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 a thermoplastic polyurethane base film and mica powder dispersed within the thermoplastic polyurethane base film. The mica powder accounts for 15wt%~45wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The particle size D50 of the mica powder is 1μm~10μm, and the particle size D90 is ≤20μm and not 0. The 3% secant modulus of the diaphragm is 20MPa~80MPa. This application improves the damping performance, low-temperature resistance, and physicochemical properties such as oxidation and hydrolysis resistance of the diaphragm by adding mica powder to the thermoplastic polyurethane base film. At the same time, the mica powder is uniformly dispersed inside the thermoplastic polyurethane base film without obvious agglomeration, and the film surface is smooth without pits. The film thickness is uniform, and it is not easily damaged during the production process, making it suitable for casting film forming processes.

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] Existing miniature loudspeaker diaphragms mostly use polyether-based TPU or thermoplastic polyester through casting. Pure TPU films with a polyurethane content of ≥95wt% have low molecular chain motion resistance and poor damping performance, making them prone to polarization during diaphragm vibration, resulting in a decrease in sound quality. Furthermore, the material's high glass transition temperature leads to a significant decrease in loudness at low temperatures. To address these issues, a diaphragm product has been proposed in related technologies, comprising TPU material and inorganic fillers added to the TPU material, such as silica or carbon black. However, these inorganic fillers tend to agglomerate and disperse unevenly within the TPU system, leading to pitting on the film surface, poor thickness consistency, and even film damage. 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 damping performance, low-temperature resistance, and physicochemical properties such as oxidation and hydrolysis resistance of the diaphragm by adding mica powder to a thermoplastic polyurethane base film. At the same time, the mica powder is uniformly dispersed inside the thermoplastic polyurethane base film without obvious agglomeration, and the film surface is smooth without pitting. The film thickness is uniform, and it is not easily damaged during the production process, making it suitable for casting film forming process.

[0004] The first aspect of this application provides a diaphragm for a sound-generating device, comprising a thermoplastic polyurethane base film and mica powder dispersed within the thermoplastic polyurethane base film, wherein the mica powder accounts for 15wt% to 45wt% of the total mass of the thermoplastic polyurethane base film and the mica powder, and the mica powder has a particle size D50 of 1μm to 10μm and a particle size D90 ≤ 20μm and not 0; the 3% secant modulus of the diaphragm is 20MPa to 80MPa.

[0005] In some embodiments of this application, the specific surface area of ​​the mica powder is ≥0.5m². 2 / g.

[0006] In some embodiments of this application, the aspect ratio of the mica powder is ≥10.

[0007] In some embodiments of this application, the aluminum element in the mica powder accounts for 8% to 16% of the mass of the mica powder.

[0008] In some embodiments of this application, the thermoplastic polyurethane base film is composed of hard segments and soft segments. The hard segments are urethane (-NH-COO-) and / or urea (-NH-CO-NH-) chain segments formed by the reaction of diisocyanate with a small molecule chain extender. The soft segments are at least one of polyether polyol, polyester polyol, and polycarbonate polyol.

[0009] In some embodiments of this application, the hard segment accounts for ≤40wt% of the mass of the thermoplastic polyurethane base film.

[0010] In some embodiments of this application, the diisocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethylphenyl dimethylene diisocyanate, terephthalic diisocyanate, naphthalene diisocyanate, and hydrogenated MDI.

[0011] In some embodiments of this application, the small molecule chain extender includes at least one selected from 1,4-butanediol, ethylene glycol, diethylene glycol, neopentyl glycol, ethylenediamine, diethyltoluenediamine, and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0012] In some embodiments of this application, the elongation at break of the diaphragm is ≥200%.

[0013] In some embodiments of this application, the diaphragm has a 23°C damping factor ≥ 0.05.

[0014] In some embodiments of this application, the melting point of the diaphragm is ≥150°C.

[0015] In some embodiments of this application, the thickness of the diaphragm is 10 μm to 120 μm.

[0016] In some embodiments of this application, the thickness tolerance of the diaphragm is ±5%.

[0017] In some embodiments of this application, the density of the diaphragm is ≤1.6 g / cm³. 3 .

[0018] In some embodiments of this application, the F0 ratio of the diaphragm under -20°C and 20°C conditions satisfies: ≤3.5; where, This indicates the resonant frequency of the diaphragm at -20℃. This indicates the resonant frequency of the diaphragm at 20℃.

[0019] In some embodiments of this application, the glass transition temperature of the diaphragm is ≤-30°C.

[0020] In some embodiments of this application, the diaphragm is formed as a composite layer structure, wherein the composite layer structure includes at least two membrane materials, each of which includes a thermoplastic polyurethane base film and mica powder dispersed within the thermoplastic polyurethane base film.

[0021] In some embodiments of this application, the composite layer structure includes a membrane material and a composite connecting layer, wherein the composite connecting layer is stacked with the membrane material, the membrane material includes a thermoplastic polyurethane base film and mica powder dispersed in the thermoplastic polyurethane base film, and the composite connecting layer is at least one of a polyacrylate film layer, a polyethylene-acrylate film layer, and an organosilicon pressure-sensitive adhesive layer.

[0022] 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.

[0023] 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.

[0024] The diaphragm for the sound-generating device of this application improves the damping performance, low-temperature resistance, and physicochemical properties such as oxidation and hydrolysis resistance of the diaphragm by adding mica powder to a thermoplastic polyurethane base film, wherein the mica powder accounts for 15wt%~45wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The particle size D50 of the mica powder is 1μm~10μm and the particle size D90 is ≤20μm and not 0. At the same time, the mica powder can be uniformly dispersed inside the thermoplastic polyurethane base film without obvious agglomeration, and the surface of the film is smooth without pits. The film thickness is uniform, and it is not easily damaged during the production process, making it suitable for casting film forming process.

[0025] 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

[0026] 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.

[0027] Figure 1 This is a schematic diagram of the structure of the sound-generating device in some embodiments of this application; Figure 2This is a six-point amplitude diagram of the miniature loudspeaker obtained by diaphragm assembly in Embodiment 1 of this application; Figure 3 This is a six-point amplitude diagram of the miniature loudspeaker obtained by diaphragm assembly in Comparative Example 1 of this application.

[0028] 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

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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).

[0035] The first aspect of this application provides a diaphragm for a sound-generating device. The diaphragm includes a thermoplastic polyurethane base film and mica powder dispersed within the thermoplastic polyurethane base film. The mica powder accounts for 15wt% to 45wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The particle size D50 of the mica powder is 1μm to 10μm, and the particle size D90 is ≤20μm and not 0. The 3% secant modulus of the diaphragm is 20MPa to 80MPa.

[0036] In particle size analysis, particle size D50 and particle size D90 are characteristic particle size values ​​derived from cumulative particle size distribution statistics; where particle size D50 refers to the particle size corresponding to 50% of the cumulative distribution; particle size D90 refers to the particle size corresponding to 90% of the cumulative distribution.

[0037] In the embodiments of this application, because the surface of mica powder is rich in oxygen-containing functional groups, when the material is subjected to shearing, the mica powder can form hydrogen bonds with the urethane bonds (-NH-COO-) and / or urea bonds (-NH-CO-NH-) in the polyurethane molecular chain. During the movement of polymer chain segments, the internal frictional resistance between the matrix resin and the mica powder is significantly increased, thereby significantly optimizing the damping performance of the thermoplastic polyurethane material, while improving its comprehensive physicochemical properties such as low-temperature resistance, oxidation resistance, and hydrolysis resistance.

[0038] Specifically, the 3% secant modulus is a key mechanical indicator characterizing the hardness and deformation resistance of membrane materials. It refers to the ratio of tensile stress to 3% strain when a membrane material sample is stretched unidirectionally to a tensile strain of 3%. It directly reflects the rigidity and deformation resistance of the membrane material in the small deformation range and is directly related to the diaphragm vibration stiffness, resonant frequency F0, high and low temperature acoustic stability and damping performance.

[0039] In some embodiments of this application, the 3% secant modulus of the diaphragm is between 20 MPa and 80 MPa. It is understood that a 3% secant modulus within the range of 20 MPa to 80 MPa balances the interfacial hydrogen bond damping effect, structural rigidity, and chain segment movement capability of the mica powder / polyurethane system: it achieves high damping, hydrolysis resistance, oxidation resistance, and low-temperature resistance through mica powder-matrix hydrogen bonds, while retaining appropriate chain segment slippage space to achieve excellent acoustic performance across the entire frequency range. When the 3% secant modulus of the diaphragm is <20 MPa, the membrane material lacks sufficient rigidity, making it prone to creep deformation during vibration; while when the 3% secant modulus of the diaphragm is >80 MPa, the membrane material is too rigid, reducing toughness and making it prone to tearing and rupture. For example, the 3% secant modulus of the diaphragm can be one of 20MPa, 22.3MPa, 24.8MPa, 25MPa, 29.5MPa, 30MPa, 31.3MPa, 35MPa, 36.9MPa, 40MPa, 45MPa, 50MPa, 55MPa, 60MPa, 61.3MPa, 62.4MPa, 62.8MPa, 65MPa, 70MPa, 75MPa, 75.2MPa, and 80MPa, or any value that satisfies the above range.

[0040] As the mass of mica powder increases, the damping factor of the diaphragm at room temperature (23°C) increases, but the elongation at break of the diaphragm decreases significantly. Especially when the mass percentage of mica powder exceeds 50%, the elongation at break of the diaphragm is below 200%, and the Young's modulus of the diaphragm is high. Therefore, when preparing products with the same performance, a thinner diaphragm strip is required. This causes two problems: first, when the elongation at break is too low, the prepared diaphragm is prone to rupture during vibration; second, when the diaphragm is thin, the product's chemical resistance is also poor, making it prone to corrosion and embrittlement. In some embodiments of this application, the mass percentage of mica powder in the thermoplastic polyurethane base film and the total mass of mica powder is 15% to 45%. For example, the mass percentage of mica powder in the total mass of the thermoplastic polyurethane base film and mica powder can be one of 15wt%, 18wt%, 20wt%, 22wt%, 25wt%, 28wt%, 30wt%, 32wt%, 35wt%, 38wt%, 40wt%, 42wt%, or 45wt%, or any value that meets the above range.

[0041] Since the thickness of the film strip (film material) used to manufacture the diaphragm is typically between 10μm and 120μm, the particle size of the mica powder directly affects the appearance of the film strip. When the particle size D50 of the mica powder is greater than 10μm and the particle size D90 is greater than 20μm, a large number of pits appear on the surface of the prepared film material, which not only destroys the overall thickness uniformity of the diaphragm but also forms particulate impurities on the surface of the finished product, seriously affecting the appearance quality. Conversely, when the particle size D50 of the mica powder is less than 1μm, small-sized mica powder will aggregate due to electrostatic effects and intermolecular forces, and cannot be uniformly dispersed in the thermoplastic polyurethane base film, which will also cause defects in the film material, and the thickness uniformity of the diaphragm will decrease significantly. In some embodiments of this application, the particle size D50 of the mica powder is 1μm to 10μm, and the particle size D90 is ≤20μm and not 0. For example, the particle size D50 of mica powder can be one of 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, and 10μm or any value that satisfies the above range. For example, the particle size D90 of mica powder can be one of 20μm, 19μm, 18μm, 17μm, 16μm, 15μm, 14μm, 13μm, 12μm, 11μm, 10μm, 9μm, 8μm, 7μm, 6μm, 5μm, 4μm, 3μm, 2μm, 1μm, 0.8μm, 0.5μm, 0.2μm, and 0.1μm or any value that satisfies the above range.

[0042] In some embodiments of this application, the diaphragm is a membrane material made by blending thermoplastic polyurethane and mica powder and then processing it. The mica powder accounts for 15wt% to 45wt% of the total mass of thermoplastic polyurethane and mica powder. The particle size D50 of the mica powder is 1μm to 10μm, and the particle size D90 is ≤20μm and not 0. The 3% secant modulus of the diaphragm is 20MPa to 80MPa.

[0043] In some embodiments of this application, the mica powder is a powdered product obtained from natural mineral mica through grinding, purification, and other processing. It is primarily a layered silicate with a crystal structure consisting of two silicon-oxygen tetrahedra sandwiching an aluminum-oxygen octahedron to form a complex silicon-oxygen layer. Its surface is rich in active functional groups such as hydrogen and carboxyl groups, allowing for substitution, oxidation, and reduction chemical reactions, resulting in excellent reinforcing effects. Simultaneously, the aluminum-oxygen bond (Al-O) has high bond energy and excellent chemical stability. When the mass fraction of aluminum in the system is controlled between 8% and 16%, the acid resistance, alkali resistance, and weather resistance of the prepared diaphragm reach their optimal levels. However, when the mass fraction of aluminum exceeds 16% or falls below 8%, its reinforcing effect significantly decreases, significantly affecting the physicochemical properties of the material.

[0044] When mica powder is added to a thermoplastic polyurethane system, the polar functional groups on the surface of the mica powder can form hydrogen bonds with urethane groups and other groups in the polyurethane molecular chain, resulting in uniform dispersion of the mica powder in the polymer matrix without agglomeration. When the polymer material is subjected to external force, the polymer chain segments can slide along the surface of the mica sheets and are not easily decoupled from the mica interface. The thermoplastic polyurethane matrix and the mica powder form a sliding and firmly bonded interface, significantly improving the overall mechanical strength of the diaphragm. For example, the mass percentage of aluminum in the mica powder can be one of 8%, 9%, 10%, 10.2%, 11%, 12%, 13%, 14%, 15%, or 16%, or any value within the above range.

[0045] In some embodiments of this application, the specific surface area of ​​the mica powder is ≥0.5m². 2 / g. It is understandable that the larger the specific surface area of ​​mica powder, the larger its contact interface with the thermoplastic polyurethane matrix, resulting in a more significant reinforcing and improving effect on the polymer material, and at the same time, better dispersion uniformity of the powder in the polymer material system. However, when the specific surface area of ​​mica powder is less than 0.5m², ... 2 When the specific surface area is 0.5 m² / g, the interfacial contact area is insufficient, resulting in poor reinforcement. Furthermore, the powder is prone to agglomeration and uneven dispersion, causing pitting, particle defects, and deterioration of thickness uniformity and appearance in the diaphragm material. For example, the specific surface area of ​​mica powder can be 0.5 m² / g. 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1m 2 / g or any value that satisfies the above range.

[0046] In some embodiments of this application, the aspect ratio of the mica powder is ≥10. The aspect ratio of mica powder is the ratio of the maximum length of the particle to its thickness. It is understood that the larger the aspect ratio of the mica powder, the more prominent its reinforcing effect on thermoplastic polyurethane, and the more significantly it can improve the flexural strength and impact strength of the polymer material. High aspect ratio sheet-like mica can construct a labyrinth barrier structure inside the polyurethane matrix, effectively blocking heat conduction and penetration, and improving the temperature stability of the polymer material; at the same time, sheet-like mica powder can enhance the entanglement between the polymer chains and the mica sheets, greatly improving the diaphragm damping performance. Exemplarily, the aspect ratio of the mica powder can be one of 10, 11, 12, 13, 14, 15, 20 or any value satisfying the above range.

[0047] In some embodiments of this application, the thermoplastic polyurethane base film (thermoplastic polyurethane) is composed of hard segments and soft segments. The soft segments impart good flexibility to the polymer material, giving it superior low-temperature resistance; the hard segments impart higher rigidity to the polymer material, giving it better heat resistance. The hard segments can be urethane (-NH-COO-) and / or urea bond (-NH-CO-NH-) segments formed by the reaction of diisocyanate with a small molecule chain extender, and the soft segments can be at least one of polyether polyol, polyester polyol, and polycarbonate polyol.

[0048] In the embodiments of this application, the hard segment accounts for ≤40 wt% of the mass of the thermoplastic polyurethane base film. It is understood that a higher proportion of hard segments results in a higher melting point, better high-temperature resistance of the film, and a lower risk of film breakage and aging in high-temperature reliability testing. However, a higher proportion of hard segments leads to a higher glass transition temperature and poorer low-temperature resistance. Therefore, it is necessary to control the mass ratio of hard and soft segments to balance high-temperature and low-temperature performance. In some embodiments of this application, the hard segment accounts for 15 wt% to 40 wt% of the mass of the thermoplastic polyurethane base film. For example, the hard segment percentage can be one of 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt%, 32 wt%, 35 wt%, 38 wt%, or 40 wt%, or any value within the above range.

[0049] In some embodiments of this application, the diisocyanate includes at least one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), tetramethylphenyl dimethylene diisocyanate (TMXDI), terephthalic diisocyanate (PPDI), naphthalene diisocyanate (NDI), and hydrogenated MDI (H12MDI).

[0050] In some embodiments of this application, the small molecule chain extender includes at least one of 1,4-butanediol (BDO), ethylene glycol (EG), diethylene glycol (DEG), neopentyl glycol (NPG), ethylenediamine (EDA), diethyltoluenediamine (DETDA), and 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA).

[0051] In some embodiments of this application, the glass transition temperature of the diaphragm is ≤-30℃. It is understood that a low glass transition temperature allows the polymer chain segments to move freely at low temperatures, maintaining the diaphragm's flexibility and elasticity, thus addressing the significant decrease in loudness at low temperatures. Simultaneously, the hydrogen bonding between the mica powder and the thermoplastic polyurethane matrix remains stable, resulting in good damping performance and effectively suppressing vibration polarization distortion, thus balancing wide-temperature acoustic stability and long-term mechanical durability. In some embodiments of this application, the glass transition temperature of the diaphragm is ≤-42℃. For example, the glass transition temperature of the diaphragm can be one of -30℃, -32℃, -35℃, -38℃, -39.8℃, -40℃, -42℃, -43.1℃, -43.3℃, ​​-43.4℃, -43.5℃, -43.6℃, ​​-43.7℃, -43.9℃, -45℃, -46.8℃, -48℃, -50℃, -51.2℃, -52℃, -55℃, and -57.3℃, or any value satisfying the above range.

[0052] In some embodiments of this application, the F0 ratio of the diaphragm under -20°C and 20°C conditions satisfies: ≤3.5. Among them, This indicates the resonant frequency of the diaphragm at -20℃. This represents the resonant frequency of the diaphragm at 20℃. It's understandable that the F0 ratio of the diaphragm at -20℃ and 20℃ is only related to the glass transition temperature of the polymer material. The glass transition temperature of the polymer material is affected by the hard and soft segments of the material. Since the ratio of the hard to soft segments of thermoplastic polyurethane is less than or equal to 40wt%, the prepared diaphragm has a low glass transition temperature, ensuring good flexibility even in extreme operating environments, guaranteeing normal product operation. As the glass transition temperature increases, the strength of the polymer material increases at low temperatures, and the F0 of the prepared diaphragm at -20℃ increases significantly. The larger the F0 ratio at -20℃ and 20℃, the lower the loudness of the product at low temperatures. When the F0 ratio of the diaphragm at -20℃ and 20℃ is ≤3.5, the variation in resonant frequency between high and low temperatures is small, the diaphragm has sufficient flexibility at low temperatures, and the loudness attenuation is slight; the membrane material damping is stable, effectively suppressing vibration polarization. When the F0 ratio of the diaphragm at -20℃ and 20℃ conditions is greater than 3.5, the low-temperature resonant frequency increases significantly, the diaphragm stiffness surges dramatically, and the output loudness decreases significantly; damping decreases, and the diaphragm is prone to polarization distortion. For example, the F0 ratio of the diaphragm at -20℃ and 20℃ conditions can be one of 3.5, 3.05, 3.02, 3.01, 3, 2.99, 2.98, 2.74, 2.5, 2.21, 2, 1.72, 1.5, or 1, or any value satisfying the above range.

[0053] In some embodiments of this application, the elongation at break of the diaphragm is ≥200%. It is understood that the higher the elongation at break of the diaphragm, the lower the likelihood of breakage due to polarization during use. When the elongation at break of the diaphragm is ≥200%, the diaphragm material has sufficient tensile deformation allowance, which can buffer the concentrated stress caused by diaphragm polarization, effectively reducing the probability of vibration-induced breakage; it exhibits excellent tear resistance and durability under high and low temperatures and high-power vibration, while the molding process is less prone to generating latent cracks, resulting in higher product reliability. Conversely, when the elongation at break of the diaphragm is <200%, the diaphragm material has insufficient tensile redundancy, making it difficult to buffer stress under polarized force, and it is extremely prone to tearing; it has poor tolerance to low temperatures and large amplitude conditions, and long-term vibration easily leads to cracking damage. In some embodiments of this application, the elongation at break of the diaphragm is ≥300%. For example, the elongation at break of the diaphragm can be one of 200%, 236.4%, 298.3%, 300%, 312.2%, 368.9%, 400%, 481.9%, 496.2%, 500%, 505.8%, 600%, 653.2%, 700%, 800%, 835.4%, 873.2%, 900%, 942.1%, 952.1%, 984.6%, 1000%, 1081.5%, 1100%, 1173.4%, 1200% or any value that satisfies the above range.

[0054] In some embodiments of this application, the melting point of the diaphragm is ≥150°C. It is understood that a higher proportion of hard segments results in a higher melting point, better high-temperature resistance of the membrane material, and a lower risk of membrane rupture and aging during high-temperature reliability testing. When the melting point of the diaphragm is ≥150°C, the membrane material exhibits excellent high-temperature resistance, is less prone to softening and creep at high temperatures, delays thermal aging, and reduces the risk of membrane rupture during high-temperature testing and high-power operation. Conversely, when the melting point of the diaphragm is <150°C, the membrane material is prone to softening and deformation under high-temperature conditions, resulting in significant attenuation of mechanical properties and easy cracking and rupture under vibration polarization. In some embodiments of this application, the melting point of the diaphragm is ≥155°C. For example, the melting point of the diaphragm can be one of 150℃, 152℃, 153.9℃, 155℃, 158℃, 160℃, 161.2℃, 162℃, 163.4℃, 165℃, 168.3℃, 168.4℃, 168.5℃, 168.6℃, 168.7℃, 168.8℃, 168.9℃, 170℃, and 180℃, or any value that satisfies the above range.

[0055] In some embodiments of this application, the damping factor of the diaphragm at 23°C is ≥0.05. It is understood that a higher room temperature (23°C) damping factor indicates better damping performance, better stability during vibration, and superior amplitude symmetry. This application adds mica powder to the diaphragm. Because the surface of mica powder is rich in oxygen-containing functional groups, when the material is subjected to shear, the mica powder can form hydrogen bonds with urethane bonds (-NH-COO-) and / or urea bonds (-NH1-CO-NHI-) in the polyurethane molecular chain. During the movement of the polymer chain segments, the internal frictional resistance between the matrix resin and the mica powder is significantly increased, thereby significantly optimizing the damping performance of the thermoplastic polyurethane material. In some embodiments of this application, the damping factor of the diaphragm at 23°C is ≥0.06. For example, the 23°C damping factor of the diaphragm can be one of 0.05, 0.06, 0.061, 0.069, 0.07, 0.075, 0.08, 0.082, 0.087, 0.09, 0.1, 0.102, 0.114, 0.123, 0.124, 0.125, 0.126, 0.135, 0.139 or any value that satisfies the above range.

[0056] In some embodiments of this application, the density of the diaphragm is ≤1.6 g / cm³. 3 It is understandable that increasing the amount of mica powder added to the system can improve the damping performance of the membrane material, but it also brings two negative effects: firstly, the toughness of the membrane material decreases, and secondly, the overall density of the membrane material increases. The mid-frequency (2000Hz~5000Hz) loudness of a sound-generating device is inversely proportional to the diaphragm mass; the higher the density of the membrane material, the greater the overall mass of the diaphragm of the same thickness, ultimately leading to a decrease in the mid-frequency loudness of the sound-generating device. To ensure a full and sufficient mid-frequency loudness, the diaphragm density must be controlled to ≤1.6g / cm³. 3 For example, the density of the diaphragm can be 1.6 g / cm³. 3 1.5g / cm 3 1.4g / cm 3 1.3g / cm 3 1.2g / cm 3 1.1g / cm 3 1g / cm 3 One of the above values ​​or any value that satisfies the above range.

[0057] In some embodiments of this application, the diaphragm thickness is 10 μm to 120 μm. It is understood that when the diaphragm thickness is within the 10 μm to 120 μm range, the mica powder is evenly dispersed, reducing the likelihood of molding defects such as pitting or excessive local thickness differences; furthermore, when the thickness is within this range, the overall mass of the diaphragm is moderate, ensuring full mid-frequency loudness while possessing sufficient mechanical toughness and damping performance. When the diaphragm thickness is less than 10 μm, the diaphragm's mechanical load-bearing capacity is weak, making it prone to tearing and rupture during vibration; when the diaphragm thickness is greater than 120 μm, it results in excessive diaphragm mass, causing mid-frequency loudness attenuation. In some embodiments of this application, the diaphragm thickness is 30 μm to 110 μm. For example, the thickness of the diaphragm can be one of 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm or any value that satisfies the above range.

[0058] In some embodiments of this application, the thickness tolerance of the diaphragm is ±5%. It is understood that by adjusting the proportion and particle size of the mica powder, on the one hand, a suitable amount of flake mica can stabilize the rheological properties of the polyurethane melt, reduce changes in the discharge flow rate caused by temperature and shear fluctuations, and at the same time, strictly control the particle size range to prevent local abrupt changes in thickness caused by large particle protrusions and filler agglomeration; on the other hand, uniformly dispersed flake mica forms a regular microscopic support skeleton inside the base film, balancing the tensile deformation and cooling shrinkage rates at various points during the hot pressing and shaping process of the diaphragm, avoiding further increases in thickness deviation in subsequent processing steps. Ultimately, the thickness fluctuation of the diaphragm can be limited to within ±5%, controlling the range of differences in diaphragm product quality and ensuring the uniformity of diaphragm thickness.

[0059] In some embodiments of this application, the diaphragm is formed as a composite layer structure, wherein the composite layer structure includes at least two membrane layers, each membrane layer comprising a thermoplastic polyurethane base film and mica powder dispersed within the thermoplastic polyurethane base film. It is understood that the diaphragm of the composite layer structure contains at least two membrane layers, each membrane layer being formed by blending thermoplastic polyurethane containing urethane bonds (-NH-COO-) and / or urea bonds (-NH-CO-NH-) with mica powder. In some embodiments of this application, the two or more membrane layers are stacked.

[0060] In some embodiments of this application, the diaphragm is formed as a composite layer structure, wherein the composite layer structure includes a membrane material and a composite connecting layer, the composite connecting layer and the membrane material are stacked together, the membrane material includes a thermoplastic polyurethane base film and mica powder dispersed in the thermoplastic polyurethane base film, and the composite connecting layer can be at least one of a polyacrylate film layer, a polyethylene-acrylate film layer, and an organosilicon pressure-sensitive adhesive layer.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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; the amounts of experimental reagents used are, unless otherwise specified, the amounts used in conventional experimental operations; and the experimental methods used are, unless otherwise specified, conventional methods. It should be further noted that the following descriptions are merely exemplary and not intended to limit the scope of this application. Moreover, the comparative examples below are selected to compare with the technical solutions of this application to demonstrate the advancement of the technical solutions of this application, and do not necessarily represent prior art in this technical field.

[0066] Example 1 This embodiment 1 provides a diaphragm for a sound-generating device. The diaphragm is formed by blending thermoplastic polyurethane containing urethane bonds (-NH-COO-) and urea bonds (-NH-CO-NH-) with mica powder under shear force, and then processing the resulting film material. The film thickness is 55 μm. The thermoplastic polyurethane consists of hard segments and soft segments. The hard segments are toluene diisocyanate (TDI) and 1,4-butanediol (BDO), and the soft segments are polyester polyols. The hard segments account for 30 wt% of the mass of the thermoplastic polyurethane base film. The mica powder accounts for 40 wt% of the total mass of the thermoplastic polyurethane and mica powder. The aluminum element in the mica powder accounts for 10.2 wt% of the mica powder mass. The mica powder has an aspect ratio of 20 and a specific surface area of ​​20.3 μm. 2 / g, the particle size D50 of the mica powder is 5.3μm and the particle size D90 is 11.2μm.

[0067] Performance testing 1.3% secant modulus test.

[0068] According to ASTM D882 standard, the width is 20mm, the clamp spacing is 30mm, the tensile rate is 300mm / min, and the preload force is 0.1N. Five samples were taken, with a sample width of 15mm.

[0069] The ratio of stress to strain at 3% strain in a test sample is the 3% secant modulus, denoted as 3% secant modulus = .

[0070] 2. Room temperature damping 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] 3. Melting point test.

[0073] According to GB / T 19466.2-2004 standard, the test temperature is -80℃ to 220℃, the heating rate is 20℃ / min, and the peak position of the melting range is taken as the melting point of the sample.

[0074] 4. Glass transition temperature test.

[0075] According to GB / T 19466.2-2004 standard, the test temperature is -80℃ to 220℃, the heating rate is 20℃ / min, and the glass transition temperature is determined using the half-height method.

[0076] 5. Elongation at break test.

[0077] According to ASTM D882 standard, the tensile rate is 300 mm / min, the gauge length is 30 mm, the temperature is 23℃±2℃, and the humidity is 50%RH±10%RH.

[0078] 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.

[0079] The resonant frequency F0 of the miniature loudspeaker assembled using the diaphragm in Example 1 is 851Hz, and its six-point amplitude is as follows: Figure 1 As shown.

[0080] Example 2 The only difference between Example 2 and Example 1 is that the mica powder accounts for 15 wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 1.

[0081] Example 3 The only difference between Example 3 and Example 1 is that the mica powder accounts for 30 wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 1.

[0082] Example 4 The only difference between Example 4 and Example 1 is that the mica powder accounts for 45 wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 1.

[0083] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that mica powder was not added. All other preparation and testing methods were the same as in Example 1, and the test results are summarized in Table 1.

[0084] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the mica powder accounts for 10 wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The rest of the preparation and testing methods are the same as those in Example 1, and the test results are summarized in Table 1.

[0085] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the mica powder accounts for 50 wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The rest of the preparation and testing methods are the same as those in Example 1, and the test results are summarized in Table 1.

[0086] Comparative Example 4 In Comparative Example 4, except that the mica powder had a particle size D50 of 12 μm and a particle size D90 of 50 μm, the same preparation and testing methods as in Example 1 were used, and the test results are summarized in Table 1.

[0087] Comparative Example 5 In Comparative Example 5, except that the mica powder had a particle size D50 of 12 μm, a particle size D90 of 50 μm, an aluminum content of 20.6 wt%, and an aspect ratio of 3, it was prepared and tested using the same methods as in Example 1, and the test results are summarized in Table 1.

[0088] Table 1

[0089] As can be seen from the test results in Table 1, as the mica powder content increases, its room temperature damping factor gradually increases, but its elongation at break decreases significantly. In particular, when the mica powder content exceeds 50%, its elongation at break is less than 200%, and its Young's modulus is relatively high. When preparing products with the same performance, a thinner diaphragm strip needs to be used, which will cause two problems: first, when the elongation at break is too low, the prepared diaphragm is prone to breakage during vibration; second, the thinner the diaphragm, the poorer the chemical resistance of the product, and the risk of corrosion and embrittlement.

[0090] pass Figure 2 and Figure 3 It can be seen that the diaphragm consistency in Example 1 is significantly better than that in Comparative Example 1 without the addition of mica powder. Moreover, in Comparative Example 1, a diaphragm strip with a thickness of 96 μm is required to ensure that the F0 of the obtained miniature loudspeaker is 853 Hz. Due to the low damping, the amplitude symmetry in Comparative Example 1 is significantly worse than that of the embodiment of this application.

[0091] In Comparative Example 5, due to the high aluminum content of mica powder, its aspect ratio of 3, and its particle size D90 of up to 50 μm, the mica powder is incompatible with thermoplastic polyurethane. It appears significantly on the surface of the polymer film and forms local agglomerates, which has a limited effect on improving the damping performance of the material. At the same time, due to the presence of a large number of defects, the elongation at break and modulus of the material are low, which does not meet the requirements for the use of the diaphragm.

[0092] In Comparative Example 4, due to the particle size D90 being as high as 50 μm, the sheet size is too large, the defects between the polymer and the sheet increase, the elongation at break decreases significantly, and the mechanical toughness is significantly reduced.

[0093] Example 5 The only difference between Example 5 and Example 1 is that the mass percentage of the hard segment in the thermoplastic polyurethane is 5 wt%. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 2.

[0094] Example 6 The only difference between Example 6 and Example 1 is that the mass percentage of the hard segment in the thermoplastic polyurethane is 15 wt%. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 2.

[0095] Example 7 The only difference between Example 7 and Example 1 is that the mass percentage of the hard segment in the thermoplastic polyurethane is 25 wt%. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 2.

[0096] Example 8 The only difference between Example 8 and Example 1 is that the mass percentage of the hard segment in the thermoplastic polyurethane is 35 wt%. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 2.

[0097] Example 9 The only difference between Example 9 and Example 1 is that the mass percentage of the hard segment in the thermoplastic polyurethane is 45 wt%. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 2.

[0098] Table 2

[0099] As can be seen from the test results in Table 2, the higher the proportion of hard segments, the higher the melting point, the better the high-temperature resistance of the material, and the lower the risk of diaphragm breakage and aging in high-temperature reliability. However, since the higher the proportion of hardness, the higher the glass transition temperature of the material, the worse the low-temperature resistance of the material. Therefore, it is necessary to control the proportion of hardness and soft segments to balance high-temperature and low-temperature resistance.

[0100] Meanwhile, as the glass transition temperature increases, the strength of the film material increases at low temperatures, and the F0 of the prepared diaphragm increases significantly at -20℃. The larger the F0@-20℃ / F0@20℃, the smaller the loudness of the product at low temperatures.

[0101] Example 10 The only difference between Example 10 and Example 1 is that the aluminum content in the mica powder is 8 wt% and the aspect ratio of the mica powder is 20. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 3.

[0102] Example 11 The only difference between Example 11 and Example 1 is that the aluminum content in the mica powder is 16 wt% and the aspect ratio of the mica powder is 20. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 3.

[0103] Example 12 The only difference between Example 12 and Example 1 is that the aluminum content in the mica powder is 7 wt% and the aspect ratio of the mica powder is 20. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 3.

[0104] Example 13 The only difference between Example 13 and Example 1 is that the aluminum content in the mica powder is 20.6 wt% and the aspect ratio of the mica powder is 20. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 3.

[0105] Example 14 The only difference between Example 14 and Example 1 is that the aluminum content in the mica powder is 20.6 wt% and the aspect ratio of the mica powder is 3. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 3.

[0106] Table 3

[0107] According to the test results in Table 3, when the aluminum content is between 8% and 16%, the elongation at break, secant modulus, and damping factor remain relatively stable due to the high and stable reinforcing effect of mica powder. However, when the aluminum content exceeds or falls below this value, the reinforcing effect decreases significantly, which significantly affects the physical and chemical properties of the material. Furthermore, when the aspect ratio of mica is 3, it cannot significantly increase the entanglement between the polymer and mica in thermoplastic polyurethane, resulting in poor damping enhancement effect.

[0108] Example 15 The only difference between Example 15 and Example 1 is that the aspect ratio of the mica powder is 5. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 4.

[0109] Example 16 The only difference between Example 16 and Example 1 is that the aspect ratio of the mica powder is 10. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 4.

[0110] Example 17 The only difference between Example 17 and Example 1 is that the aspect ratio of the mica powder is 25. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 4.

[0111] Example 18 The only difference between Example 18 and Example 1 is that the aspect ratio of the mica powder is 50. The rest of the preparation and testing methods are the same as in Example 1, and the test results are summarized in Table 4.

[0112] Table 4

[0113] As shown in Table 4, the larger the aspect ratio, the better the reinforcing effect of mica powder in polymer materials, which can effectively improve the bending and impact resistance of the diaphragm. High aspect ratio sheet-like mica can form a "maze effect" in thermoplastic polyurethane, effectively blocking heat conduction and penetration, thereby improving the temperature stability of the membrane material. At the same time, it increases the entanglement between polymer chains and mica, which can significantly improve the damping performance of the diaphragm.

[0114] In this embodiment, mica powder (addition amount ≥15wt%) is added to the polyurethane system. By controlling the elemental composition, particle size, and specific surface area of ​​the mica powder, the mica powder is uniformly dispersed in the polyurethane system. This significantly increases the frictional resistance between the polymer chains and the mica powder during movement, improves the damping performance, and reduces the glass transition temperature of the membrane material by adjusting the ratio of soft and hard segments in the polyurethane, thus preparing a diaphragm with better low-temperature resistance.

[0115] 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 a thermoplastic polyurethane base film and mica powder dispersed within the thermoplastic polyurethane base film. The mica powder accounts for 15wt% to 45wt% of the total mass of the thermoplastic polyurethane base film and the mica powder. The mica powder has a particle size D50 of 1μm to 10μm and a particle size D90 ≤ 20μm and not equal to 0; the 3% secant modulus of the diaphragm is 20MPa to 80MPa.

2. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The specific surface area of ​​the mica powder is ≥0.5m². 2 / g, and / or, the aspect ratio of the mica powder is ≥10.

3. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The aluminum element in the mica powder accounts for 8% to 16% of the mass of the mica powder.

4. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The thermoplastic polyurethane-based film is composed of hard segments and soft segments. The hard segment is a carbamate and / or urea bond segment formed by the reaction of diisocyanate with a small molecule chain extender. The soft segment is at least one of polyether polyol, polyester polyol, and polycarbonate polyol; And / or, the hard segment accounts for ≤40wt% of the mass of the thermoplastic polyurethane base film.

5. The diaphragm for a sound-generating device as described in claim 4, characterized in that, The diisocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethylphenyl diisocyanate, terephthalic diisocyanate, naphthalene diisocyanate, and hydrogenated MDI. The small molecule chain extender includes at least one of 1,4-butanediol, ethylene glycol, diethylene glycol, neopentyl glycol, ethylenediamine, diethyltoluenediamine, and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

6. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The elongation at break of the diaphragm is ≥200%; And / or, the diaphragm's 23°C damping factor is ≥0.05; And / or, the melting point of the diaphragm is ≥150°C.

7. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The thickness of the diaphragm is 10μm~120μm; And / or, the thickness tolerance of the diaphragm is ±5%; And / or, the density of the diaphragm is ≤1.6 g / cm³. 3 .

8. The diaphragm for a sound-generating device as described in claim 1, characterized in that, The F0 ratio of the diaphragm under -20℃ and 20℃ conditions satisfies: ≤3.5; where, This indicates the resonant frequency of the diaphragm at -20℃. This indicates the resonant frequency of the diaphragm at 20℃. And / or, the glass transition temperature of the diaphragm is ≤-30°C.

9. 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 two membrane layers, each of which includes a thermoplastic polyurethane base film and mica powder dispersed within the thermoplastic polyurethane base film. And / or, the composite layer structure includes a membrane material and a composite connecting layer, wherein the composite connecting layer is stacked with the membrane material, the membrane material includes a thermoplastic polyurethane base film and mica powder dispersed in the thermoplastic polyurethane base film, and the composite connecting layer is at least one of a polyacrylate film layer, a polyethylene-acrylate film layer, and an organosilicon pressure-sensitive adhesive layer.

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

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

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