JPS5821998B2 - Multilayer diaphragm for acoustic transducer and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer diaphragm for an acoustic transducer used for a speaker, a diaphragm for a microphone, a cantilever of a pickup cartridge for reproducing records, and a method for manufacturing the same.

In general, the physical properties required of the diaphragm for an acoustic transducer include (1) being lightweight, (2) having high rigidity and high elasticity, and (2) not exhibiting sharp resonance.

In particular, a diaphragm plate for a high-pitched speaker is required to exhibit smooth frequency characteristics up to a high frequency range.

In order to satisfy these required characteristics, the material constituting the diaphragm must have a large Young's modulus E, a small specific gravity ρ, that is, a large E/ρ, and a large internal friction. However, developing a material that satisfies all of these properties is extremely difficult.

However, even if sharp resonance cannot be avoided, if E/ρ is set sufficiently large, smooth frequency characteristics can be obtained up to a fairly high frequency range, so we believe that materials with high E/ρ should be used instead. It will be done.

Therefore, considering E/ρ as an important characteristic, research has been increasingly conducted in recent years with the aim of developing diaphragm materials with high E/ρ characteristics.

On the other hand, metal materials such as aluminum or titanium are usually used as diaphragm materials for metal speakers, but these materials all have relatively low E/ρ, and therefore have low rigidity as mentioned above. There is a need for a diaphragm material that is a metallic material with a large E/ρ and has a much larger E/ρ than the metallic material.

Recently, a vibration plate with an extremely large E/ρ has been developed and is beginning to be used, but as is well known, this material is extremely toxic and difficult to handle, and requires equipment to prevent pollution. Therefore, for these reasons, there is a strong demand for the development of a diaphragm material that is not as toxic as Beam and has a large E/ρ. This is the current situation.

In order to obtain a diaphragm that is lightweight, has high rigidity, and high elasticity, that is, has a high E/ρ value at a low cost, from the above-mentioned viewpoints, the present inventors made a diaphragm with a larger E/ρ than beryllium. As a result of research focusing on boron, which is not toxic in manufacturing, we found that (1) Boron alone is brittle and lacks strength, making it difficult to use as a diaphragm for high-input speakers; however, titanium, which has high toughness, Or if you use titanium alloy together,
The lack of strength of boron can be overcome.

(2) However, adhesion between titanium or titanium alloy and boron is relatively low, and with such low adhesion, sufficient strength improvement cannot be expected. The adhesion between the titanium or titanium alloy and boron can be significantly improved by interposing a metal layer made of one of metals from group 58 and group 6a of the periodic table and hafnium as an intermediate layer.

(3) Formation of the boron layer on the intermediate layer by OVD method (
If done by chemical vapor deposition method, the adhesion will be extremely high.

The findings shown in items (1) to (3) above were obtained.

This invention was made based on the above findings, and
The main process is to first coat the surface of a base metal substrate with a predetermined surface shape with a lower layer made of titanium or titanium alloy as a first layer with a layer thickness of 5 to 20 μm by a normal method, and then coat the lower layer on the lower layer. , 5 of the periodic table as the second layer by OVD method or physical vapor deposition method (hereinafter referred to as PVD method).
An intermediate layer made of one of Group A and Group 6A metals and hafnium is formed with a layer thickness of 0.1 to 2 μm, and the base metal substrate on which the lower layer and intermediate layer are formed is placed in a pyrolysis reactor. A third pyrolysis reaction is carried out by introducing a mixed gas containing boron halide vapor and hydrogen as main components into the pyrolysis reactor to cause a decomposition reaction.
By forming an upper layer of boron as a layer with a layer thickness of 5 to 30 μm on the intermediate layer, and then dissolving and removing the underlying metal substrate, titanium or titanium with a layer thickness of 5 to 20 μm is formed. a fourth layer made of an alloy; a second layer as an intermediate layer made of one of the group 5a and 6a metals of the periodic table and hafnium with a layer thickness of 0.1 to 2 μm; The present invention is characterized in that it manufactures a multilayer diaphragm for an acoustic transducer, which is composed of a third layer made of boron.

In this invention, titanium or a titanium alloy is used as the first layer (hereinafter referred to as the lower layer) because these metals are strong and have low density, and can withstand the temperature increase when boron is deposited by the OVD method. The reason why the thickness of the lower layer is limited to the range of 5 to 20 μm is that
This is because if the thickness is less than 20 μm, the required toughness cannot be obtained, whereas if it exceeds 20 μm, the Young's modulus of the entire laminated diaphragm becomes low.

In addition, as the second layer (hereinafter referred to as the middle layer), 5
The reason why a metal layer made of one of group a and group 6a metals and hafnium is interposed between the lower layer and the third layer (hereinafter referred to as upper layer) is as follows.

That is, the conditions required for the above-mentioned intermediate layer are as follows: (1) There is no significant difference in thermal expansion coefficient between boron as the upper layer and titanium or titanium alloy as the lower layer, and no cracking or peeling occurs near the interface.

■ Excessive reaction between the upper and lower layers, resulting in a reaction product layer with undesirable properties.

Examples include.

Regarding the above item (2), the thermal expansion coefficient of boron is 6.5 to 8.
Since the coefficient of thermal expansion of titanium or titanium alloy is 8.4 to 10.4 x 10'/'C at 2X10'7G, it is desirable that the coefficient be close to these values.

Regarding (1) above, there is a reaction between boron as the intermediate layer and the upper layer, or titanium or titanium alloy as the intermediate layer and the lower layer at the temperature at which boron is deposited by the OVD method (900 to 1100°C as described later). It is desirable that the reaction does not proceed excessively, that is, the intermediate layer acts as a barrier to the reaction between the upper and lower layers.

From the above, groups 5a and 6 of the periodic table are considered as intermediate layers.
Metals consisting of Group A metals and one type of hafnium were used.

These will be explained in more detail below.

That is, the metals of group 5a and group 6a of the periodic table, as well as hafnium, all have high melting points and are known as refractory metals, and their coefficient of thermal expansion is 5 to 10 x 10.
'/℃, which is relatively close to the coefficient of thermal expansion of boron.

Furthermore, when an upper layer is formed on the intermediate layer made of these metals, a thin poride layer is formed between the intermediate layer and the boron layer as the upper layer, and this poride layer prevents the adhesion between the intermediate layer and the upper layer. It helps improve sex.

On the other hand, with respect to titanium or a titanium alloy as the lower layer, there may be a difference in thermal expansion coefficient of nearly 100% depending on the metal forming the intermediate layer.

However, by carefully considering the method of vapor deposition on the lower layer or the cooling conditions after vapor deposition, it is possible to prevent the occurrence of undesirable cranking due to the difference in coefficient of thermal expansion.

As mentioned above, since the metals forming the intermediate layer all have high melting points, diffusion reactions with the boron layer as the upper layer or the titanium or titanium alloy layer as the lower layer occur to some extent, but the progress is generally slow. Therefore, it can sufficiently function as an intermediate layer, that is, improve adhesion and suppress diffusion reactions between upper and lower layers.

Furthermore, as described above, it is generally desirable for a diaphragm to be lightweight, so from this point of view, the intermediate layer cannot be allowed to be too thick, and must be 2 μm or less.

On the other hand, if it is too thin, it cannot function as an intermediate layer sufficiently, so a minimum layer thickness of 0.1 μm is required.

For these reasons, the preferable range of the thickness of the intermediate layer is set to 0.1 to 2 μm.

Furthermore, in order to improve the Young's modulus of the entire diaphragm, it is better to make the thickness of boron formed on the intermediate layer as an upper layer as thick as possible, but it is preferable to exceed 30 μm due to the constraint that it must be lightweight. On the other hand, 5#
If it is less than 1, a sufficiently high E/ρ cannot be obtained as a diaphragm, so the range is set to 5 to 30 μm.

Next, the formation of an intermediate layer consisting of one of the group 5a and 6a metals of the periodic table and hafnium on the base metal substrate with titanium or titanium alloy formed as a lower layer on the surface is performed by sputtering, ion blasting, etc. P such as
It can be deposited on the lower layer at a relatively low temperature by a VD method, or by an OVD method that utilizes a thermal decomposition reaction of metal chlorides.

In this way, the periodic table 5a as an intermediate layer is added to the lower layer.
Once the metal layer consisting of one of Group 6a and Group 6a metals and hafnium is formed, the coated base metal substrate is charged into a pyrolysis reactor, and a material such as boron trichloride is placed in the pyrolysis reactor. A mixed gas containing boron halide vapor and hydrogen as main components is introduced to cause a decomposition reaction.

Thereby, an upper layer consisting of a boron layer as a third layer may be formed on the intermediate layer with a layer thickness of 5 to 30 μm.

In this case, the deposition conditions are as follows: the temperature of the underlying metal substrate is 900-1100°C, the ratio of 1H2/BCl3 is 25°C,
It is good to set it to ~30.

Next, the present invention will be explained using examples.

A mild steel block with a diameter of 40 φ is prepared as a base metal base, the surface of this mild steel block is processed to match the shape of the speaker diaphragm to be manufactured, and the respective materials shown in Table 1 are applied to the surface of the mild steel block. Multilayer diaphragms 1 to 3 of the present invention were manufactured by forming a multilayer consisting of an upper layer, an intermediate layer, and a lower layer having the components and layer thicknesses shown, and then melting and removing the mild steel block.

The lower layer was formed on the mild steel block by an ion-blasting method, the intermediate layer was formed on the lower layer by a sputtering method, and the upper layer was formed on the intermediate layer by an OVD method.

In this case, surfaces other than those where boron formation was required were masked to facilitate later dissolution of the mild steel block with acid.

For the purpose of comparison, a comparative diaphragm 1.2 was manufactured with the components (titanium and titanium alloy) and layer thickness shown in Table 1.

The characteristics of the thus obtained coated diaphragms 1 to 3 of the present invention and comparative diaphragm 1.2 were measured, and the measurement results are also shown in Table 1.

As shown in Table 1, it is clear that the multilayer diaphragm of the present invention has a lower density and a significantly higher Young's modulus than the comparative diaphragm, and thus a significantly higher E/ρ value. Ru.

As described above, the present invention provides a diaphragm for an acoustic transducer that is lightweight, has high rigidity and high elasticity, and exhibits smooth frequency characteristics up to a high frequency range, at a low cost. It can be manufactured.

Claims (1)

[Scope of Claims] 1. A first layer made of titanium or a titanium alloy with a layer thickness of 5 to 20 μm, and a layer made of one of the group 53 and group 6a metals of the periodic table and hafnium with a layer thickness of 0.1 to 2 A1 m. A multilayer diaphragm for an acoustic transducer, comprising: a second layer as an intermediate layer; and a third layer made of boron and having a layer thickness of 5 to 30 An. 2. First, a lower layer of titanium or titanium alloy is formed as a first layer with a layer thickness of 5 to 20 μm on the surface of a base metal substrate having a predetermined surface shape by a normal method, and then a chemical coating is applied on the lower layer. An intermediate layer consisting of metals from groups 5a and 6a of the periodic table and one of hafnium is deposited as a second layer by a targeted vapor deposition method or a physical vapor deposition method.
．． The base metal substrate with a layer thickness of 1 to 2 μm and the lower and intermediate layers formed thereon is charged into a pyrolysis reactor, and boron halide vapor and hydrogen are introduced into the pyrolysis reactor. By introducing a mixed gas containing as a main component and causing a decomposition reaction, an upper layer made of boron as a third layer is formed on the intermediate layer with a layer thickness of 5 to 30 μm, and then the base metal substrate is formed. A method for manufacturing a multilayer diaphragm for an acoustic transducer, characterized in that the main process consists of melting and removing.