JPS61128700A - Diaphragm for speaker - Google Patents

Abstract

PURPOSE:To obtain a diaphragm of a dense and even thickness composed of a diamond multi-crystal body by using a thin layer of a diamond of a density of 3.2-3.5g/cm<2>, Young's modulus of 0.5-1.2X10<12>N/m<2>. CONSTITUTION:Grains of a diamond as a base plate are collided with one another by an ultrasonic wave, and an Si wafer of a diameter of one inch and having numerous and dense and fine flaws is used. This is placed 5mm downward from a center of a plasma generated by a micro wave of 2.45GHz and a temperature of the base plate is maintained at 850 deg.C by a pyrometer measuring, a gas of CH4/H2:1:99 is conducted to produce a diamond dense and fine crystal on a surface of the base plate. After operating for 20hr, the Si wafer is dissolved by HF and a diamond thin layer is obtained. This thin layer has a base plate side surface being smooth and is a film of a multi-crystal body of 1 inch in diameter having a coarse surface, thickness of 20+ or -1mum density of rho:3.51g/cm<2>, Young's modulus of E:1X10<12>N/m<2>, specific resiliency E/rho:29X10<8> m<2>/sec. The figure shows a frequency characteristic of a film diaphragm.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a diaphragm for high-frequency speakers made of a thin layer of polycrystalline diamond, which is an aggregate of fine crystals deposited by vapor phase growth (CVD). Regarding.

[Prior art]

As is well known, the characteristics required for a speaker diaphragm are: 0. ) High Young's modulus (hereinafter referred to as X) in order to obtain shrinkability.

(2) The density (hereinafter referred to as ρ) must be small in order to increase the vibration Kumamoto.

In other words, when the specific elastic modulus c or less (denoted as E/ρ) is large.

(31 In order to suppress unnecessary resonance, the internal loss C or less is written as −δ) is appropriately thick.

is required.

However, which of the above three conditions is more important depends on whether the diaphragm is used for full frequency range, bass, midrange, or treble, or whether it is used for classical music or light music. etc., depending on the purpose and target sound quality.

For example, for bass sounds, diaphragms whose main component is paper are often used. In this case, ρ is usually small for paper, but not for TV, so ′! A/ρ cannot be made very large, but this is not a problem since it is used for bass sounds. ζ et al. In a bass diaphragm, abnormal vibrations and distortion components generated in the area where the piston no longer vibrates are easily felt by the ears in the low frequency range, so the wax δ must be large so that this can be quickly reduced. .

On the other hand, paper is also used as a diaphragm for high-pitched sounds, but metal diaphragms have recently become more popular. Metal plates have a small hδ, but despite this, metal plates have come to be used for high-pitched sounds because the P of metal is several times thicker than that of paper.
I! Furthermore, since VC is 1 to 2 orders of magnitude larger, R1/p
This is because Fi is increased by one order of magnitude, and even if abnormal vibrations occur, they are relatively difficult to hear because they are in the high frequency range, and they do not need to be reduced as quickly as they are in the low frequency range.

In other words, the criteria for determining the quality of high-pitched diaphragm materials is K/
The ρ value is larger.

Conventional metal diaphragm materials include aluminum, titanium,
Single substances such as beryllium, or those coated with equivalent alumina, beryllium, etc., are used. The values of ρ, z, and x/p of these metal diaphragms are as shown in Table 1, for example.

In this way, although 1+//) of the metal diaphragm material is large,
In addition, the search for new materials with large I/C1!14/P is underway.

Diamond is p: 3529/cra11it
: 1.2)<10"N/m, ]Ill/p : A
4 x 10' 7 FIl/Sec', which is the best physical material for high-temperature diaphragm materials, but normally obtained diamonds, both natural and artificial, are granular and are not sintered, so they cannot be used as plates. It was difficult to use as a material for diaphragms because it could not be easily molded.

On the other hand, there have been recent patents (Sumitomo Electric, etc.) of speaker diaphragms made of diamond, but Ili.
The physical property value of /ρ has not been measured, and diamond is
It is a carbon film with far inferior characteristics.

Recently, CVD technology has advanced, and it has been confirmed that diamond microcrystals can be precipitated on a substrate using hydrocarbons as a raw material, and that by selecting the conditions, it is possible to obtain a film of coalesced polycrystals. ing.

[Object and structure of the present invention]

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a diaphragm made of a diamond multibody with a dense and uniform thickness. 97M, Young's modulus: 0.5-12X
IQ"N/Ill" on the speaker diaphragm.

To make a thin layer of polycrystalline diamond, a gas or a mixture of easily vaporized hydrocarbon and hydrogen is usually heated at 800%
Produced by thermal decomposition on a substrate heated to ~900℃ (
% Kaisho 59-5098).

As methods for heating the substrate, methods using excitation energy such as heat, high frequency, microwave, etc. have been proposed, and microwave excitation is efficient.

Generally, the above hydrocarbons include methane (CI), which is easy to handle.
, ) is preferable, and the substrate is S1 with a small difference in thermal expansion.
Wafers are preferred. CH4/H.

Plasma is induced by injecting microwaves into the mixed gas, and when a surface-treated substrate is placed in the center of the plasma, it is easily heated, and diamond microcrystals precipitate and grow on the substrate surface.

When using the microwave excitation method, diamond nucleation depends on the surface treatment of the substrate, and the growth rate depends on the temperature of the substrate and the concentration of CH.

Although the concentration of CH4 can be sufficiently controlled by the mass controller 70, it becomes difficult to maintain the temperature of the substrate uniformly as the substrate becomes larger and more convoluted, making it impossible to form a uniformly thick and thin layer. Furthermore, when microwaves with a commercial frequency of 2.45 GH2 are used, the excitation space is spherical with a diameter of about 30 mm, and within this space, diamond precipitation takes place preferentially, but even within the spherical shape, precipitation is biased. There is. for example,
When C'VD is performed on a 1-inch-diameter 81 wafer polished with diamond abrasive grains by fili-J at the plasma center, diamond microcrystals of 3 to 5 μm are densely formed in the periphery, and in the center. Only a thin layer is produced, making it impossible to form a thin layer suitable for a diaphragm. However, by lowering the position where the S1 wafer is held by 5 to 10 degrees from the plasma center, CVD
When this is done, fine crystals are precipitated to a uniform thickness. By melting the 81 substrate on which these fine crystals have precipitated with HF, a thin diamond layer having a uniform thickness ζ and consisting of an aggregate of fine crystals having the same area as the substrate surface is obtained. The thickness can be controlled by the deposition time, but is usually 20 to 50 μm.

This diamond thin layer has ρ: 55~A 51g/ca
1:(L8~1.0×1011N/7FLl, 1/ρ:
The value is λ3~Z 9 X 10 "d/SeC", which is close to the literature value of diamond crystal, and is suitable as a high-pitched diaphragm for a speaker. This diamond film was composed of only diamond in terms of Xa, and its Raman spectrum showed that although it contained a small amount of 1-carbon, it was extremely close to natural diamond.

〔Example〕

Using the "Example", it was positioned 05 mm below the center of the plasma induced by microwaves of 2-45 G['lz, and the substrate temperature was determined to be 850"C by pyrometer measurement.
The IC was held and a gas of CH,/H,: 1:99 was introduced to deposit fine diamond crystals on the substrate surface. During the processing time of this substrate, it rotates at 5 rps to make the temperature distribution inside the substrate as uniform as possible? As a result, the difference in m degrees depending on location was within ±5°C.

After 20 hours of operation, the S1 wafer was dissolved with HF to obtain a thin diamond layer. The obtained thin # is a polycrystalline film with a diameter of 1 inch, with a smooth surface on the substrate side and a rough surface, thickness: 20 ± 1 μm 1 ρ: i 51 p/Cd, 2
1! : t OX 10"N/m', X/p :2
．． The size was 9×10"rri"/See and the appearance was almost colorless.

The frequency characteristics of this film are shown in FIG. For reference, Be
Add the frequency characteristics of the film imaging plate. The one of the present invention is 20
It can be seen that it has a wide range of 00 to 5 Q, 000 Hz (7 rat characteristics).

"Example 2" Using CH4/H,: 1.5/9 al) gas, the position of the substrate was set 10.5 cm from the plasma center. A thin diamond layer was obtained by performing the same summation as in Example 1 except for the lower part. The obtained thin layer was a polycrystalline film with a diameter of 1 inch and a smooth surface on the substrate side and a rough surface, and a thickness of 32 ± 2 μm.
p: 5. ．． 5fi/ctJ, E:18X f O”
N / m s ” / /': l 5 X'
0' z / Se! l:' and had a gray appearance.

The frequency characteristics of the membrane of Example 2 were almost the same as those of Example 1, but the highest reproducible tone in the ninth part was 40.000112.

[Effects of the Invention] Since the speaker diaphragm according to the present invention is made of polycrystalline diamond, it essentially has a much larger E/ρ than that of a gold JA motion plate, etc. Moreover, it has a uniform thickness, making it an extremely excellent diaphragm for high-pitched sounds.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the frequency characteristics of diamond and beryllium films.

Claims (1)

[Claims] Diamond thin layer density: 3.2~3.5g/cm^3
A diaphragm for a speaker having a Young's modulus of 0.5 to 1.2×10^1^2 N/m^2.