【発明の詳細な説明】[Detailed description of the invention]
本発明はスピーカ用振動板に関するものであ
り、その目的とするところは比弾性率が高く、か
つ内部損失の大きいスピーカ用振動板を提供する
ことにある。
一般にスピーカの特性は使用する振動板の物性
と大きな関係があり、周波数帯域は比弾性率
（Ｅ／Ｐ）に、周波数特性の平坦性は内部損失
（tanδ）に関連している。従来からスピーカ用振
動板には紙が多く用いられてきたが、近年になつ
て高分子材料や金属材料を素材にした振動板が使
われるようになつていた。しかし、スピーカ用振
動板に要求される比弾性率、内部損失の両者を同
時に十分満足するものは見当らない。比弾性率と
内部損失は相反する性質のものであり、単一材料
では両者を同時に満足させることは無理である。
現在のところ樹脂にフレークを混ぜたものが有力
と考えられているが、この場合はフレークの含有
率を相当高くしないと高比弾性率が得られない。
これはフレークのアスペクト比が小さく、弾性率
への寄与が少ないためである。そして、この様な
フレークの含有率の多い材料はスピーカ用振動板
は脆性破壊を起し易く、小さな衝撃にも破れが生
じる欠点があり、また、重量面でもフレークの含
有量が多いと重くなる欠点があつた。
本発明はこのような従来の欠点を解消するもの
である。本発明のスピーカ用振動板は断面形状が
偏平なアラミド繊維を含有することにより、高比
弾性率でかつ高内部損失の物性を同時に満足する
特長を有するものである。ここで、アラミド繊維
とはたとえば米国デユポン社のKevlar−49（商品
名）に代表される芳香族ポリアミドであり、液晶
紡糸後に繊維を緊張状態で熱処理して結晶化を進
めたものである。
第１表に各種の繊維の物性を示す。
The present invention relates to a diaphragm for a speaker, and an object thereof is to provide a diaphragm for a speaker that has a high specific modulus of elasticity and a large internal loss. In general, the characteristics of a speaker are largely related to the physical properties of the diaphragm used, and the frequency band is related to the specific modulus of elasticity (E/P), and the flatness of the frequency characteristics is related to the internal loss (tan δ). Traditionally, paper has often been used for speaker diaphragms, but in recent years diaphragms made of polymeric or metallic materials have come into use. However, no material has yet been found that simultaneously satisfies both the specific elastic modulus and internal loss required of a speaker diaphragm. Specific modulus of elasticity and internal loss have contradictory properties, and it is impossible to satisfy both simultaneously with a single material.
At present, a mixture of resin and flakes is considered to be effective, but in this case, a high specific modulus cannot be obtained unless the flake content is considerably increased.
This is because the aspect ratio of the flakes is small and their contribution to the elastic modulus is small. Materials with a high flake content have the disadvantage that speaker diaphragms are prone to brittle fracture and break even with the slightest impact, and in terms of weight, the higher the flake content, the heavier the speaker diaphragm becomes. There were flaws. The present invention overcomes these conventional drawbacks. The speaker diaphragm of the present invention contains aramid fibers with a flat cross-sectional shape, and thus has the feature of simultaneously satisfying physical properties of high specific modulus and high internal loss. Here, the aramid fiber is an aromatic polyamide represented by, for example, Kevlar-49 (trade name) manufactured by DuPont in the United States, and is obtained by heat-treating the fiber under tension after liquid crystal spinning to promote crystallization. Table 1 shows the physical properties of various fibers.
【表】
第１表より明らかなように、アラミド繊維は比
重が小さく、弾性率もガラス繊維より高い。炭素
繊維に較べ弾性率は若干落ちるが、引張強さで勝
り、非導電性であるため間接リードタイプにも使
用可能で用途が広い。樹脂との複合材料において
はアラミド繊維の断面形状が偏平であるため、複
合材料中における繊維間でのまさつが大きい。そ
して、フレーク状のものは層が重なり合うため、
まさつ面が広く内部損失が大きくなる。よつて、
断面形状が偏平なアラミド繊維を強化材に使用す
ることによつて軽量で、高比弾性率、高内部損失
のスピーカ用振動板材料を可能にする。この際、
高内部損失を得るにはアラミド繊維として長軸／
短軸比の少なくとも３以上のものを用いることが
望ましい。第１図にアラミド繊維の長軸／短軸比
と内部損失の関係を示す。断面形状が偏平なアラ
ミド繊維の製造方法としては偏平なノズルによる
紡糸法と、フイルムを切断する方法の２通りがあ
る。
以下、本発明のスピーカ用振動板の一実施例に
ついて説明する。
実施例 １
長軸／短軸比が４のノズルを用いアラミド繊維
を紡糸し、さらにこれを10倍に延伸して長軸30μ
ｍ、短軸10μｍ、長軸／短軸比３の断面形状が偏
平なアラミド繊維を得た。この偏平なアラミド繊
維を繊維長1.5mmに切断し、強化材に使用した。
基材としてポリエチレンを用い、８：２の比で偏
平なアラミド繊維とよく混練して切断し、マスタ
ーペレツトを作つた。このマスターペレツトを用
いて再びＴダイを装着した押出し機により、厚さ
0.2mmの強化ポリエチレンシートを得た。次にこ
のシートを遠赤外線で十数秒加熱、軟化した時点
で冷間プレスで成形を行ない振動板を得た。この
振動板の物性値を第２表に示した。尚、基材とし
てポリエチレンの代わりにポリプロピレン、
TPX、ポリカーボネート、ポリエチレンテレフ
タレート等の熱可塑性樹脂を使用して同様の結果
を得た。
実施例 ２
長軸／短軸比が４のノズルを用いてアラミド繊
維を紡糸し、さらにこれを10倍に延伸して長軸
30μｍ、短軸10μｍ、長軸／短軸比３の断面形状
が偏平なアラミド繊維を得た。この偏平なアラミ
ド繊維より織布を作り、次にこの織布にフエノー
ル樹脂を含浸させ、溶剤を除去したのち金型温度
200℃の条件で熱プレス成形を行ない、アフター
キユア150℃、２時間で振動板を得た。この振動
板の物性値を第２表に示す。フエノール樹脂だけ
でなくエポキシ等の熱硬化性樹脂でも同様の結果
を得た。
実施例 ３
長軸／短軸比が４のノズルを用いてアラミド繊
維を紡糸し、さらにこれを10倍に延伸して長軸
30μｍ、短軸10μｍ、長軸／短軸比３の断面形状
が偏平なアラミド繊維を得た。そして、この偏平
なアラミド繊維を1.5mmに切断した。次にこの繊
維長1.5mmの偏平なアラミド繊維20wt％と木材パ
ルプ（NUKP）80wt％とを水溶液中で混合し、
これをコーン形状に抄造して吸水後、熱プレス成
形を行ない振動板を得た。この振動板の物性値を
第２表に示す。
実施例 ４
長軸／短軸比が４のノズルを用いてアラミド繊
維を紡糸し、さらにこれを10倍に延伸して長軸
30μｍ、短軸10μｍ、長軸／短軸比３の断面形状
が偏平なアラミド繊維を得、これを1.5mmの長さ
に切断した。そして、この繊維長1.5mmの偏平な
アラミド繊維20wt％と高密度ポリエチレン合成
パルプ80wt％とを水溶液中で混合した。この時、
高密度ポリエチレン合成パルプには叩解度210ml
のものを使用し、偏平なアラミド繊維とよく撹拌
して分散させた。その後丸網シリンダーで抄造を
行ない、次にこの抄造シートを遠赤外線で加熱
し、シートが軟化した時点で冷間プレスで成形し
て振動板を得た。この振動板の物性値を第２表に
示す。又この振動板を用いた10cmスピーカの周波
数特性を第２図の曲線Ａに示す。尚、高密度ポリ
エチレン合成パルプの代りにポリプロピレン、
TPX等の熱可塑性合成パルプを使用して同様の
結果を得た。
尚、第２図の曲線Ｂは従来の紙コーン振動板を
用いた10cmスピーカの周波数特性を示している。[Table] As is clear from Table 1, aramid fibers have a lower specific gravity and a higher elastic modulus than glass fibers. Although its elastic modulus is slightly lower than that of carbon fiber, it has superior tensile strength and is non-conductive, so it can be used in indirect lead types and has a wide range of uses. In a composite material with a resin, since the aramid fiber has a flat cross-sectional shape, there is a large amount of spacing between the fibers in the composite material. And since the flaky ones have overlapping layers,
The surface area is wide and the internal loss becomes large. Then,
By using aramid fibers with a flat cross-sectional shape as a reinforcing material, it is possible to create a speaker diaphragm material that is lightweight, has a high specific modulus, and has a high internal loss. On this occasion,
To obtain high internal loss, aramid fibers with long axes/
It is desirable to use a material with a minor axis ratio of at least 3 or more. Figure 1 shows the relationship between the long axis/short axis ratio of aramid fibers and internal loss. There are two methods for producing aramid fibers with a flat cross-sectional shape: a spinning method using a flat nozzle and a method of cutting a film. An embodiment of the speaker diaphragm of the present invention will be described below. Example 1 Aramid fibers were spun using a nozzle with a long axis/short axis ratio of 4, and then stretched 10 times to a long axis of 30μ.
An aramid fiber having a flat cross-sectional shape with a short axis of 10 μm and a long axis/short axis ratio of 3 was obtained. This flat aramid fiber was cut into fiber lengths of 1.5 mm and used as reinforcing materials.
Using polyethylene as a base material, it was thoroughly kneaded with flat aramid fibers at a ratio of 8:2 and cut to make master pellets. Using this master pellet, the thickness is
A 0.2 mm reinforced polyethylene sheet was obtained. Next, this sheet was heated with far infrared rays for ten seconds or so, and when it softened, it was cold pressed and formed to obtain a diaphragm. The physical properties of this diaphragm are shown in Table 2. In addition, polypropylene is used instead of polyethylene as the base material.
Similar results were obtained using thermoplastics such as TPX, polycarbonate, and polyethylene terephthalate. Example 2 Aramid fibers were spun using a nozzle with a long axis/short axis ratio of 4, and then stretched 10 times to increase the long axis.
Aramid fibers having a flat cross-sectional shape of 30 μm, a short axis of 10 μm, and a long axis/short axis ratio of 3 were obtained. A woven fabric is made from these flat aramid fibers, and then this woven fabric is impregnated with phenolic resin, the solvent is removed, and the mold temperature is
Hot press molding was performed at 200°C, and a diaphragm was obtained after curing at 150°C for 2 hours. Table 2 shows the physical properties of this diaphragm. Similar results were obtained not only with phenolic resin but also with thermosetting resins such as epoxy. Example 3 Aramid fibers were spun using a nozzle with a long axis/short axis ratio of 4, and then stretched 10 times to increase the long axis.
Aramid fibers having a flat cross-sectional shape of 30 μm, a short axis of 10 μm, and a long axis/short axis ratio of 3 were obtained. Then, this flat aramid fiber was cut into 1.5 mm pieces. Next, 20wt% of this flat aramid fiber with a fiber length of 1.5mm and 80wt% of wood pulp (NUKP) were mixed in an aqueous solution.
This was made into a cone shape, and after absorbing water, hot press molding was performed to obtain a diaphragm. Table 2 shows the physical properties of this diaphragm. Example 4 Aramid fibers were spun using a nozzle with a long axis/short axis ratio of 4, and then stretched 10 times to increase the long axis.
An aramid fiber having a flat cross-sectional shape of 30 μm, a short axis of 10 μm, and a long axis/short axis ratio of 3 was obtained and cut into a length of 1.5 mm. Then, 20 wt% of this flat aramid fiber with a fiber length of 1.5 mm and 80 wt% of high density polyethylene synthetic pulp were mixed in an aqueous solution. At this time,
High-density polyethylene synthetic pulp has a beatability of 210ml.
was used and thoroughly stirred and dispersed with the flat aramid fibers. Thereafter, papermaking was carried out in a round mesh cylinder, and then this papersheet was heated with far infrared rays, and when the sheet softened, it was molded in a cold press to obtain a diaphragm. Table 2 shows the physical properties of this diaphragm. Curve A in Figure 2 shows the frequency characteristics of a 10cm speaker using this diaphragm. In addition, polypropylene is used instead of high-density polyethylene synthetic pulp.
Similar results were obtained using thermoplastic synthetic pulp such as TPX. Incidentally, curve B in FIG. 2 shows the frequency characteristics of a 10 cm speaker using a conventional paper cone diaphragm.
【表】
第２表の物性値より明らかなように実施例１〜
４の振動板はいずれの場合も高比弾性率、高内部
損失の物性を同時に満足していることがわかる。
又、第２図より明らかなように周波数特性もあば
れの少ない平坦でかつ高域が伸びたものとなつて
おり、偏平なアラミド繊維がスピーカ用振動板材
料として非常に優れていることがわかる。
以上のように本発明によれば、断面形状が偏平
なアラミド繊維を含有するので、高比弾性率、高
内部損失の物性を同時に満足し、周波数特性のす
ぐれたスピーカー用振動板を得ることができるも
のである。[Table] As is clear from the physical property values in Table 2, Examples 1-
It can be seen that the diaphragm No. 4 simultaneously satisfies the physical properties of high specific modulus and high internal loss in all cases.
Moreover, as is clear from FIG. 2, the frequency characteristics are flat with few flaws and the high range is extended, which shows that flat aramid fibers are very excellent as a material for speaker diaphragms. As described above, since the present invention contains aramid fibers with a flat cross-sectional shape, it is possible to obtain a speaker diaphragm that simultaneously satisfies the physical properties of high specific modulus and high internal loss and has excellent frequency characteristics. It is possible.
【図面の簡単な説明】[Brief explanation of drawings]
第１図はアラミド繊維の長軸／短軸比と内部損
失の関係曲線図、第２図は本発明の一実施例のス
ピーカ用振動板と従来の紙コーン振動板の周波数
特性の比較曲線図である。
Figure 1 is a curve diagram of the relationship between the long axis/minor axis ratio of aramid fibers and internal loss, and Figure 2 is a comparison curve diagram of the frequency characteristics of a speaker diaphragm according to an embodiment of the present invention and a conventional paper cone diaphragm. It is.