JP2547651C

JP2547651C -

Info

Publication number: JP2547651C
Authority: JP
Original assignee: Nippon Sheet Glass Co Ltd
Current assignee: Nippon Sheet Glass Co Ltd
Publication date: 1999-06-07

Description

【発明の詳細な説明】〔産業上の利用分野〕本発明はガラス等の非磁性基板を備えた磁気ディスク用基板を用いた磁気記録媒体に関し、特に磁気特性が良好で生産性の高い磁気ディスクを作製できる磁気
ディスク用基板を用いた磁気記録媒体に関する。〔従来の技術〕一般にガラス基板は表面の平滑性に優れ、硬く、変形抵抗が大きくかつ表面欠
陥が少ない等の理由から、高密度磁気ディスク用基板として注目されている。（
例えば特開昭４９−１２２７０７、特開昭５２−１８００２）又上記ガラス基板に物理的方法および／または化学的方法で表面をエッチング
して凹凸を形成し、磁気ディスクと磁気ヘッドとの接触特性（ＣＳＳ特性、ヘッ
ドスティック性）を向上させる方法が知られている。（例えば特開昭６３−１６
００１０）又上記ガラス基板表面に、有機金属化合物の溶液の微小な液滴を噴霧する方法
を用いて凹凸を形成し、該接触特性を改善する方法も知られている。（例えば特
開昭６３−１６００１４）更に、上記ガラス基板上にＡｌからなる凹凸形成層を形成し、該接触特性を改
善する方法が知られている。（特開昭６２−２５６２１５）〔発明が解決しようとする課題〕上記表面凹凸を形成したガラス基板を用いて磁気ディスクを作成すると、該接
触特性の改善はみられるものの、磁気特性が期待される程度に実現されないとい
う問題点があった。又表面をエッチングする方法では、表面に凹凸を形成するのが煩雑であり、し
かもガラス基板の強度を低下させたり平滑性を阻害したりする問題があった。上記有機金属化合物を用いる方法においては、エッチングを行なわないため、
基板の強度の低下や平滑性の悪化が生じない利点を有するものの、磁気ディスク
の磁気特性を低下させるガスが有機金属化合物から発生し易いために該基板上に
作製した磁性膜に性能低下部分が生じやすく、磁気特性の低いものしか得られな
いという問題点があった。上記Ａｌによる基板表面の凹凸形成は、高温状態にある基板表面で被着金属（
本文において、「金属」とは、金属単体と合金の両方を含んでいる）であるＡｌ
の凝集エネルギーが大きいために生じるものである。そこで、基板と被着金属の付着力に注目すると凹凸を形成しうる被着金属は基板−被着金属間の相互作用に
比べて、被着金属原子間の凝集エネルギーが大きいために、基板との付着力は一
般的に強くない。従って、単純にＡｌをガラス基板上に形成しただけでは、ＣＳ
Ｓ試験の際に生じる強い摩擦力によって、Ａｌ／ガラス界面での膜の剥離が生じ
る。このことは、一般に問題とされるＣＳＳ試験時のヘッドとディスクの摩擦に
よる摩擦係数を論ずる以前の問題であって、磁気ディスクの信頼性という面で、
大きな問題点であった。本発明の目的は、上記した問題点の解消にあり、磁気特性が良好で生産性の高
い磁気ディスクとしての磁気記録媒体を提供することである。〔課題を解決するための手段〕本発明は、その表面上に凹凸を形成するための凹凸形成用物質が被着された非
磁性支持体の前記表面と保護層との間に磁性層を介在させた磁気記録媒体におい
て、前記凹凸形成用物質は、融点が１，１００℃以下の金属単体または合金であ
り、前記凹凸形成用物質により構成された多数の島状構造が、前記非磁性支持体
の前記表面上に、この表面の面方向において相互の間が不連続でありかつ前記不
連続な部分において前記非磁性支持体側が露出するように形成され、前記多数の
島状構造のピッチは０．１〜０．５μｍであり、前記多数の島状構造の高さは１
０〜５０ｎｍであり、前記非磁性支持体と前記磁性層との間にこの磁性層のため
の下地層が設けられ、さらに、前記非磁性支持体とこの下地層との間に酸素トラ
ップ層が設けられたことを特徴としている。本発明に係る非磁性支持体としては、例えば、ガラス板、セラミックス板、ア
ルミニウム板、チタニウム金属板が挙げられる。これらの中でも、表面の平坦性
の面からガラス板の使用が好ましく、またガラス板の中でもとりわけフロート法
で製造されたソーダライム組成のガラス板の使用は最も安価に入手できるので特
に好ましい。本発明に係る凹凸形成用物質としては、融点が１１００℃以下と比較的低融点
の金属単体又は合金であればよく、例えば、Ａｇ、Ａｌ、Ｃｕ、Ａｕ、Ｚｎ、Ｐ
ｂからなる群より選ばれた１種の金属単体又は２種以上の金属単体からなる合金
が挙げられる。これらの中でも、被着したときに金属原子間の凝集エネルギーが大きな島状構造を形成しやすいためＡｇ、Ａｌ、Ｃｕ、およびＡｕからなる群よ
り選ばれた１種又は２種以上の合金の使用が好ましい。本発明に係る表面に多数の島状構造を有する凹凸を形成する方法としては、例
えばスパッタリング式真空蒸着等の物理的蒸着法を適用すればよい。凹凸形成用物質は、例えば真空蒸着法、真空スパッタリング法等の物理的蒸着
法で非磁性支持体の温度を比較的高くして被着金属が非磁性支持体上で凝集しう
る様にしながら蒸着させる初期段階で不規則的な凹凸を有する島状の形状に被覆
できる。非磁性支持体の温度及び蒸着量を調整することにより、該凹凸形状は調整され
ることができる。通常、非磁性支持体は１００〜４００℃の温度に加熱されて島
状構造を有する凹凸膜は形成される。この非磁性支持体の温度は高くすると凹凸
の深さが大きくなり、蒸着量を増加させると凹凸のピッチが減少する。非磁性支持体の表面上の多数の島状構造が形成された領域（すなわち、多数の
島状構造とそれらの間の網目状の不連続な部分との両方を含む領域）を凹凸形成
用物質により被覆する被覆率は、その値が特に制限されるものではないが、好ま
しくは、８５％以上では、非磁性支持体と磁性膜との密着性が低下し、一方１０
％以下では所望の凹凸が得られにくくなるので１０〜８５％である。また、島状
構造を有する物質が表面に設けられた非磁性支持体の表面凹凸の粗さは平均粗さ
が、通常、１〜１５nmであり、好ましくはビットシフトを小さく抑える点から２
〜８nmである。更に好ましくは２〜６ｎｍである。また島状構造における島の深
さ（すなわち、島の高さまたは凹凸の深さ）は、最大粗さが１５０ｎｍを越えな
いようにし、ヘッド走行をスムーズにするために、また最上層の保護膜に好まし
い凹凸を与えるために、１０〜５０ｎｍである必要がある。更に、凹凸のピッチ
（すなわち、島のピッチ）は、好ましい凹凸を最上層の表面に与えるために、ま
た、ヘッドの走行をスムーズにするために、０．１〜０．５μｍである必要があ
る。本発明の磁気記録媒体は、非磁性支持体上に比較的低融点の金属からなる物質
により凹凸を設けたものであるが、通常は支持体上に設ける磁性膜の下には、磁
性膜の結晶性を向上する下地膜を設けている。該下地膜は、磁性膜としてＣｏＮｉ系の材料を用いる場合には、Ｃｒ又はＣｒ
を主成分とする合金が通常用いられている。該下地膜は磁気特性を飛躍的に向上させるが、該下地膜の下に酸素トラップ層
を設けると磁気特性はさらに向上する。該酸素トラップ層としては、Ｔｉ、Ｚｒ、Ｖ、Ｎｂ、Ｔａ、Ｙよりなる群から
選ばれた１種の金属単体又は２種以上の金属単体からなる合金が例示できる。こ
れらの中でも、Ｔｉが非磁性支持体との密着力が良好で、かつ酸素を良くトラッ
プするので好ましい。該酸素トラップ層は非磁性支持体からの酸素の上昇を防止し、下地膜の結晶性
を向上させ、それによって磁気特性も向上する。該酸素トラップ層は島状構造を有する凹凸形成物質の上下いずれであってもよ
い。〔実施例〕実施例１良く洗浄されたソーダライムガラス基板（円盤状に加工され化学強化された物
）を真空中で２００℃に加熱し、Ａｒガスを用いたＤＣマグネトロンスパッタ法
によりAgを成膜した。成膜条件は通常１００〜２００nm厚のAg膜を成膜する条件
から換算して約２５ｎｍ厚のAg膜が成膜される条件で行なった。作製されたAg膜を電子顕微鏡を用いて観察すると第１図に示す様な高さ約２５
ｎｍ、横方向の巾約１００ｎｍ程度の大きさの山脈状凸部が不規則に分離した島
状構造となっていた。またこのときのAg膜の被覆率は８４％あった。上記方法で作製された磁気ディスク用基板１に、同じくArガスを用いたＤＣマ
グネトロンスパッタ法によりＴｉ膜３を約４０ｎｍ厚被覆し、基板を２００℃ま
で加熱した後Ｃｒ膜４、ＣＯ_0.70Ｎｉ_0.30膜５及びカーボンからなる保護膜６を
順次それぞれ１５０ｎｍ厚、６０ｎｍ厚、３０ｎｍ厚の厚さで被覆した。この時Ti膜３の被覆からカーボンからなる保護膜６の被覆までは、インライン
型のスパッタリング装置により、真空状態を破ることなく連続的に行なった。こうして作製された磁気ディスクの保磁力を測定した所１５００〔Ｏｅ〕程度
の値であった。又該磁気ディスク上に潤滑剤を塗布した後ＣＳＳ試験（コンタクト・スタート・ストップ試験）を実施した所３万回ＣＳＳを行なっても摩擦係数
は０．２以下であった。上記実施例においては、Ｃｒ下地膜４の下に酸素トラップ金属層としてＴｉ膜
３を設けているが、該Ｔｉ膜３は基板側からのガスの発生を防止し、Ｃｒ膜の結
晶性を向上させ磁気特性を良化する効果を持つ。事実Ｔｉ膜を設けなかった以外
は実施例と同様の操作で作製した磁気ディスクの保磁力は１３００〔Ｏｅ〕と低
く、Ｘ線回折法により求めたＣｒ膜の１１０面の回折強度の半値幅はＴｉ膜３上
に設けたＣｒ膜のそれよりも広がっていた。上記実施例においては、Ａｇ膜の被覆状態の確認を行なうためＡｇ膜の被覆を
磁性膜の被覆工程と切りはなして実施しているが、該Ag膜の被覆は磁性膜の被覆
の前段として実施することができる。又上記実施例においては、比較的低融点の金属の蒸着方法としてＤＣマグネト
ロンスパッタ法を用いているが、該蒸着法はＤＣマグネトロンスパッタに限らず
、ＲＦスパッタ法、真空蒸着法等であってもかまわない。実施例２洗浄後のソーダライムガラス基板（円盤状に加工され化学強化された物）を真
空中で２６０℃に加熱し、Ａｒガスを用いたＤＣマグネトロンスパッタ法により
Ａｌを被覆した。このＡｌの表面粗さを触針計（小坂研究所製、model ＡＹ−３
１）で測定したところ、平均粗さＲａは６ｎｍで、最大粗さは６０ｎｍであった
。凹凸形状を第３図（ａ）に示す。このときのＡｌは島状構造になっているため、基板表面の一部は露出している
。このときのＡｌ被覆率は約５７％であった。ここでいうＡｌ被覆率とは、電子
顕微鏡で撮影した写真に対角線を引き、各対角線と交わるＡｌ粒子の長さをすべ
て積算した値を分子とし、各対角線の長さを分母として算出した平均値である。上記方法で作製された磁気ディスク用基板１に同じくＡｒガスを用いたＤＣマ
グネトロンスパッタ法によりＴｉ膜３を約４０ｎｍ厚被覆し、基板を２００℃ま
で加熱した後Ｃｒ膜４、Ｃｏ_0.70Ｎｉ_0.30膜５およびＣ膜６を順次それぞれ１５
０ｎｍ厚、６０ｎｍ厚、３０ｎｍ厚の厚さで被覆した。この時Ti膜３の被覆からカーボンからなる保護膜６の被覆までは、インライン型のスパッタリング装置により、真空状態を破ることなく連続的に行なった。また、Ａｌ被覆率が７０％、８０％、９３％と異なる磁気ディスク用基板を作
製した。それぞれの基板の島状構造を第３図（ｂ）〜（ｄ）に示す。また平均粗
さＲａは、それぞれ、５．４ｎｍ、５．２ｎｍ、４．９ｎｍであった。これらの基板上にＴｉ膜、Ｃｒ下地膜、ＣｏＮｉＣｒ合金膜、カーボン保護膜
を同一成膜条件にて被覆した。こうして作製された、Ａｌ被覆率の異なる磁気ディスク上にパーフロロアルキ
ルポリエーテル（商品名：Fomblin AM2001、潤滑剤）を塗布した後、ＣＳＳ試験
を実施した。その結果を実施例１で得たサンプルと併せて第４図に示す。この図において、Ａｌ被覆率が９３％、すなわち連続膜に近い膜構造をもつデ
ィスクにおいては、２０００回のＣＳＳを行なった時点で膜はがれを生じ、摩擦
係数μが測定不可能となった。またＡｌ被覆率が８４％以下のものについては、
１６０００回のＣＳＳを行なっても摩擦係数が０．５以下と良好であった。さ
らにＡｌの被覆率が１０％以下になるとＡｌ粒子がつくる凹凸の平均粗さが２ｎ
ｍ以下になるために、ヘッドとディスクの吸着現象が発生した。実施例３実施例２と同様にして、ガラス基板上にＡｌ膜を形成した。ここではＡｌ膜が
形成する凹凸を変えるために、基板温度を可変させて、１ｎｍから７ｎｍまで平
均粗さ（Ｒａ）を有する基板を９枚作製した。この上に実施例２と同一の被覆条件でＴｉ膜、Ｃｒ膜、ＣｏＮｉＣｒ合金膜お
よびカーボンからなる保護膜を形成した。各ディスクの保磁力は１４７０±５０
〔Ｏｅ〕の範囲内であった。これらのディスクにパーフルオロアルキルエーテルを塗布した後、ディスク評
価機（Guzik RWA-201B）を用い、薄膜ヘッド（３３７０型、テーパフラットスラ
イダ）によりビットシフト測定を行なった。ビットシフト量は、１６進法表示の
ＡＢＣＤ、およびＦＦＦＦパターンの書き込みを行なって測定した。第５図は、
各ディスクの平均粗さＲａとビットシフト量の関係を示したものである。この図
から、ディスクの表面粗さが平均粗さＲａ８ｎｍを越えるとビットシフト量が急
激に増大する。ビットシフト量が増大すると記録した信号の読み取りエラーが生じることになるため、磁気ディスクの品質上問題である。よってヘッド飛行高さが７５ｎｍ付近の場合、ディスクの表面凹凸は、平均粗
さRa２〜５ｎｍがより好ましい。比較例Ａｌの被覆をおこなうときの被覆スピードを小さくしてＡｌを被覆し、ガラス
基板上に平均粗さが５．３ｎｍで、厚みが７０ｎｍの連続膜からなる凹凸形成層
とした以外は実施例２と同様にして磁気ディスクを製作した。この磁気ディスク
の凹凸形成物質は被覆率が１００％であり、ＣＳＳ試験をおこなったところ、１
０００回転でＡｌとガラス支持体との界面で剥離が生じた。〔発明の効果〕本発明は、物理的方法および／または化学的方法で非磁性支持体の表面をエッ
チングする必要がなくて、成膜技術だけで非磁性支持体の表面上に凹凸を形成す
ることができるから、非磁性支持体の表面上に凹凸を形成する操作が簡単で生産
性が高く、また、歩留りを飛躍的に改善することができ、しかも、非磁性支持体
の強度を低下させたりその表面の平滑性を阻害したりすることもない。また、凹凸形成用物質により構成された多数の島状構造を、非磁性支持体の表
面上に、この表面の面方向において相互の間が不連続でありかつ前記不連続な部
分において非磁性支持体側が露出するように形成し、前記多数の島状構造のピッ
チを０．１〜０．５μｍとし、前記多数の島状構造の高さを１０〜５０ｎｍとし
たから、非磁性支持体側と、凹凸形成用物質のすぐ上側に形成される酸素トラッ
プ層、磁性層用の下地層などの上側層とをこれら多数の島状構造の不連続な部分
においてきわめて効果的に網目状に付着させることができ、このために、この上
側層の剥離や凹凸形成用物質の非磁性支持体側からの剥離をきわめて効果的に防
止することができる。また、多数の島状構造を構成している凹凸形成用物質は、有機金属化合物では
なくて、融点が１，１００℃以下の金属単体または合金であり、凹凸形成用物質
により非磁性支持体の表面上に形成された多数の島状構造のピッチを０．１〜０
．５μｍとし、前記多数の島状構造の高さを１０〜５０ｎｍとしたから、磁気デ
ィスクの磁気特性を低下させるガスが凹凸形成用物質から発生せず、このために
、磁気特性が良好な磁気ディスクを提供することができ、また、凹凸形成用物質の
金属原子間の凝集エネルギーが大きいために非磁性支持体の表面上に凝集し易く
て所望のピッチおよび所望の高さを有する好ましい多数の島状構造を簡単に形成
することができ、しかも、磁気記録媒体の表面を好ましい表面粗さにするのが容
易であるために、凹凸形成用物質の非磁性支持体からの剥離をきわめて効果的に
防止し得ることとあいまって、磁気記録媒体の表面におけるヘッド走行をスムー
ズに行うことができ、したがって、ビットシフト量を小さく抑えることができて
、磁気記録媒体に記録した信号の読取エラーが生じにくい。さらに、非磁性支持体と磁性層との間にこの磁性層のための下地層が設けられ
、また、非磁性支持体とこの下地層との間に酸素トラップ層が設けられているか
ら、非磁性支持体から発生する酸素を酸素トラップ層によりきわめて有効的にト
ラップすることができ、このために、下地層の結晶性を良好にすることができ、
したがって、この結晶性の良好な下地層により磁性層の結晶性をきわめて良好に
することができる。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium using a magnetic disk substrate provided with a nonmagnetic substrate such as glass, and more particularly to a magnetic disk having good magnetic properties and high productivity. The present invention relates to a magnetic recording medium using a magnetic disk substrate on which a magnetic disk can be manufactured. [Prior Art] In general, a glass substrate has been attracting attention as a substrate for a high-density magnetic disk because of its excellent surface smoothness, hardness, large deformation resistance, and few surface defects. (
(For example, JP-A-49-122707 and JP-A-52-18002) Also, the surface of the above glass substrate is etched by a physical method and / or a chemical method to form irregularities, and the contact characteristics between a magnetic disk and a magnetic head ( Methods for improving the CSS characteristics and the head stick property) are known. (For example, JP-A-63-16
[0010] A method is also known in which irregularities are formed on the surface of the glass substrate by spraying fine droplets of a solution of an organometallic compound to improve the contact characteristics. Further, there is known a method of forming a concavo-convex formation layer made of Al on the glass substrate to improve the contact characteristics. (Problem to be Solved by the Invention) When a magnetic disk is produced using a glass substrate having the above-mentioned surface irregularities, the contact characteristics are improved, but the magnetic characteristics are expected. There was a problem that it was not realized to an extent. In addition, in the method of etching the surface, it is complicated to form irregularities on the surface, and there is a problem that the strength of the glass substrate is reduced or the smoothness is impaired. In the method using the organometallic compound, since etching is not performed,
Although there is an advantage that the strength of the substrate is not reduced and the smoothness is not deteriorated, the performance of the magnetic film formed on the substrate is reduced due to the fact that a gas that reduces the magnetic properties of the magnetic disk is easily generated from the organometallic compound. This is problematic in that only those having low magnetic properties can be obtained. The formation of the irregularities on the substrate surface by Al is performed by using a metal (
In the present text, “metal” includes both simple metals and alloys).
This is caused by the large cohesive energy of Therefore, focusing on the adhesive force between the substrate and the adhered metal, the adhered metal that can form irregularities has a larger cohesive energy between the adhered metal atoms than the interaction between the substrate and the adhered metal. Is generally not strong. Therefore, simply forming Al on a glass substrate will result in CS
The strong frictional forces that occur during the S test cause the film to peel at the Al / glass interface. This is a problem before discussing the friction coefficient due to the friction between the head and the disk during the CSS test, which is generally considered a problem, and in terms of the reliability of the magnetic disk,
It was a big problem. An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a magnetic recording medium as a magnetic disk having good magnetic properties and high productivity. [Means for Solving the Problems] The present invention has a magnetic layer interposed between the protective layer and the surface of a non-magnetic support on which a substance for forming concavities and convexities for forming concavities and convexities on the surface is provided. In the magnetic recording medium, the material for forming unevenness is a simple metal or an alloy having a melting point of 1,100 ° C. or less, and a large number of island-like structures constituted by the material for forming unevenness are formed on the nonmagnetic support.
On said surface is discontinuous between each other in the plane direction of said surface and said discontinuity
The nonmagnetic support side is formed to be exposed in a continuous portion,
The pitch of the island structures is 0.1 to 0.5 μm, and the height of the plurality of island structures is 1
0 to 50 nm, an underlayer for the magnetic layer is provided between the nonmagnetic support and the magnetic layer, and an oxygen trap layer is further provided between the nonmagnetic support and the underlayer. It is characterized by being provided. Examples of the non-magnetic support according to the present invention include a glass plate, a ceramic plate, an aluminum plate, and a titanium metal plate. Among these, the use of a glass plate is preferred in terms of surface flatness, and the use of a glass plate having a soda lime composition produced by a float method is particularly preferred among the glass plates because it can be obtained at the lowest cost. The substance for forming concavities and convexities according to the present invention may be a metal simple substance or an alloy having a relatively low melting point of 1100 ° C. or less, for example, Ag, Al, Cu, Au, Zn, P
and a metal alloy selected from the group consisting of one or more metal elements selected from the group consisting of b. Among these, the use of one or more alloys selected from the group consisting of Ag, Al, Cu, and Au, because they tend to form an island-like structure in which the cohesion energy between metal atoms is large when applied. Is preferred. As a method for forming irregularities having a large number of island structures on the surface according to the present invention, for example, a physical vapor deposition method such as a sputtering type vacuum vapor deposition method may be applied. The material for forming concavities and convexities is vapor-deposited by a physical vapor deposition method such as a vacuum vapor deposition method or a vacuum sputtering method so that the temperature of the non-magnetic support is relatively high so that the adhered metal can aggregate on the non-magnetic support. In the initial stage of the formation, it can be coated in an island shape having irregular irregularities. The irregular shape can be adjusted by adjusting the temperature and the amount of vapor deposition of the nonmagnetic support. Usually, the nonmagnetic support is heated to a temperature of 100 to 400 ° C. to form an uneven film having an island structure. As the temperature of the nonmagnetic support increases, the depth of the irregularities increases, and as the deposition amount increases, the pitch of the irregularities decreases. The region on the surface of the non-magnetic support where a large number of islands are formed (that is, a region including both the large number of islands and the discontinuous portion between the islands) is formed of a material for forming unevenness. Although the value of the coating ratio of the non-magnetic support is not particularly limited, it is preferably 85% or more, whereby the adhesion between the non-magnetic support and the magnetic film is reduced.
% Or less, it is difficult to obtain desired unevenness, so the content is 10 to 85%. In addition, the roughness of the surface irregularities of the nonmagnetic support having a substance having an island structure on the surface is usually 1 to 15 nm, preferably 2 to reduce bit shift.
８8 nm. More preferably, it is 2 to 6 nm. Island depth in island-like structures
The height (ie, the height of the island or the depth of the irregularities) is such that the maximum roughness does not exceed 150 nm.
For better head running and for the top protective layer.
It is necessary that the thickness be 10 to 50 nm in order to provide a rough surface. Furthermore, the pitch of unevenness
(I.e., island pitch) to provide the desired topography with the topography.
Further, in order to make the head run smoothly, it is necessary that the thickness is 0.1 to 0.5 μm.
You. The magnetic recording medium of the present invention is provided with irregularities on a non-magnetic support by a substance made of a metal having a relatively low melting point. A base film for improving crystallinity is provided. When a CoNi-based material is used as the magnetic film, the underlayer is made of Cr or Cr.
An alloy mainly composed of is generally used. The underlayer dramatically improves the magnetic properties, but if an oxygen trap layer is provided under the underlayer, the magnetic properties are further improved. Examples of the oxygen trap layer include a single metal element selected from the group consisting of Ti, Zr, V, Nb, Ta, and Y, or an alloy including two or more metal elements. Among these, Ti is preferable because it has good adhesion to the nonmagnetic support and traps oxygen well. The oxygen trap layer prevents oxygen from rising from the nonmagnetic support, improves the crystallinity of the underlayer, and thereby improves the magnetic properties. The oxygen trap layer may be above or below the concavo-convex forming material having an island structure. EXAMPLES Example 1 A well-washed soda-lime glass substrate (a disk-shaped and chemically strengthened material) was heated to 200 ° C. in a vacuum, and Ag was formed by DC magnetron sputtering using Ar gas. Filmed. The film formation was performed under the condition that an Ag film having a thickness of about 25 nm was formed, as calculated from the conditions for forming an Ag film having a thickness of 100 to 200 nm. Observation of the prepared Ag film using an electron microscope showed a height of about 25 as shown in FIG.
nm, and a mountain-shaped convex portion having a width of about 100 nm in the lateral direction had an island-like structure in which the convex portions were irregularly separated. At this time, the coverage of the Ag film was 84%. The magnetic disk substrate 1 manufactured by the above method is coated with a Ti film 3 to a thickness of about 40 nm by DC magnetron sputtering using the same Ar gas, and after heating the substrate to 200 ° C., the Cr film 4 and CO _0.70 Ni _0.30 The film 5 and the protective film 6 made of carbon were sequentially coated with a thickness of 150 nm, 60 nm, and 30 nm, respectively. At this time, the process from the coating of the Ti film 3 to the coating of the protective film 6 made of carbon was continuously performed without breaking the vacuum state by an in-line type sputtering apparatus. When the coercive force of the magnetic disk thus manufactured was measured, it was about 1500 [Oe]. Further, after applying a lubricant to the magnetic disk, a CSS test (contact start / stop test) was conducted. When the CSS was performed 30,000 times, the friction coefficient was 0.2 or less. In the above embodiment, the Ti film 3 is provided as an oxygen trapping metal layer under the Cr underlayer 4, but the Ti film 3 prevents generation of gas from the substrate side and improves the crystallinity of the Cr film. This has the effect of improving magnetic properties. In fact, the coercive force of the magnetic disk manufactured by the same operation as the example except that the Ti film was not provided was as low as 1300 [Oe], and the half value width of the diffraction intensity of the 110 surface of the Cr film determined by the X-ray diffraction method was It was wider than that of the Cr film provided on the Ti film 3. In the above embodiment, in order to confirm the coating state of the Ag film, the coating of the Ag film is performed separately from the step of coating the magnetic film. However, the coating of the Ag film is performed before the coating of the magnetic film. can do. In the above embodiment, the DC magnetron sputtering method is used as a method for depositing a metal having a relatively low melting point. However, the vapor deposition method is not limited to the DC magnetron sputtering method, but may be an RF sputtering method, a vacuum deposition method, or the like. I don't care. Example 2 A washed soda-lime glass substrate (a disk-shaped and chemically strengthened substrate) was heated to 260 ° C. in a vacuum and coated with Al by DC magnetron sputtering using Ar gas. The surface roughness of this Al was measured using a stylus meter (model AY-3, manufactured by Kosaka Laboratory).
As a result of the measurement in 1), the average roughness Ra was 6 nm, and the maximum roughness was 60 nm. The uneven shape is shown in FIG. At this time, since Al has an island structure, a part of the substrate surface is exposed. The Al coverage at this time was about 57%. Here, the Al coverage is an average value obtained by drawing a diagonal line on a photograph taken by an electron microscope, integrating all lengths of Al particles intersecting each diagonal line as a numerator, and calculating the length of each diagonal line as a denominator. It is. The magnetic disk substrate 1 produced by the above method is coated with a Ti film 3 to a thickness of about 40 nm by DC magnetron sputtering using the same Ar gas, and after heating the substrate to 200 ° C., the Cr film 4 and the Co _0.70 Ni _0.30 film are formed. 5 and C film 6 are successively 15
It was coated with a thickness of 0 nm, 60 nm, and 30 nm. At this time, the process from the coating of the Ti film 3 to the coating of the protective film 6 made of carbon was continuously performed without breaking the vacuum state by an in-line type sputtering apparatus. In addition, magnetic disk substrates having Al coverages different from 70%, 80%, and 93% were produced. FIGS. 3 (b) to 3 (d) show the island structure of each substrate. The average roughness Ra was 5.4 nm, 5.2 nm, and 4.9 nm, respectively. These substrates were coated with a Ti film, a Cr underlayer, a CoNiCr alloy film, and a carbon protective film under the same film forming conditions. After perfluoroalkyl polyether (trade name: Fomblin AM2001, lubricant) was applied to the magnetic disks thus produced having different Al coverages, a CSS test was performed. The results are shown in FIG. 4 together with the sample obtained in Example 1. In this figure, in a disk having an Al coverage of 93%, that is, a film having a film structure close to a continuous film, the film peeled off after the CSS was performed 2,000 times, and the friction coefficient μ could not be measured. For those having an Al coverage of 84% or less,
The coefficient of friction was as good as 0.5 or less even after performing 16000 times of CSS. Further, when the Al coverage is 10% or less, the average roughness of the irregularities formed by the Al particles is 2n.
m, the head and the disk attracted. Example 3 In the same manner as in Example 2, an Al film was formed on a glass substrate. Here, in order to change the irregularities formed by the Al film, the substrate temperature was varied, and nine substrates having an average roughness (Ra) from 1 nm to 7 nm were produced. A protective film made of a Ti film, a Cr film, a CoNiCr alloy film, and carbon was formed thereon under the same coating conditions as in Example 2. The coercive force of each disk is 1470 ± 50
[Oe]. After applying perfluoroalkyl ether to these disks, bit shift measurement was performed with a thin film head (3370 type, taper flat slider) using a disk evaluation machine (Guzik RWA-201B). The bit shift amount was measured by writing a hexadecimal ABCD and FFFF pattern. FIG.
The relationship between the average roughness Ra of each disk and the amount of bit shift is shown. From this figure, it can be seen that when the surface roughness of the disk exceeds the average roughness Ra of 8 nm, the bit shift amount sharply increases. If the bit shift amount increases, a read error of the recorded signal occurs, which is a problem in the quality of the magnetic disk. Therefore, when the flying height of the head is around 75 nm, the surface roughness of the disk preferably has an average roughness Ra of 2 to 5 nm. Comparative Example An example except that the coating speed at the time of coating Al was reduced and Al was coated to form a concavo-convex formation layer consisting of a continuous film having a mean roughness of 5.3 nm and a thickness of 70 nm on a glass substrate. In the same manner as in Example 2, a magnetic disk was manufactured. The unevenness forming material of this magnetic disk has a coverage of 100%.
At 000 revolutions, peeling occurred at the interface between Al and the glass support. [Effects of the Invention] The present invention does not require etching the surface of the nonmagnetic support by a physical method and / or a chemical method, and forms irregularities on the surface of the nonmagnetic support only by a film forming technique. Therefore, the operation of forming irregularities on the surface of the non-magnetic support is easy and the productivity is high, and the yield can be dramatically improved, and the strength of the non-magnetic support is reduced. Nor does it impair the smoothness of its surface. In addition, a large number of island-like structures composed of the concavo-convex forming material are displayed on the surface of the non-magnetic support.
On the surface, the surface is discontinuous in the plane direction of the surface and the discontinuity
In such a manner that the non-magnetic support side is exposed in the
And the height of the plurality of island-like structures is set to 10 to 50 nm.
Therefore, the oxygen trap formed on the non-magnetic support side and immediately above the concavo-convex forming substance
And the upper layer such as the underlayer for the magnetic layer,
Can be attached very effectively in a mesh,
Extremely effective prevention of exfoliation of the side layer and exfoliation of the concavo-convex material from the non-magnetic support side
Can be stopped. In addition, the substance for forming concavities and convexities constituting a large number of island-like structures is an organometallic compound.
And a simple substance or alloy with a melting point of 1,100 ° C or less
The pitch of a large number of island-shaped structures formed on the surface of the non-magnetic support is 0.1 to 0.
. 5 μm, and the height of the plurality of island-like structures was 10 to 50 nm.
Gases that degrade the magnetic properties of the disk are not generated from the concavo-convex forming material.
, Can provide a magnetic disk having good magnetic properties,
Large aggregation energy between metal atoms makes it easy to aggregate on the surface of non-magnetic support
Simple formation of multiple preferred islands with desired pitch and desired height
And it is desirable to make the surface of the magnetic recording medium a preferable surface roughness.
It is easy to remove the unevenness forming material from the non-magnetic support very effectively.
Combined with the ability to prevent head movement over the surface of the magnetic recording medium.
And the bit shift amount can be kept small.
In addition, errors in reading signals recorded on a magnetic recording medium are unlikely to occur. Further, an underlayer for the magnetic layer is provided between the nonmagnetic support and the magnetic layer, and an oxygen trap layer is provided between the nonmagnetic support and the underlayer. Oxygen generated from the magnetic support can be trapped very effectively by the oxygen trapping layer , so that the crystallinity of the underlayer can be improved,
Therefore, the crystallinity of the magnetic layer can be made extremely good by the underlayer having good crystallinity.

【図面の簡単な説明】第１図は実施例１で作製した金属凹凸膜の電子顕微鏡写真から表面の凹凸状態
を模式的に示す図、第２図は実施例で作製した磁気ディスクの概略を示す断面図
、第３図は実施例２で作製した金属凹凸膜の電子顕微鏡写真から表面の凹凸状態
を模式的に示す図、第４図は実施例２で作製したディスクのＣＳＳ試験結果を示
す図、第５図は実施例３で作製したディスクにおけるディスク表面粗さとビット
シフト量の関係を示す図である。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view schematically showing an uneven state of a surface from an electron micrograph of a metal uneven film produced in Example 1, and FIG. 2 is a schematic view of a magnetic disk produced in Example. FIG. 3 is a diagram schematically showing the surface unevenness state from an electron micrograph of the metal uneven film produced in Example 2, and FIG. 4 is a CSS test result of the disk produced in Example 2. FIG. 5 is a diagram showing the relationship between the disk surface roughness and the bit shift amount in the disk manufactured in Example 3.

Claims

Claims: 1. A magnetic recording medium having a magnetic layer interposed between a protective layer and a surface of a non-magnetic support on which a substance for forming irregularities for forming irregularities is formed on the surface thereof. The material for forming unevenness is a metal simple substance or an alloy having a melting point of 1,100 ° C. or less, and a large number of island-like structures constituted by the material for forming unevenness are formed on the nonmagnetic support.
On the surface, there is a discontinuity between the surfaces in the plane direction of the surface and the discontinuity
The nonmagnetic support side is formed to be exposed in a continuous portion, the pitch of the plurality of islands is 0.1 to 0.5 μm, and the height of the plurality of islands is 10 to 50 nm. There, the underlying layer for the magnetic layer between the nonmagnetic support and the magnetic layer is provided, furthermore, that the oxygen trap layer between the nonmagnetic support and this undercoat layer is provided A magnetic recording medium characterized by the above-mentioned. 2. The material for forming concavities and convexities covers a region on the surface of the non-magnetic support, on which the plurality of island-shaped structures are formed, at a coverage of 10 to 85%. 2. The magnetic recording medium according to 1. 3. The magnetic recording medium according to claim 1, wherein an average roughness of the concavo-convex forming material deposited on the surface of the nonmagnetic support is 2 to 8 nm. 4. The material for forming concavities and convexities is a single metal selected from the group consisting of Ag, Al, Cu and Au, or an alloy of two or more single metals. The magnetic recording medium according to claim 1. 5. The magnetic recording medium according to claim 1, wherein the non-magnetic support is a float glass plate having a soda lime composition.