Transparent directional heat conduction element, its preparation method and application

Abstract

This invention relates to transparent directional heat-conducting components, their preparation methods, and applications. The preparation method includes: providing a transparent conductive film of metal nanowires comprising a layered transparent substrate and a layer of metal nanowires; preparing a first dispersion by mixing thermally conductive powder, magnetic powder, PVDF powder, and an organic solvent; preparing one-dimensional nanofibers from the first dispersion using a spinning process; mixing the one-dimensional nanofibers with DMF to obtain a one-dimensional nanofiber dispersion, and then ultrasonically mixing it with a resin solution to obtain a second dispersion; forming a coating on the surface of the metal nanowire layer using the second dispersion, while continuously applying a directional magnetic field perpendicular to the metal nanowire layer; and obtaining a transparent directional heat-conducting component after curing, wherein the coating thickness is greater than the length of the one-dimensional nanofibers, and the magnetic field strength of the directional magnetic field is 0.05T-5T. This preparation method enables the transparent directional heat-conducting component to maintain a high light transmittance of over 90% while achieving directional heat conduction and excellent thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of transparent conductive thin film technology, and in particular to a transparent directional heat-conducting element, its preparation method, and its application. Background Technology

[0002] When metal nanowire transparent conductive films are used in heaters, the total heat generation can be increased by reducing sheet resistance, or the required large temperature rise on the outer surface can be achieved by increasing the thermal conductivity of the protective layer (OCA layer) and reducing lateral thermal conductivity. One way to reduce lateral thermal conductivity is to create directional heat conduction. Traditional methods typically use a strong magnetic field to guide the directional distribution of magnetic materials to achieve directional heat conduction. However, this directional distribution method is selective for magnetic materials, and the magnetic materials have low thermal conductivity. Furthermore, it affects the light transmittance of the metal nanowire transparent conductive film, leading to reduced image clarity when used in camera windows. Summary of the Invention

[0003] Therefore, it is necessary to provide a transparent directional heat conduction element, its preparation method, and its application to address the above problems; the preparation method enables the transparent directional heat conduction element to achieve directional heat conduction and excellent heat transfer effect while maintaining a high light transmittance of over 90%.

[0004] A method for fabricating a transparent directional heat-conducting component includes the following steps:

[0005] A transparent conductive film of metal nanowires is provided, the transparent conductive film of metal nanowires comprising a transparent substrate and a metal nanowire layer stacked thereon;

[0006] A first dispersion was prepared by mixing thermally conductive powder, magnetic powder, polyvinylidene fluoride powder, and organic solvent. The first dispersion was then used to prepare one-dimensional nanofibers by spinning.

[0007] The one-dimensional nanofibers were mixed with N,N-dimethylformamide solvent to obtain a one-dimensional nanofiber dispersion, and then the one-dimensional nanofiber dispersion was ultrasonically mixed with a resin solution to obtain a second dispersion.

[0008] A coating is formed on the surface of the metal nanowire layer using the second dispersion, while a directional magnetic field perpendicular to the metal nanowire layer is continuously applied. After curing, a transparent directional heat-conducting component is obtained, wherein the thickness of the coating is greater than the length of the one-dimensional nanofiber, and the magnetic field strength of the directional magnetic field is 0.05T-5T.

[0009] In one embodiment, the length of the one-dimensional nanofiber is 200nm-500nm;

[0010] And / or, the thickness of the coating is 600nm-1200nm.

[0011] In one embodiment, the mass ratio of the polyvinylidene fluoride powder to the thermally conductive powder and the magnetic powder is 1:(0.1-0.5):(0.1-0.5).

[0012] In one embodiment, the total mass of the thermally conductive powder and the magnetic powder is 15%-60% of the mass of the first dispersion.

[0013] And / or, the mass fraction of the one-dimensional nanofibers in the one-dimensional nanofiber dispersion is 15%-65%;

[0014] And / or, the one-dimensional nanofibers have a mass fraction of 5%-40% in the second dispersion.

[0015] In one embodiment, the particle size of the thermally conductive powder is 20nm-50nm;

[0016] And / or, the particle size of the magnetic powder is 50nm-100nm.

[0017] In one embodiment, the ultrasonic frequency of the ultrasonic mixture is 10Hz-20Hz.

[0018] In one embodiment, during the step of continuously applying a directional magnetic field perpendicular to the metal nanowire layer, the magnetic field strength of the directional magnetic field increases, and the increasing magnetic field strength is selected from any range of 0.05T-5T.

[0019] And / or, the magnetic field strength of the directional magnetic field is constant, and the magnetic field strength is at least 0.5T.

[0020] In one embodiment, the metal nanowire layer has a diameter of 10 nm-500 nm and an aspect ratio of 200-2000.

[0021] And / or, the thickness of the metal nanowire layer is 200nm-2000nm;

[0022] And / or, the transmittance of the transparent conductive film of the metal nanowire is 90%-95%;

[0023] And / or, the metal nanowires in the metal nanowire layer are selected from silver nanowires or copper nanowires.

[0024] A transparent directional heat-conducting element prepared by the method described above includes a transparent substrate, and a metal nanowire layer and a transparent directional heat-conducting layer sequentially stacked on the surface of the transparent substrate. The transparent directional heat-conducting layer includes one-dimensional nanofibers, on which thermally conductive powder and magnetic powder are distributed, and the one-dimensional nanofibers are perpendicular to the metal nanowire layer.

[0025] A transparent directional heat-conducting component as described above is used for a camera viewport.

[0026] In the preparation method of the transparent directional heat-conducting element of the present invention, polyvinylidene fluoride is used as a carrier, and one-dimensional nanofibers with thermally conductive powder and magnetic powder are prepared by spinning process. Under the synergistic effect of ultrasonic dispersion and strong polar N,N-dimethylformamide solvent, on the one hand, the one-dimensional nanofibers can achieve initial flipping, so that the one-dimensional nanofibers can maintain a distribution state with an angle of less than 75° with the normal in the second dispersion liquid; on the other hand, the hydrogen bond between the N,N-dimethylformamide solvent and the end of the one-dimensional nanofibers makes the one-dimensional nanofibers appear dumbbell-shaped, which is more conducive to the flipping of the one-dimensional nanofibers.

[0027] Furthermore, under the influence of an applied directional magnetic field perpendicular to the metal nanowire layer and a specific magnetic field strength, dumbbell-shaped one-dimensional nanofibers with an angle of less than 75° to the normal can easily flip, thereby achieving a directional distribution of one-dimensional nanofibers. Simultaneously, because the one-dimensional nanofibers are uniformly dispersed longitudinally in the transparent directional heat-conducting component, the influence of the lateral distribution of the one-dimensional nanofibers on the light transmittance of the transparent directional heat-conducting component is reduced, allowing the transparent directional heat-conducting component to maintain excellent light transmittance.

[0028] Therefore, the transparent directional heat-conducting component prepared by the method described in this invention has a high light transmittance of over 90% and excellent heat conduction effect. It can be used for directional heating of camera windows, giving the camera windows excellent defogging and defrosting functions, and solving problems such as unclear images caused by fogging and frosting of the windows. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the process for preparing a transparent directional heat-conducting component according to one embodiment of the present invention;

[0030] Figure 2 This is a scanning electron microscope image of the one-dimensional nanofibers prepared in Example 1 of the present invention.

[0031] Among them, 10 is a transparent substrate; 20 is a metal nanowire layer; 30 is a transparent directional thermally conductive layer; 301 is a one-dimensional nanofiber; 3011 is a thermally conductive powder; and 3012 is a magnetic powder. Detailed Implementation

[0032] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the invention.

[0034] Combination Figure 1 The diagram shows a method for preparing a transparent directional heat-conducting element provided by the present invention, comprising the following steps:

[0035] S1, a transparent conductive film of metal nanowires is provided, the transparent conductive film of metal nanowires includes a transparent substrate 10 and a metal nanowire layer 20 stacked together;

[0036] S2, a first dispersion is prepared by mixing thermally conductive powder 3011, magnetic powder 3012, polyvinylidene fluoride powder and organic solvent, and the first dispersion is prepared into one-dimensional nanofibers 301 by spinning process.

[0037] S3, the one-dimensional nanofiber 301 is mixed with N,N-dimethylformamide solvent to obtain a one-dimensional nanofiber dispersion, and then the one-dimensional nanofiber dispersion is ultrasonically mixed with a resin solution to obtain a second dispersion;

[0038] S4, a coating is formed on the surface of the metal nanowire layer 20 using the second dispersion, while a directional magnetic field perpendicular to the metal nanowire layer 20 is continuously applied. After curing, a transparent directional heat-conducting component is obtained, wherein the thickness of the coating is greater than the length of the one-dimensional nanofiber, and the magnetic field strength of the directional magnetic field is 0.05T-5T.

[0039] In step S1, the preparation method of the transparent conductive metal nanowire film is not limited, including but not limited to template method, polyol method, electrodeposition method, etc. In order to improve the bonding force between the metal nanowire layer 20 and the transparent substrate 10, it is preferable to perform plasma modification treatment on the transparent substrate 10 to graft carboxyl and hydroxyl groups on the surface of the transparent substrate 10, so as to achieve chemical bonding with the metal nanowire layer 20.

[0040] Optionally, the transparent substrate 10 is selected from a glass substrate, a polycarbonate (PC) substrate, a polymethyl methacrylate (PMMA) substrate, a polyethylene terephthalate (PET) substrate, or a polyimide (PI) substrate.

[0041] In the metal nanowire layer, the diameter of the metal nanowire is preferably 10nm-500nm, the aspect ratio is preferably 200-2000; and / or, the thickness of the metal nanowire layer is preferably 200nm-2000nm.

[0042] Optionally, the metal nanowires in the metal nanowire layer are selected from silver nanowires or copper nanowires.

[0043] Preferably, the transparent conductive film of the metal nanowire has a light transmittance of 90%-95%.

[0044] In traditional techniques, thermally conductive materials are typically directly composited with magnetic materials, allowing the thermally conductive material to achieve directional distribution under the influence of the surface-mounted magnetic material. However, this composite method is selective in its application to magnetic materials, and because magnetic materials have low thermal conductivity, the overall thermal conductivity of the composite material decreases, which is detrimental to improving directional heat conduction.

[0045] In step S2 of this invention, polyvinylidene fluoride (PVDF) is used as a carrier to prepare one-dimensional nanofibers 301 through a spinning process. Thermally conductive powder 3011 and magnetic powder 3012 are uniformly distributed in the one-dimensional nanofibers 301, so that the thermally conductive powder 3011 and magnetic powder 3012 are indirectly composited through the PVDF one-dimensional nanofiber carrier. This not only effectively reduces the agglomeration of thermally conductive powder 3011 and magnetic powder 3012, but also helps to give full play to the high thermal conductivity of thermally conductive powder 3011.

[0046] The preferred spinning process is electrospinning. More preferably, the electrospinning voltage is 10kV-30kV, the needle distance from the receiving device is 10cm-25cm, the injection rate is 0.05mm / min-0.25mm / min, and the electrospinning roller rotation speed is 200r / min-650r / min. This allows the length of the one-dimensional nanofiber 301 to be preferably 200nm-500nm, which is beneficial for the one-dimensional nanofiber 301 to be fully flipped in the subsequent preparation process, achieving a high flipping rate and thus realizing excellent directional distribution effect.

[0047] The preferred mass ratio of the polyvinylidene fluoride powder to the thermally conductive powder 3011 and the magnetic powder 3012 is 1:(0.1-0.5):(0.1-0.5), more preferably 1:(0.1-0.3):(0.1-0.5). By precisely controlling the amount of polyvinylidene fluoride powder, thermally conductive powder 3011, and magnetic powder 3012 added, the formation of one-dimensional nanofibers 301 can be guaranteed, while the uniform distribution of thermally conductive powder 3011 and magnetic powder 3012 can be achieved.

[0048] More preferably, the total mass of the thermally conductive powder 3011 and the magnetic powder 3012 is 15%-60% of the mass of the first dispersion, more preferably 15%-30%, which helps to ensure the high light transmittance of the transparent directional thermally conductive component while achieving a more efficient and uniform thermal conductivity.

[0049] Wherein, the thermally conductive powder 3011 has a particle size of 20nm-50nm; and / or, the magnetic powder 3012 has a particle size of 50nm-100nm.

[0050] Specifically, the thermally conductive powder 3011 is selected from at least one of silicon carbide (SiC) powder, aluminum nitride (AlN) powder, and aluminum oxide (Al2O3) powder, preferably SiC powder.

[0051] The magnetic powder 3012 is selected from at least one of iron tetroxide (Fe3O4) powder, cobalt oxide (CoO) and nickel oxide (NiO), preferably Fe3O4 powder.

[0052] The organic solvent is selected from at least one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and N,N-dimethylacetamide (DMA), preferably DMF.

[0053] In one embodiment, PVDF powder can be uniformly dispersed in an organic solvent first, and then thermally conductive powder 3011 and magnetic powder 3012 can be added, which can make the thermally conductive powder 3011 and magnetic powder 3012 more uniformly dispersed in the first dispersion.

[0054] It should be noted that thermally conductive powder 3011 and magnetic powder 3012 are distributed both inside and on the surface of the one-dimensional nanofiber 301. The thermally conductive powder 3011 and magnetic powder 3012 distributed on the surface can be completely exposed or partially exposed on the surface and partially embedded inside the one-dimensional nanofiber 301. This invention does not limit this.

[0055] In step S3, under the synergistic effect of ultrasonic dispersion and the highly polar N,N-dimethylformamide solvent, on the one hand, the one-dimensional nanofibers 301 can achieve initial flipping, so that the one-dimensional nanofibers 301 can maintain a distribution state with an angle of less than 75° with the normal in the second dispersion; on the other hand, the hydrogen bonds between the N,N-dimethylformamide solvent and the ends of the one-dimensional nanofibers 301 make the one-dimensional nanofibers 301 appear dumbbell-shaped, which is more conducive to the flipping of the one-dimensional nanofibers 301.

[0056] Meanwhile, the N,N-dimethylformamide solvent will not corrode the one-dimensional nanofibers 301, which can ensure that the thermally conductive powder 3011 and magnetic powder 3012 distributed in the one-dimensional nanofibers 301 will not fall off, thereby ensuring that the thermally conductive powder 3011 and magnetic powder 3012 can fully exert their directional heat conduction effect.

[0057] Preferably, the mass fraction of the one-dimensional nanofiber 301 in the one-dimensional nanofiber dispersion is 15%-65%, more preferably 15%-40%, which is more conducive to achieving uniform dispersion of the one-dimensional nanofiber 301 in the second dispersion.

[0058] Furthermore, the mass fraction of the one-dimensional nanofiber 301 in the second dispersion is preferably 5%-40%, more preferably 5%-35%, which allows the one-dimensional nanofiber 301 to fully rotate, which is more conducive to achieving a higher rotation rate and ensuring the high light transmittance of the transparent directional heat conduction element, while achieving improved efficient and uniform heat conduction effect.

[0059] The resin solution may be selected from at least one of trimethylcyclohexanol polyacrylate, cyclohexyl methacrylate, and epoxy resin, preferably trimethylcyclohexanol polyacrylate.

[0060] It should be noted that in the step of mixing the one-dimensional nanofibers with N,N-dimethylformamide solvent to obtain a one-dimensional nanofiber dispersion, ultrasonic mixing or other mixing methods can be used. The present invention does not limit this, but ultrasonic mixing is preferred.

[0061] The preferred ultrasonic frequency during ultrasonic mixing is 10Hz-20Hz, which is more conducive to the initial flipping of one-dimensional nanofiber 301.

[0062] In step S4, under the influence of an applied directional magnetic field perpendicular to the metal nanowire layer 20 and a specific magnetic field strength, the dumbbell-shaped one-dimensional nanofibers 301 with an angle of less than 75° to the normal can be easily flipped, thereby achieving a directional distribution of the one-dimensional nanofibers 301. Simultaneously, because the one-dimensional nanofibers 301 exhibit a highly dispersed longitudinal distribution in the transparent directional heat-conducting component, it helps to reduce the impact of the lateral distribution of the one-dimensional nanofibers 301 on the light transmittance of the transparent directional heat-conducting component, enabling the transparent directional heat-conducting component to maintain excellent light transmittance.

[0063] Preferably, the coating has a thickness of 600nm-1200nm, which provides sufficient space for the one-dimensional nanofibers 301 to fully rotate.

[0064] More preferably, when the length of the one-dimensional nanofiber 301 is 200nm-500nm and the coating thickness of the second dispersion is 600nm-1200nm, the flipping effect of the one-dimensional nanofiber 301 is better.

[0065] It should be noted that the present invention does not limit the way the magnetic field strength of the directional magnetic field changes. In the step of continuously applying the directional magnetic field perpendicular to the metal nanowire layer, the directional magnetic field can be a constant magnetic field strength, and the magnetic field strength is preferably 0.5T; the directional magnetic field can also be a linearly or non-linearly changing magnetic field strength, and the strength can be in the range of 0.05T-5T.

[0066] Preferably, in the step of continuously applying a directional magnetic field perpendicular to the metal nanowire layer, the magnetic field strength of the directional magnetic field increases incrementally, and the increasing magnetic field strength is selected from any range of 0.05T-5T, such as increasing from 0.05T to 5T, from 0.05T to 4.5T, from 0.1T to 5T, from 0.1T to 4T, from 0.5T to 4T, from 1T to 3T, etc., resulting in a higher flip rate and better directional thermal conductivity of the one-dimensional nanofiber 301.

[0067] Therefore, the preparation method described in this invention can not only achieve directional heat conduction, but also maintain a high light transmittance of over 90% for transparent directional heat conduction components. Without limiting the selection of magnetic materials, this method is conducive to promoting the further application of transparent directional heat conduction components in the field of heaters.

[0068] The present invention provides a transparent directional heat-conducting element prepared by the method described above, comprising a transparent substrate 10, and a metal nanowire layer 20 and a transparent directional heat-conducting layer 30 sequentially stacked on the surface of the transparent substrate 10, wherein the transparent directional heat-conducting layer 30 includes one-dimensional nanofibers 301, and thermally conductive powder 3011 and magnetic powder 3012 are distributed on the one-dimensional nanofibers 301, and the one-dimensional nanofibers 301 are perpendicular to the metal nanowire layer 20.

[0069] The present invention also provides a transparent directional heat-conducting component as described above for use in a camera window.

[0070] The transparent directional heat-conducting component can be used for directional heating of the camera window, achieving efficient and uniform surface heating, giving the camera window excellent defogging and defrosting functions, and solving problems such as unclear images caused by fogging and frosting of the window.

[0071] The following specific embodiments will further illustrate the transparent directional heat conduction element, its preparation method, and its application.

[0072] Example 1

[0073] The glass substrate was ultrasonically cleaned with ethanol solution for 20 min, then rinsed with ultrapure water, and finally surface activated with plasma cleaning for 15 min. A silver nanowire slurry with a concentration of 1 mg / mL was prepared using a polyol method and coated onto the surface of the glass substrate. After natural drying, a transparent conductive silver nanowire film was obtained. The silver nanowires had a diameter of 100 nm, an aspect ratio of 500, a thickness of 200 nm, and a light transmittance of 95%.

[0074] 10g of PVDF powder was uniformly dispersed in 20mL of DMF solvent, followed by the addition of 2.3g of SiC powder (particle size approximately 30nm) and 1.8g of Fe3O4 powder (particle size approximately 80nm). After uniform dispersion, a first dispersion was obtained. Then, using electrospinning technology at a voltage of 20kV and a rotation speed of 230r / min, one-dimensional nanofibers with a length of approximately 300nm were fabricated from the first dispersion. Figure 2 As shown.

[0075] Under ultrasonic stirring conditions, 2g of one-dimensional nanofibers were first uniformly dispersed in 10mL of DMF solvent, and then added to 16mL of trimethylcyclohexanol polyacrylate for mixing and dispersion to obtain a second dispersion.

[0076] A second dispersion was uniformly coated onto the surface of the silver nanowire layer to form a coating with a thickness of approximately 600 nm. Simultaneously, a directional magnetic field perpendicular to the silver nanowire layer was continuously applied, with the magnetic field strength increasing from 0.05 T to 5 T. After standing in the magnetic field for 30 minutes, the coating completely cured, resulting in a transparent directional heat-conducting component made of silver nanowires.

[0077] Example 2

[0078] A nanowire transparent conductive film was prepared using the same method as in Example 1.

[0079] 20g of PVDF powder was uniformly dispersed in 40mL of DMF solvent, and then 3.1g of SiC powder (particle size approximately 40nm), 1.5g of AlN powder (particle size approximately 25nm), and 7.2g of Fe3O4 powder (particle size approximately 70nm) were added. After uniform dispersion, a first dispersion was obtained. Then, one-dimensional nanofibers with a length of approximately 350nm were prepared from the first dispersion by electrospinning under the preparation conditions of 20kV voltage and 500r / min rotation speed.

[0080] Under ultrasonic stirring conditions, 5g of one-dimensional nanofibers were first uniformly dispersed in 25mL of DMF solvent, and then added to 40mL of trimethylcyclohexanol polyacrylate for mixing and dispersion to obtain a second dispersion.

[0081] The second dispersion was uniformly coated onto the surface of the silver nanowire layer to form a coating with a thickness of approximately 600 nm. Simultaneously, a directional magnetic field perpendicular to the silver nanowire layer was continuously applied, with the magnetic field strength increasing from 0.1 T to 5 T. After standing in the magnetic field for 30 minutes, the coating completely cured, resulting in a transparent directional heat-conducting component made of silver nanowires.

[0082] Example 3

[0083] A nanowire transparent conductive film was prepared using the same method as in Example 1.

[0084] 50g of PVDF powder was uniformly dispersed in 100mL of DMF solvent, and then 8g of SiC powder (particle size of about 40nm) and 12.5g of Fe3O4 powder (particle size of about 60nm) were added. After uniform dispersion, a first dispersion was obtained. Then, one-dimensional nanofibers with a length of about 400nm were prepared from the first dispersion by electrospinning under the preparation conditions of 20kV voltage and 650r / min rotation speed.

[0085] Under ultrasonic stirring conditions, 10g of one-dimensional nanofibers were first uniformly dispersed in 50mL of DMF solvent, and then added to 80mL of trimethylcyclohexanol polyacrylate for mixing and dispersion to obtain a second dispersion.

[0086] A second dispersion was uniformly coated onto the surface of the silver nanowire layer to form a coating with a thickness of approximately 850 nm. Simultaneously, a directional magnetic field perpendicular to the silver nanowire layer was continuously applied, with the magnetic field strength increasing from 0.05 T to 4.5 T. After standing in the magnetic field for 30 minutes, the coating completely cured, resulting in a transparent directional heat-conducting component made of silver nanowires.

[0087] Example 4

[0088] The difference between Example 4 and Example 1 is that a constant directional magnetic field strength of 5T is applied.

[0089] Example 5

[0090] The difference between Example 5 and Example 1 is that a constant directional magnetic field strength of 0.5T is applied.

[0091] Comparative Example 1

[0092] The difference between Comparative Example 1 and Example 1 is that Fe3O4 powder with a positive surface charge is mixed with SiC powder with a negative surface charge, so that they are electrostatically adsorbed and combined to form a mixture. Then, the mixture is mixed with organosilicon to obtain a dispersion. The dispersion is sprayed onto the surface of the metal nanowire layer by a spinning process, while a directional magnetic field perpendicular to the silver nanowire layer is continuously applied. After curing, a transparent directional heat-conducting silver nanowire is obtained.

[0093] Comparative Example 2

[0094] The difference between Comparative Example 2 and Example 1 is that methanol solvent was used instead of DMF solvent to disperse one-dimensional nanofibers.

[0095] Comparative Example 3

[0096] The difference between Comparative Example 3 and Example 1 is that polytetrafluoroethylene (PTFE) powder was used instead of PVDF powder to prepare one-dimensional nanofibers.

[0097] Comparative Example 4

[0098] The difference between Comparative Example 4 and Example 1 is that a magnetic stirrer was used instead of ultrasonic stirring for dispersion.

[0099] Comparative Example 5

[0100] The difference between Comparative Example 5 and Example 1 is that a constant directional magnetic field strength of 10T is applied.

[0101] The transparent directional heat-conducting silver nanowires prepared in Examples 1-5 and Comparative Examples 1-5 were tested for light transmittance and performance: the time required for the outer surface temperature of the glass to reach the same 45°C at room temperature and under a DC voltage of 12V, and the stable temperature reached by the outer surface temperature of the glass after heating for 60s.

[0102] Table 1

[0103]

[0104] As shown in Table 1, the transparent directional heat-conducting silver nanowires prepared by the preparation method provided by the present invention not only have a high light transmittance of over 90%, but also high thermal conductivity and excellent heat conduction effect.

[0105] Comparative Example 1 directly composited thermally conductive SiC powder and magnetic Fe3O4 powder via electrostatic interaction, and then prepared a directional thermally conductive layer using spinning spraying under a directional magnetic field. On the one hand, the low thermal conductivity of magnetic Fe3O4 powder, when combined with the high thermal conductivity of SiC powder, led to a decrease in the overall thermal conductivity of the composite material, which was detrimental to improving the directional thermal conductivity. On the other hand, the structure of the thermally conductive layer prepared by spinning spraying was mainly a transversely stacked layer distribution, which severely affected the light transmittance of the transparent directional thermally conductive silver nanowire component. Therefore, the transparent directional thermally conductive silver nanowire component obtained in Comparative Example 1 had a light transmittance of only 86% and poor thermal conductivity.

[0106] In Comparative Example 2, methanol solvent was used instead of DMF solvent to disperse one-dimensional nanofibers. Since methanol does not chemically bond with one-dimensional nanofibers, the one-dimensional nanofibers failed to flip further under the action of magnetic field. Therefore, the thermal conductivity of the transparent directional heat-conducting device made of silver nanowires in Comparative Example 2 was poor.

[0107] In Comparative Example 3, PTFE powder was used instead of PVDF powder to prepare one-dimensional nanofibers. Since the polarity of PTFE is much lower than that of PCDF, the dispersion effect of magnetic powder and thermally conductive powder in the fiber is not good. Therefore, the thermal conductivity of the transparent directional thermally conductive silver nanowire obtained in Comparative Example 3 is not good.

[0108] Comparative Example 4 uses a magnetic stirrer to disperse the material instead of ultrasonic stirring. Since the one-dimensional nanofibers in the second dispersion failed to achieve an angle of less than 75° with the normal, they failed to further rotate under the action of the magnetic field. Therefore, the thermal conductivity of the transparent directional heat-conducting silver nanowires prepared in Comparative Example 4 is not as good as that in Examples 1-5.

[0109] In Comparative Example 5, the applied magnetic field strength was too high, causing the one-dimensional nanofibers to stop flipping at a certain angle, thus affecting the flipping rate of the one-dimensional nanofibers. Therefore, the thermal conductivity of the transparent directional heat-conducting silver nanowires prepared in Comparative Example 5 was not as good as that in Examples 1-5.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a transparent directional heat-conducting element, characterized in that, Includes the following steps: A transparent conductive film of metal nanowires is provided, the transparent conductive film of metal nanowires comprising a transparent substrate and a metal nanowire layer stacked thereon; A first dispersion was prepared by mixing thermally conductive powder, magnetic powder, polyvinylidene fluoride powder, and organic solvent. The first dispersion was then used to prepare one-dimensional nanofibers by spinning. The one-dimensional nanofibers were mixed with N,N-dimethylformamide solvent to obtain a one-dimensional nanofiber dispersion, and then the one-dimensional nanofiber dispersion was ultrasonically mixed with a resin solution to obtain a second dispersion. A coating is formed on the surface of the metal nanowire layer using the second dispersion, while a directional magnetic field perpendicular to the metal nanowire layer is continuously applied. After curing, a transparent directional heat-conducting component is obtained, wherein the thickness of the coating is greater than the length of the one-dimensional nanofiber, and the magnetic field strength of the directional magnetic field is 0.05T-5T.

2. The method for preparing a transparent directional heat-conducting element according to claim 1, characterized in that, The length of the one-dimensional nanofiber is 200nm-500nm; And / or, the thickness of the coating is 600nm-1200nm.

3. The method for preparing a transparent directional heat-conducting element according to claim 1, characterized in that, The mass ratio of the polyvinylidene fluoride powder to the thermally conductive powder and the magnetic powder is 1:(0.1-0.5):(0.1-0.5).

4. The method for preparing a transparent directional heat-conducting element according to claim 1, characterized in that, The total mass of the thermally conductive powder and the magnetic powder is 15%-60% of the mass of the first dispersion. And / or, the mass fraction of the one-dimensional nanofibers in the one-dimensional nanofiber dispersion is 15%-65%; And / or, the one-dimensional nanofibers have a mass fraction of 5%-40% in the second dispersion.

5. The method for preparing a transparent directional heat-conducting element according to claim 1, characterized in that, The particle size of the thermally conductive powder is 20nm-50nm; And / or, the particle size of the magnetic powder is 50nm-100nm.

6. The method for preparing a transparent directional heat-conducting element according to claim 1, characterized in that, The ultrasonic frequency of the ultrasonic mixture is 10Hz-20Hz.

7. The method for preparing a transparent directional heat-conducting element according to claim 1, characterized in that, In the step of continuously applying a directional magnetic field perpendicular to the metal nanowire layer, the magnetic field strength of the directional magnetic field increases, and the increasing magnetic field strength is selected from any range of 0.05T-5T. And / or, the magnetic field strength of the directional magnetic field is constant, and the magnetic field strength is at least 0.5T.

8. The method for preparing a transparent directional heat-conducting element according to claim 1, characterized in that, In the metal nanowire layer, the diameter of the metal nanowires is 10nm-500nm and the aspect ratio is 200-2000; And / or, the thickness of the metal nanowire layer is 200nm-2000nm; And / or, the transmittance of the transparent conductive film of the metal nanowire is 90%-95%; And / or, the metal nanowires in the metal nanowire layer are selected from silver nanowires or copper nanowires.

9. A transparent directional heat-conducting element prepared by the method of any one of claims 1-8, characterized in that, The material includes a transparent substrate, and a metal nanowire layer and a transparent directional thermally conductive layer sequentially stacked on the surface of the transparent substrate. The transparent directional thermally conductive layer includes one-dimensional nanofibers, on which thermally conductive powder and magnetic powder are distributed, and the one-dimensional nanofibers are perpendicular to the metal nanowire layer.

10. A transparent directional heat-conducting element as described in claim 9 for a camera window.

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