JP2663843B2 - Optical information recording medium - Google Patents
Optical information recording mediumInfo
- Publication number
- JP2663843B2 JP2663843B2 JP5205569A JP20556993A JP2663843B2 JP 2663843 B2 JP2663843 B2 JP 2663843B2 JP 5205569 A JP5205569 A JP 5205569A JP 20556993 A JP20556993 A JP 20556993A JP 2663843 B2 JP2663843 B2 JP 2663843B2
- Authority
- JP
- Japan
- Prior art keywords
- layer
- recording
- optical information
- recording medium
- reflective 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.)
- Expired - Fee Related
Links
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- Optical Record Carriers And Manufacture Thereof (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、熱履歴の違いにより誘
起される相変化に伴う光学定数の変化を利用して情報の
記録・消去を行う光学情報記録媒体に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium for recording / erasing information by utilizing a change in an optical constant accompanying a phase change induced by a difference in thermal history.
【０００２】[0002]
【従来の技術】レーザ光の照射によって情報の記録・消
去・再生を行う光学情報記録媒体としては、光磁気ディ
スクや相変化型光ディスクなどが知られている。このう
ち、例えば相変化型光ディスクでは、図３に示すよう
に、基板１上に下部保護層２、記録層３、上部保護層４
および反射層７がこの順に設けられた４層構成が通常用
いられる。情報の記録・消去はレーザ光の照射による昇
温・冷却の熱履歴の違いによって誘起される記録層の非
晶質・結晶間の相変化を利用して行われる。すなわち、
記録層を溶融し急冷することにより非晶質化させ記録を
行い、また、結晶化温度以上に一定時間保持することに
より結晶化させ、消去を行う。信号の再生は非晶質・結
晶間の反射率差を利用して行われる。下部保護層２、記
録層３、上部保護層４および反射層７のそれぞれの膜厚
は、感度、Ｃ／Ｎ、消去率、書換可能繰り返し回数など
の観点から最適化される。2. Description of the Related Art As an optical information recording medium for recording, erasing, and reproducing information by irradiating a laser beam, a magneto-optical disk, a phase change optical disk, and the like are known. Among them, for example, in the case of a phase-change optical disk, as shown in FIG. 3, a lower protective layer 2, a recording layer 3, and an upper protective layer 4 are formed on a substrate 1.
A four-layer structure in which the reflective layer 7 is provided in this order is usually used. Recording and erasing of information is performed by utilizing a phase change between amorphous and crystalline layers of the recording layer induced by a difference in thermal history of heating and cooling by irradiation with laser light. That is,
The recording layer is melted and quenched to make it amorphous by making it amorphous, and recording is performed. Further, the recording layer is kept at a temperature higher than the crystallization temperature for a certain time to be crystallized and erased. Reproduction of a signal is performed using the difference in reflectance between the amorphous and the crystal. The thickness of each of the lower protective layer 2, the recording layer 3, the upper protective layer 4, and the reflective layer 7 is optimized from the viewpoint of sensitivity, C / N, erasure rate, number of rewritable repetitions, and the like.
【０００３】[0003]
【発明が解決しようとする課題】書換可能な光ディスク
が現在市販されているが、光ディスクにはさらなる高速
化・高密度化が要求されている。高密度化には、記録マ
ークの両端に情報を持たせる幅記録が有効である。しか
し、信号の再生に結晶・非晶質間の反射率差を利用して
いる相変化型光ディスクでは、結晶状態の吸収率と非晶
質状態の吸収率が異なる場合が多く、一般に、非晶質状
態の吸収率が結晶状態の吸収率より大きくなっている。
このような場合、形成されるマークの幅や長さは、新た
に記録する前の状態が結晶であったか、非晶質であった
かによって影響され、図４に示すように、オーバライト
によってジッタが大きく増加してしまう。従って、相変
化型光ディスクにおいてジッタを低減し、幅記録を実現
するには、非晶質状態と結晶状態の吸収率を等しくする
必要がある。結晶状態の方が融解に伴う潜熱が大きいこ
とを考慮すると、結晶状態の吸収率が非晶質状態の吸収
率より大きくなるように設計するのが望ましい。このよ
うな媒体を提供する手段として、特開平０１−１４９２
３８号公報、特開平０２−１２８３３０号公報などに記
載された技術が知られているが、特開平０２−１２８３
３０号公報では、感度を高めるために記録層の膜厚が１
００ｎｍ以上とかなり厚く、特開平０１−１４９２３８
号公報では金属を反射層として用いて吸収率の制御をし
ているために、反射層の膜厚が２０ｎｍと薄い。記録層
の膜厚が厚い場合には、よく知られているように、情報
の記録・消去の繰り返しによって記録層が流動しやす
く、特性が早期に劣化してしまうという問題がある。ま
た、反射層の膜厚が極端に薄い場合は、熱的な負荷が高
くなるため、情報の記録・消去の繰り返しによって熱変
形が生じやすく、特性が早期に劣化してしまうという問
題がある。本発明は、このような従来の問題点を解決す
るためになされたもので、幅記録時のジッタが小さく、
かつ、繰り返し特性に優れた光学情報記録媒体を提供す
ることを目的とする。[0005] Rewritable optical disks are currently on the market, but optical disks are required to have higher speed and higher density. To increase the density, width recording in which information is provided at both ends of a recording mark is effective. However, in a phase change type optical disk utilizing the difference in reflectance between crystalline and amorphous phases for signal reproduction, the absorptance in the crystalline state and the absorptivity in the amorphous state are often different. The absorptivity in the crystalline state is higher than the absorptivity in the crystalline state.
In such a case, the width and length of the mark to be formed are affected by whether the state before the new recording is crystalline or amorphous, and as shown in FIG. Will increase. Therefore, in order to reduce jitter and achieve width recording in a phase-change optical disk, it is necessary to make the absorptivity of the amorphous state equal to that of the crystalline state. Considering that the latent heat associated with melting is greater in the crystalline state, it is desirable to design the absorptance in the crystalline state to be greater than the absorptivity in the amorphous state. As means for providing such a medium, Japanese Patent Application Laid-Open No. 01-1492
Japanese Unexamined Patent Application Publication No. 38128 and Japanese Patent Application Laid-Open No. 02-128330 are known.
In Japanese Patent Publication No. 30, the thickness of the recording layer is set at 1 to increase the sensitivity.
00 nm or more,
In Japanese Patent Application Laid-Open Publication No. H06-27138, since the absorptance is controlled using a metal as the reflection layer, the thickness of the reflection layer is as thin as 20 nm. When the thickness of the recording layer is large, as is well known, there is a problem that the recording layer easily flows due to repetition of recording and erasing of information, and the characteristics are deteriorated early. Further, when the thickness of the reflective layer is extremely small, the thermal load becomes high, so that there is a problem that thermal deformation is apt to occur due to repetition of recording and erasing of information, and characteristics are quickly deteriorated. The present invention has been made to solve such a conventional problem, and has a small jitter at the time of width recording.
It is another object of the present invention to provide an optical information recording medium having excellent repetition characteristics.
【０００４】[0004]
【課題を解決するための手段】本発明は、基板上に、下
部保護層、レーザ光照射によって相変化を起こす記録
層、上部保護層、第１反射層および第２反射層が順次積
層された光学情報記録媒体であって、第１反射層と第２
反射層とが、それぞれ一方がＳｉで他方がダイヤモンド
状カーボンで形成され、かつ、記録層の膜厚が１０〜２
０ｎｍで、第１反射層および第２反射層の膜厚がそれぞ
れ５０ｎｍ以上であり、かつ結晶状態における記録層の
吸収率が非晶質状態における記録層の吸収率より大きい
ことを特徴とする光学情報記録媒体である。本発明によ
れば、繰り返し特性に優れ、かつオーバライトによるジ
ッタ増加の少ない媒体を提供することが可能となる。According to the present invention, a lower protective layer, a recording layer which undergoes a phase change by laser light irradiation, an upper protective layer, a first reflective layer and a second reflective layer are sequentially laminated on a substrate . An optical information recording medium, comprising: a first reflective layer and a second reflective layer.
Reflective layers, one of which is Si and the other is diamond
And a recording layer having a thickness of 10 to 2
At 0 nm, the thicknesses of the first reflective layer and the second reflective layer are respectively
Of the recording layer in a crystalline state.
Absorptivity is higher than that of recording layer in amorphous state
An optical information recording medium characterized in that: According to the present invention, excellent Repetitive return characteristics, and it is possible to provide a small media jitter increases due to overwriting.
【０００５】[0005]
【作用】反射層の膜厚を厚くして吸収率を制御するに
は、特開平２−２１８３３４号公報に記載されているよ
うに透過性の反射層を用いるのが有効である。例えば、
反射層としてＳｉを用いた場合、図５に示すように、容
易に上記の条件を満たすことができる。しかしながら、
通常のスパッタリング法で作製したＳｉは熱伝導率が低
いため、図３に示すような通常の構成で反射層として用
いた場合、書換え繰り返し可能回数は、熱変形等の影響
により５万回程度に制限されてしまう。一方、スパッタ
リング法で作製可能であり、かつ熱伝導率が高い透過性
の膜としてダイヤモンド状カーボン（以後、ＤＬＣと記
す。）があるが、屈折率が１．５〜２．２と小さいため
そのままでは光学的な反射層として用いることが難し
い。そこで図２に示すように、透過性の膜であり、か
つ、熱伝導率が高く熱負荷を低減することができるＤＬ
Ｃと、屈折率が大きく透過性の膜であるＳｉとを組み合
わせて第１および第２の反射層５、６として用いること
により、幅記録時のジッタが小さく、かつ、繰り返しに
優れた光学情報記録媒体を提供することが可能となる。
このような構成では、図１に示すように、記録層の膜厚
を２０ｎｍ以下と薄くし、反射層の膜厚を５０ｎｍ以上
としても、結晶状態の記録膜の吸収率を非晶質状態の記
録膜の吸収率より高くすることができるので、オーバラ
イトによるジッタの増加を抑制することができ、かつ、
繰り返しに伴う記録膜の流動や反射膜の熱変形を防ぐこ
とができる。記録層の膜厚はできるだけ薄くすることが
望ましいが、感度・膜質の観点から１０ｎｍ以上は必要
である。なお、第１反射層としてＳｉを用い、第２反射
層としてＤＬＣを用いても、光学的な特性は図１とほと
んど変わらず結晶状態の吸収率を非晶質状態の吸収率よ
り高くすることができるので、幅記録時のジッタが小さ
く、かつ繰り返しに優れた光学情報記録媒体を提供する
ことが可能になる。In order to control the absorptance by increasing the thickness of the reflective layer, it is effective to use a transmissive reflective layer as described in JP-A-2-218334. For example,
When Si is used as the reflective layer, the above condition can be easily satisfied as shown in FIG. However,
Since Si produced by a normal sputtering method has a low thermal conductivity, when used as a reflective layer in a normal configuration as shown in FIG. 3, the number of rewrite repetitions is about 50,000 due to the influence of thermal deformation and the like. You will be restricted. On the other hand, there is diamond-like carbon (hereinafter referred to as DLC) as a transparent film which can be formed by a sputtering method and has a high thermal conductivity, but has a small refractive index of 1.5 to 2.2, so that it is used as it is. However, it is difficult to use it as an optical reflection layer. Therefore, as shown in FIG. 2, a DL that is a permeable membrane and has a high thermal conductivity and can reduce a thermal load.
By using C as the first and second reflective layers 5 and 6 in combination with Si, which is a transparent film having a large refractive index, the optical information having a small jitter at the time of width recording and excellent in repetition. It is possible to provide a recording medium.
In such a configuration, as shown in FIG. 1, even if the thickness of the recording layer is made as thin as 20 nm or less and the thickness of the reflective layer is made as 50 nm or more, the absorptivity of the crystalline recording film is reduced to that of the amorphous state. Since it can be higher than the absorption rate of the recording film, an increase in jitter due to overwriting can be suppressed, and
It is possible to prevent the flow of the recording film and the thermal deformation of the reflection film due to the repetition. It is desirable that the thickness of the recording layer be as small as possible, but it is necessary that the thickness be 10 nm or more from the viewpoint of sensitivity and film quality. Even when Si is used as the first reflective layer and DLC is used as the second reflective layer, the optical characteristics are almost the same as those in FIG. 1 and the absorptance in the crystalline state is higher than that in the amorphous state. Therefore, it is possible to provide an optical information recording medium with small jitter during width recording and excellent repetition.
【０００６】[0006]
【実施例】以下、本発明の実施例について、図面を参照
して説明する。図２は本発明に係る光学情報記録媒体の
断面図である。基板１上に下部保護層２、記録層３、上
部保護層４、第１反射層５、第２反射層６を順次積層し
た構成である。以下、同図に基づいて各実施例を説明す
る。Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of the optical information recording medium according to the present invention. In this configuration, a lower protective layer 2, a recording layer 3, an upper protective layer 4, a first reflective layer 5, and a second reflective layer 6 are sequentially laminated on a substrate 1. Hereinafter, each embodiment will be described with reference to FIG.
【０００７】実施例１ 基板１としてポリカーボネート（ＰＣ）を用い、下部保
護層２としてＺｎＳ−ＳｉＯ2を１６０ｎｍ、記録層３
としてＧｅ2Ｓｂ2Ｔｅ5を１５ｎｍ、上部保護層４とし
てＺｎＳ−ＳｉＯ2を１８ｎｍ、第１反射層５としてＤ
ＬＣを５０ｎｍ、第２反射層６としてＳｉを６５ｎｍを
順次スパッタリングにより積層した。この構成では、非
晶質状態の記録層の吸収率および結晶状態の記録層の吸
収率はそれぞれ６０％と７０％であった。上記ディスク
を線速２０ｍ／ｓで回転させ、波長８３０ｎｍの半導体
レーザを用いて記録・消去を行った。２．１２ＭＨｚ，
ｄｕｔｙ＝５０％の信号に３．３９ＭＨｚ，ｄｕｔｙ＝
５０％の信号を交互にオーバライトして、Ｃ／Ｎ、消去
率、ジッタを測定した。その結果、図６に示すように、
オーバライト後でもジッタは２ｎｓ以下の良好な値であ
った。また、ジッタは図７の○印で示すように、１００
万回の繰り返しオーバライト後もほとんど変化しなかっ
た。Example 1 Polycarbonate (PC) was used as a substrate 1, ZnS-SiO 2 was 160 nm as a lower protective layer 2, and a recording layer 3 was used.
Ge 2 Sb 2 Te 5 as 15 nm, ZnS—SiO 2 as upper protective layer 4 as 18 nm, and D as first reflective layer 5
50 nm of LC and 65 nm of Si as the second reflective layer 6 were sequentially laminated by sputtering. In this configuration, the absorptance of the amorphous recording layer and the absorptivity of the crystalline recording layer were 60% and 70%, respectively. The disk was rotated at a linear velocity of 20 m / s, and recording / erasing was performed using a semiconductor laser having a wavelength of 830 nm. 2.12 MHz,
3.39 MHz for a signal of duty = 50%, duty =
C / N, erasure rate, and jitter were measured by alternately overwriting a 50% signal. As a result, as shown in FIG.
Even after overwriting, the jitter was a good value of 2 ns or less. In addition, as shown by the circle in FIG.
There was almost no change even after overwriting repeatedly 10,000 times.
【０００８】実施例２ 基板１としてポリカーボネート（ＰＣ）を用い、下部保
護層２としてＺｎＳ−ＳｉＯ2を２５０ｎｍ、記録層３
としてＧｅ2Ｓｂ2Ｔｅ5を１５ｎｍ、上部保護層４とし
てＺｎＳ−ＳｉＯ2を１８ｎｍ、第１反射層５としてＳ
ｉを６５ｎｍ、第２反射層６としてＤＬＣを５０ｎｍを
順次スパッタリングにより積層した。この構成では、非
晶質状態の記録層の吸収率及び結晶状態の記録層の吸収
率はそれぞれ５０％と６０％であった。実施例１と同じ
測定条件で、繰り返しに伴うＣ／Ｎ、ジッタの変化を調
べた。その結果、図７の◎印で示すように、実施例１と
同様に１００万回の繰り返しオーバライト後もジッタは
ほとんど変化しなかった。Example 2 Polycarbonate (PC) was used as a substrate 1, ZnS-SiO 2 was 250 nm as a lower protective layer 2, and a recording layer 3 was used.
Ge 2 Sb 2 Te 5 as 15 nm, ZnS—SiO 2 as upper protective layer 4 as 18 nm, and S as first reflective layer 5
i was 65 nm, and DLC 50 nm as the second reflective layer 6 was sequentially laminated by sputtering. In this configuration, the absorptance of the amorphous recording layer and the absorptivity of the crystalline recording layer were 50% and 60%, respectively. Under the same measurement conditions as in Example 1, changes in C / N and jitter due to repetition were examined. As a result, as shown by the mark 印 in FIG. 7, the jitter hardly changed even after repeated overwriting 1,000,000 times, as in Example 1.
【０００９】比較例１ 繰り返し特性に及ぼす記録層の膜厚の影響を調べるた
め、上記実施例１とほぼ同様の媒体構成で、記録層の膜
厚のみを３０ｎｍと厚くしたディスクの特性を測定し
た。実施例１と同じ測定条件で、繰り返しに伴うＣ／
Ｎ、ジッタの変化を調べた。その結果、図８の△印で示
すように、繰り返し回数１０万回以上では、ノイズ、ジ
ッタが大幅に増加し、特性が劣化することが確認され
た。Comparative Example 1 In order to examine the effect of the recording layer thickness on the repetition characteristics, the characteristics of a disk having a recording layer thickness of only 30 nm were measured with a medium configuration substantially the same as that of the above-mentioned Example 1. . Under the same measurement conditions as in Example 1, C /
N, a change in jitter was examined. As a result, as shown by the mark in FIG. 8, when the number of repetitions was 100,000 or more, it was confirmed that noise and jitter were significantly increased and characteristics were deteriorated.
【００１０】比較例２ 繰り返し特性に及ぼす反射層の膜厚の影響を調べるた
め、ＰＣ基板上に下部保護層としてＺｎＳ−ＳｉＯ2を
１５０ｎｍ、記録層としてＧｅ2Ｓｂ2Ｔｅ5を１５ｎ
ｍ、上部保護層としてＺｎＳ−ＳｉＯ2を４０ｎｍ、反
射層としてＳｉを３０ｎｍを順次スパッタリングにより
積層したディスクの特性を測定した。上記実施例１と同
じ測定条件で、繰り返しに伴うＣ／Ｎ、ジッタの変化を
調べた。その結果、図８の□印で示すように、繰り返し
回数５０００回以上では、ノイズ、ジッタが大幅に増加
し特性が劣化することが確認された。Comparative Example 2 In order to examine the effect of the thickness of the reflective layer on the repetition characteristics, ZnS—SiO 2 was used as a lower protective layer on a PC substrate at 150 nm, and Ge 2 Sb 2 Te 5 was used as a recording layer at 15 n.
m, 40 nm and ZnS-SiO 2 as the upper protective layer, the characteristics of disks stacked in this order by sputtering 30nm of Si as a reflection layer were measured. Under the same measurement conditions as in Example 1, changes in C / N and jitter due to repetition were examined. As a result, as indicated by the squares in FIG. 8, it was confirmed that when the number of repetitions was 5000 or more, the noise and jitter were significantly increased and the characteristics were deteriorated.
【００１１】[0011]
【発明の効果】以上説明したように、本発明によれば、
繰り返し特性を劣化させることなく、幅記録時のジッタ
が小さい媒体を提供することができるので、高密度化を
実現することができる。As described above, according to the present invention,
A medium with small jitter during width recording can be provided without deteriorating the repetition characteristics, so that high density can be realized.
【図１】本発明にかかる光学情報記録媒体の光学設計の
一例における下部保護層膜厚と反射率および吸収率との
関係を示す図である。FIG. 1 is a diagram showing the relationship between the thickness of a lower protective layer and the reflectance and absorptance in an example of an optical design of an optical information recording medium according to the present invention.
【図２】本発明にかかる相変化型光ディスクの媒体構成
の一例の断面図である。FIG. 2 is a cross-sectional view of an example of a medium configuration of a phase change optical disc according to the present invention.
【図３】従来の光学情報記録媒体の媒体構成の一例の断
面図である。FIG. 3 is a cross-sectional view of an example of a medium configuration of a conventional optical information recording medium.
【図４】従来の光学情報記録媒体における消去パワと消
去率およびジッタとの関係を示す図である。FIG. 4 is a diagram showing the relationship between erasing power, erasing rate, and jitter in a conventional optical information recording medium.
【図５】従来の光学情報記録媒体の光学設計の一例にお
ける下部保護層膜厚と反射率および吸収率との関係を示
す図である。FIG. 5 is a diagram showing the relationship between the thickness of a lower protective layer and the reflectance and absorptance in an example of an optical design of a conventional optical information recording medium.
【図６】本発明の光学情報記録媒体における消去パワと
消去率およびジッタとの関係を示す図である。FIG. 6 is a diagram showing the relationship between erasing power, erasing rate, and jitter in the optical information recording medium of the present invention.
【図７】本発明の実施例の光学情報記録媒体における繰
り返しオーバライトによるジッタおよびＣ／Ｎの変化を
示す図である。FIG. 7 is a diagram illustrating changes in jitter and C / N due to repeated overwriting in the optical information recording medium according to the embodiment of the present invention.
【図８】比較例の光学情報記録媒体における繰り返しオ
ーバライトによるジッタおよびＣ／Ｎの変化を示す図で
ある。FIG. 8 is a diagram showing changes in jitter and C / N due to repeated overwriting in an optical information recording medium of a comparative example.
１ 基板 ２ 下部保護層 ３ 記録層 ４ 上部保護層 ５ 第１反射層 ６ 第２反射層 ７ 反射層 DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower protective layer 3 Recording layer 4 Upper protective layer 5 First reflective layer 6 Second reflective layer 7 Reflective layer
Claims (1)
よって相変化を起こす記録層、上部保護層、第１反射層
および第２反射層が順次積層された光学情報記録媒体で
あって、第１反射層と第２反射層とが、それぞれ一方が
Ｓｉで他方がダイヤモンド状カーボンで形成され、か
つ、記録層の膜厚が１０〜２０Ｏｎｍで、第１反射層お
よび第２反射層の膜厚がそれぞれ５０ｎｍ以上であり、
かつ結晶状態における記録層の吸収率が非晶質状態にお
ける記録層の吸収率より大きいことを特徴とする光学情
報記録媒体。 An optical information recording medium in which a lower protective layer, a recording layer that undergoes a phase change by laser light irradiation, an upper protective layer, a first reflective layer, and a second reflective layer are sequentially laminated on a substrate.
Then, the first reflection layer and the second reflection layer
The other is made of diamond-like carbon with Si,
First, the thickness of the recording layer is 10 to 20 nm, and the first reflective layer and
And the thickness of the second reflective layer is 50 nm or more,
And the absorptance of the recording layer in the crystalline state is
An optical information recording medium characterized by having an absorptance higher than that of a recording layer .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5205569A JP2663843B2 (en) | 1993-07-29 | 1993-07-29 | Optical information recording medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5205569A JP2663843B2 (en) | 1993-07-29 | 1993-07-29 | Optical information recording medium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0744892A JPH0744892A (en) | 1995-02-14 |
| JP2663843B2 true JP2663843B2 (en) | 1997-10-15 |
Family
ID=16509069
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5205569A Expired - Fee Related JP2663843B2 (en) | 1993-07-29 | 1993-07-29 | Optical information recording medium |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2663843B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2806274B2 (en) * | 1994-10-19 | 1998-09-30 | 日本電気株式会社 | Optical information recording medium |
| US6231945B1 (en) | 1997-09-09 | 2001-05-15 | Hitachi, Ltd. | Information recording medium |
| KR20030004747A (en) * | 2001-07-06 | 2003-01-15 | 엘지전자 주식회사 | Optical disc structure of near field recording media |
-
1993
- 1993-07-29 JP JP5205569A patent/JP2663843B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0744892A (en) | 1995-02-14 |
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