JPS63196200A - Diaphragm for acoustic equipment - Google Patents

Abstract

PURPOSE:To improve an acoustic characteristic by utilizing a superior physical characteristic attached on a carbon, by forming a case hardening layer made of a diamond shaped carbon film on the surface of a diaphragm base material consisting of a thin film of full carbonaceous material. CONSTITUTION:The diamond shaped carbon film is vapor phase deposited on the surface of a diaphragm raw material consisting of full carbonaceous thin film. For example, after applying a post hardening processing on a diaphragm forming body in an oven with a temperature of 150 deg.C for five hours, it is heated up to 500 deg.C at temperature rise speed of 150 deg.C/hour, and between 500-1000 deg.C at that of 50 deg.C/hour. Furthermore, after being held at 1000 deg.C, it is cooled naturally, and baking is completed. The diaphragm of glass shaped carbonaceous material having 25mmphi and film thickness of 50mum obtained in such way is set as the base material, and vapor-deposition is applied on a diamond shaped film by a well-known filament method. As a result, when the physical properties of the base material before vapor-depositing is compared, elastic modulus can be improved by 40-50%, and the physical characteristic of acoustic velocity can be improved by around 10%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a diaphragm for audio equipment. Specifically, the present invention has excellent acoustic properties as a diaphragm for speakers and microphones because it has higher hardness, higher strength, higher elasticity, and is lighter than conventional diaphragm materials. The present invention relates to a diaphragm for audio equipment having a diaphragm for audio equipment.

(Prior Art) Generally, it is desirable that a diaphragm for a speaker etc. satisfy the following conditions.

(1) Low density.

(2) Young's coefficient is large.

(3) The propagation speed of longitudinal waves is high.

(4) The internal loss of vibration is appropriately large.

Furthermore, from the formula V=(E/ρ)1' (where V: velocity of sound; E: Young's modulus; ρ: density), in order to increase the velocity of sound, a material with low density and high Young's modulus is required. .

Conventionally, acoustic diaphragms with large Young's modulus include aluminum, titanium, magnesium, beryllium,
Some use light metals such as boron.

However, acoustic diaphragms made of aluminum, titanium, magnesium, etc. cannot obtain a sufficiently satisfactory specific Young's modulus E/ρ, and acoustic diaphragms made of beryllium, boron, etc. have an extremely large specific Young's modulus. However, since these materials are extremely expensive and industrially difficult to process, there is a problem that they are extremely expensive compared to other materials.

(Problems to be Solved by the Invention) In view of the above-mentioned drawbacks of conventional diaphragm materials, an object of the present invention is to provide a diaphragm having excellent acoustic properties by taking advantage of the excellent physical properties of carbon. It is.

(Means for solving the problem) As is well known, carbon has an extremely wide range of physical and chemical properties, ranging from crystalline carbon such as diamond and graphite to amorphous carbon such as carbon black and charcoal. are doing.

The inventor of the present application has conducted extensive research in order to express various desired functional characteristics by designing and combining these carbon materials according to the required functions. Invented a method for manufacturing an all-carbon diaphragm obtained by preforming the mixture into a film, shaping it into a diaphragm shape, and firing it in an inert atmosphere, and filed a patent application. (Unexamined Japanese Patent Publication No. 6 O-
121895). Furthermore, he invented a method for manufacturing a glass-like carbon diaphragm using only a thermosetting resin as a raw material, and filed a patent application (Japanese Patent Laid-Open No. 61-65596).

The diaphragms according to these inventions can be manufactured industrially at low cost and have excellent physical properties, but the inventor of the present application has conducted extensive research to further improve the physical properties of these diaphragms. , the theoretical elastic modulus of diamond is 12
By vapor-depositing a diamond-like carbon film on the surface of a diaphragm material made of an all-carbon thin film, we developed a material with superior acoustic properties than a diaphragm made of an all-carbon thin film alone. This led to the invention of the diaphragm.

In recent years, many proposals have been made regarding methods for synthesizing diamond-like carbon films from the gas phase, and the film structure is gradually becoming clearer using analysis methods such as X-ray and electron beam diffraction and Raman spectroscopy. In addition, known synthesis methods include CVD, plasma, and ion beam evaporation, and depending on the synthesis method and synthesis conditions, the resulting thin film may vary from diamond polycrystals to diamond crystals mixed with amorphous carbon. There are a wide variety of types, including those that contain hydrogen, and those that contain hydrogen. The CVD method is a method in which diamond is precipitated by decomposing hydrocarbon gas such as methane by heating to approximately 1000°C under reduced pressure, but it is difficult to deposit a diamond film on a substrate other than a diamond single crystal. , mainly using the hot filament method. In this method, hydrocarbon gas diluted with hydrogen gas is thermally decomposed using a tungsten filament heated to over 2000°C, and a diamond-like film is deposited on a substrate placed near the filament. The substrate is heated to 700-1000°C. If the substrate temperature is lower than this, a large amount of amorphous carbon and graphite will be mixed in.

In the plasma CVD method, in the process of thermally decomposing hydrocarbon gas, a mixed gas of hydrocarbons diluted with hydrogen is heated with high frequency,
Or by plasma decomposition using microwaves, 700
This is a method in which a diamond-like film is deposited on a substrate heated to ~1000°C. The structure of the film obtained by this method depends on the heating temperature of the substrate, and to obtain a crystalline diamond film, a heating temperature of 700° C. or higher is required. At temperatures below 700°C, the resulting film is amorphous. Therefore, in order to obtain a crystalline diamond film, a material that allows the substrate to withstand heat of 700° C. or higher is required. One of the features of the present invention is that since an all-carbon thin film with excellent heat resistance is used as a substrate, crystalline diamond can be deposited without deformation of the substrate due to heating.

As for the ion beam evaporation method, the American Eisenhamp method is famous, and in principle, carbon as a target is irradiated with an ion beam from an ion source to sputter the carbon. This is a method in which spattered carbon is ionized into carbon in an arc discharge space, and a diamond-like film is deposited on a substrate to which a negative potential is applied. This method allows the substrate temperature to be set lower than other methods.
Furthermore, when deposited at room temperature, amorphous carbon, which has properties similar to diamond such as resistivity and hardness, is often precipitated.
These are also called i-carbons.

Any of these known methods may be used to deposit the diamond carbon film in the present invention, but metal materials commonly used for diaphragms, such as aluminum and titanium, deform under high temperatures of 700°C or higher. Because of this, diamond-like films that can be deposited are usually amorphous.

On the other hand, since the all-carbon thin film substrate of the present invention has excellent heat resistance, it is possible to selectively deposit a crystalline film or an amorphous film depending on the purpose. Judging from the fact that the substrate alone has excellent acoustic properties, it can be said to be the most suitable substrate material.

(Examples) The present invention will be explained in detail below using Examples, but the present invention is not limited by the Examples.

1" Rainbow-1 To 100% by weight of the initial condensate of furfuryl alcohol/furfural-based resin (UF502 manufactured by Hitachi Chemical), 4% by weight of p-toluenesulfonic acid 50% methanol solution was added as a curing agent, and high speed After sufficiently stirring with a mixer, the mixture was applied onto a bank sheet using a coater equipped with a doctor blade and precured to obtain a preformed sheet in a B-stage state.

Next, the back sheet was removed, the product was molded into a dome shape using a vacuum molding machine, heated and cured, and demolded to obtain a diaphragm molded product. This molded body was placed in an air oven at 150°C for 5 minutes.
After applying post-curing treatment for 50 hours,
15℃/hour up to 0℃, 50℃ from 500 to 1000℃
After heating at a temperature increase rate of /hour and further holding at 1000°C for 3 hours, the baking was completed by natural cooling. Using the thus obtained glassy carbonaceous diaphragm having a diameter of 25 mm and a film thickness of 50 μm as a base material, a diamond-like film was deposited by a known filament method.

The membrane synthesis conditions are such that the methane concentration relative to hydrogen is 5 Volχ
Then, the mixed gas was introduced into the Pel jar under conditions of a pressure of 30 torr and a flow rate of 20 m1/min. On the other hand, the filament substrate distance is 7 mm, the filament temperature is 2000°C,
The substrate temperature was maintained at 800° C. and vapor deposition was performed for 6 hours. The thickness of the obtained film was 5.5 mm, and when the surface was analyzed by electron beam diffraction, it was confirmed that it was crystalline diamond.

Two fuels were mixed in a Warner mixer: 60% by weight of an initial condensate of furfuryl alcohol/furfural resin (UF502 manufactured by Hitachi Chemical) and 40% by weight of natural scaly graphite (average particle size 1 μm). After uniformly dispersing the mixture, a three-roll ink kneading roller was used to perform high-level dispersion to obtain a raw material paste composition. Based on 100% by weight of the raw material paste composition,
4% by weight of 50% p-)luenesulfonic acid in methanol was added as a curing agent, and the same operations as in Example 1 were performed to obtain an all-carbon diaphragm having a thickness of 25 m+wφ and a film thickness of 40 μm. Using this all-carbon diaphragm as a base material, known plasma C
A diamond-like film was deposited using the VD method.

The membrane synthesis conditions are the concentration of methane relative to hydrogen IVolχ
Then, the mixed gas was introduced into the Pel jar under conditions of a pressure of 30 torr and a flow rate of 20 m1/min. On the other hand, the substrate temperature was maintained at 900° C., plasma was induced by 2.45 GH 8° microwaves, and the film was deposited for 4 hours. The thickness of the obtained film was 0, and the surface was analyzed by electron beam diffraction, and it was confirmed that it was crystalline diamond.

(Effects of the Invention) The table below shows the results of comparing the characteristics of the diaphragm obtained by the present invention with those of conventional diaphragm materials.

Material name Speed of sound Young's modulus Density Km/
sec GPa d Aluminum 5.1? 0.0 2.
7 Titanium 4.9 110.0 4.
5 Beryllium 12.2 270.0 1.
8 Example 1 (Base material) 7.5 78.0
1.40 Example 2 (base material) 11.0 1?5.
0 1.45 Example 1 (after vapor deposition) 8.5 1
16.0 1.60 Example 2 (after vapor deposition) 12.0
238.0 1.65 As judged from this table, when comparing the physical properties of the base material before vapor deposition in both Example 1.2, the elastic modulus is 40 to 50%, and the sonic velocity is about 10%.
% improvement in physical properties can be seen. Note that the effects of the present invention are not limited to the above embodiments, and by increasing the thickness of the deposited film, it is possible to further improve the physical properties.

These excellent characteristics of the diaphragm of the present invention allow it to fully demonstrate its capabilities as a diaphragm for digital audio equipment, which has become popular recently.

Claims (1)

[Claims] A diaphragm for audio equipment, characterized in that a surface hardening layer made of a diamond-like carbon film is formed on the surface of a diaphragm base material made of an all-carbon thin film.