JPH0470840B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a speaker diaphragm made of a sanderch structure in which a skin material is bonded to the surface of a core material. An object of the present invention is to provide a method for manufacturing a speaker diaphragm in which a membrane of the present invention can be bonded to a core material.

In general, a speaker diaphragm follows the driving force provided by the electromagnetic conversion system with sufficient linearity within the frequency band in which it is used, and its entire surface vibrates in the same phase (piston vibration). That is considered ideal. Furthermore, from the perspective of sound wave radiation characteristics, a so-called flat diaphragm with a flat radiation surface is considered ideal. In this planar diaphragm, in order to prevent split resonance and widen the piston vibration band, the thickness of the diaphragm is increased to increase its rigidity, which has the disadvantage of increasing the weight of the diaphragm and reducing the efficiency of the speaker. are doing. As a method to improve this drawback, a diaphragm using a sanderch structure in which a skin material is bonded to the surface of a core material made of a hollow core has been put into practical use. It was difficult to adapt. Furthermore, when the material constituting the sanderch structure is made thinner to reduce its weight, there is a problem in that the strength of the vibrating body decreases, causing partial resonance (plane noise phenomenon) and deteriorating acoustic characteristics. To improve this, materials with low density and high elastic modulus are desired. Boron and beryllium are materials that meet this requirement, but these materials have poor workability and, like aluminum and titanium,
It was impossible to produce foil by rolling to a thickness of 20 μm. Therefore, attempts have been made to use boron and beryllium materials in foil using vapor deposition techniques such as PVD and CVD, but conventional speaker diaphragms using beryllium, boron, and their composite materials All of these were limited to dome or cone shapes. This is because internal stress remains in films produced by the PVD method due to various factors such as lattice defects, surface tension, and phase transitions, and this residual stress can cause warping and distortion of the produced film. This is probably due to the fact that in dome-shaped or cone-shaped diaphragms, the rigidity due to the shape is sufficiently large compared to the internal stress of the vapor-grown film, so shape distortion is not a big problem. . However, in the planar shape, shape distortion due to internal stress has been an important drawback. In particular, boron and beryllium are highly brittle, so it is impossible to mechanically stretch warped or distorted films flat, so an improved method of reducing the residual stress in the formed film through post-formation heat treatment has been developed. Even when used, sufficient effects could not be obtained.

The present invention eliminates these drawbacks of the conventional method, and provides a flat skin material having low density and high elastic modulus, thereby realizing a high-performance plane vibration plate.

A method for manufacturing a skin material, which is the gist of the present invention, will be explained. In the conventional PVD method, regardless of the presence or absence of ionized particles, internal stress remains in the produced film as described above, causing warpage and distortion in the produced film. In particular, in the vapor phase growth method using ion particles, stress was generated significantly due to the impactful embedding of ions. In order to reduce such internal stress, a method is used in which vapor phase growth is performed while heating the substrate, but there are many limitations to obtaining a flat film without warping or distortion. for example,
In the case of boron film formation, the inventors' experience is that a film with fairly good flatness can be obtained if the substrate is heated to 600°C or higher, but if the substrate is heated to 600°C or higher in vacuum, In addition to thermal distortion and deformation of the substrate, the temperature rise from the heating section, substrate, and equipment walls causes severe degassing, which limits the gas pressure and atmospheric conditions during production, resulting in a decline in the quality of the produced film. occurs. Furthermore, when using a substrate drive mechanism such as a planetary device, problems arise in the design of the device, such as the heat resistance of the rotating mechanism and the capacity of the heating device (infrared heating, etc.), making stable operation difficult.
On the other hand, the PVD method according to the present invention can eliminate the warping of the produced film due to residual stress at a low substrate temperature of around 400° C., thereby eliminating the drawbacks of the conventional method described above. Furthermore, to explain the mechanism that can prevent warping of the film produced by the PVD method of the present invention, for example, when a film is produced on a substrate by vacuum evaporation, the substrate is Radiant heat from the source, heat conduction from the evaporated particles, heat of reaction between the evaporated particles and the substrate or coating, etc. are transmitted, which causes temperature changes over time. At this time,
The surface of the substrate or generated film on which the evaporated particles re-solidify is greatly influenced by radiant heat, conduction heat from the evaporated particles, and continues to undergo thermal expansion. When evaporated particles adhere to such a surface, the film-forming surface expands with thermal expansion and receives more evaporated particles.
After the film is deposited under these conditions,
As the temperature decreases, shrinkage occurs, resulting in a difference in shrinkage in the thickness direction within the produced film. That is, the expansion-contraction force of the film at the initial stage of vapor deposition is large, and this stress becomes small at the end of vapor deposition. The film is curved due to such a stress difference inside the produced film, and if the substrate is thin, the film is curved in the direction in which the stress of the film and the stress of the substrate are added. The inventors discovered that the curved shape of the substrate is different from the curved shape of the produced film itself, and based on this idea, by controlling the substrate temperature so that it is the same as the surface on which the film is formed, the film can be formed. It has been achieved that it is possible to prevent the curvature (curl) of the material. in this case,
The rate of decrease in substrate temperature during generation varies depending on the substrate material, evaporation material, amount of radiant heat from the evaporation source, etc.
Although it is difficult to make a general determination, qualitatively better results can be obtained when the temperature gradient is in a decreasing state.
That is, the basis of the PVD method according to the present invention is not to increase the substrate temperature during vapor deposition. but,
During deposition, the substrate receives radiant heat from the deposition source, so the temperature of the substrate increases with the deposition time. Therefore, since the required minimum temperature for heating the substrate is determined by the amount of radiant heat from the evaporation source, the distance between the evaporation source and the substrate, and the evaporation time, consideration must be given to this point when setting the conditions.

Hereinafter, a method for manufacturing a speaker diaphragm according to the present invention will be described in detail based on Examples.

Example 1 First, as shown in FIG. 1, a core material 12 made of a chrysanthemum-shaped hollow core material is created by knitting an aluminum ribbon 11, and a pure boron skin material 13 with a thickness of 20 μm is placed on both sides of the core material 12 at a temperature of 200 μm. ~230℃, pressure 1~2Kg/
A flat diaphragm 14 having a diameter of 28 mm and a thickness of about 1 mm was produced by thermocompression bonding with an adhesive under conditions of cm ² . At this time,
The boron skin material 13 was created by electron beam evaporation using a vacuum evaporation device. The vacuum evaporation apparatus is a bell jar 6 equipped with an exhaust system 7 as shown in FIG.
A crucible 8 containing a substrate 1 provided on a heating device 2 and an evaporation source 3 is placed facing each other in the crucible 8.
An electron beam heating device 5 is disposed adjacent to the substrate 1, and a thermocouple 4 for measuring the temperature of the substrate 1 is provided.
It is equipped with the following. Then, set the vacuum evaporation equipment to 1
After exhausting the air to ~3×10 ¹⁵ Torr and heating the substrate 1 to 420°C as shown in curve A in Figure 3 using the substrate heating device 2, the substrate temperature was continuously lowered at a rate of about 10°C/min. By electron beam evaporation, boron as the evaporation source 3 was evaporated under conditions of an electron beam power of 12 KW for 25 minutes to form a 20 μm thick boron layer on a titanium substrate as the substrate 1. The substrate 1 is made of titanium foil with a thickness of 50 μm, and its surface is
Cover with a mask material with a 28 mm hole (equivalent to the diameter of the diaphragm), and a hole of 28 mm in diameter and 20 μm in thickness is placed on the titanium substrate.
produced a boron film. After the boron film was formed, the titanium substrate was dissolved and removed with a hydrofluoric acid solution having a concentration of 0.5 to 1% to produce a boron skin material 13 having a diameter of 28 mm and a thickness of 20 μm.

The speaker diaphragm constructed in this way has the advantage that it is possible to obtain a flat and unwarped boron skin material 13, so it can be bonded to the core material 12 by thermocompression using an adhesive, and its frequency characteristics are shown in Figure 4. It is shown by the solid line. In FIG. 4, a indicates the sound pressure frequency characteristic of the speaker diaphragm of this embodiment, and b indicates its second harmonic distortion characteristic.

Comparative Example 1 Pure boron skin material with a thickness of 20 μm was thermocompression bonded to both sides of a core material consisting of a hollow core made of aluminum ribbon woven into a chrysanthemum shape at a temperature of 200 to 230°C and a pressure of 1 to 2 kg/cm ² to form a material with a diameter of 28 mm. A flat plate diaphragm with a thickness of about 1 mm was fabricated. At this time, the boron skin material is evacuated to 1 to 3 x 10 ^-5 Torr using the vacuum evaporation equipment shown in Figure 2, heated to 420°C using the substrate heating equipment, and then deposited using electron beam evaporation. Beam power 12KW, 25
Boron was deposited under the conditions of 1 minute to form a 20 μm thick boron layer on the titanium substrate. At this time, the substrate surface temperature changed as shown by curve B in FIG. A titanium foil with a thickness of 50 μm is used for the substrate, and its surface is covered with a mask material with a hole of 28 mm in diameter (corresponding to the diameter of the diaphragm).
A 20μm boron film was produced. After the boron film was formed, the titanium substrate was dissolved and removed using a hydrofluoric acid solution with a concentration of 0.5 to 1% to produce a boron skin material with a diameter of 28 mm and a thickness of 20 μm.

In such speaker diaphragms, the boron film serving as the skin material is warped due to its internal stress, and is destroyed when it is thermocompressed to the core material using an adhesive.

Comparative Example 2 Pure boron skin material with a thickness of 20 μm is thermocompressed on both sides of a core material made of a hollow core made of aluminum ribbon woven into a chrysanthemum shape at a temperature of 200 to 230°C and a pressure of 1 to 2 Kg/cm ² to form a material with a diameter of 28 mm. A flat diaphragm with a thickness of about 1 mm was manufactured. At this time, the boron skin material was evacuated to 1 to 3 x 10 ^-5 Torr using the vacuum evaporation equipment shown in Fig. 2, and was deposited using an electron beam (EB) evaporation method with an electron beam power of 12 KW without heating the substrate. Boron was deposited for 25 minutes to form a 20 μm thick boron layer on the titanium substrate. At this time, the substrate surface temperature changed as shown by curve C in FIG. The substrate has a thickness
A 50 μm titanium foil was used, and its surface was covered with a mask material with a hole of 28 mm in diameter (equivalent to the diameter of the diaphragm), and a boron film with a diameter of 28 mm and a thickness of 20 μm was formed on the titanium substrate. After the boron film was formed, the titanium substrate was dissolved and removed using a hydrofluoric acid solution with a concentration of 0.5 to 1% to produce a boron skin material with a diameter of 28 mm and a thickness of 20 μm.

In such speaker diaphragms, the boron film serving as the skin material is warped due to its internal stress, and is destroyed when it is thermocompressed to the core material using an adhesive.

Comparative Example 3 Aluminum skin materials with a thickness of 20 μm were thermocompression bonded to both sides of a core material consisting of a hollow core made of aluminum ribbons woven into a chrysanthemum shape at a temperature of 200 to 230°C and a pressure of 1 to 2 Kg/cm ² to form a material with a diameter of 28 mm. A flat diaphragm with a thickness of approximately 1 mm was manufactured. The sound pressure-frequency characteristics of this speaker diaphragm are shown by broken line C in FIG. Since the boron skin materials according to Comparative Examples 1 and 2 were warped due to residual stress, they cracked during thermocompression bonding with the core, making it impossible to put them into practical use as diaphragms. The boron skin material produced under the conditions of this example did not crack during the bonding process and could be used as a flat diaphragm. Also, the fourth
In comparing the sound pressure-frequency characteristics of the flat plate diaphragms of this example and comparative example 3 shown in the figure, the first The next resonance frequency increases from 12.1KHz to 19.3KHz, and the efficiency is 1.5~
It was improved by about 2dB.

Although boron was mentioned in the above description, it goes without saying that the laminate can also be used as a skin material without separating the substrates.

As described above in detail, the manufacturing method of the present invention has the advantage that it is possible to manufacture a flat boron skin material, and it is possible to realize a high-performance speaker diaphragm.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the manufacturing process of the speaker diaphragm of the present invention, Fig. 2 is a schematic configuration diagram showing a vapor deposition apparatus for obtaining the skin material of the diaphragm, and Fig. 3 is a substrate of the vapor deposition apparatus. FIG. 4 is a comparison diagram of the sound pressure-frequency characteristics of the same diaphragm and a conventional diaphragm. 1...Substrate, 2...Heating device, 3...Evaporation source,
4...Thermocouple, 5...Electron beam heating device, 6...
... Belgear, 7... Exhaust system, 12... Heartwood, 1
3...Skin material.

Claims (1)

[Claims] 1. When a boron layer is generated on a substrate by physical vapor deposition, residual stress in the generated boron layer is reduced by maintaining the surface temperature of the substrate in a lowered state. A method for manufacturing a speaker diaphragm, which comprises obtaining a laminated material with little warpage, and then thermocompressing the laminated material as a skin material onto the surface of a core material of a hollow core having an arbitrary shape using an adhesive. 2. The method of manufacturing a speaker diaphragm according to claim 1, characterized in that the substrate on which the boron layer has been formed is separated and a skin material made only of boron is taken out.