CN116528118A

CN116528118A - Diaphragm for loudspeaker and method for manufacturing the same

Info

Publication number: CN116528118A
Application number: CN202310057432.5A
Authority: CN
Inventors: 佐藤宏亮
Original assignee: Awa Paper Manufacturing Co Ltd
Current assignee: Awa Paper Manufacturing Co Ltd
Priority date: 2022-01-31
Filing date: 2023-01-18
Publication date: 2023-08-01

Abstract

The invention provides a diaphragm for a speaker and a method for manufacturing the same, which can inhibit the generation of valleys in frequency characteristics. The diaphragm for a speaker contains reinforcing fibers and a matrix resin, and has a phase-change air permeability resistance of 4.0 to 20 seconds. Contains 20 to 30vol% of reinforcing fiber. In addition, the phase-change air permeability resistance is 5.0 to 20 seconds. The reinforcing fiber includes a first fiber and a second fiber, the first fiber is at least one of carbon fiber, aramid fiber, liquid crystal polyester fiber, ultra-high molecular weight polyethylene fiber, PBO fiber, glass fiber, basalt fiber, and metal fiber, and the second fiber is at least one of aramid small fiber, acrylic pulp, cellulose nanofiber, conifer pulp, hardwood pulp, cotton pulp, rayon, fruit fiber, bamboo, hemp, chitin nanofiber, wool, and silk.

Description

Diaphragm for loudspeaker and method for manufacturing the same

Technical Field

The present disclosure relates to a diaphragm for a speaker and a method of manufacturing the same.

Background

In general, as a diaphragm material for a speaker, various materials such as a material for making short fibers such as pulp, a material for molding a metal thin plate, and a material for injection molding a thermoplastic resin such as polypropylene have been proposed.

In recent years, heat resistance and rigidity capable of withstanding heat generated from a coil and a large driving force have been demanded due to the increase in power of speaker systems. Among various diaphragm materials, fiber reinforced resins (FRPs) molded by impregnating synthetic fibers, woven fabrics of natural fibers, and nonwoven fabrics with thermosetting resins such as epoxy resins and unsaturated polyester resins are excellent, and thus diaphragms using FRPs are often used. As the FRP vibration plate, there is generally a vibration plate obtained by impregnating a reinforcing fiber woven fabric of carbon fibers and glass fibers with an epoxy resin as a matrix resin and thermally curing the same (for example, patent document 1).

Such an FRP vibration plate has a very excellent elastic modulus, but the internal loss (tan δ) is extremely small. As a result, since a steep peak occurs at Fh (high frequency resonance frequency), there is a problem that a difference in tone color is large.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 4049179

Patent document 2: japanese patent publication No. 7-32511

Disclosure of Invention

An object of the present disclosure is to provide a speaker diaphragm capable of suppressing the occurrence of a valley in frequency characteristics, and a method for manufacturing the same.

According to the speaker diaphragm according to claim 1 of the present invention, the speaker diaphragm contains the reinforcing fiber and the matrix resin, and the phase change air permeation resistance is 4.0 seconds to 20 seconds.

In addition, according to the speaker diaphragm according to claim 2 of the present invention, the reinforcing fiber is contained in an amount of 20 to 30vol% in addition to the speaker diaphragm. According to the above configuration, the speaker diaphragm in which the occurrence of the valley in the frequency characteristic is suppressed can be obtained without changing the internal loss.

In addition, according to the speaker diaphragm according to claim 3 of the present invention, the phase-change air permeation resistance is 5.0 seconds to 20 seconds in addition to any of the speaker diaphragms. According to the above configuration, occurrence of a sudden drop in frequency characteristics can be suppressed.

Further, according to the speaker diaphragm of claim 4 of the present invention, in addition to any of the speaker diaphragms described above, the first fiber is at least one of carbon fiber, aramid fiber, liquid crystal polyester fiber, ultra-high molecular weight polyethylene fiber, PBO fiber, glass fiber, basalt fiber, and metal fiber, and the second fiber is at least one of aramid small fiber, acrylic pulp, cellulose nanofiber, conifer pulp, hardwood pulp, cotton pulp, rayon, fruit fiber, bamboo, hemp, chitin nanofiber, wool, and silk. According to the above configuration, occurrence of a sudden drop in frequency characteristics can be suppressed.

Further, according to the speaker diaphragm of claim 5 of the present invention, in addition to any of the speaker diaphragms, the reinforcing fibers contain 20% to 50% by volume of the second fibers.

Further, according to the speaker diaphragm of claim 6 of the present invention, in addition to the speaker diaphragm, the frequency characteristic exhibits a characteristic that no drop of 10dB/20 μpa or more occurs in either the +250Hz range or the-250 Hz range of the specific frequency with respect to the specific frequency of 12500Hz or less.

Further, according to the speaker diaphragm according to claim 7 of the present invention, the storage modulus is 7.1GPa or more in addition to any of the speaker diaphragms.

Further, according to the speaker diaphragm of claim 8 of the present invention, in addition to any of the speaker diaphragms described above, the matrix resin is a thermoplastic resin.

Further, according to the speaker diaphragm of claim 9 of the present invention, in addition to any of the speaker diaphragms described above, the thermoplastic resin is at least one of polyethylene, polypropylene, polyvinyl acetate, polymethyl methacrylate, polyethylene terephthalate (PET), nylon, polyamide, polyoxymethylene, polycarbonate, polybutylene terephthalate, phenoxy, polyetherimide, polyaryletherketone, thermoplastic polyimide, polysulfone, polyethersulfone, polyphenylene sulfide, and polyamideimide.

Further, according to the speaker diaphragm according to claim 10 of the present invention, the inorganic filler is contained in an amount of 10 to 30vol% in addition to any of the speaker diaphragms.

Further, according to the speaker diaphragm of claim 11 of the present invention, the expanded graphite is contained in an amount of 20vol% in addition to any of the speaker diaphragms.

Further, according to the invention according to claim 12, there is provided a method for manufacturing a speaker diaphragm, comprising: a step of forming a base material including a nonwoven fabric or woven fabric composed of first fibers and second fibers as reinforcing fibers, and a matrix resin; and a step of heating and pressurizing the base material to produce a molded article, wherein the phase-change air permeability resistance is 4.0 to 20 seconds.

Drawings

Fig. 1 is a graph showing an equal loudness curve.

Fig. 2 is a graph showing characteristics of generating a drop exceeding 10dB/20 μpa in the range of ±250Hz of a specific frequency a.

Fig. 3 is a graph showing frequency characteristics of the speaker diaphragm according to embodiment 1.

Fig. 4 is a graph showing frequency characteristics of the speaker diaphragm according to embodiment 2.

Fig. 5 is a graph showing frequency characteristics of the speaker diaphragm according to example 3.

Fig. 6 is a graph showing frequency characteristics of the speaker diaphragm according to example 4.

Fig. 7 is a graph showing frequency characteristics of the speaker diaphragm according to example 5.

Fig. 8 is a graph showing frequency characteristics of the speaker diaphragm according to comparative example 1.

Fig. 9 is a graph showing frequency characteristics of the speaker diaphragm according to comparative example 2.

Fig. 10 is a graph showing frequency characteristics of the speaker diaphragm according to comparative example 3.

Fig. 11 is a graph showing frequency characteristics of the speaker diaphragm according to example 4 and comparative example 2 superimposed.

Fig. 12 is a graph showing the relationship between the amount of aromatic polyamide pulp to be blended and the phase change air permeation resistance of the speaker diaphragms according to examples 1 to 5 and comparative examples 1 to 3.

Fig. 13 is a graph showing frequency characteristics of the speaker diaphragm according to example 6.

Fig. 14 is a graph showing frequency characteristics of the speaker diaphragm according to example 7.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following embodiments. In addition, the present specification does not identify the components shown in the claims as components of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the constituent members described in the embodiments are not particularly described, and the gist of the present invention is not limited to the above, but is merely a simple explanation. In addition, the sizes, positional relationships, and the like of the components shown in the drawings may be exaggerated for the sake of clarity of description. In the following description, the same names and reference numerals denote the same or similar components, and detailed description thereof is appropriately omitted. In addition, each element constituting the present invention may be a plurality of elements formed by the same member and may be a member that serves as a plurality of elements, or may be a member that is shared by a plurality of members to realize the functions of one member.

As a diaphragm used for a speaker, paper has been conventionally used. On the other hand, as the speaker system has higher power, the diaphragm is required to have heat resistance, elastic modulus, and weight reduction (lower specific gravity) that can withstand heat generated from the coil and a large driving force. Accordingly, there is known an FRP vibration plate obtained by impregnating a reinforcing fiber woven cloth such as carbon fiber with a thermosetting resin such as an epoxy resin as a matrix resin and thermally curing the reinforcing fiber woven cloth (for example, refer to patent document 1).

However, such an FRP diaphragm has an excellent elastic modulus, but has a problem in that a steep peak occurs at a high-frequency resonance frequency, and thus the influence on sound is large. In particular, there are the following problems: the frequency characteristics do not sufficiently output sounds in a specific frequency domain, that is, a valley region is generated, and as a result, sounds in a wide frequency domain cannot be accurately expressed.

In this case, the frequency characteristic of the sound-level sensation (loudness), i.e., the isotone curve (origin: "full-field precise determination of two-dimensional isotone curve" < https:// www.nedo.go.jp/content/100084730.Pdf >) is shown in fig. 1. As shown in this figure, regarding ISO226: a two-dimensional equal-loudness curve defines a sound pressure level (vertical axis) in a range (horizontal axis) of 20 to 12,500 Hz corresponding to the human audible range. Thus, it can be confirmed that: in the treble region where the frequency is high, the graph curve generates valleys. In practice, if a speaker is manufactured using an FRP diaphragm, the frequency characteristics change according to the FRP diaphragm used, and the drop in this specific frequency becomes more abrupt, thereby affecting the reproducibility of sound. In general, a material having a specific modulus E/ρ and an internal loss tan δ is required as a speaker diaphragm material. The higher the specific modulus, the more excellent the piston movement region is obtained, and the greater the internal loss, the more the effect of flattening the reproduction frequency characteristic is expected. However, with respect to the material characteristics, materials with higher specific moduli have smaller internal losses or have opposite characteristics, and these 2 characteristics are in a trade-off relationship. Conventionally, attempts have been made to reduce such degradation by adjusting the internal loss of a speaker diaphragm. However, since the internal loss is an inherent value depending on the material constituting the speaker diaphragm, it is difficult to adjust the internal loss, and the above problem has not been completely eliminated.

Thus, the present inventors have made various studies in order to attenuate such a decrease, and as a result, have found that: the present invention has been completed by adding specific fibers to reinforcing fibers constituting a speaker diaphragm using a fiber-reinforced resin such as an FRP diaphragm or adjusting the amount of the reinforcing fibers to obtain a lowering suppressing effect. The following description is given.

In the present specification, in order to quantitatively represent a sudden drop in frequency characteristics, in a range of 12500Hz or less in frequency characteristics, as shown in fig. 2, a characteristic in which a drop exceeding 10dB/20 μpa does not occur is defined as a speaker diaphragm in which a steep valley does not occur in any of a +250Hz range or a-250 Hz range of a minimum frequency a [ Hz ] with respect to a specific frequency a [ Hz ] corresponding to the minimum value.

The speaker diaphragm according to the embodiment of the present invention includes reinforcing fibers and a matrix resin. For example, the reinforcing fibers can be used as a short fiber mat, woven fabric, or nonwoven fabric.

Preferably 20 to 30vol% of reinforcing fibers. This can suppress the occurrence of the valley without increasing the internal loss.

The fiber volume content Vf is defined by the following formula in ASTM D3171.

[ math 1 ]

In the above formula, rρ is the density of the resin, fρ is a weighted average of the densities of the first fiber and the second fiber, weighted by weight, and Wf is the fiber weight content (i.e., the proportion of the reinforcing fiber weight in the composite weight).

(phase-change air-permeable resistance)

The phase-change air permeability of the speaker diaphragm is preferably set to 4.0 seconds to 20 seconds. In particular, the reduction in frequency can be reduced by the combination with the reinforcing fiber containing 20 to 30 vol%.

Alternatively, the phase change air permeability resistance may be from 5.0 seconds to 20 seconds. In this case, it can be confirmed by experiments by the inventors of the present application: even if the amount of the reinforcing fiber is not limited to the above range, an effect of reducing the decrease in frequency is obtained (described in detail later). The phase-change air permeation resistance test was carried out in accordance with JIS P8117:2009 (model G-BSC, manufactured by eastern fine machine corporation) was tested by changing the gasket and the fastening plate so that the inner diameter thereof at the time of fixing the gasket became 9.0mm, and measuring the time (seconds) from when 0mL of the reticle passed the edge of the outer tube to when 300mL of the reticle passed the edge of the outer tube. Here, the variable phase air permeability resistance means a fixed pressure and a fixed volume of air passing through the test piece, and a larger value means a lower air permeability.

In the conventional speaker diaphragm, the air permeability is preferably low so as not to cause air leakage, but according to the test conducted by the present inventors, it was found that it is not necessary to assert that the air permeability is preferably low from the viewpoint of suppressing the occurrence of a rapid drop in frequency characteristics.

(storage modulus)

The storage modulus of the speaker diaphragm is preferably 7.1GPa or more.

(reinforcing fiber)

The reinforcing fibers include first fibers and second fibers. The second fibers preferably comprise 20% to 50% by volume of all reinforcing fibers taken as 100%.

Carbon fibers may be utilized for the first fibers. For example, PAN-based carbon fibers, pitch-based carbon fibers, high elastic modulus carbon fibers, and the like can be used. Alternatively, the fiber is not limited to carbon fiber, and organic synthetic fibers such as aramid fibers, liquid crystal polyester fibers, ultra-high molecular weight polyethylene fibers, and poly-p-Phenylene Benzobisoxazole (PBO) fibers, glass fibers, basalt fibers, and metal fibers may be used. The fiber has a high elastic modulus required for a speaker, and the elastic modulus is substantially 50GPa or more. These fibers may be discontinuous fibers, continuous fibers, or surface treatments such as plating and modification as needed. Further, the fiber may be a commercially available product or a fiber recycled from scraps or the like. In addition, the carbon fibers and the organic synthetic fibers may be produced from biomass raw materials.

As the second fiber, an organic synthetic fiber such as an aramid small fiber (fibers) or an acrylic pulp can be used. The aramid fibrils are film-like or fiber-like fine particles composed of an aramid, and are sometimes referred to as aramid pulp or fibrillated aramid fibers (for the aramid fibrils, refer to Japanese patent publication No. 35-11851, japanese patent publication No. 37-5752, etc.). In addition, animal fibers such as chitin nanofibers, wool, and silk can be used; at least one of cellulose nanofiber, conifer pulp, broad-leaved tree pulp, cotton linter pulp, rayon, fruit fiber, bamboo, hemp and other plant fibers. The fibers are softer than the first fibers, and most of the fibers contain finer (fibrillated) fibers, and have an apparent elastic modulus of substantially less than 50GPa. The fibers may be those obtained by recycling scraps and the like, which are commercially available. In addition, the organic synthetic fibers may be made from biomass feedstock. Thus, by adding the second fiber, the occurrence of a sharp drop in frequency characteristics can be suppressed. In particular, aramid pulp is preferable in that it can suppress the occurrence of a sharp drop in sound pressure level in a wide range of frequency bands.

(matrix resin)

As the matrix resin, a thermoplastic resin or an uncured thermosetting resin can be used. Thermoplastic resins are particularly preferred. As the thermoplastic resin, polyethylene, polypropylene, polyvinyl acetate, polymethyl methacrylate, polyethylene terephthalate (PET), nylon, polyamide, polyoxymethylene, polycarbonate, polybutylene terephthalate, phenoxy, polyetherimide, polyaryletherketone, thermoplastic polyimide, polysulfone, polyethersulfone, polyphenylene sulfide, polyamideimide, polyimide, and the like can be used. As the thermosetting resin, epoxy, unsaturated polyester, urea, melamine, phenol, diallyl phthalate, and the like can be used. The matrix resin may be modified resin, or may be mixed with 2 or more kinds. But may also be made from recycled or biomass feedstock.

The diaphragm for a speaker may contain 10 to 30vol% of an inorganic filler. Thus, a speaker diaphragm in which no steep valley is formed can be obtained. In order to adjust the phase change air permeability resistance, a scaly filler or a filler filling the void is preferable as the inorganic filler. Examples of the filler formed into a flake shape include expanded graphite and flake particles (examples include flake graphite, mica, alumina, boehmite, kaolin, talc, and glass flakes). As a filler for filling the voids, for example, porous minerals (for example, vermiculite, fly ash, silicon balls, glass balls, pearlite, and the like are used. The inorganic filler may be added internally or may be coated. It is particularly preferable to add expanded graphite. When 20vol% of the expanded graphite is added, the vertical amplitude of sound pressure can be made small (flat state) at 8500 to 10500 Hz.

[ method for manufacturing diaphragm for speaker ]

(substrate Forming step)

The method for manufacturing the diaphragm for the loudspeaker comprises the following steps. First, a base material is formed, which includes a nonwoven fabric or woven fabric composed of first fibers and second fibers as reinforcing fibers, and a matrix resin. The matrix resin may be blended in the form of resin fibers or particles at the time of forming the base material, or a resin impregnated in the reinforcing fibers may be used, or may be impregnated after forming the base fabric of the reinforcing fibers before. From the viewpoint of simplifying the manufacturing process, it is preferable that the resin fibers be blended at the time of forming the base material. In addition, the substrate may contain an adhesive component.

(molding step)

In order to manufacture a speaker diaphragm, the base material is heated and pressurized to manufacture a molded body. In this step, the resin blended in the base material is caused to flow and cure to form a matrix resin. The molded article may be processed into a vibration plate shape after the hot pressing step, or may be pressed using a mold having a desired shape. This can suppress the occurrence of a sudden drop in frequency characteristics.

Examples (example)

Hereinafter, the speaker diaphragms according to examples 1 to 5 and comparative examples 1 to 3 were produced. In all examples and comparative examples, PET was used for the matrix resin.

The frequency characteristics of the obtained diaphragms for speakers of examples and comparative examples were measured. According to JIS C5532:2014 and measuring the frequency by using a portable acoustic vibration multiplex analyzer.

Further, the phase change air permeability test was performed for each sample of the speaker diaphragm of each of the examples and comparative examples.

Further, the density of each sample was measured. According to JIS P8118:2014, and measuring the density.

Further, storage modulus (GPa) and internal loss (tan δ) of example 4 and comparative examples 1 to 3 were measured. According to JIS K7244-4:1999 the determination of the storage modulus was carried out under stretch mode conditions using a dynamic viscoelasticity measuring device (METRAVIB; DMA+100). The measurement frequency was 1Hz, and the amplitude of the dynamic strain was 0.01%.

Fig. 3 to 11 show measurement results of frequency characteristics of each sample. In these drawings, fig. 3 shows a graph of the frequency characteristics of the speaker diaphragm according to example 1, fig. 4 shows a graph of the frequency characteristics of the speaker diaphragm according to example 2, fig. 5 shows a graph of the frequency characteristics of the speaker diaphragm according to example 3, fig. 6 shows a graph of the frequency characteristics of the speaker diaphragm according to example 4, fig. 7 shows a graph of the frequency characteristics of the speaker diaphragm according to example 5, fig. 8 shows a graph of the frequency characteristics of the speaker diaphragm according to comparative example 1, fig. 9 shows a graph of the frequency characteristics of the speaker diaphragm according to comparative example 2, and fig. 10 shows a graph of the frequency characteristics of the speaker diaphragm according to comparative example 3. Fig. 11 is a graph showing the frequency characteristics of example 4 and comparative example 2 superimposed for comparison. In fig. 8 to 10, a region surrounded by a broken line indicates a valley of frequency characteristics. In addition, with respect to the above samples, fig. 12 shows the relationship between the amount of the second fiber and the phase change air permeation resistance. In the figure, examples are drawn by o and comparative examples are drawn by x.

In example 1, as the first fiber, a fiber containing only 25vol% of para-aramid was used. The valley of the frequency characteristic of the obtained diaphragm for a speaker is a region surrounded by a broken line circle in fig. 3, and the minimum frequency is 47dB at 15200Hz, but this is outside the human audible range described above, namely, 20 to 12500 Hz. That is, excellent characteristics in which a drop of 10dB/20 μPa or more does not occur, in other words, a steep valley does not occur, are exhibited in the audible range.

Likewise, in example 2, 20vol% carbon fiber, 10vol% aramid pulp was used. As shown in fig. 4, the valley of the frequency characteristic of the obtained diaphragm for a speaker shows 80dB at 1800Hz, 88dB at-250 Hz (left side in fig. 4) and 93dB at +250Hz (right side in fig. 4) with a very small frequency. The difference from the minimum frequency was 8dB and 13dB, respectively, the former showed no characteristic of a drop of 10dB/20 μPa or more.

Likewise, in example 3, 20vol% carbon fiber, 5vol% aramid pulp was used. As shown in fig. 5, the valley of the frequency characteristic of the obtained diaphragm for a speaker shows that the minimum frequency is 81dB at 1800Hz, 90dB at-250 Hz, and 93dB at +250 Hz. The difference from the minimum frequency was 9dB and 12dB, respectively, and the former showed the characteristic that no drop of 10dB/20 μPa or more occurred.

In example 4, 15vol% of carbon fiber and 5vol% of aramid pulp were used. As shown in fig. 6, the valley of the frequency characteristic of the obtained diaphragm for a speaker shows 84dB at 1700Hz, 93dB at-250 Hz, and 92dB at +250 Hz. The difference from the minimum frequency was 9dB and 8dB, respectively, and the excellent characteristics of no steep valley, in which no drop of 10dB/20 mu Pa or more occurred, were exhibited.

Further, in example 5, 15vol% of carbon fiber was used, and 5vol% of acrylic pulp was used as the second fiber instead of aramid pulp. As shown in fig. 7, the valley of the frequency characteristic of the obtained diaphragm for a speaker shows 80dB at 1600Hz, 94dB at-250 Hz, and 84dB at +250 Hz. The difference from the minimum frequency was 14dB and 4dB, respectively, which showed the characteristic that no drop of 10dB/20 μPa or more occurred.

On the other hand, in comparative example 1, the carbon fiber was set to 15vol% only as the reinforcing fiber, and no second fiber was added. As shown in fig. 8, the valley of the frequency characteristic of the obtained diaphragm for a speaker shows that the minimum frequency is 64dB at 10400Hz, 78dB at-250 Hz, and 74dB at +250 Hz. The difference from the minimum frequency was 14dB and 10dB, respectively, and the characteristic that the drop of 10dB/20 mu Pa or more occurred was exhibited.

In comparative example 2, carbon fibers were used as reinforcing fibers in an amount of only 20vol%. As shown in fig. 9, the valley of the frequency characteristic of the obtained diaphragm for a speaker shows 65dB at 8100Hz, 78dB at-250 Hz, and 78dB at +250 Hz. The difference from the minimum frequency was 13dB, and the characteristic of a drop of 10dB/20 mu Pa or more was exhibited.

Finally, in comparative example 3, 15vol% of the aramid pulp was added as the second fiber, with 15vol% of the carbon fiber as the first fiber. As shown in fig. 10, the valley of the frequency characteristic of the obtained diaphragm for a speaker shows that the minimum frequency is 81dB at 1700Hz, 93dB at-250 Hz, and 95dB at +250 Hz. The difference from the minimum frequency was 12dB and 14dB, respectively, and the characteristic that the drop of 10dB/20 mu Pa or more occurred was exhibited.

Here, fig. 11 is a graph showing a superimposed display of frequency characteristics of the speaker diaphragm according to example 4 and comparative example 2 in which reinforcing fibers are 20vol%. As shown in the figure, it can be confirmed that: in contrast to the comparative example 2, which had large valleys around 8100Hz, the occurrence of such valleys was suppressed in example 4, and a speaker diaphragm having improved sound reproduction was obtained.

Table 1 shows the results of measurement of the compositions and characteristics (phase change air permeability resistance, density, storage modulus, and internal loss) of each example and comparative example.

[ Table 1 ]

In comparison between example 4 and comparative example 2, the storage modulus was increased in example 4 in which the reinforcing fibers were 20vol%, but the carbon fibers were small as the first fibers. In addition, compared with comparative example 2 in which carbon fibers were further added in an amount of 5vol% to 20vol% in addition to comparative example 1 in which carbon fibers were contained in an amount of 15vol%, the storage modulus of example 4 in which aramid pulp was added in an amount of 5vol% as the second fiber was higher. As above, it can be confirmed that: the storage modulus can be improved without increasing the carbon fiber.

On the other hand, with respect to comparative example 3 in which 15vol% of aramid pulp was added as the second fiber, the storage modulus was lowered as compared with example 4 in which 5vol% of aramid pulp was added. This can determine that: if the aramid pulp is added excessively, the storage modulus decreases. Thus, from the viewpoint of improving the storage modulus, it can be said that the second fibers are preferably made smaller than the first fibers. According to an embodiment, the second fibers are 25% to 50% of the first fibers, and a good storage modulus can be obtained.

Example 6, 7

Further, as examples 6 and 7, a diaphragm for a speaker containing 20vol% of expanded graphite as an inorganic filler was produced. In examples 6 and 7, 20vol% of carbon fibers were used as reinforcing fibers, and no second fibers were used. In addition, polyamide (PA 6) is used as a matrix resin. Fig. 13 to 14 are graphs showing the results of measuring the frequency characteristics of the obtained samples of examples 6 and 7. In these drawings, fig. 13 is a graph showing the frequency characteristics of the speaker diaphragm according to example 6, and fig. 14 is a graph showing the frequency characteristics of the speaker diaphragm according to example 7. In fig. 13 to 14, the area surrounded by the broken line also represents a valley of the frequency characteristic. The results of the measurement of the composition and the characteristics (phase change air permeability resistance, density) of examples 6 and 7 are shown in table 2. The method and apparatus for measuring each characteristic such as frequency characteristic are the same as those of the above examples and comparative examples.

[ Table 2 ]

As shown in the graphs of fig. 13 to 14, in examples 6 and 7, it was confirmed that a speaker diaphragm having no steep valley was obtained, and the effectiveness of the inorganic filler was confirmed. Specifically, in example 6, as shown in fig. 13, regarding the valley of the frequency characteristic, the extremely small frequency is shown as 85dB at 700Hz, 89dB at-250 Hz (left side in the drawing) and 95dB at +250Hz (right side in the drawing) thereof. The difference from the minimum frequency was 4dB and 10dB, respectively, the former showed no characteristic of a drop of 10dB/20 μPa or more. Further, the sound pressure between 8500Hz and 10500Hz (the region surrounded by the one-dot chain line in the figure) is converged between 91 and 93dB.

Further, in example 7, as shown in fig. 14, regarding the valley of the frequency characteristic, the extremely small frequency was shown as 84dB at 700Hz, 88dB at-250 Hz (left side in the drawing) and 94dB at +250Hz (right side in the drawing) thereof. The difference from the minimum frequency was 4dB and 10dB, respectively, and the former showed the characteristic that no drop of 10dB/20 μPa or more occurred. Further, the sound pressure between 8500Hz and 10500Hz (the region surrounded by the one-dot chain line in the figure) is converged between 91 and 94dB.

[ industrial utilization possibility ]

The speaker diaphragm and the method of manufacturing the same according to the present invention can be suitably used for a speaker for outdoor use such as a vehicle speaker and a PA speaker, or any suitable speaker such as a speaker for headphones.

Claims

1. A diaphragm for a speaker, characterized in that,

the diaphragm for a speaker contains reinforcing fibers and a matrix resin,

the phase-change air permeability resistance is 4.0 to 20 seconds.

2. A diaphragm for a speaker according to claim 1, wherein,

the diaphragm for a speaker contains 20 to 30vol% of reinforcing fibers.

3. A diaphragm for a speaker according to claim 1 or 2,

the phase-change air permeability resistance is 5.0 to 20 seconds.

4. A diaphragm for a speaker according to claim 1 or 2,

the reinforcing fibers include first fibers and second fibers,

the first fiber is at least any one of carbon fiber, aramid fiber, liquid crystal polyester fiber, ultra-high molecular weight polyethylene fiber, PBO fiber, glass fiber, basalt fiber and metal fiber,

the second fiber is at least any one of aramid small fiber, acrylic pulp, cellulose nanofiber, conifer pulp, broad-leaved tree pulp, cotton linter pulp, rayon, fruit fiber, bamboo, hemp, chitin nanofiber, wool and silk.

5. The diaphragm for a speaker according to claim 4, wherein,

the reinforcing fiber contains 20-50% of the second fiber by volume ratio.

6. A diaphragm for a speaker according to claim 1 or 2,

in the frequency characteristics, the characteristic that a drop of 10dB/20 μPa or more does not occur in either the +250Hz range or the-250 Hz range of the specific frequency with respect to the specific frequency of 12500Hz or less is exhibited.

7. A diaphragm for a speaker according to claim 1 or 2,

the storage modulus is 7.1GPa or more.

8. A diaphragm for a speaker according to claim 1 or 2,

the matrix resin is a thermoplastic resin.

9. The diaphragm for a speaker according to claim 8, wherein,

the thermoplastic resin is at least one of polyethylene, polypropylene, polyvinyl acetate, polymethyl methacrylate, polyethylene terephthalate (PET), nylon, polyamide, polyoxymethylene, polycarbonate, polybutylene terephthalate, phenoxy, polyether imide, polyaryletherketone, thermoplastic polyimide, polysulfone, polyether sulfone, polyphenylene sulfide and polyamide imide.

10. A diaphragm for a speaker according to claim 1 or 2,

the diaphragm for a speaker further contains 10 to 30vol% of an inorganic filler.

11. A diaphragm for a speaker according to claim 1 or 2,

the diaphragm for a speaker further contains 20vol% of expanded graphite.

12. A method for manufacturing a diaphragm for a speaker, characterized in that,

the method for manufacturing the vibrating plate for the loudspeaker comprises the following steps:

a step of forming a base material including a nonwoven fabric or woven fabric composed of first fibers and second fibers as reinforcing fibers, and a matrix resin; and

a step of heating and pressurizing the base material to produce a molded body,

the phase-change air permeability resistance is 4.0 to 20 seconds.