JP4154132B2 - Optical information recording medium - Google Patents

Optical information recording medium Download PDF

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JP4154132B2
JP4154132B2 JP2001134163A JP2001134163A JP4154132B2 JP 4154132 B2 JP4154132 B2 JP 4154132B2 JP 2001134163 A JP2001134163 A JP 2001134163A JP 2001134163 A JP2001134163 A JP 2001134163A JP 4154132 B2 JP4154132 B2 JP 4154132B2
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information recording
recording medium
optical information
wavelength
light
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JP2002334480A (en
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雅温 秋葉
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Fujifilm Corp
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Fujifilm Corp
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Description

【0001】
【発明の属する技術分野】
本発明はレーザー光による情報書き込みが可能な光情報記録媒体およびそれを用いた記録方法に関するものである。特に本発明は非共鳴な2光子以上の非共鳴多光子吸収を用いて情報を記録するのに適した光情報記録媒体およびそれを用いた記録方法に関するものである。
【0002】
【従来の技術】
従来からレーザー光を用いて情報を記録する記録媒体としてCD−RやCD−RWのような光ディスクが知られている。これらの光ディスクでは約780nmの波長のレーザーが用いられている。近年、情報技術の急速な発展にともない、記録媒体の高容量化、高密度化がますます強く求められている。高容量化、記録密度を実現するには、情報記録のためのレーザー光の半径をできるだけ小さく絞ることが有効であるが、回折限界を超えて絞り込むことはできない。回折限界はレーザー光の波長に依存しており、短波長であるほど小さいことが理論的に知られている。このため、従来から用いられている780nmより短波長のレーザーを用いて記録再生が可能な光ディスクの開発が進められており、例えばDVD−RやDVD−RWと称される光ディスクが提案されている。DVD−RやDVD−RWでは600nm〜700nmの波長のレーザーが用いられており、CD−RやCD−RWよりも高容量かつ高密度の記録が可能となっている。しかしながらレーザーの短波長化はようやく600nm台まで実現されたレベルであり、更なる短波化は非常に困難である。
【0003】
そこで、短波長のレーザーを用いること無く高容量かつ高密度な情報記録媒体を得るための手段として、非線形光学効果の一つである非共鳴2光子吸収過程を利用することが提案されている。
【0004】
非共鳴2光子吸収とは、分子が2つの光子を同時に吸収して励起される非線形現象であり、照射したレーザー光波長に対応する光子の2倍のエネルギーを分子が吸収するため、線形吸収の存在しないより長波な波長領域の光を用いても分子を励起することが可能である。さらに、非共鳴2光子吸収の起こる確率は照射する光強度の2乗に比例するため、非共鳴2光子吸収を誘起するレーザー光の強度分布が半値幅の狭まったより鋭い形状になる。これはレーザー光の半径をより絞り込むことに相当し、したがって照射光の半径よりも小さい半径領域での情報記録が可能となる。また、同様の理由から焦点位置の極近傍でしか非共鳴2光子吸収が起こらないため、3次元的な情報記録も可能である。これらの性質により、非共鳴2光子吸収を用いれば、原理的には短波長のレーザーを用いなくともより高密度な情報記録が可能となる。
【0005】
非共鳴2光子吸収を示す有機化合物を用いた光情報記録媒体に関しては、例えばChemical Reviews,100,1777(2000)に紹介されており、実際に近赤外レーザーを用いても高密度な記録が可能であることが示されている。
【0006】
非共鳴2光子吸収化合物として用いる化合物は、用いる近赤外レーザーの波長領域には線形吸収帯を有さないが、通常は可視光領域に線形吸収帯が存在するため、その線形吸収が起こると記録情報の光劣化が起こってしまう。
【0007】
【発明が解決しようとする課題】
ところで、情報記録媒体は初期において記録−再生特性が良好であるのは勿論であるが、長期間にわたっても安定に記録−再生が行えなければならない。このためには、記録媒体は湿度や熱および光に対して十分に安定である必要がある。ところが光情報記録媒体は、光を吸収することにより生成する光励起状態を経由して何らかの化学的または物理的変化を誘起することで情報の記録を行うため、原理的に光に対する安定性が低いという問題点を有する。
【0008】
【課題を解決するための手段】
本発明は、非共鳴2光子または非共鳴多光子吸収を利用して情報を記録する光記録媒体において、2光子または多光子吸収化合物の線形吸収を防止することで、該光記録媒体の耐光性を著しく向上させることが可能となった。本発明の目的は、下記の手段により達成された。
【0009】
(1) 支持体上に少なくとも光情報記録層を設けた光情報記録媒体において、前記光情報記録層が非共鳴2光子吸収または非共鳴多光子吸収を示し、かつ、該光情報記録層の線形吸収を防止する層を設けたことを特徴とする光情報記録媒体。
(2) 該線形吸収を防止する層を該光情報記録層の両側に設けたことを特徴とする上記(1)記載の光情報記録媒体。
(3) 該線形吸収を防止する層が光学フィルターであり、該光学フィルター層は、該光情報記録層の線形吸収帯が存在する波長範囲の光を透過させず、それよりも長波の光のみを透過させることを特徴とする上記(1)または(2)記載の光情報記録媒体。
(4) 該光学フィルターの透過させない光の波長が、記録層に含まれる化合物に由来する吸収帯の吸収端波長と同じかそれよりも長波長で、かつ記録光に用いる光の波長よりも短波な波長範囲であることを特徴とする上記(2)または(3)に記載の光情報記録媒体。ここで吸収端波長とは、透過スペクトルにおいて、記録層に由来する吸収帯の長波長側の裾で透過率が直線状となる部分を基準に引いた直線に対して、透過率が低くなる最も長波長側の点の波長とする。
(5) 非共鳴2光子吸収または非共鳴多光子吸収を起こす化合物が有機化合物であることを特徴とする上記(1)〜(4)のいずれかに記載の光情報記録媒体。
(6) 上記(1)〜(5)のいずれかに記載の光情報記録媒体に、該記録媒体の記録層に含まれる化合物が有する線形吸収帯より長波長でかつ線形吸収の存在しない波長のレーザー光を照射して誘起された非共鳴2光子以上の非共鳴多光子吸収を利用する情報の記録方法。
【0010】
【発明の実施の形態】
以下に、本発明の光情報記録媒体について詳しく説明する。本発明は、非共鳴2光子または多光子吸収を利用した光情報記録媒体であって、記録媒体に入射してくる光の波長のなかで、ある特定波長よりも長い波長の光のみを透過させることのできる機構を具備することを特徴とするものである。
【0011】
有機化合物の光劣化(光退色)は、化合物の線形吸収によって生成する光励起状態を経由して進行する場合が多い。したがって、線形吸収を防ぐことができれば、光劣化を減少させることができる。本発明の光情報記録媒体は、特に保存時における光劣化を防止するために、記録媒体の線形吸収を防止する層として、ある特定波長よりも長い波長の光のみを透過させるフィルターを設けたものである。
【0012】
ところが、これまでに知られている光情報記録媒体では、情報の書き込みや読み込みの際に、必ず化合物の線形吸収を利用するため、フィルター等を用いて線形吸収を防ぐことは原理的に不可能であった。一方、非共鳴2光子または多光子吸収を用いると、線形吸収の全く存在しない長波長の光を用いて化合物の電子励起を誘起することが可能となる。例えば、400nmに線形吸収を有し、またそれよりも長波長側には全く吸収の存在しない化合物を800nm付近の光で電子励起することが可能である。したがって、記録媒体が有する線形吸収の波長領域をフィルターにより覆い、その波長領域の光が全く透過しなくても、書き込みも読み出しも可能である。
【0013】
本発明の光情報記録媒体に用いられるフィルターは、分光測定や写真撮影の際に光学フィルターとして用いられるシャープカットフィルターのように、ある特定波長よりも短波長の光を吸収することによって、フィルター自体に吸収されない長波長の光のみを透過させるものである。
【0014】
本発明の光情報記録媒体に設けられる該フィルターは、所望の波長より短波長の光は吸収し、長波長の光は透過させる性質を有するものであれば、如何なるものであっても構わないが、JIS B−7113に定める波長傾斜幅が5〜200nmの範囲のものが望ましく、5〜100nmの範囲のものがさらに望ましく、5〜50nmの範囲のものが最も望ましい。
【0015】
本発明の光情報記録媒体に設けられる該フィルターは、所望のシャープカットフィルターを記録媒体の表面を覆うように部分的または全面的に接着したり、適当な色素または色素混合物をフィルター層として記録媒体の表面または記録媒体を構成するいくつかの層の中間に中間層として成形することにより実現する。
【0016】
ところで本発明の光情報記録媒体は、2光子または多光子吸収に由来する何らかの化学的もしくは物理的変化を誘起することで情報を記録する。また、2光子または多光子吸収により何らかの変化が誘起されて情報が記録される部分を記録層と呼ぶ。本発明の記録層は、2光子または多光子吸収を行うことでそれ自身が何らかの化学的、物理的変化を起こす化合物のみから成るか、2光子または多光子吸収化合物と、その2光子または多光子吸収により何らかの化学的、物理的変化が誘起される第二の化合物とから成るか、2光子または多光子吸収化合物と、該化合物の2光子または多光子吸収に誘起されて化学的、物理的変化を起こす第二の化合物の他に、さらにこれらの記録の仕組みを調整する役割の、第三の化合物が含まれてもよい。本発明ではこれらの化合物をまとめて記録化合物と呼ぶ。
係る記録化合物は米国特許5770732号、同5859251号、特願2000−297219、特願2001−110119等に記載されている。
【0017】
本発明における記録層は、CD−RやDVD−Rのように、記録化合物が薄膜状に形成されたものでも、該化合物がマトリックス中に分散されたブロック状のものでもよい。ここで言うマトリックスとは、記録化合物を分散させるホスト材料のことである。
【0018】
マトリックスを構成する材料は光に対して一定の透過性を有することが好ましく、有機高分子材料であっても、ガラス等の無機材料であってもよいが、有機高分子化合物がより好ましい。
【0019】
本発明の光情報記録媒体が、記録化合物をポリマーマトリックス中に分散させたブロック状の場合、分散させるポリマーマトリックスとしては特に制限はなく、ポリカーボネート、ポリメチルメタクリレート等のアクリル樹脂、エポキシ樹脂、アモルファスポリオレフィン、ポリエステル、塩化ビニル系樹脂、ポリエチレンテレフタレート等を用いることができる。
【0020】
ポリマーマトリックス中に含まれる記録化合物は、1〜90質量%の割合で含まれる必要があり、5〜80質量%の割合で含まれることが好ましい。また、プロックの形状は縦、横、高さがそれぞれ独立に1〜100mmの立方体または直方体であることが好ましい。
【0021】
記録化合物をポリマーマトリックス中に分散させる方法には特に制限はなく、種々の方法を用いることができる。例えぱ、ポリマー化合物を溶解し、これに記録化合物を添加し、均一に混合した後、放冷するか、ポリマー化合物と記録化合物を適当な溶媒に溶解させて、加熱しながら溶媒を蒸発させる方法、もしくは記録化合物を相当するモノマーに溶解させて重合反応によりポリマー化させる方法等が挙げられる。
【0022】
記録層が薄膜状の場合には、該フィルター層は記録層の上面および/または下面に配置されるが、両面を覆うことが好ましい。ただし、該フィルター層は記録層と密着していても、間に別の層が存在しても構わない。一方、記録層がブロック状の場合には、記録層のどれか1つの面のみに該フィルター層が配置されるのみでも構わないが、すべての面を覆うように配置することが好ましい。また、記録層と該フィルター層は密着していても、その他の層が存在しても構わない。
【0023】
該フィルター層は、記録層の線形吸収帯が存在する波長範囲の光を透過させず、それよりも長波の光のみを透過させることが好ましい。さらに該フィルター層の透過させない光の波長範囲が、記録層に含まれる化合物の線形吸収帯の吸収端波長と同じか、それよりも長波長で、記録光に用いる光の波長よりも短波な波長範囲であることが好ましい。
【0024】
ここで吸収端波長について説明する。図1には、例として仮想的な記録層の透過スペクトルを示した。この透過スペクトルには、吸収帯の長波長側には吸収が無く透過率の高い直線状の部分が存在する。この部分を元に直線を延長した時(図中の点線の部分)、この直線よりも透過率が低くなる最も長波長側の点を吸収端と定義し、この吸収端の波長を吸収端波長とする。
【0025】
該フィルター層としては、ガラス製シャープカットフィルタや高分子製シャープカットフィルタを用いることができるが、これらに限定されるものではない。また、光に対して堅牢な色素や顔料を高分子マトリクスに分散させて所望のフィルター性能を有するフィルター層を形成してもよく、さらには、そのような色素や顔料をスピンコート法や真空蒸着法などの方法により直接記録媒体上に形成しても良い。
【0026】
【実施例】
(実施例1)
耐光性評価用サンプルの作製
耐光性評価用の記録媒体サンプルは以下のように作製した。特願2000−297219記載の下記構造を有する化合物(1)1gをアセトン100mlに溶解し、色素層形成用塗布液を得た。
【0027】
【化1】

Figure 0004154132
【0028】
この塗布液をHOYA社製シャープカットフィルタO−56上にスピンコート法により塗布し、該ガラスフィルター上に色素膜を形成した。なお、化合物(1)を同様の方法により無色透明ガラス基板上に製膜した場合の吸収端波長は540nmであるため、O−56フィルターを用いると、記録層の線形吸収帯が存在する波長範囲の光で、かつ、フィルター側から入射する光は全てカットできることになる。
(実施例2)
実施例1記載の記録媒体サンプルの色素膜面側にもう一枚のO−56フィルターを重ねて、2枚のシャープカットフィルタの間に色素膜が挟まれた構造の記録媒体サンプルを作製した。
(実施例3)
実施例1において用いたシャープカットフィルターO−56の代わりに、フィルターの透過させる光の波長がより短波なL−37フィルターを用いた以外は実施例1と同様にして、L−37フィルター上に色素膜が形成されたサンプルを作製した。L−37を用いると、化合物1の線形吸収帯の一部は、L−37が透過させる光の波長領域に存在することになる。さらにこの記録媒体サンプルの色素面側にシャープカットフィルタL−37を重ねて、2枚のシャープカットフィルタの間に色素膜が挟まれた構造の記録媒体サンプルを作製した。
【0029】
(比較例1)
実施例1において、シャープカットフィルタO−56の代わりに、無色透明なガラス基板を用いた以外は実施例1と同様の方法により、無色透明ガラス基板上に色素膜が形成されたサンプルを作製した。さらに、このようにして作製したサンプルの色素面上にもう一枚の無色透明ガラス基板を重ねて、2枚のガラス基板の間に色素膜が挟まれた構造の記録媒体サンプルを作製した。
(情報の記録および読み出し)
実施例1,2,3および比較例1で作製した記録媒体サンプルの色素膜部分に、780nmのレーザー光をフォーカスして照射することで、色素膜への情報の記録を行った。書き込まれた情報の読み出しにはAFMを使用し、色素膜に形成された記録マークの凹凸を観測した。情報の読み出しの際に、実施例2,3および比較例1のサンプルにおいては、重ねたガラスフィルターまたはガラス基板を取り除いて、色素膜に形成された記録マークをAFMにより観測した。
実施例1,2,3および比較例1のいずれの記録媒体サンプルにおいても、情報の記録後には、おおよそ0.75μm程度の明瞭な記録マークが形成されていた。
(耐光性の評価)
上記のように情報を記録した記録媒体サンプルに、Xeランプ(20万ルックス)を12時間照射し、光照射前と光照射後で観測したAFM像のコントラストの差を比較した。なお、実施例2,3および比較例1の記録媒体サンプルでは、再びガラスフィルターまたはガラス基板を重ねたものを用いた。
Xe光の照射前後でのAFM像の変化の大きさを観察し、下記の各水準にランク付けした。
A:ほとんど変化していない
B:僅かに変化している
C:大きく変化している
得られた評価結果を表1に示した。
【0030】
【表1】
Figure 0004154132
【0031】
実施例1の記録媒体サンプルにフィルター面よりXe光を照射したところ、光照射後の記録マークの輪郭は照射前に比べ僅かに不鮮明になっていた。
実施例2の記録媒体サンプルでは、Xe光照射の前後で記録マークのAFM像にほとんど変化が見られなかった。
実施例3の記録媒体サンプルでは、Xe光の照射後の記録マークの輪郭は僅かに不鮮明に変化した。
比較例1の記録媒体サンプルでは、Xe光照射後の記録マークはほぼ消失し、Xe光照射前後での変化が非常に大きかった。
これらの結果から明らかなように、実施例3および実施例1の場合には、色素層は僅かな光劣化にとどまったが、比較例1の場合には、ほとんどの色素が光褪色している。また、用いたフィルターのカットする波長が、色素層の吸収帯全てを覆わない場合には、かなりの光褪色が観測された。
このように、記録層の線形吸収をフィルターによりカットすることで、記録層の光劣化を防止することが可能である。
【0032】
【発明の効果】
2光子および多光子吸収を利用した光情報記録媒体に、フィルターを設けることによって、高い耐光性を有する光情報記録媒体を提供することができる。
【図面の簡単な説明】
【図1】仮想的な記録層の透過スペクトル。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical information recording medium capable of writing information with a laser beam and a recording method using the same. In particular, the present invention relates to an optical information recording medium suitable for recording information using nonresonant multiphoton absorption of nonresonant two or more photons, and a recording method using the same.
[0002]
[Prior art]
Conventionally, optical discs such as CD-R and CD-RW are known as recording media for recording information using laser light. In these optical disks, a laser having a wavelength of about 780 nm is used. In recent years, with the rapid development of information technology, there is an increasing demand for higher capacity and higher density recording media. In order to realize a high capacity and recording density, it is effective to reduce the radius of the laser beam for information recording as small as possible, but it is not possible to narrow it beyond the diffraction limit. The diffraction limit depends on the wavelength of the laser beam, and it is theoretically known that the shorter the wavelength, the smaller the diffraction limit. For this reason, development of an optical disc capable of recording / reproducing using a laser having a wavelength shorter than 780 nm, which has been conventionally used, has been promoted. For example, optical discs called DVD-R and DVD-RW have been proposed. . A DVD-R or DVD-RW uses a laser with a wavelength of 600 nm to 700 nm, and recording with a higher capacity and higher density than CD-R or CD-RW is possible. However, the shortening of the laser wavelength has finally been achieved up to the 600 nm range, and further shortening of the wavelength is very difficult.
[0003]
Therefore, it has been proposed to use a non-resonant two-photon absorption process, which is one of nonlinear optical effects, as means for obtaining a high-capacity and high-density information recording medium without using a short wavelength laser.
[0004]
Non-resonant two-photon absorption is a nonlinear phenomenon in which a molecule is excited by simultaneously absorbing two photons, and the molecule absorbs twice as much energy as a photon corresponding to the wavelength of the irradiated laser beam. It is possible to excite molecules even using light of a longer wavelength region that does not exist. Further, since the probability of non-resonant two-photon absorption is proportional to the square of the intensity of light to be irradiated, the intensity distribution of laser light that induces non-resonant two-photon absorption becomes a sharper shape with a narrowed half-value width. This corresponds to narrowing down the radius of the laser beam, and therefore information recording is possible in a radius region smaller than the radius of the irradiation beam. For the same reason, non-resonant two-photon absorption occurs only in the vicinity of the focal position, so that three-dimensional information recording is possible. Due to these properties, if non-resonant two-photon absorption is used, in principle, higher-density information recording is possible without using a short wavelength laser.
[0005]
An optical information recording medium using an organic compound exhibiting non-resonant two-photon absorption has been introduced in, for example, Chemical Reviews, 100, 1777 (2000), and high-density recording can be performed even when a near-infrared laser is actually used. It has been shown to be possible.
[0006]
The compound used as the non-resonant two-photon absorption compound does not have a linear absorption band in the wavelength region of the near-infrared laser to be used, but usually there is a linear absorption band in the visible light region. Photodegradation of recorded information occurs.
[0007]
[Problems to be solved by the invention]
By the way, the information recording medium has good recording / reproducing characteristics in the initial stage, but it must be able to stably record / reproduce for a long period of time. For this purpose, the recording medium needs to be sufficiently stable against humidity, heat and light. However, an optical information recording medium records information by inducing some chemical or physical change via a photoexcited state generated by absorbing light, so that in principle it has low stability to light. Has a problem.
[0008]
[Means for Solving the Problems]
The present invention relates to an optical recording medium that records information by utilizing non-resonant two-photon or non-resonant multi-photon absorption, thereby preventing linear absorption of the two-photon or multi-photon absorbing compound, thereby improving the light resistance of the optical recording medium. Can be significantly improved. The object of the present invention has been achieved by the following means.
[0009]
(1) In an optical information recording medium in which at least an optical information recording layer is provided on a support, the optical information recording layer exhibits nonresonant two-photon absorption or nonresonant multiphoton absorption, and the linearity of the optical information recording layer An optical information recording medium provided with a layer for preventing absorption.
(2) The optical information recording medium as described in (1) above, wherein layers for preventing the linear absorption are provided on both sides of the optical information recording layer.
(3) a layer optical filter der to prevent the linear absorption is, the optical filter layer does not transmit light in the wavelength range of the linear absorption band of the optical information recording layer is present, long wave light than it only the above, wherein the Rukoto not transmit (1) or (2) above, wherein the optical information recording medium.
(4) The wavelength of light not transmitted through the optical filter is the same as or longer than the absorption edge wavelength of the absorption band derived from the compound contained in the recording layer, and shorter than the wavelength of the light used for the recording light. The optical information recording medium as described in (2) or (3) above, which has a wide wavelength range. Here, the absorption edge wavelength means that the transmittance is the lowest in the transmission spectrum with respect to a straight line drawn with reference to a portion where the transmittance is linear at the bottom of the long wavelength side of the absorption band derived from the recording layer. The wavelength of the long wavelength side point.
(5) The optical information recording medium as described in any one of (1) to (4) above, wherein the compound causing non-resonant two-photon absorption or non-resonant multi-photon absorption is an organic compound.
(6) The optical information recording medium according to any one of (1) to (5) above, having a wavelength longer than the linear absorption band of the compound contained in the recording layer of the recording medium and having no linear absorption. An information recording method using non-resonant multiphoton absorption of two or more non-resonant induced by irradiating a laser beam.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The optical information recording medium of the present invention will be described in detail below. The present invention is an optical information recording medium using non-resonant two-photon or multi-photon absorption, and transmits only light having a wavelength longer than a specific wavelength among wavelengths of light incident on the recording medium. It is characterized by having a mechanism that can.
[0011]
In many cases, photodegradation (photobleaching) of an organic compound proceeds via a photoexcited state generated by linear absorption of the compound. Therefore, light degradation can be reduced if linear absorption can be prevented. The optical information recording medium of the present invention is provided with a filter that transmits only light having a wavelength longer than a specific wavelength, as a layer for preventing linear absorption of the recording medium, in order to prevent light deterioration particularly during storage. It is.
[0012]
However, optical information recording media known so far always use linear absorption of compounds when writing or reading information, so it is impossible in principle to prevent linear absorption using a filter or the like. Met. On the other hand, when non-resonant two-photon or multi-photon absorption is used, it is possible to induce electronic excitation of a compound using light having a long wavelength without any linear absorption. For example, it is possible to electronically excite a compound having linear absorption at 400 nm and having no absorption at the longer wavelength side with light near 800 nm. Therefore, writing and reading can be performed even when the linear absorption wavelength region of the recording medium is covered with a filter and light in that wavelength region is not transmitted at all.
[0013]
The filter used in the optical information recording medium of the present invention absorbs light having a wavelength shorter than a specific wavelength, such as a sharp cut filter used as an optical filter at the time of spectroscopic measurement or photography. Only light having a long wavelength that is not absorbed by the light is transmitted.
[0014]
The filter provided in the optical information recording medium of the present invention may be any filter as long as it has a property of absorbing light having a wavelength shorter than a desired wavelength and transmitting light having a longer wavelength. The wavelength slope defined in JIS B-7113 is preferably in the range of 5 to 200 nm, more preferably in the range of 5 to 100 nm, and most preferably in the range of 5 to 50 nm.
[0015]
The filter provided in the optical information recording medium of the present invention is a recording medium in which a desired sharp cut filter is bonded partially or entirely so as to cover the surface of the recording medium, or an appropriate dye or dye mixture is used as a filter layer. This is realized by forming an intermediate layer in the middle of several layers constituting the surface of the recording medium or the recording medium.
[0016]
By the way, the optical information recording medium of the present invention records information by inducing some chemical or physical change derived from two-photon or multiphoton absorption. A portion where information is recorded by inducing some change by two-photon or multiphoton absorption is called a recording layer. The recording layer of the present invention consists of a compound that itself undergoes some chemical or physical change by performing two-photon or multi-photon absorption, or a two-photon or multi-photon absorbing compound and the two-photon or multi-photon. It consists of a second compound in which some chemical or physical change is induced by absorption, or a two-photon or multi-photon absorption compound and a chemical or physical change induced by two-photon or multi-photon absorption of the compound In addition to the second compound that causes the above, a third compound that plays a role of adjusting the recording mechanism may be included. In the present invention, these compounds are collectively referred to as recording compounds.
Such recording compounds are described in US Pat. Nos. 5,770,732 and 5,859,251, Japanese Patent Application Nos. 2000-297219, 2001-110119, and the like.
[0017]
The recording layer in the present invention may be one in which the recording compound is formed in a thin film like CD-R or DVD-R, or one in which the compound is dispersed in a matrix. The matrix here is a host material in which a recording compound is dispersed.
[0018]
The material constituting the matrix preferably has a certain transparency to light, and may be an organic polymer material or an inorganic material such as glass, but an organic polymer compound is more preferable.
[0019]
When the optical information recording medium of the present invention is in the form of a block in which a recording compound is dispersed in a polymer matrix, the polymer matrix to be dispersed is not particularly limited, and acrylic resins such as polycarbonate and polymethyl methacrylate, epoxy resins, and amorphous polyolefins Polyester, vinyl chloride resin, polyethylene terephthalate, etc. can be used.
[0020]
The recording compound contained in the polymer matrix needs to be contained in a proportion of 1 to 90% by mass, and is preferably contained in a proportion of 5 to 80% by mass. The shape of the block is preferably a cube or a rectangular parallelepiped having a length, width and height of 1 to 100 mm independently.
[0021]
There is no particular limitation on the method for dispersing the recording compound in the polymer matrix, and various methods can be used. For example, a method in which a polymer compound is dissolved and a recording compound is added thereto and mixed uniformly and then allowed to cool, or the polymer compound and the recording compound are dissolved in a suitable solvent, and the solvent is evaporated while heating. Or a method in which a recording compound is dissolved in a corresponding monomer and polymerized by a polymerization reaction.
[0022]
When the recording layer is in the form of a thin film, the filter layer is disposed on the upper surface and / or the lower surface of the recording layer, but preferably covers both surfaces. However, the filter layer may be in close contact with the recording layer, or another layer may be present therebetween. On the other hand, when the recording layer is in a block shape, the filter layer may be disposed on only one surface of the recording layer, but it is preferable to dispose all the surfaces. Further, the recording layer and the filter layer may be in close contact, or other layers may be present.
[0023]
It is preferable that the filter layer does not transmit light in a wavelength range in which the linear absorption band of the recording layer exists, but transmits only light having a longer wavelength than that. Further, the wavelength range of the light not transmitted through the filter layer is the same as or longer than the absorption edge wavelength of the linear absorption band of the compound contained in the recording layer, and a wavelength shorter than the wavelength of the light used for the recording light. A range is preferable.
[0024]
Here, the absorption edge wavelength will be described. FIG. 1 shows a transmission spectrum of a virtual recording layer as an example. In this transmission spectrum, there is a linear portion with no absorption on the long wavelength side of the absorption band and high transmittance. When the straight line is extended based on this part (dotted line part in the figure), the point on the longest wavelength side where the transmittance is lower than this straight line is defined as the absorption edge, and the wavelength of this absorption edge is the absorption edge wavelength. And
[0025]
As the filter layer, a glass sharp cut filter or a polymer sharp cut filter can be used, but is not limited thereto. In addition, a dye layer or pigment that is light-resistant may be dispersed in a polymer matrix to form a filter layer having a desired filter performance. Furthermore, such a dye or pigment may be formed by spin coating or vacuum deposition. You may form directly on a recording medium by methods, such as a method.
[0026]
【Example】
(Example 1)
Production of Light Resistance Evaluation Sample A recording medium sample for light resistance evaluation was produced as follows. 1 g of compound (1) having the following structure described in Japanese Patent Application No. 2000-297219 was dissolved in 100 ml of acetone to obtain a coating solution for forming a dye layer.
[0027]
[Chemical 1]
Figure 0004154132
[0028]
This coating solution was applied on a sharp cut filter O-56 manufactured by HOYA by a spin coating method to form a dye film on the glass filter. Since the absorption edge wavelength when the compound (1) is formed on a colorless transparent glass substrate by the same method is 540 nm, the wavelength range in which the linear absorption band of the recording layer exists when an O-56 filter is used. All of the light incident from the filter side can be cut.
(Example 2)
Another O-56 filter was placed on the dye film surface side of the recording medium sample described in Example 1 to produce a recording medium sample having a structure in which a dye film was sandwiched between two sharp cut filters.
(Example 3)
In place of the sharp cut filter O-56 used in Example 1, an L-37 filter having a shorter wavelength of light transmitted through the filter was used in the same manner as in Example 1 on the L-37 filter. A sample on which a dye film was formed was prepared. When L-37 is used, a part of the linear absorption band of Compound 1 is present in the wavelength region of light transmitted by L-37. Further, a recording medium sample having a structure in which a dye film was sandwiched between two sharp cut filters was manufactured by superimposing a sharp cut filter L-37 on the dye surface side of the recording medium sample.
[0029]
(Comparative Example 1)
In Example 1, a sample in which a dye film was formed on a colorless transparent glass substrate was produced by the same method as in Example 1 except that a colorless transparent glass substrate was used instead of the sharp cut filter O-56. . Furthermore, another colorless and transparent glass substrate was stacked on the dye surface of the sample thus prepared, and a recording medium sample having a structure in which a dye film was sandwiched between two glass substrates was prepared.
(Recording and reading of information)
Information was recorded on the dye film by focusing and irradiating the 780 nm laser beam on the dye film portion of the recording medium samples prepared in Examples 1, 2, 3 and Comparative Example 1. An AFM was used to read out the written information, and the unevenness of the recording marks formed on the dye film was observed. When reading information, in the samples of Examples 2 and 3 and Comparative Example 1, the stacked glass filter or glass substrate was removed, and the recording marks formed on the dye film were observed by AFM.
In any of the recording medium samples of Examples 1, 2, 3 and Comparative Example 1, a clear recording mark of about 0.75 μm was formed after information recording.
(Evaluation of light resistance)
The recording medium sample on which information was recorded as described above was irradiated with an Xe lamp (200,000 lux) for 12 hours, and the difference in contrast between the AFM images observed before and after the light irradiation was compared. In the recording medium samples of Examples 2 and 3 and Comparative Example 1, a glass filter or a glass substrate laminated again was used.
The magnitude of change in the AFM image before and after irradiation with Xe light was observed and ranked in the following levels.
A: Almost unchanged B: Slightly changed C: Largely changed Table 1 shows the obtained evaluation results.
[0030]
[Table 1]
Figure 0004154132
[0031]
When the recording medium sample of Example 1 was irradiated with Xe light from the filter surface, the outline of the recording mark after the light irradiation was slightly blurred compared to before the irradiation.
In the recording medium sample of Example 2, there was almost no change in the AFM image of the recording mark before and after the Xe light irradiation.
In the recording medium sample of Example 3, the outline of the recording mark after the Xe light irradiation was slightly changed.
In the recording medium sample of Comparative Example 1, the recording marks after the Xe light irradiation almost disappeared, and the change before and after the Xe light irradiation was very large.
As is clear from these results, in the case of Example 3 and Example 1, the dye layer was only slightly degraded by light, but in the case of Comparative Example 1, most of the dye was light-faded. . In addition, considerable light fading was observed when the wavelength cut by the filter used did not cover the entire absorption band of the dye layer.
In this way, it is possible to prevent light degradation of the recording layer by cutting the linear absorption of the recording layer with a filter.
[0032]
【The invention's effect】
An optical information recording medium having high light resistance can be provided by providing a filter in an optical information recording medium using two-photon and multiphoton absorption.
[Brief description of the drawings]
FIG. 1 is a transmission spectrum of a virtual recording layer.

Claims (4)

支持体上に少なくとも光情報記録層を設けた光情報記録媒体において、前記光情報記録層が非共鳴2光子吸収または非共鳴多光子吸収を示し、かつ、該光情報記録層の線形吸収を防止する層を設けたことを特徴とする光情報記録媒体。In an optical information recording medium having at least an optical information recording layer on a support, the optical information recording layer exhibits non-resonant two-photon absorption or non-resonant multi-photon absorption, and prevents linear absorption of the optical information recording layer An optical information recording medium, characterized in that a layer is provided. 線形吸収を防止する層が光学フィルター層であり、該光学フィルター層は、該光情報記録層の線形吸収帯が存在する波長範囲の光を透過させず、それよりも長波の光のみを透過させることを特徴とする請求項1に記載の光情報記録媒体。The layer that prevents linear absorption is an optical filter layer, and the optical filter layer does not transmit light in a wavelength range in which the linear absorption band of the optical information recording layer exists, and transmits only light having a longer wavelength than that. The optical information recording medium according to claim 1. 該光フィルター層の透過させない光の波長範囲が、該光情報記録層の線形吸収帯の吸収端波長と同じか、それよりも長波長で、記録光に用いる光の波長よりも短波な波長範囲であることを特徴とする請求項2に記載の光情報記録媒体。The wavelength range of light that is not transmitted through the optical filter layer is the same as or longer than the absorption edge wavelength of the linear absorption band of the optical information recording layer, and a wavelength range that is shorter than the wavelength of light used for recording light The optical information recording medium according to claim 2, wherein: 請求項1〜3のいずれかに記載の光情報記録媒体に、該記録媒体の記録層に含まれる化合物が有する線形吸収帯より長波長でかつ線形吸収の存在しない波長のレーザー光を照射して誘起された非共鳴2光子以上の非共鳴多光子吸収を利用する光情報記録方法。Irradiating the optical information recording medium according to any one of claims 1 to 3 with a laser beam having a wavelength longer than the linear absorption band of the compound contained in the recording layer of the recording medium and having no linear absorption An optical information recording method using non-resonant multiphoton absorption of induced non-resonant two-photons or more.
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