Flexible graphite structure

Abstract

Disclosed is a flexible graphite structure that can be used as a heat dissipation sheet for flexible electronic devices using a graphite sheet unit that includes stretchable regions formed as cut regions or overlap regions. The disclosed flexible graphite structure includes a graphite sheet unit that includes a single graphite sheet layer or multiple graphite sheet layers having at least one stretchable region, and a stretchable sheet layer attached to at least one of both outermost surfaces of the graphite sheet unit and configured to cover the at least one stretchable region, where the at least one stretchable region is formed by providing at least a pair of cutout regions in the single graphite sheet layer or by providing overlap regions where the single graphite sheet layer or multiple graphite sheet layers overlap.

Description

Technical Field

[0001] The present disclosure is a flexible graphite structure formed by using a graphite sheet unit including a stretchable region by a notch region or an overlapping region as a heat dissipation layer, and adhering a stretchable sheet layer to at least one outermost surface of the graphite sheet unit to protect the graphite sheet unit.

Background Art

[0002] As portable devices / mobile devices such as cameras, mobile phones, mobile computers, and tablets have evolved over the decades, the needs and capabilities of these devices have also evolved. In each generation of devices, the devices enable users to create, modify, and distribute content from their devices, and to provide more content to the users of the devices in a more user-friendly format with higher bandwidth than ever before. As the convenience of these devices has improved, the power required by the devices has increased, and the technologies associated with the batteries of these devices have improved. Today's generation of devices contains more energy, generates more power, and as a result generates more heat. In addition to the battery, the hardware products of the devices (e.g., wireless units, displays, and processing units) have also become more robust, similarly bringing additional heat problems to these devices.

[0003] In order to solve such heat problems, technologies for attaching a graphite sheet layer having a high thermal conductivity to the heat-generating portion of an electronic device have been devised. When a graphite sheet layer is attached to the back surface of a portion where a lot of heat is generated in an electronic device, the in-plane thermal conductivity of the graphite sheet layer is relatively large compared to the thermal conductivity in the thickness direction of the graphite sheet layer. Therefore, heat efficiently diffuses and moves, and thus the heat generated in the electronic device is radiated to the outside through the graphite sheet layer.

[0004] In recent years, as portable / mobile device technology has advanced further, devices equipped with various displays, such as bendable flexible displays and foldable displays that can be folded and unfolded, have been developed. To dissipate heat from such devices, the thermal pad itself needs to be flexible. However, the use of graphite sheets, which have excellent horizontal heat transfer properties, in flexible electronic devices has been limited due to their low flexibility. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] This disclosure solves the problem that graphite sheets are difficult to use as heat dissipation sheets in flexible electronic devices due to their low flexibility, and provides a flexible graphite structure that can be used as a heat dissipation sheet in flexible electronic devices using a graphite sheet unit that includes a stretchable region including a notched region or an overlapping region. [Means for solving the problem]

[0006] A flexible graphite structure according to one embodiment of the present disclosure includes a graphite sheet unit comprising a single graphite sheet layer or a plurality of graphite sheet layers having at least one stretchable region, and a stretchable sheet layer attached to at least one of the outermost surfaces of the graphite sheet unit and configured to cover at least one stretchable region, wherein the at least one stretchable region is formed by providing at least a pair of notched regions in a single graphite sheet layer, or by providing overlapping regions where a single graphite sheet layer or a plurality of graphite sheet layers overlap.

[0007] The overlapping region may be formed by providing at least two foldable portions in a single graphite sheet layer so that an overlapping region is provided between the foldable portions, or by overlapping portions of multiple graphite sheet layers.

[0008] At least one pair of notched regions may be provided point-symmetrically on a single graphite sheet layer, and the single graphite sheet layer may be connected as a single sheet in the regions other than the notched regions.

[0009] At least one pair of notched regions may have a length shorter than the graphite sheet layer in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure.

[0010] The length of at least one pair of notched regions may be 90% or less, or 75% or less, of the length of the graphite sheet layer in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure.

[0011] At least one stretchable region may include a void extending in a direction perpendicular to the stretching direction of the flexible graphite structure.

[0012] The void can be defined between a graphite sheet layer located in a region other than the overlapping region and a graphite sheet layer located in the overlapping region, or it can be defined by at least one pair of notched regions.

[0013] When force is applied to a flexible graphite structure, the graphite sheet units are stretched, and the stretchable sheet layers are stretched in the direction in which the graphite sheet units are stretched, potentially narrowing the width of the overlapping region.

[0014] When the force is released, the stretchable sheet layer contracts, and the width of the overlapping area may widen.

[0015] When force is applied to a flexible graphite structure, the graphite sheet unit is stretched, and the stretchable sheet layer is stretched in the direction in which the graphite sheet unit is stretched, which can increase the size of the void in at least one pair of notched regions.

[0016] When the force is released, the stretchable sheet layer contracts, and the size of the gaps in at least one pair of notched regions may decrease.

[0017] The graphite sheet layer may contain compressed particles of graphitized polymer or expanded graphite, or a combination thereof.

[0018] The stretchable sheet layer may contain at least one selected from the group consisting of polydimethylsiloxane (PDMS), epoxy resin, styrene-based material, olefin-based material, polyolefin, polyurethane, thermoplastic polyurethane, thermoplastic elastomer, polyamide, synthetic rubber, polybutadiene, polyisobutylene, polychloroprene, and silicone.

[0019] The stretchable sheet layer may have an elongation rate of 175% or more, 200% or more, or 250% or more.

[0020] The stretchable sheet layer may contain a thermally conductive material.

[0021] The graphite sheet layer may have a thickness of 15 μm to 19 μm, or 16 μm to 18 μm.

[0022] The graphite sheet unit may include an adhesive layer provided on the graphite sheet layer, and the graphite sheet unit may have a uniform thickness.

[0023] The adhesive layer may contain at least one selected from the group consisting of pressure-sensitive adhesives (PSA), thermosetting adhesives, photocuring adhesives, optically transparent adhesives (OCA), optically transparent resins (OCR), double-sided adhesive films, and single-sided adhesive films.

[0024] When an adhesive layer is formed between a plurality of mutually separated graphite sheet layers, the adhesive layer may be a double-sided adhesive film.

[0025] When an adhesive layer is formed between the graphite sheet layer and the stretchable sheet layer, the adhesive layer may be a single-sided adhesive film.

[0026] The single-sided adhesive film may be adhered to the surface facing the graphite sheet layer.

[0027] The adhesive layer formed between the graphite sheet layer and the stretchable sheet layer may be divided along the foldable portion of the graphite sheet layer.

[0028] The graphite sheet layer may have an in-plane thermal conductivity of 150 W / mK to 1700 W / mK.

[0029] When the stretchable sheet layer is stretched, the length of the stretchable sheet layer corresponding to the divided portion of the adhesive layer may be extended from more than 0 to 50% or less, or from more than 0 to 30% or less.

Advantages of the Invention

[0030] According to the disclosed flexible graphite structure, by including at least one stretchable region formed by providing a notch region or an overlapping region in the graphite sheet unit, the graphite structure can be used as a heat dissipation sheet in a flexible electronic device to ensure excellent heat dissipation performance.

[0031] The accompanying drawings incorporated herein and constituting a part of this specification illustrate embodiments of the present disclosure.

Brief Description of the Drawings

[0032] [Figure 1A] It is a cross-sectional view of a flexible graphite structure according to an embodiment in which an overlapping region is formed as a stretchable region. [Figure 1B] Figure 1A is a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the direction of expansion and contraction. [Figure 2A] This is a cross-sectional view of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 2B] Figure 2A is a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the stretching direction. [Figure 3A] This is a cross-sectional view of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 3B] Figure 3A is a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the expansion and contraction direction. [Figure 4A] This is a cross-sectional view of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 4B] Figure 4A is a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the direction of expansion and contraction. [Figure 5A] This is a cross-sectional view of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 5B] Figure 5A is a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the stretching direction. [Figure 6A] This is a cross-sectional view of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 6B] Figure 6A is a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the stretching direction. [Figure 7A] This is a cross-sectional view of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 7B] Figure 7A is a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the expansion and contraction direction. [Figure 8A]This is a cross-sectional view of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 8B] Figure 8A shows a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the stretching direction. [Figure 9A] This is a cross-sectional view of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 9B] Figure 9A shows a cross-sectional view of the flexible graphite structure when the flexible graphite structure is stretched in the stretching direction. [Figure 10A] This is a plan view of a graphite sheet layer according to one embodiment in which the notched region is formed as an expandable region. [Figure 10B] Figure 10A shows a cross-sectional view of the graphite sheet layer when the graphite sheet layer is stretched in the expansion and contraction direction. [Figure 11A] This is a plan view of a graphite sheet layer according to one embodiment in which the notched region is formed as an expandable region. [Figure 11B] Figure 11A shows a cross-sectional view of the graphite sheet layer when the graphite sheet layer is stretched in the expansion and contraction direction. [Figure 12A] This is an actual photograph of a flexible graphite structure according to one embodiment in which the overlapping region is formed as an expandable region. [Figure 12B] Figure 12A is an actual photograph of a flexible graphite structure when flexible graphite is stretched in the direction of expansion and contraction. [Figure 13A] This is an actual photograph of a flexible graphite structure according to one embodiment in which the notched region is formed as an expandable region. [Figure 13B] Figure 13A is an actual photograph of a flexible graphite structure when flexible graphite is stretched in the direction of expansion and contraction. [Modes for carrying out the invention]

[0033] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings, so that those skilled in the art in which the present disclosure pertains can readily implement the present disclosure. However, the present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. For the purpose of clearly illustrating the present disclosure with reference to the drawings, parts irrelevant to the description have been omitted, and similar parts throughout this specification are denoted by the same reference numerals.

[0034] Throughout this specification, where one part is “connected” to another part, this includes not only “direct connection” but also “electrical connection” with another element in between. Where a particular part contains a particular component, it means that, unless otherwise specified, that particular part may contain other elements rather than excluding them.

[0035] Figure 1A is a cross-sectional view of a flexible graphite structure 100 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0036] Referring to Figure 1A, the flexible graphite structure 100 includes a graphite sheet layer 110 and stretchable sheet layers 120a and 120b attached to both sides of the graphite sheet layer 110.

[0037] The graphite sheet layer 110 contains compressed particles of graphitized polymer or exfoliated graphite and has excellent thermal conductivity in both the longitudinal and transverse directions on a two-dimensional plane, so that it can be used as a heat dissipation sheet to dissipate heat from a heating element to the outside.

[0038] The graphite sheet layer 110 has a thickness of approximately 14 μm to 940 μm. The graphite sheet layer 110 may have a thickness of approximately 14 μm to 20 μm, including approximately 15 μm to 19 μm and approximately 16 μm to 18 μm. When the graphite sheet layer 110 is used in a flexible electronic device with a large internal allowable thickness, the graphite sheet layer 110 may have a thickness of approximately 20 μm to 30 μm, including approximately 27 μm to 37 μm, approximately 35 μm to 45 μm, and approximately 40 μm to 50 μm. Alternatively, the graphite sheet layer 110 may have a thickness of 40 μm to 940 μm. As the thickness of the graphite sheet layer 110 increases, the heat dissipation performance of the graphite sheet layer may improve. However, the thickness of the graphite sheet layer 110 can be determined according to the size of the allowable space in the flexible electronic device to which the graphite sheet layer 110 is attached.

[0039] The in-plane thermal conductivity of the graphite sheet layer 110 can be approximately 150 W / mK to 1700 W / mK.

[0040] The graphite sheet layer 110 includes at least two foldable portions 130 formed by folding the graphite sheet layer 110, and an overlapping region OL is formed between the two foldable portions 130. The overlapping region OL refers to the region where the portions of the graphite sheet layer 110 overlap each other when viewed in the vertical direction of Figure 1A, i.e., in the depth direction of the flexible graphite structure 100.

[0041] The stretchable sheet layers 120a and 120b are attached to both sides of the graphite sheet layer 110, with an overlapping region OL formed by two foldable portions 130 on the graphite sheet layer 110. The stretchable sheet layer contains any material having an elongation ratio as described later, and may, but is not limited to, at least one selected from the group consisting of polydimethylsiloxane (PDMS), epoxy resin, styrene-based material, olefin-based material, polyolefin, polyurethane, thermoplastic polyurethane, thermoplastic elastomer, polyamide, synthetic rubber, polybutadiene, polyisobutylene, polychloroprene, and silicone.

[0042] When a force is applied in the longitudinal or lateral direction, the stretchable sheet layers 120a and 120b are stretched along the direction of the applied force, and when the force is released, the stretchable sheet layers 120a and 120b return to their original lengths. The stretchable sheet layers 120a and 120b may have an elongation ratio of 175% or more, 200% or more, or 250% or more, where the elongation ratio is the ratio of the length of the stretchable sheet layer when a force is applied to the original length of the stretchable sheet when no force is applied. For example, if the original length is 100%, then an elongation ratio of 175% is 75% greater than the original length (100%). In another example, an elongation ratio of 200% is twice the original length (100%).

[0043] The stretchable sheet layers 120a and 120b may contain a thermally conductive material. The thermally conductive material may be, but is not limited to, metal beads or polymer beads having high thermal conductivity. Because the stretchable sheet layers 120a and 120b contain a thermally conductive material, when the flexible graphite structure 100 is used as a heat dissipation sheet for an electronic device, the heat generated by the electronic device can be radiated to the outside more efficiently.

[0044] The foldable portion 130 of the graphite sheet layer 110 and the stretchable sheet layers 120a and 120b are not bonded to each other, and voids may be defined. That is, the overlapping region OL may contain voids, and these voids may extend in a direction perpendicular to the stretchability of the flexible graphite structure 100. Due to the presence of voids, when a force is applied to the flexible graphite structure 100, the flexible graphite structure 100 may be stretched in the direction of the force.

[0045] Figure 1B is a cross-sectional view of the flexible graphite structure 100 when it is extended in the stretching direction.

[0046] Referring to Figure 1B, the flexible graphite structure 100 may be used as a heat dissipation sheet in electronic devices equipped with a bendable flexible display or a foldable display that can be folded and unfolded, and when a user operates the electronic device to bend or fold the display of the electronic device, a force pulling the flexible graphite structure 100 on both sides may be applied to the flexible graphite structure 100.

[0047] When a tensile force is applied to the flexible graphite structure 100, the stretchable sheet layers 120a and 120b are stretched along the direction of the force, and since the graphite sheet layer 110 is integrally bonded to the stretchable sheet layers 120a and 120b, the graphite sheet layer 110 is also extended on both sides along the direction of the force. Since the graphite sheet layer 110 is not stretchable, if the graphite sheet layer is a flat graphite sheet, it will not be extended even when a force is applied. However, the graphite sheet layer 110 of the flexible graphite structure 100 according to this embodiment has an overlapping region OL formed by two foldable portions 130, so as the foldable portions 130 of the graphite sheet layer 110 are unfolded in response to the application of force, the graphite sheet layer 110 can also be extended on both sides along the direction of the force.

[0048] As the graphite sheet layer 110 is extended on both sides, the width of the overlapping region OL gradually narrows, and when the graphite sheet layer 110 is extended to its maximum extent, the overlapping region OL may disappear.

[0049] Because the graphite sheet layer 110 according to this embodiment has a bifold shape including two foldable portions 130, the length of the maximally extended flexible graphite structure 100 shown in Figure 1B can be twice the length of the overlapping region OL compared to the length of the flexible graphite structure 100 before extension as shown in Figure 1A.

[0050] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the pulling force on the flexible graphite structure 100 is released. When the pulling force on both sides of the flexible graphite structure 100 is released, the stretchable sheet layers 120a and 120b contract back to their original lengths, and thus the width of the overlapping region OL widens, while two foldable portions 130 are also formed in the graphite sheet layer 110. Once the contraction of the stretchable sheet layers 120a and 120b is complete, the flexible graphite structure 100 returns to its original shape, i.e., the shape shown in Figure 1A.

[0051] When force is applied to and released from the flexible graphite structure 100, the above-described operation is repeated. This operation allows for smooth heat dissipation from flexible electronic devices, even when the graphite structure, which has high thermal conductivity but low flexibility, is used as a heat dissipation sheet.

[0052] Figure 2A is a cross-sectional view of a flexible graphite structure 200 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0053] Referring to Figure 2A, the flexible graphite structure 200 includes a graphite sheet unit 215 containing two graphite sheet layers 210a and 210b, and stretchable sheet layers 220a and 220b attached to both sides of the graphite sheet unit 215.

[0054] The graphite sheet layers 210a, 210b and the stretchable sheet layers 220a, 220b may each be formed from the same material as the graphite sheet layer 110 and the stretchable sheet layers 120a, 120b described above, and redundant explanations will be omitted.

[0055] The graphite sheet unit 215 includes an overlapping region OL formed by stacking two graphite sheet layers 210a and 210b. The overlapping region OL refers to the area where the two graphite sheet layers 210a and 210b overlap each other when viewed in the vertical direction of Figure 2A, i.e., in the depth direction of the flexible graphite structure 200.

[0056] The stretchable sheet layers 220a and 220b are attached to both sides of the graphite sheet unit 215 in a state where an overlapping region OL is formed by stacking the two graphite sheet layers 210a and 210b on top of the graphite sheet unit 215.

[0057] In the region where a step is formed in the graphite sheet unit 215, i.e., the overlapping region OL, the edges of the graphite sheet layers 210a and 210b and the stretchable sheet layers 220a and 220b are not bonded to each other, and a gap is defined. That is, the overlapping region OL may contain gaps on both sides, and these gaps may extend in a direction perpendicular to the stretching direction of the flexible graphite structure 200. Due to the presence of these gaps, when a force is applied to the flexible graphite structure 200, the flexible graphite structure 200 can be stretched in the direction of the force.

[0058] Figure 2B is a cross-sectional view of the flexible graphite structure 200 when it is stretched in the expansion and contraction direction.

[0059] Referring to Figure 2B, when a user manipulates an electronic device so that the display of the electronic device is bent or folded, a force may be applied to the flexible graphite structure 200 that causes it to bulge on both sides.

[0060] When a force is applied to the flexible graphite structure 200 that causes it to expand on both sides, the stretchable sheet layers 220a and 220b are extended along the direction of the force. Since the graphite sheet unit 215 is integrally bonded to the stretchable sheet layers 220a and 220b, the graphite sheet layer 210a of the graphite sheet unit 215 moves in one direction, while the graphite sheet layer 210b moves in the opposite direction. In particular, although the two graphite sheet layers 210a and 210b are not bonded to each other, they are stacked on top of each other, so the graphite sheet layers can slide in opposite directions when a force is applied. As the two graphite sheet layers 210a and 210b move in opposite directions, the graphite sheet unit 215 is also extended on both sides.

[0061] As the graphite sheet unit 215 is extended on both sides, the width of the overlapping region OL gradually narrows, allowing the flexible graphite structure 200 to be extended until the overlapping region OL formed by the two graphite sheet layers 210a and 210b completely disappears.

[0062] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the force pulling the flexible graphite structure 200 on both sides is released. Once the force pulling the flexible graphite structure 200 on both sides is released, the stretchable sheet layers 220a and 220b contract back to their original lengths, and therefore the width of the overlapping region OL of the graphite sheet unit 215 widens. Once the contraction of the stretchable sheet layers 220a and 220b is complete, the flexible graphite structure 200 returns to its original shape, i.e., the shape shown in Figure 2A.

[0063] The above-described operation is repeated in response to the force applied to and released from the flexible graphite structure 200. This operation allows for smooth heat dissipation from flexible electronic devices, even when the graphite structure, which has high thermal conductivity but low flexibility, is used as a heat dissipation sheet.

[0064] Figure 3A is a cross-sectional view of a flexible graphite structure 300 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0065] Referring to Figure 3A, the flexible graphite structure 300 includes a graphite sheet unit 350 comprising a graphite sheet layer 310 and adhesive layers 320a and 320b formed on the graphite sheet layer 310, and stretchable sheet layers 330a and 330b attached to the outermost surfaces of the graphite sheet unit 350.

[0066] The graphite sheet layer 310 and the stretchable sheet layers 330a and 330b may be formed from the same materials as the graphite sheet layer and stretchable sheet layer described above, and redundant explanations will be omitted.

[0067] The graphite sheet layer 310 includes at least two foldable portions 340 formed by folding the graphite sheet layer 310, and an overlapping region OL is formed between the two foldable portions 340. The overlapping region OL refers to the region where the portions of the graphite sheet layer 310 overlap each other when viewed in the vertical direction of Figure 3A, i.e., in the depth direction of the flexible graphite structure 300.

[0068] The adhesive layers 320a and 320b may be formed in areas where the overlapping region OL of the graphite sheet layer 310 is not formed, and by using the adhesive layers 320a and 320b, it is possible to make the thickness of the graphite sheet unit 350 substantially uniform.

[0069] The adhesive layers 320a and 320b may, but are not limited to, include at least one of the following: pressure-sensitive adhesive (PSA), thermosetting adhesive, photocurable adhesive, optical clear adhesive (OCA), optical clear resin (OCR), double-sided adhesive film, and single-sided adhesive film. The single-sided or double-sided adhesive film may include, for example, a base layer (not shown) formed from at least one of polyethylene terephthalate (PET), polycarbonate (PC), aluminum foil, copper foil, and polyimide (PI), and an adhesive layer (not shown) in which an adhesive is applied to one or both sides of the base layer.

[0070] The type and shape of the adhesive layers 320a and 320b are not particularly limited, but if the adhesive layers 320a and 320b are, for example, in the form of a single-sided adhesive film, the adhesive layers 320a and 320b may be positioned on the surface where the adhesive layer of the single-sided adhesive film faces the graphite sheet layer 310, and bonded together to form between the graphite sheet layer 310 and the stretchable sheet layers 330a and 330b.

[0071] The foldable portion 340 of the graphite sheet layer 310 and the adhesive layers 320a and 320b are not bonded to each other, and voids may be defined. That is, the overlapping region OL may contain voids on both sides, and these voids may extend in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure 300. Due to the presence of voids, when a force is applied to the flexible graphite structure 300, the flexible graphite structure 100 may be stretched along the direction of the force.

[0072] Figure 3B is a cross-sectional view of the flexible graphite structure 300 when it is extended in the expansion and contraction direction.

[0073] Referring to Figure 3B, when a user manipulates an electronic device so that the display of the electronic device is bent or folded, a force may be applied to the flexible graphite structure 300 that pulls it to both sides.

[0074] When a force is applied to the flexible graphite structure 300 that pulls it to both sides, the stretchable sheet layers 330a and 330b are stretched along the direction of the force, and the graphite sheet unit 350 is integrally bonded to the stretchable sheet layers 330a and 330b. Since the graphite sheet layer 310 of the flexible graphite structure 300 includes an overlapping region OL formed by two foldable portions 340, the foldable portions 340 of the graphite sheet layer 310 are unfolded in response to the application of force, and the graphite sheet layer 310 can also be extended to both sides along the direction of the force. Furthermore, since both sides of the adhesive layer 320a are fixedly bonded to the graphite sheet layer 310 and the stretchable sheet layer 330a, and both sides of the adhesive layer 320b are fixedly bonded to the graphite sheet layer 310 and the stretchable sheet layer 330b, the adhesive layers 320a and 320b separate from each other in proportion to the extension of the stretchable sheet layers 330a and 330b and the graphite sheet layer 310.

[0075] As the graphite sheet unit 350 is extended on both sides, the width of the overlapping region OL gradually narrows, and when the graphite sheet portion 350 is extended to its maximum extent, the overlapping region OL may disappear.

[0076] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the force pulling the flexible graphite structure 300 on both sides is released. Once the force pulling the flexible graphite structure 300 on both sides is released, the stretchable sheet layers 330a and 330b contract back to their original lengths, and therefore the width of the overlapping region OL of the graphite sheet portion 350 widens. Once the contraction of the stretchable sheet layers 330a and 330b is complete, the flexible graphite structure 300 returns to its original shape, i.e., the shape shown in Figure 3A.

[0077] The above-described operation is repeated in response to the force applied to and released from the flexible graphite structure 300. This operation allows for smooth heat dissipation from flexible electronic devices, even when a graphite structure with high thermal conductivity but low flexibility is used as a heat dissipation sheet. In the flexible graphite structure 300 according to this embodiment, the thickness of the graphite sheet unit 350 can be made substantially uniform in its pre-extension state by using adhesive layers 320a and 320b, making it possible to easily attach the graphite structure to flexible electronic devices.

[0078] Figure 4A is a cross-sectional view of a flexible graphite structure 400 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0079] Referring to Figure 4A, the flexible graphite structure 400 includes a graphite sheet unit 450 comprising three graphite sheet layers 410a, 410b, 410c and adhesive layers 420a, 420b, 420c formed on the graphite sheet layers 410a, 410b, 410c, and stretchable sheet layers 430a, 430b attached to the outermost surfaces of the graphite sheet unit 450.

[0080] The three graphite sheet layers 410a, 410b, and 410c, the adhesive layers 420a, 420b, and 420c, and the stretchable sheet layers 430a and 430b may each be formed from the same materials as the graphite sheet layers, adhesive layers, and stretchable sheet layers described above, and redundant explanations will be omitted.

[0081] The graphite sheet unit 450 includes an overlapping region OL formed by stacking three graphite sheet layers 410a, 410b, and 410c. The overlapping region OL is the area where the three graphite sheet layers 410a, 410b, and 410c overlap each other when viewed in the vertical direction of Figure 4A, i.e., in the depth direction of the flexible graphite structure 400.

[0082] The adhesive layers 420a, 420b, and 420c may be formed in areas where the overlapping region OL of the three graphite sheet layers 410a, 410b, and 410c is not formed, the adhesive layer 420a may be formed between two graphite sheet layers 410b and 410c, and the adhesive layers 420b and 420c may be formed between the graphite sheet layer 410a and the stretchable sheet layers 430a and 430b. By using the adhesive layers 420a, 420b, and 420c, it is possible to make the thickness of the graphite sheet unit 450 substantially uniform.

[0083] The type and shape of the adhesive layer 420a formed between two spaced-apart graphite sheet layers 410b and 410c are not particularly limited. However, if the adhesive layer 420a is, for example, in the form of an adhesive film, it is preferable that the adhesive layer be a double-sided adhesive film, since adhesive layers are required on both sides facing the graphite sheet layers 410b and 410c in order to adhere to them.

[0084] If the adhesive layers 420b and 420c formed between the graphite sheet layer 410a and the stretchable sheet layers 430a and 430b are, for example, in the form of adhesive films, then it is sufficient for each adhesive layer to have an adhesive layer on the surface facing the graphite sheet layer 410a; therefore, it may be a single-sided adhesive film as well as a double-sided adhesive film.

[0085] In the overlapping region OL, the edges of the three graphite sheet layers 410a, 410b, and 410c and the adhesive layers 420a, 420b, and 420c are not bonded to each other, and voids may be defined. That is, the overlapping region OL may contain voids on both sides, and these voids may extend in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure 400. Due to the presence of voids, when a force is applied to the flexible graphite structure 400, the flexible graphite structure 100 may be stretched along the direction of the force.

[0086] Figure 4B is a cross-sectional view of the flexible graphite structure 400 when it is extended in the stretching direction.

[0087] Referring to Figure 4B, when a user manipulates an electronic device so that the display of the electronic device is bent or folded, a force may be applied to the flexible graphite structure 400 that pulls it to both sides.

[0088] When a tensile force is applied to both sides of the flexible graphite structure 400, the stretchable sheet layers 430a and 430b are extended along the direction of the force, and because the graphite sheet unit 450 is integrally bonded to the stretchable sheet layers 430a and 430b, the graphite sheet layer 410a of the graphite sheet unit 450 moves in one direction, while the graphite sheet layers 410b and 410c move in the opposite direction. In particular, although the three graphite sheet layers 410a, 410b, and 410c are not bonded to each other, they are stacked on top of each other, so the graphite sheet layers can slide in opposite directions when a force is applied. Because the graphite sheet layer 410a and the two graphite sheet layers 410b and 410c move in opposite directions, the graphite sheet unit 450 is also extended on both sides.

[0089] As the graphite sheet unit 450 is extended on both sides, the width of the overlapping region OL gradually narrows, allowing the flexible graphite structure 400 to be extended until the overlapping region OL formed by the three graphite sheet layers 410a, 410b, and 410c completely disappears.

[0090] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the force pulling the flexible graphite structure 400 on both sides is released. Once the force pulling the flexible graphite structure 400 on both sides is released, the stretchable sheet layers 430a and 430b contract back to their original lengths, and therefore the width of the overlapping region OL of the graphite sheet portion 450 widens. Once the contraction of the stretchable sheet layers 430a and 430b is complete, the flexible graphite structure 400 returns to its original shape, i.e., the shape shown in Figure 4A.

[0091] The above-described operation is repeated in response to the force applied to and released from the flexible graphite structure 400. This operation allows for smooth heat dissipation from flexible electronic devices, even when a graphite structure with high thermal conductivity but low flexibility is used as a heat dissipation sheet. In the flexible graphite structure 400 according to this embodiment, the thickness of the graphite sheet unit 450 can be made substantially uniform in its pre-extension state by using adhesive layers 420a, 420b, and 420c, making it possible to easily attach the graphite structure to a flexible electronic device.

[0092] Figure 5A is a cross-sectional view of a flexible graphite structure 500 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0093] Referring to Figure 5A, the flexible graphite structure 500 includes a graphite sheet unit 550 comprising two graphite sheet layers 510a, 510b and adhesive layers 520a, 520b formed on the graphite sheet layers 510a, 510b, and stretchable sheet layers 530a, 530b attached to the outermost surfaces of the graphite sheet unit 550.

[0094] The two graphite sheet layers 510a, 510b, the adhesive layers 520a, 520b, and the stretchable sheet layers 530a, 530b may each be formed from the same materials as the graphite sheet layer, adhesive layer, and stretchable sheet layer described above, and redundant explanations will be omitted.

[0095] The graphite sheet unit 550 includes an overlapping region OL formed by stacking two graphite sheet layers 510a and 510b. The overlapping region OL refers to the area where the two graphite sheet layers 510a and 510b overlap each other when viewed in the vertical direction of Figure 5A, i.e., in the depth direction of the flexible graphite structure 500.

[0096] The adhesive layers 520a and 520b may be formed in areas where the overlapping region OL of the graphite sheet layers 510a and 510b is not formed, and by using the adhesive layers 520a and 520b, it is possible to make the thickness of the graphite sheet unit 550 substantially uniform.

[0097] The type and shape of the adhesive layers 520a and 520b are not particularly limited, but if the adhesive layers 520a and 520b are, for example, in the form of a single-sided adhesive film, the adhesive layers 520a and 520b may be formed between the graphite sheet layers 510a and 510b and the stretchable sheet layers 530a and 530b by being positioned such that the adhesive layer of the single-sided adhesive film is positioned on the surface facing the graphite sheet layers 510a and 510b and then bonded together.

[0098] In the overlapping region OL, the edges of the two graphite sheet layers 510a and 510b and the adhesive layers 520a and 520b are not bonded to each other, and voids may be defined. That is, the overlapping region OL may contain voids on both sides, and these voids may extend in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure 500. Due to the presence of voids, when a force is applied to the flexible graphite structure 500, the flexible graphite structure 500 may be stretched along the direction of the force.

[0099] Figure 5B is a cross-sectional view of the flexible graphite structure 500 when it is stretched in the expansion and contraction direction.

[0100] Referring to Figure 5B, when a user manipulates an electronic device so that the display of the electronic device is bent or folded, a force may be applied to the flexible graphite structure 500 that pulls it to both sides.

[0101] When a force is applied to the flexible graphite structure 500 that pulls it to both sides, the stretchable sheet layers 530a and 530b are stretched along the direction of the force, and since the graphite sheet unit 550 is integrally bonded to the stretchable sheet layers 530a and 530b, the graphite sheet layer 510a of the graphite sheet unit 550 moves in one direction, and the graphite sheet layer 510b moves in the opposite direction. Also, since both sides of the adhesive layer 520a are fixedly bonded to the graphite sheet layer 510b and the stretchable sheet layer 530a, and both sides of the adhesive layer 520b are fixedly bonded to the graphite sheet layer 510a and the stretchable sheet layer 530b, the adhesive layers 520a and 520b move away from each other in accordance with the extension of the stretchable sheet layers 530a and 530b and the graphite sheet layers 510a and 510b. In particular, although the two graphite sheet layers 510a and 510b are not bonded to each other, they are stacked on top of each other, so the graphite sheet layers can slide in opposite directions when force is applied. As the two graphite sheet layers 510a and 510b move in opposite directions, the graphite sheet unit 550 is also extended in opposite directions.

[0102] As the graphite sheet unit 550 is extended on both sides, the width of the overlapping region OL gradually narrows, allowing the flexible graphite structure 500 to be extended until the overlapping region OL formed by the two graphite sheet layers 510a and 510b completely disappears.

[0103] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the force pulling the flexible graphite structure 500 on both sides is released. Once the force pulling the flexible graphite structure 500 on both sides is released, the stretchable sheet layers 530a and 530b contract back to their original lengths, and therefore the width of the overlapping region OL of the graphite sheet unit 550 widens. Once the contraction of the stretchable sheet layers 530a and 530b is complete, the flexible graphite structure 500 returns to its original shape, i.e., the shape shown in Figure 5A.

[0104] When force is applied to the flexible graphite structure 500 and then released, the above-described operation is repeated. This operation allows for smooth heat dissipation from flexible electronic devices, even when a graphite structure with high thermal conductivity but low flexibility is used as a heat dissipation sheet. In the flexible graphite structure 500 according to this embodiment, the thickness of the graphite sheet unit 550 can be made substantially uniform in its pre-extension state by using adhesive layers 520a and 520b, making it possible to easily attach the graphite structure to flexible electronic devices.

[0105] Figure 6A is a cross-sectional view of a flexible graphite structure 600 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0106] Referring to Figure 6A, the flexible graphite structure 600 includes a graphite sheet unit 650 comprising three graphite sheet layers 610a, 610b, 610c and adhesive layers 620a, 620b formed on the graphite sheet layers 610a, 610b, 610c, and stretchable sheet layers 630a, 630b attached to the outermost surfaces of the graphite sheet unit 650.

[0107] The graphite sheet layers 610a, 610b, 610c, the adhesive layers 620a, 620b, and the stretchable sheet layers 630a, 630b may each be formed from the same materials as the graphite sheet layers, adhesive layers, and stretchable sheet layers described above, and redundant explanations will be omitted.

[0108] The graphite sheet layer 610a includes at least two foldable portions 640 formed by folding the graphite sheet layer 610a, and an overlapping region OL is formed between the two foldable portions 640. The overlapping region OL refers to the region where the portions of the graphite sheet layer 610a overlap each other when viewed in the vertical direction of Figure 6A, i.e., in the depth direction of the flexible graphite structure 600.

[0109] The adhesive layers 620a and 620b may be formed in areas where the overlapping region OL of the graphite sheet layers 610a, 610b, and 610c is not formed. The adhesive layer 620a may be formed between the graphite sheet layer 610a and the graphite sheet layer 610b, and the adhesive layer 620b may be formed between the graphite sheet layer 610a and the graphite sheet layer 610c. By using the adhesive layers 620a and 620b and the graphite sheet layers 610b and 610c, it is possible to make the thickness of the graphite sheet unit 650 substantially uniform.

[0110] The type and shape of the adhesive layers 620a and 620b formed between the spaced-apart graphite sheet layers 610a, 610b, and 610c are not particularly limited. However, if the adhesive layers 620a and 620b are in the form of an adhesive film, for example, adhesive layers are required on both sides facing the graphite sheet layers 610a, 610b, and 610c in order to adhere to them, so it is preferable that the adhesive layers be double-sided adhesive films.

[0111] The foldable portion 640 of the graphite sheet layer 610a, the adhesive layers 620a and 620b, and the graphite sheet layers 610b and 610c are not bonded to each other, and voids may be defined. That is, the overlapping region OL may contain voids on both sides, and these voids may extend in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure 600. Due to the presence of voids, when a force is applied to the flexible graphite structure 600, the flexible graphite structure 600 may be stretched along the direction of the force.

[0112] Figure 6B is a cross-sectional view of the flexible graphite structure 600 when it is stretched in the expansion and contraction direction.

[0113] Referring to Figure 6B, when a user manipulates an electronic device so that the display of the electronic device is bent or folded, a force may be applied to the flexible graphite structure 600 that pulls it to both sides.

[0114] When a force is applied to the flexible graphite structure 600 that pulls it to both sides, the stretchable sheet layers 630a and 630b are stretched along the direction of the force, and the graphite sheet unit 650 is integrally bonded to the stretchable sheet layers 630a and 630b. Since the graphite sheet layer 610a of the flexible graphite structure 600 includes an overlapping region OL formed by two foldable portions 640, the foldable portions 640 of the graphite sheet layer 610a are unfolded in response to the application of force, and the graphite sheet layer 610a can also be extended to both sides along the direction of the force. Furthermore, since both sides of the adhesive layers 620a and 620b are fixed and attached between the graphite sheet layers 610a, 610b, and 610c, and both sides of the graphite sheet layers 610b and 610c are fixed and attached between the stretchable sheet layers 630a and 630b and the adhesive layers 620a and 620b, the adhesive layers 620a and 620b and the graphite sheet layers 610b and 610c also separate from each other in accordance with the extension of the stretchable sheet layers 630a and 630b and the graphite sheet layer 610a.

[0115] As the graphite sheet unit 650 is extended on both sides, the width of the overlapping region OL gradually narrows, and when the graphite sheet portion 650 is extended to its maximum extent, the overlapping region OL may disappear.

[0116] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the force pulling the flexible graphite structure 600 on both sides is released. Once the force pulling the flexible graphite structure 600 on both sides is released, the stretchable sheet layers 630a and 630b contract back to their original length, and therefore the width of the overlapping region OL of the graphite sheet unit 650 widens. Once the contraction of the stretchable sheet layers 630a and 630b is complete, the flexible graphite structure 600 returns to its original shape, i.e., the shape shown in Figure 6A.

[0117] When force is applied to the flexible graphite structure 600 and then released, the above-described operation is repeated. This operation allows for smooth heat dissipation from flexible electronic devices, even when a graphite structure with high thermal conductivity but low flexibility is used as a heat dissipation sheet. In the flexible graphite structure 600 according to this embodiment, by using adhesive layers 620a, 620b and graphite sheet layers 610b, 610c, the thickness of the graphite sheet unit 650 can be made substantially uniform in its pre-extension state, making it possible to easily attach the graphite structure to a flexible electronic device.

[0118] Figure 7A is a cross-sectional view of a flexible graphite structure 700 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0119] Referring to Figure 7A, the flexible graphite structure 700 includes a graphite sheet unit 750 comprising four graphite sheet layers 710a, 710b, 710c, 710d and adhesive layers 720a, 720b formed on the graphite sheet layers 710a, 710b, 710c, 710d, and stretchable sheet layers 730a, 730b attached to the outermost surfaces of the graphite sheet unit 750.

[0120] The graphite sheet layers 710a, 710b, 710c, 710d, the adhesive layers 720a, 720b, and the stretchable sheet layers 730a, 730b may each be formed from the same materials as the graphite sheet layers, adhesive layers, and stretchable sheet layers described above, and redundant explanations will be omitted.

[0121] The graphite sheet unit 750 includes an overlapping region OL formed by stacking two graphite sheet layers 710a and 710b. The overlapping region OL refers to the area where the two graphite sheet layers 710a and 710b overlap each other when viewed in the vertical direction of Figure 7A, i.e., in the depth direction of the flexible graphite structure 700.

[0122] The adhesive layers 720a and 720b may be formed in areas where the overlapping region OL of the graphite sheet layers 710a, 710b, 710c, and 710d is not formed. The adhesive layer 720a may be formed between the graphite sheet layer 710b and the graphite sheet layer 710c, and the adhesive layer 720b may be formed between the graphite sheet layer 710a and the graphite sheet layer 710d. By using the adhesive layers 720a and 720b and the graphite sheet layers 710c and 710d, it is possible to make the thickness of the graphite sheet unit 750 substantially uniform.

[0123] The type and shape of the adhesive layers 720a and 720b formed between the spaced-apart graphite sheet layers 710a, 710b, 710c, and 710d are not particularly limited. However, if the adhesive layers 720a and 720b are in the form of an adhesive film, for example, adhesive layers are required on both sides facing the graphite sheet layers 710a, 710b, 710c, and 710d in order to adhere to them, so it is preferable that the adhesive layers be double-sided adhesive films.

[0124] In the overlapping region OL, the edges of the two graphite sheet layers 710a and 710b are not adhered to the adhesive layers 720a and 720b and the graphite sheet layers 710c and 710d, and voids may be defined. That is, the overlapping region OL may contain voids on both sides, and these voids may extend in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure 700. Due to the presence of voids, when a force is applied to the flexible graphite structure 700, the flexible graphite structure 100 may be stretched along the direction of the force.

[0125] Figure 7B is a cross-sectional view of the flexible graphite structure 700 when it is extended in the stretching direction.

[0126] Referring to Figure 7B, when a user manipulates an electronic device so that the display of the electronic device is bent or folded, a force may be applied to the flexible graphite structure 700 that pulls it to both sides.

[0127] When a force is applied to the flexible graphite structure 700 that pulls it on both sides, the stretchable sheet layers 730a and 730b are stretched along the direction of the force, and because the graphite sheet unit 750 is integrally bonded to the stretchable sheet layers 730a and 730b, the graphite sheet layer 710a of the graphite sheet unit 750 moves in one direction, while the graphite sheet layer 710b moves in the opposite direction. Furthermore, since both sides of the adhesive layers 720a and 720b are fixedly attached between the graphite sheet layers 710a, 710b, 710c, and 710d, and both sides of the graphite sheet layers 710c and 710d are fixedly attached between the stretchable sheet layers 730a and 730b and the adhesive layers 720a and 720b, the adhesive layers 720a and 720b and the graphite sheet layers 710c and 710d also move away from each other in accordance with the extension of the stretchable sheet layers 730a and 730b and the graphite sheet layers 710a and 710b. In particular, although the two graphite sheet layers 710a and 710b are not bonded to each other, they are stacked on top of each other, so the graphite sheet layers can slide in opposite directions when force is applied. As the two graphite sheet layers 710a and 710b move in opposite directions, the graphite sheet unit 750 is also extended on both sides.

[0128] As the graphite sheet unit 750 is extended on both sides, the width of the overlapping region OL gradually narrows, allowing the flexible graphite structure 700 to be extended until the overlapping region OL formed by the two graphite sheet layers 710a and 710b completely disappears.

[0129] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the force pulling the flexible graphite structure 700 on both sides is released. Once the force pulling the flexible graphite structure 700 on both sides is released, the stretchable sheet layers 730a and 730b contract back to their original lengths, and therefore the width of the overlapping region OL of the graphite sheet unit 750 widens. Once the contraction of the stretchable sheet layers 730a and 730b is complete, the flexible graphite structure 700 returns to its original shape, i.e., the shape shown in Figure 7A.

[0130] When force is applied to and released from the flexible graphite structure 700, the above-described operation is repeated. This operation allows for smooth heat dissipation from flexible electronic devices, even when a graphite structure with high thermal conductivity but low flexibility is used as a heat dissipation sheet. In the flexible graphite structure 700 according to this embodiment, by using adhesive layers 720a, 720b and graphite sheet layers 710c, 710d, the thickness of the graphite sheet unit 750 can be made substantially uniform in its pre-extension state, making it possible to easily attach the graphite structure to a flexible electronic device.

[0131] Figure 8A is a cross-sectional view of a flexible graphite structure 800 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0132] Referring to Figure 8A, the flexible graphite structure 800 includes a graphite sheet unit 870 comprising three graphite sheet layers 810a, 810b, 810c and adhesive layers 820a, 820b, 830a, 830b, 840a, 840b formed on the graphite sheet layers 810a, 810b, 810c, and stretchable sheet layers 850a, 850b attached to the outermost surfaces of the graphite sheet unit 870.

[0133] The graphite sheet layers 810a, 810b, 810c, the adhesive layers 820a, 820b, 830a, 830b, 840a, 840b, and the stretchable sheet layers 850a, 850b may each be formed from the same materials as the graphite sheet layers, adhesive layers, and stretchable sheet layers described above, and redundant explanations will be omitted.

[0134] The graphite sheet layer 810a includes at least two foldable portions 860 formed by folding the graphite sheet layer 810a, and an overlapping region OL is formed between the two foldable portions 860. The overlapping region OL refers to the region where the portions of the graphite sheet layer 810a overlap each other when viewed in the vertical direction of Figure 8A, i.e., in the depth direction of the flexible graphite structure 800.

[0135] The adhesive layers 820a and 820b may be formed in areas where the overlapping region OL of the graphite sheet layers 810a, 810b, and 810c is not formed. The adhesive layer 820a may be formed between the graphite sheet layer 810a and the graphite sheet layer 810b, and the adhesive layer 820b may be formed between the graphite sheet layer 810a and the graphite sheet layer 810c. The adhesive layers 830a and 830b may be formed between the graphite sheet layers 810a and 810b and the stretchable sheet layer 850a, and the adhesive layers 840a and 840b may be formed between the graphite sheet layers 810a and 810c and the stretchable sheet layer 850b. Furthermore, the adhesive layers 830a, 830b, 840a, and 840b formed between the graphite sheet layers 810a, 810b, and 810c and the stretchable sheet layers 850a, 850b may be divided along the foldable portion 860 of the graphite sheet layer 810a. By using the adhesive layers 820a, 820b, 830a, 830b, 840a, 840b and the graphite sheet layers 810b and 810c, it is possible to make the thickness of the graphite sheet unit 850 substantially uniform.

[0136] The type and shape of the adhesive layers 820a and 820b formed between the spaced-apart graphite sheet layers 810a, 810b, and 810c are not particularly limited. However, if the adhesive layers 820a and 820b are in the form of, for example, an adhesive film, it is preferable that the adhesive layers be double-sided adhesive films, since adhesive layers are required on both sides facing the graphite sheet layers 810a, 810b, and 810c in order to adhere to them.

[0137] If the adhesive layers 830a, 830b, 840a, and 840b formed between the graphite sheet layers 810a, 810b, and 810c and the stretchable sheet layers 850a, 850b are, for example, in the form of an adhesive film, then each adhesive layer only needs to have an adhesive layer on the surface facing the graphite sheet layers 810a, 810b, or 810c. Therefore, it may be a single-sided adhesive film as well as a double-sided adhesive film.

[0138] The foldable portions 860 of the graphite sheet layer 810a, adhesive layers 820a, 820b, and graphite sheet layers 810b, 810c are not bonded to each other, and the adhesive layers 830a, 830b, 840a, 840b are separated along the foldable portions 860, with voids defined between them. Thus, the overlapping region OL may contain voids on both sides, and these voids may extend in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure 800. Due to the presence of voids, when a force is applied to the flexible graphite structure 800, the flexible graphite structure 800 may be stretched along the direction of the force.

[0139] Figure 8B is a cross-sectional view of the flexible graphite structure 800 when it is stretched in the expansion and contraction direction.

[0140] Referring to Figure 8B, when a user manipulates an electronic device so that the display of the electronic device is bent or folded, a force may be applied to the flexible graphite structure 800 that pulls it to both sides.

[0141] When a force is applied to the flexible graphite structure 800 that pulls it to both sides, the stretchable sheet layers 850a and 850b are stretched along the direction of the force, and the graphite sheet unit 870 is integrally bonded to the stretchable sheet layers 850a and 850b. Since the graphite sheet layer 810a of the flexible graphite structure 800 includes an overlapping region OL formed by two foldable portions 860, the foldable portions 860 of the graphite sheet layer 810a are unfolded in response to the application of force, and the graphite sheet layer 810a can also be extended to both sides along the direction of the force. Furthermore, since the adhesive layers 820a, 820b, 830a, 830b, 840a, 840b and the graphite sheet layers 810b, 810c are fixed and stacked between the graphite sheet layer 810a and the stretchable sheet layers 850a, 850b, the adhesive layers 820a, 830a, 840b and the graphite sheet layer 810b separate from the adhesive layers 820b, 830b, 840a and the graphite sheet layer 810c in accordance with the extension of the stretchable sheet layers 850a, 850b and the graphite sheet layer 810a.

[0142] When the stretchable sheet layers 850a and 850b are stretched, the stretchable sheet layers 850a and 850b corresponding to the separation between the adhesive layers 830a and 830b and the separation between the adhesive layers 840a and 840b can be stretched from more than 0 to 50% or from more than 0 to 30%.

[0143] As the graphite sheet unit 870 is extended on both sides, the width of the overlapping region OL gradually narrows, and when the graphite sheet portion 870 is extended to its maximum extent, the overlapping region OL may disappear.

[0144] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the force pulling the flexible graphite structure 800 on both sides is released. Once the force pulling the flexible graphite structure 800 on both sides is released, the stretchable sheet layers 850a and 850b contract back to their original lengths, and therefore the width of the overlapping region OL of the graphite sheet unit 870 widens. Once the contraction of the stretchable sheet layers 850a and 850b is complete, the flexible graphite structure 800 returns to its original shape, i.e., the shape shown in Figure 8A.

[0145] Figure 9A is a cross-sectional view of a flexible graphite structure 900 according to one embodiment of the present disclosure, in which the overlapping region is formed as an expandable region.

[0146] Referring to Figure 9A, the flexible graphite structure 900 includes a graphite sheet unit 960 comprising four graphite sheet layers 910a, 910b, 910c, 910d, and adhesive layers 920a, 920b, 930a, 930b, 940a, 940b formed on the graphite sheet layers 910a, 910b, 910c, 910d, and stretchable sheet layers 950a, 950b attached to the outermost surfaces of the graphite sheet unit 960.

[0147] The graphite sheet layers 910a, 910b, 910c, 910d, the adhesive layers 920a, 920b, 930a, 930b, 940a, 940b, and the stretchable sheet layers 950a, 950b may each be formed from the same materials as the graphite sheet layers, adhesive layers, and stretchable sheet layers described above, and redundant explanations will be omitted.

[0148] The graphite sheet unit 960 includes an overlapping region OL formed by stacking two graphite sheet layers 910a and 910b. The overlapping region OL refers to the area where the two graphite sheet layers 910a and 910b overlap each other when viewed in the vertical direction of Figure 9A, i.e., in the depth direction of the flexible graphite structure 900.

[0149] The adhesive layers 920a and 920b may be formed in areas where the overlapping region OL of the graphite sheet layers 910a, 910b, 910c, and 910d is not formed. The adhesive layer 920a may be formed between the graphite sheet layer 910b and the graphite sheet layer 910c, and the adhesive layer 920b may be formed between the graphite sheet layer 910a and the graphite sheet layer 910d. The adhesive layers 930a and 930b may be formed between the graphite sheet layers 910a and 910c and the stretchable sheet layer 950a, and the adhesive layers 940a and 940b may be formed between the graphite sheet layers 910b and 910d and the stretchable sheet layer 950b. Furthermore, the adhesive layers 930a, 930b, 940a, and 940b formed between the graphite sheet layers 910a, 910b, 910c, and 910d and the stretchable sheet layers 950a, 950b may be divided along the edges of the graphite sheet layers 910a, and 910b in the overlapping region OL. By using the adhesive layers 920a, 920b, 930a, 930b, 940a, and 940b and the graphite sheet layers 910c and 910d, it is possible to make the thickness of the graphite sheet unit 960 substantially uniform.

[0150] The type and shape of the adhesive layers 920a and 920b formed between the spaced-apart graphite sheet layers 910a, 910b, 910c, and 910d are not particularly limited. However, if the adhesive layers 920a and 920b are in the form of, for example, an adhesive film, it is preferable that the adhesive layers be double-sided adhesive films, as adhesive layers are required on both sides facing the graphite sheet layers 910a, 910b, 910c, and 910d in order to adhere to them.

[0151] If the adhesive layers 930a, 930b, 940a, and 940b formed between the graphite sheet layers 910a, 910b, 910c, and 910d and the stretchable sheet layers 950a, 950b are, for example, in the form of an adhesive film, then it is sufficient for each adhesive layer to have an adhesive layer on the surface facing the graphite sheet layers 910a, 910b, 910c, or 910d; therefore, it may be a single-sided adhesive film as well as a double-sided adhesive film.

[0152] In the overlapping region OL, the edges of the two graphite sheet layers 910a and 910b are not adhered to the adhesive layers 920a and 920b and the graphite sheet layers 910c and 910d, and the adhesive layers 930a, 930b, 940a, and 940b are separated along the edges of the graphite sheet layers 910a and 910b, so that voids can be defined between them. Therefore, the overlapping region OL may contain voids on both sides, and these voids may extend in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure 900. Due to the presence of voids, when a force is applied to the flexible graphite structure 900, the flexible graphite structure 900 may be stretched along the direction of the force.

[0153] Figure 9B is a cross-sectional view of the flexible graphite structure 900 when it is stretched in the expansion and contraction direction.

[0154] Referring to Figure 9B, when a user manipulates an electronic device so that the display of the electronic device is bent or folded, a force may be applied to the flexible graphite structure 900 that pulls it to both sides.

[0155] When a force is applied to the flexible graphite structure 900 that pulls it on both sides, the stretchable sheet layers 950a and 950b are stretched along the direction of the force, and because the graphite sheet unit 960 is integrally bonded to the stretchable sheet layers 950a and 950b, the graphite sheet layer 910a of the graphite sheet unit 960 moves in one direction, while the graphite sheet layer 910b moves in the opposite direction. Furthermore, since the adhesive layers 920a, 920b, 930a, 930b, 940a, 940b and the graphite sheet layers 910c, 910d are fixed and stacked between the graphite sheet layers 910a, 910b and the stretchable sheet layers 950a, 950b, the adhesive layers 920a, 930a, 940b and the graphite sheet layer 910c separate from the adhesive layers 920b, 930b, 940a and the graphite sheet layer 910d in accordance with the extension of the stretchable sheet layers 950a, 950b and the graphite sheet layers 910a, 910b. In particular, although the two graphite sheet layers 910a, 910b are not bonded to each other, they are stacked on top of each other, so the graphite sheet layers can slide in opposite directions when force is applied. As the two graphite sheet layers 910a and 910b move in opposite directions, the graphite sheet unit 960 is also extended on both sides.

[0156] As the graphite sheet unit 960 is extended on both sides, the width of the overlapping region OL gradually narrows, allowing the flexible graphite structure 900 to be extended until the overlapping region OL formed by the two graphite sheet layers 910a and 910b completely disappears.

[0157] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the force pulling the flexible graphite structure 900 on both sides is released. Once the force pulling the flexible graphite structure 900 on both sides is released, the stretchable sheet layers 950a and 950b contract back to their original lengths, and therefore the width of the overlapping region OL of the graphite sheet unit 960 widens. Once the contraction of the stretchable sheet layers 950a and 950b is complete, the flexible graphite structure 900 returns to its original shape, i.e., the shape shown in Figure 9A.

[0158] Figure 10A is a plan view of a graphite sheet layer 10 applicable to a flexible graphite structure according to one embodiment of the present disclosure, in which the notched region is formed as an expandable region.

[0159] Referring to Figure 10A, the graphite sheet layer 10 includes two notched regions 12a and 12b, which are symmetrically arranged on the graphite sheet layer 10. The graphite sheet layer 10 may be formed from the same material as the graphite sheet layer described above, and redundant explanations will be omitted.

[0160] The lengths of the two notched regions 12a and 12b perpendicular to the expansion / contraction direction E of the graphite sheet layer 10 may be shorter than the vertical length of the graphite sheet layer 10, with notched region 12a cutting off one end of the graphite sheet layer 10 and notched region 12b cutting off the other end of the graphite sheet layer 10. Furthermore, the lengths of the two notched regions 12a and 12b perpendicular to the expansion / contraction direction E are 90% or less, or 75% or less, of the vertical length of the graphite sheet layer 10.

[0161] Since the length of the notched regions 12a and 12b perpendicular to the expansion / contraction direction E is shorter than the vertical length of the graphite sheet layer 10, the graphite sheet layer 10 is connected as a single sheet in areas other than the notched regions 12a and 12b.

[0162] The graphite sheet layer 10 is defined by notched regions 12a and 12b, and the voids extend in a direction perpendicular to the expansion and contraction direction E.

[0163] Figure 10B is a plan view of the graphite sheet layer 10 when it is a flexible graphite structure in which stretchable sheet layers (not shown) formed on both sides of the graphite sheet layer 10 are extended in the stretch direction E.

[0164] Referring to Figure 10B, a flexible graphite structure including a graphite sheet layer 10 may be used as a heat dissipation sheet in electronic devices equipped with a bendable flexible display or a foldable display that can be folded and unfolded. When a user manipulates the electronic device to bend or fold the display of the electronic device, a force may be applied to the graphite sheet layer 10 of the flexible graphite structure, pulling it to both sides.

[0165] When a tensile force is applied to the graphite sheet layer 10 in the stretching direction E, the stretchable sheet layers formed on both sides of the graphite sheet layer 10 are stretched along the direction of the force. Since the graphite sheet layer 10 is integrally bonded to the stretchable sheet layers, the graphite sheet layer 10 also extends in the stretching direction E along the direction of the force.

[0166] Since the graphite sheet layer 10 is not elastic, if the graphite sheet layer is a flat graphite sheet, it will tear rather than stretch when force is applied. However, because the graphite sheet layer 10 includes notched regions 12a and 12b, the graphite sheet layer 10 can also be stretched in the expansion / contraction direction E along the direction of the force in response to the application of force.

[0167] When the user returns the electronic device to its original state after bending or folding the display of the electronic device, the tensile force in the stretching direction E is released from the graphite sheet layer 10 of the flexible graphite structure. When the force pulling the graphite sheet layer 10 in the stretching direction E is released, the stretchable sheet layer contracts back to its original length, and therefore the notched regions 12a and 12b of the graphite sheet layer 10 also shrink. Once the contraction of the stretchable sheet layer is complete, the graphite sheet layer 10 returns to its original shape, i.e., the shape shown in Figure 10A.

[0168] Figure 11A is a plan view of a graphite sheet layer 20 applicable to a flexible graphite structure according to one embodiment of the present disclosure, in which the notched region is formed as an expandable region. Figure 11B is a plan view of the graphite sheet layer 20 when it is a flexible graphite structure in which expandable sheet layers (not shown) formed on both sides of the graphite sheet layer 20 are extended in the expansion direction E.

[0169] Referring to Figures 11A and 11B, the graphite sheet layer 20 includes two notched regions 22a and 22b, each of which may have a shape in which one end is bent in the expansion direction E. The characteristics of the graphite sheet layer 20 and the two notched regions 22a and 22b are the same as those of the graphite sheet layer 10 and the two notched regions 12a and 12b described above, so their description is omitted.

[0170] Figure 12A is an actual photograph of a flexible graphite structure according to one embodiment in which the overlapping region is provided as an expandable region, in the state before the overlapping region is formed, that is, before a force pulling the flexible graphite structure on both sides is applied to the flexible graphite structure.

[0171] Figure 12B is an actual photograph of the flexible graphite structure in Figure 12A when it is stretched in the stretch direction. When a force is applied to the flexible graphite structure in Figure 12A, pulling it on both sides, the width of the overlapping region gradually narrows, while the stretchable sheet layer and graphite sheet layer of the flexible graphite structure are stretched on both sides along the direction of the force. When the graphite sheet layer is stretched to its maximum extent, the overlapping region disappears, and the shape shown in Figure 12B may be observed.

[0172] When the pulling force on both sides of the flexible graphite structure in Figure 12B is released, the stretchable sheet layer contracts back to its original length, thus re-forming the overlapping region so that the flexible graphite structure can return to the shape of Figure 12A.

[0173] Figure 13A is an actual photograph of a flexible graphite structure according to one embodiment in which the notched regions are formed as expansion and contraction regions. The flexible graphite structure has two notched regions formed perpendicular to the expansion and contraction direction. Since the lengths of the two notched regions are shorter than the lengths of the graphite sheet layer in the direction parallel to the notched regions, the graphite sheet layer is connected as a single sheet except for the two notched regions.

[0174] Figure 13B is an actual photograph of the flexible graphite structure in Figure 13A when it is stretched in the direction of expansion and contraction. When a tensile force is applied to both sides of the flexible graphite structure in Figure 13A, the notched area of ​​the graphite sheet layer can be widened, and the graphite sheet layer can also be stretched along the direction of the force.

[0175] When the tensile force applied to both sides of the flexible graphite structure in Figure 13B is released, the stretchable sheet layer contracts back to its original length, and therefore the notched area of ​​the graphite sheet layer also shrinks. Once the contraction of the stretchable sheet layer is complete, the flexible graphite structure can return to its original shape, i.e., the shape shown in Figure 13A.

[0176] When force is applied to and released from the graphite sheet layers 10 and 20 of the flexible graphite structure, the above-described operation is repeated. This operation allows for smooth heat dissipation of flexible electronic devices, even when a graphite structure with high thermal conductivity but low flexibility is used as a heat dissipation sheet.

[0177] While flexible graphite structures have been described above with reference to embodiments shown in the drawings, these are merely illustrative. Those skilled in the art will understand that various modifications and equivalent other embodiments are possible from these embodiments. Although the embodiments shown in the drawings include up to four graphite sheet layers within the graphite structure, it should be understood that the graphite structures of this disclosure include, but are not limited to, a single graphite sheet layer, or multiple graphite sheet layers, including at least two, at least three, at least four, at least five, and so on. Accordingly, the embodiments disclosed herein should be considered in a descriptive rather than restrictive manner. The scope of this disclosure is expressed in the appended claims and not in the above description, and all differences within the scope equivalent to the claims should be understood to be included within the scope of this disclosure.

[0178] While specific embodiments have been described, these embodiments are presented as examples only and are not intended to limit the scope of this disclosure. In fact, the embodiments described herein may be embodied in various other forms. Furthermore, various omissions, substitutions, and modifications of the embodiments described herein may be made without departing from the spirit of this disclosure. The appended claims and their equivalents are intended to encompass forms and modifications that fall within the scope and spirit of this disclosure.

Claims

1. A graphite sheet unit comprising a single graphite sheet layer or multiple graphite sheet layers having at least one stretchable region, A stretchable sheet layer is attached to at least one of the outermost surfaces of the graphite sheet unit and configured to cover at least one stretchable region, Includes, The at least one stretchable region is formed by providing at least one pair of notched regions in the single graphite sheet layer, or by providing overlapping regions in which the plurality of graphite sheet layers overlap in the depth direction of the flexible graphite structure. The overlapping region is formed by the overlap of one end portion of the plurality of graphite sheet layers. Flexible graphite structure.

2. The flexible graphite structure according to claim 1, wherein the overlapping ends of the plurality of graphite sheet layers are stacked on top of each other and not bonded to each other.

3. The at least one pair of notched regions are provided point-symmetrically on the single graphite sheet layer, The flexible graphite structure according to claim 1, wherein the single graphite sheet layer is connected as a single sheet in the region other than the notched region.

4. The flexible graphite structure according to claim 3, wherein the at least pair of notched regions have a length shorter than the graphite sheet layer in a direction perpendicular to the expansion and contraction direction of the flexible graphite structure.

5. The flexible graphite structure according to claim 4, wherein the length of the at least pair of notched regions is 90% or less or 75% or less of the length of the graphite sheet layer in the direction perpendicular to the expansion and contraction direction of the flexible graphite structure.

6. The flexible graphite structure according to claim 1, wherein the at least one stretchable region includes a void extending in a direction perpendicular to the stretching direction of the flexible graphite structure.

7. The flexible graphite structure according to claim 6, wherein the void is defined between a graphite sheet layer provided in a region other than the overlapping region and a graphite sheet layer provided in the overlapping region, or is defined by the at least one pair of notched regions.

8. The flexible graphite structure according to claim 1, wherein when force is applied to the flexible graphite structure, the graphite sheet unit is extended, the stretchable sheet layer is stretched in the direction in which the graphite sheet unit is extended, and the width of the overlapping region is narrowed.

9. The flexible graphite structure according to claim 8, wherein when the force is released, the stretchable sheet layer contracts and the width of the overlapping region widens.

10. The flexible graphite structure according to claim 3, wherein when force is applied to the flexible graphite structure, the graphite sheet unit is extended, the stretchable sheet layer is stretched in the direction in which the graphite sheet unit is extended, and the size of the gap in the at least pair of notched regions is increased.

11. The flexible graphite structure according to claim 10, wherein when the force is released, the stretchable sheet layer contracts, and the size of the gap in the at least pair of notched regions is reduced.

12. The flexible graphite structure according to claim 1, wherein the graphite sheet layer comprises compressed particles of a graphitized polymer or expanded graphite, or a combination thereof.

13. The flexible graphite structure according to claim 1, wherein the stretchable sheet layer comprises at least one selected from the group consisting of PDMS (polydimethylsiloxane), epoxy resin, styrene-based material, olefin-based material, polyolefin, polyurethane, thermoplastic polyurethane, thermoplastic elastomer, polyamide, synthetic rubber, polybutadiene, polyisobutylene, polychloroprene, and silicone.

14. The flexible graphite structure according to claim 1, wherein the stretchable sheet layer has an elongation rate of 175% or more, or 200% or more, or 250% or more.

15. The flexible graphite structure according to claim 1, wherein the stretchable sheet layer includes a thermally conductive material.

16. The flexible graphite structure according to claim 1, wherein the graphite sheet layer has a thickness of 15 μm to 19 μm, or 16 μm to 18 μm.

17. The flexible graphite structure according to claim 1, wherein the graphite sheet unit includes an adhesive layer provided on the graphite sheet layer, and the graphite sheet unit has a uniform thickness.

18. The flexible graphite structure according to claim 17, wherein the adhesive layer comprises at least one selected from the group consisting of pressure-sensitive adhesive (PSA), thermosetting adhesive, photocurable adhesive, optical transparent adhesive (OCA), optical transparent resin (OCR), double-sided adhesive film, and single-sided adhesive film.

19. The flexible graphite structure according to claim 18, wherein when the adhesive layer is formed between the plurality of spaced-apart graphite sheet layers, the adhesive layer is a double-sided adhesive film.

20. The flexible graphite structure according to claim 18, wherein, when the adhesive layer is formed between the graphite sheet layer and the stretchable sheet layer, the adhesive layer is a single-sided adhesive film.

21. The flexible graphite structure according to claim 20, wherein the single-sided adhesive film is adhered to the surface facing the graphite sheet layer.

22. The flexible graphite structure according to claim 12, wherein the graphite sheet layer has an in-plane thermal conductivity of 150 W / mK to 1700 W / mK.

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