CN116199918B

CN116199918B - Preparation method of vibrating diaphragm of sound generating device, vibrating diaphragm and sound generating device

Info

Publication number: CN116199918B
Application number: CN202111446832.2A
Authority: CN
Inventors: 王伟超; 王婷; 李春
Original assignee: Goertek Inc
Current assignee: Goertek Inc
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2024-05-03
Anticipated expiration: 2041-11-30
Also published as: CN116199918A

Abstract

The application discloses a preparation method of a vibrating diaphragm of a sound generating device, the vibrating diaphragm and the sound generating device, wherein the vibrating diaphragm comprises a casting polyurethane film layer, and the preparation method comprises the following steps: dissolving a polyurethane prepolymer, a chain extender, a catalyst and other compounding aids into a solvent to form a mixed slurry, wherein the end groups of the polyurethane prepolymer comprise a partially end-capped-NCO; coating the mixed slurry into a preset thickness, and heating and volatilizing to form the casting polyurethane film layer with the preset thickness, wherein the tensile strength sigma of the casting polyurethane film layer meets the relation: sigma is more than or equal to 0.1MPa and less than or equal to 10MPa; and placing the casting polyurethane film layer on a die of a thermoforming machine, and forming the casting polyurethane film layer into the vibrating diaphragm with the preset shape through hot-pressing crosslinking. The preparation method of the vibrating diaphragm is convenient to operate, not only can save the production cost of the vibrating diaphragm, but also can solve the shrinkage problem caused by solidification during the compression molding of the vibrating diaphragm, and the prepared vibrating diaphragm has good dimensional stability and acoustic performance.

Description

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

Technical Field

The application belongs to the technical field of diaphragms, and particularly relates to a preparation method of a diaphragm of a sound generating device, the diaphragm obtained by the preparation method and the sound generating device comprising the diaphragm.

Background

At present, the rubber vibrating diaphragm depends on the die pressing of an upper die cavity and a lower die cavity in the preparation process, and because the F0 of the miniature loudspeaker is low, the required vibrating diaphragm thickness is thinner, so the requirements on the upper die cavity and the lower die cavity are very high, the tolerance of the upper die cavity and the lower die cavity is required to be in a micron level, the price of the high-precision die is high, and the popularization of rubber materials is limited. In addition, since rubber compression molding shrinks more during molding, there is a certain difference from the designed acoustic requirements.

Disclosure of Invention

An object of the present application is to provide an improved method for manufacturing a diaphragm of a sound generating device, which is convenient to operate, not only can save the production cost of the diaphragm, but also can solve the shrinkage problem caused by solidification during compression molding of the diaphragm.

It is still another object of the present application to provide a diaphragm prepared by the above preparation method.

It is still another object of the present application to provide a sound generating apparatus having the above-mentioned diaphragm.

According to a first aspect of the present application, there is provided a method for manufacturing a diaphragm of a sound generating apparatus, the diaphragm including a casting polyurethane film layer, the method comprising: dissolving a polyurethane prepolymer, a chain extender, a catalyst and other compounding aids into a solvent to form a mixed slurry, wherein the end groups of the polyurethane prepolymer comprise a partially end-capped-NCO; coating the mixed slurry into a preset thickness, and heating and volatilizing to form the casting polyurethane film layer with the preset thickness, wherein the tensile strength sigma of the casting polyurethane film layer meets the relation: sigma is more than or equal to 0.1MPa and less than or equal to 10MPa; and placing the casting polyurethane film layer on a die of a thermoforming machine, and forming the casting polyurethane film layer into the vibrating diaphragm with the preset shape through hot-pressing crosslinking.

Optionally, the thickness of the casting polyurethane film layer is 15-200 μm.

Optionally, the hardness of the casting polyurethane film layer is 50A-95A.

Optionally, the solid content of the mixed slurry is 20% -70%.

Optionally, the polyurethane prepolymer is composed of a soft segment, a hard segment and a capping agent, wherein the capping agent is connected with one end of the hard segment at the end part, which is far away from the soft segment.

Optionally, the end capping agent is one or more of phenols, caprolactam, acetylacetone, methyl ketoxime, imidazole compounds, sodium bisulphite, 3, 5-lutidine and ethyl acetoacetate.

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

Optionally, the chain extender is one or more of a small molecule polyol or a small molecule polyamine.

Optionally, the catalyst is one or more of butyl tin dilaurate, stannous octoate, phosphoric acid, oleic acid, adipic acid, azelaic acid and ferric acetylacetonate.

Optionally, the other auxiliary agent comprises a filler, wherein the filler is one or more of carbon black, white carbon black, talcum powder, calcium carbonate, graphite and titanium dioxide.

Optionally, the other auxiliary agents include an anti-aging auxiliary agent, wherein the anti-aging auxiliary 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-S, anti-aging agent NBC and anti-aging agent MB.

Optionally, the other auxiliary agents comprise at least one of plasticizer, anti-hydrolysis agent, ultraviolet absorbent, release agent and color paste.

Optionally, the casting polyurethane film layer is placed on a die of a thermoforming machine, and is prepared by adopting a gas heating forming mode in the step of forming the diaphragm into a preset shape through hot pressing, wherein the forming temperature is 120-200 ℃, the forming time is 50-1200 s, and the forming pressure is 0.05-5 MPa.

The application also provides a vibrating diaphragm prepared by the method in any embodiment.

The application also provides a sound generating device, which comprises a vibration system and a magnetic circuit system matched with the vibration system, wherein the vibration system comprises a vibrating diaphragm and a voice coil combined on one side of the vibrating diaphragm, the magnetic circuit system drives the voice coil to vibrate so as to drive the vibrating diaphragm to generate sound, and the vibrating diaphragm is the vibrating diaphragm in any embodiment.

The application also provides a sound generating device, which comprises a shell, and a magnetic circuit system and a vibration system which are arranged in the shell, wherein the vibration system comprises a voice coil, a first vibrating diaphragm and a second vibrating diaphragm, the top of the voice coil is connected with the first vibrating diaphragm, the magnetic circuit system drives the voice coil to vibrate so as to drive the first vibrating diaphragm to generate sound, two ends of the second vibrating diaphragm are respectively connected with the shell and the bottom of the voice coil, and the second vibrating diaphragm is the vibrating diaphragm in any embodiment.

The application has the technical effects that the CPU film layer is prepared by a coating method, the adjustable range of the film thickness is large, the adjustment cost is low, films with different hardness and thickness can be coated according to the design requirement of products, the limitation of a forming die and a forming mode is avoided, and the formula design and the manufacturing cost of the CPU diaphragm are obviously reduced. Meanwhile, the components in the CPU film prepared by the method are uniformly distributed, and when the film is coated, molecular chains can be oriented freely, and residual stress is almost avoided in the film. This is beneficial to reduce shrinkage problems caused by curing of the CPU material during diaphragm formation. Compared with the traditional mould pressing integrated process, the size of the vibrating diaphragm prepared by the method is closer to a design value, and good acoustic performance and dimensional stability of the product can be better ensured.

Other features of the present application and its advantages will become apparent from the following detailed description of exemplary embodiments of the application, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description, serve to explain the principles of the application.

FIG. 1 is a graph of the total harmonic distortion test for example 1 and comparative example 1 provided by the present application;

fig. 2 is a flowchart of a method for preparing a diaphragm according to an embodiment of the present application.

FIG. 3 is a schematic diagram of the overall structure of a sound generating apparatus according to an embodiment of the present application;

FIG. 4 is a schematic view of a part of a sound generating apparatus according to an embodiment of the present application;

FIG. 5 is a cross-sectional view of a sound emitting device according to an embodiment of the present application;

fig. 6 is an exploded view of a sound emitting device according to an embodiment of the present application.

Reference numerals

A sound generating device 100;

a housing 10; a voice coil 11; a first diaphragm 12; a second diaphragm 13; a magnetic circuit system 14;

A diaphragm 15; a folded ring portion 151; ball top 152.

Detailed Description

Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present application unless it is specifically stated otherwise.

The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the application, its application, or uses.

Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of exemplary embodiments may have different values.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

The diaphragm, the preparation method of the diaphragm and the sound generating device according to the embodiment of the application are described in detail below with reference to the specific drawings.

The vibrating diaphragm of the sound generating device comprises a casting polyurethane film layer. The preparation method of the vibrating diaphragm comprises the following steps:

The polyurethane prepolymer, chain extender, catalyst and other compounding ingredients are dissolved into a solvent to form a mixed slurry, wherein the end groups of the polyurethane prepolymer include a partially end-capped-NCO.

And coating the mixed slurry to a preset thickness, and heating and volatilizing to form a casting polyurethane film layer with the preset thickness. For example, the mixed slurry may be applied to a release film and formed into a cast polyurethane film layer of a certain thickness, and then the molded cast polyurethane film layer and a tape composed of the release film are heated to volatilize the solvent in the tape. Wherein, tensile strength sigma of the casting polyurethane film layer satisfies the relation: sigma is more than or equal to 0.1MPa and less than or equal to 10MPa.

And placing the casting polyurethane film layer on a die of a thermoforming machine, and forming the casting polyurethane film layer into the vibrating diaphragm with the preset shape through hot-pressing crosslinking.

In other words, the diaphragm of the sound generating device according to the embodiment of the application comprises a casting polyurethane film layer, and the casting polyurethane film layer is mainly prepared by dissolving polyurethane prepolymer, chain extender, catalyst and other auxiliary agents into a solvent to form mixed slurry, and coating the mixed slurry. For example, the polyurethane prepolymer, the chain extender, the catalyst and other auxiliary agents are dissolved into a solvent to form a mixed slurry, and the mixed slurry is coated into a film with a certain thickness by adopting a coating mode. After the film is heated at 50-150 ℃, the solvent volatilizes, and the Casting Polyurethane (CPU) film layer with a certain thickness is obtained. The Casting Polyurethane (CPU) film layer is placed on a die of a thermoforming machine, and after heating and pressurizing for a certain time, the vibrating diaphragm with a required structure can be obtained.

Furthermore, the end groups of the polyurethane prepolymer comprise a partially blocked NCO. Since the-NCO activity is high, the polyurethane prepolymer and the chain extender react to complete crosslinking at normal temperature or at high temperature after being mixed. When the mixed slurry is formed, gel is generated, the coating thickness is uneven, and after the mixed slurry is prepared into a film, the film becomes insoluble and infusible substances due to cross-linking reaction, and secondary forming processing cannot be performed, so that the polyurethane prepolymer needs to be partially blocked and then is coated for use, blocked-NCO generates-NHCO which is relatively stable at normal temperature, and only when the temperature is higher than the decomposition temperature (120 ℃), deblocking reaction can occur, and the-NCO is generated again. That is, the blocked polyurethane prepolymer may be coated to prepare a film, subjected to secondary processing, further reacted, and subjected to pneumatic heating molding to cause deblocking.

Further, the tensile strength σ of the cast polyurethane film layer satisfies the relation: the sigma is more than or equal to 0.1MPa and less than or equal to 10MPa, and the tensile strength can represent the crosslinking degree of the casting polyurethane film layer, so that the film layer meeting the tensile strength requirement in the range can be manufactured into the diaphragm meeting the size and the use requirement. Alternatively, the tensile strength sigma of the cast polyurethane film layer may be 0.1MPa, 0.3MPa, 0.5MPa, 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa, etc. In addition, since the cast polyurethane is in a liquid form at a high temperature and is difficult to be molded by air pressure, it is necessary to partially crosslink into a solid in advance, and the polyurethane film has a strength such that the polyurethane film does not flow or break during air pressure molding, and the strength of the polyurethane film after pre-crosslinking should satisfy the above range. Before molding, the tensile strength σ of the cast polyurethane film layer needs to satisfy the relation: sigma is more than or equal to 0.1MPa and less than or equal to 10MPa, and if the strength is too small, the membrane is easy to break during secondary air pressure molding; too high strength, high crosslinking density, difficult secondary molding, preferably 0.5 to 8MPa, and in this range, molding is easier, shrinkage after molding is small, and design size is easy to achieve.

The CPU film layer is prepared by the coating method, the thickness adjustable range of the CPU film layer is large, the adjustment cost is low, films with different hardness and thickness can be coated according to the design requirement of products, the limitation of a forming die and a forming mode is avoided, and the formula design and the manufacturing cost of the CPU diaphragm are obviously reduced. Meanwhile, the components in the CPU film obtained by the preparation method are uniformly distributed, and when the film is coated, molecular chains can be oriented freely, and residual stress is almost avoided in the film. This is beneficial to reduce shrinkage problems caused by curing of the CPU material during diaphragm formation. Compared with the traditional mould pressing integrated process, the size of the vibrating diaphragm prepared by the method is closer to a design value, and good acoustic performance and dimensional stability of the product can be better ensured.

According to one embodiment of the application, the thickness of the cast polyurethane film layer is 15 μm to 200 μm, preferably 30 μm to 150 μm. It should be noted that if the thickness of the casting polyurethane film layer is too thin, the damping performance of the diaphragm is poor and the listening performance is poor; if the thickness of the casting polyurethane film layer is too thick, the coating is needed for multiple times, the cost is increased, the meaning of cost reduction is lost, and the thickness is increased, so that the weight reduction requirement of wearing products cannot be met. When the thickness of the casting polyurethane film layer is between 15 and 200 mu m, the damping performance of the vibrating diaphragm is good, the sound production effect of the vibrating diaphragm can be improved, the weight of the vibrating diaphragm is moderate, and the weight reduction requirement of sound production equipment is met.

In some embodiments of the application, the cast polyurethane film has a hardness of 50A to 95A. It should be noted that if the hardness is too small, the thickness is increased to match with the proper F0 of the product, and the cost is increased after multiple coating; if the hardness is too high, the elongation at break of the CPU becomes small, the membrane is easy to break in low-temperature reliability verification to cause product failure, and the F0 of the vibrating membrane is too high to obtain perfect sound effect.

According to one embodiment of the application, the mixed slurry has a solids content of 20% to 70%. If the solid content is too low, the slurry has low viscosity and poor moldability, which wastes the solvent, and requires a larger number of repeated coating steps when a thicker film is required to be formed, resulting in an increase in cost; if the solid content is too high, the slurry cannot be dissolved, the viscosity of the slurry is high, the defoaming is difficult, the coating difficulty is high, and the film is easy to have defects. Alternatively, the solids content of the mixed slurry may be 20%, 30%, 40%, 50%, 60%, 70%, etc.

In some embodiments of the present application, the polyurethane prepolymer is composed of a soft segment, a hard segment, and an end capping agent attached to the end of the hard segment at the end distal from the soft segment.

Wherein the hard segment is one or more of toluene diisocyanate, diphenylmethane diisocyanate, 1, 5-Naphthalene Diisocyanate (NDI), p-phenylene diisocyanate, 3 ' -dimethyl-4, 4' -biphenyl diisocyanate, isophorone diisocyanate, m-dimethylene diisocyanate, 4' -dicyclohexylmethane diisocyanate, hydrogenated toluene diisocyanate and trimethylhexamethylene diisocyanate.

Wherein the hard segment of the polyurethane prepolymer is mainly prepared from isocyanate. The polarity of isocyanate is larger, the bonding capability between molecules of the hard segment is strong, the intermolecular acting force is strong, and the addition of the hard segment improves the hardness and modulus of the CPU and also increases the temperature resistance of the material. If the hard segment content is low, higher tensile strength or tensile strength cannot be achieved, and reliability problems may exist; if the hard segment content is too high, the elongation at break is reduced, and the probability of occurrence of film folding after reliability is increased.

Optionally, the soft segments of the prepolymer are one or more of polyester polyols, polycarbonate polyols, polycaprolactone, polyether polyols, polybutadiene polyols, castor oil polyols, tetrahydrofuran-propylene oxide copolyols, epoxy resin modified polyols. For example, polytetrahydrofuran ether (PTMG) may be used for the soft segment.

Among them, polyurethane is also called carbamate, and is a high molecular polymer with more carbamate in its main chain. The soft segment is composed of polyalcohol, the molecular weight is generally within 800-1800, the addition of the soft segment endows the CPU with certain elasticity, and the CPU has higher elongation at break and higher strength through the cooperation of the soft segment and the hard segment. When the soft segment of the prepolymer is prepared from polyester polyol, polycarbonate polyol, polycaprolactone polyol and epoxy resin modified polyol, the internal polarity of the material is larger, the intermolecular binding capacity of the soft segment is strong, the intermolecular acting force is strong, the prepared CPU has higher strength, and the prepared CPU is prepared from the soft segment of polyether polyol, polybutadiene polyol, castor oil polyol and tetrahydrofuran-propylene oxide copolyol, has soft segment, small steric hindrance and larger free volume between molecules, and has larger elongation at break.

According to one embodiment of the application, the capping agent is one or more of phenols (e.g., arOH), caprolactam, acetylacetone, methyl ketoxime, imidazoles, sodium bisulphite, 3, 5-lutidine, ethyl acetoacetate.

In some embodiments of the application, the solvent is one or more of Tetrahydrofuran (THF), N-Dimethylformamide (DMF), acetone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, toluene, xylene, chlorobenzene.

In actual operation, materials consisting of polyurethane prepolymer, chain extender, catalyst and other auxiliary agents can be added into a solvent to be continuously stirred, the rotating speed is about 200r/min to 1000r/min, and after dissolution is completed, defoaming is carried out to carry out coating. Different solvents can be selected for different requirements, for example, when DMF and butyl acetate are used in a 1:1 compounding way, not only the solubility is increased through DMF, but also the solvent volatilization can be quickened when butyl acetate is coated to form a film, so that the coating slurry with perfect dissolution can be obtained.

According to one embodiment of the application, the chain extender is one or more of a small molecule polyol and a small molecule polyamine. For example, the chain extender is one or more of 3,3 '-dichloro-4, 4' -diaminodiphenylmethane, 1, 4-butanediol, trimethylolpropane, triisopropanolamine, 3, 5-dimethylthiotoluenediamine, 1, 4-dihydroethoxybenzene, hydroquinone bishydroxyethyl ether, resorcinol-bis (P-Hydroxyethyl) Ether (HER). Under the reaction of the chain extender and the polyurethane prepolymer, the CPU is converted from a linear structure into a three-dimensional network structure, and the hardness and the modulus are improved to become an insoluble material. The usage amount of the chain extender has great influence on the crosslinking reaction and the properties of the crosslinked sizing material, and the fact that if the chain extender is too small, the crosslinking reaction speed is low, the crosslinking degree is low, the number of chemical bonds is small, the molecular chain movement capability is enhanced along with the increase of temperature, and the modulus is rapidly reduced is needed to be described; if the amount of the chain extender is too large, the crosslinking degree increases, the hardness increases, the temperature increases due to the limitation of the crosslinking point, the molecular chain cannot move, the segment movement capability decreases, the modulus changes less with the temperature increase, but the tear strength and the elongation at break decrease linearly.

In some embodiments of the application, the catalyst is one or more of butyltin dilaurate, stannous octoate, phosphoric acid, oleic acid, adipic acid, azelaic acid, iron acetylacetonate. The catalyst has the effects of accelerating the reaction and improving the preparation efficiency of the vibrating diaphragm. The catalyst may be one or more of the above materials.

According to one embodiment of the application, the other compounding auxiliary agent comprises a filler, wherein the filler is one or more of carbon black, white carbon black, talcum powder, calcium carbonate, graphite and titanium dioxide. Taking carbon black as an example, carbon black is an amorphous structure, and particles form aggregates by physicochemical bonds with each other. The primary structure of carbon black is composed of aggregates, and van der Waals forces or hydrogen bonds exist between the aggregates, so that the aggregates can be aggregated into a space network structure, namely, a secondary structure of carbon black. When the carbon black is added into CPU, the molecular chain slides on the carbon black surface easily due to the strong interaction between the carbon black surface and the interface of CPU, but is not easy to separate from the carbon black, the elastomer and the carbon black form a strong bond capable of sliding, and the mechanical strength is increased. Although the particle size of the filler such as carbon black or white carbon black is small, the filler is extremely easy to agglomerate, impurities of tens or hundreds of micrometers are easy to form after agglomeration, bad membrane rupture is easy to cause, the best method for reducing the agglomeration is to reduce the dosage, and in the dissolving process, the excessive filler content also increases the coating risk. When the polyurethane prepolymer is 100 parts by mass, the filler is used in an amount of 5 to 50 parts by mass, so that not only the mechanical strength between the elastomer and the filler can be increased, but also the aggregation of the filler can be reduced.

According to one embodiment of the application, the other compounding ingredients include antioxidants, which are 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-S, antioxidant NBC, and antioxidant MB. Wherein the antioxidant is capable of slowing or inhibiting the progress of the oxidation process of the polymer. When the polyurethane prepolymer is 100 parts by mass, the dosage of the antioxidant is 0.5-5 parts by mass, so that the polyurethane prepolymer has a protective effect and realizes the functions of oxidation resistance and ageing resistance.

In some embodiments of the present application, the other compounding aid comprises at least one of a plasticizer, an anti-hydrolysis agent, an ultraviolet absorber, a mold release agent, and a color paste. For example, the hydrolysis inhibitor is a carbodiimide, and the amount of the carbodiimide to be used is 0 to 5 parts by mass, preferably 2 to 3 parts by mass, based on 100 parts by mass of the polyurethane prepolymer. It should be noted that, since a large number of polar groups are contained in the polyurethane, the hydrophobicity is reduced and the affinity with water molecules is increased, and these polar groups, particularly ester groups, are easily degraded under high temperature and high humidity, the molecular chain is broken, and the product is disabled, a certain amount of anti-hydrolysis auxiliary agent is needed to be added. The hydrolysis resistance auxiliary agent reacts with carboxylic acid generated by the hydrolysis of carboxylic acid or ester group to generate a ureide derivative, thereby neutralizing carboxyl groups in the polyester, preventing further aggravation of the hydrolysis and playing a role in chain scission regeneration.

According to one embodiment of the application, the plasticizer is one or more of alkanes, cycloalkanes, aromatics, tri-wire oils, vaseline, paraffin, coumarone resin, coal tar, coal pitch, pine tar, pine oil, tall oil, ointments, glycerin, castor oil, soybean oil, oleic acid, phthalates, aliphatic dibasic acid esters, fatty acids, phosphates, polyesters, epoxies, chlorine-containing species, octyl phthalate (DOP), diisosunflower phthalate (DIDP), dibutyl phthalate (DBP), dioctyl adipate (DOA), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS), oleic acid esters, castor oil, pentaerythritol fatty acid esters, citric acid esters, trimethylphenyl esters (TCP), trioctyl phthalate (TOP), sebacic acid polyester plasticizers, adipic acid polyester plasticizers, phthalic acid polyester plasticizers, epoxidized soybean oil, epoxidized castor oil.

Wherein the amount of the plasticizer is 2 to 80 parts by mass when the polyurethane prepolymer is 100 parts by mass. The molecular weight of the plasticizer is generally lower, and when the plasticizer is matched with the CPU, the acting force among the molecules of the CPU can be reduced, and the infiltration capacity of the CPU and other matched auxiliary agents is increased. Meanwhile, the appearance of the plasticizer can improve the hardness of the matrix, and the hardness of the CPU material after crosslinking is generally higher and is difficult to be lower than 35A without the cooperation of the plasticizer. It can be seen that a plasticizer is an indispensable material for obtaining a low-hardness CPU, and at the same time, cold resistance of the material can be improved.

According to one embodiment of the application, the casting polyurethane film layer is arranged on a die of a thermoforming machine, and is prepared by adopting a gas heating forming mode in the step of forming the diaphragm into a preset shape by hot pressing, wherein the forming temperature is 120-200 ℃, preferably 130-190 ℃; the molding time is 50 s-1200 s, preferably 50 s-600 s; the molding pressure is 0.05MPa to 5MPa. In the forming process, the CPU film layer is tightly attached to the die head due to the pressurization of high-pressure gas, so that a folded ring and patterns are formed, and if the air pressure is too small, the diaphragm cannot be formed into a perfect shape when the die head is designed; in the process of temperature rise, the film is continuously softened, and if the molding air pressure is too large, the film breaking phenomenon is easy to occur, so that the molding pressure adopts the pressure range of the embodiment.

That is, the diaphragm according to the embodiment of the present application is formed by air pressure. Wherein, the crosslinking of the CPU is the process of reacting the polyurethane prepolymer with the chain extender, and growing molecular chains to form a three-dimensional network structure. Because the polyurethane prepolymer of the application is blocked, the polyurethane prepolymer can be subjected to a crosslinking reaction with a chain extender after deblocking, and deblocking and crosslinking can occur during air pressure molding under set conditions.

The application also discloses a vibrating diaphragm, which is prepared by the method according to any embodiment. The vibrating diaphragm is obtained by adopting the air pressure forming mode, so that the cost of the vibrating diaphragm can be reduced.

As shown in fig. 3 and 4, the sound generating apparatus includes a diaphragm 15 according to the above embodiment of the present application, the diaphragm 15 may be composed of a folded ring portion 151 and a dome portion 152, and the micro-porous polyurethane elastomer film layer may be applied to the folded ring portion 151 of the diaphragm. Those skilled in the art can make corresponding adjustment according to the actual product requirement, for example, the folded ring portion 151 protrudes toward the voice coil 11, the top portion 152 is located on the lower surface of the folded ring portion 151, and a centering support plate is added in the vibration system.

As shown in fig. 5 and 6, the sound generating device 100 according to the third embodiment of the present application includes a housing 10, and a magnetic circuit system 14 and a vibration system disposed in the housing 10, where 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, two ends of the second diaphragm 13 are respectively connected to the housing 10 and the bottom of the voice coil 11, and the second diaphragm 13 is a diaphragm of the above embodiment.

That is, the sound generating apparatus 100 according to the embodiment of the present application may further include two diaphragms, i.e., the first diaphragm 12 and the second diaphragm 13, which are manufactured by the above-described embodiments of the present application, the first diaphragm 12 may be used for vibration sound generation, and the second diaphragm 13 may be used for balancing the vibration of the voice coil 11. Specifically, when the sound generating device 100 works, the voice coil 11 can vibrate up and down under the action of the magnetic field force of the magnetic circuit system 14 after the voice coil 11 is electrified to drive the first diaphragm 12 to vibrate, and sound can be generated when the first diaphragm 12 vibrates. The second vibrating diaphragm 13 can also vibrate up and down along with the voice coil 11, and as the two ends of the second vibrating diaphragm 13 are respectively connected with the bottom of the shell 10 and the bottom of the voice coil 11, the second vibrating diaphragm 13 can balance the vibration of the voice coil 11, and can prevent the voice coil 11 from generating polarization, thereby improving the sounding effect of the sounding device 100.

It should be noted that the first diaphragm 12 and the second diaphragm 13 may be the diaphragms according to the above embodiments of the present application, or one of the first diaphragm 12 and the second diaphragm 13 may be the diaphragm according to the above embodiments of the present application, which is not particularly limited.

The method for preparing the diaphragm and the diaphragm according to the embodiment of the application are described in detail below with reference to specific embodiments.

Comparative example 1 and example 1 were used in the present application, wherein the selection of comparative example and example was based on diaphragms having similar F0.

Example 1

Firstly, a hard segment (1, 5-Naphthalene Diisocyanate (NDI)) is used, and after the reaction of a soft segment (polytetrahydrofuran ether) is completed, methyl ketoxime is added to prepare the polyurethane prepolymer.

Then, the polyurethane prepolymer, the chain extender (1, 4-butanediol), the catalyst (stannous octoate), the filler (carbon black), the antioxidant (anti-aging agent 4010) and the anti-hydrolysis agent (carbodiimide) are dissolved into a compound solution of DMF and ethyl acetate to form mixed slurry with the solid content of 35 percent.

Subsequently, the mixed slurry was coated and the solvent was evaporated at 100℃to obtain a cast polyurethane film layer having a thickness of 32. Mu.m, and the cast polyurethane film layer was prepared into a diaphragm by air pressure molding at 150℃for 600s under a pressure of 5MPa.

The diaphragm obtained in example 1 had a hardness of 95A and a thickness of 32. Mu.m.

Comparative example 1

Firstly, using hard segment (NDI), after the soft segment (polytetrahydrofuran ether) reaction is completed, adding methyl ketoxime to prepare polyurethane prepolymer.

Then, polyurethane prepolymer, chain extender (1, 4-butanediol), catalyst (stannous octoate), filler (carbon black), antioxidant (anti-aging agent 4010) and anti-hydrolysis agent (carbodiimide) are stirred and mixed at a high speed at the temperature of 80 ℃, and the mixed solution is poured into a mould of the vibrating diaphragm in a hot mode, and the vibrating diaphragm is prepared through hot press molding, wherein the molding temperature is 150 ℃, the time is 600s, and the pressure is 8MPa.

The diaphragm obtained in comparative example 1 had a hardness of 93A and a thickness of 32. Mu.m.

Comparing example 1 with comparative example 1, it can be seen that comparative example 1 and example 1 respectively use different methods to prepare diaphragms.

The following performance tests were conducted on comparative examples and examples, respectively.

(1) Mechanical property test

To verify the mechanical properties of the diaphragm raw materials of the examples of the present application, an elongation at break tensile strength test was performed:

The diaphragm materials in comparative example 1 and example 1 were vulcanized and molded, and then tested for elongation at break and elongation at break according to the test conditions of ASTM-D882, gauge length 30mm, and tensile rate 300mm/min, and the test results are shown in Table 1 below.

TABLE 1 elongation at break and Strength data for the diaphragm raw materials of comparative example 1 and example 1

Vibrating diaphragm raw material	Elongation at break/%	Tensile Strength/MPa
			Comparative example 1	420	76
Example 1	480	86

As can be seen from Table 1, comparative example 1 and example 1 each have a good elongation at break, and the cast polyurethane film layer obtained by the coating scheme of example 1 was compared with the film obtained by direct die press molding of comparative example 1 at the same hardness, and it was found that the elongation at break was similar to the strength, and the difference was not large.

(2) Influence of the solids content

To verify the effect of different solids content on the coating effect, different concentrations of mixed slurries were separately prepared for coating. The mixed slurries in example 1 were coated once with different solid contents to obtain the maximum value of the cast polyurethane film, and the thickness of the cast polyurethane film was measured. Wherein the solid content is 20%, 30%, 40%, 50%, 60%, 70% respectively. The thickness of the cast polyurethane film corresponding to the different solids contents in example 1 is shown in Table 2 below.

TABLE 2 thickness of cast polyurethane film obtained by coating at different solids contents in example 1

As can be seen from table 2, the amount of the solid content directly affects the maximum thickness of the primary coating film, and the thickness of the cast polyurethane film layers formed by coating with different solid contents is greatly different, so that the solid content can be properly increased if a thicker cast polyurethane film layer is required.

(3) Diaphragm vulcanization molding shrinkage test

In order to verify the difference between the forming size and design of the CPU material in the embodiment of the application, the difference between the diameter of the vibrating diaphragm and the design value is tested.

First, the diameter L0 of the tooling was tested, the diameters L1 of the diaphragms were vulcanized and tested for comparative example 1 and example 1, respectively, and the molding shrinkage = (L0-L1)/L0 × 100%

TABLE 3 Molding shrinkage of the diaphragm materials of comparative example 1 and example 1

As can be seen from Table 3, comparative example 1 was compared with example 1, and the molding shrinkage of example 1 was smaller and more similar to the design value. In the mixed slurry, the molecular chains can be fully stretched for free arrangement, and the internal stress is small, so that the shrinkage is smaller during molding.

(4) THD Curve test

To verify the acoustic distortion of the examples of the present application, the diaphragms of comparative example 1 and example 1 were respectively subjected to a Total Harmonic Distortion (THD) test, and the THD curves of the test are recorded in fig. 2.

As can be seen from the test data of fig. 2, the shrinkage of example 1 is smaller and the diaphragm size is more matched to the design value than that of comparative example 1, so the THD of example 1 is lower.

In summary, according to the preparation method of the vibrating diaphragm provided by the embodiment of the application, the prepared vibrating diaphragm has the advantages of large adjustable space of the thickness of the casting polyurethane film layer, low adjustment cost, capability of solving the shrinkage problem caused by solidification and the like by adopting a coating mode. The vibrating diaphragm prepared by the method for preparing the vibrating diaphragm and the sound generating device with the vibrating diaphragm have good acoustic performance and lower production cost.

While certain specific embodiments of the application have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the application. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the application. The scope of the application is defined by the appended claims.

Claims

1. The preparation method of the vibrating diaphragm of the sound production device is characterized in that the vibrating diaphragm comprises a casting polyurethane film layer, and comprises the following steps:

Dissolving a polyurethane prepolymer, a chain extender, a catalyst and other compounding aids into a solvent to form a mixed slurry, wherein the end groups of the polyurethane prepolymer comprise a partially end-capped-NCO;

Coating the mixed slurry into a preset thickness, and heating and volatilizing to form the casting polyurethane film layer with the preset thickness, wherein the tensile strength sigma of the casting polyurethane film layer meets the relation: sigma is more than or equal to 0.1MPa and less than or equal to 10MPa;

placing the casting polyurethane film layer on a die of a thermoforming machine, and forming a diaphragm with a preset shape through hot-pressing crosslinking;

the thickness of the casting polyurethane film layer is 15-200 mu m, the hardness of the casting polyurethane film layer is 50-95A, the solid content of the mixed slurry is 20-70%, the polyurethane prepolymer consists of a soft section, a hard section and a blocking agent, and the blocking agent is connected with one end, far away from the soft section, of the hard section at the end part.

2. The method for preparing a diaphragm of a sound generating device according to claim 1, wherein the end-capping agent is one or more of phenols, caprolactam, acetylacetone, methyl ketoxime, imidazole compounds, sodium bisulphite, 3, 5-lutidine and ethyl acetoacetate.

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

4. The method for preparing a diaphragm of a sound generating device according to claim 1, wherein the chain extender is one or more of small molecular polyols and small molecular polyamine compounds.

5. The method for preparing a diaphragm of a sound generating apparatus according to claim 1, wherein the catalyst is one or more of butyl tin dilaurate, stannous octoate, phosphoric acid, oleic acid, adipic acid, azelaic acid, and iron acetylacetonate.

6. The method for preparing a vibrating diaphragm of a sound generating device according to claim 1, wherein the other auxiliary agents include a filler, and the filler is one or more of carbon black, white carbon black, talcum powder, calcium carbonate, graphite and titanium dioxide.

7. The method for preparing a vibrating diaphragm of a sound generating device according to claim 1, wherein the other auxiliary agents include an anti-aging auxiliary agent, and the anti-aging auxiliary agent is one or more of an antioxidant 1010, an antioxidant 2, an antioxidant 6, an antioxidant 4, an antioxidant 1076, an antioxidant 168, an antioxidant RD, an antioxidant AW, an antioxidant DD, an antioxidant BLE, an antioxidant 4010, 4010NA, 4020, 4030, 4040, an antioxidant DNP, an antioxidant H, an antioxidant A, an antioxidant D, an antioxidant SP, an antioxidant 264, an antioxidant 2246-S, an antioxidant NBC, and an antioxidant MB.

8. The method of claim 1, wherein the other auxiliary agents include at least one of plasticizer, anti-hydrolysis agent, ultraviolet absorbent, mold release agent, and color paste.

9. The method for manufacturing a diaphragm of a sound generating apparatus according to claim 1, wherein the step of placing the casting polyurethane film layer on a mold of a thermoforming machine and forming the diaphragm into a predetermined shape by hot press molding is performed by gas heating forming, the forming temperature is 120-200 ℃, the forming time is 50-1200 s, and the forming pressure is 0.05-5 MPa.

10. A diaphragm, characterized in that the diaphragm is a diaphragm obtained by the method according to any one of claims 1 to 9.

11. The utility model provides a sound generating device, its characterized in that includes vibration system and with vibration system matched with magnetic circuit, vibration system includes the vibrating diaphragm and combines the voice coil loudspeaker voice coil of vibrating diaphragm one side, magnetic circuit drives the voice coil loudspeaker voice coil vibrates in order to drive the vibrating diaphragm sound production, the vibrating diaphragm is the vibrating diaphragm of claim 10.

12. The utility model provides a sound generating device, its characterized in that includes the casing and establishes magnetic circuit and vibration system in the casing, vibration system includes voice coil loudspeaker voice coil, first vibrating diaphragm and second vibrating diaphragm, the top of voice coil loudspeaker voice coil with first vibrating diaphragm links to each other, magnetic circuit drives the voice coil loudspeaker voice coil vibrates in order to drive first vibrating diaphragm sound production, the both ends of second vibrating diaphragm respectively with the casing with the bottom of voice coil loudspeaker voice coil links to each other, the second vibrating diaphragm is the vibrating diaphragm of claim 10.