CN111263568B - Heat dissipation material, preparation method thereof and electronic equipment - Google Patents
Heat dissipation material, preparation method thereof and electronic equipment Download PDFInfo
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- CN111263568B CN111263568B CN202010076317.9A CN202010076317A CN111263568B CN 111263568 B CN111263568 B CN 111263568B CN 202010076317 A CN202010076317 A CN 202010076317A CN 111263568 B CN111263568 B CN 111263568B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K7/00—Constructional details common to different types of electric apparatus
- H05K7/20—Modifications to facilitate cooling, ventilating, or heating
- H05K7/2039—Modifications to facilitate cooling, ventilating, or heating characterised by the heat transfer by conduction from the heat generating element to a dissipating body
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
- F28F21/02—Constructions of heat-exchange apparatus characterised by the selection of particular materials of carbon, e.g. graphite
Abstract
The application provides a heat dissipation material, including the graphite alkene membrane, the graphite alkene membrane includes the fold district, the fold district includes a plurality of fold structures, just the fold district is equipped with fretwork portion. By arranging the graphene film with excellent thermal conductivity, the heat dissipation performance of the heat dissipation material is effectively improved, and the heat dissipation performance of the electronic equipment is further improved; meanwhile, the graphene film is provided with a fold area, so that the bending resistance of the heat dissipation material is improved, the stress of the heat dissipation material in the bending process is further relieved by the hollow part, the service life of the heat dissipation material is prolonged, and the application of the heat dissipation material in electronic equipment is further facilitated. The application also provides a preparation method of the heat dissipation material and electronic equipment.
Description
Technical Field
The application belongs to the technical field of heat dissipation, and particularly relates to a heat dissipation material, a preparation method thereof and electronic equipment.
Background
With the rapid development of the electronic industry, electronic devices are becoming more compact, multifunctional, and high-performance, and the amount of heat generated per unit area is also increasing rapidly, so that heat dissipation is a critical issue, and the performance and reliability of electronic devices are being restricted.
Disclosure of Invention
In view of this, the present application provides a heat dissipation material having excellent heat dissipation properties, a method of preparing the same, and an electronic device.
In a first aspect, the present application provides a heat dissipation material, including a graphene film, the graphene film includes a wrinkle region, the wrinkle region includes a plurality of wrinkle structures, and the wrinkle region is provided with a hollow portion.
In a second aspect, the present application provides a method for preparing a heat dissipation material, comprising:
providing an elastomer, and stretching the elastomer;
providing a graphene film, and attaching the graphene film to the surface of the stretched elastomer;
releasing the stretched elastomer, and extruding the graphene film to form a corrugated area, wherein the corrugated area comprises a plurality of corrugated structures;
and peeling the elastic body, and hollowing out the wrinkle area to form a hollow part, so as to obtain the heat dissipation material.
In a third aspect, the present application provides an electronic device, including a bendable heating element and a heat dissipation material disposed on the heating element, the heat dissipation material includes a graphene film, the graphene film includes a wrinkle region, the wrinkle region includes a plurality of wrinkle structures, and the wrinkle region is provided with a hollow portion, the wrinkle region is attached to the bendable heating element.
The application provides a heat dissipation material, a preparation method thereof and electronic equipment, wherein the heat dissipation performance of the heat dissipation material is effectively improved by arranging a graphene film with excellent heat conductivity, so that the heat dissipation performance of the electronic equipment is improved; meanwhile, the graphene film is provided with a fold area, so that the bending resistance of the heat dissipation material is improved, the stress of the heat dissipation material in the bending process is further relieved by the hollow part, the service life of the heat dissipation material is prolonged, and the application of the heat dissipation material in flexible electronic equipment is facilitated.
Drawings
In order to more clearly explain the technical solution in the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be described below.
Fig. 1 is a top view of a heat dissipation material according to an embodiment of the present disclosure.
Fig. 2 is a schematic cross-sectional view of the dotted area in fig. 1 in the direction a-a.
Fig. 3 is a top view of a heat dissipation material according to another embodiment of the present disclosure.
Fig. 4 is a schematic flow chart illustrating a method for preparing a heat dissipation material according to an embodiment of the present disclosure.
Fig. 5 is a schematic cross-sectional view illustrating a bendable heat generating element and a heat dissipating material attached together according to an embodiment of the present application.
FIG. 6 is an enlarged view of the corrugated area of the heat dissipating material prepared in example 1.
Description of the drawings:
the heat radiating device comprises a wrinkle area-10, a wrinkle structure-101, a hollow-out part-102, a leveling layer-103, a first wrinkle sub-area-11, a second wrinkle sub-area-12, a leveling area-20, a heat radiating material-100 and a bendable heating element-200.
Detailed Description
The following is a preferred embodiment of the present application, and it should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present application, and these improvements and modifications are also considered as the protection scope of the present application.
The following disclosure provides many different embodiments or examples for implementing different features of the application. In order to simplify the disclosure of the present application, specific example components and arrangements are described below. Of course, they are merely examples and are not intended to limit the present application. Moreover, the present application may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, examples of various specific processes and materials are provided herein, but one of ordinary skill in the art may recognize applications of other processes and/or use of other materials.
Referring to fig. 1, a top view of a heat dissipation material according to an embodiment of the present disclosure includes a graphene film, the graphene film includes a corrugated region 10, and the corrugated region 10 is provided with a hollow portion 102. Fig. 2 is a schematic cross-sectional view of the dotted line area in fig. 1 along a-a direction, wherein the corrugated area 10 has a plurality of corrugated structures 101. In the application, the graphene film has excellent heat dissipation performance, is beneficial to improving the heat dissipation capacity of the heat dissipation material, can be used in electronic equipment, and can improve the heat dissipation performance of the electronic equipment in unit area and improve the service performance and reliability of the electronic equipment, especially for miniaturized, multifunctional and high-performance electronic equipment.
In the related art, electronic devices are increasingly developed in a flexible direction, for example, foldable electronic devices and the like, and heat dissipation devices such as a temperature equalization plate and a heat pipe are made of metal, which is not flexible well, so that the overall structure of the heat dissipation device has high rigidity, and is easy to break during bending, thereby affecting heat dissipation and further limiting the use of the heat dissipation device in the electronic devices. In the heat dissipation material provided by the application, the graphene film has a relatively loose internal structure except for excellent heat dissipation performance, and has better flexibility compared with a temperature equalization plate and a heat pipe; more importantly, the graphene film has the fold area 10, the fold structure 101 of the fold area 10 can be unfolded in the bending process, the stress generated in the bending process can be effectively relieved, the damage to the heat dissipation material caused by the repeated bending process can be avoided, and the stress generated in the bending process in the fold area 10 can be further relieved by the hollow part 102, so that the heat dissipation material provided by the application has excellent bending resistance while taking heat dissipation performance into consideration, and the application of the heat dissipation material in electronic equipment is facilitated. In addition, in the heat dissipation material provided by the application, the graphene film is light and thin, so that when the graphene film is applied to electronic equipment, the weight and the volume of the electronic equipment cannot be obviously increased, and the light and thin of the electronic equipment are facilitated.
As can be appreciated, the corrugated structure 101 is a deformation exhibited by the graphene film bending when subjected to a force. In the heat dissipation material provided by the application, the graphene film has a plurality of fold structures 101, and the plurality of fold structures 101 can be stretched, bent, twisted and the like to a certain extent to realize the unfolding of the fold structures 101, so that the effect of the force applied to the heat dissipation material in the process is relieved, the heat dissipation material cannot break, and can be bent and deformed greatly, and the heat dissipation material is favorably applied to flexible electronic equipment, especially foldable electronic equipment. In an embodiment of the present application, before and after the corrugated structure 101 is completely unfolded, the ratio of the dimension of the corrugated structure 101 in the unfolding direction is 1: (2-5). That is, after the corrugated structure 101 is unfolded, the size in the unfolding direction is increased to 2-5 times, so that the heat dissipation material can be bent for more than 10 ten thousand times in the bending process with a bending angle of 180 degrees and a bending radius of 5 mm. Further, before and after the corrugated structure 101 is completely unfolded, the dimension ratio of the corrugated structure 101 in the unfolding direction is 1: (2-4). In another embodiment of the present application, the graphene film has a transverse direction and a longitudinal direction perpendicular to each other on a surface thereof, and before and after the pleated structure 101 is completely unfolded, a dimension ratio of the pleated structure 101 in the transverse direction is 1: (2-5), and/or the ratio of the dimensions of the corrugated structure 101 in the longitudinal direction is 1: (2-5). That is to say, the heat dissipation material that this application provided can bear and buckle in horizontal direction and/or longitudinal direction, and at the in-process of buckling, rugate structure 101 expandes, and the process of buckling can not produce too big effect to heat dissipation material itself, and then makes the heat dissipation material can apply to in the electronic equipment effectively.
In the present application, the shape of the corrugated structure 101 is determined by different manufacturing processes. In an embodiment of the present application, the corrugated structure 101 may be at least one of an arc shape, a conical shape and a zigzag shape, and may also be an irregular shape, and specifically, the desired corrugated structure 101 may be realized by controlling the manufacturing process. In the present application, the shape of the wrinkle structure 101 is not limited. In this application embodiment, a plurality of fold structures 101 are irregularly arranged on fold district 10, and preparation simple process, the fold district 10 that makes can satisfy the heat dissipation demand, can also compromise resistant performance of buckling simultaneously, satisfies heat sink material's application demand. In one embodiment of the present application, the pitch between adjacent corrugated structures 101 is 5 μm to 500 μm.
In the present embodiment, the corrugated structure 101 has a height of 20 μm to 500 μm and a width of 20 μm to 200 μm. Further, the height of the corrugated structure 101 is 30 μm to 450 μm, and the width is 30 μm to 180 μm. Further, the corrugated structure 101 has a height of 50 μm to 400 μm and a width of 50 μm to 150 μm. In the present application, the corrugated region 10 has a plurality of corrugated structures 101, and also has a leveling layer 103, and the leveling layer 103 is used to connect two adjacent corrugated structures 101. It is understood that the dimensions of the corrugated structure 101 are based on the planarization layer 103, and the height of the corrugated structure 101 is the distance between the point of the corrugated structure 101 farthest from the planarization layer 103 and the planarization layer 103. Referring to fig. 2, the height of the plurality of corrugated structures 101 in the corrugated area 10 is H1It is understood that the heights of the plurality of corrugated structures 101 may be the same or different; the thickness of the planarization layer 103 is H2. In this application, before and after the corrugated structure 101 is bent, that is, before and after the corrugated structure 101 is unfolded, an orthographic projection area of the corrugated structure 101 on a horizontal plane where the leveling layer 103 is located is increased, for example, but not limited to, the larger the height and the larger the width of the corrugated structure 101 are, the more the area increment after the unfolding is, the larger a deformation effect can be borne, and then the bending resistance of the heat dissipation material is improved, that is, the size of the corrugated structure 101 further improves the bending resistance of the heat dissipation material. The area of the orthographic projection of the corrugated structure 101 changes before and after deployment, that is, the area of the orthographic projection of the corrugated region 10 changesAnd (4) transforming. In this application, the area of the wrinkled region 10 is the area of the orthographic projection of the wrinkled region 10 on the horizontal plane of the flat region 20. In an embodiment of the present application, before and after the corrugated structure 101 is unfolded, the area ratio of the corrugated area 10 is 1: (2-25). Further, before and after the corrugated structure 101 is unfolded, the area ratio of the corrugated area 10 is 1: (2-12). Further, before and after the corrugated structure 101 is unfolded, the area ratio of the corrugated area 10 is 1: (3-8).
In the present embodiment, the corrugated structure 101 may be, but is not limited to, formed by extruding a graphene film. In an embodiment of the present application, the planarization layer 103 has a thickness greater than 60 μm. In one embodiment, the planarizing layer 103 has a thickness in a range of 60 μm to 100 μm. That is, the corrugated structure 101 is formed by bending a graphene film having a thickness of 60 μm to 100 μm by a force, for example, by pressing. In one embodiment, the wrinkled region 10 is formed by a graphene film, and the graphene film has a uniform thickness, so that the thickness of the planarization layer 103 is the same. With continued reference to FIG. 2, it will be appreciated that the thickness H of the crumple zone 100Is the thickness H of the corrugated structure 1011And the thickness H of the planarization layer 1032The maximum value of the sum. In another embodiment, the thickness of the crumpled zone 10 is 80 μm-600 μm. In embodiments of the present application, the graphene film has a thermal conductivity of greater than or equal to 1500W/(m.k), and an average density of greater than or equal to 1.8g/cm3The heat dissipation material has excellent heat conduction performance, and improves the heat dissipation performance of the heat dissipation material. In the application, the graphene film has excellent heat conducting performance, is relatively loose in the interior and has certain flexibility, but can still cause irreversible damage, such as fracture and the like, to the graphene film after being repeatedly bent for a long time, and particularly, the graphene film is more easily damaged due to a thicker graphene film. The graphene film provided by the application has a relatively thick thickness, can be repeatedly bent for a long time due to the corrugated structure 101, cannot be damaged by fracture and the like in the process, and has excellent flexibility and bending resistance.
In the present embodiment, the wrinkled region 10 of the graphene film is provided with a hollowed-out portion 102. In particular, the crumple zone 10 is provided with at least one cutout 102. The hollow-out portion 102 can effectively relieve the stress effect of the fold region 10 in the bending process, further improve the bending resistance of the heat dissipation material, and simultaneously give consideration to the heat dissipation performance of the heat dissipation material. In an embodiment of the present application, an area of the hollow portion 102 is 5% to 50% of an area of the wrinkle region 10, so that the bending-resistant times of the heat dissipation material in bending at a bending angle of 180 degrees and a bending radius of 5mm are greater than 10 ten thousand times. That is, the total area of all the hollowed-out portions 102 accounts for 5% -50% of the area of the unexpanded corrugated region 10. Furthermore, in order to achieve better heat dissipation and improve the heat dissipation performance of the heat dissipation material, the area of the hollow-out portion 102 is 5% to 30% of the area of the folded graphene film. Specifically, the area of the hollowed-out portion 102 may be, but is not limited to, 5%, 10%, 15%, 20%, 25%, 30% of the area of the folded graphene film. In the present application, the shape of the cross section of the hollow-out portion 102 may be, but is not limited to, at least one of a circle, an ellipse, a square, a rectangle and a diamond, and specifically, may be selected according to actual needs.
In the embodiment of the present application, the wrinkle region 10 includes a plurality of wrinkle sub-regions arranged at intervals, and the hollow portion 102 is arranged between adjacent wrinkle sub-regions. In an embodiment, the wrinkle region 10 is provided with a plurality of hollow-out portions 102, and the plurality of hollow-out portions 102 are disposed at intervals on the wrinkle region 10. Referring to fig. 1, the wrinkle area 10 is provided with a plurality of hollow-out portions 102, the hollow-out portions 102 are disposed at intervals on the wrinkle area 10, and the hollow-out portions 102 are regularly arranged on the wrinkle area 10. In another embodiment, please refer to fig. 3, which is a top view of the heat dissipation material according to an embodiment of the present disclosure, the corrugated region 10 includes a first corrugated sub-region 11 and a second corrugated sub-region 12 that are disposed at intervals, and the hollow portion 102 is disposed in the first corrugated sub-region 11 and the second corrugated sub-region 12. That is, the hollow portion 102 separates the first wrinkle subregion 11 and the second wrinkle subregion 12. In yet another embodiment, the wrinkle region 10 includes at least three wrinkle sub-regions arranged at intervals, and then the wrinkle region 10 has at least two hollows 102, and the hollows 102 are arranged between adjacent wrinkle sub-regions.
In the present embodiment, the heat dissipation material further includes an elastic body, and the elastic body is disposed on the surface of the wrinkle region 10. In the application, the graphene film has conductive performance, and the elastic body can protect the wrinkle region 10 to prevent the conductive performance, thereby being beneficial to the application of the heat dissipation material in electronic equipment. In an embodiment, the graphene film may be, but is not limited to, a graphene film having the wrinkled region 10 obtained by fixing the graphene film on an elastomer after stretching and releasing the elastomer, and in this case, the elastomer does not need to be peeled off, which further saves the preparation process of the heat dissipation material. In the present application, since the wrinkle area 10 has the hollow portion 102, the position of the elastic body corresponding to the hollow portion 102 can be hollowed, and when the elastic body is applied to the flexible electronic device, the stress generated inside the elastic body in the bending process can be reduced; and the elastomer can be free of hollowing, and can meet the application requirement because the elastomer has excellent bending resistance and is free of hollowing. In an embodiment of the present application, the material of the elastomer includes at least one of thermoplastic polyurethane and silicone. In one embodiment, the elastomer is adhesively bonded to the surface of the crumpled zone 10 by acrylic double-sided tape. In one embodiment of the present application, the elastomer has a thickness of 5 μm to 30 μm. The thickness of the elastic body is thinner, so that the weight of the heat dissipation material is not increased too much, and the application of the heat dissipation material is facilitated. Further, the thickness of the elastomer is 5 μm to 20 μm. Further, the elastomer has a thickness of 5 μm to 15 μm.
In the present embodiment, the graphene film further includes a flat region 20 adjacent to the wrinkled region 10. In one embodiment of the present application, the flat region 20 and the corrugated region 10 are a single structure. When the heat dissipation material is applied, the wrinkled area 10 may be disposed opposite to a bendable element, and the flat area 20 may be disposed opposite to an unbent element, so as to improve the heat dissipation range of the heat dissipation material, and facilitate the application thereof. In one embodiment of the present application, the planarized region 20 has a thermal conductivity greater than 1500W/(m.k) and an average density greater than or equal to 1.8g/cm3And has excellent heat dissipation performance. Further, the flat area 20 has a thermal conductivity of 1800W/(m.k) or more and an average density of 2g/cm or more3. In one embodiment of the present application, the planarized region 20 has a thickness of 60 μm to 100 μm.
In the present application, the graphene has conductivity, and in order to make the heat dissipation material better used in electronic devices, the graphene may further include a protective film, and the protective film is disposed on the surface of the planarization region 20. In an embodiment of the present application, a material of the protective film includes at least one of polyethylene terephthalate, polyvinylidene fluoride, polyimide, and polycarbonate. In one embodiment of the present application, the thickness of the protective film is 5 μm to 30 μm, which protects the planarization region 20 from conduction; meanwhile, the thickness of the protective film is thin, so that the weight of the heat dissipation material is not increased too much, and the application of the heat dissipation material is facilitated. Further, the thickness of the protective film is 5 μm to 20 μm. Further, the thickness of the protective film is 5 μm to 10 μm. Specifically, the thickness of the protective film is 5 μm, 7 μm, 8 μm, 9 μm, 15 μm, or 22 μm. In an embodiment of the present application, when the graphene film has a wrinkled region and a flat region, and the elastic body and the protective film are disposed at the same time, the elastic body and the protective film are disposed at the same side. Further, when the application is performed, a back adhesive is disposed on the surface of the leveling region 20 on the opposite side of the protective film, so that the heat dissipation material is disposed in the electronic device, and at this time, the back adhesive does not need to be disposed in the wrinkle region 10, which is more beneficial for the application.
In the heat dissipation material provided by the application, the graphene film has excellent heat dissipation performance, so that the heat dissipation performance of the heat dissipation material is greatly improved, the heat dissipation material is favorably applied to electronic equipment, and the heat dissipation of the electronic equipment is ensured and improved; meanwhile, the graphene film is provided with the fold area 10, the fold structure 101 can be unfolded in the bending process, damage to the heat dissipation material in the bending process is effectively avoided, the stress effect generated inside the fold area 10 in the bending process is further relieved by the hollow part 102, the bending resistance of the heat dissipation material is improved, and the application of the heat dissipation material in flexible electronic equipment is facilitated.
The application also provides a preparation method of the heat dissipation material, and the preparation method is used for preparing the heat dissipation material provided by any one of the embodiments. Referring to fig. 4, a schematic flow chart of a method for preparing a heat dissipation material according to an embodiment of the present application includes the following steps:
operation 101: providing an elastomer, and stretching the elastomer.
In operation 101, the size of the elastomer can be selected according to actual needs, for example, the thickness of the elastomer can be, but is not limited to, 5 μm to 30 μm. In one embodiment, the elastomer is stretched at a stretch ratio of 200% to 500%. Further, the stretching ratio is 220-400%. In another embodiment, stretching the elastomeric body comprises stretching the elastomeric body in the transverse direction and/or in the longitudinal direction. In one embodiment, the elastic modulus of the elastomer is greater than 500 MPa. Specifically, the material of the elastomer may be, but is not limited to, at least one of thermoplastic polyurethane and silicone.
Operation 102: providing a graphene film, and attaching the graphene film to the surface of the stretched elastomer.
In operation 102, providing the graphene film includes: providing a substrate and a graphene oxide solution, coating the graphene oxide solution on the surface of the substrate, drying, peeling off the substrate, and carbonizing and graphitizing to obtain the graphene film.
In an embodiment of the present application, providing a graphene oxide solution includes uniformly dispersing graphite oxide in water to obtain a graphite oxide solution; and then dissociating and crushing to obtain a graphene oxide solution. Further, defoaming treatment is carried out on the graphene oxide solution. In one embodiment, the graphite oxide solution has a pH of 6.5-7.5, a viscosity of 20000cps-35000cps, and a solid content of 5 wt% to 10 wt%. In one embodiment, the viscosity of the graphene oxide is 30000cps50000cps, wherein the viscosity of the graphene oxide is too high, and the subsequent film formation is not easy to occur due to high solid content; the viscosity is too low, the solid content is low, the thickness is thin during subsequent film forming, and the yield is low.
In an embodiment of the present application, the substrate may be, but not limited to, polypropylene mesh. The polypropylene fiber mesh cloth is formed by taking medium-alkali or alkali-free glass fiber mesh cloth as a base material and coating modified acrylate copolymerization glue solution, and has the characteristics of light weight, high strength, temperature resistance, alkali resistance, water resistance, corrosion resistance, cracking resistance, stable size and the like. Wherein the thickness of the substrate may be, but is not limited to, 100 μm to 1000 μm.
In an embodiment of the present application, the drying process may include drying the substrate coated with the graphene oxide solution at 50 ℃ to 100 ℃ for 10min to 60 min. The drying treatment can remove moisture and solvent in the graphene oxide solution, and is favorable for film formation. In a specific embodiment, the substrate coated with the graphene oxide solution is placed in a dryer having a plurality of drying tunnels to be dried. In an embodiment of the present application, a graphene oxide film is formed on the substrate after drying, and the graphene oxide film is peeled off from the substrate. Further, the graphene oxide film after peeling is dried again. When the graphene oxide film is peeled off from the substrate, humidity may be added for peeling, and thus the peeled graphene oxide film needs to be dried again to sufficiently remove moisture and solvent. Specifically, the drying time can be, but is not limited to, 1min to 10min at 80 ℃ to 150 ℃.
In an embodiment of the present application, the carbonizing includes placing the graphene oxide film in a carbonizing furnace, and carbonizing at 1200 ℃ -1800 ℃. In one embodiment of the present application, the graphitization treatment includes performing the graphitization treatment at 2300 deg.C to 3000 deg.C. In an embodiment of the present application, the method further includes performing a pressing process on the graphitized graphene film, specifically, but not limited to, the pressing process is performed at more than 10kgf/cm2And carrying out pressing treatment under pressure so as to improve the compactness of the graphene film and further improve the heat dissipation performance. In an embodiment of the present application, the obtained material may be cut, but not limited to, after any of the drying, carbonization, and graphitization steps are finished, so as to meet the requirements of practical applications.
In an embodiment of the present application, the graphene film has a thickness greater than 60 μm. Further, the graphene film has a thickness of 60 μm to 100 μm. In an embodiment of the present disclosure, the graphene film has a thermal conductivity greater than or equal to 1500W/(m-k) and an average density greater than or equal to 1.8g/cm3. Further, the graphene film has a thermal conductivity of more than 1800W/(m.k), and an average density of more than or equal to 2g/cm3。
In an embodiment of the present application, when the graphene film is attached to the surface of the stretched elastomer, the stretched elastomer may be fixed, and then the graphene film is attached to the surface of the stretched elastomer. Specifically, the graphene film is bonded to the surface of the stretched elastomer. In one embodiment, the graphene film is bonded to the surface of the stretched elastomer by acrylic double-sided tape. The stretch ratio of the stretched elastomer may be selected as needed, but is not limited to 200% to 500%. In the following examples, but not limited to, the graphene film was selected to be attached to the surface of the stretched elastomer at a stretch ratio of 350%. In one embodiment, the entire graphene film is attached to the surface of the stretched elastomer, or a portion of the graphene film may be attached to the surface of the stretched elastomer.
Operation 103: releasing the stretched elastomer, and extruding the graphene film to form a wrinkled area 10, wherein the wrinkled area 10 comprises a plurality of wrinkled structures 101.
In operation 103, the stretched elastomer is released, and the graphene film deforms as the elastomer retracts, forming the wrinkled region 10 with the wrinkled structure 101. The plurality of fold structures 101 can be unfolded under the stretching, bending, twisting and other actions to a certain degree, so that the action of force on the heat dissipation material in the process is relieved, the phenomenon of fracture of the heat dissipation material cannot occur, and large bending deformation can be presented. The stretch ratio of the elastomer affects the dimensional change of the pleated structure 101 before and after deployment. In actual operation, the release rates of the elastomers can be controlled to be the same or different, the change of the performance is compared, and the release rates are specifically selected according to actual needs. In an embodiment of the present application, before and after the corrugated structure 101 is completely unfolded, the ratio of the dimension of the corrugated structure 101 in the unfolding direction is 1: (2-5).
In an embodiment of the present application, the corrugated structure 101 may be at least one of an arc shape, a cone shape, and a zigzag shape, and may also be an irregular shape. In one embodiment of the present application, the spacing between adjacent corrugated structures 101 is 5 μm to 500 μm, the height of the corrugated structures 101 is 20 μm to 500 μm, and the width is 20 μm to 200 μm. In the present application, the corrugated region 10 has a plurality of corrugated structures 101, and also has a leveling layer 103, and the leveling layer 103 is used to connect two adjacent corrugated structures 101. In an embodiment of the present application, the planarization layer 103 has a thickness greater than 60 μm. In one embodiment, the planarizing layer 103 has a thickness in a range of 60 μm to 100 μm. In an embodiment of the present application, before and after the corrugated structure 101 is unfolded, the area ratio of the corrugated area 10 is 1: (2-25).
Operation 104: and peeling off the elastic body, and hollowing out the wrinkle area 10 to form a hollow-out part 102, so as to obtain the heat dissipation material.
In operation 104, the hollowed-out portion 102 may be formed by, but not limited to, performing a hollowed-out process by laser, knife molding, or the like. In particular, the crumple zone 10 is provided with at least one cutout 102. The hollow-out portion 102 can effectively relieve the stress effect of the fold region 10 in the bending process, further improve the bending resistance of the heat dissipation material, and simultaneously give consideration to the heat dissipation performance of the heat dissipation material. In an embodiment of the present application, the area of the hollow portion 102 is 5% to 50% of the area of the wrinkle region 10. Furthermore, in order to achieve better heat dissipation and improve the heat dissipation performance of the heat dissipation material, the area of the hollow-out portion 102 is 5% to 30% of the area of the folded graphene film. In the present application, the shape of the cross section of the hollow-out portion 102 may be, but is not limited to, circular, oval, square, rectangular, diamond, etc.
In an embodiment, the wrinkle region 10 includes a plurality of wrinkle sub-regions arranged at intervals, and the hollow portion 102 is arranged between adjacent wrinkle sub-regions. In another embodiment, the corrugated area 10 is provided with a plurality of hollow-outs 102, and the plurality of hollow-outs 102 are disposed at intervals on the corrugated area 10. The plurality of hollow-outs 102 may be, but is not limited to, regularly arranged on the wrinkle region 10.
In an embodiment of the present application, operation 104 may not be performed. The graphene film has conductive performance, the elastic body can protect the wrinkle region 10 to prevent the conductive performance, the application of the heat dissipation material in electronic equipment is facilitated, the elastic body does not need to be peeled off, and the preparation process of the heat dissipation material is saved.
In one embodiment of the present application, all of the graphene films are bonded to the surface of the stretched elastomer, and the formed graphene film has only the wrinkled regions 10. In another embodiment of the present application, a portion of the graphene film is attached to the surface of the stretched elastomer to form a graphene film comprising a wrinkled region 10 and a flat region 20 adjacent to the wrinkled region 10. In one embodiment, the thickness of the planarized region 20 is 60 μm to 100 μm. In the present application, the graphene has conductivity, and in order to make the heat dissipation material better used in electronic devices, the graphene may further include a protective film, and the protective film is disposed on the surface of the planarization region 20. In one embodiment, the material of the protective film includes at least one of polyethylene terephthalate, polyvinylidene fluoride, polyimide and polycarbonate, and the thickness of the protective film is 5 μm to 30 μm, so as to protect the flat region 20 from conduction; meanwhile, the thickness of the protective film is thin, so that the weight of the heat dissipation material is not increased too much, and the application of the heat dissipation material is facilitated.
In the preparation method provided by the application, the graphene film has excellent heat dissipation performance and compactness, and the performance of the heat dissipation material can be greatly improved; meanwhile, the graphene film also has a wrinkle region 10, and wrinkle combination and the hollow-out part 102 in the graphene film can improve the bending resistance of the heat dissipation material, thereby being beneficial to the application of the heat dissipation material.
The application also provides an electronic device, which comprises a bendable heating element 200 and a heat dissipation material 100 arranged on the heating element, wherein the heat dissipation material 100 is the heat dissipation material 100 prepared in any embodiment. It is understood that the electronic device may be, but is not limited to, a battery, a mobile phone, a tablet computer, a notebook computer, a watch, an MP3, an MP4, a GPS navigator, a bluetooth headset, a digital camera, etc., and particularly a flexible electronic device.
In an embodiment, the electronic device includes a bendable heating element 200 and a heat dissipation material 100 disposed on the heating element, the heat dissipation material 100 includes a graphene film, the graphene film includes a corrugated region 10, the corrugated region 10 includes a plurality of corrugated structures 101, and the corrugated region 10 is provided with a hollow portion 102, the corrugated region 10 is attached to the bendable heating element 200, so that the corrugated structures 101 on the corrugated region 10 can be unfolded along with the bendable heating element 200 during a bending process, thereby preventing the heat dissipation material 100 from being broken during the bending process, and meanwhile, the heat dissipation material 100 has excellent heat dissipation performance, and can effectively dissipate heat of the electronic device, thereby improving performance of the electronic device. Specifically, the bendable heat generating element 200 may be, but is not limited to, a bendable display screen or the like, and in the present application, the bendable heat generating element 200 includes, but is not limited to, a foldable, flexible or the like heat generating element. In another embodiment, the graphene film further includes a flat region 20 adjacent to the wrinkled region 10. It is understood that the bendable heat generating element 200 has a bending portion and a flat portion, the folded region 10 of the heat dissipating material 100 may correspond to the bending portion of the bendable heat generating element 200, and the flat region 20 may correspond to the flat portion of the heat generating element. Please refer to fig. 5, which is a schematic cross-sectional view illustrating a bonding arrangement of the bendable heating element 200 and the heat dissipation material 100 according to an embodiment of the present application, wherein the folding region 10 of the heat dissipation material 100 corresponds to a bending portion of the bendable heating element 200, and the leveling region 20 corresponds to a leveling portion of the bendable heating element 200, so as to achieve heat dissipation.
Example 1
(1) Preparation of graphene film
Preliminarily dispersing a graphite oxide filter cake with the solid content of 40-50% in deionized water, and then adjusting the pH value of the solution to 7.2 by using an alkaline solution; pre-dispersing by using a double-planet stirrer, wherein the viscosity of the obtained graphite oxide solution is 200000cps, and the solid content is 6.4 wt%.
And (3) physically dissociating and crushing by using a high-pressure homogenizer to obtain a uniform graphene oxide solution, wherein the viscosity of the obtained graphene oxide solution is about 40000cps, and defoaming treatment is carried out in vacuum by using a continuous vacuum centrifugal defoaming machine.
The graphene oxide solution is coated on a porous grid polypropylene substrate with the thickness of 0.4mm by adopting a scraper coating mode to form a graphene oxide film with the thickness of 2mm, and then the graphene oxide film is obtained by low-temperature baking through a baking channel of a coating machine, wherein the temperature of the baking channel (section 8) is 60 ℃, 70 ℃, 80 ℃, 75 ℃, 65 ℃ and 60 ℃.
And peeling and rolling the graphene oxide film from the substrate, and then cutting the graphene oxide film into sheets in sections.
And (3) stacking the graphite paper at intervals, placing the graphite paper in a graphite clamp, and placing the graphite clamp into an oven at the temperature of 130 ℃ for continuous vacuum baking.
And putting the preliminarily reduced graphene oxide film and the clamp into a carbonization furnace, and heating the graphene oxide film to 1500 ℃ from room temperature under the continuous vacuum condition for carbonization treatment.
And (3) putting the carbonized film into an electromagnetic induction high-temperature graphitization furnace, and quickly heating to 2850 ℃ under the protection of argon gas for graphitization treatment to obtain the graphene film.
And pressing the graphitized graphene film to obtain a compact graphene film, wherein the thickness of the graphene film is 80 μm.
(2) Forming a corrugated structure
Providing a Thermoplastic Polyurethane (TPU) elastomer, stretching the TPU elastomer, and bonding the middle part of the graphene film prepared in the way to the stretched TPU elastomer.
And releasing the TPU elastomer, and extruding and deforming the graphene film along with the retraction of the TPU elastomer to form a wrinkle area with a wrinkle structure and flat areas positioned on two sides of the wrinkle area.
(3) Hollowing out treatment
And hollowing out the prepared graphene film with the wrinkle area, forming a plurality of hollow parts arranged at intervals in the wrinkle area, wherein the area of each hollow part is 5% of that of the wrinkle area, and thus obtaining the heat dissipation material.
The heat dissipating material prepared as described above was examined and the structure of the wrinkle region was observed, and as a result, as shown in fig. 6, the wrinkle structures were irregularly arranged in the wrinkle region, and the widths of the wrinkle structures were measured at A, B points therein, which were 117.87 μm and 44.67 μm, respectively.
Example 2
The preparation process was substantially the same as that of example 1 except that the graphene film had a thickness of 60 μm.
Example 3
The preparation process was substantially the same as that of example 1 except that the graphene film had a thickness of 100 μm.
Example 4
The preparation process was substantially the same as that of example 3 except that the area of the hollowed-out portion was 30% of the area of the wrinkled region.
Example 5
The preparation process was substantially the same as that of example 3 except that the area of the hollowed-out portion was 40% of the area of the wrinkled region.
Comparative example 1
The preparation process was substantially the same as that of example 1, except that the step of forming the wrinkled structure was not performed, and thus a graphene film without a wrinkled structure was obtained.
Comparative example 2
The preparation process was substantially the same as that of example 3, except that no hollow-out treatment was performed, and a graphene film without a hollow-out portion was obtained.
Effects of the embodiment
The prepared heat dissipation material has high heat conductivity coefficient and good heat dissipation performance when subjected to heat conductivity coefficient detection. Meanwhile, the prepared heat dissipation material is bent for multiple times under the conditions of a bending angle of 180 degrees and a bending radius of 5mm, firstly, one point T1 and one point T2 are respectively selected from the flat areas at two sides of a graphene film fold area before bending, heating power and time are fixed, and the temperature difference delta T1 of T1 and T2 is calculated; after bending, heating T1 and T2 with the same power and time, calculating the temperature difference delta T2 of T1 and T2 again, analyzing the change of the temperature difference between T1 and T2 before and after bending, namely the change of delta T (| delta T1-delta T2|), and the change rate of the temperature difference before and after bending, namely the change rate of delta T (| delta T1-delta T2 |/delta T1), and comparing the bending resistance of the heat dissipation material, wherein the results are shown in Table 1.
TABLE 1 comparison of bending resistance of Heat sink materials
As can be seen from table 1, the heat dissipating material provided by the present application has excellent heat dissipating performance and bending resistance, wherein the Δ T change rate of the heat dissipating material in comparative example 1 without a wrinkle structure after being bent for 5 ten thousand times almost reaches 10%, which is similar to the Δ T change rate of the heat dissipating material provided by the present application after being bent for more than 10 ten thousand times, and the heat dissipating material in comparative example 1 attenuates after being bent for more than 10 ten thousand times by 21.4%, and the Δ T change rate reflects the attenuation of the heat dissipating material during the heat dissipating process. Therefore, compared with the comparative example 1, the fold structure in the heat dissipation material provided by the application can greatly improve the bending resistance of the heat dissipation material, so that the heat dissipation material still has lower attenuation after being bent for 10 ten thousand times, and the original heat dissipation performance is maintained to the maximum extent; meanwhile, compared with the comparative example 2, the hollow part in the heat dissipation material provided by the application can further relieve the application generated in the bending process, further reduce the delta T change rate, namely reduce the attenuation of the heat dissipation performance caused by bending, has excellent bending resistance, and ensures the heat dissipation performance. Meanwhile, the graphene film has more excellent heat dissipation performance and bending resistance when the thickness is 60-100 μm, the thinner graphene film slightly influences the heat dissipation performance of the heat dissipation material, and the thicker graphene film slightly influences the bending resistance of the heat dissipation material; when the area of the hollow-out part of the heat dissipation material is smaller than 50% of the area of the corrugated area, for example, when the area of the hollow-out part is smaller than 40% of the area of the corrugated area, or the area of the hollow-out part is smaller than or equal to 30% of the area of the corrugated area, the heat dissipation performance and the bending resistance of the heat dissipation material can be both considered, and the application of the heat dissipation material is facilitated.
The foregoing detailed description has provided for the embodiments of the present application, and the principles and embodiments of the present application have been presented herein for purposes of illustration and description only and to facilitate understanding of the methods and their core concepts; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (15)
1. The heat dissipation material is characterized by comprising a graphene film, wherein the graphene film comprises a wrinkle area, the wrinkle area comprises a plurality of wrinkle structures, the wrinkle area is provided with a hollow part, the area of the hollow part is 5% -50% of the area of the wrinkle area, the wrinkle structures are completely unfolded and then folded, and the dimension ratio of the wrinkle structures in the unfolding direction is 1: (2-5), wherein the area ratio of the corrugated areas is 1: (2-25), the height of the corrugated structure is 20-500 μm, and the width of the corrugated structure is 20-200 μm.
2. The heat dissipating material of claim 1, wherein a plurality of the corrugated structures are arranged irregularly in the corrugated region.
3. The heat dissipating material of claim 1, wherein the corrugated region has a thickness of 80 μm to 600 μm.
4. The heat dissipating material of claim 1, wherein the corrugated regions comprise a plurality of corrugated sub-regions arranged at intervals, and the hollowed-out portions are arranged between adjacent corrugated sub-regions.
5. The heat dissipating material of claim 1, wherein the corrugated region has a plurality of the hollowed-out portions, and the hollowed-out portions are spaced apart from each other on the corrugated region.
6. The heat dissipating material of claim 1, wherein the graphene film further comprises a flat region adjacent to the corrugated region.
7. The heat dissipating material of claim 6, wherein the planarized region has a thickness of 60 μm to 100 μm.
8. The heat dissipating material of claim 6, further comprising a protective film disposed on a surface of the planarized region.
9. The heat dissipating material of claim 8, wherein the protective film comprises at least one of polyethylene terephthalate, polyvinylidene fluoride, polyimide, and polycarbonate, and has a thickness of 5 μm to 30 μm.
10. The heat dissipating material of claim 1, further comprising an elastomer disposed on a surface of the corrugated region.
11. The heat dissipating material of claim 10, wherein the elastomer comprises at least one of thermoplastic polyurethane and silicone, and the elastomer has a thickness of 5 μm to 30 μm.
12. A method for preparing a heat dissipation material is characterized by comprising the following steps:
providing an elastomer, and stretching the elastomer;
providing a graphene film, and attaching the graphene film to the surface of the stretched elastomer;
releasing the stretched elastomer, and extruding the graphene film to form a corrugated area, wherein the corrugated area comprises a plurality of corrugated structures;
peeling off the elastic body, hollowing out the wrinkle area to form a hollow-out part, wherein the area of the hollow-out part is 5% -50% of the area of the wrinkle area, and a heat dissipation material is obtained, wherein before and after the wrinkle structure is completely unfolded, the size ratio of the wrinkle structure in the unfolding direction is 1: (2-5), wherein the area ratio of the corrugated areas is 1: (2-25), the height of the corrugated structure is 20-500 μm, and the width of the corrugated structure is 20-200 μm.
13. The method for producing a heat dissipating material of claim 12, wherein the elastic body is stretched at a stretch ratio of 200% to 500%.
14. The method of preparing a heat dissipating material of claim 12, wherein the providing a graphene film comprises:
providing a substrate and a graphene oxide solution, coating the graphene oxide solution on the surface of the substrate, drying, peeling off the graphene oxide solution from the substrate, and carbonizing and graphitizing to obtain the graphene film.
15. The electronic equipment is characterized by comprising a bendable heating element and a heat dissipation material arranged on the heating element, wherein the heat dissipation material comprises a graphene film, the graphene film comprises a wrinkle area, the wrinkle area comprises a plurality of wrinkle structures, the wrinkle area is provided with a hollow part, the area of the hollow part is 5% -50% of the area of the wrinkle area, the wrinkle structures are completely unfolded and back, and the size ratio of the wrinkle structures in the unfolding direction is 1: (2-5), wherein the area ratio of the corrugated areas is 1: (2-25), the height of the fold structure is 20-500 μm, the width is 20-200 μm, and the fold region is attached to the bendable heating element.
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| CN112767838B (en) * | 2021-01-19 | 2022-10-21 | Oppo（重庆）智能科技有限公司 | Flexible display screen and electronic equipment |
| CN113292971A (en) * | 2021-06-01 | 2021-08-24 | 江西德思恩新材料有限公司 | Artificial graphite film with enhanced tensile strength for heat dissipation function and preparation method thereof |
| CN113851047B (en) * | 2021-09-15 | 2023-12-29 | 武汉华星光电半导体显示技术有限公司 | Display panel, manufacturing method thereof and mobile terminal |
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