JPS6333100A - Diaphragm and its production - Google Patents

Abstract

PURPOSE:To obtain the diaphragm of high sound quality having a light weight, a high rigidity and a proper internal loss by mixing metallic boron and/or boron carbide with a thermosetting resin, thermally molding this mixture to a diaphragm form and heating it in an inert atmosphere. CONSTITUTION:A mold 1 is one for producing a dome shape diaphragm and constituted of a protruding male mold 1A and a recessed female mold 1B. This mold 1 is heated to a prescribed temperature, and the mixture 2 of the metallic boron and the boron carbide is evenly sprayed or applied on the male mold 1A by the use of a sieve or the like. According to this thermocompression processing, the mixture 2 is molten, set and integrated to obtain a dome shape molded member 3. Then, this molded member 3 is taken out from the mold 1, put into a furnace, heated under a non-oxidizing atmosphere, carbonized or graphitized. According to this heating, a resin component in the molded member 3 is carbonized by a thermal decomposition reaction, further a part thereof is graphitized, reacts with a part of the metallic boron to be the boron carbide.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an acoustic diaphragm and a method for manufacturing the same. It is possible to obtain a moving board with high rigidity, appropriate internal loss, and good sound quality.

[Prior art and its problems] General information: The materials constituting the acoustic diaphragm must be: ■ lightweight (low density), ■ high rigidity (high Young vehicle), ■ There is a requirement to have a moderate internal loss (tan δ).

Carbon-based materials such as carbon and graphite are known as one of the acoustic diaphragm materials that satisfy these conditions. This material has a rigidity modulus of 10 (1-150GP
a and high (density 1.3 to 1.8 g/13 and small) (particularly suitable for medium and high frequency range imaging plate 1).

However, when using an acoustic diaphragm with very high sound quality, C
: requires even higher rigidity and lower internal loss. It is conceivable to use boron or boron carbide, which have high rigidity and low loss, but these have the problem of being brittle and having low workability, making it difficult to make them into diaphragms.

c Means for Solving Problem A] Therefore, in the present invention, thermosetting resin ζ: boron and/or boron carbide is added, this is thermoformed to form a diaphragm-shaped molded body, and then, This is heated in an inert atmosphere to carbonize or graphitize the thermosetting resin, and at the same time generate boron carbide from this carbon and a part of the boron. The above problem was solved by dispersing boron carbide.

The present invention will be explained in detail below.

The thermosetting resin used here needs to be solid in a semi-cured state. The type of resin is not particularly limited, but resins with high carbonization yields such as phenolic resins and polyimide resins are suitable in terms of dimensional precision after carbonization or graphitization. Specifically, when using phenolic resin, mix 210 to 15 wt% of hexamethylene natrami as a curing agent to novolac resin and heat at 100 to 130°C.
The particle size of the resin powder that is heated and kneaded to form a powder is one whose average particle size is 100 μnpJ or less, preferably 50 μm or less, and whose particle size variation is ±10 μm or less. When the powder particle size exceeds 100 μm, when the resin powder is melted in the mold, there will be a -5 point difference in the melting speed, and the thickness of the molded body will partially oscillate, causing the thickness 'P! In addition, liquid thermosetting resins such as polyimide brevomer and epoxy resins can also be used, as well as furan resins and petroleum pitch, and these various Powdered gold R boron and/or boron carbide may be added to the thermosetting resin C, which may be a blend of two or more thermosetting resins.As the metal boron, particle size of 50 μm or less, Preferably 5μm or less purity 90 as or more, preferably 95 as
Crystalline or non-excellent! If the particle size exceeds 50 μm, it will not be possible to mix uniformly with the heat-curing resin.It is preferable to use one with less impurities such as iron. Yaha force particle size 5
A particle size of 0 μm or less, preferably 15 μm or less is used. If the particle size exceeds 50 μm, homogeneous mixing with the thermosetting resin is impossible, so particles with as uniform a particle size as possible are preferable.

The proportion of metallic boron, boron carbide, and mixtures thereof in the thermosetting resin ranges from 5 to 95 inches by weight. If it is less than 5 cm, the square root m of the specific elastic modulus E/ρ (E: Young's modulus, P: density), that is, the sound velocity, will not be sufficiently large, in other words, the degree of improvement in the cleanliness factor will not be sufficient, or If it exceeds 995 yen, the strength of the vibration plate obtained decreases, making it unsuitable as a diaphragm.

In addition, when using a mixture of metallic boron and carbon and arsenic, the mixing ratio of metallic boron and boron carbide is 7 by weight.
The 'Ri range is 95:5 to 0:30.

And on! 2) The resin, metallic boron, and/or boron carbide are uniformly heated and made into a powder or putty-like mixture.

For example, prepare a mold as shown in Figure 1 (:7) This mold 1 is for mounting a dome-shaped diaphragm, and consists of a convex lower mold IA and a concave upper mold IB. It consists of

This mold 1 is heated to a predetermined temperature (: in advance), and the lower plate IA is heated.
Spread or apply the above mixture uniformly using a sieve or the like. When using phenolic resin powder, the mold temperature is set to about 14(') to 150°C. Next, upper type IB
is placed on the lower mold IA, and the pressure is 1.0 to 2- OMP a.
Heat and pressure treatment at a moderate temperature.

The time and temperature during the heat-pressure treatment are determined as appropriate, depending on the type 1 resin and the amount of the mixture applied. Through this heat-pressure treatment C2, which is determined appropriately taking into account the rate, the two mixtures are melted, hardened, and integrated to form a second dome-shaped molded body 3. This sucking body 3 is taken out, placed in a heating furnace, heated under a non-oxidizing atmosphere, and carbonized or graphitized.Resistance 1!o Heat furnace furnace 2
In any high-temperature furnace, the molded body 3 is stored in a stress-free state by a method such as hanging, and the inside of the furnace is evacuated.
2. Replace with Ar gas – and 3oS80”
Raise the temperature to 6nO to 8oo"c at a heating rate of C/hour,
The temperature is maintained for 0.5 to 2 hours, and the temperature is further raised to C300 to b°C, and maintained for about 0.5 to 1 hour.

Due to this heating C2, the resin content in the molded body 3 is carbonized by a thermal spectroscopic reaction (2), and a part 6 of it is graphitized and reacts with a part of I+, KT4 boron, It becomes reddish carbide.Final;!'II a When the temperature is high (the graphitization of carbonaceous material progresses, and most of the metallic boron changes to boron carbide.However, C2 heating above 2400℃) Deroto 5: The hydrogen chloride melts and changes the shape of the molded body 3, which is undesirable.Also, the maximum temperature reached is 1600°C.
In Mitaka, graphitization is insufficient and rigidity increases771)it
and internal loss cannot be sufficiently reduced.

By this heat treatment, X
Preferably, the content of lead is at least 10% by weight, and the content of boron carbide is at least 501% by weight, which is necessary in order to obtain a diaphragm with high density, rigidity, and internal loss.

Note that mold 1 can also be heated from room temperature after spraying mixture 2 to obtain a planar shape vJ'X. This method can also be used for the S-combination, and it is also possible to heat the ζ-1 molded body 3 in a non-oxidizing atmosphere while it is pressed into the mold 1. 1st order,
Mixture 2C: A small amount of high elastic graphite short fibers may be added to increase the mechanical strength.

[Effect]

In such an imaging plate, a desired amount of high-rigidity, low-loss boron carbide is dispersed uniformly and in a compatible state in graphite. It is possible to make a high-quality diaphragm with internal loss. Also, since the diaphragm is made into a diaphragm by thermoforming from a powder or putty state, the amount of the mixture to be sprayed can be partially adjusted. That (
2, it is possible to change the thickness at any part within a single diaphragm, and the thickness can be changed at any location within a single diaphragm. [Example] Novolac type phenolic resin 100 Mfiltration part C: Powdered phenolic resin 1 with an average particle size of 5.0 mm, which was milled with a ball mill to which 15"x parts of hexamethylenetetramine was added.
009, metallic boron powder with a purity of 97% (average particle size 1μ
100.9270 m) and dry mixed to obtain a mixed powder. This powder was spread on the lower mold shown in FIG. The temperature of the lower mold was 140°C.

After spreading, an upper mold at the same temperature was placed and heat-pressure treatment was performed at a pressure of 1.0 MPa for 5 minutes to obtain a dome-shaped molded product. This molded body was heated to 600'C in a graphite resistance furnace under an inert atmosphere at a heating rate of 60°C/hour, and then 4 [10°C/hour].
The temperature was raised to 1900°C at a temperature increase rate of 1 hour, and after heating at 1900°C for 30 minutes, it was cooled to room temperature in the furnace to form a diaphragm.

The density of this imaging plate was 2-359/cm s, the Young's modulus was 430 GPa%, and the internal loss was 0.04. When this diaphragm was analyzed for its composition by X-resonance diffraction, the chart shown in Figure 3 was obtained. From this chart, it appears that a considerable portion of the metallic boron has changed to boron carbide, and that the resin content has also been converted to graphite. ] I can see that progress is being made.

Also, Figure @4 shows the measurement results of the frequency characteristics of this diaphragm.

Figure 2g5 is the above example of the top and bottom (:, final arrival @ degree is 1
It is a graph showing the sound velocity and internal loss of the curdle plate obtained by changing the temperature from 400°C to 2400°C.

This graph shows that by setting the temperature to 1600° C. or higher, a sufficiently high sound velocity and low internal loss can be obtained.

FIG. 6 shows the mixture of metallic boron in the above Example 1]
The change in sound speed and internal loss at that time is
The gold dust is expressed as a ratio to the sound velocity and internal loss when the nine elements are not mixed, the vertical axis is the change ratio of the sound velocity or internal loss, and the vertical axis is the mixing ratio of metallic boron (°C).

This graph shows that when the mixing ratio of metallic boron is 5% or more, the effect of improving sound velocity and internal loss appears.

[Effects of the Invention] As explained above, the diaphragm of the present invention and its manufacturing method include adding metallic boron and/or boron carbide to a thermosetting resin, and thermoforming it into a diaphragm shape. Then, since the material is heated for 71Q in an inert atmosphere, metallic boron or boron carbide is uniformly dispersed in the carbonaceous or graphitic material, and a diaphragm in a friendly state can be obtained. Therefore, Young's modulus is approximately 500Qpa.

Boron carbide with a density of 2.5/1 and a Young's modulus of 120~
It is a composite system with carbonaceous or graphite with a density of 1.5 to 1.8g/c*, and carbonization can be done without reducing the lightness of the carbonaceous or graphite. (2) As a result, the overall Young's modulus is greatly improved, which increases the sound velocity sufficiently to enable a wide reproduction band7.Furthermore, the internal loss also decreases (1,
If the CI is around 0.03 to 0.04, it will have appropriate pressure damping characteristics.Also, since the amorphous mixture is thermoformed into the shape of a diaphragm, it can be made into a vibration plate shape of any shape. Free and easy (-9 can be built,

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an example of the layered (two-phase) mold of the present invention, Fig. 2 is a sectional view showing -flj of a molded product which is an intermediate product, and Fig. 3 is a wt example. Figure 4 is a graph showing the X-ray diffraction chart of the obtained diaphragm. Figure 4 is a graph showing the frequency characteristics of the diaphragm obtained in the same example. Figure 5 is a graph showing the frequency characteristics of the diaphragm obtained in Example C. FIG. 6 is a graph showing the relationship between the ratio of unmixed metals and the rate of change in sound speed and internal loss in Examples. 1 (IA, IB)...Mold, 2...Mixture, 3...Molded body. Applicant: Nippon Raku PAWZO Co., Ltd. Figure 1, Figure 2, 111 Ichime Shuun number (Hz) Fig. 4.2e Fig. 8 1.4 1.6 +, 8 2.0 2
2 2.4-＠End) 1 degree of water ('C) xlo' 5th interval 0 50 to
.

Claims (2)

[Claims] (1) A diaphragm in which metallic boron and boron carbide are dispersed in a carbonaceous and/or graphitic matrix. (2) Vibration characterized by mixing metallic boron and/or boron carbide with a thermosetting resin, thermoforming this mixture into a diaphragm shape, and then heating this in an inert atmosphere. The manufacturing method of the board.