JP4307053B2 - Information recording medium, recording / reproducing method thereof, and recording / reproducing apparatus - Google Patents

Description

【００１４】
〔上記の式（ｉ）においてＡは下記の置換基（ｉｉ）または置換基（ｉｉｉ）｛置換基（ｉｉ）および置換基（ｉｉｉ）においてＲ¹はアルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、シアノ基または置換されていてもよいアリール基を表し、Ｒ²およびＲ³はそれぞれ独立して水素原子、アルキル基、アルコキシ基、ハロゲン原子、トリフルオロメチル基、シアノ基、置換されていてもよいアリール基または下記の置換基（ｉｖ）または置換基（ｖ）｛置換基（ｉｖ）および置換基（ｖ）においてＲ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶、Ｒ⁷、Ｒ⁸、Ｒ⁹、Ｒ¹⁰、Ｒ¹¹、Ｒ¹²およびＲ¹³はそれぞれ独立に水素原子、ハロゲン原子、アルキル基、アルコキシ基、トリフルオロメチル基，シアノ基、または置換されていてもよいアリール基を表す｝を表し、Ｘは−Ｏ−、−Ｓ−または−ＮＲ⁴−（Ｒ⁴は水素原子、置換されていてもよいアルキル基、置換されていてもよいアリール基または置換されていてもよいシクロアルキル基を表す）を表す｝を表し、
【００１５】
【化８】

【００１６】
Ｂは下記の置換基（ｖｉ）または置換基（ｖｉｉ）｛置換基（ｖｉ）および置換基（ｖｉｉ）においてＲ¹はアルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、シアノ基または置換されていてもよいアリール基を表し、Ｒ²およびＲ³はそれぞれ独立して水素原子、アルキル基、アルコキシ基、ハロゲン原子、トリフルオロメチル基、シアノ基、置換されていてもよいアリール基または下記の置換基（ｖｉｉｉ）または置換基（ｉｘ）｛置換基（ｖｉｉｉ）および置換基（ｉｘ）においてＲ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶、Ｒ⁷、Ｒ⁸、Ｒ⁹、Ｒ¹⁰、Ｒ¹¹、Ｒ¹²およびＲ¹³はそれぞれ独立に水素原子、ハロゲン原子、アルキル基、アルコキシ基、トリフルオロメチル基，シアノ基、または置換されていてもよいアリール基を表す｝を表し、Ｘは−Ｏ−、−Ｓ−または−ＮＲ⁴−（Ｒ⁴は水素原子、置換されていてもよいアルキル基、置換されていてもよいアリール基または置換されていてもよいシクロアルキル基を表す）を表す｝を表す〕
【００１７】
【化９】

【００１８】
請求項３に記載の発明は、基板上にフォトクロミック材料からなる記憶層を備えるとともに、該記憶層上には第２波長の再生光を入射するための媒質が隣接して設けられて使用され、第１波長の記録光が照射され近接場光の滲み出しが生じてエネルギーが付与されると、記録光が照射された記憶層の屈折率が可逆的に変化し記録領域を形成する情報記録媒体に記録光を照射して記録し、第２の波長の再生光を照射して再生を行う記録・再生方法であって、基板、記憶層、媒質の屈折率を基板、初期状態の記憶層、記録光の照射後の記憶層、媒質の順で大きくなるように構成し、記録時には記憶層に記録光でエネルギーを付与して屈折率の変化により情報を記録し、再生時には全反射の臨界角以下の角度で再生光を入射し、記憶層を透過させて基板へ放射させることにより反射光強度を低下させ、記録領域の互いに異なる屈折率を有する領域間で異なった反射光強度を検出することを特徴とする情報記録媒体の記録・再生方法であって、特定波長の吸収に依存せず記録媒体の感度のない波長を用いても記録・再生が可能となる。
【００２０】
請求項４に記載の発明は、請求項３において、フォトクロミック材料は下記の一般式（ｉ）で表される分子構造を有するフォトクロミック色素を含有する透明高分子複合材料またはフォトクロミック色素それ自身からなるアモルファス透明材料から成ることを特徴とする情報記録媒体の記録・再生方法であって、フォトクロミック材料の開環もしくは閉環に寄与する特定波長以外の光を再生光として用いることによって、記録情報の消去もしくはオーバーライトを抑制し、再生ができる。
【００２１】
【化１０】

【００２２】
〔上記の式（ｉ）においてＡは下記の置換基（ｉｉ）または置換基（ｉｉｉ）｛置換基（ｉｉ）および置換基（ｉｉｉ）においてＲ¹はアルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、シアノ基または置換されていてもよいアリール基を表し、Ｒ²およびＲ³はそれぞれ独立して水素原子、アルキル基、アルコキシ基、ハロゲン原子、トリフルオロメチル基、シアノ基、置換されていてもよいアリール基または下記の置換基（ｉｖ）または置換基（ｖ）｛置換基（ｉｖ）および置換基（ｖ）においてＲ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶、Ｒ⁷、Ｒ⁸、Ｒ⁹、Ｒ¹⁰、Ｒ¹¹、Ｒ¹²およびＲ¹³はそれぞれ独立に水素原子、ハロゲン原子、アルキル基、アルコキシ基、トリフルオロメチル基，シアノ基、または置換されていてもよいアリール基を表す｝を表し、Ｘは−Ｏ−、−Ｓ−または−ＮＲ⁴−（Ｒ⁴は水素原子、置換されていてもよいアルキル基、置換されていてもよいアリール基または置換されていてもよいシクロアルキル基を表す）を表す｝を表し、
【００２３】
【化１１】

【００２４】
Ｂは下記の置換基（ｖｉ）または置換基（ｖｉｉ）｛置換基（ｖｉ）および置換基（ｖｉｉ）においてＲ¹はアルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、シアノ基または置換されていてもよいアリール基を表し、Ｒ²およびＲ³はそれぞれ独立して水素原子、アルキル基、アルコキシ基、ハロゲン原子、トリフルオロメチル基、シアノ基、置換されていてもよいアリール基または下記の置換基（ｖｉｉｉ）または置換基（ｉｘ）｛置換基（ｖｉｉｉ）および置換基（ｉｘ）においてＲ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶、Ｒ⁷、Ｒ⁸、Ｒ⁹、Ｒ¹⁰、Ｒ¹¹、Ｒ¹²およびＲ¹³はそれぞれ独立に水素原子、ハロゲン原子、アルキル基、アルコキシ基、トリフルオロメチル基，シアノ基、または置換されていてもよいアリール基を表す｝を表し、Ｘは−Ｏ−、−Ｓ−または−ＮＲ⁴−（Ｒ⁴は水素原子、置換されていてもよいアルキル基、置換されていてもよいアリール基または置換されていてもよいシクロアルキル基を表す）を表す｝を表す〕
【００２５】
【化１２】

【００２７】
請求項５に記載の発明は、請求項３又は４において、記録領域に記録光とは異なる第３の波長の消去光を照射して、記録領域に記録された情報を消去することを特徴とする情報記録媒体の記録・再生方法であって、書き換え可能とすることができる。
【００２８】
請求項６に記載の発明は、基板上にフォトクロミック材料からなる記憶層を備えるとともに、該記憶層上には第２波長の再生光を入射するための媒質が隣接して設けられて使用され、第１波長の記録光が照射され近接場光の滲み出しが生じてエネルギーが付与されると、記録光が照射された記憶層の屈折率が可逆的に変化し記録領域を形成する情報記録媒体に記録光を照射して記録し、第２の波長の再生光を照射して再生を行う情報記録媒体の記録・再生装置であって、情報記録媒体の記憶層に記録光の照射によりエネルギーを付与する記録手段と、第２の波長の再生光を出射する再生用光源と、媒質として再生光入射媒体とが設けられ、基板、記憶層、媒質の屈折率が基板、初期状態の記憶層、記録光の照射後の記憶層、媒質の順で大きくなるように構成され、全反射の臨界角以下の角度で再生光を入射する再生光入射手段と、記録領域の互いに異なる屈折率を有する領域間で異なった反射光強度を有する反射光を受光する光検出器とを、具備し、再生時に再生光を記憶層の透過で基板に放射させることにより反射光強度を低下させることを特徴とする情報記録媒体の記録・再生装置であって、特定波長の吸収に依存せず記録媒体の感度のない波長を用いても記録・再生が可能となる。
【００３０】
請求項７に記載の発明は、請求項６において、記録領域に記録光とは異なる第３の波長の消去光を照射して、記録領域に記録された情報を消去する消去手段を備えたことを特徴とする情報記録媒体の記録・再生装置であって、書き換え可能とすることができる。
【００３１】
（実施の形態１）
以下に、本発明の実施の形態１による情報記録媒体及びその記録・再生方法並びに記録・再生装置について図面を用いて説明する。
【００３２】
まず、本発明の実施の形態１による情報記録媒体への記録方法について述べる。
【００３３】
図１は本発明の実施の形態１による情報記録媒体の記録装置の構成模式図である。
【００３４】
図１において、１は情報記録媒体、２は記録層、３は基板であり、４は記録光光源、５は対物レンズ、６は半球レンズを示している。
【００３５】
情報記録媒体１は基板３上に記録層２が形成され、記録層２は記録領域を備える。なお、本実施の形態１では、記録層２が特定波長の光を照射することにより、屈折率が可逆的に変化するフォトクロミック材料で構成されている場合で説明する。
【００３６】
そして、本発明の実施の形態１による情報記録媒体の記録は、近接場光を照射することにより行う。
【００３７】
まず、記録光光源４から出射された光は、対物レンズ５へ導かれる。対物レンズ５を通過した光は半球レンズ６の中心に焦点を結び集光されている。基板１上にフォトクロミック材料からなる記録層２を成膜した情報記録媒体１は半球レンズ６の直下に近接して配置され、半球レンズ６の底面から出射される近接場光が照射される。
【００３８】
ここで、情報記録についての原理を説明する。図２は本発明の実施の形態１によるフォトクロミック材料の光吸収特性を示すグラフである。
【００３９】
図２に示すように、このフォトクロミック材料は、光波長４００ｎｍ以下および６００ｎｍ近傍に顕著な吸収ピークを持つ材料であり、４００ｎｍ以下の光は開環から閉環への変化に、６００ｎｍ近傍の光は閉環から開環状態への変化に寄与する。なお、本材料は開環から閉環、閉環から開環の状態変化に伴い、材料そのものの色が透明から青、青から透明へと変化する。
【００４０】
また、このフォトクロミック材料としては、上記で示した一般式（ｉ）で表される分子構造を有するフォトクロミック色素を含有する透明高分子複合材料またはフォトクロミック色素それ自信からなるアモルファス透明材料を好適に用いることができる。そして、このフォトクロミック材料の具体的化合物（１）の構造式を下記に示す。
【００４１】
【化１３】

【００４２】
更に、これらフォトクロミック材料の種々の具体例や合成方法としては、「“Ｓｙｎｔｈｅｓｉｓ ｏｆ Ｆｌｕｏｒｅｓｃｅｎｔ Ａｍｏｒｐｈｏｕｓ Ｄｉａｒｙｌｅｔｈｅｎｅｓ，”Ｃｈｅｍｉｓｔｒｙ Ｌｅｔｔｅｒｓ，ｐ．７０２−７０３，２００１」、「“Ｓｙｎｔｈｅｓｉｓ ａｎｄ Ｐｈｏｔｏｃｈｒｏｍｉｓｍ ｏｆ Ａｍｏｒｐｈｏｕｓ Ｄｉａｒｙｌｅｔｈｅｎｅ Ｈａｖｉｎｇ Ｓｔｙｒｙｌ Ｓｕｂｓｔｉｔｕｅｎｔｓ，”Ｍｏｌ．Ｃｒｙｓｔ．Ｌｉｑ．Ｃｒｙｓｔ．，３４５，ｐｐ．２５１−２５５，２０００」、「“Ｄｉａｒｙｌｅｔｈｅｎｅｓ ｆｏｒ Ｍｅｍｏｒｉｅｓ ａｎｄ Ｓｗｉｔｃｈｅｓ，”Ｃｈｅｍｉｃａｌ Ｒｅｖｉｅｗｓ，１００，ｐｐ．１６８５−１７１６，２０００」に記載されている。
【００４３】
なお、上記した一般式（ｉ）で表される分子構造を有するフォトクロミック材料に限定されるものではなく、同じ特性を備えるものであれば、他の分子構造を有する材料を用いる事もできる。
【００４４】
このようなフォトクロミック材料で構成される情報記録媒体１の記録層２に記録を行う場合、記録光の波長は顕著な吸収ピークを持つ光波長を選択する。図２の特性から判断すると、４００ｎｍもしくは６００ｎｍ付近の光を使用するのが望ましい。半球レンズ６の底面中心に集光されるスポットサイズ（＝ＳＤ）は、光波長（＝λ）、対物レンズ５の開口数と対物レンズ５に対する記録光の入射位置およびそのビーム径から決定される出射角度（＝ＮＡ＝ｓｉｎθ）、半球レンズ６の屈折率（ｎ）により、以下の式で導かれ、
式（１） ＳＤ＝λ／（ｎ×ＮＡ）
フォトクロミック材料に形成される記録ピットは、ほぼこのスポットサイズを反映する。ゆえに、光波長λ＝４００ｎｍ、対物レンズ５から出射される記録光の角度（ＮＡ＝０．６）、半球レンズ６の屈折率ｎ＝１．８を用いれば、約３７０ｎｍのピット形成が可能となる。同様に、光波長λ＝６００ｎｍであればＳＤ＝５５０ｎｍである。
【００４５】
なお、半球レンズを用いた場合の近接場光の滲み出し深さｈは
式（２） ｈ＝λ／（２π×（（ｎ×ｓｉｎθ）²−１）^1/2）
で与えられる。
【００４６】
ゆえに、記録の際、半球レンズ６と情報記録媒体１は光波長λ＝４００ｎｍの場合は１５０ｎｍ以下、６００ｎｍの場合は２３０ｎｍ以下で近接させる必要がある。
【００４７】
例えば、初期状態をフォトクロミック材料の閉環状態とし、記録状態を開環状態とする場合では、記録光の波長を６００ｎｍとし、上記条件において、半球レンズ６と情報記録媒体１は２３０ｎｍ以下で近接させればよい。そして、６００ｎｍの光を照射することで、フォトクロミック材料を閉環から開環状態に変えて記録を行う。更に、４００ｎｍの光を照射することで、フォトクロミック材料を開環から閉環状態に変えて初期状態とすることができ、記録された情報の消去を行うことができる。よって、記録光の波長が６００ｎｍ、消去光の波長が４００ｎｍとなる。
【００４８】
或いは、初期状態をフォトクロミック材料の開環状態とし、記録状態を閉環状態とする場合には、記録光の波長を４００ｎｍとし、上記条件において、半球レンズ６と情報記録媒体１は１５０ｎｍ以下で近接させればよい。そして、４００ｎｍの光を照射することで、フォトクロミック材料を開環から閉環状態に変えて記録を行う。更に、６００ｎｍの光を照射することで、フォトクロミック材料を閉環から開環状態に変えて初期状態とすることができ、記録された情報の消去を行うことができる。よって、記録光の波長が４００ｎｍ、消去光の波長が６００ｎｍとなる。
【００４９】
なお、消去光の光源は、図１で示す記録光光源４と共に消去光光源を設けても良いし、情報記録媒体１の記録層２の全面を照射できるような消去光光源を設けてもよい。
【００５０】
次に、本発明の実施の形態１による情報記録媒体への再生方法について述べる。
【００５１】
図３は本発明の実施の形態１による情報記録媒体の再生装置の構成模式図である。
【００５２】
図３において、７は再生光光源、８は再生光入射媒体、９は光検出器を示している。
【００５３】
そして、本発明の実施の形態１による情報記録媒体の再生は、記録と同様に、近接場光を照射することにより行う。
【００５４】
なお、詳細は後述するが、再生光に使用する波長は、フォトクロミック材料の吸収がない領域の波長の光を用いる。この場合では、赤外光が好ましく、例えば、ＣＤ−ＲＯＭの再生用の７８０ｎｍ等の赤外光を発するレーザーが挙げられる。
【００５５】
まず、再生光光源７から出射された光は、対物レンズ５を通過し、再生光入射媒体８に入射され、所定の角度θで情報記録媒体１の記録層２に近接場光が照射される。
【００５６】
そして、情報記録媒体１からの反射信号光は、再生光入射媒体８を通過し、対物レンズ５を介して光検出器９に導かれる。
【００５７】
ここで、情報再生の原理について説明する。フォトクロミック材料の長所は、極微弱光にも感応し、開環および閉環の状態変化が可能なことであるが、同時にこの長所は短所にもなり得る。図２において、λ＝４００ｎｍ以下および６００ｎｍ付近に光の吸収帯があることは先に述べた。しかし、これらの光波長を用いて再生を行うと、再生光の光パワーを極端に小さくしても、記録情報のオーバーライトもしくは消去という現象が起こる。ゆえに、情報記録に用いる顕著な光吸収を持つ光波長での再生は実用上困難となる。
【００５８】
そこで、フォトクロミック材料が閉環状態から開環状態に変化する際、屈折率が微小に変化することに着目した。フォトクロミック材料の閉環状態を初期状態として、λ＝６００ｎｍ付近の記録光で情報記録を行うと光を照射した部位のみが開環状態となり、微小に屈折率が低下する。この屈折率変化（＝Δｎ）は０．０１〜０．１０程度である。
【００５９】
そして、本発明者らは、再生光の入射角度を特定な角度として入射したとき、フォトクロミック材料の閉環状態と開環状態とでは再生光の反射光強度が異なることを見出し、この微小な屈折率の差異を検出することを可能とした。
【００６０】
即ち、再生光入射媒体８から情報記録媒体１の記録層２に入射される再生光の入射角θを、再生光入射媒体８を構成する媒質の屈折率と、情報記録媒体１の基板３の屈折率とで決定される再生光の全反射の臨界角以下の角度として入射する。なお、臨界角以下の角度である入射角θとは、臨界角をθ₀とすると、θ₀＞θであることを意味する。
【００６１】
再生光を全反射の臨界角以下の角度として入射したとき、この再生光は、基板３へのリークモード、即ち、記録層２を透過し基板３への放射モードに変わる。そして、このリークモードにおいて、フォトクロミック材料の閉環状態と開環状態とでは再生光の反射光強度が異なることが判明した。ところで、リークモードの再生光は、記録層２の屈折率が異なることに起因して、層内や界面における反射或いは吸収の差異が生じ、結果として反射光強度の差異に繋がるものと考えられるが、屈折率の大小と反射光強度の大小との相関関係についての詳細は明らかではない。
【００６２】
これらの事項は、本発明者らが実験から得られたものであり、以下実験内容及び結果について説明する。
【００６３】
まず、情報記録媒体１として、基板３にガラス基板（屈折率＝１．５６１）を用い、記録層２に上記具体的化合物（１）のフォトクロミック材料を用いた。なお、このフォトクロミック材料は、閉環状態の屈折率は１．６４８、開環状態の屈折率は１．６１１であり、初期状態をフォトクロミック材料の閉環状態、記録状態を開環状態とし、記録光の波長を６００ｎｍで、図１に示した記録装置を用いて記録を行った。
【００６４】
次に、図３に示す再生装置を用い、記録層２における初期状態の閉環状態である領域（非記録領域）と、記録層２における記録状態の開環状態である領域（記録領域）に対し、それぞれ再生光の入射角θを変更して入射し、反射光強度を光検出器９で検出した。また、再生光入射媒体８として半球レンズ（屈折率＝１．９５２）を用い、再生光の波長は８１７ｎｍの赤外光を用いた。
【００６５】
そして、非記録領域と記録領域における反射光強度の測定結果を図４に示す。なお、図４は本発明の実施の形態１による入射角θと反射光強度の関係を示すグラフである。
【００６６】
ここで、スネルの法則に従えば、再生光入射媒体８の屈折率（１．９５２）と、基板３の屈折率（１．５６１）とで決定される再生光の全反射の臨界角は、５３．１°となる。
【００６７】
そして、図４の結果から明らかなように、入射角θがこの臨界角５３．１°以下のとき、非記録領域と記録領域とは、共に全反射から前述のリークモードとなって反射光強度が低下する。また、非記録領域と記録領域とで、その反射光強度が異なっている。
【００６８】
よって、再生光入射媒体８から情報記録媒体１の記録層２に入射される再生光の入射角θを、再生光入射媒体８を構成する媒質の屈折率と、情報記録媒体１の基板３の屈折率とで決定される再生光の全反射の臨界角以下の角度として入射することにより、フォトクロミック材料の閉環状態と開環状態との間で再生光の反射光強度の差異を検出することができる。即ち、非記録領域と記録領域を判別できるので、情報記録媒体１の記録層２に記録された情報を再生することが可能である。
【００６９】
ここで、基板３、記録層２、再生光入射媒体８の屈折率の関係は、基板３の屈折率（１．５６１）＜記録層２の屈折率（閉環状態＝１．６４８、開環状態＝１．６１１）＜再生光入射媒体８の屈折率（１．９５２）であり、少なくともこの関係を満たせば、上述した再生原理は成立する。よって、この屈折率の関係を満足するように、基板３、記録層２、再生光入射媒体８の材料を適宜選択すればよい。更に、記録層２の上に記録層２よりも屈折率の高い材料の膜を形成して、再生光入射媒体８と同じ働きを持たせることも可能である。
【００７０】
なお、図４において、入射角５３．５°で閉環状態である非記録領域の反射光強度が低下しているが、これは、特定の条件を満たすことにより、記録層２が二次元導波路となり、再生光が記録層２の内部を導波モードとして伝搬した結果である。
【００７１】
以上、本実施の形態１について説明したが、便宜上、記録装置と再生装置を個別に図示して説明したが、図３で示した再生装置の再生光光源７と共に記録光光源４を設けて、再生光入射媒体８と半球レンズ６を共用し、一体化しても良いのは言うまでもない。そして、再生光光源７と記録光光源４に更に消去光光源を設けてもよい。
【００７２】
なお、本実施の形態１について説明した再生装置、再生方法は、特定波長の光照射により屈折率が可逆的に変化するフォトクロミック材料を再生する例で説明したが、場合によっては、このフォトクロミック材料以外の材料を記録層として備える情報記録媒体にも適用できる。
【００７３】
即ち、エネルギーを付与することによって、屈折率が変化する材料、例えば、熱によって屈折率が変化する液晶、電圧により屈折率が変化するポリフッ化ビニリデン等の強誘電体が考えられ、いずれの材料であっても、上述した再生原理に基づき、リークモードにおける屈折率差が反射光強度の差として検出されれば適用可能である。
【００７４】
更に、本実施の形態１において説明した、フォトクロミック材料の特性、光学系の構成、使用光源および使用光源の中心波長、対物レンズおよび半球レンズの仕様は一例であり、その他様々な構成で、本実施の形態１と同様に情報記録媒体の記録／再生、消去を行うことができる。
【００７５】
【発明の効果】
本発明によれば、エネルギーを付与することによって屈折率が変化する記録領域を備えた情報記録媒体、特に、屈折率が可逆的に変化するフォトクロミック材料で構成される記録領域を備えた情報記録媒体に記録された情報を消去、オーバーライトをすることなく、再生可能な情報記録媒体及びその記録・再生方法並びに記録・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】本発明の実施の形態１による情報記録媒体の記録装置の構成模式図
【図２】本発明の実施の形態１によるフォトクロミック材料の光吸収特性を示すグラフ
【図３】本発明の実施の形態１による情報記録媒体の再生装置の構成模式図
【図４】本発明の実施の形態１による入射角θと反射光強度の関係を示すグラフ
【符号の説明】
１ 情報記録媒体
２ 記録層
３ 基板
４ 記録光光源
５ 対物レンズ
６ 半球レンズ
７ 再生光光源
８ 再生光入射媒体
９ 光検出器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an information recording medium having a recording area in which a refractive index changes by applying energy, a recording / reproducing method thereof, and a recording / reproducing apparatus,
The present invention relates to an information recording medium having a recording region composed of a photochromic material whose refractive index changes reversibly by irradiating light of a specific wavelength, a recording / reproducing method thereof, and a recording / reproducing apparatus.
[0002]
[Prior art]
In recent years, various optical recording / reproducing techniques have been studied in response to the need for higher density optical disks. Furthermore, in addition to increasing the density, a phase change type optical disk is also known as an optical disk capable of recording / erasing / reproducing information.
[0003]
These phase-change-type rewritable optical discs have recently been increased in density by developing practical short-wavelength lasers, but the upper limit is the diffraction limit of recording / reproducing light. Depending on the wavelength of the laser used as light, there is a limit to increasing the density.
[0004]
Therefore, in order to further improve the recording density, an optical recording / reproducing technique using near-field light has been studied. In an optical recording / reproducing technique using near-field light, a photochromic material is used for the optical recording medium. This photochromic material can record information with extremely weak light, and attempts have been made to increase the density by performing optical recording and reproduction using near-field light. For example, (patent document 1) has the indication.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-251282 [0006]
[Problems to be solved by the invention]
However, these conventional techniques have the following problems. Although the photochromic material used for the recording layer of optical information recording media can record information with extremely weak light such as near-field light, it is so sensitive that it utilizes the difference in light absorption characteristics of the photochromic material itself. In near-field light reproduction, there is a problem that recorded information is erased or overwritten.
[0007]
The present invention has been made in view of such a conventional problem, and is an information recording medium provided with a recording region whose refractive index changes by applying energy, in particular, a photochromic material whose refractive index changes reversibly. It is an object to provide an information recording medium that can be reproduced without erasing and overwriting information recorded on an information recording medium having a recording area composed of the recording area, a recording / reproducing method thereof, and a recording / reproducing apparatus. And
[0008]
[Means for Solving the Problems]
The information recording medium of the present invention includes a storage layer made of a photochromic material on a substrate , and a storage medium is provided adjacent to a medium for entering reproduction light of the second wavelength. 1 when the recording light wavelength Ru is granted energy caused bleeding out of the near-field light irradiating the information recording medium in which the refractive index of the recording light is irradiated storage layer forms a reversibly changed record area The substrate, the initial storage layer, the storage layer irradiated with the recording light, and the medium have a refractive index that increases in order, and when the reproduction light is incident at an angle less than the critical angle of total reflection during reproduction. and a configuration in which reproduction light is transmitted through the radiation into the substrate storage layer to reduce the reflected light intensity, and the reflected light intensity of the reproducing light between the regions having different refractive indexes of the recording area is detected as different .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 is provided with a storage layer made of a photochromic material on a substrate , and a medium for entering reproduction light of the second wavelength is provided adjacent to the storage layer and used. When the recording light of the first wavelength Ru is granted energy caused bleeding out of the near-field light irradiating the information recording medium in which the refractive index of the recording light is irradiated storage layer forms a reversibly changed record area The refractive index increases in the order of the substrate, the initial storage layer, the storage layer irradiated with the recording light, and the medium, and the reproduction light is incident at an angle less than the critical angle of total reflection during reproduction. When, that reproducing light is transmitted radiates into the substrate storage layer to reduce the reflected light intensity, and the reflected light intensity of the reproducing light between the regions having different refractive indexes of the recording area is detected as different An information recording medium characterized by a change in refractive index Can be recorded information, a change in the refractive index and the recorded information can be rewritable.
[0012]
Amorphous The invention according to claim 2, in claim 1, comprising a photochromic material transparent polymer composite or a photochromic dye which confidence containing a photochromic dye having a molecular structure represented by the following formula (i) An information recording medium comprising a transparent material, wherein a change in refractive index due to ring opening or ring closing of the photochromic material can be used as recording information and can be rewritten.
[0013]
[Chemical 7]

[0014]
[In the above formula (i), A represents the following substituent (ii) or substituent (iii) {in substituent (ii) and substituent (iii), R ¹ represents an alkyl group, an alkoxy group, a halogen atom, a halogenated group) Represents an alkyl group, a cyano group or an optionally substituted aryl group, and R ² and R ³ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a trifluoromethyl group, a cyano group, or a substituted group. An aryl group which may be substituted, or the following substituent (iv) or substituent (v) {in the substituent (iv) and the substituent (v), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , ^{R 7, R 8, R 9} , R 10, R 11, R 12 and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a trifluoromethyl group, a cyano group, or optionally substituted Represents} represents a have aryl groups, X is -O -, - S- or -NR ⁴ - (R ⁴ is a hydrogen atom, an optionally substituted alkyl group, also aryl group or a substituted substituted Represents an optionally substituted cycloalkyl group),
[0015]
[Chemical 8]

[0016]
B is the following substituent (vi) or substituent (vii) {in the substituent (vi) and substituent (vii), R ¹ is an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a cyano group or a substituted group. R ² and R ³ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a trifluoromethyl group, a cyano group, an optionally substituted aryl group, or the following Substituent (viii) or Substituent (ix) {In Substituent (viii) and Substituent (ix) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ^{9 , R 10, R 11, R} 12 and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a trifluoromethyl group, a cyano group or an optionally substituted aryl, Represents represents} a, X is -O -, - S- or -NR ⁴ - (R ⁴ is a hydrogen atom, an optionally substituted alkyl group, be also aryl group or a substituted substituted Represents a good cycloalkyl group)}
[0017]
[Chemical 9]

[0018]
The invention according to claim 3 is provided with a storage layer made of a photochromic material on the substrate , and a medium for entering the reproduction light of the second wavelength is provided adjacent to the storage layer and used. When the recording light of the first wavelength Ru is granted energy caused bleeding out of the near-field light irradiating the information recording medium in which the refractive index of the recording light is irradiated storage layer forms a reversibly changed record area Is a recording / reproducing method in which recording is performed by irradiating recording light, and reproducing is performed by irradiating reproduction light of a second wavelength, wherein the refractive index of the substrate, the storage layer, and the medium is the substrate, the storage layer in the initial state, The storage layer after irradiation of the recording light is configured to increase in the order of the medium. During recording, energy is applied to the storage layer with the recording light to record information by changing the refractive index , and during reproduction, the critical angle of total reflection is recorded. Reproducing light is incident at the following angle and transmitted through the memory layer. Reduce the reflected light intensity by radiation to the plate, an information recording recording and reproducing method of the medium and detecting the reflected light intensity differed between regions having different refractive indexes of the recording area, Recording / reproduction is possible even when using a wavelength with no sensitivity of the recording medium without depending on absorption of a specific wavelength.
[0020]
According to a fourth aspect of the present invention, in the third aspect , the photochromic material is an amorphous material comprising a transparent polymer composite material containing a photochromic dye having a molecular structure represented by the following general formula (i) or the photochromic dye itself: A recording / reproducing method for an information recording medium comprising a transparent material, wherein the recorded information is erased or overwritten by using light other than a specific wavelength that contributes to ring opening or ring closing of the photochromic material as reproducing light. Light can be suppressed and replayed.
[0021]
[Chemical Formula 10]

[0022]
[In the above formula (i), A represents the following substituent (ii) or substituent (iii) {in substituent (ii) and substituent (iii), R ¹ represents an alkyl group, an alkoxy group, a halogen atom, a halogenated group) Represents an alkyl group, a cyano group or an optionally substituted aryl group, and R ² and R ³ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a trifluoromethyl group, a cyano group, or a substituted group. An aryl group which may be substituted, or the following substituent (iv) or substituent (v) {in the substituent (iv) and the substituent (v), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , ^{R 7, R 8, R 9} , R 10, R 11, R 12 and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a trifluoromethyl group, a cyano group, or optionally substituted Represents} represents a have aryl groups, X is -O -, - S- or -NR ⁴ - (R ⁴ is a hydrogen atom, an optionally substituted alkyl group, also aryl group or a substituted substituted Represents an optionally substituted cycloalkyl group),
[0023]
Embedded image

[0024]
B is the following substituent (vi) or substituent (vii) {in the substituent (vi) and substituent (vii), R ¹ is an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a cyano group or a substituted group. R ² and R ³ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a trifluoromethyl group, a cyano group, an optionally substituted aryl group, or the following Substituent (viii) or Substituent (ix) {In Substituent (viii) and Substituent (ix) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ^{9 , R 10, R 11, R} 12 and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a trifluoromethyl group, a cyano group or an optionally substituted aryl, Represents represents} a, X is -O -, - S- or -NR ⁴ - (R ⁴ is a hydrogen atom, an optionally substituted alkyl group, be also aryl group or a substituted substituted Represents a good cycloalkyl group)}
[0025]
Embedded image

[0027]
The invention according to claim 5 is characterized in that, in claim 3 or 4 , the information recorded in the recording area is erased by irradiating the recording area with erasing light having a third wavelength different from the recording light. The information recording medium recording / reproducing method can be rewritable.
[0028]
The invention according to claim 6 is provided with a storage layer made of a photochromic material on a substrate , and a storage medium is provided adjacent to the medium for entering the reproduction light of the second wavelength. When the recording light of the first wavelength Ru is granted energy caused bleeding out of the near-field light irradiating the information recording medium in which the refractive index of the recording light is irradiated storage layer forms a reversibly changed record area Is a recording / reproducing apparatus for an information recording medium that performs recording by irradiating with recording light and reproducing by irradiating reproduction light of a second wavelength, and energy is applied to the storage layer of the information recording medium by irradiation of the recording light. recording means for imparting a reproduction light source for emitting the reproducing light of the second wavelength, and the reproducing light incident medium is provided as a medium, the substrate, the storage layer, the refractive index of the substrate of the medium, the storage layer in the initial state, Storage layer after recording light irradiation, medium increases in order Is configured so that, for receiving the reproduction light incident means is incident reproduction light, the reflected light having different reflected light intensity between regions with different refractive indexes of the recording area at the critical angle following the angle of the total reflection A recording / reproducing apparatus for an information recording medium, comprising: a light detector, wherein the intensity of reflected light is reduced by radiating the reproduction light to the substrate through the storage layer at the time of reproduction; Recording / reproduction is possible even when using a wavelength that does not depend on the absorption of the recording medium and does not have the sensitivity of the recording medium.
[0030]
The invention described in claim 7, that the claim 6, comprising a deletion means for irradiating erasing light of a different third wavelength to the recording light to the recording area, erasing recorded in the recording area information An information recording medium recording / reproducing apparatus characterized in that can be rewritable.
[0031]
(Embodiment 1)
Hereinafter, an information recording medium, a recording / reproducing method thereof, and a recording / reproducing apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings.
[0032]
First, a recording method on an information recording medium according to Embodiment 1 of the present invention will be described.
[0033]
FIG. 1 is a schematic configuration diagram of a recording apparatus for an information recording medium according to Embodiment 1 of the present invention.
[0034]
In FIG. 1, 1 is an information recording medium, 2 is a recording layer, 3 is a substrate, 4 is a recording light source, 5 is an objective lens, and 6 is a hemispherical lens.
[0035]
In the information recording medium 1, a recording layer 2 is formed on a substrate 3, and the recording layer 2 includes a recording area. In the first embodiment, the case where the recording layer 2 is made of a photochromic material whose refractive index reversibly changes when irradiated with light of a specific wavelength will be described.
[0036]
Recording on the information recording medium according to Embodiment 1 of the present invention is performed by irradiating near-field light.
[0037]
First, the light emitted from the recording light source 4 is guided to the objective lens 5. The light passing through the objective lens 5 is focused on the center of the hemispherical lens 6 and is condensed. An information recording medium 1 in which a recording layer 2 made of a photochromic material is formed on a substrate 1 is disposed in close proximity to the hemispherical lens 6 and irradiated with near-field light emitted from the bottom surface of the hemispherical lens 6.
[0038]
Here, the principle of information recording will be described. FIG. 2 is a graph showing the light absorption characteristics of the photochromic material according to Embodiment 1 of the present invention.
[0039]
As shown in FIG. 2, this photochromic material is a material having a remarkable absorption peak at a light wavelength of 400 nm or less and in the vicinity of 600 nm. Light having a wavelength of 400 nm or less changes from ring-opening to ring-closing, and light near 600 nm is closed. It contributes to the change from open to open state. Note that the color of the material itself changes from transparent to blue and from blue to transparent as the state changes from ring-opening to ring-closing and from ring-closing to ring-opening.
[0040]
In addition, as the photochromic material, a transparent polymer composite material containing a photochromic dye having the molecular structure represented by the general formula (i) shown above or an amorphous transparent material composed of a photochromic dye or the like is preferably used. Can do. And the structural formula of the specific compound (1) of this photochromic material is shown below.
[0041]
Embedded image

[0042]
Furthermore, various specific examples and synthesis methods of these photochromic materials include ““ Synthesis of Fluoresient Amorphous Diarythenes ”,“ Chemistry Letters, p. Mol. Cryst.
[0043]
Note that the material is not limited to the photochromic material having the molecular structure represented by the general formula (i), and a material having another molecular structure can be used as long as it has the same characteristics.
[0044]
When recording is performed on the recording layer 2 of the information recording medium 1 composed of such a photochromic material, a light wavelength having a remarkable absorption peak is selected as the wavelength of the recording light. Judging from the characteristics shown in FIG. 2, it is desirable to use light of 400 nm or near 600 nm. The spot size (= SD) collected at the center of the bottom surface of the hemispherical lens 6 is determined from the light wavelength (= λ), the numerical aperture of the objective lens 5, the incident position of the recording light with respect to the objective lens 5, and its beam diameter. From the emission angle (= NA = sin θ) and the refractive index (n) of the hemispherical lens 6,
Formula (1) SD = λ / (n × NA)
The recording pit formed in the photochromic material almost reflects this spot size. Therefore, if the light wavelength λ = 400 nm, the angle of the recording light emitted from the objective lens 5 (NA = 0.6), and the refractive index n = 1.8 of the hemispherical lens 6, a pit of about 370 nm can be formed. Become. Similarly, if the light wavelength λ = 600 nm, SD = 550 nm.
[0045]
Note that the depth h of near-field light penetration when using a hemispherical lens is expressed by the following equation (2) h = λ / (2π × ((n × sin θ) ² −1) ^1/2 ).
Given in.
[0046]
Therefore, at the time of recording, the hemispherical lens 6 and the information recording medium 1 need to be close to each other at 150 nm or less when the light wavelength λ = 400 nm and 230 nm or less when 600 nm.
[0047]
For example, when the initial state is a ring-closed state of the photochromic material and the recording state is the ring-opened state, the wavelength of the recording light is 600 nm. Under the above conditions, the hemispherical lens 6 and the information recording medium 1 are brought close to each other at 230 nm or less. That's fine. Then, by irradiating with light of 600 nm, recording is performed by changing the photochromic material from a closed ring to an open state. Furthermore, by irradiating with light of 400 nm, the photochromic material can be changed from a ring-opening state to a ring-closing state to be in an initial state, and recorded information can be erased. Therefore, the wavelength of the recording light is 600 nm and the wavelength of the erasing light is 400 nm.
[0048]
Alternatively, in the case where the initial state is the ring-opening state of the photochromic material and the recording state is the ring-closing state, the wavelength of the recording light is 400 nm, and the hemispherical lens 6 and the information recording medium 1 are close to each other at 150 nm or less under the above conditions. Just do it. Then, the photochromic material is changed from a ring-opened state to a ring-closed state by irradiating light of 400 nm, and recording is performed. Further, by irradiating with light of 600 nm, the photochromic material can be changed from a closed ring to an opened state to be in an initial state, and recorded information can be erased. Therefore, the wavelength of the recording light is 400 nm and the wavelength of the erasing light is 600 nm.
[0049]
As the erasing light source, an erasing light source may be provided together with the recording light source 4 shown in FIG. 1, or an erasing light source capable of irradiating the entire recording layer 2 of the information recording medium 1 may be provided. .
[0050]
Next, a method for reproducing information on the information recording medium according to Embodiment 1 of the present invention will be described.
[0051]
FIG. 3 is a schematic diagram of the structure of the information recording medium reproducing apparatus according to Embodiment 1 of the present invention.
[0052]
In FIG. 3, 7 is a reproduction light source, 8 is a reproduction light incident medium, and 9 is a photodetector.
[0053]
Then, reproduction of the information recording medium according to Embodiment 1 of the present invention is performed by irradiating near-field light in the same manner as recording.
[0054]
In addition, although mentioned later for details, the wavelength used for reproduction | regeneration light uses the light of the wavelength of the area | region which does not absorb photochromic material. In this case, infrared light is preferable, for example, a laser emitting infrared light such as 780 nm for reproduction of a CD-ROM.
[0055]
First, the light emitted from the reproduction light source 7 passes through the objective lens 5 and is incident on the reproduction light incident medium 8, and the recording layer 2 of the information recording medium 1 is irradiated with the near-field light at a predetermined angle θ. .
[0056]
The reflected signal light from the information recording medium 1 passes through the reproduction light incident medium 8 and is guided to the photodetector 9 through the objective lens 5.
[0057]
Here, the principle of information reproduction will be described. The advantages of photochromic materials are that they are sensitive to very low light and can change the state of ring opening and ring closure, but at the same time, this advantage can be a disadvantage. In FIG. 2, it has been described above that there is a light absorption band at λ = 400 nm or less and in the vicinity of 600 nm. However, when reproduction is performed using these optical wavelengths, a phenomenon of overwriting or erasing recorded information occurs even if the optical power of the reproduction light is extremely reduced. Therefore, it is practically difficult to reproduce at an optical wavelength having remarkable light absorption used for information recording.
[0058]
Therefore, attention was paid to the fact that the refractive index slightly changes when the photochromic material changes from the closed state to the open state. When information recording is performed with recording light in the vicinity of λ = 600 nm with the ring-closed state of the photochromic material as the initial state, only the portion irradiated with light is in the ring-opened state, and the refractive index is slightly reduced. This refractive index change (= Δn) is about 0.01 to 0.10.
[0059]
The inventors have found that when the incident angle of the reproduction light is incident at a specific angle, the reflected light intensity of the reproduction light is different between the ring-closed state and the ring-open state of the photochromic material. It was possible to detect the difference.
[0060]
That is, the incident angle θ of the reproduction light incident on the recording layer 2 of the information recording medium 1 from the reproduction light incident medium 8, the refractive index of the medium constituting the reproduction light incident medium 8, and the substrate 3 of the information recording medium 1. Incident light is incident at an angle equal to or smaller than the critical angle of total reflection of reproduction light determined by the refractive index. In addition, the incident angle θ which is an angle equal to or smaller than the critical angle means that θ ₀ > θ when the critical angle is θ ₀ .
[0061]
When the reproduction light is incident at an angle less than the critical angle of total reflection, the reproduction light is changed into a leak mode to the substrate 3, that is, a radiation mode to the substrate 3 through the recording layer 2. And in this leak mode, it turned out that the reflected light intensity | strength of reproduction | regeneration light differs in the ring-closing state and ring-opening state of a photochromic material. By the way, it is considered that the reproduction light in the leak mode has a difference in reflection or absorption in the layer or at the interface due to the difference in the refractive index of the recording layer 2, resulting in a difference in reflected light intensity. Details regarding the correlation between the magnitude of the refractive index and the magnitude of the reflected light intensity are not clear.
[0062]
These matters were obtained from experiments by the present inventors, and the contents and results of the experiments will be described below.
[0063]
First, as the information recording medium 1, a glass substrate (refractive index = 1.561) was used for the substrate 3, and a photochromic material of the specific compound (1) was used for the recording layer 2. This photochromic material has a refractive index in the ring-closed state of 1.648 and a refractive index in the ring-opened state of 1.611. The initial state is the ring-closed state of the photochromic material and the recording state is the ring-opened state. Recording was performed at a wavelength of 600 nm using the recording apparatus shown in FIG.
[0064]
Next, using the reproducing apparatus shown in FIG. 3, an area in the recording layer 2 that is in the initial ring-closed state (non-recording area) and a region in the recording layer 2 that is in the ring-opened state (recording area) The incident angle θ of the reproduction light was changed and incident, and the reflected light intensity was detected by the photodetector 9. Further, a hemispherical lens (refractive index = 1.952) was used as the reproduction light incident medium 8, and infrared light having a wavelength of 817 nm was used as the reproduction light.
[0065]
And the measurement result of the reflected light intensity in a non-recording area | region and a recording area is shown in FIG. FIG. 4 is a graph showing the relationship between the incident angle θ and the reflected light intensity according to the first embodiment of the present invention.
[0066]
Here, according to Snell's law, the critical angle of total reflection of the reproduction light determined by the refractive index (1.952) of the reproduction light incident medium 8 and the refractive index (1.561) of the substrate 3 is 53.1 °.
[0067]
As is apparent from the results of FIG. 4, when the incident angle θ is less than or equal to the critical angle of 53.1 °, the non-recording area and the recording area both change from the total reflection to the leak mode described above, and the reflected light intensity. Decreases. Further, the reflected light intensity differs between the non-recording area and the recording area.
[0068]
Therefore, the incident angle θ of the reproduction light incident on the recording layer 2 of the information recording medium 1 from the reproduction light incident medium 8, the refractive index of the medium constituting the reproduction light incident medium 8, and the substrate 3 of the information recording medium 1. It is possible to detect a difference in reflected light intensity of the reproduction light between the ring-closed state and the ring-open state of the photochromic material by entering as an angle that is less than the critical angle of the total reflection of the reproduction light determined by the refractive index. it can. That is, since the non-recording area and the recording area can be discriminated, the information recorded on the recording layer 2 of the information recording medium 1 can be reproduced.
[0069]
Here, the relationship between the refractive indexes of the substrate 3, the recording layer 2, and the reproducing light incident medium 8 is as follows: the refractive index of the substrate 3 (1.561) <the refractive index of the recording layer 2 (ring-closed state = 1.648, ring-opened state). = 1.611) <Refractive index (1.952) of the reproduction light incident medium 8, and the above-described reproduction principle is satisfied if at least this relationship is satisfied. Therefore, the material of the substrate 3, the recording layer 2, and the reproduction light incident medium 8 may be appropriately selected so as to satisfy this refractive index relationship. Further, a film made of a material having a refractive index higher than that of the recording layer 2 can be formed on the recording layer 2 to have the same function as the reproducing light incident medium 8.
[0070]
In FIG. 4, the reflected light intensity of the non-recording area in the closed state is reduced at an incident angle of 53.5 °. This is because the recording layer 2 is a two-dimensional waveguide by satisfying a specific condition. This is a result of the reproduction light propagating through the recording layer 2 as a waveguide mode.
[0071]
As described above, the first embodiment has been described. For convenience, the recording apparatus and the reproducing apparatus are illustrated and described separately. However, the recording light source 4 is provided together with the reproducing light source 7 of the reproducing apparatus illustrated in FIG. Needless to say, the reproducing light incident medium 8 and the hemispherical lens 6 may be shared and integrated. Further, an erasing light source may be further provided on the reproducing light source 7 and the recording light source 4.
[0072]
In addition, although the reproducing | regenerating apparatus and reproducing | regenerating method demonstrated about this Embodiment 1 demonstrated in the example which reproduces | regenerates the photochromic material from which a refractive index changes reversibly by the light irradiation of a specific wavelength, depending on the case, other than this photochromic material The present invention can also be applied to an information recording medium having the above material as a recording layer.
[0073]
That is, a material whose refractive index changes by applying energy, such as a liquid crystal whose refractive index changes with heat, or a ferroelectric such as polyvinylidene fluoride whose refractive index changes with voltage, can be considered. Even if it exists, it is applicable if the refractive index difference in the leak mode is detected as a difference in reflected light intensity based on the above-described reproduction principle.
[0074]
Furthermore, the characteristics of the photochromic material, the configuration of the optical system, the used light source and the center wavelength of the used light source, the specifications of the objective lens and the hemispherical lens described in the first embodiment are examples, and the present embodiment is implemented in various other configurations. As in the first embodiment, recording / reproduction and erasure of the information recording medium can be performed.
[0075]
【The invention's effect】
According to the present invention, an information recording medium provided with a recording area whose refractive index changes by applying energy, particularly an information recording medium provided with a recording area composed of a photochromic material whose refractive index changes reversibly. It is possible to provide an information recording medium that can be reproduced without erasing and overwriting information recorded on the recording medium, a recording / reproducing method thereof, and a recording / reproducing apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a recording apparatus for an information recording medium according to Embodiment 1 of the present invention. FIG. 2 is a graph showing the light absorption characteristics of a photochromic material according to Embodiment 1 of the present invention. FIG. 4 is a schematic diagram of the configuration of a reproducing apparatus for an information recording medium according to Embodiment 1. FIG. 4 is a graph showing the relationship between incident angle θ and reflected light intensity according to Embodiment 1 of the present invention.
DESCRIPTION OF SYMBOLS 1 Information recording medium 2 Recording layer 3 Substrate 4 Recording light source 5 Objective lens 6 Hemispherical lens 7 Reproducing light source 8 Reproducing light incident medium 9 Photo detector

Claims (7)

A storage layer made of a photochromic material is provided on the substrate , and a medium for inputting reproduction light of the second wavelength is provided adjacent to the storage layer and used, and the recording light of the first wavelength is irradiated. When energy is Ru granted bleeding of near-field light is generated, the refractive index of the recording light is irradiated storage layer is an information recording medium to form a reversibly changed recording area,
The substrate, the storage layer in the initial state, the storage layer irradiated with the recording light, and the medium have a refractive index that increases in this order, and the reproduction light is incident at an angle less than the critical angle of total reflection during reproduction. When the reproduction light passes through the storage layer is emitted to reduce the reflected light intensity to the substrate, and the recording area of the detected as different reflected light intensity of the reproduction beam with each other between the regions having a different refractive index An information recording medium characterized by that. To claim 1 wherein the photochromic material is characterized by comprising an amorphous transparent material made of a transparent polymer composite or photochromic dye itself contains a photochromic dye having a molecular structure represented by the following formula (i) The information recording medium described.

[In the above formula (i), A represents the following substituent (ii) or substituent (iii) {in substituent (ii) and substituent (iii), R ¹ represents an alkyl group, an alkoxy group, a halogen atom, a halogenated group) Represents an alkyl group, a cyano group or an optionally substituted aryl group, and R ² and R ³ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a trifluoromethyl group, a cyano group, or a substituted group. An aryl group which may be substituted, or the following substituent (iv) or substituent (v) {in the substituent (iv) and the substituent (v), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , ^{R 7, R 8, R 9} , R 10, R 11, R 12 and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a trifluoromethyl group, a cyano group, or optionally substituted Represents} represents a have aryl groups, X is -O -, - S- or -NR ⁴ - (R ⁴ is a hydrogen atom, an optionally substituted alkyl group, also aryl group or a substituted substituted Represents an optionally substituted cycloalkyl group),

B is the following substituent (vi) or substituent (vii) {in the substituent (vi) and substituent (vii), R1 is an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a cyano group or a substituted group. R2 and R3 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a trifluoromethyl group, a cyano group, an optionally substituted aryl group or the following substituent ( viii) or substituent (ix) {in substituent (viii) and substituent (ix), R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12 and R13 are each independently Hydrogen atom, halogen atom, alkyl group, alkoxy group, trifluoromethyl group, cyano group, or optionally substituted X represents —O—, —S— or —NR 4 — (R 4 represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted group; Represents a good cycloalkyl group)}

A storage layer made of a photochromic material is provided on the substrate , and a medium for inputting reproduction light of the second wavelength is provided adjacent to the storage layer and used, and the recording light of the first wavelength is irradiated. When energy is Ru granted bleeding of near-field light is generated, the refractive index of the recording light is irradiated storage layer is irradiated with the recording light on the information recording medium to form a reversibly changed record area A recording / reproducing method for recording and reproducing by irradiating reproduction light of a second wavelength ,
The refractive index of the substrate, the storage layer, and the medium is configured to increase in the order of the substrate, the storage layer in the initial state, the storage layer after irradiation of the recording light, and the medium.
When recording, information is recorded by changing the refractive index by applying energy to the storage layer with the recording light ,
Area where the reproduction light is incident at an angle less than the critical angle of total reflection at the time of reproduction, and the reflected light intensity is reduced by transmitting through the storage layer and radiating to the substrate, and the recording area has different refractive indexes. A method for recording / reproducing information recording medium, characterized by detecting reflected light intensities that differ between the two. The photochromic material in claim 3, characterized in that it consists of an amorphous transparent material made of a transparent polymer composite or photochromic dye itself contains a photochromic dye having a molecular structure represented by the following formula (i) A recording / reproducing method of the information recording medium described.

[In the above formula (i), A represents the following substituent (ii) or substituent (iii) {in substituent (ii) and substituent (iii), R ¹ represents an alkyl group, an alkoxy group, a halogen atom, a halogenated group) Represents an alkyl group, a cyano group or an optionally substituted aryl group, and R ² and R ³ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a trifluoromethyl group, a cyano group, or a substituted group. An aryl group which may be substituted, or the following substituent (iv) or substituent (v) {in the substituent (iv) and the substituent (v), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , ^{R 7, R 8, R 9} , R 10, R 11, R 12 and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a trifluoromethyl group, a cyano group, or optionally substituted Represents} represents a have aryl groups, X is -O -, - S- or -NR ⁴ - (R ⁴ is a hydrogen atom, an optionally substituted alkyl group, also aryl group or a substituted substituted Represents an optionally substituted cycloalkyl group),

B is the following substituent (vi) or substituent (vii) {in the substituent (vi) and substituent (vii), R ¹ is an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a cyano group or a substituted group. R ² and R ³ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a trifluoromethyl group, a cyano group, an optionally substituted aryl group, or the following Substituent (viii) or Substituent (ix) {In Substituent (viii) and Substituent (ix) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ^{9 , R 10, R 11, R} 12 and R ¹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a trifluoromethyl group, a cyano group or an optionally substituted aryl, Represents represents} a, X is -O -, - S- or -NR ⁴ - (R ⁴ is a hydrogen atom, an optionally substituted alkyl group, be also aryl group or a substituted substituted Represents a good cycloalkyl group)}

5. The information recording medium according to claim 3 , wherein the information recorded in the recording area is erased by irradiating the recording area with erasing light having a third wavelength different from that of the recording light. -Playback method. A storage layer made of a photochromic material is provided on the substrate , and a medium for inputting reproduction light of the second wavelength is provided adjacent to the storage layer and used, and the recording light of the first wavelength is irradiated. When energy is Ru granted bleeding of near-field light is generated, the refractive index of the recording light is irradiated storage layer is irradiated with the recording light on the information recording medium to form a reversibly changed record area A recording / reproducing apparatus for an information recording medium for recording and reproducing by irradiating reproduction light of a second wavelength ,
Recording means for applying energy to the storage layer of the information recording medium by irradiation of the recording light ;
A reproduction light source for emitting the reproducing light of the second wavelength, and the reproducing light incident medium is provided as the medium,
The refractive index of the substrate, the storage layer, and the medium is configured to increase in the order of the substrate, the storage layer in the initial state, the storage layer after irradiation of the recording light, and the medium.
Reproduction light incident means for entering the reproduction light at an angle less than the critical angle of total reflection, and a photodetector for receiving reflected light having different reflected light intensities between regions having different refractive indexes in the recording region; The information recording medium recording / reproducing apparatus is characterized in that the intensity of reflected light is reduced by radiating reproduction light to the substrate through the storage layer during reproduction. 7. The information according to claim 6, further comprising erasing means for erasing information recorded in the recording area by irradiating the recording area with erasing light having a third wavelength different from that of the recording light. Recording / recording device for recording media.

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