JPH10294991A - Speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive speaker that is easily manufactured by effectively interrupting thermal conduction between eyelets and a diaphragm. SOLUTION: A contact 1 is formed to a diaphragm 2, a wire to conduct a signal current is connected to a voice coil via the contact 1, and a thermal foaming polymer resin layer 3 is formed to the entire face of the diaphragm 2 or around the contact 1 of the diaphragm 2. Through the configuration above, when the surrounding of the contact 1 reaches a prescribed temperature or over, the thermal foaming polymer resin layer 3 is foamed and a foamed carbide layer is formed around the contact 1. The foamed carbide layer insulates the heat from the contact layer 1 effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm for a loudspeaker used in audio equipment and the like, and more particularly to a technique for effectively insulating heat generated by eyelets provided on the diaphragm.

[0002]

2. Description of the Related Art A loudspeaker is a device for converting an electric signal from an amplifier into a sound wave. As shown in FIG. 7, a loudspeaker has a magnetic circuit 20 composed of a magnet 21, a center pole 22 and a yoke 23, and a voice coil 31. , Voice coil bobbin 32, damper 40, speaker frame 50
And the diaphragm 12 and the like.

In the speaker shown in FIG. 7,
Magnet 2 between center pole 22 and yoke 23
1 generates a magnetic field. When a signal current is applied to the voice coil 31 provided so that the current flows perpendicularly to the direction of the uniformly generated magnetic field, a force is applied to the voice coil 31 and the voice coil bobbin 32. The diaphragm 12 adhered to the voice coil bobbin 32 moves with the piston and vibrates the air to emit sound waves.

In the speaker configured and functioning as described above, it is necessary to connect a wire (not shown) for guiding an external signal current to the voice coil 31.
This wire is guided from the terminal 51 installed on the speaker frame 50 to the voice coil 31 and connected thereto. As the connection method, the following two methods are used. The first method is a method of soldering a copper wire extending from the voice coil 31 to the eyelet 11 provided on the diaphragm 12 and further connecting the eyelet 11 to the terminal 51 with a gold wire. In this method, a gold thread wire soldered to a wire is directly bonded to the voice coil bobbin 32, and the voice coil 31 and the terminal 51 are connected with the gold thread wire.

[0005] The first method of wiring via eyelets (hereinafter referred to as "eyelet wiring") prevents abnormal amplitude due to the eccentricity of the vibration system due to the weight of the gold wire, and prevents distortion due to resonance of the gold wire. In order to prevent the occurrence of such a phenomenon, the loudspeaker is used for a speaker which requires a large input diameter or a large amplitude. The second method is mainly used for a small-diameter, low-amplitude speaker having a small input.

In a loudspeaker configured using this “wire through the eyelet”, when an excessive current exceeding the rated input flows through the wire, the loudspeaker has a lower resistance than copper or aluminum used for the wire. Heat generation may occur in a large eyelet or a solder part of the eyelet. When heat is generated in the eyelet portion and a sudden temperature rise occurs, the heat is transmitted from the eyelet to the diaphragm, whereby the temperature of the diaphragm increases, and there is a possibility that a failure may occur in the speaker.

In this case, if the loudspeaker is performing a normal operation, the heated eyelet and its solder portion are cooled by the flow of air generated by the amplitude of the diaphragm, so that no particular problem occurs.

[0008] Further, in order to cut off heat transfer between the eyelet and the diaphragm, an attempt has been made to press-fit the eyelet by sandwiching a heat-resistant rubber, a heat-resistant fiber, a heat-resistant resin film or the like between the eyelet and the diaphragm. I have.

[0009]

However, in the loudspeaker according to the prior art described above, the voice coil bobbin has a large diameter and a large amplitude when a large input is made.
The top plate may ride or deform and be fixed in the magnetic gap. When this happens,
The diaphragm cannot perform normal operation, and does not generate air flow. Then, the heat generated in the eyelet portion is transmitted from the eyelet to the diaphragm, so that the temperature of the diaphragm increases, and there is a possibility that a failure may occur in the speaker.

Further, in a configuration in which a heat-resistant rubber or the like is interposed between the eyelet and the diaphragm, the ignition temperature of the paper pulp or the like constituting the diaphragm and the polymer constituting the heat-resistant rubber, heat-resistant fiber, heat-resistant resin film, etc. The decomposition and destruction temperatures of the material are approximately equal to about 400 ° C., respectively, while the temperature instantaneously generated when an excessive current flows through the coil is 1000 ° C.
It is not practical because it reaches the level.

[0011] Furthermore, although the "wiring via eyelet" has such a problem, it is difficult to substitute another wiring method in view of the acoustic characteristics of a large-diameter, large-amplitude speaker.

The present invention has been made to solve such a problem, and provides a speaker which effectively blocks heat transfer between an eyelet and a diaphragm, is inexpensive and easy to manufacture. The purpose is to:

[0013]

According to a first aspect of the present invention, there is provided a loudspeaker in which a contact portion is formed on a diaphragm, and a wire for guiding a signal current is passed through the contact portion. A heat-expandable polymer resin layer is formed on the entire surface of the diaphragm or around the contact portion of the diaphragm.
According to the loudspeaker according to the first configuration, even when the contact portion is heated by solder having a large electrical resistance value as compared with a copper wire or an aluminum wire, an excessive input voltage exceeding the rating is applied. Since the heat-foamable polymer resin foams due to heat and a foamed carbonized layer is formed around the contact portion, it is possible to effectively prevent the heat at the contact portion from being transmitted to the diaphragm.

In a speaker according to a second configuration of the present invention, a first contact portion and a second contact portion are formed on a diaphragm, and a wire for leading a signal current is connected to the first contact portion. A wire from a voice coil is connected to the second contact portion, and the first contact portion and the second contact portion are electrically connected by a conductive resin film, and each of the contact portions is When the temperature is equal to or higher than a predetermined value, the conductive resin film is broken so that the electrical connection between the first contact portion and the second contact portion is cut off. And a heat-expandable polymer resin layer is formed. According to the loudspeaker according to the second configuration, similarly to the first configuration, by forming a foamed carbon layer around each of the contact portions, heat at the respective contact portions is effectively insulated. In addition, since the electrical connection between the first contact portion and the second contact portion is cut off, generation of heat at a contact portion connecting the contact portions can be prevented.

Further, in the speaker according to the second configuration of the present invention, on one surface of the diaphragm, a peripheral portion including the first contact portion and the second contact portion is provided with the heat-foamable material. A polymer resin layer is formed, and on the other surface of the diaphragm, the heat-foamable polymer resin is formed on a peripheral portion including only one of the first contact portion and the second contact portion. A layer is formed, and the first contact portion and the second contact portion on the other surface of the diaphragm are superimposed on the heat-expandable polymer resin layer formed on the other surface of the diaphragm. It is preferable that the conductive resin film is formed in a peripheral portion including the following. According to this preferred example, when heat is generated in the contact portions and the contact portions connecting the contact portions, the heat expands the thermo-expandable polymer resin, and expands and foams around the contact portions. A layer is formed,
Further, the conductive resin film is lifted by the foamed carbonized layer, and is disconnected. Therefore, it is possible to effectively insulate the heat at each of the contact portions and to prevent the generation of heat at the contact portions connecting the contact portions.

Further, in the loudspeaker according to the second configuration of the present invention, the thermally foamable polymer is attached to the diaphragm so that a spark generated when the conductive resin film is broken does not directly contact the diaphragm. Preferably, a resin layer is formed. According to this preferred example, even if a spark occurs when the conductive resin film is broken, the heat-foamable polymer resin layer is formed so that the spark does not directly contact the diaphragm. The spark does not ignite the diaphragm.

Further, in the speaker according to the second configuration of the present invention, the conductive resin film in a region on the other surface of the diaphragm between the first contact portion and the second contact portion. It is preferable that the heat-foamable polymer resin layer is formed on the extension of the broken portion at the time of breaking. According to this preferred example, since the spark generated when the conductive resin film is broken often falls on the extension of the disconnected portion, it is possible to effectively prevent the spark from directly contacting the diaphragm. it can.

Further, in the speaker according to the present invention,
It is preferable that at least one of the thermally foamable polymer resin layer and the conductive resin film is formed by screen printing or spray printing. According to this preferred example, the mass productivity of the diaphragm constituting the speaker can be improved.

Further, in the speaker according to the present invention,
Preferably, the heat-expandable polymer resin layer is a heat-expandable polymer resin film formed on the diaphragm, and the heat-expandable polymer resin layer further comprises a heat-expandable polymer resin. It is preferable that the diaphragm is a heat-foamable polymer resin-impregnated layer formed by impregnating the diaphragm. According to this preferred example, the heat-foamable polymer resin layer can be formed relatively easily.

Further, in the speaker according to the present invention,
It is preferable that the contact portion is formed using eyelets. According to this preferred example, it is possible to configure the contact portion relatively easily and at low cost.

In the speaker according to the present invention,
It is preferable that the vibrating plate is formed using a base material impregnated with a halogen-based or phosphorus-based flame retardant. According to this preferred example, the noncombustibility of the diaphragm is improved.

In the speaker according to the present invention,
It is preferable that the resin constituting the thermally foamable polymer resin layer is an acrylic resin. The acrylic resin is a general term for a polymer of acrylic acid and its derivatives, and includes polymers and copolymers of acrylic acid and its esters, acrylamide, acrylonitrile, methacrylic acid and its esters, and the like.

In the speaker according to the present invention,
The resin constituting the heat-expandable polymer resin layer is an acrylonitrile, an acrylic ester, or an acrylic resin containing at least one resin selected from a polymer of methyl methacrylate and a copolymer thereof, or a component thereof. It is preferably a polymer resin.

In the speaker according to the present invention,
The foaming agent constituting the heat-foamable polymer resin layer is at least one selected from ammonium polyphosphate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium carbonate, amyl acetate, butyl acetate, and diazoaminobenzene. preferable.

In the speaker according to the present invention,
It is preferable that the heat-foamable polymer resin layer starts foaming at a predetermined temperature, and the resin portion forms a carbonized layer.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a top view of a diaphragm constituting a speaker according to a first embodiment of the present invention. FIG. 2 is a sectional view taken along line XX of FIG. Less than,
A method for manufacturing a diaphragm constituting a speaker according to the present embodiment and its function will be described.

The diaphragm 2 shown in FIGS. 1 and 2 is formed using paper, for example. First, a heat-expandable polymer resin is applied to a peripheral portion of a portion (contact portion) of the diaphragm 2 where the eyelet 1 is mounted. In the present embodiment, the heat-expandable polymer resin film 3 having a thickness of about 100 μm and a radius of about 1.5 times the diameter of the eyelet 1 is applied to the diaphragm 2 by applying the heat-expandable polymer resin. On both sides. Then, the thermally foamable polymer resin film 3 is
After drying in an atmosphere of 0 ° C. for 1 hour, the eyelet 1 is attached to the heat-expandable polymer resin film 3 at substantially the center. In the present embodiment, a state in which two contact portions are provided is shown, but the present invention is not limited to this configuration.
One or three or more locations may be provided as necessary.

The heat-foamable polymer resin used here is, for example, a resin obtained by adding a foaming agent such as ammonium polyphosphate to an acrylic resin as a base material.
The thermally foamable polymer resin starts foaming at around 200 ° C., and at the same time, the acrylic resin as the base material forms a foamed carbonized layer. As the acrylic resin, at least one resin selected from a polymer of acrylonitrile, an acrylate or methyl methacrylate, and a copolymer thereof is preferable. Examples of the foaming agent include ammonium carbonate, amyl acetate, butyl acetate, diazoaminobenzene, and the like.

The loudspeaker according to this embodiment is constituted by using the diaphragm 2 obtained as described above. The configuration of the speaker is basically the same as that of FIG. Next, the function of the speaker according to the present embodiment will be described with reference to FIGS. First, a wire from a voice coil constituting a speaker and a gold wire are solder-bonded with an eyelet 1, and then one of the gold wire is bonded to an external terminal. As shown in FIG. 3, the solder joint 8 is connected to the eyelet 1. Next, in order to apply a voltage to the speaker, a voltage cord is connected to an electrode of the speaker, and a slider is connected. Then, the voltage is gradually increased while adjusting the sliding (that is, the eyelet 1).
Gradually increase the temperature of the part). As a result, the thermo-foamable polymer resin film 3 around the eyelet 1 started foaming around the voltage of 40 V, and the foaming of the thermo-foamable polymer resin film 3 continued until the voice coil was disconnected and broken. The ignition of the diaphragm 2 by the heat from No. 1 did not occur.

This is because even when the temperature of the eyelet 1 suddenly rises, the heat generated in the eyelet 1 causes the thermally expandable polymer resin film 3 to foam to form the foamed carbonized layer 4. This is because the layer 4 protects the diaphragm 2 from a sudden temperature rise in the eyelet 1 portion. FIG. 3 shows a sectional view of the diaphragm at this time. As shown in FIG. 3, since the foamed carbon layer 4 is interposed between the eyelet 1 and the diaphragm 2, in the loudspeaker according to the present embodiment (the structure around the eyelet), the abrupt portion at the eyelet 1 portion. The diaphragm 2 can be protected from an excessive temperature rise.

Hereinafter, the situation around the eyelet portion in the process of forming the carbonized foam layer will be described more specifically. When the foamed carbonized layer is generated, water vapor and carbon dioxide are generated, so that the oxygen concentration around the eyelet decreases. That is, when the base material such as paper (pulp) constituting the diaphragm is burned, the necessary oxygen concentration is reduced to give a choking effect. At the same time, it takes away the heat of reaction and produces a cooling effect. Further, the formed carbonized carbon layer prevents oxygen from entering from outside and completely covers the surface of the base material, and thus has the function of suppressing the generation of flame.

Furthermore, since the foamed carbon layer also covers the eyelet itself, the foam cells formed inside the foamed carbon layer have a heat insulating effect, and have an effect of delaying the time for transferring heat to the base pulp. In this manner, in a state where the eyelets are covered with the foamed carbonized layer, even if the temperature of the eyelet portion continues to rise further, the substrate is only carbonized in the steamed state inside the foamed carbonized layer. As long as it is sufficiently covered with the foamed carbon layer, no ignition occurs.

By impregnating the vicinity of the contact portion on the diaphragm with a flame-retardant substance such as a halogen-based or phosphorus-based substance,
Further, heat transfer from the contact portion (around the eyelet portion) to the diaphragm can be reduced, and the possibility of combustion of the diaphragm can be reduced.

(Second Embodiment) FIG. 4 is a top view of a diaphragm constituting a speaker according to a second embodiment of the present invention. FIG. 5 is a sectional view taken along line XX of FIG. Hereinafter, a method of manufacturing the diaphragm constituting the speaker according to the present embodiment and its function will be described.

The diaphragm 2 according to this embodiment is made of, for example, paper as in the first embodiment. The difference between the present embodiment and the first embodiment is that the shape of the heat-expandable polymer resin films 3a and 3b formed on the diaphragm 2 and the contact portions (first Eyelet 1
a, the second eyelet 1b) is made conductive using the conductive resin film 5. The heat-expandable polymer resin and the like used in the present embodiment are basically the same as those in the first embodiment. Hereinafter, a specific description will be given.

First, the first eyelet 1 on the surface 2a of the diaphragm
a thermofoamable polymer resin film 3a is formed around the area a, and the thermofoamable polymer resin film 3b is formed around the area including the first eyelet 1a and the second eyelet 2b on the back surface 2b of the diaphragm. I do. Here, the thermally foamable polymer resin films 3a and 3b
The thickness is about 0 μm. Then, in a 50 ° C. atmosphere,
Let dry for hours.

Next, the first eyelet 1 on the surface 2a of the diaphragm
The conductive resin film 5 is formed so as to overlap with the thermally foamable polymer resin film 3a which is a region including the second eyelet 2a and the second eyelet 2b and formed on the surface 2a of the diaphragm. Here, the conductive resin film 5 has a thickness of about 100 μm. Then, it is dried at room temperature for 24 hours. On the extension of the boundary portion 6 where the heat-expandable polymer resin film 3a and the conductive resin film 5 overlap, the heat-expandable polymer resin film 3a is formed slightly longer.

The loudspeaker according to the present embodiment is constituted by using the diaphragm 2 obtained as described above. The configuration of the speaker is similar to that of FIG. Next, the function of the speaker according to the present embodiment will be described with reference to FIGS. First, after a wire from a voice coil constituting a speaker and a gold wire are soldered to each other with the first eyelet 1a and the second eyelet 1b, one of the gold wire lines is bonded to an external terminal. As shown in FIG. 6, the solder joint 8 is connected to the eyelets 1a and 1b. As described above, the first eyelet 1a and the second eyelet 1b are electrically connected by the conductive resin film 5 provided on the surface 2a of the diaphragm.

As in the first embodiment, in order to apply a voltage to the speaker, a voltage cord is connected to the speaker electrode, and a slidac is connected. And
The voltage is gradually increased while adjusting the sliding (that is, the temperature of the eyelet 1 portion is gradually increased). As a result, also in the present embodiment, the voltage is 40 V
Thermofoamable polymer resin film 3 around eyelets 1a and 1b
Started foaming.

In this embodiment, as shown in FIG. 5, the heat-expandable polymer resin films 3a and 3b and the conductive resin film 5
Is applied on the diaphragm 2 so that the heat-expandable polymer resin film 3a and the conductive resin film 5 partially have a two-layer structure (the heat-expandable polymer resin film 3a is a lower layer). Therefore, the conductive resin film 5 on the thermally foamable polymer resin film 3a is lifted by the foaming of the thermally foamable polymer resin film 3a,
The boundary portion 6 is broken and disconnected, continuity is lost, and a further rise in temperature of the diaphragm 2 can be prevented. That is, in the present embodiment, the two-layer structure portion of the thermally foamable polymer resin film 3a and the conductive resin film 5 functions as a so-called "fuse". FIG. 6 shows this state. As shown in FIG. 6, in the present embodiment, even if the contact portion having a high electrical resistance value reaches a high temperature at which a member such as a diaphragm or a voice coil is broken due to excessive input or the like, the lower layer has high thermal foaming property. Molecular resin film 3a
Reacts to form the carbonized foam layer 4 and lifts the upper conductive resin film 5, so that the boundary portion 6 is destroyed and the disconnection portion 7 occurs. In this case, the disconnection portion 7 occurs due to heat generation of the conductive resin film portion rather than the contact portion. As is apparent from FIG. 6, the thermally foamable polymer resin film 3 foams while protecting the eyelets 1 and the diaphragm 2 to form a foamed carbonized layer 4. As a result, the conductive resin film 5 is lifted, and a broken portion 7 is generated.

As described above, in the present embodiment, non-combustibility around the eyelet 1 using the heat-expandable polymer resin 3 is achieved.
By using both a print-type “fuse” using the heat-expandable polymer resin film 3 a and the conductive resin film 5,
Even if the temperature near the contact portion formed by eyelets or the like rises and exceeds the ignition point temperature of the paper pulp, it is possible to prevent the diaphragm from being ignited.

Further, in the present embodiment, when the conductive resin film 5 on the thermally foamable polymer resin film 3a is lifted and the boundary portion 6 is broken, and the disconnection portion 7 occurs, Sparks can occur. If this spark directly contacts the diaphragm 2, the diaphragm 2 may ignite, which is not preferable. Therefore, in the present embodiment, as described above, the thermally foamable polymer resin film 3a is formed slightly longer on the extension of the boundary portion 6 (FIG. 4).
reference). With such a structure, the spark generated along the fracture surface falls on the thermo-expandable polymer resin film 3a, and it is possible to prevent the diaphragm 2 from coming into direct contact with the spark. .

In the present embodiment, a conductive resin film is formed on the surface of the diaphragm to form a boundary portion (fuse portion).
However, the present invention is not limited to this, and a boundary portion (fuse portion) may be formed by forming a conductive resin film on the back surface of the diaphragm.

Further, in each of the above embodiments, when a resin film is formed on the diaphragm by performing a printing process by screen printing, spray printing, or the like, mass productivity can be improved.

Further, in each of the above embodiments, the case where the heat-expandable polymer resin is applied to one or both surfaces of the diaphragm to form the heat-expandable polymer resin film has been described. However, the present invention is not limited to this configuration. For example, a sheet-like heat-expandable polymer resin film may be disposed at a predetermined position, or a diaphragm may be impregnated with the heat-expandable polymer resin. A configuration may be used.

[0046]

As described above, according to the present invention,
The heat transfer between the eyelet and the diaphragm is effectively blocked, and a speaker that is inexpensive and easy to manufacture can be obtained.

[Brief description of the drawings]

FIG. 1 is a top view of a diaphragm constituting a speaker according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a cross-sectional view taken along the line XX of FIG. 1 after foaming the thermally foamable polymer resin film (after forming a foamed carbonized layer).

FIG. 4 is a top view of a diaphragm constituting a speaker according to a second embodiment of the present invention.

FIG. 5 is a sectional view taken along line XX of FIG. 4;

FIG. 6 is a cross-sectional view taken along the line XX of FIG. 4 after foaming the thermally foamable polymer resin film (after forming a foamed carbonized layer).

FIG. 7 is a schematic configuration diagram of a speaker.

[Explanation of symbols]

 Reference Signs List 1 eyelet 1a first eyelet 1b second eyelet 2 diaphragm 2a surface of diaphragm 2b back surface of diaphragm 3, 3a, 3b thermally foamable polymer resin film 4 foamed carbon layer 5 conductive resin film 6 boundary portion 7 Disconnection 8 Solder joint

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04R 9/00 H04R 9/00 F

Claims (14)

[Claims] 1. A contact portion is formed on a diaphragm, and a wire for guiding a signal current is connected to a voice coil via the contact portion, and a whole surface of the diaphragm or a peripheral portion of the contact portion of the diaphragm is provided. Speaker formed with a thermally foamable polymer resin layer. 2. A first contact portion and a second contact portion are formed on the diaphragm, a wire for guiding a signal current is connected to the first contact portion, and a voice is connected to the second contact portion. A wire from a coil is connected, the first contact portion and the second contact portion are electrically connected by a conductive resin film, and when the temperature of each contact portion is equal to or higher than a predetermined value, A heat-expandable polymer resin layer is formed in a predetermined area of the diaphragm so that the conductive resin film is broken to cut off electrical connection between the first contact portion and the second contact portion. Speaker. 3. The heat-expandable polymer resin layer is formed on one surface of the diaphragm at a peripheral portion including the first contact portion and the second contact portion, and On the other surface, the heat-foamable polymer resin layer is formed on a peripheral portion including only one of the first contact portion and the second contact portion, and the other of the vibration plate The conductive resin film is superimposed on the heat-foamable polymer resin layer formed on the surface, and is provided on the other surface of the diaphragm at a peripheral portion including the first contact portion and the second contact portion. The speaker according to claim 2, wherein the speaker is formed. 4. The heat-expandable polymer resin layer is formed on the diaphragm so that sparks generated when the conductive resin film is broken do not directly contact the diaphragm. The described speaker. 5. The heat-dissipating film in an area between the first contact portion and the second contact portion on the other surface of the vibration plate, which is an extension of a broken portion of the conductive resin film when the conductive resin film is broken. The speaker according to claim 4, wherein a foamable polymer resin layer is formed. 6. The speaker according to claim 1, wherein at least one of the thermally foamable polymer resin layer and the conductive resin film is formed by screen printing or spray printing. 7. The heat-expandable polymer resin film formed on the vibration plate, wherein the heat-expandable polymer resin layer is a heat-expandable polymer resin film.
The speaker according to any one of claims 1 to 6. 8. The heat-expandable polymer resin layer is a heat-expandable polymer resin-impregnated layer formed by impregnating the diaphragm with a heat-expandable polymer resin. The speaker according to claim 1. 9. The loudspeaker according to claim 1, wherein said contact portion is formed using eyelets. 10. The speaker according to claim 1, wherein the diaphragm is formed using a base material impregnated with a halogen-based or phosphorus-based flame retardant. 11. The loudspeaker according to claim 1, wherein the resin constituting the thermally foamable polymer resin layer is an acrylic resin. 12. The resin constituting the heat-foamable polymer resin layer is at least one resin selected from a polymer of acrylonitrile, acrylate, or methyl methacrylate and a copolymer thereof, or a resin thereof. 2. An acrylic polymer resin containing a component.
0. The speaker according to any one of 0. 13. The foaming agent constituting the thermally foamable polymer resin layer is at least one selected from ammonium polyphosphate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium carbonate, amyl acetate, butyl acetate, and diazoaminobenzene. 13. One of claims 1 to 12
The speaker according to the item. 14. The speaker according to claim 1, wherein the thermally foamable polymer resin layer starts foaming at a predetermined temperature, and the resin portion forms a carbonized layer.