A method for preparing a flexible piezoelectric film

Abstract

The present invention relates to a method for preparing a flexible piezoelectric film. The method for preparing the flexible piezoelectric film comprises: S1, weighing raw materials; S2, weighing solvents; S3, heating in a water bath and dissolving; S4, patterning the mixed solution on a flexible substrate by screen printing, spin coating or coating to form a film, first baking at a temperature of 40 to 80°C for 20 to 60 minutes, then baking at 80 to 120°C for 20 to 60 minutes, and finally annealing at 120 to 140°C for 0.5 to 8 hours to obtain a flexible piezoelectric film semi-finished product; S5, polarizing the annealed flexible piezoelectric film semi-finished product at room temperature in air, with a polarization voltage of 10 to 35 MV / cm and a time of 1 to 60 minutes to obtain a flexible piezoelectric film finished product. The present invention prepares a piezoelectric film with a high piezoelectric constant by using a mixed solvent of a high boiling point and a low boiling point, which meets the requirements of the piezoelectric constant of the piezoelectric film sensor.

Description

Technical Field

[0001] The invention relates to the technical field of piezoelectric films, in particular to a method for preparing a flexible piezoelectric film. Background Art

[0002] The traditional and most commonly used piezoelectric sensors mainly use piezoelectric ceramics as piezoelectric materials. Although this type of sensor has a long history and mature technology, piezoelectric ceramics have disadvantages such as high brittleness, high density, and poor flexibility. They cannot meet the complex and diverse usage environments, especially in the fields of medical health, robotics, biomechanics, smart wearables, etc., which have higher requirements for the flexibility, lightness, and biocompatibility of piezoelectric materials.

[0003] As a new type of polymer piezoelectric functional material, copolymer polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) piezoelectric material has the advantages of good flexibility, high mechanical strength, easy acoustic impedance matching, wide frequency response range, resistance to chemical and oily corrosion, and can be processed into large areas and complex shapes. It has been widely studied. It contains a high piezoelectric phase β phase, and the film preparation process does not require uniaxial stretching. However, the current preparation method of flexible piezoelectric film has a low density and many defects. It is easy to cause high-voltage breakdown during the polarization process, and the polarization is uneven, resulting in a low piezoelectric constant. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a flexible piezoelectric film that is easy to process and prepare. The prepared flexible piezoelectric film has a simple structure, high sensitivity, good flexibility and a high piezoelectric constant.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a flexible piezoelectric film, comprising the following steps:

[0006] S1. Weigh 10-25%wt polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) powder;

[0007] S2, weighing a high boiling point solvent and a low boiling point solvent and mixing them to prepare a mixed solvent;

[0008] S3, dissolving polyvinylidene fluoride-trifluoroethylene powder in the above-mentioned mixed solvent, stirring in a water bath for 1 to 8 hours, the water bath temperature is 50 to 80° C., and the stirring speed is 200 to 2000 rpm to obtain a mixed solution;

[0009] S4, patterning the mixed solution into a film on a flexible substrate by screen printing, spin coating or coating, first baking at 40-80° C. for 20-60 min, then baking at 80-120° C. for 20-60 min, and finally annealing at 120-140° C. for 0.5-8 hours to obtain a flexible piezoelectric film semi-finished product;

[0010] S5. Polarize the annealed flexible piezoelectric film semi-finished product in air at room temperature, with a polarization voltage of 10 to 35 MV / cm and a time of 1 to 60 min, to obtain a flexible piezoelectric film finished product.

[0011] Furthermore, the content of polyvinylidene fluoride-trifluoroethylene powder in S1 is 15-18%wt.

[0012] Furthermore, the mass ratio of the high boiling point solvent to the low boiling point solvent in S2 is: (1:4) to (4:1).

[0013] Furthermore, the high boiling point solvent in S2 is one of dimethylformamide, triethyl phosphate, propylene carbonate, triacetin or N-methyl-2-pyrrolidone, and the low boiling point solvent is any one of acetone, methyl ethyl ketone, ethylene glycol ethyl ether or n-butyl acetate.

[0014] The flexible piezoelectric film prepared by the present invention is composed of many tiny interlocking crystal regions with positive and negative charges. When compression or mechanical stress is applied, the film can generate an output voltage proportional to the compression amount.

[0015] The beneficial effects of the present invention are: the present invention has reasonable design, simple operation and the following advantages:

[0016] (1) The present invention uses a mixed solvent of high boiling point and low boiling point to prepare the solution, thereby avoiding deformation caused by uneven casting of the edge of the film during the molding process, and also avoiding processing difficulties caused by the volatility of the low boiling point solvent;

[0017] (2) The mixed solvent volatilization process adopts segmented baking to ensure that different solvents evaporate slowly to obtain a denser film. The film surface obtained in this way has no defects such as pinholes and wrinkles, which improves the film quality of the piezoelectric film and greatly reduces the voltage breakdown during the polarization of the film, which is more conducive to the complete polarization of the piezoelectric film and improves the piezoelectric constant of the piezoelectric film.

[0018] (3) The flexible piezoelectric film prepared by the present invention has the advantages of strong piezoelectric effect, high flexibility, low acoustic impedance, and ultra-thinness, and can be widely used in the preparation of flexible piezoelectric sensors, wearable devices, medical health and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0020] Figure 1 It is a process flow chart of the present invention;

[0021] Figure 2 The piezoelectric constant in Example 1 changes with decreasing proportion of N,N-dimethylformamide;

[0022] Figure 3 This is the relationship between the piezoelectric constant in Example 2 and the decreasing proportion of N,N-dimethylformamide. DETAILED DESCRIPTION

[0023] The present invention will now be described in further detail in conjunction with the accompanying drawings and preferred embodiments. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0024] A method for preparing a flexible piezoelectric film, such as Figure 2 As shown, the following steps are included:

[0025] S1. Weigh 10-25%wt polyvinylidene fluoride-trifluoroethylene powder;

[0026] S2. Weigh a high boiling point solvent and a low boiling point solvent and mix them to prepare a mixed solvent, wherein the mass ratio of the high boiling point solvent to the low boiling point solvent is: (1:4) to (4:1);

[0027] S3, dissolving polyvinylidene fluoride-trifluoroethylene powder in the above-mentioned mixed solvent, stirring in a water bath for 1 to 8 hours, the water bath temperature is 50 to 80° C., and the stirring speed is 200 to 2000 rpm to obtain a mixed solution;

[0028] S4, forming a film of the mixed solution on a flexible substrate by screen printing, spin coating or coating, first baking at 40-80° C. for 20-60 min, then baking at 80-120° C. for 20-60 min, and finally annealing at 120-140° C. for 0.5-8 hours to obtain a flexible piezoelectric film semi-finished product;

[0029] S5. Polarize the annealed flexible piezoelectric film semi-finished product in air at room temperature, with a polarization voltage of 10 to 35 MV / cm and a time of 1 to 60 min, to obtain a flexible piezoelectric film finished product.

[0030] The high boiling point solvent in S2 is one of dimethylformamide, triethyl phosphate, propylene carbonate, triacetin or N-methyl-2-pyrrolidone, and the low boiling point solvent is any one of acetone, methyl ethyl ketone, ethylene glycol ethyl ether or n-butyl acetate.

[0031] Example 1

[0032] A method for preparing a flexible piezoelectric film comprises the following steps:

[0033] S1. Weigh 18%wt polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) powder;

[0034] S2. Weigh N,N-dimethylformamide solvent and acetone solvent according to the ratio in Table 1 and mix them to prepare a mixed solvent;

[0035] S3, dissolving polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) powder in a mixed solvent, stirring continuously, and heating in a water bath for 2 h at a water bath temperature of 60°C;

[0036] S4, bonding to the substrate by coating, first baking at 60° C. for 30 min, then baking at 100° C. for 50 min, and finally annealing at 130° C. for 4 hours to obtain a flexible piezoelectric film semi-finished product;

[0037] S5. Polarize the annealed flexible piezoelectric film semi-finished product in air at room temperature with a polarization voltage of 15 MV / cm for 20 min to obtain a flexible piezoelectric film finished product.

[0038] The piezoelectric constants measured in this embodiment are shown in Table 1.

[0039] Table 1

[0040]

[0041]

[0042] Example 2

[0043] A method for preparing a flexible piezoelectric film comprises the following steps:

[0044] S1. Weigh 15%wt polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) powder;

[0045] S2. Weigh triethyl phosphate solvent and acetone solvent according to the ratio in Table 2 and mix them to prepare a mixed solvent;

[0046] S3, dissolving polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) powder in a mixed solvent, stirring continuously, and heating in a water bath at 70°C for 1 h;

[0047] S4, bonding to the substrate by coating, first baking at 80° C. for 60 min, then baking at 110° C. for 60 min, and finally annealing at 140° C. for 4 hours to obtain a flexible piezoelectric film semi-finished product;

[0048] S5. Polarize the annealed flexible piezoelectric film semi-finished product in air at room temperature with a polarization voltage of 35 MV / cm for 10 min to obtain a flexible piezoelectric film finished product.

[0049] The piezoelectric constants measured in this embodiment are shown in Table 2.

[0050] Table 2

[0051]

[0052] Depend on Figures 1 to 3 As can be seen from Tables 1 and 2, the present invention prepares a piezoelectric film with a high piezoelectric constant by using a mixed solvent of a high boiling point and a low boiling point, which meets the requirements of the piezoelectric film sensor for the piezoelectric constant.

[0053] The above description only describes the specific implementation mode of the present invention. Various examples do not limit the essential content of the present invention. After reading the description, ordinary technicians in the relevant technical field can modify or deform the specific implementation modes described above without departing from the essence and scope of the invention.

Claims

1. A method for preparing a flexible piezoelectric film, characterized in that: The steps include: S1. Weigh 10-25%wt polyvinylidene fluoride-trifluoroethylene powder; S2, weighing a high boiling point solvent and a low boiling point solvent and mixing them to prepare a mixed solvent, wherein the high boiling point solvent in S2 is one of dimethylformamide, triethyl phosphate, propylene carbonate, triacetin or N-methyl-2-pyrrolidone, and the low boiling point solvent is any one of acetone, methyl ethyl ketone, ethylene glycol ethyl ether or n-butyl acetate; S3, dissolving polyvinylidene fluoride-trifluoroethylene powder in the above-mentioned mixed solvent, stirring in a water bath for 1 to 8 hours, the water bath temperature is 50 to 80° C., and the stirring speed is 200 to 2000 rpm to obtain a mixed solution; S4, patterning the mixed solution into a film on a flexible substrate by screen printing, spin coating or coating, first baking at 40-80° C. for 20-60 min, then baking at 80-120° C. for 20-60 min, and finally annealing at 120-140° C. for 0.5-8 hours to obtain a flexible piezoelectric film semi-finished product; S5. Polarize the annealed flexible piezoelectric film semi-finished product in air at room temperature with a polarization voltage of 10 to 35 MV / cm for 1 to 60 min to obtain a flexible piezoelectric film finished product.

2. The method for preparing a flexible piezoelectric film according to claim 1, characterized in that: The content of polyvinylidene fluoride-trifluoroethylene powder in S1 is 15-18%wt.

3. The method for preparing a flexible piezoelectric film according to claim 1, characterized in that: The mass ratio of the high boiling point solvent to the low boiling point solvent in S2 is: (1:4) to (4:1).

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