Silver nanowire directional heat conduction component, preparation method and application thereof

Abstract

The present invention relates to a silver nanowire directional heat conductor and its preparation method and application. The preparation method comprises: providing a silver nanowire transparent conductive film, the silver nanowire transparent conductive film comprising a first transparent substrate and a silver nanowire layer stacked in layers; using a resin composition to prepare a semi-cured transparent heat-conducting layer on the surface of the silver nanowire layer, and continuously applying a directional magnetic field perpendicular to the silver nanowire layer during the preparation process, the resin composition comprising silver nanowires coated with magnetic nanoparticles and a thermosetting resin; press-bonding a second transparent substrate on the surface of the semi-cured transparent heat-conducting layer, and continuously applying a directional magnetic field perpendicular to the semi-cured transparent heat-conducting layer during the press-bonding process, with a semi-cured transparent heat-conducting layer thickness of 1 μm as a reference, and a pressure of 5N-12N for press-bonding; after press-bonding, completely curing the semi-cured transparent heat-conducting layer to obtain a silver nanowire directional heat conductor. The preparation method of the present invention can achieve directional heat conduction and has excellent heat conduction effect.

Description

Technical Field

[0001] The present invention relates to the technical field of transparent conductive films, and in particular to a silver nanowire directional heat conductor and a preparation method and application thereof. Background Art

[0002] When silver nanowire transparent conductive film is used in the field of heaters, the total heat generation can be increased by reducing the square resistance, or the larger temperature rise required on the outer surface can be achieved by increasing the thermal conductivity of the protective layer and reducing the lateral thermal conductivity. Among them, one of the ways to reduce lateral thermal conductivity is to construct directional heat conduction. Traditional methods usually 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 thermal conductivity of magnetic materials is low. In addition, directional heat conduction can also be achieved by preparing a directional array structure through a mold, but it is still selective for materials and the process is complicated, which limits the further application of directional heat conduction in the field of heaters. Summary of the Invention

[0003] Based on this, it is necessary to provide a silver nanowire directional heat conductor and its preparation method and application to address the above problems; the preparation method can achieve directional heat conduction and excellent heat conduction effect.

[0004] A method for preparing a silver nanowire directional heat conductor comprises the following steps:

[0005] A silver nanowire transparent conductive film is provided, wherein the silver nanowire transparent conductive film comprises a first transparent substrate and a silver nanowire layer stacked together;

[0006] A semi-cured transparent thermally conductive layer is prepared on the surface of the silver nanowire layer using a resin composition, and an oriented magnetic field perpendicular to the silver nanowire layer is continuously applied during the preparation process, wherein the resin composition comprises silver nanowires coated with magnetic nanoparticles and a thermosetting resin;

[0007] Pressing and laminating a second transparent substrate on the surface of the semi-cured transparent thermally conductive layer, and continuously applying a directional magnetic field perpendicular to the semi-cured transparent thermally conductive layer during the press-lamination process, wherein the pressure of the press-lamination is 5N-12N based on the thickness of the semi-cured transparent thermally conductive layer of 1 μm;

[0008] After pressurizing and laminating, the semi-cured transparent heat-conducting layer is completely cured to obtain a silver nanowire directional heat-conducting member.

[0009] In one embodiment, the thickness of the semi-cured transparent heat-conducting layer is 50 μm-80 μm.

[0010] In one embodiment, the method for preparing the resin composition comprises the following steps:

[0011] Mixing a first silver source, a reducing agent, a protective agent, and a polar solvent to obtain a first mixture, and reacting the first mixture to prepare a silver nanocrystal seed dispersion, wherein the reducing agent is an aldehyde-containing acid anhydride;

[0012] The silver nanocrystal seed dispersion is mixed with a second silver source, magnetic nanoparticles, and a thermosetting resin to obtain a second mixture, the second mixture is irradiated with ultraviolet light, and then the polar solvent is removed to obtain a resin composition, wherein the viscosity of the second mixture is less than or equal to 200 Pa·s.

[0013] In one embodiment, in the step of irradiating the second mixture with ultraviolet light, the wavelength of the ultraviolet light is 340nm-400nm, and the irradiation time is 12h-36h.

[0014] In one embodiment, the silver nanowires coated with magnetic nanoparticles are of a core-shell structure, wherein the core is the silver nanowire and the shell is composed of magnetic nanoparticles.

[0015] In one embodiment, the resin composition further includes a curing accelerator.

[0016] In one embodiment, in the step of preparing a semi-cured transparent thermal conductive layer on the surface of the silver nanowire layer, the semi-curing temperature is 130° C.-150° C., and the time is 4 min-7 min.

[0017] In one embodiment, in the step of completely curing the semi-cured transparent heat-conducting layer, the temperature for complete curing is 150° C.-220° C., and the time is 30 min-90 min.

[0018] A silver nanowire directional heat conductor prepared by the method for preparing the silver nanowire directional heat conductor as described above comprises a first transparent substrate, and a silver nanowire layer, a transparent directional heat conductor layer and a second transparent substrate sequentially stacked on the surface of the first transparent substrate.

[0019] A silver nanowire directional heat conductor as described above is used for a camera window.

[0020] The method for preparing the silver nanowire directional thermal conductor described in the present invention uses a resin composition containing silver nanowires with surface-coated magnetic nanoparticles to prepare a semi-cured transparent thermal conductive layer on the surface of the silver nanowire layer, and continuously applies a directional magnetic field perpendicular to the silver nanowire layer during the preparation process. This allows the silver nanowires to achieve excellent directional arrangement in the semi-cured transparent thermal conductive layer under the guidance of the surface-coated magnetic nanoparticles.

[0021] Furthermore, the semi-cured transparent thermal conductive layer is bonded and assembled under the conditions of a directional magnetic field and specific applied pressure. On the one hand, since the elastic modulus of the semi-cured transparent thermal conductive layer is relatively low, the specific applied pressure can not only destroy the magnetic nanoparticles coated on the surface of the silver nanowires, enhance the heat conduction between the silver nanowires, and improve the thermal conductivity of the silver nanowire directional thermal conductor, but also make the contact between the silver nanowires closer through the extrusion effect, thereby solving the problem of reduced thermal conductivity caused by the loose directional arrangement structure of the silver nanowires; on the other hand, by continuously providing a directional magnetic field during the pressurized bonding process, the silver nanowires can maintain a directional arrangement, which is beneficial to improving the directional heat conduction effect of the silver nanowire directional thermal conductor.

[0022] Therefore, the silver nanowire directional heat conductor prepared by the preparation method of the present invention has excellent heat conduction effect and can be used for directional heating of camera windows, so that the camera windows have excellent defogging and defrosting functions, and can solve the problem of unclear shooting images caused by fogging and frosting of the windows. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of the silver nanowire directional heat conductor prepared in Example 1 of the present invention;

[0024] Figure 2 This is a schematic structural diagram of the silver nanowire directional heat conductor prepared in Comparative Example 1 of the present invention;

[0025] Figure 3 This is a schematic structural diagram of the silver nanowire directional heat conductor prepared in Comparative Example 2 of the present invention.

[0026] Among them, 101 is a first transparent substrate; 102 is a silver nanowire layer; 103 is a transparent directional heat conducting layer; and 104 is a second transparent substrate. DETAILED DESCRIPTION

[0027] To facilitate understanding of the present invention, the present invention 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. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention.

[0029] The present invention provides a method for preparing a silver nanowire directional heat conductor, comprising the following steps:

[0030] S1, providing a silver nanowire transparent conductive film, wherein the silver nanowire transparent conductive film comprises a first transparent substrate 101 and a silver nanowire layer 102 stacked together;

[0031] S2, preparing a semi-cured transparent thermal conductive layer on the surface of the silver nanowire layer 102 using a resin composition, and continuously applying an oriented magnetic field perpendicular to the silver nanowire layer during the preparation process, wherein the resin composition comprises silver nanowires coated with magnetic nanoparticles and a thermosetting resin;

[0032] S3, pressing and laminating the second transparent substrate 104 on the surface of the semi-cured transparent thermal conductive layer, and continuously applying a directional magnetic field perpendicular to the semi-cured transparent thermal conductive layer during the pressing and laminating process, wherein the pressure of the pressing and laminating is 5N-12N based on the thickness of the semi-cured transparent thermal conductive layer of 1 μm;

[0033] S4, after pressurizing and laminating, completely solidifying the semi-cured transparent heat-conducting layer to obtain a silver nanowire directional heat-conducting member.

[0034] In step S1, the silver nanowire transparent conductive film can be prepared by any method, but is preferably prepared using a typical polyol method. To enhance the bonding strength between the silver nanowire layer 102 and the first transparent substrate 101, the first transparent substrate 101 is preferably subjected to a plasma modification treatment to graft carboxyl and hydroxyl groups onto the surface of the first transparent substrate 101, thereby achieving chemical bonding with the silver nanowire layer 102.

[0035] Optionally, the first transparent substrate 101 is selected from a polyethylene terephthalate (PET) substrate or a poly (arylene ether nitrile) (PEN) substrate, and the thickness of the silver nanowire layer 102 is preferably 100 nm-200 nm.

[0036] In step S2, the method for preparing the resin composition comprises the following steps:

[0037] S21, mixing a first silver source, a reducing agent, a protective agent, and a polar solvent to obtain a first mixture, and reacting the first mixture to prepare a silver nanocrystal seed dispersion, wherein the reducing agent is an aldehyde-containing acid anhydride;

[0038] S22, mixing the silver nanocrystal seed dispersion with a second silver source, magnetic nanoparticles, and a thermosetting resin to obtain a second mixture, irradiating the second mixture with ultraviolet light, and then removing the polar solvent to obtain a resin composition, wherein the viscosity of the second mixture is less than or equal to 200 Pa·s.

[0039] In the preparation method of the resin composition, an ultraviolet reduction method is combined with a seed crystal method to prepare silver nanowires in situ in a thermosetting resin, and magnetic nanoparticles are introduced at the same time. When the silver nanocrystal seeds are prepared by the seed crystal method, an aldehyde-containing acid anhydride is used as a reducing agent. On the one hand, when the prepared silver nanocrystal seed dispersion is mixed with the magnetic nanoparticles and the thermosetting resin, the viscosity of the second mixture can be significantly adjusted, promoting the sufficient mixing and diffusion of the silver nanocrystal seeds and the magnetic nanoparticles, facilitating the Ostwald growth of the silver nanocrystal seeds, ensuring that the silver nanowires grown in situ can be uniformly dispersed, and allowing the magnetic nanoparticles to be coated on the surface of the silver nanowires. On the other hand, the aldehyde-containing acid anhydride can also be used as a curing agent after reduction as a reducing agent, ensuring that the thermosetting resin can be fully cured, and at the same time, the subsequently prepared semi-cured transparent thermal conductive layer has excellent bonding strength.

[0040] Preferably, by adopting the preparation method of the resin composition, the obtained silver nanowires coated with magnetic nanoparticles can be made into a core-shell structure, wherein the core is the silver nanowire and the shell is composed of magnetic nanoparticles.

[0041] It should be noted that the silver nanowires coated with magnetic nanoparticles include, but are not limited to, core-shell structures. As long as the magnetic nanoparticles are coated on the surface of the silver nanowires and can be guided to align and distribute in a magnetic field, the present invention is not limited thereto. Therefore, other methods for preparing silver nanowires coated with magnetic nanoparticles are also applicable to the present invention and will not be further described.

[0042] In step S21, the first silver source is selected from at least one of silver nitrate, silver acetate, silver perchlorate, and silver fluoride, and the mass fraction of the first silver source in the first mixture is 0.08%-2%, preferably 0.1%-1%, and more preferably 0.1%-0.5%.

[0043] Specifically, the reducing agent is selected from at least one of 5-formyl-2-thiopheneboronic acid and 2-formylfuran-5-boronic acid, and the mass fraction of the reducing agent in the first mixture is 1%-10%, preferably 4%-8%.

[0044] Specifically, the protective agent is selected from at least one of polyvinyl pyrrolidone and cetyltrimethylammonium bromide, and the mass fraction of the protective agent in the first mixture is 0.2%-4%, preferably 0.3%-3%, and more preferably 0.3%-1.5%.

[0045] In one embodiment, the reaction time of the first mixture is 0.5 h to 2 h, which can make the grain size of the silver nanocrystals reach 2 nm to 10 nm, so that the silver nanocrystals can form silver nanowires with a higher aspect ratio during the in situ growth process.

[0046] In step S22, the second silver source is selected from at least one of silver nitrate, silver acetate, silver perchlorate, and silver fluoride. The mass fraction of the second silver source in the second mixture is 0.08% to 2%, preferably 0.1% to 1%, and more preferably 0.1% to 0.5%. It should be noted that the second silver source and the first silver source may be the same or different, and this is not limited in the present invention.

[0047] Specifically, the magnetic nanoparticles are selected from at least one of ferroferric oxide nanoparticles, iron oxide nanoparticles, cobalt oxide nanoparticles, and nickel oxide nanoparticles. The mass fraction of the magnetic nanoparticles in the second mixture is 0.08%-2%, which is more conducive to promoting the oriented distribution of silver nanowires, further preferably 0.1%-1%, and more preferably 0.1%-0.5%.

[0048] Specifically, the thermosetting resin is selected from at least one of bisphenol resin, silicone resin, polyimide, and polyurethane, and the mass fraction of the thermosetting resin in the second mixture is 30%-70%.

[0049] In one embodiment, in the step of irradiating the second mixture with ultraviolet light, the wavelength of the ultraviolet light is preferably 340nm-400nm, and the irradiation time is preferably 12h-36h, which can make the diameter of the silver nanowires in the silver nanowire dispersion reach 30nm-100nm, and the length reach 3μm-10μm.

[0050] By removing the polar solvent, the viscosity of the resin composition can be increased again, so that the resin composition can be more easily formed into a film when deposited on the surface of the silver nanowire layer 102, while ensuring that the semi-cured transparent thermal conductive layer has a strong bonding force with the silver nanowire layer 102.

[0051] Optionally, the method of removing the polar solvent may be selected from evaporation.

[0052] In one embodiment, the resin composition further includes a curing accelerator, which is selected from at least one of 2-ethyl-4-methylimidazole and 2,4,5-tris(dimethylaminomethyl)phenol, and the mass fraction of the curing accelerator in the resin composition is 0.08%-2%, preferably 0.1%-1%, and more preferably 0.1%-0.5%.

[0053] In one embodiment, the semi-curing temperature is 130° C.-150° C. and the time is 4 min-7 min, which can make the semi-cured transparent thermal conductive layer have a certain elastic modulus and bonding strength, which is conducive to improving the bonding force between the semi-cured transparent thermal conductive layer and the silver nanowire layer 102.

[0054] Preferably, the thickness of the semi-cured transparent heat-conducting layer is 50 μm-80 μm, which is more conducive to ensuring the compatibility of transmittance and thermal conductivity of the silver nanowire directional heat-conducting element, and more preferably 60 μm-70 μm.

[0055] In step S2, a semi-cured transparent thermally conductive layer is prepared on the surface of the silver nanowire layer by using a resin composition containing silver nanowires coated with magnetic nanoparticles, and a directional magnetic field perpendicular to the silver nanowire layer is continuously applied during the preparation process. This allows the silver nanowires to achieve excellent directional arrangement in the semi-cured transparent thermally conductive layer under the guidance of the magnetic nanoparticles coated on the surface.

[0056] Then, in step S3, the semi-cured transparent thermal conductive layer is bonded and assembled under the conditions of a directional magnetic field and specific applied pressure. On the one hand, since the elastic modulus of the semi-cured transparent thermal conductive layer is relatively low, the use of a specific applied pressure can not only destroy the magnetic nanoparticles coated on the surface of the silver nanowires, enhance the heat conduction between the silver nanowires, and improve the thermal conductivity of the silver nanowire directional thermal conductor, but also make the contact between the silver nanowires closer through the extrusion effect, thereby solving the problem of reduced thermal conductivity caused by the loose directional arrangement structure of the silver nanowires; on the other hand, by continuously providing a directional magnetic field during the pressurized bonding process, the silver nanowires can maintain a directional arrangement, which is beneficial to improving the directional heat conduction effect of the silver nanowire directional thermal conductor.

[0057] It should be noted that based on quantitative testing of the thickness of the semi-cured transparent thermally conductive layer, it was found that for every 1 μm of semi-cured transparent thermally conductive layer thickness, a pressing and laminating pressure of 5N-12N is required. Specifically, when the thickness of the semi-cured transparent thermally conductive layer is preferably 50μm-80μm, the required pressing and laminating pressure is 250N-960N, and more preferably 400N-600N.

[0058] In order to improve the bonding strength between the second transparent substrate 104 and the semi-cured transparent thermal conductive layer, the second transparent substrate 104 is preferably subjected to plasma modification treatment to graft carboxyl groups and hydroxyl groups on the surface of the second transparent substrate 104 to achieve chemical bonding with the semi-cured transparent thermal conductive layer.

[0059] Specifically, the second transparent substrate is preferably a hard substrate such as glass, so that the silver nanowire directional heat conductor can be directly used as a camera window, etc.

[0060] In step S4, the temperature for complete curing is 150° C.-220° C., and the time is 30 min-90 min.

[0061] Therefore, the preparation method described in the present invention can not only achieve directional heat conduction and excellent heat conduction effect, but also does not limit the selection of magnetic materials and has a simple and easy-to-implement process, which is conducive to promoting the further application of directional heat conduction in the field of heaters.

[0062] Combine Figure 1 The figure shows a silver nanowire directional heat conductor prepared by the method for preparing the silver nanowire directional heat conductor provided by the present invention, comprising a first transparent substrate 101, and a silver nanowire layer 102, a transparent directional heat conductor layer 103, and a second transparent substrate 104 stacked in sequence on the surface of the first transparent substrate 101. This silver nanowire directional heat conductor has excellent heat conduction performance and has broad prospects for commercial application.

[0063] The present invention also provides an application of the silver nanowire directional heat conductor described above in a camera window.

[0064] The silver nanowire directional heat conductor can be used for directional heating of camera windows, achieving rapid and uniform surface heating effects, giving the camera windows excellent defogger and defroster functions, and solving problems such as unclear images caused by fogging and frosting of the windows.

[0065] Hereinafter, the silver nanowire directional heat conductor, its preparation method and application will be further described through the following specific examples.

[0066] Example 1

[0067] Under ultrasonic conditions, the PET substrate was cleaned with acetone and anhydrous ethanol for 15 minutes respectively. After drying, the PET substrate was placed in a plasma cleaner for surface plasma modification, and carboxyl groups and hydroxyl groups were grafted on the surface. Then, a silver nanowire slurry with a concentration of 1 mg / mL prepared by a polyol method was coated on the surface of the PET substrate. After natural drying, a silver nanowire transparent conductive film was obtained, wherein the thickness of the silver nanowire layer was 100 nm.

[0068] 0.01g of silver nitrate, 0.45g of 5-formyl-2-thiopheneboronic acid, 0.31g of PVP, and 10g of ethanol were added to a beaker and stirred for 2 hours to obtain a silver nanocrystal seed dispersion with a grain size of 2nm. Then, 0.09g of silver nitrate, 0.09g of ferroferric oxide nanoparticles, and 1g of bisphenol resin were added to the silver nanocrystal seed dispersion to obtain a mixture with a viscosity of 80 Pa·s. The mixture was irradiated with ultraviolet light for 24 hours to obtain a silver nanowire dispersion with a diameter of 30nm-65nm and a length of 5μm-9μm. The ethanol in the silver nanowire dispersion was removed by thermal evaporation, and 0.01 g of 2-ethyl-4-methylimidazole was added and dispersed with ultrasonic stirring. It was then evenly coated on the surface of the silver nanowire layer by a Meyer bar coating method. The layer was then placed in an oven at 130°C while continuously applying a directional magnetic field perpendicular to the direction of the silver nanowire layer. The layer was cured for 5 minutes to obtain a semi-cured transparent thermal conductive layer with a thickness of 50 μm.

[0069] Under ultrasonic conditions, the glass substrate was cleaned with acetone and anhydrous ethanol for 15 minutes respectively. After drying, the glass substrate was placed in a plasma cleaner for surface plasma modification, and carboxyl and hydroxyl groups were grafted on the surface. Then, a pressure of 500N was applied to flip-chip bond the semi-cured transparent thermal conductive layer to the surface of the glass substrate. During the pressurized bonding process, a directional magnetic field perpendicular to the direction of the semi-cured transparent thermal conductive layer was continuously applied.

[0070] After bonding, place it in an oven at 160°C and cure for 60 minutes to obtain a silver nanowire directional heat conductor. Figure 1 As shown in FIG, it is a structural schematic diagram of the silver nanowire directional heat conductor.

[0071] Example 2

[0072] The difference between Example 2 and Example 1 is that the thickness of the semi-cured transparent heat-conductive layer is 60 μm.

[0073] Example 3

[0074] Under ultrasonic conditions, a PEN substrate was cleaned with acetone and anhydrous ethanol for 15 minutes respectively. After drying, the PEN substrate was placed in a plasma cleaner for surface plasma modification, and carboxyl and hydroxyl groups were grafted on the surface. Then, a silver nanowire slurry with a concentration of 1 mg / mL prepared by a polyol method was coated on the surface of the PEN substrate. After natural drying, a silver nanowire transparent conductive film was obtained, wherein the thickness of the silver nanowire layer was 150 nm.

[0075] A silver nanowire dispersion was prepared using the same preparation method as in Example 1. Ethanol was removed from the silver nanowire dispersion by thermal evaporation, and 0.01 g of 2,4,5-tris(dimethylaminomethyl)phenol was added and dispersed with ultrasonic stirring. The mixture was then evenly coated on the surface of the silver nanowire layer using a Meyer bar coating method. The mixture was then placed in an oven at 140°C while continuously applying a directional magnetic field perpendicular to the silver nanowire layer and cured for 7 minutes to obtain a semi-cured transparent thermally conductive layer with a thickness of 80 μm.

[0076] Under ultrasonic conditions, the glass substrate was cleaned with acetone and anhydrous ethanol for 15 minutes respectively. After drying, the glass substrate was placed in a plasma cleaner for surface plasma modification, and carboxyl and hydroxyl groups were grafted on the surface. Then, a pressure of 400N was applied to flip-chip bond the semi-cured transparent thermal conductive layer to the surface of the glass substrate. During the pressurized bonding process, a directional magnetic field perpendicular to the direction of the semi-cured transparent thermal conductive layer was continuously applied.

[0077] After bonding, it was placed in an oven at 220° C. and cured for 90 minutes to obtain a silver nanowire directional heat conductor.

[0078] Example 4

[0079] Under ultrasonic conditions, a PET substrate was cleaned with acetone and anhydrous ethanol for 15 minutes respectively. After drying, the PET substrate was placed in a plasma cleaner for surface plasma modification, and carboxyl and hydroxyl groups were grafted on the surface. Then, a silver nanowire slurry with a concentration of 1 mg / mL prepared by a polyol method was coated on the surface of the PET substrate. After natural drying, a silver nanowire transparent conductive film was obtained, wherein the thickness of the silver nanowire layer was 200 nm.

[0080] 0.02g of silver acetate, 0.75g of 2-formylfuran-5-boric acid, 0.5g of hexadecyltrimethylammonium bromide, and 9.5g of ethanol were added to a beaker and stirred for 1.5 hours to produce a silver nanocrystal seed dispersion with a grain size of 5nm. Then, 0.12g of silver nitrate, 0.1g of iron oxide nanoparticles, and 1g of polyurethane were added to the silver nanocrystal seed dispersion to produce a mixture with a viscosity of 100 Pa·s. The mixture was irradiated with ultraviolet light for 24 hours to produce a silver nanowire dispersion with a diameter of 50nm-100nm and a length of 3μm-10μm. The ethanol in the silver nanowire dispersion was removed by thermal evaporation, and 0.01 g of 2-ethyl-4-methylimidazole was added and dispersed with ultrasonic stirring. It was then evenly coated on the surface of the silver nanowire layer by a Meyer bar coating method. The layer was then placed in an oven at 150°C while continuously applying a directional magnetic field perpendicular to the direction of the silver nanowire layer. The layer was cured for 4 minutes to obtain a semi-cured transparent thermal conductive layer with a thickness of 50 μm.

[0081] Under ultrasonic conditions, the glass substrate was cleaned with acetone and anhydrous ethanol for 15 minutes respectively. After drying, the glass substrate was placed in a plasma cleaner for surface plasma modification, and carboxyl and hydroxyl groups were grafted on the surface. Then, a pressure of 600N was applied to flip-chip bond the semi-cured transparent thermal conductive layer to the surface of the glass substrate. During the pressurized bonding process, a directional magnetic field perpendicular to the direction of the semi-cured transparent thermal conductive layer was continuously applied.

[0082] After bonding, it was placed in an oven at 150° C. and cured for 80 minutes to obtain a silver nanowire directional heat conductor.

[0083] Comparative Example 1

[0084] The difference between Comparative Example 1 and Example 1 is that after the semi-cured transparent heat-conducting layer is flip-chip bonded to the surface of the glass substrate with a pressure of 500N, it is directly placed in a 160°C oven for curing for 60 minutes to obtain a silver nanowire directional heat-conducting member. Figure 2 As shown in FIG, it is a structural schematic diagram of the silver nanowire directional heat conductor.

[0085] Comparative Example 2

[0086] The difference between Comparative Example 2 and Example 1 is that the semi-cured transparent heat-conducting layer is directly flip-chip bonded to the surface of the glass substrate to obtain a silver nanowire directional heat-conducting member. Figure 3 As shown in FIG, it is a structural schematic diagram of the silver nanowire directional heat conductor.

[0087] Comparative Example 3

[0088] The difference between Comparative Example 3 and Example 1 is that a pressure of 200N is applied to flip-chip bond the semi-cured transparent heat-conductive layer to the surface of the glass substrate.

[0089] Comparative Example 4

[0090] The difference between Comparative Example 4 and Example 1 is that a pressure of 650N is applied to flip-chip bond the semi-cured transparent heat-conducting layer to the surface of the glass substrate.

[0091] The silver nanowire directional heat conductors prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to performance tests: the time required for the outer surface temperature of the glass to reach the same 45°C at room temperature under a DC voltage of 12V, and the stable temperature reached by the outer surface of the glass after heating for 60s.

[0092] Table 1

[0093]

[0094]

[0095] It can be seen from Table 1 that the silver nanowire directional heat conductor prepared by the preparation method provided by the present invention has high thermal conductivity and excellent thermal conductivity effect.

[0096] Combine Figure 2 As shown, since comparative example 1 did not undergo orientation treatment during the press-bonding process, some silver nanowires tilted during the press-bonding process, resulting in a lateral heat conduction problem in the final heat-conducting layer structure. At the same time, there may be a certain gap between the heat-conducting layer and the glass. Therefore, the final outer surface temperature of the silver nanowire oriented heat-conducting member is lower than that of Examples 1-4.

[0097] Combine Figure 3 As shown, since no pressure was applied during the bonding process in Comparative Example 2, the magnetic nanoparticles coated on the surface of the silver nanowires were not damaged. As a result, the presence of the magnetic nanoparticles resulted in poor heat conduction between the silver nanowires. At the same time, gaps may exist between the silver nanowires in the vertical direction, thereby significantly reducing the thermal conductivity. Therefore, the overall heat conduction of the silver nanowire directional heat conductor is not as good as that of Examples 1-4.

[0098] In Comparative Example 3, however, only a pressure of 200 N was applied under the condition of a semi-cured transparent thermal conductive layer thickness of 50 μm, which did not reach the failure pressure limit of the magnetic nanoparticles coated on the surface of the silver nanowires, resulting in poor heat conduction between the silver nanowires. Therefore, the overall heat conduction of the silver nanowire directional heat conductor was inferior to that of Examples 1-4. In Comparative Example 4, a pressure of up to 650 N was applied under the condition of a semi-cured transparent thermal conductive layer thickness of 50 μm, which completely separated the magnetic nanoparticles from the surface of the silver nanowires, causing the silver nanowires to tilt during the pressurized bonding process. Therefore, the overall heat conduction of the silver nanowire directional heat conductor was inferior to that of Examples 1-4.

[0099] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0100] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a silver nanowire directional heat conductor, characterized in that: The steps include: A silver nanowire transparent conductive film is provided, wherein the silver nanowire transparent conductive film comprises a first transparent substrate and a silver nanowire layer stacked together; A semi-cured transparent thermally conductive layer is prepared on the surface of the silver nanowire layer using a resin composition, and an oriented magnetic field perpendicular to the silver nanowire layer is continuously applied during the preparation process, wherein the resin composition comprises silver nanowires coated with magnetic nanoparticles and a thermosetting resin; Pressing and laminating a second transparent substrate on the surface of the semi-cured transparent thermally conductive layer, and continuously applying a directional magnetic field perpendicular to the semi-cured transparent thermally conductive layer during the press-lamination process, wherein the pressure of the press-lamination is 5N-12N based on the thickness of the semi-cured transparent thermally conductive layer of 1 μm; After pressurizing and laminating, the semi-cured transparent heat-conducting layer is completely cured to obtain a silver nanowire directional heat-conducting member.

2. The method for preparing the silver nanowire directional heat conductor according to claim 1, characterized in that: The thickness of the semi-cured transparent heat-conducting layer is 50 μm-80 μm.

3. The method for preparing the silver nanowire directional heat conductor according to claim 1, characterized in that: The preparation method of the resin composition comprises the following steps: Mixing a first silver source, a reducing agent, a protective agent, and a polar solvent to obtain a first mixture, and reacting the first mixture to prepare a silver nanocrystal seed dispersion, wherein the reducing agent is an aldehyde-containing acid anhydride; The silver nanocrystal seed dispersion is mixed with a second silver source, magnetic nanoparticles, and a thermosetting resin to obtain a second mixture, the second mixture is irradiated with ultraviolet light, and then the polar solvent is removed to obtain a resin composition, wherein the viscosity of the second mixture is less than or equal to 200 Pa·s.

4. The method for preparing the silver nanowire directional heat conductor according to claim 3, wherein: In the step of irradiating the second mixture with ultraviolet light, the wavelength of the ultraviolet light is 340nm-400nm, and the irradiation time is 12h-36h.

5. The method for preparing the silver nanowire directional heat conductor according to claim 1, 3 or 4, wherein: The silver nanowires coated with magnetic nanoparticles are of a core-shell structure, wherein the core is the silver nanowire and the shell is composed of magnetic nanoparticles.

6. The method for preparing the silver nanowire directional heat conductor according to claim 1, characterized in that: The resin composition further includes a curing accelerator.

7. The method for preparing a silver nanowire directional heat conductor according to claim 1, wherein: In the step of preparing a semi-cured transparent heat-conducting layer on the surface of the silver nanowire layer, the semi-curing temperature is 130° C.-150° C., and the time is 4 min-7 min.

8. The method for preparing the silver nanowire directional heat conductor according to claim 1, characterized in that: In the step of completely curing the semi-cured transparent heat-conducting layer, the temperature for complete curing is 150° C.-220° C., and the time is 30 min-90 min.

9. A silver nanowire directional heat conductor prepared by the method for preparing a silver nanowire directional heat conductor according to any one of claims 1 to 8, characterized in that: The silver nanowire directional heat conducting element includes a first transparent substrate, and a silver nanowire layer, a transparent directional heat conducting layer and a second transparent substrate which are sequentially stacked on the surface of the first transparent substrate.

10. The silver nanowire directional heat conductor according to claim 9 is used for a camera window.

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