JPS63226198A - Acoustic diaphragm - Google Patents

Abstract

PURPOSE:To obtain a characteristic excellent in high-frequency characteristic by forming a surface layer consisting of diamond, and a carbon compound of amorphous carbon, titanium carbide, silicon carbide, boron carbide, and boron carbide and nitride on one face or both faces of a glass-shaped diaphragm base material made of carbon. CONSTITUTION:On both faces of a glass-shaped carbon diaphragm base material 1, surface layers 1a, 1b consisting of diamond, and a carbon compound of titanium carbide, silicon carbide, boron carbide, and boron carbide and nitride, including amorphous carbon are formed by a reactive ion plating method. By forming such surface layers 1a, 1b, an acoustic constant can be improved remarkably, and a frequency characteristic in high compass can be improved. Also, a pinhole of the diaphragm can be prevented without special processing, therefore, a manufacturing process of the diaphragm can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a diaphragm for a speaker, and particularly to an acoustic diaphragm that is optimal as a diaphragm for a tweeter or a squawker speaker.

(B) Conventional technology Conventionally used acoustic diaphragms include, for example, a green sheet made from a mixture of cellulose fibers and thermosetting resin, which is then heated in a mold to form a diaphragm shape. After molding, an acoustic diaphragm is known that has a graphite structure in which carbon atoms are arranged in a hexacyclic atomic arrangement through primary carbonization for several hundred degrees and final firing for several hundred degrees.

This graphite diaphragm has a ratio of Young's modulus E to density ρ (
This is effective in increasing the specific modulus of elasticity (E/ρ), increasing the frequency at which the piston vibrates, and expanding the high frequency reproduction limit.

(c) Problems to be Solved by the Invention However, in the above-mentioned conventional device, since the carbon atoms are rearranged by heating, there is a limit to the arrangement structure of the atoms, and the problem is the internal loss when used as a speaker diaphragm.
Since an δ is small and the ratio of Young's modulus E to density ρ (E/ρ) is not sufficient, there is a problem in that resonance is significant in the high frequency range.

Furthermore, since the diaphragm is fired, the surface of the diaphragm becomes rough and requires polishing, which makes it difficult to mass-produce.

This invention was made in view of the above points, and a surface layer is formed on glassy carbon made by firing the diaphragm base material, and the ratio of Young's modulus E to density ρ (E/ρ) , aiming to improve the performance of internal loss (janδ),
Furthermore, it is an object of the present invention to provide an acoustic diaphragm that eliminates defects in appearance.

(d) Means for solving the problem The acoustic diaphragm according to the present invention has diamond, amorphous carbon (C), titanium carbide (Tie) on one or both sides of the glass-like carbon diaphragm base material. ), a surface layer made of a carbon compound of silicon carbide (Sin), boron carbide (84G), and boron carbonitride (BNG) was formed using a reactive ion blating method.

(E) Function A surface layer consisting of diamond and a carbon compound such as amorphous carbon is formed on the surface of a glass-like carbon diaphragm base material, and a diaphragm for a speaker such as a dome shape is formed.

The diaphragm obtained in this way has a density of, for example, 1
．． 51X 10' Kg/m3, and a sufficient effect can be obtained even if the surface layer is extremely thin, making it possible to obtain a diaphragm that is lightweight, has increased internal loss, and has extremely excellent high-frequency characteristics for speakers. .

(f) Examples Examples of the acoustic diaphragm according to the present invention are shown in Figures 1 to 4.
This will be explained based on the diagram.

FIG. 1 shows a cross-sectional view of a dome-shaped acoustic diaphragm.
, lb are respectively formed. FIG. 2 is a sectional view of a dome-shaped acoustic diaphragm showing another embodiment.
It is formed by a.

FIG. 3 shows a schematic diagram of a reactive ion brating device used in forming the acoustic diaphragm of the present invention. FIG. 4 is a frequency characteristic diagram comparing the acoustic diaphragm according to the present invention with a conventional acoustic diaphragm.

The embodiment shown in FIGS. 1 and 2 is a dome-shaped diaphragm, and both surfaces (the first
(Fig. 2), or surface layers 1a, lb consisting of carbide compounds of titanium carbide, silicon carbide, boron carbide, and boron carbonitride, including diamond and amorphous carbon, are coated with reactive ions on one side (Fig. 2). It was formed by a brating method.

Hereinafter, an example will be described in which diamond and amorphous carbon are used as materials for forming the surface layers 1a and Ib.

It is a well-known method to use a glass-like carbon diaphragm base material 1 as a diaphragm base material. However, since the acoustic characteristics differ depending on the material and firing conditions, the experiment was carried out under the following conditions.

■Cellulose fiber; melted kraft paper ■Fiber length: 5~IOm/m ■Thermosetting resin: phenolic resin ■Blending ratio: Cellulose fiber carbide/thermosetting resin carbide = 30/1
00 ■Material shape: Sheet-like thickness 50μm ■Forming: Dome shape Heating at 150°C, 50g, 10 minutes ■First firing: 350°C heating rate 1.5°C/hour ■Second Firing: 1+00°C, heating rate: 50°C/hour ■Zero Air: Argon A glassy carbon diaphragm substrate 1 was prepared under the above conditions, and the glass-like carbon diaphragm substrate 1 was coated on both or one side of the substrate 1 as shown in FIG. Surface layers 1a and Ib made of diamond and amorphous carbon were formed using a reactive ion blating device such as the above.

The reactive ion blating apparatus shown in FIG. 3 includes a crucible 4. It is equipped with a probe 6, a filament 7, a shutter 8, etc., and gases such as nitrogen and argon are fed through an inlet 9. 1 is a glass-like carbon diaphragm base material forming the surface layers 1a and 1b, and 5 is an evaporation material (graphite in this case) for the surface layers la and lb set in the crucible 4.

The conditions for forming the surface layers 1a and 1b using the reactive ion blating apparatus shown in FIG. 3 are as follows.

(2) Clean the glassy carbon diaphragm base material 1 and set it so that a surface layer is formed on both sides of the base material 1.

■Vacuum evacuation; 1O-6 Torr or less ■Ion bombardment: Zero argon atmosphere 5X 1O-2 Torr500V (
DC) 10 minutes 0 reactive ion brating; Evaporation source Graphite 99.9% Electron gun 1O to W Reaction gas Nitrogen gas (N2) Argon and nitrogen mixed gas pressure 5x 10-' Torr Mixing ratio 1:2 Evaporation rate 200 ( ■Surface layer; Thickness 8000 (In) ■Cooling; Natural cooling Leave for 30 minutes.The surface layer formed using the above reactive ion plate ink process was analyzed by electron beam diffraction and photoelectron spectroscopy. As a result, it was found to be composed of diamond and amorphous carbon, and contained an extremely small amount of hydrogen.

After showing the acoustic physical constants according to the above embodiments, the specific manufacturing process of the acoustic diaphragm will be explained next.

First, in the reactive ion plating process for the glassy carbon diaphragm substrate 1, the glassy carbon diaphragm substrate 1 with a thickness of 50 μm is cleaned, and then the reactive ion plating process shown in FIG. 3 is performed. Inside the vacuum chamber 2, 1O-6To
After reducing the pressure to rr, argon ion irradiation is performed at 500 V DC in a zero argon atmosphere of 10-2 Torr. Vapor deposition was performed at a vacuum level of 5X10-' Torr (argon +
Nitrogen; mixed gas).

In this way, a surface layer 1a made of diamond and amorphous carbon is formed on the surface of the glassy carbon diaphragm base material 1.
, lb are formed, and after natural cooling, a dome-shaped diaphragm is completed. Note that a cone type, a flat type, etc. can also be formed in the same manner.

The dome-shaped diaphragm obtained in this way is thin and lightweight, and has an increased internal loss. High-frequency characteristics of the plate A diaphragm with extremely excellent high-frequency characteristics as shown in ◎ can be obtained.

In addition to the above-mentioned embodiments, the following methods can be considered as methods for forming the surface layers 1a and 1b.

■A method of forming a surface layer made of carbon compounds using vacuum evaporation.

(2) A method of forming a surface layer made of a carbon compound using a chemical vapor deposition (C, V, D) method.

■A method of forming a surface layer made of carbon compounds using electroless plating.

■A method of forming a surface layer made of carbon compounds using plasma radiation method.

■A method of increasing the firing temperature of the diaphragm base material to increase the crystalline component in the glassy carbon.

(G) Effects of the Invention According to the acoustic diaphragm of the present invention, since a surface layer made of a carbon compound of diamond and amorphous carbon is formed on a low-density glassy carbon diaphragm base material, By significantly improving the constant, it is possible to improve frequency characteristics in the high frequency range.

As a result, it is particularly effective as a diaphragm for tweeter and squawker speakers. In addition, since the surface of the diaphragm base material is covered with a surface layer made of a carbon compound, pinholes in the diaphragm base material can be prevented without special treatment, simplifying the diaphragm manufacturing process. can be achieved. As described above, since mass productivity is also good, it is possible to provide a diaphragm with excellent effects without reducing costs. Furthermore, since both the diaphragm base material and the surface layer are made of carbon-based ceramics having the same coefficient of thermal expansion, the adhesion between the two forming the diaphragm is extremely excellent.

[Brief explanation of drawings]

1 to 4 show embodiments of this invention,
Figures 1 and 2 are cross-sectional views of the dome-shaped diaphragm;
The figure is a schematic diagram of a reactive ion blating apparatus used in forming the surface layer. FIG. 4 is a characteristic diagram comparing the high frequency characteristics of the acoustic diaphragm according to the present invention and a conventional acoustic diaphragm. 1: Glass-shaped carphone diaphragm base material la, lb; Surface layer 2: Vacuum chamber 3: Electron beam 4 Nil pot 5: Evaporation material (Example: Daraphite) 6: Probe 7: Filament 8: Shutter
9: Introductory patent applicant Kenwood Co., Ltd. Figure 1 13th

Claims (1)

[Claims] To one or both sides of the glassy carbon diaphragm base material,
An acoustic diaphragm comprising a surface layer made of diamond and a carbon compound of amorphous carbon, titanium carbide, silicon carbide, boron carbide, and boron carbonitride.