WO2022247911A1 - Diaphragm that may be used in sound generating device and preparation method therefor, and sound generating device - Google Patents

Abstract

The present invention relates to a diaphragm that may be used in a sound generating device and a preparation method therefor, and a sound generating device. A diaphragm that may be used in a sound generating device has a multi-layer composite structure, and at least one surface layer is a thermoplastic polyester elastomer film; the thermoplastic polyester elastomer is formed by the copolymerization of a polyester hard segment obtained by reacting an aromatic dicarboxylic acid with a diol and a soft segment containing an aliphatic polycarbonate; and the thickness of the diaphragm is 10-200 μm, and the loss factor of the thermoplastic polyester elastomer film in a 23°C environment is 0.1-0.3. The thermoplastic polyester elastomer of the present invention is composed of a polyester hard segment and an aliphatic polycarbonate soft segment. Said material not only solves the problems in existing thermoplastic elastomers of poor high temperature resistance and chemical resistance, but also improves sensitivity; meanwhile, said material also balances very well basic properties such as stiffness, resilience, and damping which are required for the vibration of a diaphragm.

Description

A vibrating membrane that can be used for a sounding device, its preparation method, and a sounding device technical field

The invention relates to the technical field of electroacoustics, in particular to a vibrating membrane that can be used for a sounding device, a preparation method thereof, and a sounding device.

Background technique

With the improvement of speaker performance requirements in the industry, more and more products are pursuing higher loudness, high-quality sound quality and high-level waterproof. Existing loudspeaker diaphragms mostly use composite structural materials, which include: engineering plastics (such as PEEK, PAR, PET, PI, PEI, etc.) as the base layer, acrylic glue, silica gel layer, etc. , as a rebound layer. When this composite film is used as a speaker diaphragm, it cannot fully match the requirements of higher loudness, high-quality sound quality, and high-level waterproofing. In recent years, because thermoplastic polyester elastomer can effectively improve the resilience of the diaphragm, reduce the folding of the diaphragm, and reduce the distortion caused by the sudden vibration of the diaphragm, more and more products use this material as the speaker diaphragm , to meet the high-quality needs of products such as sound quality and waterproof. However, the polyether-polyester thermoplastic polyester elastomer commonly used in the industry still has certain deficiencies in terms of high temperature resistance and chemical resistance.

At present, the thermoplastic polyester elastomer commonly used in the loudspeaker industry is polyether-polyester type, which still has certain deficiencies in high temperature resistance and chemical resistance. Although more types of thermoplastic polyester elastomers have been reported in other industries, such as thermoplastic polyester elastomers synthesized from polybutylene terephthalate hard segments and aliphatic polycarbonate soft segments, due to their It is used as insulating material, shell material and other materials that are different from sound-generating purposes, so it pays more attention to the optimization of properties such as insulation and tensile strength, while ignoring the acoustic properties such as chemical resistance, damping, and the lowest resonance frequency, which makes it impossible to be used in diaphragm.

For this reason, the present invention is proposed.

Contents of the invention

The main purpose of the present invention is to provide a diaphragm that can be used for sounding devices, wherein the thermoplastic polyester elastomer is composed of a polyester hard segment and an aliphatic polycarbonate soft segment. This material not only solves the problem of the existing thermoplastic elastomer The problem of poor high temperature resistance and chemical resistance is improved, and the sensitivity is improved. At the same time, the basic properties such as stiffness, resilience, and damping required for Gu Gu membrane vibration are well combined.

Another object of the present invention is to provide a method for preparing the above-mentioned diaphragm, which only involves conventional procedures, has a simple process, and does not have harsh process conditions.

The third aspect of the present invention aims to provide a sound generating device composed of the above diaphragm.

In order to achieve the above objectives, the present invention provides the following technical solutions.

According to the diaphragm for a sound emitting device according to the embodiment of the first aspect of the present invention, the diaphragm is a multi-layer composite structure, and at least one surface layer is a thermoplastic polyester elastomer film;

The thermoplastic polyester elastomer is formed by copolymerizing polyester hard segments obtained by reacting aromatic dicarboxylic acids with diols and soft segments containing aliphatic polycarbonate;

Wherein, the thickness of the diaphragm is 10-200 μm, and the loss factor of the thermoplastic polyester elastomer film is 0.1-0.3 at 23°C.

According to some embodiments of the present invention, the aliphatic polycarbonate includes polyhexamethylene polycarbonate diol, which accounts for more than 70% by weight of the soft segment.

According to some embodiments of the present invention, the soft segment further includes one or more of polycaprolactone, polybutylene adipate, polytetrahydrofuran ether, and polyethylene oxide.

According to some embodiments of the present invention, the soft segment accounts for 20%-80% by weight of the thermoplastic polyester elastomer.

According to some embodiments of the present invention, the soft segment accounts for 30%-60% by weight of the thermoplastic polyester elastomer.

According to some embodiments of the present invention, the hard segment comprises polybutylene terephthalate.

According to some embodiments of the present invention, the loss factor of the diaphragm is 0.1-0.2 in an environment of 23°C.

According to some embodiments of the present invention, in an environment of 23°C,

When the lowest resonance frequency F0 of the sound generating device is ≤ 500Hz, the tensile modulus of the thermoplastic polyester elastomer film is 20-100Mpa;

When the lowest resonance frequency F0 of the sound generating device is >500 Hz, the tensile modulus of the thermoplastic polyester elastomer film is 50-400 MPa.

According to some embodiments of the present invention, the ratio between the storage moduli in the MD and TD directions of the diaphragm is 80-120:100.

According to some embodiments of the present invention, the vibrating membrane is a structure in which the thermoplastic polyester elastomer film and glue layers are alternately stacked, and the two surface layers are the thermoplastic polyester elastomer film layers.

According to some embodiments of the present invention, the thickness of the thermoplastic polyester elastomer film is 5-50 μm, and the adhesive layer is one or more of a silicone layer and an acrylic adhesive layer with a thickness of 2-50 μm.

According to some embodiments of the present invention, the glass transition temperature of the adhesive layer is ≤ -10°C.

The method for preparing a diaphragm according to the embodiment of the second aspect of the present invention includes:

The prepolymer of the hard segment and the prepolymer of the soft segment are subjected to a copolymerization reaction, the temperature of the copolymerization reaction is preferably 230-265° C., and the reaction time is preferably 0.5-2 h; after that, pelletize and extrude the film material.

According to some embodiments of the present invention, the molecular weight of the prepolymer of the hard segment is 15000-30000; the molecular weight of the prepolymer of the soft segment is 10000-50000.

The sound generating device according to the embodiment of the third aspect of the present invention includes a vibration system and a magnetic circuit system matched with the vibration system, the vibration system includes a diaphragm and a voice coil combined on one side of the diaphragm, the The magnetic circuit system drives the voice coil to vibrate to drive the diaphragm to produce sound, and the diaphragm is the diaphragm according to the above-mentioned embodiment of the present invention.

According to the fourth aspect of the present invention, the sound generating device includes a housing, a magnetic circuit system and a vibration system disposed in the housing, the vibration system includes a voice coil, a first diaphragm and a second diaphragm, the 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 produce sound, and the two ends of the second diaphragm are respectively connected to the housing Connected to the bottom of the voice coil, the second diaphragm is the diaphragm according to the above embodiment of the present invention.

Compared with the prior art, the present invention utilizes the respective advantages of the polyaromatic dicarboxylic acid glycol ester hard segment and the soft segment containing polyhexamethylene polycarbonate diol, and increases the polyhexamethylene polycarbonate in the soft segment. The ratio of carbonate diols, so as to play a synergistic effect, maximize strengths and avoid weaknesses. The film formed after copolymerization is more suitable for the diaphragm, which can significantly improve high temperature resistance, chemical resistance and sensitivity, and can improve the product's long-term high temperature and/or Reliability under high humidity environment; at the same time, the diaphragm in the present invention can also take into account various acoustic performances such as stiffness, resilience, damping, distortion, etc., and can solve the polarization and distortion problems that occur during the vibration process of the product.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention.

Fig. 1 is the infrared spectrogram of the resin material of embodiment and comparative example;

Figure 2 is a graph showing the displacement change curve of the material at different temperatures under a 1MPa force;

Fig. 3 is the structural representation of the loudspeaker provided by the present invention;

Fig. 4 is a structural schematic diagram of the sounding vibration unit in Fig. 3;

Fig. 5 is the structural representation of diaphragm in the present invention;

Fig. 6 is the total harmonic distortion curve of the embodiment and the comparative example.

Detailed ways

Embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only for illustrating the present invention, and should not be considered as limiting the scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The original drugs, reagents or instruments used are not indicated by the manufacturer, and they are all conventional products that can be purchased from the market or can be prepared according to the existing technology.

The invention provides a vibrating membrane that can be used for a sounding device, the vibrating membrane is a multi-layer composite structure, and at least one surface layer is a thermoplastic polyester elastomer film;

The thermoplastic polyester elastomer is formed by the copolymerization of polyester hard segment obtained by reaction of aromatic dicarboxylic acid and glycol and soft segment containing aliphatic polycarbonate; wherein, the thickness of the diaphragm is 10-200 μm , the loss factor of the thermoplastic polyester elastomer film is 0.1-0.3 under the environment of 23°C.

The present invention utilizes the respective advantages of the hard segment of polyaromatic dicarboxylic acid diol ester and the soft segment of aliphatic polycarbonate to exert synergistic effect, enhance strengths and avoid weaknesses, and the film material formed after copolymerization is more suitable for diaphragm, and can significantly improve the resistance to vibration. High temperature resistance, chemical resistance and sensitivity can improve the working reliability of products in long-term high temperature and/or high humidity environments; at the same time, the diaphragm in the present invention can also take into account stiffness and resilience, damping, distortion, etc. In terms of performance, it can solve the polarization and distortion problems that occur during the vibration process of the product. Diaphragms made with the thermoplastic polyester elastomer film layer of the present invention have been tested to have significant advantages over diaphragms without aliphatic polycarbonate esters, especially in terms of high temperature resistance, chemical resistance and sensitivity etc.

The aromatic dicarboxylic acid described in the present invention can be terephthalic acid, diphenyl dicarboxylic acid, naphthalene dicarboxylic acid, isophthalic acid or the above substituted aromatic dicarboxylic acid, preferably terephthalic acid .

The dihydric alcohol described in the present invention can be ethylene glycol, butanediol, propylene glycol, cyclopentanediol, cyclohexanediol, etc., and can be optionally one of the above alcohols or a combination of multiple alcohols.

The above-mentioned aromatic dicarboxylic acid and dihydric alcohol are polymerized to form a hard segment, which can be a kind of aromatic dicarboxylic acid and a kind of dibasic alcohol polymerized, or a kind of aromatic dicarboxylic acid and a variety of dibasic alcohols The polymerization may also be the polymerization of multiple aromatic dicarboxylic acids and one diol, or the polymerization of multiple aromatic dicarboxylic acids and multiple diols.

One or more of polycaprolactone, polybutylene adipate, polytetrahydrofuran ether, and polyethylene oxide may also be added to the soft segment of the present invention. Adding a small amount of the above polymers can help improve the blockiness of the polycarbonate soft segment and the polymerizability with the hard segment while maintaining the good strength, stiffness and resilience of the material. However, if the amount exceeds 30%, it will It affects the block structure characteristics of the entire material, resulting in the loss of the overall rigidity and resilience of the material. Because aliphatic polycarbonate has stronger polarity, it is better than polyester or polyether block in terms of moisture resistance and chemical resistance, so the content of aliphatic polycarbonate block in the soft segment is dominant, and the material's Overall performance should be better. Correspondingly, the weight percentage of the aliphatic polycarbonate in the soft segment is preferably above 70%, such as 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc. Polycaprolactone is preferred as the polymer that is compatible with aliphatic polycarbonate to form the soft segment.

At the same time, the proportion of hard segment and soft segment in the thermoplastic polyester elastomer of the present invention has a significant impact on properties such as temperature resistance and damping. Usually, the weight percentage of soft segment is preferably 20% to 80%, such as 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc. The more the soft segment content, the lower the rigidity and strength of the material, and the diaphragm needs to vibrate. Good rigidity and strength are necessary characteristics. According to the structural characteristics of the material, the soft segment content is not higher than 80%. When the soft segment content is low, the hard segment characteristics of the entire material are dominant. Although the stiffness and strength of the material are significantly improved, the flexibility is reduced. Not less than 25%. According to the requirements of modulus, strength and resilience required for speaker diaphragm vibration, the soft segment content is more preferably 25% to 60%, such as 25%, 30%, 35%, 40%, 45%, 50%, 55% %, 60%, etc.

In addition, due to the complexity of the chemical composition of polymers, their properties need to be limited in combination with practical applications.

As far as it is used for a diaphragm, when the loss factor of the thermoplastic polyester elastomer film layer of the present invention is 0.1 to 0.3 (using DMA temperature scanning mode, 1Hz vibration frequency, 3°C/min heating rate, the loss factor is 23°C data), it will have good damping properties and can meet the needs of products for high performance and low performance. Due to the presence of polycarbonate segments in the thermoplastic polyester elastomer of the present invention, relative to polyester segments or polyether segments, polycarbonate segments have higher polarity, and the steric hindrance of segment movement is larger , when subjected to an external force, it can consume more energy, so it has better damping properties than other types of thermoplastic elastomer materials, which can easily reach 0.1-0.3. When the loss factor is lower than 0.1, there is no advantage in distortion compared to polyether-polyester thermoplastic polyester elastomer; when the loss factor is higher than 0.2, the increase in damping of the material will lose the transient response of the material, and the diaphragm cannot be perfect To realize the feedback of the input signal, the sound quality will be sacrificed. On this basis, it is more preferably 0.1 to 0.2, such as 0.12, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2 and the like.

In some embodiments, the tensile modulus of the thermoplastic polyester elastomer film layer is 20-500Mpa (using DMA temperature scanning mode, 1Hz vibration frequency, 3°C/min heating rate, data at 23°C). When the modulus is too low, the stiffness of the diaphragm is insufficient. If the F0 (minimum resonance frequency) required by the product is achieved, it can only be achieved by increasing the thickness, but the increase in thickness will increase the quality of the diaphragm and lose its vibration space and reduces the sensitivity of the quality control zone. When the modulus is high, the flexibility and resilience of the material become poor. In order to obtain high loudness, the product requires a large displacement of the diaphragm. At this time, the increase of the modulus will inevitably bring adverse effects. According to product design and performance requirements, the recommendation is as follows: when the minimum resonance frequency F0 of the sound generating device is ≤ 500 Hz, the tensile modulus of the thermoplastic polyester elastomer film is 20-100 Mpa; the minimum resonance frequency F0 of the sound generating device When >500 Hz, the tensile modulus of the thermoplastic polyester elastomer film is 50-400 MPa. For example, when the lowest resonance frequency F0 of the sound generating device is 400 Hz, the tensile modulus of the thermoplastic polyester elastomer film may be 70 MPa. For example, when the lowest resonance frequency F0 of the sound generating device is 800 Hz, the tensile modulus of the thermoplastic polyester elastomer film may be 350 MPa.

In some embodiments, in order to ensure the consistency of the vibration of the loudspeaker diaphragm and reduce the polarization of the product, the selected film material, the ratio between the storage modulus in the MD and TD directions of the thermoplastic polyester elastomer film layer is 80 ~120:100. In other words, the storage modulus difference between the MD and TD directions of the thermoplastic polyester elastomer film layer is controlled within ±20%, preferably within ±10%.

The vibrating membrane of the present invention is a multi-layer composite structure, which at least includes a thermoplastic polyester elastomer film, preferably a structure in which it is alternately stacked with adhesive film layers, and the thermoplastic polyester elastomer film is the surface layer. If a composite structure is adopted, due to the strong rigidity of the thermoplastic polyester elastomer film, it can meet the use requirements when it is set very thin, thereby avoiding the loss of sensitivity and vibration space caused by excessive material thickness. The thickness of the thermoplastic polyester elastomer film layer is preferably 5 to 50 μm.

In a specific embodiment of the present invention, the diaphragm can include a three-layer structure, wherein the middle layer is an adhesive film layer, and the two surface layers are thermoplastic polyester elastomer film layers, and the thermoplastic polyester elastomer film layers are made of aromatic dicarboxylic acid. The polyester hard segment obtained by reacting with glycol and the soft segment containing aliphatic polycarbonate are copolymerized, and the middle layer is arranged between the two surface layers.

In another specific embodiment of the present invention, the vibrating membrane may include a five-layer structure, the five-layer structure is alternately superimposed and distributed with thermoplastic polyester elastomer film layers and adhesive film layers, and its two surface layers are thermoplastic polyester elastomer film layers, The thermoplastic polyester elastomer film layer is formed by the copolymerization of the polyester hard segment obtained by the reaction of aromatic dicarboxylic acid and diol and the soft segment containing aliphatic polycarbonate.

The adhesive layer in the composite film may be a typical adhesive in the field, such as one or more of a silicone layer and an acrylic adhesive layer with a thickness of 2-50 μm, preferably a pressure-sensitive adhesive film. The pressure-sensitive adhesive film is easy to use, and the lamination between layers can be realized through a simple lamination process. The 180° peeling force after lamination must meet: not less than 150g/25mm. In order to ensure that the speaker diaphragm can still maintain good sound quality at low temperatures, the glass transition temperature of the adhesive layer should not be higher than -10°C. When the temperature is higher than -10°C, the modulus of the adhesive film layer will increase rapidly, resulting in excessive rigidity of the material, a significant increase in the F0 of the product, and a decrease in the toughness of the diaphragm, which is prone to the risk of film cracking.

For the preparation method of the thermoplastic polyester elastomer film layer in the present invention, it only involves conventional procedures, including copolymerization reaction, making granular resin, and then using extrusion equipment to form a film material, and finally bonding it with other films to form the diaphragm .

Among them, the process conditions of the copolymerization reaction have a certain influence on the performance of the thermoplastic polyester elastomer. Usually, the raw materials are guaranteed to be in a molten state, and the hard segment and the soft segment are both selected as prepolymers.

In some preferred embodiments, the polyester hard segment prepolymer obtained by reacting aromatic dicarboxylic acid and diol is selected to have a molecular weight of 15,000-30,000, such as 15,000, 20,000, 25,000, 30,000, etc. The prepolymer of the aliphatic polycarbonate soft segment preferably has a molecular weight of 10,000-50,000, such as 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, etc. The temperature of the copolymerization reaction is preferably 230-265° C., and the reaction time is preferably 0.5-2 h.

Usually also add catalyst and crosslinking agent in the copolymerization reaction, the type that both selects can be typical auxiliary agent, for example described stabilizing agent is preferably polycarbodiimide, and described catalyst is preferably n-butyl titanate, the consumption of both It can be adjusted according to the actual situation. The end point of the copolymerization reaction is usually when the resin becomes uniform and transparent.

Granulation is usually carried out in a slicer or pelletizer.

For the extrusion film forming process, it is usually carried out in an extruder, and an appropriate amount of processing aids (such as plasticizers, slip agents, lubricants, etc.) can also be added to the screw to melt, and then output after being dispersed and mixed by the screw. To the T die head, in order to reduce the orientation of the film, after the melt flows out from the T die head, an auxiliary material of a certain thickness (such as a release film or release paper, etc.) can be added to one surface of the film before the supercooling roll to spread After flattening, roll together. The types and amounts of processing aids are typical in the art.

The vibrating membrane provided by the present invention can form a sounding device of any structure, such as the following typical sounding device: comprising a vibrating system and a magnetic circuit system matched with the vibrating system, the vibrating system includes a vibrating membrane and a magnetic circuit system combined with the vibrating Voice coil on one side of the membrane. When the sound generating device is working, the voice coil can vibrate up and down under the action of the magnetic field force of the magnetic circuit system after the voice coil is energized to drive the vibration of the diaphragm, and the sound can be produced when the diaphragm vibrates.

According to another embodiment of the present invention, the sound generating device may include a housing and a magnetic circuit system and a vibration system disposed in the housing. The vibration system may include a voice coil, a first diaphragm and a second diaphragm, and the top of the voice coil Connected with the first diaphragm, the magnetic circuit system drives the voice coil to vibrate to drive the first diaphragm to produce sound, and the two ends of the second diaphragm are respectively connected with the shell and the bottom of the voice coil. Wherein, the second diaphragm may be the diaphragm according to the foregoing embodiments of the present invention.

That is to say, the first diaphragm can be used to vibrate and produce sound, and the second diaphragm can be used to balance the vibration of the voice coil. Specifically, when the sound generating device is working, the voice coil can vibrate up and down under the action of the magnetic field force of the magnetic circuit system after the voice coil is energized to drive the first diaphragm to vibrate, and the first diaphragm can vibrate to produce sound. The second diaphragm can also vibrate up and down with the voice coil. Since the two ends of the second diaphragm are respectively connected to the bottom of the shell and the voice coil, the second diaphragm can balance the vibration of the voice coil and prevent the polarization of the voice coil. Therefore, the sounding effect of the sounding device can be improved.

It should be noted that the first diaphragm and the second diaphragm can use the diaphragm of the above-mentioned embodiment of the present invention at the same time, or one of the first diaphragm and the second diaphragm can adopt the diaphragm of the above-mentioned embodiment of the present invention. The diaphragm, which is not specifically limited in the present invention. The following is a specific description in conjunction with the examples.

Example 1

The first step is to make resin particles

In the reaction tank of inert gas atmosphere, add the polyhexamethylene polycarbonate diol that the data molecular weight of 70 mass parts is 25000 polybutylene terephthalate prepolymers, 25 mass parts number average molecular weights and 5 parts by mass of polycaprolactone and 0.15 parts by mass of n-butyl titanate are used as catalysts, 0.5 parts by mass of polycarbodiimide is added, and the temperature is slowly raised to a molten state (230-265°C), and the reaction is continued for about 1 hour. Until the resin becomes uniform and transparent, after cooling, cut it into granules with a slicer or granulator for film production. The infrared spectrum of the resin is shown in Figure 1, which shows that there is an obvious characteristic absorption peak of C=O of soft segment polycarbonate near 1743cm ^-1 .

The second step is to make the membrane

The method of melt extrusion casting is adopted. Before film making, the particles are first dried and dehydrated, then added to the screw to melt, dispersed and mixed by the screw, and then output to the T-die. In order to reduce the orientation of the film, after the melt flows out of the T-die, it can be added before the cooling roll A certain thickness of auxiliary material (such as release film or release paper, etc.) is applied to one surface of the film, and after being flattened and shaped, it is rolled together. By controlling the speed of the vehicle and the pressure between the cooling rollers, etc., it is ensured that the difference of the storage modulus of the obtained thermoplastic polyester elastomer film in the MD and TD directions is within ±10%.

Example 2

The first step is to make resin particles

In the reaction tank of inert gas atmosphere, add the polyhexamethylene polycarbonate diol that the data molecular weight of 70 mass parts is 25000 polybutylene terephthalate prepolymers, 30 mass parts number average molecular weights, and 0.15 parts by mass of n-butyl titanate as a catalyst, adding 0.5 parts by mass of polycarbodiimide, slowly heating up to a molten state (230-265°C), and continuing to react for about 1 hour until the resin becomes uniform and transparent. After cooling, use a slicer or granulator to cut into granules for film production. The infrared spectrum of the resin is shown in Figure 1, which shows that there is an obvious characteristic absorption peak of C=O of soft segment polycarbonate near 1743cm ^-1 .

The second step is to make the membrane

The method of melt extrusion casting is adopted. Before film making, the particles are first dried and dehydrated, then added to the screw to melt, dispersed and mixed by the screw, and then output to the T-die. In order to reduce the orientation of the film, after the melt flows out of the T-die, it can be added before the cooling roll A certain thickness of auxiliary material (such as release film or release paper, etc.) is applied to one surface of the film, and after being flattened and shaped, it is rolled together. By controlling the speed of the vehicle and the pressure between the cooling rollers, etc., it is ensured that the difference of the storage modulus of the obtained thermoplastic polyester elastomer film in the MD and TD directions is within ±10%.

comparative example

The first step is to make resin particles

Add 70 mass parts of polybutylene terephthalate prepolymers with a number average molecular weight of 25000 and 30 mass parts of polytetrahydrofuran ether blocks with a data molecular weight of 2000 in the reaction tank of an inert gas atmosphere, and 0.15 Parts by mass of n-butyl titanate as a catalyst, add 0.5 parts by mass of polycarbodiimide, slowly heat up to a molten state (230-265°C), and continue to react for about 1 hour until the resin becomes uniform and transparent. After cooling, Cut into granules with a slicer or a granulator for film production. The infrared spectrum of the resin is shown in Figure 1.

The second step is to make the membrane

The method of melt extrusion casting is adopted. Before film making, the particles are first dried and dehydrated, then added to the screw to melt, dispersed and mixed by the screw, and then output to the T-die. In order to reduce the orientation of the film, after the melt flows out of the T-die, it can be added before the cooling roll A certain thickness of auxiliary material (such as release film or release paper, etc.) is applied to one surface of the film, and after being flattened and shaped, it is rolled together. By controlling the speed of the vehicle and the pressure between the cooling rollers, etc., it is ensured that the difference of the storage modulus of the obtained thermoplastic polyester elastomer film in the MD and TD directions is within ±10%.

Examining the properties of different thermoplastic elastomer films

1. Evaluation of heat resistance

Test method: adopt TMA equipment, select the film (thermoplastic polyester elastomer film) material with a thickness of 20 μm as the comparative example, embodiment 1 and embodiment 2, adopt the tensile mode, maintain the tensile stress at 1MPa, and follow the 3°C/ The heating rate of min increases from room temperature to 200°C, and the instrument will record and output the length change curve of the material at different temperatures during the test.

The results show that as shown in Figure 2, the length of the material will increase as the temperature increases under the stress state. It is not difficult to understand that the greater the change in length with temperature, the worse the material's high temperature resistance. It can be seen that in terms of heat resistance, Example 2 is better than Example 1, and better than Comparative Example.

2. Oil absorption test

Test method: Cut out materials with similar quality and weigh them with an analytical balance to record the mass M ₁ , soak in oleic acid for 24 hours, take out the oleic acid on the surface with a dust-free cloth and weigh M ₂ , and compare the materials before and after oleic acid absorption Changes in quality, so that the advantages and disadvantages of chemical resistance can be drawn.

The result shows: as shown in Table 1, the oil absorption rate of the comparative example is the highest, and the oil absorption rate of the embodiment 2 is the lowest. It can be speculated that the presence of polycarbonate soft segments is beneficial to block the immersion of small organic molecules and improve the chemical resistance of the entire material.

Table 1 Comparison of oil absorption

sample	M 1 /g	M 2 /g	Oil absorption
comparative example	0.1091	0.1233	13.02%
Example 1	0.1115	0.1209	8.43%
Example 2	0.1507	0.1579	4.78%

3. Test the tensile modulus and loss factor of thermoplastic polyester elastomer film

Test method: Use a cutting knife or a utility blade to take a flat rectangular sample with a width of 5-10mm from the film, and use the ASTM D412-2016 standard for testing. The vibration frequency of the test is 1Hz and the temperature is 23°C.

The result shows: as shown in table 2, comparative example and embodiment 2 have close storage modulus at room temperature, but the modulus at high temperature of embodiment 2 is higher than comparative example, illustrates that the present invention has more stable at high temperature Structural strength. The peak temperature of the loss modulus is the glass transition temperature of the material, which represents the onset temperature at which the thermoplastic polyester elastomer material has high elastic properties. From the curve of loss modulus with temperature, it can be seen that the present invention has a lower glass transition temperature. It can be seen from the above that the thermoplastic polyester elastomer of the present invention has a wider service temperature range. In addition, it can be seen from FIG. 2 that Example 2 has higher damping properties (loss factor of the material=ratio of loss modulus to storage modulus).

Table 2

Test F0, Sensitivity and Total Harmonic Distortion Curves of Diaphragms Made of Different Thermoplastic Polyester Elastomers

1. Make the diaphragm

The thermoplastic polyester elastomer films in Example 2 and Comparative Example were respectively selected to make diaphragms. Wherein, the diaphragms in Example 2 and Comparative Example all adopt a three-layer composite structure, including a middle layer and two surface layers, the middle layer is an acrylic adhesive layer, and the two surface layers are respectively corresponding thermoplastic polyester elastomer layers, and the middle layer The thickness of both surface layers is 20 μm. That is to say, the difference between the diaphragm in Example 2 and the comparative example is only that the materials of the thermoplastic polyester elastomer film layers of the two surface layers are different. The manufacturing method of the diaphragm in Embodiment 2 and the comparative example is the same, as follows:

Using composite equipment, the prepared thermoplastic polyester elastomer film layer and acrylic adhesive layer are laminated alternately to form a composite structure of thermoplastic polyester elastomer film layer + acrylic adhesive layer + thermoplastic polyester elastomer film layer, thus making Composite tape required. Place the above-mentioned composite strip on a thermocompression molding machine for secondary molding to prepare the required diaphragm shape, cut it to the product size and assemble it into the micro speaker unit together with the voice coil, magnetic circuit system and other components (as shown in the figure 3 and Figure 4).

2. Test method:

Product performance tests were performed on the microspeakers (SPK) equipped with the diaphragms in the above-mentioned embodiment 2 and the comparative example, respectively. The micro-speaker adopts the structure shown in Fig. 3, which includes a vibration system and a magnetic circuit system matched with the vibration system, and the vibration system includes a diaphragm and a voice coil combined on one side of the diaphragm. The loudspeaker vibration unit is shown in FIG. 4 , and those skilled in the art can make corresponding adjustments according to actual product requirements. For example, as shown in Figures 3 and 4, the vibrating membrane 1 is composed of a ring portion 11 and a ball top 12, and the thermoplastic polyester elastomer layer can be located at the ring portion 11 of the diaphragm, or at the ring portion 11 and the ball top. 12. Surround portion 11 protrudes toward the side away from voice coil 2; ball top 12 is connected to surround portion 11; a centering strut is provided in the vibration system, which can improve the anti-polarization ability of the vibration system, etc. The vibrating film 3 is composed of the thermoplastic polyester elastomers of Example 2 and Comparative Example respectively, and both adopt a three-layer structure of "thermoplastic polyester elastomer film layer 31-adhesive layer 32-thermoplastic polyester elastomer film layer 31", as Figure 5 shows.

The result shows: as shown in table 3 and Fig. 6, with respect to comparative example SPK product (being the SPK product of the thermoplastic polyester elastomer film layer in application comparative example), embodiment SPK product (being the thermoplastic polyester elastomer film layer in application example 2) SPK product with polyester elastomer film) F0 is 8Hz lower, and the sensitivity of the product at 500Hz (SPL@500Hz) is 1dB higher. On the premise that the product F0 of the SPK of Example 2 is slightly lower than that of the Comparative Example, it has lower distortion than the SPK product of the Comparative Example.

table 3

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (16)

1. A diaphragm that can be used in a sounding device, characterized in that the diaphragm is a multi-layer composite structure, and at least one surface layer is a thermoplastic polyester elastomer film;

   The thermoplastic polyester elastomer film is formed by copolymerizing polyester hard segments obtained from the reaction of aromatic dicarboxylic acids and glycols and soft segments containing aliphatic polycarbonate;

   Wherein, the thickness of the diaphragm is 10-200 μm, and the loss factor of the thermoplastic polyester elastomer film is 0.1-0.3 at 23°C.
2. The diaphragm according to claim 1, wherein the aliphatic polycarbonate comprises polyhexamethylene polycarbonate diol and accounts for more than 70% by weight of the soft segment.
3. The diaphragm according to claim 1, wherein the soft segment further comprises one or more of polycaprolactone, polybutylene adipate, polytetrahydrofuran ether, and polyethylene oxide .
4. The diaphragm according to any one of claims 1-3, characterized in that, the soft segment accounts for 20%-80% of the weight of the thermoplastic polyester elastomer.
5. The diaphragm according to claim 4, wherein the soft segment accounts for 30%-60% of the weight of the thermoplastic polyester elastomer.
6. The diaphragm of claim 1, wherein the hard segment comprises polybutylene terephthalate.
7. The diaphragm according to claim 1, characterized in that, the loss factor of the diaphragm in an environment of 23° C. is 0.1˜0.2.
8. The diaphragm according to any one of claims 1-3 or 6 or 7, characterized in that, in an environment of 23°C,

   The lowest resonance frequency F0 of the sound generating device is ≤500Hz, and the tensile modulus of the thermoplastic polyester elastomer film is 20-100Mpa;

   or,

   The lowest resonance frequency F0 of the sound generating device is >500 Hz, and the tensile modulus of the thermoplastic polyester elastomer film is 50-400 MPa.
9. The diaphragm according to any one of claims 1-3 or 6 or 7, characterized in that the ratio between the storage moduli in the MD and TD directions of the diaphragm is 80-120:100.
10. According to any one of claims 1-3 or 6 or 7, the diaphragm is characterized in that, the diaphragm is a structure in which the thermoplastic polyester elastomer film and the glue layer are alternately stacked, and the two surface layers are the The thermoplastic polyester elastomer film.
11. The diaphragm according to claim 10, characterized in that, the thickness of the thermoplastic polyester elastomer film is 5-50 μm, and the adhesive layer is one of a silica gel layer and an acrylic adhesive layer with a thickness of 2-50 μm or Various.
12. The diaphragm according to claim 10, characterized in that, the glass transition temperature of the adhesive layer is ≤ -10°C.
13. The preparation method of the diaphragm according to any one of claims 1-12, characterized in that the thermoplastic polyester elastomer film is prepared by the following method:

    Copolymerize the prepolymer of the hard segment and the prepolymer of the soft segment, the temperature of the copolymerization reaction is 230-265°C, and the reaction time is 0.5-2h; after that, granulate and extrude the film material;

    After that, the thermoplastic polyester elastomer film and other layers are laminated to form the diaphragm.
14. The method for preparing a diaphragm according to claim 13, wherein the molecular weight of the prepolymer of the hard segment is 15000-30000, and the molecular weight of the prepolymer of the soft segment is 10000-50000.
15. A sounding device, characterized in that it includes a vibration system and a magnetic circuit system matched 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 The system drives the voice coil to vibrate to drive the diaphragm to produce sound, and the diaphragm adopts the diaphragm described in any one of claims 1-12.
16. A sounding device, characterized in that it includes a housing and a magnetic circuit system and a vibration system arranged in the housing, the vibration system includes a voice coil, a first diaphragm and a second diaphragm, the voice coil The top is connected with the first diaphragm, the magnetic circuit system drives the voice coil to vibrate to drive the first diaphragm to produce sound, and the two ends of the second diaphragm are respectively connected to the housing and the The bottom of the voice coil is connected, and the second diaphragm is the diaphragm according to any one of claims 1-12.

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