JP2004142952A

JP2004142952A - Method for manufacturing glass molding

Info

Publication number: JP2004142952A
Application number: JP2002266250A
Authority: JP
Inventors: Hiroyuki Sakai; 坂井　裕之; Shinji Namita; 波田　伸司
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2002-08-26
Filing date: 2002-09-12
Publication date: 2004-05-20
Anticipated expiration: 2022-09-12
Also published as: JP4156887B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a glass molding such as a lens by which the release from a molding die is easily carried out to obtain a product having a high precision surface shape even in the case of a temperature condition or a molding shape which cause the strong sticking on the upper side. <P>SOLUTION: This method for manufacturing the glass molding is performed by press-molding a heated and softened glass base material using a manufacturing apparatus having an upper die and a lower die opposed to each other and containing a cylindrical member surrounding directly or indirectly the upper die and the lower die or a manufacturing apparatus containing an upper die and a lower die opposed to each other and having forcibly releasing means around the upper die and the lower die. After the press-molding and before the molded glass molding is taken out from the manufacturing apparatus, at least one of the upper die and the lower die is vertically reciprocated one or more times. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、レンズなどのガラス成形体の製造方法であって、成形用型に張り付き易いガラス光学素子、例えば、凹面を有するレンズであっても、成形用型に張り付くのを防止して、連続稼働を可能にする、ガラス成形体の製造方法に関する。
【０００２】
【従来の技術】
従来知られているレンズの成形方法としては、例えば、ガラス素材と成形用型を、ガラス素材が軟化する温度（１０^７．５〜１０^１１ポアズのガラス粘度に相当する温度）まで加熱した後に、ガラス素材を型によってプレス成形する方法がある。プレス成形後、ガラスの転移温度（１０^１３ポアズ）付近或いはそれ以下まで冷却した後、離型し、レンズを型から取り出す。
【０００３】
この成形方法では、離型の際に成形されたレンズが成形面に貼り付いたままとなることがある。成形用型は、通常、上型及び下型からなり、下型にレンズが貼り付いた場合、離型の後のレンズ取り出し工程で、レンズの取り出しが行なえない場合がある。また、上型に貼り付いた場合、レンズの取り出しができないだけでなく、その後、下型上などに落下して、種々のトラブルの原因となる。さらに、上型に貼りついたままで下型成形面に次のガラス素材が供給されると、連続稼働の妨げとなる。型への貼り付きは、成形面の形状が凹面の場合よりも凸面の場合に生じやすい。成形面が凸面の場合には、ガラスと型との熱膨張率が相違する（ガラスの熱膨張率が大きい）ために、冷却によるガラスレンズの熱収縮が成形型より大きく、その結果、ガラスレンズが成形面に密着するためである。
【０００４】
このような貼り付きを防止するための手段として、例えば、特開平２−１８４５３１号公報には、成形されたレンズと成形型の間にくさび部材を挿入する方法が開示されている。また、特開平２−１８４５３３号公報には、上型と下型の隙間からレンズに不活性ガスを噴射させる方法が開示されている。さらに特開２００１−１９２２１５号公報には、成形体周縁部の少なくとも一部と接触し、成形体を下方向へ押し下げる強制離型手段を用いる方法が開示されている。
【０００５】
【発明が解決しようとする課題】
しかしながら、特開平２−１８４５３１号公報に開示されている、成形されたレンズと成形型の間にくさび部材を挿入する方法では、レンズおよび成形面にキズをつけやすいという問題がある。また、特開平２−１８４５３３号公報に記載の方法では、上型と下型の隙間からレンズに不活性ガスを噴射させる必要があるため、型の周囲を他の部材で覆うことができない。そのため、上下型の位置ずれが生じやすく、均熱性が損なわれやすいという問題がある。さらに特開２００１−１９２２１５号公報に記載の方法では、ある程度の効果はあるものの、上貼りつきの激しい温度や成形体形状の場合、例えば、比較的高温（例えば、Ｔｇ以上）で離型する場合、曲率半径の大きい凹面、凸面、又は平面形状を有するレンズの場合に対しては充分な効果が得られなかった。
【０００６】
そこで本発明の目的は、このような問題点を解決する新たな手段を提供することであり、より具体的には、上記のような上貼りつきの激しい温度や成形体形状の場合であっても、成形型からの離型を容易に行え、高精度な面形状の製品が得られるレンズ等のガラス成形体の製造方法を提供することにある。
【０００７】
【課題を解決するための手段】
上記課題を解決する発明の手段は以下の通りである。
［請求項１］　対向する上型及び下型並びにこれら上型及び下型を直接及び／又は間接的に包囲する筒状部材を含む製造装置により、加熱軟化したガラス素材を加圧成形することによってガラス成形体を製造する方法において、
加圧成形後、成形されたガラス成形体を製造装置から取出す前に、上型及び下型の少なくとも一方を１往復以上、上下動させることを特徴とする、ガラス成形体の製造方法（以下、本発明の第１の製造方法という）。
［請求項２］前記上下動を２〜７回繰り返す請求項１に記載の製造方法。
［請求項３］上型、下型及び筒状部材により形成される空間（以下、成形キャビティと呼ぶ）が、上下動の際に、一時的に減圧状態及び増圧状態になる請求項１または２に記載の製造方法。
［請求項４］成形キャビティ内が減圧状態になったときに成形キャビティ外から成形キャビティ内に気体が流入する請求項３に記載の製造方法。
［請求項５］成形キャビティ内が増圧状態になったときに成形キャビティ内から成形キャビティ外に気体が排出される請求項３に記載の製造方法。
［請求項６］前記上型及び下型の少なくとも一方の上下動を筒状部材による包囲が外れない範囲で行う請求項１〜５のいずれか１項に記載の製造方法。
［請求項７］前記製造装置は、上型又は下型の周囲に強制離型手段をさらに有し、前記上下動の際に、強制離型手段が成形されたガラス成形体の周縁部の少なくとも一部に下方向又は上方向への力を加えることを特徴とする、請求項１〜６のいずれか１項に記載の製造方法。
［請求項８］強制離型手段が上型の周囲に配置され、前記上下動の度に、強制離型手段がレンズの周縁部の少なくとも一部に下方向への力を加える請求項７に記載の製造方法。
［請求項９］対向する上型及び下型を含み、かつこれら上型又は下型の周囲に強制離型手段を有する製造装置により、加熱軟化したガラス素材を加圧成形することによってガラス成形体を製造する方法において、
加圧成形後、成形されたガラス成形体を製造装置から取出す前に、上型及び下型の少なくとも一方を１往復以上、上下動させ、前記強制離型手段が成形されたガラス成形体の周縁部の少なくとも一部に下方向又は上方向への力を加えることを特徴とする、ガラス光学素材の製造方法（以下、本発明の第２の製造方法という）。
［請求項１０］強制離型手段が上型の周囲に配置され、前記上下動の度に、強制離型手段がガラス成形体の周縁部の少なくとも一部に下方向への力を加える請求項９に記載の製造方法。
【０００８】
【発明の実施の態様】
本発明の第１の製造方法は、対向する上型及び下型並びにこれら上型及び下型を直接及び／又は間接的に包囲する筒状部材を含む製造装置により、加熱軟化したガラス素材を加圧成形することによってガラス成形体を製造する方法である。本発明の第１の製造方法に使用する製造装置の一例の断面形状を図１に示す。
この製造装置Ａは、相互に離間及び接近が可能な上型１及び下型２を備え、前記上型及び下型は対向する成形面を有する。さらに、この製造装置は、前記上型と前記下型とが、ガラス素材の下型成形面への供給及びガラス成形体の下型成形面からの取り出しの際に離間し得る構造を有する。このような構成を有する装置、上型及び下型の材質や構造、並びにガラス素材の下型成形面への供給及びガラス成形体の下型成形面からの取り出しの際の上型と下型との離間の仕方に関しては、例えば、特開平１１−４９５２３号に記載されている。
【０００９】
製造装置Ａは、上型１及び下型２以外に、上型１及び下型２を包囲する筒状部材であるスリーブ５を有する。スリーブ５は、上型１及び下型２を直接包囲している。
製造装置Ａは、上型１、下型２及び筒状部材であるスリーブ５により形成される空間である成形キャビティ８を有する。本発明の製造方法で用いる製造装置は、後述の実施例で詳述するように、上型１、下型２及びスリーブ５以外に上母型６や下母型７等を有することもできる。
【００１０】
上型及び下型の材質としては、例えばＭｏ、Ｗ等の金属、ＷＣ等の超硬合金、炭化珪素、窒化硅素、炭化チタン、窒化チタン、窒化アルミニウム、炭化タングステン等のセラミックス等が挙げられる。さらに上型及び下型の成形面には、耐酸化性、耐久性及び耐融着性の向上等を目的として保護膜が形成さていることが好ましい。保護膜としては、Ｐｔ、Ｒｈ、Ａｕ、Ｒｅ、Ｏｓ、Ｉｒ等を含む貴金属材料からなる薄膜、硬質炭素膜、ダイヤモンドライクカーボン等の炭素系薄膜、ＳｉＣ、Ｓｉ_３Ｎ_４、炭化チタン、窒化チタン、アルミナ等のセラミックス材料及びこれらの複合材料等からなる薄膜等が挙げられる。保護膜は、例えば、スパッタリング法、イオンプレーティング法、ＣＶＤ法等により形成でき、単層膜または異なる材料からなる多層膜であってもよい。
【００１１】
本発明の製造方法においては、加熱軟化したガラス素材を加圧成形することによってガラス成形体を製造する。本発明において、ガラス素材のガラス組成、形状及び寸法には特に制限はなく、成形型の成形面に融着しやすいガラス組成を有するガラス素材からであっても、良好にガラス成形体を製造することができる。また、ガラス素材及び成形型の加熱条件や加圧成形のためのプレス条件や方法等にも特に制限はない。
【００１２】
本発明の製造方法に適用できる、ガラス素材の加圧工程、加圧されたガラス成形体の冷却工程、冷却されたガラス成形体を離型する工程などを含むガラス成形体の製造方法や、ガラス素材の種類や各工程の条件等は、例えば、特開平１１−４９５２３号公報に記載の方法を利用することができる。また、本発明の製造方法により製造されるガラス成形体は、例えば、光学素子であることができる。より具体的には、光学素子は、凹レンズ、凸レンズ、メニスカスレンズ、凹メニスカスレンズ等の非球面レンズ、シリンドリカルレンズ等の各種光学素子であることができる。また、ガラス成形体は、例えば、ディスク用基板等の電子デバイス用基板であることもできる。
【００１３】
本発明の製造方法は、加圧成形後、成形されたガラス成形体を製造装置から取出す前に、上型及び下型の少なくとも一方を１往復以上、上下動させることを特徴とする。
より具体的には、例えば、上下成形型を加熱し、加熱したガラス体を下型上に供給した後、下型を上昇させて上下型間でガラス体を加圧成形する。加圧成形と同時に、または加圧成形後に冷却を行ない、型および成形体が所定の温度まで低下したところで、下型をわずかに低下させて離間する。引き続き下型を１往復以上の上下動をさせる。上下動の回数は１〜１０回の範囲であることが適当であり、２〜７回が好ましい。回数が多くなりすぎると、必要以上に時間を要し生産効率を低下させる原因となる。上下動の後、下型を大きく降下させて、下型２を筒状部材であるスリーブ５による包囲を外れた位置まで移動させて、下型２上の成形体を取り出して回収する。
【００１４】
尚、上型及び下型の少なくとも一方の上下動は、筒状部材であるスリーブ５による包囲が外れない範囲であることが適当である。上記例では、下型２を、スリーブ５による包囲を外れない範囲で上下動させることができる。
【００１５】
上下動の速度は０．１〜５００ｍｍ／ｓｅｃの範囲であることが好ましく、さらに好ましくは１〜１００ｍｍ／ｓｅｃである。移動速度が０．１ｍｍ／ｓｅｃ未満では上下動に時間がかかるばかりではなく、キャビティ内の圧力を低下させる効果も得られにくくなる。また、５００ｍｍ／ｓｅｃを超えると上下動の安定性が悪くなり、成形体を上型に押し付けてキズを生じ易くなる。
【００１６】
前記成形キャビティは、上下動の際に、一時的に減圧状態及び増圧状態になる。さらに、成形キャビティ内が減圧状態になったときに成形キャビティ外から成形キャビティ内に気体が流入する。また、成形キャビティ内が増圧状態になったときに成形キャビティ内から成形キャビティ外に気体が排出される。
下型２が下降すると成形キャビティ内は、一時的に減圧状態となり、スリーブ、上型、下型の空隙から気体がリークして、成形キャビティ内に流入する。成形キャビティ内に流入した気体は成形体に接触し、成形体の冷却を促進することができる。次いで、下型を上昇させると、キャビティ内は一時的に増圧状態となるが、スリーブ、上型、下型の空隙から気体がリークしてキャビティ外に排出される。この減圧及び増圧を、好ましくは２回〜７回繰り返すことで、キャビティ内を効果的に換気することができ、冷却効率を高めることもできる。更に、下型が下降する際に、キャビティ内が減圧状態となるため、上型に張り付いたガラス成形体を上型から引き離そうとする力が生ずる。これが繰り返されることで、成形体の上型への貼りつきを解除する効果も得られる。
【００１７】
さらに本発明の第１の製造方法に使用する製造装置は、成形面に密着したガラス成形体を離型させる強制離型手段を備えることが好ましい。この強制離型手段は、上型または下型に対して相対的に移動させるための移動手段を有する事が好ましい。
【００１８】
図２には、強制離型手段の一例として、成形面に密着したガラス成形体Ｇ’を、ガラス成形体の周縁部の少なくとも一部と接触することで離型させる手段（離型リング２０）を有する製造装置Ｂを示す。強制離型手段と成形面に密着したガラス成形体の周縁部の少なくとも一部との接触は、後述の移動手段の作用により、強制離型手段を上型または下型（図２の例では上型）に対して相対的に移動させることで行われる。さらに、この移動は、強制離型手段と接触したガラス成形体が成形面から剥離するように行われる。即ち、前記強制離型手段は、ガラス成形体が成形面から剥離する程度の距離を、上型または下型に対して相対的に移動する。強制離型手段のガラス成形体剥離時の動作は、後述の移動手段の説明で詳述する。また、強制離型手段は、上型と下型とがガラス素材を加圧するために接近した際に、下型により直接的または間接的に押し上げられるか、または上型により直接的または間接的に押し下げられて、加圧により形成されたガラス成形体との非接触状態となり得るものであることができる。これにより、ガラス素材を加圧してガラス成形体に成形する間は強制離型手段とガラス成形体とは非接触状態にあり、ガラス成形体の成形を妨げることがない。そして、ガラス成形体を離型する為に上型と下型とが離間したときに初めてガラス成形体は強制離型手段と接触して成形面から剥離される。
【００１９】
強制離型手段は、より好ましくは、上型成形面に密着したガラス成形体を、ガラス成形体の周縁部の少なくとも一部と接触することで離型させるためのものである。但し、強制離型手段は、下型成形面に密着したガラス成形体を、ガラス成形体の周縁部の少なくとも一部と接触することで下型成形面から離型させるためのものでもよく、また両者を併用しても良い。
【００２０】
成形面に密着したガラス成形体のための強制離型手段は、例えば、筒状やリング状であり、かつ成形面に密着したガラス成形体の周縁部の少なくとも一部と接触し得るように上型又は下型に外嵌されているものであることができる。
【００２１】
図２では、上型の周囲に強制離型手段（離型リング２０）を配置し、一対の成形型の離間時にこの強制離型手段がレンズの周縁部の少なくとも一部に接触して、成形体に下方向への力を加える構造をし、強制離型手段は上下型が接近した際に、下型により直接的または間接的に押し上げられて、ガラス成形体と非接触状態を形成する構成となっている。
【００２２】
また、離間時の下型の上下動の上限位置は強制離型手段が成形体に接触せず、かつ成形体が上型成形面に押しつけられない位置とし、下限位置は強制離型手段が成形体の周縁部の少なくとも一部に接触して成形体に下方向への力を加えられる位置に設定される。
【００２３】
強制離型手段のガラス成形体との接触部と上型または下型との間隔は、前記接触部分がガラス成形体の最外周縁部付近と接触できるように設定されることが適当である。例えば、強制離型手段のガラス成形体との接触部と上型の成形面の外周部とのクリアランスは、前記接触部分がガラス成形体の最外周縁部付近と接触できるように設定されることが適当である。また、強制離型手段のガラス成形体との接触部分と下型の成形面の外周部とのクリアランスは、前記接触部分がガラス成形体の最外周縁部付近と接触できるように設定されることが適当である。具体的には、強制離型手段のガラス成形体との接触部と上型または下型の成形面の外周部とのクリアランスは、例えば、０．０１５〜０．１ｍｍの範囲とすることが適当である。
【００２４】
移動手段は、上型と下型とが離間する際に、強制離型手段がガラス成形体の周縁部の少なくとも一部と接触し、かつガラス成形体を成形面から剥離するように、強制離型手段を上型または下型に対して相対的に移動させるためののものである。
【００２５】
強制離型手段が上型成形面に密着したガラス成形体を離型させるためのものである場合、移動手段は、強制離型手段が下型により直接的または間接的に押し上げられることで圧縮されて付勢力を蓄える付勢手段であることができる。下型による強制離型手段の押し上げは、ガラス素材を加圧する際に、上型と下型とが接近し、それとともに強制離型手段も下型と接近することで起こる。強制離型手段の下型による押し上げは、成形装置の構造（構成部材）応じて、下型と当接しながら直接行うことも、下母型等を介して間接的に行うこともできる。このような付勢手段は、上型と下型とが離間する際に、強制離型手段を下型に追動させることができる。付勢手段により下型に追動する強制離型手段は、追動の途中で、上型成形面に密着したガラス成形体と接触し、さらにこれを剥離することができる。
【００２６】
また、強制離型手段が下型成形面に密着したガラス成形体を下型成形面から離型させるものである場合、移動手段は、強制離型手段が上型により直接的または間接的に押し下げられることで、圧縮されて付勢力を蓄える付勢手段であることができる。上型による強制離型手段の押し下げは、ガラス素材を加圧する際に、上型と下型とが接近し、それとともに強制離型手段も上型と接近することで起こる。強制離型手段の上型による押し下げは、成形装置の構造（構成部材）応じて、上型と当接しながら直接行うことも、上母型等を介して間接的に行うこともできる。このような付勢手段は、上型と下型とが離間する際に、強制離型手段を上型に追動させることができる。付勢手段により上型に追動する強制離型手段は、追動の途中で、下型成形面に密着したガラス成形体と接触し、さらにこれを剥離することができる。
【００２７】
上記付勢手段は、例えば、コイル状バネ、棒状バネ、板バネ等の弾性体であることができる。移動手段は付勢手段以外の手段であることもできるが、付勢手段とすることで、取付や装置の構成を簡素化できるという利点がある。
付勢手段以外の移動手段としては、高圧の気体による加圧、シリンダやモーターによる加圧機構を用いる事もできる。
強制離型手段は、耐熱性素材、例えばＳＵＳ（ステンレス鋼）やタングステン合金等で構成することができる。また、付勢手段は、耐熱性素材、例えばジルコニア等のセラミックスからなる弾性体であり得る。
【００２８】
本発明の製造方法で使用する製造装置は、上記のように強制離型手段及び移動手段を有することで、上型又は下型の成形面からのガラス成形体の離型をより確実に行うことができる。このため、ガラス成形体の生産性を維持することが可能となる。
【００２９】
例えば、強制離型手段を有する製造装置を用いる製造方法の場合であって、強制離型手段が上型成形面に密着したガラス成形体を離型させるためのものである場合、加圧成形工程におけるガラス素材の加圧は、ガラス成形体の外径が、上型の成形面の外径より大きくなるように行う。その後、冷却を行なった後、離型リングがガラス成形体の周縁部に接触する位置まで下型を下降させて、ガラス成形体に下方向への力を加える事によって離型を促す。次いで、下型を上昇させる事によって一旦離型リングと成形体との接触を解除する。この際、ガラス成形体が上型に押しつけられない位置までに下型の上昇をとどめることが適当である。冷却固化したガラス成形体を型に押し付ける事は、ガラス成形体および成形面に損傷を与える恐れがあるためである。上昇した下型は再度下降し、離型リングとガラス成形体とを接触させる事により離型を促す。
【００３０】
このように、強制離型手段が、ガラス成形体に複数回力を作用することで、ガラス成形体を確実に上型から剥離することができる。即ち、下型が複数回上下動する動きによって、ガラス成形体の周縁部に離型リングを複数回押し当てる事により、強制離型手段の効果を更に向上させることができる。
【００３１】
強制離型手段の上下動の位置や移動速度は、上記のとおり精度よく管理されることが適当である。強制離型手段の上下動は、必ずしも下型、又は上型の動きに追随させる必要は無いが、下型又は上型は、プレス成形に際して精密に動きと位置を制御する機構を有しているため、これを利用して、強制離型手段を上下動させることが簡便でかつ効率がよい。
【００３２】
例えば、下型を上下動させる場合、上下動の間および上下動から下型の下降動作に移行する間に、下型の上下動を停止させる待ち時間を設定することもできる。下降から上昇への間に待ち時間を設定することにより離型リングを成形体周縁部に確実に押し当てる事ができると供に成形体に力を加える時間を延ばすことができる。逆に上昇から下降への間に待ち時間を設定することによりキャビティ内の温度の高い気体をキャビティ外へ充分排気することが可能となるとともに、それに続く下降時にキャビティ内の圧力変化を大きくする事ができる。
【００３３】
この待ち時間は、例えば、０〜１０秒の範囲であることが好ましく、さらに０〜３秒であることがより好ましい。上記効果を得るためにはこの範囲の時間で充分であり、これより待ち時間を長くしても生産効率を低下させるだけである。
【００３４】
本発明の第２の製造方法では、対向する上型及び下型を含み、かつこれら上型又は下型の周囲に強制離型手段を有する製造装置を用いる。この製造装置は、図２に示す製造装置において、上型１１及び下型１２を包囲する筒状部材であるスリーブ１５を除き（本発明の第２の製造方法で使用する製造装置はスリーブ１５を有さなくてもよい）、同様の構造及び機能を有する。本発明の第２の製造方法については後述する実施例３において、図４に基づいて説明する。
【００３５】
このように、本発明の製造方法では、上型成形面に密着したガラス成形体を、特別な工程を付加することなく、上型及び下型の上下動のみで確実に離型させることができる。従って、従来のガラス成形体と同等以上の生産性を得ることが可能である。
【００３６】
【実施例】
以下、添付図面を参照して、本発明の実施の形態について、さらに説明する。実施例１
図２に本発明の製造方法に使用するガラス成形体製造装置Ｂの断面形状を示す。
上主軸１３と下主軸１４は高精度に軸合わせされている。上型１１、下型１２、スリーブ１５は炭化ケイ素で構成され、少なくとも上、下型の成形面はＣＶＤ法で作られたものである。成形面には保護膜として硬質炭素膜を被覆した。上母型１６、下母型１７、上プレート１８、下プレート１９はタングステン合金である。強制離型手段である離型リング２０はステンレス、バネ２１はジルコニアで構成されている。上下一対の成形型の周囲には、加熱手段（図示せず）が配置される。加熱手段としては、高周波誘導加熱コイルなどが使用できる。炭化ケイ素等は高周波誘導加熱されないため、タングステン合金からなる母型を誘導加熱し、それによって炭化ケイ素で構成される上型１１、下型１２、スリーブ１５を間接加熱した。昇温スピードを速くする上で高周波加熱は極めて有利である。また、高周波加熱の場合、成形型の周囲にはコイルしかなく、保温するものがないので、降温スピードも速くできる。
【００３７】
上記のようにして組み立てられた製造装置を非酸化性雰囲気にし、成形型の周囲に設けた高周波誘導加熱コイル（図示せず）で成形型を加熱した。下型１２を降下させて、下型１２と上型１１とを離間させ、成形装置とは別の場所で所定の温度に加熱されて軟化した被成形ガラス素材をガラス材料を保持する治具により下型１２の成形面上に移送した。この実施の形態において、前記ガラス素材の加熱軟化は、該ガラス素材体を気流により浮上させながら行うことができ、加熱軟化したガラス素材は、ヒータ（図示せず）により所定の温度に予熱された下型１２に移送される。
【００３８】
ガラス素材が、その自重によって変形する程の低粘性域においては、加熱の際にガラス素材を保持する治具とガラスの融着を防止するのは非常に困難である。これに対して、治具の内部よりガスを噴出することにより、ガラス素材を気流により浮上させることで、治具面とガラス両面にガスのレイヤーを形成し、その結果、治具とガラスが反応することなく、加熱軟化することが好ましい。さらに、ガラス素材がプリフォームの場合、プリフォームの形状を維持しつつ加熱軟化することができる。また、ガラス素材がガラスゴブであり、不規則な形状で表面にシワ等の表面欠陥がある場合でも、加熱軟化しながら気流により浮上させることで、形状を整え、表面欠陥を消去することも可能である。
【００３９】
上述した、ガラス素材の浮上や加熱軟化したガラス素材の予熱した成形型への移送は、たとえば、特開平８−１３３７５８号公報に開示されている。ガラス素材の加熱は、常温から所定温度に加熱する場合、ある程度の温度のガラス素材を用いてさらに加熱する場合、さらに所定温度に既に加熱されているガラス素材を用いる場合を含む。たとえば、ガラス素材がガラスゴブの場合、溶融ガラスから作製されたガラスゴブを冷却することなく用いることもできる。また、ガラス素材を室温で成形型に導入し、成形型内で加熱してもよい。
【００４０】
このようにしてガラス素材が下型１２の成形面上に搬送されて、下型を上昇させてプレス成形を行った（本実施例ではプレス径が２０ｍｍの凸メニスカスレンズを成形）。図３（ａ）はプレス成形の直前の状態を示す。下型１２の成形面上にガラス素材Ｇが配置されている。また、離型リング２０はバネ２１により押し下げられているが離型リング止め２２で止められている。図３　（ｂ）はプレス成形中の状態である。このとき、離型リング止め２２で止められていた離型リング２０の下面２０ａが下型１２上面（成形面）の周辺部とぶつかることによって押し上げられ、離型リング２０の段部２３は、成形の際に押し出されるガラス成形体の周辺部と接触しない位置である上型１１の成形面より上方に移動する。また、離型リング２０の押し上げによりバネ２１は圧縮され、付勢力を蓄える。
【００４１】
プレスによってガラス成形体Ｇ’の外径は図３　（ｂ）に示すように上型１１の成形面の外径よりわずかに大きくなる。プレス時には、離型リング２０の段部２３は図３　（ｂ）のように上型１１の外周に位置し、ガラス成形体の外周部より上方にあるので、離型リング２０の段部２３とガラス成形体Ｇ’とは非接触状態である。尚、プレス開始条件は、成形型の温度が１０^７．５〜１０^１２ポアズのガラス粘度に対応する温度で、被成形ガラス素材の温度が成形型と等しい温度またはそれ以上の温度を適宜選択して行い、１００ｋｇ／ｃｍ^２の圧力で所定の肉厚より約０．０２ｍｍ厚いところまで加圧し、減圧して断電冷却し（ガスで強制冷却してもよい）、３０ｋｇ／ｃｍ^２の圧力で残りの０．０２ｍｍを伸ばした。
【００４２】
成形型の温度がガラスの転移点以下になったところで、図３（ｃ）に示すように離型リング２０がガラス成形体Ｇ’の周縁部に接触する位置まで下型を下降させて、ガラス成形体Ｇ’に下方向への力を加える事によって離型を促した。その後下型を上昇させる事によって一旦離型リング２０と成形体Ｇ’との接触を解除した（図３（ｄ））。この際、ガラス成形体Ｇ’が上型１１又は下型１２に押しつけられない位置までに下型１２の上昇をとどめた。この上下動を３回繰り返した後、下型１２を大きく降下させ（図３（ｅ））、取りだし手段（図示せず）によって下型１２上のガラス成形体Ｇ’を回収した。この時上下動の速度は１０ｍｍ／ｓｅｃとし、上昇と下降の間には毎回０．５秒の待ち時間を設定した。
【００４３】
ガラス成形体Ｇ’を下型１２上から取り出した後に、成形型の温度を高周波誘導加熱により直ちに回復させ、次の成形を行った。得られたガラス成形体は肉厚、面精度、軸ずれ、傾きのいずれもが極めて良好であった。外径については後工程で心取りして、最終製品にすることができる。この方法により連続プレスを５００回実施したが、上貼りつきは生ずる事が無かった。
【００４４】
比較としてこの上下動を行なうことなく、離間後そのまま下型を取りだし位置まで大きく降下させた場合には、５００回のプレス中８回上貼りつきが発生し、そのたびに装置の稼働を停止させる必要があった。
【００４５】
また、下型を離型リングがガラス成形体の周縁部に接触し、離型リングを下型の接触がなくなる位置まで下降させ、３回の上下動に要する時間である５秒間停止させた後取りだし位置まで大きく降下させた場合にも、５００回のプレス中６回上貼りつきが発生し、そのたびに装置の稼働を停止させる必要があった。
【００４６】
実施例２
図１に示す成形体製造装置Ａを非酸化性雰囲気にし、成形型の周囲に設けた高周波誘導加熱コイル（図示せず）で成形型を加熱した。下型２を降下させて、下型２と上型１とを離間させ、成形装置とは別の場所で所定の温度に加熱されて軟化した被成形ガラス素材Ｇをガラス材料を保持する治具により下型２の成形面上に移送した。
ガラス素材が下型２の成形面上に搬送されて、下型を上昇させてプレス成形を行った（本実施例ではプレス径が１８ｍｍの凹メニスカスレンズを成形）。
【００４７】
成形型の温度がガラスの転移点以下になったところで、スリーブと下型の嵌合が保たれている位置である１５ｍｍ下まで下型を下降させ、引き続きストローク１２ｍｍの上下動を３回繰り返した後、下型を大きく降下させ、取りだし手段によって下型上のガラス成形体を回収した。この時上下動の速度は８０ｍｍ／ｓｅｃとし、上昇と下降の間には毎回１秒の待ち時間を設定した。
ガラス成形体Ｇ’を下型２上から取り出した後に、成形型の温度を高周波誘導加熱により直ちに回復させ、次の成形を行った。得られたガラス成形体は肉厚、面精度、軸ずれ、傾きのいずれもが極めて良好であった。外径については後工程で心取りして、最終製品にすることができる。
この方法により連続プレスを１００回実施したが、上貼りつきは生しなかった。
【００４８】
比較としてこの上下動を行なうことなく、離間後そのまま下型を取りだし位置まで大きく降下させた場合には、上貼りつきが頻発し連続稼動ができなかった。
【００４９】
実施例３
図４に示す製造装置を用いた以外は、実施例１と同様の条件で、ガラス素材を成形型に供給し、プレス成形を行った。この装置は、上下型を包囲する筒状部材を備えていない一方、型素材などは図２のものと同様である。図４（ａ）はプレス成形の直前の状態を示す。下型１２の成形面上にガラス素材Ｇが配置されている。また、離型リング２０はバネ２１により押し下げられているが離型リング止め２２で止められている。図４　（ｂ）はプレス成形中の状態である。このとき、離型リング止め２２で止められていた離型リング２０の下面２０ａが下型１２上面（成形面）の周辺部とぶつかることによって押し上げられ、離型リング２０の段部２３は、成形の際に押し出されるガラス成形体の周辺部と接触しない位置である上型１２の成形面より上方に移動する。また、離型リング２０の押し上げによりバネ２１は圧縮され、付勢力を蓄える。
【００５０】
プレスによってガラス成形体Ｇ’の外径は図４　（ｂ）に示すように上型１の成形面の外径よりわずかに大きくなる。プレス時には、離型リング２０の段部２３は図３　（ｂ）のように上型１１の外周に位置し、ガラス成形体の外周部より上方にあるので、離型リング２０の段部２３とガラス成形体Ｇ’とは非接触状態である。尚、プレス開始条件は、成形型の温度が１０^７．５〜１０^１２ポアズのガラス粘度に対応する温度で、被成形ガラス素材の温度が成形型と等しい温度またはそれ以上の温度を適宜選択して行い、１００ｋｇ／ｃｍ^２の圧力で所定の肉厚より約０．０２ｍｍ厚いところまで加圧し、減圧して断電冷却し（ガスで強制冷却してもよい）、３０ｋｇ／ｃｍ^２の圧力で残りの０．０２ｍｍを伸ばした。
【００５１】
成形型の温度がガラスの転移点以下になったところで、図４（ｃ）に示すように離型リング２３がガラス成形体Ｇ’の周縁部に接触する位置まで下型１２を下降させて、ガラス成形体Ｇ’に下方向への力を加える事によって離型を促した。その後実施例１と同様に下型の上下動を３回繰り返した後、下型を大きく降下させ、取りだし手段によって下型上のガラス成形体を回収した。この時上下動の速度は１０ｍｍ／ｓｅｃとし、上昇と下降の間には毎回０．５秒の待ち時間を設定した。
得られたガラス成形体は肉厚、面精度、軸ずれ、傾きともに良好であった。
この方法により連続プレスを３００回実施したが、上貼りつきは１回しか発生しなかった。
【００５２】
【発明の効果】
本発明によれば、生産性を維持しつつ、面精度の優れたガラス成形体の成形方法を提供することが可能となる。即ち、本発明のガラス成形法によれば、上型又は下型の成形面へのガラス成形体の張りつきを防止でき、その結果、ガラス成形体の生産性を向上させることができる。
【図面の簡単な説明】
【図１】本発明の製造方法に使用するガラス成形体製造装置の一例の断面形状。
【図２】本発明の製造方法に使用するガラス成形体製造装置（強制離型手段を有する）の一例の断面形状。
【図３】図２示す製造装置（強制離型手段を有する）を用いたガラス成形体の製造例。
【図４】強制離型手段を有する製造装置を用いたガラス成形体の製造例。
【符号の説明】
Ａ　製造装置
Ｇ　ガラス素材
Ｇ’　ガラス成形体
１、１１　上型
２、１２　下型
３、１３　　上主軸
４、１４　　下主軸
５、１５　スリーブ
６、１６　上母型
７、１７　下母型
１８　上プレート
１９　下プレート
２０　離型リング
２１　バネ
２２　離型リング止め
２３　段部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a method for producing a glass molded body such as a lens, and a glass optical element that easily sticks to a molding die, for example, even a lens having a concave surface, preventing sticking to a molding die, and The present invention relates to a method for producing a glass molded body that can be operated.
[0002]
[Prior art]
As a conventionally known lens molding method, for example, a glass material and a molding die are heated to a temperature (10 ° C.) at which the glass material softens. ^7.5 -10 ¹¹ After heating to a temperature corresponding to the glass viscosity of Poise), there is a method in which a glass material is press-molded with a mold. After press molding, the glass transition temperature (10 ^Thirteen After cooling to near or below poise, the mold is released and the lens is removed from the mold.
[0003]
In this molding method, the lens molded during release may remain stuck to the molding surface. The molding die usually includes an upper die and a lower die. When the lens is stuck to the lower die, the lens may not be able to be taken out in the lens taking-out step after release. In addition, when the lens sticks to the upper mold, not only cannot the lens be taken out, but also it falls on the lower mold and the like, causing various troubles. Further, if the next glass material is supplied to the lower mold forming surface while being attached to the upper mold, continuous operation is hindered. Sticking to the mold is more likely to occur when the shape of the molding surface is convex than when it is concave. When the molding surface is convex, the thermal expansion coefficient of the glass and the mold is different (the thermal expansion coefficient of the glass is large), so that the thermal contraction of the glass lens due to cooling is larger than that of the molding die. Is to adhere to the molding surface.
[0004]
As means for preventing such sticking, for example, Japanese Patent Application Laid-Open No. 2-184531 discloses a method of inserting a wedge member between a molded lens and a molding die. Also, Japanese Patent Application Laid-Open No. 2-184533 discloses a method of injecting an inert gas to a lens from a gap between an upper mold and a lower mold. Further, Japanese Patent Application Laid-Open No. 2001-192215 discloses a method using forced release means for contacting at least a part of a peripheral portion of a molded body and pushing the molded body downward.
[0005]
[Problems to be solved by the invention]
However, the method of inserting a wedge member between a molded lens and a mold disclosed in JP-A-2-184531 has a problem that the lens and the molding surface are easily scratched. Further, in the method described in Japanese Patent Application Laid-Open No. 2-184533, since it is necessary to inject an inert gas to the lens from the gap between the upper mold and the lower mold, the periphery of the mold cannot be covered with another member. For this reason, there is a problem that the upper and lower molds are easily displaced and the heat uniformity is easily impaired. Further, the method described in Japanese Patent Application Laid-Open No. 2001-192215 has a certain degree of effect, but in the case of a severely sticking temperature or a molded article, for example, in the case of releasing the mold at a relatively high temperature (for example, Tg or more), Sufficient effects could not be obtained for lenses having a concave, convex, or planar shape with a large radius of curvature.
[0006]
Therefore, an object of the present invention is to provide a new means for solving such a problem, and more specifically, even in the case of the above-mentioned severe temperature of sticking or the shape of a molded article. Another object of the present invention is to provide a method for manufacturing a glass molded body such as a lens, which can easily be released from a molding die and can obtain a product having a highly accurate surface shape.
[0007]
[Means for Solving the Problems]
Means of the invention for solving the above problems are as follows.
[Claim 1] By pressure-forming a heat-softened glass material by a manufacturing apparatus including an upper die and a lower die facing each other and a tubular member directly and / or indirectly surrounding the upper die and the lower die. In the method for producing a glass molded body,
A method of manufacturing a glass molded body (hereinafter, referred to as a method) in which at least one of an upper mold and a lower mold is moved up and down one or more times before and after removing the molded glass molded body from the manufacturing apparatus after the pressure molding. This is referred to as a first manufacturing method of the present invention).
[2] The manufacturing method according to [1], wherein the vertical movement is repeated 2 to 7 times.
[Claim 3] The space defined by the upper mold, the lower mold, and the cylindrical member (hereinafter referred to as a molding cavity) is temporarily decompressed and increased when it moves up and down. 3. The production method according to 2.
[4] The method according to [3], wherein a gas flows into the molding cavity from outside the molding cavity when the pressure inside the molding cavity is reduced.
[5] The manufacturing method according to [3], wherein when the pressure inside the molding cavity is increased, gas is discharged from inside the molding cavity to outside the molding cavity.
[6] The manufacturing method according to any one of [1] to [5], wherein the up and down movement of at least one of the upper mold and the lower mold is performed within a range where the surrounding by the tubular member does not come off.
[Claim 7] The manufacturing apparatus further has a forced mold releasing means around an upper mold or a lower mold, and at the time of the vertical movement, at least a peripheral portion of a glass molded body molded with the forced mold releasing means. The method according to any one of claims 1 to 6, wherein a downward or upward force is applied to a part.
[Claim 8] The forcible mold releasing means is disposed around the upper mold, and the forced releasing means applies a downward force to at least a part of the peripheral portion of the lens every time the vertical movement is performed. The manufacturing method as described.
[Claim 9] A glass molded body obtained by press-molding a heat-softened glass material by a manufacturing apparatus including an opposing upper mold and a lower mold, and having forced releasing means around the upper mold and the lower mold. In the method for producing
After the pressure molding, before taking out the molded glass molded article from the manufacturing apparatus, at least one of the upper mold and the lower mold is moved up and down one or more times, and the forcible mold release means is used to move the periphery of the molded glass molded article. A method for producing a glass optical material, which comprises applying a downward or upward force to at least a part of a part (hereinafter, referred to as a second production method of the present invention).
[Claim 10] The forced release means is disposed around the upper mold, and each time the vertical movement is performed, the forced release means applies a downward force to at least a part of the periphery of the glass molded body. 10. The production method according to 9.
[0008]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the first manufacturing method of the present invention, a glass material which has been heated and softened is heated by a manufacturing apparatus including an upper die and a lower die facing each other and a cylindrical member directly and / or indirectly surrounding the upper die and the lower die. This is a method of producing a glass molded body by pressing. FIG. 1 shows a cross-sectional shape of an example of a manufacturing apparatus used in the first manufacturing method of the present invention.
The manufacturing apparatus A includes an upper mold 1 and a lower mold 2 that can be separated from and approached to each other, and the upper mold and the lower mold have opposing molding surfaces. Further, the manufacturing apparatus has a structure in which the upper mold and the lower mold can be separated from each other when the glass material is supplied to the lower mold forming surface of the glass material and removed from the lower mold forming surface of the glass molded body. The apparatus having such a configuration, the upper mold and the lower mold when the material and the structure of the upper mold and the lower mold, and the supply of the glass material to the lower mold molding surface and the removal of the glass molded body from the lower mold molding surface. The method of separation is described, for example, in JP-A-11-49523.
[0009]
The manufacturing apparatus A has a sleeve 5 which is a tubular member surrounding the upper mold 1 and the lower mold 2 in addition to the upper mold 1 and the lower mold 2. The sleeve 5 directly surrounds the upper mold 1 and the lower mold 2.
The manufacturing apparatus A has a molding cavity 8 which is a space formed by the upper mold 1, the lower mold 2 and the sleeve 5 which is a cylindrical member. The production apparatus used in the production method of the present invention may include an upper mold 6, a lower mold 7, and the like in addition to the upper mold 1, the lower mold 2, and the sleeve 5, as will be described in detail in Examples below.
[0010]
Examples of the material of the upper mold and the lower mold include metals such as Mo and W, cemented carbides such as WC, and ceramics such as silicon carbide, silicon nitride, titanium carbide, titanium nitride, aluminum nitride, and tungsten carbide. Further, it is preferable that a protective film is formed on the molding surfaces of the upper mold and the lower mold for the purpose of improving oxidation resistance, durability and fusion resistance. As the protective film, a thin film made of a noble metal material containing Pt, Rh, Au, Re, Os, Ir, etc., a hard carbon film, a carbon-based thin film such as diamond-like carbon, SiC, Si ₃ N ₄ , A ceramic material such as titanium carbide, titanium nitride, and alumina, and a thin film made of a composite material thereof. The protective film can be formed by, for example, a sputtering method, an ion plating method, a CVD method, or the like, and may be a single-layer film or a multilayer film made of different materials.
[0011]
In the production method of the present invention, a glass molded body is produced by pressure-molding a heat-softened glass material. In the present invention, the glass composition, shape, and dimensions of the glass material are not particularly limited, and a glass molded body is favorably produced even from a glass material having a glass composition that is easily fused to a molding surface of a mold. be able to. In addition, there is no particular limitation on the heating conditions of the glass material and the molding die, the pressing conditions and the method for pressure molding, and the like.
[0012]
Applicable to the production method of the present invention, a method for manufacturing a glass molded body including a step of pressing a glass material, a step of cooling a pressed glass molded body, a step of releasing the cooled glass molded body, The method described in JP-A-11-49523 can be used for the type of material and the conditions of each step, for example. Further, the glass molded body manufactured by the manufacturing method of the present invention can be, for example, an optical element. More specifically, the optical element can be various optical elements such as an aspheric lens such as a concave lens, a convex lens, a meniscus lens, and a concave meniscus lens, and a cylindrical lens. Further, the glass molded body can be, for example, a substrate for an electronic device such as a disk substrate.
[0013]
The production method of the present invention is characterized in that at least one of the upper mold and the lower mold is moved up and down one or more times after the pressure molding and before taking out the molded glass molded article from the production apparatus.
More specifically, for example, after heating the upper and lower molds and supplying the heated glass body onto the lower mold, the lower mold is raised and the glass body is pressure-formed between the upper and lower molds. Cooling is performed at the same time as or after the pressure molding, and when the mold and the molded body have decreased to a predetermined temperature, the lower mold is slightly lowered and separated. Subsequently, the lower mold is moved up and down one or more times. The number of vertical movements is suitably in the range of 1 to 10 times, preferably 2 to 7 times. If the number of times is too large, it takes more time than necessary and causes a reduction in production efficiency. After the vertical movement, the lower mold is largely lowered, and the lower mold 2 is moved to a position outside the surroundings of the sleeve 5 which is a cylindrical member, and the molded body on the lower mold 2 is taken out and collected.
[0014]
It is appropriate that the vertical movement of at least one of the upper mold and the lower mold is within a range where the surrounding by the sleeve 5 as the cylindrical member does not come off. In the above example, the lower mold 2 can be moved up and down within a range that does not deviate from the surroundings of the sleeve 5.
[0015]
The vertical movement speed is preferably in the range of 0.1 to 500 mm / sec, more preferably 1 to 100 mm / sec. If the moving speed is less than 0.1 mm / sec, not only does it take time to move up and down, but also it is difficult to obtain the effect of reducing the pressure in the cavity. On the other hand, if it exceeds 500 mm / sec, the stability of the vertical movement is deteriorated, and the molded body is pressed against the upper mold, so that the molded body is easily damaged.
[0016]
The molding cavity temporarily enters a reduced pressure state and a increased pressure state when moving up and down. Further, when the pressure in the molding cavity is reduced, gas flows from outside the molding cavity into the molding cavity. Further, when the pressure inside the molding cavity is increased, gas is discharged from inside the molding cavity to outside the molding cavity.
When the lower mold 2 descends, the inside of the molding cavity is temporarily depressurized, and gas leaks from the gaps of the sleeve, the upper mold and the lower mold and flows into the molding cavity. The gas that has flowed into the molding cavity comes into contact with the molded body and can promote cooling of the molded body. Next, when the lower mold is raised, the inside of the cavity is temporarily in a pressure-increasing state, but gas leaks from the gaps of the sleeve, the upper mold and the lower mold and is discharged out of the cavity. This pressure reduction and pressure increase is preferably repeated two to seven times, so that the inside of the cavity can be effectively ventilated and the cooling efficiency can be increased. Further, when the lower mold is lowered, the inside of the cavity is decompressed, so that a force is generated to separate the glass molded body attached to the upper mold from the upper mold. By repeating this, the effect of releasing the sticking of the molded body to the upper mold can be obtained.
[0017]
Furthermore, it is preferable that the manufacturing apparatus used in the first manufacturing method of the present invention includes a forced mold releasing means for releasing the glass molded body which is in close contact with the molding surface. It is preferable that the forcible mold releasing means has a moving means for relatively moving the upper mold or the lower mold.
[0018]
FIG. 2 shows, as an example of a forced mold release means, a means for releasing the glass molded body G ′ in close contact with the molding surface by contacting at least a part of the periphery of the glass molded body (release ring 20). Is shown. Contact between the forcible release means and at least a part of the peripheral edge of the glass molded body in close contact with the molding surface is performed by moving the forcible release means to an upper mold or a lower mold (in the example of FIG. (Type). Further, this movement is performed so that the glass molded body that has come into contact with the forcible mold release means is separated from the molding surface. That is, the forcible mold release means moves relative to the upper mold or the lower mold by a distance enough to separate the glass molded body from the molding surface. The operation of the forcible mold releasing means at the time of peeling the glass molded body will be described in detail in the description of the moving means described later. Further, when the upper mold and the lower mold approach each other to press the glass material, the forced mold is directly or indirectly pushed up by the lower mold, or directly or indirectly by the upper mold. It can be pressed down so as to be in a non-contact state with the glass molded body formed by pressurization. Thereby, while the glass material is pressed and formed into a glass molded body, the forced release means and the glass molded body are not in contact with each other, and do not hinder the molding of the glass molded body. Then, only when the upper mold and the lower mold are separated from each other in order to release the glass molded body, the glass molded body comes into contact with the forced release means and is peeled off from the molding surface.
[0019]
More preferably, the forcible mold releasing means is for releasing the glass molded body that is in close contact with the upper mold forming surface by contacting at least a part of the peripheral edge of the glass molded body. However, the forcible mold release means may be for releasing the glass molded body in close contact with the lower mold molding surface from the lower mold molding surface by contacting at least a part of the periphery of the glass molded body, You may use both together.
[0020]
The forcible mold release means for the glass molded body in close contact with the molding surface is, for example, cylindrical or ring-shaped, and is formed so as to be able to contact at least a part of the peripheral portion of the glass molded body in close contact with the molding surface. It can be externally fitted to the mold or lower mold.
[0021]
In FIG. 2, forcible mold release means (release ring 20) is arranged around the upper mold, and when the pair of molds is separated, the forced mold release means contacts at least a part of the peripheral edge of the lens to form the mold. A structure in which a downward force is applied to the body, and the forcible mold release means is pushed up directly or indirectly by the lower mold when the upper and lower molds approach to form a non-contact state with the glass molded body. It has become.
[0022]
The upper limit of the vertical movement of the lower mold at the time of separation is a position where the forcible release means does not contact the molded body and the molded body is not pressed against the upper mold forming surface, and the lower limit position is the position where the forcible release means is formed. The molded body is set at a position where a downward force can be applied to the molded body by contacting at least a part of the periphery of the body.
[0023]
It is appropriate that the distance between the contact portion of the forced mold release means with the glass molded body and the upper mold or the lower mold is set so that the contact portion can come into contact with the vicinity of the outermost peripheral edge of the glass molded body. For example, the clearance between the contact portion of the forced mold release means with the glass molded body and the outer peripheral portion of the molding surface of the upper mold is set such that the contact portion can come into contact with the vicinity of the outermost peripheral edge of the glass molded body. Is appropriate. Further, the clearance between the contact portion of the forced mold release means with the glass molded body and the outer peripheral portion of the molding surface of the lower mold is set so that the contact portion can come into contact with the vicinity of the outermost peripheral edge of the glass molded body. Is appropriate. Specifically, the clearance between the contact portion of the forced mold release means with the glass molded body and the outer peripheral portion of the molding surface of the upper mold or the lower mold is, for example, preferably in the range of 0.015 to 0.1 mm. It is.
[0024]
The moving means is forcibly released so that when the upper mold and the lower mold are separated from each other, the forced mold releasing means comes into contact with at least a part of the peripheral edge of the glass molded body and peels the glass molded body from the molding surface. This is for moving the mold means relatively to the upper mold or the lower mold.
[0025]
When the forcible release means is for releasing the glass molded body in close contact with the upper mold forming surface, the moving means is compressed by the forcible release means being directly or indirectly pushed up by the lower mold. Biasing means for storing the biasing force. Pushing up of the forced release means by the lower mold occurs when the upper mold and the lower mold approach when the glass material is pressed, and the forced mold release means also approaches the lower mold. Depending on the structure (components) of the molding apparatus, the forcible release means can be pushed up by the lower mold directly while contacting the lower mold or indirectly via a lower mold. Such an urging means can cause the forced release means to follow the lower mold when the upper mold and the lower mold are separated from each other. The forcible release means, which follows the lower mold by the urging means, comes into contact with the glass molded body in close contact with the molding surface of the upper mold during the follow-up, and can peel it off.
[0026]
Further, when the forcible release means is for releasing the glass molded body in close contact with the lower mold forming surface from the lower mold forming surface, the moving means is such that the forcible release means is directly or indirectly pushed down by the upper mold. By doing so, it can be an urging means that is compressed and stores an urging force. The lowering of the forced release means by the upper mold occurs when the upper mold and the lower mold approach when the glass material is pressed, and the forced mold release means also approaches the upper mold. Depending on the structure (components) of the molding apparatus, the forced release means can be pressed down by the upper mold directly while contacting the upper mold, or indirectly via an upper matrix or the like. Such an urging means can cause the forced release means to follow the upper mold when the upper mold and the lower mold are separated. The forcible mold release means that follows the upper mold by the urging means comes in contact with the glass molded body that is in close contact with the lower mold forming surface during the follow-up, and can further separate it.
[0027]
The urging means may be, for example, an elastic body such as a coil spring, a bar spring, and a leaf spring. The moving means may be means other than the urging means, but using the urging means has an advantage that the mounting and the configuration of the device can be simplified.
As moving means other than the urging means, a pressurizing mechanism using a high-pressure gas or a pressurizing mechanism using a cylinder or a motor can be used.
The forced release means can be made of a heat-resistant material, for example, SUS (stainless steel) or a tungsten alloy. Further, the biasing means may be an elastic body made of a heat-resistant material, for example, ceramics such as zirconia.
[0028]
The production apparatus used in the production method of the present invention includes the forced release means and the moving means as described above, so that the glass molded body can be more reliably released from the molding surface of the upper mold or the lower mold. Can be. For this reason, it becomes possible to maintain the productivity of the glass molded body.
[0029]
For example, in the case of a manufacturing method using a manufacturing apparatus having a forced mold release means, and in a case where the forced mold release means is for releasing the glass molded body in close contact with the upper mold forming surface, a pressure forming step Is performed such that the outer diameter of the glass molded body is larger than the outer diameter of the molding surface of the upper mold. Thereafter, after cooling, the lower mold is lowered to a position where the release ring contacts the peripheral portion of the glass molded body, and the mold is urged by applying a downward force to the glass molded body. Next, the contact between the release ring and the molded body is temporarily released by raising the lower mold. At this time, it is appropriate to stop the lower mold from rising to a position where the glass molded body is not pressed against the upper mold. Pressing the cooled and solidified glass molded body against the mold is likely to damage the glass molded body and the molding surface. The raised lower mold is lowered again, and the mold release ring is urged by bringing the mold release ring into contact with the glass molded body.
[0030]
As described above, the forced mold release means applies a force to the glass molded body a plurality of times, so that the glass molded body can be reliably separated from the upper mold. That is, the effect of the forcible mold release means can be further improved by pressing the mold release ring a plurality of times against the periphery of the glass molded body by the movement of the lower mold moving up and down a plurality of times.
[0031]
It is appropriate that the position and the moving speed of the vertical movement of the forcible mold release means be managed with high precision as described above. The vertical movement of the forcible mold release means does not necessarily need to follow the movement of the lower mold or the upper mold, but the lower mold or the upper mold has a mechanism for precisely controlling the movement and position during press molding. Therefore, it is simple and efficient to move the forced release means up and down by using this.
[0032]
For example, when the lower die is moved up and down, a waiting time for stopping the vertical movement of the lower die can be set during the vertical movement and during the transition from the vertical movement to the lowering operation of the lower die. By setting the waiting time between the descent and the ascent, the release ring can be reliably pressed against the periphery of the molded body, and the time for applying force to the molded body can be extended. Conversely, by setting a waiting time between rising and falling, it is possible to sufficiently exhaust high-temperature gas in the cavity to the outside of the cavity, and to increase the pressure change in the cavity during the subsequent descending. Can be.
[0033]
This waiting time is, for example, preferably in the range of 0 to 10 seconds, and more preferably 0 to 3 seconds. The time in this range is sufficient to obtain the above effects, and if the waiting time is longer than this, the production efficiency is only reduced.
[0034]
In the second manufacturing method of the present invention, a manufacturing apparatus including an upper die and a lower die facing each other and having forced release means around the upper die or the lower die is used. This manufacturing apparatus is the same as the manufacturing apparatus shown in FIG. 2 except for a sleeve 15 which is a cylindrical member surrounding the upper mold 11 and the lower mold 12 (the manufacturing apparatus used in the second manufacturing method of the present invention is the same as the manufacturing apparatus shown in FIG. 2). Having the same structure and function. A second manufacturing method of the present invention will be described in a third embodiment described later with reference to FIG.
[0035]
As described above, in the manufacturing method of the present invention, the glass molded body in close contact with the upper mold molding surface can be reliably released only by the vertical movement of the upper mold and the lower mold without adding a special process. . Therefore, it is possible to obtain productivity equal to or higher than that of a conventional glass molded body.
[0036]
【Example】
Hereinafter, embodiments of the present invention will be further described with reference to the accompanying drawings. Example 1
FIG. 2 shows a cross-sectional shape of a glass molded body manufacturing apparatus B used in the manufacturing method of the present invention.
The upper spindle 13 and the lower spindle 14 are aligned with high accuracy. The upper mold 11, the lower mold 12, and the sleeve 15 are made of silicon carbide, and at least the molding surfaces of the upper and lower molds are made by the CVD method. The molded surface was covered with a hard carbon film as a protective film. The upper mold 16, the lower mold 17, the upper plate 18, and the lower plate 19 are made of a tungsten alloy. The release ring 20 which is a forced release means is made of stainless steel, and the spring 21 is made of zirconia. A heating means (not shown) is arranged around the pair of upper and lower molds. As the heating means, a high frequency induction heating coil or the like can be used. Since silicon carbide or the like is not subjected to high-frequency induction heating, a master die made of a tungsten alloy was induction-heated, thereby indirectly heating the upper die 11, the lower die 12, and the sleeve 15 made of silicon carbide. In order to increase the heating speed, high-frequency heating is extremely advantageous. In the case of high-frequency heating, since there is only a coil around the mold and there is nothing to keep the temperature, the temperature can be reduced at a high speed.
[0037]
The manufacturing apparatus assembled as described above was placed in a non-oxidizing atmosphere, and the mold was heated by a high-frequency induction heating coil (not shown) provided around the mold. The lower mold 12 is lowered, the lower mold 12 and the upper mold 11 are separated from each other, and the glass material to be molded which has been softened by being heated to a predetermined temperature in a place different from the molding apparatus is held by a jig for holding the glass material. It was transferred onto the molding surface of the lower mold 12. In this embodiment, the heating and softening of the glass material can be performed while the glass material body is floated by an air current, and the heated and softened glass material is preheated to a predetermined temperature by a heater (not shown). It is transferred to the lower mold 12.
[0038]
In a low-viscosity region where the glass material is deformed by its own weight, it is very difficult to prevent the glass from being fused with the jig holding the glass material during heating. On the other hand, a gas layer is formed on the jig surface and on both sides of the glass by ejecting gas from the inside of the jig, causing the glass material to float by the air current, and as a result, the jig and the glass react. It is preferable to heat-soften without heating. Furthermore, when the glass material is a preform, it can be softened by heating while maintaining the shape of the preform. In addition, even if the glass material is a glass gob and has an irregular shape with surface defects such as wrinkles, it is possible to adjust the shape and erase the surface defects by floating by airflow while heating and softening. is there.
[0039]
The above-mentioned floating of the glass material and transfer of the heat-softened glass material to a preheated mold are disclosed in, for example, JP-A-8-133758. The heating of the glass material includes a case where the glass material is heated from room temperature to a predetermined temperature, a case where the glass material having a certain temperature is further heated, and a case where a glass material already heated to a predetermined temperature is used. For example, when the glass material is a glass gob, a glass gob made of molten glass can be used without cooling. Alternatively, the glass material may be introduced into the mold at room temperature and heated in the mold.
[0040]
In this way, the glass material was conveyed onto the molding surface of the lower mold 12, and the lower mold was raised to perform press molding (in this example, a convex meniscus lens having a press diameter of 20 mm was formed). FIG. 3A shows a state immediately before press molding. A glass material G is arranged on the molding surface of the lower mold 12. The release ring 20 is pushed down by a spring 21 but is stopped by a release ring stopper 22. FIG. 3B shows a state during press molding. At this time, the lower surface 20a of the release ring 20 stopped by the release ring stopper 22 hits the periphery of the upper surface (forming surface) of the lower die 12 and is pushed up, and the step portion 23 of the release ring 20 is formed. At this time, it moves upward from the molding surface of the upper mold 11 which is a position not in contact with the peripheral portion of the extruded glass molded body. Further, the spring 21 is compressed by pushing up the release ring 20, and accumulates the urging force.
[0041]
By pressing, the outer diameter of the glass molded body G ′ becomes slightly larger than the outer diameter of the molding surface of the upper mold 11 as shown in FIG. At the time of pressing, the step 23 of the release ring 20 is located on the outer periphery of the upper mold 11 as shown in FIG. 3B and is higher than the outer periphery of the glass molded body. It is in a non-contact state with the glass molded body G ′. The press start condition is that the temperature of the mold is 10 ^7.5 -10 ¹² At a temperature corresponding to the glass viscosity of Poise, the temperature of the glass material to be molded is equal to or higher than the temperature of the molding die, and is appropriately selected. ² Pressurized to a place about 0.02 mm thicker than the predetermined thickness, and then decompressed and cooled down by electricity (may be forcibly cooled with gas), 30 kg / cm ² The remaining 0.02 mm was stretched by the pressure described above.
[0042]
When the temperature of the mold falls below the glass transition point, the lower mold is lowered to a position where the release ring 20 comes into contact with the periphery of the glass molded body G ′ as shown in FIG. The mold release was promoted by applying a downward force to the molded body G ′. Thereafter, the lower mold was raised to release the contact between the release ring 20 and the molded body G ′ (FIG. 3D). At this time, the lower mold 12 was kept from rising to a position where the glass molded body G ′ was not pressed against the upper mold 11 or the lower mold 12. After repeating this up and down movement three times, the lower mold 12 was largely lowered (FIG. 3E), and the glass molded body G ′ on the lower mold 12 was recovered by a removing means (not shown). At this time, the vertical movement speed was set to 10 mm / sec, and a waiting time of 0.5 seconds was set between the ascending and descending each time.
[0043]
After removing the glass molded body G 'from the lower mold 12, the temperature of the mold was immediately recovered by high-frequency induction heating, and the next molding was performed. The obtained glass molded body was extremely good in all of the wall thickness, surface accuracy, axis deviation, and inclination. The outer diameter can be taken into account in a later process to produce a final product. The continuous pressing was performed 500 times by this method, but no sticking occurred on the upper side.
[0044]
As a comparison, when the lower mold is taken out as it is, and the lower die is largely lowered to the take-out position without performing the vertical movement, the upper sticking occurs eight times during 500 presses, and the operation of the apparatus is stopped each time. Needed.
[0045]
Further, after the lower mold release ring is brought into contact with the periphery of the glass molded body, the lower mold ring is lowered to a position where the lower mold does not come into contact, and the lower mold is stopped for 5 seconds, which is the time required for three vertical movements. Even when it was lowered significantly to the take-out position, upper sticking occurred six times during 500 presses, and it was necessary to stop the operation of the apparatus each time.
[0046]
Example 2
The molding manufacturing apparatus A shown in FIG. 1 was set to a non-oxidizing atmosphere, and the molding die was heated by a high-frequency induction heating coil (not shown) provided around the molding die. A jig for lowering the lower mold 2 to separate the lower mold 2 and the upper mold 1 and holding the glass material G to be softened by being heated to a predetermined temperature and softened at a place different from the molding apparatus. And transferred onto the molding surface of the lower mold 2.
The glass material was conveyed onto the molding surface of the lower mold 2, and the lower mold was raised to perform press molding (in this embodiment, a concave meniscus lens having a press diameter of 18 mm).
[0047]
When the temperature of the molding die became equal to or lower than the glass transition point, the lower die was lowered to 15 mm below the position where the engagement between the sleeve and the lower die was maintained, and the vertical movement with a stroke of 12 mm was repeated three times. Thereafter, the lower mold was largely lowered, and the glass molded body on the lower mold was recovered by a removing means. At this time, the vertical movement speed was set to 80 mm / sec, and a waiting time of 1 second was set every time between rising and falling.
After removing the glass molded body G 'from the lower mold 2, the temperature of the mold was immediately recovered by high-frequency induction heating, and the next molding was performed. The obtained glass molded body was extremely good in all of the wall thickness, surface accuracy, axis deviation, and inclination. The outer diameter can be taken into account in a later process to produce a final product.
The continuous pressing was performed 100 times by this method, but no sticking occurred on the upper side.
[0048]
As a comparison, when the lower mold was taken out and separated to a great extent and lowered to the position after the separation without performing the up and down movement, sticking of the upper part occurred frequently and continuous operation could not be performed.
[0049]
Example 3
A glass material was supplied to a mold under the same conditions as in Example 1 except that the manufacturing apparatus shown in FIG. 4 was used, and press molding was performed. This apparatus does not include a tubular member surrounding the upper and lower molds, while the mold material and the like are the same as those in FIG. FIG. 4A shows a state immediately before press molding. A glass material G is arranged on the molding surface of the lower mold 12. The release ring 20 is pushed down by a spring 21 but is stopped by a release ring stopper 22. FIG. 4B shows a state during press molding. At this time, the lower surface 20a of the release ring 20 stopped by the release ring stopper 22 hits the periphery of the upper surface (forming surface) of the lower die 12 and is pushed up, so that the step 23 of the release ring 20 is formed. At this time, it moves upward from the molding surface of the upper mold 12 which is a position not in contact with the peripheral portion of the glass molded body extruded. Further, the spring 21 is compressed by pushing up the release ring 20, and accumulates the urging force.
[0050]
By pressing, the outer diameter of the glass molded body G ′ becomes slightly larger than the outer diameter of the molding surface of the upper mold 1 as shown in FIG. At the time of pressing, the step 23 of the release ring 20 is located on the outer periphery of the upper mold 11 as shown in FIG. 3B and is higher than the outer periphery of the glass molded body. It is in a non-contact state with the glass molded body G ′. The press start condition is that the temperature of the mold is 10 ^7.5 -10 ¹² At a temperature corresponding to the glass viscosity of Poise, the temperature of the glass material to be molded is equal to or higher than the temperature of the molding die, and is appropriately selected. ² Pressurized to a place about 0.02 mm thicker than the predetermined thickness, and then decompressed and cooled down by electricity (may be forcibly cooled with gas), 30 kg / cm ² The remaining 0.02 mm was stretched by the pressure described above.
[0051]
When the temperature of the mold falls below the glass transition point, the lower mold 12 is lowered to a position where the release ring 23 comes into contact with the periphery of the glass molded body G ′ as shown in FIG. The mold release was promoted by applying a downward force to the glass molded body G ′. Thereafter, the vertical movement of the lower mold was repeated three times in the same manner as in Example 1, and then the lower mold was largely lowered, and the glass molded body on the lower mold was recovered by a removing means. At this time, the vertical movement speed was set to 10 mm / sec, and a waiting time of 0.5 seconds was set between the ascending and descending each time.
The obtained glass molded body had good thickness, surface accuracy, axial deviation, and inclination.
The continuous pressing was performed 300 times by this method, but the upper sticking occurred only once.
[0052]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method of the glass molding excellent in surface precision, maintaining productivity. That is, according to the glass forming method of the present invention, sticking of the glass formed body to the forming surface of the upper mold or the lower mold can be prevented, and as a result, the productivity of the glass formed body can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an example of a glass molded body manufacturing apparatus used in the manufacturing method of the present invention.
FIG. 2 is a cross-sectional view of an example of a glass molded body manufacturing apparatus (having forced release means) used in the manufacturing method of the present invention.
FIG. 3 is a production example of a glass molded body using the production apparatus (having forced release means) shown in FIG. 2;
FIG. 4 is a production example of a glass molded body using a production apparatus having a forced releasing means.
[Explanation of symbols]
A Manufacturing equipment
G glass material
G 'glass molding
1,11 Upper type
2,12 lower mold
3, 13 Upper spindle
4, 14 Lower spindle
5, 15 sleeve
6, 16 Upper mold
7, 17 Lower mold
18 Upper plate
19 Lower plate
20 Release ring
21 Spring
22 Release ring stopper
23 steps

Claims

A glass molded body is manufactured by press-molding a heat-softened glass material by a manufacturing apparatus including a facing upper mold and a lower mold and a cylindrical member directly and / or indirectly surrounding the upper mold and the lower mold. In the method
A method for producing a glass molded body, comprising: moving at least one of an upper mold and a lower mold up and down one or more times before and after removing a molded glass molded body from a manufacturing apparatus after pressure molding.

The method according to claim 1, wherein the vertical movement is repeated 2 to 7 times.

3. The manufacturing method according to claim 1, wherein a space defined by the upper mold, the lower mold, and the cylindrical member (hereinafter, referred to as a molding cavity) is temporarily reduced in pressure and increased in pressure when moving up and down. Method.

4. The method according to claim 3, wherein a gas flows into the molding cavity from outside the molding cavity when the pressure inside the molding cavity is reduced.

4. The manufacturing method according to claim 3, wherein when the pressure inside the molding cavity is increased, gas is discharged from inside the molding cavity to outside the molding cavity.

The manufacturing method according to any one of claims 1 to 5, wherein the vertical movement of at least one of the upper mold and the lower mold is performed within a range where the surrounding by the tubular member does not come off.

The manufacturing apparatus further includes forced release means around an upper mold or a lower mold, and at the time of the vertical movement, at least a part of a peripheral edge portion of the glass molded body on which the forced release means is formed. The method according to any one of claims 1 to 6, wherein an upward force is applied.

8. The manufacturing method according to claim 7, wherein the forcible release means is disposed around the upper mold, and the forcible release means applies a downward force to at least a part of the peripheral portion of the lens each time the up and down movement is performed.

In a method of manufacturing a glass molded body by press-molding a heat-softened glass material by a manufacturing apparatus including an opposing upper mold and a lower mold, and having forced releasing means around the upper mold or the lower mold. ,
After the pressure molding and before taking out the molded glass molded article from the manufacturing apparatus, at least one of the upper mold and the lower mold is moved up and down one or more times, and the forcible release means is used to move the periphery of the molded glass molded article. A method for producing a glass optical material, wherein a downward or upward force is applied to at least a part of the portion.

The manufacturing method according to claim 9, wherein the forcible release means is disposed around the upper mold, and the forcible release means applies a downward force to at least a part of the peripheral portion of the glass molded body every time the forcible movement is performed. Method.