JP2004295997A - Optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium having a substrate which has excellent transferability of a signal, excellent rigidity, and little warpage at the time when molding is performed, the optical information recording medium wherein the surface defect of the substrate caused when molding is performed is reduced, and the optical information recording medium using the substrate having small change of warpage when the substrate absorbs water and having excellent signal characteristics. <P>SOLUTION: In the optical information recording medium which has the substrate, a signal layer disposed on the substrate, and a light transmission layer layered on the signal layer and having ≤300 μm thickness and wherein a laser beam is made incident from the light transmission layer side to make it possible to perform write and read of recording and track pitch of a signal has ≤0.35 μm pitch, the substrate consists of a resin composition containing 0.01 to 40 pts.wt. specific biphenyl compound (e.g. p-benzylbiphenyl) to 100 pts.wt. aromatic polycarbonate having viscosity average molecular weight of 10,000 to 40,000. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

（式中、Ｒは同一又は異なる置換基を表し、ｐ及びｒは０〜５の整数を、ｑは０〜４の整数を、ｎ及びｍは１〜５の整数を表す。）
【００１５】
【発明の実施の形態】
本発明の光学情報記録媒体はその信号のトラックピッチが０．３５μｍ以下の高密度情報記録媒体である。信号であるピットやグルーブの円周方向に連続的に位置されており，トラックピッチとは半径方向の隣り合った間隔を示し，トラックピッチが小さいほど単位面積当たりの記録密度が大きくなる。具体的には，トラックピッチが０．３０μｍで１２０φの光ディスクで片面２０ＧＢ以上の記録が可能になる。トラックピッチは小さい方が望ましいが，ピットやグルーブの転写を生産性の優れる射出成形で行う場合は０．１０〜０．３０μｍが望ましい。
【００１６】
本発明の光ディスクは基板、基板上に配置された信号層、信号層上に積層された厚み３００μｍ以下の光透過層を有し、光透過層側からレーザー光を入射させて記録の書き込みと読み取りが可能とされてなる光学情報記録媒体に特に効果がある。このような構造の光ディスクはより高密度記録が可能になる。光透過層の厚みは基板の反りに対するマージンを大きくするためできるだけ薄い方が好ましいが，５０μｍ以下になると厚みのばらつきが大きくなるために好ましくない。５０〜１５０μｍの範囲の厚みが好ましい。
【００１７】
基板を構成するとして樹脂は、粘度平均分子量が１０，０００〜４０，０００、好ましくは１４，０００〜２３，０００の芳香族ポリカーボネートが使用される。芳香族ポリカーボネートは機械強度，耐熱性，寸法安定性等に優れており、特定のビフェニル化合物を添加することによって，本発明の課題を容易に達成できる。分子量が１０，０００未満であると、機械的強度が低下するので好ましくない。また、分子量が４０，０００を超えると、成形時の流動性が低下し、成形時の転写性が劣るので好ましくない。
なお、本発明において粘度平均分子量（Ｍ）とは、塩化メチレンを溶媒とし、オストワルド粘度計を使用して極限粘度［η］を求め、次のＳｃｈｎｅｌｌの粘度式、すなわち、
［η］＝１．２３×１０^−５×Ｍ^０．８５
から算出される値を意味する。極限粘度［η］を求める際の溶液濃度の単位はｇ／Ｌである。
【００１８】
芳香族ポリカーボネートの製造法は特に限定されるものではなく、例えば、ホスゲンと芳香族ジヒドロキシ化合物とを原料として水及び有機溶媒系で反応する界面法、及び芳香族ジヒドロキシ化合物と炭酸ジエステルとを原料として溶融状態で反応するエステル交換法により製造し得る。
芳香族ポリカーボネートは一般的には界面法で得られるものが広く普及しているが，本発明者らの知見によれば、同じ反可塑剤の添加量で比較すると、エステル交換法で得られたものの方が信号の転写性や剛性増加，反りの低減，吸水による寸法変化の低減効果がより一層向上させることができる。さらには，エステル交換法によって製造される芳香族ポリカーボネートは，界面法で得られた芳香族ポリカーボネートに比べて，同一の分子量でガラス転移温度が約３℃低いために，射出成形時の樹脂表面の固化層の発達が遅れるために信号の転写性に優れる。
【００１９】
芳香族ポリカーボネートの原料となる炭酸ジエステルとしては、例えば、ジメチルカーボネート、ジエチルカーボネート、ジ−ｔ−ブチルカーボネート等のジアルキルカーボネート、ジフェニルカーボネート及びジトリルカーボネート等の置換ジフェニルカーボネート等が挙げられるが、好ましくはジフェニルカーボネート、置換ジフェニルカーボネートであり、特にジフェニルカーボネートが好ましい。これらの炭酸ジエステルは、単独又は２種以上混合して使用してもよい。
【００２０】
また、上記のような炭酸ジエステルと共に、好ましくはその５０モル％以下、さらに好ましくは３０モル％以下の量で、ジカルボン酸又はジカルボン酸エステルを併用してもよい。このようなジカルボン酸又はジカルボン酸エステルとしては、テレフタル酸、イソフタル酸、テレフタル酸ジフェニル、イソフタル酸ジフェニル等が用いられる。このようなカルボン酸又はカルボン酸エステルを、炭酸ジエステルと併用した場合には、ポリエステルカーボネートが得られる。
【００２１】
芳香族ポリカーボネートのもう一つの原料である芳香族ジヒドロキシ化合物としては、例えば、２，２−ビス（４−ヒドロキシフェニル）プロパン［＝ビスフェノールＡ］、２，２−ビス（４−ヒドロキシ−３，５−ジメチルフェニル）プロパン、２，２−ビス（４−ヒドロキシ−３，５−ジエチルフェニル）プロパン、２，２−ビス（４−ヒドロキシ−（３，５−ジフェニル）フェニル）プロパン、２，２−ビス（４−ヒドロキシフェニル）ペンタン、２，４’−ジヒドロキシ−ジフェニルメタン、ビス（４−ヒドロキシフェニル）メタン、ビス（４−ヒドロキシ−５−ニトロフェニル）メタン、１，１−ビス（４−ヒドロキシフェニル）エタン、３，３−ビス（４−ヒドロキシフェニル）ペンタン、１，１−ビス（４−ヒドロキシフェニル）シクロヘキサン、４，４’−ジヒドロキシジフェニルエーテル、４，４’−ジヒドロキシ−２，５−ジエトキシジフェニルエーテル等が挙げられる。これらの中でも、ビスフェノールＡが好ましい。また、これらの芳香族ジヒドロキシ化合物は、単独又は２種以上を混合して用いることができる。
【００２２】
炭酸ジエステルと芳香族ジヒドロキシ化合物との混合比率は、所望する芳香族ポリカーボネートの分子量と末端ヒドロキシル基量により決められる。末端ヒドロキシル基量は、芳香族ポリカーボネートの熱安定性と加水分解安定性に大きな影響を及ぼし、実用的な物性を持たせるためには、芳香族ポリカーボネートの重量に対して１，０００ｐｐｍ以下にすることが必要となる。従って、芳香族ジヒドロキシ化合物１モルに対して、炭酸ジエステルを等モル量以上の割合で用いるのが一般的であり、１．０１〜１．３０モル、好ましくは１．０１〜１．２０モルの割合で用いるのが望ましい。
【００２３】
エステル交換法により芳香族ポリカーボネートを製造する際には、通常エステル交換触媒が使用される。エステル交換触媒としては、主として、アルカリ金属化合物及び／又はアルカリ土類金属化合物が使用され、補助的に、塩基性ホウ素化合物、塩基性リン化合物、塩基性アンモニウム化合物又はアミン系化合物等の塩基性化合物を併用することも可能である。これらの触媒は、１種類で使用してもよく、２種以上を組み合わせて使用してもよい。
【００２４】
触媒量は、通常芳香族ジヒドロキシ化合物１モルに対して、１×１０^−８〜１×１０^−５モルの範囲で用いられる。この量より少なければ、所定の分子量、末端ヒドロキシル基量の芳香族ポリカーボネートを製造するのに、充分な重合活性が得られず、この量より多い場合は、芳香族ポリカーボネートの色相が悪化し、ゲルの発生による異物量も増大する傾向となる。特に、アルカリ金属化合物及び／又はアルカリ土類金属化合物を用いる場合、それらの金属量として１×１０^−８〜２×１０^−６モルの範囲が好ましく、０．５×１０^−７〜１×１０^−６モルの範囲が特に好ましい。
【００２５】
アルカリ金属化合物としては、リチウム、ナトリウム、カリウム、ルビジウム、セシウムの水酸化物、炭酸水素塩、炭酸塩、酢酸塩、リン酸水素塩、フェニルリン酸塩等の無機アルカリ金属化合物や、ステアリン酸、安息香酸等の有機酸類、メタノール、エタノール等のアルコール類，石炭酸、ビスフェノールＡ等のフェノール類との塩等の有機アルカリ金属化合物等が挙げられる。
【００２６】
アルカリ土類金属化合物としては、ベリリウム、カルシウム、マグネシウム、ストロンチウム、バリウムの水酸化物、炭酸水素塩、炭酸塩、酢酸塩等の無機アルカリ土類金属化合物や、有機酸類、アルコール類、フェノール類との塩等の有機アルカリ土類金属化合物等が挙げられる。
【００２７】
塩基性ホウ素化合物の具体例としては、テトラメチルホウ素、テトラエチルホウ素、テトラプロピルホウ素、テトラブチルホウ素、トリメチルエチルホウ素、トリメチルベンジルホウ素、トリメチルフェニルホウ素、トリエチルメチルホウ素、トリエチルベンジルホウ素、トリエチルフェニルホウ素、トリブチルベンジルホウ素、トリブチルフェニルホウ素、テトラフェニルホウ素、ベンジルトリフェニルホウ素、メチルトリフェニルホウ素、ブチルトリフェニルホウ素、等の水素化物、ナトリウム塩、カリウム塩、リチウム塩、カルシウム塩、マグネシウム塩、バリウム塩、或いはストロンチウム塩等が挙げられる。
【００２８】
塩基性リン化合物としては、例えば、トリエチルホスフィン、トリ−ｎ−プロピルホスフィン、トリイソプロピルホスフィン、トリ−ｎ−ブチルホスフィン、トリフェニルホスフィン、トリブチルホスフィン、又は四級ホスホニウム塩等が挙げられる。
【００２９】
塩基性アンモニウム化合物としては、例えば、テトラメチルアンモニウムヒドロキシド、テトラエチルアンモニウムヒドロキシド、テトラプロピルアンモニウムヒドロキシド、テトラブチルアンモニウムヒドロキシド、トリメチルエチルアンモニウムヒドロキシド、トリメチルベンジルアンモニウムヒドロキシド、トリメチルフェニルアンモニウムヒドロキシド、トリエチルメチルアンモニウムヒドロキシド、トリエチルベンジルアンモニウムヒドロキシド、トリエチルフェニルアンモニウムヒドロキシド、トリブチルベンジルアンモニウムヒドロキシド、トリブチルフェニルアンモニウムヒドロキシド、テトラフェニルアンモニウムヒドロキシド、ベンジルトリフェニルアンモニウムヒドロキシド、メチルトリフェニルアンモニウムヒドロキシド、ブチルトリフェニルアンモニウムヒドロキシド等が挙げられる。
【００３０】
アミン系化合物としては、例えば、４−アミノピリジン、２−アミノピリジン、Ｎ，Ｎ−ジメチル−４−アミノピリジン、４−ジエチルアミノピリジン、２−ヒドロキシピリジン、２−メトキシピリジン、４−メトキシピリジン、２−ジメチルアミノイミダゾール、２−メトキシイミダゾール、イミダゾール、２−メルカプトイミダゾール、２−メチルイミダゾール、アミノキノリン等が挙げられる。
【００３１】
エステル交換反応は、一般には二段階以上の多段工程で実施される。具体的には、第１段目の反応は、減圧下に１４０〜２６０℃、好ましくは１８０〜２４０℃の温度で、０．１〜５時間、好ましくは０．５〜３時間反応させる。反応圧力は、８００ｍｍＨｇ以下の条件で行い、減圧度を上げながら、副生するモノフェノール化合物をラインから連続的に除去しながら反応を行う。このとき、必要に応じて、窒素等の不活性ガスを流通させることもできる。また、モノフェノール化合物に同伴する原料を反応槽に戻すために、分留塔を反応器に付設することもできる。最終的には、２ｍｍＨｇ以下の減圧下、２４０〜３２０℃の温度で重縮合反応を行う。この条件で減圧度、温度、反応時間等を選択することによって粘度平均分子量１０，０００〜４０，０００の芳香族ポリカーボネートが得られる。
【００３２】
反応の方式は、バッチ式、連続式又はバッチ式と連続式との組合せの、いずれでもよい。使用する装置は、槽型、管型又は塔型の、いずれの形式であってもよく、各種の攪拌翼を具備した、縦型重合槽、横型１軸タイプの重合槽及び／又は横型２軸タイプの重合槽等を使用することができる。
【００３３】
反応は、実質的に無酸素下で行われることが好ましく、例えば、運転開始前に原料調整槽、反応装置及び配管内を窒素ガス等の不活性ガスで置換しておく。通常、芳香族ジヒドロキシ化合物と炭酸ジエステルとの溶融混合物を、縦型反応装置に供給する。触媒は、原料とは別のラインで第１反応槽に直接供給してもよいし、第１反応槽に入る手前の配管内でスタティックミキサー等により原料と混合した状態で供給させてもよい。必要に応じて、触媒を溶解又は懸濁するための溶媒が用いられる。好ましい溶媒としては、水、アセトン、フェノール等が挙げられる。
【００３４】
各槽の液供給口は、反応槽側壁液相部にあり、抜き出し口は、反応槽底部にあるのが好ましい。また、各槽から反応液を連続して抜き出す方法、落差を利用する方法、圧力差を利用する方法、ギアポンプ等の送液ポンプを用いる方法等、反応液の物性に適応した方法で行うのが好ましい。
【００３５】
重合終了後、又は重合終了の直前に、製造された芳香族ポリカーボネート中に含まれるアルカリ金属及び／又はアルカリ土類金属触媒を中和するために中和剤を添加する必要がある。かかる中和剤としては後記する硫黄含有酸性化合物が好ましい。
【００３６】
重合終了後、製造された芳香族ポリカーボネートは、通常、ペレットとして回収されるが、その際、ポリマー中に残存するモノマーや副生物等の低分子量成分を除去するため、ベント式押出機を通すことも可能である。
【００３７】
上記の工程により得られるポリマー中の触媒、特にアルカリ金属及び／又はアルカリ土類金属触媒を中和するための中和剤は、触媒金属に対して、０．５〜１０当量、好ましくは１〜５当量添加する。すなわち、通常、芳香族ポリカーボネートの重量に対して０．０１〜１０ｐｐｍ、好ましくは３〜７ｐｐｍ添加する。１０ｐｐｍを超えると基板中に存在する酸性成分が多くなるので好ましくない。また０．０１ｐｐｍ以下では，塩基性触媒を十分に中和することができずに，重合時に着色が発生したり，所望の分子量を得ることができない。
【００３８】
上記中和剤としては、硫黄含有酸性化合物、リン酸、亜リン酸等が使用できるが、特に硫黄含有酸性化合物が好ましい。例えば、スルホン酸、スルフィン酸又はそれらのエステル等の誘導体が挙げられる。具体的には、ｐ−トルエンスルホン酸、ベンゼンスルホン酸及びドデシルベンゼンスルホン酸、それらのメチル、エチル、ブチル、ｔ−ブチル、オクチル、ドデシル、フェニル、ベンジル、フェネチル等のエステル類、ベンゼンスルフィン酸、トルエンスルフィン酸、ナフタレンスルホン酸等が挙げられる。これらの化合物の内、スルホン酸又はその誘導体が好ましく、ｐ−トルエンスルホン酸のエステル又はベンゼンスルホン酸のエステルが特に好ましい。また、これらの化合物を２種以上使用してもよい。さらに、これらの化合物のアルカリ金属塩を、これらの化合物と併用すると、分散性が向上し失活効果が高まるので好ましい。併用する量としては、非アルカリ金属塩に対してアルカリ金属塩を、重量比で０．３〜３程度の量用いることが好ましい。
【００３９】
硫黄含有酸性化合物の芳香族ポリカーボネートへの添加方法は、任意の方法により行うことができる。例えば、硫黄含有酸性化合物を、直接又は希釈剤で希釈して、溶融又は固体状態にある芳香族ポリカーボネートに添加し、分散させることができる。具体的には、重縮合反応器中、反応器からの移送ライン中、押出機中に供給して混合することができ、通常は押出機中に供給される。硫黄含有酸性化合物を溶液で押出機に添加、混練させる際には、添加位置の押出機内部の樹脂圧力よりも上流側に添加位置よりも圧力を高めるスクリュー構成にすると、硫黄含有酸性化合物の上流側への逃散を防止し、少量で効率良く反応し、触媒を中和させることができるので好ましい。また、ミキサー等で、芳香族ポリカーボネートや他種ポリマーのペレット、フレーク、粉末等と混合後、サイドフィーダー等を用いて、押出機に供給して混練することもできる。以上の中では、芳香族ポリカーボネートのフレークに硫黄含有酸性化合物の原液を添加し、ミキサー等で混合後、マスターバッチとして添加することが好ましい。さらに、重量フィーダー等を用いて添加量を精度良く制御することも好ましい。
【００４０】
また、押出機で、ベントによる減圧処理を行う場合、又は、水、熱安定剤、離型剤、染料、顔料、紫外線吸収剤、帯電防止剤、防曇剤、有機・無機充填剤等を添加する場合は、これらの添加及び処理は、硫黄含有酸性化合物の添加と同時に行ってもよいが、硫黄含有酸性化合物を最初に添加混練した後に行うのが好ましい。
【００４１】
本発明の芳香族ポリカーボネートに反可塑剤を含有させる方法としては，上記硫黄含有酸性化合物の添加と同様にあるいは同時にエステル交換反応の重合の最終段階の押出機中に供給される。また、ミキサー等で、芳香族ポリカーボネートや他種ポリマーのペレット、フレーク、粉末等と混合後、サイドフィーダー等を用いて、押出機に供給して混練することもできる。芳香族ポリカーボネートのフレークに反可塑剤をミキサー等で混合後、マスターバッチとして添加することが好ましい。さらに、重量フィーダー等を用いて添加量を精度良く制御することも好ましい。得られた混合物を押出機によって溶融・混練してペレット化する。
【００４２】
本発明の芳香族ポリカーボネートは、目的を損なわない範囲で耐熱安定剤、紫外線吸収剤、離型剤、着色剤、帯電防止剤、スリップ剤、アンチブロッキング剤、滑剤、防曇剤、天然油、合成油、ワックス、有機系充填剤、無機系充填剤等の添加剤が配合されたものでもよい。このような添加剤は、溶融状態にある芳香族ポリカーボネート樹脂に添加することもできるし、また、一旦ペレット化した後、必要に応じて芳香族ポリカーボネート樹脂を再溶融して、添加することもできる。
【００４３】
本発明で用いられるビフェニル化合物は、下記一般式（１）で表される。
【化３】

（式中、Ｒは同一又は異なる置換基を表し、ｐ及びｒは０〜５の整数を、ｑは０〜４の整数を、ｎ及びｍは１〜５の整数を表す。）
【００４４】
前記一般式（１）において、ｎ及びｍは１〜５、好ましくは１〜４の間で選ばれる。ｎ及びｍが６以上であると、芳香族ポリカーボネート樹脂組成物の耐熱性が不足するので、好ましくない。ｎ，ｍが０であると，化合物が成形時にガスとなりやすく，基板の表面欠陥の原因となる。各フェニル基には置換基Ｒがあってもよく、中でも好ましいのは、ハロゲン原子、炭素数１〜３のアルキル基、メトキシ基、エトキシ基等である。この中で最も望ましいのは、ｐ＝ｑ＝ｒ＝０、ｎ＝ｍ＝１のベンジルビフェニルである。それぞれのフェニル基の結合形態はオルト，メタ，パラのいずれかから選ばれるがパラ位が最も好ましい。具体的には、下記［化４］に例示する化合物を挙げることができる。
【化４】

【００４５】
基板のベース樹脂となる芳香族ポリカーボネート１００重量部に対し、上記ビフェニル化合物を０．０１〜４０重量部、好ましくは０．０５〜３０重量部、特に好ましくは０．１〜２０重量部配合する。配合量（含有量）が０．０１重量部未満では、芳香族ポリカーボネートの剛性の向上、ガラス転移温度の低下効果が顕著でなく、４０重量部を超えると、剛性の向上効果およびガラス転移温度の低下効果は飽和する。
一般式（１）で表わされるビフェニル化合物を配合する際には、１種でも２種類以上を混合することもできる。
【００４６】
本発明に係る光学情報記録媒体における基板の厚さは、０．５〜３ｍｍの範囲で選ぶのが好ましい。信号層は、例えば、反射膜、ピット、グルーブ、記録膜、保護膜などから形成されている。再生型の光学情報記録媒体では、信号層は通常反射膜およびピットから構成されており、書き換え型の光学情報記録媒体では、信号層は通常反射膜、ピット、グルーブ、記録膜および保護膜から構成されている。反射膜は、基板上に形成され、入射されたレーザー光を反射する。反射膜に用いることができる材料としては、アルミニウム、銀、金などが挙げられる。反射膜の厚さは、１０〜２００ｎｍ程度である。再生型の光学情報記録媒体では、基板上に配置されているピットなどからなる信号層の信号を読み取ることによって、信号の再生を行ない、書き換え型の光学情報記録媒体では、基板上に配置されているピット、グルーブ、記録膜などからなる信号層の信号を、書き込みまたは読み取りする。
【００４７】
記録膜は、例えば、相変化膜であるＧｅ−Ｓｂ−Ｔｅで構成され、厚さは１０〜２００ｎｍ程度である。保護膜は記録膜の両面にそれぞれ積層されており、記録膜から発生する熱を吸収する。保護膜は透明であって、例えばＺｎ−ＳｉＯ_２で構成され、厚さは１０〜３００ｎｍ程度である。信号層と光透過層とは、通常、透明な接着膜によって接着され、接着膜は、例えば、ＵＶ硬化型樹脂や接着シートで形成される。接着膜の厚さは、１０〜１００μｍ程度である。接着膜の上には、２０〜３００μｍ程度の光透過層が形成される。
【００４８】
書き換え型の光学情報記録媒体において、書き込む場合または消去する場合は、レーザー光は光透過層の表面から入射し、接着膜、保護膜を通して記録膜に焦点を合わせることによって、記録や消去を行なう。書き換え型の光学情報記録媒体において読み取る場合は、レーザー光は光透過層の表面から入射し、接着膜、保護膜、記録膜および保護膜を通して反射膜で反射される。再生型の光学情報記録媒体では、レーザー光は光透過層の表面から入射し、接着膜を通して反射膜で反射される。
【００４９】
本発明に係る光学情報記録媒体は、射出成形法によって製造した不透明であってもよい基板の上に、信号層などを積層し、その上に０．０２〜０．３ｍｍ程度の厚さの光透過（カバー）層と呼ばれる透明な樹脂フィルムを、接着剤または接着フィルムを介して貼り合わせることによって、容易に製造することができる。本発明に係る光学情報記録媒体は、光透過層を構成する樹脂フィルムは、透明性、剛性、表面平滑性、および厚さ精度などに優れ、かつ、複屈折率が小さく、位相差も小さいものを用いると、高密度化と高品質化が達成される。
【００５０】
光透過層入射型の光学情報記録媒体の例を、図１および図２に示す。図１は、再生型の光学情報記録媒体の一例の縦断面説明図である。再生型の光学情報記録媒体１は、基板２、基板２の上に配置されたピット３０と反射膜３２からなる信号層、信号層の上に接着層４を介して配置された光透過層５などによって構成されており、光透過層５側からレンズ６を通してレーザー光７を入射させ、信号の読み取りが可能とされた構造のものである。
【００５１】
図２は、書き換え型の光学情報記録媒体の一例の縦断面説明図である。書き換え型の光学情報記録媒体１１は、基板２２、基板２２の上に配置されたピットとグルーブ３１、反射膜３２、記録膜３３および保護膜３４からなる信号層、信号層の上に接着層４を介して配置された光透過層５などによって構成されており、光透過層５側からレンズ６を通してレーザー光７を入射させ、信号の書き込みと信号の読み取りが可能とされた構造のものである。レーザー光の光源は、従来の６５０ｎｍに比べて短波長の４００ｎｍ程度のものを用い、レンズ７の開口数（ＮＡ）は、従来の０．６から０．８５程度と大きくすることによって、レーザースポット径を小さくすることが可能であり、より小さな信号の書き込み、読み取りが可能となり、結果として、より高密度化が達成される。
【００５２】
【実施例】
以下、本発明を実施例に基づいてさらに詳しく説明するが、本発明はその要旨を超えない限り、以下の記載例に限定されるものではない。なお、芳香族ポリカーボネート及びその組成物の分析は以下の方法により行った。
（１）ガラス転移温度
示差熱分析計（セイコー社製、型式：ＳＳＣ−５０００）によって、ペレットを窒素気流下に室温から１０℃／分の速度で昇温し、変曲点をガラス転移温度とした。
（２）分子量
オストワルド粘度計を用いて、塩化メチレンを溶媒とする溶液の２０℃における極限粘度［η］を測定し、Ｓｃｈｎｅｌｌの粘度式から算出する。
［η］＝１．２３×１０^−５×Ｍ^０．８５
（３）曲げ弾性率
ＡＳＴＭ Ｄ−７９０に準拠して測定した。
【００５３】
［実施例１］
１．ポリカーボネートの調製
芳香族ジヒドロキシ化合物としてビスフェノールＡ、炭酸ジエステルとしてジフェニルカーボネートを用いるエステル交換法により合成した。芳香族ジヒドロキシ化合物１モルに対して、炭酸ジエステルを１．１０モルの割合で用いた。重合触媒として炭酸セシウムを芳香族ジヒドロキシ化合物１モルに対して、１．０×１０^−７モルの割合で用いた。エステル交換反応は、二段階で実施した。具体的には、第１段目の反応は、減圧下に２２０℃の温度で、２時間反応させた。反応圧力は、６００ｍｍＨｇの条件で行った。２段階目は、１ｍｍＨｇの減圧下、３１０℃の温度で２時間重縮合反応を行った。
得られた反応生成物を押し出し機中に導入し、触媒失活剤としてｐ−トルエンスルホン酸ブチルを芳香族ポリカーボネートに対して５ｐｐｍ含有するように、また、パラベンジルビフェニル（新日鉄化学社製）を，上記芳香族ポリカーボネート１００重量部に対して５重量部含有するように定量フイーダーを用いて押し出し機に導入した。その後押し出し機のダイスから吐出されるストランドを冷却し，ペレット化して成形用ペレットを得た。パラベンジルビフェニルを配合した組成物のガラス転移温度は１１７℃であった。
尚、上記重縮合反応後の反応生成物をサンプリングし、得られた芳香族ポリカーボネートの粘度とガラス転移温度を測定したところ、粘度平均分子量は１６，０００であり、ガラス転移温度は１４３℃であった。
【００５４】
２．光学情報記録媒体の調製
光ディスク製造用金型を装備した射出成形機（住友重機社製、型式：ＤＩＳＫ３）によって、上記芳香族ポリカーボネート樹脂を、シリンダー温度３６０℃、金型温度を１１０℃、成形サイクルを１２秒として、トラックピッチ０．３μｍ、グルーブ深さ６０ｎｍのスタンパーに刻印されている信号を転写させ、直径１２０ｍｍで厚さが１．１ｍｍの光ディスク基板を製造した。この基板の片面に、スパッタリング法により、反射膜であるＡｇを主成分としてＰｄを０．９重量％、Ｃｕを１．０重量％添加した Ａｇ_９８．１ Ｐｄ_０．９ Ｃｕ_１．０ 金属反射膜を７０ｎｍ、ＺｎＳ−ＳｉＯ_２ 誘電体膜を２５ｎｍ、ＧｅＳｂＴｅ記録膜を１３ｎｍ、ＺｎＳ−ＳｉＯ_２ 誘電体膜を１６０ｎｍを順次形成した。この誘電体層の上に、２５μｍ厚さの両面接着剤をラミネーターを用いて塗布した後、再度ラミネーターを用いて、１００μｍの厚みのポリカーボネート樹脂フィルムを張力を負荷しながら貼り合わせた。その後、樹脂フィルムをはさみでディスク状にカットして、光学情報記録媒体を得た。
【００５５】
３．光学情報記録媒体用基板の評価
下記の方法で、信号の転写性、成形基板の反り、吸水による反りの変化及び基板の表面欠陥を評価し、結果を表１に示した。
（１）信号の転写性
成形基板表面のグルーブの深さを原子間力顕微鏡（オリンパス社製、ＮＶ２１００）にて測定した。半径方向５８ｍｍの位置のグルーブのエッジと底面の最大距離を円周方向で４点測定し，４点平均で評価とした。グルーブ深さが深いほど信号特性が良好となる。
（２）成形基板の反り
成形基板の反りをディスク反り角自動測定装置（アドモンサイエンス社）を使用し、上記２で得られた光学情報記録媒体を６０ｒｐｍで回転させながら、光ディスク基板の半径方向２５ｍｍ、３７ｍｍ、４９ｍｍ、５７ｍｍの位置であって円周に沿った４箇所に、半導体レーザーからの波長７８０ｎｍのレーザー光線を照射して測定した。上記の測定値の最大値を、半径方向のそり角度（ｄｅｇｒｅｅ）とした。この数値は小さい方が、優れていることを意味する。
（３）吸水による反りの変化
信号層，光透過層を有する光学情報記録媒体を１２０℃×１０時間乾燥させた直後の反りを上記と同様な方法で測定し，その後８０℃×相対湿度８５％で１００時間放置して、その間の反りの変化（ｄｅｇｒｅｅ）を測定した。（４）基板の表面欠陥
２０００ショット連続成形し，２０００ショット目の基板表面全体を光学顕微鏡（ｘ５００）で観察し，基板１枚当たりの信号面の表面欠陥の数を数えた。
【００５６】
［実施例２］
芳香族ポリカーボネートの調製の際、２段目反応（重縮合反応）を、３１０℃、２時間に代えて、３２０℃、３時間とした以外は実施例１と同様な方法で行った。以下同様にして光学情報記録媒体を製造した。結果を表１に示した。
【００５７】
［実施例３］
ビフェニル化合物として、パラベンジルビフェニルの代わりにメタベンジルビフェニル（新日鉄化学社製）を用いた以外は実施例１と同様な方法で行った。結果を表１に示した。
【００５８】
［実施例４］
パラベンジルビフェニルの含有量を１０重量部とした以外は実施例１と同様な方法で行った。結果を表１に示した。
【００５９】
［実施例５］
ビフェニル化合物として、一般式（１）のｎ，ｍ，ｐ，ｑ，ｒがいずれも１であり、その置換基がいずれもメチル基で、結合がパラ／オルト／パラ／パラ位である下記化合物［化５］を用いた以外は実施例１と同様な方法で行った。結果を表１に示した。
【化５】

【００６０】
［比較例１］
ビフェニル化合物を配合しない以外は実施例１と同様な方法で行った。結果を表２に示した。
【００６１】
［比較例２］
実施例１におけるポリカーボネートの調製において２段階目の反応を１ｍｍＨｇの減圧下、３３０℃の温度で４時間重縮合反応を行った以外は実施例１と同様の操作を行い、粘度平均分子量４２，０００のポリカーボネートを得た。この芳香族ポリカーボネートを用いた以外は実施例１と同様な方法で行った。結果を表２に示した。
【００６２】
［比較例３］ビフェニル化合物としてビフェニル（東京化成社製）を用いた以外は実施例１と同様な方法で行った。結果を表２に示した。
【００６３】
【表１】

【００６４】
【表２】

【００６５】
【発明の効果】
本発明によれば、信号の転写性に優れ、剛性に優れ、吸水による寸法変化が小さく，生産性に優れた高密度化された高品質の光学情報記録媒体が得られる。
【図面の簡単な説明】
【図１】光透過層入射型の光学情報記録媒体（再生型）の一例の縦断面説明図
【図２】光透過層入射型の光学情報記録媒体（書き換え型）の一例の縦断面説明図
【符号の説明】
１、１１：光学情報記録媒体
２，２２：基板
３０：信号層（ピット）
３１：信号層（ピットおよびグルーブ）
３２：信号層（反射膜）
３３：信号層（記録膜）
３４、３４´：信号層（保護膜）
４：接着層
５：光透過層
６：レンズ
７：レーザー光[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical information recording medium. More specifically, the present invention relates to a high-density, high-quality optical information recording medium excellent in signal transferability, excellent in rigidity, small in dimensional change due to water absorption, and excellent in productivity.
[0002]
[Prior art]
Conventionally, optical disks such as write-once compact disks (CD-R), magneto-optical disks (MO), and digital versatile disks (DVD) have been used as high-density recording media. In a conventional optical disk, generally, a signal layer is arranged on a transparent substrate, and a laser beam is incident from the transparent substrate side to record on the signal layer and read the recorded signal.
[0003]
However, in recent years, in order to further increase the recording density of an optical disc, a technique called a light-transmitting layer incident type, in which laser light is incident from the signal side through a very thin light-transmitting layer (light transmitting layer). There has been proposed an optical disk having a higher density, which employs an incident type technology (for example, see Patent Documents 1 and 2; see Non-Patent Document 1).
[0004]
Among the optical information recording media of the light transmission layer incident type, for example, the reproduction type optical information recording medium is formed by bonding pits or grooves arranged on a substrate, a reflective film thereon, a recording layer, and a recording layer. It is composed of a light transmitting layer or the like arranged via a layer, and has a structure in which a laser beam is made incident from the light transmitting layer side through a lens so that a signal can be read.
As the light transmitting layer, a transparent light curable resin is used, or a method of adhering a polycarbonate resin sheet has been proposed. In any case, the thickness of the light transmitting layer is desirably 0.3 mm or less. This is because the thinner the thickness, the larger the laser focus margin with respect to the warpage or tilt of the substrate, even if the numerical aperture (NA) of the lens increases.
[0005]
A rewritable optical information recording medium is composed of pits and grooves arranged on a substrate, a recording layer composed of a reflective film, a recording film and a protective film, and a light transmission layer arranged on the recording layer via an adhesive layer. It has a structure in which a laser beam is made incident from the light transmitting layer side through a lens so that a signal can be written and a signal can be read. The light source of the laser light has a shorter wavelength of about 400 nm than that of the conventional 650 nm, and the numerical aperture (NA) of the lens 7 is increased from about 0.6 to 0.85 of the conventional laser spot. The diameter can be reduced, and smaller signals can be written and read, and as a result, higher density can be achieved.
[0006]
For the molding of the substrate, the thermoplastic resin melted in the cylinder of the molding machine is filled at high speed into a mold loaded with a stamper on which signals such as pits and grooves are imprinted, and the pit and groove signals are transferred to the substrate. The technique to make it common is. Examples of the material for a substrate of a high-density optical disk having this structure include a thermoplastic resin such as an aromatic polycarbonate, a methacrylic resin, and an amorphous polyolefin resin, and a mixture of a filler, a reinforcing agent, and various additives (for example, Patent Documents 3 and 4). Aromatic polycarbonate has excellent properties such as heat resistance, strength, and dimensional stability, and is suitable for high-density optical disk substrates. However, in general, aromatic polycarbonate for optical disks and other thermoplastic resins are single-sided. In the case of a large-capacity and high-density optical disk of 20 GB or more, since the interval between grooves and pits is as small as 0.3 μm, transfer failure occurred during injection molding, and it was very difficult to obtain a good signal.
[0007]
As a method of accurately transferring the fine unevenness onto the substrate surface of the molded article (improving the transferability), a method of setting a high mold temperature at the time of manufacturing the substrate is known. However, this method has a disadvantage that when the mold temperature is set high, the warpage of the substrate increases, and when the warpage of the substrate increases, there arises a problem that the signal cannot be reproduced. Increasing the rigidity of the thermoplastic resin reduces the warpage of the substrate. A technique of using a liquid crystal polymer having low anisotropy for the purpose of improving the rigidity of a substrate of a thin light transmission layer incident type optical disk is known (for example, see Patent Document 5), but the rigidity of the polymer itself is high. Even if the anisotropy is small, it is impossible to completely reduce the warpage during molding, and a flat molded substrate cannot be obtained.
[0008]
Therefore, it is common to add glass flake, mica, talc, metal flake, and graphite-based filler to the substrate material in order to improve the rigidity of the substrate. For example, a method of blending a reinforcing material such as carbon fiber has been attempted (for example, see Patent Document 6). A reinforcing material such as carbon fiber often emerges on the surface of a molded product, which causes poor appearance of the molded product and poor transfer of signals. Further, fibrous additives such as carbon fibers have a high anisotropy and are oriented in the flow direction during injection molding, so that there is a disadvantage that warpage is likely to occur particularly in the case of a thin molded product such as an optical disk substrate. . Therefore, no technique has yet been found that achieves both the transferability of signals and the reduction of warpage.
[0009]
Another important problem of the optical disk of the present invention is to suppress deformation of the substrate due to water absorption in a high humidity environment. Because the numerical aperture of the lens increases, the distance between the lens and the optical disk decreases. If the warp of the optical disk substrate changes due to water absorption, the lens and the optical disk come into contact with each other, causing a problem that the signal reading surface of the light transmitting layer is damaged. In order to solve this problem, it has been proposed to use an olefin-based low water-absorbing resin (for example, Patent Documents 7 and 8), but the water absorption of the light-transmitting layer side is extremely low because the water absorption is extremely low. Since the balance with the dimensional change cannot be obtained, the warpage cannot be completely reduced.
[0010]
In addition, aromatic polycarbonates having low water absorption by reducing the polar group density per unit weight have been proposed (for example, see Patent Document 9), but have poor adhesion to a signal film and a reflection film. There is a problem that the film is easily peeled off in the environmental test.
In addition, a technique has been proposed in which a hard coat is applied on a light transmitting layer so that no scratch occurs even when the lens comes into contact with a lens (for example, see Patent Documents 10 and 11). Since it cannot be performed, it is not enough to prevent a signal reading failure due to an increase in warpage. Therefore, to date, there has been no technique that has a sufficient effect on reducing warpage due to water absorption of the substrate.
[0011]
Also, a technique is described in which biphenyl or the like is added to an aromatic polycarbonate to lower the glass transition temperature and simultaneously increase rigidity to achieve both transfer and warpage (for example, see Patent Document 12). No effect is described for an optical disk having a thin, light-transmitting layer structure having a small light transmission layer structure, and dimensional change of warpage due to water absorption is not discussed. Further, the exemplified additives such as biphenyl and terphenyl tend to become gases at the time of injection molding, resulting in surface defects of the substrate. This surface defect causes a signal error, and no technology for reducing this surface defect has ever been found.
[0012]
[Patent Document 1] JP-A-2000-11449
[Patent Document 2] Japanese Patent Application Laid-Open No. 2000-82236
[Patent Document 3] JP-A-8-235638
[Patent Document 4] JP-A-11-203726
[Patent Document 5] JP-A-11-306594
[Patent Document 6] JP-A-10-334508
[Patent Document 7] JP-A-2001-64367
[Patent Document 8] JP-A-2002-25108
[Patent Document 9] JP-A-2002-92943
[Patent Document 10] JP-A-11-203726
[Patent Document 11] JP-A-2002-245672
[Patent Document 12] JP-A-2000-195099
[0013]
[Problems to be solved by the invention]
In view of the above situation, the present inventors have conducted intensive studies in order to eliminate the above-mentioned drawbacks which existed conventionally in a thin light-transmitting layer-incidence type optical disc. As a result, a specific biphenyl was specified for an aromatic polycarbonate having a specific molecular weight range. The inventors have found that the above problem can be solved by compounding the compound, and have reached the present invention.
That is, an object of the present invention is to provide an optical information recording medium having a substrate which is excellent in signal transferability, has excellent rigidity, and has little warpage at the time of molding. It is another object of the present invention to provide an optical information recording medium having reduced surface defects, and a further object is to provide an optical information recording medium having excellent signal characteristics by using a substrate having a small change in warpage when absorbing water.
[0014]
[Means for Solving the Problems]
That is, the gist of the present invention is to provide a substrate, a signal layer disposed on the substrate, a light transmitting layer having a thickness of 300 μm or less laminated on the signal layer, and a laser beam incident from the light transmitting layer side for recording. An optical information recording medium which is writable and readable and has a signal track pitch of 0.35 μm or less, wherein the substrate is as follows based on 100 parts by weight of an aromatic polycarbonate having a viscosity average molecular weight of 10,000 to 40,000. An optical information recording medium comprising a resin composition containing 0.01 to 40 parts by weight of a biphenyl compound represented by the general formula (1).
Embedded image

(In the formula, R represents the same or different substituent, p and r represent an integer of 0 to 5, q represents an integer of 0 to 4, and n and m represent an integer of 1 to 5.)
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The optical information recording medium of the present invention is a high-density information recording medium whose track pitch is 0.35 μm or less. The pits or grooves, which are signals, are continuously located in the circumferential direction, and the track pitch indicates an adjacent interval in the radial direction. The smaller the track pitch, the higher the recording density per unit area. More specifically, it is possible to record data of 20 GB or more on one side of an optical disk having a track pitch of 0.30 μm and 120φ. The track pitch is desirably small, but is preferably 0.10 to 0.30 μm when pits and grooves are transferred by injection molding with excellent productivity.
[0016]
The optical disk of the present invention has a substrate, a signal layer disposed on the substrate, and a light transmitting layer having a thickness of 300 μm or less laminated on the signal layer. Recording and reading are performed by irradiating a laser beam from the light transmitting layer side. This is particularly effective for an optical information recording medium that is made possible. An optical disc having such a structure enables higher density recording. The thickness of the light transmitting layer is preferably as thin as possible in order to increase the margin for the warpage of the substrate. However, if the thickness is less than 50 μm, it is not preferable because the variation in thickness becomes large. Preference is given to a thickness in the range from 50 to 150 μm.
[0017]
As the resin constituting the substrate, an aromatic polycarbonate having a viscosity average molecular weight of 10,000 to 40,000, preferably 14,000 to 23,000 is used. Aromatic polycarbonate is excellent in mechanical strength, heat resistance, dimensional stability and the like, and the subject of the present invention can be easily achieved by adding a specific biphenyl compound. When the molecular weight is less than 10,000, the mechanical strength decreases, which is not preferable. On the other hand, when the molecular weight exceeds 40,000, the fluidity at the time of molding is reduced, and the transferability at the time of molding is inferior.
In the present invention, the viscosity-average molecular weight (M) is defined as the intrinsic viscosity [η] using an Ostwald viscometer using methylene chloride as a solvent, and the following Schnell viscosity equation, that is,
[Η] = 1.23 × 10^-5× M^0.85
Means the value calculated from The unit of the solution concentration when obtaining the intrinsic viscosity [η] is g / L.
[0018]
The method for producing the aromatic polycarbonate is not particularly limited.For example, an interface method in which phosgene and an aromatic dihydroxy compound are reacted as a raw material in water and an organic solvent system, and an aromatic dihydroxy compound and a carbonic acid diester are used as raw materials. It can be produced by a transesterification method which reacts in a molten state.
Generally, aromatic polycarbonates obtained by the interfacial method are widely used, but according to the knowledge of the present inventors, when compared with the same amount of the same anti-plasticizer, the aromatic polycarbonate was obtained by the transesterification method. With this, the effect of transferring signals, increasing rigidity, reducing warpage, and reducing dimensional changes due to water absorption can be further improved. Furthermore, the aromatic polycarbonate produced by the transesterification method has the same molecular weight and a lower glass transition temperature of about 3 ° C. than the aromatic polycarbonate obtained by the interfacial method. Since the development of the solidified layer is delayed, the transferability of signals is excellent.
[0019]
Examples of the carbonic acid diester serving as a raw material of the aromatic polycarbonate include, for example, dimethyl carbonate, diethyl carbonate, dialkyl carbonates such as di-t-butyl carbonate, and substituted diphenyl carbonates such as diphenyl carbonate and ditolyl carbonate. Diphenyl carbonate and substituted diphenyl carbonate are preferred, and diphenyl carbonate is particularly preferred. These carbonic acid diesters may be used alone or in combination of two or more.
[0020]
In addition, a dicarboxylic acid or a dicarboxylic acid ester may be used together with the carbonic acid diester as described above, preferably in an amount of 50 mol% or less, more preferably 30 mol% or less. As such a dicarboxylic acid or dicarboxylic acid ester, terephthalic acid, isophthalic acid, diphenyl terephthalate, diphenyl isophthalate and the like are used. When such a carboxylic acid or carboxylic acid ester is used in combination with a carbonic acid diester, a polyester carbonate is obtained.
[0021]
Examples of the aromatic dihydroxy compound as another raw material of the aromatic polycarbonate include 2,2-bis (4-hydroxyphenyl) propane [= bisphenol A] and 2,2-bis (4-hydroxy-3,5 -Dimethylphenyl) propane, 2,2-bis (4-hydroxy-3,5-diethylphenyl) propane, 2,2-bis (4-hydroxy- (3,5-diphenyl) phenyl) propane, 2,2- Bis (4-hydroxyphenyl) pentane, 2,4′-dihydroxy-diphenylmethane, bis (4-hydroxyphenyl) methane, bis (4-hydroxy-5-nitrophenyl) methane, 1,1-bis (4-hydroxyphenyl) ) Ethane, 3,3-bis (4-hydroxyphenyl) pentane, 1,1-bis (4-hydroxyphenyl) ) Cyclohexane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-2,5-diethoxy diphenyl ether. Among these, bisphenol A is preferred. These aromatic dihydroxy compounds can be used alone or in combination of two or more.
[0022]
The mixing ratio between the carbonic acid diester and the aromatic dihydroxy compound is determined by the desired molecular weight of the aromatic polycarbonate and the amount of terminal hydroxyl groups. The amount of terminal hydroxyl groups has a significant effect on the thermal stability and hydrolysis stability of the aromatic polycarbonate, and should be 1,000 ppm or less based on the weight of the aromatic polycarbonate in order to have practical physical properties. Is required. Therefore, it is common to use the carbonate diester in an equimolar amount or more with respect to 1 mole of the aromatic dihydroxy compound, and 1.01 to 1.30 moles, preferably 1.01 to 1.20 moles. It is desirable to use in proportion.
[0023]
When an aromatic polycarbonate is produced by the transesterification method, a transesterification catalyst is usually used. As the transesterification catalyst, an alkali metal compound and / or an alkaline earth metal compound is mainly used, and a basic compound such as a basic boron compound, a basic phosphorus compound, a basic ammonium compound, or an amine compound is supplementarily used. Can also be used in combination. These catalysts may be used alone or in combination of two or more.
[0024]
The amount of the catalyst is usually 1 × 10^-8~ 1 × 10^-5Used in the molar range. If the amount is less than this, a predetermined molecular weight and a sufficient amount of polymerization activity cannot be obtained to produce an aromatic polycarbonate having a terminal hydroxyl group amount.If the amount is more than this amount, the hue of the aromatic polycarbonate deteriorates and the gel is deteriorated. The tendency is that the amount of foreign matter due to the occurrence of odor increases. In particular, when an alkali metal compound and / or an alkaline earth metal compound is used, their metal content is 1 × 10^-8~ 2 × 10^-6Molar range is preferred, 0.5 × 10^-7~ 1 × 10^-6A molar range is particularly preferred.
[0025]
As the alkali metal compound, lithium, sodium, potassium, rubidium, cesium hydroxide, hydrogen carbonate, carbonate, acetate, hydrogen phosphate, phenyl phosphate and the like inorganic alkali metal compounds, stearic acid, Organic acids such as benzoic acid; alcohols such as methanol and ethanol; phenolic acid; and organic alkali metal compounds such as salts with phenols such as bisphenol A.
[0026]
Examples of the alkaline earth metal compounds include inorganic alkaline earth metal compounds such as beryllium, calcium, magnesium, strontium, barium hydroxide, hydrogen carbonate, carbonate, and acetate, and organic acids, alcohols, and phenols. And organic alkaline earth metal compounds such as salts of the above.
[0027]
Specific examples of the basic boron compound include tetramethyl boron, tetraethyl boron, tetrapropyl boron, tetrabutyl boron, trimethylethyl boron, trimethylbenzyl boron, trimethylphenyl boron, triethylmethyl boron, triethylbenzyl boron, triethylphenyl boron, tributyl Hydrides such as benzylboron, tributylphenylboron, tetraphenylboron, benzyltriphenylboron, methyltriphenylboron, butyltriphenylboron, sodium salt, potassium salt, lithium salt, calcium salt, magnesium salt, barium salt, or And strontium salts.
[0028]
Examples of the basic phosphorus compound include triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine, tributylphosphine, and a quaternary phosphonium salt.
[0029]
Examples of the basic ammonium compound include, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylbenzylammonium hydroxide, trimethylphenylammonium hydroxide, Triethylmethylammonium hydroxide, triethylbenzylammonium hydroxide, triethylphenylammonium hydroxide, tributylbenzylammonium hydroxide, tributylphenylammonium hydroxide, tetraphenylammonium hydroxide, benzyltriphenylammonium hydroxide, methyltriphenylammonium hydroxide Sid, butyl triphenyl ammonium hydroxide, and the like.
[0030]
Examples of the amine compound include 4-aminopyridine, 2-aminopyridine, N, N-dimethyl-4-aminopyridine, 4-diethylaminopyridine, 2-hydroxypyridine, 2-methoxypyridine, 4-methoxypyridine, -Dimethylaminoimidazole, 2-methoxyimidazole, imidazole, 2-mercaptoimidazole, 2-methylimidazole, aminoquinoline and the like.
[0031]
The transesterification is generally performed in two or more steps. Specifically, the first-stage reaction is performed under reduced pressure at a temperature of 140 to 260 ° C, preferably 180 to 240 ° C, for 0.1 to 5 hours, preferably 0.5 to 3 hours. The reaction is performed at a reaction pressure of 800 mmHg or less, and the reaction is performed while continuously removing the by-produced monophenol compound from the line while increasing the degree of pressure reduction. At this time, if necessary, an inert gas such as nitrogen can be circulated. In addition, a fractionating tower may be attached to the reactor in order to return the raw materials accompanying the monophenol compound to the reaction tank. Finally, the polycondensation reaction is performed at a temperature of 240 to 320 ° C. under a reduced pressure of 2 mmHg or less. An aromatic polycarbonate having a viscosity average molecular weight of 10,000 to 40,000 can be obtained by selecting the degree of pressure reduction, temperature, reaction time and the like under these conditions.
[0032]
The reaction system may be any of a batch system, a continuous system, or a combination of a batch system and a continuous system. The apparatus to be used may be any of a tank type, a tube type and a tower type, and is equipped with various stirring blades, a vertical polymerization tank, a horizontal single-axis polymerization tank and / or a horizontal two-axis polymerization tank. A type polymerization tank or the like can be used.
[0033]
The reaction is preferably carried out under substantially oxygen-free conditions. For example, before starting the operation, the inside of the raw material adjusting tank, the reaction apparatus and the piping is replaced with an inert gas such as nitrogen gas. Usually, a molten mixture of an aromatic dihydroxy compound and a carbonic acid diester is fed to a vertical reactor. The catalyst may be supplied directly to the first reaction tank on a separate line from the raw material, or may be supplied in a state of being mixed with the raw material by a static mixer or the like in a pipe before entering the first reaction tank. If necessary, a solvent for dissolving or suspending the catalyst is used. Preferred solvents include water, acetone, phenol and the like.
[0034]
The liquid supply port of each tank is preferably located at the liquid phase on the side wall of the reaction tank, and the outlet is preferably located at the bottom of the reaction tank. In addition, a method adapted to the physical properties of the reaction solution, such as a method of continuously extracting the reaction solution from each tank, a method using a head, a method using a pressure difference, a method using a liquid feed pump such as a gear pump, etc. preferable.
[0035]
After the polymerization is completed or immediately before the polymerization is completed, it is necessary to add a neutralizing agent to neutralize the alkali metal and / or alkaline earth metal catalyst contained in the produced aromatic polycarbonate. As such a neutralizing agent, a sulfur-containing acidic compound described later is preferable.
[0036]
After the polymerization is completed, the produced aromatic polycarbonate is usually recovered as pellets. In this case, the aromatic polycarbonate is passed through a vented extruder to remove low molecular weight components such as monomers and by-products remaining in the polymer. Is also possible.
[0037]
The neutralizing agent for neutralizing the catalyst in the polymer obtained by the above step, particularly the alkali metal and / or alkaline earth metal catalyst, is 0.5 to 10 equivalents, preferably 1 to 10 equivalents to the catalyst metal. Add 5 equivalents. That is, usually 0.01 to 10 ppm, preferably 3 to 7 ppm is added to the weight of the aromatic polycarbonate. If it exceeds 10 ppm, the amount of acidic components present in the substrate increases, which is not preferable. On the other hand, when the content is less than 0.01 ppm, the basic catalyst cannot be sufficiently neutralized, and coloration occurs during polymerization or a desired molecular weight cannot be obtained.
[0038]
As the neutralizing agent, a sulfur-containing acidic compound, phosphoric acid, phosphorous acid and the like can be used, and a sulfur-containing acidic compound is particularly preferable. For example, a derivative such as sulfonic acid, sulfinic acid or an ester thereof can be used. Specifically, p-toluenesulfonic acid, benzenesulfonic acid and dodecylbenzenesulfonic acid, esters thereof such as methyl, ethyl, butyl, t-butyl, octyl, dodecyl, phenyl, benzyl, phenethyl, benzenesulfinic acid, Examples include toluenesulfinic acid and naphthalenesulfonic acid. Of these compounds, sulfonic acids or derivatives thereof are preferred, and esters of p-toluenesulfonic acid or esters of benzenesulfonic acid are particularly preferred. Further, two or more of these compounds may be used. Furthermore, it is preferable to use an alkali metal salt of these compounds in combination with these compounds, because the dispersibility is improved and the deactivating effect is enhanced. As the amount used in combination, it is preferable to use the alkali metal salt in an amount of about 0.3 to 3 in a weight ratio to the non-alkali metal salt.
[0039]
The sulfur-containing acidic compound can be added to the aromatic polycarbonate by any method. For example, a sulfur-containing acidic compound can be added to or dispersed in an aromatic polycarbonate in a molten or solid state, directly or diluted with a diluent. Specifically, it can be supplied and mixed in a polycondensation reactor, a transfer line from the reactor, and an extruder, and is usually supplied into an extruder. When the sulfur-containing acidic compound is added to the extruder in the form of a solution and kneaded, a screw configuration that raises the pressure higher than the addition position on the upstream side of the resin pressure inside the extruder at the addition position, the upstream of the sulfur-containing acidic compound This is preferable because escape to the side can be prevented, the reaction can be efficiently performed with a small amount, and the catalyst can be neutralized. Further, after mixing with aromatic polycarbonate or other polymer pellets, flakes, powders and the like with a mixer or the like, the mixture can be supplied to an extruder using a side feeder or the like and kneaded. Among the above, it is preferable to add the stock solution of the sulfur-containing acidic compound to the flakes of the aromatic polycarbonate, mix them with a mixer or the like, and then add them as a master batch. Further, it is also preferable to control the addition amount with high accuracy using a weight feeder or the like.
[0040]
In addition, when performing decompression treatment by venting with an extruder, or adding water, heat stabilizer, release agent, dye, pigment, ultraviolet absorber, antistatic agent, antifogging agent, organic / inorganic filler, etc. In this case, the addition and treatment may be performed simultaneously with the addition of the sulfur-containing acidic compound, but it is preferable to perform the addition and kneading after the sulfur-containing acidic compound is first added and kneaded.
[0041]
As a method of adding an anti-plasticizer to the aromatic polycarbonate of the present invention, the aromatic polycarbonate is supplied to an extruder at the final stage of polymerization in a transesterification reaction in the same manner as or simultaneously with the addition of the sulfur-containing acidic compound. Further, after mixing with aromatic polycarbonate or other polymer pellets, flakes, powders and the like with a mixer or the like, the mixture can be supplied to an extruder using a side feeder or the like and kneaded. It is preferable that the anti-plasticizer is mixed with the flakes of the aromatic polycarbonate by a mixer or the like and then added as a master batch. Further, it is also preferable to control the addition amount with high accuracy using a weight feeder or the like. The obtained mixture is melted and kneaded by an extruder to form pellets.
[0042]
The aromatic polycarbonate of the present invention is a heat-resistant stabilizer, an ultraviolet absorber, a release agent, a coloring agent, an antistatic agent, a slip agent, an antiblocking agent, a lubricant, an antifogging agent, a natural oil, and a synthetic agent as long as the purpose is not impaired. Additives such as oil, wax, organic fillers and inorganic fillers may be blended. Such an additive can be added to the aromatic polycarbonate resin in a molten state, or after pelletizing once, the aromatic polycarbonate resin can be re-melted if necessary and added. .
[0043]
The biphenyl compound used in the present invention is represented by the following general formula (1).
Embedded image

(In the formula, R represents the same or different substituent, p and r represent an integer of 0 to 5, q represents an integer of 0 to 4, and n and m represent an integer of 1 to 5.)
[0044]
In the general formula (1), n and m are selected from 1 to 5, preferably from 1 to 4. When n and m are 6 or more, the heat resistance of the aromatic polycarbonate resin composition is insufficient, which is not preferable. If n and m are 0, the compound is likely to become a gas at the time of molding, which causes surface defects on the substrate. Each phenyl group may have a substituent R, and among them, a halogen atom, an alkyl group having 1 to 3 carbon atoms, a methoxy group, an ethoxy group and the like are preferable. Most preferred among these is benzylbiphenyl, where p = q = r = 0 and n = m = 1. The bonding form of each phenyl group is selected from any of ortho, meta and para, but the para position is most preferred. Specifically, compounds exemplified in the following [Formula 4] can be exemplified.
Embedded image

[0045]
The biphenyl compound is added in an amount of 0.01 to 40 parts by weight, preferably 0.05 to 30 parts by weight, particularly preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the aromatic polycarbonate serving as the base resin of the substrate. If the compounding amount (content) is less than 0.01 part by weight, the effect of improving the rigidity of the aromatic polycarbonate and lowering the glass transition temperature is not significant, and if it exceeds 40 parts by weight, the effect of improving the rigidity and reducing the glass transition temperature is obtained. The lowering effect saturates.
When blending the biphenyl compound represented by the general formula (1), one kind may be used, or two or more kinds may be mixed.
[0046]
The thickness of the substrate in the optical information recording medium according to the present invention is preferably selected in the range of 0.5 to 3 mm. The signal layer is formed of, for example, a reflective film, a pit, a groove, a recording film, a protective film, and the like. In a read-type optical information recording medium, the signal layer is usually composed of a reflective film and pits. In a rewritable optical information recording medium, the signal layer is usually composed of a reflective film, pits, grooves, a recording film and a protective film. Have been. The reflection film is formed on the substrate and reflects the incident laser light. Examples of a material that can be used for the reflective film include aluminum, silver, and gold. The thickness of the reflection film is about 10 to 200 nm. In a reproduction type optical information recording medium, a signal is reproduced by reading a signal in a signal layer composed of pits and the like arranged on a substrate, and in a rewritable type optical information recording medium, the signal is disposed on a substrate. A signal of a signal layer including pits, grooves, recording films, and the like is written or read.
[0047]
The recording film is made of, for example, Ge-Sb-Te which is a phase change film, and has a thickness of about 10 to 200 nm. The protective films are laminated on both surfaces of the recording film, respectively, and absorb heat generated from the recording film. The protective film is transparent, for example, Zn-SiO₂And the thickness is about 10 to 300 nm. The signal layer and the light transmitting layer are usually bonded by a transparent adhesive film, and the adhesive film is formed of, for example, a UV-curable resin or an adhesive sheet. The thickness of the adhesive film is about 10 to 100 μm. A light transmission layer of about 20 to 300 μm is formed on the adhesive film.
[0048]
In a rewritable optical information recording medium, when writing or erasing, recording or erasing is performed by irradiating a laser beam from the surface of the light transmitting layer and focusing on the recording film through an adhesive film and a protective film. When reading on a rewritable optical information recording medium, laser light enters from the surface of the light transmitting layer and is reflected by the reflective film through the adhesive film, the protective film, the recording film, and the protective film. In a reproduction-type optical information recording medium, laser light enters from the surface of the light transmission layer and is reflected by the reflection film through the adhesive film.
[0049]
The optical information recording medium according to the present invention is obtained by laminating a signal layer or the like on an opaque substrate manufactured by an injection molding method, and forming a light layer having a thickness of about 0.02 to 0.3 mm thereon. It can be easily manufactured by bonding a transparent resin film called a transmission (cover) layer via an adhesive or an adhesive film. The optical information recording medium according to the present invention is such that the resin film constituting the light transmitting layer is excellent in transparency, rigidity, surface smoothness, thickness accuracy, etc., and has a small birefringence and a small phase difference. By using, high density and high quality are achieved.
[0050]
FIGS. 1 and 2 show examples of the optical information recording medium of the light transmission layer incident type. FIG. 1 is an explanatory longitudinal sectional view of an example of a reproduction type optical information recording medium. The reproduction-type optical information recording medium 1 includes a substrate 2, a signal layer including pits 30 and a reflection film 32 disposed on the substrate 2, and a light transmission layer 5 disposed on the signal layer via an adhesive layer 4. It has a structure in which a laser beam 7 is incident from the light transmitting layer 5 side through a lens 6 so that a signal can be read.
[0051]
FIG. 2 is an explanatory longitudinal sectional view of an example of a rewritable optical information recording medium. The rewritable optical information recording medium 11 includes a substrate 22, a signal layer including pits and grooves 31, a reflection film 32, a recording film 33 and a protective film 34 disposed on the substrate 22, and an adhesive layer 4 on the signal layer. The light transmitting layer 5 and the like are disposed through the laser light 7 through the lens 6 from the side of the light transmitting layer 5 to enable signal writing and signal reading. . The light source of the laser light has a shorter wavelength of about 400 nm than that of the conventional 650 nm, and the numerical aperture (NA) of the lens 7 is increased from about 0.6 to 0.85 of the conventional laser spot. The diameter can be reduced, and smaller signals can be written and read, and as a result, higher density can be achieved.
[0052]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Description Examples as long as the gist is not exceeded. The analysis of the aromatic polycarbonate and its composition was performed by the following method.
(1) Glass transition temperature
The pellet was heated at a rate of 10 ° C./min from room temperature under a nitrogen stream by a differential thermal analyzer (manufactured by Seiko, model: SSC-5000), and the inflection point was taken as the glass transition temperature.
(2) Molecular weight
The intrinsic viscosity [η] of the solution using methylene chloride as a solvent at 20 ° C. is measured using an Ostwald viscometer, and is calculated from the Schnell viscosity equation.
[Η] = 1.23 × 10^-5× M^0.85
(3) Flexural modulus
It measured according to ASTM D-790.
[0053]
[Example 1]
1. Preparation of polycarbonate
It was synthesized by a transesterification method using bisphenol A as an aromatic dihydroxy compound and diphenyl carbonate as a carbonic acid diester. Carbonic acid diester was used at a ratio of 1.10 mol per 1 mol of the aromatic dihydroxy compound. Cesium carbonate was used as a polymerization catalyst in an amount of 1.0 × 10^-7Used in molar proportions. The transesterification reaction was performed in two steps. Specifically, the first-stage reaction was performed at 220 ° C. under reduced pressure for 2 hours. The reaction pressure was set at 600 mmHg. In the second step, a polycondensation reaction was performed at a temperature of 310 ° C. for 2 hours under a reduced pressure of 1 mmHg.
The obtained reaction product was introduced into an extruder, and parabenzyl biphenyl (manufactured by Nippon Steel Chemical Co., Ltd.) was added as a catalyst deactivator so that butyl p-toluenesulfonate was contained at 5 ppm based on the aromatic polycarbonate. The amount of the aromatic polycarbonate was introduced into the extruder using a quantitative feeder so as to be 5 parts by weight based on 100 parts by weight. Thereafter, the strand discharged from the die of the extruder was cooled and pelletized to obtain a molding pellet. The glass transition temperature of the composition containing parabenzylbiphenyl was 117 ° C.
The reaction product after the polycondensation reaction was sampled, and the viscosity and glass transition temperature of the obtained aromatic polycarbonate were measured. The viscosity average molecular weight was 16,000, and the glass transition temperature was 143 ° C. Was.
[0054]
2. Preparation of optical information recording medium
Using an injection molding machine (model: DISK3, manufactured by Sumitomo Heavy Industries, Ltd.) equipped with a mold for manufacturing an optical disk, the above aromatic polycarbonate resin was set at a cylinder temperature of 360 ° C., a mold temperature of 110 ° C., and a molding cycle of 12 seconds. A signal imprinted on a stamper having a pitch of 0.3 μm and a groove depth of 60 nm was transferred to produce an optical disk substrate having a diameter of 120 mm and a thickness of 1.1 mm. On one surface of this substrate, 0.9% by weight of Pd and 1.0% by weight of Cu were added with Ag as a reflective film as a main component by sputtering._98.1Pd_0.9Cu_1.070 nm metal reflective film, ZnS-SiO₂25 nm dielectric film, 13 nm GeSbTe recording film, ZnS-SiO₂A 160 nm thick dielectric film was sequentially formed. On this dielectric layer, a double-sided adhesive having a thickness of 25 μm was applied using a laminator, and then a polycarbonate resin film having a thickness of 100 μm was bonded again using a laminator while applying tension. Thereafter, the resin film was cut into a disk shape with scissors to obtain an optical information recording medium.
[0055]
3. Evaluation of substrates for optical information recording media
The following methods were used to evaluate signal transferability, warpage of a molded substrate, change in warpage due to water absorption, and surface defects of the substrate. The results are shown in Table 1.
(1) Transferability of signal
The depth of the groove on the surface of the molded substrate was measured with an atomic force microscope (Olympus NV2100). The maximum distance between the edge of the groove and the bottom surface at a position of 58 mm in the radial direction was measured at four points in the circumferential direction, and the four points were averaged. The deeper the groove depth, the better the signal characteristics.
(2) Warpage of molded substrate
Using a disk warpage angle automatic measuring device (Admon Science) to measure the warpage of the molded substrate, while rotating the optical information recording medium obtained in 2 above at 60 rpm, 25 mm, 37 mm, 49 mm, and 57 mm in the radial direction of the optical disk substrate And a laser beam having a wavelength of 780 nm from a semiconductor laser was irradiated at four positions along the circumference. The maximum value of the above measured values was defined as the radial warpage angle (degree). The smaller the value, the better.
(3) Change in warpage due to water absorption
Immediately after the optical information recording medium having the signal layer and the light transmitting layer was dried at 120 ° C. for 10 hours, the warpage was measured by the same method as described above, and then left at 80 ° C. × 85% relative humidity for 100 hours. The degree of warpage (degree) was measured. (4) Substrate surface defects
2000 shots were continuously formed, and the entire surface of the 2000th shot substrate was observed with an optical microscope (x500), and the number of surface defects on the signal surface per substrate was counted.
[0056]
[Example 2]
In the preparation of the aromatic polycarbonate, the same procedure as in Example 1 was carried out except that the second-stage reaction (polycondensation reaction) was changed to 320 ° C. for 3 hours instead of 310 ° C. for 2 hours. Thereafter, an optical information recording medium was manufactured in the same manner. The results are shown in Table 1.
[0057]
[Example 3]
The same procedure as in Example 1 was carried out except that metabenzylbiphenyl (manufactured by Nippon Steel Chemical Co., Ltd.) was used instead of parabenzylbiphenyl as the biphenyl compound. The results are shown in Table 1.
[0058]
[Example 4]
The procedure was performed in the same manner as in Example 1 except that the content of parabenzylbiphenyl was changed to 10 parts by weight. The results are shown in Table 1.
[0059]
[Example 5]
As the biphenyl compound, the following compound in which n, m, p, q, and r in the general formula (1) are all 1, the substituents are all methyl groups, and the bond is para / ortho / para / para. The same procedure as in Example 1 was performed except that [Formula 5] was used. The results are shown in Table 1.
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[0060]
[Comparative Example 1]
The procedure was performed in the same manner as in Example 1 except that the biphenyl compound was not blended. The results are shown in Table 2.
[0061]
[Comparative Example 2]
In the preparation of the polycarbonate in Example 1, the same operation as in Example 1 was carried out except that the polycondensation reaction was carried out at 330 ° C. for 4 hours under a reduced pressure of 1 mmHg in the second stage reaction, and the viscosity average molecular weight was 42,000. Was obtained. The procedure was performed in the same manner as in Example 1 except that this aromatic polycarbonate was used. The results are shown in Table 2.
[0062]
Comparative Example 3 The same procedure as in Example 1 was carried out except that biphenyl (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the biphenyl compound. The results are shown in Table 2.
[0063]
[Table 1]

[0064]
[Table 2]

[0065]
【The invention's effect】
According to the present invention, it is possible to obtain a high-density, high-quality optical information recording medium having excellent signal transfer properties, excellent rigidity, small dimensional change due to water absorption, and excellent productivity.
[Brief description of the drawings]
FIG. 1 is an explanatory longitudinal sectional view of an example of an optical information recording medium (reproducing type) of a light transmitting layer incident type;
FIG. 2 is an explanatory longitudinal sectional view of an example of an optical information recording medium of a light transmission layer incident type (rewritable type).
[Explanation of symbols]
1, 11: Optical information recording medium
2, 22: substrate
30: signal layer (pit)
31: signal layer (pit and groove)
32: signal layer (reflection film)
33: signal layer (recording film)
34, 34 ': signal layer (protective film)
4: adhesive layer
5: Light transmission layer
6: Lens
7: Laser light

Claims (3)

It has a substrate, a signal layer disposed on the substrate, and a light-transmitting layer having a thickness of 300 μm or less laminated on the signal layer. A laser beam is incident from the light-transmitting layer side to enable writing and reading of recording. An optical information recording medium having a signal track pitch of 0.35 μm or less, wherein the substrate is represented by the following general formula (1) with respect to 100 parts by weight of an aromatic polycarbonate having a viscosity average molecular weight of 10,000 to 40,000. An optical information recording medium comprising a resin composition containing 0.01 to 40 parts by weight of a biphenyl compound.

(In the formula, R represents the same or different substituent, p and r represent an integer of 0 to 5, q represents an integer of 0 to 4, and n and m represent an integer of 1 to 5.) The optical information recording medium according to claim 1, wherein the biphenyl compound is parabenzylbiphenyl. The optical information recording medium according to claim 1 or 2, wherein the aromatic polycarbonate is obtained by a transesterification reaction between an aromatic dihydroxy compound and a carbonic acid diester.

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