JP2676158B2 - Diaphragm for electroacoustic transducer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a so-called soft dome diaphragm, which is formed by molding a diaphragm base cloth made of a woven cloth of natural fibers or synthetic fibers into a predetermined shape.

[Prior Art] As a dome diaphragm of an electroacoustic transducer, a so-called soft dome diaphragm is known, which is formed by forming a diaphragm base cloth made of a woven fabric of natural fibers or synthetic fibers into a predetermined dome shape. , This type of diaphragm has a flexible elasticity that can maintain its shape against vibration and a large vibration loss rate that suppresses resonance (generally, tan δ of about 0.06 or more is often used). Material is used.

In addition, it is used for the high frequency range like the hard dome diaphragm made of metal such as aluminum and titanium, and the voice coil bobbin and the magnetic coil are magnetized due to the tilt and abnormal resonance of the voice coil bobbin due to the deformation of the dome and edge of the diaphragm. Since the plate portion forming the void is in contact with each other and abnormal noise is easily generated, it is required that the deformation due to temperature, humidity or heat is small.

To meet these demands, a diaphragm base fabric made of a woven fabric of natural fibers such as cotton and silk has been conventionally impregnated with a shape-imparting material such as a phenol resin, an epoxy resin, or a melamine resin, and formed into a dome shape. A diaphragm made of a woven fabric of thermoplastic polymer fibers such as polyester and nylon. A film of vibration loss material resin such as acrylic resin and urethane resin is formed on the surface of the base fabric, and then heated and pressed to form a dome shape. It is well known that the structure is molded into.

However, the former has a large hygroscopic deformation due to the use of natural fibers, and the latter is superior to the former in terms of moisture absorption resistance but is not yet sufficient, and has a problem of large thermal deformation. is there. And, even in the latter structure using acrylic resin as the vibration loss material resin, especially in vehicle, musical instrument, etc., moisture resistance, heat resistance,
Insufficient in oil resistance.

In the latter case, the heating and pressure molding conditions are high (about 19
Since the vibration loss material resin (acrylic resin) adheres to the molding die, fluorine resin,
Since a mold release agent such as a silicone resin must be applied for each molding, there is a problem in mass productivity, and transfer of the mold release agent to the vibration loss material resin surface occurs. The electrodynamic speaker having the structure as shown has a problem that the lead portion 6a of the voice coil 6 is poorly adhered.

Therefore, in recent years, JP-A-59-6558 and JP-A-61-22 have been proposed.
In Japanese Patent No. 5998 and Japanese Patent Laid-Open No. 61-267499, for the purpose of improving moisture resistance, heat resistance and oil resistance, as shown in FIG. 8, fluorine is provided on the surface of the base fabric 1 with an acrylic resin layer 3 interposed therebetween. There has been proposed a structure having a resin film 4 formed therein, or a structure having a fluorine resin film formed directly on the surface of a base fabric without an acrylic resin layer interposed therebetween.

[Problems to be Solved by the Invention] However, the fluorine resin coating has heat resistance and good mold releasability, which is advantageous in manufacturing, but it is relatively chemically inert. Therefore, it has almost no adhesiveness with other members.

Therefore, an actual electroacoustic transducer, for example, an electrodynamic speaker has the following problems.

As shown in FIG. 8, the lead portion 6a of the voice coil 6 wound around the voice coil bobbin 5 must be led out to the outside through the edge portion 7 of the diaphragm. Since the base resin coating 4 is formed,
There is a problem that the lead portion 6a of the voice coil 6 cannot be bonded. Therefore, in order to enable the bonding between the edge portion 7 and the lead portion 6a of the voice coil 6, the surface of the fluorine resin coating film 4 is activated by applying a low temperature oxygen plasma treatment such that the diaphragm is not thermally deformed. Therefore, the adhesiveness must be imparted, which is not practical and causes a cost increase.

Further, in the structure in which the fluorine resin coating is formed on both front and back surfaces of the diaphragm, there is a problem that the voice coil bobbin 5 cannot be even adhered, and the same processing as above must be performed.

The former one having a structure in which the fluorine resin coating film 4 is formed on the surface of the base fabric 1 via the acrylic resin layer 3 increases the weight of the diaphragm and has a low sound pressure radioactivity, which is not practical. The fluorine resin coating 4 is made as thin as possible. Therefore, the moisture permeates the thin fluorine resin coating 4 on the surface and permeates the acrylic resin layer 3 and the base cloth 1 inside, so that the vibration plate is deformed and the acrylic resin layer 3 is softened.
Due to this, abnormal resonance of the diaphragm occurs at high input,
There is also a problem that the initial characteristics of the speaker cannot be maintained because the initial stability changes with time.

In the latter structure having a fluorine resin coating directly on the surface, the vibration loss rate tan δ is about 0.0
It is as small as 35 to 0.045, and there is a problem that the unnecessary vibration, which is a feature of the soft dome diaphragm, is insufficiently suppressed.

[Means for Solving the Problem] The present invention comprises a mixed composition layer of a vibration loss material resin and a fluorine resin formed directly on the surface of a vibration plate base cloth or through a vibration loss material resin layer. An inorganic powder is mixed in the mixed composition layer of the vibration loss material resin and the fluorine resin.

[Operation] In the first aspect of the invention, in the mixed composition layer of the acrylic resin, the fluorine resin and the acrylic resin composition formed on the surface of the diaphragm base fabric, the acrylic resin composition functioning as a vibration loss material is used even under high temperature and high humidity. Since the fluororesin composition having a small change in the stayness is mixed, the change in the stayness of the diaphragm is small even under high temperature and high humidity, and the speaker incorporating the diaphragm of the present invention has a f0 of the vibration system and a high limit frequency. There is almost no characteristic change in the vicinity, and the deformation of the diaphragm is small even under high temperature and high humidity.

In the second aspect of the present invention, since the vibration loss material resin, the fluorine resin, and the inorganic powder are mixed in the mixed composition layer, as shown in FIG. 9, by mixing the inorganic powder, the coating of the diaphragm base cloth is performed. Since the surface becomes uneven and the contact area with the mold surface is small, the mold releasability is good and continuous automatic molding without the need to apply a mold release agent to the mold every time as in the past. In addition, since the mold releasability is good and uniform, when the molded diaphragm is removed from the mold, the diaphragm is not deformed, and the stability of the diaphragm can be increased. it can.

[Examples] Representative examples of the present invention will be described below.

First, in order to facilitate the comparison between this example and the conventional example, the following vibration loss material resin compositions A, B and C were used.
A liquid was prepared.

Solution A (acrylic resin composition): 85 parts of emulsion solution (resin concentration 35 wt%) of acrylic acid ester copolymer mixed with 30 parts of methyl acrylate and 70 parts of butyl acrylate, and 3 parts of trimethylolmelamine as a crosslinking accelerator. Add and mix to prepare emulsion solution.

Ammonia water is added to the solution A and the viscosity is increased by stirring to prepare a coating solution A having a viscosity of about 7,000 CPS.

Solution B (mixture composition of acrylic resin and fluorine resin): Solution A with fluorine resin solution having a skeleton of C ₇ F ₁₇ (resin concentration 2
(5 wt%) 12 parts were added and mixed to prepare an emulsion solution.

Liquid C (fluorine resin composition): 3 parts of isopropyl alcohol and 87 parts of water were mixed with 10 parts of the fluorine resin liquid (resin concentration: 25 wt%) to prepare a coating C liquid in which the fluorine resin was suspended. Prepared.

Then, a base cloth prepared by plain weaving polyester fibers of 100 warps to 81 wefts / inch and 52 g / m ² is prepared.

(Example 1) (Fig. 1) Liquid B (acrylic resin, fluorine resin and mixed composition) was coated on a base cloth 1 by a doctor knife coating method, and then at about 130 ° C for 5 minutes in a hot air dryer. After drying and film formation, a diaphragm base fabric having a surface on which a mixed composition layer 2 of an acrylic resin and a fluorine resin was formed was manufactured. The diaphragm base fabric weighed 68.2 g / m ² .

Then, this diaphragm base fabric is heated and pressed under the molding conditions of a mold temperature of 195 to 205 ° C, a press pressure of 200 kg / cm ² and a mold clamping time of 12 seconds, and is molded into a dome shape to have a diameter of 25 mm and a depth of 6.5 mm. Completed the diaphragm.

(Example 2) (Fig. 2) Liquid A (acrylic resin composition) was used as the base fabric 1 (Example 1).
After coating with the same method as above, drying and film formation under the same conditions to form the acrylic resin composition layer 3, and the weight is 6
A base fabric of 3.3 g / m ² was produced.

Further, liquid B (a mixed composition of acrylic resin and fluorine resin) was coated on the surface of the acrylic resin composition layer 3 by the same method as in (Example 1), and then dried and film-formed under the same conditions. A diaphragm base cloth having a mixed composition layer 2 of an acrylic resin and a fluorine resin was manufactured. Liquid A, B
The coating amount of the liquid is 1 / each of the weight ratio (Example 1).
And 2.

The diaphragm base fabric weighed 68.9 g / m ² .

Next, this diaphragm base fabric is heated and pressed under the same conditions as in (Example 1) to form a dome shape, diameter 25 mm, depth 6.5 m.
Completed the m diaphragm.

 The following was manufactured as a comparative column of this example.

(Comparative Example 1) (Fig. 3) Liquid A (acrylic resin composition) was used as the base fabric 1 (Example 1).
After being coated by the same method as above, it was dried and film-formed under the same conditions to manufacture a diaphragm base cloth having the acrylic resin composition layer 3 formed on the surface thereof. The diaphragm base fabric weighed 68.3 g / m ² .

Next, this diaphragm base fabric is heated and pressed under the same conditions as in (Example 1) to form a dome shape, diameter 25 mm, depth 6.5 m.
Completed the m diaphragm.

(Comparative Example 2) (FIG. 4) After spraying the liquid C (fluorine resin composition) on the surface of (Comparative Example 1), that is, the surface of the acrylic resin composition layer 3 by a spray method, the temperature is about 130 ° C. A diaphragm base fabric having a fluorine resin composition layer 4 formed on the surface through an acrylic resin composition layer 3 was manufactured by drying in a hot air drier for 3 minutes to form a film. The diaphragm base fabric weighed 68.9 g / m ² .

Next, this diaphragm base fabric is heated and pressed under the same conditions as in (Example 1) to form a dome shape, diameter 25 mm, depth 6.5 m.
Completed the m diaphragm.

Next, in each of these Examples and Comparative Examples, a high temperature and high humidity test was performed, and the top dome of the dome portion was left standing for 96 hours at a temperature of 25 ° C and a humidity of 60% RH. It was measured under the condition of RH for 96 hours, and the change rate of each was obtained.

As for the method of measuring the stiffness, as shown in FIG. 5, a diaphragm was placed on a jig, the top was pressed, and the force required to displace 2 mm was measured.

 The measurement results are as follows.

According to the above measurement results, the rate of change in the stability of (Example 1) was as low as 5.6%, which was about 1/3 of that of the other comparative examples, and the rate of change of (Example 2) was 9.9%. It can be confirmed that it is about 1 / 1.5-1.8 as compared with other comparative examples.

This is because in the mixed composition layer 2 of the acrylic resin and the fluorine resin formed on the surface of the base cloth 1, the acrylic resin composition functioning as a vibration loss material has a small change in the stability even under high temperature and high humidity. This is because the base resin composition is mixed.

In addition, (Example 1) and (Comparative Example 2) were incorporated into a speaker having the same specifications, and the sound pressure frequency characteristics before and after the high temperature and high humidity test and the admittance characteristics showing f0 of the vibration system were measured.

According to the measurement results, in (Example 1), as shown by the solid line in FIG. 6, there is almost no characteristic change in the vicinity of f0 and the high limit frequency of the vibration system, whereas in (Comparative example 2), the solid line in FIG. As shown in, the f0 of the vibration system is reduced by about 25 Hz, the high limit frequency is reduced by about 700 Hz in the high range, and the sound pressure is also about 2 dB.
Dropped.

(Example 3) (FIG. 9) 130 parts of emulsion solution (resin concentration 35 wt%) of acrylic acid ester copolymer mixed with 30 parts of methyl acrylate and 70 parts of butyl acrylate, and fluorine resin solution (resin concentration 2)
5 wt%) 12 parts by mixing and stirring, and as an inorganic powder,
50 parts of 2 wt% titanium oxide powder suspension is added and mixed to prepare coating liquid D.

Then, this liquid D was coated on the base cloth 1 by the same method as in (Example 1), dried and film-formed under the same conditions, and titanium oxide was formed on the surface of the mixed composition layer 2 of acrylic resin and fluorine resin. A vibrating plate base cloth having a vibrating loss material layer in which the powder 8 of FIG.

That is, in (Example 1), the titanium oxide powder 8 was mixed in the mixed composition layer 2 of the acrylic resin and the fluorine resin.

Next, this diaphragm base fabric was heated and pressed under the same conditions as in (Example 1) and molded into a dome shape to complete the diaphragm.

(Example 4) (Fig. 10) In (Example 2), liquid D was coated on the surface of the acrylic resin composition layer 3 of the base fabric 1 by the same method as (Example 3), and then dried under the same conditions. Then, a diaphragm base fabric was formed by forming a film on the surface of which a vibration loss material layer in which the titanium oxide powder 8 was mixed in the mixed composition layer 2 of acrylic resin and fluorine resin was formed.

That is, in (Example 2), the titanium oxide powder 8 was mixed in the acrylic resin / fluorine resin / mixed composition layer 2.

Next, this diaphragm base fabric was heated and pressed under the same conditions as in (Example 1) and molded into a dome shape to complete the diaphragm.

If the acrylic resin liquid is mixed after mixing the titanium oxide powder liquid and the fluorine resin liquid when preparing the liquid D, the fluorine resin concentration on the surface of the titanium oxide powder becomes higher than that of other portions, and the hygroscopic property is prevented. The effect is further improved.

(Embodiment 5) (Fig. 11) In (Embodiment 2), 32 wt% titanium oxide powder liquid as an inorganic powder was added to and mixed with liquid A (acrylic resin composition) on the surface of the base fabric 1 for coating E After coating the liquid in the same manner as in (Example 1), drying and film formation under the same conditions to form an acrylic resin composition layer 3 containing titanium oxide powder 8 mixed on the surface, and further, this acrylic resin Liquid D (a mixed composition of acrylic resin and fluorine resin mixed with titanium oxide powder 8) was coated on the surface of the composition layer 3 by the same method as in (Example 1), and then dried and produced under the same conditions. A film is formed to form a mixed composition layer 2 of an acrylic resin and a fluorine resin in which titanium oxide powder 8 is mixed to form a diaphragm base cloth, which is heated and pressed under the same conditions as in (Example 1), The diaphragm was completed by forming it into a dome shape.

Next, in each of these examples, a high temperature and high humidity test was conducted, and the top part of the dome was left to stand for 96 hours under the conditions of room temperature and normal humidity (before the test), temperature 43 ° C and humidity 92% RH. It measured and calculated each change rate.

The method of measuring the stiffness is the same as in (Example 1) and (Example 2).

 The measurement results are as follows.

According to the above measurement results, in Example 3 and Example 5, the stability of the diaphragm is increased by about 25% as compared with Comparative Example 1, and the rate of change of the stability due to humidity is 12.1 each.
%, 8.9%, which is lower than 18.3% of Comparative Example 1.

The increase in the stability is because the titanium oxide powder is mixed in the mixed composition layer of the vibration loss material resin and the fluorine resin or the vibration loss material resin layer.

When the mold releasability at the time of molding is examined for each of the above-mentioned Examples and Comparative Examples, (Comparative Example 1), since it is fused to the mold, it is necessary to apply a mold release agent to the mold. It was

(Comparative Example 2) The mold releasability was good, and application of a mold release agent was unnecessary.

(Examples 1 and 2) It is not necessary to apply a release agent,
It was necessary to adjust the release force so that the diaphragm would not deform during release.

(Examples 3, 4, and 5) The mold releasability was good, and it was unnecessary to apply a mold release agent.

As described above, particularly in (Examples 3, 4 and 5), the mixing of the inorganic powder causes the coating surface of the diaphragm base cloth to become uneven as shown in FIG. 9, resulting in a contact area with the mold surface. Is smaller, the mold releasability becomes better, and continuous automatic molding is possible without the need to apply a mold release agent to the mold each time as in the past, and the mold releasability is good. In addition, since it becomes uniform, when the molded diaphragm is removed from the mold, the diaphragm is not deformed.

Further, in (Example 3) to (Example 5), the same is true even if silicon oxide powder is used instead of titanium oxide powder as the inorganic powder.

[Effects of the Invention] First invention: a diaphragm having a mixed composition layer of a vibration loss material resin and a fluorine resin formed directly or through a vibration loss material resin layer on the surface of a diaphragm base fabric. Since the vibration loss material resin layer is mixed with fluorine resin having a small stiffness change with respect to temperature and humidity, the change in the stiffness of the diaphragm is small even under high temperature and high humidity, and the speaker incorporating the diaphragm of the present invention is It is possible to provide a stable speaker of quality with little change over time, with almost no characteristic changes near the f0 and high limit frequencies of the vibration system. Further, since the change in the stiffness of the diaphragm is small even under high temperature and high humidity, it is possible to suppress the occurrence of abnormal sound due to the inclination of the voice coil bobbin and the abnormal resonance due to the deformation of the diaphragm, and the fluorine resin is mixed in the surface layer. Because it is excellent in water resistance,
In particular, it is suitable for applications such as automobile door-mounted speakers and outdoor-use musical instrument speakers, which have a large degree of water droplets and oil adhesion.

2nd invention: In addition to the effect of 1st invention, in the diaphragm characterized by mixing inorganic powder in the mixed composition layer of said vibration loss material resin and fluorine resin, in addition to the effect of 1st invention, a diaphragm Therefore, the abnormal resonance of the diaphragm is unlikely to occur at the time of a large input, the input resistance is improved, and the high frequency limit is expanded, and the vibration loss material resin and the fluorine resin are Since the inorganic powder is mixed in the mixed composition layer of, the coating surface of the vibration plate base cloth becomes uneven, the contact area with the mold surface becomes small, and the separation between the mold and the molded diaphragm is made. The moldability is good, there is no need to apply a mold release agent to the mold every time molding is required, continuous automatic molding is possible, and not only mass productivity is improved,
Molding cost can be reduced, and the mold releasability is good and uniform, so when the molded diaphragm is removed from the mold, the diaphragm does not deform and the shape as designed can be realized. It is possible to eliminate abnormal resonance due to deformation and abnormal shape during molding, realize ideal vibration mode, suppress abnormal resonance at high input, and improve input resistance. .

[Brief description of the drawings]

FIG. 1 is a diagram showing the structure of a typical embodiment (first embodiment) of the diaphragm for electroacoustic transducers of the first invention according to the present invention, and FIG. 2 is the same as the second embodiment. Figure showing the structure, 3rd
FIGS. 4 and 5 are views showing the structures of the first and second comparative examples, and FIG.
FIG. 7 is a schematic diagram showing a method for measuring the stayness, FIG. 6 is a diagram showing sound pressure frequency characteristics and a admittance characteristic of a speaker incorporating the first embodiment before and after a humidity test.
Fig. 8 shows the sound pressure frequency characteristics and the admittance characteristics of the speaker incorporating the second comparative example before and after the humidity test. Fig. 8 shows the conventional electroacoustic transducer diaphragm (corresponding to the second comparative example). FIG. 9 is a diagram showing the structure, FIG. 9 is a diagram showing the structure of a typical embodiment (third embodiment) of the diaphragm for an electroacoustic transducer according to the second invention, FIG. 10, FIG. FIG. 11 is a view showing the structures of the fourth and fifth embodiments of the same.

Continuation of the front page (56) Reference JP-A-59-6558 (JP, A) JP-A-61-267499 (JP, A) JP-A-54-74726 (JP, A) JP-A-61-225998 (JP , A) JP 63-261988 (JP, A) JP 61-114696 (JP, A) JP 60-100899 (JP, A) JP 54-86321 (JP, A) 54-100717 (JP, U)

Claims (2)

(57) [Claims] 1. A mixed composition layer (2) of a vibration loss material resin and a fluorine resin is formed directly or through a vibration loss material resin layer (3) on the surface of a diaphragm base fabric (1). A diaphragm for an electroacoustic transducer, which is characterized in that 2. The vibration for an electroacoustic transducer according to claim 1, wherein an inorganic powder (8) is mixed in the mixed composition layer (2) of the vibration loss material resin and the fluorine resin. Board.