JP2004178651A - Optical recording and reproducing medium, and optical recording and reproducing device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording and reproducing medium of practically high recording density wherein the amplitude of a push pull signal is made sufficiently large and a stable tracking servo signal is made possible even when the height of the level difference of a groove is made low in order to make recording and reproducing characteristics satisfactory, and to provide an optical recording and reproducing device using the same. <P>SOLUTION: In the optical recording and reproducing medium 10, at least a groove 3 is formed on a formed substrate 1 and at least a recording layer 6 and a protective layer 19 are formed on the groove 3. A high refractive index filling layer 8 consisting of a material having a high refractive index compared with the refractive indices of the substrate 1 and the protective layer 19 is formed by embedding the rugged part of the groove 3. <P>COPYRIGHT: (C)2004,JPO

Description

【００８６】
なお、上記化１において、Ｒ^１ 及びＲ^２ は、それぞれ独立に、炭素原子数１〜３のアルキル基を表わし、Ｒ^３ は炭素原子数１〜４のアルキル基、炭素原子数２〜４のアルコキシアルキル基又は炭素原子数１〜４のフッ化アルキル基を表わし、Ｘ_１ ⁻ はアニオンを表わす。上記のタイプ４においては、以下に示す材料とした。
【００８７】
Ｒ_１ ：ＣＨ_３
Ｒ_２ ：ＣＨ_３
Ｒ_３ ：ｎ−Ｃ_４ Ｈ_９
Ｘ_１ ⁻ ：Ｃｌ_４ ⁻
上述のタイプ４においては、このシアニン色素とクエンチャーを溶質として、フッ素アルコールを溶媒として、液濃度２％〜５％程度に調節してシアニン色素溶液を作成した。
【００８８】
塗布方法は以下の通りである。
先ずスピンコーターの載置台に基板を固定する。
その後載置台を回転させる。この時の回転数は３００ｓ^−１（回／秒）から５００ｓ^−１の間に維持する。
次に、上述のシアニン色素溶液を基板に滴下する。
そして回転数を１０００ｓ^−１とした後、更に回転数を２０００ｓ^−１とする。
【００８９】
最後に回転数を４０００ｓ^−１から５０００ｓ^−１にして、１秒〜２秒程度保持する。停止後、基板を取り出し、乾燥後、接着層及び保護層を被着する。
上述の例においては、載置台の回転数を調節して膜厚の調整を行った。
【００９０】
このような構成における光学記録再生媒体の各例を、上述の図４において説明した光学記録再生装置においてプッシュプル信号振幅を測定した。なお、トラックピッチは上述したように０．３２μｍ、グルーブ幅は１２５ｎｍ程度であった。
各例におけるプッシュプル信号振幅量を、位相深さの指標となるλ／（ｄ×ｎ）（λ：再生用光の波長、ｄ：グルーブ深さ、ｎ：グルーブの凹凸を埋め込む媒質の屈折率）とともに、以下の表１に示す。
【００９１】
【表１】

【００９２】
上記表１においてプッシュプル信号振幅が０．１３以下の場合は安定なトラッキングサーボを行うことができなかった。すなわち、タイプ１の光学記録再生媒体Ｆ、タイプ３の光学記録再生媒体Ａ、タイプ５の光学記録再生媒体Ａ及びＢである。その他の光学記録再生媒体の構成例では、プッシュプル信号振幅が十分であり、安定したトラッキングサーボを行うことができた。更にこれらの光学記録再生媒体、ウォブルグルーブのアドレス情報を安定に再生することができた。
【００９３】
この結果から明らかなように、高屈折率充填層を設けない従来構成の光学記録再生媒体においては、グルーブの深さが２０ｎｍより小さくなると十分なプッシュプル信号振幅が得られず、安定したトラッキングサーボが行えないが、高屈折率充填層を設ける本発明構成によれば、グルーブ深さが２０ｎｍ以下となり、すなわちλ／１３ｎ以下の段差になっても十分なプッシュプル信号振幅が得られ、安定したトラッキングサーボを行うことができることがわかる。特に高屈折率充填層の材料を屈折率２．０以上とすることによって、良好なトラッキングサーボを行うことができることがわかる。
【００９４】
なお、タイプ３の光学記録再生媒体Ａにおいては、十分なプッシュプル信号振幅が得られていないが、このようにグルーブの深さを１２ｎｍと浅くする場合は、屈折率が２．３以上の材料の高屈折率充填層を設ける場合に、十分なプッシュプル信号振幅が得られることがわかる。
また、深さが２４ｎｍ以上の場合においては、高屈折率充填層を設けない従来構成のタイプ５においても、十分なプッシュプル信号振幅が得られることがわかる。
したがって、本発明においては、グルーブの深さが１２ｎｍ以上２０ｎｍ以下とするときに、有意な効果を得ることができることがわかる。
【００９５】
次に、上述の各例において、トラッキングサーボ及びウォブルグルーブのアドレス情報を安定に再生できる領域、すなわち上記表１においてプッシュプル信号振幅が０．１４以上得られた領域のグルーブ上に、１−７変調で記録再生を行い、ジッターを測定した。この結果を以下の表２に示す。
【００９６】
【表２】

［イメージ］
【００９７】
上記表２において、「−」は十分なプッシュプル信号が得られず、ジッターを測定できないことを示す。
【００９８】
この結果からわかるように、ＤＶＲ型構成の光学記録再生媒体において、グルーブの深さが小さいほうが、ジッター等の記録再生特性が良好となることが明らかである。このことから、ＤＶＲ、Ｂｌｕ−ｒａｙ Ｄｉｓｃ等の高密度光学記録再生媒体においては、グルーブの深さを２５ｎｍ以下とすることが望ましいことがわかる。
【００９９】
すなわち、上記表２の結果から、光学記録再生媒体Ｅ、Ｆの測定を行うことができた領域では、ジッターが１０％以上であり、良好な記録再生特性を実現することは難しいことがわかる。
これに対し、光学記録再生媒体Ａ〜Ｄの安定なトラッキングサーボを得ることができたタイプにおいて、ジッターが９％程度以下であり、良好な記録再生特性を実現できた。
また、タイプ５の従来構成において、光学記録再生媒体Ｃ及びＤのみが良好な記録再生特性を実現することができたが、本発明構成の高屈折率充填層を有するタイプ１，２，３及び４は更に光学記録再生媒体Ａ及びＢにおいても、安定なトラッキングサーボを得た領域で７％ 台の比較的低いジッターを実現することができた。つまり、グルーブの深さが２０ｎｍより小さい光学記録再生媒体においても、更に良好な記録再生特性を実現可能であることがわかる。
【０１００】
前述したように、ＤＶＲのトラックピッチ０．３２μｍは、カットオフ周波数のトラックピッチ（０２３９μｍ）の４／３程度しかなく、従来必要とされた３／２未満（０．３２／０．２３９＝１．３３９）であり、充分なトラッキングサーボ信号振幅（プッシュプル信号振幅）が得られなかったが、本発明構成とすることによって、安定なトラッキングサーボを実現することができた。
【０１０１】
更に、グルーブ深さを２０ｎｍ程度以下とする光学記録再生媒体においても、２．０以上の屈折率材料の高屈折率充填層を設けることによって、安定したトラッキングサーボを行うことができ、良好な記録再生特性を実現できた。
【０１０２】
なお、上述の例においては、グルーブについて再生特性を測定したものであるが、本発明を、図５に示すように、ピット２をグルーブ３に混在して設ける構成とする場合においても、同様の効果を得ることができるのはいうまでもない。
【０１０３】
尚、トラックピッチをカットオフ周波数に対応するトラックピッチの３／２倍以上とするときは、グルーブの深さを２０ｎｍ程度以下とする必要がなく、充分なプッシュプル信号が得られることから、カットオフ周波数のトラックピッチの４／３以上３／２未満のトラックピッチとするときに、本発明による有意な効果が得られることがわかる。
【０１０４】
上述したように、本発明においては、ランドグルーブ記録方式を採る場合と同様に、トラック密度を従来の２倍に高密度化をはかり、グルーブの良好な再生特性を実現できた。読み取り面に近い側にグルーブをピットと混在して形成し、フォーカス点を変えることなく良好なピット信号の再生特性とグルーブの記録再生特性を両立できる光学記録再生媒体を提供することができる。
【０１０５】
以上本発明の実施の形態と実施例の各例を説明したが、本発明は上述の実施例に限定されることなく、相変化材料による記録層等の各層の材料構成を変更するなど、本発明構成を逸脱しない範囲で種々の変形変更が可能であることはいうまでもない。
【０１０６】
また、情報としては記録情報に限定されることなく、信号の記録再生や或いは情報及び信号の記録再生両方の機能を有する光学記録再生媒体及びこれを用いた光学記録再生装置にも適用することができる。
【０１０７】
【発明の効果】
上述したように、本発明によれば、少なくともグルーブを有する光学記録再生媒体において、グルーブの凹凸を埋め込んで、基板及び保護層の屈折率より高い屈折率材料の高屈折率充填層を設けることによって、グルーブの深さが記録再生特性を良好にするために比較的浅くされる場合においても、屈折率の高い高屈折率充填層を介して再生用光をグルーブに入射させることによって、光学的に光路差を補償することができて、再生用光の波長λと媒質の屈折率をｎとしたときに、λ／８ｎ程度にその深さを近づけることができ、安定なトラッキングサーボを可能とすることができる
【０１０８】
特に、高屈折率充填層を、屈折率が２．０以上の材料より構成することによって、プッシュプル信号振幅を十分大として、良好な記録再生特性を得ることができた。
【０１０９】
また、グルーブのトラックピッチがカットオフ周波数の４／３以上３／２未満とされる場合、または再生用光の波長λを４０５ｎｍ±１０ｎｍ、対物レンズの開口数ＮＡを０． ８５±０．０５とする場合において、ＤＶＲやＢｌｕ−ｒａｙ Ｄｉｓｃ型の光学記録再生媒体におけるように、グルーブの深さを２５ｎｍ程度以下としても、本発明によれば、高屈折率充填層を設けることによって光路差を最適化し、十分なプッシュプル信号振幅が得られるようにすることができ、記録再生特性の向上を図ることができる。
【０１１０】
更に、グルーブの少なくとも一部をウォブリンググルーブとする場合においても、本発明構成とすることによって、安定にトラッキングサーボを行って、ウォブル信号を安定に再生することができる。
また、グルーブと混在してピットが形成される場合においても、同様にグルーブと同程度に浅く形成されるピットの読み取りにあたって、高屈折率充填層を設けることによって光路差を補償することによって、その再生特性の向上をはかることができる。
【０１１１】
したがって、本発明によれば、高密度化と共に安定なトラッキングサーボ特性が得られ、良好な記録再生特性の光学記録再生媒体を得ることができて、高記録密度で記録再生特性に優れた光学記録再生媒体及びこれを用いた光学記録再生装置を提供することができる。
【図面の簡単な説明】
【図１】光学記録再生媒体の一例の要部の略線的拡大断面図である。
【図２】Ａは光学記録再生媒体製造用スタンパの一例の製造工程図である。
Ｂは光学記録再生媒体製造用スタンパの一例の製造工程図である。
Ｃは光学記録再生媒体製造用スタンパの一例の製造工程図である。
【図３】光学記録装置の一例の構成図である。
【図４】光学記録再生装置の一例の構成図である。
【図５】光学記録再生媒体の一例の要部の略線的拡大平面図である。
【符号の説明】
１ 基板、２ ピット、３ グルーブ、４ 光反射層、５ 第１の誘電体層、６記録層、７ 第２の誘電体層、８ 高屈折率充填層、９ 接着層、１０ 光学記録再生媒体、１１ 原盤用基板、１２ 感光層、１３ ピットパターン、１３ｎ 反転ピットパターン、１４ グルーブパターン、１４ｎ 反転グルーブパターン、１５ スタンパ、１６ マザースタンパ、１９ 保護層、２５ 光源、３０ 第１の変調光学系、３１ 駆動用ドライバ、３２ 音響光学変調器、４０ 第２の変調光学系、４１ 駆動用ドライバ、４２ 音響光学変調器、４５ 移動光学テブル、４７ ウェッジプリズム、４８ 音響光学偏向器、４９ ウェッジプリズム、５０ 駆動用ドライバ、５１ 電圧制御発振器、５２ 対物レンズ、５４ 光ピックアップ ６１ 光源、６２ コリメートレンズ、６３ グレーティング、６４ 偏光ビームスプリッタ（ＰＢＳ）、６５ １／４波長板、６６ 光ピックアップ、６７ 磁気ヘッド、６８ 回転手段、７０ 偏光ビームスプリッタ、７１ 組み合わせレンズ、７２ フォトダイオード、７３ ディテクタ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording / reproducing medium in which at least a groove is formed on a molded substrate, and at least a recording layer and a protective layer are formed on the groove, and an optical recording / reproducing apparatus using the same.
[0002]
[Prior art]
As an optical recording / reproducing medium, various types of optical disks, which are formed in a disk shape and are optically recorded and / or reproduced, have been put to practical use. Such optical discs include a read-only optical disc in which emboss pits corresponding to data are formed in advance on a disc substrate, a magneto-optical disc for recording data using a magneto-optical effect, and a phase change of a recording film. There is a phase change type optical disk for recording data by utilizing the same.
[0003]
Of these optical disks, writable optical disks such as magneto-optical disks and phase-change optical disks usually have grooves formed along the recording tracks on the disk substrate. Here, the groove is a so-called guide groove formed along a recording track in order to mainly perform tracking servo, and a space between the groove and the opening end of the groove is referred to as a land.
[0004]
In an optical disk having a groove formed thereon, tracking servo is normally performed by a tracking error signal based on a push-pull signal obtained from light reflected and diffracted by the groove. Here, the push-pull signal is to detect the light reflected and diffracted by the groove by two photodetectors arranged symmetrically with respect to the track center, and to take the difference between the outputs from the two photodetectors. Is obtained by
[0005]
By the way, conventionally, in these optical disks, a high recording density has been achieved by improving the reproduction resolution of an optical pickup mounted on a reproduction apparatus. The improvement of the reproduction resolution of the optical pickup is mainly achieved by shortening the wavelength λ of the laser light used for reproducing the data or increasing the numerical aperture NA of the objective lens for condensing the laser light on the optical disk. As a result, it has been realized optically.
[0006]
Conventionally, a so-called write-once CD-R of a CD (Compact Disc), a rewritable MD (Mini Disc) of a magneto-optical disk, a write-once DVD-R or DVD + R of a DVD (Digital Versatile Disc), or a rewritable DVD. In each type of so-called DVD + RW or DVD-RW (both are registered trademarks of optical disks), a groove recording format for recording in a groove has been proposed. For each format of the ISO-based magneto-optical disk, a land recording format for recording on a land has been proposed.
[0007]
On the other hand, in a DVD-RAM (Random Access Memory) or the like, as one method for realizing a higher density of an optical disk, the track density is doubled by increasing the track density by recording on both the groove and the land. A so-called land-groove recording method has been proposed.
[0008]
In addition, land-groove recording methods have been studied for high-density optical disks such as DVR (Digital Video Recordable) or Blu-ray Disc, which are being developed as next-generation optical disks in recent years, and μ-Discs with a reduced MD. As a result, a higher recording density has been achieved.
[0009]
However, when performing land / groove recording on a DVD-RAM or the like, optimal recording / reproduction characteristics cannot be obtained unless the focus point is adjusted during recording / reproduction in recording on a land and recording on a groove. There was a drawback that it caused complication.
[0010]
In addition, in "ISOM 2000 Simulation of Heat Generation and Production On Land / Groove Disc", it is apparent from the report that the recording beam shape is different between the recording on the land and the recording on the groove. It is difficult to equalize the characteristics and the groove recording / reproducing characteristics, and there is a problem that regions having different recording / reproducing characteristics exist in the same optical recording / reproducing medium.
[0011]
Furthermore, in a high-density optical disk such as a DVR, the recording / reproducing characteristics on the land near the reading surface, that is, in the case of DVR, are good, but in the case of the DVR, which is far from the reading surface, that is, in the case of DVR. It has been difficult to maintain good recording / reproducing characteristics in a groove far from the light irradiation side.
[0012]
In a DVR-ROM (Read Only Memory) disk or the like, it is currently possible to directly record a signal in such a land-groove recording format, but the recording / reproducing characteristics between recording on a land and recording on a groove are possible. Is desired to be good and uniform.
[0013]
As described above, in a high-density optical disk such as a DVR, the groove portion is far from the reading surface, and it is difficult to improve the recording / reproducing characteristics in the groove portion.
[0014]
On the other hand, in the manufacturing process of the optical recording / reproducing medium, a method of manufacturing by inverting the concave / convex pattern formed on the substrate is considered. That is, in a normal manufacturing process of an optical recording / reproducing medium, after forming a fine uneven pattern on a photosensitive layer on a glass master by photolithography or the like, a master stamper made of, for example, Ni is formed by plating or the like.
[0015]
Then, the master stamper is placed on a mold or the like to inject resin, or, for example, an ultraviolet curable resin is applied on a substrate, and the stamper is pressed on the resin layer to obtain the desired unevenness. By a so-called 2P (Photo-Polymerization) method of forming a pattern, a substrate of an optical recording / reproducing medium having a predetermined fine uneven pattern formed on the surface can be formed.
[0016]
Therefore, as described above, when the groove portion is provided on the side far from the reading light and the recording / reproducing characteristics cannot be maintained satisfactorily, a copy stamper of the above-mentioned master stamper, that is, a so-called mother stamper is transferred by an electroplating method or the like. By forming, the groove pattern on the substrate is provided on the side close to the reading light by reversing the concavo-convex pattern, so that the recording / reproducing characteristics can be improved.
[0017]
However, in the case of employing the groove recording or land recording format, in order to achieve the same high recording density as in the case of employing the land / groove recording format, the track density is to be twice that in the case of employing the land / groove recording format, that is, It is necessary to reduce the track pitch by half, and the amplitude of a tracking servo signal such as a push-pull signal becomes small, so that stable tracking and reproduction of a wobble signal become difficult.
[0018]
For example, in the land / groove recording format, the track pitch is 0.60 μm, that is, the land width is 0.30 μm, the groove width is 0.30 μm, and the push-pull signal amplitude is about 90%.
[0019]
However, in order to achieve the same recording density in the groove recording format, if the track pitch is set to 0.32 μm, the amplitude of the push-pull signal is about 18%.
[0020]
In a conventional optical disc, the track pitch is set to be about twice to 3/2 of the track pitch of the cutoff frequency of the optical pickup of the reproducing apparatus. Here, the cutoff frequency is a frequency at which the amplitude of the reproduction signal becomes substantially zero, the wavelength of the laser light used for reproducing the data is λ, and the aperture of the objective lens for condensing the laser light on the optical disk. When the number is NA, it is represented by 2NA / λ.
[0021]
In the case of the above-mentioned DVR, since the numerical aperture NA is 0.85 and the wavelength of the reproduction light is λ = 406 nm, the cutoff frequency (2NA / λ) is 4187 lines / mm, and the track pitch in this case is 0. 239 μm.
Assuming that the track pitch of the DVR is 0.32 μm, the track pitch is about ／ (0.32 / 0.239 = 1.339) of the track pitch (0.239 μm) corresponding to the cutoff frequency.
[0022]
Normally, the track pitch is set to about 2 to 3/2 of the track pitch corresponding to the cutoff frequency because the tracking servo signal amplitude is sufficient to realize stable tracking servo and stable wobble signal reproduction. It is necessary to obtain at the level.
[0023]
In recent high-density optical disks, a push-pull signal is used as a tracking error signal. To stably perform tracking servo, the push-pull signal amplitude ratio needs to be about 0.14 or more. Further, it is desired to stably reproduce the wobble signal.
[0024]
On the other hand, in the optical recording / reproducing medium in which the recording layer such as the DVR is made of a phase change material, data with good recording / reproducing characteristics such as jitter is obtained when the depth of the groove is small, and the depth of the groove is small. Is being considered to be 25 nm or less.
[0025]
The depth of the groove having the maximum push-pull signal amplitude is about １ ／ n of the wavelength λ of the reproduction light (n is the refractive index of the medium from the incident surface of the reproduction light to the groove). Here, the refractive index n is 1.49 for PMMA (polymethyl methacrylate), 1.58 for PC (polycarbonate), 1.49 for UV resin, and 1.48 for PSA (Pressure Sensitive Adhesion) as an adhesive. It is about.
[0026]
In the case of the above DVR, the wavelength λ of the reproduction light is 405 nm ± 10 nm, for example, about 406 nm, and the reproduction light is incident from the protective layer side. In this case, the depth λ / 8n at which the push-pull signal amplitude becomes the maximum is 406 (nm) / (8 × 1.49) = 34 (nm).
The push-pull signal amplitude cannot be sufficiently obtained when the amplitude is about λ / 11n or less. However, as described above, when the groove depth is set to 25 nm or less so as to improve the reproduction characteristics in the recording layer made of the phase change material, the λ becomes / 11n or less, a sufficient amplitude of the push-pull signal cannot be obtained, and stable tracking servo cannot be performed.
[0027]
In an optical disc having a recording layer made of a dye material, a high refractive index layer having a relatively high refractive index is provided on the recording layer, and the thickness of the high refractive index layer and the thickness of the recording layer are appropriately selected. As a result, an optical recording medium has been proposed in which the reflectance in the recording layer is reduced to increase the amount of light absorbed by the entire recording layer, thereby increasing the sensitivity and the degree of modulation (for example, see Patent Document 1).
However, when the track pitch is set to about 4/3 or less of the cutoff frequency for the purpose of increasing the recording density as described above, the groove depth is set to about 25 nm or less in order to improve the recording and reproducing characteristics. However, no technique for stabilizing the tracking servo has been reported.
[0028]
[Patent Document 1]
Japanese Patent Publication No. 7-62917
[0029]
[Problems to be solved by the invention]
The present invention solves the above-described problem, and in a high-density optical recording / reproducing medium, the push-pull signal amplitude is sufficiently increased even when the groove depth is reduced in order to improve the recording / reproducing characteristics. It is an object of the present invention to provide a practical high-density optical recording / reproducing medium and an optical recording / reproducing apparatus using the same, enabling stable tracking servo.
[0030]
[Means for Solving the Problems]
The present invention relates to an optical recording / reproducing medium in which at least a groove is formed on a molded substrate, and at least a recording layer and a protective layer are formed on the groove. Is provided with a high refractive index filling layer made of a material having a higher refractive index than the refractive index.
[0031]
Further, according to the present invention, in the above-described configuration, the refractive index of the high refractive index filling layer is set to 2. 0 or more.
Further, according to the present invention, in the above-described configuration, the track pitch of the groove is set to four times the track pitch of the cutoff frequency corresponding to the wavelength λ of the reproducing light for reproducing the recording information of the optical recording and reproducing medium and the numerical aperture NA of the objective lens. It is configured as / 3 or more and less than 3/2.
[0032]
Still further, according to the present invention, in the above-mentioned configuration, the wavelength λ of the reproducing light for reproducing the recorded information of the optical recording / reproducing medium is 405 nm ± 10 nm, and the numerical aperture NA of the objective lens is 0.1. Configure as 85 ± 0.05.
Further, according to the present invention, in the above-described configuration, the depth of the groove is set to be 12 nm or more and 20 nm or less.
[0033]
Further, in the present invention, in the above-described configuration, at least a part of the groove is configured as a wobbling groove.
Further, according to the present invention, in the above structure, pits are formed on the substrate in a manner mixed with the grooves.
[0034]
As described above, in the present invention, in an optical recording / reproducing medium having at least a groove, a high refractive index filling layer of a refractive index material higher than the refractive index of the substrate and the protective layer is provided by embedding the unevenness of the groove. With such a configuration, even when the depth of the groove is made relatively shallow in order to improve the recording / reproducing characteristics, the light for reproduction is supplied to the groove through the high refractive index filling layer having a high refractive index. By making the light incident, the optical path difference can be compensated optically, and when the wavelength λ of the reproducing light and the refractive index of the medium are set to n, the depth can be approximated to λ / 8n, Enables stable tracking servo
[0035]
In particular, by forming the high-refractive-index filling layer from a material having a refractive index of 2.0 or more, as will be described in detail in a later example, the amplitude of the push-pull signal is made sufficiently large to obtain good recording / reproducing characteristics. Could be obtained.
[0036]
When the track pitch of the groove is 4/3 or more and less than 3/2 of the cutoff frequency, or when the wavelength λ of the reproducing light is 405 nm ± 10 nm and the numerical aperture NA of the objective lens is 0. In the case of 85 ± 0.05, according to the present invention, even if the groove depth is set to about 25 nm or less as in the above-mentioned DVR type optical disk, the optical path difference is optimized by providing the high refractive index filling layer. , A sufficient amplitude of the push-pull signal can be obtained, and the recording / reproducing characteristics can be improved.
[0037]
Further, even when at least a part of the groove is formed as a wobbling groove, by adopting the configuration of the present invention, the tracking servo can be performed stably and the wobble signal can be reproduced stably.
Also, in the case where pits are formed coexisting with the groove, when reading the pit formed similarly as shallow as the groove, the optical path difference is compensated by providing a high refractive index filling layer. The reproduction characteristics can be improved.
[0038]
Therefore, according to the present invention, it is possible to obtain an optical recording / reproducing medium capable of improving the recording / reproducing characteristics together with the increase in the recording density and obtaining a stable tracking servo characteristic, and having excellent recording / reproducing characteristics at a high recording density. An optical recording / reproducing medium and an optical recording / reproducing apparatus using the same can be provided.
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following example, a case where the present invention is applied to the above-described DVR or Blu-ray Disc will be described. It is needless to say that various configurations can be adopted without departing from the configuration of the present invention.
[0040]
FIG. 1 is a schematic enlarged sectional view of a main part of an example of an optical recording / reproducing medium according to the present invention. In FIG. 1, reference numeral 1 denotes a substrate on which pits 2 and grooves 3 made of PC, PMMA or the like are formed with a predetermined depth d. On this substrate 1, a light reflection layer 4 made of, for example, an Al alloy, ZnS-SiO₂A first dielectric layer 5 made of a material such as a GeSbTe alloy; a recording layer 6 made of a phase change material such as a GeSbTe alloy;₂A second dielectric layer 7 is sequentially stacked, and a high-refractive-index filling layer 8 made of a material having a higher refractive index than the substrate 1 and a protective layer 9 described later fills the unevenness of the groove 3 thereon. Formed. Then, the adhesive layer 9 made of, for example, a PSA or the like and a protective layer 19 are adhered on the high refractive index filling layer 8, thereby forming the optical recording / reproducing medium 10. Reference numeral 54 denotes an objective lens of the optical pickup, for example, and L denotes reproduction light such as a laser.
[0041]
In this example, the pits 2 and the grooves 3 are formed as protrusions protruding from the substrate 1, but may be formed in a so-called recessed shape. In the illustrated example, the depth d of the groove is the height of the projection.
[0042]
In this case, the protective layer 19, the adhesive layer 9 and the high-refractive-index filling layer 8 serve as a medium from the light incident surface to the pits. The medium becomes the high refractive index filling layer 8.
[0043]
The method for embedding the high refractive index filling layer 8 is as follows: after the first dielectric layer 5, the recording layer 6, and the second dielectric layer 7, the high refractive index filling layer 8 is deposited by sputtering or the like. The upper surface can be formed as a flat surface by performing relatively long etching, for example, plasma etching so as to eliminate a step at the upper portion of the substrate.
[0044]
Next, an example of a manufacturing process of such an optical recording / reproducing medium will be described with reference to manufacturing process diagrams of FIGS.
[0045]
2A, reference numeral 11 denotes a master substrate made of glass or the like. A photosensitive layer 12 made of a photoresist or the like is adhered and formed on the surface of the master substrate 11, and a pit pattern 13 and a groove pattern 13 corresponding to recorded information are formed by predetermined pattern exposure and development by an optical recording device described later. 14 is formed so as to expose, for example, the surface of the master substrate 11, that is, as a so-called concave pattern from which the photosensitive layer 12 is removed.
[0046]
After that, although not shown, a conductive film made of a nickel film or the like is entirely applied by electroless plating or the like so as to cover the patterned photosensitive layer 12, and then the conductive film is applied. The master substrate 11 is attached to an electroforming apparatus, and a nickel plating layer is formed on the conductive film layer by electroplating so as to have a thickness of, for example, about 300 ± 5 μm.
[0047]
Subsequently, the nickel plating layer was peeled off with a cutter or the like from the master substrate 11 on which the nickel plating layer was thickly adhered, and the photosensitive layer on which the uneven pattern was formed was washed with acetone or the like. As shown, a stamper 15 having an inverted pit pattern 13n of an inverted pit pattern 13 on the master 11 and an inverted groove pattern 14n of an inverted pattern of the groove pattern 14, that is, a so-called master stamper is formed.
[0048]
After that, for example, a release agent is applied on the surface of the stamper 15 on which the concavo-convex pattern is formed, and then, as shown in FIG. 2C, a mother stamper 16 to which the concavo-convex pattern of the stamper 15 is transferred is formed by, for example, electroplating. I do.
[0049]
This mother stamper 16 has a predetermined pit pattern 13 and a groove pattern 14 formed in a concave shape, similarly to the pattern of the photosensitive layer 12 on the master substrate 11 described in FIG. 2A. Therefore, the groove on the substrate formed by injection molding or the like from the mother stamper 16 is a pattern protruding from the substrate, and the groove surface can be on the side closer to the light-receiving side of the reproduction light.
[0050]
Next, a specific exposure process for the photosensitive layer 12 on the master 11 described with reference to FIG. 2A will be described in detail together with a configuration example of the optical recording apparatus.
[0051]
First, the configuration of the optical recording device will be described.
In the above-described pattern exposure step, a method of condensing a laser beam with an objective lens and exposing a photoresist on a master disk substrate is generally employed. FIG. 3 shows an example of such an optical recording apparatus.
[0052]
In FIG. 3, reference numeral 25 denotes a light source such as a gas laser. The light source is not particularly limited and can be appropriately selected and used. In this example, a laser source that oscillates a recording laser beam of a Kr laser (wavelength λ = 351 nm) was used.
[0053]
The laser beam LB0 emitted from the light source 20 is partially reflected by the beam splitter BS2 and the beam splitter BS1. Although not shown, a photodetector, an electric modulator, and the like are provided at the subsequent stage of the beam splitter BS2, so that the laser light output is detected and feedback is applied, so that more stable laser light can be obtained.
[0054]
The laser beams LB1 and LB2 reflected by the beam splitters BS1 and BS2 are guided to first and second modulation optical systems 30 and 40. In the first modulation optical system 30, the laser light is condensed by the lens L11, and an acousto-optic modulator (AOM (Acoustic Optical Modulator) 1) 32 is arranged on the focal plane.
[0055]
Ultrasonic waves corresponding to the recording signal are input from the driver 31 to the acousto-optic modulator 32, and the intensity of the laser beam is intensity-modulated based on the ultrasonic waves. The laser light is diffracted by the diffraction grating of the acousto-optic modulator 32, and only the first-order diffracted light of the diffracted light is transmitted through the slit.
[0056]
The first-order diffracted light having undergone the intensity modulation is condensed by the lens L12, reflected by the mirror M1, bent in the traveling direction by 90 °, and then transmitted to the moving optical table 45 via the λ / 2 wave plate HWP. It is introduced horizontally and along the optical axis and enters a polarizing beam splitter (PBS).
[0057]
Similarly, in the second modulation optical system 40, the laser light is condensed by the lens L21, is incident on the acousto-optic modulator (AOM2) 42 disposed on the focal plane, and is recorded by the driver 31. Is intensity-modulated on the basis of the ultrasonic wave corresponding to. The divergent laser light is similarly condensed by the lens L22, then reflected by the mirror M2, the traveling direction is bent by 90 °, and introduced into the moving optical table 45 horizontally and along the optical axis, and the deflecting optical system Introduced to OD.
[0058]
When a groove is formed by the laser beam LB2 and the groove is formed as a wobble groove, the beam is optically deflected by the deflection optical system OD on the moving optical table 45, is reflected by the mirror M4, and changes its traveling direction again. The beam is bent by 90 ° and enters the polarizing beam splitter PBS.
[0059]
The laser beam LB1 transmitted through the polarizing beam splitter PBS and the laser beam LB2 whose traveling direction is bent again by 90 ° by the polarizing beam splitter PBS are reflected by the mirror M5 after having a predetermined beam diameter by the magnifying lens L3. Then, the light is guided to the objective lens 54, and is focused on the photosensitive layer 12 on the master substrate 11 by the objective lens 54. The master substrate 11 is rotated as shown by an arrow a by a rotation driving means (not shown). The dashed line c indicates the central axis of the substrate 11.
[0060]
The recording laser beams LB1 and LB2 are translated by the moving optical table 45. As a result, a latent image corresponding to the concavo-convex pattern corresponding to the laser beam irradiation locus is formed over the entire surface of the photosensitive layer 12.
[0061]
Here, the deflection optical system OD includes a wedge prism 47, an acousto-optic deflector (AOD) 48, and a wedge prism 49. The laser beam LB2 enters the acousto-optic deflector 48 via the wedge prism 47, and is subjected to optical deflection by the acousto-optic deflector 48 so as to correspond to a desired exposure pattern.
[0062]
As an acousto-optic element used for the acousto-optic deflector 48, for example, tellurium oxide (TeO₂An acousto-optical element comprising: The laser light LB2 optically deflected by the acousto-optic deflector 48 is emitted from the deflection optical system OD via the wedge prism 49.
[0063]
The wedge prisms 47 and 49 receive the laser beam LB2 so as to satisfy the Bragg condition on the lattice plane of the acousto-optic device of the acousto-optic deflector 48, and the acousto-optic deflector 48 applies the laser beam LB2 to the laser beam LB2. It has a function to keep the horizontal height of the beam unchanged even when optical deflection is performed. In other words, the wedge prisms 47 and 49 and the acousto-optic deflector 48 have the grating surface of the acousto-optic element of the acousto-optic deflector 48 satisfying the Bragg condition with respect to the laser beam LB2, and are emitted from the deflection optical system OD. The laser light is arranged so that the horizontal height of the laser light does not change.
[0064]
A driving driver 50 for driving the acousto-optic deflector 48 is attached to the acousto-optic deflector 48, and the driving driver 50 has a voltage controlled oscillator (VCO) 51. Is supplied by being modulated with a sine wave. When the photosensitive layer is exposed, a signal corresponding to a desired exposure pattern is input from the voltage controlled oscillator 51 to the driving driver 50, and the driving driver 50 drives the acousto-optic deflector 48 in response to the signal. As a result, the laser beam LB2 is subjected to optical deflection corresponding to the desired wobbling.
[0065]
Specifically, for example, when address information is added to a groove by wobbling the groove at a frequency of 956.5 kHz, for example, a high-frequency signal having a center frequency of 224 MHz is converted into a control signal having a frequency of 956.5 kHz. Thus, a sine wave signal is supplied from the voltage controlled oscillator 51 to the driving driver 50.
[0066]
In response to this signal, the driving driver 50 drives the acousto-optic deflector 48 to change the Bragg angle of the acousto-optic element of the acousto-optic deflector 48, thereby supporting wobbling at a frequency of 956.5 kHz. Optical deflection is performed on the laser light. Thus, optical deflection was performed so that the spot position of the laser beam condensed on the photosensitive layer vibrated in the radial direction of the master substrate 11 at a frequency of 956.5 kHz and an amplitude of ± 10 nm.
[0067]
Here, the polarization beam splitter PBS reflects S-polarized light and transmits P-polarized light, and the optically deflected laser beam LB2 is S-polarized and is reflected at the PBS.
[0068]
Further, the laser beam LB1 emitted from the first modulation optical system 30 is rotated by 90 ° by passing through the λ / 2 wavelength plate HWP, so that the laser beam LB1 becomes P-polarized light and transmits through PBS. I do.
[0069]
In the examples described later, the numerical aperture NA of the objective lens 54 was set to 0.9. As the acousto-optic modulators 32 and 42 of the first and second modulation optical systems 30 and 40, tellurium oxide (TeO₂) Was used. The signal supplied from the input terminal via the driver 41 is, for example, a 1-7 modulation signal when forming a pit, and is a constant level DC (direct current) signal when forming a groove.
[0070]
In the embodiments described later, as the optical lenses of the modulation optical systems 30 and 40, the focal lengths of the condenser lenses L11 and L21 are set to 80 mm, the focal lengths of the collimating lenses L12 and L22 are set to 100 mm. The focal length of the magnifying lens L3 was set to 50 mm.
[0071]
Further, the exposure conditions of the optical recording apparatus in the embodiments described below are such that the laser power is set to 0.4 mJ / m for the wobble groove, the track pitch is set to 0.32 μm by DC modulation by the second modulation optical system 40, and the master substrate 11 The upper photosensitive layer 12 was subjected to pattern exposure in a spiral pattern.
[0072]
Then, after performing the above-described pattern exposure, the master substrate 11 is placed on a turntable of a developing machine such that the photosensitive layer 12 is on the top, and the surface of the master substrate 11 is horizontal. Rotate. In this state, a developing solution is dropped on the photosensitive layer 12 to perform development processing of the photosensitive layer 12, and a concavo-convex pattern based on a recording signal is formed in a signal forming area. Form a master for media production.
[0073]
Thereafter, in the manufacturing process described with reference to FIGS. 2B to 2C, a stamper for manufacturing an optical recording / reproducing medium in which a concave / convex pattern formed by inverting the concave / convex pattern formed by the pattern exposure and development steps by the above-described optical recording device is formed. In this case, a so-called mother stamper is formed, and a substrate for an optical recording / reproducing medium made of a light-transmissive resin such as polycarbonate is formed from the mother stamper by injection molding or 2P method in an embodiment described later. Mold.
[0074]
Then, the thickness of the formed substrate is set to 1.1 mm, and the light reflection layer 4 made of an Al alloy or the like and the first dielectric layer made of ZnS-SiO2 or the like are formed on the signal forming surface as described in FIG. 5, a recording layer 6 made of a phase change material made of a GeSbTe alloy or the like, ZnS-SiO₂A second dielectric layer 7 made of a material having a high refractive index, which is made of a material having a higher refractive index than the material of the substrate and a protective layer to be described later. Etching such as plasma etching is performed until the upper surface of 8 is flattened. Thereafter, a protective layer 19 made of a thermoplastic resin sheet or the like is adhered on the high refractive index filling layer 8 via an adhesive layer 9 made of PSA or the like.
[0075]
Through such a manufacturing process, the optical recording / reproducing medium of, for example, the DVR format according to the present invention described with reference to FIG. 1 is formed.
[0076]
The evaluation of the reproduction characteristics of the concavo-convex pattern of the optical recording / reproducing medium thus formed is performed using an optical recording / reproducing apparatus having an optical system having a wavelength λ = 406 nm and a numerical aperture NA = 0.85. FIG. 4 shows a schematic configuration of this device.
[0077]
In FIG. 4, reference numeral 61 denotes a light source such as a semiconductor laser having a wavelength λ = 406 nm, for example. A laser beam emitted from the light source is collimated by a collimator lens 62, and a zero-order light (main beam) and It is divided into three beams of ± primary light (sub beam). These three beams (P-polarized light) pass through the polarization beam splitter 64 and the quarter-wave plate 65 as circularly polarized light, and as described with reference to FIG. 1, the objective lens having the numerical aperture NA = 0.85. The light is focused on a predetermined recording track of the optical recording / reproducing medium 10 by the optical pickup 66. The spot at the center of the main beam is used for recording and reproduction of recorded information, and the light spot of the sub beam is used for detecting a tracking error. Reference numeral 68 denotes a rotating means for rotating the optical recording / reproducing medium 10 as shown by an arrow b. The solid line d indicates the rotation axis of the optical recording / reproducing medium 10.
[0078]
Then, the reflected light from the optical recording / reproducing medium 10 passes through the optical pickup 66 and the 波長 wavelength plate 65 again, so that the circularly polarized light becomes S-polarized light, is reflected by the polarization beam splitter 64, and is incident on the combination lens 71.
[0079]
The laser light incident on the combination lens 71 is incident on the photodiode 72 via a lens that gives astigmatism to the laser beam, is converted into an electric signal corresponding to the intensity of the beam, and is converted into a servo signal (focus error signal and tracking signal). The error signal is output to the servo circuit. The photodiode 72 has divided detectors 73 (A to H). The return light of the main beam enters the four-divided detectors A to D located at the center of the detector 73, and the return light of the sub-beam enters E to H located on both sides of the detector 73.
[0080]
The signals A to H output from the detectors A to H are subjected to addition and subtraction processing in a predetermined circuit system (not shown) as follows, and a predetermined signal is output. In this example, a tracking servo signal was obtained by a differential push-pull (DPP) method using the three laser beams irradiated at predetermined intervals. That is,
Reproduction signal of optical recording / reproduction medium = (A + B + C + D)
Pit reproduction signal (for example, EFM signal) = (A + B + C + D)
Push-pull signal = (B + C)-(A + D)
Differential push-pull (tracking servo) signal = (B + C)-(A + D) -k ((EF) + (GH))
(K is a predetermined constant)
And
With the optical recording / reproducing apparatus having such a configuration, the above-described optical recording / reproducing medium according to the present invention was evaluated in the following examples.
[0081]
【Example】
In the following example, the depth of the groove is changed from 12 nm to 34 nm by changing the thickness of the photosensitive layer 12 in the type 1 to type 5 configuration in which the material of the high refractive index filling layer 8 is changed. I let it. In the following examples, an optical recording / reproducing medium A of 12 nm, an optical recording / reproducing medium B of 16 nm, an optical recording / reproducing medium C of 20 nm, an optical recording / reproducing medium D of 24 nm, an optical recording / reproducing medium E of 29 nm, An optical recording / reproducing medium F having a thickness of 34 nm was formed.
The materials and the refractive index n of the high refractive index filling layer in types 1 to 4 are as follows. Type 5 has a configuration in which a high refractive index filling layer is not provided.
[0082]
Type 1: Titanium oxide (TiO₂), N = 2.6
Type 2: zinc sulfide (ZnS), n = 2.3
Type 3: Neodymium oxide (Nd₂O₃), N = 2.0
Type 4: low reactive cyanine dye, n = 2.4
[0083]
The high-refractive-index filling layers of types 1 to 3 have a degree of vacuum of 10^-3After setting the pressure to about Pa, the respective materials were targeted in an Ar gas atmosphere of about 1 to 3 Pa, and the film was formed with an output of 1 to 3 KW. For each row, the film thickness was adjusted by adjusting the film forming time, and the film was formed on the second dielectric layer so as to embed the groove at each depth.
[0084]
Further, as the type 4 cyanine dye, a material represented by the following chemical formula 1 was used. The film thickness was adjusted by using fluorine alcohol as a solvent, the viscosity was adjusted, and the rotation speed of spin coating was adjusted to form a groove so as to embed the groove on the second dielectric layer.
[0085]
Embedded image

[0086]
In the above formula 1, R¹And R²Each independently represents an alkyl group having 1 to 3 carbon atoms;³Represents an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 2 to 4 carbon atoms or a fluorinated alkyl group having 1 to 4 carbon atoms;₁ ⁻Represents an anion. In the above-mentioned type 4, the following materials were used.
[0087]
R₁: CH₃
R₂: CH₃
R₃: NC₄H₉
X₁ ⁻: Cl₄ ⁻
In the type 4 described above, a cyanine dye solution was prepared by adjusting the liquid concentration to about 2% to 5% using the cyanine dye and the quencher as a solute and using a fluoroalcohol as a solvent.
[0088]
The application method is as follows.
First, the substrate is fixed on the mounting table of the spin coater.
Thereafter, the mounting table is rotated. The rotation speed at this time is 300s^-1(Times / sec) to 500s^-1Keep between.
Next, the above-mentioned cyanine dye solution is dropped on the substrate.
And the rotation speed is 1000s^-1After that, further increase the rotation speed to 2000s^-1And
[0089]
Finally, set the rotation speed to 4000s^-1From 5000s^-1And hold for about 1 to 2 seconds. After stopping, the substrate is taken out, and after drying, the adhesive layer and the protective layer are applied.
In the above example, the film thickness was adjusted by adjusting the rotation speed of the mounting table.
[0090]
For each example of the optical recording / reproducing medium having such a configuration, the push-pull signal amplitude was measured in the optical recording / reproducing apparatus described with reference to FIG. As described above, the track pitch was 0.32 μm, and the groove width was about 125 nm.
The amplitude of the push-pull signal in each example is defined as λ / (d × n) (λ: wavelength of light for reproduction, d: groove depth, n: refractive index of a medium for embedding concaves and convexes of the groove, which is an index of phase depth. ) Are shown in Table 1 below.
[0091]
[Table 1]

[0092]
In Table 1, when the push-pull signal amplitude was 0.13 or less, stable tracking servo could not be performed. That is, a type 1 optical recording / reproducing medium F, a type 3 optical recording / reproducing medium A, and a type 5 optical recording / reproducing medium A and B. In the other examples of the configuration of the optical recording / reproducing medium, the push-pull signal amplitude was sufficient, and stable tracking servo could be performed. Further, the address information of the optical recording / reproducing medium and the wobble groove could be reproduced stably.
[0093]
As is apparent from the results, in the conventional optical recording / reproducing medium having no high refractive index filling layer, when the groove depth is smaller than 20 nm, a sufficient push-pull signal amplitude cannot be obtained, and a stable tracking servo is not obtained. However, according to the configuration of the present invention in which the high refractive index filling layer is provided, a sufficient push-pull signal amplitude can be obtained even when the groove depth is 20 nm or less, that is, a step of λ / 13 n or less, and stable. It turns out that tracking servo can be performed. In particular, it can be seen that good tracking servo can be performed by setting the material of the high refractive index filling layer to have a refractive index of 2.0 or more.
[0094]
In the type 3 optical recording / reproducing medium A, a sufficient push-pull signal amplitude is not obtained. However, when the groove depth is reduced to 12 nm, a material having a refractive index of 2.3 or more is used. It can be seen that a sufficient push-pull signal amplitude can be obtained when the high refractive index filling layer is provided.
In addition, when the depth is 24 nm or more, a sufficient push-pull signal amplitude can be obtained even in Type 5 having the conventional configuration in which the high refractive index filling layer is not provided.
Therefore, in the present invention, it can be seen that a significant effect can be obtained when the depth of the groove is 12 nm or more and 20 nm or less.
[0095]
Next, in each of the above examples, 1-7 are set on the groove in the area where the address information of the tracking servo and the wobble groove can be stably reproduced, that is, in the area where the push-pull signal amplitude is 0.14 or more in Table 1 above. Recording and reproduction were performed by modulation, and jitter was measured. The results are shown in Table 2 below.
[0096]
[Table 2]

[image]
[0097]
In Table 2, "-" indicates that a sufficient push-pull signal was not obtained and jitter could not be measured.
[0098]
As can be seen from the results, it is clear that, in the optical recording / reproducing medium of the DVR type configuration, the smaller the groove depth, the better the recording / reproducing characteristics such as jitter. From this, it is understood that in a high-density optical recording / reproducing medium such as DVR or Blu-ray Disc, it is desirable to set the groove depth to 25 nm or less.
[0099]
That is, from the results in Table 2, it can be seen that in the region where the optical recording / reproducing media E and F could be measured, the jitter was 10% or more, and it was difficult to achieve good recording / reproducing characteristics.
On the other hand, in the type in which the stable tracking servo of the optical recording / reproducing media A to D was obtained, the jitter was about 9% or less, and good recording / reproducing characteristics were realized.
In the conventional type 5 configuration, only the optical recording / reproducing media C and D were able to achieve good recording / reproducing characteristics. However, the type 1, 2, 3, and 4 having the high refractive index filling layer according to the present invention configuration. In No. 4, even in the optical recording / reproducing media A and B, a relatively low jitter of the order of 7% could be realized in a region where a stable tracking servo was obtained. That is, it can be seen that even with an optical recording / reproducing medium having a groove depth of less than 20 nm, even better recording / reproducing characteristics can be realized.
[0100]
As described above, the track pitch of DVR of 0.32 μm is only about 4/3 of the track pitch of the cutoff frequency (0239 μm), and is less than 3/2 (0.32 / 0.239 = 1) conventionally required. .339), and a sufficient tracking servo signal amplitude (push-pull signal amplitude) could not be obtained. However, with the configuration of the present invention, stable tracking servo could be realized.
[0101]
Further, even in an optical recording / reproducing medium having a groove depth of about 20 nm or less, by providing a high refractive index filling layer of a refractive index material of 2.0 or more, stable tracking servo can be performed and good recording can be performed. The reproduction characteristics were realized.
[0102]
In the above-described example, the reproduction characteristic is measured for the groove. However, the same applies to the case where the present invention is configured to provide the pits 2 in the groove 3 as shown in FIG. It goes without saying that the effect can be obtained.
[0103]
When the track pitch is set to 3/2 times or more of the track pitch corresponding to the cut-off frequency, the groove depth does not need to be set to about 20 nm or less, and a sufficient push-pull signal can be obtained. It can be seen that a significant effect according to the present invention can be obtained when the track pitch is not less than 4/3 and less than 3/2 of the off-frequency track pitch.
[0104]
As described above, in the present invention, as in the case where the land-groove recording method is adopted, the track density is increased to twice the conventional one, and good reproduction characteristics of the groove can be realized. It is possible to provide an optical recording / reproducing medium in which a groove is formed on the side close to the reading surface in a manner mixed with pits, and both good pit signal reproduction characteristics and good groove recording / reproduction characteristics can be achieved without changing the focus point.
[0105]
Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described examples, and the present invention is not limited to the above-described examples, such as changing the material configuration of each layer such as a recording layer made of a phase change material. It goes without saying that various modifications can be made without departing from the scope of the invention.
[0106]
Further, the information is not limited to recorded information, and may be applied to an optical recording / reproducing medium having a function of recording / reproducing a signal or recording / reproducing both information and a signal, and an optical recording / reproducing apparatus using the same. it can.
[0107]
【The invention's effect】
As described above, according to the present invention, in an optical recording / reproducing medium having at least a groove, by embedding unevenness of the groove, by providing a high refractive index filling layer of a refractive index material higher than the refractive index of the substrate and the protective layer. Even when the depth of the groove is made relatively shallow in order to improve the recording / reproducing characteristics, the reproduction light is made incident on the groove through the high refractive index filling layer having a high refractive index, so that the optical path is optically controlled. The difference can be compensated, and when the wavelength λ of the reproducing light and the refractive index of the medium are set to n, the depth can be made close to λ / 8n, thereby enabling stable tracking servo. Can
[0108]
In particular, by forming the high refractive index filling layer from a material having a refractive index of 2.0 or more, the amplitude of the push-pull signal was made sufficiently large, and good recording / reproducing characteristics could be obtained.
[0109]
When the track pitch of the groove is 4/3 or more and less than 3/2 of the cutoff frequency, or when the wavelength λ of the reproducing light is 405 nm ± 10 nm and the numerical aperture NA of the objective lens is 0. In the case of 85 ± 0.05, according to the present invention, a high refractive index filling layer is provided even if the depth of the groove is set to about 25 nm or less, as in a DVR or Blu-ray Disc type optical recording / reproducing medium. As a result, the optical path difference can be optimized, a sufficient push-pull signal amplitude can be obtained, and the recording / reproducing characteristics can be improved.
[0110]
Further, even when at least a part of the groove is formed as a wobbling groove, by adopting the configuration of the present invention, the tracking servo can be performed stably and the wobble signal can be reproduced stably.
Also, in the case where pits are formed coexisting with the groove, when reading the pit formed similarly as shallow as the groove, the optical path difference is compensated by providing a high refractive index filling layer. The reproduction characteristics can be improved.
[0111]
Therefore, according to the present invention, stable tracking servo characteristics can be obtained along with the increase in density, and an optical recording / reproducing medium having good recording / reproducing characteristics can be obtained. A reproducing medium and an optical recording / reproducing apparatus using the same can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic enlarged cross-sectional view of a main part of an example of an optical recording / reproducing medium.
FIG. 2A is a manufacturing process diagram of an example of a stamper for manufacturing an optical recording / reproducing medium.
B is a manufacturing process diagram of an example of a stamper for manufacturing an optical recording / reproducing medium.
C is a manufacturing process diagram of an example of a stamper for manufacturing an optical recording / reproducing medium.
FIG. 3 is a configuration diagram of an example of an optical recording device.
FIG. 4 is a configuration diagram of an example of an optical recording / reproducing apparatus.
FIG. 5 is a schematic enlarged plan view of a main part of an example of an optical recording / reproducing medium.
[Explanation of symbols]
Reference Signs List 1 substrate, 2 pits, 3 grooves, 4 light reflecting layers, 5 first dielectric layer, 6 recording layer, 7 second dielectric layer, 8 high refractive index filling layer, 9 adhesive layer, 10 optical recording / reproducing medium , 11 master substrate, 12 photosensitive layer, 13 pit pattern, 13n inverted pit pattern, 14 groove pattern, 14n inverted groove pattern, 15 stamper, 16 mother stamper, 19 protective layer, 25 light source, 30 first modulation optical system, 31 driving driver, 32 acousto-optic modulator, 40 second modulation optical system, 41 driving driver, 42 acousto-optic modulator, 45 moving optical table, 47 wedge prism, 48 acousto-optic deflector, 49 wedge prism, 50 Driving driver, 51 Voltage controlled oscillator, 52 Objective lens, 54 Optical pickup 61 Light source, 62 Torenzu, 63 grating 64 a polarization beam splitter (PBS), 65 1/4 wavelength plate, 66 optical pickup, 67 a magnetic head 68 rotating device, 70 a polarizing beam splitter, 71 a combination lens, 72 a photodiode, 73 a detector

Claims (14)

An optical recording / reproducing medium in which at least a groove is formed on a molded substrate, and at least a recording layer and a protective layer are formed on the groove,
An optical recording / reproducing medium, characterized by comprising a high refractive index filling layer made of a material having a higher refractive index than the refractive index of the substrate and the protective layer by embedding the concaves and convexes of the groove. The refractive index of the high refractive index filling layer is 2. 2. The optical recording / reproducing medium according to claim 1, wherein the value is 0 or more. The track pitch of the groove is at least 4/3 and less than 3/2 of the track pitch of the cutoff frequency corresponding to the wavelength λ of the reproducing light for reproducing the recording information of the optical recording / reproducing medium and the numerical aperture NA of the objective lens. The optical recording / reproducing medium according to claim 1, wherein the optical recording / reproducing medium is formed. The wavelength λ of the reproducing light for reproducing the information recorded on the optical recording / reproducing medium is 405 nm ± 10 nm, and the numerical aperture NA of the objective lens is 0. 2. The optical recording / reproducing medium according to claim 1, wherein the value is set to 85 ± 0.05. 2. The optical recording / reproducing medium according to claim 1, wherein the groove has a depth of 12 nm or more and 20 nm or less. 2. The optical recording / reproducing medium according to claim 1, wherein at least a part of the groove is formed as a wobbling groove. 2. The optical recording / reproducing medium according to claim 1, wherein pits are formed on the substrate in combination with the grooves. An optical recording and reproducing apparatus using an optical recording and reproducing medium in which at least a groove is formed on a molded substrate and at least a recording layer and a protective layer are formed on the groove,
The optical recording medium according to claim 1, wherein the optical recording / reproducing medium is provided with a high refractive index filling layer formed of a material having a high refractive index compared to the refractive index of the substrate and the protective layer by embedding the concaves and convexes of the groove. Recording and playback device. The high refractive index filling layer of the optical recording / reproducing medium has a refractive index of 2. The optical recording / reproducing apparatus according to claim 8, wherein the value is 0 or more. The track pitch of the groove of the optical recording / reproducing medium is 4/3 of the track pitch of the cutoff frequency corresponding to the wavelength λ of the reproducing light for reproducing the recording information of the optical recording / reproducing medium and the numerical aperture NA of the objective lens. The optical recording / reproducing apparatus according to claim 8, wherein the ratio is less than 3/2. The wavelength λ of the reproducing light for reproducing the information recorded on the optical recording / reproducing medium is 405 nm ± 10 nm, and the numerical aperture NA of the objective lens is 0. 9. The optical recording / reproducing apparatus according to claim 8, wherein 85 ± 0.05 is set. 9. The optical recording / reproducing apparatus according to claim 8, wherein the groove of the optical recording / reproducing medium has a depth of 12 nm or more and 20 nm or less. 9. The optical recording / reproducing medium according to claim 8, wherein at least a part of the groove is a wobbling groove.
The optical recording / reproducing apparatus according to claim 1. 9. The optical recording / reproducing apparatus according to claim 8, wherein pits are formed on the substrate of the optical recording / reproducing medium in a manner mixed with the grooves.

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