Acoustic diaphragm and method for manufacturing the same

Abstract

The acoustic diaphragm (10) includes a metal foil (11) and a thermoplastic resin film (12) laminated on the metal foil (11). The ratio CTEZ / CTEX of the coefficient of linear thermal expansion CTEZ in the thickness direction of the thermoplastic resin film (12) to the coefficient of linear thermal expansion CTEX is 3.0 or more and 10.0 or less. The total of the unit area weights of the metal foil (11) and the thermoplastic resin film (12) is 45 g / m<supgt;2< / supgt; or more and 150 g / m<supgt;2< / supgt; or less.

Description

Technical Field

[0001] The present invention relates to an acoustic diaphragm and a method for manufacturing the same. Background Art

[0002] As an acoustic diaphragm used in acoustic devices such as speakers and sonar sensors, a laminate formed by laminating a metal foil and a thermoplastic resin film is known.

[0003] For example, Patent Document 1 discloses an acoustic diaphragm obtained by thermocompression bonding a laminate formed by laminating an aluminum metal foil and an unstretched thermoplastic resin film. As the unstretched thermoplastic resin film, a polyurethane-based thermoplastic resin film, a polyamide-based thermoplastic resin film, or a polyester-based thermoplastic resin film is used.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent No. 3911935 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] When manufacturing the acoustic diaphragm of Patent Document 1, in a state where the aluminum metal foil and the unstretched thermoplastic resin film are overlapped, it is heated to around the melting temperature of the unstretched thermoplastic resin film, and a lamination step of pressing the unstretched thermoplastic resin film onto the aluminum metal foil is performed. Since the aluminum metal foil and the unstretched thermoplastic resin film constituting the acoustic diaphragm have different coefficients of thermal expansion, large warpage occurs in the acoustic diaphragm obtained through the lamination step. The warpage of the acoustic diaphragm causes a reduction in workability when processing the acoustic diaphragm into a speaker shape or the like.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide an acoustic diaphragm that is less likely to warp.

[0010] Means for Solving the Problems

[0011] The acoustic diaphragm for solving the above problems includes a metal foil and a thermoplastic resin film laminated on the metal foil. The ratio of the coefficient of linear expansion in the thickness direction of the thermoplastic resin film to the smaller coefficient of linear expansion in the MD direction and the TD direction is 3.0 or more and 10.0 or less, and the total unit area weight of the metal foil and the thermoplastic resin film is 45 g / m 2 or more and 150 g / m 2 or less.

[0012] In several embodiments, the specific gravity of the metal foil may be 1.7 or more and 5.0 or less.

[0013] In several embodiments, the difference between the smaller of the linear expansion coefficients in the MD direction and the TD direction of the thermoplastic resin film and the linear expansion coefficient of the metal foil may be 0 ppm / K or more and 15 ppm / K or less.

[0014] In several embodiments, the linear expansion coefficient of the metal foil may be 5.0 ppm / K or more and 35 ppm / K or less.

[0015] In several embodiments, the smaller of the linear expansion coefficients in the MD direction and the TD direction of the thermoplastic resin film may be 10 ppm / K or more and 50 ppm / K or less.

[0016] In several embodiments, the thermoplastic resin film may include at least one polyimide film adjacent to the metal foil.

[0017] The method for manufacturing an acoustic diaphragm for solving the above problems includes a lamination step of thermocompression bonding the metal foil and the thermoplastic resin film.

[0018] Effect of the Invention

[0019] According to the present invention, warping generated in the acoustic diaphragm can be suppressed. Description of the Drawings

[0020] Figure 1 is a cross-sectional view of an acoustic diaphragm according to an embodiment.

[0021] Figure 2 is a cross-sectional view of an acoustic diaphragm according to a modification.

[0022] Figure 3 is a cross-sectional view of an acoustic diaphragm according to another modification. Detailed Embodiments

[0023] Hereinafter, an embodiment of the present invention will be described.

[0024] As Figure 1 shown, the acoustic diaphragm 10 is a laminate including a sheet-like metal foil 11 and a thermoplastic resin film 12 laminated on one side of the sheet-like metal foil 11. The acoustic diaphragm 10 is applied as a conversion member for acoustic vibration in an acoustic device. Examples of the acoustic device to which the acoustic diaphragm 10 is applied include a speaker, a sonar sensor, and a microphone.

[0025] (Metal Foil)

[0026] Examples of the metal constituting the metal foil 11 include aluminum, titanium, magnesium, copper, and alloys composed of any two or more of them. Among these metals, those with a specific gravity of 1.7 or more and 5.0 or less are preferred, and those with a specific gravity of 2.4 or more and 4.9 or less are more preferred. In this case, when the acoustic diaphragm 10 is applied to a speaker, the sound quality is improved.

[0027] The coefficient of thermal expansion CTEM of the metal foil 11 is preferably, for example, 5.0 ppm / K or more and 35 ppm / K or less, more preferably 7.0 ppm / K or more and 30 ppm / K or less, and still more preferably 8.0 ppm / K or more and 28 ppm / K or less. By setting the coefficient of thermal expansion CTEM of the metal foil 11 within the above range, the difference in the coefficient of thermal expansion from the thermoplastic resin film 12 is reduced, and the effect of suppressing warping of the acoustic diaphragm 10 due to the difference in the coefficient of thermal expansion is improved.

[0028] The thickness of the metal foil 11 is preferably, for example, 10 μm or more and 50 μm or less, more preferably 14 μm or more and 35 μm or less.

[0029] The weight per unit area of the metal foil 11 is preferably, for example, 27 g / m 2 or more and 130 g / m 2 or less, and more preferably 37 g / m 2 or more and 90 g / m 2 or less.

[0030] (Thermoplastic resin film)

[0031] Specific examples of the thermoplastic resin film 12 include polyimide films such as multilayer aromatic polyimide films and single-layer polyimide films, polyetherimide films, polyester films (including liquid crystal films), polyamide films (including aromatic polyamide films), vinyl ester films, fluorine thermoplastic resin films, polyether ketone films (including polyether ether ketone films), and polysulfone films. The multilayer aromatic polyimide film is formed by forming polyimide layers having thermocompression bonding properties on both sides of a non-pressure-bonding aromatic polyimide film. For example, commercially available products such as UPILEX VT (trade name) manufactured by Ube Industries, Ltd. can be used. Such multilayer aromatic polyimide films are described, for example, in Japanese Patent Laid-Open No. 2001-270033. Among them, the thermoplastic resin film 12 is particularly preferably a polyimide film.

[0032] The thermoplastic resin film 12 may contain other components such as additives.

[0033] The thermoplastic resin film 12 may be a foamed body or the like having voids inside the resin.

[0034] For the thermoplastic resin film 12, within the range where it can be bonded to the metal foil 11 and does not hinder the effects and acoustic characteristics of the invention, it may have a structure combined with a non-thermoplastic resin film. For example, it may be a multilayer structure in which the thermoplastic resin film 12 is bonded to one or both sides of the non-thermoplastic resin film, or it may be an island structure in which the thermoplastic resin film 12 is the sea component and the non-thermoplastic resin film is the island component.

[0035] For the thermoplastic resin film 12, the ratio CTEZ / CTEX of the coefficient of linear thermal expansion CTEZ in the thickness direction to the smaller coefficient of linear thermal expansion CTEX among the coefficient of linear thermal expansion in the MD direction and the coefficient of linear thermal expansion in the TD direction is 3.0 or more and 10.0 or less. Additionally, the ratio CTEZ / CTEX is preferably 4.0 or more and 9.5 or less, and more preferably 5.0 or more and 9.0 or less.

[0036] The ratio CTEZ / CTEX being 3.0 or more means that the molecules in the thermoplastic resin film 12 are oriented in the plane direction at a specific level or above, thereby suppressing the warping generated in the acoustic diaphragm 10. Additionally, by the ratio CTEZ / CTEX being 10.0 or less, the durability reduction of the thermoplastic resin film 12 against shear in the plane direction can be suppressed, and the elongation in the plane direction is ensured. Thereby, the workability during the processing of the acoustic diaphragm 10 is improved. For example, the acoustic diaphragm 10 can be easily drawn and processed into a specified shape such as a dome shape.

[0037] The coefficient of linear thermal expansion CTEX of the thermoplastic resin film 12 is, for example, preferably 10 ppm / K or more and 50 ppm / K or less, more preferably 12 ppm / K or more and 43 ppm / K or less, and further preferably 14 ppm / K or more and 35 ppm / K or less. By setting the coefficient of linear thermal expansion CTEX within the above range, the elongation in the plane direction is ensured and the workability during the processing of the acoustic diaphragm 10 is improved.

[0038] The thickness of the thermoplastic resin film 12 is, for example, preferably 12 μm or more and 90 μm or less, and more preferably 16 μm or more and 75 μm or less.

[0039] The basis weight per unit area of the thermoplastic resin film 12 is, for example, preferably 18 g / m 2 above and 120 g / m 2 below, and more preferably 22 g / m 2 above and 100 g / m 2 below.

[0040] (Acoustic diaphragm)

[0041] Preferably, the difference CTEX-M (absolute difference) between the coefficient of linear expansion CTEX of the thermoplastic resin film 12 and the coefficient of linear expansion CTEM of the metal foil 11 in the acoustic diaphragm 10 is 0 ppm / K or more and 15 ppm / K or less, more preferably 0 ppm / K or more and 12 ppm / K or less. By setting the difference CTEX-M within the above range, the effect of suppressing warping generated in the acoustic diaphragm 10 is improved.

[0042] The thickness of the acoustic diaphragm 10 is, for example, preferably 22 μm or more and 100 μm or less, more preferably 25 μm or more and 85 μm or less.

[0043] The weight per unit area of the acoustic diaphragm 10, that is, the total of the weight per unit area of the metal foil 11 and the thermoplastic resin film 12 is 45 g / m 2 or more and 150 g / m 2 or less, preferably 45 g / m 2 or more and 130 g / m 2 or less. By setting the weight per unit area of the acoustic diaphragm 10 within the above range, warping generated in the acoustic diaphragm 10 can be suppressed. In addition, since the weight per unit area of the acoustic diaphragm 10 is 150 g / m 2 or less, a decrease in sound pressure due to an increase in weight can be suppressed. Since the weight per unit area of the acoustic diaphragm 10 is 45 g / m 2 or more, the rigidity of the acoustic diaphragm 10 is improved, and it is easy to ensure self-supportability even when used in acoustic devices such as large-sized speakers.

[0044] For the acoustic diaphragm 10, preferably, the resin ratio, that is, the volume ratio of the thermoplastic resin film 12 in the total volume of the metal foil 11 and the thermoplastic resin film 12 is 60% or less, more preferably 40% or less. By setting the resin ratio of the thermoplastic resin film 12 within the above range, warping generated in the acoustic diaphragm 10 can be effectively suppressed. In addition, when the acoustic diaphragm 10 is applied to a speaker, suppression of warping generated in the acoustic diaphragm 10 and improvement of sound quality can be achieved at a high level. The lower limit value of the resin ratio of the thermoplastic resin film 12 is, for example, 10%.

[0045] The adhesive strength between the metal foil 11 and the thermoplastic resin film 12 in the acoustic diaphragm 10 is, for example, preferably 0.4 N / mm or more. In this case, generation of peeling when the acoustic diaphragm 10 is processed into a specified shape can be suppressed.

[0046] Preferably, the internal loss tanδ of the acoustic diaphragm 10 is 0.02 or more and 0.08 or less. In this case, when the acoustic diaphragm 10 is applied to a speaker, the sound quality in the high frequency range and the sound quality in the low frequency range are improved.

[0047] The acoustic diaphragm 10 is processed into a specified shape such as a flat plate shape or a dome shape according to its use and is applied to an acoustic device.

[0048] The acoustic diaphragm 10 can be manufactured, for example, by a lamination process in which a metal foil 11 and a thermoplastic resin film 12 are overlapped and thermocompression-bonded. There is no particular limitation on the specific method of thermocompression bonding in the lamination process. For example, known methods such as a method using a roll laminating device and a method using a double-belt press device can be used.

[0049] Next, the effects of the present embodiment will be described.

[0050] (1) The acoustic diaphragm 10 includes a metal foil 11 and a thermoplastic resin film 12 laminated on the metal foil 11. The ratio CTEZ / CTEX of the coefficient of linear expansion CTEZ in the thickness direction of the thermoplastic resin film 12 to the coefficient of linear expansion CTEX is 3.0 or more and 10.0 or less. The total of the unit area weights of the metal foil 11 and the thermoplastic resin film 12 is 45 g / m 2 or more and 150 g / m 2 or less.

[0051] Based on the above technical features, warpage generated in the acoustic diaphragm 10 can be suppressed. Thereby, the workability during processing of the acoustic diaphragm 10 is improved.

[0052] (2) The specific gravity of the metal foil 11 is 1.7 or more and 5.0 or less.

[0053] Based on the above technical features, when the acoustic diaphragm 10 is applied to a speaker, the sound quality is improved.

[0054] (3) The difference CTEX-M between the coefficient of linear expansion CTEX of the thermoplastic resin film 12 and the coefficient of linear expansion CTEM of the metal foil 11 is 0 ppm / K or more and 15 ppm / K or less.

[0055] Based on the above technical features, the effect of suppressing warpage generated in the acoustic diaphragm 10 is significantly obtained.

[0056] (4) The coefficient of linear expansion CTEM of the metal foil 11 is 5.0 ppm / K or more and 35 ppm / K or less.

[0057] Based on the above technical features, it is easy to set the difference CTEX-M between the coefficient of linear expansion CTEX of the thermoplastic resin film 12 and the coefficient of linear expansion CTEM of the metal foil 11 within the above range.

[0058] (5) The coefficient of linear expansion CTEX of the thermoplastic resin film 12 is 10 ppm / K or more and 50 ppm / K or less.

[0059] With the above technical features, the elongation in the plane direction is ensured, and the workability during the processing of the acoustic diaphragm 10 is improved.

[0060] (6) The resin ratio of the acoustic diaphragm 10 is 40% or less.

[0061] With the above technical features, the effect of suppressing the warpage generated in the acoustic diaphragm 10 is obtained more significantly. In addition, when the acoustic diaphragm 10 is applied to a speaker, the sound quality is further improved.

[0062] (7) The thermoplastic resin film 12 is a polyimide film.

[0063] With the above technical features, the effect of suppressing the warpage generated in the acoustic diaphragm 10 is obtained more significantly.

[0064] (8) The manufacturing method of the acoustic diaphragm 10 has a lamination process of thermocompression bonding the metal foil 11 and the thermoplastic resin film 12.

[0065] With the above technical features, an acoustic diaphragm 10 that is not easily warped can be manufactured.

[0066] It should be noted that this embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented by combining them with each other within the range where there is no technical contradiction.

[0067] · The number of layers of the metal foil 11 constituting the acoustic diaphragm 10 is not limited to 1 layer, and the acoustic diaphragm 10 can have 2 or more layers of the metal foil 11.

[0068] For example Figure 2 In the shown acoustic diaphragm 10, the first metal foil 11a, the thermoplastic resin film 12, and the second metal foil 11b are laminated in sequence from one side in the lamination direction. That is, they are laminated in such a way that the thermoplastic resin film 12 is located between the first metal foil 11a and the second metal foil 11b. In this case, the effect of suppressing the warpage generated in the acoustic diaphragm 10 is obtained more significantly.

[0069] When there are multiple layers of the metal foil 11, the acoustic diaphragm 10 can have a portion where the metal foils 11 are continuously laminated with each other in the lamination direction. The multiple layers of the metal foil 11 can be all the same metal foil or different metal foils respectively.

[0070] · The number of layers of the thermoplastic resin film 12 constituting the acoustic diaphragm 10 is not limited to 1 layer, and the acoustic diaphragm 10 can have 2 or more layers of the thermoplastic resin film 12.

[0071] For example Figure 3The acoustic diaphragm 10 shown is formed by laminating a first thermoplastic resin film 12a, a metal foil 11, and a second thermoplastic resin film 12b in this order from one side in the lamination direction. That is, the first thermoplastic resin film 12a and the second thermoplastic resin film 12b are laminated on both sides of the metal foil 11. In this case, the effect of suppressing the warping generated in the acoustic diaphragm 10 is obtained more significantly.

[0072] In the case where the multilayer thermoplastic resin film 12 is provided, the acoustic diaphragm 10 may have a portion where the thermoplastic resin films 12 are continuously laminated with each other in the lamination direction. The multilayer thermoplastic resin film 12 may be all the same thermoplastic resin film or may be different thermoplastic resin films respectively.

[0073] In the case where the multilayer thermoplastic resin film 12 is provided, at least one thermoplastic resin film 12 in contact with the metal foil 11 is preferably a polyimide film. In this case, the effect of the above (7) can be obtained.

[0074] · The acoustic diaphragm 10 may further include other layers such as a protective layer in addition to the metal foil 11 and the thermoplastic resin film 12.

[0075] Next, the technical idea that can be grasped from the above-described embodiments and modification examples will be described below.

[0076] (1) According to the aforementioned acoustic diaphragm, wherein the volume ratio of the aforementioned thermoplastic resin film in the total volume of the aforementioned metal foil and the aforementioned thermoplastic resin film is 40% or less.

[0077] (2) According to the aforementioned acoustic diaphragm, wherein the aforementioned thermoplastic resin film includes a first thermoplastic resin film and a second thermoplastic resin film laminated on both sides of the aforementioned metal foil.

[0078] (3) According to the aforementioned acoustic diaphragm, wherein the aforementioned metal foil includes a first metal foil and a second metal foil, and the aforementioned thermoplastic resin film is laminated between the first metal foil and the second metal foil.

[0079] Examples

[0080] Next, examples and comparative examples will be listed to more specifically illustrate the embodiments.

[0081] Hereinafter, the difference CTEX-M between the coefficient of linear expansion CTEX of the thermoplastic resin film and the coefficient of linear expansion CTEM of the metal foil in the acoustic diaphragm will be referred to as "CTE difference".

[0082] <Test 1>

[0083] (Example 1)

[0084] The aluminum foil AL with a thickness of 20 μm (material: 1N30) and the polyimide film PI with a thickness of 25 μm (UPILEX VT manufactured by Ube Industries, Ltd.) were laminated and thermocompression-bonded using a double-belt pressing device to obtain the acoustic diaphragm of Example 1. The specific gravity and coefficient of thermal expansion in the machine direction CTEM of the metal foil of the acoustic diaphragm of Example 1, and the coefficients of thermal expansion in the machine direction CTEX and cross direction CTEZ and the weight per unit area of the thermoplastic resin film are shown in Table 1. In addition, the CTE difference, weight per unit area, and resin ratio of the acoustic diaphragm of Example 1 are shown in Table 2.

[0085] The coefficient of thermal expansion CTEX and coefficient of thermal expansion CTEZ of the thermoplastic resin film and the coefficient of thermal expansion CTEM of the metal foil were measured as follows.

[0086] (Measurement of coefficient of thermal expansion CTEX)

[0087] For the specimen cut from the thermoplastic resin film, as a pretreatment, heat treatment was performed at 300 °C for 30 minutes. The heat-treated specimen was installed in a TMA (Thermal Mechanical Analysis) device (TMA-Q400 manufactured by TA Instruments), and the thermal expansion amount from 50 °C to 200 °C was measured while heating at a heating rate of 10 °C / min to obtain the coefficient of thermal expansion. The specimen was collected from two parts in the machine direction (MD) and transverse direction (TD) of the thermoplastic resin film, and the smaller value of the measured values of the two specimens was taken as the coefficient of thermal expansion CTEX.

[0088] (Measurement of coefficient of thermal expansion CTEZ)

[0089] The specimen cut from the thermoplastic resin film was installed in a laser interferometry type thermal dilatometer (L1X-1, laser thermal dilatometer manufactured by Ulvac-Riko Inc.). As a pretreatment, it was heated to 300 °C, held for 5 minutes, and then cooled to room temperature. Then, the thermal expansion amount from 50 °C to 200 °C was measured while heating at a heating rate of 2 °C / min to obtain the coefficient of thermal expansion CTEZ.

[0090] (Measurement of coefficient of thermal expansion CTEM)

[0091] For the specimen cut from the metal foil, as a pretreatment, heat treatment was performed at 300 °C for 30 minutes. The heat-treated specimen was installed in a TMA (Thermal Mechanical Analysis) device (TMA-Q400 manufactured by TA Instruments), and the thermal expansion amount from 50 °C to 200 °C was measured while heating at a heating rate of 10 °C / min to obtain the coefficient of thermal expansion. The specimen was collected from two parts in the machine direction (MD) and transverse direction (TD) of the metal foil, and the smaller value of the measured values of the two specimens was taken as the coefficient of thermal expansion CTEM.

[0092] (Example 2)

[0093] As the metal foil, an aluminum foil AL (5052) with a thickness of 20 μm was used. Other aspects were the same as in Example 1.

[0094] (Example 3)

[0095] As the metal foil, a titanium foil with a thickness of 20 μm was used. As the thermoplastic resin film, a polyimide film PI with a thickness of 12.5 μm was used. Other aspects were the same as in Example 1.

[0096] (Comparative Example 1)

[0097] An aluminum foil AL (1N30) with a thickness of 30 μm was used as the acoustic diaphragm of Comparative Example 1.

[0098] (Comparative Example 2)

[0099] An aluminum foil AL (5052) with a thickness of 30 μm was used as the acoustic diaphragm of Comparative Example 2.

[0100] (Comparative Example 3)

[0101] A titanium foil with a thickness of 20 μm was used as the acoustic diaphragm of Comparative Example 3.

[0102] (Comparative Example 4)

[0103] A titanium foil with a thickness of 25 μm was used as the acoustic diaphragm of Comparative Example 4.

[0104] (Comparative Example 5)

[0105] A magnesium alloy foil (AZ31B) with a thickness of 44 μm was used as the acoustic diaphragm of Comparative Example 5.

[0106] (Comparative Example 6)

[0107] A thermoplastic resin film formed by laminating and thermocompression bonding a first polyimide film PI (UPILEX VT manufactured by Ube Industries, Ltd.) with a thickness of 25 μm and a second polyimide film PI (UPILEX VT manufactured by Ube Industries, Ltd.) with a thickness of 50 μm in the above order using a double belt pressing device was used as the acoustic diaphragm of Comparative Example 6. The respective values shown in the thermoplastic resin film column of Table 1 are the values of the thermoplastic resin film after thermocompression bonding. The ratio CTEZ / CTEX of the coefficient of linear thermal expansion CTEZ of the first polyimide film PI was 5.3, and the ratio CTEZ / CTEX of the coefficient of linear thermal expansion CTEZ of the second polyimide film PI was 6.1.

[0108] (Comparative Example 7)

[0109] The thermoplastic resin film formed by laminating and thermocompression bonding an aluminum foil AL(1N30) with a thickness of 20 μm, a first polyimide film PI with a thickness of 25 μm, and a second polyimide film PI with a thickness of 50 μm in the above order using a double-belt pressing device was used as the acoustic diaphragm of Comparative Example 7.

[0110] (Comparative Example 8)

[0111] As the metal foil, an aluminum foil AL(1N30) with a thickness of 6 μm was used, and as the thermoplastic resin film, a polyimide film PI with a thickness of 12.5 μm was used. Other aspects were the same as those in Example 1.

[0112] (Comparative Example 9)

[0113] As the thermoplastic resin film, a polyethylene terephthalate film PET with a thickness of 25 μm was used. Other aspects were the same as those in Example 1.

[0114] (Evaluation of warpage)

[0115] The warpage generated in the acoustic diaphragms of each example and each comparative example was evaluated.

[0116] After specimens with a size of 10 cm in length × 10 cm in width were cut out from the acoustic diaphragms of each example and each comparative example and left standing in an environment of 23°C and 65% RH for more than 24 hours, they were placed on a horizontal table with the concave surface of the generated warpage facing upward. The floating height of the highest part floating from the table in the specimen was measured, and the warpage of the acoustic diaphragm was evaluated according to the following criteria. The results are shown in Table 2.

[0117] A: The floating height is less than 2 mm.

[0118] B: The floating height is 2 mm or more and less than 5 mm.

[0119] C: The floating height is 5 mm or more and less than 10 mm.

[0120] D: The floating height is 10 mm or more, and the specimen curls into a tubular shape.

[0121] (Evaluation of processability)

[0122] The processability of the acoustic diaphragms of each example and each comparative example was evaluated.

[0123] Using the acoustic diaphragms of each example and each comparative example, the operation of processing the sheet-like acoustic diaphragm into a dome shape through a mold was performed 10 times respectively. The number of processing defects generated during the 10 times of processing was measured, and the processability of the acoustic diaphragm was evaluated according to the following criteria. The results are shown in Table 2.

[0124] A: The acoustic vibration plate can be easily installed in the mold, and no processing defects are generated.

[0125] B: It is difficult to install the acoustic vibration plate in the mold, but no processing defects are generated.

[0126] C: Processing defects occur more than once.

[0127] D: It cannot be processed.

[0128] (Evaluation of sound quality)

[0129] Speakers are produced by bonding voice coils to the back of the acoustic vibration plates of each example and each comparative example processed into a dome shape with a diameter of 34 mm. Five experts listen to the sound output by the produced speakers, and evaluate the sound quality of the acoustic vibration plates according to the following criteria. The results are shown in Table 2. For acoustic vibration plates that cannot be processed, the evaluation of sound quality is omitted.

[0130] A: The number of experts who judge the sound quality to be excellent is 5.

[0131] B: The number of experts who judge the sound quality to be excellent is 4.

[0132] C: The number of experts who judge the sound quality to be excellent is 3.

[0133] D: The number of experts who judge the sound quality to be excellent is 2 or less.

[0134] In addition, the internal loss tanδ of the acoustic vibration plates of each example and each comparative example at 25°C and 100 Hz is measured using a dynamic viscoelasticity measuring machine. The results are shown in Table 2.

[0135] (Evaluation of adhesion)

[0136] The adhesion of the acoustic vibration plates of each example and Comparative Examples 7 to 9 is evaluated.

[0137] From the acoustic vibration plates of each example and Comparative Examples 7 to 9, strip specimens with a width of 1 cm × a length of 20 cm are made for the MD direction and the TD direction, and the adhesion is evaluated by the 90° peel method described in JIS C 6471. Among the results of evaluating each 3 times for the MD direction and the TD direction respectively, the minimum value is taken as the adhesion of the vibration plate.

[0138] (Evaluation of long-term reliability)

[0139] The long-term reliability of the acoustic vibration plates of each example and Comparative Examples 7 to 9 is evaluated.

[0140] The acoustic vibration plates of each example and Comparative Examples 7 to 9 are subjected to a heating cycle test under the following temperature cycle conditions, and the adhesion thereafter is evaluated by the same method as the above evaluation of adhesion.

[0141] Heating cycle test conditions: Maintain at -50°C for 10 minutes, then heat up to 150°C in 2 hours, maintain at 150°C for 10 minutes, and then cool down to -50°C in 2 hours. This cycle is counted as one time and repeated 3000 times.

[0142] [Table 1]

[0143]

[0144] [Table 2]

[0145]

[0146] As shown in Table 1 and Table 2, the acoustic diaphragms of Comparative Examples 1 to 6 formed of only one of the metal foil and the thermoplastic resin film did not warp, but the acoustic diaphragms of Comparative Examples 7 to 9 formed by laminating the metal foil and the thermoplastic resin film warped significantly. Moreover, when processing the acoustic diaphragms of Comparative Examples 7 to 9, the workability was poor or the processing itself could not be performed.

[0147] On the other hand, even for an acoustic diaphragm formed by laminating a metal foil and a thermoplastic resin film, when the ratio CTEZ / CTEX of the coefficient of linear expansion CTEZ of the thermoplastic resin film is 3.0 or more and 10.0 or less, and the total unit area weight is 45 g / m 2 or more and 150 g / m 2 or less, the acoustic diaphragms of Examples 1 to 3 did not warp significantly. Moreover, the acoustic diaphragms of Examples 1 to 3 did not have processing defects and could be easily processed.

[0148] From the results of the evaluation of sound quality, the evaluation of adhesion, and the evaluation of long-term reliability, it can be seen that the acoustic diaphragms of Examples 1 to 3 can be used as acoustic diaphragms for speakers. Although the specific content is omitted, when measuring the frequency characteristics of the acoustic diaphragms of Examples 1 to 3, good sound pressure reproducibility was exhibited over the entire frequency range.

[0149] <Test 2>

[0150] As shown in Table 3, acoustic diaphragms of Examples 4 to 8 with different thicknesses and configurations of the metal foil and the thermoplastic resin film were fabricated, and various evaluations were performed in the same manner as in Test 1. The results are shown in Table 4.

[0151] (Example 4)

[0152] As the thermoplastic resin film, polyimide film PI with a thickness of 12.5 μm was used. In other aspects, it was the same as Example 1.

[0153] (Example 5)

[0154] As the metal foil, an aluminum foil AL (1N30) with a thickness of 12 μm was used, and as the thermoplastic resin film, a polyimide film PI with a thickness of 12.5 μm was used. Other aspects were the same as those of Example 1.

[0155] (Example 6)

[0156] As the thermoplastic resin film, a polyimide film PI having a thickness of 50 μm was used. The other aspects were the same as those of Example 1.

[0157] (Example 7)

[0158] The acoustic diaphragm of Example 7 was obtained by laminating and thermocompression-bonding the same polyimide film PI having a thickness of 12.5 μm on both sides of an aluminum foil AL (1N30) having a thickness of 20 μm using a double belt press.

[0159] (Example 8)

[0160] The acoustic diaphragm of Example 8 was obtained by laminating and thermocompression-bonding the same aluminum foil AL (1N30) having a thickness of 12 μm on both sides of a polyimide film PI having a thickness of 25 μm using a double belt press apparatus.

[0161] [Table 3]

[0162]

[0163] [Table 4]

[0164]

[0165] As shown in Tables 3 and 4, the results of Examples 1 and 4 to 6 show that as the resin ratio decreases, warpage is suppressed and the sound quality evaluation improves. In particular, when the resin ratio is 60% or less, a high warpage suppression effect and sound quality improvement effect are obtained. When the resin ratio is 40% or less, the sound quality is further improved.

[0166] Furthermore, from the results of Examples 7 and 8, it is understood that the effect of suppressing warping is more significantly obtained by forming an acoustic vibration plate having a laminated structure in which a metal foil is sandwiched by thermoplastic resin films and a laminated structure in which a thermoplastic resin film is sandwiched by metal foil.

[0167] Industrial Applicability

[0168] The present invention can be processed into a dome-shaped loudspeaker by using a mold easily, and can be suitably used as a vibration plate for an active loudspeaker and a support for a voice coil. In addition, due to its good acoustic properties, it can be suitably used for a vibration plate for a flat loudspeaker, a vibration plate for a headphone, a vibration plate for an earphone, etc.

[0169] Explanation of reference numerals

[0170] 10…Acoustic diaphragm, 11…Metal foil, 11a…First metal foil, 11b…Second metal foil, 12…Thermoplastic resin film, 12a…First thermoplastic resin film, 12b…Second thermoplastic resin film.

Claims

1. An acoustic vibrating plate, comprising a metal foil and a thermoplastic resin film laminated on the metal foil, The ratio of the linear expansion coefficient in the thickness direction of the thermoplastic resin film to the smaller linear expansion coefficient among the linear expansion coefficients in the MD direction and the TD direction is 3.0 or more and 10.0 or less, The total basis weight per unit area of the metal foil and the thermoplastic resin film is 45 g / m 2 or more and 150 g / m 2 or less.

2. The acoustic diaphragm according to claim 1, wherein, The specific gravity of the metal foil is 1.7 or more and 5.0 or less.

3. The acoustic diaphragm according to claim 1 or 2, wherein The difference between the smaller linear expansion coefficient among the linear expansion coefficients in the MD direction and the TD direction of the thermoplastic resin film and the linear expansion coefficient of the metal foil is 0 ppm / K or more and 15 ppm / K or less.

4. The acoustic diaphragm according to claim 3, wherein, The linear expansion coefficient of the metal foil is 5.0 ppm / K or more and 35 ppm / K or less.

5. The acoustic diaphragm according to any one of claims 1, 2, and 4, wherein The smaller linear expansion coefficient among the linear expansion coefficients in the MD direction and the TD direction of the thermoplastic resin film is 10 ppm / K or more and 50 ppm / K or less.

6. The acoustic diaphragm according to claim 3, wherein, The smaller linear expansion coefficient among the linear expansion coefficients in the MD direction and the TD direction of the thermoplastic resin film is 10 ppm / K or more and 50 ppm / K or less.

7. The acoustic diaphragm according to any one of claims 1, 2, 4, and 6, wherein The thermoplastic resin film includes at least one polyimide film adjacent to the metal foil.

8. The acoustic diaphragm according to claim 3, wherein, The thermoplastic resin film includes at least one polyimide film adjacent to the metal foil.

9. The acoustic diaphragm according to claim 5, wherein, The thermoplastic resin film includes at least one polyimide film adjacent to the metal foil.

10. A method for manufacturing an acoustic diaphragm, characterized in that, It is a method for manufacturing the acoustic vibrating plate according to any one of claims 1 to 9, and has a lamination step of thermocompression bonding the metal foil and the thermoplastic resin film.

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