JP3759489B2 - Manufacturing method and manufacturing apparatus for disk substrate - Google Patents

Description

【００４６】
表１より複屈折が５０ｎｍ以下になるのは最小キャビティ厚さが所望基板厚さより０．１ｍｍ以下薄い場合である。この垂直入射で複屈折５０ｎｍのポリカーボネート樹脂基板に斜め入射させると複屈折は大きな値になる。３０度入射の場合は約１００ｎｍになる。また、光ディスクへの照射光は集束光であり、開口度が０．６以上の高い対物レンズを用いる高密度の光ディスクでは再生型のものでも垂直入射の複屈折は５０ｎｍは必要である。また、所望基板厚さを得るためには、金型間は開く方向しか制御できないので、最小キャビティ厚さは所望基板厚さより厚くはできない。したがって、最小キャビティ厚さは所望基板厚さに対して０ｍｍから０．１ｍｍ薄くすれば良いことが確認できた。
【００４７】
次に最大キャビティ厚さについて検討した。最小キャビティ厚さを所望基板厚さより０．０５ｍｍ薄くする。基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。スタンパ１１の信号領域は、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１２５℃、スプル温度は６０℃とした。型締め力は４０トンで行った。射出圧縮力は溶融樹脂の充填時は４トン、保圧後の圧縮工程では２０トンで行った。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。測定結果を表２に示す。
【００４８】
【表２】

【００４９】
表２から圧縮代が大きくなるほど複屈折は良くなり、板厚のショットばらつきは大きくなる。圧縮代が大きくなるほど、キャビティ１０内に溶融樹脂が充填される際のキャビティ１０の厚さが厚くなるため溶融樹脂は流れやすい反面、基板の板厚を調整するためには樹脂が冷却される際に金型を閉じる移動量が多く必要だからである。
【００５０】
表２から複屈折の絶対値が５０ｎｍ以下なのは圧縮代が０．１５ｍｍ以上であり、板厚のショットばらつきが±３５μｍ以下なのは圧縮代が０．３ｍｍ以下の場合である。ここで、板厚のばらつきの基準を±３５μｍとしたが、板厚のばらつきが±３５μｍを越えると収差が大きくなって信号の読み出し等に影響を及ぼすからである。複屈折の基準５０ｎｍは表１のところで説明した通りである。
【００５１】
表２より圧縮代、すなわち、最大キャビティ厚さと最小キャビティ厚さとの差は０．１５ｍｍ以上０．３ｍｍ以下が良いことを確認できた。
【００５２】
表３に溶融樹脂の充填時の射出圧縮力と複屈折との関係を示す。最小キャビティ厚さは所望基板厚さより０．０５ｍｍ薄くし、圧縮代は０．２ｍｍとした。また、基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。スタンパ１１の信号領域は、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１２５℃、スプル温度は６０℃とした。型締め力は４０トンで行った。保圧後の圧縮工程での射出圧縮力は２０トンで行った。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。
【００５３】
【表３】

【００５４】
表３から複屈折の絶対値が５０ｎｍ以下になるのは樹脂充填時の射出圧縮力が１０トン以下の場合であった。この場合、溶融樹脂がキャビティ１０の内に充填される前はキャビティ１０の厚さは射出圧縮力によって最小になっているが、キャビティ１０の内に溶融樹脂が充填されると樹脂圧の方が大きいためにキャビティ１０の厚さは最大まで広がり、その結果、樹脂の流動が良くなって樹脂が受ける応力が低減され複屈折が良くなる。
【００５５】
（実施の形態２）
本実施の形態では成形装置が直圧方式の場合を説明する。図７（ｂ）に示すようにトグル方式の成形装置の場合は、金型の開閉と金型の型締めと射出圧縮が、それぞれ、油圧回路１０８、油圧回路１１１、油圧回路１１２に分かれて駆動される。これに対して、図７（ａ）に示すように直圧方式の場合は金型の開閉と金型の型締めと射出圧縮を油圧回路１０６だけで行う。
【００５６】
金型の構造を図２に示す。コア部を移動させる方式の図１の場合と比べて固定金型ガイドリング２３と可動金型ガイドリング２２がない構造になっている。図１の場合は最小キャビティ厚さと最大キャビティ厚さとを規定する構造になっていたのに対して、図２の場合は最小キャビティ厚さのみを規定する構造になっている。
【００５７】
表４に最小キャビティ厚さ（室温時、所望基板厚さ基準）と制御可能な最小板厚（所望基板厚さ基準）と所望基板厚さでの複屈折の最大絶対値との対応を示す。最大キャビティ厚さは所望基板厚さより０．２ｍｍ厚くした。基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。スタンパ１１の信号領域は、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１２５℃、スプル温度は６０℃とした。第１型締め力は４トン、第２型締め力は２０トンで行った。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。
【００５８】
【表４】

【００５９】
表４より複屈折が５０ｎｍ以下になるのは最小キャビティ厚さが所望基板厚さより０．１ｍｍ以下薄い場合である。また、所望基板厚さを得るためには、金型間は開く方向しか制御できないので、最小キャビティ厚さは所望基板厚さより厚くはできない。したがって、最小キャビティ厚さは所望基板厚さに対して０ｍｍから０．１ｍｍ薄くすれば良いことが確認できた。
【００６０】
次に最大キャビティ厚さについて検討する。最小キャビティ厚さを所望基板厚さより０．０５ｍｍ薄くする。金型の開き量をレーザ変位計を用いて測定した。基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。スタンパ１１の信号領域は、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１２５℃、スプル温度は６０℃とした。第１型締め力は４トン、第２型締め力は２０トンで行った。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。測定結果を表５に示す。
【００６１】
【表５】

【００６２】
表５から圧縮代が大きくなるほど複屈折は良くなり、板厚のショットばらつきは大きくなる。
【００６３】
表５から複屈折の絶対値が５０ｎｍ以下なのは圧縮代が０．１５ｍｍ以上であり、板厚のショットばらつきが±３５μｍ以下なのは圧縮代が０．３ｍｍ以下の場合である。したがって、圧縮代、すなわち、最大キャビティ厚さと最小キャビティ厚さとの差は０．１５ｍｍ以上０．３ｍｍ以下が良いことを確認できた。
【００６４】
表６に溶融樹脂の充填時の第１型締め力と複屈折との関係を示す。最小キャビティ厚さは所望基板厚さより０．０５ｍｍ薄くし、圧縮代は０．２ｍｍとした。また、基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。スタンパ１１の信号領域は、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１２５℃、スプル温度は６０℃とした。第２型締め力は２０トンで行った。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。
【００６５】
【表６】

【００６６】
表６から複屈折の絶対値が５０ｎｍ以下になるのは第１型締め力が１０トン以下の場合であった。この場合、溶融樹脂がキャビティ１０の内に充填されると樹脂圧の方が大きいためにキャビティ１０の厚さは広がり、その結果、樹脂の流動が良くなって樹脂が受ける応力が低減され複屈折が良くなる。
【００６７】
本実施の形態では、直圧方式の成形装置の場合を示したが、トグル方式の成形装置の場合でも、図２の構造の金型を用いて同様の動作を行うことができる。トグル方式の成形装置の場合には、実施の形態１のようなコア部を移動させる射出圧縮機構を用いず、型締め機構のみを用いて型締めを行う。このようにしてトグル方式の成形装置に直圧方式の成形装置の場合と同じ成形条件を設定した結果、同様の結果が得られることを確認した。
【００６８】
（実施の形態３）
実施の形態１および実施の形態２ではキャビティ１０を押す力を２段にし、かつ、第１力を低く、第２力を高く設定した。ここでは、キャビティ１０を押す力が１段の場合を検討した。金型は図２の構造のものを用いた。成形装置は直圧方式のものを用いた。
【００６９】
表７に最小キャビティ厚さ（室温時、所望基板厚さ基準）と制御可能な最小板厚（所望基板厚さ基準）と所望基板厚さでの複屈折の最大絶対値との対応を示す。最大キャビティ厚さは所望基板厚さより０．２ｍｍ厚くした。基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。スタンパ１１の信号領域は、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１３０℃、スプル温度は６０℃とした。型締め力は８トンで行った。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。
【００７０】
【表７】

【００７１】
表７より複屈折が５０ｎｍ以下になるのは最小キャビティ厚さが所望基板厚さより０．１ｍｍ以下薄い場合である。また、所望基板厚さを得るためには、金型間は開く方向しか制御できないので、最小キャビティ厚さは所望基板厚さより厚くはできない。したがって、最小キャビティ厚さは所望基板厚さに対して０ｍｍから０．１ｍｍ薄くすれば良いことが確認できた。
【００７２】
次に最大キャビティ厚さについて検討する。最小キャビティ厚さを所望基板厚さより０．０５ｍｍ薄くする。金型の開き量をレーザ変位計を用いて測定した。基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。スタンパ１１の信号領域は、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１３０℃、スプル温度は６０℃とした。型締め力は８トンで行った。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。測定結果を表８に示す。
【００７３】
【表８】

【００７４】
表８から圧縮代が大きくなるほど複屈折は良くなり、板厚のショットばらつきは大きくなる。
【００７５】
表８から複屈折の絶対値が５０ｎｍ以下なのは圧縮代が０．１５ｍｍ以上であり、板厚のショットばらつきが±３５μｍ以下なのは圧縮代が０．３ｍｍ以下の場合である。したがって、圧縮代、すなわち、最大キャビティ厚さと最小キャビティ厚さとの差は０．１５ｍｍ以上０．３ｍｍ以下が良いことを確認できた。
【００７６】
表９に溶融樹脂の充填時の型締め力と複屈折および板厚との関係を示す。最小キャビティ厚さは所望基板厚さより０．０５ｍｍ薄くし、圧縮代は０．２ｍｍとした。また、基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。スタンパ１１の信号領域は、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１３０℃、スプル温度は６０℃とした。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。
【００７７】
【表９】

【００７８】
表９から複屈折の絶対値が５０ｎｍ以下になるのは型締め力が１０トン以下の場合であった。この場合、溶融樹脂がキャビティ１０の内に充填されると樹脂圧の方が大きいためにキャビティ１０の厚さは広がり、その結果、樹脂の流動が良くなって樹脂が受ける応力が低減され複屈折が良くなる。また、板厚のショットばらつきが±３５ｎｍ以下になるのは型締め力が６トン以上の場合であった。これは型締め力が高いほど最大キャビティ厚さが薄くなり、冷却時にキャビティの面の移動量が減少するためである。したがって、型締め力が１段の場合は型締め力は６トン以上１０トン以下が良いことを確認できた。
【００７９】
本実施の形態では、直圧方式の成形装置の場合を示したが、トグル方式の成形装置の場合でも、同様の動作を行うことができる。トグル方式の成形装置の場合にも、実施の形態１のようなコア部を移動させる射出圧縮機構を用いず、型締め機構のみを用いて型締めを行う。このようにしてトグル方式の成形装置に直圧方式の成形装置の場合と同じ成形条件を設定した結果、同様の結果が得られることを確認した。
【００８０】
（実施の形態４）
実施の形態１から実施の形態３までのような製造方法によって、ポリカーボネート樹脂で、外径が１２０ｍｍ、厚さが０．６ｍｍ、信号領域が、トラックピッチ１．０μｍ、深さ１１０ｎｍのピットの基板を成形した場合、複屈折の絶対値が５０ｎｍ以下の特性は樹脂温度が３８０℃では金型温度が１２０℃以上で得られる。この場合、ピットの転写は十分である。
【００８１】
そこで、さらに高密度の信号部分をもつ基板成形の場合を検討した。スタンパ１１の信号領域は、トラックピッチ０．６μｍ、深さ１１０ｎｍのピットとした。 この場合、実施の形態１および実施の形態２の製造方法で成形するとピット深さが７０ｎｍ台、複屈折の最大絶対値が８０ｎｍ台であった。まず、トグル方式の成形装置について検討した。
【００８２】
転写を良くするために、図１の金型の場合は射出圧縮力を大きくするとキャビティ１０内の樹脂に歪が生じて複屈折の絶対値が大きくなった。また、図２の金型の場合は型締め力を大きくすると複屈折の絶対値が大きくなった。そこで、複屈折の絶対値が５０ｎｍ以下になる成形条件である金型温度とスプル温度を変えてピット深さを測定した結果を表１０に示す。金型温度は固定金型６と可動金型７とで同じになるように制御した。ポリカーボネートの分解開始温度を考慮して樹脂温度は上限と考えられる３８０℃に固定した。成形サイクルは１５秒で行った。
【００８３】
【表１０】

【００８４】
表１０から金型温度は１３０℃あればトラックピッチ０．６μｍ、ピット深さ１１０ｎｍを転写することがわかる。ただし、金型温度が１４５℃で成形した基板はプロペラ状に反っているため光ディスク用の基板には使用できないことがわかった。また、スプル温度の影響は小さいことがわかった。
【００８５】
金型温度とは一般に金型内を流れている媒体の制御温度のことを呼ぶ。しかし、実際の成形では溶融した樹脂が流入するキャビティ１０の温度が重要である。そこで、成形の１サイクルのうちで上がったり下がったりするキャビティ１０の表面近傍の鏡面温度を測定し、溶融した樹脂が流入する際の温度を求め、この温度をここでは金型鏡面温度と呼ぶことにする。基板がプロペラ状に反った金型温度１４５℃の際の金型鏡面温度はポリカーボネートのガラス転移温度１５０℃であった。そこで、金型鏡面温度は樹脂材料のガラス転移温度より低く、好ましくは、５℃以上低く制御しなければならないことがわかった。また、金型温度１３０℃の際の金型鏡面温度は１３５℃であった。
【００８６】
ここで、スタンパ１１が装着されている可動金型７の温度を１３５℃に固定して固定金型６の温度を変えた結果を表１１に示す。スプル温度は６０℃とした。
【００８７】
【表１１】

【００８８】
表１１からスタンパを装着していない方の金型温度は転写に影響がないことがわかる。したがって、少なくともスタンパを装着した方の金型温度が１３０℃以上あればトラックピッチ０．６μｍ、深さ１１０ｎｍのピットの転写は良好である。
【００８９】
以上のことから、外径が１２０ｍｍ、厚さが０．６ｍｍの基板を成形して実用可能な製品を得るためには、少なくともスタンパを装着した方の金型鏡面温度が樹脂材料のガラス転移温度より５Ｋ以上２５Ｋ以下、好ましくは５Ｋ以上１５Ｋ以下低くしなければならないことがわかった。
【００９０】
ここでは成形サイクルを１５秒に固定して検討した。この成形サイクルを短くすると金型温度は同じでも金型鏡面温度は高くなる。そこで、成形サイクルを１５秒、１２秒、８秒と変えて金型鏡面温度と転写および複屈折との関係を調べると、十分な転写および５０ｎｍ以下の複屈折が得られる金型鏡面温度は成形サイクルに依らないことがわかった。
【００９１】
また、図２の金型を直圧方式の成形装置に載せて成形を行っても、図１や図２の金型をトグル方式の成形装置に載せた場合と同じで、外径が１２０ｍｍ、厚さが０．６ｍｍの基板を成形して実用可能な製品を得るためには、少なくともスタンパを装着した方の金型鏡面温度が樹脂材料のガラス転移温度より５Ｋ以上２５Ｋ以下、好ましくは５Ｋ以上１５Ｋ以下低くしなければならないことがわかった。
【００９２】
（実施の形態５）
次に溶融樹脂が受ける圧力と複屈折との関係を調べた。ここでは、図１の金型をトグル方式の成形装置に載せた場合について説明する。溶融樹脂の受ける圧力を直接検出することはできないので、溶融樹脂の反力としてスクリューが受けた圧力で代用し、図３の油圧回路８に設けた圧力計によって検出する。この場合の検出圧力は図４のような時間変化を示した。射出工程でピーク圧をもち、保圧工程の始めのころに極小値を示し、徐々に圧力が上昇している。ピーク圧を示すのは溶融樹脂がキャビティ１０内に満たされた後も溶融樹脂を充填しようとするからであり、極小値を保圧工程で示すのはキャビティ１０に入りきらなかった溶融樹脂がスプルブッシュ２７、ノズル９、スクリュー３と還流し、スクリュー３によって押し出される溶融樹脂と衝突するからと考えられる。また、その後、徐々に樹脂の圧力が上昇するのは保圧のためと考えられる。
【００９３】
この図４の圧力変化をもと溶融樹脂の圧力が極小となる時間の近傍でキャビティ１０への溶融樹脂の充填を止めた。具体的には、図１のカットパンチ１８を突き出した。また、射出圧縮力をカットパンチ１８を突き出すとほぼ同時に４トンから２０トンにした。すなわち、圧縮工程を開始した。表１２に結果を示す。
【００９４】
基板外径は１２０ｍｍであり、所望基板厚さは０．６ｍｍで行った。最小キャビティ厚さは所望基板厚さより０．０５ｍｍ薄くし、圧縮代は０．２ｍｍとした。また、スタンパ１１の信号領域は、トラックピッチ０．６μｍ、深さ１１０ｎｍのピットとした。樹脂材料はポリカーボネート樹脂を用いた。樹脂温度は３８０℃、金型温度は１３５℃、スプル温度は６０℃とした。型締め力は４０トンで行った。成形サイクルは１５秒で行った。複屈折測定にはヘリウムネオンガスレーザを用い、平行光を垂直入射させ、ダブルパスの値を求めた。
【００９５】
【表１２】

【００９６】
表１２から複屈折の絶対値が５０ｎｍ以下になるのは溶融樹脂の受ける圧力が極小となる時間から０．３秒後より以前の時間である。
【００９７】
圧縮工程の開始はキャビティ１０への溶融樹脂の充填を止めたのと同時か早い方がよい。これは、圧縮工程の開始によってキャビティ１０内の樹脂に働く圧力が緩和されるからである。また、溶融樹脂の受ける圧力が極小となる時間から０．１５秒より早い時間では、基板の板厚ばらつきが±５０μｍ以上と大きくなった。したがって、溶融樹脂の受ける圧力が極小となる時間より０．１秒前から０．３秒後に溶融樹脂を充填する注入口を閉じるか、または圧縮工程を開始することが好ましい。
【００９８】
本実施の形態は、成形装置がトグル方式であったが直圧方式でも第１型締め力を４トン、第２型締め力を２０トンとし、他の条件はトグル方式の場合と同じに設定して行ったが同様の結果が得られた。
【００９９】
実施の形態１乃至５はポリカーボネート樹脂を取り扱ったが、もちろん、他の樹脂でも構わない。
【０１００】
（実施の形態６）
実施の形態５ではキャビティ１０内の樹脂が受けた圧力と複屈折との関係を調べた。このキャビティ１０内の溶融樹脂の圧力の極小時間は成形装置によって、また、成形条件によってばらつきがある。そこで、本発明のディスク基板の製造装置はこのキャビティ１０内の溶融樹脂の圧力の極小時間を検出してこの圧力が最小となる時間から０秒乃至０．３秒後に、キャビティ内に溶融樹脂を流入する入口を閉じる動作、または圧縮工程の開始動作を行うようにするものである。
【０１０１】
具体的な仕組みは図５に示すとおりである。すなわち、スクリューの受ける圧力の検出器２９でキャビティ１０内の圧力の時間変化を検出し電圧変化に変換する。次に、圧力極小時間検出器３０で圧力が極小となる時間を検出する。具体的には、スクリューの受ける圧力の検出器２９からの電気信号を微分して保圧工程での最初のゼロクロス時間を検出する。図６にこのゼロクロス時間の検出方法を示す。信号（ａ）はスクリューの受ける圧力の検出器２９からの信号である。信号（ｂ）は信号（ａ）の微分信号である。この信号（ｂ）のゼロクロスの検出パルス信号が信号（ｃ）である。信号（ｄ）は保圧工程以降でプラス値を示すゲート信号である。ここで、信号（ｃ）と信号（ｄ）との積を求めると信号（ｅ）となり、この信号（ｅ）が保圧工程で最初に信号（ｂ）がゼロクロスとなる時間を示す。この信号（ｂ）から信号（ｅ）までの処理が圧力極小時間検出器３０で行われる。
【０１０２】
次にこの圧力極小時間を起点にタイマー３１および３２を作動させ、図２のようなコア押し機構のない金型の場合はカットパンチ突出油圧回路３３および型締め油圧回路３４を所定の時間後に作動させてカットパンチの突出と第１型締めから第２型締めに切り替える。図１のようにコア押し機構のある金型の場合はカットパンチ突出油圧回路３３および射出圧縮油圧回路３５を所定の時間後に作動させてカットパンチの突出と射出圧縮力の高圧への切り替えを行う。タイマー３１およびタイマー３２の時間は０秒乃至０．３秒で、タイマー３２の時間の方がタイマー３１の時間と同じか短いことが望ましい。
【０１０３】
以上の結果、実施の形態５と同様の結果が得られた。
【０１０４】
本発明のディスク基板の製造装置の全体構成は、一対の金型を開閉する開閉手段と、樹脂を溶融する加熱手段と、溶融樹脂を閉じた一対の金型間のキャビティ内に充填する射出手段と、キャビティ内に充填した樹脂の流入側への逆流防止のための保圧手段と、充填後に一対の金型をより締める圧縮手段と、キャビティ内に充填する樹脂の圧力が最小となる時間を検出する手段を有するものであり、前記圧力が最小となる時間から０秒乃至０．３秒後に、キャビティ内に溶融樹脂を流入する入口を閉じる動作、または圧縮工程の開始動作を行うものである。
【０１０５】
【発明の効果】
以上説明したように、本発明によれば、閉じた一対の金型間に形成されたキャビティ内に充填された溶融樹脂の受ける圧力が最小となる時間の近傍で樹脂の流入口を閉じるため溶融樹脂内の残留応力が低減されるとともに、樹脂が固化する前に圧縮工程を開始することで、成形された樹脂基板の転写、複屈折が良くなる。また、金型鏡面の調整温度を適切に選ぶことでも転写、複屈折が良くなる。
【０１０６】
さらに、閉じた一対の金型間に形成されたキャビティ内に充填された溶融樹脂の受ける圧力が極小となる時間は成形条件によって変化するが、この時間を検出して溶融樹脂の流入口を閉じる動作と圧縮工程を開始することで常に安定した基板の転写と複屈折を得ることができる。
【０１０７】
また本発明の製造装置によれば、キャビティに樹脂を充填する際にキャビティ厚さと射出圧縮力を特定にして樹脂にかかる応力を低減し、複屈折を低下させる。また、金型温度を特定にして樹脂流動を良くさせるとともに樹脂充填時の圧力が極小である時間に樹脂流入を止め、かつ、圧縮工程を開始することで良好な転写と複屈折の低減を図ることができる。この結果、合理的に、かつ、効率よくディスク用基板を製造できる。
【０１０８】
本発明の製造装置によれば、閉じた一対の金型間に形成されたキャビティ内に溶融樹脂が充填される際に、キャビティ厚さを金型を完全に閉じた場合より広げているので樹脂の流動が良くなり、かつ、金型から溶融樹脂にかける圧力を板厚が制御可能な限り低くしているため溶融樹脂内に生じる応力も低減されて、成形された樹脂基板の複屈折が小さくなる。
【０１０９】
また、閉じた一対の金型間に形成されたキャビティ内に充填された溶融樹脂の受ける圧力が最小となる時間の近傍で樹脂の流入口を閉じるため溶融樹脂内の残留応力が低減されるとともに、樹脂が固化する前に圧縮工程を開始することで、成形された樹脂基板の転写、複屈折が良くなる。また、金型鏡面の調整温度を適切に選ぶことでも転写、複屈折が良くなる。
【０１１０】
さらに、閉じた一対の金型間に形成されたキャビティ内に充填された溶融樹脂の受ける圧力が極小となる時間は成形条件によって変化するが、この時間を検出して溶融樹脂の流入口を閉じる動作と圧縮工程を開始することで常に安定した基板の転写と複屈折を得ることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態１、実施の形態４〜６に用いた金型の構成を示した断面側面図である。
【図２】本発明の実施の形態２〜４、実施の形態６に用いた金型の構成を示した断面側面図である。
【図３】本発明の実施の形態１〜６に用いた成形装置の構成を示した断面側面図である。
【図４】本発明の一実施の形態のスクリューが受ける圧力の時間変化を示す図である。
【図５】図５（ａ）（ｂ）は本発明の実施の形態６に示す成形装置の機能説明構成図である。
【図６】図６（ａ）（ｂ）（ｃ）（ｄ）（ｅ）は本発明の実施の形態６に示す成形装置のスクリューの受ける圧力の検出器及び圧力極小時間検出器での信号処理を示した図である。
【図７】図７（ａ）（ｂ）は従来の成形装置の機構部の概略を示す平面図である。
【符号の説明】
１ 材料乾燥装置
２ ホッパ
３ スクリュー
４ モータ
５ 加熱シリンダ
６ 固定金型
７ 可動金型
８ 油圧回路
９ ノズル
１０ キャビティ
１１ スタンパ
１２ スタンパ内周押さえ
１３ スタンパ外周押さえ
１４ 可動金型ミラー部
１５ 冷却水路
１６ 可動金型基盤
１７ フローティングパンチ
１８ カットパンチ
１９ 突出ピン
２０ 可動金型突当リング
２１ 固定金型突当リング
２２ 可動金型ガイドリング
２３ 固定金型ガイドリング
２４ 固定金型基盤
２５ 固定金型ミラー部
２６ 冷却水路
２７ スプルブッシュ
２８ 固定側ブッシュ
２９ スクリューの受ける圧力の検出器
３０ 圧力極小時間検出器
３１、３２ タイマー
３３ カットパンチ突出油圧回路
３４ 型締め油圧回路
３５ 射出圧縮油圧回路
３６ 架台
１０１ 固定金型
１０２ 可動金型
１０３、１０４ 大プレート
１０５ タイバー
１０６、１０８、１１１、１１２ 油圧回路
１０７、１０９ ピストン
１１０ トグル
１１３ 油圧パイプ[0001]
[Industrial application fields]
The present invention relates to a method and an apparatus for manufacturing a disk substrate for forming a substrate used for an optical disk or the like.
[0002]
[Prior art]
In recent years, optical disks have attracted attention as large-capacity, high-speed memory media. As optical disks, read-only optical disks (CD, VD, CD-ROM, etc.), recording / reproducing optical disks (write-once type), recording / reproducing erasable optical disks (rewritable type), and the like are known. As a substrate for these optical disks, a resin substrate (polycarbonate resin, acrylic resin, polyolefin resin, etc.) is generally used.
[0003]
These disk substrates are generally formed using an injection molding method or an injection compression molding method from the viewpoint of productivity. That is, a pit formed on a stamper by attaching an annular flat stamper in a cavity formed in a clamped state between a fixed mold and a movable mold and injecting a molten resin material into the cavity As a result, a flat disk substrate to which the grooves are transferred is formed.
[0004]
Molding devices are roughly classified into two types, a direct pressure method and a toggle method (for example, Non-Patent Document 1). FIG. 7 shows a schematic view of the conventional two-type mechanism.
[0005]
FIG. 7A shows the case of the direct pressure method. Reference numeral 101 denotes a fixed mold, which is attached to the large plate 103 with bolts or the like. A movable mold 102 is attached to the large plate 104 with bolts or the like. The movable mold 102 is driven by the hydraulic circuit 106 to drive the piston 107 and translates using the tie bar 105 provided on the large plate 104 as a guide, and is engaged with or separated from the fixed mold 101. In this case, clamping of the fixed mold 101 and the movable mold 102 and adjustment of the clamping pressure are performed by the hydraulic circuit 106.
[0006]
FIG. 7B shows the toggle method. Reference numeral 101 denotes a fixed mold, which is attached to the large plate 103 with bolts or the like. A movable mold 102 is attached to the large plate 104 with bolts or the like. The movable mold 102 moves the toggle 110 by driving the piston 109 by the hydraulic circuit 108, and moves in parallel with the tie bar 105 provided on the large plate 104 as a guide so that the movable mold 102 can be engaged with or separated from the fixed mold 101. To do. Adjustment of the clamping pressure between the fixed mold 101 and the movable mold 102 is performed by a hydraulic circuit 111 provided via hydraulic pipes 113 connected to the four tie bars 105. The injection compression pressure after closing the mold is applied to the large plate 104 by a hydraulic circuit 112 provided at a position facing the movable mold 102.
[0007]
Attempts have been made to mold a substrate for a higher density optical disk using the molding apparatus.
[0008]
[Non-Patent Document 1]
"Plastic Technology Reader" by Yujiro Sakurauchi, Industrial Research Committee, 1993
[0009]
[Problems to be solved by the invention]
However, as an example, it is difficult to form a polycarbonate resin substrate having an outer diameter of about 120 mm, a plate thickness of about 1.2 mm, a track pitch of about 1.0 μm, and a pit depth of about 110 nm from the viewpoint of transferability.
[0010]
Further, in order to increase the density, it is necessary to increase the aperture of the objective lens in order to improve the aperture of the light irradiated to the optical disk. In this case, the aberration due to tilt is proportional to the plate thickness and proportional to the third power of the aperture. Therefore, if the plate thickness is not reduced, it becomes difficult to control the pickup. Such a thin substrate molding causes a resin to flow through a thinner gap, and there is a problem that birefringence and warpage are worsened because the resin is easily cooled and transfer is difficult to obtain and stress is easily received. Such thin substrate molding causes a resin to flow through a narrower gap, and since the resin is easily cooled, there is a problem that transfer is difficult to obtain and birefringence and warpage deteriorate. In other words, since resin flows through a narrower gap, a large velocity gradient occurs near the mold surface, and shear stress is generated between the solid layer generated by cooling on the mold wall surface and the fluidized bed in the center due to viscous friction. To do. As a result, the resin undergoes molecular orientation and solidifies without being relaxed, and the residual stress is frozen. In the central part, the residual stress is frozen while receiving a uniform hydrostatic pressure. Certain atomic groups in the polymer are oriented in a certain direction due to stress, resulting in birefringence. Further, the residual stress is not uniform in the surface direction of the substrate and is not necessarily symmetric in the thickness direction, and warps.
[0011]
In order to solve the above-described conventional problems, the present invention provides a method for producing a high-density optical disk substrate that is practically sufficient for transfer and birefringence of a substrate as a disk in molding a thin resin substrate having a plate thickness of 1 mm or less, and An object is to provide a manufacturing apparatus.
[0012]
[Means for Solving the Problems]
In order to solve the above-described object, the disk substrate manufacturing method according to the present invention injects molten resin into a cavity having an inlet formed between a pair of molds, and presses the mold to increase the cavity thickness. In the injection compression molding method of the disk substrate for narrowing the depth, an inlet for filling the molten resin between 0.1 second before and 0.3 second after the time when the pressure of the resin filled in the cavity is minimized is provided. The compression process is started upon closing.
[0013]
In the above method, it is preferable to control at least the temperature of the mold mirror surface on the side where the stamper is mounted to be lower than the glass transition temperature of the resin material in the range of 5K to 25K.
[0014]
In the above method, A step of drying the resin before injecting the molten resin into the cavity, and melting the resin after drying It is preferable.
[0015]
Next, the disk substrate manufacturing apparatus of the present invention injects molten resin into a cavity formed between a pair of molds, and presses the mold to reduce the cavity thickness. In the molding apparatus, an opening / closing means for opening and closing the pair of molds, a heating means for melting the resin, an injection means for filling the cavity between the pair of closed molds, and a resin filled in the cavity Pressure holding means for preventing backflow to the inflow side, compression means for tightening the pair of molds after filling, and means for detecting a time during which the pressure of the resin filled in the cavity is minimized, the pressure At least one operation selected from the operation of closing the inlet for injecting the molten resin into the cavity and the operation of starting the compression process is performed from 0.3 min to a time after 0.3 sec. .
[0016]
The apparatus of the present invention preferably includes a control means for controlling the temperature of at least the mold mirror surface on the side where the stamper is mounted to be lower than the glass transition temperature of the resin material in the range of 5K to 25K.
[0017]
In the apparatus of the present invention, in the pressure holding process, the pressure received by the screw after injecting the molten resin is monitored, the first zero cross time of the signal obtained by differentiating the monitor signal is detected, and the metal without the core pushing mechanism is detected. It is preferable to provide means for operating the cut punch protrusion hydraulic circuit and the mold clamping hydraulic circuit after a predetermined time for the mold to switch the cut punch protrusion and the mold clamping force from low pressure to high pressure.
[0018]
In the apparatus of the present invention, in the pressure holding process, the pressure received by the screw after injecting the molten resin is monitored, the first zero cross time of the signal obtained by differentiating the monitor signal is detected, and the metal having the core pushing mechanism is detected. It is preferable that the die is provided with means for operating the cut punch protrusion hydraulic circuit and the injection compression hydraulic circuit after a predetermined time to switch the cut punch protrusion and injection compression force from low pressure to high pressure.
[0019]
The apparatus of the present invention preferably further comprises means for drying the resin before melting the resin.
[0020]
According to the manufacturing method of the present invention, it is possible to manufacture a high-density optical disk substrate that is excellent in transferability and has a birefringence that is practically sufficient as a disk by using a thin resin substrate. That is, when molten resin is filled in a cavity formed between a pair of closed molds, the cavity thickness is wider than when the mold is completely closed, so that the resin flow is improved, and Since the pressure applied from the mold to the molten resin is made as low as possible to control the plate thickness, the stress generated in the molten resin is also reduced, and the birefringence of the molded resin substrate is reduced.
[0021]
In addition, since the resin inlet is closed in the vicinity of the time when the pressure received by the molten resin filled in the cavity formed between the pair of closed molds is minimized, the residual stress in the molten resin is reduced. By starting the compression process before the resin is solidified, transfer and birefringence of the molded resin substrate are improved. Also, transfer and birefringence can be improved by appropriately selecting the adjustment temperature of the mold mirror surface.
[0022]
Furthermore, the time during which the pressure received by the molten resin filled in the cavity formed between the pair of closed molds is minimized varies depending on the molding conditions, and this time is detected to close the molten resin inlet. By starting the operation and compression process, stable substrate transfer and birefringence can always be obtained.
[0023]
Further, according to the manufacturing apparatus of the present invention, when the resin is filled into the cavity, the cavity thickness and the injection compression force are specified to reduce the stress applied to the resin and to reduce the birefringence. In addition, the mold temperature is specified to improve the resin flow, stop the resin inflow when the pressure at the time of resin filling is minimal, and start the compression process to achieve good transfer and reduction of birefringence. be able to. As a result, a disk substrate can be manufactured reasonably and efficiently.
[0024]
According to the manufacturing apparatus of the present invention, when the molten resin is filled in the cavity formed between the pair of closed molds, the cavity thickness is wider than when the mold is completely closed. The pressure applied to the molten resin from the mold is as low as possible to control the plate thickness, so the stress generated in the molten resin is also reduced, and the birefringence of the molded resin substrate is reduced. Become.
[0025]
In addition, since the resin inlet is closed in the vicinity of the time when the pressure received by the molten resin filled in the cavity formed between the pair of closed molds is minimized, the residual stress in the molten resin is reduced. By starting the compression process before the resin is solidified, transfer and birefringence of the molded resin substrate are improved. Also, transfer and birefringence can be improved by appropriately selecting the adjustment temperature of the mold mirror surface.
[0026]
Furthermore, the time during which the pressure received by the molten resin filled in the cavity formed between the pair of closed molds is minimized varies depending on the molding conditions, and this time is detected to close the molten resin inlet. By starting the operation and compression process, stable substrate transfer and birefringence can always be obtained.
[0027]
Further, if a means for drying the resin is further provided before the resin is melted, a decrease in molecular weight due to hydrolysis of the resin can be prevented.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described more specifically with reference to embodiments.
[0029]
(Embodiment 1)
First, an injection compression molding method in the case of a toggle type molding apparatus will be described.
[0030]
FIG. 3 is a schematic view showing a configuration of a molding apparatus according to an embodiment used in the present invention. 1 is a material drying apparatus, and resin materials used for general disk molding such as polycarbonate resin, poly (meth) acrylate resin, urethane resin, and polyester resin absorb moisture in the air. This is to prevent the molecular weight from decreasing due to hydrolysis. The drying method is preferably hot air circulation drying or vacuum drying. As a preferable drying condition of the hot air circulation drying, when a polycarbonate resin is taken as an example, the polycarbonate resin pellets are dried in a temperature range of 100 to 130 ° C. for 2 to 10 hours. In the case of vacuum drying, vacuum drying is performed at a temperature in the range of 60 to 120 ° C. for 1 to 10 hours and in a vacuum degree of about 0.1 to 100 torr. It is preferable that the water absorption of the polycarbonate resin pellets is 0.015 wt% or less by this drying treatment. In the following examples, a drying process was performed using a hot air circulating dryer under the conditions of temperature: 120 ° C. and time: 6 hours. The water absorption of the polycarbonate resin pellet was set to 0.015 wt% or less.
[0031]
In addition, the polycarbonate resin used in the following examples was a resin having a melting point of 240 ° C. and a glass transition temperature of 150 ° C.
[0032]
Resin material is supplied from the material drying device 1 to the hopper 2 by warm air. As the resin material, pellets having a certain size are used. The resin material in the hopper 2 is guided to the screw 3. The screw 3 is rotated by the motor 4 and the resin material is heated by the heating cylinder 5. In this process, the resin is melt-kneaded. 6 is a stationary mold, and 7 is a movable mold. As shown in FIG. 7B, the fixed mold 6 and the movable mold 7 are fixed to the large plate with bolts or the like. Further, the movable mold 7 is separated from or fitted to the fixed mold 6 by the mold opening and closing mechanism shown in FIG. In addition, 36 of FIG. 3 is a mount.
[0033]
A mold clamping pressure is applied in a state where the fixed mold 6 and the movable mold 7 are closed, and the screw 3 is advanced by the hydraulic circuit 8 without rotating. As a result, the molten resin material is injected into the cavity 10 through the nozzle 9 (injection process). Since the time of the injection process is a short time of 1 second or less, it is controlled by the position of the screw.
[0034]
When the resin material is filled into the cavity 10, the resin material tends to recirculate to the screw 3 side, so that pressure is applied to the screw 3 by the hydraulic circuit 8 (pressure holding step).
[0035]
Next, in a state where the movable mold 7 is clamped to the fixed mold 6 by the hydraulic circuit 111 via the tie bar 105, the injection compression pressure is applied to the core portion of the movable mold 7 by the hydraulic circuit 112 (see FIG. 7B). And then cooled to a temperature below the glass transition temperature of the polymer (cooling step), the movable mold 7 is separated from the fixed mold 6, and the molded substrate is taken out. The compression step and the cooling step may be performed separately or simultaneously.
[0036]
Next, the structure of the mold used in the present embodiment is shown in FIG. The case where the stamper 11 is mounted on the movable mold 7 side is shown. A stamper inner periphery presser 12 is attached to the inner periphery of the stamper 11, and a stamper outer periphery presser 13 is attached to the outer periphery of the stamper 11. The stamper outer periphery presser 13 also serves to define the outer diameter of the molded substrate.
[0037]
The stamper 11 is in intimate contact with the movable mold mirror section 14, and the movable mold mirror section 14 is provided with a cooling water passage 15, and is controlled so that the cooling water flows and reaches a constant temperature. The movable mold mirror unit 14 is integrated with the movable mold base 16 through bolts or the like via an O-ring.
[0038]
A floating punch 17, a cut punch 18, and a protruding pin 19 are provided at the center of the movable mold 7. The cut punch 18 is provided with a hole in the central portion of the molded substrate. The floating punch 17 and the projecting pin 19 operate so as to mechanically push out the substrate product portion and the unnecessary portion (sprue portion) that becomes a hole, respectively, when the substrate is taken out after molding.
[0039]
There is a movable mold abutting ring 20 on the outer peripheral portion of the movable mold 7, and the minimum thickness of the cavity 10 formed in the mold is defined by abutting against the fixed mold abutting ring 21 of the fixed mold 6. is doing. Further, there is a movable mold guide ring 22 outside the movable mold abutting ring 20, and the maximum thickness of the cavity 10 formed in the mold is defined by abutting against the fixed mold guide ring 23. . That is, the mold is clamped by contact with the movable mold guide ring 22 and the fixed mold guide ring 23, and the movable mold 7 is fixed until the movable mold abutment ring 20 and the fixed mold abutment ring 21 are in contact with each other. The core part moves and injection compression is performed.
[0040]
In the fixed mold 6, a fixed mold abutment ring 21, a fixed mold guide ring 23, and a fixed mold mirror unit 25 are attached to the fixed mold base 24. The fixed mold mirror unit 25 is provided with a cooling water passage 26, and the cooling water is supplied to the fixed die mirror unit 25 so that the temperature becomes constant.
[0041]
There is a sprue bush 27 at the center of the fixed mold 6, and the molten resin injected from the nozzle 9 (see FIG. 3) flows into the cavity 10 through the sprue bush 27. In order to remove the resin in the sprue bush 27 after the molding, the sprue bush 27 is cooled, and the resin contracts and peels when solidified. A fixed bush 28 is provided around the sprue bush 27 and serves to insulate the sprue bush 27 and the fixed mold mirror 25.
[0042]
In order to peel the molded substrate from the stamper 11, an air blow is used in addition to the mechanical mechanism of the floating punch 17, and from the movable mold 7 side, between the stamper inner peripheral presser 12 and the floating punch 17, the fixed mold 6. On the side, compressed air is blown (or passed) from between the fixed mold mirror 25 and the fixed bush 28.
[0043]
Table 1 shows the correspondence between the minimum cavity thickness (at room temperature, desired substrate thickness reference), the minimum controllable plate thickness (desired substrate thickness reference), and the maximum absolute value of birefringence at the desired substrate thickness. The maximum cavity thickness was 0.2 mm thicker than the desired substrate thickness. The difference between the maximum and minimum values of the cavity thickness is called a compression allowance. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 125 ° C., and the sprue temperature was 60 ° C. The clamping force was 40 tons. The injection compression force was 4 tons when the molten resin was filled, and 20 tons in the compression step after holding pressure. The molding cycle was 15 seconds.
[0044]
Birefringence refers to one of the properties of light propagating in an anisotropic polymer, and refers to a phenomenon in which two refracted lights appear when light enters the anisotropic polymer. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value.
[0045]
[Table 1]

[0046]
From Table 1, birefringence is 50 nm or less when the minimum cavity thickness is 0.1 mm or less than the desired substrate thickness. The birefringence becomes a large value when obliquely incident on a polycarbonate resin substrate having a birefringence of 50 nm by this normal incidence. In the case of 30 degree incidence, it is about 100 nm. In addition, the irradiation light to the optical disk is focused light, and a high-density optical disk using a high objective lens having a high aperture of 0.6 or more requires a birefringence of 50 nm for vertical incidence even if it is a reproduction type. Further, in order to obtain the desired substrate thickness, only the opening direction between the molds can be controlled, so that the minimum cavity thickness cannot be greater than the desired substrate thickness. Therefore, it was confirmed that the minimum cavity thickness should be reduced from 0 mm to 0.1 mm with respect to the desired substrate thickness.
[0047]
Next, the maximum cavity thickness was examined. The minimum cavity thickness is made 0.05 mm thinner than the desired substrate thickness. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 125 ° C., and the sprue temperature was 60 ° C. The clamping force was 40 tons. The injection compression force was 4 tons when the molten resin was filled, and 20 tons in the compression step after holding pressure. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value. The measurement results are shown in Table 2.
[0048]
[Table 2]

[0049]
From Table 2, the larger the compression allowance, the better the birefringence and the greater the shot variation in the plate thickness. The larger the compression allowance, the thicker the cavity 10 becomes when the molten resin is filled into the cavity 10, so that the molten resin flows more easily, but the resin is cooled to adjust the thickness of the substrate. This is because it requires a large amount of movement to close the mold.
[0050]
From Table 2, the absolute value of birefringence is 50 nm or less when the compression allowance is 0.15 mm or more, and the shot variation of the plate thickness is ± 35 μm or less when the compression allowance is 0.3 mm This is the case. Here, the reference for the variation in the plate thickness is ± 35 μm. However, if the variation in the plate thickness exceeds ± 35 μm, the aberration increases and affects reading of the signal. The reference birefringence of 50 nm is as described in Table 1.
[0051]
From Table 2, it was confirmed that the compression allowance, that is, the difference between the maximum cavity thickness and the minimum cavity thickness is preferably 0.15 mm or more and 0.3 mm or less.
[0052]
Table 3 shows the relationship between the injection compression force and the birefringence during filling of the molten resin. The minimum cavity thickness was 0.05 mm thinner than the desired substrate thickness, and the compression allowance was 0.2 mm. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 125 ° C., and the sprue temperature was 60 ° C. The clamping force was 40 tons. The injection compression force in the compression process after holding pressure was 20 tons. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, parallel light was vertically incident, and a double pass value was obtained.
[0053]
[Table 3]

[0054]
From Table 3, the absolute value of birefringence was 50 nm or less when the injection compression force during resin filling was 10 tons or less. In this case, before the molten resin is filled into the cavity 10, the thickness of the cavity 10 is minimized by the injection compression force. However, when the molten resin is filled into the cavity 10, the resin pressure is better. Since it is large, the thickness of the cavity 10 increases to the maximum. As a result, the flow of the resin is improved, the stress applied to the resin is reduced, and the birefringence is improved.
[0055]
(Embodiment 2)
In the present embodiment, the case where the molding apparatus is a direct pressure system will be described. In the case of a toggle-type molding apparatus as shown in FIG. 7B, the opening and closing of the mold, the clamping of the mold and the injection compression are divided into a hydraulic circuit 108, a hydraulic circuit 111 and a hydraulic circuit 112, respectively. Is done. On the other hand, as shown in FIG. 7A, in the case of the direct pressure system, the opening and closing of the mold, the mold clamping and the injection compression are performed only by the hydraulic circuit 106.
[0056]
The structure of the mold is shown in FIG. Compared with the case of FIG. 1 in which the core is moved, the structure is such that there is no fixed mold guide ring 23 and no movable mold guide ring 22. In the case of FIG. 1, the structure defines the minimum cavity thickness and the maximum cavity thickness, whereas in FIG. 2, the structure defines only the minimum cavity thickness.
[0057]
Table 4 shows correspondence between the minimum cavity thickness (at room temperature, desired substrate thickness reference), the minimum controllable plate thickness (desired substrate thickness reference), and the maximum absolute value of birefringence at the desired substrate thickness. The maximum cavity thickness was 0.2 mm thicker than the desired substrate thickness. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 125 ° C., and the sprue temperature was 60 ° C. The first mold clamping force was 4 tons, and the second mold clamping force was 20 tons. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value.
[0058]
[Table 4]

[0059]
From Table 4, the birefringence is 50 nm or less when the minimum cavity thickness is 0.1 mm or less than the desired substrate thickness. Further, in order to obtain the desired substrate thickness, only the opening direction between the molds can be controlled, so that the minimum cavity thickness cannot be greater than the desired substrate thickness. Therefore, it was confirmed that the minimum cavity thickness should be reduced from 0 mm to 0.1 mm with respect to the desired substrate thickness.
[0060]
Next, consider the maximum cavity thickness. The minimum cavity thickness is made 0.05 mm thinner than the desired substrate thickness. The opening amount of the mold was measured using a laser displacement meter. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 125 ° C., and the sprue temperature was 60 ° C. The first mold clamping force was 4 tons, and the second mold clamping force was 20 tons. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value. Table 5 shows the measurement results.
[0061]
[Table 5]

[0062]
From Table 5, the larger the compression allowance, the better the birefringence, and the shot variation of the plate thickness increases.
[0063]
From Table 5, the absolute value of birefringence is 50 nm or less when the compression allowance is 0.15 mm or more, and the shot variation of the plate thickness is ± 35 μm or less when the compression allowance is 0.3 mm This is the case. Therefore, it was confirmed that the compression allowance, that is, the difference between the maximum cavity thickness and the minimum cavity thickness is preferably 0.15 mm or more and 0.3 mm or less.
[0064]
Table 6 shows the relationship between the first mold clamping force and the birefringence when the molten resin is filled. The minimum cavity thickness was 0.05 mm thinner than the desired substrate thickness, and the compression allowance was 0.2 mm. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 125 ° C., and the sprue temperature was 60 ° C. The second mold clamping force was 20 tons. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value.
[0065]
[Table 6]

[0066]
From Table 6, the absolute value of birefringence was 50 nm or less when the first mold clamping force was 10 tons or less. In this case, when the molten resin is filled in the cavity 10, the resin pressure is larger, so that the thickness of the cavity 10 is widened. As a result, the flow of the resin is improved, the stress received by the resin is reduced, and the birefringence is reduced. Will be better.
[0067]
In the present embodiment, the case of the direct pressure type molding apparatus is shown, but even in the case of the toggle type molding apparatus, the same operation can be performed using the mold having the structure of FIG. In the case of the toggle type molding apparatus, the mold clamping is performed using only the mold clamping mechanism without using the injection compression mechanism for moving the core portion as in the first embodiment. In this way, it was confirmed that the same results were obtained as a result of setting the same molding conditions as in the case of the direct pressure molding apparatus in the toggle molding apparatus.
[0068]
(Embodiment 3)
In the first embodiment and the second embodiment, the force pushing the cavity 10 is set in two stages, the first force is set low, and the second force is set high. Here, the case where the force pushing the cavity 10 is one stage was examined. A mold having the structure of FIG. 2 was used. A direct pressure type molding apparatus was used.
[0069]
Table 7 shows the correspondence between the minimum cavity thickness (at room temperature, desired substrate thickness reference), the minimum controllable plate thickness (desired substrate thickness reference), and the maximum absolute value of birefringence at the desired substrate thickness. The maximum cavity thickness was 0.2 mm thicker than the desired substrate thickness. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 130 ° C., and the sprue temperature was 60 ° C. The clamping force was 8 tons. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value.
[0070]
[Table 7]

[0071]
From Table 7, the birefringence is 50 nm or less when the minimum cavity thickness is 0.1 mm or less than the desired substrate thickness. Further, in order to obtain the desired substrate thickness, only the opening direction between the molds can be controlled, so that the minimum cavity thickness cannot be greater than the desired substrate thickness. Therefore, it was confirmed that the minimum cavity thickness should be reduced from 0 mm to 0.1 mm with respect to the desired substrate thickness.
[0072]
Next, consider the maximum cavity thickness. The minimum cavity thickness is made 0.05 mm thinner than the desired substrate thickness. The opening amount of the mold was measured using a laser displacement meter. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 130 ° C., and the sprue temperature was 60 ° C. The clamping force was 8 tons. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value. Table 8 shows the measurement results.
[0073]
[Table 8]

[0074]
From Table 8, the larger the compression allowance, the better the birefringence and the greater the shot thickness variation.
[0075]
From Table 8, the absolute value of birefringence is 50 nm or less when the compression allowance is 0.15 mm or more, and the shot variation of the plate thickness is ± 35 μm or less when the compression allowance is 0.3 mm This is the case. Therefore, it was confirmed that the compression allowance, that is, the difference between the maximum cavity thickness and the minimum cavity thickness is preferably 0.15 mm or more and 0.3 mm or less.
[0076]
Table 9 shows the relationship between the mold clamping force, the birefringence and the plate thickness at the time of filling the molten resin. The minimum cavity thickness was 0.05 mm thinner than the desired substrate thickness, and the compression allowance was 0.2 mm. The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The signal area of the stamper 11 was a pit having a track pitch of 1.0 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 130 ° C., and the sprue temperature was 60 ° C. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value.
[0077]
[Table 9]

[0078]
From Table 9, the absolute value of birefringence was 50 nm or less when the mold clamping force was 10 tons or less. In this case, when the molten resin is filled in the cavity 10, the resin pressure is larger, so that the thickness of the cavity 10 is widened. As a result, the flow of the resin is improved, the stress received by the resin is reduced, and the birefringence is reduced. Will be better. Moreover, the shot variation of the plate thickness became ± 35 nm or less when the clamping force was 6 tons or more. This is because the maximum cavity thickness decreases as the mold clamping force increases, and the amount of movement of the cavity surface decreases during cooling. Therefore, it was confirmed that when the clamping force is one step, the clamping force is preferably 6 to 10 tons.
[0079]
In the present embodiment, the case of a direct pressure type molding apparatus is shown, but the same operation can be performed even in the case of a toggle type molding apparatus. Also in the case of a toggle type molding apparatus, the mold clamping is performed using only the mold clamping mechanism without using the injection compression mechanism for moving the core portion as in the first embodiment. In this way, it was confirmed that the same results were obtained as a result of setting the same molding conditions as in the case of the direct pressure molding apparatus in the toggle molding apparatus.
[0080]
(Embodiment 4)
According to the manufacturing method as in the first to third embodiments, a pit substrate made of polycarbonate resin, having an outer diameter of 120 mm, a thickness of 0.6 mm, a signal area of a track pitch of 1.0 μm, and a depth of 110 nm. In the case of molding, the characteristic that the absolute value of birefringence is 50 nm or less can be obtained when the resin temperature is 380 ° C. and the mold temperature is 120 ° C. or more. In this case, the transfer of pits is sufficient.
[0081]
Therefore, the case of forming a substrate having a higher density signal portion was examined. The signal area of the stamper 11 was a pit having a track pitch of 0.6 μm and a depth of 110 nm. In this case, when formed by the manufacturing method of the first and second embodiments, the pit depth was in the 70 nm range and the maximum absolute value of birefringence was in the 80 nm range. First, a toggle type molding apparatus was examined.
[0082]
In order to improve the transfer, in the case of the mold shown in FIG. 1, when the injection compression force is increased, the resin in the cavity 10 is distorted and the absolute value of birefringence is increased. In the case of the mold shown in FIG. 2, the absolute value of the birefringence increased when the clamping force was increased. Therefore, Table 10 shows the results of measuring the pit depth by changing the mold temperature and the sprue temperature, which are molding conditions for which the absolute value of birefringence is 50 nm or less. The mold temperature was controlled to be the same between the fixed mold 6 and the movable mold 7. The resin temperature was fixed at 380 ° C. which is considered to be the upper limit in consideration of the decomposition start temperature of the polycarbonate. The molding cycle was 15 seconds.
[0083]
[Table 10]

[0084]
Table 10 shows that if the mold temperature is 130 ° C., a track pitch of 0.6 μm and a pit depth of 110 nm are transferred. However, it was found that a substrate molded at a mold temperature of 145 ° C. cannot be used as a substrate for an optical disk because it is warped in a propeller shape. It was also found that the influence of the sprue temperature was small.
[0085]
The mold temperature generally refers to the control temperature of the medium flowing in the mold. However, in actual molding, the temperature of the cavity 10 into which the molten resin flows is important. Therefore, the mirror surface temperature in the vicinity of the surface of the cavity 10 that rises and falls within one molding cycle is measured, and the temperature at which the molten resin flows in is determined. This temperature is referred to as the mold mirror surface temperature here. To do. The mold mirror surface temperature at a mold temperature of 145 ° C. in which the substrate was warped in a propeller shape was a glass transition temperature of polycarbonate of 150 ° C. Thus, it has been found that the mold mirror surface temperature must be controlled to be lower than the glass transition temperature of the resin material, preferably 5 ° C. or more. The mold mirror surface temperature at the mold temperature of 130 ° C. was 135 ° C.
[0086]
Here, Table 11 shows the result of changing the temperature of the fixed mold 6 by fixing the temperature of the movable mold 7 on which the stamper 11 is mounted to 135 ° C. The sprue temperature was 60 ° C.
[0087]
[Table 11]

[0088]
It can be seen from Table 11 that the mold temperature without the stamper does not affect the transfer. Therefore, if the temperature of the mold on which the stamper is mounted is at least 130 ° C., the transfer of pits with a track pitch of 0.6 μm and a depth of 110 nm is satisfactory.
[0089]
From the above, in order to obtain a practical product by forming a substrate having an outer diameter of 120 mm and a thickness of 0.6 mm, at least the mold mirror surface temperature of the stamper mounted is the glass transition temperature of the resin material. Further, it has been found that it must be 5K or more and 25K or less, preferably 5K or more and 15K or less.
[0090]
Here, the molding cycle was fixed at 15 seconds. When this molding cycle is shortened, the mold mirror surface temperature is increased even if the mold temperature is the same. Therefore, if the molding cycle is changed to 15 seconds, 12 seconds, and 8 seconds, and the relationship between the mold mirror surface temperature and transfer and birefringence is examined, the mold mirror surface temperature at which sufficient transfer and birefringence of 50 nm or less can be obtained is the molding temperature. It turns out that it does not depend on the cycle.
[0091]
2 is the same as the case where the mold of FIG. 1 or FIG. 2 is mounted on a toggle type molding apparatus, the outer diameter is 120 mm, In order to obtain a practical product by molding a substrate having a thickness of 0.6 mm, at least the mold mirror surface temperature of the stamper mounted is 5K or more and 25K or less, preferably 5K or more than the glass transition temperature of the resin material. It was found that it must be lowered by 15K or less.
[0092]
(Embodiment 5)
Next, the relationship between the pressure applied to the molten resin and birefringence was examined. Here, the case where the metal mold | die of FIG. 1 is mounted in the toggle type | molding apparatus is demonstrated. Since the pressure received by the molten resin cannot be directly detected, the pressure received by the screw is substituted for the reaction force of the molten resin and detected by a pressure gauge provided in the hydraulic circuit 8 of FIG. The detected pressure in this case showed a time change as shown in FIG. The injection process has a peak pressure, shows a minimum value at the beginning of the pressure holding process, and gradually increases in pressure. The peak pressure is indicated because the molten resin is filled even after the molten resin is filled in the cavity 10, and the minimum value is indicated in the pressure holding step because the molten resin that has not fully entered the cavity 10 is sprue. The reason is that the bush 27, the nozzle 9, and the screw 3 circulate and collide with the molten resin extruded by the screw 3. In addition, it is considered that the pressure of the resin gradually increases after that because of holding pressure.
[0093]
Based on the pressure change in FIG. 4, the filling of the molten resin into the cavity 10 was stopped in the vicinity of the time when the pressure of the molten resin was minimized. Specifically, the cut punch 18 of FIG. 1 was protruded. Further, the injection compression force was changed from 4 tons to 20 tons almost simultaneously when the cut punch 18 was protruded. That is, the compression process was started. Table 12 shows the results.
[0094]
The substrate outer diameter was 120 mm, and the desired substrate thickness was 0.6 mm. The minimum cavity thickness was 0.05 mm thinner than the desired substrate thickness, and the compression allowance was 0.2 mm. The signal area of the stamper 11 is a pit having a track pitch of 0.6 μm and a depth of 110 nm. Polycarbonate resin was used as the resin material. The resin temperature was 380 ° C., the mold temperature was 135 ° C., and the sprue temperature was 60 ° C. The clamping force was 40 tons. The molding cycle was 15 seconds. For birefringence measurement, a helium neon gas laser was used, and parallel light was vertically incident to obtain a double pass value.
[0095]
[Table 12]

[0096]
From Table 12, the absolute value of the birefringence is 50 nm or less from 0.3 hours after the time when the pressure received by the molten resin is minimized.
[0097]
The compression process should be started at the same time or earlier when the filling of the molten resin into the cavity 10 is stopped. This is because the pressure acting on the resin in the cavity 10 is relieved by the start of the compression process. Further, in the time earlier than 0.15 seconds from the time when the pressure received by the molten resin is minimized, the thickness variation of the substrate is as large as ± 50 μm or more. Therefore, it is preferable to close the injection port for filling the molten resin 0.1 seconds before and 0.3 seconds after the time when the pressure received by the molten resin is minimized, or to start the compression process.
[0098]
In the present embodiment, the molding apparatus is a toggle system, but even with the direct pressure system, the first mold clamping force is 4 tons and the second mold clamping force is 20 tons, and other conditions are set the same as in the toggle system. However, similar results were obtained.
[0099]
Embodiments 1 to 5 deal with polycarbonate resin, but other resins may of course be used.
[0100]
(Embodiment 6)
In the fifth embodiment, the relationship between the pressure received by the resin in the cavity 10 and birefringence was examined. The minimum time of the pressure of the molten resin in the cavity 10 varies depending on the molding apparatus and molding conditions. Therefore, the disk substrate manufacturing apparatus of the present invention detects the minimum time of the pressure of the molten resin in the cavity 10 and puts the molten resin in the cavity after 0 to 0.3 seconds from the time when the pressure becomes minimum. The operation of closing the inlet port or the operation of starting the compression process is performed.
[0101]
The specific mechanism is as shown in FIG. That is, the pressure detector 29 receives a change in pressure in the cavity 10 over time and converts it into a voltage change. Next, the pressure minimum time detector 30 detects the time when the pressure is minimized. Specifically, the first zero cross time in the pressure holding process is detected by differentiating the electric signal from the pressure detector 29 received by the screw. FIG. 6 shows a method of detecting this zero crossing time. The signal (a) is a signal from the detector 29 of the pressure received by the screw. Signal (b) is a differential signal of signal (a). The zero cross detection pulse signal of the signal (b) is the signal (c). The signal (d) is a gate signal indicating a positive value after the pressure holding process. Here, when the product of the signal (c) and the signal (d) is obtained, the signal (e) is obtained, and this signal (e) indicates the time when the signal (b) first becomes a zero cross in the pressure holding process. Processing from this signal (b) to signal (e) is performed by the pressure minimum time detector 30.
[0102]
Next, the timers 31 and 32 are operated based on the minimum pressure time, and in the case of a die without a core pushing mechanism as shown in FIG. 2, the cut punch protrusion hydraulic circuit 33 and the mold clamping hydraulic circuit 34 are operated after a predetermined time. Then, the protrusion of the cut punch and the first mold clamping are switched to the second mold clamping. In the case of a die having a core pushing mechanism as shown in FIG. 1, the cut punch protrusion hydraulic circuit 33 and the injection compression hydraulic circuit 35 are operated after a predetermined time to switch the cut punch protrusion and the injection compression force to a high pressure. . The time of the timer 31 and the timer 32 is 0 second to 0.3 second, and the time of the timer 32 is preferably equal to or shorter than the time of the timer 31.
[0103]
As a result, the same result as in the fifth embodiment was obtained.
[0104]
The entire configuration of the disk substrate manufacturing apparatus of the present invention includes an opening / closing means for opening and closing a pair of molds, a heating means for melting the resin, and an injection means for filling the molten resin into a cavity between the pair of closed molds. Pressure holding means for preventing backflow of the resin filled in the cavity to the inflow side, compression means for tightening the pair of molds after filling, and time for minimizing the pressure of the resin filled in the cavity. It has means for detecting, and after 0 to 0.3 seconds from the time when the pressure becomes minimum, the operation for closing the inlet for flowing the molten resin into the cavity or the operation for starting the compression process is performed. .
[0105]
【The invention's effect】
As described above, according to the present invention, the resin inlet is closed in the vicinity of the time when the pressure received by the molten resin filled in the cavity formed between the pair of closed molds is minimized. Residual stress in the resin is reduced, and the compression and birefringence of the molded resin substrate is improved by starting the compression step before the resin is solidified. Also, transfer and birefringence can be improved by appropriately selecting the adjustment temperature of the mold mirror surface.
[0106]
Furthermore, the time during which the pressure received by the molten resin filled in the cavity formed between the pair of closed molds is minimized varies depending on the molding conditions, and this time is detected to close the molten resin inlet. By starting the operation and compression process, stable substrate transfer and birefringence can always be obtained.
[0107]
Further, according to the manufacturing apparatus of the present invention, when the resin is filled into the cavity, the cavity thickness and the injection compression force are specified to reduce the stress applied to the resin and to reduce the birefringence. In addition, the mold temperature is specified to improve the resin flow, stop the resin inflow when the pressure at the time of resin filling is minimal, and start the compression process to achieve good transfer and reduction of birefringence. be able to. As a result, a disk substrate can be manufactured reasonably and efficiently.
[0108]
According to the manufacturing apparatus of the present invention, when the molten resin is filled in the cavity formed between the pair of closed molds, the cavity thickness is wider than when the mold is completely closed. The pressure applied to the molten resin from the mold is as low as possible to control the plate thickness, so the stress generated in the molten resin is also reduced, and the birefringence of the molded resin substrate is reduced. Become.
[0109]
In addition, since the resin inlet is closed in the vicinity of the time when the pressure received by the molten resin filled in the cavity formed between the pair of closed molds is minimized, the residual stress in the molten resin is reduced. By starting the compression process before the resin is solidified, transfer and birefringence of the molded resin substrate are improved. Also, transfer and birefringence can be improved by appropriately selecting the adjustment temperature of the mold mirror surface.
[0110]
Furthermore, the time during which the pressure received by the molten resin filled in the cavity formed between the pair of closed molds is minimized varies depending on the molding conditions, and this time is detected to close the molten resin inlet. By starting the operation and compression process, stable substrate transfer and birefringence can always be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional side view showing a configuration of a mold used in Embodiments 1 and 4 to 6 of the present invention.
FIG. 2 is a cross-sectional side view showing a configuration of a mold used in Embodiments 2 to 4 and Embodiment 6 of the present invention.
FIG. 3 is a cross-sectional side view showing a configuration of a molding apparatus used in Embodiments 1 to 6 of the present invention.
FIG. 4 is a diagram showing a change with time of pressure received by a screw according to an embodiment of the present invention.
FIGS. 5 (a) and 5 (b) are functional explanatory block diagrams of a molding apparatus shown in Embodiment 6 of the present invention.
FIGS. 6 (a), (b), (c), (d), and (e) are signals at a pressure detector and a pressure minimum time detector received by a screw of a molding apparatus according to Embodiment 6 of the present invention. It is the figure which showed the process.
7 (a) and 7 (b) are plan views showing an outline of a mechanism portion of a conventional molding apparatus.
[Explanation of symbols]
1 Material dryer
2 Hoppers
3 Screw
4 Motor
5 Heating cylinder
6 Fixed mold
7 Movable mold
8 Hydraulic circuit
9 nozzles
10 cavities
11 Stamper
12 Stamper inner circumference presser
13 Stamper outer periphery presser
14 Movable mold mirror part
15 Cooling channel
16 Movable mold base
17 Floating punch
18 Cut punch
19 Protruding pin
20 Movable mold abutment ring
21 Fixed die abutment ring
22 Movable mold guide ring
23 Fixed mold guide ring
24 Fixed mold base
25 Fixed mold mirror part
26 Cooling water channel
27 Sprue bush
28 Fixed bushing
29 Pressure detector for screw
30 Pressure minimum time detector
31, 32 timer
33 Cut punch protruding hydraulic circuit
34 Clamping hydraulic circuit
35 Injection compression hydraulic circuit
36 frame
101 Fixed mold
102 Movable mold
103, 104 large plate
105 tie bar
106, 108, 111, 112 Hydraulic circuit
107, 109 piston
110 toggle
113 Hydraulic pipe

Claims (8)

  In a method for injection compression molding of a substrate for a disk, in which molten resin is injected into a cavity having an inlet formed between a pair of molds and the cavity thickness is reduced by pressing the mold, the cavity is filled. And closing the inlet for filling the molten resin between 0.1 seconds before and 0.3 seconds after the time when the pressure of the molten resin is minimized, and starting the compression process .   The stamper is mounted on at least one surface forming the cavity, and the temperature of the mold mirror surface on the side where the stamper is mounted is controlled to be lower than the glass transition temperature of the resin material in the range of 5K to 25K. A method for producing a disk substrate as described in 1. above. The method for manufacturing a disk substrate according to claim 1 , comprising a step of drying the resin before injecting the molten resin into the cavity, and melting the resin after drying .   In a disk substrate injection compression molding apparatus in which molten resin is injected into a cavity formed between a pair of molds, one of which has a stamper, and the mold is pressed, the pair of molds Open / close means for opening and closing, heating means for melting the resin, injection means for filling the cavity between the pair of molds in which the molten resin is closed, and prevention of backflow to the inflow side of the resin filled in the cavity Pressure holding means, compression means for further tightening the pair of molds after filling, and means for detecting the time when the pressure of the resin filled in the cavity becomes minimum, and the time from when the pressure becomes minimum is reduced to 0. 0. Manufacture of a disk substrate characterized by performing at least one operation selected from an operation of closing an inlet for flowing molten resin into a cavity and an operation of starting a compression process within a time period up to 3 seconds later Location.   5. The apparatus for manufacturing a disk substrate according to claim 4, further comprising control means for controlling at least the temperature of the mold mirror surface on the side on which the stamper is mounted within a range of 5K to 25K with respect to the glass transition temperature of the resin material. .   In the pressure holding process, the pressure received by the screw after the molten resin is injected is monitored, the first zero cross time of the signal obtained by differentiating this monitor signal is detected, and the cut punch protrusion hydraulic pressure is applied to the mold without the core pushing mechanism. 5. The disk substrate manufacturing apparatus according to claim 4, further comprising means for operating the circuit and the mold clamping hydraulic circuit after a predetermined time to switch the cut punch protrusion and the mold clamping force from low pressure to high pressure.   In the pressure holding process, the pressure received by the screw after injecting the molten resin is monitored, the first zero cross time of the signal obtained by differentiating this monitor signal is detected, and the cut punch protrusion hydraulic pressure is applied to the mold with the core pushing mechanism. The disk substrate manufacturing apparatus according to claim 4, further comprising means for operating the circuit and the injection compression hydraulic circuit after a predetermined time to switch the protrusion of the cut punch and the injection compression force from low pressure to high pressure.   The disk substrate manufacturing apparatus according to claim 4, further comprising means for drying the resin before melting the resin.

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