JP3055712B2 - Speaker diaphragm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker diaphragm having excellent acoustic characteristics.

[0002]

2. Description of the Related Art The acoustic characteristics of an electroacoustic transducer represented by an electrodynamic loudspeaker mainly depend on the physical characteristics of a vibration system. Above all, the diaphragm is an important member that greatly affects the performance of the speaker.

As shown in FIG. 1, for example, the diaphragm 10 is formed in a cone shape, and the periphery of the edge 11 is fixed to a speaker frame 20 by a gasket 21. A center cap 30 is arranged in the center of the inside of the diaphragm 10, and a voice coil 32 is wound around a coil bobbin 31. A magnetic circuit is formed by the center pole 41, the yoke 42, the magnet 43, and the plate 44 housed in the coil bobbin 31, and the voice coil 32 is movable in the middle of the magnetic circuit, that is, between the center pole 41 and the plate 44. To place. Reference numeral 12 indicates a damper.

The materials used for the diaphragm 10 and the center cap 30 incorporated in the speaker are required to have the following characteristics. The density ρ must be small in order to improve efficiency. A large specific elastic modulus E / ρ in order to widen the reproduction band. Have moderate internal loss to dampen resonance and flatten sound pressure frequency characteristics.

As materials satisfying these required characteristics,
Pre-preg sheet moldings such as cross carbon, polypropylene-based sheet moldings, and polypropylene-based injection moldings have come to be used as alternatives to conventional paper and pulp. .

[0006]

The molded articles of prepreg sheets represented by cross carbon, molded articles of polypropylene sheets, injection molded articles, and the like are required characteristics of recent digitization as compared with paper and pulp. It can be said that the diaphragm material satisfies the following. However, these materials each have advantages and disadvantages, and there is room for improvement in density ρ, specific elastic modulus E / ρ, internal loss, and the like.

For example, a molded product of a prepreg sheet is:
Although having excellent rigidity, the density ρ is large and the internal loss is small. In the case of molded products such as polypropylene sheets,
In order to increase rigidity more than paper, pulp, etc., it is necessary to mix carbon fiber, mica, whisker, and the like. However, this formulation increases the density. Moreover,
Polypropylene sheets have the fatal disadvantage of being vulnerable to heat.

On the other hand, a conventional diaphragm made of paper, pulp or the like has a low density, and has an appropriate rigidity and an internal loss. In addition, since it is manufactured by papermaking, the degree of freedom in material selection is excellent. For this reason, diaphragms of this type are still used today. However, a diaphragm made of paper, pulp, or the like is susceptible to humidity. For example, a loudspeaker that is compatible with digital cannot respond to the stiffness of pulp alone. In order to solve this drawback, it has been proposed to mix carbon fibers and aramid fibers into paper, pulp and the like in JP-A-61-245791 and JP-A-61-2.
No. 45797 and the like. However, since carbon fibers, aramid fibers and the like do not have a self-bonding force, the more these fibers are blended, the lower the Young's modulus of the diaphragm tends to be.

The present invention has been devised to solve such a problem. When inorganic fibers, organic synthetic fibers, inorganic scaly substances and the like are made into a speaker diaphragm by papermaking, the bast fiber is used. By using fine fibers as a binder, it is excellent in density, specific elastic modulus, heat resistance, moisture resistance, etc.
It is an object of the present invention to provide a speaker diaphragm having an appropriate internal loss.

[0010]

SUMMARY OF THE INVENTION A speaker diaphragm according to the present invention is provided with a wood pulp, a bast,
It is characterized by being obtained by forming a blend of a raw material suspension mainly composed of seed wool fibers and the like and highly fibrillated bast fiber fine fibers.

As the raw material suspension, an inorganic fiber, an organic synthetic fiber or a blend of these fibers, a raw material suspension mainly composed of flaky inorganic substances, and the like are also used. Alternatively, two or three of these raw material suspensions may be blended and blended with highly fibrillated bast fiber fine fibers. Further, a thermoplastic resin or a thermosetting resin may be attached to the formed diaphragm. The diaphragm of the present invention is used as the diaphragm 10, the center cap 30, and the like shown in FIG.

[0012]

[Action] As the microfibrillated cellulose-based binder, not only bast fiber but also wood pulp as a starting material may be used. However, when wood pulp is used as a starting material, it takes a long time to fibrillate to a predetermined beating degree.

As shown in FIG. 2, the wood fiber is a primary film S
Have internal tissue C consisting of the secondary layer S ₂ wrapped in _one. Secondary film S ₂ is the outer layer S _21, the intermediate layer S ₂₂ and the inner layer S
_{It has 23} three-layer structures. When beating wood fibers having this fiber structure with a defibrating machine such as a beater, the degree of beating is set to 30 ° ^SR or less in consideration of water retention. Under these conditions,
With the removal of the primary membrane S _1, a secondary film S ₂ of swelling and partial fibrillation is carried out. However, in wood fibers, the angle at which the fibrils are wound with respect to the fiber longitudinal direction is large, and the fibers tend to be cut before being fibrillated. Therefore, as the degree of beating is increased, the fiber form is broken.

On the other hand, in bast fibers such as manila hemp, mitsumata, sisal hemp, flax, jute, ramie, ganpi, mulberry, mulberry, corn, sweet, bamboo, espart, etc., the cellulose fibers are oriented in the fiber longitudinal direction. Are running almost in parallel.
Therefore, when beating the bast fiber, longitudinal cracks are likely to occur,
Fibrillation proceeds. For example, flax pulp had a fiber form shown in Figure 7 while defibration, the fibers as shown in FIG. 8 with freeness 40 ° ^SR is beaten, further 9
At 0 ° ^SR , microfibrillation occurs as shown in FIG.
However, if the bast fiber is simply beaten with a beater or the like, a mixture of long fibers and short fibers is obtained, and the binder effect varies.

Therefore, the present inventors examined the effect of the fiber length on the fibrillated bast fiber. Flax highly fibrillated by a beater was converted to JIS P-8
207, a 20-mesh residue (second tank), a 28-mesh residue (third tank), 48
Mesh residue (fourth tank) and 300 mesh residue (fifth tank)
(Tank). The 20-mesh residue has a fiber length of about 1
~ 1.5mm, 28 mesh residue is about 0.7 ~ fiber length
1 mm, 48 mesh residue is about 0.3-0.7 fiber length
mm, the 300 mesh residue is about 0.05-0.
3 mm. Then, N.BKP was disintegrated and each of the classified portions was added at 10% by weight, and the physical properties were measured.

The measurement results are shown in FIG. 3 and FIG. FIG.
(A) to (d) show values obtained by measuring the density, Young's modulus, internal loss, and propagation velocity, respectively, by the vibration reed method. 4A to 4D are JIS P-8, respectively.
117 Air permeability measured by "Test method for air permeability of paper and paperboard", JIS P-8112 Burst resistance measured by "Test method for bursting strength of paper and paperboard with Mullen low-pressure tester", JIS P- 8114 "Folding strength test method for paper and paperboard using a shopper type tester" and JIS P-8113 "Test method for tensile strength of paper"
Shows the breaking length measured in.

F ₀ , F ₂₀ , F ₂₈ and F ₃₀₀ shown on the horizontal axis in FIGS. 3 and 4 were each obtained by disintegrating N.BKP, and 10 wt% of a 20 mesh residue was added thereto. 10% by weight of a 28-mesh residue, 10% by weight of a 48-mesh residue, and 10% by weight of a 300-mesh residue. The larger the mesh, the higher the fibrillation of flax pulp.

As is clear from FIGS. 3 and 4, short fibers have a larger binder effect. Moreover, despite the improvement in Young's modulus, the internal loss is almost constant. In this respect, a tendency different from that of a normal diaphragm material is shown in that the internal loss usually decreases as the Young's modulus increases. From this, it is meant that a material containing short fibers is most suitable as a material used for a speaker diaphragm.

Further, fibrillated flax pulp is added to N-UKP, N-BKP and BLT (linter) as a binder, and the blending amount is changed.
Physical properties were measured by the same test method. 5 and 6
Shows the measurement results. Natural fibers themselves have a self-binding force and exhibit predetermined physical properties and strength. However, it is shown in FIG. 6 that when the fibrillated flax pulp is added as a binder, the strength is further improved.

From the above, when the bast fiber is used as a binder, the preferable fiber length is 48 to 30.
It can be seen that the residue of 0 mesh is more effective.
However, from the viewpoint of cost, it is advantageous to use one having a residue of 20 to 300 mesh.

The comparison of the physical properties in FIG. 5 and FIG.
Natural fibers such as KP, N-BKP and BLT (linter) are used. However, since the fibrillated bast fiber has a large entangled fiber form, it has a binder for various fibers such as aramid, nylon, acrylic, polyester, aromatic polyester, carbon, glass, phenol, ceramics, etc., which do not have a self-binding force. Is also effective. Therefore, a wide range of fiber materials can be used, and the fibers can be arbitrarily blended, so that a new speaker diaphragm that has never existed before can be obtained.

Mica, carbon graphite, various whiskers, etc. can be mixed at a high yield by entanglement of microfibrils and mechanical filtration. Furthermore, when an additive such as polyacrylamide that neutralizes the surface charge is added during papermaking, the yield is further improved.

The rigidity, Young's modulus, density, etc. of the diaphragm can be adjusted as appropriate by attaching a thermoplastic resin, a thermosetting resin, or the like to the diaphragm. These resins can be attached to the diaphragm by immersing the diaphragm in a resin solution dissolved or suspended in a solvent, or spraying the resin liquid on the diaphragm.

[0024]

The present invention will be specifically described below with reference to examples. Table 1 shows the mixing ratio of the material for manufacturing a diaphragm using, as a binder, fine fibers obtained by fibrillating bast fibers. The binder fibers in Table 1 are fine fibers obtained by fibrillating bast fibers.

[0025]

[Table 1]

Further, those obtained by impregnating Examples 1 to 10 with an acrylic resin were prepared as Examples 11 to 20, and those obtained by impregnating with an epoxy resin were prepared as Examples 21 to 30. The epoxy resins in Examples 21 to 30 and Comparative Example 3 were cured by a heat treatment held at 210 ° C. for 2 minutes.

Tables 2 to 4 show the properties of the diaphragm obtained by paper-making these compounds.

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

As is apparent from Tables 2 to 4, the diaphragms according to the embodiments of the present invention exhibit excellent characteristics in density, Young's modulus, internal loss, and the like. Also, by using fibrillated bast fiber as a binder,
It has also become possible to produce synthetic fibers and inorganic fibers, which have conventionally been considered impossible materials.

By selecting this material, the diaphragms of Examples 1 to 8 and 10 have weather resistance and good flame retardancy. Further, when an acrylic resin or an epoxy resin having excellent flame retardancy was used as the acrylic resin or the epoxy resin used in Examples 11 to 20 and 21 to 30, or when an acrylic resin or an epoxy resin subjected to a flame retarding treatment was used, 11 to 30 can be a diaphragm excellent in flame retardancy.

Further, when the diaphragms of Examples 1 to 8, 10, 21 to 28 and 30 are treated with a heat-resistant resin such as a phenol resin or a melamine resin in addition to the epoxy resin, heat resistance and moisture resistance are obtained. Etc. can also be given.

[0033]

As described above, according to the present invention, by using fibrillated bast fibers as a binder, various fibers can be blended and formed into a speaker diaphragm. Taking advantage of flame retardancy, TV,
It can be used safely near a power source such as a radio. In addition to the diaphragm, it can be provided to the market as various prepreg materials.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of an electrodynamic speaker.

Fig. 2 Model showing the fiber structure of wood fiber

Fig. 3 Fiber length of fibrillated flax pulp is N-
Graph showing the effect of BKP on physical properties

Fig. 4 Fiber length of fibrillated flax pulp is N-
Graph showing the effect of BKP on other physical properties

FIG. 5 shows that the blending ratio of fibrillated flax pulp is N
-Graph showing the effect of BKP on physical properties

FIG. 6 shows that the blending ratio of fibrillated flax pulp is N
-Graph showing the effect of BKP on other physical properties

FIG. 7 is a photograph showing the fiber shape of disintegrated flax pulp.

FIG. 8 is a photograph showing the fiber shape of flax pulp fibrillated at a beating degree of 40 ° ^SR.

Fig. 9 48 fibrillated at a beating degree of 90 ° ^SR or more
Photograph showing the fiber shape of flax pulp with ~ 300 mesh residue

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-53995 (JP, A) JP-A-62-230298 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04R 7/02 H04R 31/00

Claims (5)

(57) [Claims] The present invention is characterized in that it is obtained by forming a blend of a raw material suspension mainly composed of wood pulp, bast, seed hair fiber and the like, and a highly fibrillated bast fiber fine fiber. Speaker diaphragm. 2. A loudspeaker characterized in that the loudspeaker is obtained by paper-making a blend of inorganic fibers, organic synthetic fibers or a raw material suspension obtained by blending these fibers with highly fibrillated bast fibers. Diaphragm. 3. A speaker diaphragm obtained by forming a mixture of a raw material suspension mainly composed of scale-like inorganic substances and highly fibrillated bast fiber fine fibers. 4. A raw material suspension according to claim 1, 2 or 3 kinds of which are blended, and a blend of highly fibrillated bast fibers is blended with the raw material suspension. A speaker diaphragm obtained as described above. 5. A diaphragm for a speaker, wherein a thermoplastic resin or a thermosetting resin is adhered to the diaphragm for a speaker according to any one of claims 1 to 4.