JPS62271599A - Acoustic vibrating material and its manufacture - Google Patents

Abstract

PURPOSE:To commercialize an acoustic vibrating material made of B4C with a high hardness and a high acoustic velocity by accelerating the boron carbide B4C under a high electric field, and coating and forming an amorphous B4C film on a substrate. CONSTITUTION:When a boron element 2' melted by the projection of an electron beam 6 passes through an acetylene and plasma atmosphere 11, the boron element and a carbon element are reacted in terms of gas phase to synthesize B4C. It is accelerated by a DC electric field impressed on the substrate, and piles up as a high energy molecule on the substrate 4. By a 12-minute reaction, for example, the B4C film 6.o mum in thickness in coated on the substrate 4. The B4C film formed on the substrate 4 in such a way has no variance in terms of strength, and never triggers the deterioration of a frequency characteristic, whereby the acoustic vibrating material with an excellent sound quality can be obtained.

Description

Detailed Description of the Invention The present invention forms an amorphous 84C (boron carbide) film suitable for use as an acoustic vibration material, particularly as a constituent material of a diaphragm diaphragm of a speaker, a cantilever of a cartridge, etc. Concerning acoustic vibration materials and their manufacturing method.

The criteria for selecting an acoustic vibration material are (i) a large Young's modulus E, a small specific gravity ρ, and a large ratio E/ρ, and (ii) resistance to cracking and cracking due to the inevitable mechanical vibrations. (iii) It is stable in environmental tests such as humidity resistance, humidity temperature cycle, salt water spray resistance, etc. and does not change over time, (iv) It has excellent productivity, etc. Among these, the characteristic (i) is important.The following is a list of potential acoustic vibration materials or those currently in use.

As can be seen from this table, 84C is an extremely excellent acoustic vibration material. Conventionally, attempts have been made to apply the characteristics of 84C to diaphragm materials, but none of them have been satisfactory and have not been put to practical use.

As conventional techniques, for example, electric field evaporation method and electron beam evaporation method heat and evaporate raw material 84G with an electron beam heat source.
It is simply vapor-deposited or vapor-deposited in an electric field of about 12 kV. However, in this case, since the melting point of 84G is extremely high at 2450°C, when the raw material 84C is irradiated with an electron beam, a so-called splash phenomenon tends to occur, and the scattered 84C is Ti.
A hole is drilled through the vapor deposition substrate. In addition, raw material B4C
is easily decarburized when it evaporates, and the film deposited on the deposition substrate has a composition that is not stoichiometric 84C but has an excess of B (boron). Furthermore, the particle energy of the evaporated particles is small at 0.1 to 1 eV, compared to the ion blating method described later, and therefore the adhesion strength is small and the throwing power is poor.

In addition, the high frequency sputtering method is a method of high frequency sputtering of 84G raw material target, but the deposition rate is 0.01
The thickness is as small as ~1 μ/ll1 inch, and is particularly impractical for diaphragms that require a film thickness of several μ or more. Since the particle energy is 1 to 10 eν, the adhesive strength is improved.

The 84C film production method using the CVD method is to deposit QCρ3 and C11, which are the constituent components of 84C, on a substrate heated to several hundred degrees Celsius.
This is a type of chemical vapor deposition in which a mixed gas of hydrocarbons such as 4 is introduced and 84G is deposited through a thermal decomposition reaction. Since the substrate becomes high temperature, aluminum and aluminum alloys are melted and cannot be used, and the substrate of ditanium drawing dies is easily deformed, so it is thought to be effective only for high melting point materials such as tungsten. Moreover, the specific gravity of tungsten etc. is ρ (=19.3)
Since it is also large, it is not suitable as a substrate for acoustic vibration materials.

As described above, the technology for forming a film using 84C as an acoustic vibration material has not yet been established and has not yet been commercialized.

In view of the above points, the present invention proposes a novel acoustic vibration material and a method for manufacturing the same.

The present invention basically gasifies the simple element of boron, and on the other hand, converts hydrocarbon gas such as acetylene and methane into plasma,
In this plasma, boron element and carbon element are chemically reacted (gas phase reaction) to synthesize 84C, and this synthesized 84C
is deposited on the surface of the desired substrate by accelerating it with a high electric field,
84C film is formed.

In this case, by optimally selecting reaction conditions such as boron evaporation rate and hydrocarbon gas pressure (gas concentration), the stoichiometric composition (B: 78.3% by weight, C: 21.Tffl
A suitable 84C film is obtained.

The means for gasifying the boron element include thermal evaporation or sputtering, and the heat source for the evaporation is a laser beam, high-frequency induction heating, electron beam heating, or the like. The melting point of boron element is conventionally 2300℃~2500℃
Although many values have been reported in the range of degrees Celsius, the most reliable value is 2075 degrees Celsius according to the latest research. This value is much lower than the melting point of 84C, 2450°C, and
This is much easier than the above-mentioned conventional technique in which C itself is evaporated. It has also been found that boron can be melted cleanly and the splash phenomenon can be avoided by optimally selecting the crucible material, beam diameter, beam scanning method, and heating rate.

As raw materials for carbon C, which is another constituent element of 84C, 01 to 4 saturated and unsaturated hydrocarbons are selected. If it is a gas at room temperature and does not contain nitrogen, oxygen, oxygen, sulfur, S, halogen, etc. in its molecules, it has no particular selectivity. ^r, IIs that are not directly related to the reaction to adjust the gas pressure
It is also possible to mix an inert gas such as. Although it is possible to react with boron vapor to some extent and synthesize 84C by simply introducing hydrocarbon gas, the reaction efficiency increases and 84C is effectively synthesized by turning the introduced hydrocarbon gas into plasma. can be generated. Methods for converting introduced hydrocarbon gas into plasma include activated reactive vapor deposition (ARE) and low pressure plasma deposition (LPPD).
) method, high frequency coil method, etc. are adopted.

In addition, by applying a DC high voltage of minus several hundred volts to minus several kilovolts to the substrate on which B4Cl1ii is deposited, and also using the so-called ion blating method, the particle energy becomes about several tens of eV to 1000 eV. The adhesion strength on the base material is improved. Cleaning of the substrate is critical to the adhesion strength of the 84C film. This generally involves (i) ultrasonic cleaning with a halogenated carbon solvent, steam cleaning, and (ii)
100°C in high vacuum (10-5 to 10-' Torr)
Dehydration and degassing by heating to ~100°C, (iii) A
A sufficiently satisfactory adhesive strength of the 84C film can be obtained by using a process such as pumping with inert gas plasma such as R.

Next, examples will be shown based on specific experimental results of the present invention.

FIG. 1 shows an activated reactive ion blating device applied to the present invention. In the figure, (1) is a vacuum chamber, and the raw material boron element (2) is inside this chamber (1).
A base material holder (5) is arranged to hold a base material (4) molded into a predetermined shape to which the 84C film is to be applied. The holder (5) is equipped with a planetary jig, and the base material (4) is rotated and revolved around its axis. - The boron element (2) is evaporated by irradiation and heating by the electron beam (6). Between the crucible (3) and the base material (4) is a ring-shaped gas introduction part (7) with pores inside for introducing a hydrocarbon gas such as acetylene gas (C2H2).
and a ring-shaped electrode (B) for turning the introduced acetylene gas into plasma. electrode(
B1 is connected to the ARE power supply and, for example, +100V is applied thereto. On the other hand, a DC voltage of approximately -2 kV is applied to each base material (4) through the holder (5).

(9) is a heater that heats the base material (4) to a predetermined temperature and is controlled by a thermocouple.

(10) is a film thickness monitor (consisting of a crystal resonator) for measuring the film thickness of the 84G film.

Example (1) Press-molded into lighter diaphragm shape with thickness of 20μ
After cleaning the base material (4) made of titanium in the cabinet with a fluorocarbon solvent and fixing it in the holder (5) of the device shown in Figure 1, the base material (
4) to 450°C and heat the inside of chamber (1) 1x.
Degas to 10-5 Torr. Next, add Ar gas to 8
The plasma was introduced to a temperature of 10-' Torr, turned into plasma by a high-frequency power source of 1-1, and bombarded for 10 minutes.

The Ar gas is stopped, and the vacuum is set to a high degree of 1×1O−5 Torr again. The temperature of the base material (4) is maintained at 450°C. Next, boron element (99
, 9%) (2) is irradiated with 54 electron beams (6), and at the same time acetylene ((1; 28
2) Gas was introduced to make the pressure 2 x 10-' Torr, and an acetylene plasma atmosphere (11
)make. For example, a DC voltage of -2 kV is applied to the base material (4). Then, after reaching a steady state, the crucible (3
) is opened and the 84C film is deposited on the substrate (4) by the method of so-called activated reactive ion blating.

That is, when the boron element (2') melted and vaporized by electron beam irradiation passes through the acetylene plasma atmosphere (11), the boron element and the carbon element react in the gas phase to form 8.
4C is synthesized, and this 84C is accelerated by a DC electric field applied to the substrate and deposited on the substrate (4) as high-energy molecules. A 6.0 μm thick 84C film was deposited on the substrate (4) after 12 minutes of reaction. Next, the base material (
4) was reversed and a 6.0 μm thick 84C film was applied to the back side in the same manner. FIG. 2 shows a diaphragm of a lighter obtained by depositing the 84C film (12) on the front and back surfaces of the titanium base material (4) in this manner. Structural analysis of this 84G film (12) by X-ray diffraction revealed that it had no crystallinity and had a completely amorphous structure. When viewed as a sound 1[1i dynamic material, it has no structural anisotropy, which is a desirable property. FIG. 3 shows the X-ray diffraction of the 84C film deposited on the glass substrate by the activated reactive ion blasting, and it is confirmed that the B4C film is an amorphous film.

The crystallinity of the 84G film (12) deposited on the base material (4) is related to the base material temperature; it becomes an amorphous film at temperatures below about 1000°C, and becomes crystalline at high temperatures (above 1000°C). become

Example (2) A B (boron)-C (carbon) based reaction product was deposited on a titanium Ti (10μ foil) substrate (4) by the same method as in Example (11). - Change the plasma pressure from IX IO-' Torr to IOX 10-'
Samples were prepared with varying Torr values, and compositional analysis and sound velocity measurements were performed.

Figure 4 is a characteristic diagram obtained by quantitatively analyzing the reaction product film of the B-C system.
(assumed to be constant), and represents a relationship in which the content of carbon C increases as the acetylene plasma pressure increases. As a result, when the electron beam output is 5k)l, exactly 84C is quantitatively synthesized at an acetylene plasma pressure of 2 x 10-' Torr.

That is, the composition closest to the stoichiometric composition is synthesized.

Figure 5 is a characteristic diagram showing the relationship between sound velocity and acetylene plasma pressure.From this curve (I[), it was found that the sound velocity is highest when the acetylene plasma pressure is 2 x 10” Torr. (III) is titanium T
The value is only for the base material of i (10μ foil). The structure of the film was amorphous in all cases as in Example (1).

Example (3) An 84C film was deposited on a titanium Ti1Oμ base material by the same method as in Example (1). At this time, the substrate temperature was set to 150
Samples were made at temperatures ranging from ℃ to 550 ℃, and the sound speed was measured. FIG. 6 is a characteristic diagram showing the relationship between the base material temperature and the speed of sound. As a result, the sound velocity does not increase when the base material temperature is low, but a large value is obtained at temperatures of 450° C. or higher.

Example (4) Titanium T of 20 μm was made using the normal ion blating method.
Boron alone was applied to a thickness of 6.0 μm on both sides of the i-foil draw-formed diaphragm. This sample and the diaphragm covered with the B+C crotch according to Example (11) were simultaneously tested at JI5
A salt water fountain Wi environmental test was conducted based on 2371. As a result, no abnormality was observed in the diaphragm coated with the 84C film, but discoloration and surface roughness were observed in the diaphragm coated with the single boron film. It was found to be resistant to environmental tests.

Example (5) Based on Example (4), an experiment was conducted in which the 84C film was given the meaning of an environmental protection layer. Boron alone was deposited on a titanium Ti foil with a thickness of 10μ by a normal ion blating method, and then further deposited by an 84C-t-activated reactive ion brazing method, so that the sum of both layers was 6.0μ. Three types of samples with different thickness balances were made. Both layers were of course applied to both sides of the titanium foil.

These three samples were combined with the <84C single film based on Example 1) and the boron single film based on Example (4) to measure the sound velocity. As a result, 84CI! Although it was observed that the sound velocity tended to be slightly higher when the Ji thickness was larger, the difference was very small. Further, according to the same salt spray test as in Example (4), no deterioration was observed in any of the three samples in which 84C was deposited on the boron layer, except for the boron single film.

This experiment confirmed that the 84C film has a sufficient effect as a protective film for the boron film.

Incidentally, in Kamishio, the acoustic vibration material was constructed by depositing a B4C film on a titanium Ti base material, but the above-mentioned 84C was deposited on an etchingable base material such as copper Cu, iron Fe, aluminum M or stainless steel SUS. It is also possible to use the 84C film as a diaphragm or cantilever by depositing it by a method and then removing the base material by etching.

According to the present invention described above, it is possible to stably produce 84C by gasifying the boron element by thermal evaporation or sputtering, and reacting the boron element with the carbon element in a hydrocarbon gas plasma. An 84G film with good adhesion can be formed by accelerating 84C using a DC electric field applied to the base material and depositing it as high-energy molecules using a brating method.

Therefore, it is possible to commercialize an ideal acoustic vibration material using 84G, which has high hardness and high sound velocity. In particular, since the 84C film formed on the base material according to the present invention has an amorphous structure, its physical properties do not differ depending on the direction. Therefore, when viewed as a diaphragm for a speaker, in the case of a crystal structure, the strength in the direction 90° with respect to the orientation is weak (in the case of a cantilever, problems in strength are fatal), and partial This can cause resonance, create unnecessary resonance peaks in terms of frequency characteristics, and cause deterioration of sound quality. On the other hand, in the case of an amorphous structure, there is no variation in strength and therefore it does not cause deterioration of frequency characteristics, so it is possible to obtain excellent sound quality.

When viewed as a cantilever, in addition to eliminating the strength problem mentioned above, the vibration of the needle tip can be transmitted well to the magnet, armature, or coil, and there is no possibility of insensitivity or sensitivity during the vibration band of the needle tip. There will be no more low spots.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an activated reactive ion blating device applicable to the present invention, and Fig. 2 shows a
A cross-sectional view of a diaphragm coated with a 4G film, Fig. 3 is an X-ray diffraction diagram of an 84C film obtained by the present invention, and Fig. 4 shows a B-C reaction film when the acetylene plasma pressure is varied. Characteristic diagram of composition analysis Figure 5 is a characteristic diagram showing the relationship between acetylene plasma pressure and sound velocity in a B-C system reaction membrane.
FIG. 6 is a characteristic diagram showing the relationship between base material temperature and sound velocity. (1) is a vacuum chamber, (2) is an elemental boron element, (3
) Crucible, (4) is base material, (5) is holder, (6)
is an electron beam, (7) is a hydrocarbon gas introduction part, (B) is an electrode for plasma generation, and (11) is a plasma atmosphere. −Thank you

Claims (1)

[Claims] 1. An acoustic vibration material characterized in that an amorphous boron carbide film is provided on a base material. 2. Boron carbide (B_4
C) is synthesized and this boron carbide is accelerated by a high electric field applied to a base material heated to a predetermined temperature to form an amorphous boron carbide film on the base material. A method for manufacturing an acoustic vibration material.