JP3873960B2 - Speaker diaphragm and manufacturing method thereof - Google Patents

Description

  The present invention relates to a speaker diaphragm and a manufacturing method thereof. More specifically, the present invention relates to a speaker diaphragm that is lightweight and has an excellent balance between rigidity and internal loss, and a simple and inexpensive method for manufacturing such a speaker diaphragm.

  In general, the characteristics required for a speaker diaphragm include a high Young's modulus (elastic modulus and rigidity) and an appropriate internal loss (tan δ). A typical example of means for improving the Young's modulus is a diaphragm using FRP made of a combination of carbon fiber and epoxy resin. As a means for improving the internal loss, a diaphragm using a synthetic resin such as polypropylene is typically mentioned.

  Each of the above diaphragms has a problem. Specifically, although the FRP diaphragm has a high Young's modulus, the internal loss of the epoxy resin that is the matrix resin is small. As a result, the internal loss of the entire diaphragm is reduced. Therefore, such a diaphragm is likely to resonate and has a frequency characteristic with many peak dips, and it is difficult to prevent the generation of sound unique to the material. Synthetic resin diaphragms often have good frequency characteristics due to their large internal loss, but their rigidity and heat resistance are insufficient.

As means for improving the rigidity (Young's modulus) and internal loss in a well-balanced manner, a diaphragm using a polyethylene naphthalate film has been proposed (see, for example, Patent Documents 1 and 2).
JP-A-1-67099 JP-A-6-181598

Furthermore, in recent years, there has been an increasing demand for weight reduction of speaker diaphragms, and various means have been studied. For example, a lightweight resin with an unfoamed structure at the surface and a foamed structure at the center by adjusting the clamping force and mold clearance applied to the mold cavity during injection molding using a thermoplastic resin with a foaming agent added A diaphragm has been proposed (see Patent Document 3). Alternatively, as an attempt to achieve both strength and weight reduction, a resin foam including two types of cell structures having different foam densities has been proposed (see Patent Document 4). This resin foam is obtained by impregnating a resin with a supercritical carbon dioxide gas having a concentration gradient and heating it to foam.
Japanese Patent No. 3135482 Japanese Patent Laid-Open No. 11-80408

  However, the techniques described in these documents have the following problems. The techniques described in Patent Documents 1 and 2 can be applied only to small-diameter speakers (so-called micro speakers). Specifically, according to the techniques described in Patent Documents 1 and 2, a diaphragm sufficient for both rigidity and internal loss can be obtained in a micro speaker application, but an internal loss is extremely large in a large aperture speaker application. A diaphragm that is insufficient and can withstand practical use cannot be obtained.

  Since the technique described in Patent Document 3 is extremely difficult to adjust the timing for foaming the foaming agent and the timing for changing the clamping force and the mold clearance, the diaphragm has an excellent balance between strength and weight. Is difficult to obtain stably. Since the technique described in Patent Document 4 impregnates a resin molded body (for example, a sheet) with a gas, it takes a very long time until the gas is sufficiently impregnated. For example, when a highly crystalline resin is used to increase the strength, the impregnation may take 100 hours or more. Therefore, this technique is not practical at all.

  As described above, a speaker diaphragm that is lightweight and has an excellent balance between rigidity and internal loss in any application (i.e., large-diameter speaker application or small-diameter speaker application) and such speaker vibration. There is a strong demand for a simple and inexpensive manufacturing method for plates.

  The present invention has been made in order to solve the above-described conventional problems, and the object of the present invention is a speaker diaphragm that is lightweight and excellent in balance between rigidity and internal loss in any application, and the speaker diaphragm. An object of the present invention is to provide a simple and inexpensive method for manufacturing such a speaker diaphragm.

  The speaker diaphragm of the present invention has at least a base material layer including a woven fabric of polyethylene naphthalate fiber and a thermosetting resin impregnated in the woven fabric, and a thermoplastic resin layer.

  In a preferred embodiment, the thermoplastic resin layer is made of nylon, polyester, polyolefin, polystyrene, polyvinyl chloride, polyurethane, polysulfone, polyether ketone, polyether ether ketone, polyacetal, polyarylate, polyamide, polyamideimide, polycarbonate, It includes at least one selected from the group consisting of modified polyphenylene ether, polyphenylene sulfide, polyacrylate, polymethyl methacrylate, polyetherimide, polyethersulfone, polytetrafluoroethylene, liquid crystal polymer, and thermoplastic elastomer.

  In a preferred embodiment, the speaker diaphragm of the present invention further has a thermoplastic elastomer layer.

  In a preferred embodiment, the thermoplastic elastomer layer includes at least one selected from the group consisting of a polyester elastomer, a polyurethane elastomer, and a polyolefin elastomer.

  In a preferred embodiment, the thermoplastic resin layer has a fine foam structure.

  In preferable embodiment, the average diameter of the bubble in the said fine foam structure is 10-60 micrometers.

  According to another aspect of the present invention, a method for manufacturing a speaker diaphragm is provided. The production method comprises the steps of impregnating and curing a polyethylene naphthalate fiber woven fabric with a thermosetting resin to form a base material layer; adding a supercritical inert gas to the molten thermoplastic resin, A step of extruding a thermoplastic resin to which an inert gas is added at a predetermined temperature and pressure to form a thermoplastic resin layer; and a step of laminating the base material layer and the thermoplastic resin layer.

  According to yet another aspect of the invention, a speaker is provided. This speaker includes the speaker diaphragm.

  As described above, according to the present invention, by providing the base material layer including the woven fabric of polyethylene naphthalate fiber and the thermosetting resin impregnated in the woven fabric, and the thermoplastic resin layer, the weight can be reduced. In addition, a speaker diaphragm having an excellent balance between rigidity and internal loss and a simple and inexpensive method for manufacturing such a speaker diaphragm can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

  FIG. 1 is a schematic cross-sectional view of a speaker diaphragm according to a preferred embodiment of the present invention. The diaphragm 100 includes a base material layer 1 and a thermoplastic resin layer 2. Furthermore, the diaphragm 100 optionally has a thermoplastic elastomer layer 3. In the speaker diaphragm of the present invention, the base material layer 1 is preferably the outermost layer (side that emits sound waves). This is because a speaker diaphragm having a glossy fiber pattern appearance with excellent design can be obtained. Other than that, there is no particular limitation on the stacking order of the layers. Therefore, as shown in FIG. 1, the order may be the base material layer, the thermoplastic resin layer, and the thermoplastic elastomer layer, or the base material layer, the thermoplastic elastomer layer, and the thermoplastic resin layer.

  The base material layer 1 includes a woven fabric of polyethylene naphthalate (PEN) fibers and a thermosetting resin impregnated in the woven fabric. Any appropriate thermosetting resin can be adopted as the thermosetting resin, but an unsaturated polyester resin or a melamine resin is preferable. Since the unsaturated polyester resin has a high curing speed and a low curing temperature, it is easy to produce and a speaker diaphragm having excellent internal loss can be obtained. Melamine resin greatly contributes to improvement in strength.

The base material layer 1 includes a woven fabric of PEN fibers. Any appropriate structure (for example, plain weave, twill weave, satin weave, or a combination thereof) can be adopted as the weave structure of this PEN woven fabric, but plain weave is preferable. This is because the vertical / horizontal strength is strong and it is easy to perform deep drawing. Therefore, it is particularly preferable for use with a large-diameter cone type diaphragm. The weave density (basis weight) in the case of plain weave is preferably 150 to 190 g / m ² , more preferably 160 to 180 g / m ² . This is because the weaving density in such a range is significantly larger than the weaving density of a normal woven fabric, so that the effect of increasing the strength is great. Further, this is because the moldability is also excellent.

Preferably, the PEN fibers constituting the woven fabric are fibers that are not twisted (untwisted fibers). By using non-twisted fibers, the thickness per unit weight can be extremely reduced, and as a result, a diaphragm having a light weight and extremely excellent strength can be obtained. For example, ordinary thermoplastic resin fibers are twisted, and the thickness of the woven fabric is about 1 mm when the basis weight is about 170 g / m ² , but the plain weave fabric of untwisted PEN fibers has the same basis weight. Is about 0.18 mm, which is less than one fifth of the thickness. Further, when such a woven fabric is used, the amount of impregnating resin can be greatly reduced (because the fiber / resin ratio of the base material layer can be greatly increased), so that the internal loss is significantly improved. (Details of the resin ratio will be described later). The thickness of the PEN fiber may be any suitable thickness depending on the purpose, but is preferably 800 to 1200 denier. When the thickness of the fiber is less than 800 denier, the basis weight is often lowered and the strength is insufficient. When the thickness of the fiber exceeds 1200 denier, the weight increases, and as a result, the sound pressure often decreases. Preferably, the PEN fiber is a monofilament. This is because, by using monofilament, irregular reflection occurs on the inner surface of the fiber, so that a speaker diaphragm having an excellent design (specifically, a glossy fiber pattern) can be obtained.

  Preferably, at least a part of the PEN fiber is coated with a second thermosetting resin. As the second thermosetting resin, any appropriate thermosetting resin other than the above-described impregnated thermosetting resin can be adopted. For example, when the thermosetting resin to be impregnated is an unsaturated polyester resin, the preferred second thermosetting resin is an epoxy resin or a melamine resin. By applying the coating with the epoxy resin or the melamine resin, the wettability of the surface of the PEN fiber with respect to the unsaturated polyester resin is improved, so that the degree of fiber reinforcement of the unsaturated polyester resin by the PEN fiber becomes very large. As a result, a speaker diaphragm having a very excellent Young's modulus can be obtained. On the other hand, the coated PEN fiber and the unsaturated polyester resin are appropriately displaced during vibration, so that an appropriate internal loss is maintained. Such coating is performed by a normal impregnation operation. The coating amount is adjusted by changing the amount of resin impregnated. As an example of an appropriate coating amount, the resin amount is 3 to 7 parts by weight, preferably around 5 parts by weight, based on 100 parts of the base material.

  The fiber / resin ratio of the base material layer 1 is preferably in the range of 60/40 to 80/20, more preferably in the range of 70/30 to 80/20. This is because by using a base material layer having a high fiber / resin ratio, a speaker diaphragm having an extremely excellent internal loss can be obtained without lowering the Young's modulus. Here, the fiber / resin ratio is a ratio between the weight of the woven fabric before impregnation and the weight of the impregnation resin. As described above, such a very high fiber / resin ratio is achieved by making the fibers (PEN fibers) constituting the base material untwisted fibers.

  The speaker diaphragm of the present invention has a thermoplastic resin layer 2. This is because it is possible to prevent the generation of natural sound that is likely to occur when the base material layer alone is used, and a speaker diaphragm having frequency characteristics without peak dip can be obtained. The thermoplastic resin layer 2 may be in any form of a woven fabric, a nonwoven fabric, or a film. For example, when the speaker diaphragm of the present invention has a two-layer structure of the base material layer 1 and the thermoplastic resin layer 2, or when the thermoplastic resin layer 2 is an intermediate layer as shown in FIG. The thermoplastic resin layer 2 is preferably a film. Since it is easy to flow into the gap of the base material layer 1 during molding, the wettability of the PEN fiber surface constituting the base material layer 1 is improved, and as a result, a speaker diaphragm having excellent rigidity (Young's modulus) is obtained. is there. For example, when the thermoplastic resin layer 2 is an innermost layer having a three-layer structure, the thermoplastic resin layer 2 is preferably a woven fabric or a non-woven fabric. This is because the resin of the intermediate layer easily flows into the gap between the thermoplastic resin layers 2.

  Examples of the resin constituting the thermoplastic resin layer 2 include nylon (for example, nylon 6, nylon 66), polyester (for example, polyethylene terephthalate, polybutylene terephthalate), polyolefin (for example, polyethylene, ultrahigh molecular weight polyethylene, polypropylene, poly- 4-methylpentene-1), polystyrene, polyvinyl chloride, polyurethane, polysulfone, polyether ketone, polyether ether ketone, polyacetal, polyarylate, polyamide, polyamideimide, polycarbonate, modified polyphenylene ether, polyphenylene sulfide, polyacrylate, poly Methyl methacrylate, polyether imide, polyether sulfone, polytetrafluoroethylene, liquid crystal polymer and thermoplastic elastomer And the like. These are used alone or in a blend of two or more. Or you may use the copolymer from these 2 or more types of these resin monomers. A preferred thermoplastic resin is polyester, nylon or polyolefin, and a particularly preferred thermoplastic resin is nylon or polyolefin. This is because the vibration damping property is excellent.

Preferably, the thermoplastic resin layer 2 has a fine foam structure. The average diameter of the bubbles in this fine foam structure is preferably 10 to 60 μm, more preferably 20 to 50 μm, and most preferably 30 to 40 μm. This is because when the thermoplastic resin layer 2 has a fine foam structure, a speaker diaphragm having excellent mechanical strength while being lightweight can be obtained. In particular, such fine bubbles are effective in improving durability and reliability. In addition, such fine bubbles have an effect of increasing the internal loss (tan δ) that is regarded as important in the acoustic member, so that unnecessary sounds radiated when the diaphragm vibrates can be reduced. . The cell density of the foam is preferably 10 ⁹ to 10 ¹⁵ pieces / cm ³ , and more preferably 10 ¹⁰ to 10 ¹⁴ pieces / cm ³ . The expansion ratio corresponding to such bubble density is 1.2 to 3.0 times. This is because the balance between strength and weight reduction can be further improved by having the cell density in such a range.

  The manufacturing procedure of the fine foam structure (foamed sheet) is as follows. First, the resin sheet is placed in a high-pressure container at room temperature. Next, the high-pressure inert gas is sufficiently dissolved in the high-pressure vessel until the saturated dissolution amount is reached. Typical examples of the inert gas include nitrogen, carbon dioxide, argon, neon, helium, oxygen, and a mixed gas thereof. Nitrogen and carbon dioxide are preferred. It is cheap and easy to handle. Next, a gas supersaturated state is created in the resin sheet by rapidly reducing the gas pressure in the high-pressure vessel at room temperature. At this time, the sheet becomes thermodynamically very unstable, and bubble nuclei are generated. The foamed sheet is obtained by heating the sheet above its softening temperature to grow cell nuclei and then cooling. Alternatively, the resin sheet is placed in a high-pressure vessel at a high temperature, and the inert gas is sufficiently dissolved under a high temperature and high pressure until the saturated dissolution amount is reached. Next, by rapidly removing the gas, gas supersaturation, bubble nucleation and bubble growth are allowed to proceed simultaneously, followed by cooling to obtain a foam sheet.

Alternatively, as shown in FIG. 2, the fine foam structure can be formed simultaneously with sheet forming by using an extruder. That is, the raw material thermoplastic resin 20 is introduced from the hopper 21 of the extruder, and the thermoplastic resin is melted in the extruder 22 (typically at 180 to 220 ° C.). A predetermined amount of a critical state inert gas (typically nitrogen, carbon dioxide, argon, neon, helium, oxygen or a mixed gas thereof) (typically 10 to 30 parts by weight per 100 parts by weight of resin) Add. Here, reference numeral 24 represents an inert gas in a liquid state, and reference numeral 25 represents a supercritical state SCF (Supercritical).
Fluid) system. Next, the molten thermoplastic resin and the inert gas are kneaded while maintaining the foaming gas in the extruder at a critical pressure or higher. By maintaining the foaming gas in a supercritical state, the inert gas enters and disperses in the molten thermoplastic resin in a very short time, and a very good compatibility state is realized. This is because the supercritical state has a lower viscosity and higher diffusibility than the liquid state. This molten thermoplastic resin / inert gas mixture is supplied to a sheet forming die 26 at a predetermined temperature (typically 130 to 150 ° C.), and a foamed sheet 27 is formed. By laminating such a foam sheet (thermoplastic resin layer 2) and a PEN woven fabric (base material layer 1), the diaphragm of the present invention can be produced. Note that the supercritical state refers to a state at or above the critical temperature and above the critical pressure. The critical temperature of nitrogen gas is −127 ° C., the critical pressure is 3.5 MPa, the critical temperature of carbon dioxide gas is 31 ° C., and the critical pressure is 7.4 MPa.

  Even when the thermoplastic resin layer 2 has a fine foam structure, the thermoplastic resin can be suitably used. In this case, a particularly preferred thermoplastic resin is a polyolefin. This is because good fine foaming is possible.

  The thermoplastic elastomer layer 3 may be in any form of woven fabric, non-woven fabric or film. For example, when the thermoplastic elastomer layer is the innermost layer as shown in FIG. 1, the thermoplastic elastomer layer 3 is preferably a woven fabric or a non-woven fabric. Since the resin constituting the thermoplastic resin layer 2 easily flows into the gaps between the thermoplastic elastomer layers 3 during molding, wettability is improved, and as a result, a speaker diaphragm having excellent rigidity (Young's modulus) is obtained. It is. For example, when the thermoplastic elastomer layer is an intermediate layer, the thermoplastic elastomer layer 3 is preferably a film. It is because it becomes easy to flow into the base material layer 1 and / or the thermoplastic resin layer 2.

  Examples of the thermoplastic elastomer constituting the thermoplastic elastomer layer 3 include polyester elastomers, polyurethane elastomers, and polyolefin elastomers. These are used alone or in combination of two or more. When the thermoplastic elastomer layer is the innermost layer, these thermoplastic elastomers preferably have a melting point higher than that of the resin constituting the thermoplastic resin layer. This is because by having such a relationship, the thermoplastic resin particularly easily flows into the gaps in the elastomer layer during molding. On the other hand, when the thermoplastic elastomer layer is an intermediate layer, these thermoplastic elastomers preferably have a lower melting point than the resin constituting the thermoplastic resin layer. This is because by having such a relationship, the thermoplastic elastomer easily flows into the gap between the base material layer and / or the thermoplastic resin layer during molding. A particularly preferred thermoplastic elastomer is a polyester elastomer. This is because a speaker diaphragm having excellent internal loss can be obtained.

  The overall thickness of the speaker diaphragm of the present invention is preferably 0.1 to 1 mm, more preferably 0.2 to 0.6 mm. This is in consideration of practicality when incorporated into a speaker unit. The thickness of the base material layer 1 is preferably 0.05 to 0.4 mm, more preferably 0.1 to 0.25 mm. This is because when the base material layer has a thickness in such a range, a speaker diaphragm particularly excellent in the balance between rigidity and internal loss can be obtained. The thickness of the thermoplastic resin layer 2 is preferably 0.05 to 0.6 mm, more preferably 0.1 to 0.35 mm. When the thermoplastic resin layer has a fine foam structure, the thickness of the thermoplastic resin layer 2 is preferably 0.05 to 0.6 mm, more preferably 0.2 to 0.4 mm. This is because the thermoplastic resin layer having a thickness in such a range can cope with speakers having various apertures while balancing rigidity and internal loss. Furthermore, when providing the thermoplastic elastomer layer 3, the thickness of the thermoplastic elastomer layer 3 becomes like this. Preferably it is 0.01-0.1 mm, More preferably, it is 0.04-0.08 mm.

  The speaker diaphragm of the present invention may further have any suitable layer. For example, when the thermoplastic resin layer 2 has a fine foam structure, an adhesive layer or another thermoplastic elastomer layer may be provided between the base material layer 1 and the thermoplastic resin layer 2. This is because the adhesion becomes stronger and the internal loss is further improved.

The operation of the present invention will be described below.
According to the present invention, there is provided a speaker diaphragm having a base material layer including a woven fabric of polyethylene naphthalate fibers and a thermosetting resin impregnated in the woven fabric, and a thermoplastic resin layer. Such a speaker diaphragm has an excellent balance between Young's modulus and internal loss. Details are as follows. By using a woven fabric for the base material layer, the fibers are easily displaced during vibration, so that the vibration energy is converted into heat energy and the internal loss increases. Furthermore, since the PEN woven fabric used in the present invention has a very high weave density, in the diaphragm after molding, only a small amount of thermosetting resin as a binder exists between the fibers constituting the woven fabric. As a result, a laminated structure having substantially a woven fabric layer and a resin layer is formed in the base material layer, and such a structure contributes to further improvement of internal loss. In addition, the excellent Young's modulus is maintained due to the very high weave density of the PEN woven fabric. Therefore, the compatibility between the Young's modulus and the internal loss, which was difficult in the prior art, is achieved. Moreover, since the speaker diaphragm of the present invention has the thermoplastic resin layer laminated on the base material layer, it is possible to prevent the generation of natural sound that is likely to occur when the base material layer is used alone. As a result, a speaker diaphragm having frequency characteristics without peak dip is obtained.

  In a preferred embodiment, the thermoplastic resin layer has a fine foam structure. Since the thermoplastic resin layer has a fine foam structure, a speaker diaphragm having excellent mechanical strength while being lightweight can be obtained. In particular, such fine bubbles are effective in improving durability and reliability. In addition, such fine bubbles have an effect of increasing the internal loss (tan δ) that is regarded as important in the acoustic member, so that unnecessary sounds radiated when the diaphragm vibrates can be reduced. . Moreover, according to the present invention, a simple and inexpensive method for manufacturing such a diaphragm is provided. This is because by using an inert gas in a supercritical state, the foaming sheet (thermoplastic resin layer) can be extruded and foamed simultaneously using an extruder for sheet forming. Since such a manufacturing method does not require large-scale high-pressure equipment, both cost and mass productivity are remarkably improved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Unless otherwise indicated, parts and percentages in the examples are based on weight.

A plain woven fabric of untwisted PEN fibers (manufactured by Teijin Limited, yarn count: 1100 × 1100 (dtex), density: 17 × 17 (lines / inch), basis weight: 166 g / m ² ) impregnated with melamine resin and Cured to form a base material layer. The impregnation amount of the melamine resin was 30 parts by weight with respect to 100 parts by weight of the PEN fiber woven fabric. Further, a polyester elastomer film (Toyobo Co., Ltd., perprene, thickness 80 μm) is used as the thermoplastic resin layer, and a polyester elastomer nonwoven fabric (Toyobo Co., Ltd., perprene, basis weight: 110 g / m ² ) is used as the thermoplastic elastomer layer. It was. The substrate layer, the thermoplastic resin layer, and the thermoplastic elastomer layer were laminated in this order from the front side (side emitting sound waves). In addition, such a nonwoven fabric is normally produced by the water jet method.

Two jigs each having a hole with a diameter of about 13 cm were prepared in the central portion of a stainless plate of about 16 cm × 16 cm, and the laminate was sandwiched between the two jigs. Subsequently, it pre-heated at 120-160 degreeC for 10 second using the far-infrared heater, and a part of thermoplastic resin layer (polyester film) was poured into the clearance gap between a base material layer and a thermoplastic elastomer layer. By performing the preliminary molding, the molding time can be shortened. Subsequently, it was molded at 130 ° C. for 30 seconds under a pressure of 90 to 140 kg / cm ² using a matched die mold having a predetermined shape. After cooling the mold, the mold was opened and the molded product was taken out. In this way, a speaker diaphragm having a diameter of 12 cm and a thickness of 0.29 mm was obtained.

  The obtained diaphragm was measured for density, weight, Young's modulus, and internal loss (tan δ) by ordinary methods. The obtained results are shown in Table 1 below together with the results of Examples 2 to 3 and Comparative Example 1 described later. Furthermore, the frequency characteristics of the speaker using the obtained diaphragm were measured. The results are shown in FIG.

(Comparative Example 1)
A plain woven fabric of Kevlar fibers (manufactured by Toray DuPont Co., Ltd., yarn count: 1100 × 1100 (dtex), density: 17 × 17 (lines / inch), basis weight: 166 g / m ² ) was impregnated with an epoxy resin. The prepreg sheet was molded at 130 ° C. for 5 minutes at a pressure of 90 to 140 kg / cm ² . The other detailed procedures were in accordance with Example 1. As a result, a speaker diaphragm having a diameter of 12 cm and a thickness of 0.29 mm was obtained. The obtained speaker diaphragm was subjected to the same evaluation as in Example 1. The results are shown in Table 1 above. Furthermore, the frequency characteristics of the speaker using the obtained diaphragm were measured. The results are shown in FIG.

  A thermoplastic resin layer having a fine foam structure was produced by the following procedure. Polypropylene (manufactured by Mitsubishi Chemical Co., Ltd., MA06) was dried with hot air, put into an extruder controlled at 200 ° C. and melted. Next, carbon dioxide whose pressure was increased to 25 MPa was injected from the center of the extruder using a pump. Carbon dioxide entered and dispersed in the molten polypropylene in a short time. The molten mixture was extruded at a die temperature of 140 ° C. and a discharge rate of 20 kg / h to obtain a foamed sheet through three rolls. The average diameter of the bubbles in the foam sheet was about 20 μm.

  A speaker diaphragm was produced in the same manner as in Example 1 except that this foamed sheet was used as the thermoplastic resin layer. The obtained speaker diaphragm was subjected to the same evaluation as in Example 1. The results are shown in Table 1 above. Furthermore, the frequency characteristics of the speaker using the obtained diaphragm were measured. The results are shown in FIG.

  A speaker diaphragm was produced in the same manner as in Example 2 except that the base material layer, the thermoplastic elastomer layer, and the thermoplastic resin layer were laminated in this order. The obtained speaker diaphragm was subjected to the same evaluation as in Example 1. The results are shown in Table 1 above. Furthermore, the frequency characteristics of the speaker using the obtained diaphragm were measured.

  As is apparent from Table 1, the speaker diaphragm of the example of the present invention has a low density (that is, light weight) and an excellent balance between rigidity (Young's modulus) and internal loss.

It is a schematic sectional drawing of the speaker diaphragm by preferable embodiment of this invention. It is the schematic explaining the method to form the thermoplastic resin layer of the speaker diaphragm by preferable embodiment of this invention. It is a graph which shows the frequency characteristic of the speaker using the speaker diaphragm of the Example of this invention. It is a graph which shows the frequency characteristic of the speaker using the speaker diaphragm of a comparative example. It is a graph which shows the frequency characteristic of the speaker using the speaker diaphragm of another Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material layer 2 Thermoplastic resin layer 3 Thermoplastic elastomer layer 100 Speaker diaphragm

Claims (8)

At least Yes a substrate layer containing a thermosetting resin impregnated in the woven fabric and the woven polyethylene naphthalate fibers, a thermoplastic resin layer,
Thermoplastic resin layer to have a fine foamed structure, the loudspeaker diaphragm. The speaker diaphragm according to claim 1 , wherein an average diameter of bubbles in the fine foam structure is 10 to 60 μm. A speaker diaphragm including at least a base material layer including a woven fabric of polyethylene naphthalate fiber and a thermosetting resin impregnated in the woven fabric, a thermoplastic resin layer, and a thermoplastic elastomer layer. The speaker diaphragm according to claim 3, wherein the thermoplastic elastomer layer includes at least one selected from the group consisting of a polyester elastomer, a polyurethane elastomer, and a polyolefin elastomer. The speaker diaphragm according to claim 3 or 4 , wherein the thermoplastic resin layer has a fine foam structure. The thermoplastic resin layer is made of nylon, polyester, polyolefin, polystyrene, polyvinyl chloride, polyurethane, polysulfone, polyether ketone, polyether ether ketone, polyacetal, polyarylate, polyamide, polyamideimide, polycarbonate, modified polyphenylene ether, polyphenylene sulfide. , polyacrylate, polymethyl methacrylate, polyether imide, polyether sulfone, polytetrafluoroethylene, containing at least one selected from the group consisting of liquid crystal polymer and a thermoplastic elastomer, according to any one of claims 1 to 5 Speaker diaphragm. Impregnating and curing a thermosetting resin into a woven fabric of polyethylene naphthalate fiber to form a base material layer;
Adding a supercritical inert gas to the molten thermoplastic resin, and extruding the thermoplastic resin to which the inert gas has been added at a predetermined temperature and pressure to form a thermoplastic resin layer;
A step of laminating the base material layer and the thermoplastic resin layer. A speaker comprising the speaker diaphragm according to claim 1.

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