Patent Translate Powered by EPO and Google Notice This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate, complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or financial decisions, should not be based on machine-translation output. DESCRIPTION JP2017126946 Abstract: To provide an acoustic diaphragm excellent in Young's modulus and internal loss (tan δ). SOLUTION: The acoustic diaphragm of the present invention is composed of a paper sheet substantially including only cellulose nanofibers. In one embodiment, the cellulose nanofibers are unoxidized cellulose nanofibers. [Selected figure] Figure 1 Acoustic diaphragm [0001] The present invention relates to an acoustic diaphragm. More particularly, the present invention relates to an acoustic diaphragm used for speakers, headphones, and the like. [0002] Generally, the characteristics required for an acoustic diaphragm used for speakers, headphones, etc. include various strengths, high airtightness, high Young's modulus (elastic modulus, rigidity), and internal loss (tan δ) Is large). In order to meet such requirements, materials and structures of acoustic diaphragms are continuously studied. [0003] JP, 2013-42405, A JP, 2011-130401, A 10-05-2019 1 [0004] The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide an acoustic diaphragm excellent in Young's modulus and internal loss (tan δ). [0005] The acoustic diaphragm of the present invention is composed of a paper sheet substantially containing only cellulose nanofibers. In one embodiment, the cellulose nanofibers are unoxidized cellulose nanofibers. [0006] The acoustic diaphragm of the present invention is excellent in Young's modulus and internal loss (tan δ) by being composed of cellulose nanofibers. [0007] It is a figure which shows the frequency characteristic of the acoustic diaphragm obtained by Example 2, the comparative example 2, and the comparative example 3. FIG. [0008] The acoustic diaphragm according to the embodiment of the present invention is obtained by papermaking of cellulose nanofibers. The acoustic diaphragm is composed of a papermaking body substantially containing only cellulose nanofibers. By using a paper body of cellulose nanofibers, an acoustic diaphragm having a fine structure in which the fibers are strongly bonded by hydrogen bonds can be obtained. As a result, an acoustic 10-05-2019 2 diaphragm having an excellent Young's modulus can be obtained. Further, the acoustic diaphragm of the present invention is excellent in density, airtightness, strength, etc., and can have a wide high-frequency reproduction band and can realize excellent sound quality. [0009] Cellulose nanofibers refer to cellulose fibers having a nanosized fiber diameter. The fiber diameter (number average diameter) of the cellulose nanofibers is, for example, 3 nm to 100 nm. The length (number average length) of the cellulose nanofibers is, for example, 0.1 μm to 100 μm. The aspect ratio (length / diameter) of cellulose nanofibers is, for example, 50 to 1000. The fiber diameter of pulp is usually 1 μm or more, and in the present specification, cellulose nanofibers and pulp are distinguished by the fiber diameter. [0010] The acoustic diaphragm according to the embodiment of the present invention is different from the conventional acoustic diaphragm in which a small amount of cellulose nanofibers of 1/1000 or less is added and mixed with pulp fibers having a large fiber diameter. The papermaking body containing only cellulose nanofibers becomes denser, strong hydrogen bonds can be generated, and the air density also becomes much larger. Therefore, as an acoustic diaphragm, it is excellent in the ability to push out the air which is a medium of a sound wave, and can realize the outstanding sound quality. [0011] As a method of producing cellulose nanofibers, for example, a water-on-collision method (ACC method) in which suspensions obtained by dispersing pulp in water are made to collide with each other to break down and make them finer; Methods are included. As the mechanical treatment, for example, treatment to refine the cellulose raw material using a low pressure homogenizer, high pressure homogenizer, grinder, cutter mill, jet mill, short screw extruder, twin screw extruder, ultrasonic stirrer etc. is mentioned. Be Cellulose nanofibers can also be produced by defibrillation of cellulose raw materials by chemical treatment such as oxygen treatment or acid 10-05-2019 3 treatment, but in the present invention, there are counter-impact collision methods in water (ACC method), machinery It is preferable to use unoxidized cellulose nanofibers obtained by chemical treatment and the like. If unoxidized cellulose nanofibers are used, a paper sheet containing only cellulose nanofibers can be formed, and an acoustic diaphragm excellent in the balance of Young's modulus, internal loss (tan δ), airtightness and various strengths can be obtained. [0012] The cellulose raw material is not particularly limited, and any appropriate cellulose raw material is used. Examples of cellulose raw materials include hardwood kraft pulp (LKP) such as hardwood bleached kraft pulp (LBKP), hardwood non-bleached kraft pulp (LUKP), softwood bleached kraft pulp (NBKP), softwood non-bleached kraft pulp (NUKP) Wood-derived kraft pulp; waste paper pulp such as sulfite pulp and deinked pulp (DIP); grand pulp (GP), pressure-type ground pulp (PGW), refiner ground pulp (RMP), thermo-mechanical pulp (TMP), chemi Mechanical pulp, such as thermo mechanical pulp (CTMP), chemi mechanical pulp (CMP), chemi grand pulp (CGP), etc. are mentioned. Alternatively, powdered cellulose obtained by pulverizing these pulps, or microcrystalline cellulose obtained by purifying pulp by chemical treatment such as acid hydrolysis may be used. Furthermore, non-wood pulp derived from kenaf, hemp, rice, bagasse, bamboo, bamboo, cotton or the like may be used. In one embodiment, softwood-derived cellulose is used as a raw material for cellulose nanofibers. By using cellulose derived from softwood, an acoustic diaphragm having a higher Young's modulus can be obtained. [0013] In the present specification, containing substantially only cellulose nanofibers means that the content ratio of cellulose nanofibers is 90 parts by weight or more with respect to 100 parts by weight of the acoustic diaphragm. The content ratio of cellulose nanofibers is preferably 95 parts by weight or more, more preferably 98 parts by weight or more, and still more preferably 100 parts by weight with respect to 100 parts by weight of the acoustic diaphragm. [0014] The acoustic diaphragm may contain a very small amount of other components in addition to the cellulose nanofibers. For example, wood pulp can be added at a content ratio of less than 10 parts by weight (preferably less than 5 parts by weight, more preferably less than 2 parts by 10-05-2019 4 weight) with respect to 100 parts by weight of the acoustic diaphragm. An acoustic diaphragm containing cellulose nanofibers and a very small amount of wood pulp can be obtained by mixing these materials. The above-mentioned wood pulp is not particularly limited, and wood pulp usually used for an acoustic diaphragm may be adopted. For example, softwood pulp, hardwood pulp and the like are used. [0015] The acoustic diaphragm may further contain other fibers as needed. Other fibers may be appropriately selected depending on the purpose. For example, high-strength fibers may be mixed if the purpose is to improve mechanical strength. Furthermore, fibers according to the purpose (for example, deodorizing fibers, negative ion releasing fibers) may be mixed. [0016] The density of the acoustic diaphragm is preferably 0.45 g / cc or more, more preferably 0.5 g / cc or more. If it is such a range, the acoustic diaphragm which is especially excellent in Young's modulus can be obtained. [0017] The folding resistance of the acoustic diaphragm is preferably 1000 or more, more preferably 2000 or more, and still more preferably 2500 or more. The folding resistance is measured in accordance with JIS P 8115. [0018] The rigidity of the acoustic diaphragm is preferably 1000 mgf to 5000 mgf, more preferably 1500 mgf to 3000 mgf. If it is such a range, the acoustic diaphragm which is especially excellent in Young's modulus can be obtained. The stiffness is measured in accordance with JIS P 8125. [0019] 10-05-2019 5 The tearing degree of the acoustic diaphragm is preferably 200 gf or more, more preferably 300 gf or more. The tearing degree is measured in accordance with JIS P 8116. [0020] The airtightness of the acoustic diaphragm is preferably 15 s / 100 cc or more, more preferably 100 s / 100 cc or more, and still more preferably 1000 s / 100 cc or more. The method of measuring the tightness will be described later. [0021] The acoustic diaphragm of the present invention can be obtained by papermaking cellulose nanofibers by any appropriate method, and thereafter forming a flat plate obtained by papermaking into a predetermined shape. Preferably, non-woven fabric is used as papermaking in papermaking. When non-woven fabric is used as a papermaking when making cellulose nanofibers with a thin fiber diameter, the paper making process can be performed well. [0022] As a material which constitutes the above-mentioned non-woven fabric, for example, polyester fiber, polyamide fiber, polyaramid fiber, polyolefin fiber, vinylon fiber, cellulose fiber, regenerated cellulose fiber, and a plurality of copolymers thereof are mentioned. Fiber etc. are mentioned. [0023] The basis weight of the non-woven fabric is preferably 50 g / m <2> to 200 g / m <2>, and more preferably 100 g / m <2> to 150 g / m <2>. If it is such a range, a papermaking process can be performed favorably. 10-05-2019 6 [0024] The thickness of the non-woven fabric is preferably 0.2 mm to 1 mm, more preferably 0.3 mm to 0.7 mm. If it is such a range, a papermaking process can be performed favorably. [0025] Any appropriate method may be employed as a method of forming a flat plate obtained by papermaking. As a specific example of the molding method, for example, heat press molding can be mentioned. Alternatively, the acoustic diaphragm may be formed into a predetermined shape suitable for a diaphragm such as a substantially cone shape, and then this may be hot-pressed. Alternatively, the acoustic diaphragm may be formed into a predetermined shape suitable for a diaphragm such as a substantially cone shape, and then formed and dried in an oven. [0026] The acoustic diaphragm of the present invention may have any suitable shape depending on the purpose. For example, the acoustic diaphragm of the present invention may have a cone shape, a dome shape, or any other shape. [0027] The acoustic diaphragm of the present invention can be applied to speakers or headphones for any application. For example, the speaker using the diaphragm of the present invention may be for on-vehicle use, for portable electronic devices (for example, a mobile phone, a portable music player), or may be stationary. For example, the speaker using the diaphragm of the present invention may have a large diameter, a medium diameter, or a small diameter. Preferably, it is used for a small diameter speaker. [0028] Hereinafter, the present invention will be more specifically described by way of examples, but the 10-05-2019 7 present invention is not limited by these examples. The evaluation methods in the examples are as follows. In the Examples and Comparative Examples, parts and percentages are by weight unless otherwise indicated. [0029] <Evaluation> 1. Measurement of Young's modulus and internal loss (tan δ) Young's modulus and internal loss (tan δ) of the obtained flat plate were measured by the vibration lead method (cantilever, resonance method). Specifically, test pieces of 40 mm × 15 mm size are cut out from the flat plates obtained in Examples and Comparative Examples, and Young's modulus and internal loss (tan δ) at 23 ° C. are measured for each test piece. did. In the table, the average value of 5 test pieces is shown. [0030] 2. Test pieces of 40 mm × 15 mm in size were cut out of 5 pieces from the flat plate obtained in the density example and the comparative example. Using a dial thickness gauge, the thickness and weight of 4 points (ie, 4 points × 5 pieces in total 20 points) were measured for each piece, and the average value of the density was determined from the values. [0031] ３． Five test pieces of 50 mm × 50 mm in size were cut out from the flat plates obtained in the airtightness examples and the comparative examples, respectively, and measured in accordance with JIS P 8117. The average value is shown in the table. [0032] Example 1 In a paper making tank using non-woven fabric (polyester microfiber (3 μm) + polyurethane resin 5%, fabric weight: 140 ± 10 g / m <2>, thickness: 0.55 ± 0.06 mm) as a wire mesh A 0.1% by weight suspension of softwood-derived cellulose nanofibers (manufactured by Chuetsu Pulp Industries Co., Ltd., fiber diameter: about 20 nm) is injected, paper making, and then heat pressing using a molding die, micronano A flat plate consisting only of fibers (basis 10-05-2019 8 weight: 43.7 g / m <2>) was obtained. The obtained flat plate was subjected to the above evaluations 1 to 3. The results are shown in Table 1. [0033] [Example 2] Paper was made under the same conditions and conditions as in Example 1, and then heat pressed using a molding die to obtain a diaphragm for a headphone driver consisting only of micro nanofibers. The frequency characteristics of the diaphragm were measured to evaluate the sound quality. The results are shown in FIG. [0034] Comparative Example 1 BKP (beating degree: 500 cc) was paper-made and press-dried to obtain a flat plate consisting only of BKP (basis weight: 48.5 g / m <2>). The obtained flat plate was subjected to the above evaluations 1 to 3. The results are shown in Table 1. [0035] [Comparative Example 2] Paper was made under the same conditions and conditions as Comparative Example 1 and then heat pressed using a molding die to obtain a headphone driver diaphragm made of only BKP. The frequency characteristics of the diaphragm were measured to evaluate the sound quality. The results are shown in FIG. [0036] Comparative Example 3 20 parts of softwood-derived cellulose nanofibers (manufactured by Chuetsu Pulp Industries Co., Ltd., fiber diameter: about 20 nm) are blended with 100 parts of BKP (beating degree of 500 cc) and mixed, and then using a molding die It was heat-pressed to obtain a diaphragm for a headphone driver. The frequency characteristics of the diaphragm were measured to evaluate the sound quality. The results are shown in FIG. [0037] 10-05-2019 9 [0038] As apparent from Table 1, the diaphragm made of only cellulose nanofibers has strong bonds between fibers, and is excellent in physical properties such as density, Young's modulus and airtightness. In addition, as is apparent from FIG. 1, such a diaphragm increases the sound pressure in the high region, and exhibits good characteristics and sound quality. In terms of sound quality, the sound pressure in the high-frequency reproduction band has increased, the amount of information has increased, the energy of the mid-high range has become easier to be radiated, the S / N is better, and the gap in the mid-high range is better. In addition, the strength of the low region was improved by improving the overall strength and air tightness. [0039] The acoustic diaphragm of the present invention can be suitably used as a speaker or headphone for any application. 10-05-2019 10
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