JP3241499B2 - Method for manufacturing speaker diaphragm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a speaker diaphragm using a thermoplastic resin having optical anisotropy when melted.
About the law .

[0002]

2. Description of the Related Art Generally, various materials are used for speaker diaphragms. Recently, speaker diaphragms using a thermoplastic resin having optical anisotropy when melted have been proposed (Japanese Patent Laid-Open No. Sho 62-62). 149296 and JP-A 1-227
No. 7100). The thermoplastic resin having optical anisotropy upon melting means a resin capable of forming an optically anisotropic molten phase, and is called a thermotropic liquid crystal polymer (hereinafter referred to as a liquid crystal polymer). is there.

Such a conventional speaker diaphragm using a liquid crystal polymer is formed by injection molding a liquid crystal polymer into a predetermined shape, and this speaker diaphragm causes a molecular orientation in the liquid crystal polymer by an injection pressure. In this case, high elastic properties are provided in the flow direction to obtain good frequency characteristics.

[0004]

[SUMMARY OF THE INVENTION] However, in the conventional speaker diaphragm made of resin alone of the liquid crystal polymer, Hibiya this flow direction, is likely to occur over a period, carbon Therefore, the liquid crystal polymer for the purpose of reinforcement Short fibers such as fibers were mixed.

When a loudspeaker diaphragm is formed by injection molding in a system in which short fibers such as carbon fibers are mixed with the liquid crystal polymer, it is difficult to form a thin film. The loudspeaker diaphragm has a thickness of about 200 μm. There was an inconvenience of being a limit.

[0006] The incorporation of this short fiber such as carbon fiber into the liquid crystal polymer impairs the high internal loss (tan δ) characteristic of the liquid crystal polymer, and has the disadvantage that the frequency characteristics cannot be denied.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to achieve both high retention of internal loss and prevention of cracks and cracks in a speaker diaphragm and to obtain a relatively thin speaker diaphragm. And

[0008]

According to the present invention, a speaker diaphragm is provided.
The production method is a thermoplastic resin that has optical anisotropy when melted.
The fat is heated and melted, and then biaxially stretched.
Forming a film having a certain thickness,
Thermoforming at a temperature 30 ° C or more lower than the melting point of the thermoplastic resin
In a predetermined shape.

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

According to the present invention, a liquid crystal polymer is biaxially stretched.
Using the obtained film, 30 ° C or less from the melting point of the liquid crystal polymer
Since it is thermoformed at a lower temperature and molded into a predetermined shape,
The molecules areotropically oriented in the plane of the biaxially stretched film.
Speed of specified shape without losing orientation
A vibrating plate can be obtained.

[0017]

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An example of the embodiment of the manufacturing method will be described.

In this example, among the liquid crystal polymers, a thermotropic liquid crystal comprising 27 mol% of 6-hydroxy-2-naphthoic acid units and 73 mol% of p-hydroxybenzoic acid units, which corresponds to a wholly aromatic polyester liquid crystal polymer. The polyester is heated and melted at 285 ° C. by a single screw extruder, melt-extruded from an inflation die (die temperature: 285 ° C.) having a diameter of 32 mm and a slit interval of 0.6 mm, and biaxially stretched (stretching ratio in the take-off direction: 2.
5, a stretching ratio of 7.0 in the direction perpendicular to the take-off direction), and then cutting the end portion to obtain a 35 μm thick film. The mechanical properties (tensile strength, tensile elastic modulus, specific elastic modulus, loss tangent, and elastic modulus) of the obtained film were measured under various conditions of changing the direction on the film surface.
The maximum value (I), the minimum value (II) and the ratio (I) /
(II) is shown in Table 1.

[0020]

[Table 1]

From the results shown in Table 1, since the value of the mechanical properties such as tensile strength in the maximum direction is less than twice the value in the minimum direction of the obtained film, It was determined that the molecules were oriented substantially isotropically in the direction.

The obtained film 1 was mounted on a pressing guide 2 as shown in FIG. 1 and was thermoformed by a vacuum forming machine for a speaker diaphragm comprising a heater 3, a mold 4 and a vacuum pump 5. That is, the surface temperature of the film 1 is lowered by 30 ° C. or more from the melting point (for example, 280 ° C.) of the liquid crystal polymer constituting the film 1 by the heater 3, for example, from 200 ° C.
At 220 ° C., the inside of the mold 4 was evacuated by the vacuum pump 5 and the film 1 was pulled to obtain a cone-shaped speaker diaphragm having an outer diameter of 25 mm. In this case, the reason why the temperature of the thermoforming is lower than the melting point (for example, 280 ° C.) of the liquid crystal polymer by 30 ° C. or more is that heat shrinkage tends to occur as the temperature at the time of thermoforming approaches the melting point, and the formability deteriorates. This is because

A plurality of samples in different directions were cut out from the obtained speaker diaphragm, and the tensile strength, tensile modulus, specific modulus, and loss tangent were measured. Table 2 shows the results and the ratio between the maximum value and the minimum value.

[0024]

[Table 2]

As is clear from Table 2, the obtained speaker diaphragm has the same mechanical properties as those of Table 1 of the film 1 of the raw material, and the mechanical properties such as the tensile strength in the maximum direction. Since the value is not more than twice the value in the minimum direction, it can be determined that the molecular orientation is substantially isotropic in the plane direction, and no cracking occurs.

The frequency characteristics of a speaker using the obtained speaker diaphragm were measured.
As shown by a , sound pressure 90 at 1,500-15,000 Hz
It has been found that the speaker diaphragm has a substantially flat response of dB or more and has good high frequency characteristics.

In the above-described liquid crystal polymer examples, the biaxial stretching conditions of the melt-extruded thermotropic liquid crystal polyester are such that the draw ratio in the take-off direction is 3.6 and the draw ratio in the direction perpendicular to the take-up direction is 5.0. As a result, a film having a thickness of 35 μm was obtained. Table 3 shows the measurement results of the mechanical properties of the obtained film.

[0028]

[Table 3]

As can be seen from the results in Table 3, this film has a maximum value of tensile strength or the like that is twice or less the minimum value, and the film is substantially isotropically oriented in the film plane. Therefore, even if this film is used as a speaker diaphragm, no cracks or cracks occur as in the case described above.

When a loudspeaker is constructed using such a film as a loudspeaker diaphragm, good frequency characteristics can be obtained although the frequency characteristics are slightly inferior to those indicated by the solid line in FIG.

However, in the above-mentioned liquid crystal polymer examples, the biaxial stretching conditions of the melt-extruded thermotropic liquid crystal polyester were set such that the stretching ratio in the take-off direction was 6.0,
The stretching ratio in the direction perpendicular to the take-off direction was changed to be 3.0, and a film having a thickness of 35 μm was obtained. The results of measuring the mechanical properties of the film were as shown in Table 4.

[0032]

[Table 4]

As can be seen from the results in Table 4, the maximum value of the tensile strength and the like of the film is more than twice the minimum value, and the anisotropy of the molecular orientation in the film plane of the film is large. Then, the speaker diaphragm is easily cracked or cracked. From the obtained diaphragm, multiple
Cut out a number of samples, tensile strength, tensile modulus, loss
The tangent was measured. The ratio of the results and the maximum and minimum values
Are shown in Table 5.

[Table 5] The frequency characteristics of the speaker using the obtained diaphragm are
As a result of the measurement, as shown by the dashed line b in FIG.
Resonance mode occurs in the frequency range, resulting in a characteristic with many peak dips.
And abnormal sounds. This diaphragm has physical properties depending on the location
Values greatly differ, the deformation of the diaphragm becomes even greater
As a result, an abnormal sound was generated.

As described above, according to the embodiment of the present invention, the speaker diaphragm is manufactured from a film which is isotropically molecularly oriented in the plane direction. There is an advantage that the speaker diaphragm has no cracks or cracks due to its properties.

Further, according to the present invention, since a film obtained by biaxially stretching a liquid crystal polymer is used, the thickness of the speaker diaphragm can be reduced to 3 μm to 200 μm, and the frequency characteristics can be improved. There is an advantage that a good speaker diaphragm having a flat frequency characteristic can be obtained.

FIGS. 3 and 4 show examples in which the speaker diaphragm according to the present invention is applied to a diaphragm for a small headphone and a diaphragm for a vehicle-mounted speaker, respectively.

Referring to FIG. 3, in FIG. 3, a film having a thickness of 3 μm to 5 μm which is substantially isotropically molecularly oriented in the plane direction obtained by the same method as in the above embodiment is used. A compact headphone diaphragm having a tangential edge having a diameter of 14.4φ was molded. This molding was carried out by adjusting the mold temperature to 200 ° C. to 220 ° C. and by pressure molding. A headphone driver was assembled using the diaphragm according to the present example molded as shown in FIGS. 3A and 3B, mounted on a small headphone, and a trial listening was performed.

As a result, good sound quality with less distortion was obtained as compared with the conventional product (a 6 μm thick polyethylene terephthalate diaphragm). This is considered to be due to the fact that the diaphragm having a higher elastic modulus has made it possible to make the diaphragm thinner than in the past, and also that the internal loss is large and the vibration in the divided vibration region has been stabilized.

Referring to FIG. 4, in FIG. 4, a film having a thickness of 200 μm having a molecular orientation substantially in the same plane as that obtained in the same manner as in the above embodiment and having a thickness of 200 μm is used. And, an elliptical diaphragm having a diameter of a minor axis of 125 mm was molded. This molding was performed by vacuum molding while adjusting the mold temperature to 200 ° C to 220 ° C.
A vehicle-mounted speaker was assembled using the molded diaphragm according to this example, and a trial listening was performed.

As a result, it was found that the sound quality was less distorted than the conventional product (polypropylene composite diaphragm). Conventionally, a diaphragm material for a vehicle uses polypropylene because of its large internal loss. However, in order to improve the elastic modulus insufficient with polypropylene, many reinforcing materials are mixed at the expense of internal loss to some extent. Even if the diaphragm of this example is made of a single polymer, it is superior to the conventional product in terms of elastic modulus and internal loss, and this is reflected in the sound quality.

Conventionally, a diaphragm having a thickness of about the above-mentioned embodiment has been used as a speaker diaphragm mainly for a vehicle and a mobile phone. The film materials used are
Although polyethylene terephthalate was mainly used, heat-resistant films and high-strength films have recently appeared and can be used properly. Table 6 shows the measurement results of those mechanical substances. In addition, each of the various resin films shown in Table 6 has a molecular orientation substantially isotropic in the film plane.

[0042]

[Table 6]

From these, it can be seen that the material having both the elastic modulus and the loss tangent is a liquid crystal polymer.

Of these, a polyethylene terephthalate film, which has been widely used, is shown in FIG.
When a cone-shaped speaker diaphragm having an outer diameter of 25 mm was obtained with a vacuum forming machine as shown in FIG. 2 and this was used as a speaker, and the frequency characteristics were measured, fluctuations at high frequencies as shown by a broken line c in FIG. Showed a big response.

In addition, since these materials have a lower elastic modulus than the above-mentioned liquid crystal polymer, the resonance frequency in a high frequency region is lowered, and the loss tangent is also low.

As is clear from this evaluation, it was found that the liquid crystal polymer film had characteristics suitable for the material of the diaphragm in both the physical properties of the material and the sound quality of the obtained diaphragm as compared with other films.

In the above examples, a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid was used as the liquid crystal polymer (Japanese Patent Application Laid-Open No. 54-77691).
However, instead of this, a copolymer of phenylhydroquinone and terephthalic acid (Japanese Patent Laid-Open Publication No.
No. 5421), a copolymer of 6-hydroxy-2-naphthoic acid, hydroquinone and terephthalic acid (Japanese Patent Application Laid-Open No. 56-1981).
10526), a copolymer of terephthalic acid, 2,6-naphthalenedicarboxylic acid, hydroquinone and p-hydroxybenzoic acid (JP-A-54-30290);
-Copolymer of hydroxybenzoic acid and polyethylene terephthalate (Japanese Patent Publication No. 56-18016), copolymer of p-hydroxybenzoic acid, terephthalic acid, resorcinol and 6-hydroxy-2-naphthoic acid (Japanese Patent Application Laid-Open No. 57-18057) 87
No. 423) and polyester carbonates from p-hydroxybenzoic acid, hydroquinone and diphenyl carbonate (Japanese Patent Publication No. 59-30727).

Further, in the above-described embodiment, the vacuum molding method or the pressure molding method is used for thermoforming, but it goes without saying that other thermoforming methods can be used instead.
In addition, the present invention is not limited to the above-described embodiment, but may adopt various other configurations without departing from the gist of the present invention.

According to the present invention, the liquid crystal polymer is biaxially stretched.
Using the film obtained from the above, the melting point of the liquid crystal polymer is 30
Thermoforming at a temperature lower than ℃
And isotropically in the plane direction of the biaxially stretched film.
The shape of a given shape without breaking the molecular orientation
There is an advantage that a peaker diaphragm can be obtained.

[0050]

[Brief description of the drawings]

FIG. 1 shows an embodiment of a method for manufacturing a speaker diaphragm according to the present invention.
It is a diagram provided for explanation of the example .

FIG. 2 is a diagram for describing the present invention.

FIG. 3 is a plan view and a partial cross-sectional view illustrating an example of a speaker diaphragm.

FIG. 4 is a plan view and a cross-sectional view illustrating an example of a speaker diaphragm.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal polymer film 2 presser guide 3 heater 4 mold 5 vacuum pump

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Ishida 1-12-39 Umeda, Kita-ku, Osaka City, Osaka Prefecture Inside Kuraray Co., Ltd. (72) Toshiaki Sato 1621 Sazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. (56) References JP-A-63-75040 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04R 7/02 B29D 31/00 H04R 31/00 B29C 69/00 B29K 67 : 00

Claims (1)

(57) [Claims] 1. A thermoplastic having optical anisotropy when melted
The resin having a predetermined thickness is melted by heating and then biaxially stretched.
To form a film , and lower the film by 30 ° C. or more from the melting point of the thermoplastic resin.
That it is thermoformed at a low temperature and molded into a predetermined shape
A method for manufacturing a speaker diaphragm.