JPS5911961B2 - Method for forming aluminum evaporated film for acoustic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The object of the present invention is to form a vapor-deposited film for acoustic components that is lightweight and has a high Young's modulus.

Acoustic components such as cantilevers for pickups and diaphragms for high-frequency speakers require lightweight materials with high sound velocity.

By the way, materials such as beryllium Be, which generally have a high sound velocity, are difficult to process, so when making a tapered cantilever, a vacuum deposition method is used.
This vacuum evaporation method is especially suitable for mass production of small parts, and has the advantage of being able to be molded even if the surface shape is complex. suitable for production. However, in order to obtain practical thicknesses, high deposition rates are required, and beryllium Be is unsuitable in this respect and is expensive. On the other hand, aluminum has been used as a vacuum evaporation material for a long time, and is a metal with which it is easy to obtain a high evaporation rate. If this is simply used, the specific gravity and sound velocity will be inferior to those of beryllium Be. 5 This invention aims to obtain a vapor deposited film using aluminum as a vapor deposition material, which is lightweight and has a high sound velocity, and is characterized by forming a multilayer vapor deposition film by varying the vapor deposition speed. It is something to do.

Aluminum can be obtained relatively freely by adjusting the deposition rate, ranging from dense aluminum with properties similar to that of bulk aluminum to porous aluminum with low specific gravity. FIG. 1 shows the results of actual measurements of the relationship between the specific gravity and sound velocity of an aluminum vacuum-deposited film, and the two have a nearly linear functional relationship. Surface temperature of material to be deposited 60
℃, evaporation rate 20μ/mm, specific gravity 2.09/c7
A deposited film of il is obtained, and if the deposition rate is increased beyond that, a light deposited film with a specific gravity of 2.0 y/1 or less can be obtained. This invention obtains a light vapor-deposited aluminum film with a high sound velocity by multilayer vapor deposition of such a light vapor-deposited film layer and a dense vapor-deposited film layer with a specific gravity of 20 close to that of bulk aluminum but with a large Young's modulus. FIG. 2 shows an example of the vapor deposition process.

In this figure, the horizontal axis represents the deposition time and the vertical axis represents the deposition layer at 25 degrees. From the start of deposition to time Tl, deposition is performed at a low deposition rate R, and then from time Tl to T2. It is shown that the vapor deposition is performed at a high vapor deposition rate R2, the original vapor deposition rate R is returned again from time T2, and the vapor deposition is completed at time T3. As a result, the evaporated film 30 has three layers, with the layer having a light specific gravity being the center, and the layers having a heavy specific gravity arranged above and below it. As an example, at an initial deposition rate of 1 μ/mm,
Deposition was performed for 0 minutes, then for 30 seconds at a deposition rate of 40μ/mm, and again for 10 minutes at a deposition rate of 1μ/mm.
35 The sound velocity of the aluminum vapor deposited film thus obtained is 6
It was 600m/s. The following table shows a comparison of the specific gravity per 1 d and sound velocity of this 40 μm thick aluminum vapor deposited film and a conventionally used 40 μm thick aluminum foil.

As is clear from this table, the material according to the present invention is lighter than the conventional aluminum foil, and has a higher sound velocity.

Comparing the specific gravity and sound velocity obtained with a multilayer film of a similar shape, even when manufactured using the method according to the present invention, the specific gravity is 2.49.
/d or more, the sound velocity does not exceed 6200 m/s, and there is no significant difference from conventional aluminum foil.

Therefore, at least one layer of the aluminum vapor-deposited film is
The specific gravity must be 2.49/CTil or less.
Note that the vapor-deposited film is formed on a base material that has been previously formed with copper foil into a predetermined shape as a speaker diaphragm,
After that, when the copper foil that is the base material is removed by chemical etching and a diaphragm made of only a vapor-deposited film is made, or when vapor-deposition is performed on a single Mylar foil, the above method is used as is. When an aluminum molded product is used as the base material, the process up to time T1 shown in FIG. 2 may be omitted.

As described above, in this invention, aluminum is alternately deposited at a plurality of different deposition rates so that at least one deposited layer with a specific gravity of 2.49/d or less is formed. It is possible to obtain a vapor-deposited film, and it is lightweight.
A deposited film with a high sound velocity can be obtained using inexpensive aluminum.

Although it is multi-layered, each layer is made of aluminum, so there is no need to take it in and out of the vacuum chamber each time you change layers.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the specific gravity of an aluminum deposited film and the speed of sound, and FIG. 2 is a graph showing an example of the process of the present invention.

Claims (1)

[Claims] 1. A method for forming an aluminum vapor-deposited film for an acoustic component, comprising alternately performing vapor deposition at a plurality of different vapor deposition rates so as to form at least one vapor-deposited layer having a specific gravity of 2.4 g/cm^3 or less.