Diaphragm for electro-acoustic transducer

Abstract

The present invention provides a vibrating plate for an electroacoustic transducer that maintains a high Young's modulus and achieves moderate internal loss. In the vibrating plate (1) for an electroacoustic transducer of the present invention, a mixed layer (11) is formed on a substrate (10) mainly composed of cellulose fiber material, wherein a mixed presence layer (11) of fiber material (20) and silk nanofiber (21) is formed.

Description

Technical Field

[0001] This invention relates to a vibrating plate for electroacoustic transducers such as loudspeakers and microphones. Background Technology

[0002] In the diaphragm of electroacoustic transducers, low density, high Young's modulus, and moderate internal loss are required. The material with the best physical properties is selected appropriately according to the application of the loudspeaker or microphone. Various materials exist for diaphragms, but due to performance and cost considerations, cellulose fibers (mainly pulp) are mostly used. However, sometimes the desired physical properties cannot be obtained.

[0003] Therefore, in such a vibrating plate, other materials are coated onto the surface of a substrate made of cellulose fibers to supplement the aforementioned physical properties. For example, Patent Document 1 describes a vibrating plate obtained by coating a substrate layer made of cellulose fibers with cellulose nanofibers.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. WO2015 / 011903 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, in Patent Document 1, although cellulose nanofibers are coated on the surface of the substrate layer, there is a problem that the internal loss (tanδ) will be reduced in this case.

[0009] The present invention was made in view of the above circumstances, and its object is to provide a vibrating plate for an electroacoustic transducer that achieves a suitable Young's modulus and internal loss for the physical properties of the substrate.

[0010] Solution for solving the problem

[0011] To achieve the above objectives, in the vibrating plate for the electroacoustic converter of the present invention, a mixed layer is formed on a substrate made of a fibrous material mainly composed of cellulose fibers, wherein the fibrous material and silk nanofibers are mixed together.

[0012] Alternatively, in the aforementioned vibrating plate for electroacoustic converters, the mixed presence layer may be formed on the surface side of the substrate.

[0013] Alternatively, in the vibrating plate for the electroacoustic converter described above, the average fiber length of the silk nanofibers may be less than 10 μm.

[0014] Alternatively, in the aforementioned vibrating plate for electroacoustic converters, the mixed presence layer can be formed by simultaneously drawing and dehydrating water from one side of the substrate while spraying a suspension containing the silk nanofibers onto the other side of the substrate.

[0015] Alternatively, in the aforementioned vibrating plate for electroacoustic converters, the surface of the substrate may be further formed with a reinforcing layer consisting of the fiber material, the silk nanofibers, and reinforcing materials.

[0016] Alternatively, in the aforementioned vibrating plate for an electroacoustic converter, the reinforcing material may be composed of a material containing mica.

[0017] Alternatively, in the aforementioned vibrating plate for electroacoustic converters, the reinforcing material may be composed of a material containing cellulose nanofibers.

[0018] Alternatively, in the aforementioned vibrating plate for electroacoustic converters, the reinforcing layer can be formed in the mixed-existence layer by simultaneously drawing and dehydrating water from one side of the substrate while spraying a suspension containing the reinforcing material and the silk nanofibers onto the other side of the substrate.

[0019] Invention Effects

[0020] As described above, according to the present invention, a vibrating plate for an electroacoustic transducer can be provided that achieves a suitable Young's modulus and internal loss for the physical properties of the substrate. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of a vibrating plate for an electroacoustic converter according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the cross-section of the vibrating plate in Embodiment A1 of the present invention.

[0023] Figure 3 This is an enlarged image of the cross-section of the vibrating plate in Embodiment A1 of the present invention.

[0024] Figure 4 This is a schematic diagram of the cross-section of the vibrating plate in Embodiment A3 of the present invention.

[0025] Figure 5 This is an enlarged image of the cross-section of the vibrating plate in Embodiment A3 of the present invention.

[0026] Figure 6 This is a graph obtained by comparing the Young's modulus of Comparative Example a of the embodiments of the present invention with that of Examples A1 to A4.

[0027] Figure 7This is a graph obtained by comparing the internal losses of Comparative Example a of the embodiments of the present invention with those of Examples A1 to A4.

[0028] Figure 8 This is a graph obtained by comparing the Young's modulus of comparative examples b1 to b3 of the embodiments of the present invention with that of examples B1 to B3.

[0029] Figure 9 This is a graph obtained by comparing the internal losses of comparative examples b1 to b3 of the embodiments of the present invention with those of examples B1 to B3.

[0030] Figure 10 This is a schematic diagram of the cross-section of the vibrating plate in Embodiment B3 of the present invention.

[0031] Figure 11 This is an enlarged image of the cross-section of the vibrating plate in Embodiment B3 of the present invention.

[0032] Figure 12 This is an enlarged image of the surface of the vibrating plate in Embodiment B3 of the present invention. Detailed Implementation

[0033] The following describes a vibrating plate (hereinafter sometimes simply referred to as a vibrating plate) for an electroacoustic converter according to an embodiment of the present invention.

[0034] Figure 1 This is a cross-sectional view of a vibrating plate for an electroacoustic transducer according to an embodiment of the present invention. Furthermore, Figure 2 This is a schematic diagram of the cross-section of the vibrating plate in Embodiment A1 of the present invention, which will be described later. Figure 3 This is a magnified image of the cross-section of the vibrating plate obtained using a microscope. Furthermore, Figure 4 This is a schematic diagram of the cross-section of the vibrating plate in Embodiment A3 of the present invention, which will be described later. Figure 5 This is a magnified image of the cross-section of the vibrating plate obtained by taking a microscope.

[0035] Figure 1 The diaphragm 1 shown (diaphragm for electroacoustic transducer) is a diaphragm for a loudspeaker according to an embodiment of the present invention, and is conical (frustum conical). The small-diameter opening side of the diaphragm 1 is fitted with a loudspeaker vibration source such as a voice coil (not shown). The inner surface of the conical portion of the diaphragm 1 becomes the sound-radiating surface (front surface), a surface that can be visually confirmed from the outside. On the other hand, various loudspeaker devices (not shown) are arranged on the outer surface (back surface) side of the conical portion of the diaphragm 1.

[0036] First, using embodiment A1 of the present invention Figure 2 , Figure 3The structure of the vibrating plate 1 of the present invention will be described below. In the vibrating plate 1, a mixed layer 11 is formed on the substrate 10, which is mainly composed of cellulose fibers 20, and silk nanofibers 21. It should be noted that in the vibrating plates of Embodiment A1 and Embodiment A3 described later, a reinforcing layer 12 is formed on the surface layer of the front surface side of the substrate 10, which is a mixture of cellulose fibers 21, silk nanofibers 21, and mica 22 as a reinforcing material.

[0037] Here, the substrate 10 is formed by conditioning cellulose fibers 20 (fiber material) that have been beaten to a freeness of 10°SR or higher and 85°SR or lower, and then forming it into a vibrating plate shape. The cellulose fibers 20 in this embodiment are cellulose fibers obtained by mixing wood pulp made from coniferous trees with non-wood pulp made from kenaf. Other wood pulps or non-wood pulps can be used as the cellulose fibers 20, as well as cellulose fibers formed by mixing wood pulp and non-wood pulp, wood pulp monomers, and non-wood pulp monomers. Furthermore, the average fiber diameter (maximum width) of the cellulose fibers 20 is preferably 5 μm or higher and 90 μm or lower. It should be noted that the fiber length of the cellulose fibers 20 is not particularly limited, and cellulose fibers with a fiber length suitable for ordinary papermaking can be appropriately selected.

[0038] like Figure 2 As shown, the mixed layer 11 is a layer in which silk nanofibers 21 are mixed in the gaps between cellulose fibers 20. The average fiber diameter of the silk nanofibers 21 is in the nanometer range, approximately 100 nm, and is finer than that of the cellulose fibers 20, penetrating between the cellulose fibers 20. Figure 2 In the example shown in the schematic diagram, silk nanofibers 21 are present from the outermost surface of the substrate 10 to the vicinity of the center in the thickness direction.

[0039] like Figure 2 As shown, the reinforcing layer 12 is a layer in which surface silk nanofibers 21 and mica 22, serving as a reinforcing material, coexist on the front surface side of the substrate 10. The particle size of mica 22 is larger than the average fiber diameter of the silk nanofibers 21, therefore it does not penetrate deeply into the substrate 10 but remains on the surface of the substrate 10. The mica 22 improves the rigidity of the surface layer of the vibrating plate 1 and increases the propagation speed of the vibrating plate surface.

[0040] It should be noted that, Figure 2 This is a schematic diagram obtained by visualizing the vibrating plate 1. Figure 2 To facilitate understanding of the relationship between cellulose fibers 20, silk nanofibers 21, and mica 22, the elements are shown in exaggerated sizes compared to their actual dimensions. (The actual dimensions are as follows...) Figure 3As shown, the thickness of the substrate 10 is an average of 0.2 mm or more and 0.25 mm or less. In contrast, the mixed layer 11 is formed on the surface of the substrate 10, and the thickness of the mixed layer 11 is approximately half the thickness of the substrate 10, averaging about 0.1 mm. It should be noted that... Figure 3 In this process, to easily identify the mixed presence layer 11 of the substrate 10, only the silk nanofibers 21 are dyed, while the cellulose fibers 20 of the substrate 10 remain undyed, forming the vibrating plate 1. For example... Figure 3 As shown, it can be confirmed that the front surface of the vibrating plate 1 is colored, and a mixed layer 11 is formed on the front surface of the vibrating plate 1 by means of silk nanofibers 21.

[0041] Regarding the mixed-existence layer 11 and the reinforcing layer 12, they are formed by drawing water from the back (one) side of the paper-making substrate 10 while simultaneously spraying a suspension containing silk nanofibers 21 and mica 22 in water onto the front (other) side of the substrate 10, for example, by spraying. This allows the silk nanofibers 21 and mica 22 to enter the surface layer of the front surface of the substrate 10. Afterwards, a vibrating plate 1 having the mixed-existence layer 11 is manufactured through a forming / drying process performed by hot pressing or the like. In this state of being drawn and dehydrated from the back side of the substrate 10, a suspension of silk nanofibers 21 and mica 22 is sprayed onto the front surface of the substrate 10 and coated onto the substrate 10. This prevents the moisture in the suspension from disrupting the arrangement of the cellulose fibers 20 in the substrate 10, allowing the silk nanofibers 21 and mica 22 to smoothly adhere to the surface of the substrate 10, forming a thin and uniform reinforcing layer 12 composed of cellulose fibers 20, silk nanofibers 21, and mica 22. Furthermore, by drawing and dehydrating from the back side of the substrate 10 being paper-made, only the finer silk nanofibers 21 in the sprayed suspension can deeply penetrate between the cellulose fibers 20, forming a mixed layer 11 deeper than the reinforcing layer 12. In contrast, the particle size of mica 22 is larger than the average fiber diameter of silk nanofibers 21 and the gaps between cellulose fibers 20 are larger. Therefore, although some of the mica 22 enters the gaps, most of the mica 22 tends to remain on the surface of the substrate 10, and the mica 22 is uniformly present on the surface, thereby forming a reinforcing layer 12 on the front surface side of the mixed presence layer 11. It should be noted that the suspension does not necessarily need to contain mica 22 as a reinforcing material. Alternatively, a suspension containing silk nanofibers 21 but not mica 22 can be sprayed to form a mixed presence layer on the vibrating plate without forming a reinforcing layer.

[0042] Silk nanofibers 21 are produced by mechanically breaking down natural silk fibers, primarily composed of protein, into nanofibers, thus miniaturizing the average fiber diameter to the nanometer scale. In the embodiments of this invention, the silk nanofibers 21 are miniaturized to an average fiber diameter of approximately 100 nm and an average fiber length of less than 10 μm. This fine average fiber diameter allows the silk nanofibers 21 to easily penetrate between the cellulose fibers 20, potentially affecting the physical properties of the substrate 10. The silk nanofibers 21 exhibit high dispersibility with water, allowing for uniform dispersion in a suspension and uniform coating on the substrate. Therefore, a vibrating plate with uniform physical properties can be formed across the entire surface of the vibrating plate.

[0043] Regarding mica 22, if the particle size is too small, it may be difficult to identify the mica 22 on the surface of the vibrating plate; if the particle size is too large, the texture may become rough, thus degrading the decorative properties of the vibrating plate 1. Furthermore, if the mica 22 particle size is too small, it is difficult to keep the mica 22 on the surface of the substrate 10; if the mica 22 particle size is too large, it is difficult to distribute the mica 22 between the cellulose fibers 20. Therefore, the particle size of the mica 22 is preferably 10. u The mica 22 is between 500 μm and 100 μm in size. It should be noted that the mica 22 can be either natural or synthetic. Furthermore, to enhance the decorative appeal of the vibrating plate 1, the mica 22 is preferably a glossy mica coated with titanium oxide, iron oxide, or similar materials. Additionally, by using larger-sized mica particles, the mica can remain on the surface of the vibrating plate, increasing the surface rigidity and thus improving the propagation speed. Furthermore, the average fiber diameter of the silk nanofibers 21 is finer than that of the mica 22 and the cellulose fibers 20, making it difficult to visually confirm their presence on the surface of the vibrating plate. However, by mixing and spraying the silk nanofibers 21 and mica 22, the larger-sized mica 22 can be identified, and the reliable spraying of the silk nanofibers 21 can be visually confirmed. Therefore, the quality of the vibrating plate as an industrial product can be guaranteed.

[0044] (First Embodiment)

[0045] The following describes the comparison results of the Young's modulus and internal loss of the test specimens for measuring the vibrating plate of the electroacoustic transducer using the first embodiment and comparative example of the present invention.

[0046] Comparative Example a uses a test sample made solely of cellulose fibers as the substrate. Examples A1 and A3 use test samples having a mixed layer of cellulose fibers and silk nanofibers mixed in the cellulose fiber substrate, and a reinforcing layer of cellulose fibers, silk nanofibers, and mica mixed on the surface of the substrate. Examples A2 and A4 use test samples having a mixed layer of cellulose fibers and silk nanofibers mixed in the cellulose fiber substrate. Examples A2 and A4 do not contain mica, therefore no reinforcing layer is formed. The conditions of the test samples in each example (mass of silk nanofibers and mica relative to the mass of the test sample: mass%) are shown in Table 1.

[0047] [Table 1]

[0048] Comparative example a Example A1 Example A2 Example A3 Example A4 Silk nanofibers none 1.90％ 2.00％ 4.75％ 5.00％ mica none 0.10％ none 0.25％ none

[0049] The test samples were prepared with a constant basis weight of 170 g / m², and cut into 40 mm long and 5 mm wide pieces. Specifically, the samples in Examples A1 and A3 were prepared by spraying a suspension of silk nanofibers and mica at a mass ratio of 95:5 onto the front surface of the substrate after the substrate was papered using a papermaking wire. This suspension was then dehydrated from the back side of the substrate while being sprayed onto the front surface. Example A1 was prepared by spraying with silk nanofibers and mica comprising 2.00% of the total sample mass, with silk nanofibers accounting for 1.90% and mica for 0.10%. Similarly, Example A3 was prepared by spraying with silk nanofibers and mica comprising 5.00% of the total sample mass, with silk nanofibers accounting for 4.75% and mica for 0.25%. Furthermore, the samples for Examples A2 and A4 were formed by spraying a suspension of silk nanofibers onto the front surface of the substrate while simultaneously drawing water from the back side of the substrate after the cellulose fibers of the substrate were formed using a papermaking wire. Example A2 was formed by spraying in a manner where the mass of the silk nanofibers constituted 2.00% of the total mass of the sample, and Example A4 was formed by spraying in a manner where the mass of the silk nanofibers constituted 5.00% of the total mass of the sample.

[0050] Figure 4 , Figure 5 This is a schematic diagram of the cross-section of the vibrating plate in Embodiment A3 of the present invention and a magnified image taken with a microscope, compared with Embodiment A1. Figure 2 , Figure 3 correspond.

[0051] like Figure 4 As shown, in the mixed presence layer 11 of Example A3, the mass of silk nanofibers is as high as 4.75% by mass relative to 1.90% by mass of Example A1, and silk nanofibers 21 are present from the outermost surface of the substrate 10 to near the back side in the thickness direction. Figure 5 As shown, the thickness of the substrate 10 is on average 0.2 mm or more and 0.25 mm or less, while the thickness of the mixed layer 11 is about 0.15 mm.

[0052] For the substrates of Comparative Example a and Examples A1 to A4, cellulose fibers were used as cellulose fibers, which were a mixture of 50% by mass of NUKP and 50% by mass of kenaf and pulped at a beating degree of 20°SR.

[0053] The silk nanofibers used in Examples A1 to A4 were model KCo-30005 manufactured by SUGINO MACHINE Co., Ltd. These silk nanofibers were produced by mechanically breaking down silk fibers, resulting in fibers with an average fiber diameter of approximately 100 nm and an average fiber length of less than 10 μm. Furthermore, the mica used in Examples A1 and A3 was model MS-100R manufactured by Kōken Kogyo Co., Ltd. This mica had a particle size of 20 μm to 100 μm and was based on natural mica, coated with titanium oxide and iron oxide to impart luster. In Examples A1 and A3, the mass-based ratio of silk nanofibers to mica was 95:5.

[0054] use Figure 6 , Figure 7 The physical properties (Young's modulus, internal loss (tanδ)) obtained by measuring the samples of Comparative Example a and Examples A1 to A4 using the vibrating Reed method are explained. It should be noted that... Figure 6 The figure shows the average value of Young's modulus measurements (n=10). Figure 7 The measured average value of internal loss is shown in the figure (n=10).

[0055] First, let's explain Young's modulus. According to... Figure 6It is evident that in Examples A1 to A4, which have a mixed-content layer containing silk nanofibers in the substrate, the Young's modulus is lower compared to Comparative Example a. Furthermore, a comparison of Comparative Example a with Examples A1 and A3, and with Examples A2 and A4, shows that the higher the amount of silk nanofibers, the lower the Young's modulus. Specifically, the Young's modulus of Comparative Example a is 4.19 [GPa], while the Young's modulus of Example A1, which contains 1.90% by mass of silk nanofibers, is 3.99 [GPa], and the Young's modulus of Example A3, which contains 4.75% by mass of silk nanofibers, is 3.94 [GPa]. In terms of Young's modulus, Example A1 is about 5% lower than Comparative Example a, and Example A3 is about 6% lower. Furthermore, Example A2, which contains 2.00% by mass of silk nanofibers, has a Young's modulus of 3.94 [GPa], while Example A4, which contains 5.00% by mass of silk nanofibers, has a Young's modulus of 3.74 [GPa]. In terms of Young's modulus, Example A2 decreased by approximately 6% compared to Comparative Example a, and Example A4 decreased by approximately 11%. Moreover, a comparison of Example A1, which contains 0.10% by mass of mica, with Example A2, which does not contain mica, and a comparison of Example A3, which contains 0.25% by mass of mica, with Example A4, clearly shows that the reduction in Young's modulus can be suppressed by having a reinforcing layer containing mica. In particular, in the comparison of Example A3 and Example A4, Example A3, which has a reinforcing layer containing mica, showed an increase in Young's modulus of approximately 5% compared to Example A4. It should be noted that, in addition to mica, cellulose nanofibers are also used as reinforcing materials to form a reinforcing layer in which mica and cellulose nanofibers are mixed, thereby further suppressing the decrease in Young's modulus.

[0056] Next, the measured value tanδ, representing internal loss, will be explained. Based on... Figure 7It is evident that, compared to Comparative Example a, the tanδ values ​​in Examples A1 to A4, which have a mixed-existence layer containing silk nanofibers in a substrate, are larger. Furthermore, a comparison of Comparative Example a with Examples A1 and A3, and with Examples A2 and A4, shows that the greater the amount of silk nanofibers, the larger the tanδ. Specifically, the tanδ of Comparative Example a is 0.0287, while the tanδ of Example A1, containing 1.90% by mass of silk nanofibers, is 0.0295, and that of Example A3, containing 4.75% by mass of silk nanofibers, is 0.0299. In terms of tanδ, Example A1 shows an increase of approximately 3%, and Example A3 shows an increase of approximately 4%, compared to Comparative Example a. Furthermore, Example A2, containing 2.00% by mass of silk nanofibers, has a tanδ of 0.0298, and Example A4, containing 5.00% by mass of silk nanofibers, has a tanδ of 0.0304. Regarding tanδ, compared to Comparative Example a, Example A2 showed an increase of approximately 4%, and Example A4 showed an increase of approximately 6%. The bond between the silk fibers constituting the silk nanofibers and the cellulose fibers of the substrate is weak. Therefore, the silk nanofibers penetrate between the cellulose fibers, thereby weakening the bonding force between the cellulose fibers and improving the attenuation effect, thus increasing the internal loss of the diaphragm. Therefore, the speaker using this diaphragm can achieve clear sound quality. On the other hand, the bonding force between the cellulose fibers is weakened by the silk nanofibers, resulting in a decrease in the Young's modulus of the diaphragm. However, by adjusting the permeability of the silk nanofibers, the decrease in Young's modulus can be suppressed, forming a diaphragm that ensures moderate internal loss.

[0057] As described above, by forming a mixed layer of cellulose fiber and silk nanofibers in a substrate of a diaphragm for an electroacoustic transducer, Young's modulus can be maintained and the internal loss properties of the substrate itself can be improved. Furthermore, the balance between Young's modulus and internal loss properties can be adjusted according to the amount of silk nanofibers present and the permeability of the mixed layer. Thus, by using silk nanofibers, a diaphragm with appropriate Young's modulus and internal loss properties for the substrate can be provided. Therefore, by using this diaphragm, the acoustic characteristics of the loudspeaker can be optimized according to the purpose of the loudspeaker.

[0058] Furthermore, by further forming a reinforcing layer containing mica and other reinforcing materials, the decrease in Young's modulus can be suppressed. Thus, by combining silk nanofibers and reinforcing materials, the internal losses and Young's modulus of the vibrating plate can be set to appropriate states.

[0059] Furthermore, by simultaneously drawing and dehydrating the substrate from one side and spraying a suspension containing silk nanofibers onto the other side, the silk nanofibers can penetrate into the interior of the substrate, effectively improving the substrate's physical properties (especially internal losses). It should be noted that the average fiber diameter of silk nanofibers is finer than that of cellulose fibers. Therefore, even when cellulose fibers and silk nanofibers are mixed during papermaking and the paper is formed, the silk nanofibers will flow out with the papermaking wastewater through the spaces between cellulose fibers and the mesh of the papermaking wire, making it difficult for them to remain inside the vibrating plate. Therefore, by spraying silk nanofibers onto the substrate after papermaking as in this embodiment, the silk nanofibers can be effectively retained between the cellulose fibers that are clogging the mesh, effectively forming a vibrating plate containing a mixture of silk nanofibers.

[0060] Furthermore, by spraying the suspension to form the mixed layer 11, the amount of water used can be reduced to a minimum. For example, comparing a conventional single-layer papermaking vibrator, a double-layer papermaking vibrator formed by overlapping the substrate and surface layer through papermaking, and a second-layer spray vibrator formed by spraying the substrate and the surface layer (mixed layer) as in this embodiment, both the double-layer papermaking vibrator and the second-layer spray vibrator are structurally double-layer vibrators, but the thickness of the surface layer differs. For example, the surface layer of the double-layer papermaking vibrator is 10% to 50% of the overall (vibrator cross-section) thickness, but the surface layer of the second-layer spray vibrator can be formed at 2% to 5% of the overall thickness. Moreover, regarding the amount of water used, in a single-layer papermaking vibrator, several liters of papermaking water are used for papermaking. In addition, in a double-layer papermaking vibrator, several liters are required for both the substrate and the surface layer. In contrast, the amount of water required for the second layer of spray vibrating plate remains unchanged at several liters for the substrate, but only a few grams to tens of grams for the suspension. Compared with the double-layer papermaking vibrating plate, this significantly reduces water usage and contributes to the reduction of drainage.

[0061] It should be noted that in the above embodiments and the first embodiment, mica was used as a reinforcing material, but the reinforcing material is not limited to mica. Other materials with high bending stiffness, carbon fiber, cellulose nanofibers and other materials with high Young's modulus can also be used, and they can also be used in appropriate combinations.

[0062] When using cellulose nanofibers as reinforcing materials, cellulose nanofibers with short average fiber lengths are preferred. When using cellulose nanofibers with short average fiber lengths, the dispersibility of both silk nanofibers and cellulose nanofibers in the suspension is higher compared to cellulose nanofibers with long average fiber lengths. Therefore, when spraying the suspension onto the front surface of a substrate, silk nanofibers and cellulose nanofibers can be sprayed uniformly, resulting in excellent manufacturability.

[0063] When cellulose nanofibers are used as a reinforcing material, while spraying a suspension containing silk nanofibers and cellulose nanofibers onto the front surface of the substrate and simultaneously drawing water from the back side of the substrate, the silk nanofibers penetrate deep into the substrate through the gaps between the cellulose fibers, whereas the cellulose nanofibers tend to remain on the surface of the substrate. This allows the formation of a reinforcing layer on the front surface of the mixed-content layer, containing cellulose fibers, silk nanofibers, and a mixture of cellulose nanofibers. The Young's modulus of cellulose nanofibers is approximately twice higher than that of cellulose fibers such as pulp. Therefore, compared to using mica alone as a reinforcing material, by using cellulose nanofibers, internal losses can be increased within the silk nanofibers without further reducing the Young's modulus of the vibrating plate.

[0064] (Second Embodiment)

[0065] The following describes the comparison results of the Young's modulus and internal loss of the test specimens for measuring the vibrating plate of the electroacoustic transducer using the second embodiment and comparative example of the present invention, which uses cellulose nanofibers as reinforcing materials.

[0066] Comparative Example b1 uses a test sample with a substrate composed solely of cellulose fibers. Comparative Example b2 uses a test sample having a layer in which short-fiber cellulose nanofibers are mixed within a substrate composed of cellulose fibers, and a layer on the surface of the substrate containing cellulose fibers, short-fiber cellulose nanofibers, and mica. Comparative Example b3 uses a test sample having a layer in which long-fiber cellulose nanofibers are mixed within a substrate composed of cellulose fibers, and a layer on the surface of the substrate containing cellulose fibers, long-fiber cellulose nanofibers, and mica.

[0067] Example B1 uses a test sample having a mixed layer of cellulose fibers and silk nanofibers mixed in a substrate made of cellulose fibers, and a reinforcing layer of cellulose fibers, silk nanofibers, and mica mixed in the surface layer of the substrate. Example B2 uses a test sample having a mixed layer of silk nanofibers mixed in a substrate made of cellulose fibers, and a reinforcing layer of short-fiber cellulose nanofibers, silk nanofibers, and mica mixed in the surface layer of the substrate. Example B3 uses a test sample having a mixed layer of silk nanofibers mixed in a substrate made of cellulose fibers, and a reinforcing layer of long-fiber cellulose nanofibers, silk nanofibers, and mica mixed in the surface layer of the substrate.

[0068] The conditions (mass of nanofibers and mica relative to the mass of the test sample) for the comparative examples b1 to b3 and examples B1 to B3 are shown in Table 2.

[0069] [Table 2]

[0070] Comparative example b1 Comparative example b2 Comparative example b3 Example B1 Example B2 Example B. Short fiber cellulose nanofibers none 1.90％ none none 0.95％ none Long-fiber cellulose nanofibers none none 1.90％ none none 0.95％ Silk nanofibers none none none 1.90％ 0.95％ 0.95％ mica none 0.10％ 0.10％ 0.10％ 0.10％ 0.10％

[0071] All test samples were prepared with a total sample mass (gram weight) of 150 g / m³. 2 The paper is produced by cutting it into pieces 40mm long and 5mm wide. It should be noted that the papermaking conditions (paper forming conditions, pressure conditions, basis weight, etc.) in the second embodiment differ from those in the first embodiment, making it impossible to uniformly compare physical property data in both embodiments.

[0072] The samples used for the determination of Comparative Examples b2, b3, and Examples B1 to B3 were as follows: After papermaking using a papermaking wire, a suspension of nanofibers and mica with a mass ratio of 95:5 was sprayed onto the front surface of the substrate while simultaneously dehydrating the substrate from the back side. More specifically, for the suspension: in Comparative Example b2, the mass ratio of short-fiber cellulose nanofibers to mica was adjusted to 95:5; in Comparative Example b3, the mass ratio of long-fiber cellulose nanofibers to mica was adjusted to 95:5; in Example B1, the mass ratio of silk nanofibers to mica was adjusted to 95:5; in Example B2, the mass ratio of short-fiber cellulose nanofibers to silk nanofibers to mica was adjusted to 47.5:47.5:5; and in Example B3, the mass ratio of long-fiber cellulose nanofibers to silk nanofibers to mica was adjusted to 47.5:47.5:5.

[0073] Comparative Example b2 was prepared by spraying in a manner where the mass of short-fiber cellulose nanofibers and mica constituted 2.00% by mass of the total sample mass, with short-fiber cellulose nanofibers comprising 1.90% by mass and mica comprising 0.10% by mass. Similarly, Comparative Example b3 was prepared by spraying in a manner where the mass of long-fiber cellulose nanofibers and mica constituted 2.00% by mass of the total sample mass, with long-fiber cellulose nanofibers comprising 1.90% by mass and mica comprising 0.10% by mass.

[0074] Example B1 was formed by spraying silk nanofibers and mica at a mass ratio of 2.00% of the total sample mass, with silk nanofibers comprising 1.90% and mica 0.10% of the total sample mass. Example B2 was formed by spraying short-fiber cellulose nanofibers, silk nanofibers, and mica at a mass ratio of 2.00% of the total sample mass, with short-fiber cellulose nanofibers and silk nanofibers each comprising 0.95% of the total sample mass, and mica 0.10% of the total sample mass. Example B3 was formed by spraying long-fiber cellulose nanofibers, silk nanofibers, and mica at a mass ratio of 2.00% of the total sample mass, with long-fiber cellulose nanofibers and silk nanofibers each comprising 0.95% of the total sample mass, and mica 0.10% of the total sample mass.

[0075] For the substrates of Comparative Examples b1 to b3 and Examples B1 to B3, cellulose fibers were used as cellulose fibers, which were pulped by mixing 50% by mass of NUKP and 50% by mass of kenaf at a beating degree of 20°SR.

[0076] The silk nanofibers in Examples B1 to B3 used model KCo-30005 manufactured by SUGINO MACHINE Co., Ltd. These silk nanofibers were obtained by mechanically breaking down silk fibers and micronizing them to an average fiber diameter of approximately 100 nm and an average fiber length of less than 10 μm. Furthermore, the mica used in Comparative Examples b2, b3, and Examples B1 to B3 used model MS-100R manufactured by Kōken Kogyo Co., Ltd. This mica has a particle size of 20 μm to 100 μm and is based on natural mica, coated with titanium oxide and iron oxide to impart luster. Additionally, the short-fiber cellulose nanofibers in Comparative Example b2 and Example B2 used model FMa-10010 manufactured by SUGINO MACHINE Co., Ltd. These short-fiber cellulose nanofibers were obtained by mechanically breaking down cellulose fibers and micronizing them to an average fiber diameter of approximately 10 to 50 nm. Furthermore, the long-fiber cellulose nanofibers used in Comparative Example b3 and Example B3 were model IMa-10005 manufactured by SUGINO MACHINE Co., Ltd. Long-fiber cellulose nanofibers are fibers that have been micronized to an average fiber diameter of approximately 10–50 nm by mechanically breaking down cellulose fibers; they are fibers with an average fiber length longer than short-fiber cellulose nanofibers.

[0077] use Figure 8 , Figure 9 The physical properties (Young's modulus, internal loss (tanδ)) obtained by measuring the samples of comparative examples b1-b3 and examples B1-B3 using the vibrating plate method are explained. It should be noted that... Figure 8 The figure shows the average value of Young's modulus measurements (n=10). Figure 9 The measured average value of internal loss is shown in the figure (n=10).

[0078] First, let's explain Young's modulus. According to... Figure 8 It is evident that in Examples B1 to B3, by incorporating silk nanofibers into the substrate, the Young's modulus decreased compared to Comparative Examples B2 and B3, which only contained cellulose nanofibers. Furthermore, among Examples B1 to B3, Example B2, which contained both short-fiber cellulose nanofibers and silk nanofibers, had the lowest Young's modulus (3.38 GPa), followed by Example B2 containing only silk nanofibers (3.43 GPa), while Example B3, which contained both long-fiber cellulose nanofibers and silk nanofibers, had the highest Young's modulus (3.59 GPa).

[0079] In Example B2, by mixing short-fiber cellulose nanofibers with silk nanofibers in the substrate, the short-fiber cellulose nanofibers inhibit the penetration of silk nanofibers into the cellulose fibers. As a result, silk nanofibers are effectively retained on the surface of the substrate, thus weakening the bonding force between the cellulose fibers and cellulose nanofibers on the surface. Compared to Comparative Examples b2 and b3, the overall Young's modulus of the vibrating plate is reduced.

[0080] In Example B3, by mixing long cellulose nanofibers and silk nanofibers together in the substrate, the highly dispersible silk nanofibers can remain effectively on the surface without penetrating into the vibrating plate.

[0081] Next, tanδ, representing internal loss, will be explained. Based on... Figure 9 It is evident that, as in Comparative Examples b2 and b3, tanδ decreases when only cellulose nanofibers are mixed in the substrate. In contrast, tanδ increases when silk nanofibers are mixed in.

[0082] For example, compared to Comparative Example B2, which only contains short-fiber cellulose nanofibers, the tanδ (0.0274) of Example B2, which contains both short-fiber cellulose nanofibers and silk nanofibers, is increased. The tanδ of Example B2 is higher than that of Example B1, which only contains silk nanofibers, (0.0278).

[0083] Furthermore, compared to Comparative Example B3, which only contains long-fiber cellulose nanofibers, the tanδ (0.0268) of Example B3, which contains both long-fiber cellulose nanofibers and silk nanofibers, is increased.

[0084] The weak bonding between silk nanofibers and the cellulose fibers of the substrate enhances attenuation, thus increasing the internal losses of the diaphragm. Therefore, loudspeakers using this diaphragm achieve clear sound quality.

[0085] then, Figure 10 , Figure 11 This is a schematic diagram of the cross-section of the vibrating plate in Embodiment B3 of the present invention and a magnified image taken with a microscope. Figure 12 These are magnified images obtained by taking pictures of the surface of the vibrating plate in Example B3 using a microscope. It should be noted that... Figure 11 In order to easily identify the mixed presence layer 11 and the reinforcing layer of the substrate 10, the silk nanofibers 21 are dyed red, while the cellulose fibers 20 of the substrate 10 are not dyed, and the cellulose nanofibers 23 are dyed black to form the vibrating plate 1.

[0086] like Figure 10 , Figure 11 As shown, the surface of the vibrating plate is darkly colored, indicating that in Example B3, most of the long cellulose nanofibers 23 remain on the surface of the substrate 10. Furthermore, as... Figure 12 As shown, it can be confirmed that: lustrous mica 22 is uniformly distributed on the surface of the vibrating plate, and silk nanofibers 21, cellulose nanofibers 23, and mica 22 are disposed on the surface of the vibrating plate. Furthermore, in Figure 11 In the diagram, the lighter-colored areas represent the mixed layer containing silk nanofibers. Thus, it can be seen that the mixed layer contains cellulose nanofibers, unlike the layer without them. Figure 3 and Figure 5 Compared to the vibrating plate in Example B3, the silk nanofibers 21 have a shallower penetration relative to the substrate 10. By mixing long-fiber cellulose nanofibers 23 and silk nanofibers 21 in this way, the silk nanofibers 21 can remain on the surface and not penetrate into the interior of the vibrating plate. Therefore, the gaps between the cellulose fibers 20 of the substrate 10 can be effectively filled in the surface of the vibrating plate, resulting in a vibrating plate with increased surface density. Furthermore, by mixing cellulose nanofibers and silk nanofibers 21, the amount of silk nanofibers 21 used can be reduced. In addition, the vibrating plate with increased surface density can suppress airflow and effectively transmit vibrations to the air, thus increasing sound pressure.

[0087] As in the second embodiments B2 and B3, not only mica but also cellulose nanofibers are mixed in with silk nanofibers as reinforcing materials, thereby enabling the manufacture of a vibrating plate that improves sound pressure and has an excellent balance between Young's modulus and internal loss.

[0088] It should be noted that mica is present in all of the second embodiments B1 to B3, but even without mica, the Young's modulus and the tendency for internal loss can be achieved with equal effect. In addition, by configuring silk nanofibers on the surface of the vibrating plate, the weather resistance of the pulp to ultraviolet light can be improved, and the fading and embrittlement of the vibrating plate can also be inhibited.

[0089] The above concludes the description of the embodiments and examples of the present invention, but the solutions of the present invention are not limited to these embodiments and examples.

[0090] In the above embodiments and examples, the shape of the vibrating plate 1 is set to conical, but the shape of the vibrating plate can also be dome-shaped or other shapes. In addition, the mixed-existing layer and the reinforcing layer can be formed not only on the front surface side of the substrate, but also on the back side, or only on the back side.

[0091] It should be noted that when referred to simply as a diaphragm, the diaphragm of a loudspeaker refers to the structure including the edges, but in this embodiment, the diaphragm refers to the main body excluding the edges.

[0092] Furthermore, the nanofibers in the papermaking substrate, which include a suspension of cellulose fibers and silk nanofibers, can be dyed with dyes, or nanofibers that have undergone size treatment can be used, or nanofibers that have undergone waterproof treatment can be used.

[0093] In addition to cellulose fibers, other materials such as carbon fiber, carbon powder, and bacterial cellulose can also be mixed into the base material of papermaking.

[0094] Explanation of reference numerals in the attached figures

[0095] 1: Vibrating plate for electroacoustic converter; 10: Substrate; 11: Mixed layer; 12: Reinforcing layer; 20: Cellulose fiber (fiber material); 21: Silk nanofiber; 22: Mica.

Claims

1. A vibrating plate for an electroacoustic transducer, wherein, A substrate composed mainly of cellulose fibers is formed with a mixed layer of the cellulose fibers and silk nanofibers, wherein the average fiber diameter of the cellulose fibers is 5 μm or more and 90 μm or less, and the silk nanofibers have an average fiber diameter that is finer than that of the cellulose fibers and are inserted between the cellulose fibers.

2. The vibrating plate for an electroacoustic transducer according to claim 1, wherein, The hybrid presence layer is formed on the surface side of the substrate.

3. The vibrating plate for an electroacoustic transducer according to claim 1 or 2, wherein, The average fiber length of the silk nanofibers is less than 10 μm.

4. The vibrating plate for an electroacoustic transducer according to claim 1 or 2, wherein, The hybrid layer is formed by simultaneously drawing water from one side of the substrate and spraying a suspension containing the silk nanofibers onto the other side of the substrate.

5. The vibrating plate for an electroacoustic transducer according to claim 1, wherein, The surface of the substrate is further reinforced with a layer consisting of the fiber material, the silk nanofibers, and reinforcing materials.

6. The vibrating plate for an electroacoustic transducer according to claim 5, wherein, The reinforcing material is composed of a material containing mica.

7. The vibrating plate for an electroacoustic transducer according to claim 5 or 6, wherein, The reinforcing material is composed of a material containing cellulose nanofibers.

8. The vibrating plate for an electroacoustic transducer according to claim 5 or 6, wherein, The reinforcing layer is formed in the mixed-existence layer by simultaneously drawing water from one side of the substrate and spraying a suspension containing the reinforcing material and the silk nanofibers onto the other side of the substrate.

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