JPH08275292A - Voice coil bobbin - Google Patents

Abstract

PURPOSE: To provide a voice coil bobbin using wooden pulp fibers, high in stiffness and light in weight, by using cellulose fibers having high crystallinity and a structure the same as wood pulp fibers as a binder. CONSTITUTION: A cellulose extracted by a wood or other plant, microorganism or animals is solved by a solvent made of an amine oxide, the solution is spinned and solidified by the air gap system to obtain recycled cellulose short fibers and wooden pulp fibers. Preferably the short fibers are mixed with the wooden pulp fibers by 5 to 15%. The fiber length of the short fibers is 1 to 4mm. In this case, the air-gap system is a spinning method in which air at a somewhat high temperature than a boiling point of the solvent is blown to the spinning liquid extracted from a thin spinning port to evaporate the solvent. Thus, the recycled cellulose fibers are made short and blended to the wooden pulp fibers and paper-made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice coil bobbin used in a speaker, and more particularly to an improvement of a voice coil bobbin using wood pulp fiber.

[0002]

2. Description of the Related Art As is well known, a voice coil used for a speaker is a functional component that faithfully operates on a voice current output from an amplifier to vibrate a diaphragm. Therefore, the characteristics of the voice coil bobbin are one of the important factors that determine the performance of the speaker.

The characteristics of the voice coil bobbin are required to have high rigidity in order to drive the diaphragm accurately and stably and be lightweight in order to increase the efficiency of the speaker.

In order to meet such demands, various materials such as kraft paper, metal foil, and polymer film have been developed and used in the voice coil bobbin, but they have been widely used as the leading role until now. For the reason that the balance between rigidity and weight is appropriate, and because of cost reasons, the one that uses paper for the vibration plate is often used, and this is the same as the vibration plate of this paper (because it is made of the same material). Because of the mutual adhesiveness,
It is a voice coil bobbin using kraft paper.

[0005]

As described above, the voice coil bobbin made of such conventional kraft paper has an excellent balance between rigidity and weight as compared with other voice coil bobbin materials. As for the voice coil bobbin, it cannot be said that the voice coil bobbin has sufficient rigidity.

The rigidity of the voice coil bobbin made of the kraft paper will be described in detail. The kraft paper is made of wood pulp fibers. However, the wood pulp fibers have a small degree of crystallinity, and therefore the elastic modulus is high. It is low and therefore less rigid.

As an example of such kraft paper with improved rigidity, there is a voice coil bobbin prepared by adding a binder such as aramid fiber or glass fiber to wood pulp fiber. However, in such a voice coil bobbin, the weight is increased by adding the binder, and the resin for bonding the wood pulp fiber and the binder is required due to the difference in the material between the binder and the wood pulp fiber. There is a new problem that the weight increases.

In view of the above, the present invention solves the above-mentioned drawbacks of the conventional example, and uses a cellulose fiber having the same structure as wood pulp fiber and high crystallinity as a binder in a voice coil bobbin using wood pulp fiber. An object of the present invention is to provide a voice coil bobbin with high rigidity and light weight by using it.

[0009]

The voice coil bobbin according to the present invention for achieving the above object is obtained by dissolving cellulose extracted from wood or other plants, microorganisms, animals, etc. in a solvent consisting of amine oxide. Of the regenerated cellulose fiber obtained by spinning and coagulating by a air gap method, and a wood pulp fiber. Further, the short fiber is 5 to 15 relative to the wood pulp fiber. %, And the fiber length of the short fibers is 1 to 4 mm.

[0010]

In the voice coil bobbin of the present invention, cellulose extracted from wood or other plants, microorganisms, animals, etc. is dissolved in a solvent consisting of amine oxide. This amine oxide has a property of being easily volatilized in air and having excellent solubility of cellulose. A regenerated cellulose fiber is obtained by spinning the solution by an air gap method (dry spinning) and coagulating it. This air gap method is a spinning method in which the spinning liquid extruded from a thin spinning port is blown with air at a temperature somewhat higher than the boiling point of the solvent to evaporate the solvent. By the spinning by the air gap method, the solvent (amine oxide) in which the cellulose molecules are dispersed is volatilized, and the intermolecular force between the cellulose molecules is increased. The spun cellulose in this state is stretched in the coagulation bath. In this air gap method and coagulation bath process, crystals inside the fibers grow and regenerated cellulose fibers with high crystallinity are obtained. The voice coil bobbin of the present invention can be obtained by shortening this regenerated cellulose fiber, mixing it with wood pulp fiber and making a paper.

In the voice coil bobbin of the present invention having such a structure, since the regenerated cellulose short fiber obtained in the above-mentioned step is rigid and has a high crystallinity, the wood pulp fiber can be added by adding it. The entanglement between the wood pulp fibers that occurred when composed only of fibers is relaxed, the bonding area of the fibers is reduced and the gap between the fibers is increased, which is composed only of conventional wood pulp fibers.
That is, the density is smaller than that of the voice coil bobbin made of kraft paper. Here, to explain the entanglement of the wood pulp fibers described above, since the wood pulp fibers have a small crystallinity of the fibers themselves, curling and twisting of the fibers in the pulp slurry are likely to occur, and the fibers are composed of only this. It becomes easy to get entangled. In the present invention,
The stiffness of the regenerated cellulose fibers alleviates this entanglement.

In the voice coil bobbin of the present invention, since the bonding area of the fibers is reduced, the elastic modulus due to this bonding area is reduced, but due to the high elastic modulus of the regenerated cellulose fiber itself having high crystallinity. The elastic modulus of the voice coil bobbin is relatively large.

Further, with respect to the rigidity of the voice coil bobbin, since the rigidity is proportional to the elastic modulus multiplied by the cube of the thickness, the density of the voice coil bobbin of the present invention is higher than that of the conventional voice coil bobbin made of kraft paper. Is small, the thickness can be increased and the rigidity can be increased when the weight is constant. Further, when the two have substantially the same rigidity, the voice coil bobbin of the present invention is lighter in weight.

In such a voice coil bobbin, the mixed paper amount of the regenerated cellulose short fibers is preferably 5 to 15% with respect to the wood pulp fibers. When it is less than 5%, the action and effect of the present invention is hard to be exhibited, and when it is 15% or more, the binding force of the regenerated cellulose fiber to wood pulp is not so strong (although stronger than inorganic fiber, organic fiber, etc.). It becomes difficult to obtain sufficient strength. Also,
The fiber length of the regenerated cellulose fiber is preferably 1 to 4 mm from the characteristics obtained in the experiment, and the most preferable characteristic of the voice coil bobbin is that the density and elasticity are well balanced.

[0015]

EXAMPLES Examples of the present invention will be described in detail.

14 g of a hydrate of cyclic amine oxide N-methylmorpholine-N-oxide (the structural formula is shown in FIG. 1), 80 mg of n-propyl gallate, and 1 g of cellulose (dissolving pulp). Was charged into a 300 cc Erlenmeyer flask, stirred at 100 ° C. for 10 minutes under a vacuum of 15 mmHg, and then immersed in an oil bath at 130 ° C. for 5 minutes under atmospheric pressure,
The contents were taken out. Here, n-propyl gallate serves as an antioxidant to stabilize the degree of polymerization of the dissolving pulp during the reaction, and gallate specifically includes zinc, aluminum, and second Metal salts such as mercury and ferric iron.

Thereafter, the contents are maintained at 100 ° C.,
Spinning was performed using a spinning device (schematically shown in FIG. 2) using a 20 μm spinneret to obtain a 10 μm yarn. Here, the air gap from the die to the coagulation bath was 10 cm, the winding linear speed was 100 m / min, and a 2 m water bath was used as the coagulation bath. The wound yarn was washed with water for 24 hours, dried, and cut into a predetermined length. [Examples 1, 2, 3] Unbleached wood pulp was beaten to CSF of 400 to 450 cc with a steel beater, and the wood pulp fiber obtained from this was regenerated by cutting the above yarn into 3 mm. 5% fiber in Example 1,
In Example 2, 10% was added, and in Example 3, 15% was added.
A flat sheet was prepared according to SP8209. This sheet was cut into a predetermined size to produce a voice coil bobbin. [Examples 4 and 5] Unbleached wood pulp was beaten to a CSF of 400 to 450 cc with a steel beater, and the wood pulp fiber obtained therefrom was mixed with 1 m of the above yarn.
In Example 5, 5% of regenerated cellulose fiber obtained by cutting into 4 mm was added, and a flat sheet was prepared according to JIS P8209. This sheet was cut into a predetermined size to produce a voice coil bobbin. [Comparative Example] Using a wood pulp fiber obtained by beating unbleached wood pulp with a steel beater to a CSF of 400 to 450 cc, a flat sheet was prepared according to JIS P8209. This sheet was cut into a predetermined size to produce a voice coil bobbin.

Table 1 shows the characteristics of the voice coil bobbins of Examples 1 to 5 and Comparative Example.

[0019]

[Table 1] As is clear from Table 1, the voice coil bobbin of the example has a low density and a high elastic modulus or is equivalent to that of the conventional voice coil bobbin composed only of wood pulp fibers. Therefore, with respect to the rigidity of the voice coil bobbin, since the voice coil bobbin of the present invention has a lower density, the thickness can be increased when the weight is constant, and the rigidity is increased. Further, when the rigidity of both is substantially the same, the voice coil bobbin of the present invention is lighter in weight.

Further, comparing the respective examples, it can be seen that when the added regenerated cellulose fibers have the same fiber length, the density and elastic modulus decrease as the addition amount increases, but within this range. It can be said that the properties are properly balanced in the addition amount of each. However, if it is below this range, the effect is difficult to be exhibited, and if it is above this range, it becomes difficult to obtain sufficiently satisfactory strength. Regarding the fiber length of the regenerated cellulose fiber, the one having a fiber length of 3 mm has the highest elastic modulus, and the balance between the density and the elastic modulus is most appropriate.

The voice coil bobbin according to the present invention has been described above in detail with reference to the representative examples. In the embodiment of the voice coil bobbin according to the present invention, for example, amine oxide is N-methylmorpholine-N-oxide. It is not limited to the structure of the above embodiment, such as dimethylethanolamine-N-oxide, but it has the constituents described in the above-mentioned claims and functions according to the present invention. The present invention can be appropriately modified and carried out as long as it has the following effects.

[0022]

[Effect] In the voice coil bobbin according to the present invention, cellulose extracted from wood or other plants, microorganisms, animals, etc. is dissolved in a solvent consisting of amine oxide, and the solution is spun by an air gap method to coagulate. Since the short fibers of the obtained regenerated cellulose fiber are rigid and have high crystallinity and are used as the binder of the wood pulp fiber, they have the following effects. (1) Entanglement of wood pulp fibers is alleviated due to the rigidity of the regenerated cellulose fibers, the bonding area of the fibers is reduced, the density is reduced, and the weight of the voice coil bobbin can be reduced. (2) Since the regenerated cellulose fiber has a high degree of crystallinity and a high elastic modulus, the elastic modulus is relatively large and the density is small, so that the rigidity can be improved.

This makes it possible to construct a voice coil that drives the diaphragm accurately and stably and improves the efficiency of the speaker.

[Brief description of drawings]

FIG. 1 is a diagram showing a structural formula of N-methylmorpholine-N-oxide, which is an amine oxide used in a voice coil bobbin of Examples.

FIG. 2 is a diagram illustrating a spinning device used in the voice coil bobbin of the embodiment.

Claims (3)

[Claims] 1. A short pulp of regenerated cellulose fibers obtained by dissolving cellulose in a solvent containing amine oxide, spinning the solution by an air gap method, and coagulating the solution, and a wood pulp fiber. Characteristic voice coil bobbin. 2. The short fibers are wood pulp fibers,
The voice coil bobbin according to claim 1, wherein the paper is mixed in an amount of 5 to 15%. 3. The voice coil bobbin according to claim 1, wherein the short fibers have a fiber length of 1 to 4 mm.