Preparation method of composite dielectric film, composite dielectric film with composite dielectric film and dielectric capacitor with composite dielectric film

Abstract

The invention provides a preparation method of a composite dielectric film, the composite dielectric film with the composite dielectric film and a dielectric capacitor with the composite dielectric film. The preparation method of the composite dielectric film comprises the following steps: stirring a first raw material comprising polyvinylidene fluoride and a solvent for the first time until the polyvinylidene fluoride is dissolved to obtain a first solution, adding polyimide into the first solution, and stirring again to obtain a first glue solution; stirring a second raw material comprising polyvinylidene fluoride and a solvent for the first time until the polyvinylidene fluoride is dissolved to obtain a second solution, adding polyimide into the second solution, stirring for the second time until the polyimide is dissolved to obtain a third solution, adding titanium dioxide into the third solution, and stirring for the third time to obtain a second glue solution; and coating at least one layer of first glue solution and at least one layer of second glue solution on a glass bottom plate through a tape casting method to obtain the composite dielectric film. By adopting the scheme provided by the invention, the problem of poor energy storage performance of the polymer film at high temperature in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the field of electronic materials, and in particular to a method for preparing a composite dielectric film and a composite dielectric film and a dielectric capacitor having the same. Background Art

[0002] A dielectric capacitor is an electronic component used to store charge and electrical energy. It consists of an insulating medium (also called a dielectric) sandwiched between two conductors. The properties of the dielectric determine the capacitance and working performance of the capacitor. Dielectric capacitors are widely used in electric vehicles, aerospace, oil and gas exploration, laser weapons, etc. due to their ultra-high power density and unique physical energy storage mechanism.

[0003] Common dielectric materials include ceramics, polyethylene, polypropylene, polytetrafluoroethylene, etc. Different dielectric materials have different dielectric constants and loss factors, which will affect the performance and stability of the capacitor. Polymer film materials account for a high proportion of dielectric capacitor materials. They have good processability, flexibility and high breakdown electric field strength. However, the dielectric constant of the commonly used polymer dielectric materials is relatively low, usually less than 10. Therefore, the lower dielectric constant limits the energy density of polymer dielectric materials. In addition, the operating environment temperature of polymer film capacitors is also increasing, such as electric vehicles (~140°C) and oil and gas exploration (170~250°C). In the prior art, the dielectric energy storage performance of polymer films is poor under high temperature conditions.

[0004] Currently, no effective solution has been proposed to the above problems. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing a composite dielectric film and a composite dielectric film and a dielectric capacitor having the same, so as to solve the problem of poor energy storage performance of polymer films at high temperatures in the prior art.

[0006] In order to achieve the above objective, according to one aspect of the present invention, a method for preparing a composite dielectric film is provided.

[0007] Furthermore, the preparation method of the composite dielectric film includes: step S1: stirring a first raw material including polyvinylidene fluoride and a solvent for the first time until the polyvinylidene fluoride is dissolved to obtain a first solution, adding polyimide to the first solution, and stirring again to obtain a first glue solution; step S2: stirring a second raw material including polyvinylidene fluoride and a solvent for the first time until the polyvinylidene fluoride is dissolved to obtain a second solution, adding polyimide to the second solution, stirring for a second time until the polyimide is dissolved to obtain a third solution, adding titanium dioxide to the third solution, and stirring for a third time to obtain a second glue solution; step S3, coating at least one layer of the first glue solution and at least one layer of the second glue solution on a glass bottom plate by a casting method to obtain a composite dielectric film.

[0008] Furthermore, at least one layer of the first glue and at least one layer of the second glue are coated on the glass substrate by the casting method, including: coating a layer of the first glue on the glass substrate by the casting method, and obtaining an initial layer after baking; coating a layer of the second glue on the initial layer by the casting method, and obtaining a composite layer after baking; and re-coating a layer of the first glue on the composite layer by the casting method, and obtaining a composite dielectric film after baking, quenching, and baking in sequence.

[0009] Furthermore, in the first raw material, the ratio of polyvinylidene fluoride to the solvent is (1 g: 4 ml), and / or in the second raw material, the ratio of polyvinylidene fluoride to the solvent is (1 g: 4 ml).

[0010] Furthermore, in the step of adding polyimide to the first solution, the ratio of polyimide to polyvinylidene fluoride is (9.5:0.5), and / or, in the step of adding polyimide to the second solution, the ratio of polyimide to polyvinylidene fluoride is (9.5:0.5), based on parts by mass.

[0011] Furthermore, in the step of adding titanium dioxide to the third solution, the ratio of titanium dioxide to polyimide is (3:100) by mass.

[0012] Furthermore, before step S3, the preparation method includes: placing the first adhesive solution and the second adhesive solution in an oven, and baking them for a first period of time under a vacuum environment.

[0013] Further, a layer of the first glue is re-coated on the composite layer by a casting method, and a composite dielectric film is obtained after baking, quenching, and baking in sequence, including:

[0014] The product obtained by re-coating a layer of the first glue solution on the composite layer by the casting method is placed in a vacuum oven and baked at a first temperature for a second period of time to obtain a first intermediate product;

[0015] placing the first intermediate product in a vacuum oven and baking it at a second temperature for a third period of time to obtain a second intermediate product;

[0016] placing the second intermediate product in an ice-water mixture at 0° C. for quenching to obtain a third intermediate product;

[0017] The third intermediate product is placed in a vacuum oven and baked at the first temperature for a fourth period of time to obtain a composite dielectric film.

[0018] Further, the first temperature is 90° C., and / or the second temperature is 150° C., and / or the second time period is 24 hours, and / or the third time period is 15 minutes, and / or the fourth time period is 1 hour.

[0019] According to another aspect of the present invention, a composite dielectric film is provided. The composite dielectric film includes a method for preparing the composite dielectric film. The method for preparing the composite dielectric film is the method for preparing the composite dielectric film described above.

[0020] According to another aspect of the present invention, a dielectric capacitor is provided. The dielectric capacitor includes an electrode and a composite dielectric film. The composite dielectric film is the composite dielectric film described above.

[0021] By applying the technical solution of the present invention, a method for preparing a composite dielectric film is designed. The composite dielectric film is composited with polyimide (PI) with excellent high temperature resistance and titanium dioxide (TIO2), an inorganic material with a high dielectric constant, to improve the energy storage density of the dielectric film. At the same time, a small amount of polyvinylidene fluoride (PVDF) is added to improve the flexibility of the dielectric film, thereby ensuring that the dielectric film can still maintain a stable dielectric constant and a very high breakdown electric field resistance at a high temperature of 150°C, and has excellent energy storage performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0023] Figure 1 A SEM image of a frozen fracture cross section of an embodiment of a composite dielectric film according to the present invention is shown. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art. In the accompanying drawings, for the sake of clarity, the thickness of the layers and regions may be enlarged, and the same reference numerals are used to represent the same devices, and thus their descriptions will be omitted.

[0028] Combination Figure 1 As shown, according to a specific embodiment of the present application, a method for preparing a composite dielectric film is provided.

[0029] Specifically, the preparation method of the composite dielectric film includes:

[0030] Step S1: Stirring a first raw material including polyvinylidene fluoride and a solvent until the polyvinylidene fluoride is dissolved to obtain a first solution, adding polyimide to the first solution, and stirring again to obtain a first glue solution;

[0031] Step S2: stirring the second raw material including polyvinylidene fluoride and a solvent for the first time until the polyvinylidene fluoride is dissolved to obtain a second solution, adding polyimide to the second solution, stirring for the second time until the polyimide is dissolved to obtain a third solution, adding titanium dioxide to the third solution, stirring for the third time to obtain a second glue solution;

[0032] Step S3, coating at least one layer of the first adhesive and at least one layer of the second adhesive on the glass substrate by a casting method to obtain a composite dielectric film.

[0033] The preparation method of the above-mentioned composite dielectric film provided by the present invention contains polyimide (PI) with high temperature resistance, polyvinylidene fluoride (PVDF) and titanium dioxide (TIO2) with high dielectric constant inorganic material. Polyimide and polyvinylidene fluoride can undergo copolymerization reaction to form a copolymer. This copolymer has the property of high temperature resistance. Titanium dioxide is added to the mixed solution of polyimide and polyvinylidene fluoride to increase the dielectric constant and capacitance of the dielectric film, thereby ensuring that the composite dielectric film has good energy storage performance at high temperature.

[0034] In particular, after a large number of experiments, the inventors have selected polyimide and polyvinylidene fluoride as the dielectric materials for manufacturing composite dielectric films. This is because compared with polyethylene, polypropylene, polytetrafluoroethylene, polyvinyl chloride, etc. commonly used in the field, polyimide and polyvinylidene fluoride as dielectric materials for composite dielectric films perform better in high temperature resistance, chemical stability and insulation properties, which can ensure that the composite dielectric film has better performance at high temperatures.

[0035] The present invention adopts a tape casting method to obtain a composite dielectric film. The tape casting method is a common method for preparing dielectric films. Its basic principle is to allow a molten polymer material to flow evenly between a pair of rotating rollers through an extruder head to form a thin film. The film then passes through a series of cooling rollers or cooling tables to gradually solidify and form, and finally obtain the desired dielectric film. The composite dielectric film prepared by the tape casting method has the following advantages: low cost, and dielectric films can be produced on a large scale; high production efficiency, the tape casting method can produce films quickly and continuously; the surface of the produced composite dielectric film is smooth and uniform, and the quality is stable and reliable; the thickness of the film can be controlled by adjusting the spacing of the extruder head and the speed of the roller, thereby meeting the production of dielectric films with different thickness requirements.

[0036] Specifically, coating at least one layer of the first glue solution and at least one layer of the second glue solution on the glass bottom plate by a casting method comprises:

[0037] A first glue liquid is coated on a glass bottom plate by a casting method, and an initial layer is obtained after baking;

[0038] A layer of second adhesive is coated on the initial layer by a casting method, and a composite layer is obtained after baking;

[0039] A layer of the first glue solution is re-coated on the composite layer by a casting method, and a composite dielectric film is obtained after baking, quenching and baking in sequence.

[0040] Alternatively, if Figure 1As shown, the composite dielectric film made by the above method has a special three-layer structure design, which can give full play to the advantages of different materials. Figure 1 It can be seen that the three-layer structure is very dense, without obvious defects such as holes, and the film thickness is about 17μm, which is also relatively small.

[0041] Optionally, the specific steps of using the casting method in this embodiment are: placing the glass base plate on the coating machine, pouring the glue on one side of the FTO conductive glass base plate, adjusting the gap between the scraper and the glass base plate to control the thickness of the dielectric film (~5μm), and coating the glue on the first layer by the casting method.

[0042] Specifically, in the first raw material, the ratio of polyvinylidene fluoride to the solvent is (1g: 4ml), and / or, in the second raw material, the ratio of polyvinylidene fluoride to the solvent is (1g: 4ml). Before the materials are proportioned, polyvinylidene fluoride and vinylidene fluoride need to be placed in an oven at 60°C for 24 hours to dry out the moisture, so that they are more suitable for proportioning and mixing. After drying the moisture, polyvinylidene fluoride and solvent are added to a beaker in a ratio of (1g: 4ml), and the solvent used here is dimethylformamide (DMF).

[0043] Optionally, polyvinylidene fluoride and a solvent are prepared into a first solution and / or a second solution, and the prepared solution is stirred at a speed of 1000 r / min using a magnetic stirrer. After most of the polyvinylidene fluoride is dissolved, the stirring is switched to a low speed of 200 r / min until the polyvinylidene fluoride is completely dissolved, at which time the liquid is clear and transparent.

[0044] Specifically, in parts by mass, in the step of adding polyimide to the first solution, the ratio of polyimide to polyvinylidene fluoride is (9.5:0.5), and / or, in the step of adding polyimide to the second solution, the ratio of polyimide to polyvinylidene fluoride is (9.5:0.5). After a large number of experiments and optimization, the inventors finally determined that the ratio of polyimide to polyvinylidene fluoride is (9.5:0.5). The use of this ratio to prepare the first glue solution can make the composite dielectric film after the film is formed by the casting method have better high temperature resistance.

[0045] Optionally, the first glue solution is first stirred at a speed of 1000 r / min using a magnetic stirrer, and after most of the polyimide is dissolved, the stirring is switched to a low speed of 200 r / min until the polyimide is completely dissolved, at which time the glue solution is brown and transparent.

[0046] Specifically, in the step of adding titanium dioxide to the third solution, the ratio of titanium dioxide to polyimide is (3:100) in parts by mass, and titanium dioxide is added to the third solution to form a second glue solution. Different ratios of titanium dioxide to polyimide will affect the performance and characteristics of the material. When the ratio of titanium dioxide to polyimide increases, the hardness and strength of the material will increase, but the flexibility and heat resistance of the material may be reduced. In addition, different ratios of titanium dioxide to polyimide may affect the thermal conductivity, corrosion resistance, wear resistance and other properties of the material. After a large number of experiments, the inventors concluded that the ratio of titanium dioxide to polyimide is (3:100), and the dielectric film obtained using this ratio can have good flexibility and high temperature resistance at a high temperature of 150°C.

[0047] Optionally, the second glue solution formed by adding titanium dioxide is stirred at a low speed of 300 r / min using a magnetic stirrer until the titanium dioxide and the glue solution are uniformly mixed, and the color of the glue solution is gray-black.

[0048] Specifically, before step S3, the preparation method includes: placing the first glue liquid and the second glue liquid in an oven and baking them for a first period of time under a vacuum environment. The stirred first glue liquid and the second glue liquid are placed in a vacuum oven for 30 minutes to remove excess bubbles. When baking in the oven, the bubbles in the first glue liquid and the second glue liquid will gradually rise to the surface of the liquid and escape, thereby reducing the gas content in the liquid, making the glue liquid more compact and uniform, and improving its bonding performance and stability. In addition, baking can also make the solvent in the glue liquid evaporate quickly, accelerate the curing speed of the glue liquid, and improve production efficiency.

[0049] Specifically, a layer of the first glue solution is re-coated on the composite layer by a casting method, and the composite dielectric film is obtained after baking, quenching, and baking in sequence, including:

[0050] The product obtained by re-coating a layer of the first glue solution on the composite layer by the casting method is placed in a vacuum oven and baked at a first temperature for a second period of time to obtain a first intermediate product;

[0051] placing the first intermediate product in a vacuum oven and baking it at a second temperature for a third period of time to obtain a second intermediate product;

[0052] placing the second intermediate product in an ice-water mixture at 0° C. for quenching to obtain a third intermediate product;

[0053] The third intermediate product is placed in a vacuum oven and baked at the first temperature for a fourth period of time to obtain a composite dielectric film.

[0054] Optionally, the composite dielectric film is obtained through three steps of baking, quenching and baking. The purpose of the whole process is to improve the performance and stability of the composite dielectric film. The specific reasons are as follows:

[0055] Baking: During the material preparation process, baking can remove moisture and organic solvents in the material, effectively remove impurities in the dielectric film, and improve the purity and stability of the material.

[0056] Quenching: Quenching in a 0°C ice-water mixture can control the cooling rate, avoid excessive internal stress, deformation or cracks caused by too fast cooling of the material, increase the density and consistency of the dielectric film, and enhance the durability and stability of the dielectric film. After the composite dielectric film is completely detached from the glass substrate in ice water, remove it.

[0057] Baking: The final baking step is to further remove residual moisture and organic matter in the material, making the structure of the dielectric film more stable while improving the thermal stability and electrical properties of the material.

[0058] Finally, the composite dielectric film is placed in an ion sputtering apparatus, and gold electrodes are plated on both sides for corresponding tests. The purpose of gold-plating electrodes on both sides of the composite dielectric film is to improve the performance and stability of the capacitor. Metal electrodes have good conductivity and chemical stability, and can effectively increase the electrode contact area of ​​the capacitor, thereby improving the capacitance and performance of the capacitor. In addition, metal electrodes can also reduce the contact resistance between the electrode and the dielectric, and improve the response speed and stability of the capacitor.

[0059] Specifically, the first temperature is 90° C., and / or the second temperature is 150° C., and / or the second time period is 24 hours, and / or the third time period is 15 minutes, and / or the fourth time period is 1 hour.

[0060] It should be noted that the instruments used in the preparation method of the composite dielectric film include: a beaker, an electronic balance, a measuring cylinder, a magnetic stirrer, a coating machine, a vacuum oven, and an FTO conductive glass bottom plate. The prepared composite dielectric film has a smooth appearance, no defects, and a light yellow color.

[0061] According to a second aspect of the present invention, a composite dielectric film is provided.

[0062] Specifically, the composite dielectric film includes a method for preparing the composite dielectric film, and the method for preparing the composite dielectric film is the method for preparing the composite dielectric film mentioned above.

[0063] According to a third aspect of the present invention, a dielectric capacitor is provided.

[0064] Specifically, the dielectric capacitor includes an electrode and a composite dielectric film, and the composite dielectric film is the composite dielectric film mentioned above.

[0065] The following is further described by experimental examples.

[0066] [Example 1]:

[0067] This embodiment prepares a composite dielectric film (PI@PVDF@TO composite film), and the specific steps are as follows:

[0068] S1: Place PVDF, PI and TiO2 raw materials in an oven at 60°C and bake for 24 hours to dry out moisture;

[0069] S2: Take two beakers A and B;

[0070] S3: Add PVDF and solvent DMF into beakers A and B at a ratio of 1 g:4 ml;

[0071] S4: First, stir at a high speed of 1000 r / min, and then switch to a low speed of 200 r / min after most of the PVDF is dissolved, until the PVDF is completely dissolved, and the glue solution is clear and transparent;

[0072] S5: Add PI to beakers A1 and A2 at a ratio of PI:PVDF = 9.5:0.5;

[0073] S5: First, stir at a high speed of 1000 r / min, and then switch to a low speed of 200 r / min after most of the PI is dissolved, until the PI is completely dissolved. At this time, the glue solution is brown and transparent, which is recorded as glue solution;

[0074] S6: Add TiO2 to a portion of glue solution A at a mass ratio of TiO2:PI=3:100;

[0075] S7: Stir at a low speed of 300 r / min until TiO2 and the glue are evenly mixed. At this time, the glue is gray-black in color and is recorded as glue B.

[0076] S8: placing the stirred glue solutions A and B in a vacuum oven for 30 minutes to remove excess bubbles;

[0077] S9: Place the glass substrate on the coating machine, pour the glue on one side of the FTO conductive glass substrate, adjust the gap between the scraper and the glass substrate to control the thickness of the dielectric film (~5μm), and apply glue A on the first layer by casting;

[0078] S10: The coating machine heats the plate to bake at 90°C for 30 min to remove the solvent DMF;

[0079] S11: Applying glue solution B on the second layer by casting method;

[0080] S12: The coating machine heats the plate to bake at 90°C for 30 min to remove the solvent DMF;

[0081] S13: coating the glue solution A on the third layer by a casting method;

[0082] S14: The coating machine heats the plate to bake at 90°C for 30 min to remove the solvent DMF;

[0083] S15: placing the prepared composite dielectric film in a vacuum oven and baking it at 90° C. for 24 hours to volatilize the remaining solvent;

[0084] S16: The dried PI@PVDF@TO composite dielectric film is placed in a vacuum oven at 150°C for 15 minutes and then immediately placed in an ice-water mixture at 0°C to complete the quenching process, so as to increase the density and consistency of the dielectric film. After the PI@PVDF@TO composite dielectric film is completely detached from the glass substrate in the ice water, it is taken out.

[0085] S17: The composite dielectric film is placed in a vacuum oven and baked at 90° C. for 1 hour to remove moisture.

[0086] S18: Place the composite dielectric film in an ion sputtering apparatus, plate gold electrodes on both sides, and perform corresponding tests.

[0087] [Comparative Example 1]:

[0088] The preparation process of the PI@PVDF composite membrane is the same as that of Example 1, except that TiO2 is not added thereto.

[0089] The inventors conducted performance tests on the PI@PVDF composite film and the PI@PVDF / TiO2 composite dielectric film, and the results are analyzed as follows:

[0090] 1. Comparison of the dielectric constants of PI@PVDF composite film and PI@PVDF@TO composite dielectric film with frequency. The dielectric constant of PI@PVDF composite film at 1000Hz is 3.5, and the dielectric constant of PI@PVDF@TO composite film is 4. The dielectric constants of the two films do not change much with the increase of frequency, indicating that the two films have good frequency stability.

[0091] 2. Comparison of the dielectric loss of PI@PVDF composite film and PI@PVDF@TO composite dielectric film with frequency. After adding titanium dioxide, the loss of the composite film increased, but the dielectric loss of the two films did not change much with the increase of frequency, and always remained at a low level of <0.04.

[0092] 3. Comparison of the dielectric constants of PI@PVDF composite film and PI@PVDF@TO composite dielectric film with temperature. The dielectric constant of PI@PVDF composite film is 3.6 at 1000Hz and room temperature 25℃, and the dielectric constant of PI@PVDF@TO composite film is 4.2. The dielectric constants of the two films do not change much with the increase of temperature, indicating that the two films have good temperature stability.

[0093] 4. Comparison of the dielectric loss of PI@PVDF composite film and PI@PVDF@TO composite dielectric film with temperature. The dielectric loss of the two films does not change much with the increase of temperature, and always remains at a very low level of <0.02 at <150°C.

[0094] 5. At room temperature of 25°C, the polarization strength of the PI@PVDF@TO composite dielectric film can reach 2.04μC / cm2, which is 15.9% higher than the 1.76μC / cm2 of the PI@PVDF composite film. The energy storage density of the PI@PVDF@TO composite dielectric film at the highest breakdown field strength is 1.54J / cm3, which is 37.5% higher than the 1.12J / cm3 of the PI@PVDF film.

[0095] 6. At high temperature of 150°C, the polarization strength of the PI@PVDF@TO composite dielectric film can reach 1.36μC / cm2, which is 49% higher than the 0.91μC / cm2 of the PI@PVDF film. The energy storage density of the PI@PVDF@TO composite dielectric film at the highest breakdown field strength is 1.36J / cm3, which is 29.5% higher than the 1.05J / cm3 of the PI@PVDF film.

[0096] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0097] 1. The present invention compounds polyimide with excellent high temperature resistance and titanium dioxide, an inorganic material with a high dielectric constant, and adds a small amount of polyvinylidene fluoride to improve the flexibility of the composite film. Compared with pure polymer film, the energy storage density of the prepared composite dielectric film is significantly improved; compared with the use temperature of commercially applied BOPP film <80°C, the prepared composite dielectric film is high temperature resistant (~150°C) and has good energy storage performance.

[0098] 2. The present invention uses a three-layer coating method to form a composite dielectric film with a special three-layer structure design, which can give full play to the advantages of different materials.

[0099] 3. The composite dielectric film of the present invention can still maintain a stable dielectric constant and a very high breakdown electric field resistance at a high temperature of 150°C. At the same time, the dielectric film of the present invention has a low production cost, an economical and environmentally friendly preparation process, and good film-forming properties, which is conducive to large-scale production and application.

[0100] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0101] In addition to the above, it should be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this specification refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of the present invention.

[0102] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite dielectric film, characterized in that: include: Step S1: Stirring a first raw material including polyvinylidene fluoride and a solvent until the polyvinylidene fluoride is dissolved to obtain a first solution, adding polyimide to the first solution, and stirring again to obtain a first glue solution; Step S2: stirring the second raw material including the polyvinylidene fluoride and the solvent for the first time until the polyvinylidene fluoride is dissolved to obtain a second solution, adding the polyimide to the second solution, stirring for the second time until the polyimide is dissolved to obtain a third solution, adding titanium dioxide to the third solution, stirring for the third time to obtain a second glue solution; Step S3, coating at least one layer of the first adhesive and at least one layer of the second adhesive on the glass substrate by a casting method to obtain the composite dielectric film.

2. The method for preparing a composite dielectric film according to claim 1, characterized in that: At least one layer of a first glue solution and at least one layer of a second glue solution are coated on a glass bottom plate by a casting method, comprising: Applying a layer of the first glue solution on the glass bottom plate by a casting method, and baking the first glue solution to obtain an initial layer; Applying a layer of the second adhesive on the initial layer by a casting method, and baking to obtain a composite layer; A layer of the first glue solution is re-coated on the composite layer by a casting method, and the composite dielectric film is obtained after baking, quenching and baking in sequence.

3. The method for preparing a composite dielectric film according to claim 1 or 2, characterized in that: In the first raw material, the ratio of the polyvinylidene fluoride to the solvent is (1 g: 4 ml), and / or in the second raw material, the ratio of the polyvinylidene fluoride to the solvent is (1 g: 4 ml).

4. The method for preparing a composite dielectric film according to any one of claims 1 to 3, characterized in that: In the step of adding polyimide to the first solution, the ratio of the polyimide to the polyvinylidene fluoride is (9.5:0.5), and / or, in the step of adding the polyimide to the second solution, the ratio of the polyimide to the polyvinylidene fluoride is (9.5:0.5), in parts by mass.

5. The method for preparing a composite dielectric film according to any one of claims 1 to 4, characterized in that: In the step of adding titanium dioxide to the third solution, the ratio of titanium dioxide to the polyimide is (3:100) by mass.

6. The method for preparing a composite dielectric film according to claim 1 or 2, characterized in that: Before step S3, the preparation method includes: placing the first adhesive solution and the second adhesive solution in an oven, and baking them for a first period of time under a vacuum environment.

7. The method for preparing a composite dielectric film according to claim 2, characterized in that: The composite dielectric film is obtained by re-coating a layer of the first glue solution on the composite layer by a casting method, and then baking, quenching, and baking in sequence, including: A product obtained by re-coating a layer of the first glue solution on the composite layer by a tape casting method is placed in a vacuum oven and baked at a first temperature for a second period of time to obtain a first intermediate product; placing the first intermediate product in a vacuum oven and baking it at a second temperature for a third period of time to obtain a second intermediate product; placing the second intermediate product in an ice-water mixture at 0° C. for quenching to obtain a third intermediate product; The third intermediate product is placed in a vacuum oven and baked at the first temperature for a fourth period of time to obtain the composite dielectric film.

8. The method for preparing a composite dielectric film according to claim 7, characterized in that: The first temperature is 90° C., and / or the second temperature is 150° C., and / or the second time period is 24 hours, and / or the third time period is 15 minutes, and / or the fourth time period is 1 hour.

9. A composite dielectric film, including a method for preparing the composite dielectric film, characterized in that: The method for preparing the composite dielectric film is the method for preparing the composite dielectric film according to any one of claims 1 to 8.

10. A dielectric capacitor comprising an electrode and a composite dielectric film, characterized in that: The composite dielectric film is the composite dielectric film described in claim 9.

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