JP6584784B2 - Method for manufacturing diaphragm for electroacoustic transducer - Google Patents

Description

This invention relates to a method of manufacturing the electroacoustic transducer diaphragm for use in a speaker and a microphone, or the like.

  As a diaphragm material for a speaker, it is generally required to have a low density, a high Young's modulus, an appropriate internal loss, and the like, and a material having optimum physical properties is appropriately selected according to the use of the speaker.

  Among various diaphragm materials, wood pulp is made of cellulose, its physical properties can be controlled relatively freely, and it can be manufactured by papermaking. ing. In this case, in order to obtain desired speaker characteristics, the physical properties can be controlled by adjusting / combining the wood pulp type and the beating degree. In addition to these, for example, chemical fibers, carbon fibers, and other materials are combined and mixed.

  In addition, cellulose produced by bacteria is cellulose as well as wood pulp, because hydrogen bonds with wood pulp are likely to occur, and because the fiber diameter is small compared to natural fibers such as wood pulp, the contact area increases. Since the bonding point increases, it can be said that it is lightweight and highly rigid when combined with wood pulp, and is an excellent material for the diaphragm.

  As a diaphragm using bacterial cellulose, there has been proposed a method in which acetic acid bacteria are statically cultured and dissociated, and the paper is made or mixed with wood pulp (Patent Document 1).

  However, when paper making this slurry containing bacterial cellulose, because of its poor drainage, the paper making time is much longer compared to ordinary wood pulp-only slurries, so productivity is poor and costs are significantly increased. There are drawbacks.

  In addition, for mass production, the amount (ratio) of bacterial cellulose may be reduced in order to shorten the paper making time, but this has the disadvantage that it is difficult to obtain sufficient performance.

  As a solution to this problem, a method of manufacturing a diaphragm is proposed in which a disaggregation solution containing bacterial cellulose (BC) is spray-coated to form a coating layer and dried (Patent Document 2).

JP-A-61-281800 JP 09-084175 A

  As shown in Patent Document 2, when a disaggregation solution containing cellulose produced by fermentation using bacterial cellulose is spray-coated on a substrate, the problem of drainage does not occur, so the amount used is limited. Things will disappear.

However, the following conditions are required for spray coating the disaggregation solution on the substrate.
a. The disaggregation solution should be homogeneous and small in size.
b. The viscosity of the disaggregation solution is not high.
c. In order to spray gelled bacterial cellulose obtained by the static culture method conventionally used for diaphragms, it is necessary to physically subdivide and disaggregate the gelled bacterial cellulose. It takes. Moreover, even if it takes a long time, if it reaches a certain granularity, it will not be further crushed and subdivided and does not reach a smooth sol form. However, the entanglement of fibers between grains is not sufficient.
d. A cost is required for a process for obtaining appropriate properties as a material for spraying.
e. In order to prevent clogging of nozzles and unevenness in spraying in small quantities, it is necessary to ensure a sufficiently homogeneous state, but this is difficult.

The present invention has been proposed in view of the above, and its main object is to form a sol-like material made from bacterial cellulose consisting of a stirring culture method when spraying cellulose onto the surface of a diaphragm base material mainly comprising cellulose. the suspension is to use a, its amount can widely set is to provide a method of manufacturing that have a suitable rigid electrical acoustic converter diaphragm was in use.
Further, by applying a fine powder to the diaphragm substrate surface instead of the spray dried sol suspension of bacterial cellulose, also provides a method for producing that electrical acoustic converter diaphragm having a rigid There is.

In order to solve the above problems, the method of manufacturing an electro-acoustic converter diaphragm of the present invention according to 請 Motomeko 1 includes the steps of papermaking fiber material mainly cellulose, with dewatering the paper body, this In the dehydration step, the surface of the paper body is sprayed with a sol-like suspension made of bacterial cellulose produced by a stirring culture method, and the multilayered paper body is formed into a predetermined shape. And a molding step.
According to a second aspect of the present invention, there is provided a method for producing a diaphragm for an electroacoustic transducer according to the present invention, comprising a step of papermaking a fiber material mainly composed of cellulose, and a bacterial cellulose produced by stirring culture on the surface of the papermaking body. A step of applying a powder body obtained by dehydrating a sol-like suspension and making it wet, a step of dehydrating the wet paper body, and molding the dehydrated paper body into a predetermined shape And a step of performing.
The method for producing a diaphragm for an electroacoustic transducer of the present invention according to claim 3 is the method for producing a diaphragm for an electroacoustic transducer according to claim 1 or 2 , wherein the average of the bacterial cellulose in the sol suspension is obtained. The fiber width is 50 to 100 nm or approximately 20 nm level.

According to the present invention of claim 1-3, wherein the material Upon be SPRAY, rather than solution prepared by macerating the gel-like bacterial cellulose by static culture as a multilayer materials, bacterial cellulose made is agitated culture Since the sol-like suspension is used, the disaggregation step is unnecessary, and the productivity is improved, so that the production cost can be reduced.
In addition, sol-like suspensions made from bacterial cellulose that is stirred and cultured have a small fiber width and excellent dispersibility and fluidity. In addition, there is an advantage that the appearance is improved.
Further, a small amount can be uniformly applied in a thin film, and can be applied to a high-frequency diaphragm and a headphone diaphragm that are required to be light and thin.

(A) Schematic diagram of microscopic observation image of bacterial cellulose in water-dispersed state by stirring culture, (b) shows the same schematic diagram of a state where bacterial cellulose gel is disaggregated by stationary culture method. The block diagram which shows the manufacturing process of Example 1 of this invention. (A) Explanatory drawing which shows the state which sprays and sprays bacterial cellulose by a stirring culture method on the surface of a corn-shaped diaphragm base material, (b) is a schematic sectional drawing of the completed diaphragm. (A) is an SEM image of the surface of a normal papermaking diaphragm, and (b) is an SEM image of the surface of the diaphragm sprayed with bacterial cellulose sprayed by the stirring culture method. (A) is a sectional view of a normal papermaking diaphragm, and (b) is a sectional view of a diaphragm sprayed with bacterial cellulose by the stirring culture method. (A) shows the plane of the diaphragm which spray-coated the sol suspension which used the bacterial cellulose by the stirring culture method as a raw material. (B) shows the plane of the diaphragm which spray-coated bacterial cellulose by the stationary culture method. Explanatory drawing which contrasted the frequency characteristic of the speaker without a spray, and the speaker which sprayed the disaggregation solution of the conventional bacterial cellulose. Explanatory drawing which contrasted the frequency characteristic of the speaker of this invention which sprayed the sol-like suspension which made the bacterial cellulose the raw material by the stirring culture method, and the speaker without a spray. The block diagram which shows the manufacturing process in Example 2 of this invention.

  The present inventor has various problems as described above when using a bacterial cellulose disaggregation solution by a stationary culture method as a spray solution, but as a result of trial and error, a sol made from bacterial cellulose by a stirring culture method is used. When the suspension is used for a diaphragm substrate for loudspeakers composed of cellulose fiber materials mainly composed of cellulose, the bacterial cellulose produced by this stirring culture method has good dispersibility and fluidity in the solution. It has been found that when the suspension is sprayed on the surface of the diaphragm base material mainly composed of cellulose based on the manufacturing method according to FIG.

  In addition, there is a new “bacterial cellulose” developed by the research group of Hokkaido University Graduate School of Engineering as bacterial cellulose by the stirring culture method. Based on this, “fermented nanocellulose (bacterial cellulose)” was further developed. It was. This bacterial cellulose has been filed under the international publication number WO 2014/104318 A1.

  Since this bacterial cellulose is finer, a very uniform aqueous dispersion can be obtained.

  Bacterial cellulose produced by ordinary agitation culture has an average fiber width of 50 to 100 nm, but “fermented nanocellulose (bacterial cellulose)” developed by a research group at Hokkaido University Graduate School of Engineering has a smaller fiber width. The level is almost 20 nm, and the dispersibility is excellent and uniform. These depend on the type of acetic acid bacteria, the composition of the medium (particularly CMC (the amount of carboxymethylcellulose)), the stirring state, and the culture conditions such as PH. For this reason, it is possible to obtain a desired bacterial cellulose sol suspension by appropriately setting the culture conditions.

  When the present inventor applies these sol suspensions to a speaker diaphragm composed of a diaphragm fiber material mainly composed of cellulose, a speaker diaphragm that is lightweight and highly rigid can be easily obtained. We focused on what we get.

  FIG. 1 (a) shows a dispersed state of bacterial cellulose having an average fiber width of about 20 nm by a stirring culture method viewed with a microscope, and FIG. 1 (b) shows a dispersed state in a state in which the bacterial cellulose gel is disaggregated by a stationary culture method.

  As can be seen from these comparisons, it is understood that the bacterial cellulose dispersion is better in the sol suspension of bacterial cellulose by the stirring culture method.

  The following table shows the physical properties of the bacterial cellulose produced by stirring culture method prepared at a bacterial cellulose concentration of 0.1% and the paper measured by the vibration lead method using bacterial cellulose produced by stationary culture method.

Physical property measurement results by vibration lead method

  As is apparent from the above, the bacterial cellulose obtained by stirring culture is superior to the bacterial cellulose obtained by stationary culture in terms of Young's modulus and sound velocity, and has appropriate internal loss and is suitable as a diaphragm physical property. I understand that.

  The production method of the present invention can be broadly divided into a step of obtaining a so-called paper diaphragm made of a fiber material mainly composed of cellulose, and a bacterial cellulose sol suspension by a stirring culture method of spraying on the diaphragm. The manufacturing process. Hereinafter, these will be described.

  First, a base material portion made of a fiber material mainly composed of cellulose was produced as follows.

  A pulp obtained by beating NBPK (pulp) to a beating degree of 30 ° SR is adjusted to about 0.1%, and is made into a diaphragm shape to obtain a base material portion.

  Also, a sol-like suspension of bacterial cellulose by the stirring culture method was prepared under the following culture conditions using a bacterium identified by Gluconacetobacter intermedius NEDO-1 strain (deposit number NITE BP-01495).

  Hestrin & Schlum (HS) medium containing 2.0% CMC (sodium carboxymethylcellulose) (glucose 2.0%, bactopeptone 0.5%, yeast extract 0.5%, Na2HPO4 0.27%, citric acid 0 115%) was used as a medium, and the bacterium was precultured.

  Next, the preculture solution is inoculated into a 5 L medium, and aerated and cultured using a fermenter under conditions of an aeration rate of 7 to 10 L / min, a rotation speed of 200 to 800 rpm, and a temperature of 30 to 37 ° C. For 3-4 days.

  The obtained culture broth was added to about twice the amount, and sodium hydroxide was added so that the final concentration was 1.0 to 4.0%. Then, it processed at 60-90 degreeC, 80 rpm, and 4 to 6 hours, and melt | dissolved the microbial cell.

  After subjecting this to centrifugation, the supernatant was removed and the precipitate was collected to remove water-soluble bacterial cell components. After the ultrapure water is added and centrifuged, the operation of removing the supernatant is repeated until the pH of the precipitate becomes 7 or less in a wet state to purify the product, and the biocellulose sol A suspension was obtained.

  Then, a paper-made base material portion having a base water content of about 77% by vacuum dehydration is sprayed to a concentration of 0.1% of the bacterial cellulose sol suspension by the stirring culture method. The aqueous dispersion prepared as described above was applied, dehydrated, and pressed with a mold heated to 200 ° C. to obtain a diaphragm in which bacterial cellulose was arranged in layers on the surface. In spray spraying, the amount of spray coating was adjusted so that the weight of the sol-like dispersion liquid was 0.5% of bacterial cellulose with respect to the pulp weight. Thereafter, it is dehydrated and pressed into a predetermined shape.

  In addition, since a uniform sol-like dispersion is used for coating, a small amount of thin film and a large amount of coating can be appropriately performed. In the present invention, the adjustment range of the coating amount is wide. It is also possible to apply partially to the diaphragm.

  FIG. 2 shows the manufacturing process.

  FIG. 3A is a schematic perspective view showing a state in which a sol-like BC suspension is sprayed through a nozzle 2 of a spray gun onto a diaphragm base 1 made in, for example, a cone shape, and FIG. FIG. A sol-form BC suspension made of bacterial cellulose by stirring culture has good dispersibility and fluidity, and the nozzle 2 is not clogged, and spray irregularity does not occur. It is also easy to apply a small amount. In this way, a two-layer diaphragm comprising the substrate 1 and a sol-form BC suspension layer thereon is obtained. In this case, since the diaphragm base material 1 and bacterial cellulose are cellulose, the layers can be firmly integrated by hydrogen bonding between the two celluloses. In addition, since bacterial cellulose is much finer than pulp fibers and the like, the bacterial cellulose applied to the interface of the diaphragm base material 1 penetrates near the surface of the diaphragm base material 1 to be more firmly integrated structurally.

  Fig.4 (a) shows the SEM image of the papermaking diaphragm surface which consists only of pulp. (B) is the SEM image of the surface of the diaphragm which sprayed the bacterial cellulose sol suspension which consists of a stirring culture method on the surface of the diaphragm base material 1. FIG.

  5A and 5B are cross sections of the diaphragm. FIG. 5A shows a cross-sectional SEM image of FIG. 4A, and FIG. 5B shows a cross-sectional SEM image of FIG.

  From these, it can be seen that the sol-like suspension made of bacterial cellulose by the stirring culture method is ultrafine, so that it is uniformly arranged on the entire surface and the surface is smooth and dense.

  FIG. 6A shows a planar appearance of a diaphragm in which a sol-like suspension of bacterial cellulose is sprayed on the surface of the diaphragm base material by a stirring culture method. In this case, the surface has no spray unevenness. On the other hand, those using a sol-like suspension of bacterial cellulose by a stationary culture method, as shown in FIG.

  FIG. 7 shows the frequency characteristics of a 16 cm full range speaker. The broken line A is a thing without spray coating, and the continuous line B is what sprayed the disaggregation solution containing the conventional bacterial cellulose. In the case of spray coating, the peak and dip are smaller than those without, and shifts to the high frequency side at 3 kHz or more.

  FIG. 8 shows a comparison of frequency characteristics between the non-sprayed one (dashed line A) and the product C of the present invention spray-coated with a sol suspension made of bacterial cellulose by a stirring culture method. As is clear from FIG. 8, the product C of the present invention has smaller peaks and dips than those without the spray, and sprayed with a sol-like suspension of bacterial cellulose by the stationary culture method indicated by the solid line B in FIG. It shifts to 3kHz or higher to the high frequency side, and the high frequency is improved.

  As described above, the product of the present invention has the advantages that the appearance is good and the frequency characteristics are improved.

  In the first embodiment, paper was made and sprayed with a sol-like suspension of bacterial cellulose consisting of a stirring culture method after dehydration. In this Example 2, as shown in FIG. It is characterized by spraying a sol-like suspension of bacterial cellulose consisting of a culture method.

  Also in this case, bacterial cellulose is disposed on the entire surface of the paper, and the surface is smooth and dense. Further, since a sol-like suspension of bacterial cellulose consisting of a stirring culture method is sprayed simultaneously with dehydration, the manufacturing process of the diaphragm can be shortened, so that productivity is good.

  In Examples 1 and 2, a bacterial cellulose sol suspension consisting of a liquid stirring culture method was sprayed onto the paper surface. In this example, the bacterial cellulose sol consisting of a stirring culture method was applied to the paper surface. The suspension is dried and pulverized, applied to the surface of the pulp diaphragm made by appropriate coating means, the bacterial cellulose is restored to a wet state for hydrogen bonding, dehydrated, pressed, and the diaphragm is I tried to get it.

That is, the sol suspension was dried by a vacuum freeze-drying method to obtain a fine powder having a particle size of about 40 μm. And this was apply | coated to the surface of the diaphragm base material by powder coating.
Also in this case, since the powder obtained by drying the suspension of bacterial cellulose that has been stirred and cultured is fine, when it is applied to the interface of the diaphragm base 1, it penetrates into the vicinity of the surface of the diaphragm base 1 and is firmly integrated. It can be a multilayer structure.

  Further, in this Example 3, since the volume and weight are significantly reduced by pulverizing the sol suspension as compared with the bacterial cellulose sol suspension, space and cost are advantageous for transportation and storage. Become. Further, since it is powdered, there is an advantage that it can be partially adhered to the diaphragm and the layered form can be locally changed.

  In the above embodiment, the two-layer diaphragm has been described. However, for example, a multilayer structure of two or more layers may be used for the purpose of increasing the rigidity.

1 Diaphragm base material 2 Nozzle

Claims (3)

  A process for making a fiber material mainly composed of cellulose, and dehydrating the paper body, and a sol-like suspension made of bacterial cellulose produced by stirring culture on the surface of the paper body in this dehydration step A process for producing a diaphragm for an electroacoustic transducer, comprising: a step of spraying and multilayering; and a step of forming the paper body multilayered in the dehydration step into a predetermined shape.   A step of paper-making a fiber material mainly composed of cellulose, and a powder body obtained by dehydrating and pulverizing a sol-like suspension made of bacterial cellulose produced by stirring culture on the surface of the paper-making body; A diaphragm for an electroacoustic transducer, comprising: a step of making a wet state; a step of dehydrating the wet papermaking body; and a step of forming the dewatered papermaking body into a predetermined shape. Production method. 3. The method for manufacturing a diaphragm for an electroacoustic transducer according to claim 1, wherein an average fiber width of the bacterial cellulose in the sol suspension is at a level of 50 to 100 nm or approximately 20 nm. Manufacturing method of transducer diaphragm.