Preparation method of diaphragm of sound generating device, diaphragm, and sound generating device

Abstract

The present application discloses a preparation method of a diaphragm of a sounding device, a diaphragm, and a sounding device. The preparation method of the diaphragm of the sounding device includes the following steps: reacting solid polyurethane raw rubber, a vulcanizing agent, a vulcanization accelerator, an anti-aging aid, a filler, other aids with a solvent to prepare a mixed slurry with a solid content of 15% to 45%; coating the mixed slurry into a film with a predetermined thickness, and after heating and volatilizing the solvent, forming a polyurethane rubber film with a preset thickness, wherein the tensile strength σ of the polyurethane rubber film satisfies the relational expression: 0.1 MPa ≤ σ ≤ 15 MPa; placing the polyurethane rubber film on a mold of a thermoforming machine, and thermally pressing and cross-linking it into a diaphragm with a predetermined shape. The preparation method of the diaphragm of the present application is convenient to operate, can not only save the production cost of the diaphragm, but also solve the shrinkage problem caused by curing during the die pressing and forming of the diaphragm, and the prepared diaphragm has good dimensional stability and acoustic performance.

Description

Technical Field

[0001] This application belongs to the technical field of diaphragms. Specifically, this application relates to a method for preparing a diaphragm of a sound generating device, a diaphragm obtained by this preparation method, and a sound generating device including this diaphragm. Background Art

[0002] Currently, in the process of preparing a rubber diaphragm, it relies on upper and lower die cavities for molding. Also, due to the low F0 of a micro speaker, the required diaphragm thickness is relatively thin. Therefore, the requirements for the upper and lower die cavities are very high, with a tolerance in the micron level. Such high-precision molds are expensive, which limits the popularization of rubber materials. In addition, due to the large shrinkage of rubber molding during forming, there is a large difference from the designed acoustic requirements. Summary of the Invention

[0003] One object of this application is to provide an improved method for preparing a diaphragm of a sound generating device. The preparation method is convenient to operate, can not only save the production cost of the diaphragm, but also solve the shrinkage problem caused by curing during the molding of the diaphragm.

[0004] Another object of this application is to provide a diaphragm prepared by the above preparation method.

[0005] Another object of this application is to provide a sound generating device having the above diaphragm.

[0006] According to the first aspect of this application, there is provided a method for preparing a diaphragm of a sound generating device, including the following steps: reacting solid polyurethane raw rubber, a vulcanizing agent, a vulcanization accelerator, an anti-aging aid, a filler, other aids with a solvent to prepare a mixed slurry with a solid content of 15% - 45%; coating the mixed slurry into a film with a predetermined thickness, and after heating and volatilizing the solvent, forming a polyurethane rubber film with a preset thickness, where the tensile strength σ of the polyurethane rubber film satisfies the relation: 0.1 MPa ≤ σ ≤ 15 MPa; placing the polyurethane rubber film on the mold of a thermoforming machine and thermally pressing and crosslinking it into a diaphragm with a predetermined shape.

[0007] Optionally, in the step of preparing the mixed slurry, the polyurethane raw rubber, the vulcanizing agent, the vulcanization accelerator, the anti-aging aid, the filler and other aids are kneaded to prepare a kneaded rubber, and the kneaded rubber is dissolved in the solvent to obtain the mixed slurry.

[0008] Optionally, in the step of preparing the mixed slurry, the polyurethane raw rubber, the anti-aging aid, the filler and other aids are kneaded to prepare a kneaded rubber, and the kneaded rubber, the vulcanizing agent and the vulcanization accelerator are dissolved in the solvent to obtain the mixed slurry.

[0009] Optionally, the thickness of the polyurethane rubber diaphragm is 15 μm - 200 μm.

[0010] Optionally, the hardness of the polyurethane rubber diaphragm is 40A to 95A.

[0011] Optionally, the raw polyurethane rubber consists of soft segments and hard segments. The hard segments are one or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, isophorone diisocyanate, m-xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hydrogenated toluene diisocyanate, and trimethylhexamethylene diisocyanate; the soft segments are one or more of polyester polyol, polycarbonate polyol, polycaprolactone, polyether polyol, polybutadiene polyol, castor oil polyol, tetrahydrofuran-propylene oxide copolymer polyol, and epoxy resin modified polyol.

[0012] Optionally, the solvent is one or more of tetrahydrofuran, N,N-dimethylformamide, acetone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, toluene, xylene, and chlorobenzene.

[0013] Optionally, the vulcanizing agent is one or more of dicumyl peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, di-tert-butyl peroxide, 2,5-dimethyl-2,5-(di-tert-butylperoxy)hexane, bis(tert-butylperoxy)isopropylbenzene, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl perbenzoate, and sulfur.

[0014] Optionally, the vulcanization accelerator is one or more of thiazoles, sulfenamides, thiurams, thioureas, dithiocarbamates, aldehyde amines, guanidines, and xanthates, and the filler is one or more of carbon black, silica, talc powder, calcium carbonate, graphite, and titanium dioxide.

[0015] Optionally, the anti-aging agent is one or more of antioxidant 1010, antioxidant 2, antioxidant 6, antioxidant 4, antioxidant 1076, antioxidant 168, anti-aging agent RD, anti-aging agent AW, anti-aging agent DD, anti-aging agent BLE, anti-aging agent 4010, 4010NA, 4020, 4030, 4040, anti-aging agent DNP, anti-aging agent H, anti-aging agent A, anti-aging agent D, anti-aging agent SP, anti-aging agent 264, anti-aging agent 2246, anti-aging agent 2246-S, anti-aging agent NBC, and anti-aging agent MB.

[0016] Optionally, the other additives are at least one of plasticizer, anti-hydrolysis agent, activator, zinc oxide, stearic acid, ultraviolet absorber, mold release agent, and color paste.

[0017] Optionally, in the step of placing the polyurethane rubber film on the mold of the thermoforming machine and thermoforming to obtain the diaphragm of the sound generating device with a predetermined shape, a gas heating and pressurizing method is adopted, the forming temperature is 100°C to 200°C, the forming time is 50 s to 600 s, and the forming pressure is 0.05 Mpa to 5 Mpa.

[0018] Another aspect of the present application further provides a diaphragm, which is the diaphragm prepared by the method described in any of the above embodiments.

[0019] Another aspect of the present application further provides a sound generating device, including a vibration system and a magnetic circuit system cooperating with the vibration system. The vibration system includes a diaphragm and a voice coil combined on one side of the diaphragm. The magnetic circuit system drives the voice coil to vibrate to drive the diaphragm to generate sound, and the diaphragm is the diaphragm described in any of the above embodiments.

[0020] Another aspect of the present application further provides a sound generating device, including a housing and a magnetic circuit system and a vibration system provided in the housing. The vibration system includes a voice coil, a first diaphragm, and a second diaphragm. The top of the voice coil is connected to the first diaphragm. The magnetic circuit system drives the voice coil to vibrate to drive the first diaphragm to generate sound. Both ends of the second diaphragm are respectively connected to the housing and the bottom of the voice coil, and the second diaphragm is the diaphragm described in any of the above embodiments.

[0021] One technical effect of the present application is that the polyurethane rubber film is prepared by a coating method. The film thickness has a large adjustable range, and the adjustment cost is low. Different performance and thickness films can be formed by coating according to the needs of product design, without being restricted by the forming mold and forming method, significantly reducing the formulation design and manufacturing cost of rubber diaphragms. At the same time, the components in the polyurethane rubber film prepared by the method of the present application are evenly distributed, and when forming the film by coating, the molecular chains can be freely oriented, and there is almost no residual stress in the film. This is beneficial to reducing the shrinkage problem caused by curing when the rubber material forms the diaphragm. Compared with the traditional molding process, the size of the diaphragm prepared by the method of the present application is closer to the design value, which can better ensure the good acoustic performance and dimensional stability of the product.

[0022] Through the following detailed description of the exemplary embodiments of the present application with reference to the accompanying drawings, other features and advantages of the present application will become clear. Description of the Drawings

[0023] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments of the present application and, together with the description, are used to explain the principles of the present application.

[0024] Figure 1It is the total harmonic distortion test curve graph of Embodiment 1 and Comparative Example 1 provided by the present application;

[0025] Figure 2 It is the flowchart of the preparation method of the diaphragm of the embodiment provided by the present application.

[0026] Figure 3 It is the overall structural schematic diagram of the sound generating device according to the embodiment of the present application;

[0027] Figure 4 It is the partial structural schematic diagram of the sound generating device according to the embodiment of the present application;

[0028] Figure 5 It is the sectional view of the sound generating device according to the embodiment of the present application;

[0029] Figure 6 It is the exploded view of the sound generating device according to the embodiment of the present application.

[0030] Reference numerals

[0031] Sound generating device 100;

[0032] Housing 10; Voice coil 11; First diaphragm 12; Second diaphragm 13; Magnetic circuit system 14;

[0033] Diaphragm 15; Folded edge portion 151; Dome top 152. Detailed implementation manners

[0034] Now, various exemplary embodiments of the present application will be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present application.

[0035] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present application or its application or use.

[0036] Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the specification.

[0037] In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Accordingly, other examples of the exemplary embodiments may have different values.

[0038] It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0039] AsFigure 1 As shown, a method for preparing a diaphragm of a sound generating device according to an embodiment of the present application includes the following steps:

[0040] React a solid polyurethane raw rubber, a vulcanizing agent, a vulcanization accelerator, an anti-aging aid, a filler, other aids with a solvent to prepare a mixed slurry with a solid content of 15% to 45%.

[0041] Coat the mixed slurry into a thin film with a predetermined thickness. After heating and volatilizing the solvent, a polyurethane rubber film with a preset thickness is formed. The tensile strength σ of the polyurethane rubber film satisfies the relationship: 0.1 MPa ≤ σ ≤ 15 MPa. For example, the mixed slurry can be coated on a release film to form a thin film of a certain thickness, that is, a polyurethane rubber film, and then the strip composed of the formed polyurethane rubber film and the release film is heated to volatilize the solvent in the strip.

[0042] Place the polyurethane rubber film on the mold of a thermoforming machine and thermally press and crosslink it into a diaphragm with a predetermined shape.

[0043] In other words, the method for preparing a diaphragm of a sound generating device according to an embodiment of the present application mainly includes the following steps: First, prepare a mixed slurry; then coat the mixed slurry into a thin film; and finally prepare the thin film into a diaphragm.

[0044] Among them, when preparing the mixed slurry, react a solid polyurethane raw rubber, a vulcanizing agent, a vulcanization accelerator, an anti-aging aid, a filler, other aids with a solvent, and the solid content of the prepared mixed slurry is 15% to 45%. Optionally, the solid content of the mixed slurry can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc. It should be noted that if the solid content of the mixed slurry is too low, the viscosity of the slurry is low and the moldability is poor, which not only wastes the solvent, but also requires more times to repeatedly coat when coating the thin film, increasing the cost. If the solid content of the mixed slurry is too high, it cannot be dissolved, and the viscosity of the slurry is high, making it difficult to defoam, with a large coating difficulty and the thin film is prone to defects. When the solid content of the mixed slurry is between 15% and 45%, the viscosity of the slurry is appropriate, the moldability is good, it is easy to defoam, reducing the coating difficulty, and the quality of the prepared thin film is good.

[0045] When coating the mixed slurry into a film, first coat the mixed slurry into a film with a predetermined thickness, and then after heating and volatilizing the solvent, a polyurethane rubber (MPU) film with a preset thickness can be formed. The tensile strength σ of the MPU film satisfies the relationship: 0.1 MPa ≤ σ ≤ 15 MPa. Optionally, the tensile strength σ of the MPU film can be 0.1 MPa, 0.3 MPa, 0.5 Mpa, 1 Mpa, 2 Mpa, 3 Mpa, 4 Mpa, 5 Mpa, 6 Mpa, 7 Mpa, 8 Mpa, 9 Mpa, 10 Mpa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, etc. In addition, it should be noted that before forming, the tensile strength σ of the MPU film needs to satisfy the relationship: 0.1 MPa ≤ σ ≤ 15 MPa. If the tensile strength exceeds this range, the MPU film will be blown out during the forming process and the product cannot be prepared. If it is higher than this strength, the crosslinking density is too high and secondary forming cannot be carried out.. Further, the tensile strength σ of the MPU film satisfies the relationship: 0.2 MPa ≤ σ ≤ 10 MPa. Within this range, the film layer is easier to form and has a small shrinkage after forming, and it is easy to reach the designed size.

[0046] That is to say, by adopting the coating method, first coat the mixed slurry into a film with a certain thickness, and then heat it at a certain temperature. After heating, the solvent volatilizes, and a polyurethane rubber film with a certain thickness can be obtained. For example, by adopting the coating method, coat the mixed slurry into a film with a certain thickness, and after heating at 50 °C to 150 °C, the solvent volatilizes, and a film layer with a certain thickness can be obtained.

[0047] When making the film into a diaphragm, place the polyurethane rubber film on the mold of a thermoforming machine and thermally press and crosslink it into a diaphragm with a predetermined shape. That is to say, by placing the polyurethane rubber film on the mold of a thermoforming machine and heating and pressing for a certain time, a diaphragm with the required structure can be obtained.

[0048] Thus, according to the method of the embodiment of the present application, a polyurethane rubber film is prepared by the coating method. The film thickness has a large adjustable space and the adjustment cost is low. According to the needs of product design, films with different properties and thicknesses can be formed by coating, which is not restricted by the forming mold and the forming method, and significantly reduces the formulation design and manufacturing cost of rubber diaphragms. At the same time, the components in the polyurethane rubber film prepared by the method of the present application are evenly distributed, and when coating into a film, the molecular chains can freely orient, and there is almost no residual stress in the film. This is beneficial to reducing the shrinkage problem caused by curing when the rubber material forms a diaphragm. Compared with the traditional molding process, the size of the diaphragm obtained by the preparation method of the present application is closer to the design value, and it can better ensure the good acoustic performance and dimensional stability of the product.

[0049] According to an embodiment of the present application, in the step of preparing the mixed slurry, the polyurethane raw rubber, vulcanizing agent, vulcanization accelerator, anti-aging agent, filler and other additives are kneaded to prepare a kneaded rubber, and the kneaded rubber is dissolved in a solvent to obtain the mixed slurry. That is to say, the polyurethane raw rubber, vulcanizing agent, vulcanization accelerator, anti-aging agent, filler and other additives are kneaded to prepare a kneaded rubber, which is dissolved in a suitable solvent to obtain the mixed slurry.

[0050] In some specific embodiments of the present application, in the step of preparing the mixed slurry, the polyurethane raw rubber, anti-aging agent, filler and other additives are used to prepare a kneaded rubber, and the kneaded rubber, vulcanizing agent and vulcanization accelerator are dissolved in a solvent to obtain the mixed slurry. That is to say, the polyurethane raw rubber, anti-aging agent, filler and other additives are used to prepare a kneaded rubber, which is dissolved in a suitable solvent together with the vulcanizing agent and vulcanization accelerator to obtain the mixed slurry.

[0051] It can be seen that any of the above methods can be selected to prepare the mixed slurry as needed. Select the appropriate time to dissolve the vulcanizing agent and vulcanization accelerator according to the formula of different rubbers. For example: for some formulas, due to shear heat generation during the preparation of the kneaded rubber or the need for heating of the equipment itself, if the temperature increases, the vulcanizing agent and vulcanization accelerator are easily scorched and vulcanized in the early stage, forming insoluble gels, which are likely to cause unevenness after coating. For some other formulas, if all the vulcanizing agent and vulcanization accelerator are added later, the vulcanizing agent is likely to precipitate, resulting in insufficient vulcanization during the later molding.

[0052] According to an embodiment of the present application, the thickness of the polyurethane rubber diaphragm is 15 μm to 200 μm, preferably 30 μm to 150 μm. It should be noted that if the thickness of the polyurethane rubber diaphragm is too thin, the damping performance of the diaphragm is poor and the sound listening performance is poor; if the thickness of the polyurethane rubber diaphragm is too thick, multiple coatings are required, the cost increases, and the meaning of cost reduction is lost. Moreover, with the increase in thickness, the weight reduction requirement of wearable products cannot be met. When the thickness of the polyurethane rubber diaphragm is between 15 μm and 200 μm, the damping performance of the diaphragm is better, which can improve the sound emission effect of the diaphragm, and the weight of the diaphragm is moderate, meeting the weight reduction requirement of the sound-emitting device.

[0053] In some specific embodiments of the present application, the hardness of the polyurethane rubber diaphragm is 40A to 95A. If the hardness is too small, in order to match the appropriate F0 of the product, the thickness needs to be increased and multiple coatings are required, resulting in an increase in cost. If the hardness is too high, the elongation at break of the rubber becomes smaller, and the film is easily broken during the low-temperature reliability verification, causing product failure, and the F0 of the diaphragm is too high to obtain a perfect sound effect. When the hardness of the polyurethane rubber diaphragm is 40A to 95A, it can not only reduce the coating times and cost, but also increase the elongation at break of the rubber and ensure the sound effect.

[0054] According to an embodiment of the present application, the polyurethane rubber raw rubber is composed of a soft segment and a hard segment. The hard segment is one or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate (NDI), p-phenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, isophorone diisocyanate, m-xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hydrogenated toluene diisocyanate, and trimethylhexamethylene diisocyanate. That is to say, the hard segment of the polyurethane rubber raw rubber is mainly prepared from isocyanate. Due to the relatively large polarity of isocyanate, the binding ability between hard segment molecules is strong, the intermolecular force is strong, and the addition of the hard segment improves the hardness and modulus of the polyurethane rubber and also increases the temperature resistance of the material. If the content of the hard segment is too low, a high tensile strength or tensile strength cannot be achieved, and there may be reliability problems. If the content of the hard segment is too high, its elongation at break decreases, and there are reliability problems such as film folding after fracture.

[0055] In some specific embodiments of the present application, the soft segment is one or more of polyester polyol, polycarbonate polyol, polycaprolactone, polyether polyol, polybutadiene-based polyol, castor oil polyol, tetrahydrofuran-propylene oxide copolymer polyol, and epoxy resin-modified polyol.

[0056] Among them, polyurethane, also known as carbamate, is a high molecular polymer with many carbamates in its main chain. The soft segment is composed of polyol, and its molecular weight is generally within 800-1800. The addition of the soft segment imparts a certain elasticity to the polyurethane rubber, and only the combination of the soft and hard segments can enable the polyurethane rubber to have a high elongation at break and high strength. When polyester polyol, polycarbonate polyol, polycaprolactone polyol, or epoxy resin-modified polyol is used in the soft segment of the polyurethane rubber raw rubber, the polarity inside the material is relatively large, the binding ability between soft segment molecules is strong, the intermolecular force is strong, and the prepared polyurethane rubber has high strength. While for the polyurethane rubber prepared with polyether polyol, polybutadiene-based polyol, castor oil polyol, or tetrahydrofuran-propylene oxide copolymer polyol as the soft segment, the chain segment is soft, the steric hindrance is small, there is a larger free volume between molecules, and the prepared polyurethane rubber has a larger elongation at break.

[0057] According to an embodiment of the present application, the solvent is one or more of tetrahydrofuran (THF), N,N-dimethylformamide (DMF), acetone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, toluene, xylene, and chlorobenzene.

[0058] For example, add materials (the materials are polyurethane raw rubber, vulcanizing agent, vulcanization accelerator, anti-aging agent, filler and other additives; or are mixed rubber and vulcanizing agent and vulcanization accelerator) into a solvent and continuously stir at a rotation speed of about 200 r / min to 1000 r / min. Generally, it takes 12 h to see no obvious gel. After defoaming, perform coating. When using butyl acetate as the solvent, after standing and defoaming, a small amount of precipitation appears at the bottom of the mixed slurry, indicating that butyl acetate cannot completely dissolve MPU. When using a 1:1 compound of DMF and butyl acetate, not only can the solubility be increased by DMF, but also the solvent evaporation can be accelerated by butyl acetate during coating film formation, so that a well-dissolved coating slurry can be obtained.

[0059] In some specific embodiments of the present application, the vulcanizing agent is one or more of dicumyl peroxide (DCP), 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane (3M), di-tert-butyl peroxide, 2,5-dimethyl-2,5-(di-tert-butylperoxy)hexane, bis(tert-butylperoxyisopropyl)benzene (BIBP), benzoyl peroxide (BP), 2,4-dichlorobenzoyl peroxide (DCBP), tert-butyl perbenzoate, sulfur.

[0060] Among them, the essence of vulcanization is crosslinking. After the peroxide decomposes, free radicals are generated, which react with the active hydrogen or unsaturated double bond on the molecule inside MPU to have a free radical reaction. Under the action of the vulcanizing agent, MPU changes from a linear structure to a three-dimensional network structure, and the hardness and modulus increase, becoming an insoluble material.

[0061] According to an embodiment of the present application, 100 parts by mass of polyurethane raw rubber and 0.5 to 10 parts by mass of vulcanizing agent are used. It should be noted that the dosage of the vulcanizing agent has a great influence on the crosslinking reaction and the properties of the crosslinked rubber compound. When the dosage of the vulcanizing agent is too small, the crosslinking reaction rate is slow, the crosslinking degree is low, and the number of chemical bonds is small. As the temperature increases, the molecular chain movement ability increases, and the modulus rapidly decreases; when the dosage of the vulcanizing agent is too large, blooming is likely to occur, and the crosslinking degree increases and the hardness rises. Due to the limitation of the crosslinking points, as the temperature increases, the molecular chain cannot move, the segment movement ability weakens, and the modulus changes little with the increase of temperature, but the tear strength and elongation at break decrease linearly. When 100 parts by mass of polyurethane raw rubber and 0.5 to 10 parts by mass of vulcanizing agent are used, not only can the crosslinking reaction rate and crosslinking degree be improved, but also the linear decrease of tear strength and elongation at break can be avoided.

[0062] According to an embodiment of the present application, the vulcanization accelerator is one or more of thiazoles, sulfenamides, thiurams, thioureas, dithiocarbamates, aldehyde amines, guanidines, and xanthates. For example, the vulcanization accelerator is thiazoles such as accelerator M and accelerator DM; sulfenamides such as accelerator CZ, accelerator NOBS, and accelerator DZ; thiurams such as accelerator TMTD and accelerator TMTM; thioureas such as accelerator NA-22; dithiocarbamates such as accelerator ZDMC and accelerator ZDC; aldehyde amines such as accelerator H; guanidines such as accelerator D; and xanthates such as accelerator ZIX. It should be noted that the role of the accelerator is to shorten the vulcanization time, reduce the dosage of the vulcanizing agent, improve efficiency, and reduce costs. The accelerator also has the effects of improving the vulcanization flatness, preventing blooming, and improving the properties of the vulcanizate. It can be seen that the addition of the vulcanization accelerator not only increases the reaction rate, reduces the total reaction time, but also increases the crosslinking density, and improves the hardness and heat resistance of the rubber compound.

[0063] According to an embodiment of the present application, the polyurethane raw rubber is 100 parts by mass, and the vulcanization accelerator is 0.5 to 5 parts by mass. When the polyurethane raw rubber is 100 parts by mass and the vulcanization accelerator is 0.5 to 5 parts by mass, not only can the crosslinking density be increased, but also the reaction rate can be increased.

[0064] In some specific embodiments of the present application, the filler is one or more of carbon black, silica, talc powder, calcium carbonate, graphite, and titanium dioxide.

[0065] Taking carbon black as an example, carbon black has an amorphous structure, and the particles form aggregates through physical and chemical bonding with each other. The primary structure of carbon black is composed of aggregates, and at the same time, there are van der Waals forces or hydrogen bonds between the aggregates, which can aggregate into a spatial network structure, that is, the secondary structure of carbon black. The surface of carbon black has groups such as hydrogen, carboxyl, lactone, free radical, and quinone groups that can undergo substitution, reduction, oxidation reactions, etc. When it is added to fluororubber, due to the strong interaction between the surface of carbon black and the rubber interface, when the material is stressed, the molecular chain is relatively easy to slide on the surface of carbon black, but it is not easy to break away from carbon black. The elastomer and carbon black form a strong and solid bond that can slide, and the mechanical strength increases. Although the particle size of fillers such as carbon black or silica is small, due to their extremely easy agglomeration, impurities of dozens or hundreds of microns are easily formed after agglomeration, which is likely to cause poor film breaking.

[0066] According to an embodiment of the present application, when the polyurethane raw rubber is 100 parts by mass, the filler is 5 to 50 parts by mass. It should be noted that the best way to reduce agglomeration is to reduce the dosage. During the dissolution process, too much filler content also increases the risk of coating. Therefore, the dosage of the filler is 5 to 50 parts by mass.

[0067] In some specific embodiments of the present application, the anti-aging agent is one or more of antioxidant 1010, antioxidant 2, antioxidant 6, antioxidant 4, antioxidant 1076, antioxidant 168, antioxidant RD, antioxidant AW, antioxidant DD, antioxidant BLE, antioxidant 4010, 4010NA, 4020, 4030, 4040, antioxidant DNP, antioxidant H, antioxidant A, antioxidant D, antioxidant SP, antioxidant 264, antioxidant 2246, antioxidant 2246-S, antioxidant NBC, and antioxidant MB.

[0068] According to an embodiment of the present application, the amount of the anti-aging agent is 0.5 to 5 parts by mass. By using the anti-aging agent in this content, the oxidation of the polymer and other aging processes can be delayed or inhibited.

[0069] In some specific embodiments of the present application, the other additives are at least one of a plasticizer, an anti-hydrolysis agent, an activator, zinc oxide, stearic acid, an ultraviolet absorber, a demolding agent, and a color paste.

[0070] According to an embodiment of the present application, the anti-hydrolysis agent is carbodiimide, and the dosage is 0 to 5 parts by mass, preferably 2 to 3 parts by mass. It should be noted that a large number of polar groups are contained inside the polyurethane, which reduces the hydrophobicity and increases the affinity with water molecules. And these polar groups, especially the ester groups, are prone to degradation at high temperature and high humidity, and the molecular chain breaks, resulting in product failure. Therefore, a certain amount of anti-hydrolysis agent needs to be added. The anti-hydrolysis agent reacts with carboxylic acid or the carboxylic acid generated by the hydrolysis of the ester group to generate acylurea derivatives, thereby neutralizing the carboxyl groups in the polyester and preventing the further intensification of hydrolysis, thus playing a role in chain-breaking regeneration.

[0071] According to an embodiment of the present application, in the step of placing the polyurethane rubber film on the mold of a thermoforming machine and thermoforming to obtain the diaphragm of the sound generating device with a predetermined shape, the thermoforming is carried out by gas heating and pressurization, and the forming conditions are: the forming temperature is 100°C to 200°C, preferably 130°C to 190°C; the forming time is 50 s to 600 s, preferably 50 s to 400 s; the forming pressure is 0.05 Mpa to 5 Mpa.

[0072] That is to say, in this embodiment, the diaphragm is formed by pneumatic forming. Among them, the crosslinking of polyurethane rubber is a process of molecular chain growth to form a three-dimensional network structure. If the forming temperature is too low, the vulcanization speed is too slow and the vulcanization is insufficient. Also, since at high temperatures, the crosslinking reaction of polyurethane rubber is a process in which crosslinking and decomposition occur simultaneously, and polyurethane rubber has poor heat resistance. If the vulcanization temperature is too high and the time cannot be accurately controlled, the decomposition speed increases, resulting in the decomposition speed being greater than the vulcanization speed, causing the reverse original phenomenon and unable to ensure the degree of crosslinking. Therefore, the forming temperature range and forming time range of this embodiment are adopted.

[0073] In addition, during the forming process, due to the use of high-pressure gas for pressurization, the polyurethane rubber film is closely attached to the die head to form a surround and patterns. If the air pressure is too small, the diaphragm cannot be formed into the perfect shape designed by the die head. During the process of temperature rise, the film continuously softens. If the forming air pressure is too large, the film is prone to breakage. Therefore, the forming pressure range of this embodiment is adopted.

[0074] It should be noted that the diaphragm of this application can also be prepared by heating the die head of the mold. When the diaphragm can be formed by pneumatic forming, the diaphragm can generally also be formed by die pressing. Under the same conditions, the thickness range of the diaphragm formed by pneumatic forming is wider, and the thickness of the diaphragm formed by die pressing is small and relatively thick.

[0075] According to an embodiment of the present application, the plasticizer is one or more of alkane, naphthene, aromatic hydrocarbon, three-line oil, vaseline, paraffin wax, coumarone resin, coal tar, coal pitch, pine tar, rosin oil, tall oil, ointment, glycerol, castor oil, soybean oil, oleic acid, phthalate esters, aliphatic dibasic acid esters, fatty acids, phosphate esters, polyesters, epoxy resins, chlorine-containing compounds, dioctyl phthalate (DOP), diisodecyl phthalate (DIDP), dibutyl phthalate (DBP), dioctyl adipate (DOA), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS), oleate, castor oil ester, pentaerythritol fatty acid ester, citrate, tricresyl phosphate (TCP), trioctyl phthalate (TOP), sebacic acid-based polyester plasticizer, adipic acid-based polyester plasticizer, phthalic acid-based polyester plasticizer, epoxidized soybean oil, epoxidized castor oil.

[0076] According to an embodiment of the present application, the content of the plasticizer is 2 to 80 parts by mass. It should be noted that the molecular weight of the plasticizer is generally relatively low. It is difficult to disperse materials such as fillers and vulcanizing agents that are indispensable in rubber. For example, white carbon black or carbon black is prone to fly during the mixing process. If it is not mixed evenly with the plasticizer in advance, a large amount of loss will occur, the formula reproduction ability is poor, and indoor dust pollution will also be caused. When the plasticizer is used in combination with rubber, it can reduce the intermolecular force of the rubber, has a strong wetting ability with rubber and other compounding agents, can improve the heat generation phenomenon during the mixing process, and can also increase the adhesiveness, processing plasticity, and fluidity of the rubber compound, providing convenience for the forming processes such as calendering and extrusion. At the same time, the appearance of the plasticizer can improve the hardness of the matrix. If the MPU material is not combined with the plasticizer, the hardness after cross-linking is generally relatively high and it is difficult to be lower than 35A. Thus, it can be seen that the plasticizer is an indispensable material to obtain a low-hardness MPU. At the same time, the plasticizer can also improve the cold resistance of the material.

[0077] As Figure 3 and Figure 4 shown, the sound generating device includes a diaphragm 15 prepared according to the above embodiment of the present application. The diaphragm 15 can be composed of a surround portion 151 and a dome portion 152. The microporous polyurethane elastomer film layer can be applied to the surround portion 151 of the diaphragm. Those skilled in the art can make corresponding adjustments according to the actual product requirements. For example, the surround portion 151 protrudes toward the voice coil 11 side, the dome portion 152 is located on the lower surface of the surround portion 151, and a centering washer is added to the vibration system.

[0078] As Figure 5 and Figure 6 shown, the sound generating device 100 according to the third aspect embodiment of the present application includes a housing 10, a magnetic circuit system 14 and a vibration system provided in the housing 10. The vibration system includes a voice coil 11, a first diaphragm 12 and a second diaphragm 13. The top of the voice coil 11 is connected to the first diaphragm 12. The magnetic circuit system 14 drives the voice coil 11 to vibrate to drive the first diaphragm 12 to generate sound. Both ends of the second diaphragm 13 are respectively connected to the housing 10 and the bottom of the voice coil 11. The second diaphragm 13 is the diaphragm of the above embodiment.

[0079] That is to say, the sound generating device 100 according to the embodiments of the present application may further include two diaphragms prepared by the above embodiments of the present application, namely a first diaphragm 12 and a second diaphragm 13. The first diaphragm 12 may be used for vibrating to generate sound, and the second diaphragm 13 may be used to balance the vibration of the voice coil 11. Specifically, when the sound generating device 100 operates, after the voice coil 11 is energized, under the action of the magnetic field force of the magnetic circuit system 14, the voice coil 11 can vibrate up and down to drive the first diaphragm 12 to vibrate, and the first diaphragm 12 can generate sound when vibrating. The second diaphragm 13 can also vibrate up and down following the voice coil 11. Since both ends of the second diaphragm 13 are respectively connected to the housing 10 and the bottom of the voice coil 11, the second diaphragm 13 can balance the vibration of the voice coil 11, and can prevent the voice coil 11 from being polarized, thereby improving the sound generating effect of the sound generating device 100.

[0080] It should be noted that both the first diaphragm 12 and the second diaphragm 13 may adopt the diaphragms of the above embodiments of the present application, or one of the first diaphragm 12 and the second diaphragm 13 may adopt the diaphragms of the above embodiments of the present application. The present application does not make specific restrictions on this.

[0081] The preparation method of the diaphragm according to the embodiments of the present application and the prepared diaphragm will be described in detail below with reference to specific embodiments.

[0082] In the present application, Comparative Example 1 and Example 1 are adopted, and the selection of the comparative example and the example is based on the similar F0 of the diaphragm.

[0083] In Comparative Example 1, the MPU was directly compression molded to obtain a diaphragm with a hardness of 80A and a thickness of 50 μm.

[0084] In Example 1, a polyurethane rubber film layer was obtained by coating and a diaphragm was prepared by air pressure forming, with a hardness of 80A and a thickness of 50 μm.

[0085] Among them, the formulations of Comparative Example 1 and Example 2 are shown in Table 1 below.

[0086] Table 1. Formulations of Comparative Example 1 and Example 1

[0087]

[0088]

[0089] As can be seen from Table 1, the formulations in Comparative Example 1 and Example 1 are the same, and the diaphragms in Comparative Example 1 and Example 1 are prepared by different methods respectively.

[0090] The performance tests of the comparative example and the example will be carried out separately below.

[0091] (1) Mechanical property test

[0092] In order to verify the mechanical properties of the diaphragm raw materials of the embodiment of the present application, the elongation at break tensile strength test was performed:

[0093] After vulcanization molding, the diaphragm raw materials in Comparative Example 1 and Example 1 were tested for their elongation at break and elongation at break according to the ASTM-D882 test standard, with a gauge length of 30 mm and a tensile rate of 300 mm / min. The test results are shown in Table 2 below.

[0094] Table 2. Elongation at break and strength data of diaphragm raw materials of comparative example 1 and embodiment 1

[0095] Diaphragm raw material Elongation at break / % Tensile strength / MPa Comparative example 1 560 42 Example 1 540 43

[0096] It can be seen from Table 2 that both Comparative Example 1 and Example 1 have good elongation at break. Under the same hardness, the mixed polyurethane film layer obtained by the coating scheme of Example 1 is compared with the film of the same material obtained by direct mold compression molding of Comparative Example 1. It is found that the elongation at break and the strength of the two are similar, with little difference.

[0097] (2) Effect of solid content

[0098] In order to verify the effect of different solid contents on coating, different concentrations of mixed slurries were prepared for coating. The mixed rubber MPU in Example 1 was coated once with different solid contents to form the maximum value of the film and test the thickness of the film. Among them, the solid contents were 15%, 20%, 25%, 30%, 35%, 40%, and 45%, respectively. The film thickness corresponding to different solid contents in Example 1 is shown in Table 3 below.

[0099] Table 3. Thickness of the film obtained by coating at different solid contents in Example 1

[0100]

[0101]

[0102] It can be seen from Table 3 that the solid content directly affects the maximum thickness of a coating. The thickness of films made by coating with different solid contents varies greatly. Therefore, if a thicker film is required, the solid content can be appropriately increased.

[0103] (3) Diaphragm vulcanization molding shrinkage test

[0104] In order to verify the difference between the MPU material molding dimensions and the design in the embodiment of the present application, the difference between the diaphragm diameter and the design value was tested.

[0105] First, test the diameter I0 of the test design tooling. Then, vulcanize Comparative Example 1 and Example 1 respectively and test the diameter I1 of the diaphragm. The molding shrinkage rate = (I0 - I1) / I0 * 100%.

[0106] Table 4. Molding Shrinkage Rates of Diaphragm Raw Materials in Comparative Example 1 and Example 1

[0107] Diaphragm raw material Molding shrinkage rate / % Comparative example 1 3.2 Example 1 1.8

[0108] As can be seen from Table 4, when comparing Comparative Example 1 with Example 1, the molding shrinkage rate of Example 1 is smaller and closer to the design value. In the mixed slurry, the molecular chains can fully unfold and arrange freely, with less internal stress, so the shrinkage during molding is smaller.

[0109] (4) THD Curve Test

[0110] To verify the acoustic distortion of the application examples, the diaphragms in Comparative Example 1 and Example 1 were respectively subjected to total harmonic distortion (THD) tests, and the tested THD curves were recorded in Figure 2 in.

[0111] From Figure 2 the test data, it can be seen that compared with Comparative Example 1, the shrinkage rate of Example 1 is smaller, and the diaphragm size is more matched with the design value, so the THD of Example 1 is lower.

[0112] All in all, according to the method for preparing a diaphragm of the embodiments of the present application, by adopting the coating method, the prepared diaphragm has the advantages of a large adjustable space for the film thickness, low adjustment cost, and the ability to solve the shrinkage problem caused by curing. The diaphragm prepared according to the method for preparing a diaphragm of the embodiments of the present application and the sound generating device having the diaphragm have good acoustic performance, and the production cost is also reduced.

[0113] Although some specific embodiments of the present application have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A method for preparing a diaphragm of a sound generating device, characterized in that, It includes the following steps: React solid polyurethane raw rubber, vulcanizing agent, vulcanization accelerator, anti-aging agent, filler, other additives with a solvent to prepare a mixed slurry with a solid content of 15% - 45%; Coat the mixed slurry into a film with a predetermined thickness, and after heating and volatilizing the solvent, form a polyurethane rubber film with a preset thickness, and the tensile strength σ of the polyurethane rubber film satisfies the relation: 0.1MPa ≤ σ ≤ 15MPa; Place the polyurethane rubber film on the mold of a thermoforming machine, and thermally press and crosslink it into a diaphragm with a predetermined shape; The thickness of the diaphragm is 15μm - 200μm; The hardness of the diaphragm is 40A - 95A.

2. The method for preparing the diaphragm of the sound generating device according to claim 1, characterized in that, In the step of preparing the mixed slurry, knead polyurethane raw rubber, vulcanizing agent, vulcanization accelerator, anti-aging agent, filler and other additives to prepare a kneaded rubber, and dissolve the kneaded rubber in the solvent to obtain the mixed slurry.

3. The method for preparing the diaphragm of the sound generating device according to claim 1, characterized in that, In the step of preparing the mixed slurry, knead polyurethane raw rubber, anti-aging agent, filler and other additives to prepare a kneaded rubber, and dissolve the kneaded rubber, vulcanizing agent and vulcanization accelerator in the solvent to obtain the mixed slurry.

4. The manufacturing method of the diaphragm of the sound generating device according to claim 1, characterized in that, The solid polyurethane raw rubber is composed of a soft segment and a hard segment, The hard segment is one or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,5 - naphthalene diisocyanate, p-phenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, isophorone diisocyanate, m-xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hydrogenated toluene diisocyanate, trimethylhexamethylene diisocyanate; The soft segment is one or more of polyester polyol, polycarbonate polyol, polycaprolactone, polyether polyol, polybutadiene-based polyol, castor oil polyol, tetrahydrofuran-propylene oxide copolymer polyol, epoxy resin-modified polyol.

5. The method for preparing the diaphragm of the sound generating device according to any one of claims 1-3, characterized in that, The solvent is one or more of tetrahydrofuran, N,N-dimethylformamide, acetone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, toluene, xylene, chlorobenzene.

6. The method for preparing the diaphragm of the sound generating device according to any one of claims 1-3, characterized in that, The vulcanizing agent is one or more of dicumyl peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, di-tert-butyl peroxide, 2,5-dimethyl-2,5-(di-tert-butylperoxy)hexane, bis(tert-butylperoxy)isopropylbenzene, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl perbenzoate, sulfur.

7. The method for preparing the diaphragm of the sound generating device according to any one of claims 1-3, characterized in that, The vulcanization accelerator is one or more of thiazoles, sulfenamides, thiurams, thioureas, dithiocarbamates, aldehyde amines, guanidines, xanthates, and the filler is one or more of carbon black, white carbon black, talcum powder, calcium carbonate, graphite, titanium dioxide.

8. The method for preparing the diaphragm of the sound generating device according to any one of claims 1-3, characterized in that, The anti-aging agent is one or more of antioxidant 1010, antioxidant 2, antioxidant 6, antioxidant 4, antioxidant 1076, antioxidant 168, anti-aging agent RD, anti-aging agent AW, anti-aging agent DD, anti-aging agent BLE, anti-aging agent 4010, 4010NA, 4020, 4030, 4040, anti-aging agent DNP, anti-aging agent H, anti-aging agent A, anti-aging agent D, anti-aging agent SP, anti-aging agent 264, anti-aging agent 2246, anti-aging agent 2246-S, anti-aging agent NBC, and anti-aging agent MB.

9. The method for preparing the diaphragm of the sound generating device according to claim 1, characterized in that, The other additives are at least one of a plasticizer, a hydrolysis inhibitor, an activator, zinc oxide, stearic acid, an ultraviolet absorber, a demolding agent, and a color paste.

10. The method for preparing the diaphragm of the sound generating device according to claim 1, wherein, In the step of placing the polyurethane rubber film on the mold of a thermoforming machine and hot-pressing to form a diaphragm of a sounding device with a predetermined shape, a gas heating and pressurizing method is adopted, the forming temperature is 100°C to 200°C, the forming time is 50 s to 600 s, and the forming pressure is 0.05 Mpa to 5 Mpa.

11. A diaphragm, characterized in that, The diaphragm is the diaphragm prepared by the method according to any one of claims 1-10.

12. A sound generating device, characterized in that, It includes a vibration system and a magnetic circuit system cooperating with the vibration system. The vibration system includes a diaphragm and a voice coil bonded to one side of the diaphragm. The magnetic circuit system drives the voice coil to vibrate to drive the diaphragm to emit sound, and the diaphragm is the diaphragm of claim 11.

13. A sound generating device, characterized in that, It includes a housing and a magnetic circuit system and a vibration system provided in the housing. The vibration system includes a voice coil, a first diaphragm, and a second diaphragm. The top of the voice coil is connected to the first diaphragm. The magnetic circuit system drives the voice coil to vibrate to drive the first diaphragm to emit sound. Both ends of the second diaphragm are respectively connected to the housing and the bottom of the voice coil, and the second diaphragm is the diaphragm of claim 11.

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