JPH0264913A - Magnetic recording medium and its production - Google Patents
Magnetic recording medium and its productionInfo
- Publication number
- JPH0264913A JPH0264913A JP21489788A JP21489788A JPH0264913A JP H0264913 A JPH0264913 A JP H0264913A JP 21489788 A JP21489788 A JP 21489788A JP 21489788 A JP21489788 A JP 21489788A JP H0264913 A JPH0264913 A JP H0264913A
- Authority
- JP
- Japan
- Prior art keywords
- magnetic recording
- magnetic
- layer
- recording medium
- chromium layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000004519 manufacturing process Methods 0.000 title claims description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 29
- 239000011651 chromium Substances 0.000 claims abstract description 29
- 238000004544 sputter deposition Methods 0.000 claims abstract description 19
- 239000007789 gas Substances 0.000 claims abstract description 18
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000000758 substrate Substances 0.000 claims abstract description 13
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000001301 oxygen Substances 0.000 claims abstract description 11
- 229910052786 argon Inorganic materials 0.000 claims abstract description 8
- 239000010410 layer Substances 0.000 claims description 35
- 238000000034 method Methods 0.000 claims description 8
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 7
- 229910001882 dioxygen Inorganic materials 0.000 claims description 7
- 239000011241 protective layer Substances 0.000 claims description 7
- 230000015572 biosynthetic process Effects 0.000 abstract description 13
- 239000008246 gaseous mixture Substances 0.000 abstract 1
- 239000010408 film Substances 0.000 description 14
- 229910000838 Al alloy Inorganic materials 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000000314 lubricant Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910000531 Co alloy Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- -1 etc. Substances 0.000 description 2
- 239000006247 magnetic powder Substances 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910020706 Co—Re Inorganic materials 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- ZGDWHDKHJKZZIQ-UHFFFAOYSA-N cobalt nickel Chemical compound [Co].[Ni].[Ni].[Ni] ZGDWHDKHJKZZIQ-UHFFFAOYSA-N 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Magnetic Record Carriers (AREA)
- Manufacturing Of Magnetic Record Carriers (AREA)
- Physical Vapour Deposition (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は、コンピュータ等の外部記憶装置（磁気ディス
ク装置）において、磁気記憶体として用いられる磁気デ
ィスク等に使用される高密度記録用の磁気記録媒体及び
その製造法に関するもので［従来の技術］
従来、コンピュータ等の記憶媒体としては磁性粉を塗Ｉ
’ｉｉ したテープ、円板状の磁気ディスクなどが用い
られている。このうち、ランダムアクセスが可能なこと
から円板状の磁気ディスクが広く用いられており、基板
にアルミ合金等を用いた磁気ディスク、いわゆるハード
ディスクが使用されるようになってきている。この磁気
ディスクは、−般に、厚さ２■程度の堅い基板上に、厚
さ１μｍ程度の磁気記録層を形成することにより構成さ
れる。磁気記録層としては、γ−Ｆ８２０３などの磁性
粉をバインダと混合し、これをディスク基板上にスピン
コード等の手法で塗布したものが用いられてきたが、こ
の磁気記録層は飽和磁化の大きさに限界が有り、高密度
記録磁性媒体としてはほぼ限界に達してきているため、
最近では、より大きい飽和磁化を有するＣｏ５Ｃｏ−Ｎ
１ ｓ Ｃｏ−ＰＬ ％ Ｃｏ−Ｒｅ 。Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a high-density recording magnetic field used in a magnetic disk used as a magnetic storage medium in an external storage device (magnetic disk device) for a computer or the like. Related to recording media and their manufacturing method [Prior art] Conventionally, storage media for computers, etc. have been coated with magnetic powder.
'ii tapes, disk-shaped magnetic disks, etc. are used. Among these, disc-shaped magnetic disks are widely used because they allow random access, and magnetic disks whose substrates are made of aluminum alloy or the like, so-called hard disks, have come into use. This magnetic disk is generally constructed by forming a magnetic recording layer about 1 .mu.m thick on a hard substrate about 2 .mu.m thick. The magnetic recording layer has been made by mixing magnetic powder such as γ-F8203 with a binder and applying it onto the disk substrate using a method such as a spin code. There is a limit to this, and we have almost reached the limit as a high-density recording magnetic medium.
Recently, Co5Co-N with larger saturation magnetization
1s Co-PL% Co-Re.
５ｓ−Ｇｏ等の金属あるいは、合金を真空蒸着、スパツ
タリング等の真空成膜技術により、ディスク基板上ある
いは、基板上に形成された下地層上に形成し、これを磁
気記録層とした磁気ディスクが開発されている。しかし
ながら、以上のような合金薄膜などの磁気記録媒体はそ
の磁気特性が、スパッタリング等の真空成膜技術により
基板上に成膜する際の成膜直前の到達真空度（バックグ
ランドプレッシャー）に大きく依存するために、真空槽
の到達真空度を良くコントロールしないと安定した高い
磁気特性を有する磁気ディスクを得るのが困難であると
いう問題がある。A magnetic disk is created by forming a metal such as 5S-Go or an alloy on a disk substrate or an underlayer formed on the substrate using a vacuum film forming technique such as vacuum evaporation or sputtering, and using this as a magnetic recording layer. being developed. However, the magnetic properties of magnetic recording media such as the alloy thin films described above are largely dependent on the degree of vacuum (background pressure) reached just before film formation when the film is formed on a substrate using vacuum film formation techniques such as sputtering. Therefore, there is a problem in that it is difficult to obtain a magnetic disk having stable and high magnetic properties unless the ultimate vacuum degree of the vacuum chamber is well controlled.
［発明が解決しようとする課題］
本発明の目的は、優れた磁気特性を有する磁気記録媒体
及び成膜する際の成膜直前の到達真空度に依存しない安
定した磁気特性を有する磁気記録媒体の製造法を提供す
ることにある。[Problems to be Solved by the Invention] An object of the present invention is to provide a magnetic recording medium with excellent magnetic properties and a magnetic recording medium with stable magnetic properties that do not depend on the degree of vacuum reached immediately before film formation. The purpose is to provide a manufacturing method.
［課題を解決するための手段］
本発明者らは上記問題点を解決するために鋭意検討を行
なった結果、下地クロム層を有する磁気記録媒体の下地
クロム層に酸素を導入することにより、磁気記録媒体の
磁気特性、特に保磁力が向上することを見出だし本発明
を完成するに至った。[Means for Solving the Problems] The present inventors have conducted intensive studies to solve the above-mentioned problems, and have found that by introducing oxygen into the underlying chromium layer of a magnetic recording medium having an underlying chromium layer, magnetic The inventors discovered that the magnetic properties of the recording medium, particularly the coercive force, can be improved and have completed the present invention.
すなわち本発明は、基板、下地クロム層、磁気記録層及
び保護層を含んでなる磁気記録媒体において、下地クロ
ム層が酸素を含むことを特徴とする磁気記録媒体及びそ
の製造法である。以下、図面に基づき本発明の詳細な説
明する。That is, the present invention is a magnetic recording medium comprising a substrate, an underlying chromium layer, a magnetic recording layer, and a protective layer, in which the underlying chromium layer contains oxygen, and a method for manufacturing the same. Hereinafter, the present invention will be explained in detail based on the drawings.
第１図は、本発明の磁気記録媒体を用いて作製した磁気
ディスクの一実施例の部分断面図である。FIG. 1 is a partial cross-sectional view of one embodiment of a magnetic disk manufactured using the magnetic recording medium of the present invention.
基板１は、例えば旧−Ｐメツキ膜、陽極酸化アルマイト
膜等を被覆したアルミ合金、窒化硅素焼結体、酸化アル
ミ焼結体等のセラミックス、ステンレス、チタン合金等
の金属、ガラス、プラスチックなどから構成される。下
地クロム層２は、基板１上に形成されたクロム膜であり
、本発明の特徴は該層が酸素を含むことにある。この層
に含まれる酸素の量は、０．０１〜５原子パーセントで
あることが好ましく、更に好ましくは０．Ｏ１〜３原子
パーセントである。酸素の量が５原子パーセントを越え
る場合、得られる磁気記録媒体の磁気特性が低下するお
それがある。また、下地クロム層２の厚みは５００〜５
０００人であることが好ましく、更に好ましくは２００
０〜４０００人である。The substrate 1 is made of, for example, an aluminum alloy coated with an old-P plating film, an anodized alumite film, etc., ceramics such as silicon nitride sintered body, aluminum oxide sintered body, metal such as stainless steel, titanium alloy, glass, plastic, etc. configured. The base chromium layer 2 is a chromium film formed on the substrate 1, and the feature of the present invention is that this layer contains oxygen. The amount of oxygen contained in this layer is preferably 0.01 to 5 atomic percent, more preferably 0.01 to 5 atomic percent. 1 to 3 atomic percent of O. If the amount of oxygen exceeds 5 atomic percent, the magnetic properties of the resulting magnetic recording medium may deteriorate. Moreover, the thickness of the base chromium layer 2 is 500 to 5
000 people, more preferably 200 people
0 to 4000 people.
下地クロム層２の上の磁気記録層３は、下地クロム層と
の密着性の点から、Ｃｒｓ Ｐｔ５Ｔａｓ Ｗｓ ８
ｍ％Ｇｄ５ＲａＳＧｅｓ Ｖ及びＭＯから選ばれる少
なくとも一種以上の添加元素を含むコバルト系合金ある
いはコバルトニッケル系合金合金であることが好ましく
、例えばスパッタリング法によって１００〜２０００人
の厚みで形成される。保護層５は、厚さ５０〜４００程
度の炭素、Ａｌ Ｏ、Ｚｒ０２等の無機物質の膜から
なり、スパッタリング法などにより形成される。更に、
必要に応じて厚さ５０〜２００人程度のクロム、チタン
、バナジウムなどの非磁性金属薄膜からなる表面層４を
、スパッタリング法などにより磁気記録層３と保護層５
の間に設けてもよい。磁気記録媒体の使用に当たっては
、必要に応じて上記保護層上に液体潤滑剤、または固体
潤滑剤、あるいはこれらの複合潤滑剤を塗布して潤滑層
６を形成して使用することができる。The magnetic recording layer 3 on the underlying chromium layer 2 is made of Crs Pt5Tas Ws 8 from the viewpoint of adhesion to the underlying chromium layer.
m%Gd5RaSGes It is preferably a cobalt-based alloy or a cobalt-nickel-based alloy containing at least one additive element selected from V and MO, and is formed to a thickness of 100 to 2000 mm by sputtering, for example. The protective layer 5 is made of a film of an inorganic material such as carbon, Al 2 O, ZrO 2 or the like and has a thickness of about 50 to 400 mm, and is formed by a sputtering method or the like. Furthermore,
If necessary, a surface layer 4 made of a thin film of non-magnetic metal such as chromium, titanium, vanadium, etc. with a thickness of about 50 to 200 layers is formed by sputtering or the like to form a magnetic recording layer 3 and a protective layer 5.
It may be provided in between. When using the magnetic recording medium, a liquid lubricant, a solid lubricant, or a combination of these lubricants may be applied on the protective layer to form a lubricant layer 6, if necessary.
本発明の磁気記録媒体の下地クロム層２を、アルゴンガ
スと酸素ガスとの混合ガスをスパッタガスとして用い、
スパッタリング法により成膜することにより、成膜する
際の成膜直前の到達真空度に依存しない安定した磁気特
性を有する磁気記録媒体を得ることができる。このとき
用いる混合ガス中の酸素ガスの割合はアルゴンガスに対
して１〜３０パーセント（流量比）が好ましく、より好
ましくは１〜１０パーセントである。酸素ガスの割合が
３０パーセントを越える場合、得られる磁気記録媒体の
磁気特性が低下するおそれがある。The base chromium layer 2 of the magnetic recording medium of the present invention is formed by using a mixed gas of argon gas and oxygen gas as a sputtering gas,
By forming a film by sputtering, it is possible to obtain a magnetic recording medium having stable magnetic properties that do not depend on the degree of vacuum reached immediately before film formation. The proportion of oxygen gas in the mixed gas used at this time is preferably 1 to 30 percent (flow rate ratio) relative to argon gas, and more preferably 1 to 10 percent. If the proportion of oxygen gas exceeds 30%, the magnetic properties of the resulting magnetic recording medium may deteriorate.
［実施例］
以下、本発明を実施例により更に詳細に説明するが、本
発明はこれらの実施例に限定されるものではない。[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.
実施例１
第１図に示す磁気記録ディスクを製造した。基板１とし
て、平均表面粗さ約１００人に研磨した旧−Ｐメツキ膜
被覆のアルミニウム合金を用い、この基板１の上に下地
クロム層２を、ＤＣスパッタリング法により厚さ３００
０人となるように形成した。下地クロム層２の成膜直前
の到達真空度は、約６ Ｘ １０ ”−７ｔｏｒｒであ
った。またこのときのスパッタリングガスとして、アル
ゴンガスと酸素ガスの混合ガス（流量比１００：１）を
用い、真空槽内に導入し全圧力を５１ｔｏｒｒとした。Example 1 A magnetic recording disk shown in FIG. 1 was manufactured. As the substrate 1, an aluminum alloy coated with a former -P plating film that has been polished to an average surface roughness of about 100 mm is used, and a base chromium layer 2 is formed on this substrate 1 to a thickness of 300 mm by DC sputtering.
It was formed so that there would be 0 people. The ultimate vacuum level immediately before the film formation of the base chromium layer 2 was approximately 6 x 10''-7 torr. Also, a mixed gas of argon gas and oxygen gas (flow rate ratio 100:1) was used as the sputtering gas at this time. , and the total pressure was set to 51 torr.
次に、得られた下地クロム層２膜の上に、ＤＣスパッタ
リング法によりニッケルを２０原子パーセント含むコバ
ルト合金薄膜を７００人磁気記録層３として形成し、該
磁気記録層の上に表面層４としてクロム層をＤＣスパッ
タリング法により厚さ１００人形成し、更にこの上に保
護層５として炭素膜をＤＣスパッタリング法により３０
０人形成し磁気記録ディスクを作製した。得られた磁気
記録ディスクの磁気特性を評価比較した。この結果を表
１に示す。Next, a cobalt alloy thin film containing 20 at. A chromium layer with a thickness of 100 mm was formed by DC sputtering, and a carbon film of 30 mm was further formed as a protective layer 5 on top of this by DC sputtering.
A magnetic recording disk was produced by 0 people. The magnetic properties of the obtained magnetic recording disks were evaluated and compared. The results are shown in Table 1.
実施例２〜４
下地クロム層２のスパッタリングの際に用いる混合ガス
の流量比を表１のとおりにかえた以外は実施例１と同様
の方法で磁気記録ディスクを得た。Examples 2 to 4 Magnetic recording disks were obtained in the same manner as in Example 1, except that the flow rate ratio of the mixed gas used in sputtering the base chromium layer 2 was changed as shown in Table 1.
得られた磁気記録ディスクの磁気特性を表１に示す。Table 1 shows the magnetic properties of the obtained magnetic recording disk.
比較例１
下地クロム層２のスパッタリングの際に用いるスパッタ
ガスに酸素を混入しなかった以外は実施例１と同様の方
法で磁気記録ディスクを得た。得られた磁気記録ディス
クの磁気特性を表１に示す。Comparative Example 1 A magnetic recording disk was obtained in the same manner as in Example 1, except that oxygen was not mixed into the sputtering gas used for sputtering the base chromium layer 2. Table 1 shows the magnetic properties of the obtained magnetic recording disk.
実施例５
実施例１と同じ方法で同じ構造の磁気ディスクを作製し
た。ただし、本実施例の場合、下地クロム層２成膜時の
アルゴンガスと酸素ガスの流量比を１００：５と一定に
し、下地クロム層２成膜直前の到達真空度を各々変化さ
せた。このとき得られた磁気記録ディスクの各磁気特性
を表２に示す。Example 5 A magnetic disk having the same structure as in Example 1 was manufactured by the same method. However, in the case of this example, the flow rate ratio of argon gas and oxygen gas during the formation of the underlying chromium layer 2 was kept constant at 100:5, and the degree of vacuum reached immediately before the formation of the underlying chromium layer 2 was varied. Table 2 shows the magnetic properties of the magnetic recording disk obtained at this time.
比較例２
実施例１と同じ方法で同じ構造の磁気ディスクを作製し
た。ただし、本比較例の場合スパッタガスとしてアルゴ
ンガスのみを使用し、下地クロム層２成膜直前の到達真
空度を各々変化させた。このとき得られた磁気記録ディ
スクの各磁気特性を表３に示す。Comparative Example 2 A magnetic disk having the same structure as in Example 1 was manufactured by the same method. However, in the case of this comparative example, only argon gas was used as the sputtering gas, and the degree of vacuum reached immediately before the formation of the base chromium layer 2 was varied. Table 3 shows the magnetic properties of the magnetic recording disk obtained at this time.
表２１表３より、本発明の方法によれば、得られる磁気
記録媒体の磁気特性は、下地クロム層成膜直前の到達真
空度の変動に左右されず、安定していることがわかる。From Table 21 and Table 3, it can be seen that according to the method of the present invention, the magnetic properties of the magnetic recording medium obtained are stable, unaffected by fluctuations in the degree of vacuum reached immediately before the formation of the underlying chromium layer.
５・・・保護層
６・・・潤滑層
［発明の効果］
以上述べたとおり、本発明の磁気記録媒体は磁気特性に
優れるものであり、更に、本発明の下地クロム層の成膜
時にアルゴンガスと共に酸素ガスを尋人する磁気記録媒
体の製造法によれば、下地クロム層の成膜直前の到達真
空度変動に対しても安定した高い磁気特性を有する磁気
記録媒体が得られるので、その生産性は向上する。5...Protective layer 6...Lubricating layer [Effects of the invention] As described above, the magnetic recording medium of the present invention has excellent magnetic properties, and furthermore, when forming the base chromium layer of the present invention, argon is not used. According to the manufacturing method of magnetic recording media that uses oxygen gas together with the gas, it is possible to obtain a magnetic recording medium that has high magnetic properties that are stable even when the degree of vacuum changes just before the formation of the underlying chromium layer. Productivity will improve.
Claims (2)
んでなる磁気記録媒体において、下地クロム層が酸素を
含むことを特徴とする磁気記録媒体。(1) A magnetic recording medium comprising a substrate, an underlying chromium layer, a magnetic recording layer, and a protective layer, wherein the underlying chromium layer contains oxygen.
合ガスをスパッタガスとして用い、スパッタリング法に
より成膜することを特徴とする特許請求の範囲１項に記
載の磁気記録媒体の製造法。(2) The method for manufacturing a magnetic recording medium according to claim 1, characterized in that the base chromium layer is formed by a sputtering method using a mixed gas of argon gas and oxygen gas as a sputtering gas.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21489788A JPH0264913A (en) | 1988-08-31 | 1988-08-31 | Magnetic recording medium and its production |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21489788A JPH0264913A (en) | 1988-08-31 | 1988-08-31 | Magnetic recording medium and its production |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0264913A true JPH0264913A (en) | 1990-03-05 |
Family
ID=16663372
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21489788A Pending JPH0264913A (en) | 1988-08-31 | 1988-08-31 | Magnetic recording medium and its production |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0264913A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0260388A (en) * | 1988-08-26 | 1990-02-28 | Matsushita Electric Ind Co Ltd | Still picture transmission equipment |
| JPH0536054A (en) * | 1991-07-31 | 1993-02-12 | Nec Corp | Magnetic recording medium and production thereof |
-
1988
- 1988-08-31 JP JP21489788A patent/JPH0264913A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0260388A (en) * | 1988-08-26 | 1990-02-28 | Matsushita Electric Ind Co Ltd | Still picture transmission equipment |
| JPH0536054A (en) * | 1991-07-31 | 1993-02-12 | Nec Corp | Magnetic recording medium and production thereof |
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