temperature. Thus, by controlling the temperature in the rigid variable portion (102) to be higher than the glass transition temperature, the rigidity of the rigid variable portion (102) can be controlled to be relatively low, thereby providing elasticity.

[0186] At this time, as a method for heating the entire flexible substrate (40), a method of heating by positioning a hot plate on the lower surface of the flexible substrate (40) is possible, but is not limited thereto, as described above.

[0187] Figures 10a and 10b are graphs for explaining the stress concentration phenomenon according to temperature variation in the flexible substrate of Figure 1.

[0188] Referring to Fig. 10a, in the elastic substrate (10) described in Fig. 1, the temperature (T) of the elastic substrate (10) is the elastic temperature (T) exemplified in Fig. 3a. stretch ) is kept smaller than (T <T stretch ), the elastic substrate (10) maintains the same rigidity as a whole. That is, the rigidity maintaining portion (200) and the rigidity variable portion (100) both have the same rigidity.

[0189] Accordingly, when an external force is applied to the flexible substrate (10) in the above environment, as the flexible substrate (10) is stretched, stress is concentrated at the portion where the electronic component (400) is mounted, and thus a defect may be caused in the mounted state of the electronic component (400).

[0190] In contrast, referring to FIG. 10b, the temperature (T) of the elastic substrate (10) is the elastic temperature (T) exemplified in FIG. 3a. stretch ) remains the same as (T=T stretch ), the elastic substrate (10) has locally different stiffness. That is, since the temperature (T) is lower than the glass transition temperature (Tg2) of the stiffness maintaining portion (200) and higher than the glass transition temperature (Tg1) of the stiffness variable portion (100), the stiffness maintaining portion (200) maintains relatively high stiffness, but the stiffness variable portion (100) becomes relatively low in stiffness.

[0191] Thus, when an external force is applied to the flexible substrate (10) in the above environment, as the flexible substrate (10) is stretched, the rigidity maintaining portion (200), which is the portion where the electronic component (400) is mounted, maintains high rigidity and minimizes deformation, but the rigidity variable portion (100) is stretched by the tensile force.

[0192] Furthermore, when the above rigid variable portion (100) is extended, stress concentration does not occur in the rigid maintenance portion (200), which is the portion where the electronic component (400) is mounted, and thus the mounting state of the electronic component (400) can be stably maintained.

[0193] Thus, even in a state of repeated stretching due to repeated application of external force, the electronic component (400) maintains a stable mounting state, and the electrical or mechanical stability of the stretchable substrate (10) can be maintained.

[0194] According to the embodiments of the present invention as described above, in the flexible substrate, only the rigidity variable portion is deformed to be elastic by lowering the rigidity when the temperature is higher than a preset temperature, so that the rigidity of a specific region is maintained as is while the rigidity of another region is controlled to be variable, thereby forming a flexible substrate having a different rigidity distribution.

[0195] In particular, if the above rigid maintenance part is formed in a specific arrangement and the element is mounted on the above rigid maintenance part, the flexible substrate has elasticity through temperature control, but the elasticity is minimized in the area where the element is mounted, so that a stable element connection state can be maintained.

[0196] Moreover, by solving the contact problem or structural instability problem at the interface between the conventional elastic and non-elastic portions, it is possible to construct an elastic substrate that can have elasticity while maintaining a stable structure at the interface with the continuous structural characteristics of the same material.

[0197] Furthermore, the temperature control can control the elasticity of the flexible substrate having a variable stiffness structure through control within the glass transition temperature range based on information about the glass transition temperatures of the stiffness variable portion and the stiffness maintaining portion. At this time, since the glass transition temperatures of the stiffness variable portion and the stiffness maintaining portion can be formed differently based on information about the temperature range in the manufacturing process or use state of the flexible substrate, the stability of the manufacturing process can be maintained by maintaining a high stiffness state during the manufacturing process, while the stiffness can be varied during actual use to improve the various usability of the flexible substrate.

[0198] By forming the glass transition temperatures of the rigid variable portion and the rigid maintenance portion differently, the glass transition temperature can be formed relatively high by providing ultraviolet rays only to the rigid maintenance portion on the flexible substrate, so that the flexible substrate can be manufactured through selection of the material for the flexible substrate and a relatively simple process.

[0199] In particular, by providing ultraviolet rays so that the light intensity of the ultraviolet rays is gradually changed to the rigid holding portion to which the ultraviolet rays are provided, or by manufacturing the opening degree of the opening of the mask portion to be gradually changed, the structural stability of the stretchable substrate in repeated stretching can be further improved through gradual stiffness variation at the interface between the rigid variable portion and the rigid holding portion. In this case, by forming the rigid holding portion to be variable in various patterns or shapes, it is possible to configure a stretchable substrate having various stiffness distributions by mounting elements on rigid holding portions of more diverse shapes.

[0200] In addition, by forming the thickness of the rigid maintenance portion relatively thick, the strain or elasticity of the rigid maintenance portion is kept lower, thereby minimizing the strain of the element mounted on the rigid maintenance portion, thereby maintaining a more stable element connection state, and thus manufacturing a flexible substrate with high electrical stability and reliability is possible.

[0201] Furthermore, the stiffness distribution in the flexible substrate can be varied through a process of heating the stiffness maintaining portion and the stiffness variable portion at different temperatures or heating only the stiffness variable portion. Through this, the areas of the stiffness maintaining portion and the stiffness variable portion can be set to have various patterns or arrangements, and by varying the stiffness distribution in various ways through a relatively simple heating method, it is possible to manufacture a flexible substrate having a more diverse self-stiffness distribution characteristic.

[0202] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. In a flexible substrate including a rigid maintenance portion and a rigid variable portion divided into different regions, The rigidity maintaining unit and the rigidity variable unit maintain the preset rigidity only below the preset temperature, A flexible substrate characterized in that only the above-mentioned rigid variable portion is deformed to be elastic by lowering the rigidity below the preset rigidity at a preset temperature or higher.

2. In paragraph 1, The above rigid maintenance part is formed with a plurality of regions having a predetermined pattern, A flexible substrate characterized in that the above rigid variable portion is formed in a region other than the above rigid maintenance portion.

3. In paragraph 2, A flexible substrate, characterized in that the length of the rigid maintenance portion along the first direction and the length of the rigid maintenance portion along the second direction perpendicular to the first direction are different from each other.

4. In paragraph 2, A flexible substrate characterized in that a component is mounted on the above rigid maintenance portion.

5. In paragraph 1, The above rigid variable portion is formed with a predetermined pattern, A flexible substrate characterized in that the rigidity maintaining portion is formed in a region other than the rigidity variable portion.

6. In the fifth paragraph, the rigid variable part is, A flexible substrate characterized by being formed along a kirigami pattern.

7. In paragraph 6, Poisson's ratio is negative, A stretchable substrate characterized in that when stretching occurs in a first direction, stretching also occurs in a second direction perpendicular to the first direction at the same rate.

8. In the first paragraph, the preset temperature is A flexible substrate characterized by the glass transition temperature of the above rigid variable portion.

9. In paragraph 1, A flexible substrate, characterized in that the glass transition temperature of the rigid variable portion is lower than the glass transition temperature of the rigid maintenance portion.

10. In the first paragraph, the rigidity maintaining portion and the rigidity variable portion, A flexible substrate characterized by containing PDMS (polydimethylsiloxane) or polyimide.

11. For a flexible substrate including a rigid maintenance portion and a rigid variable portion divided into different areas, a step of positioning the mask portion so that the opening is aligned with the rigid retaining portion; and A method for manufacturing a flexible substrate, comprising a step of providing ultraviolet rays from the upper portion of the mask portion to only the rigid maintenance portion.

12. In the 11th paragraph, since only the rigid maintenance part is provided with ultraviolet rays, A method for manufacturing a flexible substrate, characterized in that the glass transition temperature of the rigidity maintaining portion is formed higher than the glass transition temperature of the rigidity variable portion.

13. In the 11th paragraph, the elastic substrate, A method for manufacturing a flexible substrate, characterized in that it includes a glycol gel.

14. In the 13th paragraph, since only the rigid maintenance part is provided with ultraviolet rays, A method for manufacturing a flexible substrate, characterized in that the above 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 increases.

15. In the 11th paragraph, the opening of the mask portion is A method for manufacturing a flexible substrate, characterized in that the degree of ultraviolet ray penetration gradually decreases from the center to the periphery of the opening.

16. In paragraph 11, the ultraviolet rays are A method for manufacturing a flexible substrate, characterized in that the light is modulated light whose intensity gradually decreases from the center to the periphery of the opening.

17. In the 15th or 16th paragraph, the glass transition temperature of the rigid maintenance part is A method for manufacturing a flexible substrate characterized in that the thickness thereof gradually decreases from the central portion to the peripheral portion, which is the boundary with the rigid variable portion.

18. In paragraph 11, A method for manufacturing a flexible substrate, characterized in that the above rigidity maintaining portion is formed to have a greater thickness than the above rigidity variable portion.

19. In the 18th paragraph, the thickness of the rigid maintenance part is A method for manufacturing a flexible substrate, characterized in that the thickness gradually decreases from the central portion to the peripheral portion, which is the boundary with the rigid variable portion.

20. For a flexible substrate including a rigid maintenance portion and a rigid variable portion divided into different areas, The above rigid maintenance part maintains the temperature, and only the rigid variable part is heated to increase the temperature, or A method for varying the stiffness distribution of a flexible substrate, characterized in that the flexible substrate is heated so that the stiffness variable portion has a higher temperature than the stiffness maintaining portion.

21. In the 20th paragraph, when only the rigid variable part is heated to increase the temperature, A method for varying the rigidity distribution of a flexible substrate, characterized in that a heater is attached to the lower surface of the above-mentioned rigid variable portion.

22. In the 20th paragraph, when the temperature of the rigid variable portion is maintained relatively higher than that of the rigid maintenance portion and the elastic substrate is heated, A method for varying the stiffness distribution of a flexible substrate, characterized in that the stiffness variable portion is formed to have a higher thermal diffusivity than the stiffness maintaining portion.

23. In the 20th paragraph, when the temperature of the rigid variable portion is maintained relatively higher than that of the rigid maintenance portion and the elastic substrate is heated, A method for varying the rigidity distribution of a flexible substrate, characterized in that the rigidity variable portion is formed to include more photothermal particles than the rigidity maintaining portion.

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