Pressure sensing ink, flexible pressure sensing structure and electronic device

Abstract

The present application provides a pressure-sensitive ink, a flexible pressure-sensing structure and an electronic device, wherein the pressure-sensitive ink comprises: an adhesive component and a conductive material and an inorganic filler dispersed in the adhesive component, wherein the surface of the inorganic filler has a hydrophobic group, and the inorganic filler is used to increase the dispersibility of the conductive material. The inorganic filler provided by the present application is used as a dispersing component to improve the uniformity of the dispersion of the conductive material, reduce the resistance change rate of the flexible pressure-sensing structure, improve the sensitivity, and also reduce the noise of the flexible pressure-sensing structure; the inorganic filler plays a supporting role in the adhesive component, which can reduce the structural collapse of the pressure-sensitive ink during the thermal curing shrinkage process, and reduce the risk of forming a concave and uneven pressure strain layer.

Description

Technical Field

[0001] The present application relates to the technical field of printed circuit boards, and in particular to a pressure sensing ink, a flexible pressure sensing structure and an electronic device. Background Art

[0002] With the continuous advancement of technology, people's depth and breadth of collecting information about the surrounding environment are constantly improving. Flexible pressure sensors, as a very important type of information collection device, are becoming more and more widely used. In addition, the use of flexible sensing technology to replace traditional sensing technology has subverted the cognition of the form and function of traditional electronic devices, sensor devices and systems. This type of device has brought revolutionary changes to many aspects of social life and may be widely used in robotics, medical diagnosis, wearable electronic devices, artificial organs, human-computer interaction, smart skin and other fields. Research on flexible pressure sensors has also become a hot topic in recent years.

[0003] Flexible pressure sensors are similar to human skin and can sense the intensity of external force stimulation. They can help robots achieve tactile sensation and are widely used in many fields such as human health monitoring. However, both human skin and flexible pressure sensors (or electronic skin) generally have a serious disadvantage, that is, the current flexible pressure sensors have complex structures, thick thickness, poor sensitivity, and high noise. Summary of the invention

[0004] In view of this, in order to overcome at least one of the above-mentioned defects, it is necessary to provide a pressure-sensitive ink.

[0005] In addition, the embodiments of the present application also provide a flexible pressure sensor and electronic device using the aforementioned pressure-sensitive ink.

[0006] An embodiment of the present application provides a pressure-sensitive ink, which includes: an adhesive component and a conductive material and an inorganic filler dispersed in the adhesive component, wherein the surface of the inorganic filler has a hydrophobic group, and the inorganic filler is used to increase the dispersibility of the conductive material in the adhesive component.

[0007] In some possible embodiments, the particles of the inorganic filler include an inner layer and a surface layer from inside to outside, the hydrophobic group is connected to the surface layer, and the inner layer is a hollow structure or has a plurality of microporous structures.

[0008] In some possible embodiments, the dielectric constant Dk of the inorganic filler is ≤3.

[0009] In some possible embodiments, the average particle size of the inorganic filler is between 10 nm and 100 nm.

[0010] In some possible embodiments, the hydrophobic group includes a group containing at least one of a fluorine atom, a methyl group, an ethyl group, and a propyl group.

[0011] In some possible embodiments, the weight percentage of the inorganic filler in the pressure sensitive ink is 5% to 10%.

[0012] In some possible embodiments, the inorganic filler is obtained by surface-modifying silicon dioxide with a hydrophobic silane compound, and the hydrophobic siloxane compound contains the hydrophobic group.

[0013] In some possible embodiments, the adhesive component includes a copolymer of ethylene, acrylic acid, methacrylic acid, or polyvinyl alcohol.

[0014] An embodiment of the present application also provides a flexible pressure sensing structure, which includes a dielectric layer, a pressure strain layer and a conductive layer stacked in sequence, and the pressure strain layer is formed by curing the pressure sensing ink as described above.

[0015] In some possible embodiments, the flexible pressure sensing structure is a strain gauge pressure sensor.

[0016] In some possible embodiments, the resistance change rate of the flexible pressure sensing structure is less than or equal to 20%, and / or the noise of the flexible pressure sensing structure is less than or equal to 1.2±0.5.

[0017] An embodiment of the present application further provides an electronic device, which includes a circuit board. The circuit board includes at least one flexible pressure sensing structure as described above, and the pressure sensing layer is electrically connected to the circuit layer of the circuit board through the conductive layer.

[0018] Compared with the prior art, in the pressure sensing ink provided by the embodiment of the present application, by adding an inorganic filler having a hydrophobic group on the surface, the conductive material can be evenly dispersed in the adhesive component, which is beneficial to improving the sensitivity of the flexible pressure sensing structure, and can also improve the stability of the flexible pressure sensing structure and reduce the noise of the flexible pressure sensing structure. In addition, the added inorganic filler can play a structural supporting role in the pressure sensing ink, which can reduce the structural collapse of the pressure sensing ink during the thermal curing shrinkage process, improve the process yield, and further improve the stability of the flexible pressure sensing structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the dispersion of inorganic fillers and conductive materials in an adhesive component provided in an embodiment of the present application.

[0020] Figure 2 It is a schematic diagram of the structure of an inorganic filler provided in one embodiment of the present application.

[0021] Figure 3 It is a schematic diagram of the structure of an inorganic filler provided in another embodiment of the present application.

[0022] Figure 4 It is a schematic diagram of the structure of an inorganic filler provided in yet another embodiment of the present application.

[0023] Figure 5 It is a schematic diagram of the structure of an inorganic filler provided in yet another embodiment of the present application.

[0024] Figure 6 It is a structural schematic diagram of a flexible pressure sensing structure provided in one embodiment of the present application.

[0025] Figure 7 It is a schematic diagram of the structure of an electronic device provided in one embodiment of the present application.

[0026] Figure 8 It is a schematic diagram of the structure of a circuit board provided in one embodiment of the present application.

[0027] Figures 9 to 16 It is a schematic diagram of the preparation process of a circuit board provided in one embodiment of the present application.

[0028] Fig.17 This is an appearance diagram of the pressure strain region of a flexible pressure sensing structure prepared using the pressure sensing ink of Example 1 of the present application.

[0029] Fig.18 Figures (a) to (c) are Fig.17 SEM photos of the cross-sections at the upper, middle and lower parts in the medium pressure strain region.

[0030] Main component symbols

[0031] Circuit board 100

[0032] Flexible pressure sensing structure 10

[0033] Dielectric layer 1

[0034] First surface 11

[0035] Second surface 12

[0036] Pressure strain layer 2

[0037] Conductive layer 3

[0038] Circuit layer 4,5

[0039] Covering film 6

[0040] Opening 7

[0041] Solder mask 8

[0042] Metal substrate 20

[0043] Metal layer 30

[0044] Surface 40

[0045] Inner layer 50

[0046] Hydrophobic group 60

[0047] Microporous structure 70

[0048] Electronic equipment 200

[0049] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0050] The technical solution of the present application will be described clearly and completely in conjunction with specific embodiments below. Obviously, the described implementation is only a part of the implementation of the present application, not all implementations.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The names of the technical means used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0052] In the absence of conflict, the following embodiments and features of the embodiments may be combined with each other.

[0053] Existing flexible pressure sensors usually use pressure capacitance technology, pressure resistance technology, and piezoelectric ceramic technology to achieve pressure sensing. Among them, pressure capacitance technology changes the capacitance by changing the spacing between metal plates, and the deformation of the metal plates is converted into pressure. Therefore, the processing accuracy of the metal plates is required to be high; pressure resistance technology changes the resistance by changing the contact area between the conductive material layer and the metal plate. The two conductive planes are in contact, and the linearity of characterizing the pressure change according to the change in contact area is poor, and the durability is poor. Piezoelectric ceramic technology sets conductive materials on the upper and lower surfaces of piezoelectric ceramics and presses them. The deformation of piezoelectric ceramics generates charge changes to characterize the pressure change. This method can only measure instantaneous pressure. Moreover, the structure of the flexible pressure sensor based on the above technologies is relatively complex. Both the upper and lower surfaces need to be pressurized, that is, a support structure needs to be set up. The overall thickness is relatively thick, the sensitivity is poor, and the noise is high.

[0054] In order to solve the above problems, an embodiment of the present application provides a pressure-sensitive ink, which can form a pressure strain layer (or pressure strain film, pressure strain gauge) after curing. The pressure strain layer can deform when subjected to pressure, so that it can be used in a flexible pressure sensing structure.

[0055] The pressure sensitive ink includes a bonding component and a conductive material dispersed in the bonding component.

[0056] In some embodiments, the adhesive component is usually a resin having a certain flexibility after curing, for example, a copolymer of ethylene, acrylic acid, methacrylic acid or a polymer resin such as polyvinyl alcohol. The adhesive component can be a transparent material.

[0057] In some embodiments, the conductive material may be conductive particles such as carbon black, graphite, and graphene.

[0058] Due to the accumulated charge and high surface energy on the surface of the conductive material, agglomeration will occur between the conductive materials under the action of van der Waals forces, surface hydrogen bonds or other chemical bonds. The agglomeration of the conductive materials in the adhesive component will affect the conductive properties of the pressure sensing ink, and further affect the sensitivity and stability (noise) of the flexible pressure sensing structure.

[0059] To this end, the embodiment of the present application further adds an inorganic filler to the pressure-sensitive ink, the surface of the inorganic filler has a hydrophobic group, and the inorganic filler can be used to increase the dispersibility of the conductive material, that is, the inorganic filler can be used as a dispersant for the conductive material. Figure 1 As shown, the purpose of the inorganic filler in the pressure sensing ink is to improve the dispersibility of the conductive material. By adding the inorganic filler to the pressure sensing ink, the conductive material can be uniformly dispersed in the adhesive component.

[0060] In some embodiments, the hydrophobic group on the surface of the inorganic filler may include a group containing at least one of a fluorine atom, a methyl group, an ethyl group, and a propyl group.

[0061] In some embodiments, the inorganic filler is obtained by surface-modifying silicon dioxide with a hydrophobic silane compound, and the hydrophobic siloxane compound contains the aforementioned hydrophobic group. The surface-hydrophobically modified silicon dioxide has a low surface energy through the hydrophobic surface due to the hydrophobic group on the surface, and the hydrophobic group can increase the steric hindrance, so that the particles of the conductive material are not easy to agglomerate, and the conductive material is evenly dispersed in the adhesive component, thereby improving the dispersion uniformity of the conductive material. In addition, after the pressure-sensitive ink is heated and cured to form a pressure strain layer, the adhesive component will shrink. By adding the inorganic filler, it can also play a role in structural support, avoiding structural collapse after the adhesive component shrinks due to heating, improving the structural stability of the adhesive component after molding, and then reducing the noise of the flexible pressure sensing structure, which is effectively applied to related products such as flexible pressure sensors, and can also improve the yield of the product.

[0062] In some embodiments, the dielectric constant Dk of the inorganic filler is less than 3, and the dielectric constant of the inorganic filler is relatively small, and the inorganic filler can be a dielectric, which can reduce the influence of the inorganic filler on the conductivity of the pressure sensing ink.

[0063] The inorganic filler is in the form of particles, the hydrophobic groups are connected to the surface of the particles, and the inorganic filler can be solid, such as Figure 2 The inorganic filler may also be hollow, such as Figure 3 Alternatively, Figure 4 and Figure 5 As shown, the inorganic filler particles include an inner layer 50 and a surface layer 40 from the inside to the outside, the hydrophobic group 60 is connected to the surface layer 40, and the inner layer 50 has a plurality of microporous structures 70, wherein the microporous structure is not limited to Figure 4 and Figure 5 The structure shown.

[0064] The inorganic filler is made hollow or has a microporous structure, and air can be introduced into the inorganic filler, thereby further reducing the dielectric property of the inorganic filler, reducing the influence of the inorganic filler on the conductivity of the pressure-sensitive ink, and improving the stability of the conductivity of the pressure-sensitive ink; moreover, the pore size of the microporous structure in the inorganic filler can be adjusted by adopting different pore-forming methods, thereby adjusting the density of the inorganic filler. In addition, the microporous structure is formed in the inner layer, and the surface layer remains intact, which can prevent the adhesive component from flowing into the microporous structure of the inorganic filler. It can also be further controlled that the inorganic filler has a larger density, that is, the space of the microporous structure is smaller, which can prevent the adhesive component from flowing into the microporous structure of the inorganic filler after the inorganic filler is damaged. Specifically, the microporous structure can be prepared by adding a pore-forming template (or pore-forming agent) to the raw material of the inorganic filler, preparing spherical inorganic filler particles by a sol-gel method, and then removing the pore-forming template in the particles to obtain an inorganic filler with a microporous structure, wherein the method of removing the pore-forming template is selected according to the type of the pore-forming template, for example, it can be removed by sintering or by dissolving.

[0065] In some embodiments, the average particle size of the inorganic filler is 10nm to 100nm, further 10nm to 80nm, further 20nm to 50nm. Exemplarily, the average particle size of the inorganic filler is 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm. By controlling the average particle size of the inorganic filler within the above range, the conductive material can have good dispersibility in the adhesive component, and it is also beneficial to improve the conductivity of the pressure-sensitive ink.

[0066] In some embodiments, the pressure-sensitive ink includes, by weight percentage, 5-10 wt% of inorganic filler, 15-25 wt% of conductive material, 15-25 wt% of adhesive component, and may also include 0-5 wt% of auxiliary agent and 50-60 wt% of solvent. The weight percentage of the inorganic filler in the pressure-sensitive ink may be 5 wt% to 10 wt%, and may be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%, etc., and the inorganic filler is uniformly stirred and dispersed in the adhesive component by three rollers. By controlling the addition amount of the inorganic filler within the above range, the conductive material can have good dispersibility in the adhesive component, and it is also beneficial to improve the conductivity of the pressure-sensitive ink.

[0067] In some embodiments, the auxiliary agent may be any one or more of a leveling agent, a defoaming agent, a photoinitiator, and the like.

[0068] In some embodiments, the solvent may be any one or more of ethylene glycol butyl ether, aromatic hydrocarbon solvents, and the like.

[0069] In the pressure sensing ink provided by the embodiment of the present application, by adding an inorganic filler having a hydrophobic group on the surface, the conductive material can be evenly dispersed in the adhesive component, which is beneficial to improving the sensitivity of the flexible pressure sensing structure, and can also improve the stability of the flexible pressure sensing structure and reduce the noise of the flexible pressure sensing structure. In addition, the added inorganic filler can play a structural support role in the pressure sensing ink, which can reduce the structural collapse of the pressure sensing ink during the thermal curing shrinkage process, improve the process yield, and further improve the stability of the flexible pressure sensing structure.

[0070] The embodiment of the present application also provides a flexible pressure sensing structure, the flexible pressure sensing structure includes a dielectric layer, a pressure strain layer and a conductive layer stacked in sequence, the pressure strain layer is formed by curing the pressure sensing ink as described above. The specific curing method is selected according to the curing method of the adhesive component in the pressure sensing ink, for example, thermal curing can be used. Figure 6 , which is a schematic diagram of a flexible pressure sensing structure 10 provided by an embodiment, includes a dielectric layer 1, a pressure strain layer 2 and a conductive layer 3 stacked in sequence. The dielectric layer 1 can play the role of insulating support, and the conductive layer 3 can be made of a metal with excellent conductivity, such as silver. The conductive layer 3 covers the pressure strain layer 2, and the electrical lead-out of the pressure strain layer 2 can be achieved through the conductive layer 3. The conductive layer 3 with excellent conductivity can improve the sensitivity of the flexible pressure sensing structure 10.

[0071] In some embodiments, the flexible pressure sensing structure may be a strain gauge pressure sensor.

[0072] By using the aforementioned pressure sensing ink to form the pressure strain layer, due to the addition of the aforementioned inorganic filler, the conductive material is dispersed more evenly, which effectively reduces the resistance change rate of the flexible pressure sensing structure, improves the sensitivity of the flexible pressure sensing structure, and also improves the stability of the flexible pressure sensing structure and reduces the noise of the flexible pressure sensing structure. In addition, the added inorganic filler can improve the structural stability of the pressure strain layer, reduce the structural collapse of the pressure sensing ink during the thermal curing shrinkage process, improve the process yield, and further improve the stability of the flexible pressure sensing structure. The resistance change rate of the flexible pressure sensing structure provided in the embodiment of the present application is less than or equal to 20%. The noise of the flexible pressure sensing structure is less than or equal to 1.2±0.5.

[0073] The embodiment of the present application also provides an electronic device, the electronic device includes a circuit board, the circuit board includes a plurality of flexible pressure sensing structures as described above, the pressure sensing layer is electrically connected to the circuit layer of the circuit board through the conductive layer. Specifically, when manufacturing the circuit board, the flexible pressure sensing structure can be manufactured in the circuit board, thereby forming a circuit board with a flexible pressure sensor.

[0074] like Figure 7 and Figure 8 As shown, an electronic device 200 is provided for an embodiment of the present application, wherein the electronic device 200 includes a circuit board 100, and the specific structure of the circuit board 100 includes: a dielectric layer 1, a pressure strain layer 2 and a circuit layer 4 located on the first surface 11 of the dielectric layer 1, another circuit layer 5 located on the second surface 12 of the dielectric layer 1, and a conductive layer 3 located on the surface of the pressure strain layer 2 and the circuit layer 4, the pressure strain layer 2 is electrically connected to the circuit layer 4 through the conductive layer 3, and the circuit layer 4 is electrically connected to the circuit layer 5, thereby realizing the electrical extraction of the pressure strain layer 2. Among them, the stacked dielectric layer 1, the pressure strain layer 2 and the conductive layer 3 constitute the aforementioned flexible pressure sensing structure 10. In some embodiments, the circuit board 100 may also include a covering film 6 covering the dielectric layer 1, the conductive layer 3 and the circuit layer 5 to play a protective role. It can be understood that there can be multiple flexible pressure sensing structures 10 in the circuit board 100. It can also be understood that other required circuit structures can be formed on the surfaces of the circuit layer 4 and the circuit layer 5 respectively by adding layers.

[0075] See also Figures 9 to 16 FIG. 1 is a schematic diagram of a method for preparing a circuit board 100. The method for preparing the circuit board 100 specifically includes the following steps:

[0076] Step S1, such as Fig. 9 As shown, a metal substrate 20 is provided. The metal substrate 20 includes a dielectric layer 1 and a metal layer 30 located on a first surface 11 and a second surface 12 opposite to the dielectric layer 1 .

[0077] Step S2, such as Fig.10 As shown, two metal layers 30 are patterned to form a circuit layer 4 located on the first surface 11 and a circuit layer 5 located on the second surface 12 respectively.

[0078] Step S3, such as Fig.11 and Fig.12 As shown, holes are punched and electroplated to electrically connect circuit layer 4 and circuit layer 5.

[0079] Step S4, such as Fig.13As shown, a cover film 6 (CVL) is attached to the first surface 11 , the second surface 12 and the surface of the circuit layer 5 , the circuit layer 4 is exposed on the surface of the cover film 6 , and the cover film 6 on the first surface 11 is patterned to form an opening 7 .

[0080] In some embodiments, the size and form of the specific opening 7 can be set according to actual needs, such as Fig.13 As shown, the opening 7 is formed around the circuit layer 4, and the cover film 6 around the circuit layer 4 is also removed at the same time, which can increase the contact area between the subsequent conductive layer and the pressure strain layer and the circuit layer 4, thereby improving sensitivity. The cover film 6 between the opening 7 and the circuit layer 4 can also be retained to avoid damage to the circuit layer 4 during the process of patterning the cover film 6.

[0081] Step S5, such as Fig.14 As shown, a pressure strain layer 2 is formed in the opening 7 . The pressure strain layer 2 is located on the first surface 11 and is spaced apart from the circuit layer 4 .

[0082] Specifically, the pressure sensing ink can be formed in the opening 7 by printing, coating, etc., and heated and cured to form the pressure strain layer 2. The thickness of the pressure sensing ink can be very thin, which is conducive to the thinning of the flexible pressure sensing structure.

[0083] Step S6, as Fig.15 As shown, a conductive layer 3 is formed in the opening 7 , and the conductive layer 3 covers the pressure strain layer 2 and the circuit layer 4 , so as to realize electrical connection between the pressure strain layer 2 and the circuit layer 4 .

[0084] The conductive layer 3 may be a conductive silver paste. By filling the conductive silver paste in the gaps around and on the surface of the pressure strain layer 2 and the circuit layer 4, the conductive layer 3 can be in full contact with the pressure strain layer 2 and the circuit layer 4, thereby improving sensitivity.

[0085] Step S7, Fig.16 As shown, a solder resist layer 8 is formed on the surface of the conductive layer 3 , and the solder resist layer 8 may also extend to the surface of the cover film 6 located on the same side.

[0086] The embodiments of the present application are further described below through specific examples.

[0087] Preparation Example

[0088] Preparation of inorganic fillers:

[0089] Step 1: Add siloxane TEOS (tetraethoxysilane) and a hydrophobic silane compound (methyl / ethyl / propyl trimethoxysilane or trimethoxy (3,3,3-trifluoropropyl) silane) into an aqueous solution at the same time, wherein the molar concentration of TEOS in the aqueous solution is 0.07 to 0.09 mol / L; and the molar concentration of the hydrophobic silane compound in the aqueous solution is 0.02 to 0.05 mol / L.

[0090] Step 2, except for solid inorganic fillers, which do not require the addition of pore-forming agents, a pore-forming template (or pore-forming agent) needs to be added to the formula for forming pores inside the inorganic filler. The pore-forming template can be Pluronic F127 (polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO) 100-(PPO) 65-(PEO) 100 triblock copolymer, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), F127; dosage: 0.5~0.8mol / L), sodium dodecyl sulfate (SDS) (0.5~0.8mol / L) or D-maltose (D-maltose, dosage: 0.8~1.2mol / L).

[0091] Step 3, adding ammonia water (NH4OH) as a catalyst to the above solution, wherein the molar concentration of the ammonia water is 0.2-0.5 mol / L, and subjecting the siloxane to a sol-gel reaction to obtain an intermediate product.

[0092] Step 4: remove the pore-forming template in the intermediate product and add The intermediate products of pore formers such as F127 or SDS are removed by low temperature calcination (250°C), and the intermediate products of pore formers such as D-maltose are added to dissolve the pore former by washing with water to achieve the purpose of removal.

[0093] Step 5: After removing the pore-forming agent, the intermediate product is washed with deionized water and dried to obtain the aforementioned surface-modified inorganic filler.

[0094] Table 1 shows the specific preparation process and dielectric constant of four different types of inorganic fillers in Preparation Examples 1 to 4. The internal structures of the inorganic fillers in Preparation Examples 1 to 4 are respectively referred to Figures 2 to 5 .

[0095] Table 1

[0096]

[0097] Example

[0098] Preparation of pressure sensitive ink:

[0099] The adhesive component, the conductive material, the inorganic filler, and other additives and solvents are mixed uniformly in proportion to obtain a pressure-sensitive ink. Specifically, the inorganic filler of Preparation Example 3 is applied to the pressure-sensitive ink, and the amount of the inorganic filler added is adjusted to obtain Examples 1 to 3. Among them, the conductive materials of Examples 1 to 3 all use carbon black.

[0100] As shown in Table 2, the specific formulas of Examples 1 to 3 and the parameters for characterizing the performance of the pressure sensing inks of Examples 1 to 3 after they are prepared into flexible pressure sensing structures.

[0101] Table 2

[0102]

[0103]

[0104] In addition, if Fig.17 As shown, the appearance of the conductive area of ​​the flexible pressure sensing structure of Example 1 is given. Fig.18 Figures (a) to (c) show the Fig.17 SEM photos of the cross-sections at the top, middle and bottom. The FSL region is where the pressure strain layer is located. Fig.18 It can be seen from Figures (a) to (c) that the upper, middle and lower regions of the pressure strain area in the circuit board all present a smooth and uniform appearance structure, without obvious particles or depressions. It can be seen that adding the inorganic filler provided in the embodiment of the present application to the pressure sensing ink can make the conductive material particles evenly dispersed, and the addition of the inorganic filler can occupy the conductive colloid space, support the colloid structure to prevent shrinkage after heating, and reduce the risk of forming depressions and unevenness in the pressure strain layer.

[0105] Therefore, the use of the inorganic filler provided in the embodiment of the present application as the dispersing component of the pressure sensing ink can improve the uniformity of the dispersion of the conductive material, effectively reduce the resistance change rate of the flexible pressure sensing structure (≤20%), improve the sensitivity of the flexible pressure sensing structure, and also improve the stability of the flexible pressure sensing structure, and reduce the noise of the flexible pressure sensing structure (≤1.2±0.5). In addition, the added inorganic filler can improve the structural stability of the pressure strain layer, reduce the structural collapse of the pressure sensing ink during the thermal curing shrinkage process, reduce the risk of forming a concave and uneven pressure strain layer, and improve the process yield.

Claims

1. A pressure-sensitive ink, characterized in that: The pressure-sensitive ink comprises: an adhesive component, and a conductive material and an inorganic filler dispersed in the adhesive component. The surface of the inorganic filler has a hydrophobic group, and the inorganic filler is used to increase the dispersibility of the conductive material in the adhesive component.

2. The pressure sensitive ink according to claim 1, characterized in that: The particles of the inorganic filler include an inner layer and a surface layer from the inside to the outside, the hydrophobic group is connected to the surface layer, and the inner layer is a hollow structure or has a plurality of microporous structures.

3. The pressure sensitive ink according to claim 1, characterized in that: The dielectric constant Dk of the inorganic filler is ≤3.

4. The pressure sensitive ink according to claim 1, characterized in that: The average particle size of the inorganic filler is between 10nm and 100nm.

5. The pressure sensitive ink according to claim 1, characterized in that: The hydrophobic group includes a group containing at least one of a fluorine atom, a methyl group, an ethyl group, and a propyl group.

6. The pressure sensitive ink according to claim 1, characterized in that: The weight percentage of the inorganic filler in the pressure sensing ink is 5% to 10%.

7. The pressure sensitive ink according to claim 1, characterized in that: The inorganic filler is obtained by surface-modifying silicon dioxide with a hydrophobic silane compound, and the hydrophobic siloxane compound contains the hydrophobic group.

8. The pressure sensitive ink according to claim 1, characterized in that: The adhesive component includes a copolymer of ethylene, acrylic acid, methacrylic acid or polyvinyl alcohol.

9. A flexible pressure sensing structure, characterized in that: The invention comprises a dielectric layer, a pressure strain layer and a conductive layer which are stacked in sequence, wherein the pressure strain layer is formed by curing the pressure sensitive ink as claimed in any one of claims 1 to 8.

10. The flexible pressure sensing structure according to claim 9, characterized in that: The flexible pressure sensing structure is a strain gauge pressure sensor.

11. The flexible pressure sensing structure according to claim 9, characterized in that: The resistance change rate of the flexible pressure sensing structure is less than or equal to 20%; and / or, The noise of the flexible pressure sensing structure is less than or equal to 1.2±0.

5.

12. An electronic device, characterized in that: It comprises a circuit board, wherein the circuit board comprises at least one flexible pressure sensing structure as claimed in any one of claims 9 to 11, and the pressure sensing layer is electrically connected to the circuit layer of the circuit board through the conductive layer.

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