Conductive ink for micro loudspeaker diaphragm, preparation method of conductive ink and micro loudspeaker diaphragm

Abstract

The invention provides conductive ink for a vibrating diaphragm of a micro loudspeaker, a preparation method of the conductive ink and the vibrating diaphragm of the micro loudspeaker. The conductive ink is prepared from 10 to 60 weight percent of conductive filler, 10 to 70 weight percent of matrix resin, 10 to 70 weight percent of dispersion medium, 0.1 to 5.0 weight percent of silane coupling agent, 0.2 to 5.0 weight percent of dispersing agent, 0.05 to 1.0 weight percent of defoaming agent, 0.05 to 2.0 weight percent of antioxidant and 0.05 to 1.5 weight percent of ultraviolet light absorber, the conductive filler comprises nanowires with a high length-diameter ratio; the matrix resin comprises acrylic acid system resin; through the mutual synergistic effect of the nanowire with the high length-diameter ratio, the acrylic acid system resin and the anti-aging filler in the conductive ink, the conductive ink can be suitable for high-frequency vibration, large-amplitude stretching, high-humidity and high-temperature application scenes of a micro loudspeaker; and the problem of dynamic reliable conduction of the diaphragm of the micro loudspeaker under high-frequency large-amplitude vibration and severe temperature and humidity can be well solved.

Description

Technical Field

[0001] This invention relates to the field of micro loudspeaker diaphragms, and more particularly to a conductive ink for micro loudspeaker diaphragms, a method for preparing the same, and the micro loudspeaker diaphragm itself. Background Technology

[0002] Miniature loudspeaker systems are evolving towards higher reliability and higher electroacoustic conversion efficiency. Traditional solutions using flexible printed circuits (FPCs) to connect the voice coil to external circuitry suffer from space constraints and are prone to solder joint fatigue failure under long-term vibration, failing to meet the higher demands of the future market. Therefore, the industry is exploring "conductive diaphragm" technology, which involves directly fabricating circuitry on the diaphragm itself.

[0003] Currently, a common approach to achieving high conductivity is to fill a polymer matrix with a high content (>70%) of conductive filler. However, while this approach achieves low resistance through high conductive filler content, excessive filler addition significantly reduces the flexibility and ductility of the composite material. Furthermore, due to their high surface energy, conductive fillers are prone to agglomeration and poor dispersion within the polymer matrix, easily leading to interfacial stress concentration. This can cause the conductive layer to crack or separate from the diaphragm substrate under conditions of significant reciprocating bending and vibration. The selection of the polymer matrix is ​​also crucial; if the chosen matrix material has poor chemical compatibility with the speaker diaphragm, insufficient interfacial stability margin will result after long-term environmental aging. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a conductive ink for a micro loudspeaker diaphragm, a method for preparing the same, and a micro loudspeaker diaphragm. The conductive ink improves the conductivity of the micro loudspeaker diaphragm while having high flexibility, fatigue resistance, and long-term environmental reliability that match the micro loudspeaker diaphragm, and is well-suited for the application requirements of micro loudspeakers.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A conductive ink for a micro loudspeaker diaphragm comprises 10-60 wt% conductive filler, 10-70 wt% matrix resin, 10-70 wt% dispersion medium, 0.1-5.0 wt% silane coupling agent, 0.2-5.0 wt% dispersant, 0.05-1.0 wt% defoamer, 0.05-2.0 wt% antioxidant, and 0.05-1.5 wt% ultraviolet absorber. The conductive filler comprises nanowires with a high aspect ratio; The matrix resin includes an acrylic resin.

[0006] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is as follows: A method for preparing the above-mentioned conductive ink for a micro loudspeaker diaphragm includes the following steps: A stable mixed base material is obtained by premixing the dispersion medium, matrix resin, defoamer, antioxidant and ultraviolet absorber; Nanowire dispersion is uniformly added to the mixed base material, followed by the addition of a dispersant to obtain conductive ink, which is then homogenized. The viscosity of the homogenized conductive ink is adjusted and then filtered.

[0007] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is as follows: A miniature loudspeaker diaphragm, comprising the aforementioned conductive ink for a miniature loudspeaker diaphragm. The beneficial effects of this invention are as follows: The conductive ink uses high aspect ratio nanowires as conductive fillers and acrylic resin as the matrix resin, with added antioxidants and ultraviolet absorbers as anti-aging fillers. The "one-dimensional" characteristic of the high aspect ratio nanowires allows them to interlock within the polymer matrix, constructing a three-dimensional conductive network and achieving "line-to-line" conductive pathways. This three-dimensional conductive network significantly reduces the "percolation threshold" of the conductive pathways, achieving extremely low impedance over a wider range of filler content, especially in the low to medium content range. Furthermore, the three-dimensional conductive network possesses excellent elasticity, allowing for reconstruction as the matrix stretches. When the speaker diaphragm vibrates significantly, the nanowires' flexibility and stretchability maintain the integrity of the conductive pathways, resulting in excellent fatigue resistance. The acrylic resin also has similar properties to commonly used diaphragms in micro-speakers (such as ethylene-acrylate rubber AEM and acrylate rubber ACM). With similar molecular backbone or side chain structures (acrylate units), this high chemical compatibility greatly helps the interfacial adhesion between the conductive ink and the diaphragm material after environmental aging. Antioxidants and UV absorbers are added as anti-aging fillers. Considering the stringent application scenarios of miniature loudspeakers (high temperature, high humidity, extreme cold, etc.), the addition of these fillers protects the chemical interface and conductive network between the conductive ink and the diaphragm, allowing the "conductive diaphragm" to function normally even in extremely harsh environments. Therefore, through the synergistic effect of the high aspect ratio nanowires, acrylic resin, and anti-aging fillers in the conductive ink, the conductive ink is suitable for applications involving high-frequency vibration, significant stretching, and high humidity and temperature in miniature loudspeakers. While improving the conductivity of the miniature loudspeaker diaphragm, the conductive ink also possesses high flexibility, fatigue resistance, and long-term environmental reliability that match the diaphragm, making it well-suited for the application requirements of miniature loudspeakers. Attached Figure Description

[0008] Figure 1This is a flowchart illustrating the steps of a method for preparing conductive ink for a miniature loudspeaker according to an embodiment of the present invention. Detailed Implementation

[0009] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0010] The conductive ink for a micro loudspeaker diaphragm described in this application, its preparation method, and the applicability of the micro loudspeaker diaphragm to various micro loudspeaker diaphragms are illustrated below through specific embodiments: In one optional embodiment, a conductive ink for a micro loudspeaker diaphragm comprises 10-60 wt% conductive filler, 10-70 wt% matrix resin, 10-70 wt% dispersion medium, 0.1-5.0 wt% silane coupling agent, 0.2-5.0 wt% dispersant, 0.05-1.0 wt% defoamer, 0.05-2.0 wt% antioxidant, and 0.05-1.5 wt% ultraviolet absorber. The conductive filler comprises nanowires with a high aspect ratio; The matrix resin includes an acrylic resin.

[0011] The conductive filler is used to provide a conductive path, including one or more of gold nanowires, silver nanowires, and copper nanowires. In an optional embodiment, silver nanowires can be used. The aspect ratio of the nanowire is 100-3000, and in an optional embodiment, it can be 800-1200; The matrix resin, as a continuous phase, includes fillers and additives to form a continuous solid film; The matrix resin may include one or more of waterborne acrylic resin, acrylate copolymer, waterborne polyurethane, and EVA emulsion. In an optional embodiment, waterborne acrylic resin may be used.

[0012] The dispersion medium is used for dissolution, dispersion, and providing viscosity, and includes one or more of deionized water, ethanol, isopropanol, and ethylene glycol.

[0013] The silane coupling agent is used to adjust the rheology of ink and prevent filler sedimentation, and may include one or more of hydroxypropyl methylcellulose and hydroxyethylcellulose.

[0014] The dispersant is used to promote filler dispersion and prevent agglomeration, and may include BYK Chemical. BYK110, BYK Chemical BYK103, BYK Chemical One or more of BYK2013 and DIGIC 755W.

[0015] The defoamer is used to eliminate bubbles generated during production and may include one or more of organosilicon and mineral oil.

[0016] The antioxidant is used to prevent thermal oxidation and may include one or more of hindered phenols (1010) and phosphites (168).

[0017] The ultraviolet absorber is used to prevent photoaging and may include one or more of benzotriazoles and benzophenones.

[0018] In another alternative implementation, such as Figure 1 As shown, a method for preparing conductive ink for a miniature loudspeaker diaphragm includes the following steps: A stable mixed base material is obtained by premixing the dispersion medium, matrix resin, defoamer, antioxidant and ultraviolet absorber; Nanowire dispersion is uniformly added to the mixed base material, followed by the addition of a dispersant to obtain conductive ink, which is then homogenized. The viscosity of the homogenized conductive ink is adjusted and then filtered.

[0019] The premixing includes: The measured dispersion medium is heated and stirred using a stirrer at a temperature of 45℃-60℃ in a water bath at a stirring speed of 450-750 m / min. After the temperature stabilizes, add the weighed base resin, defoamer, antioxidant and ultraviolet absorber while stirring; After adding, adjust the speed to 900. 1200 r / min, continue dispersing for 8 minutes. After 12 minutes, the water bath heating and agitator were turned off, and a stable mixed base material was discharged.

[0020] The conductive ink obtained by uniformly adding nanowire dispersion to the mixed base material, followed by adding a dispersant, comprises: The mixed base material is placed in a mixing tank and stirred at a low speed, for example, at a first speed. The nanowire dispersion is slowly and evenly added to the mixing tank, or at a second speed. Finally, the dispersant is added, and the rotation speed is adjusted to 500-800 r / min. The mixture is stirred for 25-35 minutes to disperse it evenly. Then, the stirring is stopped, and the conductive ink is discharged.

[0021] The first speed can be 300-500 r / min. By setting the first speed, the mixing base material is a mixture of resin, additives and solvent with moderate viscosity. This speed can ensure that the components are fully mixed and avoid introducing air bubbles. The second speed can be 100-300 r / min. This step involves adding the nanowire dispersion, which requires extremely low rotation speed. By setting the second speed, the nanodispersion can be uniformly diffused into the system under a mild shear environment, thereby avoiding the breakage or aggregation of nanowires caused by local high-temperature shear.

[0022] The homogenization process includes: transferring the obtained mixed ink to a planetary mixer for homogenization and dispersion, setting the stirring speed to 400-800 rpm for 15-30 minutes, until the system is uniform and stable with no obvious agglomerates.

[0023] The viscosity adjustment and filtration includes: Deionized water or alcohol solvent is added to the homogenized conductive ink to adjust the conductive ink to a preset viscosity. The ink is then filtered using a 400-mesh filter to remove any large particles or gel that may be present, thus obtaining the final highly flexible conductive ink.

[0024] In another alternative embodiment, a miniature speaker diaphragm includes a conductive ink for a miniature speaker diaphragm as described in any of the embodiments above.

[0025] The conductive ink is disposed at any position on the long or short side of the micro loudspeaker diaphragm.

[0026] In practice, when preparing the micro loudspeaker diaphragm, the substrate is first treated, and the ethylene-acrylate rubber (AEM) diaphragm is prepared by air pressure molding process. The surface of the diaphragm is then subjected to plasma treatment to ensure surface cleanliness. Next, coating and curing are carried out: the conductive ink is prepared onto the above-treated substrate using a mask spraying process, and then heated and cured at 70-120℃ for 5-30 minutes to form a conductive film layer.

[0027] The following examples and comparative examples illustrate this: Example 1 Calculated by mass fraction. Add 45 parts of acrylic resin to 65 parts of deionized water and dissolve by high-speed stirring. Then add 3-5 parts of dispersant polyether-modified polysiloxane, 0.5 parts of antioxidant 1010, and 2 parts of silane coupling agent KH-560 sequentially. Finally, add 225 parts of silver nanowire dispersion (silver nanowire content 20%, aspect ratio 1000, length 20μm, particle size 20nm-50nm). The mass ratio of silver nanowires to acrylic resin is 1:1. Prepare a conductive ink with a medium silver nanowire content. Use a multimeter to test the resistance of the conductive part, 10% tensile resistance, and 25% tensile resistance. Test the adhesion of the conductive ink according to GB / T 9286-2021. Test the product resistance change rate after aging (500h) with double 85 according to GB / T 2423.3-2016.

[0028] Example 2 Calculated by mass parts. Add 65 parts of acrylic resin to 35 parts of deionized water and stir at high speed to dissolve. Then add 3-5 parts of dispersant (polyether-modified polysiloxane), 0.5 parts of antioxidant 1010, and 2 parts of silane coupling agent KH-560 sequentially. Finally, add 125 parts of silver nanowire dispersion (silver nanowire content 20%, aspect ratio 1000, length 20 μm, particle size 20 nm). (50nm). The mass ratio of silver nanowires to acrylic resin is 5:13. A conductive ink with low silver nanowire content was prepared. Referring to the above "Preparation Method of Conductive Ink", a "conductive diaphragm" with low silver nanowire content was prepared. Referring to Example 1, a series of tests such as resistance and adhesion were performed.

[0029] Example 3 Add 30 parts of acrylic resin to 70 parts of deionized water and stir at high speed to dissolve. Then add 3-5 parts of dispersant polyether-modified polysiloxane, 0.5 parts of antioxidant 1010, and 2 parts of silane coupling agent KH-560 in sequence. Finally, add 350 parts of purchased silver nanowire dispersion (silver nanowire content 20%, aspect ratio 1000, length 20μm, particle size 20nm-50nm). The mass ratio of silver nanowires to acrylic resin is 7:3. Prepare a conductive ink with high silver nanowire content. Refer to Example 1 and conduct a series of tests such as resistance and adhesion.

[0030] Comparative Example 1 The aqueous acrylic resin matrix in Example 1 was replaced in equal amounts with the silane-modified polyether adhesive system mentioned in patent CN115955638A to prepare a comparative sample. The effects of different matrices on the "conductive diaphragm" were compared.

[0031] Comparative Example 2 The silver nanowires in Example 1 were replaced with an equal amount of spherical micron-sized silver powder (particle size 1-3 μm) by mass. A conductive ink with a medium silver powder content was prepared. The effects of different conductive fillers on the "conductive diaphragm" were compared.

[0032] Comparative Example 3 Using the water-based acrylic resin from Example 1 as the matrix, without adding antioxidants, UV absorbers, or other anti-aging additives, a comparative sample was prepared. The effects of anti-aging additives on the "conductive diaphragm" were compared. Table 1 shows a comparison of the performance data between the above examples and the comparative examples.

[0033] Table 1 Comparison of performance data between the examples and comparative examples. The comparison in Table 1 shows that: Conductive ink: The three-dimensional conductive network constructed by high aspect ratio silver nanowires has a higher conductivity than the zero-point "point contact" conductive network constructed by spherical silver powder. Moreover, the silver content is not necessarily better the higher it is, and it needs to be balanced with the resin content: (1) In the conductive ink, with the same amount of silver content (comparative Example 1 and Comparative Example 2), the impedance of the silver nanowire formulation (0.35Ω) is only 1 / 16 of that of the spherical silver powder formulation (5.71Ω). This proves that the conductivity is higher when "line-to-line" overlap is compared with "point-to-point" contact; (2) The impedance gradually decreases (0.47Ω → 0.21Ω) from low (Example 2) to high (Example 3) silver nanowire content. However, in Example 3, the adhesion decreases and cracks easily appear at high content, indicating that the 1:1 ratio of silver nanowires and resin in Example 1 achieves the best balance between conductivity and interfacial bonding, and has the best effect.

[0034] The waterborne acrylic resin matrix exhibits better chemical affinity with the AEM rubber diaphragm, resulting in superior adhesion. Examples 1-3 using waterborne acrylic resin as the matrix achieved adhesion grades of 0 or 1, while Comparative Example 1, using a silane-modified polyether adhesive, only achieved grade 2. Furthermore, under 30% strain, no delamination occurred between the conductive ink and the diaphragm in Example 1, while delamination did occur in Comparative Example 1. This confirms the intrinsic adhesion advantages of acrylate structures.

[0035] The waterborne acrylic resin system, combined with anti-aging additives, exhibits better weather resistance. The resistivity change rate after aging with double 85: The resistivity change rate (+10% ~ +25%) of the acrylic-based Examples 1-3 after aging was significantly lower than that of Comparative Example 3 (+40%), which did not contain any anti-aging additives.

[0036] In summary, the conductive ink for micro loudspeaker diaphragms, its preparation method, and the micro loudspeaker diaphragm provided by this invention utilizes high aspect ratio nanowires as conductive fillers and acrylic resin as the matrix resin, with added antioxidants and ultraviolet absorbers as anti-aging fillers. The one-dimensional nature of the high aspect ratio nanowires allows them to interlock within the polymer matrix, constructing a three-dimensional conductive network and achieving "line-to-line" conductive pathways. This three-dimensional conductive network significantly reduces the "percolation threshold" of the conductive pathways, achieving extremely low impedance over a wider filler content range, especially in the low to medium content range. Furthermore, the three-dimensional conductive network possesses excellent elasticity, reconstructing itself with matrix stretching. During significant vibrations of the loudspeaker diaphragm, the nanowires' flexibility and stretchability maintain the integrity of the conductive pathways, resulting in excellent fatigue resistance. The acrylic resin shares similar composition with commonly used micro loudspeaker diaphragms (such as ethylene-acrylate rubber AEM and acrylate rubber ACM). The main chain or side chain structure (acrylate unit) provides high chemical compatibility, which greatly helps the interfacial adhesion between the conductive ink and the diaphragm material after environmental aging. Antioxidants and UV absorbers are added as anti-aging fillers. Considering the stringent application scenarios of miniature loudspeakers (high temperature, high humidity, extreme cold, etc.), the addition of these fillers protects the chemical interface and conductive network between the conductive ink and the diaphragm, allowing the "conductive diaphragm" to function normally even in extremely harsh environments. Therefore, through the synergistic effect of the high aspect ratio nanowires, acrylic resin, and anti-aging fillers in the conductive ink, the conductive ink is suitable for applications involving high-frequency vibration, significant stretching, and high humidity and temperature in miniature loudspeakers. While improving the conductivity of the miniature loudspeaker diaphragm, the conductive ink also possesses high flexibility, fatigue resistance, and long-term environmental reliability that match the diaphragm, making it well-suited for the application requirements of miniature loudspeakers and effectively solving the dynamic reliability conductivity problem of the miniature loudspeaker diaphragm under "high-frequency large-amplitude vibration + severe temperature and humidity".

[0037] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A conductive ink for a miniature loudspeaker diaphragm, characterized in that, It includes 10-60 wt% conductive filler, 10-70 wt% matrix resin, 10-70 wt% dispersion medium, 0.1-5.0 wt% silane coupling agent, 0.2-5.0 wt% dispersant, 0.05-1.0 wt% defoamer, 0.05-2.0 wt% antioxidant and 0.05-1.5 wt% ultraviolet absorber; The conductive filler comprises nanowires with a high aspect ratio; The matrix resin includes an acrylic resin.

2. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The nanowires include one or more of gold nanowires, silver nanowires, and copper nanowires.

3. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The aspect ratio of the nanowires is 100-3000.

4. The conductive ink for a micro loudspeaker diaphragm according to claim 3, characterized in that, The aspect ratio of the nanowires is 800-1200.

5. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The body resin includes one or more of waterborne acrylic resin, acrylate copolymer, waterborne polyurethane, and EVA emulsion.

6. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The dispersion medium includes one or more of deionized water, ethanol, isopropanol, and ethylene glycol.

7. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The silane coupling agent includes one or more of hydroxypropyl methylcellulose and hydroxyethyl cellulose.

8. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The dispersant includes BYK Chemical. BYK110, BYK Chemical BYK103, BYK Chemical One or more of BYK2013 and DIGIC 755W.

9. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The defoamer includes one or more of organosilicon and mineral oil.

10. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The antioxidants include one or more of hindered phenols (1010) and phosphites (168).

11. The conductive ink for a micro loudspeaker diaphragm according to claim 1, characterized in that, The ultraviolet absorber includes one or more of benzotriazoles and benzophenones.

12. A method for preparing a conductive ink for a micro loudspeaker diaphragm according to any one of claims 1 to 11, characterized in that, Including the following steps: A stable mixed base material is obtained by premixing the dispersion medium, matrix resin, defoamer, antioxidant and ultraviolet absorber; Nanowire dispersion is uniformly added to the mixed base material, followed by the addition of a dispersant to obtain conductive ink, which is then homogenized. The viscosity of the homogenized conductive ink is adjusted and then filtered.

13. A method for preparing conductive ink for a micro loudspeaker diaphragm according to claim 12, characterized in that, The premix includes: The dispersion medium is heated and stirred using a stirrer at a temperature of 45℃-60℃, using a water bath, and the stirring speed is 450-750 / min. After the temperature stabilizes, add the base resin, defoamer, antioxidant and ultraviolet absorber while stirring; After adding, adjust the speed to 900. 1200 r / min, continue dispersing for 8 minutes. After 12 minutes, the water bath heating and agitator were turned off, and a stable mixed base material was discharged.

14. A method for preparing conductive ink for a micro loudspeaker diaphragm according to claim 12, characterized in that, The conductive ink obtained by uniformly adding nanowire dispersion to the mixed base material, followed by adding a dispersant, comprises: The mixed base material is placed in a mixing tank. While continuously stirring at a first speed, the nanowire dispersion is added uniformly to the mixing tank at a second speed. Finally, the dispersant is added, and the rotation speed is adjusted to 500-700 r / min. The mixture is stirred for 25-35 min to ensure uniform dispersion. Then, stirring is stopped, and the conductive ink is discharged.

15. A method for preparing conductive ink for a micro loudspeaker diaphragm according to claim 12, characterized in that, The homogenization process includes: transferring the obtained mixed ink to a planetary mixer for homogenization and dispersion, setting the stirring speed to 400-800 rpm for 15-30 minutes, until the system is uniform and stable with no obvious agglomerates.

16. A method for preparing conductive ink for a micro loudspeaker diaphragm according to claim 12, characterized in that, The viscosity adjustment includes: Deionized water or alcohol solvent is added to the homogenized conductive ink to adjust the conductive ink to a preset viscosity.

17. A miniature loudspeaker diaphragm, characterized in that, Includes a conductive ink for a micro loudspeaker diaphragm as described in any one of claims 1 to 11.

18. A miniature loudspeaker diaphragm according to claim 17, characterized in that, The conductive ink is disposed at any position on the long or short side of the micro loudspeaker diaphragm.

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