JP2004354712A

JP2004354712A - Hologram recording medium and recording and reproducing apparatus

Info

Publication number: JP2004354712A
Application number: JP2003152522A
Authority: JP
Inventors: Takashi Kuhara; 隆久原; Haruhiko Kono; 治彦河野; Takeshi Kusakabe; 毅日下部; Toshiyuki Ogawa; 敏幸尾川; Kanji Tsuji; 寛司辻
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-05-29
Filing date: 2003-05-29
Publication date: 2004-12-16
Anticipated expiration: 2023-05-29
Also published as: JP4281416B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording medium capable of performing recording and reproduction without putting in a light shielding case and to provide a recording and reproducing apparatus. <P>SOLUTION: A lower shielding layer 2 for absorbing and shielding information light and reproduction light for recording is formed on a transparent substrate 1. Then, a hologram layer 3 as an information layer on which information is recorded by volume holography is disposed on the layer 2. An upper shielding layer 4 for absorbing and shielding information light and reproduction light for recording is further formed on the hologram layer 3. A layer of 20 μm thickness comprising phthalocyanine may be provided as the upper shielding layer 4. A protective layer 5 of a polycarbonate which is also used for the substrate 1 is then disposed on the layer 4 to fabricate the objective multilayer recording medium 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明はホログラム記録媒体と、このホログラム記録媒体を用いた記録再生装置に関する。
【０００２】
【従来の技術】
近年、情報記録技術の向上に従い、磁気記録媒体、光磁気記録媒体、熱相変化媒体の記録密度は飛躍的に上がっている。しかし、各記録方式ともｂｉｔｂｙｂｉｔの記録方式であり、１ｂｉｔ単位で記録再生を行わざるを得ないため、データ転送速度に限界があり、高速多重通信の時代の要請に答えられないという問題を生じている。このような、時代の進展に対し、次世代の高記録密度、高速データ転送速度を兼ね備えた記録方式として、ホログラムメモリが注目されている（例えば、特許文献１に記載）。
【０００３】
ホログラムメモリの開発においては、高速で安定して記録再生でき、安価な記録メディアであることが必要となる。現状では無機又は有機ホログラム材料の開発が行われており、ニオブ酸リチウム、カルコゲナイト系材料、フォトポリマー、アゾベンゼン系材料、フォトリフラクティブ材料、ジアリールエテン系材料、フルキド系材料などの材料が検討されている。
【０００４】
特にフォトポリマーやアゾベンゼン系材料等が注目されているが、フォトポリマーなどの材料は感光性が強く、蛍光灯の下や太陽光に直接暴露すると感光されてしまい、情報の記録ができなくなる。そのため、光を透過しない感光防止ケースに入れ、記録用窓を設けて、シャッタ機構などを用いて、記録時だけ光が記録媒体に入射するように工夫されている。
【０００５】
また、シャッタ機構を設けない場合は、感光防止ケースごとドライブ内にローディングして、ドライブ内で外光の影響を受けない状態で感光防止ケースから記録媒体を取り出し記録再生するという方法を取るという試みもなされている。
【０００６】
【特許文献１】
特開２００１−６６９７６号公報
【０００７】
【発明が解決しようとする課題】
しかし、感光防止ケースに入れることにより、記録媒体の大きさが大きくなり持ち運びにくくなると共に、同一のドライブで従来のＣＤ−ＲＯＭ、ＣＤ−Ｒ／ＲＷ、ＤＶＤ−ＲＡＭ、ＤＶＤ＋Ｒ／ＲＷ、ＤＶＤ−Ｒ／ＲＷなどの記録媒体との互換性が保てなくなる。また、感光防止ケースのローディングやシャッタの開け閉め機構などが複雑になるという問題点がある。
【０００８】
そこで本発明は、感光防止のケースに入れることなく、記録再生できるホログラム記録媒体および記録再生装置を提供することを目的とする。
【０００９】
【課題を解決するための手段】
この課題を解決するために本発明は、情報光と記録用参照光との干渉によって生じる干渉縞を記録して、再生用参照光により前記情報光を再生させることによって、情報を記録再生させるホログラム記録装置で用いられるホログラム記録媒体において、少なくとも情報を記録する記録層の周囲に、情報光及び記録用再生光を吸収または反射し遮蔽するための光遮蔽層を設け、この光遮蔽層に対し特定の波長で閾値強度以上の光が照射されている時だけ光遮蔽層の光の透過率が増加して遮蔽層を光が透過して、前記記録層への干渉縞の書き込みと前記記録層からの情報の再生を可能とするホログラム記録媒体である。
【００１０】
これにより、シャッタ機構などの機械的遮光手段を用いることなく、情報の記録時と再生時にだけ記録層に光が照射されるため、外光による感光の影響を受けずに情報の記録と再生が可能なホログラム記録媒体を実現することができる。
【００１１】
また、感光防止ケースを用いる必要がないため、ホログラム記録媒体の小型化が可能となる。
【００１２】
【発明の実施の形態】
本発明の請求項１記載の発明は、情報光と記録用参照光との干渉によって生じる干渉縞を記録して、再生用参照光により情報光を再生させることによって、情報を記録再生させるホログラム記録装置で用いられるホログラム記録媒体において、少なくとも情報を記録する記録層の周囲に、情報光及び記録用再生光を吸収または反射し遮蔽するための光遮蔽層を設け、この光遮蔽層に対し特定の波長で閾値強度以上の光が照射されている時だけ光遮蔽層の光の透過率が増加して遮蔽層を光が透過して、記録層への干渉縞の書き込みと記録層からの情報の再生を可能とするホログラム記録媒体であり、光遮蔽層に対し特定の波長で閾値強度以上の光が照射されている時だけ光遮蔽層の光の透過率が増加して遮蔽層を光が透過することにより、情報の記録時と再生時にだけ記録層に光が照射される。
【００１３】
請求項２記載の発明は、情報光と記録用参照光との干渉によって生じる干渉縞を記録して、再生用参照光により情報光を再生させることによって、情報を記録再生させるホログラム記録装置で用いられるホログラム記録媒体において、少なくとも情報を記録する記録層の周囲に、情報光及び記録用再生光を吸収または反射し遮蔽するための光遮蔽層を設け、この光遮蔽層に対して特定の波長で閾値強度以上の光が照射されて、非可逆的に光遮蔽層の光の透過率が増加して、記録層への干渉縞の書き込みと記録層からの情報の再生を可能とするホログラム記録媒体であり、光遮蔽層に対して特定の波長で閾値強度以上の光が照射されて、非可逆的に光遮蔽層の光の透過率が増加することにより、情報の記録時と再生時にだけ記録層に光が照射される。
【００１４】
請求項３記載の発明は、情報光と記録用参照光との干渉によって生じる干渉縞を記録して、再生用参照光により情報光を再生させることによって、情報を記録再生させるホログラム記録装置で用いられるホログラム記録媒体において、基板上に設けられた光反射層の上に情報を記録する記録層を設け、少なくとも記録層の周囲に、情報光及び記録用再生光を吸収または反射し遮蔽するための光遮蔽層を設け、この光遮蔽層に対し特定の波長で閾値強度以上の光が照射されている時だけ光遮蔽層の光の透過率が増加して遮蔽層を光が透過して、記録層への干渉縞の書き込みと記録層からの情報の再生を可能とするホログラム記録媒体であり、光反射層を設けたホログラム記録媒体においても、光遮蔽層に対し特定の波長で閾値強度以上の光が照射されている時だけ光遮蔽層の光の透過率が増加して遮蔽層を光が透過することにより、情報の記録時と再生時にだけ記録層に光が照射される。
【００１５】
請求項４記載の発明は、情報光と記録用参照光との干渉によって生じる干渉縞を記録して、再生用参照光により情報光を再生させることによって、情報を記録再生させるホログラム記録装置で用いられるホログラム記録媒体において、基板上に設けられた光反射層の上に情報を記録する記録層を設け、少なくとも記録層の周囲に、情報光及び記録用再生光を吸収または反射し遮蔽するための光遮蔽層を設け、この光遮蔽層に対して特定の波長で閾値強度以上の光が照射されて、非可逆的に光遮蔽層の光の透過率が増加して、記録層への干渉縞の書き込みと記録層からの情報の再生を可能とするホログラム記録媒体であり、光反射層を設けたホログラム記録媒体においても、光遮蔽層に対して特定の波長で閾値強度以上の光が照射されて、非可逆的に光遮蔽層の光の透過率が増加することにより、情報の記録時と再生時にだけ記録層に光が照射される。
【００１６】
請求項５記載の発明は、請求項１、２、３、４記載のホログラム記録媒体において、記録層の材料がフォトポリマーであることを特徴とする。
【００１７】
請求項６記載の発明は、請求項１、２、３、４記載のホログラム記録媒体において、記録層の材料がアゾベンゼンまたはその化合物であることを特徴とする。
【００１８】
請求項７記載の発明は、請求項１、２、３、４記載のホログラム記録媒体において、記録層の材料がカルコゲナイト系化合物であることを特徴とする。
【００１９】
請求項８記載の発明は、請求項１、２、３、４記載のホログラム記録媒体において、記録層の材料がニオブ酸リチウム系化合物であることを特徴とする。
【００２０】
請求項９記載の発明は、請求項１、２、３、４記載のホログラム記録媒体において、記録層の材料がフォトリフラクティブ材料であることを特徴とする。
【００２１】
請求項５から請求項９記載のいずれの発明においても、記録層の材料として上記のものを用いることにより、大容量記録が可能なホログラム記録媒体を実現することができる。
【００２２】
請求項１０記載の発明は、請求項１、２、３、４記載のホログラム記録媒体において、光遮蔽層の材料がシアニン系色素、フタロシアニン系色素、アゾ系色素、ジアリールエテン系色素、フルキド系色素またはスピロピラン系色素のいずれかまたは混合物であることを特徴とする。
【００２３】
光遮蔽層の材料をこれらのものとすることにより、光遮蔽層に対し特定の波長で閾値強度以上の光が照射されている時だけ光遮蔽層の光の透過率を増加させ、あるいは、光遮蔽層に対して特定の波長で閾値強度以上の光を照射して、非可逆的に光遮蔽層の光の透過率を増加させることができ、情報の記録時と再生時にだけ記録層に光が照射されることを可能とすることができる。
【００２４】
請求項１１記載の発明は、請求項３、４記載のホログラム記録媒体において、光反射層の材料がアルミニウムであることを特徴とする。
【００２５】
光反射層をアルミニウムで形成することにより、低コストで反射率が良好で、基板及び記録層との密着性が高く安定な反射層を得るという作用効果を得ることができる。
【００２６】
請求項１２記載の発明は、請求項１から請求項１１のいずれかに記載のホログラム記録媒体に参照光と信号光とを干渉させて、情報を書き込む光学系を備え、ホログラム記録媒体に書き込まれた情報を読取るための検出器を備えたことを特徴とする記録再生装置である。
【００２７】
これにより、シャッタ機構などの機械的遮光手段を用いることなく、情報の記録時と再生時にだけ記録層に光を照射して記録再生が可能であるため、簡単な構成で、外光による感光の影響を受けずに情報の記録と再生が可能な記録再生装置を実現することができる。
【００２８】
以下、本発明の具体的な実施の形態について図１から図３に基づいて説明するが、本発明がこれらの実施の形態に限定されるものでないことは言うまでもない。
【００２９】
図１は本発明の実施の形態における光情報記媒体の基本的構成を示す構成図である。
【００３０】
図２は本発明の実施の形態における光情報記録媒体と記録再生装置の全体構成を示す構成図である。図３は本発明の実施の形態における光情報記録のメカニズムを示す構成図である。
【００３１】
始めに、図１を用いて、本実施の形態における光情報記録媒体の構成について説明する。この光情報記録媒体は、厚さが０．６ｍｍ以下のポリカーボネート等によって形成された円板状若しくは、カード状の透明基板１の一面に形成される。
【００３２】
この透明基板１の上に、情報光及び記録用再生光を吸収し遮蔽するための下部遮蔽層２を、通常の室内光や太陽光の透過光が透過しない程度の厚さ、例えば１０μｍ以上の適宜検討された厚さとなるように形成する。下部遮蔽層２を形成する物質としては、フォトンモードやサーマルモードで光の透過率が変化する材料であれば使用でき、材料系としては、フォトクロミック材料、染料、サーモクロミック材料などが使用できる。本実施の形態ではフタロシアニンからなり、厚さ２０μｍの下部遮蔽層２を設けた。
【００３３】
その後、ボリュームホログラフィを利用して情報が記録される情報層としてのホログラム層３を設ける。ホログラム材料としては、ニオブ酸リチウム、カルコゲナイト系材料、フォトポリマー、アゾベンゼン系材料、フォトリフラクティブ材料、ジアリールエテン系材料、フルキド系材料などの材料が使用可能である。
【００３４】
本実施の形態では、デュポン社製フォトポリマーＨＲＦ−６００（製品名）等を使用している。このホログラム層３の上に更に、情報光及び記録用再生光を吸収し遮蔽するための上部遮蔽層４を形成する。ここでは、フタロシアニンからなり、厚さ２０μｍの上部遮蔽層４を設けた。その後、透明基板１と同材質のポリカーボネートの保護層５を設け、この順番で積層して、多層構造の記録媒体６を構成する。
【００３５】
次にこの多層の記録媒体６を図２に示された記録再成装置７に取り付ける。
【００３６】
この記録再成装置７においては、記録時は、レーザー光源８からの光をレンズ９を通して光束１０を広げた後、ビームスプリッター１１により２方向の光束に分割する。この片方の光束１０の光路に空間変調器１２を挿入し外部信号を平面空間変調した後、光を空間変調器１２に入力し強度変調して信号光１３とする。もう片方の光束１０の光路に反射鏡１４、１５を入れて光路を変更し、参照光１６とする。
【００３７】
その後、この参照光１６を強度変調した信号光１３と交差させて干渉するように設定した。信号光１３と参照光１６が交差干渉する位置に、図１で説明した構造を持つ多層記録媒体１７を挿入する。
【００３８】
次に上部遮蔽層４の機能と本発明のメカニズムを図３により説明する。
【００３９】
参照光１６と信号光１３との重なり領域が、記録媒体６の上部遮蔽層４の位置で最大となり、ホログラム層３にホログラム干渉領域１９が重なるように、光学系を調整する。この時、レーザー光の強度は上部遮蔽層４で最大となる。
【００４０】
上部遮蔽層４を形成するフタロシアニンは、基底状態では波長７００ｎｍ近傍に強い吸収極大域が存在するが、レーザー光照射により励起状態が生成されて基底状態の強い吸収が減少し、この波長帯域の光の透過率が増加する。
【００４１】
すると参照光１６と信号光１３とが重なっている上部遮蔽層４の領域にレーザー光の窓が空いた、スルホール領域１８が出現する。この時、参照光１６と信号光１３とがホログラム層３にまで到達し、ホログラム記録が可能となる。読み出し時には強度を調整した参照光１６を照射する事により、上部遮蔽層４と下部遮蔽層２に、上述した原理に基づいてレーザー光の窓を開け再生読み出しを行うことができる。
【００４２】
このように、上部遮蔽層４での透過率の増加は照射されたレーザー光の強度によって制御される。レーザー光の照射中は、レーザー光の光強度に依存して励起状態が定常的に生成し高い透過率を保持するが、レーザー光の照射を止めると可逆的に元の低い透過率に戻る。この特性を利用すると書き込み時には遮蔽層にレーザー光の窓が空くために、書き込み光が記録層にまで到達し、ホログラム記録が可能となる。読み出し時には参照光を照射する事により、遮蔽層にレーザー光の窓を開け再生読み出しを行うことができる。
【００４３】
以上においては、上部遮蔽層４をフタロシアニンによって形成する場合について説明したが、これに限定されるものではなく、本発明によるホログラム記録媒体では、遮蔽層を形成する物質としては、フォトンモードやサーマルモードで光の透過率が変化する材料であればよく、フォトクロミック材料、染料、サーモクロミック材料などが使用できる。一例をあげるとシアニン系色素、フタロシアニン系色素、アゾ系色素、ジアリールエテン系色素、フルキド系色素、スピロピラン系色素を使用することができる。
【００４４】
フルキド化合物は波長３５０ｎｍ付近に吸収極大域があり紫外線を照射すると可視域である波長４９０ｎｍに吸収極大を持つフルキド閉環体となり、波長６３２近傍の光を吸収しない特性となる。また、波長４９０ｎｍの光を照射すると無色のフルキド化合物に戻る。このことから、波長４９０ｎｍ近傍の光で遮蔽層に窓を開け書き込み読み出しを行うことができる。
【００４５】
また、特開平３−１１１４０２号公報に記載されたシアニン系色素と有機ホウ素のアンモニウム塩の混合物は通常青色発色していて、近赤外領域に吸収極大を持ち、通常の室内の光では退色しないが、波長８２０ｎｍ近傍の光を照射する事により分解が起こり無色となり光を透過するようになる。その他のフォトクロミック材料やサーモクロミック材料でも光または熱による脱色作用を利用して、遮断層に可逆的または非可逆的に窓を開けることができ、記録層に安定に情報を記録し、読み出すことが可能となる。
【００４６】
また、透明基板１の上に金属などからなる光反射層を設け、その上に情報記録層であるホログラム層を設けた記録媒体に対して、上述した遮蔽層を形成することもできる。
【００４７】
【発明の効果】
以上のように、本発明のホログラム記録媒体によれば、シャッタ機構などの機械的遮光手段を用いることなく、情報の記録時と再生時にだけ記録層に光が照射されるため、外光による感光の影響を受けずに情報の記録と再生が可能となる。
【００４８】
これにより、フォトポリマーやアゾベンゼンなどの材料で、蛍光灯の下や太陽光のもとで、光を透過しない感光防止ケースに入れたり、シャッタ機構の付いた記録用窓を設けなくとも記録媒体に容易に記録再生でき、同一のドライブで従来のＣＤ−ＲＯＭ、ＣＤ−Ｒ／ＲＷ、ＤＶＤ−ＲＡＭ、ＤＶＤ＋Ｒ／ＲＷ、ＤＶＤ−Ｒ／ＲＷなどの記録媒体との互換性を保って使用できるホログラム記録媒体を実現できる。
【００４９】
また、本発明の記録再生装置によれば、シャッタ機構などの機械的遮光手段を用いることなく、情報の記録時と再生時にだけ記録層に光を照射して記録再生が可能であるため、簡単な構成で、外光による感光の影響を受けずに情報の記録と再生が可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態における光情報記媒体の基本的構成を示す構成図
【図２】本発明の実施の形態における光情報記録媒体と記録再生装置の全体構成を示す構成図
【図３】本発明の実施の形態における光情報記録のメカニズムを示す構成図
【符号の説明】
１透明基板
２下部遮蔽層
３ホログラム層
４上部遮蔽層
５保護層
６記録媒体
７記録再成装置
８レーザー光源
９レンズ
１０光束
１１ビームスプリッター
１２空間変調器
１３信号光
１４反射鏡
１５反射鏡
１６参照光
１７多層記録媒体
１８スルホール領域
１９ホログラム干渉領域[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hologram recording medium and a recording / reproducing apparatus using the hologram recording medium.
[0002]
[Prior art]
In recent years, the recording density of magnetic recording media, magneto-optical recording media, and thermal phase change media has been dramatically increased with the improvement of information recording technology. However, each recording method is a bit-by-bit recording method, and since recording and reproduction must be performed in units of 1 bit, the data transfer speed is limited, and there is a problem that it cannot meet the demands of the era of high-speed multiplex communication. ing. A hologram memory has been attracting attention as a recording system having both a high recording density and a high data transfer rate of the next generation in response to the progress of the times (for example, Patent Document 1).
[0003]
In the development of a hologram memory, it is necessary to use an inexpensive recording medium that can record and reproduce information stably at high speed. At present, inorganic or organic hologram materials are being developed, and materials such as lithium niobate, chalcogenite-based materials, photopolymers, azobenzene-based materials, photorefractive materials, diarylethene-based materials, and fluid-based materials are being studied.
[0004]
In particular, attention has been paid to photopolymers and azobenzene-based materials. However, materials such as photopolymers have high photosensitivity, and are exposed to light under fluorescent lamps or directly exposed to sunlight, so that information cannot be recorded. For this reason, a recording window is provided in a photosensitive prevention case that does not transmit light, a recording window is provided, and light is incident on the recording medium only during recording using a shutter mechanism or the like.
[0005]
If the shutter mechanism is not provided, an attempt is made to load the entire photosensitive prevention case into the drive, take out the recording medium from the photosensitive prevention case without being affected by external light in the drive, and perform recording and reproduction. Has also been made.
[0006]
[Patent Document 1]
JP 2001-66976 A
[Problems to be solved by the invention]
However, when the recording medium is placed in a photosensitive prevention case, the size of the recording medium becomes large and it is difficult to carry the recording medium, and the same drive can be used for conventional CD-ROM, CD-R / RW, DVD-RAM, DVD + R / RW, DVD-R. Compatibility with recording media such as / RW cannot be maintained. In addition, there is a problem that the loading of the photosensitive prevention case and the mechanism for opening and closing the shutter become complicated.
[0008]
Therefore, an object of the present invention is to provide a hologram recording medium and a recording / reproducing apparatus which can record / reproduce without being put in a case for preventing exposure.
[0009]
[Means for Solving the Problems]
In order to solve this problem, the present invention provides a hologram that records and reproduces information by recording interference fringes generated by interference between an information light and a recording reference light and reproducing the information light with a reproduction reference light. In a hologram recording medium used in a recording device, a light shielding layer for absorbing or reflecting and shielding information light and recording reproduction light is provided at least around a recording layer for recording information, and a specific light shielding layer is provided. The light transmittance of the light shielding layer increases only when light having a threshold intensity or more is irradiated at the wavelength of the light, the light is transmitted through the shielding layer, writing of interference fringes on the recording layer and from the recording layer. This is a hologram recording medium that enables reproduction of the information.
[0010]
This allows the recording layer to be irradiated with light only during recording and reproduction of information without using a mechanical light shielding means such as a shutter mechanism, so that recording and reproduction of information can be performed without being affected by exposure to external light. A possible hologram recording medium can be realized.
[0011]
In addition, since it is not necessary to use a photosensitive prevention case, the size of the hologram recording medium can be reduced.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
According to a first aspect of the present invention, there is provided a hologram recording apparatus for recording and reproducing information by recording interference fringes generated by interference between an information light and a recording reference light and reproducing the information light with the reproduction reference light. In the hologram recording medium used in the device, a light shielding layer for absorbing or reflecting and blocking information light and recording reproduction light is provided at least around a recording layer for recording information, and a specific light shielding layer is provided. The light transmittance of the light shielding layer increases only when light having a wavelength or more than the threshold intensity is applied, and the light is transmitted through the shielding layer to write interference fringes on the recording layer and to transfer information from the recording layer. A hologram recording medium that enables reproduction. The light transmittance of the light-shielding layer increases only when the light-shielding layer is irradiated with light at a specific wavelength or higher than the threshold intensity. By doing the information Light is irradiated to only the recording layer during reproduction and recording.
[0013]
The invention according to claim 2 is used in a hologram recording apparatus that records and reproduces information by recording interference fringes generated by interference between the information light and the recording reference light and reproducing the information light with the reproduction reference light. In the hologram recording medium to be provided, at least around a recording layer for recording information, a light shielding layer for absorbing or reflecting and shielding information light and recording reproduction light is provided, and a specific wavelength is provided for the light shielding layer. A hologram recording medium capable of irreversibly increasing light transmittance of a light shielding layer by irradiating light having a threshold intensity or higher and writing interference fringes on a recording layer and reproducing information from the recording layer. The light shielding layer is irradiated with light having a threshold intensity or more at a specific wavelength, and the light transmittance of the light shielding layer is irreversibly increased. Layer illuminated by light That.
[0014]
The invention according to claim 3 is used in a hologram recording apparatus for recording and reproducing information by recording an interference fringe generated by interference between the information light and the recording reference light and reproducing the information light with the reproduction reference light. In the hologram recording medium to be provided, a recording layer for recording information is provided on the light reflection layer provided on the substrate, and at least around the recording layer, for absorbing or reflecting information light and recording reproduction light for shielding. A light shielding layer is provided, and the light transmittance of the light shielding layer increases only when the light shielding layer is irradiated with light at a specific wavelength or higher than the threshold intensity, and the light is transmitted through the shielding layer to record. A hologram recording medium that enables writing of interference fringes to a layer and reproduction of information from a recording layer.In a hologram recording medium provided with a light reflection layer, the light shielding layer has a threshold intensity higher than or equal to a threshold at a specific wavelength. Light shines By only light transmittance of the light-shielding layer is transmitted through the light shielding layer is increased when being, light is irradiated to only the recording layer during reproduction and the time of recording information.
[0015]
The invention according to claim 4 is used in a hologram recording apparatus for recording and reproducing information by recording an interference fringe generated by interference between the information light and the recording reference light and reproducing the information light by the reproduction reference light. In the hologram recording medium to be provided, a recording layer for recording information is provided on the light reflection layer provided on the substrate, and at least around the recording layer, for absorbing or reflecting information light and recording reproduction light for shielding. A light shielding layer is provided, and the light shielding layer is irradiated with light having a threshold intensity or more at a specific wavelength, irreversibly increasing the light transmittance of the light shielding layer, and causing interference fringes on the recording layer. This is a hologram recording medium that enables writing of data and reproduction of information from the recording layer, and even in a hologram recording medium provided with a light reflection layer, light having a threshold intensity or more at a specific wavelength is applied to the light shielding layer. Not allowed By light transmittance of the light-shielding layer is increased, the light to only the recording layer during reproduction and the time of recording information is irradiated.
[0016]
According to a fifth aspect of the present invention, in the hologram recording medium according to the first, second, third, or fourth aspect, the material of the recording layer is a photopolymer.
[0017]
According to a sixth aspect of the present invention, in the hologram recording medium according to the first, second, third, or fourth aspect, the material of the recording layer is azobenzene or a compound thereof.
[0018]
According to a seventh aspect of the present invention, in the hologram recording medium of the first, second, third, or fourth aspect, the material of the recording layer is a chalcogenite-based compound.
[0019]
According to an eighth aspect of the present invention, in the hologram recording medium according to the first, second, third or fourth aspect, the material of the recording layer is a lithium niobate-based compound.
[0020]
According to a ninth aspect of the present invention, in the hologram recording medium according to the first, second, third, or fourth aspect, the material of the recording layer is a photorefractive material.
[0021]
In any of the fifth to ninth aspects of the present invention, a hologram recording medium capable of large-capacity recording can be realized by using the above-mentioned material for the recording layer.
[0022]
According to a tenth aspect of the present invention, in the hologram recording medium according to the first, second, third, or fourth aspect, the material of the light shielding layer is a cyanine dye, a phthalocyanine dye, an azo dye, a diarylethene dye, a fluid dye or It is a spiropyran dye or a mixture thereof.
[0023]
By using these materials for the light shielding layer, it is possible to increase the light transmittance of the light shielding layer only when the light shielding layer is irradiated with light having a threshold intensity or more at a specific wavelength, or By irradiating the shielding layer with light having a threshold intensity or more at a specific wavelength, the light transmittance of the light shielding layer can be irreversibly increased, and the light is applied to the recording layer only when recording and reproducing information. Can be illuminated.
[0024]
According to an eleventh aspect of the present invention, in the hologram recording medium according to the third or fourth aspect, the material of the light reflection layer is aluminum.
[0025]
By forming the light reflection layer from aluminum, it is possible to obtain the effect of obtaining a stable reflection layer that has good reflectance at low cost and high adhesion to the substrate and the recording layer.
[0026]
According to a twelfth aspect of the present invention, the hologram recording medium according to any one of the first to eleventh aspects includes an optical system for writing information by causing reference light and signal light to interfere with each other. Recording / reproducing apparatus characterized by comprising a detector for reading the information.
[0027]
As a result, recording and reproduction can be performed by irradiating light to the recording layer only during recording and reproduction of information without using a mechanical light shielding unit such as a shutter mechanism. A recording / reproducing apparatus capable of recording and reproducing information without being affected can be realized.
[0028]
Hereinafter, specific embodiments of the present invention will be described with reference to FIGS. 1 to 3, but it goes without saying that the present invention is not limited to these embodiments.
[0029]
FIG. 1 is a configuration diagram showing a basic configuration of an optical information recording medium according to an embodiment of the present invention.
[0030]
FIG. 2 is a configuration diagram showing the overall configuration of the optical information recording medium and the recording / reproducing apparatus according to the embodiment of the present invention. FIG. 3 is a configuration diagram showing a mechanism of optical information recording according to the embodiment of the present invention.
[0031]
First, the configuration of the optical information recording medium according to the present embodiment will be described with reference to FIG. This optical information recording medium is formed on one surface of a disc-shaped or card-shaped transparent substrate 1 made of polycarbonate or the like having a thickness of 0.6 mm or less.
[0032]
On this transparent substrate 1, a lower shielding layer 2 for absorbing and shielding information light and recording reproduction light is formed to a thickness such that ordinary room light or transmitted light of sunlight is not transmitted, for example, 10 μm or more. It is formed to have a thickness appropriately studied. As a material for forming the lower shielding layer 2, any material can be used as long as light transmittance changes in a photon mode or a thermal mode. As a material system, a photochromic material, a dye, a thermochromic material, or the like can be used. In the present embodiment, the lower shielding layer 2 made of phthalocyanine and having a thickness of 20 μm is provided.
[0033]
Thereafter, a hologram layer 3 is provided as an information layer on which information is recorded using volume holography. As the hologram material, materials such as lithium niobate, chalcogenite-based materials, photopolymers, azobenzene-based materials, photorefractive materials, diarylethene-based materials, and fluid-based materials can be used.
[0034]
In the present embodiment, a photopolymer HRF-600 (product name) manufactured by DuPont is used. An upper shielding layer 4 for absorbing and shielding information light and recording reproduction light is further formed on the hologram layer 3. Here, an upper shielding layer 4 made of phthalocyanine and having a thickness of 20 μm was provided. Thereafter, a protective layer 5 made of polycarbonate of the same material as that of the transparent substrate 1 is provided and laminated in this order to form a recording medium 6 having a multilayer structure.
[0035]
Next, this multilayer recording medium 6 is attached to the recording / regenerating apparatus 7 shown in FIG.
[0036]
In the recording regenerating apparatus 7, at the time of recording, the light from the laser light source 8 spreads the light beam 10 through the lens 9, and is then split into two-direction light beams by the beam splitter 11. After the spatial modulator 12 is inserted into the optical path of the one light beam 10 and the external signal is spatially modulated in the plane, the light is input to the spatial modulator 12 and intensity-modulated to obtain the signal light 13. The reflecting mirrors 14 and 15 are put in the optical path of the other light beam 10 to change the optical path to be used as the reference light 16.
[0037]
After that, the reference light 16 was set to intersect with the intensity-modulated signal light 13 so as to interfere therewith. A multi-layer recording medium 17 having the structure described with reference to FIG. 1 is inserted at a position where the signal light 13 and the reference light 16 interfere with each other.
[0038]
Next, the function of the upper shielding layer 4 and the mechanism of the present invention will be described with reference to FIG.
[0039]
The optical system is adjusted so that the overlapping area of the reference light 16 and the signal light 13 becomes maximum at the position of the upper shielding layer 4 of the recording medium 6 and the hologram interference area 19 overlaps the hologram layer 3. At this time, the intensity of the laser beam becomes maximum at the upper shielding layer 4.
[0040]
The phthalocyanine forming the upper shielding layer 4 has a strong absorption maximum in the vicinity of a wavelength of 700 nm in the ground state, but the excited state is generated by irradiation with laser light, and the strong absorption in the ground state is reduced. Increase in transmittance.
[0041]
Then, a through-hole region 18 in which a window of the laser light is opened in a region of the upper shielding layer 4 where the reference light 16 and the signal light 13 overlap with each other appears. At this time, the reference light 16 and the signal light 13 reach the hologram layer 3, and hologram recording becomes possible. By irradiating the reference light 16 whose intensity has been adjusted at the time of reading, a window of a laser beam can be opened on the upper shielding layer 4 and the lower shielding layer 2 based on the above-described principle, and reproduction reading can be performed.
[0042]
As described above, the increase in the transmittance in the upper shielding layer 4 is controlled by the intensity of the irradiated laser light. During laser light irradiation, an excited state is steadily generated depending on the light intensity of the laser light and maintains a high transmittance. However, when the laser light irradiation is stopped, the transmittance reversibly returns to the original low transmittance. When this characteristic is used, the window of the laser beam is opened in the shielding layer at the time of writing, so that the writing light reaches the recording layer and hologram recording becomes possible. At the time of reading, by irradiating the reference light, a window of a laser beam can be opened in the shielding layer, and reproduction reading can be performed.
[0043]
Although the case where the upper shielding layer 4 is formed of phthalocyanine has been described above, the invention is not limited to this. In the hologram recording medium according to the present invention, the material forming the shielding layer may be a photon mode or a thermal mode. Any material can be used as long as it changes the light transmittance, and a photochromic material, a dye, a thermochromic material, or the like can be used. For example, a cyanine dye, a phthalocyanine dye, an azo dye, a diarylethene dye, a fluid dye, and a spiropyran dye can be used.
[0044]
Fluid compounds have an absorption maximum in the vicinity of a wavelength of 350 nm, and when irradiated with ultraviolet light, become a fluid closed ring having an absorption maximum in a visible region of a wavelength of 490 nm, and do not absorb light near a wavelength of 632. Irradiation with light having a wavelength of 490 nm returns to a colorless fluid compound. Accordingly, writing and reading can be performed by opening a window in the shielding layer with light having a wavelength of about 490 nm.
[0045]
Further, the mixture of a cyanine dye and an ammonium salt of an organic boron described in JP-A-3-111402 normally emits blue color, has an absorption maximum in the near infrared region, and does not fade with ordinary room light. However, when irradiated with light having a wavelength of about 820 nm, the light is decomposed to be colorless and light is transmitted. Other photochromic and thermochromic materials can be used to reversibly or irreversibly open windows in the blocking layer by using the decolorizing effect of light or heat, so that information can be stably recorded and read on the recording layer. It becomes possible.
[0046]
Further, the above-mentioned shielding layer can be formed on a recording medium in which a light reflection layer made of metal or the like is provided on the transparent substrate 1 and a hologram layer as an information recording layer is provided thereon.
[0047]
【The invention's effect】
As described above, according to the hologram recording medium of the present invention, the recording layer is irradiated with light only at the time of recording and reproducing information without using a mechanical light shielding means such as a shutter mechanism. Recording and reproduction of information can be performed without being affected by the information.
[0048]
This allows materials such as photopolymers and azobenzene to be applied to recording media without placing them in a light-blocking case that does not transmit light under fluorescent light or under sunlight, or without providing a recording window with a shutter mechanism. Hologram recording that can be easily recorded and reproduced and used with the same drive while maintaining compatibility with conventional recording media such as CD-ROM, CD-R / RW, DVD-RAM, DVD + R / RW, and DVD-R / RW A medium can be realized.
[0049]
Further, according to the recording / reproducing apparatus of the present invention, recording and reproduction can be performed by irradiating light to the recording layer only at the time of recording and reproducing information without using a mechanical light blocking means such as a shutter mechanism. With such a configuration, recording and reproduction of information can be performed without being affected by exposure to light from outside light.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a basic configuration of an optical information recording medium according to an embodiment of the present invention. FIG. 2 is a configuration diagram illustrating an overall configuration of an optical information recording medium and a recording / reproducing apparatus according to an embodiment of the present invention. FIG. 3 is a configuration diagram showing a mechanism of optical information recording according to an embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Lower shielding layer 3 Hologram layer 4 Upper shielding layer 5 Protective layer 6 Recording medium 7 Recording reproducing device 8 Laser light source 9 Lens 10 Light flux 11 Beam splitter 12 Spatial modulator 13 Signal light 14 Reflecting mirror 15 Reflecting mirror 16 See Light 17 Multilayer recording medium 18 Through hole area 19 Hologram interference area

Claims

A hologram recording medium used in a hologram recording apparatus that records and reproduces information by recording an interference fringe generated by interference between the information light and the recording reference light and reproducing the information light with the reproduction reference light. A light shielding layer for absorbing or reflecting and blocking information light and recording reproduction light is provided around a recording layer for recording information, and the light shielding layer is irradiated with light having a specific wavelength or higher than a threshold intensity. The light transmittance of the light shielding layer is increased only when the light is transmitted, the light is transmitted through the shielding layer, and writing of interference fringes on the recording layer and reproduction of information from the recording layer are enabled. Hologram recording medium.

A hologram recording medium used in a hologram recording apparatus that records and reproduces information by recording an interference fringe generated by interference between the information light and the recording reference light and reproducing the information light with the reproduction reference light. A light shielding layer for absorbing or reflecting and blocking information light and recording reproduction light is provided around a recording layer for recording information, and the light shielding layer is irradiated with light having a specific wavelength and a threshold intensity or more at a specific wavelength. A hologram recording medium, wherein the transmittance of light of the light shielding layer is irreversibly increased to enable writing of interference fringes on the recording layer and reproduction of information from the recording layer. .

A hologram recording medium used in a hologram recording apparatus that records and reproduces information by recording an interference fringe generated by interference between the information light and the recording reference light and reproducing the information light by the reproduction reference light. A recording layer for recording information is provided on the light reflection layer provided thereon, and at least around the recording layer, a light shielding layer for absorbing or reflecting information light and recording / reproducing light for shielding is provided, Only when the light shielding layer is irradiated with light having a threshold intensity or more at a specific wavelength, the light transmittance of the light shielding layer increases and the light passes through the shielding layer, and the interference fringes on the recording layer A hologram recording medium capable of writing data and reproducing information from the recording layer.

A hologram recording medium used in a hologram recording apparatus that records and reproduces information by recording interference fringes generated by interference between information light and recording reference light and reproducing the information light with reproduction reference light. A recording layer for recording information is provided on the light reflection layer provided thereon, and at least around the recording layer, a light shielding layer for absorbing or reflecting information light and recording / reproducing light for shielding is provided, The light shielding layer is irradiated with light having a threshold intensity or more at a specific wavelength, the light transmittance of the light shielding layer is irreversibly increased, and the interference fringe is written on the recording layer and the recording is performed. A hologram recording medium capable of reproducing information from a layer.

5. The hologram recording medium according to claim 1, wherein a material of the recording layer is a photopolymer.

5. The hologram recording medium according to claim 1, wherein the material of the recording layer is azobenzene or a compound thereof.

5. The hologram recording medium according to claim 1, wherein the material of the recording layer is a chalcogenite compound.

5. The hologram recording medium according to claim 1, wherein the material of the recording layer is a lithium niobate-based compound.

5. The hologram recording medium according to claim 1, wherein the material of the recording layer is a photorefractive material.

The material of the light shielding layer is any one or a mixture of a cyanine dye, a phthalocyanine dye, an azo dye, a diarylethene dye, a fluid dye or a spiropyran dye, wherein 5. The hologram recording medium according to 4.

The hologram recording medium according to claim 3, wherein a material of the light reflection layer is aluminum.

An optical system for writing information by causing reference light and signal light to interfere with the hologram recording medium according to any one of claims 1 to 11, and detection for reading information written on the hologram recording medium. A recording / reproducing apparatus comprising a device.