JP2910084B2 - Signal reproducing method of the magneto-optical recording medium - Google Patents

Signal reproducing method of the magneto-optical recording medium

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JP2910084B2
JP2910084B2 JP22939589A JP22939589A JP2910084B2 JP 2910084 B2 JP2910084 B2 JP 2910084B2 JP 22939589 A JP22939589 A JP 22939589A JP 22939589 A JP22939589 A JP 22939589A JP 2910084 B2 JP2910084 B2 JP 2910084B2
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真澄 太田
勝久 荒谷
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ソニー株式会社
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【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、磁気光学特性によって記録信号の読み出しを行う光磁気記録媒体における信号再生方法に関するものであり、特に線記録密度,トラック密度を向上するための技術に関するものである。 DETAILED DESCRIPTION OF THE INVENTION The present invention [relates] is related to the signal reproducing method of the magneto-optical recording medium for reading the recording signals by the magneto-optical properties, particularly improved linear recording density, track density to a technique for.

〔発明の概要〕 SUMMARY OF THE INVENTION

本発明は、光磁気記録媒体の記録層を磁気的に結合される再生層と記録保持層とを含む多層膜で構成し、予め再生層の磁化の向きを揃えて消去状態としておくとともに、再生時にはレーザ光の照射によって再生層を所定の温度以上に昇温し、この昇温された領域でのみ記録保持層に書き込まれた磁気信号を再生層に転写しながら読み取るようにすることにより、クロストークを解消して線記録密度,トラック密度の向上を図ろうとするものである。 The present invention, the recording layer of the magneto-optical recording medium formed of a multilayer film including a magnetically coupled by reproducing layer and the recording holding layer, together keep the erased state by aligning the direction of magnetization of the previously reproduced layer, reproduction sometimes heated regeneration layer above a predetermined temperature by irradiation of a laser beam, by to read while transferring a magnetic signal written on the recording holding layer only in this heated area to the reproducing layer, the cross linear recording density to eliminate the talk, it is an attempt is made to improve the track density.

〔従来の技術〕 [Prior art]

光磁気記録方式は、磁性薄膜を部分的にキュリー点または温度補償点を越えて昇温し、この部分の保磁力を消滅させて外部から印加される記録磁界の方向に磁化の向きを反転させることを基本原理とするもので、したがって光磁気記録媒体の構成としては、例えばポリカーボネート等からなる透明基板の一主面に、膜面と垂直方向に磁化容易軸を有し優れた磁気光学効果を有する記録磁性層(例えば希土類−遷移金属合金非晶質薄膜)や反射層、誘電体層を積層することにより記録部を設け、透明基板側からレーザ光を照射して信号の読み取りを行うようにしたものが知られている。 Magneto-optical recording method, a magnetic thin film partially heated beyond the Curie point or a temperature compensation point, to reverse the direction to the magnetization direction of the recording magnetic field applied from the outside is extinguished the coercive force of this portion it intended to basic principle, therefore as the structure of a magneto-optical recording medium, for example, on one main surface of a transparent substrate made of polycarbonate or the like, an excellent magneto-optical effect has an axis of easy magnetization in the film plane perpendicular direction recording magnetic layer (e.g., a rare earth - transition metal alloy amorphous thin film) having or reflecting layer, a recording unit provided by laminating a dielectric layer, is irradiated with a laser beam from the transparent substrate side so as to read the signal It has been known that.

ところで、光磁気記録媒体に限らず、デジタル・オーディオ・ディスク(いわゆるコンパクトディスク)やビデオディスク等の光ディスクの線記録密度は、主として再生時のS/Nによって決められており、また再生信号の信号量は記録されている信号のピット列の周期と再生光学系のレーザ波長,対物レンズの開口数に大きく依存する。 However, not limited to the magneto-optical recording medium, a linear recording density of an optical disk such as a digital audio disk (so-called compact disks) and video disks are determined primarily by playback of S / N, also reproduced signal of the signal the amount periodic and reproducing optical system laser wavelength of pit row of the signal being recorded, largely depends on the numerical aperture of the objective lens.

現状では再生光学系のレーザ波長λと対物レンズの開口数NAが決まると、検出限界となるピット周期fが決まる。 If at present the numerical aperture NA of the laser wavelength λ and an objective lens of the reproducing optical system are determined, the pit period f as the detection limit is determined. すなわち、 f=λ/2・NA である。 That is, f = λ / 2 · NA.

一方、トラック密度は、主としてクロストークによって制限されている。 On the other hand, the track density is mainly limited by crosstalk. そして、このクロストークは、主に媒体面上でのレーザビームの分布(プロフィル)で決まり、前記ピット周期と同様やはりλ/2・NAの関数で概略表される。 The crosstalk is mainly determined by the distribution of the laser beam on the medium surface (profile), it represented schematically as a function of the pit period and similarly again λ / 2 · NA.

したがって、従来の光ディスクで高密度化を実現するためには、再生光学系のレーザ波長λを短くし、対物レンズの開口数NAを大きくするというのが基本姿勢である。 Therefore, in order to realize a high density in a conventional optical disk, shortening the laser wavelength λ of the reproducing optical system, because increasing the numerical aperture NA of the objective lens is a basic posture.

しかしながら、レーザ波長や対物レンズの開口数の改善にも限度があり、一方では記録媒体の構成や読み取り方法を工夫し、記録密度を改善する技術が開発されている。 However, there is a limit to the improvement of the numerical aperture of the laser wavelength and an objective lens, on the one hand, by devising a structure and method of reading a recording medium, a technique for improving the recording density has been developed.

例えば、本願出願人は、先に特開平1−143041号,特開平1−143042号において、記録ピット(磁区)を再生時に拡大,消滅させながら再生することにより再生分解能を向上させる方式を提案している。 For example, applicant has proposed previously in Japanese Patent Laid-Open No. 1-143041, Japanese Patent Laid-Open No. 1-143042, a larger recording pits (magnetic domains) at the time of reproduction, a method of improving the reproducing resolution by reproducing while disappear ing. この方式は、再生層,中間層,記録層からなる交換結合多層膜を記録媒体とし、再生時において再生光ビームで加熱された再生層の磁区を拡大あるいは消去することにより、再生時の符号間干渉を減少させ、光の回折限界以下の周期の信号を再生可能とするものである。 This method, reproducing layer, an intermediate layer, the exchange coupling multilayered film composed of a recording layer and a recording medium, by enlarging or erasing the magnetic domains of the reproducing layer heated by the playback light beam during reproduction, between codes during reproduction interference reduces, is a signal of less than the diffraction limit of the period of light which can be reproduced.

〔発明が解決しようとする課題〕 [Problems that the Invention is to Solve]

しかしながら、前述の方式では、線記録密度については改善されるものの、クロストークについては通常の光ディスクと同様であり、トラック密度を改善することは難しい。 However, in the above method, although being improved for linear recording density is the same as the conventional optical disk for crosstalk, it is difficult to improve the track density.

本発明は、かかる従来の実情に鑑みて提案されたものであって、クロストークを解消することができ、線記録密度ばかりでなくトラック密度も向上することが可能な信号再生方法を提供することを目的とする。 The present invention, which was proposed in view of such conventional circumstances, it is possible to eliminate cross-talk, to provide a signal reproducing method capable of improved track density as well as linear recording density With the goal.

〔課題を解決するための手段〕 [Means for Solving the Problems]

本発明は、上記目的を達成するために、互いに交換結合された再生層と記録保持層とが積層形成された多層膜を有する光磁気記録媒体を用い、前記記録保持層に対し信号記録を行うとともに、再生に先立って再生層の磁化の向きを揃え、再生時に、前記再生層にレーザ光を照射することにより当該再生層を昇温させ、前記記録保持層に記録された信号を、前記昇温による再生層の温度分布に応じて再生スポット内の一部でのみ転写させながら磁気光学効果により光学信号に変換して読み取ることを特徴とするものである。 The present invention, in order to achieve the above object, using a magneto-optical recording medium having a multilayer film and exchange coupled reproducing layer and a recording holding layer are laminated to each other, performing signal recording to said recording holding layer together, aligned direction of magnetization of the reproducing layer prior to reproduction, during reproduction, the reproducing layer is heated to the reproducing layer by irradiating a laser beam on the signal recorded on the recording holding layer, the temperature while only by transferring a part of the reproduction spot in accordance with the temperature distribution in the reproduction layer due to temperature it is characterized in that the reading is converted into an optical signal by magneto-optical effect.

すなわち、本発明は、再生層と記録保持層とを少なくとも有する多層膜を記録媒体とし、信号の再生前には再生層は全面同一状態(消去状態)としておき、再生光が照射されある温度以上となった領域でのみ予め記録保持層に記録された信号が再生層に転写されるように設定し、前記温度以下の領域は信号に何ら関与せず光学的にはその部分がマスクされてるのと等価な状態となし、線記録密度とトラック密度の両者を改善するものである。 That is, the present invention provides a multilayer film recording medium having at least a reproducing layer and a recording holding layer, the reproducing layer before reproducing the signal is left as an entirely identical state (erase state), or the temperature at which the reproducing light is irradiated since pre signal recorded on the recording holding layer only in the region is set to be transferred to the reproducing layer, the said temperature following areas are the no without optically in part its involvement in signal masked with equivalent state and without, is intended to improve both the linear recording density and track density.

本発明において、使用される光磁気記録媒体の記録層は、少なくとも垂直磁化膜の2層膜(再生層及び記録保持層)で構成されれば良く、例えば希土類−遷移金属合金薄膜からなる交換結合多層膜(少なくとも2層膜,3層膜。できれば4層膜以上であることが好ましい。)等が好適である。 In the present invention, the recording layer of the magneto-optical recording medium used may be made of a two-layer film of at least the vertical magnetization film (reproducing layer and the recording holding layer), such as rare earth - exchange coupling comprising a transition metal alloy thin film multilayer film (at least two-layer film, it is preferable that the three-layer film. hopefully 4 layer film or more.) and the like. 勿論、これに限らず、ガーネット膜やCoC Of course, the present invention is not limited to this, garnet film and CoC
r,PtCo,PdCo等の垂直磁化膜であってもよいし、さらにはバリウムフェライト等の六方晶系フェライト粉末を分散した磁性塗料の塗膜であっても良い。 r, PtCo, may be a vertically magnetized film such as PdCo, ​​further may be a coating of a magnetic coating material obtained by dispersing the hexagonal ferrite powders such as barium ferrite. ただし、前記再生層と記録保持層とは、静磁結合あるいは交換結合によって磁気的に結合していることが必要である。 However, the the reproducing layer and the recording holding layer, it is necessary that are magnetically coupled by magnetostatic coupling or exchange coupling. また、再生層については、大きなカー回転角,ファラデー回転角を有することが必要である。 Further, the reproduction layer has a large Kerr rotation angle, it is necessary to have a Faraday rotation angle.

前記記録保持層には、通常の光磁気記録媒体と同様、 Wherein the recording holding layer, as in the conventional magneto-optical recording medium,
光変調方式あるいは磁界変調方式で信号を記録するようにすればよいが、さらには記録保持層に接して垂直磁化膜を設け、この垂直磁化膜に垂直磁気記録媒体と同様に磁気ヘッドで磁気信号を記録した後、レーザ光の照射により垂直磁化膜に記録された磁気信号を記録保持層に転写するようにしてもよい。 Although it suffices to record the signal in the optical modulation method or the magnetic field modulation system, furthermore provided with a perpendicular magnetization film in contact with the recording holding layer, a magnetic signal the magnetic head similarly to the perpendicular magnetic recording medium in the perpendicular magnetization film after recording the may be transferred magnetic signal recorded on the perpendicular magnetic film in the recording holding layer by laser light irradiation.

そして、第1図に示すように、上述の構成を有する光磁気記録媒体の記録保持層(1)に信号を記録し、一方再生層(2)は磁化の向きを揃えて消去状態としておく。 As shown in FIG. 1, the signal was recorded on the recording holding layer of the magneto-optical recording medium (1) having the above-described configuration, whereas the reproducing layer (2) is kept in an erased state by aligning the magnetization direction. 本例では、再生層(2)の磁化の向きは図中上向きに揃えられている。 In this example, the direction of magnetization of the reproducing layer (2) is aligned upwards in the figure.

ここで再生層(2)の消去は、外部磁界H ERで行えば良い。 Clear here reproducing layer (2) may be performed by an external magnetic field H ER. すなわち、H ER >Hc 1 〔ただしHc 1は再生層(2) That, H ER> Hc 1 [proviso Hc 1 is reproducing layer (2)
の磁化反転磁界〕としておけば、再生層(2)の磁化の向きを前記外部磁界H ERの方向に揃えることができる。 Once you have the magnetization reversal field], it is possible to align the direction of magnetization of the reproducing layer (2) in the direction of the external magnetic field H ER.
また、このときH ER <<Hc 2 〔ただしHc 2は記録保持層(1)の磁化反転磁界〕としておけば、記録保持層(1)に記録された信号が影響を受けることはない。 Also, at this time H ER << Hc 2 [however Hc 2 the magnetization reversal field of the recording holding layer (1)] Oke as a, the signal recorded on the recording holding layer (1) is not affected.

再生時には、再生層(2)にレーザ光LBが照射され、 In reproduction, the laser beam LB is irradiated on the reproducing layer (2),
レーザ光LBが照射された領域が加熱されて温度が上昇する。 Temperature rises laser beam LB is heated is irradiated region.

このとき、第2図に示すように、再生層(2)がある一定の温度T PB以上になると、記録保持層(1)に記録された信号が再生層(2)へ転写される。 At this time, as shown in FIG. 2, at the above constant temperature T PB in the reproducing layer (2), the signal recorded on the recording holding layer (1) is transferred to the reproducing layer (2).

例えば、前記記録保持層(1)と再生層(2)とが静磁結合によって磁気的に結合されているとすると、記録保持層(1)からの浮遊磁界Hs 2 ,再生層(2)の反磁界 For example, assuming that it is magnetically coupled said recording holding layer (1) by the reproducing layer (2) transgressions magnetostatic coupling, stray field Hs 2 of the recording holding layer (1), the reproduction layer (2) anti-magnetic field
Hd 1 ,再生層(2)の磁区発生磁界Hn 1 ,再生時に印加される外部印加磁界H PBが、前記所定の温度T PB以下のときに、 Hs 2 +Hd 1 ±H PB <Hn 1・・・(1) なる式を満たし、また前記所定の温度T PB以上のときに Hs 2 +Hd 1 ±H PB >Hn 1・・・(2) なる式を満たすように各層の磁化,保磁力,膜厚等を設定しておけば、前記温度T PB以上に加熱された領域でのみ前記記録保持層(1)から発生する浮遊磁界に従って信号が転写される。 Hd 1, the magnetic domain generated magnetic field Hn 1 of the reproducing layer (2), the external applied magnetic field H PB applied during reproduction, when: the predetermined temperature T PB, Hs 2 + Hd 1 ± H PB <Hn 1 ·· - (1) comprising satisfies expression and magnetization of each layer so as to satisfy the predetermined temperature T PB above when the Hs 2 + Hd 1 ± H PB > Hn 1 ··· (2) becomes equation, coercive force, film by setting the thickness and the like, the signal is transferred in accordance with the stray magnetic field generated from the recording holding layer only in the heated area (1) above the temperature T PB.

同様に、前記記録保持層(1)と再生層(2)とが交換結合によって磁気的に結合されているとすると、再生層(2)に働く交換力による等価な磁界Hw 1 〔=σw/2Ms Similarly, the the recording holding layer (1) and the reproducing layer (2) is assumed to be magnetically coupled by exchange coupling, the reproducing layer (2) equivalent by exchange force acting on magnetic field Hw 1 [= .sigma.w / 2Ms
1 h 1 :ただしσwは再生層(2)と再生層(2)に接する磁性層との層間に生ずる界面磁壁エネルギー密度であり、Ms 1は再生層(2)の飽和磁化、h 1は再生層(2) 1 h 1: However σw is the interface wall energy density occurring between the layers of the magnetic layer in contact with the reproducing layer (2) and the reproducing layer (2), Ms 1 is the saturation magnetization of the reproducing layer (2), h 1 is reproduced layer (2)
の膜厚である。 It is a film thickness. 〕が再生層(2)の磁区発生磁界Hn 1に対して、前記所定の温度T PB以下のときに、 Hw 1 ±H PB <Hn 1・・・(3) であり、所定の温度T PB以上のときに Hw 1 ±H PB >Hn 1・・・(4) であれば、前記温度T PB以上に加熱された領域でのみ前記記録保持層(1)との交換力により信号が転写される。 ] Is relative magnetic domain generated magnetic field Hn 1 of the reproducing layer (2), when: the predetermined temperature T PB, Hw 1 is ± H PB <Hn 1 ··· ( 3), the predetermined temperature T PB if Hw 1 ± H PB> Hn 1 a (4) when the above signal is transferred by the exchange force of the recording holding layer (1) only in the heated above the temperature T PB region that.

転写された磁気信号は、再生層(2)の磁気光学効果(カー効果あるいはファラデー効果)によって光学信号に変換され、先のレーザ光LBのカー回転角を検出することで再生される。 Transferred magnetic signal is converted into an optical signal by magneto-optical effect of the reproduction layer (2) (Kerr effect or Faraday effect), it is reproduced by detecting the Kerr rotation angle of the previous laser beam LB.

再生に際しては、第3図に示すように、再生トラック In reproduction, as shown in FIG. 3, the reproduction track
t aと隣接トラックt bとの境界での温度T Nが、T N <T PBとなるような温度分布としておけば、隣接トラックt bの下の記録保持層(1)に記録された信号が再生層(2)に転写されてくることはなく、クロストークは完全に解消される。 signal t a temperature T N at the boundary between adjacent tracks t b is, if a temperature distribution such that T N <T PB, which is recorded in the recording holding layer below the adjacent tracks t b (1) There never come transferred to the reproducing layer (2), the crosstalk is completely eliminated.

〔作用〕 [Action]

本発明の信号再生方法では、信号の読み取りを行う再生層は、磁化の向きが揃えられ全面同一状態(消去状態)とされており、レーザ光が照射された領域でのみ信号が転写されて読み出される。 The signal reproduction method of the present invention, the reproducing layer to read the signal is the magnetization direction is aligned entirely same state (erased state), read signal only in the region where the laser light is irradiated is transferred It is.

したがって、隣接するトラックの影響は皆無となり、 Thus, the effect of the adjacent track will be completely eliminated,
クロストークが解消される。 Cross talk is eliminated.

また、レーザ光を照射した際の温度分布により、レーザ光の走行方向前方端は前記消去状態が維持されてあたかもマスクされたような形となり、ピット周期がレーザ光のビーム径よりも小さい場合にも見掛け上の空間周波数が抑えられ、高C/Nで再生される。 Further, the temperature distribution when irradiated with laser light, the traveling direction front end of the laser light becomes a shape such as the erase state is as if the mask is maintained, when the pit period is less than the diameter of the laser beam also suppressed the spatial frequency of the apparent, it is reproduced at a high C / N.

〔実施例〕 〔Example〕

以下、本発明を適用した具体的な実施例について図面を参照しながら説明する。 Hereinafter, specific examples of the present invention will be described with reference to the drawings.

実施例1 本例は、記録保持層と再生層の磁気的な結合に静磁結合を用いた例である。 One example embodiment is an example in which a magnetostatic coupling to the magnetic coupling of the recording holding layer and the reproducing layer.

本実施例の光磁気記録媒体は、第4図に示すように、 Magneto-optical recording medium of the present embodiment, as shown in Figure 4,
ポリカーボネートやガラス等からなる透明基板(11)上に、第1の再生層(12),第2の再生層(13)及び記録保持層(14)を、誘電体膜(15),(16)を介して積層形成し、さらに最外層にも誘電体膜(17)を設けてなるものである。 On a transparent substrate made of polycarbonate, glass, or the like (11), the first reproducing layer (12), a second reproducing layer (13) and the recording holding layer (14), a dielectric layer (15), (16) laminated form through, but also formed by providing a dielectric film (17) further outermost layer. 誘電体膜(15),(16),(17)の材料としては、窒化ケイ素,酸化ケイ素,窒化アルミニウム等の透明誘電材料が使用可能である。 A dielectric film (15), the material (16), (17), silicon nitride, silicon oxide, a transparent dielectric material such as aluminum nitride can be used.

第1の再生層(12)は、キュリー点が高く(例えば20 First reproducing layer (12) has a high Curie point (for example 20
0℃以上)、カー回転角が大きく、しかも保磁力が数百エルステッド以下の垂直磁化膜である。 0 ℃ or higher), a large Kerr rotation angle, yet is less perpendicular magnetization film several hundred oersteds coercivity.

第2の再生層(13)は、垂直磁気異方性が大きく、キュリー点は低く(例えば200℃以下)、保磁力は室温で2キロエルステッド(kOe)前後の垂直磁化膜である。 Second reproducing layer (13) has a large perpendicular magnetic anisotropy, Curie point is low (for example 200 ° C. or less), the coercive force is perpendicularly magnetized film of 2 kOe (kOe) back and forth at room temperature.

なお、これら第1の再生層(12)と第2の再生層(1 Incidentally, these first reproducing layer (12) and the second reproducing layer (1
3)とは交換結合されている。 3) has been replaced bind to.

このように再生層を2層構造とすると、再生層の磁化反転磁界の温度依存性がある温度を境に急峻に変化し、 With this the reproducing layer and two-layer structure, abruptly changing the boundary temperature with the temperature dependence of the magnetization reversal field of the reproducing layer,
しかも第2の再生層(13)のキュリー点以上で反転磁界を100(Oe)程度の低い値とすることができ、微小ビットの安定な転写が可能となる。 Moreover it is possible to second low as 100 (Oe) the switching field above the Curie point of the reproducing layer (13), thereby enabling stable transfer of small bits.

一方、記録保持層(14)は、垂直磁気異方性が大きく、キュリー点が前記第2の再生層(13)のキュリー点よりも高い材料によって構成される。 On the other hand, the recording holding layer (14) has a large perpendicular magnetic anisotropy, constituted by material higher than the Curie point of the Curie point second reproducing layer (13). 当該記録保持層(14)のキュリー点は、読み出しと書き込みに使用するレーザ光の出力のマージンを設定する目安となり、第2 Curie point of the recording holding layer (14), which is a measure for setting the margin of the output of the laser light used for reading and writing, the second
の再生層(13)のキュリー点よりも50℃以上高くする必要がある。 It is necessary to increase 50 ° C. or higher than the Curie point of the reproducing layer (13).

実際には、第1の再生層(12)をGdFeCo,第2の再生層(13)をTbFe,記録保持層(14)をTbFeCoとし、特に記録保持層(14)のキュリー点は280℃,保磁力は10(k In fact, the first reproducing layer (12) GdFeCo, a second reproducing layer (13) TbFe, recording holding layer (14) and TbFeCo, particularly Curie point of the recording holding layer (14) is 280 ° C., the coercive force is 10 (k
Oe)以上に設定した。 Oe) was set to at least.

かかる光磁気記録媒体を用い、記録保持層(14)に記録された信号を再生光によって再生層(12)に転写しながら再生したところ、非常に高いC/Nが実現された。 Such light using the magnetic recording medium, recorded in the recording holding layer (14) signals were reproduced with transferred to the reproducing layer (12) by the reproducing light, a very high C / N is achieved.

実施例2 本例は、記録保持層と再生層の磁気的な結合に交換結合を用いた例である。 Example 2 This example is an example using an exchange coupling to the magnetic coupling between the recording holding layer reproducing layer.

交換結合を用いた光磁気記録媒体の構成としては、第5図に示すように再生層(21)と記録保持層(22)からなる交換結合2層膜としたもの(以下、媒体Aと称する。)、第6図に示すように再生層(23)と記録保持層(24)の間に中間層(25)を介在せしめたもの(以下、 The structure of the magneto-optical recording medium using the exchange coupling, those exchange coupling two-layer film made from the reproducing layer as shown in FIG. 5 (21) and the recording holding layer (22) (hereinafter, referred to as medium A .), which intermediate layer (25) was allowed interposed between the reproducing layer as shown in FIG. 6 (23) and the recording holding layer (24) (hereinafter,
媒体Bと称する。 It is referred to as a media B. )、第7図に示すように再生層を先の実施例1と同様に第1の再生層(26),第2の再生層(27)の2層構造とし、中間層(28)を介して記録保持層(29)を積層したもの(以下、媒体Cと称する。)が考えられる。 ), The first reproducing layer reproduction layer as shown in FIG. 7 in the same manner as Example 1 above (26), a two-layer structure of the second reproducing layer (27), via an intermediate layer (28) recording holding layer (29) a laminate of Te (hereinafter, referred to as medium C.) can be considered.

ここで、媒体Aでは、前述の(3)式及び(4)式の条件を満足するためには、再生層(21)と記録保持層(22)の膜厚を厚くせざるを得ず、レーザーパワーに制約があるために線速度が速い場合には記録,消去を行うことができなくなる虞れがある。 Here, in the medium A, in order to satisfy the condition of the above (3) and (4) is forced to not give not increase the thickness of the reproducing layer (21) and the recording holding layer (22), If the linear velocity due to the constraints on laser power is fast recording, there is a possibility that it becomes impossible to erase.

そこで、中間層を介在せしめることで界面磁壁エネルギー密度を低下させ、各層の膜厚が薄くて済むようにすればよいものと考えられるが、媒体Bでは、交換力による等価な磁界Hw 1が再生層の磁区発生磁界Hn 1と等しくなる温度が膜組成,膜厚等に非常に敏感なものとなり、ディスク周上のムラが顕著に影響して再生時にノイズやジッターが大きくなる傾向にある。 Therefore, to reduce the interfacial magnetic domain wall energy density by allowed to intervening intermediate layer, it is considered that it is sufficient to avoid thin film thickness of each layer, the medium B, the exchange force by an equivalent magnetic field Hw 1 is reproduced magnetic domain generated magnetic field Hn 1 and equal temperature film composition layer becomes very sensitive ones to the film thickness, etc., tend to noise or jitter during reproduction unevenness on the disc periphery is markedly effect increases.

これに対して、媒体Cでは、第1の再生層(26)をキュリー点が高く、カー回転角が大きく、保磁力の小さい材料で構成し、第2の再生層(27)をキュリー点が低く、保磁力が2(kOe)程度の材料で構成することで、 In contrast, in the medium C, higher first reproducing layer (26) is the Curie point, a large Kerr rotation angle, and composed of a material having a small coercive force, the second reproducing layer (27) is Curie point low, since the coercive force is composed of about 2 (kOe) material,
再生S/Nの良好な光磁気記録媒体とすることができる。 It can be a good magneto-optical recording medium of the reproducing S / N.

本発明者等は、ポリカーボネート基板上に、Si 3 N 4からなる誘電体層(膜厚800Å)、GdFeCoからなる第1の再生層(膜厚300Å)、TbFeからなる第2の再生層(膜厚150Å)、GdFeCoからなる中間層(膜厚100Å)、TbFe The present inventors have on the polycarbonate substrate, a dielectric layer made of Si 3 N 4 (thickness 800 Å), the first reproducing layer (thickness 300 Å) composed of GdFeCo, a second reproducing layer (film made of TbFe thickness 150 Å), an intermediate layer (thickness 100Å consisting GdFeCo), TbFe
Coからなる記録保持層(膜厚350Å)、Si 3 N 4からなる誘電体層(膜厚800Å)をスパッタリングにより順次積層形成し、サンプルディスクを作成した。 Recording holding layer made of Co (film thickness 350 Å), a dielectric layer composed of Si 3 N 4 (thickness 800 Å) are sequentially laminated by sputtering to prepare a sample disk.

そして、記録保持層に5MHzのキャリア信号を書き込み、線速度5m/秒,再生外部磁界500(Oe)として、キャリアー及びノイズの再生出力のレーザ出力依存性を調べた。 Then, write the carrier signal of 5MHz in the recording holding layer, the linear velocity 5 m / sec, as the reproduction external magnetic field 500 (Oe), was investigated laser output dependency of the reproduction output of carrier and noise. 同時に、クロストークについても測定した。 At the same time, it was also measured for the cross-talk. クロストークは、基板に幅0.8μmのグループを0.8μm間隔で形成し(したがってグルーブ部の間には幅0.8μmのランド部が形成される。)、ランド部及びグルーブ部にそれぞれ4.8MHzの信号を記録して測定した。 Crosstalk (land portion width 0.8μm between the thus grooves are formed.) To form a group of width 0.8μm on the substrate at 0.8μm intervals, land portions and each 4.8MHz signal in the groove portion It was measured to record.

結果を第8図に示す。 The results are shown in Figure 8. 図中、線iはキャリアの再生出力、線iiはノイズの再生出力、線iiiはクロストークを表す。 In the figure, line i the reproduction output of the carrier, the line ii reproduction output of the noise, the line iii represent crosstalk.

レーザ出力1.6mW以下でキャリアが観測されないのは、このパワーでは媒体温度が転写に必要な温度に達していないことによる。 The laser output 1.6mW carrier below are not observed is because the temperature of the medium in this power does not reach the temperature required for transcription.

これに対して、レーザ出力2.0mW以上では、急激にキャリアが観測される。 In contrast, in the laser output 2.0mW more sharply carrier is observed. クロストークはレーザ出力2.5mW Crosstalk laser output 2.5mW
以下ではほとんど検出されず、したがってこのサンプルディスクでは、レーザ出力を2.0mW以上,2.5mW以下とすることで、クロストークが無く高C/Nでの信号再生が可能である。 Hardly detected in the following, therefore in this sample disc, the laser output 2.0mW or higher, is set to lower than or equal to 2.5 mW, it is possible to reproduce the signal by the crosstalk without high C / N.

そこでさらに、転写しながら再生することによる優位性を確認するために、C/Nのピット周期依存性を調べた。 Accordingly Furthermore, in order to confirm the superiority due to play while the transfer was investigated pit periodic dependency of C / N. 測定に際しての線速度は5m/秒,再生磁界は500(O The linear velocity of the time of measurement is 5 m / sec, the reproducing magnetic field is 500 (O
e),レーザ波長は780nm,対物レンズレンズの開口数N. e), the laser wavelength is 780 nm, the numerical aperture of the objective lens lens N.
A.は0.53である。 A. is 0.53. 結果を第9図に示す。 The results are shown in FIG.

第9図中、曲線aは再生層を3.5(kOe)の外部磁界で初期化した後、レーザ出力2.8mWで磁区を転写しながら再生した場合の特性を示すものであり、曲線bは同様の条件で一度再生した後、初期化せずにそのままレーザ出力1.4mWで再生した場合の特性を示すものである。 In FIG. 9, after the curve a has been initialized by an external magnetic field of the reproducing layer 3.5 (kOe), and shows the characteristics when the reproduced while transferring the magnetic domain in the laser output 2.8 mW, the curve b is the same after playing once the condition shows the characteristics in a case where it is reproduced by laser power 1.4mW without initializing. したがって、曲線bは、通常の再生でのC/Nに相当する。 Thus, the curve b corresponds to the C / N as in normal playback.

この第9図を見ると、本発明方法を採用することでC/ Looking at this Figure 9, C by employing the present invention method /
Nが大幅に改善されることがわかる。 N is found to be greatly improved.

〔発明の効果〕 〔Effect of the invention〕

以上の説明からも明らかなように、本発明においては、記録保持層に記録された磁気信号を再生層に転写しながら読み出すようにしているので、クロストークを解消することができ、トラック密度及び線記録密度が高い場合にも高C/Nで信号を再生することが可能である。 As apparent from the above description, in the present invention, since the read out while transferring the magnetic signals recorded on the recording holding layer to the reproducing layer, it is possible to eliminate crosstalk, track density and even when the linear recording density is high it is possible to reproduce a signal at a high C / N.

したがって、光磁気記録媒体における高密度記録化を達成する上で非常に有用で、その意義は大きい。 Thus, very useful in achieving the high density recording in magneto-optical recording medium, the significance is great.

【図面の簡単な説明】 BRIEF DESCRIPTION OF THE DRAWINGS

第1図及び第2図は本発明の再生原理を示す模式図であり、第1図は初期状態,第2図は再生状態を示すものである。 FIGS. 1 and 2 is a schematic view showing a reproduction principle of the present invention, FIG. 1 the initial state, FIG. 2 shows a playback state. 第3図はレーザ光を照射した場合のトラック幅方向での温度分布を示す模式図である。 Figure 3 is a schematic diagram showing a temperature distribution in the track width direction when the laser beam. 第4図は静磁結合を用いた光磁気記録媒体の一構成例を示す概略断面図である。 Figure 4 is a schematic sectional view showing a configuration example of a magneto-optical recording medium using a magneto-static coupling. 第5図は交換結合を用いた光磁気記録媒体の一構成例を示す概略断面図であり、第6図は交換結合を用いた光磁気記録媒体の他の構成例を示す概略断面図、第7図は交換結合を用いた光磁気記録媒体のさらに他の構成例を示す概略断面図である。 FIG. 5 is a schematic sectional view showing a configuration example of a magneto-optical recording medium using the exchange coupling, Figure 6 is a schematic sectional view showing another example of the configuration of a magneto-optical recording medium using the exchange coupling, the FIG. 7 is a schematic sectional view showing still another example of the configuration of a magneto-optical recording medium using the exchange coupling. 第8図は再生層に磁区を転写しながら再生したときのキャリア出力及びクロストークのレーザ出力依存性を示す特性図であり、第9図は磁区を転写しながら再生した場合のC/Nのピット周期依存性を通常の再生の場合のそれと比較して示す特性図である。 Figure 8 is a graph showing the laser output dependency of carrier output and crosstalk when reproduced while transferring the magnetic domain to the reproducing layer, the C / N if Figure 9 is reproduced while transferring the magnetic domain pits cycle-dependent is a characteristic diagram showing a comparison to that in the case of the normal reproduction.

Claims (1)

    (57)【特許請求の範囲】 (57) [the claims]
  1. 【請求項1】互いに交換結合された再生層と記録保持層とが積層形成された多層膜を有する光磁気記録媒体を用い、 前記記録保持層に対し信号記録を行うとともに、再生に先立って再生層の磁化の向きを揃え、 再生時に、前記再生層にレーザ光を照射することにより当該再生層を昇温させ、前記記録保持層に記録された信号を、前記昇温による再生層の温度分布に応じて再生スポット内の一部でのみ転写させながら磁気光学効果により光学信号に変換して読み取ること を特徴とする光磁気記録媒体における信号再生方法。 1. A and exchange coupled reproducing layer and a recording holding layer is used the magneto-optical recording medium having a multilayer film that is laminated to one another, performs signal recording to said recording holding layer, reproduced prior to reproduction aligning the magnetization direction of the layer, during reproduction, the reproducing layer is heated to the reproducing layer by irradiating a laser beam on the signal recorded on the recording holding layer, the temperature distribution of the readout layer by the heating signal reproducing method of the magneto-optical recording medium, wherein the reading is converted into an optical signal by magneto-optic effect while only is transferred in part in the reproduction spot in accordance with the.
JP22939589A 1989-09-06 1989-09-06 Signal reproducing method of the magneto-optical recording medium Expired - Lifetime JP2910084B2 (en)

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EP19900116773 EP0415449B1 (en) 1989-08-31 1990-08-31 Playback method for magnetooptical recording
DE1990618544 DE69018544T2 (en) 1989-08-31 1990-08-31 Playback method of magneto-optical recording.
DE1990618544 DE69018544D1 (en) 1989-08-31 1990-08-31 Playback method of magneto-optical recording.

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