JP2953743B2 - Acoustic diaphragm and manufacturing method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic diaphragm used for a loudspeaker and the like and a method for producing the same, and particularly to an acoustic diaphragm using microfibrillated cellulose and a method for producing the same. It is about the method.

[Summary of the Invention]

An object of the present invention is to provide an acoustic diaphragm excellent in physical properties such as Young's modulus and tensile strength by making microfibrillated cellulose into paper.

Further, the present invention provides a paper made by reinforcing a microfibrillated cellulose with a reinforcing member placed on a papermaking net, thereby making it possible to handle even if the wet strength of the paper is low, and achieving excellent acoustic characteristics. This enables the plate to be manufactured with high productivity.

[Conventional technology]

Conventionally, cone paper made from pulp has been widely used for acoustic diaphragms such as speakers.

Corn paper is made through the process of beating pulp, dispersing the beaten pulp in water and swelling, and making the pulp dispersed in water into the required shape, etc. Dispersing the obtained pulp in water and making paper does not give a crisp feeling but also has a low strength and cannot be used as a diaphragm. This is because the fibers constituting the pulp and the fibers are not firmly fixed to each other.

The sticking force is obtained by softening the fibers and further loosening them to fibrils constituting the fibers, that is, performing so-called fibrillation to increase the number of contact points between the fibers and increase the hydrogen bonding.

Such mechanical fibrillation of the fiber is called beating, and is usually performed by a device called a beater.

Incidentally, the acoustic diaphragm is required to have a high longitudinal wave propagation speed (sound speed C), and therefore, a material having a small acoustic diaphragm and a large Young's modulus is advantageous.

The physical properties of cone paper, such as Young's modulus and tensile strength, are determined by the degree of beating as described above. In order to produce cone paper with a large Young's modulus, use cellulose with a high degree of beating that has been fibrillated as much as possible. There is a need.
That is, in the case of cone paper used as an acoustic diaphragm, it is considered that the higher the beating degree of cellulose used in papermaking, the higher the Young's modulus.

[Problems to be solved by the invention]

However, when the beating degree of cellulose used for making corn paper is high, the strength in the wet state during paper making is extremely reduced, and it is difficult to handle and maintain the shape. There is a risk that the shape will be lost when the transfer is made to a mold or the like.

In addition, cellulose tends to enter the paper net complicatedly, and if the paper (corn paper) is to be peeled off from the paper net after drying, an excessive force is applied at once due to the high rigidity of the paper net. There is a risk of damaging the paper.

Alternatively, if the sheet is formed into a desired shape by press working with a metal mold after the sheet is formed into a flat plate, there is a high possibility that breakage will occur due to local excessive force.

Therefore, although it is expected to be advantageous in terms of characteristics, it is difficult to make cellulose that has been highly fibrillated due to manufacturing problems into an acoustic diaphragm, and it is particularly difficult to form a thin diaphragm. Implementation is said to be very difficult.

Therefore, the present invention has been proposed in view of the above-described conventional circumstances, and has as its object to provide an acoustic diaphragm excellent in physical properties such as Young's modulus and tensile strength. A further object of the present invention is to make it possible to handle even a paper having low wet strength and to efficiently produce an acoustic diaphragm having a high Young's modulus made of microfibrillated cellulose.

[Means for solving the problem]

To achieve the above object, the acoustic vibration of the present invention is:
The present invention is characterized in that microfibrillated cellulose is made into a woven or nonwoven fabric and integrated therewith.

Further, the production method of the present invention, after the papermaking of the microfibrillated cellulose in a state where the reinforcing member for ensuring wet strength is placed on the papermaking net, the papermaking by papermaking the above-mentioned reinforcing member At the same time, it is removed from the papermaking net, formed into a diaphragm shape and dried.

In the present invention, cellulose used in papermaking,
Highly microfibrillated cellulose,
Here, cellulose having a Canadian standard freeness of 300 ml or less is used. The reason for setting the Canadian standard freeness to 300 ml or less is that if the Canadian standard freeness exceeds 300 ml, the Young's modulus of the acoustic diaphragm to be made is insufficient, and problems due to wet strength during paper making are reduced.

Examples of the cellulose having a Canadian standard freeness of 300 ml or less (hereinafter referred to as microfibril cellulose) include, for example, those obtained by mechanically beating pulp with a beater or the like. In this case, a Canadian standard freeness of 300 ml or less can be easily achieved by appropriately setting the beating conditions (for example, the beating time, the strength applied during the beating) by the beater.

Alternatively, bacterial cellulose produced microbiologically by culturing certain bacteria under predetermined conditions is also suitable.

The bacterial cellulose is composed of α-cellulose having high crystallinity, has extremely high strength due to extremely high surface orientation and the like, and has a very fine thickness of 200 to 500 °.

Acetic bacteria are typical of bacteria that produce bacterial cellulose. ventriculi), Bacterium xyloides, Acetobacter pasteurianus, Agrobacterium tumefacien
s), and Pseudomonas
as) and Rhizobium.

The above-described bacterial cellulose is obtained by a method of producing a gel-like substance having a certain thickness at the interface between the culture medium and the air, or by aeration-agitation culture method, and the obtained bacterial cellulose is disintegrated in water. Paper can be made.

In papermaking, carbon fibers and glass fibers, as well as polymer fibers such as aramid fibers, polyolefin fibers, ultra-stretched polyolefin fibers, and polyester fibers can be blended with the above-mentioned microfibril cellulose as a reinforcing material. Further, a paper additive such as a so-called sizing agent or a paste may be added as necessary.

On the other hand, the reinforcing member placed on the papermaking net is used to supplement the wet strength of the paper made of the microfibril cellulose, and is about 100 mesh (pore size 200 μm).
A woven or nonwoven fabric having a gap of about m) and having a certain degree of flexibility is suitable.

The material, thickness, etc. of these woven or non-woven fabrics are optional in the case where they are simply used to reinforce a paper-made product. May be selected according to the characteristics of the target acoustic diaphragm. In the case where the reinforcing member is simply used as a reinforcement for papermaking as described above, the reinforcing member, that is, the woven or nonwoven fabric is preferably a material that is easily peeled off from microfibril cellulose,
When integrated with the paper making of microfibril cellulose as it is, it is preferable that the material be easily adhered to microfibril cellulose and have high strength and high elastic modulus.

Specifically, woven or non-woven fabrics such as carbon fiber, glass fiber, polyester fiber, aramid fiber, and silk can be used, and the material may be selected from these considering the above requirements.

In the present invention, in order to make microfibril cellulose, first, as shown in FIG. 1, a papermaking net (2) is attached to the bottom of a papermaking machine (1), and the above-mentioned reinforcing member (3) is attached to the papermaking machine. It is placed on a net (2), and a suspension (4) in which microfibril cellulose is dispersed is supplied onto the net (2) to make a papermaking product (5).

Next, the papermaking product (5) is transferred to a drying step in order to dry the papermaking product (5). At this time, the papermaking product (5) made of microfibril cellulose is placed on the papermaking net (2) together with the reinforcing member (3). The process may be shifted to the drying step with the sheet placed, or may be taken out of the papermaking net (2) together with the reinforcing member (3), placed in another mold, and then shifted to the drying step. In the latter case, since the paper (5) made of microfibril cellulose is handled together with the reinforcing member (3), even if the wet strength of the paper (5) is low, there is little risk of breakage or deformation.

After drying, the reinforcing member is peeled off from the microfibril cellulose paper (cone paper), and only the paper made of the microfibril cellulose may be used as the acoustic diaphragm. A nonwoven fabric composite diaphragm may be used.

According to the above-mentioned method, the shape of the obtained cone paper is determined by the shape of the papermaking net (2). In the present invention, for example, after microfibril cellulose is made into a flat sheet, drawing is performed by a die or the like. It is also possible to give a desired shape.

In each case, a normal papermaking net (2) can be used. For example, a wire netting or a metal plate having been subjected to a punching process called punching is used.

[Action]

In the acoustic diaphragm of the present invention, since the cone paper is composed of microfibrillated cellulose, the number of contact points between fibers increases, hydrogen bonding increases, and physical properties such as Young's modulus and tensile strength increase. Can be Further, the mechanical strength is further improved by being integrated with the reinforcing member.

On the other hand, in the production method of the present invention, the microfibril cellulose is made on a reinforcing member placed on a papermaking net. Here, the paper made of microfibril cellulose has low wet strength, but is reinforced by the reinforcing member, so that it can be easily handled even in a wet state, and its shape is maintained.

Further, when the reinforcing member is peeled from the paper after drying, since the reinforcing member has flexibility, it can be gradually peeled off from the paper, and the paper (acoustic diaphragm) is inadvertently removed. No large force is applied.

〔Example〕

Hereinafter, specific examples to which the present invention is applied will be described.

Example 1 First, bacterial cellulose produced by acetic acid bacteria was disintegrated using a mixer, and then papermaking was performed on a papermaking wire mesh (11) to which a polyester fiber woven fabric (12) was attached as shown in FIG. 2A. A composite comprising cellulose (13) and woven fabric (12) was prepared. The papermaking conditions, the type of the polyester fiber woven fabric (12) as the reinforcing member, and the drying conditions are as follows.

Microfibril cellulose: Disintegration of bacterial cellulose produced by acetic acid bacteria Papermaking concentration: 1 g / Polyester fiber woven fabric: 100 mesh (pore size: 200 μm) NBC Industries, NO 120 S Drying conditions: Mold temperature 140 ° C., 5 minutes As shown in FIG. 2B, the cellulose (1
The composite formed of 3) and the woven fabric (12) is subjected to drawing by a mold (14A) having a hemispherical concave portion and a mold (14B) having a convex portion corresponding to the shape of the concave portion, Second
A dome-shaped composite diaphragm as shown in FIG. C was obtained.

Example 2 After performing papermaking and drawing under the same conditions as in Example 1, the woven polyester fiber fabric (12) was peeled off to obtain a dome-shaped diaphragm made of only cellulose (13).

Example 3 Softwood bleached kraft pulp (NBKP) was beaten to a Canadian standard freeness of 300 ml with a Hollander beater, followed by papermaking and drawing in the same manner as in Example 1, and a dress made of cellulose and polyester fiber woven fabric. A diaphragm was obtained.

In Examples 1 and 3 described above, in order to improve the adhesion between cellulose and the polyester fiber woven fabric, a binder (Nipol latex, manufactured by Zeon Corporation) was used for the cellulose suspension before papermaking. LX-300) at a cellulose solids ratio of 10% by weight, a retention improver (wet paper strength enhancer)
(Dick Hercules Co., Ltd., Sponge 557-H) was added in an amount of 5% by weight based on the cellulose solidification ratio.

With respect to the diaphragm obtained by the above method, the internal loss (tan δ), the Young's modulus E and the sound velocity C were measured by the vibration lead method. The results are shown in the following table. As a comparative example, measurement results of a general paper diaphragm (a diaphragm made of cellulose having a Canadian standard freeness of 560 ml) are shown in the following table.

Comparing the characteristics of the diaphragm obtained in each embodiment and the general paper diaphragm, the diaphragm obtained in each embodiment has a Young's modulus that is two to three times that of the general paper diaphragm. You can see that.

In addition, the diaphragm obtained in each example has a film shape and no pinhole unlike the conventional paper diaphragm,
It was not necessary to apply and impregnate a material called a seal which was indispensable for a paper diaphragm, and it was possible to produce a thin film diaphragm having a thickness of about 10 μm.

〔The invention's effect〕

As is clear from the above description, in the acoustic diaphragm of the present invention, since microfibrillated cellulose is made of paper, and further laminated and integrated with the reinforcing member, the physical properties are greatly improved. It is possible to provide an acoustic diaphragm excellent in Young's modulus, tensile strength and the like.

Further, in the production method of the present invention, since a reinforcing member is placed on a papermaking net and cellulose is made on the reinforcing member, even when cellulose having low wet strength such as microfibril cellulose is made. The handling can be facilitated. Therefore, it is possible to efficiently manufacture an acoustic diaphragm having a high Young's modulus.

Furthermore, according to the production method of the present invention, it is possible to easily produce a diaphragm made of a composite material in which various materials are blended with microfibrillated cellulose, and to produce a diaphragm having various characteristics according to an application or the like. It is possible to

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a paper making process using a cone-shaped paper net. 2A to 2C show a manufacturing process of a dome-shaped diaphragm by drawing, FIG. 2A is a schematic cross-sectional view of a flat cellulose-woven fabric composite, and FIG. FIG. 2C is a schematic cross-sectional view showing a draw-forming process, and FIG. 2C is a schematic cross-sectional view of a cellulose-woven fabric composite formed in a dome shape. 2 ... papermaking net 3 ... reinforcement member 5 ... papermaking (cellulose)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-88199 (JP, A) JP-A-60-171262 (JP, A) JP-A-62-36467 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H04R 7/02 H04R 31/00

Claims (6)

(57) [Claims] An acoustic diaphragm in which microfibrillated cellulose is made and integrated with a woven or nonwoven fabric. 2. The acoustic diaphragm according to claim 1, wherein said woven or nonwoven fabric is made of at least one selected from carbon fiber, glass fiber, polyester fiber, aramid fiber and silk. . 3. The acoustic diaphragm according to claim 1, wherein the microfibrillated cellulose is cellulose obtained by beating pulp to a Canadian standard freeness of 300 ml or less. 4. The acoustic diaphragm according to claim 1, wherein said microfibrillated cellulose is bacterial cellulose produced by culturing bacteria. 5. A paper made of microfibrillated cellulose in a state where a reinforcing member for ensuring wet strength is placed on the paper making net, and the paper made by the paper making is removed from the paper making net together with the reinforcing member. A method for producing an acoustic diaphragm, comprising removing, shaping into a diaphragm shape, and drying. 6. The method for producing an acoustic diaphragm according to claim 5, wherein the reinforcing member is peeled off from the paper after drying.