JP3933432B2

JP3933432B2 - Glass substrate clamping jig, glass substrate processing method, and glass substrate

Info

Publication number: JP3933432B2
Application number: JP2001317136A
Authority: JP
Inventors: 高正吉川; 浩治奥畑; 賢介松野; 武夫渡辺
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2001-09-10
Filing date: 2001-10-15
Publication date: 2007-06-20
Anticipated expiration: 2021-10-15
Also published as: JP2003159639A; MY136450A; US20050101230A1; US20030082999A1

Description

【０００１】
【発明の属する技術分野】
本発明は多数の円環状のガラス基板を重ねて保持するクランプ治具、このクランプ治具を用いて多数の円環状ガラス基板の内周端と外周端に研削（面取り又は研磨）を施す方法およびこの方法によって得られたガラス基板に関する
【０００２】
【従来の技術】
ガラスはアルミニウムに比較して、耐衝撃性、剛性、硬度、強度の面で優れているため、ハードディスクドライブ等に内蔵される磁気記録媒体として使用されつつある。
特に、最近ではパーソナルコンピュータの形態が、デスクトップ型からノートブック型やモバイル型に移行しつつあり、アルミニウム基板に代わって、平坦性、高密度化に優れるガラス基板の需要が増している。
【０００３】
磁気記録媒体用ガラス基板を得るには、ガラス素板から円盤状（ドーナッツ状）に切り抜き、この円盤状ガラス基板の周端面（内周端と外周端）に例えば特開平１０−１５４３２１号公報にも開示されるようにダイヤモンド砥石によるラッピングと、酸化セリウム懸濁液によるポリッシングを施し、この後、表裏の記録面（主表面）にアルミナ砥粒によるラッピングと、酸化セリウム懸濁液によるポリッシングを施すようにしている。
【０００４】
上述の方法ではガラス基板の加工が枚葉式で効率が悪いため、多数枚のガラス基板を同時に研磨する方法が特開平１１−２２１７４２号公報に開示されている。この公報では、ガラス基板をそのままの状態で多数枚積層してクランプしてブロック状にし、このブロックの内孔に研磨ブラシまたは研磨パッドを臨ませ、研磨液を供給しながら内孔即ち、多数のガラス基板の内周端を同時に研磨するようにしている。
【０００５】
【発明が解決しようとする課題】
上述した先行技術は以下の課題を有している。
先ず第１に、ガラス基板の内周端については、多数のガラス基板を同時に研磨できるが、外周端については基板ケース内にガラス基板を収めたままであるので、外周端については内周端の研磨加工とは全く別の工程で研磨加工しなければならない。即ち、基板ケース内から多数のガラス基板を取り出し、枚葉で外周端を研磨加工するか、或いは別のクランパに持ち換えて同時に研磨加工することになる。しかしながら、枚葉で処理すると効率が悪くなり、また他のクランパに持ち換えるのは工程が複雑になるだけでなく、持ち換えの際に芯ずれを起こし、加工精度が悪くなる。
【０００６】
また第２に、ガラス基板同士を直接積層しているので、記録面に傷が生じやすい。即ち、研磨作業の現場では多数のカレット（ガラス粉）が発生し、このカレットがガラス基板間に挟まれ、クランプの圧力でガラス基板側に埋入すると、深いクラック（２５μｍ以上）を発生させる。このように、ガラス基板の記録面にクラックが存在すると、均一な磁性膜を形成することに支障が生じるため、クラックが消失するまで研磨を行わなければならない。研磨代が厚くなればそれだけ研磨時間が長くなり、ガラス基板自体も当該研磨代を見込んで製造する必要があるので、厚くなってしまう。
【０００７】
【課題を解決するための手段】
上記課題を解決するため、本発明に係るクランプ治具は、ガラス基板を多数枚重ねたガラス基板ブロックの両端面に押し付けられ中央に締結具挿通穴が形成された一対の第１プレートと、前記ガラス基板ブロックの内孔に挿通され両端部が前記第１プレートの締結具挿通穴に結着される第１の締結具と、この第１の締結具の軸方向外側に配置され内径が前記第１プレートの外径よりも小さく、且つ前記ガラス基板の内径より大きな一対の第２プレートと、前記ガラス基板ブロックの外側において一対の前記第２プレートを締め付ける第２の締結具とを備え、前記ガラス基板の外端部を研削する場合には、前記第１プレートを前記ガラス基板ブロックの両端面に当て、前記第１プレートの締結具挿通穴及び前記ガラス基板ブロックの内孔に前記第１の締結具を挿通して前記ガラス基板ブロックを前記ガラス基板ブロックの径方向の内側からクランプした状態で行い、前記ガラス基板の内端部を研削する場合には、前記ガラス基板ブロックを前記ガラス基板ブロックの径方向の内側からのクランプ状態を維持したまま、前記第２プレートを前記第１プレートの第１の締結具の軸方向外側から当て、更に前記第２プレート間に前記第２の締結具を挿通して前記ガラス基板ブロックを前記ガラス基板ブロックの径方向の外側からクランプし、前記第１の締結具によるクランプ状態を解除して行う。
このクランプ治具によれば、ガラス基板を多数枚重ねたガラス基板ブロックのクランプ状態を解除することなく、連続して内周端と外周端のラッピングまたはポリッシングを行うことができる。
【０００８】
また、本発明に係るガラス基板の加工方法は、円環状をなすガラス基板の間に、当該ガラス基板の内周端および外周端からはみ出さないように緩衝シートを挟み込むとともに多数のガラス基板を重ね合せて外側または内側からクランプし、内側からクランプした状態で多数のガラス基板の外周端を同時に研削し、外側からクランプした状態で多数のガラス基板の内周端を同時に研削し、更に前記内周端と外周端の研削の切り替えの際にもガラス基板のクランプ状態を維持する。
上記において、外周端の研削と内周端の研削はどちらを先に行ってもよい。また、研削には面取り、粗研磨（ラッピング）及び研磨（ポリッシング）を含む。
【０００９】
本発明によれば、多数のガラス基板の内周端と外周端を連続して研削することができ、更にはラッピング終了後にそのままポリッシングを行うことも可能である。
【００１３】
更に、前記緩衝シートとして、内周縁または外周縁に凸部を有するものを用い、この凸部がガラス基板の内周端または外周端にかかるように緩衝シートをガラス基板に重ね合わせて研削を施し、ガラス基板の内周縁または外周縁のうち前記凸部に対応する部分を研削不完全部分として残すことで、品質管理用などのマークを研削と同時にガラス基板に形成することができる。
【００１４】
【発明の実施の形態】
以下に本発明の実施の形態を添付図面に基づいて説明する。図１は磁気記録媒体用ガラス基板の製作手順を示すブロック図であり、先ず、ガラス素板を打ち抜き円環状（円盤状）ガラス基板とし、このガラス基板の外端部と内端部に面取り加工を施し、次いで外端部と内端部に研磨（ポリッシング）を施し、この後記録面の粗研磨（ラッピング）を行った後、記録面の研磨（ポリッシング）を行い、更にスクラブ洗浄の後、表面を化学強化し、洗浄した後に検査を行って製品とする。本発明は上記の工程のうち、ガラス基板の面取り及び端面の研磨に適用される。
【００１５】
図２は本発明の実施に用いるクランプ冶具の斜視図である。クランプ冶具は一対の第１プレート１，１、一対の第２プレート２，２、一対の第１プレート１，１間に挿着される第１の締結具３、一対の第２プレート２，２間に挿着される第２の締結具４からなる。
【００１６】
第１プレート１は外径がガラス基板ｇの外径よりも小さく、内径がガラス基板ｇの内径と略同一の円環状をなし、第２プレート２は外径がガラス基板ｇの外径よりも大きく、内径が第１プレート１の外径よりも小さい円環状をなす。そして第１および第２の締結具３，４はいずれもボルトとナットの組み合わせからなり、第２の締結具４は第２プレート２の周方向に等間隔で３本設けられる。
【００１７】
上記のクランプ冶具を用いてガラス基板ｇの外端部を研削する場合には、後で図８に基づいて詳しく述べるように、第１プレート１，１と第１の締結具３を用い、ガラス基板ｇの内端部を研削する場合には、後で図９に基づいて詳しく述べるように、第１プレート１，１と第２プレート２，２と第２の締結具４を用いる。
【００１８】
図３はガラス基板ｇを多数枚積層したガラス基板ブロックＧを示し、本発明はこのガラス基板ブロックＧに対して面取り、ラッピング、ポリッシング等を施す。ガラス基板ブロックＧはガラス基板ｇの間に緩衝シート５を介在させている。
【００１９】
ガラス基板ｇを直接積層した際に間にカレットなどの異物が存在すると、記録面にクラックが入ることがある。そこで、緩衝シート５を介在させ、カレットなどの異物を緩衝シート５に埋入せしめクラックが入るのを防止する。このような目的のため、緩衝シート５はガラス基板ｇよりも柔らかい材料を用いる必要がある。ただし、あまり柔らかいと積層してクランプしてもガラス基板ｇが研磨中にずれるおそれがあるため、緩衝シート５の好ましい硬度としてはロックウェル硬度で５以上である。
【００２０】
また、研削の際に緩衝シート５がガラス基板の内端又は外端からはみ出ていると、その部分が研削できないことになるので、緩衝シート５の内径は図４に示すように、ガラス基板ｇの内径よりも例えば０．０１ｍｍ〜５．０ｍｍ大きく、ガラス基板ｇの外径よりも例えば０．０３ｍｍ〜１０．０ｍｍ小さくしている。
【００２１】
また、ガラス基板ｇ間に緩衝シート５をセットする際に、ずれてセットされてもガラス基板ｇの外周から緩衝シート５がはみ出さないためには、ガラス基板ｇの外径寸法と緩衝シート５の外径寸法の差が、ガラス基板ｇの内径寸法と緩衝シート５の内径寸法の差の２倍以上とすることが好ましい。
【００２２】
また、図５（ａ）および（ｂ）は緩衝シートの別実施例をしめす断面図であり、緩衝シート５としては、（ａ）に示すように、軟質層５１と硬質層５２の２層構造とするか、（ｂ）に示すように、硬質層５２の両面を軟質層５１で挟んだ３層構造としてもよい。また硬質層５２としては圧縮弾性率が１００ＭPa以上好ましくは１０００ＭPa以上の材料を用いる。
【００２３】
圧縮弾性率とロックウェル硬度との関係は図１４に示す通りであり、圧縮弾性率が１００ＭPa以上の材料としては、ＰＰ（ポリプロピレン）、ＰＶＣ（ポリ塩化ビニル）、ＰＥＴ（ポリエチレンテレフタレート）およびＰＳ（ポリエステル）が挙げられる。
本発明の緩衝シートは、硬質層および軟質層を構成するものの圧縮弾性率Ｙ（Ｍｐａ）とロックウェル硬度Ｒの関係が、図１４の二つの点線で示される式、logＹ＝０．０２２Ｒ＋０．７８およびlogＹ＝０．０２２Ｒ−０．４２で挟まれる領域にある材料のシートの一つまたはそれらの積層体で構成される。
【００２４】
図６はＲＣ（Radial Curvature）と緩衝シートの厚さとの関係を示すグラフである。ここで、ＲＣは図７に示すように、円盤状のガラス基板ｇの中心から所定寸法距離だけ離れた半径Ｒ１の位置と記録面のほぼ端に相当する円盤状のガラス基板ｇの中心から半径Ｒ２の位置との間で、半径方向に生じるガラス基板ｇのだれ部分ＡＢ間において測定した最大距離で示される特性で、一般にＲＣが４２μｍ以下が要求される。この要求を満たすには図６から緩衝シート５の厚みは０．２ｍｍ以下とすべきであることが分かる。
【００２５】
次に、ガラス基板ｇの外端部と内端部に面取りを行う手順を図８及び図９に基づいて説明する。
先ず、多数の円環状ガラス基板ｇを間に緩衝シート５を挟んで積層してガラス基板ブロックＧとする。そして、前記クランプ治具の第１プレート１，１をガラス基板ブロックＧの両端面に当て、第１プレート１，１及びガラス基板ブロックＧの中央穴に第１の締結具３を挿通し、ガラス基板ブロックＧを内側からクランプし、外端面を回転砥石６にて面取り加工する。
【００２６】
回転砥石６は台金にダイヤモンド砥粒を固着し、外周面形状は目的とする面取り形状に合わせた凹凸形状となっている。そして、ガラス基板ｇの内端部を面取りするにはガラス基板ブロックＧを回転しつつ、回転砥石６も回転せしめる。
【００２７】
上記によって多数のガラス基板ｇの外端部の面取り加工を同時に行った後、ガラス基板ブロックＧを崩すことなく、クランプ状態を維持したまま、クランプ治具の第２プレート２，２を第１プレート１，１の外側に当て、更に第２プレート２，２間に３本の第２の締結具４を挿通し、ガラス基板ブロックＧを外側からクランプする。この後、第１の締結具３を取り外し、図９に示すように、ガラス基板ブロックＧの中央穴内に別の回転砥石７を用いて多数のガラス基板ｇの内端部を同時に面取り加工する。
【００２８】
この後、図１０及び図１１に示すように、研磨液を供給しつつナイロンなどの研磨ブラシまたは研磨パッド８，９を用いて、多数のガラス基板ｇをブロックＧの状態にして、面取りした外端部および内端部を酸化セリウム微粒子が懸濁した研磨液を用いて研磨（ポリッシング）する。
【００２９】
尚、実施例ではガラス基板ｇの外端部を先に加工し、この後内端部の加工を行うようにしたが、どちらを先に加工してもよい。
【００３０】
図１２は緩衝シートの別実施例を示し、（ａ）に示す緩衝シート５は外周部に凸部５ａを有し、（ｂ）に示す緩衝シート５は内周部に凸部５ｂを有している。このように外周部または内周部に凸部５ａ,５ｂを有する緩衝シート５を、当該凸部５ａ,５ｂがガラス基板ｇの外端部または内端部にかかるように重ね、この状態でラッピングまたはポリッシングを行うことで、当該凸部５ａ,５ｂに覆われる部分が十分にラッピングまたはポリッシングされないことになり、図１３に示すように、外端部または内端部に積極的にマークｍを形成することができる。
【００３１】
上記マークｍは、例えばロットごとの製品番号、生産工場、生産日時などの製品管理に用いることができる。ただし、あまり研磨不充分な箇所が多くなると品質に影響してくるため、凸部５ａ,５ｂの大きさ及び数は品質に影響しない範囲とする。
【００３２】
次に、材料と層構造を異ならせた各種緩衝シートを用いて研磨した実験結果を以下の（表）に示す。実験は以下の条件で行った。
外周および内周の端面・面取加工は、それぞれ外径寸法８０ｍｍφおよび外径寸法２２ｍｍφを有し、所定断面形状の溝を１０個有する１０溝タイプ研削砥石を使用して、クランプ冶具で束ねた１０枚のガラスを同時に加工した。砥石は１０個の溝に♯５００のダイヤモンド砥石を台金に付着させた砥石を用いた。このとき種々の材質の緩衝シートをガラス板の間に挟んで行った。その後行った研磨ポリッシングは、ナイロンブラシロールを用いて酸化セリウム粒子を懸濁させた研磨液を供給しながら行った。
その後ガラスをクランプ冶具からはずして、ガラスの束ねを解除してガラス板の主表面（記録面）を平均粒度０．５〜１．７μｍの酸化セリウム研磨砥粒を含む研磨液と研磨パッドを用いて、片面あたり２５μｍ研磨し、洗浄、乾燥をした。
続いて硝酸カリウムと硝酸ナトリウムの混合溶融塩を用いるイオン交換による化学強化処理を行い、再度洗浄乾燥して、主表面についてのキズの検査を行った。なお、ダイヤモンド砥石を用いるガラス基板の外周端面加工及び内周端面加工（研削）を１枚づつ枚葉式で行い、その後酸化セリウム研磨液を供給しながら、研磨パッドまたは研磨ブラシを用いて行う内周端および外周端の研磨加工を、多数枚のガラス基板をクランプで束ねて保持固定し、多数枚のガラス基板を一括研磨方式で行ってもよい。
【００３３】
【表１】

【００３４】
上記（表）において、実施例１〜６は、いずれもロックウェル硬度が４０ＭＰａ以下の単層からなる緩衝シートを用いた例であり、ガラス主表面のキズの発生は抑制され、５００Ｗの照明ランプで照射した目視検査法では、キズが認められないことを合格としたときの歩留まりとして、９２％以上の高い数値が得られた。このうち、実施例１は、緩衝シートの全厚味が０．２７５ｍｍと最も厚く、このときラジアルカーベチャーが１７８ｎｍと大きな値を示した。これに対して、実施例２〜７の緩衝シートは厚味を０．２ｍｍ以下の薄い厚味にしたので、ラジアルカーベチャーは４５ｎｍ以下の小さい特性が得られた。
比較例１〜３は硬質材料からなる単層の緩衝シートであり、主表面のキズ発生が見られ、キズ歩留まりは７８％以下と低い値であった。比較例の三者の中でも、厚味が厚い比較例２は、ラジアルカーベチャーが大きな値を示し、磁気記録媒体用基板の製造用としては、適していないことが分る。
また緩衝シートの作業性は、シートの厚味、材質に起因する濡れた状態でのガラスとの密着性、腰の強さなどにより、ガラス面へのセットのし易さ、濡れたガラス面からはずすときで作業性評価点が異なったものと考えられる。
【００３５】
【発明の効果】
以上に説明したように本発明によれば、磁気記録媒体などとして用いるガラス基板の内周端及び外周端をラッピングまたはポリッシングするにあたり、多数枚を同時に処理できるため、大幅なコストダウンを図ることができる。
【００３６】
また、内周端のラッピングまたはポリッシングに引き続いて外周端のラッピングまたはポリッシングを行うにあたり、多数のガラス基板のクランプ状態を解除せずにそのままの状態を維持することができるので、持ち替えの際のずれが生じることがない。
【００３７】
また、多数枚のガラス基板を積層する際に、ガラス基板間に緩衝シートを挟み込むようにしたので、仮にカレットなどの異物がガラス基板間に挟み込まれた場合でも、緩衝シートに埋入し、ガラス基板の記録面にクラックなどを生じることがない。
【００３９】
更に、緩衝シートの一部に凸部を設け、この凸部がガラス基板の内端部や外端部にかかるようにラッピングまたはポリッシングすることで、簡単に品質などを管理するためのマークを形成することができる。
【図面の簡単な説明】
【図１】磁気記録媒体用ガラス基板の製作手順を示すブロック図
【図２】クランプ治具の斜視図
【図３】多数のガラス基板を積層したガラス基板ブロックの側面図
【図４】ガラス基板の上に緩衝シートを重ねた状態を示す平面図
【図５】（ａ）および（ｂ）は緩衝シートの別実施例をしめす断面図
【図６】ＲＣ（Radial Curvature）と緩衝シートの厚さとの関係を示すグラフ
【図７】ＲＣ（Radial Curvature）の概念図
【図８】ガラス基板の外端部を面取りしている状態の側面図
【図９】ガラス基板の内端部を面取りしている状態の側面図
【図１０】ガラス基板の外端部を研磨している状態の側面図
【図１１】ガラス基板の内端部を研磨している状態の側面図
【図１２】（ａ）は外周部に凸部を有する緩衝シートの平面図、（ｂ）は内周部に凸部を有する緩衝シートの平面図
【図１３】凸部を有する緩衝シートを用いて製作されたガラス基板を示す図
【図１４】弾性圧縮率とロックウェル硬度との関係を示す図
【符号の説明】
１…クランプ治具の第１プレート、２…クランプ治具の第２プレート、３…クランプ治具の第１の締結具、４…クランプ治具の第２の締結具、５…緩衝シート、５ａ、５ｂ…凸部、５１…軟質層、５２…硬質層、６,７…回転砥石、８,９…研磨ブラシまたは研磨パッド、ｇ…ガラス基板、Ｇ…ガラス基板ブロック、ｍ…マーク。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a clamp jig for holding a large number of annular glass substrates in a stacked manner, a method for grinding (chamfering or polishing) inner peripheral ends and outer peripheral ends of a large number of annular glass substrates using the clamp jig , and The glass substrate obtained by this method is related to
[Prior art]
Since glass is superior in impact resistance, rigidity, hardness, and strength to aluminum, it is being used as a magnetic recording medium incorporated in a hard disk drive or the like.
In particular, the form of personal computers is recently shifting from desktop types to notebook types and mobile types, and the demand for glass substrates with excellent flatness and high density is increasing in place of aluminum substrates.
[0003]
In order to obtain a glass substrate for a magnetic recording medium, a disk-like (doughnut-like) shape is cut out from a glass base plate, and a peripheral end surface (inner peripheral end and outer peripheral end) of this disc-shaped glass substrate is disclosed in, for example, Japanese Patent Laid-Open No. 10-154321. , Lapping with a diamond grindstone and polishing with a cerium oxide suspension are performed, and thereafter, lapping with alumina abrasive grains and polishing with a cerium oxide suspension are performed on the front and back recording surfaces (main surface). I am doing so.
[0004]
In the above-described method, the processing of the glass substrate is a single-wafer type and is inefficient, and therefore, a method of simultaneously polishing a large number of glass substrates is disclosed in Japanese Patent Application Laid-Open No. 11-221742. In this publication, a large number of glass substrates are laminated and clamped as they are to form a block shape. A polishing brush or a polishing pad is exposed to the inner hole of the block, and an inner hole, that is, a large number of holes is supplied while supplying a polishing liquid. The inner peripheral edge of the glass substrate is polished simultaneously.
[0005]
[Problems to be solved by the invention]
The prior art described above has the following problems.
First, for the inner peripheral edge of the glass substrate, a large number of glass substrates can be polished simultaneously, but the outer peripheral edge remains in the substrate case, so the outer peripheral edge is polished at the inner peripheral edge. Polishing must be performed in a completely different process from the processing. That is, a large number of glass substrates are taken out from the substrate case, and the outer peripheral edge is polished with a single sheet, or is transferred to another clamper and simultaneously polished. However, if the processing is performed on a single sheet, the efficiency is lowered, and changing to another clamper not only complicates the process, but also causes misalignment during the changing, resulting in poor processing accuracy.
[0006]
Second, since the glass substrates are directly laminated, the recording surface is likely to be damaged. That is, a large number of cullet (glass powder) is generated at the site of polishing work, and when this cullet is sandwiched between the glass substrates and embedded in the glass substrate side by the pressure of the clamp, deep cracks (25 μm or more) are generated. As described above, if a crack exists on the recording surface of the glass substrate, it will hinder the formation of a uniform magnetic film. Therefore, polishing must be performed until the crack disappears. The thicker the polishing allowance, the longer the polishing time, and the glass substrate itself must be manufactured in anticipation of the polishing allowance, resulting in an increase in thickness.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a clamping jig according to the present invention is a pair of first plates that are pressed against both end faces of a glass substrate block in which a large number of glass substrates are stacked and a fastener insertion hole is formed in the center, a first fastener opposite ends are inserted into the inner hole of the glass substrate blocks are bound to the fastener insertion hole of the first plate, the inner diameter is disposed axially outwardly of the first fastener said third rather smaller than the outer diameter of the first plate, and includes a pair of second plate big than the inner diameter of the glass substrate, and a second fastener tightening a pair of the second plate on the outside of the glass substrate block, wherein when grinding the outer end portion of the glass substrate, the first plate against the end faces of the glass substrate blocks, said the inner hole of the fastener insertion hole and the glass substrate block of the first plate Performs the glass substrate block by inserting a fastener in a state of being clamped from the inside in the radial direction of the glass substrate blocks, in the case of grinding the inner end portion of the glass substrate, the glass the glass substrate blocks The second plate is applied from the axially outer side of the first fastener of the first plate while the clamped state from the inner side in the radial direction of the substrate block is maintained, and the second fastening is further performed between the second plates. A tool is inserted and the glass substrate block is clamped from outside in the radial direction of the glass substrate block, and the clamped state by the first fastener is released .
According to this clamping jig, the inner peripheral end and the outer peripheral end can be continuously wrapped or polished without releasing the clamped state of the glass substrate block in which many glass substrates are stacked.
[0008]
The glass substrate processing method according to the present invention includes a buffer sheet sandwiched between glass substrates that form an annular shape so as not to protrude from the inner and outer peripheral ends of the glass substrate, and a large number of glass substrates are stacked. In addition, the outer peripheral ends of many glass substrates are ground at the same time while being clamped from the outside or the inside, and the inner peripheral ends of the many glass substrates are simultaneously ground while being clamped from the outside. The clamp state of the glass substrate is maintained even when switching between the grinding of the end and the outer peripheral end.
In the above, either the outer peripheral end grinding or the inner peripheral end grinding may be performed first. The grinding includes chamfering, rough polishing (lapping) and polishing (polishing).
[0009]
According to the present invention, it is possible to continuously grind the inner and outer peripheral ends of a large number of glass substrates, and it is also possible to perform polishing as it is after lapping is completed.
[0013]
Further, as the buffer sheet, a sheet having a convex portion on the inner peripheral edge or the outer peripheral edge is used, and the buffer sheet is superposed on the glass substrate and ground so that the convex portion is applied to the inner peripheral edge or the outer peripheral edge of the glass substrate. By leaving the portion corresponding to the convex portion of the inner or outer peripheral edge of the glass substrate as an incompletely ground portion, a mark for quality control or the like can be formed on the glass substrate simultaneously with grinding.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a manufacturing procedure of a glass substrate for a magnetic recording medium. First, a glass base plate is punched into an annular (disc-shaped) glass substrate, and chamfering is performed on the outer end portion and the inner end portion of the glass substrate. And then polishing the outer and inner ends (polishing), followed by rough polishing (lapping) of the recording surface, polishing of the recording surface (polishing), and further scrub cleaning, The surface is chemically strengthened, cleaned, and inspected to make a product. The present invention is applied to chamfering of the glass substrate and polishing of the end face among the above steps.
[0015]
FIG. 2 is a perspective view of a clamp jig used for carrying out the present invention. The clamp jig includes a pair of

first plates

1, 1, a pair of

second plates

2, 2, a first fastener 3 inserted between the pair of

first plates

1, 1, and a pair of

second plates

2, 2. It consists of the 2nd fastener 4 inserted in between.
[0016]
The first plate 1 has an outer diameter smaller than the outer diameter of the glass substrate g, the inner diameter is substantially the same as the inner diameter of the glass substrate g, and the second plate 2 has an outer diameter larger than the outer diameter of the glass substrate g. The ring shape is large and the inner diameter is smaller than the outer diameter of the first plate 1. Each of the first and

second fasteners

3 and 4 is a combination of a bolt and a nut, and three second fasteners 4 are provided at equal intervals in the circumferential direction of the second plate 2.
[0017]
When the outer end portion of the glass substrate g is ground using the clamp jig described above, the

first plate

1, 1 and the first fastener 3 are used as described later in detail with reference to FIG. When grinding the inner end portion of the substrate g, the

first plate

1, 1, the

second plate

2, 2 and the second fastener 4 are used as will be described in detail later with reference to FIG. 9.
[0018]
FIG. 3 shows a glass substrate block G in which a large number of glass substrates g are laminated. In the present invention, the glass substrate block G is chamfered, lapped, polished, and the like. The glass substrate block G has a buffer sheet 5 interposed between the glass substrates g.
[0019]
If a foreign material such as cullet is present between the glass substrates g directly laminated, a crack may occur on the recording surface. Therefore, the buffer sheet 5 is interposed, and foreign matters such as cullet are embedded in the buffer sheet 5 to prevent cracks. For such a purpose, it is necessary to use a material softer than the glass substrate g for the buffer sheet 5. However, since the glass substrate g may be displaced during polishing even if it is laminated and clamped if it is too soft, the buffer sheet 5 preferably has a Rockwell hardness of 5 or more.
[0020]
In addition, if the buffer sheet 5 protrudes from the inner end or the outer end of the glass substrate during grinding, the portion cannot be ground, so the inner diameter of the buffer sheet 5 is as shown in FIG. For example, it is 0.01 mm to 5.0 mm larger than the inner diameter of the glass substrate, and 0.03 mm to 10.0 mm smaller than the outer diameter of the glass substrate g.
[0021]
Further, when the buffer sheet 5 is set between the glass substrates g, the outer diameter of the glass substrate g and the buffer sheet 5 are prevented so that the buffer sheet 5 does not protrude from the outer periphery of the glass substrate g even if the buffer sheet 5 is set to be shifted. It is preferable that the difference in the outer diameter of the glass substrate g be at least twice the difference between the inner diameter of the glass substrate g and the inner diameter of the buffer sheet 5.
[0022]
5 (a) and 5 (b) are sectional views showing another embodiment of the buffer sheet. As the buffer sheet 5, a two-layer structure of a soft layer 51 and a hard layer 52 as shown in FIG. 5 (a). Alternatively, as shown in (b), a three-layer structure in which both sides of the hard layer 52 are sandwiched between the soft layers 51 may be adopted. The hard layer 52 is made of a material having a compression elastic modulus of 100 MPa or more, preferably 1000 MPa or more.
[0023]
The relationship between the compression elastic modulus and Rockwell hardness is as shown in FIG. 14, and materials having a compression elastic modulus of 100 MPa or more include PP (polypropylene), PVC (polyvinyl chloride), PET (polyethylene terephthalate) and PS ( Polyester).
In the buffer sheet of the present invention, the relationship between the compression elastic modulus Y (Mpa) and the Rockwell hardness R of the hard and soft layers is expressed by the formula shown by the two dotted lines in FIG. 14, log Y = 0.022R + 0.78. And logY = 0.022R−0.42 and one of the sheets of material in the region sandwiched between them or a laminate thereof.
[0024]
FIG. 6 is a graph showing the relationship between RC (Radial Curvature) and the thickness of the buffer sheet. Here, as shown in FIG. 7, RC is a radius from the center of the disk-shaped glass substrate g corresponding to the position of the radius R1 that is a predetermined dimensional distance away from the center of the disk-shaped glass substrate g and almost the end of the recording surface. Generally, the RC is required to be 42 μm or less with the characteristic indicated by the maximum distance measured between the drooping portions AB of the glass substrate g generated in the radial direction with respect to the position of R2. It can be seen from FIG. 6 that the thickness of the buffer sheet 5 should be 0.2 mm or less in order to satisfy this requirement.
[0025]
Next, a procedure for chamfering the outer end portion and the inner end portion of the glass substrate g will be described with reference to FIGS.
First, a large number of annular glass substrates g are laminated with a buffer sheet 5 interposed therebetween to form a glass substrate block G. Then, the

first plates

1 and 1 of the clamp jig are applied to both end faces of the glass substrate block G, the first fastener 3 is inserted into the central holes of the

first plates

1 and 1 and the glass substrate block G, and the glass The substrate block G is clamped from the inside, and the outer end surface is chamfered with the rotating grindstone 6.
[0026]
The rotating grindstone 6 has diamond abrasive grains fixed to a base metal, and the outer peripheral surface has an uneven shape that matches the intended chamfered shape. Then, in order to chamfer the inner end portion of the glass substrate g, the rotating grindstone 6 is also rotated while the glass substrate block G is rotated.
[0027]
After the chamfering of the outer end portions of a large number of glass substrates g is simultaneously performed as described above, the

second plates

2 and 2 of the clamp jig are maintained in the clamped state without breaking the glass substrate block G. 1, 1, three second fasteners 4 are inserted between the

second plates

2, 2, and the glass substrate block G is clamped from the outside. Then, the 1st fastener 3 is removed, and as shown in FIG. 9, the inner edge part of many glass substrates g is simultaneously chamfered using the another rotating grindstone 7 in the center hole of the glass substrate block G. As shown in FIG.
[0028]
Thereafter, as shown in FIG. 10 and FIG. 11, a large number of glass substrates g are put into a block G using a polishing brush such as nylon or a polishing pad 8, 9 while supplying a polishing liquid, and the chamfered outside. The end portion and the inner end portion are polished (polishing) using a polishing liquid in which cerium oxide fine particles are suspended.
[0029]
In the embodiment, the outer end portion of the glass substrate g is processed first, and then the inner end portion is processed. However, either one may be processed first.
[0030]
FIG. 12 shows another embodiment of the buffer sheet. The buffer sheet 5 shown in FIG. 12A has a convex portion 5a on the outer peripheral portion, and the buffer sheet 5 shown in FIG. 12B has a convex portion 5b on the inner peripheral portion. ing. In this way, the buffer sheet 5 having the

convex portions

5a and 5b on the outer peripheral portion or the inner peripheral portion is overlapped so that the

convex portions

5a and 5b cover the outer end portion or the inner end portion of the glass substrate g, and wrapping is performed in this state. Alternatively, by polishing, the portions covered by the

convex portions

5a and 5b are not sufficiently lapped or polished, and as shown in FIG. 13, marks m are positively formed at the outer end portion or the inner end portion. can do.
[0031]
The mark m can be used for product management such as product number for each lot, production factory, production date and time. However, since the quality is affected when there are too many insufficiently polished portions, the size and number of the

convex portions

5a and 5b are set in a range that does not affect the quality.
[0032]
Next, the following (Table) shows the experimental results of polishing using various buffer sheets having different materials and layer structures. The experiment was performed under the following conditions.
The outer peripheral and inner peripheral end faces and chamfering were bundled with a clamp jig using a 10-groove type grinding wheel having an outer diameter of 80 mmφ and an outer diameter of 22 mmφ and 10 grooves of a predetermined cross-sectional shape. Ten glasses were processed simultaneously. As the grindstone, a grindstone in which a diamond grindstone of # 500 was attached to a base metal in 10 grooves was used. At this time, buffer sheets of various materials were sandwiched between glass plates. The subsequent polishing polishing was performed while supplying a polishing liquid in which cerium oxide particles were suspended using a nylon brush roll.
Thereafter, the glass is removed from the clamp jig, the glass bundle is released, and the main surface (recording surface) of the glass plate is used with a polishing liquid and a polishing pad containing cerium oxide abrasive grains having an average particle size of 0.5 to 1.7 μm. Then, each side was polished by 25 μm, washed and dried.
Subsequently, chemical strengthening treatment by ion exchange using a mixed molten salt of potassium nitrate and sodium nitrate was performed, followed by washing and drying again to inspect the main surface for scratches. In addition, the outer peripheral end face processing and inner peripheral end face processing (grinding) of a glass substrate using a diamond grindstone are performed one by one, and then performed using a polishing pad or a polishing brush while supplying a cerium oxide polishing liquid. The polishing of the peripheral edge and the outer peripheral edge may be performed by bundling a large number of glass substrates by bundling them with a clamp and performing a lump polishing method on a large number of glass substrates.
[0033]
[Table 1]

[0034]
In the above (table), Examples 1 to 6 are examples using a buffer sheet composed of a single layer having a Rockwell hardness of 40 MPa or less, and the generation of scratches on the glass main surface is suppressed, and a 500 W illumination lamp In the visual inspection method irradiated with, a high value of 92% or more was obtained as a yield when it was determined that no scratch was observed. Among them, in Example 1, the total thickness of the buffer sheet was as thick as 0.275 mm, and at this time, the radial curve showed a large value of 178 nm. On the other hand, since the buffer sheets of Examples 2 to 7 had a thin thickness of 0.2 mm or less, the radial curve had a small characteristic of 45 nm or less.
Comparative Examples 1 to 3 were single-layered buffer sheets made of a hard material, the main surface was scratched, and the scratch yield was a low value of 78% or less. Among the three comparative examples, comparative example 2 having a large thickness shows a large radial curve and is not suitable for manufacturing a magnetic recording medium substrate.
In addition, the workability of the buffer sheet is determined by the ease of setting on the glass surface due to the thickness of the sheet, the adhesion to the glass in a wet state due to the material, the strength of the waist, etc. It is considered that the workability evaluation points differed when removed.
[0035]
【The invention's effect】
As described above, according to the present invention, when wrapping or polishing the inner and outer edges of a glass substrate used as a magnetic recording medium or the like, a large number of sheets can be processed at the same time, so that a significant cost reduction can be achieved. it can.
[0036]
In addition, when lapping or polishing the outer peripheral edge following lapping or polishing of the inner peripheral edge, it is possible to maintain the same state without releasing the clamped state of a large number of glass substrates. Will not occur.
[0037]
Also, when laminating a large number of glass substrates, the buffer sheet is sandwiched between the glass substrates, so even if foreign matter such as cullet is sandwiched between the glass substrates, No cracks or the like occur on the recording surface of the substrate.
[0039]
In addition, a convex part is provided on a part of the buffer sheet, and lapping or polishing is performed so that the convex part covers the inner end or outer end of the glass substrate, thereby forming a mark for easy quality control. can do.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a manufacturing procedure of a glass substrate for a magnetic recording medium. FIG. 2 is a perspective view of a clamp jig. FIG. 3 is a side view of a glass substrate block in which a large number of glass substrates are laminated. FIG. 5 (a) and (b) are cross-sectional views showing another embodiment of the buffer sheet. FIG. 6 shows RC (Radial Curvature) and the thickness of the buffer sheet. FIG. 7 is a conceptual diagram of RC (Radial Curvature). FIG. 8 is a side view of a state where the outer end of the glass substrate is chamfered. FIG. 9 is a diagram where the inner end of the glass substrate is chamfered. FIG. 10 is a side view of a state where the outer end of the glass substrate is being polished. FIG. 11 is a side view of a state where the inner end of the glass substrate is being polished. Is a plan view of a buffer sheet having a convex portion on the outer peripheral portion, and (b) has a convex portion on the inner peripheral portion. Figure [EXPLANATION OF SYMBOLS] showing the relationship between the buffer plan view of the sheet 13 is a diagram [14] showing a glass substrate fabricated by using a buffer sheet having a convex portion elastic compressibility and the Rockwell hardness
DESCRIPTION OF SYMBOLS 1 ... 1st plate of a clamp jig, 2 ... 2nd plate of a clamp jig, 3 ... 1st fastener of a clamp jig, 4 ... 2nd fastener of a clamp jig, 5 ... Buffer sheet, 5a 5b ... convex portion, 51 ... soft layer, 52 ... hard layer, 6, 7 ... rotating grindstone, 8, 9 ... polishing brush or polishing pad, g ... glass substrate, G ... glass substrate block, m ... mark.

Claims

In a clamp jig for holding a large number of glass substrates in an annular shape, the clamp jig is pressed against both end faces of a glass substrate block in which a large number of glass substrates are stacked, and a pair of fastener insertion holes are formed in the center. The first plate, a first fastener that is inserted into the inner hole of the glass substrate block and whose both ends are connected to the fastener insertion holes of the first plate, and an axially outer side of the first fastener. placed inside diameter rather smaller than the outer diameter of the first plate, and the pair of second plate big than the inner diameter of the glass substrate, the second fastening the pair of the second plate on the outside of the glass substrate blocks With fasteners,
When grinding the outer end portion of the glass substrate, the first plate is applied to both end surfaces of the glass substrate block, and the first plate is inserted into the fastener insertion hole of the first plate and the inner hole of the glass substrate block. In a state where the glass substrate block is clamped from the radial inner side of the glass substrate block by inserting the fastener of
When grinding the inner end portion of the glass substrate, the second plate is fixed to the first plate of the first plate while the glass substrate block is maintained in a clamped state from the inside in the radial direction of the glass substrate block. Abutting from the outside in the axial direction of the fastener, further inserting the second fastener between the second plates to clamp the glass substrate block from the outside in the radial direction of the glass substrate block, and the first fastener A clamping jig for a glass substrate, wherein the clamping is performed by releasing the clamping state .

A buffer sheet is sandwiched between glass substrates forming an annular shape so as not to protrude from the inner and outer peripheral ends of the glass substrate, and a large number of glass substrates are stacked and clamped from the outside or the inside, and clamped from the inside. In this state, the outer peripheral edges of many glass substrates are ground at the same time, the inner peripheral edges of many glass substrates are ground at the same time clamped from the outside, and the glass is also used when switching between the inner peripheral edge and the outer peripheral edge. Maintaining the clamped state of the substrate, the buffer sheet having a convex portion on the inner or outer peripheral edge is used, and the buffer sheet is placed on the glass substrate so that the convex portion covers the inner peripheral edge or the outer peripheral edge of the glass substrate. Overlapping and grinding are performed, and a portion of the inner or outer peripheral edge of the glass substrate corresponding to the convex portion is left as an incompletely ground portion. Method.

A glass substrate obtained by the glass substrate processing method according to claim 2, wherein a mark is formed by incomplete grinding at an inner peripheral end or / and an outer peripheral end.