Vibration plate and method for manufacturing vibration plate

Abstract

In a diaphragm 1 for an electro-acoustic transducer composed of a papermaking base material 10 in which cellulose fibers 20 are a main component, the total mass of coloring particles 21 contained in a first surface side region 12 is greater than the total mass of coloring particles 21 contained in a second surface side region 14, wherein the first surface side region 12 is a region of a prescribed thickness from a first surface of the papermaking base material 10, and the second surface side region 14 is a region of a prescribed thickness from a second surface which is the opposite surface of the first surface of the papermaking base material 10.

Description

Technical Field

[0001] This disclosure relates to a vibrating plate for an electroacoustic transducer such as a loudspeaker or microphone, and a method for manufacturing the vibrating plate. Background Technology

[0002] Generally, diaphragms for electroacoustic transducers are required to have low density, high Young's modulus, and moderate internal losses. The material with the most suitable physical properties is selected based on the application of the loudspeaker and microphone. Cellulose fibers, in particular, are widely used due to their low cost, lightweight nature, and moderate internal losses, which contribute to their excellent performance as diaphragms.

[0003] Furthermore, since the diaphragm appears in the appearance of the speaker, it is sometimes colored for aesthetic reasons. As shown in Patent Document 1, direct dyes are known to be used in the coloring of cellulose fibers, which serve as the material for the diaphragm. Coloring based on direct dyes has the advantages of easy staining of the diaphragm, good color development, and low cost while maintaining the diaphragm's lightweight nature.

[0004] Existing technical documents

[0005] Patent documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 60-148295 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, diaphragms colored with direct dyes have the problem of weather resistance, such as fading when exposed to direct sunlight. As a countermeasure, sulfur dyes are considered as having high weather resistance, but sulfur dyes may cause brittleness of the cellulose fibers.

[0009] Therefore, techniques for coloring with pigments instead of direct dyes are known. However, when pigments color cellulose fibers, their color development tends to be inferior to that of direct dyes. Therefore, when using the same mass of pigment as direct dyes, it is difficult to achieve the same color development. As a countermeasure, increasing the mass of the pigment is considered; however, increasing the overall mass of the vibrating plate and changing its physical properties may reduce the electroacoustic conversion characteristics.

[0010] This disclosure is made in order to solve at least part of this problem, and its purpose is to provide a diaphragm for an electroacoustic transducer with improved weather resistance.

[0011] Problem-solving methods

[0012] To achieve the above objectives, the vibrating plate of this disclosure is as follows: In a vibrating plate for an electroacoustic transducer composed of a single layer of papermaking substrate mainly composed of cellulose fibers, the total mass of coloring particles impregnated in the first side region is greater than the total mass of coloring particles impregnated in the second side region, wherein the first side region is a region of a predetermined thickness from the first surface of the papermaking substrate toward the second surface, and the second side region is a region of a predetermined thickness from the second surface, which is the opposite side of the first surface, toward the first surface.

[0013] Furthermore, the average particle size of the coloring particles can be below 700 nm.

[0014] Furthermore, the average particle size of the coloring particles can be below 400 nm.

[0015] Furthermore, the papermaking substrate can be dyed with direct dyes.

[0016] In addition, the coloring particles can be carbon black.

[0017] Furthermore, the first side region may be a region having a thickness of at least 1 / 10 of the thickness of the papermaking substrate.

[0018] Furthermore, the total mass of the coloring particles contained in the first side region can be more than twice the total mass of the coloring particles contained in the second side region.

[0019] Furthermore, the papermaking substrate can be generally conical, and the reverse side of the generally conical shape can be the second side of the papermaking substrate.

[0020] In addition, diaphragms can be used in car speakers.

[0021] Furthermore, to achieve the above objectives, the manufacturing method of the vibrating plate is as follows: The manufacturing method of a vibrating plate for an electroacoustic transducer made of a papermaking substrate includes: an impregnation step, wherein a coloring coating in which coloring particles are dispersed in a solvent is impregnated into a layer of papermaking substrate mainly composed of cellulose fibers; and a drying step, wherein the papermaking substrate impregnated with the coloring coating is dried, wherein the drying is performed such that the vapor pressure of the solvent in the space in contact with a second surface, which is the opposite side of the first surface of the papermaking substrate, is greater than the vapor pressure of the solvent in the space in contact with the first surface of the papermaking substrate, such that the total mass of the coloring particles impregnated in the first-side region is greater than the total mass of the coloring particles impregnated in the second-side region, wherein the first-side region is a region of a predetermined thickness from the first surface of the papermaking substrate toward the second surface, and the second-side region is a region of a predetermined thickness from the second surface toward the first surface.

[0022] Invention Effects

[0023] As described above, according to this disclosure, a vibrating plate for an electroacoustic transducer with improved weather resistance can be provided. Attached Figure Description

[0024] Figure 1 This is a perspective view of a vibrating plate for an electroacoustic converter according to an embodiment of the present disclosure;

[0025] Figure 2 This is a cross-sectional view of a vibrating plate for an electroacoustic transducer according to an embodiment of the present disclosure;

[0026] Figure 3 This is a schematic cross-sectional view of a vibrating plate for an electroacoustic transducer according to an embodiment of the present disclosure;

[0027] Figure 4 This is an optical microscope photograph of the cross-section of the vibrating plate for the electroacoustic transducer according to an embodiment of the present disclosure;

[0028] Figure 5 This is a graph showing the L values ​​of the diaphragm for an electroacoustic transducer under different drying conditions. Detailed Implementation

[0029] The vibrating plate for an electroacoustic converter according to an embodiment of the present disclosure will be described below.

[0030] Figure 1 This is a perspective view of a vibrating plate for an electroacoustic transducer according to an embodiment of the present disclosure. Figure 2 This is its cross-sectional view. Figure 3 This is a schematic cross-sectional view of the vibrating plate for the electroacoustic transducer according to an embodiment of the present disclosure. Figure 4 These are optical microscope photographs.

[0031] Figure 1 , Figure 2 The diaphragm 1 shown is a loudspeaker (electroacoustic transducer) diaphragm, shaped like a frustum of a cone (roughly conical). The small-diameter opening side of this diaphragm 1 is mounted on the vibration source of the loudspeaker, such as a voice coil (not shown). When the voice coil is energized, the diaphragm 1 vibrates, causing the air to vibrate, thereby emitting sound. That is, electroacoustic conversion is possible. The inner surface of the conical portion of the diaphragm 1 is the sound-emitting surface, the surface visible from the outside (first surface 11). On the other hand, various loudspeaker components (not shown) are arranged on the outer side of the conical portion of the diaphragm 1, i.e., the reverse side (second surface 13).

[0032] The vibrating plate 1 is formed from a papermaking substrate 10, which is composed of a fibrous material mainly composed of cellulose fibers 20.

[0033] In detail, the papermaking substrate 10 is formed by preparing a liquid of cellulose fiber 20 (fiber material) beaten at a freeness of 10°SR or higher and 50°SR or lower, and then forming the paper into a vibrating plate shape. In this embodiment, the cellulose fiber 20 is pulp primarily made from coniferous trees. Furthermore, the cellulose fiber 20 can be wood pulp or non-wood pulp such as kenaf, or a mixture of other wood pulps and non-wood pulps, wood pulp alone, or non-wood pulp alone. Additionally, the average fiber diameter (maximum width) of the cellulose fiber 20 is preferably 5 μm or higher and 90 μm or lower. It should be noted that the fiber length of the cellulose fiber 20 is not particularly limited, and a fiber length commonly used in papermaking can be appropriately selected.

[0034] exist Figures 2 to 4 In this description, the papermaking substrate 10 is illustrated as having a first side region 12, a middle region 15, and a second side region 14 in the thickness direction. The papermaking substrate 10 is dyed entirely with a black direct dye (e.g., Direct Black 19). Figure 3 As shown in the schematic diagram, in the papermaking substrate 10, pigment as coloring particles 21 is contained on the surface of the cellulose fibers 20 or between the fibers of the cellulose fibers 20. The pigment is, for example, carbon black. From the viewpoint of color development, it is desirable that the average particle size of the coloring particles 21 is 700 nm or less. This is because the larger the particle size of the coloring particles 21, the lower the color development. Furthermore, due to the small particle size, the coloring particles 21 easily move between the cellulose fibers 20 during the drying step described later. Therefore, it is more preferable that the average particle size of the coloring particles 21 is 400 nm or less. It should be noted that... Figure 3 In order to illustrate the relationship between cellulose fibers 20 and coloring particles 21 in an easy-to-understand manner, the elements are shown in exaggerated sizes compared to their actual dimensions.

[0035] like Figure 3As shown, the amount of coloring particles 21 contained in the first-side region 12, which is a region of thickness t starting from the first surface 11, is greater than the amount of coloring particles 21 contained in the second-side region 14, which is a region of the same thickness t starting from the second surface 13. That is, when the mass of each coloring particle 21 is the same, the total mass of coloring particles 21 contained in the first-side region 12, which is a region of thickness t starting from the first surface 11, is greater than the total mass of coloring particles 21 contained in the second-side region 14, which is a region of thickness t starting from the second surface 13. Furthermore, when the intermediate region 15 between the first-side region 12 and the second-side region 14 is also divided into regions of the same thickness t, that is, when the first-side region 12, the second-side region 14, and the intermediate region 15 are all divided into regions of the same thickness, the amount of coloring particles 21 contained in the first-side region 12 is greater than the amount of coloring particles 21 contained in the intermediate region 15. That is, the total mass of the coloring particles 21 contained in the first side region 12 is greater than the total mass of the coloring particles 21 contained in the region of thickness t in the middle region 15.

[0036] Figure 4 This is an optical microscope photograph of the cross-section of the papermaking substrate 10 of the vibrating plate 1. Figure 4 In order to easily understand the coloring state based on the coloring particles 21, the paper substrate 10 is not colored with direct dyes, but only with carbon black (coloring particles 21). Figure 4 As shown, the total thickness of the papermaking substrate 10 is approximately 0.22 mm. It can be seen that in the papermaking substrate 10, the first side region 12, which is a region with a thickness of 0.04 mm from the surface of the first side 11, is colored black and is darker due to the coloring particles 21. Furthermore, the first side region 12 is a region with a thickness of at least 1 / 10 or more relative to the thickness of the papermaking substrate 10 (0.22 mm). The second side region 14 of the papermaking substrate 10 is lighter in color than the first side region 12. Additionally, the intermediate region 15 is also lighter in color than the first side region 12. This indicates that, as described above, the amount of coloring particles 21 contained in the first side region 12 is greater than the amount of coloring particles 21 contained in the second side region 14. That is, the total mass of the coloring particles 21 contained in the first side region 12 is greater than the total mass of the coloring particles 21 contained in the second side region 14, and the difference is at least twice. It should be noted that the mass of the coloring particles 21 contained in each region of the papermaking substrate 10 can be calculated, for example, by using the amount and density of the coloring particles 21 observed in a specified region from an image such as a scanning electron microscope (SEM).

[0037] As described above, in the vibrating plate 1 of this disclosure, by localizing the arrangement of the coloring particles 21 of the paper substrate 10 in the first side region 12, the surface unevenness of the vibrating plate 1 can be suppressed and the blackness can be improved by increasing the amount of coloring particles 21 on the surface of the paper substrate 10 while reducing the amount of coloring particles 21 used in the paper substrate 10.

[0038] Compared to direct dyes such as Direct Black 19, the carbon black particles 21 used for coloring are less prone to changes caused by light exposure, especially ultraviolet light exposure, and suppress fading. Therefore, it is possible to provide a diaphragm that is less prone to color changes caused by fading when viewed from the first side 11 and has high weather resistance (light resistance).

[0039] Furthermore, by reducing the amount of carbon black used, the increase in the mass of the diaphragm can be suppressed, and the degradation of electroacoustic conversion characteristics, i.e., sound quality degradation, caused by changes in the physical properties of the diaphragm 1 can be prevented. Further, by reducing the amount of carbon black used, cost reduction can be achieved. Moreover, since the amount of coloring particles 21 on the surface of the first side 11 of the paper substrate 10 is increased, the weather resistance of the diaphragm 1 to light is improved, thus making it suitable for automotive loudspeakers requiring environmental resistance.

[0040] Furthermore, since the papermaking substrate 10 of the vibrating plate 1 of this disclosure is dyed with direct dyes, a darker color development can be achieved compared to the case where only carbon black is used for coloring, and unevenness can be better suppressed. Moreover, by localizing the carbon black in the first side region 12 to absorb and reflect ultraviolet rays, ultraviolet rays can be prevented from penetrating into the interior of the papermaking substrate 10, and the fading of the direct dyes can be suppressed.

[0041] (Manufacturing method)

[0042] Next, the manufacturing process of the vibrating plate for the electroacoustic transducer according to an embodiment of this disclosure will be described. In the following description, Direct Black 19 will be used as the direct dye and carbon black will be used as the coloring particles.

[0043] First, a liquid of cellulose fiber 20 (fiber material) colored with direct dye is prepared, the paper is made into a vibrating plate shape, and then dried and shaped into a papermaking substrate 10.

[0044] Next, a dispersion of coloring particulate carbon black in the organic solvent ethyl acetate is used as a coloring coating and is impregnated onto the entire paper substrate 10 for approximately 5 to 10 seconds (impregnation step). In this embodiment, the coloring coating is an ethyl acetate solution containing 1 to 5% by mass of carbon black. Then, the paper substrate 10 is colored by drying the paper substrate 10 impregnated with the coloring coating and evaporating the dried ethyl acetate (drying step).

[0045] In the drying step, drying is performed such that the vapor pressure of ethyl acetate in the space contacting the second surface 13 of the papermaking substrate 10 is greater than the vapor pressure of ethyl acetate in the space contacting the first surface 11 of the papermaking substrate 10. Specifically, the space contacting the first surface 11 and the space contacting the second surface 13 are physically separated by clamps or the like, with the space contacting the first surface 11 being an open space (or a substantially open space) and the space contacting the second surface 13 being a closed space (or a substantially closed space). Furthermore, the space contacting the second surface 13 is made smaller than the space contacting the first surface 11. By drying the papermaking substrate 10 under these conditions, the vapor pressure of ethyl acetate in the space contacting the second surface 13 rapidly reaches its saturation vapor pressure, while the vapor pressure of ethyl acetate in the space contacting the first surface 11 remains relatively low. For this reason, the solvent ethyl acetate of the coloring coating impregnated throughout the papermaking substrate 10 actively evaporates from the first surface 11 side. Consequently, in the papermaking substrate 10, ethyl acetate moves from the second side 13 to the first side 11. As the ethyl acetate moves, carbon black also moves from the second side 13 to the first side 11. Therefore, after the ethyl acetate evaporates and dries, the amount of carbon black in the first side region 12 of the papermaking substrate 10 is greater than that in the second side region 14.

[0046] Here, a papermaking substrate 10, which is dried by evaporation from both sides without physically separating the space in contact with the first surface 11 and the space in contact with the second surface 13, will be described as a comparative example. In the comparative example, since ethyl acetate evaporates from both the first surface 11 and the second surface 13, carbon black also moves to both the first surface side region 12 and the second surface side region 14.

[0047] Figure 5 This is a graph showing the L-values ​​of the first (surface) and second (reverse) sides of vibrating plates produced by the evaporation drying method (single-sided drying) of the embodiments of this disclosure and the evaporation drying method (two-sided drying) of the comparative examples. The L-value refers to the lightness of the color possessed by a specified substance, and is an index expressed as a value between 0 and 100. When the L-value is 100, it displays white; as the L-value decreases, the color becomes darker; when the L-value is 0, it displays black. It should be noted that for... Figure 5 The paper substrate 10 with measured L value was used to easily understand the difference in L value caused by different drying methods. Therefore, the paper substrate 10 was not colored with direct dyes, but only with coloring granular carbon black.

[0048] As a comparative example, the L value of the surface of the papermaking substrate 10, which underwent double-sided drying, was approximately 33, and that of the reverse side was approximately 32. In contrast, the L value of the surface of the papermaking substrate 10, which underwent single-sided drying according to the embodiments of this disclosure, was approximately 30, and that of the reverse side was approximately 48. In the comparative example, there was almost no difference in the L values ​​between the surface and the reverse side. On the other hand, in the embodiments, the L value of the surface was smaller than that of the reverse side, indicating a deeper black color and a greater amount of carbon black on the surface side.

[0049] As described above, the manufacturing method of the vibrating plate according to the embodiments of this disclosure allows the amount of coloring particles 21 contained in the first side region 12 to be greater than the amount of coloring particles 21 contained in the second side region 14, that is, the total mass of the coloring particles 21 contained in the first side region 12 is greater than the total mass of the coloring particles 21 contained in the second side region 14. It should be noted that the impregnation method for impregnating the paper substrate 10 with the coloring coating in the impregnation step can be performed by spraying the coloring coating onto the surface of the paper substrate 10, by dripping the coloring coating onto the surface or reverse side of the paper substrate 10 and spreading it for impregnation, or by directly spreading the coloring coating onto the surface of the paper substrate 10 with a pen or the like for impregnation; the method of applying and impregnating the coloring coating is not limited. In the drying step, by controlling the vapor pressure of the solvent in the space in contact with the first side 11 and the second side 13 of the paper substrate 10, the coloring particles 21 can be easily and uniformly distributed across the entire surface of the vibrating plate 1 (first side 11). When the amount of coloring particles 21 contained in the first side region 12 increases and reaches a certain density, the apparent blackness of the first side 11 becomes saturated and no longer changes. By drying one side, the coloring particles 21 can be aggregated on that single side (surface), thus ensuring that the density of coloring particles across the entire surface is above a certain density and preventing unevenness. Furthermore, by using an organic solvent in the coloring coating, rapid drying during evaporation drying can be ensured, and the processing time can be shortened.

[0050] It should be noted that ethyl acetate was used as the solvent in the above embodiments, but other solvents can also be used. Furthermore, for example, hydrophilic groups such as hydroxyl groups can be provided on the surface of coloring particles such as carbon black, and water can be used as a solvent to adjust the dispersion, thus creating a coloring coating.

[0051] Thus, in the vibrating plate 1 for an electroacoustic transducer made of a papermaking substrate 10 with cellulose fibers 20 as the main component, the total mass of the coloring particles 21 contained in the first side region 12, which is a region with a defined thickness from the first surface 11 of the papermaking substrate 10, is greater than the total mass of the coloring particles 21 contained in the second side region 14, which is a region with a defined thickness from the second surface 13, which is the opposite side of the first surface 11 of the papermaking substrate 10.

[0052] The pigment used as the coloring particle 21 is less prone to changes caused by light exposure, especially ultraviolet light exposure, compared to direct dyes, and fading is suppressed. Therefore, it is possible to provide a vibrating plate 1 that is less prone to color changes caused by fading when viewed from the first side 11, and has improved weather resistance.

[0053] In the above description of the embodiments, carbon black, a black pigment, was used as an example of the coloring particles, but the coloring particles are not limited to this. For example, colored pigments composed of inorganic and organic pigments such as zinc white, lead white, titanium dioxide, and precipitated barium sulfate; red pigments such as red lead oxide, iron oxide red, bright carmine, and quinacridone red; yellow pigments such as chrome yellow, zinc yellow, and diazo yellow; and blue pigments such as ultramarine blue, potassium ferrocyanide, and phthalocyanine blue can be used, or other pigments can be used. Furthermore, the color of the direct dye used to color the paper substrate 10 can be selected according to the hue of these pigments.

[0054] Furthermore, dyeing the paper substrate 10 with direct dyes is not necessarily necessary; it can be appropriately selected based on the requirements of the loudspeaker used in the diaphragm 1.

[0055] It should be noted that a dispersion in which the coloring particles 21, nitrocellulose, and solvent are separately mixed and adjusted can also be used as a coloring coating. Thus, after the solvent is evaporated and dried, a film (coating) of nitrocellulose is formed on the first surface 11 of the papermaking substrate 10. This improves the adhesion of the coloring particles 21 to the papermaking substrate 10. Furthermore, the first surface 11 of the vibrating plate 1 can be made glossy. In addition, instead of nitrocellulose, drying oils, natural resins, synthetic resins, cellulose derivatives, and other polymeric substances can be used.

[0056] This concludes the description of the embodiments of this disclosure, but the solutions disclosed herein are not limited to the embodiments described above.

[0057] In the above embodiment, the inner surface of the conical portion of the vibrating plate 1 is described as the first surface 11, and the outer surface of the conical portion of the vibrating plate 1 is described as the second surface. However, the outer surface of the conical portion can also be designated as the first surface 11, with a greater number of coloring particles 21 present on the outer surface side region 12. Furthermore, in the above embodiment, the shape of the vibrating plate 1 is approximately conical, but the shape of the vibrating plate can also be other shapes.

[0058] Explanation of reference numerals in the attached figures

[0059] 1 Vibrating plate

[0060] 10 Papermaking substrate

[0061] Page 1 of 11

[0062] 12 First side region

[0063] Page 2 of 13

[0064] 14 Second side region

[0065] 15. Middle Area

[0066] 20. Cellulose fiber (fiber material)

[0067] 21 Coloring Particles

Claims

1. A vibrating plate, characterized in that, In a vibrating plate for an electroacoustic transducer, which is composed of a single layer of paper substrate mainly composed of cellulose fibers, The total mass of coloring particles impregnated in the first side region is greater than the total mass of coloring particles impregnated in the second side region. The first side region is a region of a predetermined thickness from the first surface of the paper substrate toward the second surface, and the second side region is a region of a predetermined thickness from the second surface, which is the opposite side of the first surface, toward the first surface.

2. The vibrating plate according to claim 1, wherein, The average particle size of the coloring particles is below 700 nm.

3. The vibrating plate according to claim 1, wherein, The average particle size of the coloring particles is below 400 nm.

4. The vibrating plate according to any one of claims 1 to 3, wherein, The papermaking substrate is dyed with direct dyes.

5. The vibrating plate according to any one of claims 1 to 3, wherein, The coloring particles are carbon black.

6. The vibrating plate according to any one of claims 1 to 3, wherein, The first side region is a region having a thickness of at least 1 / 10 of the thickness of the papermaking substrate.

7. The vibrating plate according to any one of claims 1 to 3, wherein, The total mass of coloring particles contained in the first side region is more than twice the total mass of coloring particles contained in the second side region.

8. The vibrating plate according to any one of claims 1 to 3, wherein, The papermaking substrate is generally conical, and the reverse side of the generally conical shape is the second side of the papermaking substrate.

9. The vibrating plate according to any one of claims 1 to 3, wherein, Vibrating plates are used in car loudspeakers.

10. A method for manufacturing a vibrating plate, characterized in that, A method for manufacturing a vibrating plate for an electroacoustic transducer made of a papermaking substrate includes: The impregnation step, wherein a coloring coating in which coloring particles are dispersed in a solvent is impregnated into a papermaking substrate mainly composed of cellulose fibers; and The drying step involves drying the paper substrate impregnated with the colored coating. In the drying step, drying is performed such that the vapor pressure of the solvent in the space in contact with the second surface, which is the opposite side of the first surface of the papermaking substrate, is greater than the vapor pressure of the solvent in the space in contact with the first surface of the papermaking substrate. This results in the total mass of the coloring particles impregnated in the first-side region being greater than the total mass of the coloring particles impregnated in the second-side region. The first-side region is a region of a predetermined thickness extending from the first surface of the papermaking substrate toward the second surface, and the second-side region is a region of a predetermined thickness extending from the second surface toward the first surface.

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