JPH0198146A - High-density information recording carrier - Google Patents
High-density information recording carrierInfo
- Publication number
- JPH0198146A JPH0198146A JP25694087A JP25694087A JPH0198146A JP H0198146 A JPH0198146 A JP H0198146A JP 25694087 A JP25694087 A JP 25694087A JP 25694087 A JP25694087 A JP 25694087A JP H0198146 A JPH0198146 A JP H0198146A
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- magneto
- layer
- optical recording
- thickness
- 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
- 239000010409 thin film Substances 0.000 claims abstract description 44
- 230000005374 Kerr effect Effects 0.000 claims abstract description 20
- 239000000758 substrate Substances 0.000 claims abstract description 19
- 239000000463 material Substances 0.000 claims abstract description 15
- 239000010408 film Substances 0.000 abstract description 15
- 239000011521 glass Substances 0.000 abstract description 15
- 238000004544 sputter deposition Methods 0.000 abstract description 8
- 230000001681 protective effect Effects 0.000 abstract description 5
- 239000004417 polycarbonate Substances 0.000 abstract description 3
- 229920000515 polycarbonate Polymers 0.000 abstract description 3
- 230000002542 deteriorative effect Effects 0.000 abstract 2
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 38
- 238000000034 method Methods 0.000 description 13
- 238000011156 evaluation Methods 0.000 description 6
- 239000004033 plastic Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 239000011241 protective layer Substances 0.000 description 3
- 239000003513 alkali Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000005240 physical vapour deposition Methods 0.000 description 2
- -1 Li5NaSK Chemical class 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910000808 amorphous metal alloy Inorganic materials 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 1
- 238000001755 magnetron sputter deposition Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
Abstract
Description
【発明の詳細な説明】
産業上の利用分野
本発明はレーザー光を用いて情報の記録・再生を行う光
学式記録・再生方式で用いられる高密度情報記録担体に
関するものであり、特に、光磁気記録・再生特性に優れ
且つジッター特性にも優れた光磁気記録・再生方式の高
密度情報記録担体に関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-density information recording carrier used in an optical recording/reproducing method that records and reproduces information using laser light, and in particular, relates to a high-density information recording carrier used in an optical recording/reproducing method that records and reproduces information using laser light. The present invention relates to a high-density information recording carrier using a magneto-optical recording/reproducing method that has excellent recording/reproducing characteristics and excellent jitter characteristics.
従来の技術とその問題点
光磁気ディスクのような光磁気記録媒体において、現在
、技術的に最も要求されている問題点は信頼性の向上を
いかにして達成するかということと、記録・再生特性を
さらに改善させることである。Conventional technology and its problems Currently, the most demanding technical problem in magneto-optical recording media such as magneto-optical disks is how to improve reliability, and how to improve recording and playback performance. The purpose is to further improve the characteristics.
特に透明基板としてプラスチック基板を用いた場合には
、その基板中に残留する水分やモノマーあるいは基板を
通して浸入してくる水分等によって記録担体が劣化、あ
るいは変質してしまうという欠点があった。本発明者は
、特開昭６１−２８９．５６０号において上記欠点を解
決する方法として、プラスチック基板と記録層の間に無
アルカリガラスの薄膜を設けることを提案した。この方
法は、光ディスクの耐久性を驚異的に延ばし、完全に満
足のゆ（ものであるが、光磁気効果は、従来のままであ
るため、Ｃ／Ｎ値は従来のものと変わらず、実用的な見
地からはさらに改良の余地があった。In particular, when a plastic substrate is used as the transparent substrate, there is a drawback that the recording carrier deteriorates or changes in quality due to moisture or monomer remaining in the substrate or moisture entering through the substrate. The present inventor proposed in Japanese Patent Application Laid-open No. 61-289.560 to provide a thin film of alkali-free glass between the plastic substrate and the recording layer as a method for solving the above-mentioned drawbacks. This method extends the durability of the optical disk tremendously and is completely satisfactory, but since the magneto-optical effect remains the same as before, the C/N value remains the same and is not suitable for practical use. From a practical standpoint, there was room for further improvement.
そこでさらに、本発明者は、上記のＣ／Ｎ値を改良する
ための方法として特開昭６２−２４．４５８号において
、カー効果エンハンスメント薄膜層を用いることにより
、実用的なＣ／Ｎ値が得られることを示した。Therefore, the present inventor further proposed in Japanese Patent Application Laid-Open No. 62-24.458 as a method for improving the above C/N value that a practical C/N value can be achieved by using a Kerr effect enhancement thin film layer. We showed that it can be obtained.
しかし、最近では、光磁気記録担体の特性を示すＣ／Ｎ
値以外に、記録パルス時間に対する再生パルス時間の標
準偏差（以後、ジッターという）を更に改善することが
強く望まれるようになっている。しかし、上記の従来の
方法では満足できるジッター特性を有する光磁気記録担
体を作ることはできなかった。However, recently, C/N, which indicates the characteristics of magneto-optical recording carriers, has been
In addition to the value, it is strongly desired to further improve the standard deviation (hereinafter referred to as jitter) of the reproduction pulse time with respect to the recording pulse time. However, it has not been possible to produce a magneto-optical record carrier with satisfactory jitter characteristics using the above-mentioned conventional methods.
従って、本発明の目的は、上記本発明者達の提供した優
れた耐久性を有し且つ高い実用的なＣ／Ｎ値を有する光
磁気記録担体において、さらに、上記ジッター特性も改
良された新規な光磁気ディスク等の光磁気記録担体を提
供することにある。Therefore, an object of the present invention is to provide a magneto-optical record carrier having excellent durability and a high practical C/N value, provided by the present inventors, and to further provide a novel magneto-optical record carrier having improved jitter characteristics. An object of the present invention is to provide a magneto-optical recording carrier such as a magneto-optical disk.
問題を解決するための手段
本発明の提供する高密度情報記録担体は、透明基板と、
この基板上に形成された光磁気記録材層と、この記録材
層の少なくとも一方の表面上に形成されたカー効果エン
ハンスメント薄膜層とを有する光磁気記録・再生方式を
用いた高密度情報記録担体において、上記光磁気記録材
層と上記カー効果エンハンスメント薄膜層との間に透明
薄膜層が設けられていることを特徴としている。Means for Solving the Problems The high-density information recording carrier provided by the present invention includes a transparent substrate,
A high-density information recording carrier using a magneto-optical recording and reproducing method, which has a magneto-optical recording material layer formed on this substrate and a Kerr effect enhancement thin film layer formed on at least one surface of this recording material layer. A transparent thin film layer is provided between the magneto-optical recording material layer and the Kerr effect enhancement thin film layer.
上記透明薄膜層の屈折率は、可視光に対して、上記カー
効果エンハンスメント薄膜層の屈折率より小さいのが好
ましい。The refractive index of the transparent thin film layer is preferably smaller than the refractive index of the Kerr effect enhancement thin film layer with respect to visible light.
本発明で用いる上記透明基板はガラス基板やエポキシ樹
脂基板などいずれのものでもよいが、特に量産性を考慮
に入れると、射出成形の可能なプラスチック基板が好ま
しく、その中でもポリカーボネートを用いたものが更に
好ましい。The above-mentioned transparent substrate used in the present invention may be either a glass substrate or an epoxy resin substrate, but especially considering mass production, a plastic substrate that can be injection molded is preferable, and among these, one using polycarbonate is more preferable. preferable.
本発明で用いられる上記カー効果エンノ１ンスメント薄
膜層自体は公知であり、その作用は一般に誘電体層を設
けて、その操り返し反射によりみかけのカー回転角を増
加させるもので、一般には、５ｉＯ１Ａ１２ｏｚ、Ａｌ
Ｎ５ＺｎＳ、５ｔｓＮａ、’ｊ ｉ Ｏ２等が用いられ
る。一般に、これらの誘電体薄膜の屈折率は、可視光に
対して１．７〜２．６の範囲である。The Kerr effect enhancement thin film layer itself used in the present invention is publicly known, and its action is generally to provide a dielectric layer and increase the apparent Kerr rotation angle by the reflected reflection. , Al
N5ZnS, 5tsNa, 'j i O2, etc. are used. Generally, the refractive index of these dielectric thin films is in the range of 1.7 to 2.6 for visible light.
これらのカー効果エンハンスメント薄膜層は周知の物理
蒸着法、例えば、スパッタリングで形成でき、その膜厚
は材料によっても異なるが、一般には５００〜１５００
Ａである。These Kerr effect enhancement thin film layers can be formed by well-known physical vapor deposition methods, such as sputtering, and the film thickness varies depending on the material, but is generally between 500 and 1500 nm thick.
It is A.
また、本発明で用いられる上記光磁気記録材は希土類−
遷移金属（ＲＥ−ＴＭ）より成るアモルファス合金薄膜
の光磁気記録・再生層であり、この光磁気記録・再生層
は周知のようにレーザービームの照射によって熱−磁気
記録され、光−磁気効果によって再生される。上記ＲＥ
−ＴＭ膜としてはＴｂＦｅ、 ＧｄＴｂＦｅ５ＴｂＦｅ
Ｃｏ等の公知の任意の材料を用いることができる。Further, the above-mentioned magneto-optical recording material used in the present invention is made of rare earth metals.
This is a magneto-optical recording/reproducing layer made of an amorphous alloy thin film made of a transition metal (RE-TM). As is well known, this magneto-optical recording/reproducing layer is thermally and magnetically recorded by laser beam irradiation, and is recorded by the optical-magnetic effect. will be played. Above RE
-TM film is TbFe, GdTbFe5TbFe
Any known material such as Co can be used.
本発明の特徴は上記光磁気記録材層と上記カー効果エン
ハンスメント薄膜層との間に透明薄膜層を介在させる点
にある。A feature of the present invention is that a transparent thin film layer is interposed between the magneto-optical recording material layer and the Kerr effect enhancement thin film layer.
この透明薄膜層を構成する材料としてはＬｉＦ、ＭｇＦ
ａ、ＭｇＯ１ＫＢｒＳＳｉ ０２、ガラス等を挙げるこ
とができる。これらの材料の屈折率は１．３〜１．７の
範囲にある。これらの透明薄膜材料の中でガラス、特に
、無アルカリガラスが好ましい。この無アルカリガラス
薄膜の屈折率は約１．５３である。Materials constituting this transparent thin film layer include LiF and MgF.
a, MgO1KBrSSi02, glass, etc. The refractive index of these materials ranges from 1.3 to 1.7. Among these transparent thin film materials, glass, particularly alkali-free glass, is preferred. The refractive index of this alkali-free glass thin film is about 1.53.
また、上記透明薄膜層の厚みは、用いる物質によって異
なるが、好ましくは１０〜１０００人であり、更に好ま
しくは５０〜５００人である。これらの透明薄膜層は周
知の物理蒸着法、例えばスパッタリングや真空蒸着法で
容易に形成できる。The thickness of the transparent thin film layer varies depending on the material used, but is preferably 10 to 1000, more preferably 50 to 500. These transparent thin film layers can be easily formed by well-known physical vapor deposition methods such as sputtering and vacuum evaporation methods.
上記の無アルカリガラス薄膜は本出願人が特開昭６１−
２８９．５６０号において、光磁気記録媒体の耐久性を
向上させるためにプラスチック基板と光磁気記録再生層
との間に設けることを提案したものと同じにすることが
できる。この無機ガラス薄膜層は、アルカリ金属すなわ
ちＬｉ５ＮａＳＫ、 Ｒｈ、 Ｃｓをアルカリ金属酸化
物に換算して１重量％以下、好ましくは０．８重量％以
下しか含まない無アルカリガラスで構成されているのが
好ましい。詳細については上記発明の明細書を参照され
たい。The above-mentioned alkali-free glass thin film was developed by the present applicant
It can be the same as that proposed in No. 289.560 to provide between the plastic substrate and the magneto-optical recording/reproducing layer in order to improve the durability of the magneto-optical recording medium. This inorganic glass thin film layer is made of alkali-free glass that contains alkali metals, such as Li5NaSK, Rh, and Cs, in an amount of 1% by weight or less, preferably 0.8% by weight or less in terms of alkali metal oxides. preferable. For details, please refer to the above specification of the invention.
発明の効果
従来、カー効果エンハンスメント薄膜層を用いることに
より、記録再生特性が良好になり、高いＣ／Ｎ値と高い
記録感度を有する高密度記録担体が得られることは公知
であったが、Ｃ／Ｎ以外の記録再生特性の内、ジッター
については、まだ実用化可能なレベルまで改良されたも
のは無く、さらに、改善が強く望まれていた。Effects of the Invention Conventionally, it has been known that by using a Kerr effect enhancement thin film layer, recording and reproducing characteristics can be improved, and a high-density recording carrier having a high C/N value and high recording sensitivity can be obtained. Of the recording and reproducing characteristics other than /N, jitter has not yet been improved to a level that can be put to practical use, and further improvement has been strongly desired.
本発明によって、こうした要請に十分応えることが可能
になった。The present invention has made it possible to fully meet these demands.
すなわち、透明薄膜層を記録層とカー効果エンハンスメ
ント薄膜層との間に設けることにより、他の特性に変化
を与えずに、上記ジッターに関する問題を解決できた。That is, by providing a transparent thin film layer between the recording layer and the Kerr effect enhancement thin film layer, the above-mentioned problem regarding jitter could be solved without changing other characteristics.
以下、実施例を用いて本発明を更に詳細に説明するが、
これによ、って本発明が限定されるものではない。Hereinafter, the present invention will be explained in more detail using Examples.
The present invention is not limited thereby.
実施例１
プラスチック基板として直径が１３０胴、厚さ１．２ｍ
ｍのポリカーボネート製基板を用意した。この基板には
、０．６μｍ幅の案内溝が設けてあり、そのピッチは１
．６μｍである。この基板上にスパッタリング装置（日
本真空技術■製ＲＦマグネトロンスパッタリング装置）
を用いて無アルカリガラスであるコーニング７０５９を
中間保護層としてスパッタリングで膜厚５００人の薄膜
に形成した。次いでカー効果エンハンスメント薄膜層と
してＺｎＳをスパッタリングによって９０ＯＡの薄膜に
し、このカー効果エンハンスメント薄膜層上に、中間保
護膜に用いた上記コーニング７０５９の無アルカリガラ
スの膜厚を２５０人の厚さに形成し、この中間保護膜の
上にさらにＴＩ］２ｓＦｅｓｓＣＯｔ （原子％）の
光磁気記録記録・再生層を上記スパッタリング装置を用
いて膜厚１０００ Ａに形成した。さらに、その上に、
上記と同じ方法で、上記コーニング７０５９をスパッタ
リングして膜厚１０００人の表面保護層を形成した。Example 1 Plastic substrate with a diameter of 130 mm and a thickness of 1.2 m
A polycarbonate substrate of 1.0 m was prepared. This board has guide grooves with a width of 0.6 μm, and the pitch is 1
．． It is 6 μm. A sputtering device (RF magnetron sputtering device manufactured by Japan Vacuum Technology Co., Ltd.) is placed on this substrate.
Corning 7059, which is a non-alkali glass, was formed as an intermediate protective layer by sputtering into a thin film with a thickness of 500 nm. Next, as a Kerr effect enhancement thin film layer, ZnS was formed into a 90 OA thin film by sputtering, and on this Kerr effect enhancement thin film layer, a film of Corning 7059 alkali-free glass used as an intermediate protective film was formed to a thickness of 250 OA. On this intermediate protective film, a magneto-optical recording/reproducing layer of TI]2sFessCOt (atomic %) was further formed to a thickness of 1000 Å using the sputtering apparatus described above. Furthermore, on top of that,
In the same manner as above, the Corning 7059 was sputtered to form a surface protective layer with a thickness of 1000 nm.
得られた光磁気ディスクのジッターの評価は書込み周波
数２ＭＨｚ、ｄｕｔｙ５０％、記録線速度４．２ｍ／ｓ
。The jitter evaluation of the obtained magneto-optical disk was performed at a writing frequency of 2 MHz, a duty of 50%, and a recording linear velocity of 4.2 m/s.
.
分解能帯域幅３０ＫＨｚで測定した。その結果、Ｃ／Ｎ
比および耐久性は従来のものとまた全く変わらずに、ジ
ッター値は５．１ ｎ５ｅｃとなった。Measurements were made with a resolution bandwidth of 30 KHz. As a result, C/N
The jitter value was 5.1 n5ec, with the ratio and durability being exactly the same as the conventional one.
実施例２
実施例１において、上記コーニング７０５９の無アルカ
リガラスの中間保護層を成膜しなかった他は全て同様な
膜構成をもつ光磁気ディスクを作成した。評価方法を実
施例１と同様にして測定した結果、ジッターは５．５
ｎ ｓｅｃとなった。Example 2 A magneto-optical disk having the same film structure as in Example 1 was prepared except that the intermediate protective layer of Corning 7059 non-alkali glass was not formed. As a result of measurement using the same evaluation method as in Example 1, the jitter was 5.5.
It became n sec.
実施例３
実施例２において、光磁気記録記録・再生層とカー効果
エンハンスメント薄膜層との間に設けたコーニング７０
５９薄膜の代わりにＭｇ Ｆ ２薄膜を膜厚２５０人に
成膜した他は、全て実施例２と同様な膜構成をもつ光磁
気ディスクを作成した。実施例１と同様な方法で評価し
た結果、ジッターは５．４ｎｓｅｃとなった〇
比較例１
実施例１において、光磁気記録記録・再生層とカー効果
エンハンスメント薄膜層との間に設けた上記コーニング
７０５９薄膜を設けなかった他は全て実施例１と同様な
膜構成をもつ光磁気ディスクを作成した。実施例１と同
様な方法で評価した結果、ジッターは７．５ ｎ ｓｅ
ｃとなった。Example 3 In Example 2, Corning 70 was provided between the magneto-optical recording/reproducing layer and the Kerr effect enhancement thin film layer.
A magneto-optical disk having the same film structure as in Example 2 was fabricated, except that a Mg F 2 thin film was formed to a thickness of 250 mm instead of the 59 mm thin film. As a result of evaluation using the same method as in Example 1, the jitter was 5.4 nsec. Comparative Example 1 In Example 1, the above corning provided between the magneto-optical recording/reproducing layer and the Kerr effect enhancement thin film layer A magneto-optical disk having the same film structure as in Example 1 was produced except that the 7059 thin film was not provided. As a result of evaluation using the same method as in Example 1, the jitter was 7.5 n se
It became c.
比較例２
実施例２において、光磁気記録記録・再生層とカー効果
エンハンスメント薄膜層との間に設けた上記コーニング
７０５９薄膜を設けなかった他は、全て、実施例２と同
様な膜構成をもつ光磁気ディスクを作成した。実施例１
と同様な方法で評価した結果、ジッターは３． Ｑ ｎ
ｓｅｃとなった。Comparative Example 2 All of the film configurations were the same as in Example 2, except that the Corning 7059 thin film provided between the magneto-optical recording/reproducing layer and the Kerr effect enhancement thin film layer was not provided in Example 2. Created a magneto-optical disk. Example 1
As a result of evaluation using the same method as above, the jitter was 3. Q n
It became sec.
比較例３
実施例３において、光磁気記録記録・再生層とカー効果
エンハンスメント薄膜層との間に設けた上記ＭｇＦ２薄
膜を設けなかった他は、全て、実施例３と同様な膜構成
をもつ光磁気ディスクを作成した。実施例１と同様な方
法で評価した結果、ジッターは８．２ｎＳｅＣとなった
。Comparative Example 3 All optical fibers had the same film structure as Example 3, except that the MgF2 thin film provided between the magneto-optical recording/reproducing layer and the Kerr effect enhancement thin film layer was not provided in Example 3. Created a magnetic disk. As a result of evaluation using the same method as in Example 1, the jitter was 8.2 nSeC.
Claims (2)
材層と、この記録材層の少なくとも一方の表面上に形成
されたカー効果エンハンスメント薄膜層とを有する光磁
気記録・再生方式を用いた高密度情報記録担体において
、上記光磁気記録材層と上記カー効果エンハンスメント
薄膜層との間に透明薄膜層が設けられていることを特徴
とする高密度情報記録担体。(1) A magneto-optical recording and reproducing system that includes a transparent substrate, a magneto-optical recording material layer formed on this substrate, and a Kerr effect enhancement thin film layer formed on at least one surface of this recording material layer. The high-density information recording carrier used herein is characterized in that a transparent thin film layer is provided between the magneto-optical recording material layer and the Kerr effect enhancement thin film layer.
記カー効果エンハンスメント薄膜層の屈折率より小さい
ことを特徴とする特許請求の範囲第１項に記載の高密度
情報記録担体。(2) The high-density information recording carrier according to claim 1, wherein the refractive index of the transparent thin film layer is smaller than the refractive index of the Kerr effect enhancement thin film layer with respect to visible light.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25694087A JPH0198146A (en) | 1987-10-12 | 1987-10-12 | High-density information recording carrier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25694087A JPH0198146A (en) | 1987-10-12 | 1987-10-12 | High-density information recording carrier |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0198146A true JPH0198146A (en) | 1989-04-17 |
Family
ID=17299476
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25694087A Pending JPH0198146A (en) | 1987-10-12 | 1987-10-12 | High-density information recording carrier |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0198146A (en) |
-
1987
- 1987-10-12 JP JP25694087A patent/JPH0198146A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4414650A (en) | Magneto-optic memory element | |
| US4489139A (en) | Magneto-optic memory medium | |
| EP0163810B1 (en) | Optical information recording carrier | |
| JPH081709B2 (en) | Magneto-optical recording medium | |
| JPH034974B2 (en) | ||
| US4943957A (en) | High-density information recording carrier | |
| US20020054564A1 (en) | Optical recording medium | |
| JPH0198146A (en) | High-density information recording carrier | |
| JP2541677B2 (en) | Optical recording medium | |
| JP2000067466A (en) | Optical recording medium and its production | |
| US20020168495A1 (en) | Phase-change optical recording media | |
| JPS61289558A (en) | High-density information recording carrier | |
| JP2671127B2 (en) | Optical information recording method and information recording medium | |
| JP2596902B2 (en) | Optical information recording medium | |
| JPH02179947A (en) | Magneto-optical recording medium | |
| JP2940176B2 (en) | Optical recording medium and recording / reproducing method thereof | |
| JPH03122845A (en) | Optical recording medium | |
| JPS63173248A (en) | Magneto-optical disk | |
| JPS6224458A (en) | Photomagnetic disk | |
| JPH0559495B2 (en) | ||
| JPS61210546A (en) | Recording medium | |
| JPH03142728A (en) | Optical recording medium | |
| JPH09115180A (en) | Optical recording medium | |
| JPH02308454A (en) | Magneto-optical recording medium | |
| JPH04284289A (en) | Optical information record medium |