JPH04150500A - Manufacture of diaphragm - Google Patents

Abstract

PURPOSE:To easily manufacture a diaphragm having an excellent acoustic characteristic by heat-treating polymer films having specific thicknesses in a specific temperature range while specific pressures are applied to the films in a vacuum or inert gas atmosphere. CONSTITUTION:Polymer films having thicknesses of <=400mum are heat-treated at a temperature of >=1,600 deg.C while pressures of 0.1-50kg/cm<2> are applied to the films in a vacuum or inert gas atmosphere. The pressures applied to the polymer films are set at 0.02-0.2kg/cm<2> per film of <=25mum in thickness, 0.2-1.0kg/cm<2> per film of 25-100mum in thickness, and 1.0-50kg/cm<2> per film of 100-400mum in thickness. Polyoxadiazole, polybenzothiazole, aromatic polyimide, aromatic polyamide, polyphenylene benzoimidazol, etc., are used for forming the polymer films.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a carbonaceous diaphragm used in audio equipment, etc., and more specifically relates to a method for manufacturing a diaphragm having characteristics optimal for speakers, microphones, etc. .

BACKGROUND OF THE INVENTION In recent years, most audio equipment has been digitized and sound quality has been dramatically improved, and since then, the performance requirements for diaphragms in speakers have become increasingly strict. Such diaphragms are required to have little deformation due to external forces, low distortion of sound, and to produce clear sound quality with a wide playback range. Excellence is required. To summarize this as a condition for specific physical property values, ■ Young's modulus (E) must be large.

■ Density (ρ) is small.

■ The speed of sound (velocity of sound wave propagation V) is high.

■ The internal vibration loss (tanδ) is appropriate.

etc. However, between V, E, and ρ, v=L'77
There is a relationship between Of course, in addition to these conditions, it goes without saying that ease of processing, ease of soldering, resistance to rust, and stability against external conditions such as heat and humidity are also important.

Conventional diaphragm materials include paper, plastic, aluminum, and titanium.

Magnesium, beryllium, boron, silica, etc. have been used as materials. These materials have been used in a variety of forms, either alone or in composites with glass fibers, carbon fibers, etc., and even as metal alloys. However, paper and plastics do not have sufficient characteristics such as Young's modulus, density, and sound velocity as diaphragms, and their frequency characteristics, especially in high frequency bands, are extremely poor. It was difficult to obtain good sound quality. In addition, although aluminum, magnesium, and titanium have fairly high sound speeds, their low internal loss of vibration causes high-frequency resonance phenomena, and this also results in insufficient characteristics for high-frequency diaphragms. Ta. On the other hand, since boron, beryllium, and the like have superior physical properties compared to the above-mentioned materials, they can provide good sound quality as a diaphragm. However, boron and beryllium have the drawbacks of being extremely expensive and having extremely poor workability.

Diaphragms using carbon materials are being developed with the aim of overcoming the drawbacks of conventional diaphragm materials as described above, having excellent high-frequency characteristics, and reproducing high-quality tones. This takes advantage of the excellent physical properties of carbon and graphite and uses them as a diaphragm. Such methods include: (1) A composite type consisting of graphite powder and polymer resin.

(2) A graphite/carbon composite type made by further sintering a composite material consisting of graphite powder and polymer resin.

(3) A method of carbonizing and graphitizing a polymer film alone.

and so on.

Among these, a typical example of method (1) is a diaphragm in which a polyvinyl chloride resin is used as a matrix and graphite powder is composited with this. Although this diaphragm is known as a diaphragm with excellent properties, it has poor humidity and temperature characteristics, and its vibration characteristics deteriorate significantly at temperatures above 30°C.

Method (2) involves mixing graphite powder with the liquid crystal component of crude oil cracking pitch, followed by heat treatment and carbonization, and using a thermosetting resin monomer or initial A method is known in which heat treatment is performed using a thermoplastic resin having a functional group that decomposes and cross-links and hardens with a polymer upon heating. These methods were developed with the aim of increasing the yield of carbon as an organic material and preventing shrinkage and deformation during heat treatment, and it is possible to obtain a diaphragm with excellent characteristics. However, these have complicated manufacturing processes and are extremely disadvantageous for industrial mass production. Furthermore, although the diaphragm obtained by this method has extremely excellent characteristics not found in the past, its characteristics are slightly inferior to that of beryllium, which is currently said to have the best characteristics, and graphite Single crystal theoretical elastic modulus 102
It was far below 0 GPa.

As the method (3), several polymer films are being considered. However, since these materials are non-graphitizable materials, the properties that were initially expected were not obtained.Furthermore, the carbon yield of the plastic materials used was low, resulting in large dimensional shrinkage during heat treatment, which caused deformation, It has the disadvantage that cracks often occur.

Therefore, as a result of repeated studies focusing on polymeric materials that are easily graphitizable in contrast to difficult-to-graphitize materials, the present inventors found that 400
Polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, aromatic polyimide having a thickness of μm or less.

When a polymeric film of aromatic polyamide, polyphenylenebenzimitazole, polyphenylenebenzobisimitazole, polythiazole, polyparaphenylenevinylene is heat treated at a specific temperature, what conventionally known It was confirmed that graphite with a higher graphitization rate can be obtained more easily than polymeric materials.

As a result, it has become clear that carbonaceous and graphite diaphragms with excellent properties can be obtained and can be manufactured in a short time.

Problems to be Solved by the Invention However, with the special polymer film mentioned above,
The method of obtaining carbonaceous and graphite diaphragms is easy and very good, but as a result of various subsequent studies, it became clear that this method had the following problems. .

The first problem is the distortion or non-uniformity of the surface caused by heat treatment of the polymer film.

This distortion and surface non-uniformity not only deteriorate the excellent properties obtained by heat treatment, but also impair the appearance.

Furthermore, if the strain is large, the surface of the diaphragm may foam and even break.

The second problem is that the acoustic properties of polymer films vary depending on factors such as the thickness of the film.

The present invention aims to improve the problems of conventional diaphragms by limiting the amount of pressure applied and the temperature range to which carbonaceous and graphite materials have excellent characteristics as acoustic diaphragms. The purpose of this invention is to provide a method for manufacturing a high-quality diaphragm.

Means for Solving the Problems In order to achieve the above-mentioned objects, the method for manufacturing a diaphragm of the present invention involves heating a polymer film having a thickness of 400 μm or less in a temperature range of 1600° C. or higher in vacuum or in an inert gas. The heat treatment is performed without applying a pressure of 0.1 Hi/C♂ and 50 kg/C-.

Effect: According to the above manufacturing method, it is possible to easily manufacture a diaphragm having much better acoustic characteristics than diaphragms made by conventional methods.

Example Examples of the present invention will be described in detail below.

The present inventors attempted to carbonize and graphitize a polymer film in order to obtain an ideal carbonaceous and graphite diaphragm. As a result, by applying pressure within a specific optimum pressure range only in a temperature range of 1600°C or higher,
It was discovered that excellent sound speed characteristics can be achieved. It has also been revealed that the pressure applied at this time is closely related to the thickness of the polymer film. The pressure ranges from 0.02 kg/- to 0.2 kg/cJ for each polymer film with a thickness of 25 μm or less.
0,2 kg/cJ to 1 per polymer film with a thickness of 25 μm to 100 μm.
, 0 kg/cd, and 1001. tm to 4
1 per sheet of polymer film with a thickness of up to 00 μm
．． 0 kg/cJ to 50 kg/ci.

Furthermore, the polymer film used in the present invention has a thickness of 400 μm.
Polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, aromatic polyimide, do, aromatic polyamide, polyphenylenebenzimitazole with the following thicknesses.

selected from polyphenylenebenzobisimitazole, polythiazole, and polyparaphenylene vinylene. Here, various aromatic polyimides are polyimides represented by the following general formulas.

O however, R1 is R2 is It is.

Further, various aromatic polyamides are represented by the following general formulas.The present invention will be explained below using specific examples, but it goes without saying that the present invention is not limited thereto.

(Example 1) A polyimide film made by DuPont (trade name: Kapton H film) having a thickness of 25 μm was sandwiched between graphite plates, and the temperature was raised at a rate of 5°C per minute in nitrogen gas to 1000°C. It was heat-treated for 1 hour. The heat-treated film thus obtained was sandwiched between graphite substrates, heated at a rate of 10°C per minute from room temperature in a stream of argon gas, treated at 3000°C for 1 hour, and cooled at a rate of 20°C per minute. Ta. At that time, 0.05 only at temperatures above 2500℃
kg/cn? of pressure was applied. After cooling to room temperature, the sample was taken out. Its characteristics are that the speed of sound is 1
The speed was 8.1 km/sec, and the internal loss was 0.16.

(Example 2) A polyimide film made by DuPont (trade name: Kapton H film) having a thickness of 100 μm was cut into a diameter of 90 mm, and the same heat treatment as in Example 1 was performed at a pressure of 0.1 kg/c-. However, wrinkles were observed in some places on the surface, and the sound velocity value was as low as 3 km/see. Therefore, when we performed the same heat treatment by changing the pressure to 1 kg/-, the surface properties were significantly improved, and the sound speed was 10.4 km/s.
It was ee.

In the above embodiments, the heat treatment was performed in an inert gas such as nitrogen gas or argon gas, but the heat treatment may also be performed in a vacuum.

Effects of the Invention As is clear from the description of the above embodiments, the method for manufacturing a diaphragm of the present invention involves heating a polymer film having a thickness of 400 μm or less at 1600° C. in vacuum or in an inert gas.
From 0.1 kg/cnl to 50 kg in the temperature range above
/ an? Because the heat treatment is performed while applying a pressure of The obtained diaphragm is ideal for audio equipment such as speakers and microphones.

Claims (3)

[Claims] (1) Polymer film with a thickness of 400 μm or less in a vacuum or inert gas at a temperature range of 1600°C or higher at 0.1 kg/cm^2 to 50 kg/cm^2
A method for manufacturing a diaphragm, characterized in that heat treatment is performed while applying pressure. (2) The applied pressure ranges from 0.02 kg/cm^2 to 0 for each polymer film with a thickness of 25 μm or less.
．． 2 kg/cm^2, and 0.2 kg/cm per sheet of polymer film with a thickness of 25 μm to 100 μm.
cm^2 to 1.0kg/cm^2 and 100μm
2. The method for manufacturing a diaphragm according to claim 1, wherein the weight per polymer film having a thickness of from 1.0 to 50 kg/cm^2 is 1.0 kg/cm^2 to 50 kg/cm^2. (3) The polymer film is polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, aromatic polyimide, aromatic polyamide, polyphenylenebenzimitazole, polyphenylenebenzobisimita 2. The method for manufacturing a diaphragm according to claim 1, wherein the diaphragm is at least one selected from sol, polythiazole, and polyparaphenylene vinylene.