JP4191525B2 - Magnetic tape - Google Patents

Description

【００７５】
実施例６：
≪下塗塗料成分≫
（１）
・酸化鉄粉末（平均粒子径：０．１１×０．０２μｍ） ６８部
・アルミナ（住友化学社製、平均粒子径：０．０７μｍ） ８部
・カーボンブラック（キャボット社製 ２４部
REGAL415、平均粒子径：２５ｎｍ）
・ステアリン酸 ２部
・塩化ビニル共重合体 ８．８部
（含有−ＳＯ₃ Ｎａ基：０.７×１０^{− 4}当量／ｇ）
・ポリエステルポリウレタン樹脂 ４．４部
（Ｔｇ：４０℃、含有−ＳＯ₃ Ｎａ基：１×１０^-4当量／ｇ）
・シクロヘキサノン ２５部
・メチルエチルケトン ４０部
・トルエン １０部
（２）
・ステアリン酸ブチル １.０部
・シクロヘキサノン ７０部
・メチルエチルケトン ５０部
・トルエン ２０部
（３）
・ポリイソシアネート １．４部
・シクロヘキサノン １０部
・メチルエチルケトン １５部
・トルエン １０部
≪磁性塗料成分≫
（１）混練希釈工程
・強磁性鉄系金属粉（磁性粉） １００部
（Ｃｏ／Ｆｅ：２４ａｔ％、
Ｙ／（Ｆｅ＋Ｃｏ）：７．９ａｔ％、
Ａｌ／（Ｆｅ＋Ｃｏ）：４．７ｗｔ％、
σｓ：１２０Ａ・ｍ² ／ｋｇ（１２０ｅｍｕ／ｇ）、
Ｈｃ：１７５ｋＡ／ｍ（２１９０Ｏｅ）、
ｐＨ：９．５、平均粒子径：６０ｎｍ）
・塩化ビニル−ヒドロキシプロピルアクリレート共重合体 １２.３部
（含有−ＳＯ₃ Ｎａ基：０．７×１０^{- ４}当量／ｇ）
・ポリエステルポリウレタン樹脂 ５.５部
（含有−ＳＯ₃ Ｎａ基：1.０×１０^-4当量／ｇ）
・α−アルミナ（平均粒子径：０．０７μｍ ）（アルミナ） １０部
・カーボンブラック（キャボット社製、モナーク１２０ １.５部
平均粒子径：７５ｎｍ、ＤＢＰ吸油量：７２ｃｃ／１００ｇ）
・メチルアシッドホスフェート（ＭＡＰ） ２.０部
・パルミチン酸アミド（ＰＡ） １.５部
・ステアリン酸ｎ−ブチル（ＳＢ） １.０部
・テトラヒドロフラン ７４部
・シクロヘキサノン １０部
・メチルエチルケトン ２５５部
・トルエン ８５部
（２）配合工程
・ポリイソシアネート（ＰＩ） ２.０部
・シクロヘキサノン ３０部
【００７６】
上記の下塗塗料成分において（１）を回分式ニーダで混練したのち、（２）を加えて攪拌の後サンドミルで滞留時間を６０分として分散処理を行い、これに（３）を加え攪拌・濾過した後、下塗層用塗料とした。
【００７７】
これとは別に、上記の磁性塗料成分（１）の内で所定量を予め高速攪拌混合しておき、その混合粉末を連続式２軸混練機で混練したのち、サンドミルで滞留時間を４５分として分散し、これに磁性塗料成分（２）を加え攪拌・濾過後、磁性塗料とした。
【００７８】
上記の下塗塗料を、芳香族ポリアミドフイルム（厚さ３．９μｍ、ＭＤ＝１１ＧＰａ、ＭＤ／ＴＤ＝０．７０、商品名：ミクトロン、東レ製）からなる非磁性支持体（ベースフィルム）上に、乾燥、カレンダ後の厚さが０.９μｍとなるように塗布し、この下塗層上に、さらに上記の磁性塗料を磁場配向処理、乾燥、カレンダ処理後の磁性層の厚さが０．０９μｍとなるようにウエット・オン・ウエットで塗布し、磁場配向処理後、ドライヤおよび遠赤外線を用いて乾燥し、磁気シートを得た。なお、磁場配向処理は、ドライヤ前にＮ−Ｎ対抗磁石（５ｋＧ）を設置し、ドライヤ内で塗膜の指蝕乾燥位置の手前側７５ｃｍからＮ−Ｎ対抗磁石（５ｋＧ）を２基５０ｃｍ間隔で設置して行った。塗布速度は１００ｍ／分とした。
【００７９】
≪バックコート層用塗料成分≫
・微粒子カーボンブラック（キャボット社製 ８０部
REGAL415、平均粒子径：２５ｎｍ）
・カーボンブラック（コロンビヤン社製、RAVEN MTP、 １０部
平均粒子径：２８０ｎｍ）
・酸化鉄（平均粒子径：０．２μｍ） １０部
・ニトロセルロース ４５部
・ポリウレタン樹脂（ＳＯ₃ Ｎａ基含有） ３０部
・シクロヘキサノン ４１０部
・メチルエチルケトン ６９０部
・トルエン ２６０部
【００８０】
上記バックコート層用塗料成分をサンドミルで滞留時間４５分として分散した後、ポリイソシアネート１５部を加えてバックコート層用塗料を調整し濾過後、上記で作製した磁気シートの磁性層の反対面に、乾燥、カレンダ後の一次厚みが０．２５μｍとなるように塗布し、乾燥した。
【００８１】
このようにして得られた磁気シートを金属ロールからなる７段カレンダで、温度１００℃、線圧１９６ｋＮ／ｍの条件で鏡面化処理し、磁気シートをコアに巻いた状態にて７０℃で７２時間エージングしたのち、１／２インチ幅に裁断し、これを２００ｍ／分で走行させながら磁性層表面をラッピングテープ研磨、ブレード研磨そして表面拭き取りの後処理を行い、磁気テープを作製した。この時、ラッピングテープにはＫ１００００、ブレードには超硬刃、表面拭き取りには東レ製トレシー（商品名）を用い、走行テンション３０ｇで処理を行った。上記のようにして得られた磁気テープを、カートリッジに組み込み、コンピュータ用テープを作製した。
【００８２】
比較例４：
バックコート層の一次厚みを、０.２５μmから０.３μmに変更した以外は、実施例７と同様にして比較例４のコンピュータ用テープを作製した。
以上のようにして得られた各コンピュータ用テープを用いて、以下のような性能評価を行った。
【００８３】
＜バックコート層一次厚み＞
テープの垂直断面をＳＥＭにて観察し、非磁性支持体とバックコート層との界面から粗粒子粉末による突起部以外のバックコート層一次表面までの距離を計測して求めるものである。前記計測を１０点行いその値の平均値をバックコート層一次厚みとした。
【００８４】
＜摩擦係数＞
表面粗度が０．２Ｓに仕上げられた直径４ｍｍのＳＵＳ３０４製円筒を水平に支持し、これにテープ状にしたサンプルのバックコート層側を接触面として９０度の角度をなすようにかけ、テープの一端に０.２９４Ｎ（３０ｇ重）の荷重を加えながら他端を水平にして１４ｍｍ／秒の速さで引っ張ったときの応力Ｔ（Ｎ）を求め、この応力Ｔを下記式に当てはめて摩擦係数μを求めた。
μ＝（２／π）Ｌｎ（Ｔ／０．２９４）
測定は繰り返し２０パスまで行い、１パス目と２０パス目の摩擦係数を求めた。
【００８５】
＜Ｃ／Ｎ比＞
テープの電磁変換特性測定には、ドラムテスターを用いた。ドラムテスターには電磁誘導型ヘッド（トラック幅２５μｍ、ギャップ0.１μｍ）とＭＲヘッド（トラック幅８μｍ）を装着し、誘導型ヘッドで記録、ＭＲヘッドで再生を行った。両ヘッドは回転ドラムに対して異なる場所に設置されており、両ヘッドを上下方向に操作することで、トラッキングを合わせることができる。磁気テープはカートリッジに巻き込んだ状態から適切な量を引き出して廃棄し、更に６０ｃｍを切り出し、更に４ｍｍ幅に加工して回転ドラムの外周に巻き付けた。
【００８６】
出力及びノイズは、ファンクションジェネレータにより波長0.２μｍの矩形波を書き込み、ＭＲヘッドの出力をスペクトラムアナライザーに読み込んだ。0.２μｍのキャリア値を媒体出力Ｃとした。また0.２μｍの矩形波を書き込んだときに、出力及びシステムノイズを差し引いた値の積分値をノイズ値Ｎとして用いた。更に両者の比をとってＣ／Ｎとし、リファレンスとして用いている比較例４テープの値との相対値を求めた。
【００８７】
＜エラーレートの測定＞
薄手テープも測定できるように改善したＳ−ＤＬＴドライブを用いて、走行前と１００パス走行後の記録・再生（記録波長0.３７μｍ）を行うことによって走行前、走行後のエラーレートを測定した。エラーレートはテストモードでの値である。以上の評価結果を表２に示す。
【００８８】
【表２】

【００８９】
上記の表１の結果より、本発明の実施例１〜６に係る評価用テープは、初期の摩擦係数が低く、かつ安定しており走行耐久性、ドロップアウトが良好なことが分かる。また実施例５のビデオＳ／Ｎが悪化しているが、テープ強度の低下による事は明らかであり磁性層表面への悪影響が抑制されていることが分かる。
【００９０】
一方、本発明からはずれる、比較例１〜４に係る評価用テープは、摩擦係数の変化が大きく、走行耐久性が著しく悪かったり、ドロップアウトが著しく悪い。また磁性層表面への悪影響によりビデオＳ／Ｎが著しく悪化している事が分かる。
【００９１】
また、表２の結果より、磁気テープの記録層側を、磁性層と下塗層の二層構造とした場合においても、上記と同様の効果が得られることが分かる。
【００９２】
【発明の効果】
上記の結果から、本発明によれば、テープ走行時において、高耐久性、高安定性で、かつ、繰り返し使用時におけるテープエッジダメージが小さく、エラーレートの増加が少ない信頼性に優れた磁気テープが得られる。
【図面の簡単な説明】
【図１】本発明の磁気テープの概念図である。
【符号の説明】
１ 非磁性支持体
２ バックコート層
３ 粗粒子非磁性粉末
４ バックコート層一次表面
５ 下塗層（ない場合もある）
６ 磁性層
Ａ バックコート層一次厚み
Ｂ 磁気テープ全厚[0001]
BACKGROUND OF THE INVENTION
The present invention relates to running and durability of a magnetic tape, and more particularly to improvement in running stability during tape running and realization of high reliability during repeated use.
[0002]
[Prior art]
In recent years, magnetic tape has a tendency to increase in capacity and recording density, as typified by computer tape, and the tape thickness tends to be reduced accordingly. Therefore, stable recording and reading in repeated use is possible. The reliability of the performance is required more than before.
[0003]
In general, a magnetic tape has a structure in which a magnetic layer is provided on a nonmagnetic support made of a flexible material such as a synthetic resin. To achieve higher capacity and higher density, increase the recording density of the magnetic layer itself, such as reducing the particle size of the magnetic powder, improving its dispersibility, or making the magnetic layer even thinner. Increasing the recording capacity by reducing the total thickness of the tape and increasing the length is an effective means. However, when the total thickness is reduced, the self-supporting property and strength of the magnetic tape are clearly decreased, and in order to maintain good running durability against repeated use, the above-mentioned support is opposite to the magnetic layer. A back coat layer is usually provided on the surface. In addition, as the thickness of the magnetic tape is reduced, the thickness of the backcoat layer tends to be relatively thin.
[0004]
Conventionally, by selecting the material included in the backcoat layer and controlling the surface roughness of the backcoat by surface heat treatment, good running durability maintenance during repeated use has been achieved (Patent Documents 1 to Patent). Reference 4) has not reached a complete improvement.
[0005]
[Patent Document 1]
Japanese Laid-Open Patent Publication No. 2-7223 (page 4-9, Table 1, Table 2, Table 3, Table 4)
[Patent Document 2]
JP-A-6-215350 (page 4-7, Table 1, Table 2)
[Patent Document 3]
JP-A-9-115134 (page 2-7, Table 1)
[Patent Document 4]
Japanese Patent Publication No. 7-40351 (page 2-4)
[0006]
[Problems to be solved by the invention]
The present invention has been made to solve the above-mentioned disadvantages of the prior art, ensuring durability and stability during running of the tape, reducing tape edge damage during repeated use, and improving reliability. The goal is to provide excellent magnetic tape.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the above-mentioned problems can be solved by making the magnetic tape have the following configuration, and the present invention has been achieved.
[0008]
That is, a magnetic layer containing ferromagnetic powder and binder resin provided on one surface of a nonmagnetic support, and a backcoat layer containing nonmagnetic powder and binder resin provided on the other surface;includingIn the magnetic tape, the primary thickness of the backcoat layer is 0.1 to 0.6 μm, the total thickness of the magnetic tape is 3 to 20 μm, and the nonmagnetic powder has two or more kinds of nonmagnetic powders having different average particle diameters. And the average particle size of the nonmagnetic powder having the maximum average particle size (hereinafter also referred to as coarse particle nonmagnetic powder or coarse particle powder) is larger than 1.0 times the primary thickness of the backcoat layer and is 2.0 times. It is characterized by the following.
[0009]
An undercoat layer containing a nonmagnetic powder and a binder resin is provided between the magnetic layer and the nonmagnetic support.
[0010]
  Hereinafter, embodiments of the present invention will be described. Similar to a general magnetic tape, a magnetic layer including a ferromagnetic powder and a binder resin provided on one surface of a nonmagnetic support, and a back including a nonmagnetic powder and a binder resin provided on the other surface. With coat layerincludingIn the magnetic tape, the primary thickness of the backcoat layer is 0.1 to 0.6 μm (more preferably 0.2 to 0.5 μm), and the total thickness of the magnetic tape is 3 to 20 μm (more preferably 4 to 18 μm). Preferably, it is configured. And the magnetic tape of this invention can be comprised similarly to the normal magnetic tape generally known except comprising a backcoat layer with a specific composition and thickness.
[0011]
The primary thickness of the backcoat layer is preferably within this range. When the thickness is less than 0.1 μm, the running durability and running stability are insufficient. When the thickness exceeds 0.6 μm, the back curl becomes large, and the entire tape This is because the recording capacity per volume becomes small as the thickness increases.
[0012]
The primary thickness of the backcoat layer here means a thickness not including the height of the protrusion on the surface of the backcoat layer made of coarse-grained nonmagnetic powder. The vertical cross section of the tape is observed with an SEM, and nonmagnetic support is provided. It is obtained by measuring the distance from the interface between the body and the backcoat layer to the primary surface of the backcoat layer other than the protrusions of the coarse particle powder. The measurement was performed at 10 points, and the average of the values was defined as the back coat layer primary thickness.
[0013]
Usually, the thickness of the coating film required is 10 sheets of non-magnetic support on which the coating film is formed, and the thickness is obtained with a micrometer. The thickness including the height of the protrusion of the nonmagnetic powder is required.
[0014]
It is preferable that the total thickness of the magnetic tape is within this range. If the thickness is less than 3 μm, the strength of the tape is small, so that the running stability is deteriorated, the head contact is deteriorated and the output is reduced. This is because the recording capacity per volume is reduced.
[0015]
The total thickness of the magnetic tape here refers to a value obtained by superimposing ten magnetic tapes and obtaining the thickness with a micrometer and converting the thickness per magnetic tape.
[0016]
  The back coat layer of the present invention includes two or more kinds of nonmagnetic powders having different average particle diameters, and is also referred to as a nonmagnetic powder having a maximum average particle diameter (hereinafter also referred to as coarse particle nonmagnetic powder or coarse particle powder). ) Is larger than 1.0 times and less than 2.0 times the primary thickness of the backcoat layer. Here, the nonmagnetic powder having the maximum average particle diameter refers to one having the maximum average particle diameter among two or more kinds of nonmagnetic powders having different average particle diameters. For example, when fine particle nonmagnetic powder (average particle size: 80 nm or less) and coarse particle nonmagnetic powder (average particle size: 120 nm or more) are included, the average particle size (120 nm) of the coarse particle nonmagnetic powder is the backcoat layer. It is larger than 1.0 times the primary thickness, preferably 2.0 times or less, and more preferably 1.2 to 1.8 times. This range is preferably 1.0 timesLess thanIf it is, the function as a solid lubricant is difficult to be exerted and the effect of the present invention is not sufficiently exhibited. Conversely, if it exceeds 2.0 times, the back coat layer surface becomes rough, noise is generated, and coarse particles are not applied. This is because the magnetic powder easily falls off, and the dropout and error ratio are likely to increase.
[0017]
The fine particle nonmagnetic powder preferably has an average particle size of 80 nm or less and 10 nm or more, and is preferably smaller than the primary thickness of the backcoat layer. The average particle diameter of the fine non-magnetic powder is preferably within this range because the smoothness of the backcoat layer surface becomes insufficient if the average particle size is outside this range.
[0018]
Although carbon black is preferably used as the fine particle nonmagnetic powder, other conductive nonmagnetic powder may be used. Moreover, you may mix powder other than electroconductive nonmagnetic powder as needed.
[0019]
The coarse particle non-magnetic powder preferably has a Mohs hardness of 3 or more and has a granular particle form. A Mohs hardness of less than 3 is not preferable because the nonmagnetic powder itself is scraped off during repeated use of the tape, causing a large change in the coefficient of friction with respect to the guide pin and causing dropout. In addition, since the particle shape is granular, the contact area with respect to the guide pin is reduced, so that the friction coefficient can be reduced, and the binding force with the binder resin is increased, so that it can be prevented from falling off the back coat layer. Become.
[0020]
The term “granular” as used herein means that the ratio of the maximum diameter to the minimum diameter of the particles is 2 or less.
[0021]
As the coarse-particle nonmagnetic powder, it is preferable to use one or a plurality of types of powders selected from carbon black, alumina powder, iron oxide powder, and chromium oxide powder. By using one or more of the nonmagnetic powders in combination, the effect of reducing the friction coefficient and maintaining the friction coefficient can be further improved without cutting the guide pin.
[0022]
The content of the coarse-particle nonmagnetic powder is preferably in the range of 5 to 30 parts by weight when the total nonmagnetic powder is 100 parts by weight. If this range is less than 5, it is difficult to sufficiently reduce the friction coefficient against the guide pin and maintain the effect, and if it exceeds 30, the backcoat layer surface becomes rough and the electromagnetic conversion characteristics deteriorate. The total amount of the non-magnetic powder in the back coat layer is preferably 50 to 200 parts by weight with respect to 100 parts by weight of the binder resin. If the content is too small, the effect of the present invention is sufficient. On the contrary, if the amount is too large, the binding force by the binder resin is insufficient, and the nonmagnetic powder falls off from the backcoat layer, resulting in a decrease in wear resistance.
[0023]
For the back coat layer of the present invention, various non-magnetic powders that have been conventionally blended in the back coat layer of magnetic recording media can be used as necessary. Specific examples thereof include C and Al.₂O₃, Cr₂O₃TiO₂, Α-Fe₂O₃, BaSo₄, CaCO₃, BaCO₃, MgCO₃Powders such as SiC, silicon resin, and cross-linked resin can be used.
[0024]
As the prior art documents disclosing that the backcoat layer contains fine particle nonmagnetic powder and coarse particle nonmagnetic powder, there are Patent Documents 1 to 4 described above.
[0025]
Patent Document 1 discloses that a fine particle carbon black having an average particle size of 0.01 to 0.08 μm, a coarse particle carbon black having an average particle size of 0.2 to 0.5 μm, and an average particle size in the backcoat layer. Although a magnetic tape containing 0.01 to 0.045 μm fine particle calcium carbonate is disclosed, the thickness of the backcoat layer is preferably 0.5 to 2.0 μm. The range of the ratio of the layer thickness is different from the range of the present invention.
[0026]
Patent Document 2 discloses a magnetic tape, carbon black (average primary particle size) containing plate-like α-iron oxide (particle size 2.0 μm, thickness 0.1 μm) and carbon black (average primary particle size 200 nm) in the backcoat layer. A magnetic tape containing carbon black (average primary particle size 200 nm) is disclosed, but the preferred thickness range of the backcoat layer is not disclosed, and in the examples is 0.5 μm, In either case, the range of the ratio of the coarse particle non-magnetic powder and the back coat layer thickness is different from the range of the present invention.
[0027]
Patent Document 3 includes fine particulate carbon black having a back coat layer thickness of 0.2 to 0.8 μm and an average particle size of 10 to 20 μm and coarse particulate carbon black having an average particle size of 230 to 300 μm. Further, it contains calcium carbonate having an average particle size of 30 to 50 μm and an inorganic powder having a Mohs hardness of 5 to 9 having an average particle size of 80 to 250 μm, and the surface roughness Ra of the backcoat layer is 0.030 to 0.060 μm. However, the ratio of the average particle diameter of the coarse non-magnetic powder and the preferred thickness range of the backcoat layer is not disclosed, and in the examples, the thickness is 0.6 μm. Only the backcoat layer is being considered, which is different from the preferred configuration of the present invention.
[0028]
In Patent Document 4, the thickness of the backcoat layer is in the range of 0.15 to 0.60 μm, and the backcoat layer has a thickness smaller than the thickness of the carbon black and the backcoat layer. Inorganic filler particles having a Mohs hardness of 5 or more, which has an average particle diameter of 1/5 or more and a maximum particle diameter of 11/10 or less of the layer thickness of the backcoat layer, are included. Although a magnetic recording medium has been disclosed, the average particle diameter is less than the layer thickness, which is different from the present invention.
[0029]
In the above four prior art documents, there is a description relating to the constitution of the present invention in which the average particle diameter of the coarse nonmagnetic powder is preferably greater than 1.0 times and less than 2.0 times the primary thickness of the backcoat layer. However, the present inventors have found that the effect as a solid lubricant can be maximized only when the particle diameter of the coarse-particle nonmagnetic powder is in the above range.
[0030]
The back coat layer according to the present invention is formed by dispersing each of the above components in a binder resin, which will be described later. As optional components, a dispersant and a lubricant conventionally used in magnetic recording media are used. Either can be used alone or in combination of two or more.
[0031]
The binder resin used for the backcoat layer can be the same as the binder resin used for the magnetic layer and the undercoat layer described later. Among these, in order to reduce the friction coefficient and improve the running property, It is preferable to use in combination with a polyurethane resin. The content of the binder resin is preferably 40 to 200 parts by weight, more preferably 50 to 150 parts by weight, and still more preferably 60 to 130 parts by weight with respect to 100 parts by weight of the total amount of the carbon black and the inorganic nonmagnetic powder. Parts, most preferably 70 to 130 parts by weight. The above range is preferable because if the amount is less than 40 parts by weight, the strength of the backcoat layer is insufficient, and if it exceeds 200 parts by weight, the friction coefficient tends to increase. It is preferable to use 30 to 80 parts by weight of a cellulose resin and 20 to 50 parts by weight of a polyurethane resin. Further, in order to further cure the binder resin, it is preferable to use a crosslinking agent such as a polyisocyanate compound.
[0032]
For the backcoat layer, the same crosslinking agent as that used for the magnetic layer and the undercoat layer described later is used. The amount of the crosslinking agent is preferably 5 to 50 parts by weight, more preferably 5 to 35 parts by weight, and still more preferably 10 to 30 parts by weight with respect to 100 parts by weight of the binder resin. The above range is preferable because if less than 5 parts by weight, the coating strength of the backcoat layer tends to be weak, and if it exceeds 50 parts by weight, the dynamic friction coefficient against SUS increases.
[0033]
The formation of the backcoat layer in the magnetic tape of the present invention may be carried out in accordance with conventional methods, and a backcoat paint comprising the aforementioned components, a binder resin and an organic solvent is prepared, and this paint is applied to a nonmagnetic support. The magnetic layer provided on one side of the non-magnetic support may be applied to one side of the nonmagnetic support after forming or before drying.
[0034]
Next, the components of the magnetic recording medium of the present invention will be described in detail.
<Non-magnetic support>
Although the thickness of a nonmagnetic support body changes with uses, Preferably, the thing of 2.0-15.0 micrometers is used. More preferably, it is 2.5-13.0 micrometers, Most preferably, it is 3.0-11.0 micrometers. Nonmagnetic supports with a thickness in this range are used because film formation is difficult if the thickness is less than 2.0 μm, and the tape strength decreases. If the thickness exceeds 15.0 μm, the total thickness of the tape increases, and one roll of tape. This is because the recording capacity per unit becomes small.
[0035]
The Young's modulus in the longitudinal direction of the non-magnetic support used in the present invention is preferably 5.9 GPa (600 kg / mm 2) or more, and more preferably 6.8 GPa (700 kg / mm 2) or more. The non-magnetic support preferably has a Young's modulus in the longitudinal direction of 5.9 GPa (600 kg / mm 2) or more because the tape running becomes unstable if the Young's modulus in the longitudinal direction is less than 5.9 GPa (600 kg / mm 2). is there. In the helical scan type, the Young's modulus in the longitudinal direction / Young's modulus in the width direction is preferably in a specific range of 0.60 to 2.00. The Young's modulus in the longitudinal direction / Young's modulus in the width direction is more preferably in the range of 0.65 to 0.75. The specific range of Young's modulus in the longitudinal direction / Young's modulus in the width direction is preferably in the range of 0.60 to 2.00. When the ratio is less than 0.60 or exceeds 2.00, the mechanism is currently unknown. This is because the output variation (flatness) between the entrance side and the exit side of the track of the magnetic head increases. This variation is minimized when the Young's modulus in the longitudinal direction / Young's modulus in the width direction is around 0.80. Furthermore, in the linear recording type, the Young's modulus in the longitudinal direction / Young's modulus in the width direction is preferably 0.70 to 1.30, although the reason is not clear. Examples of the resin film satisfying such characteristics include a biaxially stretched polyethylene terephthalate film, a polyethylene naphthalate film, an aromatic polyamide film, and an aromatic polyimide film.
[0036]
<Undercoat layer>
In order to improve the short wavelength recording characteristics by reducing the thickness of the magnetic layer, it is preferable to provide an undercoat layer between the magnetic layer and the nonmagnetic support because the smoothness and durability of the magnetic layer can be improved.
[0037]
The thickness of the undercoat layer is preferably in the range of 0.2 to 2.2 μm. This range is preferable if less than 0.2, the supply of lubricant to the magnetic layer is insufficient, or the smoothing effect of the magnetic layer is reduced, and if it exceeds 2.2 μm, the total thickness of the tape is increased. This is because the capacity per tape roll is reduced.
[0038]
For the purpose of improving conductivity, carbon black and iron oxide are preferably added to the undercoat layer for the purpose of controlling the tape rigidity. The undercoat layer is 15 to 35% by weight of carbon black having an average particle diameter of 10 to 100 nm, an average major axis diameter of 0.05 to 0.20 μm, an average based on the weight of all inorganic powders in the undercoat layer When nonmagnetic iron oxide having a minor axis diameter of 5 to 200 nm is contained in an amount of 35 to 83% by weight, it is preferable because the thickness unevenness of the magnetic layer formed on and wet-on-wet is reduced. . In addition, although nonmagnetic iron oxide is usually acicular, when granular or amorphous nonmagnetic iron oxide is used, iron oxide having an average particle diameter of 5 to 200 nm is preferable.
[0039]
Carbon black or nonmagnetic iron oxide is preferably added to the undercoat layer. As carbon black (CB) added to the undercoat layer, acetylene black, furnace black, thermal black, and the like can be used. An average particle size of 5 to 200 nm is used, but an average particle size of 10 to 100 nm is preferable. This range is preferable because carbon black has a structure, so that dispersion of CB is difficult when the average particle diameter is 10 nm or less, and smoothness is deteriorated when the average particle diameter is 100 nm or more. The amount of CB added varies depending on the particle size of CB, but is preferably 15 to 35% by weight based on the weight of the total inorganic powder in the undercoat layer. This range is preferable because if the amount is less than 15% by weight, the effect of improving conductivity is poor, and if it exceeds 35% by weight, the effect is saturated. It is more preferable to use 15 to 35% by weight of CB having a particle size of 15 to 80 nm, and further preferable to use 20 to 30% by weight of CB having a particle size of 20 to 50 nm. By adding carbon black having such a particle size and amount, electric resistance is reduced, generation of electrostatic noise and tape running unevenness are reduced, and the thickness unevenness of the far-infrared dried magnetic layer is reduced.
[0040]
The nonmagnetic iron oxide added to the undercoat layer preferably has an average major axis diameter of 50 to 200 nm and an average minor axis diameter of 5 to 200 nm in the case of needles. A particle size of 5 to 200 nm is preferred. Needle-shaped ones are more preferable because the orientation of the magnetic layer is improved. The addition amount is preferably 35 to 90% by weight based on the weight of the total inorganic powder in the undercoat layer. The average particle diameter in this range (short axis diameter in the case of needles) is preferable because uniform dispersion is difficult when the average particle diameter is less than 5 nm, and unevenness at the interface between the undercoat layer and the magnetic layer increases when it exceeds 200 nm. Because. The addition amount within this range is preferable because if the amount is less than 35% by weight, the effect of improving the coating film strength is small, and if it exceeds 90% by weight, the coating film strength is lowered.
[0041]
<Lubricant>
Lubricants with different roles are used in the coating layer composed of the undercoat layer and the magnetic layer. When the undercoat layer contains 0.5 to 4.0% by weight of higher fatty acid and 0.2 to 3.0% by weight of higher fatty acid ester, the friction with the head This is preferable because the coefficient is small. The addition of higher fatty acids within this range is preferable when the content is less than 0.5% by weight, and the effect of reducing the friction coefficient is small, and when the content exceeds 4.0% by weight, the undercoat layer is plasticized and the toughness is lost. The addition of higher fatty acid esters within this range is preferable because the effect of reducing the friction coefficient is small if it is less than 0.2% by weight, and the amount transferred to the magnetic layer is too large if it exceeds 3.0% by weight. This is because there are side effects such as sticking the head.
[0042]
When the magnetic layer contains 0.5 to 3.0% by weight of fatty acid amide and 0.2 to 3.0% by weight of higher fatty acid ester with respect to the ferromagnetic powder, friction during tape running This is preferable because the coefficient is small. Fatty acid amides in this range are preferred if less than 0.5% by weight, the direct contact at the head / magnetic layer interface is likely to occur, and the effect of preventing seizure is small. Defects such as out occur. As the fatty acid amide, amides such as palmitic acid and stearic acid can be used. Further, the higher fatty acid ester addition in the above range is preferable because the effect of reducing the friction coefficient is small if it is less than 0.2% by weight, and there is a side effect such as sticking to the head if it exceeds 3.0% by weight. The mutual movement of the lubricant in the magnetic layer and the lubricant in the undercoat layer is not excluded.
[0043]
<Magnetic layer>
The average particle diameter of the magnetic powder contained in the magnetic layer is preferably in the range of 10 to 300 nm, more preferably in the range of 15 to 100 nm. This range is preferred because if the average particle size is less than 10 nm, the surface energy of the particles becomes large and dispersion becomes difficult, and if the average particle size exceeds 300 nm, noise increases. As the magnetic powder, ferromagnetic iron-based metal magnetic powder, iron nitride magnetic powder, plate-shaped hexagonal Ba-ferrite magnetic powder, and the like are preferable.
[0044]
The ferromagnetic iron-based metal magnetic powder may contain a transition metal such as Mn, Zn, Ni, Cu, and Co as an alloy. Among these, Co 2 and Ni 2 are preferable, and Co 2 is particularly preferable because it can improve saturation magnetization most. As a quantity of said transition metal element, it is preferable to set it as 5-50 atomic% with respect to iron, and it is more preferable to set it as 10-30 atomic%. Further, at least one rare earth element selected from yttrium, ytterbium, cesium, praseodymium, samarium, lanthanum, europium, neodymium, terbium and the like may be included. Among these, when neodymium, samarium, terbium, and yttrium are used, a high coercive force is obtained, which is preferable. The amount of the rare earth element is 0.2 to 20 atomic%, preferably 0.3 to 15 atomic%, more preferably 0.5 to 10 atomic% with respect to iron.
[0045]
Boron may be included in the ferromagnetic iron-based metal magnetic powder. By containing boron, granular or elliptical ultrafine particles having an average particle diameter of 50 nm or less can be obtained. The amount of boron is 0.5 to 30 atom%, preferably 1 to 25 atom%, more preferably 2 to 20 atom%, based on iron in the entire magnetic powder. Both the above-mentioned atomic% are values measured by fluorescent X-ray analysis (reference document: Japanese Patent Laid-Open No. 2001-181754).
[0046]
As the iron nitride magnetic powder, a known one can be used, and the shape can be an indeterminate shape such as a spherical shape or a cubic shape in addition to a needle shape. Regarding the particle size and specific surface area, in order to clear the required characteristics as magnetic powder for magnetic recording, it is necessary to make the production conditions of the limited magnetic powder (reference patent: Japanese Patent Laid-Open No. 2000-277311). .
[0047]
The coercive force of the ferromagnetic iron-based metal magnetic powder and the iron nitride magnetic powder is preferably 80 to 320 kA / m, and the saturation magnetization is 80 to 200 A · m.² / Kg (80 to 200 emu / g) is preferable, 100 to 180 A · m² / Kg (100 to 180 emu / g) is more preferable.
[0048]
The average particle size of the ferromagnetic iron-based metal magnetic powder and the iron nitride magnetic powder is preferably 10 to 300 nm, and more preferably 15 to 100 nm. This range is preferable when the average particle size is less than 10 nm, the coercive force is reduced, the surface energy of the particles is increased, so that dispersion in the paint becomes difficult, or the average particle size is greater than 300 nm. This is because the particle noise based on the particle size becomes large. The ferromagnetic powder has a BET specific surface area of 35 m.² / G or more is preferable, 40 m² / G or more is more preferable, 50 m² / G or more is most preferable. Usually 100m² / G or less.
[0049]
The coercive force of the hexagonal Ba-ferrite magnetic powder is preferably 120 to 320 kA / m, and the saturation magnetization is 40 to 70 A · m.² / Kg (40-70 emu / g) is preferred. Note that the magnetic properties of these ferromagnetic powders all refer to values measured with an external magnetic field of 1273.3 kA / m (16 kOe) using a sample vibration magnetometer. Further, the particle size (size in the plate surface direction) is preferably 10 to 50 nm, more preferably 10 to 30 nm, and further preferably 10 to 20 nm. When the particle size is less than 10 nm, the surface energy of the particles increases, so that dispersion in the paint becomes difficult. When the particle size exceeds 50 nm, particle noise based on the particle size increases. The average particle diameter is measured by measuring the maximum diameter of each particle (the major axis diameter for needle-like powder and the plate diameter for plate-like powder) from a photograph taken with a transmission electron microscope (TEM). The average value is obtained. The plate ratio (plate diameter / plate thickness) is preferably 2 to 10, more preferably 2 to 5, and still more preferably 2 to 4. The hexagonal Ba-ferrite magnetic powder has a BET specific surface area of 1 to 100 m.² / G is preferably used.
[0050]
The binder resin used for the magnetic layer (same for the undercoat layer) is vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl alcohol copolymer resin, vinyl chloride-vinyl acetate-vinyl alcohol copolymer. A combination of a polyurethane resin and at least one selected from cellulose resins such as resins, vinyl chloride-vinyl acetate-maleic anhydride copolymer resins, vinyl chloride-hydroxyl group-containing alkyl acrylate copolymer resins, and nitrocellulose resins. Is mentioned. Among these, it is preferable to use a vinyl chloride-hydroxyl group-containing alkyl acrylate copolymer resin and a polyurethane resin in combination. Examples of the polyurethane resin include polyester polyurethane resin, polyether polyurethane resin, polyether polyester polyurethane resin, polycarbonate polyurethane resin, polyester polycarbonate polyurethane resin, and the like.
[0051]
-COOH, -SO as functional groups_Three M, -OSO_Three M, -P = O (OM)_Three , -OP = O (OM)₂ [M is a hydrogen atom, an alkali metal base or an amine salt], —OH, —NR′R ″, —N⁺ R '' 'R' '' 'R' '' '' [R ′, R ″, R ′ ″, R ″ ″, R ′ ″ ″ are hydrogen or hydrocarbon groups], epoxy groups A resin such as a urethane resin made of a polymer having The reason why such a resin is used is that the dispersibility of magnetic powder and the like is improved as described above. When two or more kinds of resins are used in combination, it is preferable to match the polarities of the functional groups._Three A combination of M groups is preferred.
[0052]
These resins are used in the range of 7 to 50 parts by weight, preferably 10 to 35 parts by weight with respect to 100 parts by weight of the ferromagnetic powder. In particular, it is most preferable to use a composite of 5 to 30 parts by weight of a vinyl chloride resin and 2 to 20 parts by weight of a polyurethane resin.
[0053]
It is desirable to use together with these resins a thermosetting cross-linking agent that bonds and crosslinks with a functional group contained in the resin. Examples of the crosslinking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, reaction products of these isocyanates with a plurality of hydroxyl groups such as trimethylolpropane, and condensation products of the above isocyanates. Various polyisocyanates are preferred. These crosslinking agents are usually used in a proportion of 10 to 50 parts by weight with respect to 100 parts by weight of the resin. More preferably, it is 15 to 35 parts by weight.
[0054]
Further, conventionally known abrasives can be added to the magnetic layer. Examples of these abrasives include α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, Artificial diamond, silicon nitride, silicon carbide, titanium carbide, titanium oxide, silicon dioxide, boron nitride, etc. are mainly used alone or in combination with a Mohs hardness of 6 or more. Among these, alumina is added with a high hardness and a small amount. The amount is particularly preferable because the head cleaning effect is excellent in amount. The particle size of the abrasive is usually preferably 0.002 to 0.30 μm in average particle size, and more preferably 0.005 to 0.20 μm in average particle size. The addition amount is preferably 5 to 20% by weight with respect to the ferromagnetic powder. More preferably, it is 8 to 18% by weight.
[0055]
Furthermore, conventionally known carbon black (CB) can be added to the magnetic layer of the present invention for the purpose of improving conductivity and surface lubricity. Examples of these carbon blacks include acetylene black, furnace black, thermal black, and thermal black. Black etc. can be used. An average particle size of 5 to 200 nm is used, but an average particle size of 10 to 100 nm is preferable. This range is preferable because when the average particle size is 5 nm or less, it is difficult to disperse the carbon black. When the average particle size is 200 nm or more, it is necessary to add a large amount of carbon black. In any case, the surface becomes rough and the output decreases. This is because it causes. The addition amount is preferably 0.2 to 5% by weight with respect to the ferromagnetic powder. More preferably, it is 0.5 to 4% by weight.
[0056]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but is not limited thereto. In addition, the part of an Example and a comparative example shows a weight part.
Example 1:
≪Magnetic paint ingredients≫
(1) Kneading dilution process
・ 100 parts of ferromagnetic iron metal powder (magnetic powder)
(Co / Fe: 3.0 at%,
Y / (Fe + Co): 1.9 at%
Al / (Fe + Co): 4.0 wt%
σs: 131 A · m² / Kg (131 emu / g),
Hc: 138 kA / m (1735 Oe),
(Average particle size: 190 nm)
・ 11 parts of vinyl chloride-hydroxypropyl acrylate copolymer
(Contains-SO_Three Na group: 0.7 × 10^{- 4}Equivalent / g)
・ Polyester polyurethane resin 5 parts
(Contains-SO_Three Na group: 1.0 × 10^-FourEquivalent / g)
・ Alumina (Sumitomo Chemical Co., Ltd., average particle size: 0.25 μm) 10 parts
・ Carbon black (manufactured by Cabot, Monarch 120, 3 parts)
(Average particle diameter: 75 nm, DBP oil absorption: 72 cc / 100 g)
・ 1.5 parts of methyl acid phosphate
・ 2.0 parts of myristic acid
・ 1.5 parts of n-butyl stearate
・ 60 parts of tetrahydrofuran
・ Cyclohexanone 120 parts
・ Methyl ethyl ketone 60 parts
・ Toluene 120 parts
(2) Compounding process
・ Polyisocyanate 6 parts
・ 54 parts of cyclohexanone
[0057]
A predetermined amount of the magnetic coating component (1) is previously stirred at high speed and the mixed powder is kneaded with a continuous biaxial kneader, and then dispersed in a sand mill with a residence time of 45 minutes. The magnetic paint component (2) was added and stirred and filtered to obtain a magnetic paint.
[0058]
On the nonmagnetic support (base film) made of the above-mentioned magnetic coating material made of polyethylene naphthalate film (thickness 5.5 μm, MD = 6.1 GPa, MD / TD = 0.93, trade name: Teonex, manufactured by Teijin) Then, coating was performed so that the thickness after magnetic field orientation treatment, drying, and calendar treatment was 1.9 μm, and after magnetic field orientation treatment, drying was performed using a dryer and far infrared rays to obtain a magnetic sheet. In the magnetic field orientation treatment, an NN counter magnet (5 kG) is installed in front of the dryer, and two NN counter magnets (5 kG) are spaced from each other at a distance of 50 cm from the front side 75 cm of the position of dry coating of the coating in the dryer. It was installed at. The coating speed was 100 m / min.
[0059]
≪Back coat layer paint component≫
・ Fine particle carbon black (88 parts made by Cabot)
REGAL415, average particle size: 25nm)
-12 parts of alumina (AKP-20 average particle size: 600 nm, manufactured by Sumitomo Chemical Co., Ltd.)
・ Nitrocellulose 45 parts
・ Polyurethane resin (SO_Three (Containing Na group) 30 parts
・ 410 parts of cyclohexanone
・ Methyl ethyl ketone 690 parts
・ Toluene 280 parts
[0060]
After the coating component for the backcoat layer is dispersed in a sand mill with a residence time of 45 minutes, 15 parts of polyisocyanate is added to adjust the coating for the backcoat layer, and after filtration, on the opposite side of the magnetic layer of the magnetic sheet prepared above , Dried and coated so that the primary thickness after calendering was 0.5 μm and dried.
[0061]
The magnetic sheet thus obtained was mirror-finished with a seven-stage calendar made of a metal roll under the conditions of a temperature of 100 ° C. and a linear pressure of 196 kN / m, and the magnetic sheet was wound on a core at 70 ° C. at 72 ° C. After time aging, it was cut into a width of 8 mm. The magnetic tape obtained as described above was assembled in a cartridge to produce an evaluation tape.
[0062]
Example 2:
The primary thickness of the backcoat layer was changed to 0.2 μm, and 12 parts of alumina (AKP-20 average particle size: 600 nm) manufactured by Sumitomo Chemical Co., Ltd., carbon black (RAVEN MTP, manufactured by Colombian Co., average particle size: 280 nm) 12 An evaluation tape of Example 2 was produced in the same manner as in Example 1 except that the part was changed to the part.
[0063]
Example 3:
Except for changing 12 parts of carbon black (Colombian, RAVEN MTP, average particle size: 280 nm) to 12 parts of carbon black (Colombian, Sebacarb MTCI, average particle size: 350 nm), the same as Example 2 Thus, an evaluation tape of Example 3 was prepared.
[0064]
Example 4:
Except for changing 12 parts of carbon black (Colombian, RAVEN MTP, average particle size: 280 nm) to 12 parts of alumina (AKP-28, average particle size: 380 nm), the same as Example 2 Thus, a sample of Example 4 was prepared.
[0065]
Example 5:
12 parts of carbon black (Colombian, RAVEN MTP, average particle size: 280 nm) is changed to 12 parts of carbon black (Columbian, Sebacarb MTCI, average particle size: 350 nm), and polyethylene naphthalate film (thickness 5) 0.5 μm, MD = 6.1 GPa, MD / TD = 0.93, trade name: Teonex, manufactured by Teijin Ltd., polyethylene terephthalate film (thickness 6.0 μm, MD = 7.3 GPa, MD / TD = 1.8) A sample of Example 5 was prepared in the same manner as in Example 2 except that the product name was changed to “trade name: Tetron, manufactured by Teijin”.
[0066]
Comparative Example 1:
Except having changed 12 parts of alumina (AKP-20 average particle diameter: 600 nm, manufactured by Sumitomo Chemical Co., Ltd.) to 12 parts of carbon black (manufactured by Colombian, Sebacarb MTCI, average particle diameter: 350 nm), the same manner as in Example 1 was performed. An evaluation tape of Comparative Example 1 was prepared.
[0067]
Comparative Example 2:
Except for changing 12 parts of carbon black (Colombian, RAVEN MTP, average particle size: 280 nm) to 12 parts of carbon black (Cabot, Sterling FT, average particle size: 180 nm), the same as Example 2 Thus, an evaluation tape of Comparative Example 2 was prepared.
[0068]
Comparative Example 3:
Example 12 except that 12 parts of carbon black (manufactured by Colombian, RAVEN MTP, average particle size: 280 nm) was changed to 12 parts of alumina (manufactured by Sumitomo Chemical Co., Ltd., AKP-30, average particle size: 450 nm). Thus, an evaluation tape of Comparative Example 2 was prepared.
[0069]
Using the evaluation tapes obtained as described above, the following performance evaluation was performed.
<Primary thickness of backcoat layer>
The vertical cross section of the tape is observed with an SEM, and the distance from the interface between the nonmagnetic support and the backcoat layer to the primary surface of the backcoat layer other than the protrusions due to the coarse particle powder is determined. The measurement was performed at 10 points, and the average of the values was defined as the back coat layer primary thickness.
[0070]
<Friction coefficient>
A SUS304 cylinder with a diameter of 4 mm with a surface roughness of 0.2 S was horizontally supported and applied to the tape so that the back coat layer side of the sample was a contact surface at an angle of 90 degrees. While applying a load of 0.294 N (30 g weight) to one end, obtain the stress T (N) when the other end is horizontal and pulled at a speed of 14 mm / sec. μ was determined.
μ = (2 / π) ln (T / 0.294)
The measurement was repeated up to 20 passes, and the friction coefficients of the 1st pass and 20th pass were obtained.
[0071]
<Video S / N ratio>
The ratio between the signal and the noise during reproduction was measured with a video color noise meter, and the value was shown as a relative value when the value of Comparative Example 1 was set to 0 dB.
[0072]
<Running Durability> An evaluation tape was set on a stationary 8 mm VTR placed in a constant temperature and humidity room set at 40 ° C. and 80% RH, and run in the order of PLAY-REW. The measurement was repeated up to 100 passes, and the tape edge after 100 passes was visually observed, ranked as follows, and evaluated.
A: Deformation is not seen at all.
○: Deformation is seen, but there are more parts where there is no deformation yet.
Δ: Completed 100 passes with many deformations.
X: Deformed and stopped traveling in less than 100 passes.
[0073]
<Dropout (D.O.)>
After measuring a dropout initial value of 15 μm or more with a dropout measuring instrument, measure the dropout value after driving again with the dropout measuring instrument after 100 passes of the running durability test, and indicate the multiple of the initial value. It was. The above evaluation results are shown in Table 1.
The evaluation results of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.
[0074]
[Table 1]

[0075]
Example 6:
≪Prime paint component≫
(1)
・ 68 parts of iron oxide powder (average particle size: 0.11 × 0.02 μm)
・ 8 parts of alumina (manufactured by Sumitomo Chemical Co., Ltd., average particle size: 0.07 μm)
・ Carbon black (24 parts manufactured by Cabot)
REGAL415, average particle size: 25nm)
・ Stearic acid 2 parts
-Vinyl chloride copolymer 8.8 parts
(Contains-SO_Three Na group: 0.7 × 10^{− Four}Equivalent / g)
・ 4.4 parts of polyester polyurethane resin
(Tg: 40 ° C, contained -SO_Three Na group: 1 × 10^-FourEquivalent / g)
・ Cyclohexanone 25 parts
・ Methyl ethyl ketone 40 parts
・ Toluene 10 parts
(2)
・ Butyl stearate 1.0 part
・ Cyclohexanone 70 parts
・ Methyl ethyl ketone 50 parts
・ Toluene 20 parts
(3)
・ Polyisocyanate 1.4 parts
・ 10 parts of cyclohexanone
・ Methyl ethyl ketone 15 parts
・ Toluene 10 parts
≪Magnetic paint ingredients≫
(1) Kneading dilution process
・ 100 parts of ferromagnetic iron metal powder (magnetic powder)
(Co / Fe: 24 at%,
Y / (Fe + Co): 7.9 at%,
Al / (Fe + Co): 4.7 wt%,
σs: 120 A · m² / Kg (120 emu / g),
Hc: 175 kA / m (2190 Oe),
(pH: 9.5, average particle size: 60 nm)
・ 12.3 parts of vinyl chloride-hydroxypropyl acrylate copolymer
(Contains-SO_Three Na group: 0.7 × 10^{- 4}Equivalent / g)
・ 5.5 parts of polyester polyurethane resin
(Contains-SO_Three Na group: 1.0 × 10^-FourEquivalent / g)
・ 10 parts of α-alumina (average particle size: 0.07 μm) (alumina)
・ Carbon black (Cabot, Monarch 120 1.5 parts)
(Average particle diameter: 75 nm, DBP oil absorption: 72 cc / 100 g)
・ 2.0 parts of methyl acid phosphate (MAP)
・ 1.5 parts of palmitic acid amide (PA)
・ 1.0 parts of n-butyl stearate (SB)
・ 74 parts of tetrahydrofuran
・ 10 parts of cyclohexanone
・ 255 parts of methyl ethyl ketone
・ Toluene 85 parts
(2) Compounding process
・ 2.0 parts of polyisocyanate (PI)
・ 30 parts of cyclohexanone
[0076]
After kneading (1) with a batch kneader in the above-mentioned undercoat paint component, add (2) and stir, and then disperse with a sand mill for a residence time of 60 minutes. Add (3) to this and stir and filter After that, a paint for an undercoat layer was obtained.
[0077]
Separately from this, a predetermined amount of the magnetic coating component (1) described above is preliminarily stirred and mixed, the mixed powder is kneaded with a continuous biaxial kneader, and the residence time is set to 45 minutes with a sand mill. This was dispersed, and the magnetic paint component (2) was added thereto, followed by stirring and filtration to obtain a magnetic paint.
[0078]
On the non-magnetic support (base film) made of an aromatic polyamide film (thickness: 3.9 μm, MD = 11 GPa, MD / TD = 0.70, trade name: Miktron, Toray) The thickness after drying and calendering was applied to 0.9 μm, and the magnetic coating was further coated on the undercoat layer with a magnetic layer thickness of 0.09 μm after magnetic field orientation treatment, drying and calendering treatment. The magnetic sheet was applied by wet-on-wet so that a magnetic sheet was aligned and then dried using a dryer and far infrared rays. In the magnetic field orientation treatment, an NN counter magnet (5 kG) is installed in front of the dryer, and two NN counter magnets (5 kG) are spaced from each other at a distance of 50 cm from the front side 75 cm of the position of dry coating of the coating in the dryer. It was installed at. The coating speed was 100 m / min.
[0079]
≪Back coat layer paint component≫
・ Fine particle carbon black (80 parts made by Cabot)
REGAL415, average particle size: 25nm)
・ Carbon black (Colombian, RAVEN MTP, 10 parts)
(Average particle size: 280 nm)
・ 10 parts of iron oxide (average particle size: 0.2 μm)
・ Nitrocellulose 45 parts
・ Polyurethane resin (SO_Three (Containing Na group) 30 parts
・ 410 parts of cyclohexanone
・ Methyl ethyl ketone 690 parts
・ 260 parts of toluene
[0080]
After the coating component for the backcoat layer is dispersed in a sand mill with a residence time of 45 minutes, 15 parts of polyisocyanate is added to adjust the coating for the backcoat layer, and after filtration, on the opposite side of the magnetic layer of the magnetic sheet prepared above It was applied so that the primary thickness after drying, calendering was 0.25 μm and dried.
[0081]
The magnetic sheet thus obtained was mirror-finished with a seven-stage calendar made of a metal roll under the conditions of a temperature of 100 ° C. and a linear pressure of 196 kN / m, and the magnetic sheet was wound on a core at 70 ° C. at 72 ° C. After aging for a period of time, the magnetic layer surface was cut into ½ inch widths, and the magnetic layer surface was subjected to post-processing such as lapping tape polishing, blade polishing and surface wiping while running at 200 m / min to produce a magnetic tape. At this time, K10000 was used for the wrapping tape, a carbide blade was used for the blade, and Toraysee (trade name) manufactured by Toray was used for wiping the surface. The magnetic tape obtained as described above was assembled in a cartridge to produce a computer tape.
[0082]
Comparative Example 4:
A computer tape of Comparative Example 4 was produced in the same manner as in Example 7 except that the primary thickness of the backcoat layer was changed from 0.25 μm to 0.3 μm.
Using the computer tapes obtained as described above, the following performance evaluation was performed.
[0083]
<Primary thickness of backcoat layer>
The vertical cross section of the tape is observed with an SEM, and the distance from the interface between the nonmagnetic support and the backcoat layer to the primary surface of the backcoat layer other than the protrusions due to the coarse particle powder is determined. The measurement was performed at 10 points, and the average of the values was defined as the back coat layer primary thickness.
[0084]
<Friction coefficient>
A SUS304 cylinder with a diameter of 4 mm with a surface roughness of 0.2 S was horizontally supported and applied to the tape so that the back coat layer side of the sample was a contact surface at an angle of 90 degrees. While applying a load of 0.294 N (30 g weight) to one end, obtain the stress T (N) when the other end is horizontal and pulled at a speed of 14 mm / sec. μ was determined.
μ = (2 / π) Ln (T / 0.294)
The measurement was repeated up to 20 passes, and the friction coefficients of the 1st pass and 20th pass were obtained.
[0085]
<C / N ratio>
A drum tester was used for measuring the electromagnetic conversion characteristics of the tape. The drum tester was equipped with an electromagnetic induction head (track width 25 μm, gap 0.1 μm) and an MR head (track width 8 μm), and recording was performed with the induction head and reproduction was performed with the MR head. Both heads are installed at different locations with respect to the rotating drum, and tracking can be adjusted by operating both heads in the vertical direction. An appropriate amount of the magnetic tape was drawn out from the state of being wound in the cartridge and discarded, and further 60 cm was cut, further processed into a width of 4 mm, and wound around the outer periphery of the rotating drum.
[0086]
For output and noise, a rectangular wave with a wavelength of 0.2 μm was written by a function generator, and the output of the MR head was read into a spectrum analyzer. The carrier value of 0.2 μm was set as the medium output C. Further, when a 0.2 μm rectangular wave was written, an integrated value obtained by subtracting the output and system noise was used as the noise value N. Furthermore, the ratio of both was taken as C / N, and the relative value with the value of the comparative example 4 tape used as a reference was determined.
[0087]
<Measurement of error rate>
Using an improved S-DLT drive that can measure thin tape, the error rate before and after running was measured by performing recording and playback (recording wavelength 0.37 μm) before running and after 100 passes. . The error rate is a value in the test mode. The above evaluation results are shown in Table 2.
[0088]
[Table 2]

[0089]
From the results of Table 1 above, it can be seen that the evaluation tapes according to Examples 1 to 6 of the present invention have a low initial friction coefficient and are stable, and have good running durability and dropout. Moreover, although the video S / N of Example 5 is deteriorated, it is clear that the tape strength is lowered and it is understood that the adverse effect on the surface of the magnetic layer is suppressed.
[0090]
On the other hand, the evaluation tapes according to Comparative Examples 1 to 4 deviating from the present invention have a large change in the friction coefficient, and the running durability is remarkably bad or the dropout is remarkably bad. It can also be seen that the video S / N is significantly deteriorated due to the adverse effect on the surface of the magnetic layer.
[0091]
Further, the results in Table 2 show that the same effect as described above can be obtained even when the recording layer side of the magnetic tape has a two-layer structure of a magnetic layer and an undercoat layer.
[0092]
【The invention's effect】
From the above results, according to the present invention, the tape has excellent durability, high stability, low tape edge damage during repeated use, and excellent reliability with little increase in error rate. Is obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a magnetic tape of the present invention.
[Explanation of symbols]
1 Non-magnetic support
2 Backcoat layer
3 Coarse particle non-magnetic powder
4 Back coat layer primary surface
5 Undercoat layer (may not be present)
6 Magnetic layer
A Back coat layer primary thickness
B Full thickness of magnetic tape

Claims (2)

In a magnetic tape comprising a magnetic layer comprising a ferromagnetic powder and a binder resin provided on one surface of a nonmagnetic support, and a backcoat layer comprising a nonmagnetic powder and a binder resin provided on the other surface The back coat layer has a primary thickness of 0.1 to 0.6 μm, the total thickness of the magnetic tape is 3 to 20 μm, and the nonmagnetic powder includes two or more kinds of nonmagnetic powders having different average particle diameters, A magnetic tape, wherein the nonmagnetic powder having an average particle size has an average particle size larger than 1.0 times and less than 2.0 times the primary thickness of the backcoat layer. The magnetic tape according to claim 1, wherein an undercoat layer containing a nonmagnetic powder and a binder resin is provided between the magnetic layer and the nonmagnetic support.

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