JP3531276B2 - Sound radiation plate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic radiation plate used in an electroacoustic transducer such as a speaker, and more particularly to improvement of an acoustic radiation plate using wood pulp fibers.

[0002]

2. Description of the Related Art As is well known, materials for diaphragms used in electroacoustic transducers such as speakers are: (1) Low density (ρ) and high elastic modulus (E) in order to increase the output level of the speaker. Is large, that is, the specific elastic modulus (E / ρ) is large,
Physical properties are required such as (2) a large elastic modulus to widen the reproduction band of the speaker, and (3) a relatively large internal loss to reduce distortion due to the divided vibration of the diaphragm. Further, since the dust cap of the speaker is used not only for the dustproof effect on the magnetic circuit but also for the high frequency reproduction of the speaker, the above characteristics are required.

In order to meet such requirements, various materials have been developed and used for the acoustic radiation plate, but those generally used as the leading role until now are those having a proper balance of characteristics and cost. For acoustic reasons, it is an acoustic radiation plate using wood pulp fibers.

A conventional acoustic radiation plate using wood pulp fibers is formed of pulp fibers alone, and MFC (microfibrillated cellulose:
The following are shown as such).

[0005]

Generally, an acoustic radiation plate using wood pulp fibers has a shape of acoustic radiation plate in a suspension in which pulp fibers obtained by beating a wood pulp sheet are dispersed. It is produced by installing a wire mesh and making paper.However, in the conventional acoustic radiation plate using only wood pulp fibers, it is difficult to control the wood pulp fibers in the water flow, and the fibers are dispersed uniformly. It is difficult to obtain a sound radiation plate that is in use, and it is necessary to adjust the water flow velocity and the suspension concentration based on the experience of a skilled engineer.

The reason why it is difficult to uniformly disperse the wood pulp fibers will be described in detail. When the acoustic radiation plate is made from the wood pulp fibers alone, the wood pulp fibers have a small crystallinity. In the pulp slurry, curling and twisting of the fibers are likely to occur, and the fibers are easily entangled with each other, so that flocs (in other words, fiber agglomeration) become large, which causes unevenness in papermaking. Therefore, when the acoustic radiation plate is made from wood pulp fibers alone, it is necessary to adjust the flow velocity of the water flow and the concentration of the suspension very delicately in order to make the fibers uniform.

Further, the acoustic radiation plate composed of fibers dispersed non-uniformly leads to instability of characteristics such as density, specific elastic modulus, rigidity, etc. and is stable (of the acoustic radiation plate itself).
Performance cannot be obtained.

Further, in an acoustic radiation plate containing only wood pulp fibers, even if the wood pulp fibers are dispersed uniformly, the fibers themselves still have entanglement due to the small crystallinity of the fibers themselves as described above. Therefore, the bonding area of the fibers becomes large, and the density becomes large. Since the wood pulp fiber itself has a low degree of crystallinity, the elastic modulus is also low, resulting in a low specific elastic modulus.

In recent years, wood pulp fibers and MFC have been used as an acoustic radiation plate that solves the problems of elastic modulus and specific elastic modulus.
An acoustic radiation plate that is a mixture of and is used. Specifically, from the problem of papermaking, about 1 to 10% of MFC is added to wood pulp fibers. MFC is made by extruding pulp at a high pressure between narrow slits of a cylinder having a difference in inner and outer diameters. It is fibrillated to submicron and has an ultrafine fiber length of 0.2 to 0.3 mm. It is a fiber.

Since the added MFC is the above-mentioned ultrafine fibers, it is buried in the gaps between the wood pulp fibers, so that in this acoustic radiation plate, the bonding area between the wood pulp fibers and the MFC becomes large, that is, as a whole. Has a large bonding area and a high elastic modulus. Furthermore, microscopically speaking, MFC has a large number of OH groups because it is fibrillated, and the large number of OH groups hydrogen-bonds with the OH groups of the wood pulp fiber, resulting in a larger bonding area and improved elastic modulus. To do. Further, in this acoustic radiation plate, since the wood pulp fibers are attracted to the MFC by hydrogen bonding, the entanglement between the pulp fibers is eliminated to some extent, and an acoustic radiation plate in which the fibers are relatively uniformly dispersed can be obtained. Therefore, the difficulty of adjustment at the time of papermaking is alleviated.

However, such wood pulp fibers and MF
In the acoustic radiation plate mixed with C, since the coupling area is large, the gap between the fibers is small, the loss of vibration transmission due to this gap is small, and the internal loss is small. For this reason, such an acoustic radiation plate has a drawback that a peak dip occurs at a high frequency, which causes a listener annoyance.

[0012] In addition, in addition, as a material in which the elastic modulus of the acoustic radiation plate using wood pulp fibers is improved, there are wood pulp fibers mixed with various binders. Due to the difference in material, the sound quality was uncomfortable.

In view of the above, the present invention solves the above-mentioned drawbacks of the conventional example, and mixes a cellulose fiber having a high degree of crystallinity as a binder with an acoustic radiation plate using wood pulp fibers to obtain a specific elastic modulus, It is an object of the present invention to provide an acoustic radiation plate that has a large loss, the fibers are uniformly dispersed, the performance is stable, and the workability during papermaking is excellent.

[0014]

The acoustic radiation plate according to the present invention for achieving the above object is obtained by dissolving cellulose extracted from wood and other plants, microorganisms, animals, etc. in a solvent consisting of amine oxide. It is characterized in that it is composed of short fibers of regenerated cellulose fibers obtained by spinning the solution by an air gap method and coagulating, and wood pulp fibers, and the short fibers are 5 to 5 times the wood pulp fibers. It is characterized in that it is mixed by 15% and the fiber length of the short fibers is 1 to 4 mm.

[0015]

In the acoustic radiation plate of the present invention, wood and other plants,
Cellulose extracted from 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, coagulation bath process,
Crystals inside the fibers grow to obtain regenerated cellulose fibers with high crystallinity. By shortening this regenerated cellulose fiber and mixing with wood pulp fiber to make paper,
The acoustic radiation plate of the present invention is obtained. For reference, rayon, which is known as regenerated cellulose fiber, is obtained by a wet spinning method in which a spinneret is in a coagulation bath and the fiber is coagulated in the coagulation bath. In this spinning method, carbon disulfide and dilute sulfuric acid are used as a solvent, and these are sensitive to oxygen and easily oxidatively decomposed. Also, in this spinning method, solution removal, lubrication, drawing, etc. are carried out by simultaneous reaction in a coagulation bath. Therefore, the rayon obtained by this spinning method has a low degree of polymerization, the crystals inside the fiber do not grow much, and the degree of crystallinity is low.

In the acoustic radiation plate of the present invention having such a structure, since the regenerated cellulose short fiber obtained in the above-mentioned step has rigidity and high crystallinity, the wood pulp fiber is added with the regenerated cellulose short fiber. The entanglement of pulp fibers is alleviated, resulting in an acoustic radiation plate with few flocs and fibers uniformly dispersed. Therefore, the difficulty of adjustment during papermaking is eliminated.

Further, in this acoustic radiation plate, since the entanglement of the wood pulp fibers is relaxed, the bonding area of the fibers is reduced, the gap between the fibers is increased, the density is reduced, and the gap between the fibers is reduced. As a result, vibration transmission is hindered, loss increases, and internal loss increases. By reducing the bonding area, the elastic modulus due to the bonding area is reduced, but the elastic modulus of the acoustic radiation plate as a whole is relatively large due to the high elastic modulus of the regenerated cellulose fiber itself having high crystallinity, As described above, since the density is small, the specific elastic modulus is large.

In such an acoustic radiation plate, the amount of the regenerated cellulose short fibers mixed is 5 to wood pulp fibers.
It is preferably 15%. When it is less than 5%, the action and effect of the present invention is difficult 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. In addition, the fiber length of the regenerated cellulose fiber is 1 to 1 according to the characteristics obtained in the experiment.
4 mm is preferable, and the most preferable characteristics of the acoustic radiation plate are well balanced in density, specific elastic modulus and internal loss.
mm.

[0019]

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

14 g of 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,
An acoustic radiation plate was produced by adding 10% in Example 2 and 15% in Example 3 and papermaking these. [Examples 4 and 5] Unbleached wood pulp was beaten to 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.
m, in Example 5, 5% of regenerated cellulose fiber obtained by cutting into 4 mm was added, and these were made into paper to prepare an acoustic radiation plate. Comparative Example Wood pulp fibers were obtained by beating unbleached wood pulp with a steel beater up to CSF 400 to 450 cc. An acoustic radiation plate was produced by making the wood pulp fibers into paper and further making paper by adding 1, 5, 10% of MFC to the wood pulp fibers.

Next, Table 1 shows the characteristics of the acoustic radiation plates of Examples 1 to 5 and Comparative Example. Here, each characteristic is based on JIS
It is a sheet manufactured according to P8209 and having the same configuration as the acoustic radiation plates of Examples 1 to 5 and Comparative Example.
In addition, Table 1 also shows the characteristics of the sheet obtained by adding 5, 10 and 15% of rayon having a fiber length of 3 mm to the wood pulp fibers used in Examples and Comparative Examples (also according to JIS P8209). It is shown as a reference example.

[0023]

[Table 1] As is clear from Table 1, the acoustic radiation plate of the example has a lower density and a higher elastic modulus or has a specific elasticity as compared with a conventional acoustic radiation plate composed of wood pulp fibers alone. The rate is increasing. And the internal loss has also improved significantly. Further, compared with an acoustic radiation plate in which wood pulp fibers and MFC are mixed and mixed, the density is low and improved, but the elastic modulus is low, so that the specific elastic modulus is lower in some cases. However, the internal loss is quite high and has improved significantly.

Further, comparing each example, when the added regenerated cellulose fibers have the same fiber length, the density and elastic modulus decrease and the internal loss increases as the addition amount increases. As can be seen, it can be said that the addition amount within this range appropriately balances the properties. 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 specific elastic modulus, and the balance of the elastic modulus, the specific elastic modulus and the internal loss is most suitable.

The acoustic radiation plate according to the present invention has been described above in detail with reference to the typical examples. In the acoustic radiation plate according to the present invention, for example, amine oxide is N-.
It is not limited to the structure of the above-mentioned examples, such as not only methylmorpholine-N-oxide but also dimethylethanolamine-N-oxide, and the constitutional requirements described in the above-mentioned claims are provided. However, as long as it exhibits the action referred to in the present invention and has the effects described below,
It can be appropriately modified and implemented.

[0026]

[Effect] In the acoustic radiation plate 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 regenerated cellulose fiber obtained by the method have rigidity and high crystallinity and are used as the binder of the wood pulp fiber, they have the effects described below. (1) Entanglement of wood pulp fibers is relaxed due to the rigidity of the regenerated cellulose fibers, and the fibers are uniformly dispersed with less flocs, resulting in a sound radiation plate with stable performance. Further, therefore, the difficulty of adjustment during papermaking is eliminated and workability is excellent. (2) Since the entanglement between the wood pulp fibers is relaxed, the coupling area of the fibers is reduced, and the acoustic radiation plate with large internal loss is obtained, and the peak dip at the high frequency due to the split resonance is eliminated and the listener can hear it. Does not cause an offensive sensation. (3) Since the bonding area of the fiber is small, the density is low,
Since the regenerated cellulose fiber has a high degree of crystallinity and a high elastic modulus, the elastic modulus is relatively large, so that the acoustic radiation plate has a large specific elastic modulus and improves the efficiency of the electroacoustic transducer.

[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 an acoustic radiation plate of an example.

FIG. 2 is a diagram illustrating a spinning device used in the acoustic radiation plate of the embodiment.

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Claims (3)

(57) [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 acoustic radiation plate. 2. The short fibers are wood pulp fibers,
The acoustic radiation plate according to claim 1, wherein the paper is mixed in an amount of 5 to 15%. 3. The acoustic radiation plate according to claim 1 or 2, wherein the fiber length of the short fibers is 1 to 4 mm.