Flexible heating film, preparation method thereof and heating device

Abstract

The invention provides a flexible heating film, a preparation method thereof and a heating device, and relates to the field of electric heating. The flexible heating film comprises a transparent flexible substrate, a transparent conductive layer, an electrode and a TPU protective layer which are stacked, the thickness of the transparent flexible substrate is 50-60 microns, the thickness of the electrode is 15-30 microns, and the thickness of the TPU protective layer is 30-40 microns. The flexible heating film has excellent heating performance, also has the advantages of being ultrathin, highly soft, excellent in waterproofness and the like, has wide applicability, can be flexibly applied to various life scenes, and meets diversified heating requirements. Moreover, the flexible heating film also has the advantages of simple structure, safety and reliability, and the production cost, the maintenance cost in the use process and the potential safety risk are reduced.

Description

Technical Field

[0001] The present application relates to the field of heating materials, and in particular to a flexible heating film, a preparation method thereof, and a heating device. Background Art

[0002] With the rapid development of modern technology, especially in the field of wearable devices, the demand for heating materials is growing. As a key component that can convert electrical energy into thermal energy, heating film plays a vital role. The ideal heating film not only needs to have good heating efficiency and uniformity, but also needs to be soft and thin enough to adapt to various complex curved surfaces and lightweight design requirements.

[0003] However, the heating films reported so far generally have some technical bottlenecks, which limit their promotion and use in high-end application fields. The primary problem is the lack of softness. Traditional heating films have poor flexibility and are difficult to adapt to deformation requirements such as bending and folding, which limits their application in wearable devices or occasions that need to fit the curves of the human body.

[0004] Secondly, the thickness problem is another urgent problem to be solved. Existing heating films often have to sacrifice the thin and light characteristics in pursuit of heating efficiency and structural strength, resulting in a larger overall thickness. This not only increases the weight of the product, but may also affect the user experience, and is also not conducive to the miniaturization and integrated design of the device.

[0005] Therefore, developing a heating film that has both excellent heating performance and is ultra-thin and highly flexible has become an urgent problem to be solved in the current field of heating materials. Summary of the invention

[0006] The purpose of the present application is to provide a flexible heating film and a preparation method thereof and a heating device to solve the above problems.

[0007] To achieve the above objectives, this application adopts the following technical solutions:

[0008] A flexible heating film comprises a transparent flexible substrate, a transparent conductive layer, an electrode and a TPU protective layer which are stacked; the transparent flexible substrate has a thickness of 50-60 μm, the electrode has a thickness of 15-30 μm, and the TPU protective layer has a thickness of 30-40 μm.

[0009] According to an embodiment of the present application, the material of the transparent conductive layer includes graphene, transparent metal grid, nano silver wire, ITO or AZO;

[0010] And / or, the transparent conductive layer has a hollow area, the electrode covers the hollow area, and the orthographic projection area of ​​the electrode on the transparent flexible substrate is larger than the area of ​​the hollow area.

[0011] According to an embodiment of the present application, the material of the transparent flexible substrate includes PET, PDMS, PI or PEN;

[0012] and / or, the material forming the electrode includes silver paste;

[0013] And / or, the electrode comprises two inner electrodes arranged in parallel, each of the inner electrodes is connected to a plurality of bus bars, and the bus bars on the two inner electrodes extend towards each other to form interdigitated electrodes arranged at equal intervals;

[0014] And / or, an electrode terminal is also installed on the electrode, and the electrode terminal is used to fix one end of the conductive wire to the electrode, and the other end of the conductive wire is used to be connected to an external power source.

[0015] According to an embodiment of the present application, the flexible heating film further includes a glue layer, and the glue layer is located between the electrode and the TPU protective layer;

[0016] And / or, the material of the adhesive layer includes acrylate.

[0017] The present application also provides a method for preparing the flexible heating film as described above, comprising:

[0018] forming a transparent conductive layer on one side of a transparent flexible substrate, and forming an electrode on a side of the transparent conductive layer away from the transparent flexible substrate to obtain a composite structure;

[0019] The composite structure is laminated to the TPU protective layer so that the electrode is located between the transparent conductive layer and the TPU protective layer to obtain a flexible heating film.

[0020] According to an embodiment of the present application, when the material of the transparent conductive layer is graphene, forming the transparent conductive layer on one side of the transparent flexible substrate includes:

[0021] Growing graphene on copper foil using chemical vapor deposition;

[0022] Laminating an electrostatic film with a copper foil on which graphene is grown to form an electrostatic film-graphene-copper foil structure, then placing the electrostatic film in an etching solution for etching to remove the copper foil to obtain an electrostatic film-graphene structure, transferring the electrostatic film-graphene structure to a transparent flexible substrate so that the graphene is located between the electrostatic film and the transparent flexible substrate, and peeling off the electrostatic film to form a graphene layer on the transparent flexible substrate;

[0023] And / or, the etching solution includes hydrogen peroxide, inorganic acid, chelated dopant and water, the concentration of hydrogen peroxide in the etching solution is 5-50g / L, the concentration of inorganic acid in the etching solution is 5-50g / L, and the concentration of chelated dopant in the etching solution is 0.5-5g / L; the inorganic acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid, and the chelated dopant includes at least one of organic phosphate compounds, imidazole, imidazole derivatives, triazole, and triazole derivatives.

[0024] According to an embodiment of the present application, before forming a transparent conductive layer on one side of the transparent flexible substrate, the method further includes: performing a pre-shrinking treatment on the transparent flexible substrate, the pre-shrinking treatment including: baking the transparent flexible substrate at a first temperature for 30-60 minutes, the first temperature being 120° C.-200° C.;

[0025] After forming the graphene layer on the transparent flexible substrate, the method further includes: baking the transparent flexible substrate-graphene layer structure at a second temperature for 30-90 minutes; the second temperature is 100° C.-180° C., and the second temperature is lower than the first temperature.

[0026] According to an embodiment of the present application, forming a transparent conductive layer on one side of a transparent flexible substrate includes: forming a whole layer of transparent conductive structure on the surface of the transparent flexible substrate, and then patterning the whole layer of transparent conductive structure to form a hollow area on the whole layer of transparent conductive structure to obtain a transparent conductive layer, wherein the transparent conductive layer has a hollow area;

[0027] and / or, the patterning process comprises laser processing;

[0028] Forming an electrode on a side of the transparent conductive layer away from the transparent flexible substrate comprises: printing silver paste on a side of the transparent conductive layer away from the transparent flexible substrate by screen printing, and drying to form an electrode;

[0029] And / or, when the transparent conductive layer has a hollow area, when forming the electrode, the method further comprises: allowing the silver paste to cover the hollow area;

[0030] And / or, the drying temperature is 100-120° C., and the drying time is 60-90 min.

[0031] According to an embodiment of the present application, after obtaining the composite structure, the method further comprises: screen printing an adhesive on one side of the TPU protective layer, heating, and forming an adhesive layer on one side of the TPU protective layer;

[0032] Laminating the TPU protective layer having the adhesive layer to the composite structure so that the adhesive layer is located between the electrode and the TPU protective layer, and performing a degassing treatment to obtain a flexible heating film;

[0033] And / or, the heating temperature is 50-60°C, and the heating time is 10-15min;

[0034] And / or, the adhesive comprises acrylate and a diluent, the mass of the diluent accounts for 1%-10% of the mass of the adhesive, and the diluent comprises at least one of xylene, ethyl acetate, propylene glycol methyl ether acetate, ethylene glycol ethyl ether, and isoamyl acetate;

[0035] And / or, the pressure applied in the degassing treatment is 3.5-4 kg, the temperature of the degassing treatment is 35-40° C., and the time of the degassing treatment is 20-30 min.

[0036] The present application also provides a heating device, which includes the flexible heating film described above or the flexible heating film prepared by the preparation method described above.

[0037] Compared with the prior art, the beneficial effects of this application include:

[0038] The flexible heating film of the present application has excellent heating performance, and also has the advantages of being ultra-thin, highly soft, and excellent in waterproofness. It has a wide range of applicability and can be flexibly applied to various life scenarios to meet diverse heating needs. Moreover, the flexible heating film of the present application also has the advantages of simple structure, safety and reliability, which reduces production costs, maintenance costs during use, and potential safety risks. Specifically, the flexible heating film of the present application uses TPU as a protective layer. This design can minimize the deformation that may be caused by high temperature during the power-on heating process, and ensure the stability of the heating film. Compared with other polymer flexible materials such as PES, TPU exhibits better elasticity, softness and comfort, and higher light transmittance, thereby improving the overall performance of the heating film. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0040] Figure 1 is a cross-sectional view of a flexible heating film in one embodiment of the present application;

[0041] Figure 2 This is a top view of a flexible heating film in one embodiment of the present application.

[0042] Description of reference numerals:

[0043] 1-transparent flexible substrate, 2-transparent conductive layer, 3-electrode, 31-inner electrode, 32-bus bar, 4-TPU protective layer, 5-electrode terminal, a-heating area. DETAILED DESCRIPTION

[0044] As used herein:

[0045] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0046] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0047] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0048] In these examples, parts and percentages are by mass unless otherwise indicated.

[0049] "Parts by mass" refers to the basic unit of measurement for expressing the mass ratio of multiple components. 1 part can represent any unit mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass of all components is not limited to 100 parts.

[0050] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0051] In order to better explain the technical solution provided by this application, before the embodiments, the technical solution is first described as a whole, as follows:

[0052] A flexible heating film, reference Figure 1 , including a transparent flexible substrate 1, a transparent conductive layer 2, an electrode 3 and a TPU protective layer 4 which are stacked; the thickness of the transparent flexible substrate 1 is 50-60 μm, the thickness of the electrode 3 is 15-30 μm, and the thickness of the TPU protective layer 4 is 30-40 μm.

[0053] The flexible heating film of the present application has a transparent property, which greatly broadens the scope of application, gives the product a sense of technology and beauty, and is conducive to improving user experience.

[0054] According to some embodiments of the present application, the thickness of the transparent flexible substrate 1 can be 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm or any value between 50 and 60 μm, and the thickness of the electrode 3 can be 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, The thickness of the TPU protective layer 4 can be 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm or any value between 30-40μm.

[0055] According to some embodiments of the present application, the thickness of the transparent conductive layer 2 is nanometer level.

[0056] According to an embodiment of the present application, the material of the transparent conductive layer 2 includes graphene, transparent metal grid, nano silver wire, ITO (tin-doped indium trioxide) or AZO (aluminum-doped zinc oxide);

[0057] And / or, the transparent conductive layer 2 has a hollow area, the electrode 3 covers the hollow area, and the orthographic projection area of ​​the electrode 3 on the transparent flexible substrate 1 is larger than the area of ​​the hollow area. The electrode 3 of the present application is in electrical contact with the transparent conductive layer 2. This structural design can ensure that the overall heating temperature of the surface heating electric heating film is evenly distributed, and effectively prevent the problem of heat concentration in the area between two adjacent inner electrodes.

[0058] According to an embodiment of the present application, the material of the transparent flexible substrate 1 includes PET (polyethylene terephthalate), PDMS (polydimethylsiloxane), PI (polyimide) or PEN (polyethylene naphthalate);

[0059] And / or, the material forming the electrode 3 includes silver paste;

[0060] According to the embodiments of the present application, reference Figure 2 The electrode 3 includes two parallel inner electrodes 31, each of which is connected to a plurality of bus bars 32, and the bus bars 32 on the two inner electrodes 31 extend toward each other to form interdigitated electrodes arranged at equal intervals; the flexible heating film has a plurality of heating areas a, and the heating area a is located in the area between the two inner electrodes 31 and two adjacent bus bars 32.

[0061] And / or, an electrode terminal 5 is also installed on the electrode 3, and the electrode terminal 5 is used to fix one end of the conductive wire to the electrode 3, and the other end of the conductive wire is used to be connected to an external power source.

[0062] According to an embodiment of the present application, the flexible heating film further includes a glue layer, and the glue layer is located between the electrode 3 and the TPU protective layer 4;

[0063] And / or, the material of the adhesive layer includes acrylate.

[0064] The present application also provides a method for preparing the flexible heating film as described above, comprising:

[0065] A transparent conductive layer 2 is formed on one side of a transparent flexible substrate 1, and an electrode 3 is formed on a side of the transparent conductive layer 2 away from the transparent flexible substrate 1 to obtain a composite structure;

[0066] The composite structure is laminated to the TPU protective layer 4 so that the electrode 3 is located between the transparent conductive layer 2 and the TPU protective layer 4 to obtain a flexible heating film.

[0067] According to an embodiment of the present application, when the material of the transparent conductive layer 2 is graphene, forming the transparent conductive layer 2 on one side of the transparent flexible substrate 1 includes:

[0068] Growing graphene on copper foil using chemical vapor deposition;

[0069] Laminating the electrostatic film with the copper foil on which graphene is grown to form an electrostatic film-graphene-copper foil structure, then placing the electrostatic film in an etching solution for etching to remove the copper foil to obtain an electrostatic film-graphene structure, transferring the electrostatic film-graphene structure to a transparent flexible substrate 1 so that the graphene is located between the electrostatic film and the transparent flexible substrate 1, and peeling off the electrostatic film to form a graphene layer on the transparent flexible substrate 1;

[0070] In the related art, the graphene layer is usually prepared by coating with a modulated ink, and the photoelectric properties of the graphene film prepared by this method are poor. Specifically, due to the strong van der Waals force between carbon nanomaterials, they are easy to aggregate in liquids. To make a coating suspension, some dispersants must be added to the liquid. These additives will affect the photoelectric properties of the film. The method for preparing a graphene layer in the present application can improve the above defects. The graphene layer prepared by the method of the present application has excellent photoelectric properties.

[0071] And / or, the etching solution includes hydrogen peroxide, inorganic acid, chelated dopant and water, the concentration of hydrogen peroxide in the etching solution is 5-50g / L, the concentration of inorganic acid in the etching solution is 5-50g / L, and the concentration of chelated dopant in the etching solution is 0.5-5g / L; the inorganic acid includes at least one of hydrochloric acid, sulfuric acid and nitric acid, and the chelated dopant includes at least one of organic phosphate compounds, imidazole, imidazole derivatives, triazole and triazole derivatives. The imidazole derivatives include but are not limited to nitrophenylimidazole.

[0072] For example, the concentration of hydrogen peroxide in the etching solution can be 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L or any value between 5-50 g / L.

[0073] The concentration of the inorganic acid in the etching solution can be 5g / L, 10g / L, 15g / L, 20g / L, 25g / L, 30g / L, 35g / L, 40g / L, 45g / L, 50g / L or any value between 5-50g / L.

[0074] The concentration of the chelating dopant in the etching solution may be 0.5 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L or any value between 0.5-5 g / L.

[0075] According to an embodiment of the present application, before forming the transparent conductive layer 2 on one side of the transparent flexible substrate 1, the method further includes: performing a pre-shrinking treatment on the transparent flexible substrate 1, the pre-shrinking treatment including: baking the transparent flexible substrate 1 at a first temperature for 30-60 minutes, the first temperature being 120° C.-200° C.;

[0076] After forming the graphene layer on the transparent flexible substrate 1, the method further includes: baking the transparent flexible substrate-graphene layer structure at a second temperature for 30-90 minutes; the second temperature is 100°C-180°C, and the second temperature is lower than the first temperature, thereby preventing deformation and ensuring the transfer effect.

[0077] For example, the baking time of the transparent flexible substrate at the first temperature can be 30 minutes, 40 minutes, 50 minutes, 60 minutes or any value between 30-60 minutes, and the first temperature can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or any value between 120°C-200°C.

[0078] The baking time of the transparent flexible substrate-graphene layer structure at the second temperature can be 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes or any value between 30-90 minutes, and the second temperature can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C or any value between 100°C-180°C.

[0079] According to an embodiment of the present application, forming a transparent conductive layer 2 on one side of a transparent flexible substrate 1 includes: forming a whole layer of transparent conductive structure on the surface of the transparent flexible substrate 1, and then patterning the whole layer of transparent conductive structure to form a hollow area on the whole layer of transparent conductive structure to obtain a transparent conductive layer 2, wherein the transparent conductive layer 2 has a hollow area;

[0080] and / or, the patterning process comprises laser processing;

[0081] Forming the electrode 3 on the side of the transparent conductive layer 2 away from the transparent flexible substrate 1 includes: printing silver paste on the side of the transparent conductive layer 2 away from the transparent flexible substrate 1 by screen printing, and drying to form the electrode 3;

[0082] And / or, when the transparent conductive layer 2 has a hollow area, when forming the electrode 3, the method further comprises: allowing the silver paste to cover the hollow area;

[0083] And / or, the drying temperature is 100-120° C., and the drying time is 60-90 min.

[0084] For example, the drying temperature may be 100° C., 110° C., 120° C. or any value between 100-120° C., and the drying time may be 60 min, 70 min, 80 min, 90 min or any value between 60-90 min.

[0085] According to an embodiment of the present application, after obtaining the composite structure, the method further comprises: screen printing an adhesive on one side of the TPU protective layer 4, heating, and forming an adhesive layer on one side of the TPU protective layer 4;

[0086] The TPU protective layer 4 having the adhesive layer is laminated to the composite structure so that the adhesive layer is located between the electrode 3 and the TPU protective layer 4, and a degassing treatment is performed to obtain a flexible heating film;

[0087] And / or, the heating temperature is 50-60°C, and the heating time is 10-15min;

[0088] For example, the heating temperature can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C or any value between 50-60°C, and the heating time can be 10min, 11min, 12min, 13min, 14min, 15min or any value between 10-15min.

[0089] And / or, the adhesive comprises acrylate and a diluent, the mass of the diluent accounts for 1%-10% of the mass of the adhesive, and the diluent comprises at least one of xylene, ethyl acetate, propylene glycol methyl ether acetate, ethylene glycol ethyl ether, and isoamyl acetate;

[0090] For example, the mass of the diluent may account for 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value between 1% and 10% of the mass of the adhesive.

[0091] According to some embodiments of the present application, the screen mesh number of the silk-screen adhesive may be 50-300 meshes.

[0092] And / or, the pressure applied in the degassing treatment is 3.5-4 kg, the temperature of the degassing treatment is 35-40° C., and the time of the degassing treatment is 20-30 min.

[0093] For example, the pressure applied for the degassing treatment can be 3.5kg, 3.6kg, 3.7kg, 3.8kg, 3.9kg, 4kg or any value between 3.5-4kg, the temperature of the degassing treatment can be 35°C, 36°C, 37°C, 38°C, 39°C, 40°C or any value between 35-40°C, and the time of the degassing treatment can be 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min, 30min or any value between 20-30min.

[0094] The present application also provides a heating device, which includes the flexible heating film described above or the flexible heating film prepared by the preparation method described above. The heating device includes wearable devices and daily heating equipment. The wearable devices include but are not limited to heating clothing, cervical massagers, and uterine warming belts. Daily heating equipment includes but is not limited to heating carpets and wall heating. The heating device of the present application can provide users with a personalized warm experience, making heating more convenient and comfortable.

[0095] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0096] Example 1

[0097] Embodiment 1 provides a flexible heating film, and the preparation method thereof comprises:

[0098] (1) Pre-shrinking the PET, placing the PET in an oven and baking it at 120° C. for 30 minutes, and the thickness of the PET after pre-shrinking is 50 μm.

[0099] (2) Forming a graphene layer on PET:

[0100] Growing graphene on copper foil using chemical vapor deposition;

[0101] The electrostatic film is laminated to the copper foil on which graphene is grown to form an electrostatic film-graphene-copper foil structure, and then placed in an etching solution for etching to remove the copper foil, and then air-dried to obtain an electrostatic film-graphene structure, and the electrostatic film-graphene structure is transferred to PET so that the graphene is located between the electrostatic film and the PET, and the electrostatic film is peeled off to form graphene on the PET;

[0102] A double layer of graphene is required on PET, so it needs to be transferred twice to 50 μm thick PET to obtain a graphene layer. After obtaining the graphene layer, the PET-graphene layer is baked at 100°C for 30 minutes.

[0103] Among them, the formula of the etching solution includes hydrogen peroxide, inorganic acid, chelating dopant and deionized water, the inorganic acid is hydrochloric acid, the chelating dopant is nitrophenylimidazole, the concentration of hydrogen peroxide in the etching solution is 27g / L, the concentration of inorganic acid in the etching solution is 35g / L, and the concentration of chelating dopant in the etching solution is 1g / L.

[0104] (3) The graphene layer obtained in step (2) is subjected to laser processing according to the drawing to form a hollow area in the graphene layer, and then silver paste is used for screen printing to cover the hollow area with the silver paste. After the screen printing is completed, the electrode is baked to obtain the electrode; wherein the baking conditions are 120° C. and 60 min.

[0105] The thickness of the electrode is 27 μm, and the electrode is an interdigitated electrode with Figure 2 The structure shown.

[0106] (4) Cut the TPU layer. The cutting size is determined according to the size of the printable area of ​​the screen. Then, the adhesive is screen-printed on the TPU layer. After the screen printing is completed, it is placed in an oven to form an adhesive layer on the TPU layer. The operating parameters of the oven are 50°C and 10 minutes.

[0107] The adhesive comprises acrylate and a diluent accounting for 3% of the mass of the acrylate, wherein the diluent is isoamyl acetate and is screen printed using a 50-300 mesh screen.

[0108] The thickness of the TPU layer was 33 μm.

[0109] (5) The TPU layer with the adhesive layer obtained in step (4) is bonded to the structure obtained in step (3), and then cut into small pieces and degassed to obtain a flexible heating film.

[0110] The pressure applied during the degassing treatment was 3.5 kg, the temperature during the degassing treatment was 35° C., and the time during the degassing treatment was 20 min.

[0111] Comparative Example 1

[0112] A flexible heating film was prepared by referring to the method of Example 1. Other conditions were the same as those of Example 1, except that in step (4) of Comparative Example 1, a PES layer of the same thickness was used to replace the TPU layer in Example 1.

[0113] The flexible heating films prepared in Example 1 and Comparative Example 1 were subjected to cold folding test and cold bending test under the same conditions.

[0114] Specifically, the cold bending test: roll the flexible heating film sample on a paper tube with a diameter of 55mm, then place the rolled sample in an environment of -30℃ for 4 hours, then open the sample at 20-25℃, reroll it from the opposite direction, repeat three times within 30 minutes, and then restore the sample at ambient temperature (room temperature) for 4 hours. After the test, check whether the electrical and mechanical properties of the product are abnormal. After the cold bending test, if the flexible heating film does not show brittleness, cracking, deformation or delamination, the appearance after bending is OK; after the cold bending test, if the flexible heating film shows at least one of the phenomena of brittleness, cracking, deformation or delamination, the appearance after bending is NG.

[0115] Cold folding test: In the cold folding test, when the temperature is maintained at -30℃±3℃, the flexible heating film sample is folded into 90°, and then the electrical and mechanical properties of the flexible heating film product are checked for abnormalities. After the cold folding test, if the insulating layer (TPU protective layer and transparent flexible substrate) of the flexible heating film is not broken, the appearance after bending is OK; if any of the TPU protective layer and transparent flexible substrate of the flexible heating film is broken, the appearance after bending is NG.

[0116] The following three conditions must be met for infrared thermal imaging distribution test of the cold-bent and cold-folded flexible heating film: 1. The difference between the highest and lowest temperatures on the surface of the flexible heating film is no more than 7°C; 2. When the electric heating film (flexible heating film) works under normal working conditions until a stable working state is established, the temperature at any point of the electrode should not be greater than the temperature of the film; 3. The temperature difference in each heating area is less than 15°C. If the cold-bent and cold-folded flexible heating film meets the above three conditions at the same time, the infrared is OK after bending; if the cold-bent and cold-folded flexible heating film does not meet the above three conditions at the same time, the infrared is NG after bending.

[0117] Among them, when the flexible heating films prepared in Example 1 and Comparative Example 1 were subjected to cold folding test and cold bending test, each item was tested twice under the same test conditions.

[0118] Table 1 Performance test table of the flexible heating film prepared in Example 1 and Comparative Example 1

[0119]

[0120] The resistance change rate in the table = (resistance after bending - original resistance) / original resistance x 100%.

[0121] It should be noted that Example 1-1, Example 1-2, Example 1-3, and Example 1-4 are all flexible heating films prepared by the method of Example 1, and Comparative Example 1-1, Comparative Example 1-2, Comparative Example 1-3, and Comparative Example 1-4 are all flexible heating films prepared by the method of Comparative Example 1.

[0122] It can be seen from Table 1 that compared with Comparative Example 1, the flexible heating film prepared in Example 1 has a lower resistance change rate after cold bending or cold folding, and has a better appearance. This shows that the use of TPU material as a protective layer not only ensures the flexible and thin characteristics of the product, but also significantly improves the overall strength and heating uniformity of the heating film.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0124] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present application and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A flexible heating film, characterized in that: It includes a transparent flexible substrate, a transparent conductive layer, an electrode and a TPU protective layer which are stacked; The thickness of the transparent flexible substrate is 50-60 μm, the thickness of the electrode is 15-30 μm, and the thickness of the TPU protective layer is 30-40 μm.

2. The flexible heating film according to claim 1, characterized in that: The material of the transparent conductive layer includes graphene, transparent metal grid, nano silver wire, ITO or AZO; And / or, the transparent conductive layer has a hollow area, the electrode covers the hollow area, and the orthographic projection area of ​​the electrode on the transparent flexible substrate is larger than the area of ​​the hollow area.

3. The flexible heating film according to claim 1, characterized in that: The material of the transparent flexible substrate includes PET, PDMS, PI or PEN; and / or, the material forming the electrode includes silver paste; And / or, the electrode comprises two inner electrodes arranged in parallel, each of the inner electrodes is connected to a plurality of bus bars, and the bus bars on the two inner electrodes extend towards each other to form interdigitated electrodes arranged at equal intervals; And / or, an electrode terminal is also installed on the electrode, and the electrode terminal is used to fix one end of the conductive wire to the electrode, and the other end of the conductive wire is used to be connected to an external power source.

4. The flexible heating film according to any one of claims 1 to 3, characterized in that: The flexible heating film further comprises a glue layer, and the glue layer is located between the electrode and the TPU protective layer; And / or, the material of the adhesive layer includes acrylate.

5. A method for preparing a flexible heating film according to any one of claims 1 to 4, characterized in that: include: forming a transparent conductive layer on one side of a transparent flexible substrate, and forming an electrode on a side of the transparent conductive layer away from the transparent flexible substrate to obtain a composite structure; The composite structure is laminated to the TPU protective layer so that the electrode is located between the transparent conductive layer and the TPU protective layer to obtain a flexible heating film.

6. The method for preparing the flexible heating film according to claim 5, characterized in that: When the material of the transparent conductive layer is graphene, forming the transparent conductive layer on one side of the transparent flexible substrate comprises: Growing graphene on copper foil using chemical vapor deposition; Laminating the electrostatic film with the copper foil on which graphene is grown to form an electrostatic film-graphene-copper foil structure, then placing the electrostatic film in an etching solution for etching to remove the copper foil to obtain an electrostatic film-graphene structure, transferring the electrostatic film-graphene structure to the transparent flexible substrate so that the graphene is located between the electrostatic film and the transparent flexible substrate, and peeling off the electrostatic film to form a graphene layer on the transparent flexible substrate; And / or, the etching solution includes hydrogen peroxide, inorganic acid, chelated dopant and water, the concentration of hydrogen peroxide in the etching solution is 5-50g / L, the concentration of inorganic acid in the etching solution is 5-50g / L, and the concentration of chelated dopant in the etching solution is 0.5-5g / L; the inorganic acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid, and the chelated dopant includes at least one of organic phosphate compounds, imidazole, imidazole derivatives, triazole, and triazole derivatives.

7. The method for preparing the flexible heating film according to claim 6, characterized in that: Before forming the transparent conductive layer on one side of the transparent flexible substrate, the method further includes: performing a pre-shrinking treatment on the transparent flexible substrate, the pre-shrinking treatment including: baking the transparent flexible substrate at a first temperature for 30-60 minutes, the first temperature being 120° C.-200° C.; After forming the graphene layer on the transparent flexible substrate, the method further includes: baking the transparent flexible substrate-graphene layer structure at a second temperature for 30-90 minutes; the second temperature is 100° C.-180° C., and the second temperature is lower than the first temperature.

8. The method for preparing the flexible heating film according to claim 5, characterized in that: Forming a transparent conductive layer on one side of the transparent flexible substrate includes: forming a whole layer of transparent conductive structure on the surface of the transparent flexible substrate, and then patterning the whole layer of transparent conductive structure to form a hollow area on the whole layer of transparent conductive structure to obtain a transparent conductive layer, wherein the transparent conductive layer has a hollow area; and / or, the patterning process comprises laser processing; Forming an electrode on a side of the transparent conductive layer away from the transparent flexible substrate comprises: printing silver paste on a side of the transparent conductive layer away from the transparent flexible substrate by screen printing, and drying to form an electrode; And / or, when the transparent conductive layer has a hollow area, when forming the electrode, the method further comprises: allowing the silver paste to cover the hollow area; And / or, the drying temperature is 100-120° C., and the drying time is 60-90 min.

9. The method for preparing a flexible heating film according to any one of claims 5 to 8, characterized in that: After obtaining the composite structure, the method further comprises: screen printing an adhesive on one side of the TPU protective layer, heating, and forming an adhesive layer on one side of the TPU protective layer; Laminating the TPU protective layer having the adhesive layer to the composite structure so that the adhesive layer is located between the electrode and the TPU protective layer, and performing a degassing treatment to obtain a flexible heating film; And / or, the heating temperature is 50-60°C, and the heating time is 10-15min; And / or, the adhesive comprises acrylate and a diluent, the mass of the diluent accounts for 1%-10% of the mass of the adhesive, and the diluent comprises at least one of xylene, ethyl acetate, propylene glycol methyl ether acetate, ethylene glycol ethyl ether, and isoamyl acetate; And / or, the pressure applied in the degassing treatment is 3.5-4 kg, the temperature of the degassing treatment is 35-40° C., and the time of the degassing treatment is 20-30 min.

10. A heating device, characterized in that: The heating device comprises the flexible heating film according to any one of claims 1 to 4 or the flexible heating film prepared by the preparation method according to any one of claims 5 to 9.

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