WO2021168750A1 - Piezoelectric film and preparation method therefor, and piezoelectric film sensor - Google Patents

Abstract

A piezoelectric film (100) and a preparation method therefor, and a piezoelectric film sensor (10). The piezoelectric film comprises a first substrate (110), a conductive layer (120), and a piezoelectric layer (130); the conductive layer is disposed on the first substrate; the conductive layer is an aged ITO layer; the crystallinity of the conductive layer is 80% or more; the piezoelectric layer is disposed on the conductive layer; the piezoelectric layer contains a fluoropolymer, and the fluoropolymer does not comprise an α-phase fluoropolymer. The piezoelectric film has a shorter crystallization time, it is easier to form a β phase, and the piezoelectric performance of the piezoelectric film is improved.

Description

[Name of invention formulated by ISA according to Rule 37.2] 　Piezoelectric film, piezoelectric film sensor and method of making the same Technical field

The invention relates to the technical field of piezoelectric films, in particular to a piezoelectric film and a preparation method thereof, and a piezoelectric film sensor.

Background technique

The piezoelectric film sensor is a dynamic strain sensor that can be applied to the surface of the human skin or implanted inside the human body to monitor vital signs. For example, it is used in wearable products such as shoes and smart bracelets to measure the mechanical data of athletes, or used in products containing touch components such as mobile phones and home appliances. It is an important sensor component in future smart wearables and smart homes. Under the action of external force, the piezoelectric film in the piezoelectric film sensor generates polarization, and at the same time, induced charges are generated on the electrodes on both sides of the piezoelectric film. By detecting the generated charges, the piezoelectric film sensor can be obtained The stress and strain received will finally realize the monitoring of life signals such as heart rate and breathing pattern. Although the current piezoelectric film sensor can realize the detection of life signals, the piezoelectric performance of the piezoelectric film sensor needs to be further improved to meet the market demand.

Summary of the invention

Based on this, it is necessary to provide a pressure membrane with good piezoelectric properties.

A piezoelectric film includes:

First substrate

A conductive layer is provided on the first substrate, the conductive layer is an aged ITO layer, and the crystallinity of the conductive layer exceeds 80%;

The piezoelectric layer is provided on the conductive layer, the piezoelectric layer contains a fluoropolymer, and the fluoropolymer does not include an α-phase fluoropolymer.

A method for preparing a piezoelectric layer includes the following steps:

Providing a substrate covered with a conductive layer, wherein the conductive layer is an aged ITO layer, and the crystallization rate of the conductive layer exceeds 80%;

Placing the raw material for preparing the piezoelectric layer on the conductive layer and baking to form a primary piezoelectric layer, the raw material for preparing the piezoelectric layer includes a fluoropolymer; and

Ground the conductive layer, and discharge corona on the side of the primary piezoelectric layer away from the conductive layer to polarize the primary piezoelectric layer to obtain a piezoelectric layer. The piezoelectric layer does not include α-phase containing Fluoropolymer.

A piezoelectric film sensor includes the piezoelectric film or the piezoelectric film prepared by the method for preparing the piezoelectric film.

A method for preparing a piezoelectric film sensor includes the following steps:

Providing a first substrate covered with a conductive layer, wherein the conductive layer is an aged ITO layer, and the crystallinity of the conductive layer exceeds 80%;

Placing the raw material for preparing the piezoelectric layer on the conductive layer and baking to form a primary piezoelectric layer, wherein the raw material for preparing the piezoelectric layer includes a fluoropolymer;

Preparing an upper electrode on the side of the primary piezoelectric layer away from the conductive layer;

Ground the conductive layer, and discharge corona on the side of the primary piezoelectric layer away from the conductive layer to polarize the primary piezoelectric layer to obtain a piezoelectric layer. The piezoelectric layer does not include α-phase containing Fluoropolymer; and

Covering the upper electrode with a second substrate and sealing it with the first substrate to form a sealed cavity, the conductive layer, the piezoelectric layer and the upper electrode are contained in the sealed cavity, The piezoelectric film sensor is obtained.

Description of the drawings

Fig. 1 is a top view of a piezoelectric film sensor according to an embodiment;

FIG. 2 is a cross-sectional view of the piezoelectric film sensor shown in FIG. 1;

3 is a top view of the first substrate containing a conductive layer of the piezoelectric film sensor shown in FIG. 1;

4 is a top view of a first substrate containing a piezoelectric layer of the piezoelectric film sensor shown in FIG. 1;

5 is a top view of the first substrate containing the upper electrode of the piezoelectric film sensor shown in FIG. 1;

6 is a bottom view of the second substrate containing the shield electrode of the piezoelectric film sensor shown in FIG. 1;

FIG. 7 is a top view of a piezoelectric film sensor according to another embodiment;

FIG. 8 is a cross-sectional view of the piezoelectric film sensor shown in FIG. 7;

FIG. 9 is a top view of the first substrate containing position lower electrodes and a conductive layer of the piezoelectric film sensor shown in FIG. 7; FIG.

FIG. 10 is a top view of the first substrate containing the piezoelectric layer of the piezoelectric film sensor shown in FIG. 7; FIG.

FIG. 11 is a top view of the first substrate containing the upper electrode of the piezoelectric film sensor shown in FIG. 7;

Fig. 12 is a bottom view of the second substrate containing the shield electrode and the upper electrode of the piezoelectric thin film sensor shown in Fig. 7.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The drawings show some embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present invention. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention.

Please refer to FIGS. 1 to 2, the piezoelectric film sensor 10 according to an embodiment includes a piezoelectric film 100.

Specifically, the piezoelectric film 100 includes a first substrate 110, a conductive layer 120, and a piezoelectric layer 130. The conductive layer 120 is provided on the first substrate 110. The conductive layer 120 is an aged ITO layer. The crystallization rate exceeds 80%. Further, the crystallinity rate of the conductive layer 120 is more than 80% and not more than 98%; the piezoelectric layer 130 is provided on the conductive layer 120, the piezoelectric layer 130 contains a fluoropolymer, and the crystal of the fluoropolymer is not α-phase containing Fluoropolymer.

The fluoropolymer applied to the piezoelectric layer 130 is mainly polyvinylidene fluoride (PVDF) and its derivatives with piezoelectric properties. Polyvinylidene fluoride is a type of semi-crystalline polymer with five different crystal forms, namely α, β, γ, δ, and ε. Among them, the piezoelectric properties of PVDF are mainly reflected by β and γ phases. , The higher the content of β phase (crystal ratio, crystal phase ratio), the higher the piezoelectric performance after PVDF polarization. The piezoelectric film 100 uses ITO with an aging crystallization rate exceeding 80% as the conductive layer 120 of the piezoelectric film 100. During the preparation of the piezoelectric layer 130, a fluoropolymer is applied to the aging crystallization rate exceeding 80%. After the surface of the ITO layer, due to the energy relationship, heterogeneous nucleation will be preferred to homogeneous nucleation, so the fluoropolymer adsorbed on the surface of the aging ITO layer will act as a crystal nucleus, accelerating the crystal growth of the fluoropolymer, and also This makes it easier to form the β phase, thereby increasing the proportion of the β phase, and thereby improving the piezoelectric performance of the piezoelectric film 100.

Specifically, the material of the first substrate 110 and the thickness of the first substrate 110 are not particularly limited. For example, the first substrate 110 may be a flexible organic film material or glass. In this embodiment, the first substrate 110 is a flexible substrate, such as organic film materials such as PET, PI, TPU, PVC, PMMA, and PE;层130. The thickness of the first substrate 110 is 10 μm to 300 μm. Further, the thickness of the first substrate 110 is 100 μm to 300 μm. Or the thickness of the first substrate 110 is 10 μm to 200 μm. The above-mentioned thickness setting of the first substrate 110 is convenient for process production. In other embodiments, the first substrate 110 is glass, and the thickness of the first substrate 110 is 0.1 mm to 1 mm.

Specifically, referring to FIG. 2 and FIG. 3, the conductive layer 120 is provided on the first substrate 110 in a contacting manner. The conductive layer 120 is an aged ITO layer, the conductive layer 120 is between the crystalline state and the amorphous state, and the crystallinity of the conductive layer 120 exceeds 80% and does not exceed 98%. Further, the crystallinity of the conductive layer 120 is 80%-95%. Because different aging conditions will affect the crystallization rate of the ITO layer, when the crystallization rate of the ITO layer is less than 80%, it is easy to cause the fluoropolymer to require a longer crystallization time to achieve a high β-phase ratio.

Specifically, the conductive layer 120 contains crystal grains. Further, the grain size of the crystal grains of the conductive layer 120 is 10 nm to 300 nm. Further, the grain size of the crystal grains of the conductive layer 120 is 10 nm to 150 nm, and further, the grain size of the crystal grains of the conductive layer 120 is 20 nm to 60 nm. When the grain size of the crystal grains is the above-mentioned grain size, it is easier for the fluorine-containing polymer crystals to grow.

In one of the embodiments, the square resistance of the conductive layer 120 is 1Ω/□˜500Ω/□. Further, the square resistance of the conductive layer 120 is 25Ω/□～150Ω/□. For example, when the conductive layer 120 on the surface of the first substrate 110 is aged ITO, such as 100Ω/□, the crystallization rate of P (20%VDF-80%TrFE) can reach more than 85%.

Specifically, referring to FIG. 2 and FIG. 4, the piezoelectric layer 130 is disposed on the surface of the conductive layer 120 away from the first substrate 110 in a contact form. The fluoropolymer is selected from vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride, P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE) ) At least one of. Select at least one of the above-mentioned vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride, P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE) A fluorine-containing polymer used as the conductive layer 120 can make the crystallization time of the piezoelectric layer 130 in the preparation process of the piezoelectric layer 130 short (it can be completed in 30 minutes) and the ratio of the β phase formed by the crystallization is high. Further, the piezoelectric layer 130 is composed of a fluoropolymer, which does not contain an α-phase fluoropolymer, the β-phase fluoropolymer accounts for 80% to 100% of the crystalline phase, and the γ-phase fluoropolymer accounts for 0%. ~20%.

In one of the embodiments, the piezoelectric layer 130 is a patterned piezoelectric layer 130. The patterned shape of the piezoelectric layer 130 may be arbitrary, such as rectangular, triangular, prismatic, and the like. The patterning of the piezoelectric layer 130 can greatly increase the utilization rate of piezoelectric materials and greatly reduce the cost.

Of course, the thickness of the conductive layer 120 and the piezoelectric layer 130 is not particularly limited. In this embodiment, the thickness of the conductive layer 120 is 3 μm to 30 μm; the thickness of the piezoelectric layer 130 is 5 μm to 200 μm. The above arrangement of the conductive layer 120 and the piezoelectric layer 130 facilitates the improvement of the piezoelectric performance of the piezoelectric layer 130 and also facilitates the thinning of the piezoelectric film sensor 10.

2 and 5, the piezoelectric film sensor 10 further includes an upper electrode 140 and a second substrate 170. The upper electrode 140 is provided on the piezoelectric layer 130. The projection of the conductive layer 120 on the first substrate 110 is completely Covering the projection of the upper electrode 140 on the first substrate 110, the second substrate 170 is disposed on the upper electrode 140, and the second substrate 170 and the first substrate 110 form a sealed cavity. The conductive layer 120, the piezoelectric layer 130 and the upper electrode 140 are contained in a sealed cavity formed by the first substrate 110 and the second substrate 170. Of course, both the upper electrode 140 and the conductive layer 120 are also electrically connected to the electrode lead.

Further, the material of the second substrate 170 and the thickness of the second substrate 170 are not particularly limited. For example, the second substrate 170 may be a flexible organic film material or glass. In this embodiment, the second substrate 170 is a flexible substrate, such as organic film materials such as PET, PI, TPU, PVC, TPU, PE, etc.; the flexible substrate facilitates the preparation of the piezoelectric film sensor 10 in a roll-to-roll manner. Further, the thickness of the second substrate 170 is 10 μm to 200 μm. The above-mentioned thickness setting of the second substrate 170 facilitates process production.

2 and 6, the piezoelectric film sensor 10 further includes a shielding electrode 160 and an insulating layer (not shown). The shielding electrode 160 is located on the side of the second substrate 170 close to the first substrate 110, and the insulating layer is provided Between the upper electrode 140 and the shield electrode 160. The shielding electrode 160 and the insulating layer are also contained in the sealed cavity formed by the second substrate 170 and the first substrate 110. The shield electrode 160 is grounded or set at a fixed potential to shield the electrical signal interference of the upper electrode 140 from the external electric field and magnetic field. The insulating layer is used to separate the shield electrode 160 and the upper electrode 140 to avoid short circuits. Further, the projection of the shielding electrode 160 on the first substrate 110 completely covers the projection of the upper electrode 140 on the first substrate 110.

In the embodiment shown in FIG. 2, the piezoelectric film sensor 10 further includes an adhesive layer 150. The adhesive layer 150 is disposed between the first substrate 110 and the second substrate 170, and connects the shielding electrode 160 to the upper substrate. The electrodes 140 are spaced apart. The adhesive layer 150 is used for the adhesion between the first substrate 110 and the second substrate 170, so that the edges of the first substrate 110 and the second substrate 170 are sealed to form a sealed cavity, and the adhesive layer 150 The distance between the shield electrode 160 and the upper electrode 140 is also used to prevent the shield electrode 160 and the upper electrode 140 from being short-circuited. Further, the material of the adhesive layer 150 is not particularly limited. For example, it can be water glue, acrylic type acrylic glue, silicone type double-sided tape, rubber type double-sided tape, and the like.

Of course, in some other embodiments, the adhesive layer 150 can be omitted. In this case, the first substrate 110 and the second substrate 170 can be sealed by thermoplastic or hot pressing; of course, if the shielding electrode 160 and the shielding electrode 160 and 170 are simultaneously present at this time. For the upper electrode 140, an insulating layer needs to be provided between the shield electrode 160 and the upper electrode 140. When the adhesive layer 150 is omitted, the piezoelectric layer 130 is directly fabricated on the conductive layer 120, and the insulating layer is directly fabricated on top, and then the shield electrode 160 is fabricated. There is no need to use the adhesive layer 150 to reduce the thickness of the piezoelectric film sensor 10. To enhance the winding property, the yellow light/photosensitive process can be used for roll-to-roll operation, which is more conducive to the maximum roll-to-roll operation, which improves efficiency and reduces costs. For example, after the adhesive layer 150 is omitted, the thickness of the piezoelectric film sensor 10 may be 100 μm or less.

The piezoelectric layer sensor 10 described above has good piezoelectric performance.

Referring to FIGS. 7-12, the piezoelectric film sensor 20 of another embodiment is substantially the same as the piezoelectric film sensor 10 described above, and includes a first substrate 210, a conductive layer 220, a piezoelectric layer 230, an upper electrode 240, and an adhesive The difference between the layer 250, the shielding electrode 260 and the second substrate 270 is that they further include a position upper electrode 280 and a position lower electrode 290. The position lower electrode 290 is arranged on the first substrate 210, the position lower electrode 290 and the conductive layer 220 are on the same side of the first substrate 210, and the position upper electrode 280 and the shield electrode 260 are arranged on the second substrate 270 close to the first substrate. One side of the substrate 210. Further, in the embodiment shown in FIG. 8, the projection of the upper electrode 280 on the first substrate 210 and the projection of the lower electrode 290 on the first substrate 210 partially overlap.

In another embodiment, the piezoelectric film sensor 20 further includes a position upper electrode 280 and a position lower electrode 290. The position lower electrode 290 is provided on the first substrate 210, and the position lower electrode 290 and the conductive layer 220 are located on the first substrate. On the same side of the material 210, the upper electrode 280 is arranged on the side of the second substrate 270 close to the insulating layer, and the upper electrode 280 and the shield electrode 260 are arranged spaced apart.

When the above piezoelectric film 100 is applied to a flexible sensor as a sleeping belt, the human body lies on the sensor, and the sensor has a pressure in the vertical direction, while the sensor has a tensile force in the length direction. Positive and negative charges with opposite charges are generated on the electrodes. The electrical signal is transmitted through the conductive layer 220 and the electrode lead of the upper electrode 240. With the human body's turning, breathing, heartbeat and other actions, the sensor can collect the corresponding electrical signals, and after analysis, the effect of sleep monitoring can be realized.

When the above-mentioned piezoelectric film sensor 20 is introduced into the position upper electrode 280 and the position lower electrode 290, the interference of other piezoelectric layers 230 can be eliminated, and the detection accuracy of the signal can be improved. For example, the pressure film sensor used for sleep monitoring is placed on the bed. Except for the area where the human body lies, there will still be other heavy objects such as quilts above the other areas; other heavy objects will also move up and down with the body’s breathing; The upper electrode 280 and the lower electrode 290 can exclude other piezoelectric signals in areas not covered by the human body. Another example is a pressure film sensor used for sleep monitoring. When two people are lying on the bed, the cooperation of the upper electrode 280 and the lower electrode 290 can determine the phenomenon of the two persons according to the obtained two targets; at the same time, according to The piezoelectric sensing signal at the corresponding position further obtains the corresponding strain law/human body action law (such as breathing law).

Further, the above-mentioned piezoelectric film sensor 20 further includes a capacitance sensor electrode for detecting a touch position.

The manufacturing method of the piezoelectric film of an embodiment includes step S110 to step S130. specifically:

Step S110: Provide a substrate covered with a conductive layer, wherein the conductive layer is an aged ITO layer, and the crystallinity of the conductive layer exceeds 80%.

Specifically, an ITO layer is prepared on the substrate, and then the ITO layer is aged to obtain a conductive layer. However, the material and thickness of the base material are not particularly limited. For example, the substrate may be a flexible organic film material or glass. In this embodiment, the substrate is a flexible substrate, such as organic film materials such as PET, PI, TPU, PE, etc.; the flexible substrate facilitates the piezoelectric film structure to prepare the piezoelectric film in a roll-to-roll manner. The thickness of the substrate is 10 μm to 300 μm. Further, the thickness of the substrate is 100 μm to 300 μm. Or the thickness of the substrate is 10 μm to 200 μm. The above-mentioned thickness setting of the substrate facilitates process production. In other embodiments, the substrate is glass, and the thickness of the substrate is 0.1 mm to 1 mm.

Of course, the method of preparing the ITO layer on the substrate is not particularly limited, and a conventional method in the art may be used, such as magnetron sputtering deposition. Similarly, the method for aging treatment of the ITO layer is not particularly limited, and conventional methods in the art may be used, such as shrinkage aging treatment. The crystallization rate of the aging-treated ITO layer (ie, conductive layer) exceeds 80% and does not exceed 98%. Furthermore, the crystallinity of the conductive layer is 80%-95%. Because different aging conditions will affect the crystallization rate of the ITO layer, when the crystallization rate of the ITO layer is less than 80%, it is easy to cause the fluoropolymer to require a longer crystallization time to achieve a high β-phase ratio.

Of course, the conductive layer contains crystal grains. Further, the grain size of the crystal grains of the conductive layer is 10 nm to 300 nm. Further, the grain size of the crystal grains of the conductive layer is 10 nm to 150 nm, and further, the grain size of the crystal grains of the conductive layer is 20 nm to 60 nm. When the grain size of the crystal grains is the above-mentioned grain size, it is easier for the fluorine-containing polymer crystals to grow. In this embodiment, the square resistance of the conductive layer is 1Ω/□ to 500Ω/□. Further, the square resistance of the conductive layer is 25Ω/□～150Ω/□.

In step S120, the raw material for preparing the piezoelectric layer is placed on the conductive layer and then baked to form a primary piezoelectric layer. The raw material for preparing the piezoelectric layer includes a fluoropolymer.

Specifically, the raw material for preparing the piezoelectric layer includes a fluoropolymer. Further, the fluoropolymer is selected from the group consisting of vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride, P(VDF-TrFE-CTFE) and P(VDF- At least one of TrFE-CFE). The raw materials for preparing the piezoelectric layer include vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride, P (VDF-TrFE-CTFE) and P (VDF-TrFE- At least one of CFE) can make the crystallization time in the piezoelectric layer preparation process short (which can be completed in 30 minutes) and the ratio of the β phase formed by the crystallization is relatively high. Further, the raw materials for preparing the piezoelectric layer are vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride, P(VDF-TrFE-CTFE) and P(VDF -At least one of TrFE-CFE).

Specifically, the method of placing the raw material for preparing the piezoelectric layer on the conductive layer includes, but is not limited to, knife coating, slit extrusion coating, glue dispensing, gravure coating, comma roll coating, silk screen printing, and spray coating.

Specifically, the baking time is within 30 minutes. Further, the baking time is 5 minutes to 20 minutes.

Step S130, grounding the conductive layer, and corona discharge on the side of the primary piezoelectric layer away from the conductive layer to polarize the primary piezoelectric layer to obtain a piezoelectric layer. The piezoelectric layer does not include an α-phase fluoropolymer.

Specifically, the voltage during the polarization process is 10 kV to 15 kV, and the gate voltage during the polarization process is 4 kV to 8 kV. Further, the voltage during the polarization process is 12 kV to 14 kV, and the gate voltage during the polarization process is 5 kV to 7 kV. In the polarization process, the above-mentioned voltage and the gate voltage have a good polarization effect. Under the same polarization time, its piezoelectric properties d33 and d31 have high values; or in order to obtain the same piezoelectric properties, the polarization time can be shorter, generally from 10 minutes to 1 minute to 2 minutes.

In one of the examples, the substrate is a flexible substrate, and the piezoelectric film is prepared in a roll-to-roll manner. Specifically, in a roll-to-roller (RTR), the exposed conductive layer on the substrate bearing the primary piezoelectric layer is grounded, and the primary piezoelectric layer is corona polarized on the side away from the conductive layer , And then separate the piezoelectric layer from the conductive layer at the receiving end of the roll-to-roll unwinder to obtain the piezoelectric film. The piezoelectric film is prepared in a roll-to-roll manner to improve production efficiency.

When the primary piezoelectric layer is polarized by the electric field, since the aged ITO layer has the conductive property as the conductive layer to ground, the direct contact area between the conductive layer and the piezoelectric film is large, which greatly improves the polarization efficiency and effect.

Of course, the thickness of the conductive layer and the piezoelectric layer is not particularly limited. In this embodiment, the thickness of the conductive layer is 3 μm to 30 μm; the thickness of the piezoelectric layer is 5 μm to 200 μm. The above arrangement of the conductive layer and the piezoelectric layer facilitates the improvement of the piezoelectric performance of the piezoelectric layer.

The method for preparing the piezoelectric film described above solves the problem that the piezoelectric layer is easily deformed during the polarization process due to its thin thickness by polarizing the piezoelectric layer and the substrate connected with the conductive layer together. In addition, in the preparation method of the piezoelectric film, an ITO layer with a crystallization rate of more than 80% is used as a conductive layer, which promotes the crystallization and crystal growth of fluoropolymers, shortens the crystallization time of fluoropolymers, and makes it easier to form β phase, thereby making The beta phase accounts for a higher proportion of the primary piezoelectric layer, which is more conducive to improving the piezoelectric performance of the piezoelectric film.

The method for preparing the piezoelectric film sensor 10 includes steps S10 to S50. specifically:

Step S10, providing a first substrate 110 covered with a conductive layer 120, wherein the conductive layer 120 is an aged ITO layer, and the crystallization rate of the conductive layer 120 exceeds 80%.

Specifically, an ITO layer is prepared on the first substrate 110, and then the ITO layer is aged to obtain the conductive layer 120. Wherein: the material of the first substrate 110 and the thickness of the first substrate 110 are not particularly limited. For example, the first substrate 110 may be a flexible organic film material or glass. In this embodiment, the first substrate 110 is a flexible substrate, such as organic film materials such as PET, PI, TPU, PVC, TPU, and PE;层130. The thickness of the first substrate 110 is 10 μm to 300 μm. Further, the thickness of the first substrate 110 is 100 μm to 300 μm. Or the thickness of the first substrate 110 is 10 μm to 200 μm. The above-mentioned thickness setting of the first substrate 110 is convenient for process production. In other embodiments, the first substrate 110 is glass, and the thickness of the first substrate 110 is 0.1 mm to 1 mm.

Of course, the method for preparing the ITO layer on the first substrate 110 is not particularly limited, and a conventional method in the art may be used, such as magnetron sputtering deposition. Similarly, the method for aging treatment of the ITO layer is not particularly limited, and conventional methods in the art may be used, such as shrinkage aging treatment. The crystallization rate of the aging-treated ITO layer (ie, the conductive layer 120) exceeds 80%. Further, the crystallinity rate of the conductive layer 120 is 80% and does not exceed 98%; further, the crystallinity rate of the conductive layer 120 is 80%-95%. Because different aging conditions will affect the crystallization rate of the ITO layer, when the crystallization rate of the ITO layer is less than 80%, it is easy to cause the fluoropolymer to require a longer crystallization time to achieve a high β-phase ratio.

Of course, the conductive layer 120 contains crystal grains. Further, the grain size of the crystal grains of the conductive layer 120 is 10 nm to 300 nm. Further, the grain size of the crystal grains of the conductive layer 120 is 20 nm to 60 nm. When the grain size of the crystal grains is the above-mentioned grain size, it is easier for the fluorine-containing polymer crystals to grow.

In this embodiment, the square resistance of the conductive layer 120 is 1Ω/□ to 500Ω/□. Further, the square resistance of the conductive layer 120 is 25Ω/□～150Ω/□. Step S20, placing the raw material for preparing the piezoelectric layer 130 on the conductive layer 120 and baking to form a primary piezoelectric layer, wherein the raw material for preparing the piezoelectric layer 130 includes a fluoropolymer.

Specifically, the raw material for preparing the piezoelectric layer 130 includes a fluoropolymer. Further, the fluoropolymer is selected from the group consisting of vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride, P(VDF-TrFE-CTFE) and P(VDF- At least one of TrFE-CFE). The raw materials for preparing the piezoelectric layer 130 include vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride, P (VDF-TrFE-CTFE) and P (VDF-TrFE) -CFE), the crystallization time during the preparation of the piezoelectric layer 130 can be short (it can be completed in 30 minutes) and the ratio of the β phase formed by the crystallization can be high. Further, the raw materials for preparing the piezoelectric layer 130 are vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride, P(VDF-TrFE-CTFE) and P( At least one of VDF-TrFE-CFE).

Specifically, methods for placing the raw materials for preparing the piezoelectric layer 130 on the conductive layer 120 include, but are not limited to, knife coating, slot extrusion coating, dispensing, gravure coating, comma roll coating, silk screen printing, and spray coating.

The raw material for preparing the piezoelectric layer 130 is placed on the conductive layer 120 according to a preset pattern and then baked to form the patterned piezoelectric layer 130. The preset graphics may be arbitrary, such as rectangles, triangles, prisms, and so on. The patterning of the piezoelectric layer 130 can greatly increase the utilization rate of piezoelectric materials and greatly reduce the cost.

In this embodiment, the thickness of the conductive layer is 3 μm to 30 μm; the thickness of the piezoelectric layer is 5 μm to 200 μm. The above arrangement of the conductive layer and the piezoelectric layer facilitates the improvement of the piezoelectric performance of the piezoelectric layer.

In step S30, an upper electrode 140 is prepared on the side of the primary piezoelectric layer away from the conductive layer 120.

Specifically, the method for preparing the upper electrode 140 is not particularly limited, and a method used in the art may be used.

In one of the embodiments, the projection of the conductive layer 120 on the first substrate 110 completely covers the projection of the upper electrode 140 on the first substrate 110.

Step S40, ground the conductive layer 120, and corona discharge the primary piezoelectric layer away from the conductive layer 120 to polarize the primary piezoelectric layer to obtain the piezoelectric layer 130. The piezoelectric layer 130 does not include α-phase fluoropolymer .

Specifically, the voltage during the polarization process is 10 kV to 15 kV, and the gate voltage during the polarization process is 4 kV to 8 kV. Further, the voltage during the polarization process is 12 kV to 14 kV, and the gate voltage during the polarization process is 5 kV to 7 kV. In the polarization process, the above-mentioned voltage and the gate voltage have a good polarization effect. Under the same polarization time, its piezoelectric properties d33 and d31 have high values; or in order to obtain the same piezoelectric properties, the polarization time can be shorter, generally from 10 minutes to 1 minute to 2 minutes.

Step S50. Cover the second substrate 170 on the upper electrode 140 and seal it with the first substrate 110 to form a sealed cavity. The conductive layer 120, the piezoelectric layer 130 and the upper electrode 140 are contained in the sealed cavity to obtain a piezoelectric Thin film sensor 10.

Specifically, the material of the second substrate 170 and the thickness of the second substrate 170 are not particularly limited. For example, the second substrate 170 may be a flexible organic film material or glass. In this embodiment, the second substrate 170 is a flexible substrate, such as organic film materials such as PET, PI, TPU, PVC, TPU, PE, etc. The flexible substrate facilitates the preparation of the piezoelectric film sensor 10 in a roll-to-roll manner. Further, the thickness of the second substrate 170 is 10 μm to 200 μm. The above-mentioned thickness setting of the second substrate 170 facilitates process production.

In one of the embodiments, the first substrate 110 and the second substrate 170 are both hot-pressed organic film materials, such as hot-pressed TPU, heat-sealed PP, etc., and the second substrate 170 and the first substrate 110 are heated It is directly sealed in the form of plastic or hot pressing to accommodate the conductive layer 120, the piezoelectric layer 130 and the upper electrode 140 in the sealed space formed by the first substrate 110 and the second substrate 170. By directly sealing the second substrate 170 and the first substrate 110 by thermoplastic or hot pressing, the thickness of the piezoelectric film sensor 10 can be reduced. At the same time, since the adhesive layer 150 is not included, the piezoelectric film sensor 10 can pass yellow light. /The photosensitive process carries out roll-to-roll operation, which greatly improves production efficiency.

In one of the embodiments, the first substrate 110 and the second substrate 170 are sealed by an adhesive layer 150.

In one of the embodiments, it further includes the steps of preparing an insulating layer on the upper electrode 140 and preparing a shield electrode 160 on the insulating layer. Specifically, after the preparation of the piezoelectric layer 130 is completed, an insulating layer and a shield electrode 160 are prepared on the upper electrode 140. The method of preparing the insulating layer and the shielding electrode 160 is not particularly limited, as long as the conventional method in the art is sufficient. Further, the projection of the shielding electrode 160 on the first substrate 110 completely covers the projection of the upper electrode 140 on the first substrate 110.

The method for preparing the piezoelectric thin film sensor 10 described above uses an aged ITO layer with a crystallinity of more than 80% as the conductive layer 120 of the piezoelectric thin film sensor 10. During the preparation of the piezoelectric layer 130, a fluoropolymer containing The raw material is coated on the surface of the aged ITO layer with a crystallization rate of more than 80%. During the crystallization process of forming the primary piezoelectric layer, due to the energy relationship, heterogeneous nucleation will be preferred to homogeneous nucleation, so it is adsorbed on the aged ITO layer The fluoropolymer on the surface will act as a crystal nucleus to accelerate the crystal growth of the fluoropolymer, and also make the β phase easier to form, thereby increasing the ratio of the β phase, thereby improving the piezoelectric performance of the piezoelectric thin film sensor 10. In addition, the preparation method of the piezoelectric thin film sensor 10 described above polarizes the piezoelectric layer 130 and the first substrate 110 connected with the conductive layer 120 together, which solves the problem that the piezoelectric layer 130 is easily generated during the polarization process due to its thin thickness. The problem of deformation is also conducive to the roll-to-roll operation. In addition, the method for preparing the piezoelectric film sensor 10 can also be used to prepare the piezoelectric film 100 in a roll-to-roll manner, which improves production efficiency and reduces production costs.

Of course, the preparation method of the piezoelectric thin film sensor 20 of another embodiment is substantially the same as the preparation method of the piezoelectric thin film sensor 10 described above. Two steps of preparing a positional electrode 280 on the substrate 170 or the insulating layer. Specifically, the lower electrode 290 is prepared on the first substrate 210, and the upper electrode 280 is prepared on the second substrate 270, so that the lower electrode 290 and the conductive layer 220 of the piezoelectric film sensor 20 are located on the first substrate 210. The electrode 280 and the shield electrode 260 are located on the same side of the second substrate 270 in position. After the first substrate 210 and the second substrate 270 are sealed, the upper electrode 280 and the lower electrode 290 are also contained in the sealed space formed by the first substrate 210 and the second substrate 270. Alternatively, a position upper electrode 280 is prepared on the insulating layer.

The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express several embodiments of the present invention, and the descriptions are more specific and detailed, but they should not be understood as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (30)

1. A piezoelectric film, characterized in that it comprises:

   First substrate

   A conductive layer is provided on the first substrate, the conductive layer is an aged ITO layer, and the crystallinity of the conductive layer exceeds 80%;

   The piezoelectric layer is provided on the conductive layer, the piezoelectric layer contains a fluoropolymer, and the fluoropolymer does not include an α-phase fluoropolymer.
2. The piezoelectric film according to claim 1, wherein the conductive layer contains crystal grains, and the crystal grains have a particle size of 10 nm to 300 nm.
3. The piezoelectric film according to claim 1, wherein the square resistance of the conductive layer is 1Ω/□ to 500Ω/□.
4. The piezoelectric film according to claim 1, wherein the fluoropolymer is selected from the group consisting of vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride , At least one of P (VDF-TrFE-CTFE) and P (VDF-TrFE-CFE).
5. The piezoelectric film according to claim 1, wherein the thickness of the piezoelectric layer is 5 μm to 200 μm; and/or the thickness of the conductive layer is 3 μm to 30 μm.
6. A method for preparing a piezoelectric film is characterized in that it comprises the following steps:

   Providing a substrate covered with a conductive layer, wherein the conductive layer is an aged ITO layer, and the crystallization rate of the conductive layer exceeds 80%;

   Placing the raw material for preparing the piezoelectric layer on the conductive layer and baking to form a primary piezoelectric layer, the raw material for preparing the piezoelectric layer includes a fluoropolymer; and

   Ground the conductive layer, and discharge corona on the side of the primary piezoelectric layer away from the conductive layer to polarize the primary piezoelectric layer to obtain a piezoelectric layer. The piezoelectric layer does not include α-phase containing Fluoropolymer.
7. 7. The method for preparing a piezoelectric film according to claim 6, wherein the conductive layer contains crystal grains, and the grain size of the crystal grains is 10 nm to 300 nm.
8. The method for preparing a piezoelectric film according to claim 6, wherein the square resistance of the conductive layer is 1Ω/□～500Ω/□.
9. The method for preparing a piezoelectric film according to claim 6, wherein the fluoropolymer is selected from the group consisting of vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride At least one of ethylene fluoride, P (VDF-TrFE-CTFE), and P (VDF-TrFE-CFE).
10. 7. The method for preparing a piezoelectric film according to claim 6, wherein the voltage during the polarization process is 10 kV to 15 kV, and the gate voltage during the polarization process is 4 kV to 8 kV.
11. The method for preparing a piezoelectric film according to any one of claims 6 to 10, wherein the substrate is a flexible substrate, and the piezoelectric layer is prepared in a roll-to-roll manner; and/or, The thickness of the substrate is 10 μm to 200 μm.
12. A piezoelectric thin film sensor, characterized by comprising the piezoelectric film according to any one of claims 1 to 5, or the piezoelectric film prepared by the method for preparing the piezoelectric film according to any one of claims 6 to 11 membrane.
13. The piezoelectric film sensor according to claim 12, wherein the piezoelectric layer is a patterned piezoelectric layer.
14. The piezoelectric film sensor according to claim 12, further comprising an upper electrode and a second substrate, the upper electrode is provided on the piezoelectric layer, and the conductive layer is on the first substrate. The projection on the upper electrode completely covers the projection of the upper electrode on the first substrate, the second substrate is disposed on the upper electrode, and the second substrate and the first substrate form a sealed cavity , The conductive layer, the piezoelectric layer and the upper electrode are contained in the sealed cavity.
15. The piezoelectric thin film sensor according to claim 14, further comprising a shielding electrode and an insulating layer, the shielding electrode is located on a side of the second substrate close to the first substrate, and the insulating layer It is arranged between the upper electrode and the shield electrode.
16. The piezoelectric film sensor according to claim 15, wherein the projection of the shield electrode on the first substrate completely covers the projection of the upper electrode on the first substrate.
17. The piezoelectric film sensor according to claim 15, further comprising a position upper electrode and a position lower electrode, the position lower electrode is provided on the first substrate, and the position lower electrode is connected to the conductive The layer is located on the same side of the first substrate.
18. The piezoelectric film sensor according to claim 15, further comprising a position upper electrode and a position lower electrode, the position lower electrode is provided on the first substrate, and the position lower electrode is connected to the conductive The layer is located on the same side of the first substrate, and the electrode and the shielding electrode are spaced apart on the side of the second substrate close to the first substrate in the position.
19. The piezoelectric film sensor according to claim 14, wherein the first substrate is a flexible substrate; and/or the second substrate is a flexible substrate.
20. A method for preparing a piezoelectric film sensor is characterized in that it comprises the following steps:

    Providing a first substrate covered with a conductive layer, wherein the conductive layer is an aged ITO layer, and the crystallinity of the conductive layer exceeds 80%;

    Placing the raw material for preparing the piezoelectric layer on the conductive layer and baking to form a primary piezoelectric layer, wherein the raw material for preparing the piezoelectric layer includes a fluoropolymer;

    Preparing an upper electrode on the side of the primary piezoelectric layer away from the conductive layer;

    Ground the conductive layer, and discharge corona on the side of the primary piezoelectric layer away from the conductive layer to polarize the primary piezoelectric layer to obtain a piezoelectric layer. The piezoelectric layer does not include α-phase containing Fluoropolymer; and

    Covering the upper electrode with a second substrate and sealing it with the first substrate to form a sealed cavity, the conductive layer, the piezoelectric layer and the upper electrode are contained in the sealed cavity, The piezoelectric film sensor is obtained.
21. 22. The method for manufacturing a piezoelectric thin film sensor according to claim 20, wherein the projection of the conductive layer on the first substrate completely covers the projection of the upper electrode on the first substrate.
22. 22. The method for manufacturing a piezoelectric thin film sensor according to claim 20, wherein the conductive layer contains crystal grains, and the grain size of the crystal grains is 10 nm to 300 nm.
23. 22. The method for manufacturing a piezoelectric thin film sensor according to claim 20, wherein the square resistance of the conductive layer is 1Ω/□～500Ω/□.
24. The method for preparing a piezoelectric film sensor according to claim 20, wherein the fluoropolymer is selected from the group consisting of vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, poly At least one of vinylidene fluoride, P (VDF-TrFE-CTFE), and P (VDF-TrFE-CFE).
25. 22. The method for manufacturing a piezoelectric thin-film sensor according to claim 20, wherein the voltage during the polarization process is 10 kV to 15 kV, and the gate voltage during the polarization process is 4 kV to 8 kV.
26. 22. The method of manufacturing a piezoelectric thin film sensor according to claim 20, wherein the first substrate is a flexible substrate; and/or the thickness of the first substrate is 10 μm to 200 μm; and/or , The second substrate is a flexible substrate; and/or, the thickness of the second substrate is 10 μm to 200 μm.
27. 22. The method for preparing a piezoelectric thin film sensor according to claim 20, wherein the raw material for preparing the piezoelectric layer is placed on the conductive layer according to a preset pattern and then baked to form a patterned piezoelectric layer .
28. The method for preparing a piezoelectric thin film sensor according to any one of claims 20-27, characterized in that, after the step of obtaining the piezoelectric layer, the method further comprises preparing an insulating layer on the upper electrode and forming an insulating layer on the upper electrode. The step of preparing a shielding electrode on the insulating layer.
29. The method for manufacturing a piezoelectric thin film sensor according to claim 28, wherein the projection of the shield electrode on the first substrate completely covers the projection of the upper electrode on the first substrate.
30. The method for preparing a piezoelectric thin film sensor according to claim 28, further comprising a step of preparing a positional lower electrode on the first substrate and preparing a lower electrode on the second substrate or the insulating layer. Position the electrodes on the steps.

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