JP5975458B2 - Method for manufacturing diaphragm for electroacoustic transducer - Google Patents

Description

The present invention relates to a method for producing a diaphragm for an electroacoustic transducer using cellulose fibers oxidized by 2,2,6,6-tetramethylpepyridinyl-1-oxy radical (TEMPO).

  Microphones, speakers, etc. have magnetic circuits, voice coils, diaphragms, etc., which convert electrical signals into mechanical vibrations by voice coils and magnetic circuits, and transmit them to the diaphragms to radiate them as sounds. It is a vessel. The diaphragm used in such an electroacoustic transducer is required to operate with the same phase and amplitude as a whole, but the diaphragm resonates and oscillates at high frequencies, causing irregularities in the frequency characteristics, and Sound pressure gradually decreases. In order to prevent the resonance and divided vibration of the diaphragm from occurring up to as high a frequency as possible and widen the region where the frequency characteristics are flat, it is necessary to increase the rigidity of the diaphragm.

  The rigidity of the diaphragm for electroacoustic transducers is due to the shape and the elastic modulus of the material, etc. When the elastic modulus is improved, the high frequency limit frequency increases and the distortion also decreases. Is an important element.

  Various materials such as paper, metal, and resin are used as the material for the diaphragm for electroacoustic transducers. Among them, paper has a low density and a high degree of freedom in shape. Since physical properties can be adjusted with a small lot, it has long been used as a diaphragm for electroacoustic transducers such as speakers. In addition, it has the advantages of being a natural material and excellent in environmental friendliness.

  However, since the paper diaphragm mainly composed of cellulose fibers has a problem in terms of rigidity, for example, carbon fibers or aramid fibers are mixed as reinforcing fibers, but a binder is added to adhere the cellulose fibers. It is necessary, the manufacturing method becomes complicated, and it is difficult to obtain desired physical properties by the additive, and the original sound quality of the paper diaphragm is impaired.

  In view of this, a diaphragm mainly composed of bacterial cellulose has been developed with the rigidity improved while maintaining the characteristics of a paper diaphragm mainly composed of cellulose fibers and a wide reproduction frequency band. This bacterial cellulose is microbial cellulose produced by microorganisms such as acetic acid bacteria, and is composed of cellulose with high crystallinity, so that good rigidity is obtained (Patent Document 1).

  In addition, there are a sheet made of bacterial cellulose and another sheet laminated to improve physical properties (Patent Document 2), and a sheet strengthened by adding carbon nanotubes to bacterial cellulose (Patent Document 3). .

  The inventor uses cellulose fibers of wood that exist abundantly in nature, has a high elastic modulus while taking advantage of the original characteristics of a paper diaphragm, is easy to manufacture, is economical, and is generally widely spread. The research of the diaphragm which can be done was repeated. In the course of its research, pulp cellulose is oxidized by 2,2,6,6-tetramethylpiperidinyl-1-oxy radical (hereinafter also referred to as TEMPO) used as an oxidation reaction catalyst in organic synthesis, Attention was focused on a technique for producing TEMPO-oxidized cellulose (Patent Document 4).

JP-A-61-281800 Japanese Patent No. 3073608 Japanese Patent No. 3827153 JP 2008-001728 A

  In the above, although the diaphragm mainly composed of bacterial cellulose is highly elastic, the acetic acid bacteria used as its raw material are aerobic bacteria, so it must be cultured while supplying oxygen in a medium containing organic substances and inorganic salts. In addition, it is time consuming and takes a long time to generate and is very expensive. Therefore, it is difficult to widely disseminate it, and it is only used for some high-end machines.

  On the other hand, the present inventor found that TEMPO-oxidized cellulose is easily available and suitable as a diaphragm for an electroacoustic transducer because TEMPO-oxidized cellulose is made from wood pulp, which is abundant in nature.

The present invention has been proposed in view of the above, and the object of the present invention is to have a high elastic modulus, which is difficult to realize with conventional pulp, to be excellent in rigidity, inexpensive and easily compared with bacterial cellulose. An object of the present invention is to provide a method for manufacturing a diaphragm for an electroacoustic transducer that can be manufactured.

In addition, by using the diaphragm for electroacoustic transducers created by the above manufacturing method, the reproduction frequency band can be expanded to a higher frequency side than the diaphragm using bacterial cellulose fibers, and the sound quality is excellent in high frequency characteristics. A good electroacoustic transducer can be obtained .

The invention described in claim 1 is characterized in that a diaphragm is produced through a molding step in which TEMPO-oxidized cellulose is dispersed in a liquid dispersion medium and a dispersion liquid as a raw material of the diaphragm is molded into a predetermined shape.
Invention of Claim 2 is a manufacturing method of the diaphragm for electroacoustic transducers of Claim 1, The following (a)-(f),
(A) At least one of pulp and cellulose other than TEMPO oxidized cellulose (b) At least one of a sizing agent and a paper strength agent for imparting water resistance as a general chemical material as paper (c) predetermined physical properties A polymer soluble in the dispersion medium to obtain (d) particles as a reinforcing agent or fibrous filler (e) a clay mineral to obtain predetermined physical properties (f) a carboxyl group for bonding between fibers A diaphragm is produced by adding at least one or all of an additive of a cation that interacts with a cation, preferably a positive charge of 2 or more valences or an ion having an arrangement number of 2 or more. .
Invention of Claim 3 is a manufacturing method of the diaphragm for electroacoustic transducers of Claim 1 or 2, The said formation process shape | molds the said dispersion liquid directly in a predetermined shape,
Or
(G) Step of casting, coating, dripping or spreading and drying (h) Step of filtration and molding (i) Sheet, film or structure by any of the steps of fiberizing and depositing by electrospinning And forming a diaphragm.
According to a fourth aspect of the present invention, in the method for manufacturing a diaphragm for an electroacoustic transducer according to the first or second aspect, the dispersion used as the raw material for the diaphragm is molded into a diaphragm shape having a composition different from that of the raw material. Alternatively, it is characterized in that a diaphragm is produced by casting, coating, dripping or spreading on an unmolded sheet, film or structure.
According to a fifth aspect of the present invention, in the method for manufacturing a diaphragm for an electroacoustic transducer according to the first or second aspect, the dispersion used as the raw material of the diaphragm is molded into a diaphragm shape having a composition different from that of the raw material. Alternatively, the diaphragm is produced by impregnating an unformed sheet, film, or structure.
A sixth aspect of the present invention is the method for manufacturing a diaphragm for an electroacoustic transducer according to the first or second aspect, wherein a dispersion liquid as a raw material of the diaphragm is molded into a diaphragm shape and then laminated on another molded body. And making a diaphragm.

  According to the production method of the present invention, a microbial culture process that requires time and labor is not required using a culture facility, and TEMPO-oxidized cellulose made from pulp existing in nature is used as a vibration plate. Compared to those using, it is easy to manufacture, excellent in productivity, and economical. In addition, TEMPO-oxidized cellulose fiber is a hydrophilic fiber that can be easily dispersed in a liquid dispersion, is generally excellent in dispersibility when mixed with pulp, is less likely to be non-uniform, is easy to manufacture, and is stable without variation. A product (diaphragm) can be produced. Moreover, since it is cellulose derived from wood, it is carbon neutral (does not increase carbon dioxide in the atmosphere during the use cycle), and is excellent in environmental properties.

According to the diaphragm produced by the above production method, TEMPO-oxidized cellulose having a high proportion of cellulose microfibrils that are easy to obtain and inexpensive and have high crystallinity and a long fiber length because pulp is the main raw material. A high elastic modulus can be realized by using.

According to the electroacoustic transducer using the diaphragm, by using TEMPO-oxidized cellulose having a high proportion of cellulose microfibrils with high crystallinity and a long fiber length, the diaphragm has a high elastic modulus and improved rigidity. The reproduction frequency band can be expanded to a higher frequency side, and good sound quality can be obtained.

The manufacturing process example of the diaphragm which concerns on this invention is shown. A specific example of manufacturing the diaphragm material of the present invention will be shown. (A), (b) shows the example which drops and shape | molds the diaphragm raw material of this invention on a type | mold. An example of the type | mold used for this invention is shown. An example of the filtration process used by this invention is shown. An example of the electrospinning method in this invention is shown. Sectional drawing of an example of the diaphragm shape | molded using the dispersion liquid in this invention is shown. An example of the cone-shaped diaphragm manufactured by this invention is shown. The schematic sectional drawing of the electroacoustic transducer incorporating the diaphragm manufactured by this invention is shown.

The diaphragm for electroacoustic transducers produced by the production method of the present invention includes TEMPO oxidized cellulose formed by oxidizing cellulose of wood pulp with TEMPO. TEMPO is obtained by oxidizing 2,2,6,6-tetrapiperidine and functions as a reoxidant and a catalyst for oxidation reaction in organic synthesis. In the present invention, TEMPO is used for oxidation of cellulose, and TEMPO oxidized cellulose. This was used as the main component of the diaphragm material. TEMPO-oxidized cellulose has high crystallinity and excellent heat resistance. Cellulose fiber of wood is hard to loosen uniformly because the fiber and fiber are strongly bonded by hydrogen bond, but it can be easily loosened by using TEMPO to make cellulose nanofiber be able to. TEMPO-oxidized cellulose is dispersed as nanofibers in a liquid dispersion medium such as water at least once during production.

  Wood used as a raw material for pulp is composed of cellulose, lignin, hemicellulose and the like. In pulping, components other than cellulose are considerably removed, but lignin, hemicellulose and the like remain, which greatly affects the strength of paper.

  The TEMPO-oxidized cellulose facilitates separation between microfibrils by selectively oxidizing and carboxylating cellulose microfibril surfaces having high crystallinity in the pulp. Thereby, components other than cellulose microfibrils, such as hemicellulose and cellulose with low crystallinity, can be removed while maintaining the crystallinity of cellulose microfibrils.

In the production method of the present invention, this is dispersed as nanofibers in a dispersion medium, and then formed into a film, for example, to form a diaphragm for an electroacoustic transducer.

  When the tensile test and the dynamic viscoelasticity measurement (DMA) of the diaphragm for electroacoustic transducers thus manufactured were performed, it was confirmed that a high elastic modulus exceeding that of bacterial cellulose was obtained. Moreover, since wood pulp can be used as a raw material and can be reacted under mild conditions, the production is easier than bacterial cellulose, and the production cost can be greatly reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIGS. 1A to 1D are process diagrams showing a method for manufacturing an electroacoustic transducer diaphragm according to a first embodiment of the present invention. The main raw material of the diaphragm according to the present invention is wood. This wood consists of cellulose, lignin, hemicellulose and the like. Wood chips are pulped through a cooking process, a washing / dehydrating process, and the like. In this process, considerable components other than cellulose are removed, but lignin, hemicellulose and the like remain.

  Next, the pulp is subjected to a TEMPO oxidation treatment using a TEMPO catalyst. That is, pulp is dispersed in water and TEMPO is added as a catalyst for the oxidation reaction, whereby the cellulose fibers of the pulp are oxidized to produce TEMPO oxidized cellulose. Cellulose fibers of pulp are aggregates of cellulose microfibrils, which are nanofibers. When pulp is oxidized using a TENPO catalyst, primary hydroxyl groups on the surface of cellulose microfibrils are selectively converted into carboxyl groups, and the separation between microfibrils is reduced. Easy and complete nano-dispersion is possible and TEMPO oxidized cellulose is produced. In this process, components other than cellulose microfibrils are removed to increase the purity.

In the present invention, as shown in FIG. 1 (a), the produced TEMPO-oxidized cellulose is dispersed at least once as a nanofiber in a dispersion medium composed of a liquid such as water by the dispersion step shown in (b). To nanofiber. In this dispersion step, a predetermined amount of a dispersion medium is injected into a tank having a rotatable stirring blade such as a screw mixer, and a predetermined amount of TEMPO-oxidized cellulose is added thereto and stirred for a predetermined time. As an example, TEMPO oxidized pulp containing water is placed in water so that the pulp concentration becomes 0.1 to 1 wt%, and dispersed by stirring with a screw mixer. In this case, since TEMPO oxidized cellulose has hydrophilicity, it has good dispersibility. This dispersion serves as a raw material for the diaphragm. This TEMPO oxidized cellulose nanofiber is the second smallest after carbon nanotube. Various additives such as the following (A) to (F) may be mixed in the dispersion used as the raw material of the diaphragm as necessary, thereby obtaining desired physical properties required for the diaphragm. be able to.
(A) Pulp and cellulose (at least one) other than TEMPO oxidized cellulose. Here, as the pulp, for example, appropriate ones such as softwood pulp, hardwood pulp, non-wood pulp and the like are used. As the cellulose, for example, plant and bacterial cellulose are used.
(I) Size and paper strength agents (at least one) for imparting water resistance as common chemicals for paper
(C) In order to obtain specific physical properties, polymer (d) soluble particles or fibrous fillers (e) desired in a solution or dispersion medium such as PVC (polyvinyl chloride) or PVA (polyvinyl alcohol) In order to bond between clay minerals (f) fibers to obtain physical properties of the cation, a cation that interacts with the carboxyl group, preferably an ion having a positive charge of two or more valences, or an ion having a number of two or more

  The said additive may be individual, may be a selective combination, and may contain all.

  As shown in the steps (c) and (d), the diaphragm body may be formed directly into a target shape such as a flat plate shape or a cone shape using a suitable shape mold. .

  The diaphragm may be produced by applying a conventional paper making process used in the production of an electroacoustic transducer. Alternatively, the dispersion liquid can be poured into a chamber having a predetermined diaphragm shape between the lower mold and the upper mold, and dried to form the same. The drying can be easily performed by providing a heater in the mold and heating the heater by energizing the heater. Of course, other drying means may be used.

Alternatively, the dispersion may be formed into a sheet, film or thin structure. This molding can be realized by any of the following means (K) to (K).
(G) The dispersion is cast, flown, applied, dripped, or distributed on a predetermined device, and dried. (K) The dispersion is filtered and formed. (K) The dispersion is fiberized and deposited by electrospinning. Make

  FIG. 2 shows an example of an apparatus and a manufacturing process in which the dispersion liquid is cast on a belt and the diaphragm body made of a thin structure is wound into a roll shape.

  This apparatus includes a tank 20 into which the dispersion liquid 1 is injected, a first belt device 21 that receives the dispersion liquid 1 flowing from the nozzle 20a of the tank 20 on a net-like belt surface 21 ′, and a belt surface 21 ′. A rotatable roller 22 that depresses the felt felt web and dehydrates the felt into a sheet, a second belt device 23 that conveys the sheet to the drying device 24, and winds the dried one A take-up roller 25 is provided.

  Although not particularly shown, the tank 20 is preferably provided with a stirring device that stirs the dispersion 1 to make it uniform.

  The first belt device 21 is provided with a vacuuming device that evacuates the dispersion 1 cast on the belt surface 21 ′, although not particularly shown. Further, a roller 21a for driving the belt and an auxiliary roller 21b are provided at appropriate places.

  The second belt device 23 is also provided with a belt driving roller 23a and an auxiliary roller 23b, and a drying device 24 for sending hot air through an incorporated heater or blowing means, for example, at an appropriate position.

  In producing the diaphragm material, first, the dispersion 1 is injected into the tank 20, the dispersion 1 is flowed through the nozzle 20 a to the net-like belt surface 21 ′, and a pulp web is formed while being drawn in a vacuum. The felt shown is pressed with a roller 22 to dehydrate and form a sheet.

  It is transferred to the second belt device 23, and after passing through a drying process via the drying device 24, the thin diaphragm body is wound around a winding roller 25.

  In the example of FIG. 2, the second belt device 23 having the drying device 24 is used. However, the drying device 24 is provided on the extension of the rotation direction of the first belt device 21, and the second belt device 23 is omitted. Of course, it is also possible.

  3A and 3B show a state in which the dispersion liquid 1 is dropped onto the upper surface of the mold 2 through the nozzle 3. In the case of spreading, the dispersion liquid 1 may be ejected through the nozzle 3.

  As the mold shape, for example, a cone-shaped mold 1A as shown in FIG. 4 may be used. Of course, other shapes may be used.

  FIG. 5 is a process explanatory diagram corresponding to the above (c), and shows an example in which the dispersion 1 is filtered through the filter 4 and molded on the filter 4.

  FIG. 6 shows an example of the above-mentioned electrospinning method. In this case, a polymer is mixed in the dispersion to obtain a polymer solution. 5 is a container containing a polymer-containing dispersion, 5a is a discharge port, 1B is a mold having a predetermined shape, 6 is a high-pressure generator, and for example, the container 5 is added via the high-pressure generator 6, and the mold 1B is negatively charged. When the high voltage at which electrospinning occurs is reached, the dispersion liquid positively charged through the container 5 exits from the discharge port 5a of the container 5 to form, for example, a conical droplet and flows out as a trickle. Then, as shown by the flight line 1a after being formed into a nanofiber state, it is scattered toward the flat mold surface 1b of the negatively charged mold body 1B and deposited on the mold surface.

  FIG. 7 shows an example in which the dispersion 1 is molded into a balance drive type speaker diaphragm 11A through a predetermined mold. The diaphragm 11A includes a dome-shaped diaphragm portion 11a at the center and a cone-shaped diaphragm portion 11b formed on the outer periphery thereof.

  After forming a sheet-like, film-like or thin structure as described above, it can be laminated and integrated, or press-molded using a mold with a desired shape, and further shaped into the desired shape to vibrate A plate can be made.

  The dispersion used as the raw material of the diaphragm is already molded into an appropriately shaped diaphragm having a composition different from that of the dispersion, or is not molded into a predetermined diaphragm shape, and the dispersion has a composition. The diaphragm can also be produced by coating, dripping, and spreading on different (eg, PET film, aluminum, etc.) sheets, films or thin structures, drying them, and forming a film sheet.

  Dispersion used as the raw material of the diaphragm is different in composition (for example, cloth, ordinary paper not containing nanofibers) that has already been molded into a diaphragm with a suitable shape, or unmolded into a specified diaphragm shape In addition, a vibration plate can be produced by impregnating a sheet, film or thin structure having a composition different from that of the dispersion (for example, PET film, aluminum, etc.) and drying and molding the sheet.

  A molded body in which the dispersion liquid used as the raw material for the diaphragm is made into a sheet, film, or thin structure is pasted on a sheet, film, or thin structure of the same or other composition (eg, PET film, aluminum, etc.) The diaphragm can also be manufactured.

  FIG. 9 shows an example of an electroacoustic transducer using a diaphragm manufactured by the process described in the above embodiment. In this example, an example provided with a cone-shaped diaphragm is shown. In the figure, 11 is a diaphragm, 12 is a cylindrical bobbin, 13 is a damper, 14 is a substantially conical frame, 15 is a magnetic circuit, 16 is an edge, and 17 is a dust cover.

  According to the electroacoustic transducer having the above-described configuration, by using a high elastic modulus diaphragm containing TEMPO-oxidized cellulose, the reproduction frequency band can be expanded to a higher frequency side while being inexpensive, and the sound quality is good. It becomes.

  In the above example, the case of applying to a general-purpose speaker using a conical diaphragm has been described as an example. However, the present invention is not limited to this example, and a diaphragm having various shapes such as a planar shape is provided. Of course, it can be applied to an electroacoustic transducer. Further, the present invention is not limited to the above-described example, and various modifications can be made without departing from the scope of the invention in the implementation stage.

DESCRIPTION OF SYMBOLS 1 Dispersion liquid 1a Flight line 1b Flat type | mold surface 1A, 1B type | mold 2 type | mold 3 nozzle 4 filter 5 container 5a discharge port 6 high pressure generator 11 diaphragm 12 voice coil 13 damper 14 type | mold surface 15 magnetic circuit 16 edge 20 tank 20a nozzle 21 First belt device 21a Driving roller 21b Auxiliary roller 21 'Belt surface 22 Roller 23 Second belt device 23a Driving roller 23b Auxiliary roller 24 Drying device 25 Rolling roller

Claims (6)

  A method of manufacturing a diaphragm for an electroacoustic transducer, wherein a diaphragm is produced through a molding process in which TEMPO-oxidized cellulose is dispersed in a liquid dispersion medium and a dispersion liquid as a raw material of the diaphragm is molded into a predetermined shape. . In the manufacturing method of the diaphragm for electroacoustic transducers of Claim 1, the following (a)-(f) to the said dispersion liquid,
(A) At least one of pulp and cellulose other than TEMPO oxidized cellulose (b) At least one of a sizing agent and a paper strength agent for imparting water resistance as a general chemical material as paper (c) predetermined physical properties A polymer soluble in the dispersion medium to obtain (d) particles as a reinforcing agent or fibrous filler (e) a clay mineral to obtain predetermined physical properties (f) a carboxyl group for bonding between fibers A diaphragm is produced by adding at least one or all of an additive of a cation that interacts with a cation, preferably a positive charge of 2 or more valences or an ion having an arrangement number of 2 or more. A method for manufacturing a diaphragm for an electroacoustic transducer. The method for manufacturing a diaphragm for an electroacoustic transducer according to claim 1 or 2, wherein the forming step directly forms the dispersion into a predetermined shape.
Or
(G) Step of casting, coating, dripping or spreading and drying (h) Step of filtration and molding (i) Sheet, film or structure by any of the steps of fiberizing and depositing by electrospinning A method for producing a diaphragm for an electroacoustic transducer, comprising forming the diaphragm into a diaphragm.   The method for manufacturing a diaphragm for an electroacoustic transducer according to claim 1 or 2, wherein a dispersion liquid that is a raw material of the diaphragm is formed into a diaphragm shape having a composition different from that of the raw material, or an unshaped sheet, film, or A method for producing a diaphragm for an electroacoustic transducer, comprising producing a diaphragm by casting, coating, dripping or spreading on a structure.   The method for manufacturing a diaphragm for an electroacoustic transducer according to claim 1 or 2, wherein a dispersion liquid that is a raw material of the diaphragm is formed into a diaphragm shape having a composition different from that of the raw material, or an unshaped sheet, film, or A method for producing a diaphragm for an electroacoustic transducer, comprising impregnating a structure to produce a diaphragm. 3. The method for manufacturing a diaphragm for an electroacoustic transducer according to claim 1, wherein a dispersion liquid as a raw material of the diaphragm is molded into a diaphragm shape and then laminated on another molded body to produce a diaphragm. A method for manufacturing a diaphragm for an electroacoustic transducer.

Images