Preparation method of self-temperature-limiting heating film

Abstract

The invention provides a preparation method of a self-temperature-limiting heating film, and belongs to the field of electric heating materials. The self-temperature-limiting heating film comprises a lower packaging layer, a base material layer, a processing layer, a conductive layer, a PTC layer, an electrode layer and an upper packaging layer which are sequentially arranged in the thickness direction. The preparation method comprises the following steps: coating one side of the base material layer with coating liquid to form the treatment layer; physically depositing a conductive layer on the processing layer; preparing a PTC layer on the conductive layer in a silk-screen printing manner, and drying the PTC layer; preparing an interdigitated electrode and attaching the interdigitated electrode to the PTC layer to form an electrode layer; and the lower packaging layer and the upper packaging layer are respectively combined with the substrate layer and the electrode layer to carry out packaging insulation. The conductive layer and the temperature limiting layer are connected in parallel to form the temperature limiting heating composite layer, and the resistance value of the whole electrothermal film is increased by increasing the resistance value of the temperature limiting layer, so that the temperature limiting function is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of electric heating materials, and in particular relates to a method for preparing a self-limiting temperature heating film. Background Art

[0002] Electric heating is an emerging winter heating method. Electric heating technology converts electrical energy directly into thermal energy. Due to the advantages of electricity being noise-free and pollution-free, electric heating has outstanding characteristics compared to traditional boilers.

[0003] At present, the main methods of electric heating include heating cables, electric heating films, electric boilers, etc. Heating cables are made into cable structures, using electricity as energy, using alloy resistance wires or carbon fiber wires as heating elements, and generating heat after being powered on to achieve the effect of heating or insulation. The use of heating cables for heating has the problem of increasing electricity capacity, especially for large-sized users, and the installation costs and procedures are relatively cumbersome. An electric boiler refers to a mechanical device that uses the combustion of electricity as energy, and uses the principles of resistance heating or electromagnetic induction heating to heat the heat medium water or organic heat carrier to certain parameters, and then outputs thermal energy with a certain working fluid. However, a boiler is a thermal energy device with high temperature and high pressure, and is one of the special equipment. It is necessary to obtain a special equipment installation and maintenance qualification certificate before engaging in the installation, maintenance, and modification of the boiler. Therefore, there are many complex engineering problems in the promotion and application of this technology.

[0004] The electric heating film is a thin film that can generate heat when powered on. It is a planar heating material that generates heat evenly and has higher heating efficiency. Therefore, electric heating films are gradually being used on a large scale in electric heating. However, most conductive heaters on the market currently do not have a temperature limit function. Electric heating is directly related to people's living scenes, and furniture or items that require a large area will inevitably be placed directly on the ground. After being placed for a long time, the heat generated by the electric heating film below cannot be dissipated, and the temperature will easily rise after the heat is gathered. Therefore, it is necessary to add a temperature limit switch or probe to ensure the safe use of the electric heating film. At the same time, the electric heating film itself has no shielding function. The method of laying an additional shielding layer not only increases the laying time and material costs, but also causes tripping and failure to close the gate due to moisture and other factors during the wet laying process.

[0005] In view of this, this application is hereby filed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a self-limiting temperature heating film, which adopts a conductive layer and a temperature limiting layer in parallel to form a temperature limiting heating composite layer, and the resistance of the entire electric heating film is increased by increasing the resistance of the temperature limiting layer, thereby achieving the temperature limiting function to solve the above-mentioned problems.

[0007] In order to achieve the above objectives, the present invention particularly adopts the following technical solutions:

[0008] A method for preparing a self-limiting temperature heating film (also called a heating film), wherein the self-limiting temperature heating film comprises a lower packaging layer, a substrate layer, a processing layer, a conductive layer, a PTC layer, an electrode layer and an upper packaging layer arranged in sequence in a thickness direction;

[0009] The method comprises:

[0010] Applying a coating liquid on one side of the substrate layer to form a treatment layer;

[0011] physically depositing a conductive layer on the handle layer;

[0012] Preparing a PTC layer on the conductive layer by screen printing and drying;

[0013] Prepare interdigitated electrodes and attach them to the PTC layer to form an electrode layer;

[0014] The lower packaging layer and the upper packaging layer are respectively combined with the substrate layer and the electrode layer for packaging and insulation.

[0015] Preferably, the self-limiting temperature heating film further comprises a shielding layer, and the shielding layer is arranged between the lower packaging layer and the substrate layer or between the electrode layer and the upper packaging layer.

[0016] Further, the shielding layer comprises a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) PEDOT:PSS film. More preferably, the PEDOT:PSS film is treated with sulfuric acid. The shielding layer is connected to the ground wire to shield the leakage current that may occur in the temperature limiting layer.

[0017] Optionally, the thickness of the shielding layer is 3-100 um.

[0018] The upper and lower packaging layers and the substrate are generally made of PET, BOPET, PI, PC and other materials, and their main functions are insulation, waterproofing, protection of internal structures and the like.

[0019] Preferably, when the shielding layer is disposed between the lower packaging layer and the substrate layer, the preparation method thereof is to coat a PEDOT:PSS film on the other side of the substrate layer to form the shielding layer, and then perform packaging insulation with the lower packaging layer; or,

[0020] As a parallel technical solution, when the shielding layer is arranged between the electrode layer and the upper packaging layer, its preparation method is to coat the PEDOT:PSS film on the side of the electrode layer facing the upper packaging layer to form a shielding layer, and then encapsulate and insulate it with the upper packaging layer.

[0021] Optionally, the coating method of the PEDOT:PSS film is spin coating.

[0022] Furthermore, the coated PEDOT:PSS film is then treated with sulfuric acid to increase conductivity.

[0023] The microstructure of the PEDOT:PSS film treated with sulfuric acid was rearranged, and the conductivity was increased by 5 times compared with that treated with formic acid and oxalic acid. This is because sulfuric acid induces the structural rearrangement of PEDOT:PSS through the transition mechanism of charge separation, forming highly ordered and densely arranged PEDOT:PSS nanofibers, which increases the carrier concentration and thus enhances the conductivity.

[0024] Preferably, the concentration of the sulfuric acid is 50-75%.

[0025] Optionally, the coating liquid can be one or more of polyester, polyurethane, acrylic, silicon solution, etc. Preferably, after the coating liquid is applied, it is dried at 60-100°C; the thickness of the treatment layer is 1-8um. During the drying process, the water in the coating liquid evaporates, and finally a uniform chemical treatment layer is formed on the surface of the substrate film. The treatment layer will increase the adhesion, so that the conductive material deposited by physical deposition can better adhere to the substrate, provide a uniform plane for the entire heating film structure, and is conducive to stable performance.

[0026] A low-resistivity material (one or more of copper, cadmium, aluminum, titanium, tungsten, tin, indium tin oxide, fluorine-doped tin oxide and aluminum-doped zinc oxide) is deposited on the treated layer in a high vacuum environment using physical deposition methods (such as radio frequency magnetron sputtering, pulsed laser deposition, vacuum evaporation and molecular beam epitaxy, etc.) to form a 10-100nm conductive layer.

[0027] Furthermore, the PTC layer, ie the temperature limiting layer, comprises a phase change material; optionally, the thickness of the PTC layer is 500-1500 um.

[0028] Furthermore, the method for preparing the slurry of the PTC layer includes:

[0029] After adding an emulsifier to paraffin for dispersion, add silicon dioxide, copolymerized methyl methacrylate and acrylic acid (due to the principle of similar polarity compatibility, the solution added later will be wrapped on the surface of the paraffin droplet during stirring), add an initiator to initiate free radical polymerization to initiate polymerization of monomer double bonds and double bonds on the surface of silicon dioxide, and obtain a phase change material with paraffin as the core and a particle size of about 10-38um; disperse graphene in an organic solvent, then add a polymer matrix and the phase change material, and then add aluminum oxide, polyacrylate, titanium dioxide and ethanol, stir or disperse evenly to obtain.

[0030] The effective doping of an appropriate amount of aluminum oxide can avoid excessive stacking and agglomeration of graphene powder, maintain the structure of graphene and good conductive properties. Because the slurry has a certain viscosity, the surface is prone to form ripples and is not smooth during coating preparation, while the alkyl side chains in polyacrylate quickly escape to the surface to form a monolayer, which increases the density of the oriented molecular structure, makes the surface tension more uniform, and alleviates the possibility of ripples on the coating surface of the overall PTC slurry due to uneven tension. The Ti-O bond in titanium dioxide has a large polarity, and the water adsorbed on the surface dissociates due to polarization to form hydroxyl groups on the surface, which can adsorb polar particles and make the solid surface charged to form a double electric layer. Because the charges are the same, the same charges repel and disperse, which can improve the overall stability of the PTC slurry. The hydroxyl group (-OH) in the ethanol molecule gives it good hydrophilicity and solvent properties. It interacts with other molecules throughout the slurry to reduce interfacial tension, and establishes a stable interaction with the dispersed matter by forming hydrogen bonds or van der Waals forces, thereby further inhibiting the agglomeration and sedimentation of conductive carbon particles. The emulsifier is generally selected from sorbitan monooleate polyoxyethylene ether.

[0031] Furthermore, in terms of weight parts, the paraffin, emulsifier, silicon dioxide, copolymerized methyl methacrylate, acrylic acid, graphene, polymer matrix, aluminum oxide, titanium dioxide, polyacrylate and ethanol are 10-20 parts, 0.5-1 parts, 0.3-0.8g parts, 6-10g parts, 1-5 parts, 25-50 parts, 80-100 parts, 0.6-10 parts, 6-10 parts, 15-20 parts and 18-20 parts respectively.

[0032] Optionally, the screen printing uses a 150-500 mesh screen.

[0033] The conductive layer and the PTC layer are stacked to form a conductive heating layer. Then, the metal foil with conductive glue is physically prepared by laser etching to form interdigitated electrodes and attached to the PTC layer, and finally the upper and lower packaging layers are used for packaging and insulation.

[0034] The resistance detected by the interpolated electrode is more sensitive than that of two ordinary electrodes. The slight resistance change between the interpolated electrode structure can be detected sensitively and the response speed is also faster. In addition, the bonding strength with the packaging material and slurry can be increased. At the same time, the room temperature resistance of the PTC layer directly contacted by the interpolated electrode is relatively large. The resistance of the overall conductive heating layer can be adjusted by adjusting the spacing and width of the interpolated electrode.

[0035] The self-limiting temperature heating film of the present application contains two functional layers with different resistance values, and the resistance values ​​of these two layer structures are connected in parallel to form the resistance value of an integrated conductive heating layer. The resistance value of the conductive layer is stable, and the PTC layer is formed by graphene powder to form a carbon chain for conductivity, and the phase change material it contains has the function of heat storage. When the temperature gradually rises to about a specific temperature, the paraffin core of the phase change material absorbs heat from a solid to a liquid, and the paraffin core wall material and the polymer will expand due to the swelling characteristics, causing the carbon chain to break and form a high resistance, so that the overall resistance of the conductive heating layer increases, and the current decreases, which ultimately affects the continuous heating of the conductive heating layer to achieve the temperature limiting function. When the temperature of the heating film decreases, the paraffin core wall material and the polymer shrink to form a loop of the conductive carbon chain, the resistance decreases, the current increases, and the temperature of the heating film increases.

[0036] Optionally, the preparation of the interdigitated electrodes is to prepare the interdigitated electrodes with a certain spacing by physically using laser etching on a metal foil with a thickness of 30-100 um and a conductive adhesive.

[0037] Optionally, the packaging is performed by hot pressing or cold pressing to provide packaging insulation.

[0038] Compared with the prior art, the present invention adopts a conductive layer and a temperature-limiting layer in parallel to form a temperature-limiting heating layer to adjust the resistance of the electric heating film. When the temperature rises, the resistance of the temperature-limiting layer increases, thereby increasing the resistance of the entire electric heating film to achieve the temperature-limiting function. In addition, the temperature-limiting layer contains a heat storage phase change material. After the electric heating film heats up and stores heat, the paraffin core wall material and the polymer expand when a specific temperature is reached to achieve the temperature-limiting function. At the same time, the use of a planar temperature-limiting layer also improves safety.

[0039] PEDOT:PSS film is used as a shielding layer to connect the ground wire to shield the leakage current that may occur in the temperature-limiting heating layer. At the same time, the thermal conductivity is lower than that of the commonly used metal shielding layer, which is more conducive to forming single-sided heating.

[0040] The self-limiting temperature heating film prepared by the present invention integrates shielding, temperature limiting and heating, and can reduce the problems of failure to close the switch and tripping. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 This is a schematic diagram of an explosion of the layered structure of the self-limiting temperature heating film of Example 1 of the present invention;

[0043] Figure 2 This is the structural schematic diagram of the paraffin core phase change material of Example 1 of the present invention;

[0044] Figure 3 It is the temperature rise diagram of the heating film of Example 1 and Comparative Example 1;

[0045] Figure 4 The power-off and temperature-lowering diagrams of the heating films of Examples 1, 2 and Comparative Example 1; Figure 5 Schematic diagram of the explosion of the layered structure of the self-limiting temperature heating film according to Example 6 of the present invention.

[0046] Description of reference numerals:

[0047] 1. Upper packaging layer; 2. Electrode layer; 3. PTC layer; 4. Conductive layer; 5. Treatment layer; 6. Base material layer; 7. Shielding layer; 8. Lower packaging layer; 9. Paraffin layer; 10. Inner wall material; 11. Outer wall material. DETAILED DESCRIPTION

[0048] The following is a detailed description of the embodiments of the present invention. The substances and raw materials in the embodiments are all commercially available products. The ratios not specifically indicated are all mass ratios and arbitrary ratios.

[0049] As used herein:

[0050] "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.

[0051] 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.

[0052] In these examples, the parts and percentages are all by mass unless otherwise specified. Elements not described, such as the thickness of each layer, should be understood as known in the art.

[0053] "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).

[0054] Example 1

[0055] A self-limiting temperature heating film comprises: a lower packaging layer 8, a shielding layer 7, a substrate layer 6, a processing layer 5, a conductive layer 4, a PTC layer 3, an electrode layer 2 and an upper packaging layer 1, such as Figure 1 shown.

[0056] The preparation method thereof comprises:

[0057] (1) 15 g of paraffin wax and 0.8 g of sorbitan monooleate polyoxyethylene ether were melted at 65° C., 135 ml of deionized water was added and dispersed at 3000 r / min for 10 min, and then a mixture of 0.5 g of silicon dioxide, 8 g of copolymerized methyl methacrylate and 3 g of acrylic acid was added to obtain a phase change material (such as Figure 2 As shown, it includes a paraffin layer 9, an inner wall material 10 and an outer wall material 11 coated sequentially from the inside to the outside; wherein the inner wall material 10 is mainly copolymerized methyl methacrylate and acrylic acid, and the outer wall material 11 is mainly silicon dioxide). 35g of graphene powder is dispersed in 70g of dimethylformamide (DMF), the obtained phase change material, 90g of acrylate and polyurethane emulsion are added thereto, and then 0.8g of aluminum oxide, 8g of titanium dioxide, 18g of acrylic emulsion, 19g of ethanol, etc. are added in sequence, and PTC slurry is prepared by mechanical stirring;

[0058] (2) Clean both sides of the substrate with pure water and ethanol and then dry them;

[0059] (3) Coating the polyester type and silicon solution coating liquid on the surface of the substrate with a roller, and then drying at 80° C. to form a treatment layer 5 of about 6 μm to increase the stability and flatness of the substrate;

[0060] (4) depositing an indium tin oxide target on the treatment layer 5 by a physical method of magnetron sputtering in a high vacuum environment to form a conductive layer 4 with a square resistance of 200 Ω / □ and a thickness of 50 nm;

[0061] (5) The PTC slurry is screen-printed on the conductive layer 4 using a 300-mesh screen to prepare a PTC layer 3 with a thickness of about 800 μm, and then placed in an oven for drying at 120° C. for 40 minutes.

[0062] (6) On the other side of the substrate, a PEDOT:PSS solvent was spin-coated at a speed of 5000 r / min for 40 seconds to form a shielding layer 7 with a thickness of about 10 μm. The conductivity was increased by treating with 72% sulfuric acid, and the conductivity was 2974 Scm -1 .

[0063] (7) A metal foil with a thickness of 50 μm and a conductive adhesive is prepared by laser etching to form interdigitated electrodes and bonded to the PTC layer 3 .

[0064] (8) Using a laminating device, the lower encapsulation layer 8 and the upper encapsulation layer 1 are respectively combined with the shielding layer 7 and the electrode layer 2 to be laminated by hot-pressing rollers.

[0065] After connecting the shielding layer 7 with the wire, connect the electrode neutral line, and connect the live zero power line from the electrode, then it can be used. When used for heating, the covering time limit temperature is about 70±5℃, and it has a heat storage effect.

[0066] Example 2

[0067] A self-limiting temperature heating film comprises: a lower packaging layer, a shielding layer, a substrate layer, a processing layer, a conductive layer, a PTC layer, an electrode layer and an upper packaging layer. The preparation method thereof comprises:

[0068] (1) 35 g of graphene powder was dispersed in 70 g of dimethylformamide (DMF), 90 g of acrylate and polyurethane emulsion were added thereto, and then 0.8 g of aluminum oxide, 8 g of titanium dioxide, 18 g of acrylic emulsion, 19 g of ethanol, etc. were added in sequence to prepare a PTC slurry by mechanical stirring;

[0069] Steps (2) to (8) are the same as those in Example 1. When heated, the covering time limit temperature is about 70±5°C.

[0070] Example 3

[0071] A self-limiting temperature heating film comprises: a lower packaging layer, a shielding layer, a substrate layer, a processing layer, a conductive layer, a PTC layer, an electrode layer and an upper packaging layer. The preparation method thereof comprises:

[0072] (1) After 10g paraffin and 0.5g sorbitan monooleate polyoxyethylene ether were melted at 65°C, 150ml deionized water was added at 2000r / min, and dispersed for 5min, and then 0.3g silica, 6g copolymerized methyl methacrylate and 1g acrylic acid were added to obtain a phase change material. 25g of graphene powder was dispersed in 60g of dimethylformamide (DMF), and the obtained phase change material, 80g of acrylate and polyurethane emulsion were added thereto, and then 0.6g of aluminum oxide, 6g of titanium dioxide, 15g of acrylic emulsion, 18g of ethanol, etc. were added in sequence to prepare PTC slurry by ultrasonic dispersion;

[0073] (2) Clean both sides of the substrate with pure water and ethanol and then dry them;

[0074] (3) Coating the polyester type and silicon solution coating liquid on the surface of the substrate with a roller, and then drying at 60°C to form a treatment layer of about 8 μm to increase the stability and flatness of the substrate;

[0075] (4) depositing an indium tin oxide target on the treated layer by a physical method of magnetron sputtering in a high vacuum environment to form a conductive layer with a square resistance of 450 Ω / □ and a thickness of 30 nm;

[0076] (5) The PTC slurry is screen-printed on the conductive layer using a 150-mesh screen to prepare a PTC layer with a thickness of about 500 μm, and then placed in an oven for drying at 80° C. for 60 min.

[0077] (6) On the other side of the substrate, a PEDOT:PSS solvent was spin-coated at a speed of 2000 r / min for 30 seconds to form a shielding layer with a thickness of about 3 μm, and then treated with 63% sulfuric acid to increase the conductivity.

[0078] (7) A metal foil with a thickness of 30 μm and a conductive adhesive is prepared by laser etching to form interdigitated electrodes and bonded to the PTC layer.

[0079] (8) Using a laminating device, the lower encapsulation layer and the upper encapsulation layer are respectively combined with the shielding layer and the electrode layer for hot-pressing roller lamination.

[0080] After connecting the wire on the shielding layer, connect the electrode neutral wire, and connect the live and neutral power lines from the electrode. Then it can be used. When used for heating, the covering time limit temperature is about 60±5℃, and it has a heat storage effect.

[0081] Example 4

[0082] A self-limiting temperature heating film comprises: a lower packaging layer, a shielding layer, a substrate layer, a processing layer, a conductive layer, a PTC layer, an electrode layer and an upper packaging layer. The preparation method thereof comprises:

[0083] (1) After 20g paraffin and 1g sorbitan monooleate polyoxyethylene ether were melted at 65°C, 150ml deionized water was added at 4000r / min, and dispersed for 15min. Then, 0.8g silica, 10g copolymerized methyl methacrylate and 5g acrylic acid were added to obtain a phase change material. 50g of graphene powder was dispersed in 80g of dimethylformamide (DMF), and the obtained phase change material, 100g of acrylate and polyurethane emulsion were added thereto. Then, 10g of aluminum oxide, 10g of titanium dioxide, 20g of acrylic emulsion, 20g of ethanol, etc. were added in sequence to prepare a PTC slurry by ultrasonic dispersion;

[0084] (2) Clean both sides of the substrate with pure water and ethanol and then dry them;

[0085] (3) Coating the polyester type and silicon solution coating liquid on the surface of the substrate by roller, and then drying at 100°C to form a treatment layer of about 5 μm to increase the stability and flatness of the substrate;

[0086] (4) Depositing the indium tin oxide target on the treated layer by magnetron sputtering in a high vacuum environment to form a sheet with a square resistance of A conductive layer with a thickness of 100 nm;

[0087] (5) The PTC slurry is screen-printed on the conductive layer using a 500-mesh screen to prepare a PTC layer with a thickness of about 1000 μm, and then placed in an oven for drying at 180° C. for 20 min.

[0088] (6) On the other side of the substrate, a PEDOT:PSS solvent was spin-coated at a speed of 10000 r / min for 50 s to form a shielding layer with a thickness of 100 um, and then treated with 55% sulfuric acid to increase the conductivity.

[0089] (7) A metal foil with a thickness of 100 μm and a conductive adhesive is prepared by laser etching to form interdigitated electrodes and bonded to the PTC layer.

[0090] (8) Using a laminating device, the lower encapsulation layer and the upper encapsulation layer are respectively combined with the shielding layer and the electrode layer for hot-pressing roller lamination.

[0091] After connecting the wire on the shielding layer, connect the electrode neutral wire, and connect the live and neutral power lines from the electrode. Then it can be used. When used for heating, the covering time limit temperature is about 40±5℃, and it has a heat storage effect.

[0092] Example 5

[0093] The difference from Example 1 is that the heating film does not include a shielding layer, and its preparation method does not include the step of spin coating the shielding layer. Finally, the lower packaging layer and the upper packaging layer are respectively combined with the substrate layer and the electrode layer for packaging and insulation.

[0094] Example 6

[0095] A self-limiting temperature heating film comprises: a lower packaging layer 8, a substrate layer 6, a processing layer 5, a conductive layer 4, a PTC layer 3, an electrode layer 2, a shielding layer 7 and an upper packaging layer 1, such as Figure 5 shown.

[0096] The preparation method thereof comprises:

[0097] (1) The preparation method of PTC slurry is the same as that of Example 1;

[0098] (2) Clean both sides of the substrate with pure water and ethanol and then dry them;

[0099] (3) Coating the polyester type and silicon solution coating liquid on the surface of the substrate with a roller, and then drying at 80° C. to form a treatment layer 5 of about 6 μm to increase the stability and flatness of the substrate;

[0100] (4) Depositing the indium tin oxide target material on the treatment layer 5 by magnetron sputtering in a high vacuum environment to form a sheet resistance of A conductive layer 4 having a thickness of 50 nm;

[0101] (5) The PTC slurry is screen-printed on the conductive layer 4 using a 300-mesh screen to prepare a PTC layer 3 with a thickness of about 800 μm, and then placed in an oven for drying at 120° C. for 40 minutes.

[0102] (6) A metal foil with a thickness of 50 μm and a conductive adhesive is prepared by laser etching to form an interdigitated electrode and bonded to the PTC layer 3 to form an electrode layer 2.

[0103] (7) On another PET surface, PEDOT:PSS solvent was spin-coated for 40 seconds at a speed of 5000 r / min to form a shielding layer 7 with a thickness of about 10 μm. The conductivity was increased by treating with 72% sulfuric acid, and the conductivity was 2974 Scm -1 .

[0104] (8) Using a laminating device, the lower encapsulation layer 8 and the upper encapsulation layer 1 are respectively combined with the substrate layer 6 and the shielding layer 7 by hot-pressing roller lamination.

[0105] After connecting the shielding layer 7 with the wire, connect the electrode neutral line, and connect the live zero power line from the electrode, then it can be used. When used for heating, the covering time limit temperature is about 80±5℃, and it has a heat storage effect.

[0106] Comparative Example 1

[0107] The difference from Example 1 is that the heating film includes: a lower packaging layer, a shielding layer, a substrate layer, a processing layer, a conductive layer, an electrode layer and an upper packaging layer, that is, the preparation process does not include the preparation of the PTC layer.

[0108] The heating film without PTC layer of comparative example 1 and the two heating films with PTC layer of the same power of examples 1 and 2 were powered on, and a 10 cm thick cover was placed on the surface. Under the same heating conditions, a temperature probe was used to collect the temperature rise under the heating film cover. Figure 3 As shown, by comparison, it is found that the heating film with a PTC layer temperature limiting layer (Example 2) stops heating when the temperature rises to about 70°C, while the heating film without a PTC layer (Comparative Example 2) continues to heat up. Therefore, the heating film without a PTC layer will have a safety hazard when covered. Figure 4 As shown, after the PTC layer heating film containing phase change material (with heat storage function) (Example 1) maintains the surface temperature for 40 minutes, the surface temperature of the heating film will gradually decrease, while the surface temperature of the heating film of Example 2 and Comparative Example 1 will gradually decrease from the beginning to room temperature.

[0109] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a self-limiting temperature heating film, characterized in that: The self-limiting temperature heating film comprises a lower packaging layer, a substrate layer, a processing layer, a conductive layer, a PTC layer, an electrode layer and an upper packaging layer which are arranged sequentially in the thickness direction; The method comprises: Applying a coating liquid on one side of the substrate layer to form a treatment layer; physically depositing a conductive layer on the handle layer; Preparing a PTC layer on the conductive layer by screen printing and drying; Prepare interdigitated electrodes and attach them to the PTC layer to form an electrode layer; The lower packaging layer and the upper packaging layer are respectively combined with the substrate layer and the electrode layer for packaging and insulation.

2. The method for preparing the self-limiting temperature heating film according to claim 1, characterized in that: The self-limiting temperature heating film further comprises a shielding layer, which is arranged between the lower packaging layer and the substrate layer or between the electrode layer and the upper packaging layer; Preferably, the shielding layer comprises a PEDOT:PSS film.

3. The method for preparing the self-limiting temperature heating film according to claim 2, characterized in that: The thickness of the shielding layer is 3-100um.

4. The method for preparing the self-limiting temperature heating film according to claim 2, characterized in that: When the shielding layer is disposed between the lower packaging layer and the substrate layer, the preparation method is to coat the other side of the substrate layer with a PEDOT:PSS film to form a shielding layer, and then perform packaging insulation with the lower packaging layer; or, When the shielding layer is arranged between the electrode layer and the upper packaging layer, the preparation method thereof is to coat the PEDOT:PSS film on the side of the electrode layer facing the upper packaging layer to form the shielding layer, and then perform packaging and insulation with the upper packaging layer.

5. The method for preparing the self-limiting temperature heating film according to claim 2, characterized in that: The method of coating the PEDOT:PSS film is spin coating; Preferably, the PEDOT:PSS film is coated and then treated with sulfuric acid to increase conductivity; Preferably, the concentration of the sulfuric acid is 50-75%.

6. The method for preparing the self-limiting temperature heating film according to claim 1, characterized in that: The PTC layer includes a phase change material; The thickness of the PTC layer is 500-1500 um.

7. The method for preparing the self-limiting temperature heating film according to claim 1 or 6, characterized in that: The method for preparing the slurry of the PTC layer comprises: After adding an emulsifier to paraffin for dispersion, adding silicon dioxide, copolymerized methyl methacrylate and acrylic acid, and adding an initiator for polymerization, a phase change material with paraffin as the core is obtained; The graphene is dispersed in an organic solvent, and then a polymer matrix and the phase change material are added, and then aluminum oxide, polyacrylate, titanium dioxide and ethanol are added, and the mixture is stirred or dispersed evenly to obtain the product.

8. The method for preparing the self-limiting temperature heating film according to claim 7, characterized in that: In terms of weight, the paraffin, emulsifier, silicon dioxide, copolymerized methyl methacrylate, acrylic acid, graphene, polymer matrix, aluminum oxide, titanium dioxide, polyacrylate and ethanol are 10-20 parts, 0.5-1 parts, 0.3-0.8g parts, 6-10g parts, 1-5 parts, 25-50 parts, 80-100 parts, 0.6-10 parts, 6-10 parts, 15-20 parts and 18-20 parts respectively.

9. The method for preparing the self-limiting temperature heating film according to claim 1, characterized in that: The drying temperature is 80-180°C.

10. The method for preparing the self-limiting temperature heating film according to claim 1, characterized in that: After the coating liquid is applied, drying is performed at 60-100°C; The thickness of the treatment layer is 1-8 um.

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