Diaphragm for sound production device, sound production device, and electronic device

Abstract

This application belongs to the field of electroacoustic technology, and specifically relates to a diaphragm for a sound-generating device, a sound-generating device, and an electronic device. The diaphragm for the sound-generating device includes at least one composite material film. The composite material film includes a thermoplastic polyurethane base film and modified particles dispersed within the thermoplastic polyurethane base film. The modified particles include modified calcium carbonate, the calcium content of which is >38wt%, and the mass percentage of the modified particles in a single layer of the composite material film is 0.5wt%~40wt%. The particle size of the modified particles is ≤20μm. The relative change rate of the resonant frequency of the diaphragm satisfies: <1. The diaphragm for the sound-generating device of this application improves the modulus, damping, and low-temperature resistance of the diaphragm through multiple synergistic effects by adding modified calcium carbonate to a TPU matrix and precisely controlling the particle size and amount of modified calcium carbonate.

Description

Technical Field

[0001] This application belongs to the field of electroacoustic technology, and specifically relates to a diaphragm for a sound-generating device, a sound-generating device, and an electronic device. Background Technology

[0002] Thermoplastic polyurethane (TPU) has become the mainstream material for miniature loudspeaker diaphragms due to its excellent acoustic performance and controllable cost. However, current commercial TPU diaphragm systems present a significant performance trade-off: to ensure normal operation of miniature loudspeakers at low temperatures, TPU materials with lower glass transition temperatures must be selected; however, this selection simultaneously degrades the material's damping performance, exacerbating high-frequency distortion, and reduces the material modulus, significantly limiting the space for optimizing the diaphragm structure design. Therefore, existing loudspeaker diaphragms still require improvement. Summary of the Invention

[0003] The purpose of this application is to provide a diaphragm for a sound-generating device, a sound-generating device, and an electronic device. The diaphragm for the sound-generating device of this application improves the modulus, damping, and low-temperature resistance of the diaphragm by adding modified calcium carbonate to a TPU matrix and precisely controlling the particle size and amount of modified calcium carbonate.

[0004] The first aspect of this application provides a diaphragm for a sound-generating device, comprising at least one composite material film, said composite material film comprising a thermoplastic polyurethane base film and modified particles dispersed within said thermoplastic polyurethane base film. The modified particles include modified calcium carbonate, wherein the calcium content of the modified calcium carbonate is >38wt%, the mass percentage of the modified particles in a single layer of the composite film is 0.5wt%~40wt%, and the particle size of the modified particles is ≤20μm and not 0; the relative rate of change of the resonant frequency of the diaphragm satisfies: <1; where, This represents the resonant frequency of the diaphragm at -10℃. This represents the resonant frequency of the diaphragm at 23°C.

[0005] In some embodiments of this application, the glass transition temperature of the thermoplastic polyurethane-based film is ≤-30°C.

[0006] In some embodiments of this application, the oil absorption value of the modified calcium carbonate is <25g / 100g.

[0007] In some embodiments of this application, the modified calcium carbonate is obtained by treating calcium carbonate raw material by at least one of the following modification methods: stearic acid modification, aluminate modification, titanate modification, or silane coupling agent modification.

[0008] In some embodiments of this application, the calcium carbonate raw material includes at least one of heavy calcium carbonate, light calcium carbonate, and nano calcium carbonate.

[0009] In some embodiments of this application, the elongation at break of a single-layer composite film is ≥300%.

[0010] In some embodiments of this application, the 3% secant modulus of the single-layer composite film is 15MPa to 150MPa.

[0011] In some embodiments of this application, the storage modulus change rate of the single-layer composite film at any temperature in the range of -20°C to 10°C is ≤10%.

[0012] In some embodiments of this application, the loss factor at 23°C of a single-layer composite film is >0.1.

[0013] In some embodiments of this application, the diaphragm is formed as a composite layer structure, wherein the composite layer structure includes at least one layer of the composite material film.

[0014] In some embodiments of this application, the composite layer structure further includes a composite connecting layer, which is stacked with the composite material film. The composite connecting layer is one or more of the following: polyurethane film, thermoplastic polyester elastomer film, polyetheretherketone film, silicone rubber film, acrylate rubber film, ethylene-acrylate rubber film, acrylic pressure-sensitive adhesive film, and organosilicon pressure-sensitive adhesive.

[0015] The second aspect of this application also provides a sound-generating device, which includes a diaphragm for the sound-generating device described in the first aspect of this application.

[0016] A third aspect of this application also provides an electronic device, which includes a diaphragm for a sound-generating device as described in the first aspect of this application or a sound-generating device as described in the second aspect of this application.

[0017] In this application, modified calcium carbonate is added to a TPU matrix. The calcium content of the modified calcium carbonate is >38wt%, and the modified particles account for 0.5wt%~40wt% of the mass of the single-layer composite film. The particle size of the modified particles is ≤20μm and not zero. By precisely controlling the particle size and addition amount of modified calcium carbonate, multiple synergistic effects achieve a triple performance breakthrough: First, the modulus of the composite film can be controlled and adjusted, expanding the design space for diaphragm thickness and cavity structure; second, the damping performance of the system is improved, optimizing the sound quality, while enriching the diaphragm structure design scheme; third, the excellent low-temperature resistance of the substrate is preserved, without having to make trade-offs between distortion performance, structural freedom, and product reliability. In this way, a diaphragm with simultaneously improved modulus, damping, and low-temperature resistance is obtained.

[0018] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the sound-generating device in some embodiments of this application; Figure 2 This is a graph showing the variation of the diaphragm resonant frequency F0 with temperature in the embodiments and comparative examples of this application; Figure 3 This is a graph showing the total harmonic distortion (THD) of the loudspeaker corresponding to the diaphragm as a function of frequency in the embodiments and comparative examples of this application.

[0021] Explanation of reference numerals in the attached figures 100 - Sound-generating device; 10-Housing; 20-Diaphragm; 30-Voice coil; 40-Magnetic circuit system. Detailed Implementation

[0022] Exemplary embodiments of this application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0023] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0024] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0025] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0027] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0028] The first aspect of this application provides a diaphragm for a sound-generating device. The diaphragm comprises at least one composite material film, wherein the composite material film includes a thermoplastic polyurethane base film and modified particles dispersed within the thermoplastic polyurethane base film. The modified particles include modified calcium carbonate, the calcium content of which is >38 wt%, the mass percentage of the modified particles in a single layer of the composite material film is 0.5 wt% to 40 wt%, and the particle size of the modified particles is ≤20 μm and not zero. The relative rate of change of the resonant frequency of the diaphragm satisfies the following: <1; where, This represents the resonant frequency of the diaphragm at -10℃. This represents the resonant frequency of the diaphragm at 23°C.

[0029] In the implementation scheme of this application, by adding modified calcium carbonate to the TPU matrix and precisely controlling the particle size, calcium content, and amount of modified calcium carbonate, a triple performance breakthrough is achieved through multiple synergistic effects: First, the modulus of the composite film can be controlled and adjusted, expanding the design space for diaphragm thickness and the cavity structure of the sound-generating device; second, the damping performance of the vibration system of the sound-generating device is improved, optimizing the sound quality, while enriching the diaphragm structure design scheme; third, the excellent low-temperature resistance of the substrate is retained, eliminating the need to make trade-offs between distortion performance, structural freedom, and product reliability. Thus, a diaphragm with simultaneously improved modulus, damping, and low-temperature resistance is obtained, and the relative rate of change of the diaphragm's resonant frequency satisfies: <1.

[0030] Specifically, the modified particles constitute 0.5 wt% to 40 wt% of the mass of the single-layer composite film. Understandably, when the modified particles, such as modified calcium carbonate, constitute less than 0.5 wt% of the mass of the single-layer composite film, the improvement in modulus and damping performance of the composite film is minimal. On one hand, the proportion of the modified calcium carbonate-TPU interface within the system is extremely low, resulting in limited energy dissipation through interfacial slip and friction, making it difficult to effectively improve material damping. On the other hand, the modified particles, such as modified calcium carbonate, are few in quantity and have large interparticle spacing, exhibiting an isolated and dispersed state, which provides insufficient constraint on the movement of TPU molecular chains, resulting in a minimal increase in the modulus of the composite film. Conversely, if the modified particles, such as modified calcium carbonate, constitute more than 40 wt% of the mass of the single-layer composite film, the processing fluidity of the composite material deteriorates significantly, and the difficulty of film molding increases significantly. Simultaneously, excessively high modified calcium carbonate content leads to excessive rigidity and insufficient toughness, increasing overall brittleness and making the material prone to fatigue failure under long-term vibration conditions, failing to meet the reliability requirements for long-term use of micro-speaker diaphragms. In some embodiments of this application, the modified particles (such as modified calcium carbonate) account for 5 wt% to 35 wt% of the mass of the monolayer composite film. Exemplarily, the mass percentage of the modified particles in the monolayer composite film can be one of the following: 0.5 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, or any value satisfying the above range.

[0031] In the embodiments of this application, the calcium content in the modified calcium carbonate is >38 wt%. If the calcium content is higher than 38%, the modifier in the calcium carbonate powder is less likely to migrate to the material surface and form frost or precipitates during long-term storage or high-temperature use; production stability is better, melt flow fluctuations are smaller, and problems such as film breakage and unstable melt state are less likely to occur; there are fewer impurities, and the mechanical properties (such as strength and elongation) of the material are better retained under aging conditions such as thermo-oxidation and ultraviolet light, and it is less prone to becoming brittle or discolored. It is understandable that when the calcium content in the modified calcium carbonate is lower than 38 wt%, it indicates insufficient purity of the raw material, often due to low purity of the ore raw material or inadequate control of the washing and carbonation processes during calcium carbonate preparation, resulting in a large amount of residual impurities in the system. These impurities can catalyze thermo-oxidative aging of the TPU matrix, accelerating material failure; at the same time, impurity components with poor compatibility can also damage the internal homogeneity of the composite film, deteriorating the overall mechanical properties of the film. For example, the calcium content in modified calcium carbonate can be one of 38wt%, 39wt%, 40wt%, or any value that meets the above range.

[0032] In the embodiments of this application, the particle size of the modified particles is ≤20μm and not zero. It is understood that modified particles, such as modified calcium carbonate, with a particle size ≤20μm can increase the contact interface between the modified particles and TPU, synergistically improving film damping and modulus, resulting in uniform particle dispersion, good film quality, and resistance to vibration fatigue. However, when the particle size of the modified particles, such as modified calcium carbonate, exceeds 20μm, it will cause insufficient two-phase interface, poor performance regulation, increased film defects, increased processing difficulty, and easy fatigue failure under long-term vibration. In some embodiments of this application, the particle size of the modified calcium carbonate is 20nm~20μm. For example, the particle size of the modified particles can be one of 20μm, 19μm, 18μm, 17μm, 16μm, 15μm, 14μm, 13μm, 12μm, 11μm, 10μm, 9μm, 8μm, 7μm, 6μm, 5μm, 4μm, 3μm, 2μm, 1μm, 60nm, 20nm or any value that satisfies the above range.

[0033] It is worth mentioning that in some embodiments of this application, the particle size D50 of the modified particles is ≤20μm and not 0. In particle size analysis, particle size D50 is a characteristic particle size value obtained based on the cumulative particle size distribution statistics; particle size D50: refers to the particle size corresponding to when the cumulative distribution reaches 50%.

[0034] In some embodiments of this application, the glass transition temperature of the thermoplastic polyurethane base film is ≤-30℃. It is understood that controlling the glass transition temperature of the thermoplastic polyurethane base film to ≤-30℃ can impart excellent low-temperature adaptability to the diaphragm. The lower the glass transition temperature of the material, the stronger its flexibility retention in low-temperature environments. The actual operating temperature of the micro-speaker must always be higher than the glass transition temperature of the material. If the ambient temperature is lower than the glass transition temperature, the movement of the polymer chain segments is frozen, the diaphragm will harden significantly, causing low-frequency acoustic parameter drift. At the same time, the material's toughness decreases significantly, and its brittleness increases, making it prone to cracking and failure under long-term vibration conditions. If the diaphragm's glass transition temperature is higher than -30℃, its cold resistance deteriorates significantly: in low-temperature usage scenarios, it is very easy to reach or even fall below the glass transition range, causing the diaphragm to harden, rigidity to change abruptly, and the low-frequency sound curve to shift and become distorted; moreover, low-temperature brittleness is exacerbated, and repeated vibration of the folding ring and the diaphragm body is prone to fatigue cracking, resulting in insufficient low-temperature reliability of the product and failing to meet the wide-temperature range usage requirements of outdoor and wearable devices. In some embodiments of this application, the glass transition temperature of the thermoplastic polyurethane base film is ≤-35°C. Exemplarily, the glass transition temperature of the thermoplastic polyurethane base film can be one of -30°C, -35°C, -49°C, -52°C, or any value satisfying the above range.

[0035] In some embodiments of this application, the oil absorption value of modified calcium carbonate is <25g / 100g. It is understood that the oil absorption value of modified calcium carbonate is determined by both particle size and surface modification state: the modifier coats the surface of calcium carbonate, filling the microporous structure of the particle surface and preventing oil penetration, effectively reducing the oil absorption value. When calcium carbonate with low oil absorption value is melt-blended with TPU, it does not adsorb a large amount of matrix resin, resulting in excellent melt flowability, stable extrusion torque and die pressure, and a stable casting process, making it suitable for continuous production of ultra-thin diaphragm films. However, when the oil absorption value of modified calcium carbonate is higher than 25g / 100g, it indicates incomplete particle coating and a large amount of exposed surface pores. High oil absorption calcium carbonate will adsorb a large amount of TPU resin matrix during the melt blending stage, causing a sharp increase in the system melt viscosity, a significant increase in extrusion torque and die melt pressure, and a significant increase in processing load; this not only easily leads to molding defects such as uneven output, film thickness fluctuations, and surface pitting, but also increases equipment wear and makes it difficult to achieve stable continuous film production. For example, the oil absorption value of modified calcium carbonate can be one of 24g / 100g, 23g / 100g, 22g / 100g, 21g / 100g, 20g / 100g, 19g / 100g, 18g / 100g, 17g / 100g, 16g / 100g or any value that meets the above range.

[0036] In some embodiments of this application, modified calcium carbonate is obtained by treating calcium carbonate raw material by at least one of the following modification methods: stearic acid modification, aluminate modification, titanate modification, or silane coupling agent modification.

[0037] In some embodiments of this application, the surface modification effect of calcium carbonate can be verified by two indicators: infrared spectroscopy can detect the characteristic absorption peaks corresponding to the modifier, such as the modified calcium carbonate having a thermal weight loss of more than 1% at 500℃; the above tests can be carried out directly on pure calcium carbonate raw materials.

[0038] If the sample is a TPU / calcium carbonate composite film, solvent separation pretreatment can be used: use tetrahydrofuran to fully dissolve the TPU matrix, filter and collect the inorganic filter residue, then wash and dry it multiple times with N,N-dimethylformamide (DMF), and carry out infrared spectroscopy and thermogravimetric analysis on the purified calcium carbonate filter residue to complete the characterization of the modified state of calcium carbonate.

[0039] The smaller the calcium carbonate particle size, the more significant the tendency for particle agglomeration. Therefore, this system requires the activation degree of calcium carbonate to be no less than 90%. If the activation degree of nano-calcium carbonate is too low, the particles are prone to agglomeration, which brings multiple negative effects: at the processing level, it will deteriorate the film-forming performance of the material, and the uniformity of film thickness will be difficult to control; at the appearance level, surface roughness, white spots, and fisheye defects are likely to occur, and the haze of the film will increase; at the material performance level, agglomerates form internal stress defects, reduce the toughness of the composite film, weaken the rigidity reinforcement effect of calcium carbonate, and at the same time, the number of two-phase interfaces is insufficient, limiting the damping improvement effect.

[0040] Calcium carbonate, one of the most abundant natural inorganic minerals, has three main natural sources: first, rocks and minerals such as limestone, marble, calcite, dolomite, and chalk; second, biological organic matter such as shells, eggshells, coral, pearls, and animal bones; and third, natural sedimentary products such as scale, stalactites in caves, and calcified soil. Based on different production methods, calcium carbonate is divided into heavy calcium carbonate and light calcium carbonate: heavy calcium carbonate is obtained through the physical crushing, ultrafine grinding, and grading of natural ores; light calcium carbonate is an artificial chemical precipitation product, prepared by calcining limestone → adding water for digestion → introducing carbon dioxide for carbonation and precipitation.

[0041] In some embodiments of this application, the calcium carbonate raw material includes at least one of heavy calcium carbonate, light calcium carbonate, and nano calcium carbonate.

[0042] In some embodiments of this application, the elongation at break of the single-layer composite film is ≥300%. It is understood that controlling the elongation at break of the composite film to ≥300% can simultaneously meet the requirements of long-term vibration reliability of the diaphragm and the molding and processing technology, offering multiple advantages: From the perspective of product performance, the diaphragm continuously withstands reciprocating stretching and rebound during operation. Its high elongation at break corresponds to excellent elastic recovery performance, which can buffer the minor damage caused by a single vibration, inhibit the accumulation of damage, greatly increase the number of fatigue cycles, and is not prone to permanent deformation. Even when subjected to large-amplitude and violent vibration, the highly ductile substrate is not prone to cracking, tearing, or breakage, thus avoiding sound quality deterioration or even device failure.

[0043] From a processing perspective, the film needs to undergo hot pressing, punching, and cutting processes. Sufficient elongation at break ensures that the film can withstand processing tension without breaking, guaranteeing the yield of the finished product. Surface-modified calcium carbonate can improve its interfacial compatibility with the TPU matrix, strengthen the interfacial bonding strength between the two phases, and effectively delay interfacial debonding and microcrack propagation under external forces, thereby maintaining the material's high elongation at break.

[0044] If the elongation at break of the composite film is less than 300%, the overall toughness and ductility of the film are insufficient, and the defects are significant. Firstly, the bond between unmodified calcium carbonate and TPU is weak, and the interface is prone to delamination and cracking under stress, which further reduces the elongation index.

[0045] Secondly, during long-term cyclic vibration, the diaphragm has poor elastic recovery ability, and micro-damage accumulates continuously, leading to rapid fatigue failure. Under large-amplitude vibration conditions, cracks and tears are very likely to occur, resulting in acoustic performance degradation and shortening product lifespan.

[0046] Third, in forming processes such as hot pressing and punching, the material's tensile strength is insufficient, and it is easy for the film to break or material to be missing during processing, making it difficult to guarantee the yield of mass production.

[0047] For example, the elongation at break of the single-layer composite film can be one of 300%, 400%, 500%, 600%, 700%, 800%, 900%, 1000% or any value that meets the above range.

[0048] In some embodiments of this application, the 3% secant modulus of the single-layer composite film is 15MPa to 150MPa. It is understood that the modulus of the diaphragm is a key parameter for measuring material stiffness. Limiting the 3% secant modulus of the composite film to the range of 15MPa to 150MPa allows for precise matching of the design requirements of the resonant frequency F0 of the micro-sound generator, enabling flexible adjustment of the diaphragm thickness and cavity space. Within this modulus range, the composite film exhibits moderate stiffness, allowing the diaphragm to maintain standard piston-like vibration: it eliminates the need for significantly thickening the film to compensate for rigidity, saving internal assembly space; it also avoids the need for extremely thin strips to avoid excessive softness, balancing molding processability and acoustic performance, resulting in smooth dynamic sound production, controllable distortion levels, and a balanced and mellow listening experience for vocals and mid-to-high frequencies. However, when the 3% secant modulus of the composite film exceeds 150MPa, the composite film becomes excessively stiff, with local bending strength far exceeding the requirements for sound generation. Under high dynamic range, the consistency of diaphragm piston movement deteriorates, resulting in uneven vibration deformation, a sharp and harsh acoustic sound, a harsh and piercing mid-range performance, and a poor sound quality experience. When the 3% secant modulus of the composite film is below 15MPa, the composite film's resistance to bending and deformation is insufficient. Under large-stroke operating conditions, the diaphragm cannot maintain a regular piston shape, exhibiting distorted vibrations with a concave center and bulging edges, causing severe slit vibration and harmonic distortion, resulting in a muddy and muffled sound and a significant decrease in resolution.

[0049] The 3% secant modulus refers to the ratio of tensile stress to 3% strain when a composite film sample is stretched unidirectionally to a tensile strain of 3%. It directly reflects the rigidity and deformation resistance of the composite film under small deformation range, and is directly related to the diaphragm vibration stiffness, resonant frequency F0, high and low temperature acoustic stability and damping performance.

[0050] In some embodiments of this application, the 3% secant modulus of the monolayer composite film is 20 MPa to 70 MPa. Exemplarily, the 3% secant modulus of the monolayer composite film can be one of 15 MPa, 17.4 MPa, 20 MPa, 25 MPa, 28.5 MPa, 30 MPa, 30.1 MPa, 32.7 MPa, 35 MPa, 40 MPa, 45 MPa, 50 MPa, 55 MPa, 60 MPa, 65 MPa, 70 MPa, 70.1 MPa, 75 MPa, 80 MPa, 85 MPa, 90 MPa, 95 MPa, 100 MPa, 105 MPa, 110 MPa, 115 MPa, 120 MPa, 125 MPa, 130 MPa, 135 MPa, 140 MPa, 145 MPa, or 150 MPa, or any value satisfying the above range.

[0051] In some embodiments of this application, the 23°C loss factor of the single-layer composite film is >0.1. It is understood that controlling the 23°C loss factor of the composite film above 0.1 is the core damping performance requirement of the diaphragm in this system, providing multiple acoustic advantages: under normal temperature and daily use conditions, a sufficient loss factor corresponds to the material's excellent damping characteristics. The addition of modified calcium carbonate generates the following mechanisms: forming numerous slippery interfaces with the polyurethane elastomer, restricting the movement of polymer chain segments, and increasing energy dissipation through friction between modified calcium carbonate and modified calcium carbonate, thereby increasing internal friction and energy loss under alternating loads, effectively suppressing segmented vibration, noise, and harmonic distortion. This optimizes sound resolution while ensuring diaphragm rigidity and stiffness, balancing acoustic sensitivity and sound quality performance. When the 23°C loss factor of the composite film is below 0.1, it is generally due to an insufficient amount of modified calcium carbonate added. The number of modified calcium carbonate-matrix two-phase interfaces in the system is insufficient, resulting in limited internal friction energy dissipation during vibration, weak damping, a significant decrease in noise reduction and distortion suppression effects, and obvious sound quality defects. For example, the 23°C loss factor of a single-layer composite film can be one of 0.1, 0.117, 0.124, 0.134 or any value that satisfies the above range.

[0052] In some embodiments of this application, the storage modulus change rate of the single-layer composite film at any temperature within the range of -20℃ to 10℃ is ≤10%. It is understood that the storage modulus change rate is the absolute value of the derivative of the storage modulus versus temperature curve. A storage modulus change rate of ≤10% for the composite film at any temperature within the range of -20℃ to 10℃ enables highly stable acoustic performance from low temperature to room temperature. Temperature changes alter the motion state of TPU molecular chains: as temperature increases, the relaxation time of polymer chain segments shortens, the film material becomes more sensitive to external forces, and the storage modulus decreases accordingly; as temperature decreases, molecular chain motion is suppressed, the relaxation time is significantly prolonged, the rigidity of the film material increases, and the storage modulus increases. Under the same driving excitation, the sound generation sensitivity of the sound-generating device is negatively correlated with the film material modulus; when the storage modulus change rate is controlled at a low level, the modulus fluctuation across the entire temperature range is weak, the diaphragm's sound generation sensitivity remains stable, and there is no significant shift in volume or frequency response in low-temperature environments, making it suitable for wearable, outdoor, and other wide-temperature-range applications. When the rate of change of the storage modulus of the composite film at any temperature within the range of -20℃ to 10℃ is greater than 10%, the difference in modulus between high and low temperatures is too large: the modulus is significantly higher at low temperatures and significantly lower at normal temperatures. Under the same input excitation, the sensitivity of the sound-generating device fluctuates drastically with temperature, easily leading to problems such as low volume at low temperatures, frequency response curve deviation, and unstable timbre. At the same time, large fluctuations in modulus will change the diaphragm resonant frequency F0, exacerbating harmonic distortion at different temperatures, resulting in poor acoustic consistency of the entire device and failing to meet the requirements for stable listening in a wide temperature range. For example, the rate of change of the storage modulus of a single-layer composite film at any temperature within the range of -20℃ to 10℃ can be one of the following: 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, -1.8%, -2.0%, -3.8%, -3.9%, -4.4%, or any value satisfying the above range.

[0053] In some embodiments of this application, the diaphragm is formed as a composite layer structure, wherein the composite layer structure includes at least two composite material films, each composite material film comprising a thermoplastic polyurethane base film and modified particles dispersed within the thermoplastic polyurethane base film. It is understood that the diaphragm of the composite layer structure contains at least two composite material films, each composite material film being formed by blending thermoplastic polyurethane containing urethane bonds (-NH-COO-) and / or urea bonds (-NH-CO-NH-) with modified particles. In some embodiments of this application, the two or more composite material films are stacked.

[0054] In some embodiments of this application, the diaphragm is formed as a composite layer structure, wherein the composite layer structure includes a composite material film and a composite connecting layer, the composite connecting layer and the composite material film are stacked together, the composite material film includes a thermoplastic polyurethane base film and modified particles dispersed in the thermoplastic polyurethane base film, and the composite connecting layer can be one or more of polyurethane film, thermoplastic polyester elastomer film, polyetheretherketone film, silicone rubber film, acrylate rubber film, ethylene-acrylate rubber film, acrylic pressure-sensitive adhesive film, and organosilicon pressure-sensitive adhesive.

[0055] The second aspect of this application provides a sound-generating device, which includes a diaphragm for the sound-generating device described in the first aspect of this application.

[0056] In some embodiments of this application, the sound-generating device may be a loudspeaker, such as a miniature loudspeaker. Figure 1 As shown, the sound-generating device 100 of this application includes a housing 10, a vibration system disposed within the housing 10, and a magnetic circuit system 40 cooperating with the vibration system. The vibration system includes a diaphragm 20 and a voice coil 30 coupled to one side of the diaphragm 20. The magnetic circuit system 40 drives the voice coil 30 to vibrate, thereby causing the diaphragm 20 to produce sound. When the sound-generating device 100 is working, an electrical signal is input to the voice coil 30. The voice coil 30 is driven by the magnetic field force of the magnetic circuit system 40 and moves with different amplitudes and directions as the signal magnitude and positive and negative directions alternate, thereby causing the diaphragm 20 to vibrate and produce sound, thus completing the process of converting electrical energy into mechanical energy into sound energy.

[0057] A third aspect of this application provides an electronic device that includes a diaphragm for a sound-generating device as described in the first aspect of this application or a sound-generating device as described in the second aspect of this application.

[0058] In the embodiments of this application, the electronic device may be, but is not limited to, a mobile phone, a tablet computer, a smartwatch, a game console, a learning machine, etc., and the electronic device has the characteristic of good acoustic effect.

[0059] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which this application pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained through commercial purchase or by existing methods; unless otherwise specified, the amounts of experimental reagents used are the amounts used in conventional experimental operations; unless otherwise specified, the experimental methods are conventional methods. It should be further noted that the following descriptions are merely exemplary and not specific limitations on this application. Moreover, the selection of the comparative examples below is for comparison with the technical solutions of this application to demonstrate the advancement of the technical solutions of this application, and does not imply that the comparative examples are necessarily prior art in this technical field.

[0060] Example 1 Embodiment 1 of this application provides a diaphragm for a sound-generating device. The diaphragm is formed by processing a single-layer composite film. The composite film is formed by a thermoplastic polyurethane base film and modified calcium carbonate dispersed within the thermoplastic polyurethane base film. The modified calcium carbonate is obtained by treating calcium carbonate with a silane coupling agent KH-550. The modified calcium carbonate has a particle size D50 of 3 μm, an oil absorption value of 16 g / 100 g, a calcium content of 38.5 wt%, and accounts for 20 wt% of the mass of the single-layer composite film. The thermoplastic polyurethane base film accounts for 80 wt% of the mass of the single-layer composite film.

[0061] Performance testing 1. Glass transition temperature test.

[0062] A dynamic thermal analyzer was used, in accordance with ASTM D5026-23 standard, in tensile mode, with a heating rate of 3℃ / min and a frequency of 1Hz.

[0063] 2. Elongation at break test.

[0064] According to ASTM D882 standard, the preload force is 0.1N, the strip width is 15mm, the clamp spacing is 30mm, and the tensile rate is 300mm / min.

[0065] 3. 3% secant modulus test.

[0066] Using a universal tensile testing machine, in accordance with ASTM D882 standard, the preload force was 0.1N, the specimen width was 15mm, the clamp spacing was 30mm, and the tensile rate was 300mm / min.

[0067] The ratio of stress to strain at 3% strain in a test sample is the 3% secant modulus, denoted as 3% secant modulus = .

[0068] 4. Energy storage modulus change rate test.

[0069] Dynamic thermomechanical analyzer was used, according to ASTM D5026-23 standard, in tensile mode, at a frequency of 1 Hz and a strain of 0.5%.

[0070] 5. Room temperature loss factor test.

[0071] According to ASTM D5026 standard, the heating rate is 3℃ / min, the strain is 0.5%, the test temperature range is -60℃ to 150℃, the tensile mode is used, and the damping factor value is read under room temperature (23℃) conditions.

[0072] The diaphragm in Example 1 was subjected to the corresponding performance tests according to the above test methods, and the test results are summarized in Table 1.

[0073] The miniature loudspeaker obtained by assembling the diaphragm in Example 1 was used to conduct tests on related performance such as resonant frequency F0.

[0074] Example 2 The only difference between Example 2 and Example 1 is that the modified calcium carbonate is prepared by modifying nano-calcium carbonate with stearic acid. The stearic acid coating amount is 2wt%, the particle size D50 of the modified calcium carbonate is 60nm, the oil absorption value is 22g / 100g, the calcium content in the modified calcium carbonate is 38.2wt%, the mass percentage of modified calcium carbonate in the single-layer composite film is 8wt%, and the mass percentage of thermoplastic polyurethane base film in the single-layer composite film is 92wt%.

[0075] Example 3 The only difference between Example 3 and Example 1 is that the modified calcium carbonate accounts for 0.5 wt% of the composite film. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 1.

[0076] Example 4 The only difference between Example 4 and Example 1 is that the modified calcium carbonate accounts for 5 wt% of the composite film. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 1.

[0077] Example 5 The only difference between Example 5 and Example 1 is that the modified calcium carbonate accounts for 35 wt% of the composite film. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 1.

[0078] Example 6 The only difference between Example 6 and Example 1 is that the modified calcium carbonate accounts for 40 wt% of the composite film. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 1.

[0079] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that: unmodified heavy calcium carbonate was used, the particle size D50 of the calcium carbonate was 3 μm, the oil absorption value was 40 g / 100 g, the calcium content in the calcium carbonate was 39.6 wt%, the mass percentage of calcium carbonate in the single-layer composite film was 23 wt%, and the mass percentage of thermoplastic polyurethane base film in the single-layer composite film was 77 wt%. The rest were prepared and tested using the same methods as in Example 1, and the test results are summarized in Table 1.

[0080] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that calcium carbonate was not added, the diaphragm was made of thermoplastic polyurethane base film and processed, and the rest were prepared and tested in the same way as in Example 1. The test results are summarized in Table 1.

[0081] Comparative Example 3 The only differences between Comparative Example 3 and Example 1 are: the modified calcium carbonate accounts for 0.4 wt% of the composite film mass, the calcium content of the modified calcium carbonate is 38.5 wt%, and the particle size D50 is 3 μm. The rest of the preparation and testing methods were the same as in Example 1, and the test results are summarized in Table 1.

[0082] Comparative Example 4 The only differences between Comparative Example 4 and Example 1 are: the modified calcium carbonate accounts for 41 wt% of the composite film mass, the calcium content of the modified calcium carbonate is 38.5 wt%, and the particle size D50 is 3 μm. The rest of the preparation and testing methods were the same as in Example 1, and the test results are summarized in Table 1.

[0083] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that the modified calcium carbonate accounts for 20 wt% of the composite film, the calcium content of the modified calcium carbonate is 37.2 wt%, and the particle size D50 is 3 μm. The rest of the preparation and testing methods were the same as in Example 1, and the test results are summarized in Table 1.

[0084] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the modified calcium carbonate accounts for 20 wt% of the composite film, the calcium content of the modified calcium carbonate is 38.4 wt%, and the particle size D50 is 21 μm. The rest of the preparation and testing methods were the same as in Example 1, and the test results are summarized in Table 1.

[0085] Table 1

[0086] Combination Figure 2 , Figure 3 As can be seen from the test data in Table 1, compared with the examples, the change in energy storage modulus in Comparative Example 2 is higher, and the modulus increases significantly at low temperatures, resulting in sensitivity of the resonant frequency F0 to temperature changes. In Example 1 of this application, the rate of change of resonant frequency is about 30%, in Example 2 it is about 40%, and in the comparative example it is about 160%, indicating that the stability of this application is significantly improved.

[0087] Comparative Example 2 exhibits significant differences in sound characteristics between cold outdoor environments and mild indoor environments during winter. Outdoor low-frequency response is severely attenuated, resulting in a "thin," "dry," and lacking fullness in the sound. In contrast, Examples 1 and 2 of this application maintain consistent, reliable low-frequency performance and overall timbre under varying temperature conditions.

[0088] In Comparative Example 1, a composite film was prepared by blending unmodified heavy calcium carbonate with thermoplastic polyurethane. Due to the poor interfacial compatibility and weak interfacial bonding strength between unmodified calcium carbonate and the TPU matrix, interfacial debonding and micro-voids easily occurred between calcium carbonate and the matrix. After the excitation signal was applied, the diaphragm material vibrated. The interfacial friction loss was low, resulting in low material damping performance and weak vibration energy dissipation. The motion of the previous moment failed to stop in time before the next excitation signal was given. In Comparative Example 1, the diaphragm material could not effectively suppress harmonic vibration, the total harmonic distortion increased significantly, and noise and distortion were prone to occur. The acoustic performance was poor and could not meet the requirements of high fidelity and low distortion for use in miniature loudspeakers.

[0089] In Comparative Examples 4 to 6, excessively high calcium carbonate content, excessively large particle size, or low calcium content can easily lead to poor stability in the film manufacturing process, as well as problems with thickness accuracy and appearance defects.

[0090] In the implementation scheme of this application, by adding modified calcium carbonate to the TPU system and precisely controlling the particle size and amount of modified calcium carbonate, the modulus can be adjusted to ensure the margin of diaphragm thickness and space design, thereby improving damping, enhancing sound quality and the diversity of surround design schemes, and maintaining low temperature resistance without compromising distortion, structure, and reliability.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A diaphragm for a sound-generating device, characterized in that, It includes at least one composite film, the composite film comprising a thermoplastic polyurethane base film and modified particles dispersed within the thermoplastic polyurethane base film. The modified particles include modified calcium carbonate, wherein the calcium content in the modified calcium carbonate is >38wt%, the mass percentage of the modified particles in the mass of a single layer of the composite film is 0.5wt%~40wt%, and the particle size of the modified particles is ≤20μm and not 0. The relative rate of change of the resonant frequency of the diaphragm satisfies: <1; where, This represents the resonant frequency of the diaphragm at -10℃. This represents the resonant frequency of the diaphragm at 23°C.

2. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The glass transition temperature of the thermoplastic polyurethane-based film is ≤-30℃.

3. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The modified calcium carbonate has an oil absorption value of <25g / 100g.

4. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The modified calcium carbonate is obtained by treating calcium carbonate raw material through at least one of the following modification methods: Stearic acid modification, aluminate modification, titanate modification, or silane coupling agent modification.

5. The diaphragm for a sound-generating device as described in claim 4, characterized in that, The calcium carbonate raw material includes at least one of heavy calcium carbonate, light calcium carbonate, and nano calcium carbonate.

6. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The elongation at break of a single-layer composite film is ≥300%; And / or, the 3% secant modulus of a single-layer composite film is 15MPa~150MPa.

7. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The storage modulus change rate of the single-layer composite film is ≤10% at any temperature within the range of -20℃ to 10℃; And / or, the loss factor at 23°C of a single-layer composite film is >0.

1.

8. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The diaphragm is formed as a composite layer structure, wherein, The composite layer structure includes at least one layer of the composite material film; And / or, the composite layer structure further includes a composite connecting layer, which is stacked with the composite material film. The composite connecting layer is one or more of the following: polyurethane film, thermoplastic polyester elastomer film, polyetheretherketone film, silicone rubber film, acrylate rubber film, ethylene-acrylate rubber film, acrylic pressure-sensitive adhesive film, and organosilicon pressure-sensitive adhesive.

9. A sound-generating device, characterized in that, The diaphragm for the sound-generating device as described in any one of claims 1 to 8.

10. An electronic device, characterized in that, The diaphragm for the sound-generating device according to any one of claims 1 to 8, or the sound-generating device according to claim 9.

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