An aerogel-graphene composite thermally conductive and heat-dissipating backplate

Abstract

This invention relates to the field of semiconductor display technology, specifically to an aerogel-graphene composite thermally conductive backplate. The backplate includes: a flexible substrate layer; an aerogel-graphene composite thermally conductive layer disposed thereon, comprising a three-dimensional porous aerogel framework with a porosity >90% and graphene distributed within the framework and overlapping to form a three-dimensional thermally conductive network, used to form efficient thermally conductive pathways in the X-Y plane to achieve heat homogenization, and to form a thermal barrier in the Z-axis normal direction to prevent vertical heat conduction; and an electromagnetic shielding layer disposed on the composite thermally conductive layer. This invention combines the super-insulating properties of aerogel with the super-conductive properties of graphene to construct an anisotropic thermally conductive structure. While achieving ultra-thinness, ultra-lightness, and high flexibility, it also possesses efficient in-plane heat homogenization, normal thermal insulation, and electromagnetic shielding functions. It can withstand repeated bending without failure, significantly improving the thermal management efficiency and service life of flexible display devices.

Description

Technical Field

[0001] This invention relates to the field of semiconductor display technology, specifically to an aerogel-graphene composite thermally conductive and heat-dissipating backplate. Background Technology

[0002] With the rapid development of flexible display technology, flexible display devices such as foldable phones, rollable TVs, and wearable devices are gradually becoming more common. These devices place stringent requirements on the integration, thinness, and mechanical reliability of their internal components. Among these, the effective management of the large amount of heat generated by high-performance chips (such as CPUs and GPUs) during operation has become a bottleneck problem that restricts device performance, affects display quality, and impacts user experience.

[0003] Traditional heat dissipation solutions, such as metal heat sinks (copper, aluminum), graphite heat dissipation films, or heat pipes / vapor chambers, have significant limitations when applied to flexible display devices. First, while metal vapor chambers offer high thermal conductivity, their rigid structure makes them unsuitable for the thousands of bends required by flexible devices, leading to fatigue fracture or detachment from surrounding structures under repeated deformation. Second, while graphite heat dissipation films possess some flexibility and in-plane thermal conductivity, their normal (thickness direction) thermal conductivity is also relatively high. This allows heat to be easily conducted vertically to the screen display area or the device casing, causing localized overheating. This negatively impacts the user experience and the stability of the display module, exhibiting a "heat conduction and temperature conduction" problem, making targeted thermal management impossible.

[0004] To address the heat dissipation problem of flexible devices, existing technologies have attempted to apply aerogel materials to electronic device heat dissipation. For example, current technologies utilize their nanoporous structure to achieve efficient thermal insulation. However, pure aerogel materials are poor conductors of heat and cannot quickly dissipate heat accumulated at hot spots such as chips, leading to heat buildup and failing to achieve a "uniform heat distribution" effect. In addition, some studies have combined graphene with polymers in hopes of obtaining thermally conductive materials, but it is usually difficult to construct an anisotropic thermally conductive structure that combines efficient in-plane thermal conductivity and normal thermal insulation while maintaining ultra-flexibility.

[0005] In summary, current technologies lack a comprehensive heat dissipation backplate solution that can simultaneously meet the multiple requirements of flexible display devices, including ultra-thinness, ultra-lightweight design, high flexibility, efficient in-plane heat dissipation, normal thermal insulation, and electromagnetic shielding. How to rapidly convert point heat sources into surface heat sources for diffusion within a limited space, while simultaneously blocking vertical heat conduction and ensuring the reliability of the material under dynamic bending, is a pressing technical challenge that needs to be addressed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention discloses an aerogel-graphene composite thermally conductive and heat-equalizing backplate, which overcomes the defects of traditional metal heat sinks that cannot be bent, graphite heat dissipation films that have high normal thermal conductivity leading to localized overheating of the screen, and pure aerogel insulation materials that cannot achieve lateral heat diffusion.

[0007] This invention is achieved through the following technical solution: The present invention provides an aerogel-graphene composite thermally conductive and heat-spreading backplate for flexible display devices, comprising a flexible substrate layer, an aerogel-graphene composite thermally conductive layer, and an electromagnetic shielding layer.

[0008] Specifically, the flexible substrate layer serves as a support carrier for the entire backsheet, providing initial mechanical strength and flexibility.

[0009] The aerogel-graphene composite thermally conductive layer is disposed on one side surface of the flexible substrate. This composite thermally conductive layer is composed of a three-dimensional porous aerogel framework and graphene material uniformly distributed within the aerogel framework and interconnected to form a three-dimensional thermally conductive network. The aerogel framework has a porosity greater than 90%, and its nanoporous structure effectively inhibits the convection and conduction of air molecules, thereby forming a highly efficient thermal barrier in the Z-axis direction perpendicular to the backplane plane, preventing heat transfer to the screen side. The three-dimensional thermally conductive network formed by the interconnected graphene material is used to construct efficient thermally conductive pathways in the XY-axis directions parallel to the backplane plane, rapidly diffusing heat from heat sources such as chips laterally, realizing the conversion from a "point heat source" to a "surface heat source," achieving a uniform heat distribution effect.

[0010] The electromagnetic shielding layer is disposed on the side surface of the aerogel-graphene composite thermally conductive layer opposite to the flexible substrate layer, and is used to provide electromagnetic shielding for the flexible display device, prevent high-frequency signals of the internal circuit from interfering with the display drive, and protect the device from external electromagnetic interference.

[0011] As a further improvement of the present invention, the backplate may further include an interface bonding layer disposed between the flexible substrate layer and the aerogel-graphene composite thermally conductive layer. The interface bonding layer is preferably composed of a flexible thermally conductive adhesive, which serves to ensure that the composite thermally conductive layer can adhere tightly and firmly to the flexible substrate, reduce contact thermal resistance, maintain good adhesion during repeated bending, and prevent interlayer delamination.

[0012] As a preferred embodiment of the present invention, the flexible substrate layer may be made of one or more of polyimide (PI) or polyethylene naphthalate (PEN), and its thickness is preferably 10-100 micrometers to ensure sufficient support strength and flexibility.

[0013] As a further limitation of the present invention, the material of the aerogel framework may be selected from silica aerogel or polymer-based aerogel; the graphene material may be selected from one or more of graphene nanosheets, reduced graphene oxide or graphene foam.

[0014] In terms of preparation process, the aerogel-graphene composite thermally conductive layer can be obtained through in-situ composite process or impregnation composite process. When using the in-situ composite process, graphene oxide can be dispersed in an aerogel precursor sol, forming a composite wet gel through sol-gel transformation. Then, a supercritical drying process is used to simultaneously achieve in-situ reduction of graphene oxide and formation of the aerogel framework, thereby obtaining a composite structure integrating the aerogel framework and the three-dimensional thermally conductive network. When using the impregnation composite process, a three-dimensional porous aerogel framework can be prepared first, and then impregnated in a dispersion containing graphene material. Through capillary action, the graphene material is adsorbed and anchored to the pore wall surface of the aerogel framework, thus constructing a three-dimensional thermally conductive network.

[0015] To achieve excellent thermal management performance, the thickness of the aerogel-graphene composite thermally conductive layer is preferably 50-500 micrometers, and its thermal conductivity in the XY axis direction can be greater than 500 W / m·K, while its thermal conductivity in the Z axis direction can be less than 0.1 W / m·K.

[0016] Regarding electromagnetic shielding, the electromagnetic shielding layer can be a transparent conductive oxide film, a metal mesh layer, or a continuous conductive network formed by conductive fillers (such as metal nanowires or conductive carbon black) doped in the aerogel-graphene composite thermally conductive layer. Preferably, the electromagnetic shielding layer has an electromagnetic shielding effectiveness greater than 30 dB in the frequency range of 30 MHz to 3000 MHz.

[0017] As a comprehensive and preferred solution, the overall thickness of the backplate can be controlled to be less than 0.5 mm, and after 100,000 repeated bending tests with a bending radius of 5 mm, its thermal conductivity attenuation rate in the XY axis direction is less than 5%. Furthermore, there is no delamination or peeling between the electromagnetic shielding layer, the aerogel-graphene composite thermally conductive layer, and the flexible substrate layer, thus ensuring its reliability throughout the entire lifecycle of the flexible display device.

[0018] The beneficial effects of this invention are as follows: This invention combines graphene, which has ultra-high in-plane thermal conductivity, with aerogel, which has ultra-low thermal conductivity, to construct an anisotropic thermally conductive structure that combines "highly efficient thermal conductivity" and "super thermal insulation." During operation, heat rapidly diffuses along the graphene network within the backplane plane, achieving uniform heat distribution and eliminating localized hotspots. Simultaneously, the nanoporous structure of the aerogel forms a highly efficient thermal insulation barrier in the normal direction, effectively preventing heat transfer to the screen or casing. This truly achieves directional thermal management that "conducts heat but not temperature," significantly improving user feel and screen display stability.

[0019] The design, combining a flexible polymer substrate with a porous composite thermally conductive layer, endows the back panel with exceptional flexibility and mechanical stability. Through optimized design of the interface bonding layer and the inherent flexibility of each material layer, the back panel can withstand thousands of dynamic bends without failure, perfectly meeting the demanding requirements of various flexible display devices, including foldable and rollable models.

[0020] This invention achieves efficient thermal management while integrating electromagnetic shielding, effectively solving the electromagnetic interference problem caused by the limited internal space and dense components of flexible devices. Through an integrated multi-layer structure design, it avoids the thickness and weight burden of adding an extra shielding layer, resulting in a final product that is both ultra-thin (overall thickness less than 0.5 mm) and ultra-light, perfectly aligning with the trend towards thinner and lighter flexible electronic devices.

[0021] Through optimized material ratios, structural parameters, and process control, the backplate of this invention exhibits significantly superior overall performance compared to existing technologies in key performance indicators such as thermal conductivity, electromagnetic shielding effectiveness, and mechanical reliability, demonstrating extremely high industrial application value and market prospects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic cross-sectional view of an aerogel-graphene composite thermally conductive and heat-dissipating backplate for a flexible display device, provided in an embodiment of the present invention.

[0024] Figure 2 for Figure 1 A schematic diagram of the microstructure of the aerogel-graphene composite thermally conductive layer is used to demonstrate the composite relationship between the graphene three-dimensional thermally conductive network and the porous aerogel framework and its thermal conductivity mechanism.

[0025] In the picture: 1. Flexible substrate layer; 2. Interface bonding layer; 3. Composite thermal conductive layer; 4. Metal mesh electromagnetic shielding layer. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0027] This embodiment provides an aerogel-graphene composite thermally conductive and heat-dissipating backplate for flexible display devices, the structure of which is as follows: Figure 1 As shown.

[0028] 1. Fabrication of the flexible substrate: A 50-micron thick polyimide (PI) film was selected as the flexible substrate. This film has a tensile strength greater than 200 MPa and an elongation at break greater than 30% at 20°C, providing good mechanical support for subsequent functional layers.

[0029] 2. Preparation of the aerogel-graphene composite thermally conductive layer (in-situ composite process): First, prepare the aerogel precursor sol: mix tetraethyl orthosilicate (TEOS), ethanol, deionized water, and hydrochloric acid in a molar ratio of 1:8:4:0.01 and stir at 60°C for 2 hours to obtain a silica sol. Second, introduce the graphene precursor: ultrasonically disperse graphene oxide (GO) in the above sol, with the amount of GO added being 5% of the final composite layer solid mass. Continue stirring for 30 minutes to ensure uniform dispersion of GO. Then, perform the sol-gel transition: pour the mixed sol into a mold, add ammonia to adjust the pH to 7.5, and allow it to stand to gel, forming a composite wet gel. Finally, perform supercritical drying: place the composite wet gel in an autoclave and perform supercritical drying with CO2 (temperature 40°C, pressure 10 MPa), achieving thermal reduction of GO while removing the solvent, to obtain the aerogel-graphene composite thermally conductive layer. The thickness of the obtained composite thermally conductive layer is approximately 200 micrometers. The microstructure of the aerogel-graphene composite thermal conductive layer is as follows: Figure 2 As shown.

[0030] 3. Fabrication of the electromagnetic shielding layer: A transparent conductive film of indium tin oxide (ITO) with a thickness of about 100 nanometers was deposited on the surface of the composite thermally conductive layer using magnetron sputtering as the electromagnetic shielding layer.

[0031] 4. Lamination and bonding: The prepared composite thermally conductive layer with the ITO film side facing up is bonded to the PI flexible substrate through a layer of silicon-based thermally conductive adhesive with a thickness of about 5 micrometers. After low-temperature hot pressing and curing at 60°C, the final aerogel-graphene composite thermally conductive and heat-dissipating backplate is obtained. Example 2

[0032] This embodiment provides another aerogel-graphene composite thermally conductive and heat-spreading backplate, which adds an interface bonding layer and uses an impregnation composite process to prepare the core layer.

[0033] 1. Preparation of flexible substrate: A 25-micron thick polyethylene naphthalate (PEN) film was selected as the flexible substrate.

[0034] 2. Preparation of the interface bonding layer: A layer of acrylate thermally conductive pressure-sensitive adhesive with a thickness of 2 micrometers is coated on the surface of the PEN film as an interface bonding layer for later use.

[0035] 3. Preparation of the aerogel-graphene composite thermally conductive layer (impregnation composite process): First, the aerogel framework was prepared independently: using resorcinol and formaldehyde as precursors, a polymer-based aerogel framework was obtained through sol-gel, aging, and supercritical CO2 drying, with a porosity of approximately 95% and a density of approximately 0.1 g / cm³. Second, a graphene impregnation solution was prepared: graphene nanosheets (thickness <5 nm, diameter 1-5 μm) were ultrasonically dispersed in ethanol to prepare a dispersion with a mass fraction of 0.5%. Then, impregnation composite was performed: the above polymer aerogel framework was immersed in the graphene dispersion and soaked for 12 hours under normal pressure, allowing the graphene nanosheets to be fully adsorbed onto the pore wall surface of the aerogel framework through capillary action. After removal, it was vacuum dried at 60℃ to remove the solvent. By controlling the number of impregnations (3 times in this example), the graphene loading reached 8% of the total mass of the composite layer, thereby constructing a continuous three-dimensional thermally conductive network inside the aerogel framework (321). The resulting composite thermally conductive layer has a thickness of approximately 150 micrometers.

[0036] 4. Preparation of electromagnetic shielding layer: Silver nanowires (approximately 30 nm in diameter and 20 μm in length) were dispersed in isopropanol to prepare an ink with a concentration of 1 mg / mL. A grid pattern (10 μm grid line width and 200 μm grid spacing) was printed on the surface of the composite thermally conductive layer using inkjet printing technology. After drying, a metal grid electromagnetic shielding layer was formed.

[0037] 5. Lamination and bonding: The PEN substrate with the interface bonding layer is aligned and bonded with the composite thermally conductive layer with the electromagnetic shielding layer. A pressure of 0.1 MPa is applied and the layers are cured at 50°C for 4 hours to ensure that the layers are tightly bonded, thus obtaining the final back sheet. Performance Testing and Comparison

[0038] To verify the beneficial effects of the present invention, the performance of the backplates prepared in Examples 1 and 2 was tested, and a commercially available brand of artificial graphite heat dissipation film (Comparative Example 1) and a pure silica aerogel heat insulation sheet (Comparative Example 2) were used as comparisons.

[0039] Test method: Thermal conductivity test: The thermal diffusivity of the sample in the XY direction (in-plane) and Z direction (normal) was tested using the laser flare method (LFA 467, Netzsch). The corresponding thermal conductivity was calculated by combining the specific heat capacity and density.

[0040] Electromagnetic shielding effectiveness test: The shielding effectiveness (SE) of the samples was tested in the frequency range of 30MHz-3000MHz using the flange coaxial method.

[0041] Flexibility and reliability testing: The sample was cut into strips of 100mm × 20mm and fixed on a bending tester. It was repeatedly folded at a bending radius of 5mm and a speed of once per second. After every 10,000 bends, the change in thermal conductivity in the X and Y directions was measured, and the cross-section was observed for delamination using a scanning electron microscope. A total of 100,000 tests were conducted.

[0042] Test results: Test Project Example 1 Example 2 Comparative Example 1 (Graphite Film) Comparative Example 2 (Aerogel Sheet) Thermal conductivity in the XY direction (W / m·K) 680 750 1100 0.03 Thermal conductivity in the Z direction (W / m·K) 0.08 0.06 15 0.02 Electromagnetic shielding effectiveness @1GHz (dB) 32 38 0 (Unblocked) 0 (Unblocked) Thermal conductivity decay rate after 100,000 bends 3.2% 2.1% Fracture (20,000 times) Shattering (5,000 times) Appearance after 100,000 bends No layering No layering Fracture failure Fracture failure Results analysis and discussion: Anisotropy of thermal conductivity: As can be seen from the data in the table, although Comparative Example 1 (graphite film) has extremely high in-plane thermal conductivity (1100 W / m·K), its normal thermal conductivity is also as high as 15 W / m·K. This means that a large amount of heat will be conducted vertically to the screen surface, causing the problem of "conducting heat but also conducting temperature". Comparative Example 2 (aerogel sheet) is the opposite. Although it has excellent normal thermal insulation performance (0.02 W / m·K), its in-plane thermal conductivity is extremely low, which cannot achieve lateral heat diffusion, resulting in heat accumulation at the heat source. In contrast, Examples 1 and 2 of this invention successfully achieved anisotropic thermal conductivity of "high in-plane thermal conductivity and super normal thermal insulation". The thermal conductivity in the XY direction is greater than 500 W / m·K, while the thermal conductivity in the Z direction is less than 0.1 W / m·K, perfectly balancing the dual requirements of "uniform heat" and "thermal insulation".

[0043] Electromagnetic shielding function: Comparative Examples 1 and 2 do not have electromagnetic shielding function. However, the embodiments of the present invention, through the setting of ITO transparent conductive film (Example 1) or silver nanowire mesh (Example 2), enable the electromagnetic shielding effectiveness of the backplane in the 1GHz frequency band to reach 32dB and 38dB respectively (>99.9% of electromagnetic waves are shielded), which meets the electromagnetic compatibility requirements of flexible electronic devices.

[0044] Flexible Reliability: In the rigorous bending test, Comparative Example 1, as a graphite film, although initially possessing a certain degree of flexibility, fractured completely after 20,000 bends. Comparative Example 2, due to the brittleness of pure aerogel, broke after 5,000 bends. In contrast, Examples 1 and 2 of this invention, after undergoing 100,000 bends, not only showed no macroscopic delamination or detachment, but also exhibited a decrease in core thermal conductivity of only 3.2% and 2.1%, respectively, demonstrating extremely excellent dynamic bending reliability and structural stability. This is attributed to the support of the flexible substrate, the buffering and bonding of the interface bonding layer, and the constraint and protection of the graphene network (321) by the aerogel framework (310). Example 3

[0045] This embodiment aims to verify the influence of different material parameters on the performance of the backsheet.

[0046] 3a: Effect of Different Substrate Thicknesses Following the preparation method of Example 2, PEN films with thicknesses of 10 μm, 50 μm, and 100 μm were used as flexible substrate layers. Test results showed that substrate thickness had a slight impact on the overall thermal resistance of the backsheet. More importantly, a 10 μm substrate made the backsheet more flexible and better conformable, but it was prone to wrinkling during operation. A 100 μm substrate provided stronger support but slightly increased the overall stiffness of the backsheet. A thickness of 50 μm achieved the best balance between flexibility and support.

[0047] 3b: Effect of Different Composite Layer Thicknesses Following the preparation method of Example 1, aerogel-graphene composite thermally conductive layers with thicknesses of 50 μm, 300 μm, and 500 μm were prepared by controlling the parameters of the coating or drying process. Tests revealed that as the composite layer thickness increased, the in-plane thermal conductivity in the XY directions decreased slightly (due to the longer heat conduction path in the thickness direction), but the thermal insulation performance in the Z direction was superior (lower thermal conductivity). The sample with a thickness of 500 μm exhibited a Z-direction thermal conductivity as low as 0.05 W / m·K. However, excessively thick composite layers increase the overall thickness of the backplate, which is detrimental to the thinning and lightening of flexible devices. Therefore, a thickness within the range of 50-500 μm can be selected based on the space and heat dissipation requirements of the specific device.

[0048] 3c: The effect of different graphene contents. Referring to the impregnation process in Example 2, composite thermally conductive layers with graphene mass fractions of 2%, 5%, 8%, and 12% were obtained by controlling the number of impregnations. Test results showed that when the graphene content was below 2%, an effective three-dimensional thermally conductive network failed to form, and the XY thermal conductivity was only about 80 W / m·K; when the content reached 5%, the thermally conductive network was initially formed, and the XY thermal conductivity increased to 450 W / m·K; when the content was 8%, the network was complete, and the thermal conductivity reached 750 W / m·K; when the content increased to 12%, the thermal conductivity increased to 820 W / m·K, but at this time the pore structure of the aerogel skeleton was over-filled, resulting in an increase in density, and the Z thermal conductivity also increased slightly (to 0.09 W / m·K), and the material flexibility decreased slightly. Taking all factors into consideration, controlling the graphene mass fraction between 5% and 10% is the preferred option.

[0049] In summary, this invention, through its unique layered composite structure design, particularly the core aerogel-graphene composite thermally conductive layer, successfully solves the problem in existing flexible display device heat dissipation solutions that cannot simultaneously achieve flexibility, efficient in-plane heat dissipation, normal thermal insulation, and electromagnetic shielding. The above embodiments are merely preferred embodiments of this invention, but the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this invention, such as replacing the aerogel material with other polymer aerogels or carbon aerogels, or forming the electromagnetic shielding layer by coating, electroplating, or other methods, as long as the core structural principles disclosed in this invention are adopted, should be covered within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An aerogel-graphene composite thermally conductive backsheet, characterized in that, The backplane comprises: a flexible substrate layer for providing mechanical support; an aerogel-graphene composite thermal conductive layer disposed on one side surface of the flexible substrate layer, the aerogel-graphene composite thermal conductive layer is composed of a three-dimensional porous aerogel skeleton and graphene material uniformly distributed inside the aerogel skeleton and interlaced to form a three-dimensional thermal conductive network; the porosity of the aerogel skeleton is greater than 90%, for forming a thermal insulation barrier in the Z-axis direction perpendicular to the backplane; the three-dimensional thermal conductive network of the graphene material is for forming a high-efficiency thermal conductive path in the X-Y-axis direction parallel to the backplane; an electromagnetic shielding layer disposed on the side surface of the aerogel-graphene composite thermal conductive layer away from the flexible substrate layer, for providing electromagnetic shielding function for the flexible display device.

2. The aerogel-graphene composite thermally conductive and uniform heat back sheet according to claim 1, characterized in that, Further comprising an interface bonding layer disposed between the flexible substrate layer and the aerogel-graphene composite thermal conductive layer, for firmly adhering the aerogel-graphene composite thermal conductive layer to the flexible substrate layer; the interface bonding layer is composed of a flexible thermal conductive adhesive.

3. The aerogel-graphene composite thermally conductive and uniform heating backplane according to claim 1 or 2, characterized in that, The flexible substrate layer is made of one or more of polyimide (PI) or polyethylene naphthalate (PEN), and the thickness is 10-100 microns.

4. The aerogel-graphene composite thermally conductive and uniform heating backplane according to claim 1 or 2, characterized in that, The material of the aerogel skeleton is silica aerogel or polymer-based aerogel; the graphene material is one or more of graphene nanosheet, reduced graphene oxide or graphene foam.

5. The aerogel-graphene composite thermally conductive and uniform heat back sheet according to claim 4, characterized in that, The aerogel-graphene composite thermal conductive layer is prepared by in-situ composite process, that is, dispersing graphene oxide in aerogel precursor sol, forming composite wet gel through sol-gel transition, and simultaneously realizing in-situ reduction of graphene oxide and formation of aerogel skeleton through supercritical drying process, so as to obtain the composite structure of the aerogel skeleton and the three-dimensional thermal conductive network.

6. The aerogel-graphene composite thermally conductive and uniform heat back sheet according to claim 4, wherein, The aerogel-graphene composite thermal conductive layer is prepared by impregnation composite process, that is, first preparing the three-dimensional porous aerogel skeleton, then immersing it in a dispersion liquid containing graphene material, and through capillary action, the graphene material is adsorbed and anchored on the pore wall surface of the aerogel skeleton, so as to construct the three-dimensional thermal conductive network.

7. The aerogel-graphene composite thermally conductive and uniform heat back sheet according to claim 1 or 2, characterized in that, The thickness of the aerogel-graphene composite thermal conductive layer is 50-500 microns, the thermal conductivity in the X-Y-axis direction is greater than 500 W / m·K, and the thermal conductivity in the Z-axis direction is less than 0.1 W / m·K.

8. The aerogel-graphene composite thermally conductive and uniform heat back sheet according to claim 1 or 2, characterized in that, The electromagnetic shielding layer is a layer of transparent conductive oxide film, metal mesh layer or continuous conductive network formed by conductive fillers doped in the aerogel-graphene composite thermal conductive layer; the conductive fillers are metal nanowires or conductive carbon black.

9. The aerogel-graphene composite thermally conductive and uniform heat back sheet according to claim 8, characterized in that, The electromagnetic shielding efficiency of the electromagnetic shielding layer in the frequency range of 30 MHz to 3000 MHz is greater than 30 dB.

10. The aerogel-graphene composite thermally conductive and uniform heat back sheet according to claim 1 or 2, characterized in that, The thickness of the backplane as a whole is less than 0.5 mm, and after 100,000 times of repeated bending test with a bending radius of 5 mm, the thermal conductivity attenuation rate in the X-Y-axis direction is less than 5%, and there is no delamination or peeling phenomenon between the electromagnetic shielding layer, the aerogel-graphene composite thermal conductive layer and the flexible substrate layer.

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