阅读说明：本技术 用于微型扬声器的音膜及其制备方法 (Sound film for micro loudspeaker and preparation method thereof ) 是由 杨超 小克里斯托弗·B·沃克 于 2020-03-17 设计创作，主要内容包括：本发明提供用于微型扬声器的音膜及其制备方法,所述音膜为单层音膜或多层音膜,包括至少一层经化学交联的热塑性聚氨酯弹性体,其中：在25℃到150℃的温度范围内,所述经化学交联的热塑性聚氨酯弹性体由流变曲线测量的损耗因子小于或等于0.4。根据本发明的技术方案的用于微型扬声器的音膜易于通过热成型制备,同时具有适当的模量、良好的强度、弹性和热稳定性。(The invention provides a sound film for a micro-speaker and a preparation method thereof, wherein the sound film is a single-layer sound film or a multi-layer sound film and comprises at least one layer of thermoplastic polyurethane elastomer subjected to chemical crosslinking, wherein: the chemically crosslinked thermoplastic polyurethane elastomer has a loss factor as measured by the rheology curve of less than or equal to 0.4 over a temperature range of 25 ℃ to 150 ℃. The sound film for the micro-speaker according to the technical scheme of the invention is easy to prepare by thermoforming, and has appropriate modulus, good strength, elasticity and thermal stability.)

1. A sound membrane for a micro-speaker, said sound membrane being a single layer sound membrane or a multilayer sound membrane comprising at least one layer of a chemically cross-linked thermoplastic polyurethane elastomer, wherein: the chemically crosslinked thermoplastic polyurethane elastomer has a loss factor as measured by the rheology curve of less than or equal to 0.4 over a temperature range of 25 ℃ to 150 ℃.

2. The sound film according to claim 1, wherein the chemically crosslinked thermoplastic polyurethane elastomer has a loss factor as measured by a rheological curve of less than or equal to 0.2 over a temperature range of 50 ℃ to 100 ℃.

3. The sound diaphragm according to claim 1 or 2, wherein the chemically crosslinked thermoplastic polyurethane elastomer has a tensile modulus in the range of 1 to 150MPa and an elongation at break in the range of 180% to 500%.

4. A sound membrane according to claim 3, wherein the thickness of said sound membrane is in the range of 5 μm to 100 μm.

5. The sound diaphragm according to claim 3, wherein the chemically crosslinked thermoplastic polyurethane elastomer is formed by radiation crosslinking.

6. The sound diaphragm of claim 5, wherein the chemically cross-linked thermoplastic polyurethane elastomer is formed by cross-linking by electron beam radiation.

7. The sound film according to claim 3, wherein said multilayer sound film is a sound film of a structure of three or more layers.

8. The diaphragm according to claim 7, wherein said multilayer diaphragm further comprises at least one damping layer.

9. The sound film according to claim 8, wherein the damping layer is selected from one or more of a silicone damping glue layer, an acrylic damping glue layer, and a polyolefin damping glue layer.

10. The sound film according to claim 7, wherein said multilayer sound film further comprises at least one plastic layer having a tensile modulus of 1-1000MPa and a yield strain of 3% to 30%.

11. The sound film according to claim 10, wherein the plastic layer is selected from one or more of a polyethylene naphthalate layer, a polyetheretherketone layer, a polyaryletherketone layer, a polyimide layer, a thermoplastic polyester elastomer layer.

12. The sound film according to claim 7, wherein the thickness of said multilayer sound film is in the range of 10 μm-100 μm.

13. The diaphragm according to claim 7, wherein the diaphragm has a tensile modulus in the range of 1MPa to 1000 MPa.

14. The sound film according to claim 7, wherein said sound film has an elongation at break in the range of 80% -500%.

15. A method of producing a sound membrane for a micro-speaker, the method comprising chemically cross-linking a thermoplastic polyurethane elastomer film, wherein: the loss factor of the thermoplastic polyurethane elastomer after chemical crosslinking treatment measured by a rheological curve is less than or equal to 0.4 in the temperature range of 25 ℃ to 150 ℃.

16. The method for producing a sound diaphragm for a micro-speaker according to claim 15, wherein the thermoplastic polyurethane elastomer after chemical crosslinking has a loss factor of 0.2 or less as measured by a rheological curve in a temperature range of 50 ℃ to 100 ℃.

17. The method of producing a sound diaphragm for a micro-speaker according to claim 15, wherein the chemically crosslinked thermoplastic polyurethane elastomer has a tensile modulus in the range of 1 to 150MPa and an elongation at break in the range of 180% to 500%.

18. The method of producing a sound diaphragm for a microspeaker as claimed in claim 17 wherein said chemical crosslinking process comprises crosslinking said thermoplastic polyurethane elastomer film with radiation.

19. The method of producing a sound diaphragm for a microspeaker as claimed in claim 18 wherein said chemical crosslinking process comprises crosslinking said thermoplastic polyurethane elastomer film using electron beam radiation.

20. The method of producing a sound membrane for a microspeaker according to any one of claims 15 to 19, wherein the sound membrane is a single layer sound membrane or a multilayer sound membrane comprising at least one layer of a chemically crosslinked thermoplastic polyurethane elastomer.

21. The method of producing a sound film for a micro-speaker as claimed in claim 20, wherein the multilayer sound film is a sound film of a three-layer or more structure.

Technical Field

The invention relates to the technical field of acoustic devices, and particularly provides a sound film for a micro-speaker and a method for preparing the sound film for the micro-speaker.

Background

With the rapid development of the mobile phone industry, the demand of customers for mobile phone multimedia applications is increasing, and the quality requirements on mobile phone sound are further improved. The miniature loudspeaker is used as a sound production part of the mobile phone, and the sound production quality of the miniature loudspeaker directly determines the multimedia sound effect of the mobile phone. The sound production principle of the micro-speaker is that the voice coil pushes the sound membrane to vibrate under the action of electromagnetic force, so as to push air to produce sound. The role of the diaphragm is to push air, provide damping and maintain a fast response during vibration. The stability of diaphragm vibration directly determines the quality of sound produced by the loudspeaker.

First, a sound membrane for a micro speaker should have certain rigidity and strength to generate high sound pressure and a wide frequency coverage; secondly, the sound film used for the micro-speaker has high damping property so as to have smooth frequency response characteristic; thirdly, the sound film used for the micro-speaker should have high resilience performance to have large amplitude, so that the speaker has high volume. It is difficult to find a material that has both high stiffness and good damping. It is often necessary to compromise the stiffness and damping of the membrane material, or to combine a stiff material with a highly damping material. Furthermore, it is difficult to have a material that has both high rigidity, high strength, and high resilience.

The sound film of early micro-speakers generally used a single-layer plastic material film, including, for example, a polypropylene (PP) film, a polyethylene terephthalate (PET) film, a Polyimide (PI) film, a polyethylene naphthalate (PEN) film, a polyether ether ketone (PEEK) film, and the like. The glass transition temperature Tg of the plastic materials is higher, so that the high rigidity can be kept at a higher use temperature, and the shape of the sound film can be maintained; meanwhile, high sound pressure can be generated, and a wider frequency range is covered. However, too high a Tg of the sound film material also increases the difficulty of the thermoforming process during the sound film manufacturing process, since the thermoforming temperature needs to be higher than the Tg of the plastic material.

With the improvement of the requirements of the terminal users on the sound quality and the volume of the loudspeaker, the multilayer composite membrane structure comprising the plastic membrane gradually appears, and comprises a three-layer membrane structure, a five-layer membrane structure and a seven-layer membrane structure. The damping glue layer is adopted in the multilayer film structure design, and the damping glue layer is mainly used for improving the stability of the sound film vibrating diaphragm, controlling the diaphragm f0 and reducing distortion, so that the sound quality is improved. The commonly adopted damping adhesive layer comprises acrylic damping adhesive, organic silicon damping pressure-sensitive adhesive and the like. The multilayer sound film adopting the damping layer can have smoother frequency response, but because the plastic material diaphragm in the sound film has stronger rigidity and poorer resilience, the applicable amplitude (volume) of the sound film is very small.

The application of the elastomer material in the sound membrane can effectively solve the problem related to resilience. In fact, in the manufacture of large loudspeakers, rubber materials are widely used for the corrugated rim parts. The bending ring structure is added on the sound film, so that the stretching of the sound film during vibration can be effectively reduced, and the stability of the sound film vibration is improved. For the micro-speaker, there is a precedent that the related art adopts liquid silicone rubber injection molding. Due to the factors of complex manufacturing process, high processing difficulty, high precision requirement of the injection mold and the like, the large-scale application of the injection mold is limited.

At present, when the sound membrane is made of thermoplastic elastomer materials, the traditional hot press molding process is still adopted to prepare the sound membrane with the corrugated rim structure. The thermoplastic elastic material, especially the thermoplastic polyurethane material, has poor thermal stability, difficult thermal forming process and poor creep resistance, does not have the mechanical property required by long-term vibration of the sound film, and is easy to lose efficacy after long-term work. When the working temperature of the sound film exceeds the thermoforming temperature of the thermoplastic elastomer material, the sound film becomes soft and permanently deforms, and the structure fails. The polyurethane film prepared by the chemical crosslinking method cannot realize hot-press molding due to the three-dimensional network structure, and is not suitable for the sound film prepared by the hot-press molding process.

There is still a great need in the industry for a sound diaphragm for a micro-speaker that is simple in manufacturing process, has good resilience, high rigidity, and high strength. Therefore, it is important to develop a sound film for a micro-speaker, which is easily prepared by thermoforming, and has a proper modulus, good strength, elasticity and thermal stability.

Disclosure of Invention

Starting from the technical problems set forth above, it is an object of the present invention to provide a sound membrane for a micro-speaker and a method for manufacturing the same, which is easily manufactured by thermoforming according to the technical scheme of the present invention, and has a proper modulus, good strength, elasticity and thermal stability.

The present inventors have made intensive studies and completed the present invention.

According to one aspect of the present invention, there is provided a sound diaphragm for a micro-speaker, the sound diaphragm being a single-layer sound diaphragm or a multi-layer sound diaphragm comprising at least one layer of a chemically cross-linked thermoplastic polyurethane elastomer, wherein: the chemically crosslinked thermoplastic polyurethane elastomer has a loss factor as measured by the rheology curve of less than or equal to 0.4 over a temperature range of 25 ℃ to 150 ℃.

According to another aspect of the present invention, there is provided a method of producing a sound diaphragm for a micro-speaker, the method comprising chemically crosslinking a thermoplastic polyurethane elastomer film, wherein: the loss factor of the thermoplastic polyurethane elastomer after chemical crosslinking treatment measured by a rheological curve is less than or equal to 0.4 in the temperature range of 25 ℃ to 150 ℃.

Compared with the prior art in the field, the invention has the advantages that the sound film for the micro-speaker according to the technical scheme of the invention is easy to prepare by thermoforming, and simultaneously has proper modulus, good strength, elasticity and thermal stability.

Drawings

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate exemplary embodiments of the invention and, together with the general description provided above and the detailed description provided below, serve to explain features of the invention.

Fig. 1 shows a schematic cross-sectional view of a sound membrane having a single-layer structure for a micro-speaker according to an embodiment of the present invention;

fig. 2 shows a schematic cross-sectional view of a multilayer sound film having a three-layer structure for a micro-speaker according to another embodiment of the present invention;

fig. 3 shows a schematic cross-sectional view of a multilayer sound film having a four-layer structure for a micro-speaker according to still another embodiment of the present invention; and

fig. 4 shows a schematic cross-sectional view of a multilayer sound film having a five-layer structure for a micro-speaker according to still another embodiment of the present invention.

Detailed Description

It is to be understood that other various embodiments can be devised and modified by those skilled in the art in light of the teachings of this specification without departing from the scope or spirit of the disclosure. The following detailed description is, therefore, not to be taken in a limiting sense.

Unless otherwise indicated, all numbers expressing feature sizes, quantities, and physical and chemical characteristics used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can be suitably varied by those skilled in the art in seeking to obtain the desired properties utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range and any range within that range, for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, and the like.

The inventor of the present invention has found in research that some thermoplastic elastomer materials can be used for the sound membrane of the micro-speaker after thermoforming. The thermoplastic elastomer material can greatly improve the resilience and consistency of the sound film and can realize high-amplitude vibration; however, the thermoplastic elastomer material generally has poor temperature resistance, cannot bear high power or high working temperature, has poor creep resistance (strength), and does not have the mechanical property required by long-term vibration of the sound film. According to the technical scheme of the invention, a specific thermoplastic polyurethane elastomer material can be crosslinked by carrying out chemical crosslinking treatment on the thermoplastic polyurethane elastomer material (preferably, by adopting an electron beam radiation mode), so that the thermal stability and the creep resistance of the sound film made of the material are greatly improved under the condition of not basically influencing the elastic property of the sound film.

Specifically, according to one aspect of the present invention, there is provided a method of producing a sound diaphragm for a micro-speaker, the method including chemically crosslinking a thermoplastic polyurethane elastomer film, wherein: the loss factor of the thermoplastic polyurethane elastomer after chemical crosslinking treatment measured by a rheological curve is less than or equal to 0.4 in the temperature range of 25 ℃ to 150 ℃.

According to the present invention, the term "thermoplastic polyurethane elastomer (TPU)" refers to an elastomer having thermoplasticity obtained by polymerizing a diisocyanate with a dihydroxy compound. Preferably, the term "thermoplastic polyurethane elastomer (TPU)" refers to a thermoplastic block copolymer composed of a soft segment and a hard segment alternately connected, wherein the hard segment is an isocyanate segment (containing an aliphatic isocyanate segment or an aromatic isocyanate segment), and the soft segment is a polyether polyol segment or a polyester polyol segment. In the thermoplastic polyurethane, in addition to the proportion of hard segments and soft segments, the type of isocyanate and polyether polyols, polyester polyols also have an influence on the properties of the thermoplastic polyurethane. The thermoplastic polyurethane elastomer can be plasticized by heating, and has no crosslinking or little crosslinking in chemical structure, and the molecules are basically linear, but have certain physical crosslinking. It is noted that the thermoplastic polyurethane elastomer is generally physically crosslinked by the interaction between urethane groups within the molecule. However, thermoplastic polyurethane elastomers containing only physical crosslinks are poor in terms of strength, elasticity, and thermal stability.

According to the technical scheme of the invention, the term "thermoplastic polyurethane elastomer subjected to chemical crosslinking" refers to the thermoplastic polyurethane elastomer containing chemical crosslinking points formed after the thermoplastic polyurethane elastomer used for manufacturing the sound membrane is subjected to chemical crosslinking treatment. The chemical crosslinking treatment causes the interior of the thermoplastic polyurethane elastomer to be bonded through chemical bonds to generate chemical crosslinking points so as to form a crosslinked network structure. It is therefore the chemically crosslinked thermoplastic polyurethane elastomer which no longer exhibits thermoplasticity. That is, the chemically crosslinked thermoplastic polyurethane elastomer is no longer a thermoplastic elastomer.

Preferably, in the sound membrane, the chemically crosslinked thermoplastic polyurethane elastomer has a loss factor, as measured by the rheological curve, of less than or equal to 0.2 in the temperature range of 50 ℃ to 100 ℃.

Preferably, the chemically crosslinked thermoplastic polyurethane elastomer has suitable mechanical properties (including strength and elasticity). The chemically crosslinked thermoplastic polyurethane elastomer single-layer sound membrane has a tensile modulus in the range of 1 to 150MPa and an elongation at break in the range of 180% to 500%. By controlling the tensile modulus and the elongation at break of the sound film within the above ranges, the basic function of the sound film for pushing air to generate sound can be realized, and the stability and the consistency of the device in long-time wide frequency range operation can be ensured.

The "rheological curve" according to the present invention is measured by using an Ares G2 rotational rheometer manufactured by TA corporation in usa, in which a chemically crosslinked thermoplastic polyurethane elastomer sample having a thickness of 1mm is clamped with an 8-inch parallel plate jig, rheological measurements are performed at different temperature points under the conditions of a temperature rise rate of 5 ℃/min, a test frequency of 1Hz, and a strain of 1% or less to obtain a storage modulus G 'and a loss modulus G ", and a loss factor value (i.e., a damping value) tan δ is calculated from the storage modulus G' and the loss modulus G" according to the following formula:

tan δ＝G”/G’。

according to the above formula, when the loss factor measured from the rheological curve by the rotational rheology method is less than or equal to 0.4 in the temperature range of 25 ℃ to 150 ℃ after the thermoplastic polyurethane elastomer is chemically crosslinked, the chemically crosslinked thermoplastic polyurethane elastomer has good thermal stability (i.e., thermal damping stability). Preferably, the chemically crosslinked thermoplastic polyurethane elastomer has excellent stability at a loss factor of 0.2 or less as measured by a rheological curve in a temperature range of 50 ℃ to 100 ℃.

The thickness of the sound film is in the range of 5 μm to 100 μm, preferably 10 μm to 75 μm and more preferably 15 μm to 50 μm.

There is no particular limitation on the specific type of thermoplastic polyurethane elastomer (TPU) that can be used in the present invention as long as it has a crosslinkable structure (including a structure having a crosslinkable group or being capable of being broken and crosslinked by electron beam irradiation) within its molecule.

The thermoplastic polyurethane elastomers (TPU) which can be used in the present invention can be prepared by known methods according to the prior art literature or are commercially available. Commercially available thermoplastic polyurethane elastomer (TPU) products that can be used in the present invention include ELASTOLLANE series TPU materials manufactured by BASF corporation, DESMOPAN series TPU materials manufactured by covesto corporation, and TPU films manufactured by Shibata corporation.

In order to provide the sound membrane with further improved thermal stability while having good strength and resilience, the thermoplastic polyurethane elastomer constituting the sound membrane must be subjected to a chemical crosslinking treatment. The means for subjecting the thermoplastic polyurethane elastomer to chemical crosslinking treatment is not particularly limited and conventional physicochemical methods, for example, electron beam radiation crosslinking, microwave radiation crosslinking, ultraviolet light radiation crosslinking, chemical crosslinking and the like can be employed.

Preferably, the thermoplastic polyurethane elastomer is cured by means of crosslinking by electron beam radiation. The electron beam irradiation comprises irradiating the thermoplastic polyurethane elastomer with an electron beam of electron beam energy of 100 to 300KV up to an electron beam dose of 1 to 12Mrad, preferably 3 to 12Mrad, to destroy weak portions in the thermoplastic polyurethane elastomer molecules and cause crosslinking through chemical bonds.

According to the technical scheme of the invention, preferably, the multilayer sound film further comprises at least one plastic layer, and the plastic layer has a tensile modulus of 1-1000MPa and a yield strain of 3% -30%. The plastic layer is selected from one or more of polyethylene naphthalate (PEN) layer, polyether ether ketone (PEEK) layer, Polyaryletherketone (PEAK) layer, Polyimide (PI) layer and thermoplastic polyester elastomer (TPEE) layer.

According to the technical scheme of the invention, in order to further improve the elasticity of the sound membrane according to actual conditions so as to provide vibration with high sensitivity, consistency and high amplitude, the sound membrane preferably has a folding structure. There is no particular limitation on the folding structure that can be used in the present invention, which may be one or a combination of more than one of any folding structures that sound films in the related art regarding micro speakers have.

According to a particular embodiment of the invention, the sound membrane is a single layer sound membrane. Fig. 1 shows a schematic cross-sectional view of a sound diaphragm 1 having a single-layer structure for a micro-speaker according to an embodiment of the present invention. The sound membrane 1 is composed of a chemically crosslinked thermoplastic polyurethane elastomer as described above.

According to another specific embodiment of the present invention, the sound diaphragm is a three-layer sound diaphragm. Fig. 2 shows a schematic cross-sectional view of a multilayer sound film 1' having a three-layer structure for a micro-speaker according to another embodiment of the present invention. The multilayer sound film 1' comprises in sequence: an elastic layer 2 ', a damping layer 3 ' and an elastic layer 4 '. The elastic layer 2 'and the elastic layer 4' are both composed of the chemically crosslinked thermoplastic polyurethane elastomer as described above. Preferably, the damping layer 3' is selected from one or more of a silicone damping glue layer, an acrylic damping glue layer and a polyolefin damping glue layer. Specific types of silicone damping gums, acrylic damping gums, and polyolefin-based damping gums that can be used in the present invention are not particularly limited, and can be selected by those skilled in the art according to their general knowledge. The three-layer sound film thickness is in the range of 30 to 100 μm, preferably 36 to 80 μm and more preferably 42 to 60 μm. Preferably, the thickness of the elastic layer 2 ' and the elastic layer 4 ' are each independently in the range of 5-30 μm, preferably 7-20 μm and more preferably 10-15 μm, and the thickness of the damping layer 3 ' is in the range of 5-60 μm, preferably 10-40 μm and more preferably 12-30 μm.

According to another particular embodiment of the invention, the sound membrane is a four-layer sound membrane. Fig. 3 shows a schematic cross-sectional view of a multilayer sound film 1 "having a four-layer structure for a micro-speaker according to still another embodiment of the present invention. The multilayer sound film 1 ' sequentially comprises an elastic layer 2 ', a plastic layer 3 ', a damping glue layer 4 ' and a plastic layer 5 '. The elastic layer 2 "is composed of a chemically crosslinked thermoplastic polyurethane elastomer as described above, and its preferred tensile modulus is 1MPa to 150 MPa. The plastic layer 3 "and the plastic layer 5" are the same or different, and are preferably selected from one or more of a polyethylene naphthalate (PEN) layer, a polyether ether ketone (PEEK) layer, a Polyaryletherketone (PEAK) layer, a Polyimide (PI) layer and a thermoplastic polyester elastomer (TPEE) layer, and are more preferably polyether ether ketone (PEEK) films including semi-crystalline polyether ether ketone (PEEK) and amorphous polyether ether ketone (PEEK) films, and the tensile modulus is 1000-2000MPa and the yield strain is 3-8%. The thermoplastic polyester elastomer (TPEE) can also be selected, and the tensile modulus is 500-1000MPa, and the yield strain is 8-30 percent. The damping glue layer 4' can be selected from one of an organic silicon damping glue layer, an acrylic damping glue layer and a polyolefin damping glue layer. The thickness of the four-layer sound film is 30 to 100 μm, preferably 42 to 60 μm.

According to yet another embodiment of the present invention, the sound diaphragm is a five-layer sound diaphragm. Fig. 4 shows a schematic cross-sectional view of a multilayer sound film 1' ″ having a five-layer structure for a micro-speaker according to still another embodiment of the present invention. The multilayer sound film 1 'sequentially comprises a plastic layer 2', a damping glue layer 3 ', an elastic layer 4', a damping glue layer 5 'and a plastic layer 6'. The elastic layer 4' "is composed of a chemically crosslinked thermoplastic polyurethane elastomer as described above, and its preferred tensile modulus is 1MPa to 150 MPa. The plastic layer 2 "'and the plastic layer 6"', which may be the same or different, are preferably selected from one or more of a polyethylene naphthalate (PEN) layer, a Polyetheretherketone (PEEK) layer, a Polyaryletherketone (PEAK) layer, a Polyimide (PI) layer, and a thermoplastic polyester elastomer (TPEE) layer, and more preferably are Polyetheretherketone (PEEK) films, including semi-crystalline Polyetheretherketone (PEEK) and amorphous Polyetheretherketone (PEEK) films, having a tensile modulus of 1000 and 2000MPa and a yield strain of 3% to 8%. The thermoplastic polyester elastomer (TPEE) can also be selected, and the tensile modulus is 500-1000MPa, and the yield strain is 8-30 percent. The damping rubber layer 3 '"and the damping rubber layer 5'" can be selected from one of an organic silicon damping rubber layer, an acrylic damping rubber layer and a polyolefin damping rubber layer. The thickness of the 5-layer sound film is 30 to 100 μm, preferably 42 to 60 μm. The thickness of the plastic layer 2 "' and the plastic layer 6" ' is each independently 3-10 μm, preferably 5-9 μm, the thickness of the damping gel layer 3 "' and the damping gel layer 5" ' is 5-30 μm, preferably 10-20 μm, and the thickness of the elastic layer 4 "' is 5-30 μm, preferably 10-20 μm.

According to another aspect of the present invention, there is provided a method of producing a sound diaphragm for a micro-speaker, the method comprising chemically crosslinking a thermoplastic polyurethane elastomer film, wherein: the loss factor of the thermoplastic polyurethane elastomer after chemical crosslinking treatment measured by a rheological curve is less than or equal to 0.4 in the temperature range of 25 ℃ to 150 ℃.

Preferably, the loss factor of the thermoplastic polyurethane elastomer after chemical crosslinking treatment as measured by a rheological curve is less than or equal to 0.2 in a temperature range of 50 ℃ to 100 ℃.

In order to provide the sound membrane with further improved thermal stability while having good strength and resilience, the thermoplastic polyurethane elastomer constituting the sound membrane is chemically cross-linked. The chemical crosslinking treatment causes the interior of the thermoplastic polyurethane elastomer to be bonded through chemical bonds to generate chemical crosslinking points so as to form a crosslinked network structure. As mentioned above, the chemically crosslinked thermoplastic polyurethane elastomer no longer has thermoplasticity.

There is no particular limitation on the specific type of thermoplastic polyurethane elastomer that can be used in the present invention as long as it satisfies the above requirements regarding the softening temperature range and has a crosslinkable structure (including a structure having a crosslinkable group or being capable of being broken and crosslinked by electron beam irradiation) within the molecule.

There are no particular limitations on the thermoplastic polyurethane elastomer (TPU) that can be used in the present invention, which can be prepared by known methods according to the prior art literature, and which is also commercially available. Commercially available thermoplastic polyurethane elastomer (TPU) products that can be used in the present invention include ELASTOLLANE series TPU materials manufactured by BASF corporation, DESMOPAN series TPU materials manufactured by covesto corporation, and TPU films manufactured by Shibata corporation.

The means for subjecting the thermoplastic polyurethane elastomer to chemical crosslinking treatment is not particularly limited and conventional physicochemical methods, for example, electron beam radiation crosslinking, microwave radiation crosslinking, ultraviolet light radiation crosslinking, chemical crosslinking and the like can be employed.

Preferably, the thermoplastic polyurethane elastomer is cured by means of crosslinking by electron beam radiation. The electron beam irradiation comprises irradiating the thermoplastic polyurethane elastomer with an electron beam of electron beam energy of 100 to 300KV up to an electron beam dose of 1 to 12Mrad, preferably 3 to 12Mrad, to destroy weak portions in the thermoplastic polyurethane elastomer molecules and cause crosslinking through chemical bonds.

In order to make the sound membrane have a certain shape, the thermoplastic polyurethane elastomer constituting the sound membrane can be subjected to a thermoforming treatment, and the thermoforming treatment can be performed before or after the chemical crosslinking treatment.

The sound film can be a single-layer film or a multi-layer film. Wherein the multilayer film comprises at least one layer of thermoplastic polyurethane elastic film which is chemically crosslinked, at least one layer of damping film, and not less than three layers in total. The modulus of the sound membrane is between 1MPa and 1000MPa and the elongation at break should be between 80% and 500%.

Preferably, the thickness of the thermoplastic polyurethane elastomer film subjected to the chemical crosslinking treatment is in the range of 5 to 100 μm.

According to an embodiment of the present invention, there is provided a method of manufacturing a multilayer sound film having a three-layer structure. A multilayer sound film 1 'is produced by a laminating method, the multilayer sound film 1' comprising, in order: elastic layer 2 ' damping layer 3 ' and elastic layer 4 '. The elastic layer 2 'and the elastic layer 4' are both composed of the chemically crosslinked thermoplastic polyurethane elastomer as described above. Preferably, the damping layer 3' is selected from one or more of a silicone damping glue layer, an acrylic damping glue layer and a polyolefin damping glue layer. Specific types of silicone damping gums, acrylic damping gums, and polyolefin-based damping gums that can be used in the present invention are not particularly limited, and can be selected by those skilled in the art according to their general knowledge. The three-layer sound film thickness is in the range of 30 to 100 μm, preferably 36 to 80 μm and more preferably 42 to 60 μm. Preferably, the thickness of the elastic layer 2 ' and the elastic layer 4 ' are each independently in the range of 5-30 μm, preferably 7-20 μm and more preferably 10-15 μm, and the thickness of the damping layer 3 ' is in the range of 5-60 μm, preferably 10-40 μm and more preferably 12-30 μm.

According to an embodiment of the present invention, there is provided a method of manufacturing a multilayer sound film having a four-layer structure. The multilayer sound film 1 "is prepared by a lamination method, and the multilayer sound film 1" sequentially comprises an elastic layer 2 ", a plastic layer 3", a damping glue layer 4 "and a plastic layer 5". The elastic layer 2 "is composed of a chemically crosslinked thermoplastic polyurethane elastomer as described above, and its preferred tensile modulus is 1MPa to 150 MPa. The plastic layer 3 "and the plastic layer 5" are the same or different, and are preferably selected from one or more of a polyethylene naphthalate (PEN) layer, a polyether ether ketone (PEEK) layer, a Polyaryletherketone (PEAK) layer, a Polyimide (PI) layer and a thermoplastic polyester elastomer (TPEE) layer, and are more preferably polyether ether ketone (PEEK) films including semi-crystalline polyether ether ketone (PEEK) and amorphous polyether ether ketone (PEEK) films, and the tensile modulus is 1000-2000MPa and the yield strain is 3-8%. The thermoplastic polyester elastomer (TPEE) can also be selected, and the tensile modulus is 500-1000MPa, and the yield strain is 8-30 percent. The damping glue layer 4' can be selected from one of an organic silicon damping glue layer, an acrylic damping glue layer and a polyolefin damping glue layer. The thickness of the four-layer sound film is 30 to 100 μm, preferably 42 to 60 μm.

According to an embodiment of the present invention, there is provided a method of manufacturing a multilayer sound film having a five-layer structure. The multilayer sound film 1 ' is prepared through a laminating method, and the multilayer sound film 1 ' sequentially comprises a plastic layer 2 ', a damping rubber layer 3 ', an elastic layer 4 ', a damping rubber layer 5 ' and a plastic layer 6 '. The elastic layer 4' "is composed of a chemically crosslinked thermoplastic polyurethane elastomer as described above, and its preferred tensile modulus is 1MPa to 150 MPa. The plastic layer 2 "'and the plastic layer 6"', which may be the same or different, are preferably selected from one or more of a polyethylene naphthalate (PEN) layer, a Polyetheretherketone (PEEK) layer, a Polyaryletherketone (PEAK) layer, a Polyimide (PI) layer, and a thermoplastic polyester elastomer (TPEE) layer, and more preferably are Polyetheretherketone (PEEK) films, including crystalline Polyetheretherketone (PEEK) and amorphous Polyetheretherketone (PEEK) films, having a tensile modulus of 1000-2000MPa and a yield strain of 3-8%. The thermoplastic polyester elastomer (TPEE) can also be selected, and the tensile modulus is 500-1000MPa, and the yield strain is 8-30 percent. The damping rubber layer 3 '"and the damping rubber layer 5'" can be selected from one of an organic silicon damping rubber layer, an acrylic damping rubber layer and a polyolefin damping rubber layer. The thickness of the 5-layer sound film is 30 to 100 μm, preferably 42 to 60 μm. The thickness of the plastic layer 2 "' and the plastic layer 6" ' is each independently 3-10 μm, preferably 5-9 μm, the thickness of the damping gel layer 3 "' and the damping gel layer 5" ' is 5-30 μm, preferably 10-20 μm, and the thickness of the elastic layer 4 "' is 5-30 μm, preferably 10-20 μm.

Various exemplary embodiments of the present invention are further illustrated by the following list of embodiments, which should not be construed as unduly limiting the invention:

embodiment 1 is a sound diaphragm for a micro-speaker, the sound diaphragm being a single-layer sound diaphragm or a multi-layer sound diaphragm comprising at least one layer of a chemically cross-linked thermoplastic polyurethane elastomer, wherein: the chemically crosslinked thermoplastic polyurethane elastomer has a loss factor as measured by the rheology curve of less than or equal to 0.4 over a temperature range of 25 ℃ to 150 ℃.

Embodiment 2 is the sound film of embodiment 1, wherein the chemically crosslinked thermoplastic polyurethane elastomer has a loss factor of less than or equal to 0.2 as measured by a rheological curve over a temperature range of 50 ℃ to 100 ℃.

Embodiment 3 is the sound diaphragm of embodiment 1 or 2, wherein the chemically crosslinked thermoplastic polyurethane elastomer has a tensile modulus in a range of 1 to 150MPa and an elongation at break in a range of 180% to 500%.

Embodiment 4 is the sound film according to any one of embodiments 1 to 3, wherein a thickness of the sound film is in a range of 5 μm to 100 μm.

Embodiment 5 is the sound diaphragm of any one of embodiments 1-4, wherein the chemically crosslinked thermoplastic polyurethane elastomer is formed by radiation crosslinking.

Embodiment 6 is the sound diaphragm of embodiment 5, wherein the chemically cross-linked thermoplastic polyurethane elastomer is cross-linked by electron beam radiation.

Embodiment 7 is the sound film according to any one of embodiments 1 to 6, wherein the multilayer sound film is a sound film having a three-layer or more structure.

Embodiment 8 is the sound film according to any one of embodiments 1 to 7, wherein the multilayer sound film further comprises at least one damping layer.

Embodiment 9 is the sound film of embodiment 8, wherein the damping layer is selected from one or more of a silicone damping glue layer, an acrylic damping glue layer, and a polyolefin damping glue layer.

Embodiment 10 is the sound film of any one of embodiments 8 to 9, wherein the multilayer sound film further comprises at least one plastic layer having a tensile modulus of 1 to 1000MPa and a yield strain of 3% to 30%.

Embodiment 11 is the sound film of embodiment 10, wherein the plastic layer is selected from one or more of a polyethylene naphthalate (PEN) layer, a Polyetheretherketone (PEEK) layer, a Polyaryletherketone (PEAK) layer, a Polyimide (PI) layer, a thermoplastic polyester elastomer (TPEE) layer.

Embodiment 12 is the sound film according to any one of embodiments 7 to 11, wherein the multilayer sound film has a thickness of 10 μm to 100 μm.

Embodiment 13 is the sound film according to any one of embodiments 1 to 12, wherein the sound film has a tensile modulus in a range of 1MPa to 1000 MPa.

Embodiment 14 is the sound film according to any one of embodiments 1 to 12, wherein the sound film has an elongation at break in a range of 80% to 500%.

Embodiment 15 is a method of producing a sound film for a microspeaker, the method comprising chemically crosslinking a thermoplastic polyurethane elastomer film, wherein: the loss factor of the thermoplastic polyurethane elastomer after chemical crosslinking treatment measured by a rheological curve is less than or equal to 0.4 in the temperature range of 25 ℃ to 150 ℃.

Embodiment 16 is the method for manufacturing a sound diaphragm for a micro-speaker according to embodiment 15, wherein the thermoplastic polyurethane elastomer after the chemical crosslinking treatment has a loss factor of 0.2 or less as measured from a rheological curve in a temperature range of 50 ℃ to 100 ℃.

Embodiment 17 is the method of manufacturing a sound film for a microspeaker of any one of embodiments 15-16, wherein the chemically crosslinked thermoplastic polyurethane elastomer has a tensile modulus in a range of 1 to 150MPa and an elongation at break in a range of 180% to 500%.

Embodiment 18 is the method of manufacturing a sound diaphragm for a microspeaker of any one of embodiments 15-17, wherein the chemical crosslinking process includes crosslinking the thermoplastic polyurethane elastomer film with radiation.

Embodiment 19 is the method of manufacturing a sound diaphragm for a microspeaker of embodiment 18, wherein the chemical crosslinking process comprises crosslinking the thermoplastic polyurethane elastomer film with electron beam radiation.

Embodiment 20 is the method of manufacturing a sound film for a microspeaker of any one of embodiments 15 to 19, wherein the sound film is a single layer sound film or a multilayer sound film comprising at least one layer of a chemically crosslinked thermoplastic polyurethane elastomer.

Embodiment 21 is the method of manufacturing a sound film for a micro-speaker according to embodiment 20, wherein the multilayer sound film is a sound film of a three-layer or more structure.

The present invention will be described in more detail with reference to examples. It should be noted that the description and examples are intended to facilitate the understanding of the invention, and are not intended to limit the invention. The scope of the invention is to be determined by the claims appended hereto.

Examples

In the present invention, unless otherwise indicated, all reagents used were commercially available products and were used without further purification treatment.

TABLE 1 raw materials List

Softening temperature of the thermoplastic polyurethane elastomer was measured by a rheometric rotary rheometer.

Test method

Tensile modulus and elongation at break

Tensile modulus (unit: MPa) and elongation at break (unit:%) of the voice film samples prepared in the following examples were each measured using a universal tester manufactured by Instron, in which the force of the jig was 100N, the size of the voice film sample was 50mm × 25.4Inch, and the test speed was 50 mm/min.

According to the present invention, a sound film sample is considered to meet the basic requirements when the tensile modulus of the sound film sample is greater than or equal to 1MPa and the elongation at break is greater than 80%.

Yield strain

Tensile modulus (unit: MPa) and elongation at break (unit:%) of the voice film samples prepared in the following examples were each measured using a universal tester manufactured by Instron, in which the force of the jig was 100N, the size of the voice film sample was 50mm × 25.4Inch, and the test speed was 50 mm/min.

The presence or absence of yield was observed in the stress-strain curve obtained according to the above method and the yield strain value (%) was calculated.

Rheological curve

The rheological curve properties of the single-layer voice film samples prepared in examples 1 to 3 were measured by the following methods, respectively, to determine the degree of change in damping properties thereof.

Specifically, the rheological curve measurement was performed using an Ares G2 rotational rheometer manufactured by TA corporation, usa. First, sound film samples having a thickness of 1mm were held by 8-inch parallel plate jigs, respectively. Then, rheological measurements were made at different temperature points with a temperature rise rate of 5 ℃/min, a test frequency of 1Hz, and a strain of 1% or less, to obtain a storage modulus G 'and a loss modulus G ″, and a loss factor value (i.e., a damping value) tan δ was calculated from the storage modulus G' and the loss modulus G ″, according to the following formula:

tan δ＝G”/G’。

maximum temperature of hot press forming

The elastic resilience of the sound film can be improved by adopting the thermoplastic polyurethane elastomer material. However, since the common thermoplastic polyurethane elastomer material is easily softened by heating and thermally shrinks, the hot press molding temperature used is limited, and finally the pattern of the sound film is unclear.

According to the embodiment of the invention, the sound film sample is hot-pressed and formed into the sound film with the folding structure (or pattern) by using a hot-pressing forming machine at the pressure of 10 MPa. The hot press molding refers to heating a mold to a preset temperature, carrying out hot pressing for 90 seconds under the pressure of 10MPa, then opening the mold, and demolding after natural cooling. The "highest temperature of hot press molding" means the lowest molding temperature (. degree. C.) at which the sound film is destroyed (including breaking, failing to release, thermal shrinkage, etc.).

Thermal stability

Each of the sound film samples obtained in the examples was processed into a voice coil product for a speaker having a pattern. The voice coil product was then heated to a range of specific temperatures and allowed to operate for 1min each. After cooling the voice coil product to room temperature, observing whether the patterns on the voice film are clear. If clear, the thermal stability of the voice film sample is characterized by the highest temperature at which the patterns in the series of specific temperatures remain clear.

Example 1

A single layer Film of the thermoplastic polyurethane elastomer TPU Film, produced by the company fagga (Shibata), with a thickness of 20 μm was selected. The single-layer film was divided into four parts of a film, B film, C film and D film. Then, the B film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 3 Mrad. In addition, the C film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 6 Mrad. Finally, the D film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 12 Mrad.

Then, for the a film, the B film, the C film, and the D film, measurements were made according to the methods for measuring the tensile modulus, the elongation at break, the rheological curve property (rheological measurement at 25 ℃ to 150 ℃), the maximum temperature of hot press molding, and the thermal stability, respectively, as described above. The test results are shown in table 2.

TABLE 2

Example 2

The thermoplastic polyurethane elastomer ELASTOLLAN C85A 10, produced by BASF corporation, was hot extruded into a single layer film having a thickness of 30 μm by using an extruder. The single-layer film was divided into three parts of a film, B film and C film. Then, the B film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 3 Mrad. In addition, the C film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 6 Mrad.

Then, for the a film, the B film, and the C film, measurements were made according to the methods for measuring tensile modulus, elongation at break, rheological curve property (rheological measurement at 25 ℃ to 220 ℃), maximum temperature of hot press molding, and thermal stability, respectively, as described above. The test results are shown in table 3 below.

TABLE 3

Example 3

The thermoplastic polyurethane elastomer ELASTOLLAN C65A, produced by BASF corporation, was heat extruded into a single layer film having a thickness of 30 μm by using an extruder. The single-layer film was divided into three parts of a film, B film and C film. Then, the B film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 3 Mrad. In addition, the C film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 6 Mrad.

Then, for the a film, the B film, and the C film, measurements were made according to the methods for measuring the tensile modulus, the elongation at break, and the rheological curve property (rheological measurement at 25 ℃ to 150 ℃), the maximum temperature of hot press molding, and the thermal stability, respectively, as described above. The test results are shown in table 4 below.

TABLE 4

In the above examples 1 to 3, sound film samples were prepared using different thermoplastic polyurethane elastomers as the base materials, respectively. From the results in tables 2 to 4, it is understood that when the acoustic diaphragm sample is cross-linked by electron beam irradiation with an electron beam energy of 150KV up to 3Mrad, 6Mrad or 12Mrad, the tensile modulus of the acoustic diaphragm sample does not change much, indicating that the strength of the acoustic diaphragm sample is substantially maintained, and further, the elongation at break of the acoustic diaphragm sample is decreased, indicating that the elasticity of the acoustic diaphragm sample is somewhat decreased, but both are more than 180%, which can satisfy the requirements for the acoustic diaphragm product for a micro-speaker. In addition, when the voice film sample is subjected to the electron beam radiation crosslinking treatment with the electron beam energy of 150KV to reach 3Mrad, 6Mrad or 12Mrad, the loss factor value tan delta of the voice film sample at different time points is basically kept unchanged, and the voice film sample subjected to the electron beam crosslinking treatment has excellent thermal stability. In addition, in examples 1 to 3, since the thermoplastic polyurethane elastomer material was chemically crosslinked by electron beam irradiation, the highest temperature for thermoforming and the thermal stability thereof were greatly improved.

The following examples 4-7 relate to the preparation and characterization of multilayer sound films.

Example 4

The PSA 6574 silicone damping gum and ELASTOLLAN C65A thermoplastic polyurethane elastomer (TPU) were extruded into a three-layer sound film by an extruder. The three-layer sound film comprises a three-layer composite structure (shown in figure 2) of a TPU film (15 mu m)/PSA 6574 silicone damping glue (10 mu m)/TPU film (15 mu m). The voice film sample is divided into A, B, C parts. Then, the B film is irradiated by electron beams with electron beam energy of 150KV to reach the electron beam dose of 3 Mrad; the C film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 6 Mrad.

Then, for the a film, the B film, and the C film, the measurement was performed according to the methods for measuring the tensile modulus, the elongation at break, the maximum temperature of hot press molding, and the thermal stability as described above, respectively. The test results are shown in table 5.

TABLE 5

Example 5

ABSORTOMER EP1001 polyolefin damping gum and ELASTOLLAN C85A 10 thermoplastic polyurethane elastomer (TPU) were extruded through an extruder into a three-layer sound film. The three-layer sound film comprises a three-layer composite structure (shown in figure 2) of a TPU film (25 mu m)/ABSORTOMER EP1001 polyolefin damping glue (25 mu m)/TPU film (25 mu m). The voice film sample is divided into A, B, C parts. Then, the B film is irradiated by electron beams with electron beam energy of 150KV to reach the electron beam dose of 3 Mrad; the C film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 6 Mrad.

Then, for the a film, the B film, and the C film, the measurement was performed according to the methods for measuring the tensile modulus, the elongation at break, the maximum temperature of hot press molding, and the thermal stability as described above, respectively. The test results are shown in table 6.

TABLE 6

Example 6

An APTIV 2000PEEK film, 3M 2567ATT acrylic damping gum, was extruded through an extruder into a four-layer sound film in BASF ELASTOLLAN C85A 10 (TPU). The four-layer sound film has a four-layer composite structure (as shown in fig. 3) of TPU film (30 μ M)/APTIV 2000PEEK film (6 μ M)/3M 2567ATT acrylic damping glue (20 μ M)/APTIV 2000PEEK film (6 μ M). The voice film sample is divided into A, B, C parts. Then, the B film is irradiated by electron beams with electron beam energy of 150KV to reach the electron beam dose of 3 Mrad; the C film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 6 Mrad.

Then, for the a film, the B film, and the C film, the measurement was performed according to the methods for measuring the tensile modulus, the elongation at break, the maximum temperature of hot press molding, and the thermal stability as described above, respectively. The test results are shown in table 7.

TABLE 7

Example 7

An APTIV1000PEEK film, 3M 2567ATT acrylic damping gum and BASF ELASTOLLAN C65A were extruded into a five-layer sound film by an extruder. The five-layer sound film has a five-layer composite structure (shown in FIG. 4) of an APTIV1000PEEK film (8 μ M)/3M 2567 acrylic damping glue (10 μ M)/TPU film (15 μ M)/3M 2567 acrylic damping glue (10 μ M)/APTIV 1000PEEK film (8 μ M). The voice film sample is divided into A, B, C parts. Then, the B film is irradiated by electron beams with electron beam energy of 150KV to reach the electron beam dose of 3 Mrad; the C film was irradiated with an electron beam of 150KV electron beam energy for an electron beam dose of 6 Mrad.

Then, for the a film, the B film, and the C film, the measurement was performed according to the methods for measuring the tensile modulus, the elongation at break, the maximum temperature of hot press molding, and the thermal stability as described above, respectively. The test results are shown in table 8.

TABLE 8

From the above examples 4-7, it can be seen that the multilayer sound film obtained according to the technical scheme of the present invention has good modulus, elasticity and thermal stability.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed in the present disclosure. Accordingly, it is intended that this invention be limited only by the claims and the equivalents thereof.

It will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention. Such modifications and variations are intended to fall within the scope of the invention as defined in the appended claims.