JP2639126B2 - Speaker manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a speaker used for audio equipment.

2. Description of the Related Art In a speaker, a diaphragm, a voice coil, an edge, a dust cap, and the like, which are vibration system components, and a frame, which is a support system component, are joined by an adhesive. In particular, these components can be used from 20Hz to 20Hz when using speakers.
Since it is constantly exposed to vibrations over a wide band of kHz, a strong and reliable adhesive force is required.

However, in recent years, due to the trend of digitalization of audio equipment, the material of the vibration system parts, particularly the diaphragm, is generally made of conventional paper pulp, such as polypropylene, polymethylpentene, and wholly aromatic polyester. Bad resin is starting to be used.

In addition, in the field of in-vehicle speakers, recent demands for weight reduction of in-vehicle parts have led to the use of resins such as frames, which are support parts for speakers, and the use of poorly adhesive resins such as polypropylene and polyacetal has been increasing. .

Resins having relatively high crystallinity and low polarity represented by these polypropylenes have difficulty in increasing the adhesiveness because their surfaces are inactive. Therefore, conventionally, a treatment method for modifying the resin surface so as to obtain high adhesiveness has been applied.

Examples of such a treatment method include a sand blast method, a flame treatment method, a corona discharge treatment method, and a method of applying a specific primer to the surface to increase adhesiveness. Hereinafter, each method will be briefly described.

The sand blast method is a method of mechanically imparting irregularities to the resin surface with grinding sand etc. to increase the adhesiveness by the anchor effect, but the resin surface is damaged and the appearance is significantly impaired, and the effect depends on the surface condition of the resin. There are drawbacks such as stability, and the adhesive strength itself cannot be expected to be so large.

The flame treatment method is a method of oxidizing the resin surface with a gas oxidizing flame. In this method, since the resin is put in a flame, the resin is liable to be deformed or melted by heat.

Corona discharge treatment is a method in which a high voltage is applied between an electrode and a counter electrode to generate a corona discharge, during which the surface is treated through a sheet or film. Has the disadvantage that processing cannot be performed.

Further, a method of increasing the adhesiveness by using a specific adhesive primer having a close SP value is employed. For example, in the case of polypropylene, it is a method of applying a primer containing hydrochloric acid-based polypropylene as a main component and bonding the primer on the primer. This method is most often used because it does not require any special equipment, but it is used only for a speaker having a small diameter and a small amplitude because the adhesive strength is not so improved.

Problems to be Solved by the Invention As described above, polypropylene, polymethylpentene, polyacetal, a wholly aromatic polyester and the like used for a vibration system component and a support system component of a speaker have relatively high crystallinity, low polarity, and a low surface. There is a problem that there is no satisfactory method as a surface treatment for bonding to an inert resin.

The present invention has been made to solve the above problems, and is a surface treatment method for giving a large adhesive force to the above resin in a short time and surely by a simple method. It is intended to provide a high-performance speaker having excellent performance.

Means for Solving the Problems In order to solve the above problems, in the present invention, at least one of the vibration system component and the support system component is irradiated with ultraviolet light, and after irradiation, a polymer having an isocyanate group at the terminal of the molecule is used. The vibration component and the support system component are bonded by providing a resin layer as a main component, or after irradiation, bonding is performed with a moisture-curing reaction type hot melt adhesive.

By irradiating the resin surface with ultraviolet rays as described above, the chemical bond on the resin surface is broken, and oxygen present in the air is bonded at this time, and carboxy groups etc. The resin surface becomes polar and hydrophilic because of the formation of a structure having a polar group, and the adhesiveness is increased as a highly polar adhesive. By providing a resin layer of a polymer having a group, a covalent bond can be formed between the resin surface and the polymer, so that greater adhesive strength can be obtained.

In addition, after the ultraviolet irradiation, by bonding with a moisture-curing reaction type hot melt adhesive, the same adhesive strength as described above can be obtained, and further, a short-time curing characteristic of the hot melt adhesive can be performed. This is because this hot melt adhesive is made by reacting a polyol with a polyisocyanate, has a chemical structure having an isocyanate group at a molecular terminal, and forms a covalent bond with the resin surface by a reaction mechanism.

Examples Hereinafter, examples of the present invention will be described using specific examples. First, a description will be given of an improvement example leading to the present invention.

(Example of improvement) A low-pressure mercury lamp (UVD-200R manufactured by Sen Special Light Source Co., Ltd.) was used for a diaphragm obtained by injection molding a polypropylene resin mixed with 10 wt% of scaly mica as a filler into a mold cavity. Ultraviolet irradiation was performed from 23 mm above the diaphragm. FIG. 1 shows the measured contact angle of the diaphragm with water while changing the irradiation time. This indicates that the polarity of the surface of the diaphragm is increased by the irradiation.

Next, the diaphragm sample irradiated for 3 minutes was bonded to a kraft paper voice coil with a chloroprene phenolic adhesive (DB-1600, manufactured by Diabond Industries, Ltd.).
The diaphragm had an inner diameter of 25 mm, an outer diameter of 110 mm, a total height of 22 mm, and a thickness of 0.2 mm, and the amount of adhesive applied was 0.5 g. As a comparative example, a non-irradiated diaphragm was bonded under the same conditions. As a result of observing the surface of the adhesive fracture surface in the same manner as measuring the adhesive strength of each, the adhesive strength was 11 kg for the diaphragm subjected to the surface treatment with the low-pressure mercury lamp for 3 minutes, and 4 kg for the diaphragm that did not. There was a clear difference in adhesion. When the surface of the fractured surface was observed, it was observed that the surface of the polypropylene resin was destroyed and mica as a filler was exposed in some places on the irradiated diaphragm. However, no exposure of mica was observed on the diaphragm not irradiated. This result indicates that the adhesive strength of the chloroprene phenolic adhesive to the diaphragm was improved only by irradiation with ultraviolet light from the low-pressure mercury lamp.

(Example 1) Next, a diaphragm made by injection molding a polypropylene resin mixed with 10 wt% of the same flaky mica as a filler as in the above-described improved example was irradiated with ultraviolet rays for 3 minutes under the same means and conditions as in the improved example. Polymer having an isocyanate group at the molecular terminal (Coronate L-55E manufactured by Nippon Polyurethane)
Was applied to the adhesive part with a brush. After air drying for about 1 hour, the voice coil and the chloroprene phenolic adhesive were adhered in the same manner as in the improved example, the adhesive strength was measured, and the surface of the fractured surface was observed.

As a result, the adhesive strength was 20 kg, which was a larger value than the improved example. When the fracture surface was observed, a portion where mica was exposed on the surface of the diaphragm and a portion where the adhesive was cohesively fractured and adhered to the surface were observed.

This is better than bonding directly after irradiation as in the improvement example.
This shows that adhesion is greater when the surface is treated with a polymer having an isocyanate group at the end as a primer and then bonded.

The formation of the surface polar group and the reaction with the isocyanate group are as follows.

(Example 2) Further, the same vibration plate as that in the improved example was irradiated with ultraviolet rays for 3 minutes under the same means and conditions as in the improved example, and then a moisture-curing reaction type hot melt adhesive (MR2031 manufactured by Konishi Co., Ltd.)
After the adhesive was sufficiently cured, the adhesive force was measured, and the surface of the fractured surface was observed.

As a result, the adhesive strength was 22 kg, which was a larger value than the improved example. Observation of the fractured surface revealed that the kraft paper of the voice coil was broken.

This indicates that the adhesive strength is higher when bonding with a moisture-curing reactive adhesive obtained by reacting a polyol and a polyisocyanate than when bonding with a chloroprene phenolic adhesive after irradiation as in the improved example.

The structure of the moisture-curable hot-melt adhesive is shown below.

Polyisocyanate (4.4'-cyphenylmethane diisocyanate) (Main component of moisture-curing reaction-type hot melt adhesive) Further, these hot melt adhesives solidified faster, and in this embodiment, solidified in about 50 seconds, and came out of the voice coil positioning gauge. This is 12 hours for the conventional chloroprene phenolic adhesive, 6 hours for the epoxy resin adhesive, and 15 hours for the acrylic resin adhesive.
It is much shorter than minutes. This eliminates the need to remove the speaker from the line once it is cured, such as with chloroprene phenolic adhesives or epoxy resin adhesives, in the speaker production line.
Unlike the acrylic adhesive, there is no need to provide a curing step on the line, and the manufacturing time is reduced.

In the above embodiment, the bonding between the diaphragm and the voice coil has been described as an example. However, the bonding strength between the diaphragm and the edge, and between the diaphragm and the dust cap can be increased by the same method. Also, when the frame of the speaker is made of polypropylene or the like, the bonding strength can be structured by irradiating the bonding portion such as the edge or the damper with ultraviolet rays.

Effect of the Invention As described above, ultraviolet irradiation is performed before bonding the vibration system component or the support system component thereof in the speaker, and a resin layer of a polymer having an isocyanate group is provided and bonded, or a moisture curing reaction type is used. By bonding with a hot-melt adhesive, a large adhesive strength can be obtained, thereby providing a high-quality speaker with strong adhesive strength.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between an ultraviolet irradiation time and a contact angle with water.

Claims (2)

(57) [Claims] An ultraviolet ray is radiated before bonding the vibration system component and the support system component in the speaker, and after the ultraviolet irradiation, a resin layer mainly composed of a polymer having an isocyanate group at a molecular terminal is provided to perform the bonding. Speaker manufacturing method. 2. A method for manufacturing a speaker, comprising irradiating an ultraviolet ray before bonding the vibration system component and the support system component in the speaker, and performing the above-mentioned bonding with a moisture-curing reaction type hot melt adhesive after the ultraviolet irradiation.