Sound production device and magnetic circuit system, magnetically conductive thermosetting adhesive and preparation method and application

Abstract

This application belongs to the field of electroacoustic technology, and specifically relates to a sound-generating device and magnetic circuit system, a magnetically conductive thermosetting adhesive, its preparation method, and its application. The magnetically conductive thermosetting adhesive includes a thermosetting adhesive and a magnetically conductive filler dispersed within the thermosetting adhesive. The magnetically conductive filler has a core-shell structure, including a magnetic material and an anti-corrosion layer covering the outer side of the magnetic material. The ratio of the thickness of the anti-corrosion layer to the particle size of the magnetic material is (0.01~0.1):(1~10). The magnetically conductive thermosetting adhesive provided by this application can effectively prevent the filler at the bonding edge from directly contacting air and moisture, fundamentally inhibiting micro-battery corrosion and significantly improving the environmental reliability of the sound-generating device under harsh operating conditions such as high-temperature and high-humidity storage and high-temperature and high-humidity power-on. Simultaneously, it possesses excellent high magnetic permeability, ensuring the magnetic flux conduction efficiency and acoustic performance of the magnetic circuit.

Description

Technical Field

[0001] This application belongs to the field of electroacoustic technology, and specifically relates to a sound-generating device and magnetic circuit system, a magnetically conductive thermosetting adhesive and its preparation method and application. Background Technology

[0002] In the field of loudspeaker design and manufacturing, the magnetic conductivity of the magnetic circuit system directly determines the overall acoustic performance of the speaker. Generally, the better the magnetic conductivity of the magnetic circuit, the more guaranteed the loudness and sound purity of the speaker's output. Therefore, the industry has placed higher demands on the magnetic flux conduction capabilities of magnetic circuit structural components such as magnets, magnetic yokes, and magnetic plates.

[0003] With the continuous trend towards thinner and smaller electronic products, adhesive bonding has become the mainstream connection method for speaker magnetic circuit components due to its advantages of small space occupation and simple assembly process. Miniature speaker magnetic circuit components use less adhesive, with an adhesive layer thickness of only 5 μm to 15 μm. However, the magnetic fillers in conventional magnetic adhesives are prone to agglomeration and sedimentation, easily causing the magnetic fillers at the bonding interface edges to be exposed and not completely covered by the adhesive layer. Therefore, under reliability testing conditions such as salt spray, high temperature and high humidity, the exposed fillers are prone to forming micro-battery effects at the bonding edges, accelerating interface corrosion failure, damaging the stability of the magnetic circuit bonding structure, and affecting acoustic performance.

[0004] Therefore, existing loudspeakers and the adhesive materials used with them still need improvement. Summary of the Invention

[0005] The purpose of this application is to provide a sound-generating device and magnetic circuit system, a magnetic thermosetting adhesive, its preparation method, and its application. The magnetic thermosetting adhesive provided in this application includes a magnetic filler comprising a magnetic material and an anti-corrosion layer covering the outside of the magnetic material. This effectively prevents the filler at the bonding edge from directly contacting air and moisture, thereby suppressing micro-battery corrosion from the source and significantly improving the environmental reliability of the sound-generating device under harsh conditions such as high-temperature and high-humidity storage and high-temperature and high-humidity power-on. At the same time, it also has excellent high magnetic permeability, ensuring the magnetic flux conduction efficiency and acoustic performance of the magnetic circuit.

[0006] The first aspect of this application provides a magnetic thermosetting adhesive, which includes a thermosetting adhesive and a magnetic filler dispersed in the thermosetting adhesive. The magnetic filler has a core-shell structure and includes a magnetic material and an anti-corrosion layer covering the outside of the magnetic material. The ratio of the thickness of the anti-corrosion layer to the particle size of the magnetic material is (0.01~0.1):(1~10).

[0007] In some embodiments of this application, the thickness of the anti-corrosion layer is 20 nm to 100 nm.

[0008] In some embodiments of this application, the particle size of the magnetic material is ≤5 μm and not 0.

[0009] In some embodiments of this application, the magnetic material includes at least one of pure iron, iron-nickel alloy, and iron-cobalt alloy.

[0010] In some embodiments of this application, the material of the anti-corrosion layer includes one of organic resin and inorganic filler.

[0011] In some embodiments of this application, the organic resin includes at least one of organosilicon-modified resin, epoxy resin, polyimide resin, and phenolic resin.

[0012] In some embodiments of this application, the inorganic filler includes silicon dioxide.

[0013] In some embodiments of this application, the particle size of the magnetic filler is ≤6 μm and not 0.

[0014] In some embodiments of this application, the specific saturation magnetization of the magnetic filler is 46 emu / g to 230 emu / g.

[0015] In some embodiments of this application, the thermosetting adhesive includes at least one of acrylate thermosetting adhesive, epoxy thermosetting adhesive, and anaerobic thermosetting adhesive.

[0016] In some embodiments of this application, the magnetically conductive thermosetting adhesive comprises the following components in parts by weight: 10-50 parts of magnetic filler and 50-90 parts of thermosetting adhesive.

[0017] In some embodiments of this application, the tensile strength of the magnetic thermosetting adhesive is ≥20 MPa.

[0018] In some embodiments of this application, the specific saturation magnetization of the magnetic thermosetting adhesive is ≥50 emu / g.

[0019] The second aspect of this application also provides a method for preparing the magnetic thermosetting adhesive described in the first aspect of this application, comprising the following steps: obtaining a magnetic filler and a thermosetting adhesive; the magnetic filler has a core-shell structure, including a magnetic material and an anti-corrosion layer covering the outside of the magnetic material; the ratio of the thickness of the anti-corrosion layer to the particle size of the magnetic material is (0.01~0.1):(1~10); mixing and stirring the magnetic filler and the thermosetting adhesive to obtain the magnetic thermosetting adhesive.

[0020] The third aspect of this application also provides the application of the magnetic thermosetting adhesive described in the first aspect or the magnetic thermosetting adhesive prepared by the preparation method described in the second aspect in the bonding of magnetic circuit components of a miniature loudspeaker, wherein the bonding strength of the magnetic circuit components bonded by the magnetic thermosetting adhesive is ≥1700 N.

[0021] In some embodiments of this application, magnetic circuit components bonded with the high-permeability thermosetting adhesive exhibit a bonding strength ≥1200 N after being stored in an environment of 80°C and 95%RH for 72 hours.

[0022] A fourth aspect of this application also provides a magnetic circuit system for a sound-generating device, comprising a magnetic yoke and a magnetic circuit assembly disposed on one side of the magnetic yoke. The magnetic circuit assembly includes a magnet and a magnetic plate, and the magnetic yoke, the magnet, and the magnetic plate are sequentially stacked along a first direction. The magnetic yoke and the magnet, and / or the magnet and the magnetic plate, are provided with the magnetic thermosetting adhesive described in the first aspect of this application, or with a magnetic thermosetting adhesive prepared using the preparation method described in the second aspect of this application.

[0023] In some embodiments of this application, the magnet includes a central magnet and side magnets spaced apart, and the magnetic guide plate includes a central magnetic guide plate and side magnetic guide plates. The central magnet and the central magnetic guide plate constitute a central magnetic part, and the side magnets and the side magnetic guide plates constitute a side magnetic part. The magnetic yoke, the central magnet, and the central magnetic guide plate are sequentially stacked along a first direction, and the central magnet and the magnetic yoke, and / or the central magnet and the central magnetic guide plate, are bonded together by the magnetic thermosetting adhesive.

[0024] In some embodiments of this application, the magnetic yoke, the side magnet, and the side magnetic plate are stacked sequentially along a first direction, and the side magnet and the magnetic yoke and / or the side magnet and the side magnetic plate are bonded together by the magnetic thermosetting adhesive.

[0025] The fifth aspect of this application also provides a sound-generating device, which includes the magnetic circuit system for the sound-generating device described in the fourth aspect of this application.

[0026] The magnetic thermosetting adhesive provided in this application adopts a composite magnetic filler structure of magnetic material + outer anti-corrosion insulating coating layer, which can effectively avoid direct contact between the filler at the bonding edge and air and moisture, suppress micro-battery corrosion from the source, and greatly improve the environmental reliability of the speaker under harsh conditions such as high temperature and high humidity storage and high temperature and high humidity power-on; at the same time, it also has excellent high magnetic permeability, ensuring magnetic circuit flux conduction efficiency and acoustic performance.

[0027] 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

[0028] 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.

[0029] Figure 1 This is a schematic diagram of the structure of a sound-generating device according to some embodiments of this application; Figure 2 The frequency response curves of the loudspeakers in Embodiment 1 and Comparative Examples 1 to 2 of this application are shown.

[0030] Explanation of reference numerals in the attached figures: 100 - Sound-generating device; 10-Housing; 20-Diaphragm assembly; 30-Magnetic yoke; 40-Center magnet; 50-Side magnet; 60-Center magnetic plate; 70-Side magnetic plate; 80-Magnetic thermosetting adhesive; 90-Voice coil. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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).

[0037] The first aspect of this application provides a magnetic thermosetting adhesive, which includes a thermosetting adhesive and a magnetic filler dispersed in the thermosetting adhesive. The magnetic filler has a core-shell structure and includes a magnetic material and an anti-corrosion layer covering the outside of the magnetic material. The ratio of the thickness of the anti-corrosion layer to the particle size of the magnetic material is (0.01~0.1):(1~10).

[0038] In the embodiments of this application, the magnetic thermosetting adhesive includes a thermosetting adhesive and a magnetic filler dispersed within the thermosetting adhesive. The ratio of the anti-corrosion layer thickness to the magnetic material particle size in the magnetic filler is (0.01~0.1):(1~10), which makes the magnetic thermosetting adhesive possess high magnetic permeability, excellent mechanical strength, and environmental reliability. It can be adapted to the bonding conditions of thin adhesive layers for small-volume components in sound-generating devices (such as miniature loudspeakers). Traditional magnetic adhesives are prone to the drawback of the magnetic filler being exposed to the air at the bonding edges, which leads to a decrease in the environmental reliability of the product. At the same time, because the magnetic material is completely covered by the insulating layer, direct contact between magnetic material particles can be avoided, effectively reducing the eddy current loss generated under the action of the external magnetic field. The extremely low eddy current loss can increase the high-frequency loudness of the sound-generating device by at least 0.05 dB under the same input power conditions. In terms of environmental resistance and drop resistance, after being stored at constant temperature and humidity of 80℃ and 95% RH for 72 hours, the sound-generating device using the magnetic thermosetting adhesive provided in this application can pass the 108-times directional drop test of 1.8 m, which fully ensures the environmental tolerance and drop resistance safety margin of the entire sound-generating device.

[0039] In some embodiments of this application, the thickness of the anti-corrosion layer is 20 nm to 100 nm. It is understood that, firstly, the coating process for an anti-corrosion layer with a thickness less than 20 nm is extremely difficult to achieve; secondly, an excessively thin anti-corrosion layer is prone to incomplete coating and the presence of micropores, making it difficult to effectively block the conductive pathways between magnetic material particles, which is detrimental to reducing eddy current losses and reduces acoustic performance and environmental reliability; while if the thickness of the anti-corrosion layer is greater than 100 nm, the excessive thickness will increase the magnetic resistance between particles, weaken the overall magnetic permeability, and hinder the smooth transmission of magnetic flux. Exemplarily, the thickness of the anti-corrosion layer can be one of 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, and 100 nm, or any value satisfying the above range.

[0040] In some embodiments of this application, the particle size of the magnetic material is ≤5 μm and not 0. It is understood that when the particle size of the magnetic material is controlled within the range of ≤5 μm, the particle size is small and uniform, allowing for good dispersion in thermosetting adhesives. This prevents agglomeration and sedimentation, making it suitable for bonding ultra-thin adhesive layers of 5 μm to 15 μm in miniature loudspeakers. It can be completely covered by an insulating and anti-corrosion layer, preventing exposed filler at the bonding edges and ensuring corrosion resistance reliability in high-temperature, high-humidity, and salt spray environments. When the particle size of the magnetic material is greater than 5 μm, the larger particles are prone to uneven distribution and defects at the bonding interface in the thin adhesive layer. This not only easily leads to incomplete material coverage and edge corrosion, but also disrupts the continuity of the magnetic network, increases magnetic reluctance and eddy current losses, and affects bonding smoothness and structural toughness, reducing drop resistance and environmental reliability. For example, the particle size of the magnetic material can be one of 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value that satisfies the above range.

[0041] By adjusting the thickness of the anti-corrosion layer and the particle size of the magnetic material within the aforementioned range, a complete and dense insulating protective coating can be formed on the magnetic material, effectively isolating it from air, moisture, and salt spray corrosion, preventing micro-battery corrosion caused by exposed magnetic materials, and ensuring the reliability of the product in high-temperature and high-humidity environments. At the same time, it can also prevent direct contact between magnetic material particles, significantly reducing eddy current losses under the action of a magnetic field, ensuring that the high-frequency loudness of the sound-generating device is improved by at least 0.05 dB, without affecting the magnetic conductivity of the magnetic filler itself. It is compatible with the thin adhesive layer bonding process of micro loudspeakers and meets the product's requirements for mechanical strength and drop resistance.

[0042] In some embodiments of this application, the magnetic material includes at least one of pure iron, iron-nickel alloy, and iron-cobalt alloy.

[0043] In some embodiments of this application, the material of the anti-corrosion layer includes one of organic resin and inorganic filler.

[0044] In some embodiments of this application, the organic resin includes at least one of organosilicon-modified resin, epoxy resin, polyimide resin, and phenolic resin.

[0045] In some embodiments of this application, the inorganic filler includes silicon dioxide.

[0046] By making appropriate choices of magnetic materials and anti-corrosion layer materials, it is possible to further form a complete and dense coating of magnetic materials, avoid micro-battery corrosion caused by exposed magnetic materials, block direct contact between magnetic material particles, and significantly reduce eddy current losses under the action of magnetic field.

[0047] In some embodiments of this application, the magnetic filler includes a magnetic material and an epoxy resin anti-corrosion layer covering the outside of the magnetic material. The preparation process of the magnetic filler includes: mixing the cleaned magnetic material with epoxy resin and curing agent in acetone, and obtaining the coating material after the solvent evaporates; then baking the coating material in an environment of 100℃~150℃ for 25 min to obtain the magnetic filler, wherein the particle size of the magnetic filler is ≤6 μm.

[0048] In some embodiments of this application, the curing agent includes one of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), ethoxylated trimethylolpropane tri(3-mercaptopropionate), and diethylamine.

[0049] In some embodiments of this application, the particle size of the magnetic filler is ≤6 μm and not 0. It is understood that a particle size of ≤6 μm allows the magnetic filler to be suitable for bonding ultra-thin adhesive layers of 5 μm to 15 μm in miniature loudspeakers. However, when the particle size of the magnetic filler is greater than 6 μm, the particle size is too large and difficult to adapt to ultra-thin adhesive layer conditions, easily leading to incomplete coating, exposed edges and corrosion problems. It also disrupts the continuity of the magnetic path, increases magnetic reluctance and eddy current loss, and affects bonding smoothness and drop resistance. For example, the particle size of the magnetic filler can be one of 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or any value satisfying the above range.

[0050] In some embodiments of this application, the specific saturation magnetization of the magnetic filler is 46 emu / g to 230 emu / g. It is understood that a moderate specific saturation magnetization can endow the magnetic filler with excellent magnetic permeability, smoothly constructing a magnetic flux conduction path. Combined with a surface anti-corrosion layer, it can prevent direct contact between particles, significantly reducing eddy current losses under an applied magnetic field. The specific saturation magnetization of pure nickel powder with an anti-corrosion layer is approximately 46 emu / g. After being mixed with a binder, its specific saturation magnetization per unit mass decreases. At this point, its own magnetic carrying capacity is insufficient, its magnetization response is weak, and it cannot effectively converge and disperse magnetic lines of force, making it difficult to reduce the magnetic reluctance at the magnetic circuit interface and achieve the effect of increasing the magnetic flux density of the magnetic circuit. The specific saturation magnetization of ferromagnetic powder after resin coating is approximately 230 emu / g. Therefore, theoretically, increasing the amount of ferromagnetic powder added is beneficial to magnetic permeability, better meeting the product's requirements for high magnetic permeability and low loss. For example, the specific saturation magnetization of the magnetic filler can be one of 46 emu / g, 50 emu / g, 55 emu / g, 60 emu / g, 65 emu / g, 70 emu / g, 75 emu / g, 80 emu / g, 85 emu / g, 90 emu / g, 95 emu / g, 100 emu / g, 110 emu / g, 120 emu / g, 130 emu / g, 140 emu / g, 150 emu / g, 160 emu / g, 170 emu / g, 180 emu / g, 190 emu / g, 200 emu / g, 210 emu / g, 220 emu / g, 230 emu / g, or any value satisfying the above range.

[0051] In some embodiments of this application, the thermosetting adhesive includes at least one of acrylate thermosetting adhesive, epoxy thermosetting adhesive, and anaerobic thermosetting adhesive.

[0052] Thermosetting adhesives can be selected from any of the following types based on their curing method: acrylic thermosetting adhesives, epoxy thermosetting adhesives, and anaerobic thermosetting adhesives. Specifically, in practical applications, the appropriate type of adhesive can be selected based on the product reliability requirements of different magnetic circuit bonding positions in the sound-generating device. For example, the central magnet has a large bonding area and high weight, and its drop resistance requirements are more stringent during use; therefore, an acrylic thermosetting adhesive or an anaerobic thermosetting adhesive with excellent elongation at break is chosen. Conversely, the side magnets have a smaller effective bonding area and are subject to the lateral attraction of the central magnet, requiring higher bonding strength; therefore, an epoxy thermosetting adhesive with superior bonding performance is chosen for the side magnets.

[0053] In some embodiments of this application, the thermosetting adhesive is an acrylate thermosetting adhesive, which comprises the following components in parts by weight: 70 parts of acrylate oligomer, 30 parts of acrylate monomer, 5 parts of thermal initiator, and 0.5 parts of curing agent.

[0054] In embodiments of this application, the acrylate oligomer includes polyurethane acrylate oligomers.

[0055] In embodiments of this application, the acrylate monomers include a mixture of 4-hexanediol morpholine, hexanediol diacrylate, acrylic acid, and hydroxyethyl methacrylate.

[0056] In embodiments of this application, the thermal initiator includes at least one of azobisisobutyronitrile, cumene hydroperoxide, and benzoyl peroxide.

[0057] In the embodiments of this application, the curing agent is an acrylate monomer carrying special functional groups in the resin, which undergoes a chemical reaction during the reaction process to achieve further cross-linking of the resin network.

[0058] In some embodiments of this application, the thermosetting adhesive is an epoxy thermosetting adhesive, which comprises the following components by weight: 100 parts of bisphenol A type epoxy resin, 64 parts of curing agent, 3 parts of accelerator, 1 part of thixotropic agent, and 1 part of antioxidant.

[0059] In embodiments of this application, the curing agent includes one of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), and ethoxylated trimethylolpropane tri(3-mercaptopropionate).

[0060] In the embodiments of this application, the accelerator includes one of DMP-30, triethylamine, and dimethylbenzylamine.

[0061] In embodiments of this application, the thixotropic agent comprises nanoscale fumed silica.

[0062] In embodiments of this application, the antioxidant includes antioxidant 1010.

[0063] In some embodiments of this application, the magnetically conductive thermosetting adhesive comprises the following components in parts by weight: 10-50 parts of magnetic filler and 50-90 parts of thermosetting adhesive.

[0064] The magnetic filler provided in this application embodiment is in the range of 10 to 50 parts by weight. It is understood that if the magnetic filler is less than 10 parts by weight, the addition amount is too low, making it difficult to form a continuous and effective magnetic path and failing to achieve a significant magnetic conduction effect. Conversely, if the magnetic filler exceeds 50 parts by weight, it will significantly increase the viscosity of the adhesive body. Since magnetic circuit assembly often uses needle dispensing technology, excessively high viscosity can easily cause poor dispensing and uneven dispensing. Forcibly increasing the dispensing air pressure can also easily lead to the problem of the dispensing tube cracking under pressure, affecting normal production operations. For example, the weight of the magnetic filler can be one of 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts, or any value within the above range.

[0065] The thermosetting adhesive provided in this application embodiment has a weight percentage of 50 to 90 parts. It is understood that if the weight percentage of the thermosetting adhesive is less than 50 parts, the resin matrix proportion is insufficient, making it difficult to form a complete and dense adhesive layer, which leads to a decrease in bond strength, toughness, and environmental resistance. Conversely, if the weight percentage of the thermosetting adhesive is greater than 90 parts, the resin matrix proportion is too high, the magnetic filler proportion is excessively diluted, making it difficult to construct a continuous and stable magnetic conductive path, and thus difficult to improve the acoustic performance of the sound-generating device. Exemplarily, the weight percentage of the thermosetting adhesive can be one of 50, 55, 60, 65, 70, 75, 80, 85, or 90 parts, or any value within the above range.

[0066] In some embodiments of this application, the tensile strength of the magnetic thermosetting adhesive is ≥20 MPa. It is understood that if the tensile strength of the magnetic thermosetting adhesive is less than 20 MPa, the adhesive's bonding and holding capacity is insufficient, and it is prone to loosening and delamination under vibration and lateral magnetic forces, damaging the integrity of the magnetic circuit structure and affecting acoustic performance. Exemplarily, the tensile strength of the magnetic thermosetting adhesive can be one of 20 MPa, 22 MPa, 24 MPa, 25 MPa, 26 MPa, 27 MPa, 28 MPa, or 30 MPa, or any value satisfying the above range.

[0067] In some embodiments of this application, the specific saturation magnetization of the magnetic thermosetting adhesive is ≥50 emu / g. It is understood that when the specific saturation magnetization of the magnetic thermosetting adhesive is below 50 emu / g, the overall magnetic permeability of the adhesive is weak, making it difficult to effectively increase the magnetic flux density of the magnetic circuit, increasing eddy current losses, significantly weakening the acoustic gain of the sound-generating device, and failing to meet the design and usage requirements of thin and light miniature loudspeaker magnetic circuits. For example, the specific saturation magnetization of the magnetic thermosetting adhesive can be one of 50 emu / g, 60 emu / g, 70 emu / g, 80 emu / g, 90 emu / g, 100 emu / g, 110 emu / g, 120 emu / g, 130 emu / g, 140 emu / g, 150 emu / g, 160 emu / g, 170 emu / g, 180 emu / g, 190 emu / g, 200 emu / g, or any value satisfying the above range.

[0068] By designing tensile strength and specific saturation magnetization within the aforementioned range, the magnetic thermosetting adhesive possesses sufficient mechanical bonding strength to firmly adhere to magnetic circuit components such as speaker magnets, magnetic yokes, and magnetic plates, and can withstand vibration, temperature changes, and drop impacts, ensuring long-term bonding stability of the magnetic circuit structure. At the same time, it has excellent saturation magnetization performance, which can construct a continuous and smooth magnetic flux conduction path, effectively improving the magnetic circuit's magnetic conductivity, reducing eddy current losses, optimizing acoustic performance, and enhancing the high-frequency loudness and environmental reliability of the sound-generating device.

[0069] The second aspect of this application also provides a method for preparing a magnetically conductive thermosetting adhesive, thereby obtaining the magnetically conductive thermosetting adhesive described in the first aspect of this application.

[0070] In some embodiments of this application, the preparation method of the magnetic thermosetting adhesive is mainly carried out according to the following steps.

[0071] (1) Obtain magnetic filler and thermosetting adhesive.

[0072] In some embodiments of this application, the magnetic filler is filtered and screened to ensure uniform particle size.

[0073] In some embodiments of this application, the particle size of the magnetic filler is ≤6 μm and not 0.

[0074] In some embodiments of this application, the specific saturation magnetization of the magnetic filler is 46 emu / g to 230 emu / g.

[0075] In some embodiments of this application, the magnetic filler has a core-shell structure, which includes a magnetic material and an anti-corrosion layer covering the outside of the magnetic material; the ratio of the thickness of the anti-corrosion layer to the particle size of the magnetic material is (0.01~0.1):(1~10).

[0076] In some embodiments of this application, the magnetic material includes at least one of pure iron, iron-nickel alloy, and iron-cobalt alloy.

[0077] In some embodiments of this application, the particle size of the magnetic material is ≤5 μm and not 0.

[0078] In some embodiments of this application, the thickness of the anti-corrosion layer is 20 nm to 100 nm.

[0079] In some embodiments of this application, the material of the anti-corrosion layer includes one of organic resin and inorganic filler.

[0080] In some embodiments of this application, the organic resin includes at least one of organosilicon-modified resin, epoxy resin, polyimide resin, and phenolic resin.

[0081] In some embodiments of this application, the inorganic filler includes silicon dioxide.

[0082] In some embodiments of this application, the thermosetting adhesive includes at least one of acrylate thermosetting adhesive, epoxy thermosetting adhesive, and anaerobic thermosetting adhesive.

[0083] (2) Mix the magnetic filler with the thermosetting adhesive, let it stand and fill it, and then degas it to obtain the magnetic thermosetting adhesive.

[0084] In the embodiments of this application, the prepared magnetic thermosetting adhesive needs to be stored at -20°C away from light to ensure that the particle size of the magnetic thermosetting adhesive is ≤50 μm.

[0085] It is worth mentioning that, in the embodiments of this application, the particle size of the magnetically conductive thermosetting adhesive is ≤50 μm and not 0. In some embodiments of this application, the particle size of the magnetically conductive thermosetting adhesive is 15 μm to 50 μm. Exemplarily, the particle size of the magnetically conductive thermosetting adhesive can be one of 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any value satisfying the above range.

[0086] The third aspect of this application also provides the application of the magnetic thermosetting adhesive described in the first aspect of this application or the magnetic thermosetting adhesive prepared by the preparation method described in the second aspect of this application in the bonding of magnetic circuit components of a miniature loudspeaker.

[0087] In some embodiments of this application, the bonding strength of magnetic circuit components bonded with magnetic thermosetting adhesive is ≥1700 N. Exemplarily, the bonding strength of magnetic circuit components bonded with magnetic thermosetting adhesive can be 1700 N, 1750 N, 1800 N, 1850 N, 1900 N, etc.

[0088] In some embodiments of this application, magnetic circuit components bonded with high-permeability thermosetting adhesive exhibit a bond strength ≥1200 N after storage in an environment of 80°C and 95%RH for 72 hours. Exemplarily, the bond strength of magnetic circuit components bonded with high-permeability thermosetting adhesive after storage in an environment of 80°C and 95%RH for 72 hours can be 1200 N, 1250 N, 1300 N, 1350 N, 1400 N, etc.

[0089] A fourth aspect of this application also provides a magnetic circuit system for a sound-generating device, combined with... Figure 1 The sound-generating device 100 includes a housing 10 and a vibration system and a magnetic circuit system disposed inside the housing 10. The vibration system includes a diaphragm assembly 20 and a voice coil 90; the magnetic circuit system includes a magnetic yoke 30 and a magnetic circuit assembly disposed on one side of the magnetic yoke 30, the magnetic circuit assembly including a magnet and a magnetic plate, the magnetic yoke, magnet, and magnetic plate being sequentially stacked along a first direction; wherein, a magnetically conductive thermosetting adhesive 80 as described in the first aspect of this application is disposed between the magnetically conductive yoke and the magnet and / or between the magnet and the magnetic plate, or a magnetically conductive thermosetting adhesive 80 prepared using the preparation method described in the second aspect of this application is disposed.

[0090] In some embodiments of this application, the magnet includes a central magnet 40 and a side magnet 50 spaced apart, and the magnetic guide plate includes a central magnetic guide plate 60 and a side magnetic guide plate 70. The central magnet 40 and the central magnetic guide plate 60 constitute a central magnetic part, and the side magnet 50 and the side magnetic guide plate 70 constitute a side magnetic part. The magnetic yoke 30, the central magnet 40 and the central magnetic guide plate 60 are stacked sequentially along a first direction, and the central magnet 40 and the magnetic yoke 30 and / or the central magnet 40 and the central magnetic guide plate 60 are bonded together by a magnetic thermosetting adhesive 80.

[0091] In some embodiments of this application, the magnetic yoke 30, the side magnet 50 and the side magnetic plate 70 are stacked sequentially along a first direction, and the side magnet 50 and the magnetic yoke 30 and / or the side magnet 50 and the side magnetic plate 70 are bonded together by a magnetic thermosetting adhesive 80.

[0092] The fifth aspect of this application also provides a sound-generating device, which includes the magnetic circuit system for the sound-generating device described in the fourth aspect of this application.

[0093] In embodiments of this application, the sound-generating device may be a miniature loudspeaker.

[0094] 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.

[0095] Example 1 This embodiment 1 provides a magnetic thermosetting adhesive and a miniature loudspeaker using the magnetic thermosetting adhesive. The magnetic thermosetting adhesive is used to bond the center magnet and the side magnet of the miniature loudspeaker. The magnetic thermosetting adhesive includes the following components in parts by weight: 50 parts thermosetting adhesive and 50 parts magnetic filler.

[0096] The magnetic filler has a particle size of 5.5 μm and a core-shell structure, comprising an iron-nickel alloy material and an anti-corrosion layer covering the outside of the iron-nickel alloy material. The ratio of the thickness of the anti-corrosion layer to the particle size of the iron-nickel alloy material is 0.01:1. The thickness of the anti-corrosion layer is 50 nm. The particle size of the iron-nickel alloy material is 5 μm. The specific saturation magnetization of the magnetic filler per unit mass is 125 emu / g.

[0097] The thermosetting adhesive is an acrylate thermosetting adhesive (acrylate thermosetting glue), comprising the following components by weight: 70 parts acrylate oligomer, 30 parts acrylate monomer, 5 parts thermal initiator, and 0.5 parts curing agent; wherein, the acrylate oligomer is a polyurethane acrylate oligomer, and the acrylate monomer is a mixture of 4-azobisisobutyronitrile, hexanediol diacrylate, acrylic acid, and hydroxyethyl methacrylate; the thermal initiator is a mixture of azobisisobutyronitrile, cumene hydroperoxide, and benzoyl peroxide; the curing agent is an acrylate monomer carrying special functional groups in the resin, which undergoes a chemical reaction during the reaction to achieve further crosslinking of the resin network.

[0098] The preparation method of this magnetically conductive thermosetting adhesive includes the following steps: S1: Add acrylate oligomer, acrylate monomer, thermal initiator, and curing agent according to the formula, mix and stir, allow to stand, fill and degas to obtain acrylate thermosetting adhesive. Store the prepared acrylate thermosetting adhesive at -20℃ in the dark. The particle size of the acrylate thermosetting adhesive is ≤50 μm and not 0.

[0099] S2: The cleaned iron-nickel alloy material is mixed with epoxy resin and curing agent in acetone. After the acetone solvent evaporates, the coated powder is obtained. The coated powder is then baked at 120℃ for 25 min to obtain a magnetic filler with a particle size of 5.5 μm.

[0100] S3: Filter and screen the magnetic packing material to ensure that the packing particle size is 5.5 μm.

[0101] S4: Add acrylate thermosetting adhesive and magnetic filler according to the formula, mix and stir, let stand and fill, then degas to obtain magnetic thermosetting adhesive. Store the prepared magnetic thermosetting adhesive at -20℃ in the dark. The particle size of the magnetic thermosetting adhesive is ≤50 μm and not 0.

[0102] Example 2 This embodiment 2 provides a magnetic thermosetting adhesive and a miniature loudspeaker using the magnetic thermosetting adhesive. The magnetic thermosetting adhesive is used to bond the center magnet and the side magnet of the miniature loudspeaker. The magnetic thermosetting adhesive includes the following components in parts by weight: 40 parts thermosetting adhesive and 60 parts magnetic filler.

[0103] The magnetic filler has a particle size of 5.5 μm and a core-shell structure, comprising an iron-nickel alloy material and an anti-corrosion layer covering the outside of the iron-nickel alloy material. The ratio of the thickness of the anti-corrosion layer to the particle size of the iron-nickel alloy material is 0.01:1. The thickness of the anti-corrosion layer is 50 nm. The particle size of the iron-nickel alloy material is 5 μm, and the specific saturation magnetization of the magnetic filler per unit mass is 125 emu / g.

[0104] The thermosetting adhesive is an acrylate thermosetting adhesive (acrylate thermosetting glue), comprising the following components by weight: 70 parts acrylate oligomer, 30 parts acrylate monomer, 5 parts thermal initiator, and 0.5 parts curing agent; wherein, the acrylate oligomer is a polyurethane acrylate oligomer, and the acrylate monomer is a mixture of 4-azobisisobutyronitrile, hexanediol diacrylate, acrylic acid, and hydroxyethyl methacrylate; the thermal initiator is a mixture of azobisisobutyronitrile, cumene hydroperoxide, and benzoyl peroxide; the curing agent is an acrylate monomer carrying special functional groups in the resin, which undergoes a chemical reaction during the reaction to achieve further crosslinking of the resin network.

[0105] The preparation method of the magnetic thermosetting adhesive in Example 2 is the same as that in Example 1.

[0106] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the magnetic filler in Comparative Example 1 is made of iron-nickel alloy material and does not contain an anti-corrosion layer, that is, it is not coated with an epoxy resin layer.

[0107] The magnetic filler has a particle size of 5 μm and a specific saturation magnetization of 128 emu / g per unit mass.

[0108] The magnetic thermosetting adhesive comprises the following components by weight: 60 parts thermosetting adhesive and 40 parts magnetic filler.

[0109] The thermosetting adhesive is an acrylate thermosetting adhesive (acrylate thermosetting glue), comprising the following components by weight: 70 parts acrylate oligomer, 30 parts acrylate monomer, 5 parts thermal initiator, and 0.5 parts curing agent; wherein, the acrylate oligomer is a polyurethane acrylate oligomer, and the acrylate monomer is a mixture of 4-azobisisobutyronitrile, hexanediol diacrylate, acrylic acid, and hydroxyethyl methacrylate; the thermal initiator is a mixture of azobisisobutyronitrile, cumene hydroperoxide, and benzoyl peroxide; the curing agent is an acrylate monomer carrying special functional groups in the resin, which undergoes a chemical reaction during the reaction to achieve further crosslinking of the resin network.

[0110] The preparation method of this magnetically conductive thermosetting adhesive includes the following steps: S1: Add acrylate oligomer, acrylate monomer, thermal initiator, and curing agent according to the formula, mix and stir, allow to stand, fill and degas to obtain acrylate thermosetting adhesive. Store the prepared acrylate thermosetting adhesive at -20℃ in the dark. The particle size of the acrylate thermosetting adhesive is ≤50 μm and not 0.

[0111] S2: Filter and screen the magnetic packing to ensure that the packing particle size is 5 μm.

[0112] S3: Add acrylate thermosetting adhesive and magnetic filler according to the formula, mix and stir, let stand and fill, then degas to obtain magnetic thermosetting adhesive. Store the prepared magnetic thermosetting adhesive at -20℃ in the dark. The particle size of the magnetic thermosetting adhesive is ≤50 μm and not 0.

[0113] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses a thermosetting adhesive without magnetic filler.

[0114] This thermosetting adhesive is an acrylate thermosetting adhesive, comprising the following components by weight: 70 parts acrylate oligomer, 30 parts acrylate monomer, 5 parts thermal initiator, and 0.5 parts curing agent; wherein the acrylate oligomer is a polyurethane acrylate oligomer, and the acrylate monomer is a mixture of 4-benzoylmorpholine, hexanediol diacrylate, acrylic acid, and hydroxyethyl methacrylate; the thermal initiator is a mixture of azobisisobutyronitrile, cumene hydroperoxide, and benzoyl peroxide; the curing agent is an acrylate monomer carrying special functional groups in the resin, which undergoes a chemical reaction during the reaction process to achieve further crosslinking of the resin network.

[0115] The preparation of this thermosetting adhesive includes: adding acrylate oligomers, acrylate monomers, thermal initiators, and curing agents according to the specified ratio, mixing and stirring, allowing it to stand, filling it into containers, and then degassing it to obtain the acrylate thermosetting adhesive. The prepared acrylate thermosetting adhesive is stored at -20℃ away from light. The particle size of the acrylate thermosetting adhesive is ≤50 μm and not zero.

[0116] Performance testing 1. Room temperature tensile strength test.

[0117] Epoxy / anaerobic / acrylic thermosetting adhesives and magnetic thermosetting adhesives were prepared into standard-sized I-shaped tensile specimens (gauge length = 25 mm) according to the curing methods of different thermosetting adhesives. Using a universal testing machine, the specimens were placed in upper and lower clamps and clamped at room temperature. The tensile speed was 500 mm / min, and the bulk strength of the thermosetting adhesive, i.e., the room temperature tensile strength, was obtained.

[0118] 2. Specific saturation magnetization test.

[0119] Using a vibrating sample magnetometer, a cured thermosetting adhesive was prepared into a cured sample block with dimensions of 1 cm × 1 cm × 1 mm. The sample block was placed in a constant magnetic field of -10000 Oe to 10000 Oe, and the MH curve was obtained to obtain the specific saturation magnetization of the sample block.

[0120] 3. Test the thickness of the adhesive layer at the interface.

[0121] Thickness was measured using a super depth-of-field 3D microscope.

[0122] 4. Anti-corrosion layer thickness test The determination was performed using a combination of indirect calculation and direct sensing methods. The specific surface area (SSA) of the alloy powder and the density of the epoxy resin were known. ; The formula calculates the average coating thickness; then, TGA thermogravimetric analysis is performed, and the epoxy resin layer is heated to 600℃ in a nitrogen atmosphere. The epoxy resin layer will decompose at 300-500℃, and the thickness of the anti-corrosion layer is calculated by the weight loss ratio.

[0123] 5. Bond strength test.

[0124] According to the national standard GB / T 7124, the bonding strength was tested using a universal testing machine.

[0125] 6. Speaker loudness test.

[0126] The Soundcheck audio testing system was used. The system played a sweep signal to drive the speaker to produce sound, while simultaneously acquiring the microphone signal; the analyzer calculated and displayed the speaker's frequency response curve in real time, and recorded the loudness of the individual speaker at high frequencies (3 K / Hz~5 K / Hz).

[0127] The magnetic thermosetting adhesives and thermosetting adhesives prepared in the examples and comparative examples were subjected to relevant performance tests. The test results are detailed in Table 1.

[0128] Table 1

[0129] Note: The loudness (dB) data is based on the values ​​of Comparative Example 2 at 3K / Hz to 5K / Hz. Positive numbers indicate that the frequency band is louder than the reference point; negative numbers indicate that the frequency band is weaker than the reference point.

[0130] Combined with Table 1 and Figure 2 The test results show that the magnetic thermosetting adhesive of this application is perfectly suited to the bonding process of ultra-thin adhesive layers for small-volume components, solving the problem of decreased product environmental reliability caused by exposed fillers in traditional magnetic adhesives. It has significant advantages in mechanical drop resistance. After being stored at 80°C and 95% RH for 72 hours, the bonding strength of the magnetic circuit component using this adhesive in Example 1 can be maintained above 1200 N. It can withstand 108 directional drop tests from 1.8 m, which is far superior to the drop resistance level of ordinary magnetic adhesive in Comparative Example 1, which is only 72 drops. This significantly improves the structural strength and reliability of the speaker.

[0131] Example 2 increased the proportion of magnetic filler, which led to an increase in the specific saturation magnetization of the magnetic adhesive and the acoustic performance of the product. However, the adhesion defects caused by the addition of powder still resulted in a decrease in adhesion. It is worth noting, however, that the product's drop resistance was not compromised after high temperature and humidity storage, proving that the anti-corrosion layer can effectively isolate air and moisture erosion, ensuring the reliability of the product in high temperature and humidity environments, and enabling it to still meet the 108-drop requirement in Comparative Example 2. The anti-corrosion layer can also prevent direct contact between magnetic material particles, significantly reducing eddy current losses under the action of a magnetic field and ensuring the improvement of the high-frequency loudness of the sound-generating device.

[0132] 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 magnetically permeable thermoset adhesive, characterized in that, It includes a thermosetting adhesive and a magnetic filler dispersed within the thermosetting adhesive. The magnetic filler has a core-shell structure and includes a magnetic material and an anti-corrosion layer covering the outside of the magnetic material. The ratio of the thickness of the anti-corrosion layer to the particle size of the magnetic material is (0.01~0.1):(1~10).

2. The magnetically permeable thermoset adhesive of claim 1, wherein, The thickness of the anti-corrosion layer is 20 nm to 100 nm; and / or, The magnetic material has a particle size of ≤5 μm and is not 0.

3. The magnetically conductive thermosetting adhesive as described in claim 1, characterized in that, The magnetic material includes at least one of pure iron, iron-nickel alloy, and iron-cobalt alloy. And / or, the material of the anti-corrosion layer includes one of organic resin and inorganic filler.

4. The magnetically conductive thermosetting adhesive as described in claim 3, characterized in that, The organic resin includes at least one of organosilicon modified resin, epoxy resin, polyimide resin, and phenolic resin; And / or, the inorganic filler includes silicon dioxide.

5. The magnetically conductive thermosetting adhesive as described in claim 1, characterized in that, The magnetic filler has a particle size of ≤6 μm and not 0, and / or the specific saturation magnetization of the magnetic filler is 46 emu / g to 230 emu / g.

6. The magnetically conductive thermosetting adhesive as described in claim 1, characterized in that, The thermosetting adhesive includes at least one of acrylate thermosetting adhesives, epoxy thermosetting adhesives, and anaerobic thermosetting adhesives.

7. The magnetically conductive thermosetting adhesive according to any one of claims 1 to 6, characterized in that, Includes the following components by weight: 10-50 parts of magnetic filler and 50-90 parts of thermosetting adhesive.

8. The magnetically conductive thermosetting adhesive according to any one of claims 1 to 7, characterized in that, The tensile strength of the magnetic thermosetting adhesive is ≥20 MPa; And / or, the specific saturation magnetization of the magnetic thermosetting adhesive is ≥50 emu / g.

9. A method for preparing a magnetically conductive thermosetting adhesive according to any one of claims 1 to 8, characterized in that, Includes the following steps: Obtain magnetic filler and thermosetting adhesive; the magnetic filler has a core-shell structure, including magnetic material and an anti-corrosion layer covering the outside of the magnetic material; the ratio of the thickness of the anti-corrosion layer to the particle size of the magnetic material is (0.01~0.1):(1~10); The magnetic filler and the thermosetting adhesive are mixed and stirred to obtain the magnetic thermosetting adhesive.

10. The application of the magnetically conductive thermosetting adhesive as described in any one of claims 1 to 8, or the magnetically conductive thermosetting adhesive prepared by the preparation method described in claim 9, in the bonding of magnetic circuit components for miniature loudspeakers, characterized in that, The bonding strength of magnetic circuit components bonded with the aforementioned magnetic thermosetting adhesive is ≥1700 N; And / or, after the magnetic circuit components bonded with the high-permeability thermosetting adhesive are stored in an environment of 80°C and 95%RH for 72 h, their bonding strength is ≥1200 N.

11. A magnetic circuit system for a sound-generating device, characterized in that, The device includes a magnetic yoke and a magnetic circuit assembly disposed on one side of the magnetic yoke. The magnetic circuit assembly includes a magnet and a magnetic plate. The magnetic yoke, the magnet, and the magnetic plate are stacked sequentially along a first direction. The magnetic yoke and the magnet and / or the magnet and the magnetic plate are provided with a magnetic thermosetting adhesive as described in any one of claims 1 to 8, or with a magnetic thermosetting adhesive prepared by the preparation method described in claim 9.

12. The magnetic circuit system for a sound-generating device as described in claim 11, characterized in that, The magnet includes a central magnet and side magnets spaced apart, and the magnetic guide plate includes a central magnetic guide plate and side magnetic guide plates. The central magnet and the central magnetic guide plate constitute a central magnetic part, and the side magnets and the side magnetic guide plates constitute a side magnetic part. The magnetic yoke, the central magnet, and the central magnetic plate are stacked sequentially along a first direction, and the central magnet and the magnetic yoke and / or the central magnet and the central magnetic plate are bonded together by the magnetic thermosetting adhesive. And / or, the magnetic yoke, the side magnet and the side magnetic plate are stacked sequentially along the first direction, and the side magnet and the magnetic yoke and / or the side magnet and the side magnetic plate are bonded together by the magnetic thermosetting adhesive.

13. A sound-generating device, characterized in that, Includes the magnetic circuit system for the sound-generating device as described in claim 11 or 12.

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