High damping diaphragm for sound production device and sound production device
By using modified talc to reinforce the ethylene-acrylate copolymer in the diaphragm, the problems of insufficient diaphragm damping and elastic recovery rate were solved, resulting in a diaphragm with high damping performance and stable sound quality, thus improving the acoustic performance of the sound-generating device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GOERTEK INC
- Filing Date
- 2022-06-21
- Publication Date
- 2026-07-10
Smart Images
Figure CN117319890B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of acoustic product technology, and in particular to a high-damping diaphragm and sound-generating device. Background Technology
[0002] Sound-generating devices are crucial acoustic components in consumer electronics, converting electrical signals into sound. In recent years, consumer electronics have developed rapidly, especially with the rapid growth of mobile phones, tablets, and other electronic devices. These devices require compact yet high-performance sound-generating devices, necessitating further improvements in their performance. Sound-generating devices typically employ diaphragms as the vibrating element that produces sound. The diaphragm plays a vital role in the sound production performance of the device, determining the quality of the electrical-to-sound energy conversion.
[0003] However, the damping properties and elastic recovery rate of the current diaphragm cannot meet the requirements of the diaphragm's reciprocating vibration. Therefore, an improved diaphragm is needed to improve the above-mentioned defects. Summary of the Invention
[0004] Based on this, according to one embodiment of the present invention, the object is to provide a high-damping diaphragm for a sound-generating device and a sound-generating device.
[0005] The above objective can be achieved through the following technical solutions:
[0006] According to one aspect of the present invention, a high-damping diaphragm for a sound-generating device is provided, the diaphragm being prepared by adding a complexing agent to the ethylene-acrylate copolymer as a base polymer and then undergoing a crosslinking reaction; wherein the complexing agent includes a reinforcing agent, the reinforcing agent being modified talc; and the amount of modified talc used is 32wt% to 65wt% based on the total amount of the base polymer and the complexing agent.
[0007] Optionally, the loss factor of the diaphragm is ≥0.14.
[0008] Optionally, the modified talc powder has an average particle size ≤20μm. Preferably, the modified talc powder has an average particle size ≤10μm.
[0009] Optionally, the modified talc powder contains 12% to 23% magnesium.
[0010] Optionally, the amount of the base polymer is 30 wt% to 93 wt%, depending on the total amount of the base polymer and the complexing agent.
[0011] Optionally, the compounding agent further includes an antioxidant and a crosslinking agent, wherein the amount of the antioxidant is 0.1 wt% to 6 wt% and the amount of the crosslinking agent is 0.5 wt% to 5 wt% based on the total amount of the base polymer and the compounding agent.
[0012] Optionally, the crosslinking agent is a peroxide crosslinking agent or an amine crosslinking agent.
[0013] Optionally, the compounding agent further includes an internal release agent, the amount of which is 1 wt% to 2.5 wt% based on the total amount of the base polymer and the compounding agent.
[0014] Optionally, the cross-linked rubber of the base polymer has a hardness of 50A to 80A, and / or the loss factor of the diaphragm is ≥0.15.
[0015] Optionally, the cross-linked rubber of the base polymer shall at least meet one of the following performance requirements: tensile strength of 6 MPa to 25 MPa and elongation at break of 165% to 300%.
[0016] According to another aspect of the present invention, a sound-generating device is provided, comprising a vibration system and a magnetic circuit system cooperating with the vibration system; the vibration system includes a diaphragm and a voice coil coupled to one side of the diaphragm, the magnetic circuit system driving the voice coil to vibrate to drive the diaphragm to generate sound, the diaphragm being the high-damping diaphragm of the sound-generating device.
[0017] Beneficial effects: In one embodiment of the present invention, an ethylene-acrylate copolymer is used as the base polymer, and modified talc is used as a reinforcing agent to reinforce it, thereby obtaining a diaphragm with high damping performance. The sound-generating device made with this high-damping diaphragm has high vibration consistency during vibration, and the sound quality and listening stability are greatly improved. Attached Figure Description
[0018] Figure 1 This is a test curve of vibration displacement at different frequencies at different locations of a high-damping diaphragm according to an embodiment of the present invention.
[0019] Figure 2 These are test curves of vibration displacement at different frequencies at different locations of a conventional AEM rubber diaphragm.
[0020] Figure 3 This is a comparison chart of the total harmonic distortion test curves of a high-damping diaphragm and a conventional AEM rubber diaphragm according to an embodiment of the present invention. Detailed Implementation
[0021] Unless otherwise specified, the raw materials and equipment used in this invention are commonly used in the art; the methods used in this invention, unless otherwise specified, are conventional methods in the art. Unless otherwise specified, the meanings of the terms in this specification are the same as those generally understood by those skilled in the art, but in case of conflict, the definitions in this specification shall prevail. The terms "comprising," "including," "containing," "having," or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term "comprising" means that other steps and components may be added without affecting the final result. The term "comprising" also includes the terms "consisting of" and "substantially consisting of." The compositions and methods / processes of this invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein.
[0022] All numerical values or expressions relating to component amounts, process conditions, etc., used in the specification and claims are to be understood to be modified with “about” in all cases. All ranges relating to the same component or property include endpoints that can be independently combined. Because these ranges are continuous, they include every value between the minimum and maximum values. It should also be understood that any numerical range referenced in this application is intended to include all subranges within that range.
[0023] With increasing demands for high acoustic performance, rubber diaphragms have begun to be used. However, current solutions for AEM rubber diaphragms have poor overall performance, exhibiting defects such as poor damping performance and low elastic recovery rate, resulting in unsatisfactory acoustic performance. Furthermore, the inventors of this application have found that carbon black or silica is commonly used as a reinforcing agent in the preparation of rubber diaphragms. However, rubber diaphragms reinforced with these agents have a low loss factor, leading to higher distortion and poor acoustic stability in sound-producing devices. Other reinforcing agents have received less attention and further research. Based on the above understanding, the inventors of this application, through continuous research and improvement, discovered that when talc is used to reinforce AEM rubber, although the material's mechanical properties decrease compared to rubber reinforced with carbon black / silica at the same hardness, the loss factor of the diaphragm using talc increases, resulting in a diaphragm with high damping performance. Sound-producing devices made with this diaphragm exhibit better sound quality and listening stability. Additionally, this high-damping diaphragm has better temperature resistance and maintains high stability during long-term use.
[0024] One embodiment of the present invention provides a high-damping diaphragm for a sound-generating device. The diaphragm is prepared by adding a complexing agent to the ethylene-acrylate copolymer as a base polymer and then performing a crosslinking reaction. The complexing agent includes a reinforcing agent, which is modified talc. Based on the total amount of the base polymer and the complexing agent, the amount of modified talc is 32wt% to 65wt%. Of course, the complexing agent may also include one or more of antioxidants, crosslinking agents, and internal release agents, as will be further described later.
[0025] By using the aforementioned amount of talc as a reinforcing agent, specifically, the talc used in this application is modified talc, which can improve the adhesion between talc and ethylene-acrylate copolymer, enhance the interaction force between the modified talc surface and the ethylene-acrylate polymer interface, and improve the reinforcing performance of talc. Since the scheme of reinforcing ethylene-acrylate copolymer crosslinked rubber with modified talc will result in some loss of mechanical properties, this application appropriately increases the amount of reinforcing agent. Specifically, the amount of modified talc accounts for 32wt% to 65wt% of the total amount of the base polymer and compounding agents. That is, when modified talc is used as a reinforcing agent, the amount of modified talc added is greater than the amount of conventional reinforcing agents (such as carbon black or silica, which are typically used in amounts of 10wt% to 45wt%). Because of the large amount of modified talc used in the base polymer and compounding agents, the friction between the modified talc and the ethylene-acrylate polymer is also greater. This results in the loss of some energy from the diaphragm, increasing the loss factor and thus producing a diaphragm with high damping performance. Furthermore, the large amount of modified talc in the AEM rubber diaphragm formulation relatively reduces the proportion of ethylene-acrylate polymer in the diaphragm formulation, thereby lowering the manufacturing cost of the AEM rubber diaphragm.
[0026] In this embodiment of the invention, the ethylene-acrylate copolymer is used as the base polymer, and the amount of the base polymer is 30 wt% to 93 wt%, based on the total amount of the base polymer and the complexing agent.
[0027] The ethylene-acrylate copolymer can be a ternary and / or binary polyethylene-acrylate copolymer. The vulcanized AEM rubber exhibits excellent heat aging resistance and good cold resistance. Further, the mass ratio of polyethylene block to polyacrylate block is 0.2–6. The polyethylene block provides toughness in the ethylene-acrylate copolymer matrix, giving the rubber good low-temperature resistance. Based on this rubber, the diaphragm still has good resilience at low temperatures. However, if the polyethylene block content is too high, the rigidity of the polyacrylate rubber is insufficient, making it difficult to meet the requirements of the diaphragm. This range satisfies the diaphragm's requirements for mechanical properties such as toughness while providing good low-temperature resistance. When it is a ternary copolymer, the block corresponding to the third monomer providing the vulcanization position accounts for 0.5–8 wt%. The higher the content, the greater the crosslinking degree of the matrix. Excessive crosslinking will cause the rubber to lose its high elasticity and increase the material rigidity. This range allows the polyacrylate copolymer to possess the glass transition temperature and elongation at break required for diaphragm performance.
[0028] Based on the aforementioned characteristics and performance advantages of the ethylene-acrylate copolymer, this invention uses modified talc to reinforce the ethylene-acrylate copolymer. By controlling the amounts of both, the modified talc is evenly dispersed in the copolymer, exhibiting good compatibility. This significantly enhances the interfacial bonding force between the modified talc surface and the ethylene-acrylate copolymer, altering the spatial structure dimension and forming a strong, sliding bond. Under stress, the molecular chains can easily slide on the surface of the modified talc but are not easily detached, greatly increasing the material's toughness, wear resistance, and other mechanical strengths. This results in excellent heat aging resistance and cold resistance for the diaphragm, and also significantly increases the diaphragm's damping performance, with a loss factor ≥0.14. This allows for high vibration consistency during vibration, improving the acoustic performance of the sound-generating device.
[0029] The inventors of this application discovered that when the amount of modified talc exceeds 65 wt%, especially exceeding 73 wt%, the tensile strength and elongation at break of the material decrease sharply, failing to meet the requirements of the diaphragm. Furthermore, the significant difference in content between the two components leads to poor dispersion uniformity, resulting in a decreasing trend in the loss factor. For example, in a specific comparative example, the base polymer (raw rubber) was 24.4%, modified talc was 73.3%, antioxidant was 0.79%, crosslinking agent was 0.53%, and internal release agent stearic acid was 0.98%. Under this formulation, although the loss factor reached 0.1913, its tensile strength was only 5.5 MPa and its elongation at break was only 36%, completely failing to meet the requirements for diaphragm use.
[0030] When the modified talc powder content is 32wt%–65wt% and the base polymer content is 30wt%–93wt%, not only can the reinforcement effect be improved, ensuring that the mechanical properties of the reinforced material meet the requirements of the diaphragm, but it also retains superior resilience. Simultaneously, the increased friction between the two materials gives the diaphragm higher damping performance, thereby improving the sound-generating device's ability to suppress polarization and enhancing sound quality and listening stability. In a specific embodiment, when the base polymer (raw rubber) is 30wt%–93wt%, the modified talc powder is 32wt%–65wt%, the antioxidant is 0.1wt%–6wt%, the crosslinking agent is 0.5wt%–5wt%, and the internal release agent stearic acid is 1wt%–2.5wt%, under this formulation, the loss factor is ≥0.15, the tensile strength is 6MPa–25MPa, and the elongation at break is 165%–300%. In this specific embodiment, the diaphragm exhibits excellent resilience and ultra-high damping performance.
[0031] This invention uses modified talc as a reinforcing agent to strengthen AEM rubber. Since the reinforcing effect of talc is lower than that of silica / carbon black, silica or carbon black is currently used to reinforce rubber diaphragms, with talc almost never used. Through further research on the reinforcing effect of talc, the inventors of this application found that, under the same hardness conditions, compared to carbon black / silica, using talc to reinforce AEM rubber produces diaphragms with the same F0 at the same hardness, but with greater damping, lower distortion, better temperature resistance, and higher stability in long-term use. However, to prepare materials with the same hardness, the amount of talc used increases significantly, and the mechanical properties of the prepared material also decrease sharply, failing to meet the requirements for diaphragm use. Further investigation revealed that by using modified talc for reinforcement, on the one hand, the reinforcement effect is improved while maintaining high damping performance. Although the mechanical properties of the material are slightly lower than those of reinforcements such as carbon black, the reduction is limited and remains within the acceptable range for the diaphragm. This reinforcement increases damping; the rubber damping factor after talc reinforcement is ≥0.14, reducing the risk of diaphragm breakage during use, improving the diaphragm's ability to suppress polarization, reducing total harmonic distortion, and improving sound quality and listening stability. On the other hand, at the same hardness, the amount of modified talc used is still higher than other reinforcement materials. Although the mechanical properties are slightly reduced, the inventors found that because the amount of talc used is greater than other reinforcement materials at the same hardness, the friction between the modified talc and the ethylene-acrylate copolymer is also greater, resulting in some energy loss from the diaphragm and a higher diaphragm damping loss factor (better damping effect). On the other hand, due to the large amount of reinforcing agent used, the proportion of the base polymer, namely ethylene-acrylate polymer, in AEM rubber is smaller, which reduces the material cost of AEM rubber diaphragm to some extent.
[0032] Talc has hydrophilic groups on its surface and is polar, while ethylene-acrylate copolymer is hydrophobic, resulting in poor compatibility between the two. Furthermore, smaller talc particles are more prone to agglomeration during processing, affecting rubber properties. Talc is an inorganic filler whose particles form aggregates through physicochemical bonding. These aggregates constitute the primary structure, while van der Waals forces or hydrogen bonds between them can form a spatial network structure, the secondary structure of talc. By modifying the talc surface to include hydrogen and carboxyl groups, substitution, reduction, and oxidation reactions can occur. When added to polyethylene-acrylate copolymer, the interaction between the talc surface and the ethylene-acrylate copolymer interface is enhanced. This allows the molecular chains to slide more easily on the talc surface under stress, but they are less likely to detach from the talc. A strong, sliding bond is formed between the elastomer and the talc, increasing the material's mechanical strength.
[0033] Furthermore, the modified talc powder is obtained by modifying talc powder as the main raw material using coupling crosslinking agents, fatty acid activators, anionic surfactants, etc. The coupling crosslinking agent is a coupling agent selected from commonly used coupling agents such as silane coupling agents, titanate coupling agents, aluminate coupling agents, organochromium complex coupling agents, and aluminum-iron coupling agents. The activator is a fatty acid or fatty acid derivative. The anionic surfactant is a sulfonate, sulfate salt, carboxylate, etc. When using a coupling agent for modification, such as a silane coupling agent, the following steps can be taken: Dissolve 50g of γ-methacryloxypropyltrimethoxysilane in 1kg of purified water to prepare solution A; select 1kg of conventional talc powder, stir and disperse it in solution A to prepare solution B; heat solution B to 60℃ and stir for 12h; raise the temperature of solution B to 100℃, evaporate the water to constant weight, grind and sieve the resulting solid to obtain modified talc powder. Preferably, the modified talc powder is prepared by mixing and modifying at least two modifiers, which further improves the reinforcing effect. Specifically, for example, the dissolved coupling agent is first stirred with talc powder until fully embedded, resulting in an inorganic powder treated with the silane coupling agent. This inorganic powder is then subjected to a secondary embedding with a dissolved activator, followed by drying at a temperature of 80℃ to 120℃. This method of first modifying with the coupling agent and then performing a secondary embedding with the activator further enhances the reinforcing effect of the modified talc powder. Furthermore, the specific amount of the modifier is not limited, but in the preferred embodiment, the modified magnesium content is controlled to be 12% to 19%. By mixing and controlling the modified magnesium content, the diaphragm loss factor can reach above 0.15, exhibiting excellent polarization suppression capability. The modified talc powder contains carboxyl groups and other groups on its surface, which improves its affinity with ethylene-acrylate copolymers, enhances the dispersibility and compatibility between talc powder and ethylene-acrylate copolymers, and fully crosslinks the talc powder with ethylene-acrylate copolymers using amine crosslinking agents, thereby improving the mechanical properties of the material and giving it high damping performance. Moreover, the crosslinking reaction based on amine crosslinking agents also makes the diaphragm forming method unrestricted, allowing for preparation by air compression molding, overcoming the limitations of compression molding and significantly reducing the preparation cost.
[0034] This invention uses modified talc as a reinforcing agent to strengthen AEM rubber. Further, after modification, the magnesium content in the modified talc is controlled to be no higher than 23%, and even further, the magnesium content is controlled to be between 12% and 23%, for example, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 21%, 23%, etc. The inventors of this application have discovered that when the modified magnesium content is higher than 23%, there are fewer polar groups in its molecules, resulting in decreased affinity with AEM colloids and poor reinforcing effect. For materials with the same hardness, a larger amount of talc is required, and its mechanical properties decrease significantly, rendering it unusable. Most preferably, the modified magnesium content is controlled to be less than 19%, thereby achieving optimal reinforcing effect and processing stability. When the modified magnesium content is below 12% and other modifying materials are excessive, the prepared modified talc powder will have high polarity, leading to increased adhesion of the AEM compound, causing it to stick to the rollers of the internal mixer and open mill, and reducing processing stability. The dispersion uniformity of the compound will also decrease, affecting subsequent crosslinking, which in turn will affect the final properties of the crosslinked rubber diaphragm, such as its resilience, thus impacting the acoustic performance of the sound-generating device. In this embodiment, by controlling the magnesium content in the modified talc powder within the aforementioned range, not only is the reinforcing effect of the talc reinforcing agent improved, but the stability of subsequent processing is also enhanced, thereby increasing the degree of subsequent crosslinking. This results in the final crosslinked rubber diaphragm exhibiting excellent resilience and high damping performance. In particular, when the magnesium content is below 19% and not below 12%, the loss factor of the diaphragm can be ≥0.15, significantly improving the diaphragm's ability to suppress polarization phenomena and resulting in excellent diaphragm vibration consistency.
[0035] Furthermore, by controlling the average particle size of the modified talc powder to ≤20μm, preferably controlling the average particle size of the modified talc powder to ≤10μm, the modified talc powder and the ethylene-acrylate copolymer have better uniform dispersion, avoiding agglomeration; moreover, talc powder with this particle size will increase the specific surface area of the reinforcing agent, and the increase in specific surface area will further improve the surface activity of the reinforcing agent, thereby further improving the reinforcing effect of the modified talc powder.
[0036] The inventors of this application discovered that the particle size of modified talc directly affects its reinforcing effect. When the average particle size is greater than 20 μm, the reinforcing effect is poor, and the tensile strength and elongation at break of the prepared AEM rubber are low. During the product's electrical reliability test, film rupture occurred, resulting in product defects. Table 1 shows the effect of modified talc with different particle sizes on the tensile strength and elongation at break of the rubber.
[0037] Testing standards: Tensile strength and elongation at break are determined according to ASTM D412-2016 standard. The specimen shape is dumbbell-shaped, the tensile rate is 500 mm / min, and each group of samples is tested 5 times and the average value is taken.
[0038] Table 1. Tensile strength and elongation at break of modified talc powder with different particle sizes for reinforcing rubber.
[0039] Modified talc particle size / μm 0.5 2 10 20 30 Tensile strength / MPa 12.3 12.1 12.4 11.2 9.6 Elongation at break / % 267.3 258.9 263.1 223.4 168.2
[0040] As shown in Table 1, within a certain range, the tensile strength and elongation at break increase with the increase of the modified talc particle size. However, when the particle size exceeds 10 μm, the increased particle size reduces the specific surface area of the modified talc, decreasing its uniform dispersion in the ethylene-acrylate copolymer and leading to reduced surface activity. This, in turn, reduces the interfacial bonding force between the modified talc and the ethylene-acrylate copolymer, resulting in a decrease in the tensile strength and elongation at break of the rubber. As shown in Table 1, when the average particle size is below 10 μm, the tensile strength and elongation at break remain essentially unchanged. When the particle size is greater than 10 μm, especially greater than 20 μm, the tensile strength and elongation at break decrease significantly, leading to a reduction in the resilience of the rubber diaphragm and increasing the risk of diaphragm breakage during use. Therefore, as a preferred method, modified talc with a particle size ≤10 μm is used to improve the ethylene-acrylate copolymer, thereby enhancing its high damping performance while ensuring the resilience of the diaphragm, resulting in excellent acoustic performance of the sound-generating device.
[0041] By reinforcing the ethylene-acrylate polymer with modified talc while controlling the particle size of the modified talc, the resilience of the diaphragm was improved, and it also exhibited high damping performance. In a specific comparative example (the only difference being the use of unmodified talc instead of modified talc), with an average particle size of 5 μm, the reinforcement effect of unmodified talc was significantly worse than that of modified talc. The hardness of the reinforced rubber was only 48A, and its tensile strength and elongation at break were also significantly reduced, with a tensile strength of only 8.7 MPa and an elongation at break of 168%. Furthermore, due to its poor bonding ability with the matrix polymer and uneven dispersion, its loss factor was significantly reduced.
[0042] In an optional embodiment, the rubber after crosslinking the ethylene-acrylate copolymer has a hardness of 50A to 80A. At room temperature, the rubber is in a highly elastic state, with easily movable molecular chains and high intermolecular friction, exhibiting good damping performance. Its loss factor at room temperature is greater than 0.14. Preferably, under the stated hardness condition, while ensuring the diaphragm meets the mechanical properties required for use, the loss factor of the diaphragm is also ≥0.15. This excellent damping performance results in a lower impedance curve for the diaphragm, improved damping, and a stronger ability to suppress polarization phenomena during vibration, leading to good vibration consistency.
[0043] AEM rubber diaphragms prepared with other commonly used reinforcing agents, such as silica, have a loss factor that is 10% to 20% lower than that of the diaphragm of this invention at the same hardness (i.e., the same F0). Table 2 shows the loss factors of silica-reinforced rubber and talc-reinforced rubber in this embodiment at various hardnesses.
[0044] Loss factor test method: Measured by dynamic thermomechanical analyzer (DMA) according to ASTM D5026-15 standard, using tensile fixtures (test temperature range -50~100℃, heating rate 3℃ / min); hardness is determined by the reinforcing agent.
[0045] Table 2 shows the loss factors of silica-reinforced rubber and talc-reinforced rubber in this example at different hardness levels.
[0046]
[0047] As can be seen from Table 2, the AEM rubber reinforced with modified talc powder of this invention has a higher loss factor than the AEM rubber reinforced with silica at the same hardness, indicating superior diaphragm damping performance. During vibration, the diaphragm exhibits less swaying vibration, resulting in better sound quality and listening stability. Furthermore, as shown in Table 2, at the aforementioned hardness, the reinforcing rubber of this invention has a loss factor of no less than 0.17, giving the diaphragm even higher damping performance.
[0048] Furthermore, based on the aforementioned hardness and the following mechanical properties, namely, the tensile strength of the rubber is 6MPa to 25MPa and the tear strength is 15N / mm to 100N / mm, the prepared diaphragm is less prone to breakage during module use, resulting in a recovery rate of over 80% at 20% strain. This further enhances the reliability of the diaphragm and improves its acoustic performance.
[0049] Furthermore, by comprehensively controlling the hardness of the cross-linked ethylene-acrylate copolymer rubber to be 50A to 80A and the diaphragm thickness to be 20μm to 200μm (e.g., 50μm, 100μm, 150μm, 180μm, etc.), the sound-generating device achieves a low F0, resulting in full bass and a comfortable listening experience. The F0 of a loudspeaker is proportional to its Young's modulus and thickness. The F0 is varied by changing the thickness and Young's modulus of the loudspeaker diaphragm. The modulus of the rubber is proportional to the content of the reinforcing agent. The aforementioned hardness of the rubber can be adjusted by the reinforcing agent content of this application. To obtain full bass and a comfortable listening experience, the sound-generating device achieves a low F0 while also ensuring the diaphragm has sufficient stiffness and damping.
[0050] The diaphragm prepared by this invention has high damping performance and can maintain a high degree of vibration consistency during vibration. Figure 1The figure shows test curves of vibration displacement at different frequencies at different parts of the high-damping diaphragm in one embodiment of the present invention. Figure 2 This paper presents test curves showing the vibration displacement of different parts of a conventional AEM rubber diaphragm reinforced with silica at different frequencies. Each curve represents a different part of the diaphragm. Test method: The diaphragm is a rectangular surround diaphragm. Test points were taken at the edge and center of the diaphragm. In the test curves, the horizontal axis represents frequency (Hz), and the vertical axis represents loudness displacement (mm). Figure 1 and Figure 2 It can be seen that: Figure 1 The curves in the middle are more concentrated, while Figure 2 The curves in the figure are relatively dispersed. This indicates that the vibration consistency of each part of the high-damping diaphragm in this embodiment of the invention is better, and the diaphragm swaying is really less during vibration, resulting in better sound quality and listening stability.
[0051] According to another aspect of the present invention, a sound-generating device is provided, comprising a vibration system and a magnetic circuit system cooperating with the vibration system; the vibration system includes a diaphragm and a voice coil coupled to one side of the diaphragm. When the micro sound-generating device is working, after the voice coil is energized, it can vibrate up and down under the driving force of the magnetic field force of the magnetic circuit system, thereby driving the diaphragm to vibrate, and sound can be generated when the diaphragm vibrates.
[0052] The sound-generating device, such as a loudspeaker, prepared using the diaphragm described in this invention has an improved ability to suppress polarization phenomena during vibration, maintains excellent vibration consistency, and improves sound quality and listening stability. Figure 3 A comparison graph of total harmonic distortion (THD) test curves of a high-damping diaphragm according to an embodiment of the present invention and a conventional AEM diaphragm is shown. Figure 3 It can be seen that the high-damping diaphragm of this embodiment of the invention has a lower THD (Total Harmonic Distortion) compared to the conventional AEM diaphragm (reinforced with silica). This indicates that the speaker diaphragm of this embodiment of the invention has better anti-polarization capability and better sound quality.
[0053] As described above, in embodiments of the present invention, the compounding agent may further include one or more of the following: antioxidant, crosslinking agent / crosslinking agent and crosslinking aid, internal release agent, etc. Specifically, based on the total amount of the base polymer and the compounding agent, the antioxidant is used at a rate of 0.1 wt% to 6 wt%, the crosslinking agent at a rate of 0.5 wt% to 5 wt%, and the internal release agent stearic acid at a rate of 1 wt% to 2.5 wt%. These dosage ranges enable the diaphragm to possess excellent resilience and ultra-high damping performance, resulting in excellent vibration consistency and improved acoustic stability of the sound-generating device. Further explanation of each compounding agent follows.
[0054] The antioxidant, based on the total amount of the base polymer and compounding agents, is used in an amount of 0.1 wt% to 6 wt%. During use, AEM rubber undergoes molecular chain breakage over time, generating free radicals that accelerate its aging. Adding an antioxidant halts the generation of autocatalytically active free radicals in AEM rubber products. Addition amounts below 0.1 wt% do not achieve the effect of extending service life, while addition amounts above 6 wt% are difficult to disperse uniformly due to poor miscibility with the ethylene-acrylate copolymer elastomer, leading to a decline in the material's mechanical properties and a tendency to precipitate onto the surface over time. Adding an antioxidant delays or inhibits the polymer oxidation process, thereby preventing polymer aging and extending its service life. Further, the antioxidant may include at least one of antioxidants N-445, 246, 4010, SP, RD, ODA, OD, WH-02, and BHT.
[0055] The crosslinking agent, based on the total amount of the base polymer and the complexing agent, is used in an amount of 0.5 wt% to 5 wt%. The crosslinking agent is a peroxide crosslinking agent or an amine crosslinking agent, preferably an amine crosslinking agent. Due to its crosslinking reaction mode, the diaphragm molding method is unrestricted; it can be prepared by air compression molding, and the preparation cost is significantly reduced compared to compression molding. The inventors of this application have found that when the amount is below 0.5 wt%, the effective crosslinking density of AEM rubber is low, resulting in poor mechanical strength and resilience. The AEM rubber diaphragm is prone to deformation and collapse during long-term use, leading to a drop in the acoustic Fr curve, and the material's vulcanization rate is slow, severely limiting production efficiency. Conversely, when the amount is above 5 wt%, the effective crosslinking density of AEM rubber is too high, resulting in a significant decrease in its elongation at break, which reduces diaphragm damping. The prepared diaphragm is prone to polarization during vibration, leading to increased acoustic distortion, and there is a risk of diaphragm breakage during repeated vibration.
[0056] Further, the peroxide crosslinking agent may include at least one selected from 1,3-1,4-di(tert-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, tert-butylperoxyisopropylbenzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)-3-hexyne, 4,4'-bis(tert-butylperoxy)valerate, 1,1'-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and 2,4-dichlorobenzoyl peroxide. The amine crosslinking agent may include at least one selected from hexamethylenediamine or hexamethylenediamine salt, hexamethylenediamine carbamate, triethylenetetramine, methylenediphenylamine, and di-o-tolueneguanidine. To improve the vulcanization rate, a co-crosslinking agent is added to the peroxide crosslinking agent or amine crosslinking agent, with the total amount of both being 0.5 wt% to 5 wt%. The co-crosslinking agent may include at least one of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, N,N'-m-phenylenebismaleimide, diallyl phthalate, triallyl isocyanate, and triallyl cyanate. Through the combined action of the above crosslinking agent and co-crosslinking agent, the effective crosslinking density of AEM rubber can be increased, and the vulcanization speed can be accelerated, thereby improving the preparation efficiency.
[0057] The internal release agent is used in an amount of 1 wt% to 2.5 wt% based on the total amount of the base polymer and compounding agents. The internal release agent may include at least one of stearic acid and stearates. As mentioned earlier, the adhesion degree of the compound is controlled by controlling the magnesium content of the modified talc powder. To further ensure that problems such as sticking to rollers and sticking to the film do not occur, an internal release agent is added to improve the processing performance of the ethylene-acrylate copolymer. However, if the amount exceeds 2.5 wt%, the adhesion of the film layer will decrease in the later stages, ultimately affecting the diaphragm performance.
[0058] In embodiments of the present invention, the diaphragm can be a single-layer diaphragm or a multi-layer composite diaphragm. A single-layer diaphragm is composed of a single layer of ethylene-acrylate copolymer rubber film. A composite diaphragm can be formed by sequentially stacking two or more layers of ethylene-acrylate copolymer rubber film, or it can be a diaphragm comprising at least one layer of ethylene-acrylate copolymer rubber film, which is then laminated with other material layers. The composite diaphragm can be two-layer, three-layer, four-layer, or five-layer composite diaphragms, and the present invention does not limit this. The other film layers can be thermoplastic elastomers and / or engineering plastics. The thermoplastic elastomer can be selected from at least one of thermoplastic polyester elastomers, thermoplastic polyurethane elastomers, thermoplastic polyamide elastomers, and silicone elastomers. The engineering plastic may be selected from at least one of polyetheretherketone, polyarylate, polyetherimide, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyethylene terephthalate, and polybutylene terephthalate.
[0059] To better understand the above-mentioned technical solutions of the present invention, the following detailed description is provided in conjunction with specific embodiments. These specific embodiments are merely preferred implementations of the present invention and are not intended to limit the scope of the invention. The raw rubber in these embodiments was purchased from DuPont.
[0060] Example 1
[0061] Formula: 100 parts raw rubber; 83 parts modified talc (average particle size 5μm, magnesium content 19%, accounting for 43.3% of the total formula); 3.5 parts stearic acid (internal release agent); 3 parts BHT (chemical resistant agent); 2.1 parts hexamethylenediamine (vulcanizing agent).
[0062] Comparative Example 1
[0063] Formula: Same as Example 1, 100 parts; reinforcing agent, silica, 45 parts; internal release agent, stearic acid, 3.5 parts; chemical resistant agent, BHT, 3 parts; vulcanizing agent, hexamethylenediamine, 2.1 parts.
[0064] The tensile strength, elongation at break, and loss factor of the rubber in Example 1 and Comparative Example 1 were tested and compared, and the results are shown in Table 3. Tensile strength and elongation at break were determined according to ASTM D412-2016 standard. The specimens were dumbbell-shaped, the tensile rate was 500 mm / min, and each group of samples was tested 5 times and the average value was taken. The loss factor was measured using a Dynamic Thermomechanical Analyzer (DMA) according to ASTM D5026-15 standard, with a tensile fixture, a test temperature range of -50 to 100 °C, and a heating rate of 3 °C / min.
[0065] Table 3. Performance test results for Example 1 and Comparative Example 1
[0066] hardness Tensile strength / MPa Elongation at break / % Loss factor Conventional AEM rubber 65A 13.1 298 0.1785 Rubber of the present invention 65A 11.9 267 0.2156
[0067] As can be seen from Table 3 above, under the same hardness, the modified talc-reinforced rubber of this embodiment of the present invention has a slightly lower tensile strength and elongation at break compared with conventional AEM rubber, but has a better loss factor than conventional AEM rubber.
[0068] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.
Claims
1. A high-damping diaphragm for a sound-generating device, characterized in that, The diaphragm is prepared by adding a complexing agent to the ethylene-acrylate copolymer as the base polymer and then performing a crosslinking reaction. The complexing agent includes a reinforcing agent, which is modified talc. The modified talc is obtained by modifying the surface of talc with a modifier, which includes at least one of a coupling crosslinking agent, a fatty acid activator, and an anionic surfactant. Based on the total amount of the base polymer and the complexing agent, the amount of modified talc is 32wt% to 65wt%.
2. The high-damping diaphragm for a sound-generating device according to claim 1, characterized in that, The loss factor of the diaphragm is ≥0.
14.
3. The high-damping diaphragm for a sound-generating device according to claim 1, characterized in that, The modified talc powder has an average particle size of ≤20μm.
4. The high-damping diaphragm for a sound-generating device according to claim 3, characterized in that, The modified talc powder has an average particle size of ≤10μm.
5. The high-damping diaphragm for a sound-generating device according to claim 1, characterized in that, The modified talc powder contains 12% to 23% magnesium.
6. The high-damping diaphragm for a sound-generating device according to claim 1, characterized in that, Based on the total amount of the base polymer and the complexing agent being 100%, the amount of the base polymer being not less than 30 wt.
7. The high-damping diaphragm for a sound-generating device according to claim 1, characterized in that, The compounding agent also includes an antioxidant and a crosslinking agent. Based on the total amount of the base polymer and the compounding agent, the amount of the antioxidant is 0.1wt% to 6wt%, and the amount of the crosslinking agent is 0.5wt% to 5wt%. The crosslinking agent is a peroxide crosslinking agent or an amine crosslinking agent.
8. The high-damping diaphragm for a sound-generating device according to claim 1, characterized in that, The compounding agent also includes an internal release agent, and the amount of the internal release agent is 1 wt% to 2.5 wt% based on the total amount of the base polymer and the compounding agent.
9. The high-damping diaphragm for a sound-generating device according to claim 1, characterized in that, The rubber after cross-linking of the base polymer has a hardness of 50A to 80A, and / or the loss factor of the diaphragm is ≥0.
17.
10. The high-damping diaphragm for a sound-generating device according to claim 1, characterized in that, The rubber after crosslinking of the base polymer shall at least meet one of the following conditions: tensile strength of 6 MPa to 25 MPa, elongation at break of 165% to 300%, and tear strength of 15 N / mm to 100 N / mm.
11. A sound-generating device, characterized in that, The device includes a vibration system and a magnetic circuit system that cooperates with the vibration system; the vibration system includes a diaphragm and a voice coil coupled to one side of the diaphragm, the magnetic circuit system drives the voice coil to vibrate so as to drive the diaphragm to produce sound, and the diaphragm is a high-damping diaphragm for a sound-producing device as described in any one of claims 1-10.