JP3558855B2

JP3558855B2 - Three-dimensional optical memory medium and method of manufacturing the same

Info

Publication number: JP3558855B2
Application number: JP03695598A
Authority: JP
Inventors: 裕己近藤; 清貴三浦; 一之平尾
Original assignee: Central Glass Co Ltd; Japan Science and Technology Agency
Current assignee: Central Glass Co Ltd; Japan Science and Technology Agency
Priority date: 1998-02-19
Filing date: 1998-02-19
Publication date: 2004-08-25
Anticipated expiration: 2018-02-19
Also published as: JPH11232706A

Description

【０００１】
【産業上の利用分野】
本発明は、微粒子分散状態が局部的に変化した単数又は複数のスポットを微粒子分散媒質内部に形成させることにより、読出しのコントラスト（Ｓ／Ｎ）を向上させた三次元光メモリー媒体及びその製造方法に関するものである。
【０００２】
【従来の技術】
ハードディスクを始めとする種々の記録媒体は、情報処理の大容量化に伴って記録密度の向上が望まれている。なかでも、記録再生に用いるレーザー光を光の回折限界にまで絞ることにより記録可能領域を用いる波長程度の大きさにできること、具体的には１ｃｍ²当り１０⁸ビットの高い記録密度が得られることから、光メモリの研究が盛んに進められており、一部が実用化されている。
光ディスクの大容量化の方向として、書込みに使用するレーザーの波長を短くすると書込み領域を小さくできることから、レーザーの波長の短波長化が挙げられる。しかし、レーザーの短波長化自体が容易でなく、短波長化に伴って材料の吸収係数が大きくなることから、現状の書込み用レーザーの波長は７００ｎｍ程度である。レーザの短波長化及び短波長化に伴う吸収係数の上昇の問題点を克服できたと仮定しても、現状の四倍程度に記録密度を増大させることが限界であるといわれている。
【０００３】
そこで、記録領域の縮小による相対的な記録密度の増大に替え、記録の空間的次元を二次元から三次元に増加させることにより、より大容量化することが検討されている。この系統に属するものとしては、光照射により透過率が変化するフォトクロミック材料を用いて三次元的に情報記録を行う方法，フォトリフラクティブ結晶を用いて三次元的に屈折率変化を起こす方法等がある。
しかしながら、フォトクロミック材料を持ちいる方法では、有機材料でフォトクロミック材料が熱や光による劣化変質を起こし易い。また、記録状態が経時変化を示したり、感度が高過ぎ、読出し光によっても光反応が進行し、記録状態が変化してしまう欠点がある。他方、フォトリフラクティブ結晶を用いる方法では、フォトリフラクティブ結晶に光学的異方性があるため、記録する際に結晶の軸方向によって記録状態が異なってしまう。
【０００４】
読出し、書込みに用いる光の波長を多重化させることによりスポット当りの記録密度を上昇させ、大容量化を図る研究も進められている。この系統に属するものとしては、光化学ホールバーニング（ＰＨＢ）がある。
光化学ホールバーニングでは、ガラス，ポリマー，イオン結晶，金属酸化物結晶等の透明な固体媒質に有機色素，希土類金属イオン等を活性中心として分散させた系において、活性中心による光吸収スペクトルの幅が媒質の持つ不均一性によって本来持っている幅（均一幅）より広がっていることを利用している。すなわち、不均一幅内の特定の波長に線幅の狭いレーザー光を照射すると、照射された波長の吸収が飽和し、吸収スペクトルに穴が開いた状態になる。この方法によるとき、原理的には１スポットあたり１０³以上の多重度が可能で、記録密度としては１ｃｍ²当り１０¹¹ビットまで増大できるといわれている。
【０００５】
しかし、大半のＰＨＢ現象が零下２００℃以下の極低温でしか観測されず、室温では動作しないことが問題である。近年、室温でもＰＨＢ現象が観測されるようになってきている（K. Hirao等，J. Lumi.，55，217(1993)）が、多重度が低く生成効率が悪い等の問題が残されている。
このような問題を解決する新規な三次元光メモリーガラスが特開平8-220688号公報で紹介されている。この三次元光メモリーガラスは、熱や光に対して安定で光学的異方性がない。ガラスマトリックスを三次元的に走査しながら、ガラスマトリックス中にパルスレーザーを集光照射するとき、光誘起屈折率変化が微小スポットで生じ、空間的な屈折率分布として情報が記録される。この手法によって、熱や光に対して安定で、耐候性に優れ、長期間安定した情報の記録が可能となり、光ディスクの記録容量の増大化が可能となる。
【０００６】
【発明が解決しようとする課題】
しかし、特開平8-220688号公報で紹介されている光メモリーガラスの場合、パルスレーザー光の集光照射によって屈折率変化を誘起するに止まり、照射される材料自体は同一である。そのため、屈折率変化が起きた部分と屈折率変化が起きていない部分との間に大きな組成変化があるわけではなく、誘起される屈折率変化量をそれほど大きくできなかった。そして、屈折率変化だけによって起こされる透過率又は反射率の変化をメモリーに利用していることから、小さな屈折率変化のため、読出しにおけるコントラスト（Ｓ／Ｎ）を大きくできない。
本発明は、このような問題を解消すべく、微粒子分散ガラス内部へのパルスレーザー光の集光照射により微粒子分散状態が局部的に変化した単数又は複数のスポットを形成することにより、読出しのコントラスト（Ｓ／Ｎ）が高い三次元光メモリー媒体を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明の三次元光メモリー媒体は、その目的を達成するため、微粒子分散ガラスを基体とし、基体内部へのパルスレーザー光の集光照射により微粒子の分散状態が局部的に変化した単数又は複数のスポットが基体内部に存在していることを特徴とする。
スポットでは、微粒子分散媒質の吸収波長領域の吸収係数が減少している。微粒子としては、Ａｕ，Ｃｕ，Ａｇ，Ｐｔ，ＣｕＣｌ，ＣｕＢｒ，ＣｄＳ，ＣｄＳｅ，ＣｄＴｅから選ばれた１種又は２種以上が使用され、微粒子分散ガラスに分散される。
この三次元光メモリー媒体は、微粒子分散状態が変化するエネルギー量を持つパルスレーザー光を微粒子分散ガラスの内部に集光し、微粒子分散ガラスの内部でパルスレーザー光の集光点を相対移動させながら、微粒子分散状態が局部的に変化した単数又は複数のスポットを微粒子分散ガラスの内部に形成することにより製造される。使用するパルスレーザ光としては、微粒子分散ガラスの透過率が２０％以上である波長領域のパルスレーザー光が好ましい。
【０００８】
【作用】
微粒子分散ガラス内部にパルスレーザー光を集光照射すると、光メモリーガラスと同様な屈折率変化が集光点で生じると共に、着色種である微粒子の分散状態、すなわち微粒子分散ガラス内部に分散している微粒子の数，微粒子のサイズ，微粒子の形態等が変化する。具体的には、微粒子の数の減少，微粒子の小サイズ化，媒質中への溶解やイオン化による微粒子の消失等が生じる。
媒質中への溶解やイオン化により微粒子として存在しなくなる場合、その部分の吸収係数は、微粒子が分散していない媒質と同じ値になり、照射前に比べて減少する。レーザー光の集光照射によって微粒子のサイズが変化する場合、微粒子のサイズ変化により吸収する波長が変化し、集光照射前に比べて集光照射後の照射波長における吸収係数は減少する。そこで、読出しに用いるレーザー光の波長を微粒子分散ガラスの吸収波長領域に設定すると、集光点以外の部分の吸収係数が照射前と同じあるのに対し、集光点では吸収係数が減少していることから、集光点でのみ透過率又は反射率が高くなり、屈折率変化だけを利用する場合に比較して読出しのコントラスト（Ｓ／Ｎ）が向上する。
【０００９】
【実施の形態】
分散媒質であるガラスに分散される微粒子としては、Ａｕ，Ｃｕ，Ａｇ，Ｐｔ等の金属微粒子やＣｄＳ，ＣｄＳｅ，ＣｄＴｅ，ＣｕＣｌ，ＣｕＢｒ等の半導体微粒子がある。これらの微粒子は、ガラス，ポリマー，イオン結晶，金属酸化物結晶等の媒質に分散される。なかでも、ガラスは、光学的に等方性であり、耐熱性、耐光性に優れていることから媒質として非常に適している。
微粒子の分散量としては０.０１〜５０重量％が好ましい。分散量が０.０１重量％未満であると、吸収係数が小さくなるために読出しのコントラストを大きくできなくなる傾向がみられる。逆に５０重量％を超える分散量では、分散している微粒子が均一に分散することなく凝集し、或いは凝集によって粒子の実質的な大きさが増大して光散乱の原因となり、読出しコントラストを低下させる傾向を示す。
【００１０】
媒質であるガラスに分散している微粒子の分散状態は、微粒子分散ガラスの内部に集光点を設定したパルスレーザ光で照射されるため、集光点及びその近傍で変化する。集光点以外の照射部分では、分散状態の変化に必要な光量が得られず、パルスレーザ光の照射前と同じ分散状態が維持される。その結果、微粒子分散ガラスの内部だけが選択的に変質する。
光源から出射されたレーザー光１は、図１に示すようにレンズ等の集光装置２で集光される。このとき、微粒子分散媒質３の内部に集光点４が位置するように、集光装置２を焦点調節する。集光点４をスポット，スポットで照射するステップスキャンを採用すると、微粒子の分散状態が変化した領域がドット状に形成される。微粒子分散ガラス３に対して集光点４を三次元的に相対移動させると、三次元的に変化した領域が微粒子分散ガラス３の内部に形成される。微粒子分散ガラス３に対する集光点４の相対移動には、集光点４を固定して微粒子分散ガラス３を移動させる方法，微粒子分散ガラス３を固定して集光点４を移動させる方法，両者の併用等が採用される。
【００１１】
パルスレーザーのピークパワーは、１パルス当りの出力エネルギー（Ｊ）をパルス幅（秒）で割った値としてワット（Ｗ）で表される。ピークパワー密度は、単位面積（ｃｍ²）当りのピークパワーであり、Ｗ／ｃｍ²で表される。
集光点におけるパルスレーザー光のピークパワー密度は、１０⁸〜１０¹⁷Ｗ／ｃｍ²の範囲にあることが望ましい。１０⁸Ｗ／ｃｍ²未満のピークパワー密度では、集光部分で屈折率変化及び微粒子分散状態が十分に変化しない。逆に１０¹⁷Ｗ／ｃｍ²を超えるピークパワー密度では、集光点以外の部分でも屈折率変化及び微粒子分散状態が変化し、目標とする変化が得られにくくなる。また、過度に大きなエネルギー量のレーザー光は、実用的にも困難である。
【００１２】
同じピークパワー密度のレーザ光で照射するとき、パルス幅の狭いレーザー光ほど屈折率変化及び微粒子分散状態の変化が生じ易い。この点、１０^-10秒以下のパルス幅をもつレーザ光が好ましい。パルス幅が広すぎるレーザー光では、屈折率変化及び微粒子分散状態の変化に非常に大きなエネルギーをもつレーザー光の照射が必要になり、微粒子分散媒質材料を破壊する虞れがある。
照射量は、屈折率変化及び微粒子分散状態の変化に必要な量に設定される。パルスレーザーの繰返し周期（パルスとパルスの間隔）は、特に限定されるものではないが、過度に短い周期（たとえば、１００ＭＨｚ）では集光部分以外でも屈折率変化及び微粒子分散状態の変化が起き始めてしまう。
【００１３】
【実施例】
実施例１：Ａｕ微粒子分散ガラス
ＳｉＯ₂，Ｂ₂Ｏ₃，Ｎａ₂ＣＯ₃，Ｓｂ₂Ｏ₃の配合原料に塩化金酸の水溶液を加え、ＳｉＯ₂：７２重量％，Ｂ₂Ｏ₃：１８重量％，Ｎａ₂Ｏ：１０重量％，Ｓｂ₂Ｏ₃：４重量％，Ａｕ：０.０２重量％の組成となるように調合した。原料粉末４００ｇを３００ｃｃ白金製ルツボに投入した後、大気中１４５０℃で２時間撹拌しながら加熱溶解した。均一に溶解したガラスを真鍮の型に流し込んで厚さ５ｍｍの板に成型し、冷却した。得られたガラスを４５０℃でアニールし、歪みを除去した。
ガラス中にＡｕ微粒子を析出させるため、電気炉を用いて昇温速度５℃／分でガラスを昇温し、６５０℃で４時間保持した後、炉内で放冷した。次いで、切断，研磨して厚み４ｍｍの試料を得た。得られたガラス試料は、金微粒子の析出によって赤色に着色されていた。また、透過型電子顕微鏡（ＴＥＭ）を用いてガラス中に分散しているＡｕ微粒子の大きさを観察したところ、平均粒径１０ｎｍの微粒子が分散していた。
【００１４】
ガラス試料の内部に集光点が位置するように集光させたパルスレーザーでガラス試料を照射した。すなわち、ＸＹＺ方向にスキャン可能な電動ステージにガラス試料３を設置し、Ｚ軸（光軸）方向を固定した状態で、図１に示すようにパルスレーザー光１を、ガラス試料３の内部に集光点４が位置するようにレンズ２で集光し、ガラス試料３を照射した。パルスレーサー光には、アルゴンレーザー励起のＴｉ−サファイアレーザーから発振されたパルス幅１.５×１０^-3秒、繰返し周期５０Ｈｚ、波長８００ｎｍの光を使用した。集光点４に形成されたスポットは、直径約１μｍであった。スポットの直径は、レンズ２の倍率及びパルスレーザー光１のビーム径を大きくすることにより更に小さくできる。
本実施例のＡｕ微粒子分散ガラスは、８００ｎｍの波長における透過率が８９％であった。ピークエネルギー密度１０¹³Ｗ／ｃｍ²で集光点４に３秒間照射した後、レーザー光１のガラス試料３への入射を止め、ガラス試料３をＸＹ軸方向にスキャンし、再度同条件で集光照射を行った。この集光照射，集光照射中止，ガラス試料３の移動操作を繰り返した後、Ｚ軸方向の電動ステージを５μｍ移動させ、ＸＹ方向へ同様に集光照射した。
【００１５】
集光照射処理されたガラス試料３を光学顕微鏡で観察したところ、集光照射部分では、図２に示すように、Ａｕ微粒子によって吸収されていた波長帯（約４００〜５８０ｎｍ）の吸収係数が減少し、赤色着色がなくなった領域５が形成されていた。一方、非集光照射部分では、色の変化が観察されなかった。
波長５３０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では、屈折率の変化と吸収係数の現象によるものと考えられる透過率の違いが検出され、屈折率変化だけを利用した比較例１と比べて著しく大きなコントラストであった。５μｍ間隔で上層と下層のスポットの読取りエラーがなく、Ｘ，Ｙ，Ｚ方向に三次元的に情報を記録できた。
【００１６】
実施例２：Ｃｕ微粒子分散ガラス
ＳｉＯ₂，Ｂ₂Ｏ₃，Ｎａ₂Ｏ₃，Ｃｕ₂Ｏ，ＳｎＯの原料粉末を、ＳｉＯ₂：７２重量％，Ｂ₂Ｏ₃：２０重量％，Ｎａ₂Ｏ：８重量％，Ｃｕ：０.５重量％，ＳｎＯ：０.２５重量％の組成に配合した。原料粉末４００ｇを３００ｃｃ白金製ルツボに投入した後、大気中１４５０℃で２時間撹拌しながら加熱溶解した。均一溶解したガラスを真鍮の型に流し込み、厚さ５ｍｍの板に成型し、冷却した。得られたガラスを４５０℃でアニールし、歪みを除去した。
ガラス中にＣｕ微粒子を析出させるため、電気炉を用い昇温速度５℃／分でガラスを昇温し、６５０℃に４時間保持した後、炉内で放冷した。析出処理後のガラスを切断・研磨し、厚さ４ｍｍの試料を作製した。このガラス試料は、Ｃｕ微粒子の析出により黄色に着色されており、透過型電子顕微鏡（ＴＥＭ）で観察したところ、平均粒径２０ｎｍのＣｕ微粒子がガラスマトリックス中に分散していた。
【００１７】
次いで、作製されたガラス試料３を実施例１と同様にパルスレーザ光で照射した。パルスレーザー光には、アルゴンレーザー励起のＴｉ−サファイアレーザーから発振されたパルス幅１.５×１０^-13秒、繰返し周期１００Ｈｚ、波長１.０μｍの光を使用した。集光点４に形成されたスポットは、直径が約２μｍであった。
本実施例のＣｕ微粒子分散ガラスは、１.０μｍの波長における透過率が９０％であった。ピークエネルギー密度１０¹¹Ｗ／ｃｍ²で集光点４に５秒間照射した後、レーザー光１のガラス試料３への入射を止め、ガラス試料３をＸＹ軸方向にスキャンさせ、再度同じ条件で集光照射した。この集光照射，集光照射中止，ガラス試料の移動操作を繰り返した。次いで、Ｚ軸方向に電動ステージを１５μｍに移動させ、ＸＹ方向へ同様に集光照射した。
【００１８】
集光照射処理されたガラス試料３を光学顕微鏡により観察したところ、図２に示すように、集光照射部分ではＣｕ微粒子によって吸収されていた波長帯（約４００〜５８０ｎｍ）の吸収係数が減少し、黄色着色がなくなり無色に変化した領域５が形成されていた。一方、非集光照射部分では、色の変化が観察されなかった。
波長５３０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では、屈折率の変化と吸収係数の現象によるものと考えられる透過率の違いが検出され、後に述べる比較例１の屈折率変化だけを利用した比較例１に比べ著しく大きなコントラストであった。また、１５μｍ間隔で上層と下層のスポットの読み取りエラーはなく、Ｘ，Ｙ，Ｚ方向に三次元的に情報を記録できた。
【００１９】
実施例３：Ａｇ微粒子分散ガラス
ＳｉＯ₂，ＣａＣＯ₃，Ｎａ₂ＣＯ₃，Ａｇ₂Ｏ，ＳｎＯを原料粉末とし、ＳｉＯ₂：７２重量％，ＣａＯ：２０重量％，Ｎａ₂Ｏ：８重量％，Ａｇ：０.４重量％，ＳｎＯ：０.２重量％の組成となるように配合した。原料粉末４００ｇを３００ｃｃ白金製ルツボに投入した後、大気中１４５０℃で２時間攪拌しながら加熱溶解した。均一に溶解したガラスを真鍮の型に流し込んで厚さ５ｍｍの板に成型し、冷却した後、４５０℃のアニールにより歪みを除去した。
ガラス中にＡｇ微粒子を析出させるため、電気炉を用いて昇温速度５℃／分でガラスを昇温し、５５０℃で４時間保持した後、炉内で放冷した。その後、切断、研磨し、厚さ４ｍｍの試料を作製した。析出処理されたガラスは、Ａｇ微粒子の析出によって黄色に着色されており、透過型電子顕微鏡（ＴＥＭ）で観察したところ、平均粒径８ｎｍのＡｇ微粒子がガラスマトリックスに分散していた。
【００２０】
析出処理されたガラス試料３を実施例１と同様にパルスレーザ光でを照射した。パルスレーザー光には、アルゴンレーザー励起のＴｉ-サファイアレーザーから発振されたパルス幅１.５×１０^-13秒、繰返し周期１ｋＨｚ、波長６００ｎｍの光を使用した。集光点４に形成されたスポットは、直径が約０.８μｍであった。
本実施例のＡｇ微粒子分散ガラスは、６００ｎｍの波長における透過率が９１％であった。ピークエネルギー密度１０¹⁴Ｗ／ｃｍ²で集光点４に３秒間照射した後、レーザー光１のガラス試料３への入射を止め、ガラス試料３をＸＹ軸方向にスキャンさせ、再度同じ条件で集光照射した。この集光照射，集光照射中止，ガラス試料の移動操作を繰り返した後、Ｚ軸方向に電動ステージを５μｍ移動させ、ＸＹ方向へ同様に集光照射した。
【００２１】
集光照射処理されたガラス試料３を光学顕微鏡で観察したところ、図２に示すように、集光照射部分ではＡｇ微粒子によって吸収されていた波長帯（約３６０〜４８０ｎｍ）の吸収係数が減少し、黄色着色がなくなり無色に変化した領域５が形成されていた。一方、非集光照射部分では、色の変化が観察されなかった。
波長４２０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では、屈折率の変化と吸収係数の減少によるものと考えられる透過率の違いが検出され、屈折率変化だけを利用した比較例２に比べて著しく大きなコントラストであった。また、５μｍ間隔で上層と下層のスポットの読み取りエラーはなく、Ｘ，Ｙ，Ｚ方向に三次元的に情報を記録できた。
【００２２】
実施例４：Ｐｔ微粒子分散ガラス
ＳｉＯ₂，Ｂ₂Ｏ₃，Ｎａ₂ＣＯ₃，Ｓｂ₂Ｏ₃の原料粉末に塩化白金酸の水溶液を加え、ＳｉＯ₂：７２重量％，Ｂ₂Ｏ₃：１８重量％，Ｎａ₂Ｏ：１０重量％，Ｓｂ₂Ｏ₃：２重量％，Ｐｔ：０.０５重量％の組成に調合した。原料粉末４００ｇを３００ｃｃ白金製ルツボに投入した後、大気中１４５０℃で２時間攪拌しながら加熱溶解した。均一溶解したガラスを真鍮の型に流し込んで厚さ５ｍｍの板に成型し、冷却した後、４５０℃でアニールすることにより歪みを除去した。
ガラス中にＰｔ微粒子を析出させるため、電気炉を用いて昇温速度５℃／分でガラスを昇温し、６００℃で４時間保持した後、炉内で放冷した。次いで、切断・研磨し、厚さ４ｍｍのガラス試料を作製した。このガラス試料は、Ｐｔ微粒子の析出によって灰色に着色しており、透過型電子顕微鏡（ＴＥＭ）による観察では平均粒径１５ｎｍのＰｔ微粒子がガラスマトリックスに分散していた。
【００２３】
析出処理されたガラス試料３を実施例１と同様にパルスレーザー光で照射した。パルスレーザー光には、アルゴンレーザー励起のＴｉ-サファイアレーザーから発振されたパルス幅１．５×１０^-13秒、繰返し周期１ｋＨｚ、波長１.０μｍの光を使用した。集光点４におけるスポットの直径は約２μｍであった。
本実施例のＰｔ微粒子分散ガラスは、１.０μｍの波長における透過率が８９％であった。ピークエネルギー密度１０¹³Ｗ／ｃｍ²で集光点４に５秒間照射した後、レーザー光１のガラス試料３への入射を止め、ガラス試料３をＸＹ軸方向にスキャンさせ、再度同じ条件で集光照射した。この集光照射，集光照射中止，ガラス試料の移動操作を繰り返した後、Ｚ軸方向に電動ステージを２０μｍ移動させ、ＸＹ方向へ同様に集光照射した。
【００２４】
集光照射処理されたガラス試料３を光学顕微鏡で観察したところ、図２に示すように、Ｐｔ微粒子により吸収されていた波長帯（約４００〜７５０ｎｍ）の吸収係数が減少し、灰色着色がなくなり無色に変化した領域５が集光照射部分に形成されていた。非集光照射部分では、色の変化が観察されなかった。
波長６００ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では、屈折率の変化と吸収係数の減少によるものと考えられる透過率の違いが検出され、屈折率変化だけを利用した比較例１に比べて著しく大きなコントラストであった。また、２０μｍ間隔で上層と下層のスポットの読取りエラーはなく、Ｘ，Ｙ，Ｚ方向に三次元的に情報を記録できた。
【００２５】
実施例５：ＣｕＣｌ微粒子分散ガラス
ＳｉＯ₂，Ａｌ₂Ｏ₃，Ｂ₂Ｏ₃，Ｌｉ₂ＣＯ₃，Ｎａ₂ＣＯ₃，Ｋ₂ＣＯ₃，ＣｕＣｌ，ＳｎＯを原料粉末として用い、ＳｉＯ₂：６５重量％，Ａｌ₂Ｏ₃：６重量％，Ｂ₂Ｏ₃：１７重量％，Ｌｉ₂Ｏ：４重量％，Ｎａ₂Ｏ：４重量％，Ｋ₂Ｏ：４重量％，ＣｕＣｌ：０.５重量％，ＳｎＯ：０.２重量％の組成に調合した。原料粉末４００ｇを３００ｃｃ白金製ルツボに投入した後、大気中１４５０℃で２時間撹拌しながら加熱溶解した。均一溶解したガラスを真鍮の型に流し込んで厚さ５ｍｍの板に成型し、冷却した後、４５０℃のアニールで歪みを除去した。
【００２６】
ガラス中にＣｕＣｌ微粒子を析出させるため、電気炉を用いて昇温速度５℃／分でガラスを昇温し、５５０℃で４時間保持した後、炉内で放冷した。次いで、切断・研磨し、厚さ４ｍｍのガラス試料を作製した。得られたガラス試料を透過型電子顕微鏡（ＴＥＭ）で観察したところ、平均粒径８ｎｍのＣｕＣｌ微粒子がガラスマトリックスに分散していた。
析出処理されたガラス試料３を実施例１と同様にパルスレーザーで照射した。パルスレーザー光には、アルゴンレーザー励起のＴｉ−サファイアレーザーから発振されたパルス幅１．５×１０^-13秒、繰返し周期１ｋＨｚ、波長５００ｎｍの光を使用した。集光点４に形成されたスポットは、直径が約０.７μｍであった。
【００２７】
本実施例のＣｕＣｌ微粒子分散ガラスは、５００ｎｍの波長における透過率が９２％であった。ピークエネルギー密度１０¹⁵Ｗ／ｃｍ²で集光点４に３秒間照射した後、レーザー光１のガラス試料３への入射をやめ、ガラス試料３をＸＹ軸方向にスキャンさせ、再度同条件で集光照射した。この集光照射，集光照射中止，ガラス試料の移動操作を繰り返した後、Ｚ軸方向に電動ステージを３μｍ移動させ、ＸＹ軸方向へ同様に集光照射した。
集光照射処理されたガラス試料を光学顕微鏡で観察したところ、図２に示すように、集光照射部分ではＣｕＣｌ微粒子によって吸収されていた波長帯（約３００〜３８５ｎｍ）に吸収係数が減少した領域５が形成されていた。一方、非集光照射部分では、色の変化が観察されなかった。
波長３７５ｎｍの光を用いて記録情報を読み出したところ、集光照射照射部と非集光照射部では、屈折率の変化と吸収係数の減少によるものと考えられる透過率の違いが検出され、屈折率変化だけを利用した比較例３に比べ著しく大きなコントラストであった。また、３μｍ間隔で上層と下層のスポットの読取りエラーはなく、Ｘ，Ｙ，Ｚ方向に三次元的に情報を記録できた。
【００２８】
実施例６：Ｃｄ(Ｓ,Ｓｅ)微粒子分散ガラス
ＳｉＯ₂，Ａｌ₂Ｏ₃，Ｂ₂Ｏ₃，Ｎａ₂ＣＯ₃，ＺｎＯ，ＣｄＳ，ＣｄＳｅを原料粉末として用い、ＳｉＯ₂：６９重量％，Ａｌ₂Ｏ₃：１重量％，Ｂ₂Ｏ₃：１２重量％，Ｎａ₂Ｏ：６重量％，ＺｎＯ：１１重量％，ＣｄＳ：０.３重量％，ＣｄＳｅ：０.２重量％の組成に調合した。原料粉末４００ｇを３００ｃｃ白金製ルツボに投入した後、大気中１４５０℃で２時間撹拌しながら加熱溶解した。均一溶解したガラスを真鍮の型に流し込んで厚さ５ｍｍの板に成型し、冷却した後、４５０℃のアニールにより歪みを除去した。
ガラス中にＣｄ(Ｓ,Ｓｅ)微粒子を析出させるため、電気炉を用いて昇温速度５℃／分でガラスを昇温し、６５０℃で４時間保持した後、炉内で放冷した。次いで、切断・研磨し、厚さ４ｍｍのガラス試料を作製した。このガラス試料は、Ｃｄ(Ｓ,Ｓｅ)微粒子の析出により赤色に着色しており、透過型電子顕微鏡（ＴＥＭ）で観察したところ平均粒径１０ｎｍのＣｄ(Ｓ,Ｓｅ)微粒子がガラスマトリックスに分散していた。
【００２９】
析出処理されたガラス試料３を実施例１と同様にパルスレーザーで照射した。パルスレーザー光には、アルゴンＡｒレーザー励起のＴｉ-サファイアレーザーから発振されたパルス幅１.５×１０^-13秒、繰返し周期１ｋＨｚ、波長６５０ｎｍの光を使用した。集光点４に形成されたスポットは、直径が約０.９μｍであった。
本実施例のＣｄ(Ｓ,Ｓｅ)微粒子分散ガラスは、６５０ｎｍの波長における透過率が８５％であった。ピークエネルギー密度１０¹⁵Ｗ／ｃｍ²で集光点４に３秒間照射した後、レーザー光１のガラス試料３への入射をやめ、ガラス試料３をＸＹ軸方向にスキャンさせ、再度同条件で集光照射した。この集光照射，集光照射中止，ガラス試料の移動操作を繰り返した後、Ｚ軸方向に電動ステージを１０μｍ移動させ、ＸＹ軸方向へ同様に集光照射した。
【００３０】
集光照射処理されたガラス試料３を光学顕微鏡で観察したところ、図２に示すように、集光照射部分ではＣｄ(Ｓ,Ｓｅ)微粒子によって吸収されていた波長帯（約４５０〜５８０ｎｍ）の吸収係数が減少し、赤色着色がなくなり無色に変化した領域５が形成されていた。一方、非集光照射部分では色の変化が観察されなかった。
波長４８０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では、屈折率の変化と吸収係数の現象によるものと考えられる透過率の違いが検出され、屈折率変化だけを利用した比較例４に比べ著しく大きなコントラストであった。また、１０μｍ間隔で上層と下層のスポットの読取りエラーはなく、Ｘ，Ｙ，Ｚ方向の三次元的に情報を記録できた。
【００３１】
実施例７：Ｃｄ(Ｓｅ,Ｔｅ)微粒子分散ガラス
ＳｉＯ₂，Ａｌ₂Ｏ₃，Ｂ₂Ｏ₃，Ｎａ₂ＣＯ₃，ＺｎＯ，ＣｄＳｅ，ＣｄＴｅを原料粉末として用い、ＳｉＯ₂：６９重量％，Ａｌ₂Ｏ₃：１重量％，Ｂ₂Ｏ₃：１２重量％，Ｎａ₂Ｏ：３重量％，ＺｎＯ：１１重量％，ＣｄＳｅ：０.３重量％，ＣｄＴｅ：０.２重量％の組成に調合した。原料粉末４００ｇを３００ｃｃ白金製ルツボに投入した後、大気中１４５０℃で２時間攪拌しながら加熱溶解した。均一溶解したガラスを真鍮の型に流し込んで厚さ５ｍｍの板に成型し、冷却した後、４５０℃のアニールにより歪みを除去した。
ガラス中にＣｄ(Ｓｅ,Ｔｅ)微粒子を析出させるため、電気炉を用いて昇温速度５℃／分でガラスを昇温し、６５０℃で４時間保持した後、炉内で放冷した。次いで、切断・研磨し、厚さ４ｍｍのガラス試料を作製した。得られたガラス試料は、Ｃｄ(Ｓｅ,Ｔｅ)微粒子の析出により赤色に着色しており、透過型電子顕微鏡（ＴＥＭ）で観察したところ、平均粒径１０ｎｍのＣｄ(Ｓｅ,Ｔｅ)微粒子がガラスマトリックスに分散していた。
【００３２】
析出処理されたガラス試料３を実施例１と同様にパルスレーザーで照射した。パルスレーザー光には、アルゴンレーザー励起のＴｉ-サファイアレーザーから発振されたパルス幅１.５×１０^-13秒、繰り返し周期１ｋＨｚ、波長１.２μｍの光を使用した。集光点４に形成されたスポットは、直径が約２μｍであった。
本実施例のＣｄ(Ｓｅ,Ｔｅ)微粒子分散ガラスは、１.２μｍの波長における透過率が８５％であった。ピークエネルギー密度１０¹⁵Ｗ／ｃｍ²で集光点４に１０秒照射した後、レーザー光１のガラス試料３への入射をやめ、ガラス試料３をＸＹ軸方向にスキャンさせ、再度同じ条件で集光照射した。この集光照射，集光照射中止，ガラス試料の移動操作を繰り返した後、Ｚ軸方向に電動ステージを２０μｍ移動させ、ＸＹ方向へ同様に集光照射した。
【００３３】
集光照射処理されたガラス試料を光学顕微鏡で観察したところ、図２に示すように、集光照射部分ではＣｄ(Ｓｅ,Ｔｅ)微粒子によって吸収されていた波長帯（約７００〜９００ｎｍ）の吸収係数が減少し、無色に変化した領域５が形成されていた。一方、非集光照射部分では、色の変化が観察されなかった。
波長７５０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では、屈折率の変化と吸収係数の現象によるものと考えられる透過率の違いが検出され、屈折率変化だけ利用した比較例４に比べ著しく大きなコントラストであった。また、２０μｍ間隔で上層と下層のスポットの読取りエラーはなく、Ｘ，Ｙ，Ｚ方向に三次元的に情報を記録できた。
【００３４】
実施例８：Ｃｄ(Ｓ,Ｔｅ)微粒子分散ガラス
ＳｉＯ₂，Ａｌ₂Ｏ₃，Ｂ₂Ｏ₃，Ｎａ₂ＣＯ₃，ＺｎＯ，ＣｄＳ，ＣｄＴｅを原料粉末として用い、ＳｉＯ₂：６９重量％，Ａｌ₂Ｏ₃：１重量％，Ｂ₂Ｏ₃：１２１重量，Ｎａ₂Ｏ：６１重量，ＺｎＯ：１１１重量，ＣｄＳ：０.３１重量，ＣｄＴｅ：０.２１重量の組成に調合した。原料粉末４００ｇを３００ｃｃ白金製ルツボに投入した後、大気中１４５０℃で２時間攪拌しながら加熱溶解した。均一に溶解したガラスを真鍮の型に流し込んで厚さ５ｍｍの板に成型し、冷却した後、４５０℃のアニールで歪みを除去した。
ガラス中にＣｄ(Ｓ,Ｔｅ)微粒子を析出させるため、電気炉を用いて昇温速度５℃／分でガラスを昇温し、６５０℃で４時間保持した後、炉内で放冷した。次いで、切断・研磨し、厚さ４ｍｍのガラス試料を作製した。得られたガラス試料は、Ｃｄ(Ｓ,Ｔｅ)微粒子の析出によって赤色に着色しており、透過型電子顕微鏡（ＴＥＭ）で観察したところ、平均粒径１０ｎｍのＣｄ(Ｓ,Ｔｅ)がガラスマトリックスに分散していた。
【００３５】
析出処理されたガラス試料３を実施例１と同様にパルスレーザーで照射した。パルスレーザー光には、アルゴンレーザー励起のＴｉ-サファイアレーザーから発振されたパルス幅１.５×１０^-13秒、繰返し周期２００ｋＨｚ、波長８００ｎｍの光を使用した。集光点４に形成されたスポットは、直径が約１.５μｍであった。
本実施例のＣｄ(Ｓ,Ｔｅ)微粒子分散ガラスは、８００ｎｍの波長における透過率が８０％であった。ピークエネルギー密度１０¹⁵Ｗ／ｃｍ²で集光点４に１０秒間照射した後、レーザー光１のガラス試料３への入射をやめ、ガラス試料３をＸＹ軸方向にスキャンさせ、再度同じ条件で集光照射した。この集光照射，集光照射中止，ガラス試料の移動操作を繰り返した後、Ｚ軸方向に電動ステージを１５μｍ移動させ、ＸＹ方向へ同様に集光照射した。
【００３６】
集光照射処理されたガラス試料３を光学顕微鏡で観察したところ、図２に示すように、集光照射部分ではＣｄ(Ｓ,Ｔｅ)微粒子によって吸収されていた波長帯（約５００〜７５０ｎｍ）の吸収係数が減少し、赤色着色がなくなり無色に変化した領域５が形成されていた。一方、非集光照射部分では、色の変化が観察されなかった。
波長５８０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では、屈折率の変化と吸収係数の減少によるものと考えられる透過率の違いが検出され、屈折率変化だけを利用した比較例４に比べ著しく大きなコントラストが得られた。また、１５μｍ間隔で上層と下層のスポットの読取りエラーはなく、Ｘ，Ｙ，Ｚ方向に三次元的に情報を記録できた。
【００３７】
比較例１
塩化金酸の水溶液を加えないことを除き実施例１と同じ原料を用いて、ＳｉＯ₂：７２重量％，Ｂ₂Ｏ₃：１８重量％，Ｎａ₂Ｏ：１０重量％，Ｓｂ₂Ｏ₃：４重量％の組成をもつガラスを作製した。得られた厚み４ｍｍのガラスを被記録材料として用い、実施例１と同様にパルスレーザ光で集光照射した。
集光照射処理されたガラスを光学顕微鏡で観察したところ、図３に示すように屈折率の変化した領域６が集光照射部分に形成されており、非集光照射部分では屈折率の変化が観察されなかった。波長５３０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では屈折率の変化によるものと思われる透過率の違い（コントラスト）がついていることが判った。しかし、コントラスト（Ｓ／Ｎ）は、実施例１，２，４に比べて非常に小さいものであった。
【００３８】
比較例２
Ａｇ₂Ｏを配合しないことを除き実施例３と同じ原料を用いて、ＳｉＯ₂：７２重量％，ＣａＯ：２０重量％，Ｎａ₂Ｏ：８重量％，ＳｎＯ：０.２重量％の組成をもつガラスを作製した。得られた厚み４ｍｍのガラスを被記録材料として用い、実施例３と同様にパルスレーザ光で集光照射した。
集光照射処理されたガラスを光学顕微鏡で観察したところ、図３に示すように集光照射部分に屈折率変化領域６が形成されていた。非集光照射部分では、屈折率の変化が観察されなかった。波長４２０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では屈折率の変化によるものと思われる透過率の違い（コントラスト）がついていることが判った。しかし、コントラスト（Ｓ／Ｎ）は、実施例３に比べて非常に小さいものであった。
【００３９】
比較例３
ＣｕＣｌを配合しないことを除き実施例５と同じ原料を用い、ＳｉＯ₂：６５重量％，Ａｌ₂Ｏ₃：６重量％，Ｂ₂Ｏ₃：１４重量％，Ｌｉ₂Ｏ：４重量％，Ｎａ₂Ｏ：４重量％，Ｋ₂Ｏ：４重量％，ＳｎＯ：０.２重量％の組成をもつガラスを作製した。得られた厚み４ｍｍのガラスを被記録材料として用い、実施例５と同様にパルスレーザ光で集光照射した。
集光照射処理されたガラス試料を光学顕微鏡で観察したところ、図３に示すように、集光照射部分に屈折率変化領域６が形成されていた。非集光照射部分では、屈折率の変化が観察されなかった。波長３７５ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では、屈折率の変化によるものと思われる透過率の違い（コントラスト）がついていることが判った。しかし、コントラスト（Ｓ／Ｎ）は、実施例５に比べて非常に小さいものであった。
【００４０】
比較例４
Ｃｄ化合物を配合しないことを除き実施例６〜８と同じ原料を用い、ＳｉＯ₂：６９重量％，Ａｌ₂Ｏ₃：１重量％，Ｂ₂Ｏ₃：１２重量％，Ｎａ₂Ｏ：６重量％，ＺｎＯ：１１重量％の組成をもつガラスを作製した。得られた厚み４ｍｍのガラスを被記録材料として用い、実施例６と同様にパルスレーザ光で集光照射した。
集光照射処理されたガラス試料を光学顕微鏡で観察したところ、図３に示すように、集光照射部分に屈折率変化領域６が形成されていた。一方、非集光照射部分では、屈折率の変化が観察されなかった。波長４８０ｎｍの光を用いて記録情報を読み出したところ、集光照射部と非集光照射部では屈折率の変化によるものと思われる透過率の違い（コントラスト）がついていることが判った。しかし、コントラスト（Ｓ／Ｎ）は、実施例６〜８に比べて非常に小さいものであった。
【００４１】
以上の実施例１〜８及び比較例１〜４における透過率変化を表１に示す。実施例と比較例との対比から明らかなように、本発明に従ったガラスでは、析出した微粒子がレーザ光の集光照射によって変化し、屈折率が変化し又は吸収係数が減少した領域５が形成される。この領域５のため、従来の屈折率変化領域６をもつガラスに比較して非常に大きなコントラスト（Ｓ／Ｎ）が得られ、三次元光メモリ媒体として優れたものであることが判る。
【００４２】

【００４３】
【発明の効果】
以上に説明したように、本発明の三次元光メモリ媒体においては、微粒子分散ガラスの内部をパルスレーザ光で集光照射することにより、微粒子分散ガラスに析出している微粒子を変質させ、屈折率が変化し又は吸収係数が減少した領域を形成させている。この領域は、パルスレーザ光の集光点に応じて微粒子分散ガラスの内部で三次元的に多数形成されるため、高密度記録に利用できる。しかも、屈折率変化だけを利用した光メモリ媒体に比較してコントラストが非常に高く、読取りエラーも少なくなる。
【図面の簡単な説明】
【図１】ガラス材料内部に集光点を調節したレーザー光で微粒子分散ガラスを照射している状態
【図２】微粒子分散ガラスの内部にスポット状の屈折率変化・吸収係数減少域が形成された三次元光メモリ媒体
【図３】微粒子分散ガラスの内部にスポット状の屈折率変化域が形成された三次元光メモリ媒体
【符号の説明】
１：パルスレーザー光２：集光装置（レンズ）３：微粒子分散ガラス（ガラス試料）４：集光点５：屈折率が変化し又は吸収係数が減少した領域６：屈折率変化領域[0001]
[Industrial applications]
The present invention relates to a three-dimensional optical memory medium in which readout contrast (S / N) is improved by forming one or more spots in which the state of dispersion of fine particles is locally changed in the fine particle dispersion medium, and a method of manufacturing the same. It is about.
[0002]
[Prior art]
Various recording media, such as hard disks, are required to have higher recording densities as the capacity of information processing increases. Above all, it is possible to reduce the laser beam used for recording / reproduction to the diffraction limit of light so that the size of the recordable area can be reduced to about the wavelength used, specifically 1 cm.^Two10 per⁸Since a high recording density of bits can be obtained, research on optical memories has been actively pursued, and some of them have been put to practical use.
As a direction for increasing the capacity of an optical disc, shortening the wavelength of a laser used for writing can reduce the writing area, and thus shortening the wavelength of the laser is cited. However, it is not easy to shorten the wavelength of the laser itself, and the absorption coefficient of the material increases with the shortening of the wavelength. Therefore, the current wavelength of the writing laser is about 700 nm. Even if it is assumed that the problem of shortening the wavelength of the laser and the increase of the absorption coefficient accompanying the shortening of the wavelength can be overcome, it is said that the limit of increasing the recording density to about four times the current state is the limit.
[0003]
Therefore, instead of increasing the relative recording density by reducing the recording area, increasing the spatial dimension of recording from two to three has been studied to increase the capacity. As a member of this system, there are a method of three-dimensionally recording information using a photochromic material whose transmittance changes by light irradiation, and a method of causing a three-dimensional change in refractive index using a photorefractive crystal. .
However, in the method having the photochromic material, the photochromic material is an organic material, and is liable to be deteriorated and deteriorated by heat or light. Further, there is a disadvantage that the recording state shows a temporal change, the sensitivity is too high, and the photoreaction proceeds even by the reading light, and the recording state changes. On the other hand, in the method using a photorefractive crystal, since the photorefractive crystal has optical anisotropy, the recording state differs depending on the axial direction of the crystal when recording.
[0004]
Research is also underway to increase the recording density per spot by multiplexing the wavelengths of light used for reading and writing to increase the capacity. As a member of this system, there is photochemical hole burning (PHB).
In photochemical hole burning, the width of the light absorption spectrum due to the active center in a system in which organic dyes, rare earth metal ions, etc. are dispersed as active centers in a transparent solid medium such as glass, polymer, ionic crystal, or metal oxide crystal is measured. Utilizing the fact that the width is wider than the original width (uniform width) due to the non-uniformity. That is, when a specific wavelength within the non-uniform width is irradiated with a laser beam having a narrow line width, absorption of the irradiated wavelength is saturated, and a hole is formed in the absorption spectrum. According to this method, in principle, 10 spots per spot^ThreeThe above multiplicity is possible, and the recording density is 1 cm^Two10 per¹¹It is said that it can be increased to a bit.
[0005]
However, there is a problem that most PHB phenomena are observed only at extremely low temperatures of 200 ° C. or lower, and do not operate at room temperature. In recent years, the PHB phenomenon has been observed even at room temperature (K. Hirao et al., J. Lumi., 55, 217 (1993)), but problems such as low multiplicity and poor generation efficiency remain. ing.
A novel three-dimensional optical memory glass that solves such a problem is introduced in Japanese Patent Application Laid-Open No. 8-220688. This three-dimensional optical memory glass is stable to heat and light and has no optical anisotropy. When a pulse laser is condensed and radiated into the glass matrix while scanning the glass matrix three-dimensionally, a light-induced refractive index change occurs in a minute spot, and information is recorded as a spatial refractive index distribution. According to this method, it is possible to record information stably with respect to heat and light, excellent in weather resistance, and stable for a long period of time, and it is possible to increase the recording capacity of the optical disk.
[0006]
[Problems to be solved by the invention]
However, in the case of the optical memory glass disclosed in Japanese Patent Application Laid-Open No. 8-220688, the change in the refractive index is only induced by the focused irradiation of the pulsed laser beam, and the irradiated material itself is the same. Therefore, there is no large change in the composition between the portion where the refractive index change has occurred and the portion where the refractive index change has not occurred, and the amount of the induced refractive index change cannot be so large. Since the change in the transmittance or the reflectance caused only by the change in the refractive index is used for the memory, the contrast (S / N) in reading cannot be increased due to the small change in the refractive index.
The present invention, in order to solve such a problem,Fine particle dispersed glassProvided is a three-dimensional optical memory medium having a high readout contrast (S / N) by forming one or more spots in which the dispersion state of fine particles is locally changed by condensing irradiation of a pulse laser beam inside. With the goal.
[0007]
[Means for Solving the Problems]
The three-dimensional optical memory medium of the present invention, in order to achieve the object, a fine particle-dispersed glass as a base, one or more of the dispersed state of the fine particles locally changed by condensing irradiation of pulsed laser light inside the base The spot is present inside the substrate.
At the spot, the absorption coefficient in the absorption wavelength region of the fine particle dispersion medium decreases. As the fine particles, one or more selected from Au, Cu, Ag, Pt, CuCl, CuBr, CdS, CdSe, and CdTe are used, and are dispersed in the fine particle dispersed glass.
This three-dimensional optical memory medium focuses pulsed laser light having an energy amount that changes the state of dispersion of fine particles inside the glass, and moves the focal point of the pulse laser light relatively inside the glass. It is manufactured by forming one or a plurality of spots in which the dispersion state of the fine particles is locally changed, inside the fine particle dispersion glass. As the pulsed laser light to be used, a pulsed laser light in a wavelength region where the transmittance of the fine particle-dispersed glass is 20% or more is preferable.
[0008]
[Action]
Fine particle dispersed glassWhen a pulsed laser beam is condensed and irradiated inside, a change in the refractive index similar to that of the optical memory glass occurs at the converging point, and the dispersion state of the fine particles that are the coloring species, that is,Fine particles Dispersion glassThe number of fine particles dispersed inside, the size of fine particles, the form of fine particles, and the like change. Specifically, the number of fine particles is reduced, the size of the fine particles is reduced, and the fine particles disappear due to dissolution or ionization in a medium.
When the particles no longer exist as fine particles due to dissolution or ionization in the medium, the absorption coefficient of that portion becomes the same value as that of the medium in which the fine particles are not dispersed, and decreases as compared to before the irradiation. When the size of the fine particles changes due to the converging irradiation of the laser beam, the absorption wavelength changes due to the change in the size of the fine particles, and the absorption coefficient at the irradiation wavelength after the converging irradiation is smaller than before the converging irradiation. Therefore, the wavelength of the laser beam used for reading isFine particle dispersed glassWhen the absorption wavelength region is set, the absorption coefficient of the part other than the focal point is the same as that before irradiation, but the absorption coefficient is reduced at the focal point, so the transmittance or reflection only at the focal point The readout contrast (S / N) is improved as compared with the case where only the change in the refractive index is used.
[0009]
Embodiment
Glass as a dispersion mediumExamples of the fine particles dispersed in the fine particles include metal fine particles such as Au, Cu, Ag, and Pt, and semiconductor fine particles such as CdS, CdSe, CdTe, CuCl, and CuBr. These fine particles are dispersed in a medium such as glass, polymer, ionic crystal, and metal oxide crystal. Among them, glass is very suitable as a medium because it is optically isotropic and has excellent heat resistance and light resistance.
ParticulateThe amount of dispersion is preferably 0.01 to 50% by weight. If the amount of dispersion is less than 0.01% by weight, there is a tendency that the readout contrast cannot be increased because the absorption coefficient becomes small. Conversely, if the amount of dispersion exceeds 50% by weight, the dispersed fine particles are aggregated without being uniformly dispersed, or the aggregates increase the substantial size of the particles, causing light scattering and lowering the read contrast. Show the tendency to do.
[0010]
Glass as a mediumThe dispersion state of the fine particles dispersed inFine particle dispersed glassIs irradiated with pulsed laser light having a focal point set therein, and therefore changes at and around the focal point. In the irradiated portion other than the focal point, the light amount required for changing the dispersion state is not obtained, and the same dispersion state as before the irradiation with the pulsed laser beam is maintained. as a result,Fine particle dispersed glassOnly the inside is selectively transformed.
The laser light 1 emitted from the light source is condensed by a condensing device 2 such as a lens as shown in FIG. At this time, the focusing of the light collecting device 2 is adjusted so that the light collecting point 4 is located inside the fine particle dispersion medium 3. When the step scan for irradiating the focal point 4 with spots and spots is adopted, a region where the dispersion state of the fine particles is changed is formed in a dot shape.Fine particle dispersed glassWhen the focal point 4 is three-dimensionally moved relative to 3, the three-dimensionally changed area isFine particle dispersed glass3 is formed inside.Fine particle dispersed glassFor the relative movement of the focal point 4 with respect to 3, the focal point 4 is fixed.Fine particle dispersed glassHow to move 3,Fine particle dispersed glassA method in which the focal point 4 is moved while the focus 3 is fixed, a combination of the two, or the like is employed.
[0011]
The peak power of the pulse laser is expressed in watts (W) as a value obtained by dividing output energy (J) per pulse by pulse width (second). The peak power density is expressed in unit area (cm^Two), And W / cm^TwoIs represented by
The peak power density of the pulsed laser light at the focal point is 10⁸-10¹⁷W / cm^TwoIt is desirable to be within the range. 10⁸W / cm^TwoIf the peak power density is lower than the above, the change in the refractive index and the state of dispersion of the fine particles in the condensed portion do not sufficiently change. Conversely 10¹⁷W / cm^TwoIf the peak power density exceeds the above range, the refractive index change and the dispersion state of the fine particles change even in a portion other than the converging point, and it becomes difficult to obtain the target change. Further, a laser beam having an excessively large energy amount is practically difficult.
[0012]
When irradiating with a laser beam having the same peak power density, a laser beam having a smaller pulse width is more likely to cause a change in a refractive index and a change in a state of dispersion of fine particles. In this regard, 10^-TenLaser light having a pulse width of less than a second is preferred. In the case of a laser beam having an excessively wide pulse width, it is necessary to irradiate a laser beam having a very large energy to change the refractive index and change the dispersion state of the fine particles, which may destroy the material of the fine particle dispersion medium.
The irradiation amount is set to an amount necessary for a change in the refractive index and a change in the dispersion state of the fine particles. The repetition period (pulse-to-pulse interval) of the pulse laser is not particularly limited, but if the period is excessively short (eg, 100 MHz), a change in the refractive index and a change in the state of dispersion of fine particles will occur even at portions other than the converging portion. I will.
[0013]
【Example】
Example 1: Au fine particle dispersed glass
SiO_Two, B_TwoO_Three, Na_TwoCO_Three, Sb_TwoO_ThreeAn aqueous solution of chloroauric acid was added to the compounding raw material of_Two: 72% by weight, B_TwoO_Three: 18% by weight, Na_TwoO: 10% by weight, Sb_TwoO_Three: 4% by weight and Au: 0.02% by weight. After 400 g of the raw material powder was put into a 300 cc platinum crucible, the mixture was heated and dissolved in the atmosphere at 1450 ° C. for 2 hours while stirring. The uniformly melted glass was poured into a brass mold, formed into a 5 mm thick plate, and cooled. The obtained glass was annealed at 450 ° C. to remove the distortion.
In order to precipitate Au fine particles in the glass, the glass was heated at a rate of 5 ° C./min using an electric furnace, kept at 650 ° C. for 4 hours, and then allowed to cool in the furnace. Then, the sample was cut and polished to obtain a sample having a thickness of 4 mm. The obtained glass sample was colored red due to the deposition of gold fine particles. When the size of the Au fine particles dispersed in the glass was observed using a transmission electron microscope (TEM), fine particles having an average particle diameter of 10 nm were dispersed.
[0014]
The glass sample was irradiated with a pulse laser focused so that the focal point was located inside the glass sample. That is, the glass sample 3 is set on an electric stage that can scan in the XYZ directions, and the pulse laser beam 1 is collected inside the glass sample 3 as shown in FIG. The light was focused by the lens 2 so that the light spot 4 was positioned, and the glass sample 3 was irradiated. The pulse racer light has a pulse width of 1.5 × 10 4 oscillated from a Ti-sapphire laser excited by an argon laser.^-3Light having a second, a repetition period of 50 Hz, and a wavelength of 800 nm was used. The spot formed at the focal point 4 had a diameter of about 1 μm. The spot diameter can be further reduced by increasing the magnification of the lens 2 and the beam diameter of the pulsed laser light 1.
The Au particle dispersed glass of this example had a transmittance of 89% at a wavelength of 800 nm. Peak energy density 10¹³W / cm^TwoAfter irradiating the focusing point 4 for 3 seconds, the incidence of the laser beam 1 on the glass sample 3 was stopped, the glass sample 3 was scanned in the XY axis directions, and the focusing irradiation was performed again under the same conditions. After repeating the condensing irradiation, the stopping of the condensing irradiation, and the moving operation of the glass sample 3, the electric stage in the Z-axis direction was moved by 5 μm, and the condensing irradiation was similarly performed in the XY directions.
[0015]
Observation of the condensed irradiation-treated glass sample 3 with an optical microscope revealed that, in the condensed irradiation part, as shown in FIG. However, the region 5 where the red coloring disappeared was formed. On the other hand, no color change was observed in the non-condensed irradiation part.
When the recorded information was read using light having a wavelength of 530 nm, a difference in transmittance between the condensed irradiating portion and the non-condensing irradiating portion, which is considered to be caused by a change in refractive index and a phenomenon of an absorption coefficient, was detected. The contrast was significantly higher than that of Comparative Example 1 using only the change. There was no reading error of the upper and lower layer spots at 5 μm intervals, and information could be recorded three-dimensionally in the X, Y and Z directions.
[0016]
Example 2: Cu fine particle dispersed glass
SiO_Two, B_TwoO_Three, Na_TwoO_Three, Cu_TwoThe raw material powder of O, SnO is_Two: 72% by weight, B_TwoO_Three: 20% by weight, Na_TwoO: 8% by weight, Cu: 0.5% by weight, SnO: 0.25% by weight. After 400 g of the raw material powder was put into a 300 cc platinum crucible, the mixture was heated and dissolved in the atmosphere at 1450 ° C. for 2 hours while stirring. The uniformly melted glass was poured into a brass mold, formed into a plate having a thickness of 5 mm, and cooled. The obtained glass was annealed at 450 ° C. to remove the distortion.
In order to precipitate Cu fine particles in the glass, the temperature of the glass was raised at a rate of 5 ° C./min using an electric furnace, and the glass was kept at 650 ° C. for 4 hours and then allowed to cool in the furnace. The glass after the precipitation treatment was cut and polished to produce a sample having a thickness of 4 mm. This glass sample was colored yellow by precipitation of Cu fine particles, and when observed by a transmission electron microscope (TEM), Cu fine particles having an average particle diameter of 20 nm were dispersed in the glass matrix.
[0017]
Next, the produced glass sample 3 was irradiated with pulsed laser light in the same manner as in Example 1. The pulse laser light has a pulse width of 1.5 × 10 4 oscillated from a Ti-sapphire laser excited by an argon laser.^-13Light having a second, a repetition period of 100 Hz, and a wavelength of 1.0 μm was used. The spot formed at the focal point 4 had a diameter of about 2 μm.
The transmittance of the Cu fine particle-dispersed glass of this example at a wavelength of 1.0 μm was 90%. Peak energy density 10¹¹W / cm^TwoAfter irradiating the focusing point 4 for 5 seconds, the laser beam 1 was stopped from being incident on the glass sample 3, the glass sample 3 was scanned in the XY axis directions, and again focused and irradiated under the same conditions. The focusing irradiation, stopping the focusing irradiation, and moving the glass sample were repeated. Next, the electric stage was moved to 15 μm in the Z-axis direction, and the light was similarly irradiated in the XY directions.
[0018]
Observation of the condensed irradiation-treated glass sample 3 by an optical microscope showed that, as shown in FIG. Thus, the colorless region 5 was formed without the yellow coloring. On the other hand, no color change was observed in the non-condensed irradiation part.
When the recorded information was read using light having a wavelength of 530 nm, a difference in the transmittance, which is considered to be caused by the change in the refractive index and the phenomenon of the absorption coefficient, was detected between the converging irradiation part and the non-condensing irradiation part, which will be described later. The contrast was significantly higher than that of Comparative Example 1 using only the change in the refractive index of Comparative Example 1. In addition, there was no reading error of the upper and lower layer spots at intervals of 15 μm, and information could be recorded three-dimensionally in the X, Y, and Z directions.
[0019]
Example 3: Ag fine particle dispersed glass
SiO_Two, CaCO_Three, Na_TwoCO_Three, Ag_TwoO, SnO as raw material powder, SiO_Two: 72% by weight, CaO: 20% by weight, Na_TwoO: 8% by weight, Ag: 0.4% by weight, SnO: 0.2% by weight. After 400 g of the raw material powder was put into a 300 cc platinum crucible, it was heated and dissolved in the atmosphere at 1450 ° C. for 2 hours while stirring. The uniformly melted glass was poured into a brass mold to form a plate having a thickness of 5 mm. After cooling, the strain was removed by annealing at 450 ° C.
In order to precipitate Ag fine particles in the glass, the glass was heated at a rate of 5 ° C./min using an electric furnace, kept at 550 ° C. for 4 hours, and then allowed to cool in the furnace. Thereafter, the sample was cut and polished to produce a sample having a thickness of 4 mm. The glass subjected to the precipitation treatment was colored yellow by the precipitation of Ag fine particles, and when observed by a transmission electron microscope (TEM), Ag fine particles having an average particle diameter of 8 nm were dispersed in the glass matrix.
[0020]
The glass sample 3 subjected to the precipitation treatment was irradiated with pulsed laser light in the same manner as in Example 1. The pulse laser light has a pulse width of 1.5 × 10 5 oscillated from a Ti-sapphire laser excited by an argon laser.^-13Light having a second, a repetition period of 1 kHz and a wavelength of 600 nm was used. The spot formed at the focal point 4 had a diameter of about 0.8 μm.
The transmittance of the Ag particle-dispersed glass of this example at a wavelength of 600 nm was 91%. Peak energy density 10¹⁴W / cm^TwoAfter irradiating the focal point 4 for 3 seconds, the incidence of the laser beam 1 on the glass sample 3 was stopped, and the glass sample 3 was scanned in the X and Y directions, and focused again under the same conditions. After repeating the condensing irradiation, the stopping of the condensing irradiation, and the operation of moving the glass sample, the electric stage was moved by 5 μm in the Z-axis direction, and the condensing irradiation was similarly performed in the XY directions.
[0021]
When the glass sample 3 subjected to the condensing irradiation treatment was observed with an optical microscope, as shown in FIG. 2, in the condensing irradiation part, the absorption coefficient in the wavelength band (about 360 to 480 nm) absorbed by the Ag fine particles decreased. Thus, the colorless region 5 was formed without the yellow coloring. On the other hand, no color change was observed in the non-condensed irradiation part.
When the recorded information was read using light having a wavelength of 420 nm, a difference in transmittance between the condensed irradiating part and the non-condensing irradiating part, which is considered to be due to a change in the refractive index and a decrease in the absorption coefficient, was detected. The contrast was significantly higher than that of Comparative Example 2 using only the change. There was no reading error of the upper and lower spots at 5 μm intervals, and information could be recorded three-dimensionally in the X, Y, and Z directions.
[0022]
Example 4: Pt fine particle dispersed glass
SiO_Two, B_TwoO_Three, Na_TwoCO_Three, Sb_TwoO_ThreeAn aqueous solution of chloroplatinic acid is added to the raw material powder of_Two: 72% by weight, B_TwoO_Three: 18% by weight, Na_TwoO: 10% by weight, Sb_TwoO_Three: 2% by weight and Pt: 0.05% by weight. After 400 g of the raw material powder was put into a 300 cc platinum crucible, it was heated and dissolved in the atmosphere at 1450 ° C. for 2 hours while stirring. The uniformly melted glass was cast into a brass mold to form a plate having a thickness of 5 mm, cooled, and annealed at 450 ° C. to remove distortion.
In order to precipitate Pt fine particles in the glass, the temperature of the glass was raised at a rate of 5 ° C./min using an electric furnace, and the glass was kept at 600 ° C. for 4 hours and then allowed to cool in the furnace. Next, it was cut and polished to produce a glass sample having a thickness of 4 mm. This glass sample was colored gray due to precipitation of Pt fine particles, and when observed by a transmission electron microscope (TEM), Pt fine particles having an average particle size of 15 nm were dispersed in the glass matrix.
[0023]
The glass sample 3 subjected to the precipitation treatment was irradiated with pulsed laser light in the same manner as in Example 1. The pulse laser light has a pulse width of 1.5 × 10 4 oscillated from a Ti-sapphire laser excited by an argon laser.^-13Light having a second, a repetition period of 1 kHz, and a wavelength of 1.0 μm was used. The spot diameter at the focal point 4 was about 2 μm.
The Pt fine particle-dispersed glass of this example had a transmittance of 89% at a wavelength of 1.0 μm. Peak energy density 10¹³W / cm^TwoAfter irradiating the focusing point 4 for 5 seconds, the laser beam 1 was stopped from being incident on the glass sample 3, the glass sample 3 was scanned in the XY axis directions, and again focused and irradiated under the same conditions. After repeating the condensing irradiation, the stopping of the condensing irradiation, and the operation of moving the glass sample, the electric stage was moved by 20 μm in the Z-axis direction, and the condensing irradiation was similarly performed in the XY directions.
[0024]
When the glass sample 3 subjected to the condensing irradiation treatment was observed with an optical microscope, as shown in FIG. 2, the absorption coefficient in the wavelength band (about 400 to 750 nm) absorbed by the Pt fine particles decreased, and the gray color disappeared. The colorless region 5 was formed in the condensed and irradiated portion. No color change was observed in the non-condensed irradiation part.
When the recorded information was read using light having a wavelength of 600 nm, a difference in transmittance between the condensed irradiating portion and the non-condensing irradiating portion, which was considered to be due to a change in the refractive index and a decrease in the absorption coefficient, was detected. The contrast was significantly higher than that of Comparative Example 1 using only the change. In addition, there was no reading error of the upper and lower spots at intervals of 20 μm, and information could be recorded three-dimensionally in the X, Y, and Z directions.
[0025]
Example 5: CuCl fine particle dispersed glass
SiO_Two, Al_TwoO_Three, B_TwoO_Three, Li_TwoCO_Three, Na_TwoCO_Three, K_TwoCO_Three, CuCl, SnO as raw material powder,_Two: 65% by weight, Al_TwoO_Three: 6% by weight, B_TwoO_Three: 17% by weight, Li_TwoO: 4% by weight, Na_TwoO: 4% by weight, K_TwoO: 4% by weight, CuCl: 0.5% by weight, SnO: 0.2% by weight. After 400 g of the raw material powder was put into a 300 cc platinum crucible, the mixture was heated and dissolved in the atmosphere at 1450 ° C. for 2 hours while stirring. The uniformly melted glass was cast into a brass mold to form a plate having a thickness of 5 mm. After cooling, the strain was removed by annealing at 450 ° C.
[0026]
In order to precipitate CuCl fine particles in the glass, the temperature of the glass was raised at a rate of 5 ° C./min using an electric furnace, and the glass was kept at 550 ° C. for 4 hours, and then allowed to cool in the furnace. Next, it was cut and polished to produce a glass sample having a thickness of 4 mm. Observation of the obtained glass sample with a transmission electron microscope (TEM) revealed that CuCl fine particles having an average particle size of 8 nm were dispersed in the glass matrix.
The glass sample 3 subjected to the precipitation treatment was irradiated with a pulse laser in the same manner as in Example 1. The pulse laser beam has a pulse width of 1.5 × 10 4 oscillated from a Ti-sapphire laser excited by an argon laser.^-13Light having a second, a repetition period of 1 kHz, and a wavelength of 500 nm was used. The spot formed at the focal point 4 had a diameter of about 0.7 μm.
[0027]
The CuCl fine particle dispersed glass of the present example had a transmittance of 92% at a wavelength of 500 nm. Peak energy density 10¹⁵W / cm^TwosoFocus point 4After irradiation for 3 seconds, the laser beam 1 was stopped from being incident on the glass sample 3, the glass sample 3 was scanned in the XY axis directions, and the light was again irradiated under the same conditions. After repeating the condensing irradiation, stopping the condensing irradiation, and moving the glass sample, the electric stage was moved by 3 μm in the Z-axis direction, and the condensing irradiation was similarly performed in the XY-axis directions.
When the glass sample subjected to the condensing irradiation treatment was observed with an optical microscope, as shown in FIG. 2, in the condensing irradiation part, the region where the absorption coefficient was reduced to the wavelength band (about 300 to 385 nm) absorbed by the CuCl fine particles. 5 had been formed. On the other hand, no color change was observed in the non-condensed irradiation part.
When the recorded information was read using light having a wavelength of 375 nm, a difference in transmittance between the condensed irradiation part and the non-condensed irradiation part, which is considered to be due to a change in the refractive index and a decrease in the absorption coefficient, was detected. The contrast was remarkably higher than that of Comparative Example 3 using only the rate change. In addition, there was no reading error between the upper and lower spots at 3 μm intervals, and information could be recorded three-dimensionally in the X, Y, and Z directions.
[0028]
Example 6: Cd (S, Se) fine particle dispersed glass
SiO_Two, Al_TwoO_Three, B_TwoO_Three, Na_TwoCO_Three, ZnO, CdS, CdSe as raw material powders,_Two: 69% by weight, Al_TwoO_Three: 1% by weight, B_TwoO_Three: 12% by weight, Na_TwoO: 6% by weight, ZnO: 11% by weight, CdS: 0.3% by weight, CdSe: 0.2% by weight. After 400 g of the raw material powder was put into a 300 cc platinum crucible, the mixture was heated and dissolved in the atmosphere at 1450 ° C. for 2 hours while stirring. The uniformly melted glass was poured into a brass mold to form a plate having a thickness of 5 mm. After cooling, the strain was removed by annealing at 450 ° C.
In order to precipitate Cd (S, Se) fine particles in the glass, the temperature of the glass was raised at a rate of 5 ° C./min using an electric furnace, and the glass was kept at 650 ° C. for 4 hours and then allowed to cool in the furnace. Next, it was cut and polished to produce a glass sample having a thickness of 4 mm. This glass sample was colored red due to precipitation of Cd (S, Se) fine particles, and when observed by a transmission electron microscope (TEM), Cd (S, Se) fine particles having an average particle diameter of 10 nm were dispersed in a glass matrix. Was.
[0029]
The glass sample 3 subjected to the precipitation treatment was irradiated with a pulse laser in the same manner as in Example 1. The pulse laser beam has a pulse width of 1.5 × 10 5 oscillated from a Ti-sapphire laser excited by an argon Ar laser.^-13Light having a second, a repetition period of 1 kHz, and a wavelength of 650 nm was used. The spot formed at the focal point 4 had a diameter of about 0.9 μm.
The Cd (S, Se) fine particle-dispersed glass of this example had a transmittance of 85% at a wavelength of 650 nm. Peak energy density 10¹⁵W / cm^TwosoFocus point 4After irradiation for 3 seconds, the laser beam 1 was stopped from being incident on the glass sample 3, the glass sample 3 was scanned in the XY axis directions, and the light was again irradiated under the same conditions. After repeating the condensing irradiation, stopping the condensing irradiation, and moving the glass sample, the electric stage was moved by 10 μm in the Z-axis direction, and the condensing irradiation was similarly performed in the XY-axis directions.
[0030]
When the glass sample 3 subjected to the condensing irradiation treatment was observed with an optical microscope, as shown in FIG. 2, the condensed irradiation part had a wavelength band (about 450 to 580 nm) absorbed by Cd (S, Se) fine particles. A region 5 in which the absorption coefficient was reduced, the red coloration was lost, and the color changed to colorless was formed. On the other hand, no color change was observed in the non-condensed irradiation part.
When the recorded information was read using light having a wavelength of 480 nm, a difference in transmittance between the condensed irradiating portion and the non-condensing irradiating portion, which is considered to be caused by a change in refractive index and a phenomenon of an absorption coefficient, was detected. The contrast was significantly higher than that of Comparative Example 4 using only the change. In addition, there was no reading error between the upper and lower spots at 10 μm intervals, and information could be recorded three-dimensionally in the X, Y, and Z directions.
[0031]
Example 7: Cd (Se, Te) fine particle dispersed glass
SiO_Two, Al_TwoO_Three, B_TwoO_Three, Na_TwoCO_Three, ZnO, CdSe, CdTe as raw material powders,_Two: 69% by weight, Al_TwoO_Three: 1% by weight, B_TwoO_Three: 12% by weight, Na_TwoO: 3% by weight, ZnO: 11% by weight, CdSe: 0.3% by weight, CdTe: 0.2% by weight. After 400 g of the raw material powder was put into a 300 cc platinum crucible, it was heated and dissolved in the atmosphere at 1450 ° C. for 2 hours while stirring. The uniformly melted glass was poured into a brass mold to form a plate having a thickness of 5 mm. After cooling, the strain was removed by annealing at 450 ° C.
In order to precipitate Cd (Se, Te) fine particles in the glass, the temperature of the glass was raised at a rate of 5 ° C./min using an electric furnace, kept at 650 ° C. for 4 hours, and then allowed to cool in the furnace. Next, it was cut and polished to produce a glass sample having a thickness of 4 mm. The obtained glass sample was colored red due to precipitation of Cd (Se, Te) fine particles, and when observed with a transmission electron microscope (TEM), the Cd (Se, Te) fine particles having an average particle diameter of 10 nm were glass. The matrix was dispersed.
[0032]
The glass sample 3 subjected to the precipitation treatment was irradiated with a pulse laser in the same manner as in Example 1. The pulse laser light has a pulse width of 1.5 × 10 5 oscillated from a Ti-sapphire laser excited by an argon laser.^-13Light having a second, a repetition period of 1 kHz, and a wavelength of 1.2 μm was used. The spot formed at the focal point 4 had a diameter of about 2 μm.
The Cd (Se, Te) fine particle dispersed glass of this example had a transmittance of 85% at a wavelength of 1.2 μm. Peak energy density 10¹⁵W / cm^TwosoFocus point 4After irradiating the glass sample 3 for 10 seconds, the incidence of the laser beam 1 on the glass sample 3 was stopped, and the glass sample 3 was scanned in the X and Y directions, and was again condensed and irradiated under the same conditions. After repeating the condensing irradiation, the stopping of the condensing irradiation, and the operation of moving the glass sample, the electric stage was moved by 20 μm in the Z-axis direction, and the condensing irradiation was similarly performed in the XY directions.
[0033]
When the glass sample subjected to the condensing irradiation treatment was observed with an optical microscope, as shown in FIG. The coefficient 5 was reduced, and the colorless region 5 was formed. On the other hand, no color change was observed in the non-condensed irradiation part.
When the recorded information was read using light having a wavelength of 750 nm, a difference in transmittance between the condensed irradiation part and the non-condensed irradiation part, which is considered to be caused by the change in the refractive index and the phenomenon of the absorption coefficient, was detected. The contrast was significantly higher than that of Comparative Example 4 in which only the change was used. In addition, there was no reading error of the upper and lower spots at intervals of 20 μm, and information could be recorded three-dimensionally in the X, Y, and Z directions.
[0034]
Example 8: Cd (S, Te) fine particle dispersed glass
SiO_Two, Al_TwoO_Three, B_TwoO_Three, Na_TwoCO_Three, ZnO, CdS, CdTe as raw material powders,_Two: 69% by weight, Al_TwoO_Three: 1% by weight, B_TwoO_Three: 121 weight, Na_TwoO: 61 wt., ZnO: 111 wt., CdS: 0.31 wt., CdTe: 0.21 wt. After 400 g of the raw material powder was put into a 300 cc platinum crucible, it was heated and dissolved in the atmosphere at 1450 ° C. for 2 hours while stirring. The uniformly melted glass was poured into a brass mold to form a plate having a thickness of 5 mm. After cooling, the strain was removed by annealing at 450 ° C.
In order to precipitate Cd (S, Te) fine particles in the glass, the temperature of the glass was raised at a rate of 5 ° C./min using an electric furnace, the glass was kept at 650 ° C. for 4 hours, and then cooled in the furnace. Next, it was cut and polished to produce a glass sample having a thickness of 4 mm. The obtained glass sample was colored red due to precipitation of Cd (S, Te) fine particles, and when observed by a transmission electron microscope (TEM), Cd (S, Te) having an average particle size of 10 nm was found to be a glass matrix. Was dispersed.
[0035]
The glass sample 3 subjected to the precipitation treatment was irradiated with a pulse laser in the same manner as in Example 1. The pulse laser light has a pulse width of 1.5 × 10 5 oscillated from a Ti-sapphire laser excited by an argon laser.^-13Light having a second, a repetition period of 200 kHz, and a wavelength of 800 nm was used. The spot formed at the focal point 4 had a diameter of about 1.5 μm.
The Cd (S, Te) fine particle-dispersed glass of this example had a transmittance of 80% at a wavelength of 800 nm. Peak energy density 10¹⁵W / cm^TwosoFocus point 4After irradiating the glass sample 3 for 10 seconds, the incidence of the laser beam 1 on the glass sample 3 was stopped, and the glass sample 3 was scanned in the XY-axis directions, and again focused and irradiated under the same conditions. After repeating the condensing irradiation, the stopping of the condensing irradiation, and the operation of moving the glass sample, the electric stage was moved by 15 μm in the Z-axis direction, and the condensing irradiation was similarly performed in the XY directions.
[0036]
Observation of the condensed irradiation-treated glass sample 3 with an optical microscope showed that the condensed irradiation portion had a wavelength band (about 500 to 750 nm) absorbed by Cd (S, Te) fine particles, as shown in FIG. A region 5 in which the absorption coefficient was reduced, the red coloration was lost, and the color changed to colorless was formed. On the other hand, no color change was observed in the non-condensed irradiation part.
When the recorded information was read out using light having a wavelength of 580 nm, a difference in transmittance between the condensed irradiating portion and the non-condensing irradiating portion, which is considered to be due to a change in the refractive index and a decrease in the absorption coefficient, was detected. An extremely large contrast was obtained as compared with Comparative Example 4 using only the change. In addition, there was no reading error of the upper and lower spots at intervals of 15 μm, and information could be recorded three-dimensionally in the X, Y, and Z directions.
[0037]
Comparative Example 1
Using the same raw materials as in Example 1 except that no aqueous solution of chloroauric acid was added,_Two: 72% by weight, B_TwoO_Three: 18% by weight, Na_TwoO: 10% by weight, Sb_TwoO_Three: A glass having a composition of 4% by weight was produced. The obtained glass having a thickness of 4 mm was used as a material to be recorded, and focused and irradiated with pulsed laser light in the same manner as in Example 1.
Observation of the condensed irradiation-treated glass with an optical microscope revealed that a region 6 having a changed refractive index was formed in the converging and irradiating portion as shown in FIG. Not observed. When the recorded information was read using light having a wavelength of 530 nm, it was found that there was a difference (contrast) in the transmittance between the condensed light-irradiated part and the non-condensed light-irradiated part, which was thought to be due to a change in the refractive index. However, the contrast (S / N) was very small as compared with Examples 1, 2, and 4.
[0038]
Comparative Example 2
Ag_TwoUsing the same raw materials as in Example 3 except that O was not blended,_Two: 72% by weight, CaO: 20% by weight, Na_TwoGlass having a composition of O: 8% by weight and SnO: 0.2% by weight was prepared. The obtained glass having a thickness of 4 mm was used as a recording material, and focused and irradiated with pulsed laser light in the same manner as in Example 3.
Observation of the condensed and irradiated glass by an optical microscope revealed that a refractive index change region 6 was formed in the condensed and irradiated portion as shown in FIG. No change in the refractive index was observed in the non-light-collected irradiation part. When the recorded information was read using light having a wavelength of 420 nm, it was found that there was a difference (contrast) in the transmittance between the condensed light irradiating part and the non-condensed light irradiating part, which was considered to be due to a change in the refractive index. However, the contrast (S / N) was much smaller than that of Example 3.
[0039]
Comparative Example 3
Using the same raw materials as in Example 5 except that CuCl was not blended,_Two: 65% by weight, Al_TwoO_Three: 6% by weight, B_TwoO_Three: 14% by weight, Li_TwoO: 4% by weight, Na_TwoO: 4% by weight, K_TwoGlass having a composition of O: 4% by weight and SnO: 0.2% by weight was prepared. The obtained glass having a thickness of 4 mm was used as a recording material, and focused and irradiated with pulsed laser light in the same manner as in Example 5.
Observation of the condensed and irradiated glass sample by an optical microscope revealed that the refractive index change region 6 was formed in the condensed and irradiated portion as shown in FIG. No change in the refractive index was observed in the non-light-collected irradiation part. When the recorded information was read using light having a wavelength of 375 nm, it was found that a difference (contrast) in transmittance between the condensed irradiating part and the non-condensing irradiating part appears to be caused by a change in the refractive index. However, the contrast (S / N) was much smaller than that of Example 5.
[0040]
Comparative Example 4
Using the same raw materials as in Examples 6 to 8 except that no Cd compound was blended,_Two: 69% by weight, Al_TwoO_Three: 1% by weight, B_TwoO_Three: 12% by weight, Na_TwoGlass having a composition of O: 6% by weight and ZnO: 11% by weight was produced. The obtained glass having a thickness of 4 mm was used as a recording material, and focused and irradiated with pulsed laser light in the same manner as in Example 6.
Observation of the condensed and irradiated glass sample with an optical microscope revealed that the refractive index change region 6 was formed in the condensed and irradiated portion as shown in FIG. On the other hand, no change in the refractive index was observed in the non-condensed irradiation part. When the recorded information was read using light having a wavelength of 480 nm, it was found that a difference (contrast) in the transmittance between the converging and irradiating portions and the non-concentrating irradiating portions was considered to be due to a change in the refractive index. However, the contrast (S / N) was much smaller than in Examples 6 to 8.
[0041]
Table 1 shows changes in transmittance in Examples 1 to 8 and Comparative Examples 1 to 4 described above. As is clear from the comparison between the example and the comparative example, in the glass according to the present invention, the region 5 in which the precipitated fine particles are changed by the condensing irradiation of the laser light, and the refractive index is changed or the absorption coefficient is reduced. It is formed. Because of this region 5, an extremely large contrast (S / N) is obtained as compared with the glass having the conventional refractive index changing region 6, and it is understood that this is an excellent three-dimensional optical memory medium.
[0042]

[0043]
【The invention's effect】
As described above, in the three-dimensional optical memory medium of the present invention,Fine particle dispersed glassBy focusing and irradiating the inside with pulsed laser light,Fine particle dispersed glassThe fine particles deposited on the surface are altered to form a region where the refractive index changes or the absorption coefficient decreases. This area depends on the focal point of the pulsed laser light.Fine particle dispersed glassBecause it is formed three-dimensionally in a large number, it can be used for high-density recording. In addition, the contrast is very high and the reading error is reduced as compared with the optical memory medium using only the change in the refractive index.
[Brief description of the drawings]
FIG.Inside glass materialWith a laser beam whose focal point has been adjustedFine particle dispersed glassIs irradiating
FIG. 2Fine particle dispersed glass-Dimensional optical memory medium in which spot-shaped refractive index change / absorption coefficient reduction area is formed inside
FIG. 3Fine particle dispersed glass-Dimensional optical memory medium having spot-shaped refractive index change area formed inside
[Explanation of symbols]
1: pulsed laser light 2: focusing device (lens) 3:Fine particle dispersed glass(Glass sample) 4: Focus point 5: Region in which refractive index has changed or absorption coefficient has decreased 6: Refractive index change region

Claims

A three-dimensional optical memory medium comprising a fine particle-dispersed glass as a base, and one or more spots in which the dispersion state of the fine particles is locally changed by condensing irradiation of a pulsed laser beam into the base.

The three-dimensional optical memory medium according to claim 1, wherein one or more spots having a reduced absorption coefficient in the absorption wavelength region of the fine particle dispersed glass are formed inside the fine particle dispersed glass.

The three-dimensional structure according to claim 1 or 2, wherein one or two or more kinds of fine particles selected from Au, Cu, Ag, Pt, CuCl, CuBr, CdS, CdSe, and CdTe are dispersed on the base of the fine particle-dispersed glass. Optical memory medium.

The pulsed laser light with the amount of energy that changes the particle dispersion state is focused inside the particle dispersion glass, and while the focal point of the pulse laser light is relatively moved inside the particle dispersion glass, the particle dispersion state locally A method for manufacturing a three-dimensional optical memory medium, wherein one or more changed spots are formed inside the fine particle dispersed glass.