JP2004106493A

JP2004106493A - Molding method of plastic molded article and mold for plastic molding

Info

Publication number: JP2004106493A
Application number: JP2002276054A
Authority: JP
Inventors: Yasuki Sugimoto; 杉本　泰規; Jun Watabe; 渡部　順
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2002-09-20
Filing date: 2002-09-20
Publication date: 2004-04-08

Abstract

【課題】使用樹脂が転写面および離隔を行わない他の面の密着力が弱い成形品であっても、低コストで、高精度な成形を安定して実現できるプラスチック成形品の成形方法及びそのような成型方法を可能とする金型を提供する
【解決手段】金型のキャビティ内に溶融樹脂を導入して行う、転写面と非転写面とを有するプラスチック成形品の成形方法であって、非転写面形成面に複数の摺動駒が設けられ、金型のキャビティ内に導入された溶融樹脂が軟化温度未満に冷却されるまでの間に、複数の摺動駒を樹脂から離隔する方向に順次摺動させて最終的に金型の該非転写面形成面の全摺動駒の樹脂からの離隔により摺動駒が設けられた非転写面形成面のそれぞれに接して所望の大きさを有する連続した１つの空隙を形成させる。
【選択図】　　　図５A molding method for a plastic molded product capable of stably realizing high-precision molding at a low cost even if the resin used is a molded product having a weak adhesion between a transfer surface and another surface where separation is not performed, and a method thereof. Provided is a mold capable of performing such a molding method. A method for molding a plastic molded article having a transfer surface and a non-transfer surface, which is performed by introducing a molten resin into a cavity of the mold. A plurality of sliding pieces are provided on the non-transfer surface forming surface, and a direction in which the plurality of sliding pieces are separated from the resin before the molten resin introduced into the cavity of the mold is cooled below the softening temperature. , And finally, the non-transfer surface forming surface of the mold has a desired size in contact with each of the non-transfer surface forming surfaces provided with the sliding members due to the separation of all the sliding pieces from the resin. One continuous void is formed.
[Selection diagram] FIG.

Description

【０００１】
【発明の属する技術分野】
本発明は、レーザ方式のデジタル複写機、レーザプリンター、又はファクシミリ装置の光学走査系、ビデオカメラ等の光学機器、光ディスク等に適用されるプラスチック成形品、殊に、高精度な鏡面を有する厚肉、偏肉形状のプラスチックレンズ、或いはプラスチックミラー等のプラスチック成形品の成形方法及び成形用金型に関し、特に高精度な鏡面や微細な凹凸のパターン等を転写可能なプラスチック成形品の成形方法及び成形用金型に関する。
【０００２】
【従来の技術】
光学部品の代表的な成形法として、射出成形法と、射出圧縮成形法があるが、射出成形法は、金型温度を成形用樹脂の軟化温度末満とした一定容積のキャビティ内に溶融樹脂を射出充填し、保圧を制御しながら冷却した後、金型を開いて成形品を取り出す方法であり、射出圧縮成形法は、金型内の転写面を形成する転写駒を摺動可能にし、金型温度を成形用樹脂の軟化温度未満とした所定容積のキャビティ内に溶融樹脂を射出充填し、保圧を制御しながら冷却する際、樹脂の体積収縮に追従して該転写駒を摺動させて樹脂に圧力を付加して、成形品形状をより高精度に形成する方法である。
【０００３】
これらの方法では所望の形状精度を確保するために、樹脂が冷却固化する時に金型内の樹脂圧力や樹脂温度が均一になることが望ましい。
しかし、射出成形法は、成形品の厚みが不均一な偏肉形状の場合、冷却時に厚肉部と薄肉部で樹脂温度が不均一になり、薄肉部に残圧が発生したり、あるいは厚肉部にひけが発生してしまうという不具合がある。また、厚肉形状の成形品を成形する場合は、樹脂の冷却過程で体積収縮量が多いためにひけが発生しやすく、ひけ発生を防止するために充填圧力を大きくすると、残留歪みが大きくなり、高精度な成形品が得られないという問題がある。
【０００４】
一方、射出圧縮成形法は、前記射出成形法より低い充填圧力で成形することができるが、偏肉形状の場合、成形品の厚みの違いで収縮量が異なり、該転写駒が樹脂の収縮に追従できず該転写駒と樹脂とが離れ、離れた部分からひけが発生し、形状精度が低下するという問題がある。
【０００５】
このような不具合を解消するために、例えば、特開平１１−２８７４５号公報（特許文献１）では、転写面以外の面を形成するキャビティ駒を樹脂から離隔するように摺動させることにより、樹脂と摺動駒の間に空隙を画成し、当該空隙に面した樹脂部分にひけを発生させることにより、転写面にひけが生じることを防止するとともに、成形品に残留する内部歪みを小さくすることができるようになっている技術が提案されている。
【０００６】
しかしながら、この特許文献１記載の技術においては、摺動駒を摺動させた時、成形品の樹脂と摺動駒との密着力によって樹脂が引っ張られて成形品を変形させ、成形品の転写面の形状精度がくずれてしまうという不具合がある。特に図１（ａ）に示すように摺動駒に形成された離隔面の対向面が転写面である場合、図１（ｂ）に示すようにキャビティ内に樹脂が導入された後、転写面は樹脂が摺動駒の離隔時に引っ張られることで転写面から樹脂が剥離し、精度は著しく悪化する（図１（ｃ）参照）。
【０００７】
このような樹脂と摺動駒との密着力を低減させる為に、例えば、特開２０００−１４１４２５号公報（特許文献２）では非転写面を形成するキャビティ駒に図２（ａ）に示すような複数のピン形状部材を有する摺動駒を用いることにより、樹脂と摺動駒との密着力を低減させる技術が提案されている。
【０００８】
しかしながら、この特許文献２に記載の技術においては、図２（ｂ）に示すようにキャビティ内に樹脂を導入した後、図２（ｃ）に示すように摺動駒の離隔させたときに、摺動駒付近には深いひけが、摺動駒がない部分には浅いひけが生じる。したがって非転写面に生じるひけが不均一となり、成形品に局所的な温度分布が生じ、成形品に残留する内部歪みが増大するという不具合がある。
【０００９】
また、特開平１１−２８７４８号公報（特許文献３）記載の成形方法および成形装置では、樹脂の充填開始から完了までの間に非転写面のうち、少なくとも一ヶ所以上の温度を転写面の温度より低くすることで、樹脂の固化を促進し、密着力を低減させている。
【００１０】
しかし、この特許文献３に記載の技術においては、成形品の温度分布の増大を促すこととなり、離型後にそりが発生する結果、転写面の形状がくずれてしまうという不具合がある。
【００１１】
また、特開０００−１８５３３７公報（特許文献４）記載の成形方法および射出成形用金型では、非転写面を形成する摺動駒を離隔する前に、摺動駒に設けられた通気口より気体を圧入させることにより、樹脂と摺動駒との密着力を低減させた後、摺動駒を離隔している。
【００１２】
しかしながら、特許文献４に記載の技術では、大きな成形品の場合、樹脂と摺動駒との密着力も増大し、通気口より圧入された気体が離隔面全体に広がらず、樹脂と摺動駒との密着力の低減が充分でないという不具合がある。
【００１３】
【特許文献１】
特開平１１−２８７４５号公報（第２頁）
【特許文献２】
特開２０００−１４１４２５号公報（第２頁）
【特許文献３】
特開平１１−２８７４８号公報（第２頁）
【特許文献４】
特開２０００−１８５３３７公報（第２頁）
【００１４】
【発明が解決しようとする課題】
本発明は、上記した従来の問題点を改善する、すなわち、使用樹脂が転写面および離隔を行わない他の面の密着力が弱い成形品であっても、低コストで、高精度な成形を安定して実現できるプラスチック成形品の成形方法及びそのような成型方法を可能とする金型を提供することを目的とする。
【００１５】
【課題を解決するための手段】
本発明のプラスチック成形品の成形方法は上記課題を解決するため、請求項１に記載の通り、金型のキャビティ内に溶融樹脂を導入して行う、少なくとも１つの転写面と少なくとも１つの非転写面とを有するプラスチック成形品の成形方法であって、上記成形物の非転写面を形成する金型の非転写面形成面の少なくとも１つに摺動駒が設けられ、該金型を樹脂の軟化温度未満の温度に加熱した後、該キャビティ内に溶融樹脂を導入し、さらに、加圧により該樹脂を転写面に密着させた後、該樹脂が軟化温度未満に冷却するまでの間に、金型の非転写面形成面に設けられた上記摺動駒を該樹脂から離隔する方向に移動させて、該摺動駒と樹脂との間に空隙を画成するプラスチック成形品の成形方法において、摺動駒が設けられた非転写面形成面のそれぞれの連続した一部分あるいは全面が複数の摺動駒により構成され、金型のキャビティ内に導入された溶融樹脂が軟化温度未満に冷却されるまでの間に、該複数の摺動駒を樹脂から離隔する方向に順次摺動させて最終的に金型の該非転写面形成面の全摺動駒の樹脂からの離隔により摺動駒が設けられた非転写面形成面のそれぞれに接して所望の大きさを有する連続した１つの空隙を形成させることを特徴とするプラスチック成形品の成形方法である。
【００１６】
このような構成を有する本発明によれば、金型の、非転写面の連続した一部分あるいは全面を複数の摺動駒で形成し、これら摺動駒を同時に樹脂から離隔するのではなく、順次離隔することで、離隔移動している摺動駒の樹脂との当接面積を小し、離隔移動している摺動駒の樹脂との密着力を低減させている。
【００１７】
その結果、樹脂が冷却されつつある成形品（成形途中品）が、離隔移動している摺動駒との密着力によって離隔方向へ引っ張られる力を極めて小さいものとすることが可能で、引張による成形品（成形途中品）の変形を最小限に留め、転写面の形状精度悪化を防ぐことができる。
【００１８】
さらに、従来技術では、非転写面の温度を転写面の温度より低くし、樹脂の固化を促進することで、樹脂と摺動駒との密着力を低減させると、離型時の非転写面と転写面との温度差が大きく、離型後に成形品にそりが発生し、その結果、転写面の形状がくずれてしまう。しかし、本発明では非転写面に複数の摺動駒を設け、それを順次離隔していくことで樹脂と摺動駒との密着力を低減させているので、非転写面と転写面との温度の差は大きくならず、その結果離型後のそりによる変形を防止できる。
【００１９】
請求項２の発明は、請求項１に記載の発明において、前記複数の摺動駒を樹脂から離隔するときの前記キャビティ内の各摺動駒に対する樹脂の圧力を０．０５ＭＰａ以上６０ＭＰａ以下にする構成を有する。
【００２０】
このような構成により、離隔時の樹脂圧力を０．０５ＭＰａ未満にした場合に生じることのある、転写面へのひけを未然に防ぎ、離隔時の樹脂圧力を６０ＭＰａ以上にした場合に生じることのある、成形品そのものの内部応力の増大による残留応力を解消することができ、成形後の変形を未然に防ぐことが可能となる。
【００２１】
請求項３の発明は、請求項１または２に記載のプラスチック成形品の成形方法において、前記成形されるプラスチック成形品が肉厚の異なる部分を有し、かつ、これら部分に対応する複数の摺動駒が金型に設けられているときに、成形品の最も薄肉の部分に対応する摺動駒から肉厚の部分に対応する摺動駒への順序でこれら摺動駒を順次樹脂から離隔し、空隙を順次形成させていくことを特徴とする。請求項３記載の発明は、上記課題を解決するために、請求項１記載の発明において、前記成形品において、前記成形品において、薄肉部に相当する部分の摺動駒を樹脂から離隔し、空隙を形成させた後、厚肉部に相当する部分の摺動駒を樹脂から離隔し、空隙を順次形成させていくことを特徴としている。
【００２２】
このような肉厚の異なる部分を有するプラスチック成形品を成形する場合、原理的には成形品薄肉部の外周部に相当する部分は早く冷却され圧力が残存しやすい。
【００２３】
従って、厚肉部に対応する摺動駒を薄肉部に対応する摺動駒より先に離隔し、樹脂と摺動駒との間に空隙を画成すると、成形品（成形途中品）の厚肉部はまだ溶融温度に近い高温を有している部分を含んでいる状態、すなわち柔軟さを有する状態で離隔することになり、摺動駒の離隔移動に応じてそれに追従し、結果としてその周辺と転写部の転写性が低下してしまう。また、薄肉部での摺動駒の離隔移動は温度低下が大きいのでその部分の固化がかなり進んでおり、摺動駒の離隔による空隙画成での樹脂の移動によるは少ないので上記問題は生じないが、キャビティ内で既に固化部に偏在した樹脂内圧が残存し、かつ、樹脂の流動性が極端に悪くなって光学歪みを生じる内部歪みの残存と転写面精度の低下が生じてしまう。
【００２４】
しかしながら上記請求項３の構成によれば、肉厚の異なる部分を有するプラスチック成形品の成形の場合、キャビティ内に樹脂を導入した（図３（ａ）参照）後、固化進行が早い成形品薄肉部に相当する部分の樹脂がまだ自由に動ける早いタイミングで、薄肉部に該当する摺動駒を優先して樹脂から離隔して空隙を形成させた後（図３（ｂ）参照）、順次厚肉部に対応する摺動駒を樹脂から離隔し（図３（ｃ）参照）、空隙を順次形成させ、最終的に金型の該非転写面形成面の全摺動駒の樹脂からの離隔により摺動駒が設けられた非転写面形成面のそれぞれに接して所望の大きさを有する連続した１つの空隙８を形成させる（図３（ｄ）参照）ことで内部歪みの増大と圧力分布による転写性の低下を防止した、高精度な成形品を得ることができる。
【００２５】
請求項４の発明は、請求項１ないし請求項３のいずれかに記載のプラスチック成形品の成形方法において、前記複数の摺動駒のそれぞれについて、摺動駒に対するキャビティ内の樹脂の圧力を検出し、該樹脂の摺動駒に対する圧力が所定値になった摺動駒からを摺動させて樹脂から離隔する構成を有する。
この構成により、各摺動駒を所定の圧力で正確に離隔し、空隙を画成することができ、内部歪みの増大と圧力分布による転写性の低下とをより一層防止することができる。
【００２６】
請求項５の発明は、請求項１ないし請求項４のいずれかに記載のプラスチック成形品の成形方法において、前記複数の摺動駒が、１つの円柱体とその円柱体及びそれぞれの周囲に同心円状に配された中空管状体からなる、１組の円柱状複合体を形成していることを特徴とする。
【００２７】
このような構成により、摺動駒作製において誤差の少ない加工が容易になり、その結果、成形時に摺動駒と摺動駒との間への溶融した樹脂の入り込みが防止しでき、成形品の形状悪化を防止することができる。
【００２８】
請求項６の発明は請求項１ないし請求項５のいずれかに記載のプラスチック成形品の成形方法において、通気口が摺動駒の非転写面形成面に少なくとも１つ設けられ、該金型の非転写面形成面の摺動駒を摺動させる際に該通気口より摺動駒の樹脂側の面と樹脂との間に気体を圧入させて樹脂を加圧することを特徴とする。
このような構成により、射出充填によってキャビティ内に適度な樹脂内圧を発生させて転写面に樹脂が密着されており、かつ、密着を維持する適度な圧力を残した状態で、摺動駒を摺動させる際に、摺動駒の非転写面形成面に少なくとも１つ設けられた通気口より摺動駒と樹脂との間に気体を圧入させ、樹脂を離隔面の対向面に押し付けることによって、空隙画成時の樹脂と摺動駒との密着力によって離隔移動する摺動駒に樹脂が引っ張られることによる変形をより一層効果的に防止することができる。
【００２９】
請求項７の発明は、請求項６に記載のプラスチック成形品の成形方法において、前記通気口が、微少な孔であって、摺動駒の非転写面形成面の全面に多数設けられていることを特徴とする。
【００３０】
このような構成により、摺動駒の非転写面形成面全面にこれら微小孔より均一に気体を送り込むことができ、樹脂を摺動駒の非転写面形成面の対向面に押し付けることによって、空隙画成時の樹脂と摺動駒との密着力によって離隔移動する摺動駒に樹脂が引っ張られることによる変形をより一層効果的に防止することできる。
【００３１】
また、ここで多孔質な材料により少なくとも摺動駒の非転写面形成面及びその付近を形成することにより上記構成を達成すれば、通気口の機械的加工等による形成工程が必要がなく、低コストに通気口を作製できる。
【００３２】
また、請求項８の発明は請求項６または請求項７に記載のプラスチック成形品の成形方法において、前記の直径が０．００１ｍｍ以上０．１ｍｍ以下であることを特徴とする。
【００３３】
その構成によれば、通気口の直径を０．００１ｍｍ未満にした場合に気体の圧入による効果が充分でないために生じる問題を回避でき、また通気口の直径を０．１ｍｍ以上にした場合に生じる、通気口への溶融樹脂の入り込みによる、成形品形状が悪化、及び、金型寿命の低下を防止することができる。
【００３４】
請求項９の発明は、請求項１ないし請求項５のいずれかに記載のプラスチック成形品の成形方法において、前記通気口を金型の摺動駒の側面に接する位置で、かつ、通気口に接する摺動駒が樹脂から離隔する方向に摺動移動したときに金型のキャビティと連通する位置に設け、摺動駒を摺動させる際に該通気口より摺動駒と樹脂との間に気体を圧入させて樹脂を加圧することを特徴とする。
【００３５】
このように、通気口を金型の摺動駒の側面に接する位置で、かつ、通気口に接する摺動駒が樹脂から離隔する方向に摺動移動したときに金型のキャビティと連通するため、通気口と樹脂とが直接接することがなくなり、通気口への溶融樹脂の入り込みへの配慮が不要となり、通気口の太径化の自由度が高くなる。通気口の太径化により、短い時間で充分な量の気体の圧入と、充分な圧力での圧入とを達成でき、気体の圧入による樹脂を摺動駒の非転写面形成面の対向面へ押し付ける力をより強固に、かつ、より広範囲なものにでき、転写面の成形精度をより高めることができる。
【００３６】
また、請求項１０の発明は、請求項６ないし請求項９のいずれかに記載のプラスチック成形品の成形方法において、前記通気口が金型外部に設けられた圧縮気体発生装置に接続されていることを特徴とする。
【００３７】
このような構成により、摺動駒の摺動移動を通気口から供給される気体の圧力によって実現することが可能となり、圧入された気体は摺動駒と樹脂との離隔による空隙の形成、及び、樹脂を摺動駒の非転写面形成面の対向面へ押し付けのみならず、樹脂と摺動駒との密着力をさらに低減し、なおかつ、樹脂を離隔面の対向面に押し付けることによって、空隙画成時の樹脂と摺動駒との密着力によって摺動移動する摺動駒により樹脂が引っ張られることによる成形物の変形をより一層防止することができる。
【００３８】
請求項１１の発明は、請求項６ないし請求項１０のいずれかに記載のプラスチック成形品の成形方法において、前記気体の圧入圧力が０．０１ＭＰａ以上５０ＭＰａ以下であることを特徴とする。
【００３９】
この構成により、気体の圧力を０．０１ＭＰａ未満にした場合に生じる、樹脂を離隔面の対向面に押し付ける力が不充分で、空隙画成時の樹脂と摺動駒との密着力によって摺動移動する摺動駒により樹脂が引っ張られることによる変形の発生を効果的に防止でき、また、気体の圧力を５０ＭＰａ以上にした場合に生じる、気体圧力によって深いひけが発生して成形品形状が悪化することをも防止できる。
【００４０】
請求項１２の発明は、請求項１ないし請求項１１のいずれかに記載のプラスチック成形品の成形方法において、前記摺動駒の非転写面形成面に、樹脂との密着力を小さくする表面処理が施してあることを特徴とする。
【００４１】
この構成によれば、、樹脂と摺動駒との密着力を更に低減し、摺動駒を樹脂から容易に離隔することができ、転写面の形状精度を向上させることができる。
【００４２】
請求項１３の発明は、請求項１ないし請求項１２のいずれかに記載のプラスチック成形品の成形方法において、キャビティ内に溶融樹脂を導入する前に、樹脂金型内の転写面にインサートを挿入するインサート成形により成形品を得ることを特徴とする。
【００４３】
インサート成形では通常、溶融樹脂の熱により溶融しない材質のインサートを選択するが、このとき、インサートと転写面との密着力はほとんど生じないので、摺動駒の摺動移動による空隙画成時の樹脂と摺動駒との密着力によって摺動移動する摺動駒により樹脂が引っ張られ、所定の形状の成形物は得られない。
【００４４】
しかしながら、転写面にインサートを挿入するインサート成形では特に本発明を応用した効果が高く、その結果、高精度な複合成形品を得ることができる。
【００４５】
請求項１４の発明は、請求項１３に記載のプラスチック成形品の成形方法において、前記インサートの表面に金属層が形成されていることを特徴とする。
このような蒸着などにより表面が金属層が形成されているインサートの場合にはインサートと転写面との密着力は全くといって生じないが、本発明を用いることで、空隙画成時の樹脂と摺動駒との密着力によって摺動移動する摺動駒により樹脂が引っ張られることによる変形がほとんどなく、高精度な一体化ミラーなどの、優れた精度を有する複合成形品を得ることができる。
【００４６】
本発明のプラスチック成形用金型は、請求項１５に記載のように、内部のキャビティ内に少なくとも１つの転写面と少なくとも１つの非転写面とを有するプラスチック成形品の成形用金型装置であって、非転写面を形成する金型の非転写面形成面の少なくとも１つの連続する一部あるいは全面が複数の摺動駒により構成され、それぞれ摺動駒はキャビティに射出充填される樹脂から離隔する方向に摺動可能であって、金型内に溶融樹脂を導入した後に、それぞれの非転写面形成面のすべての摺動駒を樹脂から離隔する方向に摺動したときに、金型内に導入された樹脂と間にそれぞれ連続した１つの空隙が形成されることを特徴とするプラスチック成形用金型であり、このような構成により、請求項１記載のプラスチック成形品の成形方法を容易に実施することが可能となり、その特有の優れた効果を得ることができる。
【００４７】
【発明の実施の形態】
以下、実施例１により本発明の詳細を説明する。
本例で、作製される成形物は図４に示すような、鏡面である転写面をもつ１００ｍｍ×１００ｍｍ厚さ６ｍｍの平板ミラーである。
【００４８】
次に用いる金型の構成を説明する。
図５（ａ）に金型の構成を示す。金型は上型１、下型２で構成され、キャビティは、側面を有するキャビティ駒３、４、鏡面である転写面５ａを有するキャビティ駒５（転写面５ａの面精度はＰＶ０．７μｍ）及び転写面の対向面である非転写面を形成する複数の摺動駒６ａ、６ｂ、６ｃで構成される。
【００４９】
各摺動駒は図示しない摺動駒駆動手段にそれぞれ接続されており、その摺動駒駆動手段により、溶融樹脂充填時は矢印Ａ方向へ、空隙形成時（離隔移動時）は矢印Ｂ方向（キャビティ内に充填される樹脂から離隔する方向）に駆動される。また、摺動駒６ａ、６ｂ及び６ｃの幅はそれぞれ３０ｍｍ、４０ｍｍ及び３０ｍｍである。また、複数の摺動駒６ａ、６ｂ及び６ｃにはそれぞれ圧力センサが設けられており、各摺動駒は圧力センサからの検出情報に基づき、摺動するようになっている。そして摺動駒の樹脂と接する面（被転写面成形面）には通気口が設けられ、その通気口は図示しない金型の外部の圧縮気体発生装置に連通している。
【００５０】
成形機は電動式射出成形機（ファナック（株）製Ｒｏｂｏｓｈｏｔ　α１００Ｂ）を用い、成形材料は非晶質樹脂であるポリカーボネート樹脂（帝人化成（株）製　パレライトＬ１２２５Ｌ　ガラス転移温度約１４５℃）を用いた。表面精度評価は、レーザー干渉計（キヤノン（株）製ＺＹＧＯ）により行った。
【００５１】
次いでこの例における本発明の作用を説明する。
金型をポリカーボネート樹脂の軟化温度未満である１３６℃に保持し、この金型のキャビティ内に２８０℃に溶融させた樹脂を射出充填する（非晶質樹脂を用いる場合にはガラス転移温度未満とする）（図５（ａ））。
【００５２】
次に表層部から中心部の平均温度がその樹脂の軟化温度以上である間に、圧力センサによる測定で複数の摺動駒６ａ、６ｂ、６ｃそれぞれに対応する樹脂内圧が５ＭＰａとなったときに、各摺動駒を順次１ｍｍ、図中Ａ方向に摺動移動させて樹脂と複数の摺動駒６ａ、６ｂ、６ｃの間に空隙を画成する（図５（ｂ）、図５（ｃ）及び図５（ｄ）を参照）。
【００５３】
この摺動駒の摺動移動の際、金型の外部の圧縮気体発生装置より通気管を通し、それぞれの摺動駒に設けられた通気口から、それぞれの摺動駒と樹脂の間に５ＭＰａの気体を圧入させ樹脂を離隔面の対向面である、転写面５ａに押し付ける。
そして、最終的に図５（ｄ）に示すように該複数の摺動駒と樹脂との間に連続した１つの空隙８を形成し、その後樹脂を完全固化させる。
【００５４】
図６に成形中の各摺動駒に設けられた圧力センサの値を示す。時間軸の（ａ）、（ｂ）及び（ｃ）はそれぞれ図５（ｂ）、図５（ｃ）及び図５（ｄ）の状態に対応している。
【００５５】
上記実施例１では、図６に示すように、まず摺動駒６ａに設けられたセンサで感知される圧力が５ＭＰａとなり、このときに所定の圧力となったとして摺動駒６ａが離隔し、次いで摺動駒６ｂに設けられたセンサで感知される圧力が５ＭＰａとなり、このときに所定の圧力となったとして摺動駒６ｂが離隔し、最後に摺動駒６ｃに設けられたセンサで感知される圧力５ＭＰａとなり、このときに所定の圧力となったとして摺動駒６ｃが離隔し、図５（ｄ）に示すように空隙８を形成した。
【００５６】
次いで、樹脂温度が１３６℃になったときに金型を型開きして成形品が変形しないようにキャビティ７内から成形品を取り出す。この成形品の転写面は８．７μｍの面精度であった。
【００５７】
このような上記例から、本発明によれば、射出充填によってキャビティ７内に適度な樹脂内圧を発生させて転写面５ａに樹脂が密着され、かつ、その後、密着を維持する適度な圧力を残した状態のときに、樹脂と複数の摺動駒６ａ、６ｂ、及び６ｃの間に空隙８が画成されることで、樹脂のこの空隙８に面した部分の樹脂表面が自由面となり、金型に接した他の面よりも動き易くなる。
このため、空隙８の存在によってこの樹脂部分からの熱伝導が低下してこの樹脂部分が最も冷却速度が遅くなる（すなわち、樹脂のこの部分がキャビティ７内で最も高温・低粘度となる）。
【００５８】
その結果、冷却によって生じる樹脂の収縮は、樹脂の最も低粘度であるこの部分が動くことによって吸収され、空隙８に面した樹脂部分が優先的にひけて、そのため、転写面にひけが生じることが防止され、短い成形サイクルであっても転写面が忠実に高精度で転写される。また、冷却時の転写面に作用する樹脂内圧を大気圧に近づけることができるため、光弾性歪みの小さい成形品を得ることができる。
【００５９】
また、上記例では成形材料としてポリカーボネート樹脂を用いているが、熱可塑性樹脂であればその他の樹脂、例えばポリスチレン、ポリプロピレン、ポリメチルメタクリレート等であっても良いが、収縮性が良好で高精度な成形品得ることが容易な非晶質樹脂を使用することが望ましい。また、上記では摺動駒の移動量を１ｍｍとしているが、樹脂と複数の摺動駒の間に空隙を画成することができる距離であれば良く、１ｍｍには限定されない。
【００６０】
また、非転写面にひけが不均一に生じると、成形品に局所的な温度分布が生じ、成形品に残留する内部歪みが増大するが、本発明においては、非転写面に複数の摺動駒を連続して設けているので、これら複数の摺動駒の離隔により、非転写面に所望の大きさの、連続したひけを均一に発生させることができるので内部歪みを小さくすることができる。また、上記実施例１では３つの摺動駒を設けているが、離隔を行う非転写面の面積、密着力などによって、摺動駒をいくつ設けても構わない。
【００６１】
また、実施例１では前記複数の摺動駒を樹脂から離隔するときの前記キャビティ内の樹脂圧力を５ＭＰａとしているが、０．５ＭＰａ以上６０ＭＰａ以下の範囲であればかまわない。なお、樹脂圧力が０．５ＭＰａ未満であるときに摺動駒の離隔を行った場合には、転写面に先にひけが発生することがあるため、好ましくなく、樹脂圧力が６０ＭＰａ超であるときに摺動駒の離隔を行った場合には、成形品そのものの内部応力が増大して残留応力が残るため好ましくない。
【００６２】
本実施例では上記のように、各摺動駒に圧力検出手段が設けてあるので、各摺動駒を所定の圧力で正確に離隔し、空隙を画成することができ、内部歪みの増大と圧力分布とによって生じる転写性の低下をより一層防止することができる。
上記実施例では、摺動駒を摺動させる際に、摺動駒の樹脂と接する面に設けた該通気口より摺動駒と樹脂の間に気体を圧入させ、その圧力で樹脂を離隔面の対向面に押し付けることによって、空隙画成時の樹脂と摺動駒との密着力によって離隔移動する摺動駒に樹脂が引っ張られることによる変形をより一層防止することできる。
【００６３】
ここで、通気口が、微少な孔であって、摺動駒の非転写面形成面の全面に多数設けられている構成であれば、摺動駒の非転写面形成面全面にこれら微小孔より均一に気体を送り込むことができ、樹脂を摺動駒の非転写面形成面の対向面に押し付けることによって、空隙画成時の樹脂と摺動駒との密着力によって離隔移動する摺動駒に樹脂が引っ張られることによる変形をより一層効果的に防止することできる。また、ここで多孔質な材料により少なくとも摺動駒の非転写面形成面及びその付近を形成することにより上記構成を達成すれば、通気口の機械的加工等による形成工程が必要がなく、低コストに通気口を作製できる。
【００６４】
上記例において通気口の幅（微小孔）の直径は０．００１ｍｍ以上０．１ｍｍ以下とする。前記通気口の幅及び微小孔の直径を０．００１ｍｍ未満にした場合、気体の圧入による効果が充分でないため、好ましくなく、前記通気口の幅及び微小孔の直径を０．１ｍｍ以上にした場合、前記通気口又は微小孔に溶融した樹脂が入り込み、成形品形状が悪化し、なおかつ、金型寿命の低下するので好ましくない。
【００６５】
また、上記実施例１では通気口より導入される気体の圧力を５ＭＰａとしているが、０．０１ＭＰａ以上５０ＭＰａ以下の範囲であればかまわない。ここで、気体の圧力を０．０１ＭＰａ未満にした場合、樹脂を離隔面の対向面に押し付ける力が不充分で、空隙画成時の樹脂と摺動駒との密着力によって離隔移動する摺動駒に樹脂が引っ張られることによる変形が発生するため、好ましくなく、気体の圧力を５０ＭＰａ以上にした場合、気体圧力によって深いひけが発生し、成形品形状が悪化するため、好ましくない。
【００６６】
ここで１つの非転写面成形面に配された複数の摺動駒がなす形状が、図７（ａ）（金型に組み込まれた状態を示す断面図）、図７（ｂ）（図７（ａ）のＬＬにおける断面図（摺動駒だけを示す））に示すように円柱状であるとなお良い。すなわち、これら複数の摺動駒が１つの円柱体（この例では摺動駒６ｇ）とその円柱体及びそれぞれの周囲に同心円状に配された、１組の中空管状体（この例では摺動駒６ｄ〜６ｆ）からなる円柱状複合体を形成していると、摺動駒作製において誤差の少ない加工が容易になり、その結果、成形時に摺動駒と摺動駒との間への溶融した樹脂の入り込みが防止しでき、成形品の形状悪化を防止することができる。
【００６７】
また、摺動駒の非転写面形成面に、樹脂との密着力を小さくする表面処理が施すことで、樹脂と摺動駒との密着力を更に低減し、摺動駒を樹脂から容易に離隔することができ、転写面の形状精度を向上させることができる。ここで、摺動駒の成形面の樹脂との密着力を低下させる材料としては、例えば、ＴｉＮ（窒化チタン）、ＴｉＣＮ（シアン化チタン）、Ｗ_２Ｃ（タングステンカーバイド）、フッ素系樹脂が挙げられ、これらを用いた表面処理を行うことで上記構成が容易に実現できる。
また、図３に示すように成形品の形状が全体が同じ厚さではなく肉厚に部分的な差がある、偏肉形状であると、成形品薄肉部の外周部に相当する部分は早く冷却されるので圧力が残存しやすい。
【００６８】
従って、厚肉部に対応する摺動駒を薄肉部に対応する摺動駒より先に離隔し、樹脂と摺動駒との間に空隙を画成すると、成形品（成形途中品）の厚肉部はまだ溶融温度に近い高温を有している部分を含んでいる状態、すなわち柔軟さを有する状態で離隔することになり、摺動駒の離隔移動に応じてそれに追従し、結果としてその周辺と転写部の転写性が低下してしまう。また、薄肉部での摺動駒の離隔移動は温度低下が大きいのでその部分の固化がかなり進んでおり、摺動駒の離隔による空隙画成での樹脂の移動によるは少ないので上記問題は生じないが、キャビティ内で既に固化部に偏在した樹脂内圧が残存し、かつ、樹脂の流動性が極端に悪くなって光学歪みを生じる内部歪みの残存と転写面精度の低下が生じてしまう。
【００６９】
しかしながら、成形品の最も薄肉の部分に対応する摺動駒から肉厚の部分に対応する摺動駒への順序でこれら摺動駒を順次樹脂から離隔し、空隙を順次形成させていけば、肉厚の異なる部分を有するプラスチック成形品の成形の場合、キャビティ内に樹脂を導入した（図３（ａ）参照）後、固化進行が早い成形品薄肉部に相当する部分の樹脂がまだ自由に動ける早いタイミングで、薄肉部に該当する摺動駒を優先して樹脂から離隔して空隙を形成させた後（図３（ｂ）参照）、順次厚肉部に対応する摺動駒を樹脂から離隔し（図３（ｃ）参照）、空隙を順次形成させ、最終的に金型の該非転写面形成面の全摺動駒の樹脂からの離隔により摺動駒が設けられた非転写面形成面のそれぞれに接して所望の大きさを有する連続した１つの空隙８を形成させる（図３（ｄ）参照）ことで内部歪みの増大と圧力分布による転写性の低下を防止した、精度に優れた成形品を得ることができる。
【００７０】
なお、上記の摺動駒の通気口（微小孔）が樹脂と摺動駒との間と、金型の外部の圧縮気体発生装置に連通する位置に形成されていると、摺動駒を摺動させる際に該通気口及び微小孔より摺動駒と樹脂の間に気体を圧入させ樹脂を離隔面の対抗面に押し付け、空隙を形成させることで、樹脂と摺動駒との密着力を更に低減し、なおかつ、樹脂を離隔面の対抗面に押し付けることによって、空隙画成時の樹脂と摺動駒との密着力によって、樹脂が摺動駒の移動の際に引っ張られることによる成形品の変形をより一層、効果的に防止することできる。
【００７１】
次に上記実施例１と比較のため従来技術に係る比較例１について説明する。
実施例１と同じ成形物を得るための転写面５ａを有する金型を用いた。その金型を図１に示す。
【００７２】
この金型は、１つの転写面と５つの非転写面とを有するプラスチック成形品の成形用金型であって、上記成形物の非転写面を形成する金型の非転写面形成面に摺動駒が設けられている。、
【００７３】
金型は上型１、下型２で構成され、キャビティ７は、側面を有するキャビティ駒３、４、鏡面である転写面５ａを有するキャビティ駒５（転写面５ａの面精度はＰＶ０．７μｍ）及び転写面の対向面にあたる非転写面を形成する１つの摺動駒６で構成される。
【００７４】
摺動駒６は図示しない駆動手段に連通しており、駆動手段により溶融樹脂充填時は矢印Ａ方向へ、空隙形成時は矢印Ｂ方向に駆動される機構になっている。
また、摺動駒の幅は１００ｍｍである。
【００７５】
成形機は電動式射出成形機（ファナック（株）製　Ｒｏｂｏｓｈｏｔ　α１００Ｂ）を用い、成形材料は非晶質樹脂であるポリカーボネート樹脂（帝人化成（株）製　パレライトＬ１２２５Ｌ　ガラス転移温度約１４５℃）を用いた。表面精度評価は、レーザー干渉計（キヤノン（株）製　ＺＹＧＯ）により行った。
【００７６】
この金型をポリカーボネート樹脂の軟化温度未満である１３６℃に保持し、この金型のキャビティ内に２８０℃に溶融させた樹脂を射出充填した（図１（ｂ）参照）。
【００７７】
次いで、樹脂の表層部から中心部の平均温度がその樹脂の軟化温度以上である間に、摺動駒６を１ｍｍ移動させて樹脂と摺動駒６の間に空隙を画成し、その後樹脂を完全固化させる（図１（ｃ）参照）。
【００７８】
その後、樹脂温度が１３６℃になったときに金型を型開きしてキャビティ７内から成形品を取り出す。この成形品の転写面の面精度は４３μｍであった。このように低い面精度は、摺動駒の離隔時に樹脂と摺動駒との密着力によって、樹脂が離隔方向へ引っ張られ、図１（ｂ）に示すように成形品が変形した結果、転写面が凹形状となったためであると思料される。
【００７９】
次に本発明で用いる他の金型の例について説明する。
図８（ａ）に示すようにこの例では、通気口を金型（下型２）の摺動駒の側面に接する位置で、かつ、通気口に接する摺動駒が樹脂から離隔する方向に摺動移動したときに金型のキャビティ７と連通する位置に設けている。通気口以外は実施例１で用いた金型と同様である。
【００８０】
このような金型のキャビティ７に溶融樹脂を射出充填した後、樹脂の軟化温度未満まで冷却する間に、複数の摺動駒６ｈ、６ｉ及び６ｊに加わる樹脂の圧力がが所定圧力になったときに順次摺動させて、非転写面の樹脂から順次離隔させる（図８（ｂ））。摺動駒が摺動した際、通気口がキャビティ７と連通し、金型の外部の圧縮気体発生装置により、金型に設けられた通気口から、摺動駒と樹脂との間に所定圧力の気体を圧入させ、その圧直で樹脂を離隔面の対向面（この例では転写面）に押し付ける。そして最終的に該複数の摺動駒６ｈ、６ｉ及び６ｊと樹脂との間に連続した１つの空隙を形成する。
【００８１】
本発明によれば、通気口を金型（下型２）の摺動駒の側面に接する位置で、かつ、通気口に接する摺動駒が樹脂から離隔する方向に摺動移動したときに金型のキャビティ７と連通する位置に設けているため、通気口と樹脂とが直接接することがなくなり、通気口への溶融樹脂の入り込みへの配慮が不要となり、通気口の太径化の自由度が高くなる。通気口の太径化により、短い時間で充分な量の気体の圧入と、充分な圧力での圧入とを達成でき、気体の圧入による樹脂を摺動駒の非転写面形成面の対向面へ押し付ける力をより強固に、かつ、より広範囲なものにでき、転写面の成形精度をより高めることができる。
【００８２】
また、図９に示すような、溶融樹脂とは異なるフィルムなどの別部材をインサートとして挿入し、転写面として一体に成形したインサート成形による複合成形品である場合、別部材は成型時には溶融しない条件で成形することが一般的であり、そのとき、転写面への密着力はほとんどなくなり、空隙画成時の樹脂と摺動駒との密着力によって、摺動移動する摺動駒の移動に伴って樹脂が引っ張られることによって転写面が変形してしまう。しかし、このようなインサート成形による複合成形品の成型方法において、本発明を応用することで上記変形がほとんどなく、高精度な複合成形品を得ることができる。
【００８３】
特に、蒸着などにより表面が金属膜層が形成されているインサートの場合にはインサート金属面と金型の転写面（金属）との密着力は全くといって生じないが、本発明を用いることで、空隙画成時の樹脂と摺動駒との密着力によって摺動移動する摺動駒により樹脂が引っ張られることによる変形がほとんどなく、高精度な一体化ミラーなどの、優れた精度を有する複合成形品を得ることができる。
【００８４】
【発明の効果】
本発明のプラスチック成形品の成形方法は金型のキャビティ内に溶融樹脂を導入して行う、少なくとも１つの転写面と少なくとも１つの非転写面とを有するプラスチック成形品の成形方法であって、上記成形物の非転写面を形成する金型の非転写面形成面の少なくとも１つに摺動駒が設けられ、該金型を樹脂の軟化温度未満の温度に加熱した後、該キャビティ内に溶融樹脂を導入し、さらに、加圧により該樹脂を転写面に密着させた後、該樹脂が軟化温度未満に冷却するまでの間に、金型の非転写面形成面に設けられた上記摺動駒を該樹脂から離隔する方向に移動させて、該摺動駒と樹脂との間に空隙を画成するプラスチック成形品の成形方法において、摺動駒が設けられた非転写面形成面のそれぞれの連続した一部分あるいは全面が複数の摺動駒により構成され、金型のキャビティ内に導入された溶融樹脂が軟化温度未満に冷却されるまでの間に、該複数の摺動駒を樹脂から離隔する方向に順次摺動させて最終的に金型の該非転写面形成面の全摺動駒の樹脂からの離隔により摺動駒が設けられた非転写面形成面のそれぞれに接して所望の大きさを有する連続した１つの空隙を形成させるプラスチック成形品の成形方法であり、その構成により、金型の、非転写面の連続した一部分あるいは全面を複数の摺動駒で形成し、これら摺動駒を同時に樹脂から離隔するのではなく、順次離隔することで、離隔移動している摺動駒の樹脂との当接面積を小し、離隔移動している摺動駒の樹脂との密着力を低減させることができる。
【００８５】
その結果、樹脂が冷却されつつある成形品（成形途中品）が、離隔移動している摺動駒との密着力によって離隔方向へ引っ張られる力を極めて小さいものとすることが可能で、引張による成形品（成形途中品）の変形を最小限に留め、転写面の形状精度悪化を防ぐことができる。
【００８６】
さらに、従来技術では、非転写面の温度を転写面の温度より低くし、樹脂の固化を促進することで、樹脂と摺動駒との密着力を低減させると、離型時の非転写面と転写面との温度差が大きく、離型後に成形品にそりが発生し、その結果、転写面の形状がくずれてしまう。しかし、本発明では上記構成により非転写面に複数の摺動駒を設け、それを順次離隔していくことで樹脂と摺動駒との密着力を低減させているので、非転写面と転写面との温度の差は大きくならず、その結果離型後のそりによる変形を防止できる。
【図面の簡単な説明】
【図１】従来技術の問題点を説明する説明図である。
（ａ）金型とその内部に形成されたキャビティを示すモデル断面図である。
（ｂ）（ａ）に樹脂が射出充填された状態を示すモデル断面図である。
（ｃ）摺動駒が樹脂から離隔する方向に摺動したときの状態を示すモデル断面図である。
【図２】他の従来技術の問題点を説明する説明図である。
（ａ）金型とその内部に形成されたキャビティを示すモデル断面図である。
（ｂ）（ａ）に樹脂が射出充填された状態を示すモデル断面図である。
（ｃ）摺動駒が樹脂から離隔する方向に摺動したときの状態を示すモデル断面である。
【図３】本発明の実施の形態の一例を示す説明図である。
（ａ）金型とその内部に形成されたキャビティ内に樹脂が射出充填された状態を示すモデル断面図である。
（ｂ）摺動駒６ａが樹脂から離隔する方向に摺動したときの状態を示すモデル断面である。
（ｃ）さらに摺動駒６ｂが樹脂から離隔する方向に摺動したときの状態を示すモデル断面である。
（ｄ）摺動駒６ｃが樹脂から離隔する方向に摺動し、金型の該非転写面形成面の全摺動駒の樹脂からの離隔により摺動駒が設けられた非転写面形成面のそれぞれに接して連続した１つの空隙を形成させるたときの状態を示すモデル断面である。
【図４】本発明の実施例で成形される成形物を示すモデル斜視図である。
【図５】本発明の実施の形態の他の一例を示す説明図である。
（ａ）金型とその内部に形成されたキャビティ内に樹脂が射出充填された状態を示すモデル断面図である。
（ｂ）摺動駒６ａが樹脂から離隔する方向に摺動したときの状態を示すモデル断面である。
（ｃ）さらに摺動駒６ｂが樹脂から離隔する方向に摺動したときの状態を示すモデル断面である。
（ｄ）摺動駒６ｃが樹脂から離隔する方向に摺動し、金型の該非転写面形成面の全摺動駒の樹脂からの離隔により摺動駒が設けられた非転写面形成面のそれぞれに接して連続した１つの空隙を形成させるたときの状態を示すモデル断面である。
【図６】実施例１での各摺動駒に対する樹脂の圧力の時間変化と、所定の圧力（５ＭＰ）になったときのタイミングを示すグラフである。
【図７】（ａ）複数の摺動駒が１つの円柱体とその円柱体及びそれぞれの周囲に同心円状に配された、１組の中空管状体からなる円柱状複合体を形成している例を示すモデル断面図である。
（ｂ）（ａ）のＬＬで切断したときの円柱状複合体を形成する上記複数の摺動駒のモデル断面図である。
【図８】（ａ）通気口を金型の摺動駒の側面に接する位置で、かつ、通気口に接する摺動駒が樹脂から離隔する方向に摺動移動したときに金型のキャビティと連通する位置に設けた金型のモデル断面図である。
（ｂ）（ａ）の摺動駒６ｈが樹脂から隔離する方向に摺動移動したときの状態を示すモデル断面図である。
【図９】（ａ）本発明の応用に適した、フィルムを転写面に挿入するインサート成形によって成形された複合成形物の断面を示すモデル断面図である。
（ｂ）本発明の応用にきわめて適した、金属層を有するフィルムを転写面に挿入するインサート成形によって成形された複合成形物の断面を示すモデル断面図である。
【符号の説明】
１　上型
２　下型
３，４，５　キャビティ駒
６ａ〜６ｊ　摺動駒[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laser molded digital copying machine, a laser printer, or an optical scanning system of a facsimile machine, an optical device such as a video camera, a plastic molded product applied to an optical disk, and the like, particularly a thick wall having a highly accurate mirror surface. The present invention relates to a molding method and a molding die for a plastic molded article such as a plastic lens having an uneven thickness or a plastic mirror, and particularly relates to a molding method and a molding for a plastic molded article capable of transferring a highly accurate mirror surface or a pattern of fine irregularities. For molds.
[0002]
[Prior art]
Typical molding methods for optical components include injection molding and injection compression molding.Injection molding is a method in which the molten resin is placed in a cavity of a fixed volume where the mold temperature is below the softening temperature of the molding resin. Injection-filling, after cooling while controlling the holding pressure, open the mold and take out the molded product.The injection compression molding method allows the transfer piece forming the transfer surface in the mold to slide. Injecting and filling a molten resin into a cavity of a predetermined volume in which the mold temperature is lower than the softening temperature of the molding resin, and cooling while controlling the holding pressure, slides the transfer piece following the volume shrinkage of the resin. This is a method in which the pressure is applied to the resin by moving the resin to form the molded product shape with higher precision.
[0003]
In these methods, in order to secure desired shape accuracy, it is desirable that the resin pressure and the resin temperature in the mold become uniform when the resin is cooled and solidified.
However, in the injection molding method, when the thickness of the molded article is uneven, the resin temperature becomes uneven between the thick part and the thin part during cooling, and a residual pressure is generated in the thin part or the thickness becomes small. There is a problem that sink occurs in the meat portion. Also, when molding thick-walled molded products, shrinkage tends to occur due to the large volume shrinkage during the resin cooling process, and when the filling pressure is increased to prevent the occurrence of shrinkage, the residual strain increases. However, there is a problem that a highly accurate molded product cannot be obtained.
[0004]
On the other hand, the injection compression molding method can be molded at a lower filling pressure than the injection molding method.However, in the case of uneven wall thickness, the amount of shrinkage differs due to the difference in the thickness of the molded product, and the transfer piece may cause shrinkage of resin. There is a problem in that the transfer piece cannot be followed and the resin is separated from the resin, and sink occurs from the separated portion, thereby lowering the shape accuracy.
[0005]
In order to solve such a problem, for example, in Japanese Patent Application Laid-Open No. H11-28745 (Patent Document 1), a cavity piece that forms a surface other than the transfer surface is slid so as to be separated from the resin. A gap is defined between the sliding piece and the sliding piece, and a sink is generated in the resin portion facing the gap, thereby preventing sink from occurring on the transfer surface and reducing internal distortion remaining in the molded product. Technologies that can be used have been proposed.
[0006]
However, in the technique described in Patent Document 1, when the sliding piece is slid, the resin is pulled by the adhesive force between the resin of the molded article and the sliding piece, thereby deforming the molded article and transferring the molded article. There is a problem that the shape accuracy of the surface is lost. In particular, when the opposite surface of the separation surface formed on the sliding piece is the transfer surface as shown in FIG. 1A, the resin is introduced into the cavity as shown in FIG. As the resin is pulled when the sliding piece is separated, the resin is separated from the transfer surface, and the accuracy is significantly deteriorated (see FIG. 1C).
[0007]
In order to reduce the adhesive force between the resin and the sliding piece, for example, in Japanese Patent Application Laid-Open No. 2000-141425 (Patent Document 2), a cavity piece forming a non-transfer surface is formed as shown in FIG. A technique has been proposed for reducing the adhesion between the resin and the sliding piece by using a sliding piece having a plurality of pin-shaped members.
[0008]
However, in the technique described in Patent Document 2, after the resin is introduced into the cavity as shown in FIG. 2B, when the sliding piece is separated as shown in FIG. A deep sink mark occurs near the moving piece, and a shallow sink mark occurs in a portion where there is no sliding piece. Therefore, there is a problem in that sink marks generated on the non-transfer surface become non-uniform, a local temperature distribution occurs in the molded product, and internal strain remaining in the molded product increases.
[0009]
In the molding method and the molding apparatus described in Japanese Patent Application Laid-Open No. H11-28748 (Patent Document 3), at least one temperature of the non-transfer surface is set to the temperature of the transfer surface during the period from the start to the completion of filling of the resin. By making it lower, the solidification of the resin is promoted, and the adhesion is reduced.
[0010]
However, the technique described in Patent Document 3 has a problem that the temperature distribution of the molded article is increased, and the shape of the transfer surface is deformed as a result of the occurrence of warpage after mold release.
[0011]
Further, in the molding method and the injection molding die described in Japanese Patent Application Laid-Open No. 000-185337 (Patent Document 4), before the sliding piece forming the non-transfer surface is separated from the sliding piece, a ventilation hole provided in the sliding piece is used. The sliding pieces are separated from each other after the pressure between the resin and the sliding pieces is reduced by pressurizing gas.
[0012]
However, according to the technology described in Patent Document 4, in the case of a large molded product, the adhesive force between the resin and the sliding piece also increases, and the gas press-fitted from the ventilation port does not spread over the entire separation surface, and the resin and the sliding piece do not spread. There is a problem that the reduction of the adhesion is not sufficient.
[0013]
[Patent Document 1]
JP-A-11-28745 (page 2)
[Patent Document 2]
JP 2000-141425 A (page 2)
[Patent Document 3]
JP-A-11-28748 (page 2)
[Patent Document 4]
JP-A-2000-185337 (page 2)
[0014]
[Problems to be solved by the invention]
The present invention solves the above-mentioned conventional problems, that is, even if the resin used is a molded product having a weak adhesion between the transfer surface and the other surface that does not separate, low-cost, high-precision molding can be performed. An object of the present invention is to provide a method for molding a plastic molded article that can be stably realized and a mold that enables such a molding method.
[0015]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a method for molding a plastic molded article, wherein at least one transfer surface and at least one non-transfer surface are formed by introducing a molten resin into a mold cavity. And a sliding piece is provided on at least one of the non-transfer surface forming surfaces of the mold that forms the non-transfer surface of the molded product, and the mold is formed of a resin. After being heated to a temperature lower than the softening temperature, a molten resin is introduced into the cavity, and further, after the resin is brought into close contact with the transfer surface by pressurizing, the resin is cooled to a temperature lower than the softening temperature. A method for molding a plastic molded product, in which the sliding piece provided on the non-transfer surface forming surface of the mold is moved in a direction away from the resin to define a gap between the sliding piece and the resin. , Non-transfer surface forming surface provided with sliding pieces Each continuous part or the entire surface is constituted by a plurality of sliding pieces, and the plurality of sliding pieces are separated from the resin until the molten resin introduced into the mold cavity is cooled below the softening temperature. The sliding members are sequentially slid in the separating direction, and finally the entire non-transfer surface forming surface of the mold comes into contact with each of the non-transfer surface forming surfaces provided with the sliding members due to the separation from the resin. A method for molding a plastic molded article, characterized by forming one continuous void having a thickness.
[0016]
According to the present invention having such a configuration, a continuous portion or the entire non-transfer surface of the mold is formed by a plurality of sliding pieces, and these sliding pieces are not separated from the resin at the same time, but sequentially. By separating the sliding pieces, the contact area of the sliding pieces moving away from the resin is reduced, and the adhesion force of the sliding pieces moving away from the resin is reduced.
[0017]
As a result, it is possible to minimize the force with which the molded product (the half-molded product) in which the resin is being cooled is pulled in the separation direction by the adhesion force to the sliding piece that is moving away. Deformation of a molded product (a product in the middle of molding) can be kept to a minimum, and deterioration of the shape accuracy of the transfer surface can be prevented.
[0018]
Further, in the prior art, the temperature of the non-transfer surface is made lower than the temperature of the transfer surface to promote the solidification of the resin, thereby reducing the adhesive force between the resin and the sliding piece. The temperature difference between the transfer surface and the transfer surface is large, and the molded product is warped after the mold release, and as a result, the shape of the transfer surface is lost. However, in the present invention, a plurality of sliding pieces are provided on the non-transfer surface, and by sequentially separating the sliding pieces, the adhesive force between the resin and the sliding piece is reduced, so that the non-transfer surface and the transfer surface can be separated. The difference in temperature does not increase, and as a result, deformation due to warpage after release can be prevented.
[0019]
According to a second aspect of the present invention, in the first aspect of the invention, the pressure of the resin on each of the sliding pieces in the cavity when the plurality of sliding pieces is separated from the resin is set to 0.05 MPa or more and 60 MPa or less. Having a configuration.
[0020]
With such a configuration, sinking to the transfer surface, which may occur when the resin pressure at the time of separation is set to less than 0.05 MPa, is prevented beforehand, and may occur when the resin pressure at the time of separation is set to 60 MPa or more. It is possible to eliminate a residual stress due to an increase in the internal stress of the molded product itself, and it is possible to prevent deformation after molding.
[0021]
According to a third aspect of the present invention, in the method for molding a plastic molded article according to the first or second aspect, the molded plastic molded article has portions having different thicknesses, and a plurality of slides corresponding to these portions. When the moving pieces are provided in the mold, these sliding pieces are sequentially separated from the resin in order from the sliding piece corresponding to the thinnest part of the molded article to the sliding piece corresponding to the thick part. Then, the gaps are sequentially formed. According to a third aspect of the present invention, in order to solve the above problem, in the first aspect of the present invention, in the molded article, a sliding piece of a portion corresponding to a thin portion in the molded article is separated from a resin, After the gap is formed, the sliding piece corresponding to the thick portion is separated from the resin, and the gap is sequentially formed.
[0022]
When molding a plastic molded product having such different thicknesses, in principle, the portion corresponding to the outer peripheral portion of the thin portion of the molded product is quickly cooled and the pressure tends to remain.
[0023]
Therefore, if the sliding piece corresponding to the thick part is separated before the sliding piece corresponding to the thin part, and a gap is defined between the resin and the sliding piece, the thickness of the molded product (product in the middle of molding) is increased. The meat portion is separated in a state that still includes a portion having a high temperature close to the melting temperature, that is, in a state having flexibility, and follows the movement according to the separation movement of the sliding piece, and as a result, the periphery thereof And the transferability of the transfer portion is reduced. In addition, since the separation movement of the sliding piece in the thin portion has a large temperature drop, the solidification of the part has considerably progressed, and the above problem does not occur because the movement of the resin in the gap definition due to the separation of the sliding piece is small. However, the internal pressure of the resin already unevenly distributed in the solidified portion in the cavity remains, and the fluidity of the resin is extremely deteriorated, so that the internal distortion that causes optical distortion and the transfer surface accuracy deteriorates.
[0024]
However, according to the configuration of the third aspect, in the case of molding a plastic molded article having portions having different wall thicknesses, after the resin is introduced into the cavity (see FIG. 3 (a)), the molded article has a thin wall that is rapidly solidified. At the early timing when the resin in the portion corresponding to the thin portion can still move freely, the sliding piece corresponding to the thin portion is preferentially separated from the resin to form a gap (see FIG. 3B), and then the thickness gradually increases. The sliding pieces corresponding to the meat portions are separated from the resin (see FIG. 3 (c)) to form gaps in order, and finally the non-transfer surface forming surface of the mold is slid by separating all the sliding pieces from the resin. A continuous gap 8 having a desired size is formed in contact with each of the non-transfer surface forming surfaces on which the moving pieces are provided (see FIG. 3 (d)), thereby increasing internal strain and transferring by pressure distribution. High-precision molded products with reduced deterioration That.
[0025]
According to a fourth aspect of the present invention, in the method for molding a plastic molded product according to any one of the first to third aspects, for each of the plurality of sliding pieces, the pressure of the resin in the cavity with respect to the sliding pieces is detected. The sliding piece, which has a predetermined pressure on the sliding piece of the resin, is slid from the sliding piece so as to be separated from the resin.
With this configuration, the sliding pieces can be accurately separated from each other with a predetermined pressure, and a gap can be defined, so that an increase in internal strain and a decrease in transferability due to a pressure distribution can be further prevented.
[0026]
According to a fifth aspect of the present invention, in the method for molding a plastic molded product according to any one of the first to fourth aspects, the plurality of sliding pieces are concentric with one cylindrical body, the cylindrical body, and each of the cylindrical bodies. A pair of columnar composites composed of hollow tubular bodies arranged in a circle.
[0027]
With such a configuration, it is easy to perform processing with less error in manufacturing the sliding piece, and as a result, it is possible to prevent molten resin from entering between the sliding pieces at the time of molding, and to form a molded product. Shape deterioration can be prevented.
[0028]
According to a sixth aspect of the present invention, in the method for molding a plastic molded product according to any one of the first to fifth aspects, at least one ventilation hole is provided on the non-transfer surface forming surface of the sliding piece, and When sliding the sliding piece on the transfer surface forming surface, the resin is pressurized by injecting gas between the resin and the resin-side surface of the sliding piece from the vent.
With this configuration, the slide piece is slid while the resin is in close contact with the transfer surface by generating an appropriate resin internal pressure in the cavity by injection filling and leaving an appropriate pressure to maintain the close contact. When moving, the gas is press-fitted between the sliding piece and the resin through at least one vent provided on the non-transfer surface forming surface of the sliding piece, and the resin is pressed against the opposing surface of the separation surface to form a gap. The deformation caused by the resin being pulled by the sliding piece that moves apart by the close contact force between the resin and the sliding piece at the time of defining can be more effectively prevented.
[0029]
According to a seventh aspect of the present invention, in the method for molding a plastic molded product according to the sixth aspect, the vents are small holes and are provided in large numbers on the entire non-transfer surface forming surface of the sliding piece. It is characterized by.
[0030]
With such a configuration, gas can be uniformly fed from these minute holes to the entire non-transfer surface forming surface of the sliding piece, and the resin is pressed against the non-transfer surface forming surface of the sliding piece to form a gap. The deformation caused by the resin being pulled by the sliding piece moving away by the close contact force between the resin and the sliding piece at that time can be more effectively prevented.
[0031]
In addition, if the above-described configuration is achieved by forming at least the non-transfer surface forming surface of the sliding piece and the vicinity thereof by using a porous material, a forming step by mechanical processing of the vent is not required, and low cost is achieved. A vent can be created in
[0032]
According to an eighth aspect of the present invention, in the method for molding a plastic molded product according to the sixth or seventh aspect, the diameter is 0.001 mm or more and 0.1 mm or less.
[0033]
According to this configuration, when the diameter of the vent is less than 0.001 mm, the problem caused by insufficient effect of gas injection can be avoided, and the problem occurs when the diameter of the vent is 0.1 mm or more. In addition, it is possible to prevent the shape of the molded product from being deteriorated due to the intrusion of the molten resin into the vent, and to reduce the life of the mold.
[0034]
According to a ninth aspect of the present invention, in the method for molding a plastic molded product according to any one of the first to fifth aspects, the vent is in contact with a side surface of a sliding piece of a mold and is in contact with the vent. When the sliding piece is slid in the direction away from the resin, the sliding piece is provided at a position communicating with the cavity of the mold. When the sliding piece is slid, gas is supplied between the sliding piece and the resin through the vent. And pressurizing the resin.
[0035]
In this way, since the ventilation port is in a position in contact with the side surface of the sliding piece of the mold, and when the sliding piece in contact with the ventilation port is slid in a direction away from the resin, it communicates with the cavity of the mold. The vent and the resin do not come into direct contact with each other, and there is no need to consider the entry of the molten resin into the vent. By increasing the diameter of the vent, a sufficient amount of gas can be pressed in and a sufficient pressure can be achieved in a short time, and the resin due to the gas is pressed against the surface opposite to the non-transfer surface forming surface of the sliding piece. The force can be made stronger and wider, and the molding accuracy of the transfer surface can be further increased.
[0036]
According to a tenth aspect of the present invention, in the method for molding a plastic molded product according to any one of the sixth to ninth aspects, the vent is connected to a compressed gas generator provided outside the mold. It is characterized by the following.
[0037]
With such a configuration, the sliding movement of the sliding piece can be realized by the pressure of the gas supplied from the vent, and the press-fitted gas forms a gap by separating the sliding piece and the resin, and In addition to pressing the resin against the non-transfer surface forming surface of the sliding piece, the adhesive force between the resin and the sliding piece is further reduced, and the resin is pressed against the facing surface of the separating surface to form a gap. The deformation of the molded product due to the resin being pulled by the sliding piece that slides due to the adhesive force between the resin and the sliding piece at that time can be further prevented.
[0038]
According to an eleventh aspect of the present invention, in the method for molding a plastic molded product according to any one of the sixth to tenth aspects, the press-fitting pressure of the gas is 0.01 MPa or more and 50 MPa or less.
[0039]
With this configuration, when the gas pressure is less than 0.01 MPa, the force for pressing the resin against the opposing surface of the separating surface is insufficient, and the resin slides due to the adhesion force between the resin and the sliding piece when the gap is defined. Deformation caused by the resin being pulled by the moving sliding piece can be effectively prevented, and when the gas pressure is increased to 50 MPa or more, a deep sink occurs due to the gas pressure and the molded product shape deteriorates. Can also be prevented.
[0040]
According to a twelfth aspect of the present invention, in the method for molding a plastic molded product according to any one of the first to eleventh aspects, the non-transfer surface forming surface of the sliding piece is provided with a surface treatment for reducing the adhesive force with resin. It is characterized by having been given.
[0041]
According to this configuration, the adhesion between the resin and the sliding piece can be further reduced, the sliding piece can be easily separated from the resin, and the shape accuracy of the transfer surface can be improved.
[0042]
According to a thirteenth aspect of the present invention, in the method for molding a plastic molded product according to any one of the first to twelfth aspects, an insert is inserted into a transfer surface in a resin mold before introducing a molten resin into a cavity. It is characterized in that a molded product is obtained by insert molding.
[0043]
In the insert molding, usually, an insert made of a material that is not melted by the heat of the molten resin is selected. At this time, there is almost no adhesion between the insert and the transfer surface. The resin is pulled by the sliding piece that slides due to the contact force between the sliding piece and the sliding piece, and a molded product having a predetermined shape cannot be obtained.
[0044]
However, the effect of applying the present invention is particularly high in insert molding in which an insert is inserted into a transfer surface, and as a result, a highly accurate composite molded product can be obtained.
[0045]
According to a fourteenth aspect of the present invention, in the method for molding a plastic molded product according to the thirteenth aspect, a metal layer is formed on a surface of the insert.
In the case of an insert in which a metal layer is formed on the surface by such evaporation or the like, the adhesive force between the insert and the transfer surface does not occur at all, but by using the present invention, the resin at the time of defining the void There is almost no deformation due to the resin being pulled by the sliding piece that slides due to the contact force between the sliding piece and the sliding piece, and it is possible to obtain a composite molded article having excellent precision, such as a highly accurate integrated mirror. .
[0046]
According to a fifteenth aspect of the present invention, there is provided a plastic molding die apparatus for molding a plastic molded product having at least one transfer surface and at least one non-transfer surface in an internal cavity. At least one continuous part or the entirety of the non-transfer surface forming surface of the mold forming the non-transfer surface is constituted by a plurality of sliding pieces, each of which is separated from the resin injected and filled into the cavity. After the molten resin is introduced into the mold, when all the sliding pieces on the respective non-transfer surface forming surfaces are slid in the direction away from the resin, A continuous cavity is formed between the resin and the resin introduced into the mold, and the plastic molding die according to claim 1 having such a configuration. It is possible to implement, it is possible to obtain the excellent effect of that specific.
[0047]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the details of the present invention will be described with reference to Example 1.
In this example, the formed product is a flat mirror having a transfer surface which is a mirror surface and having a thickness of 100 mm × 100 mm and a thickness of 6 mm as shown in FIG.
[0048]
Next, the configuration of the mold used will be described.
FIG. 5A shows the configuration of the mold. The mold is composed of an upper mold 1 and a lower mold 2. The cavities are cavity pieces 3 and 4 having side surfaces, a cavity piece 5 having a transfer surface 5a that is a mirror surface (the surface accuracy of the transfer surface 5a is PV 0.7 μm), and It is composed of a plurality of sliding pieces 6a, 6b, 6c forming a non-transfer surface which is a surface facing the transfer surface.
[0049]
Each sliding piece is connected to a sliding piece driving means (not shown), and the sliding piece driving means moves in the direction of arrow A when filling the molten resin, and in the direction of arrow B when forming a gap (at the time of separating movement). (In a direction away from the resin filled in the cavity). The widths of the sliding pieces 6a, 6b and 6c are 30 mm, 40 mm and 30 mm, respectively. Each of the plurality of sliding pieces 6a, 6b, and 6c is provided with a pressure sensor, and each sliding piece slides based on detection information from the pressure sensor. A vent is provided on the surface of the sliding piece that is in contact with the resin (transfer surface molding surface), and the vent communicates with a compressed gas generator outside the mold (not shown).
[0050]
The molding machine used was an electric injection molding machine (Roboshot α100B manufactured by FANUC CORPORATION), and the molding material used was a polycarbonate resin which was an amorphous resin (Pallalite L1225L manufactured by Teijin Chemicals Limited, glass transition temperature: about 145 ° C.). . The surface accuracy was evaluated by a laser interferometer (ZYGO manufactured by Canon Inc.).
[0051]
Next, the operation of the present invention in this example will be described.
The mold is held at 136 ° C., which is lower than the softening temperature of the polycarbonate resin, and the resin melted at 280 ° C. is injected and filled into the cavity of the mold (when the amorphous resin is used, the temperature is lower than the glass transition temperature. (FIG. 5A).
[0052]
Next, while the average temperature from the surface layer portion to the central portion is equal to or higher than the softening temperature of the resin, when the internal pressure of the resin corresponding to each of the plurality of sliding pieces 6a, 6b, 6c becomes 5 MPa as measured by the pressure sensor. Each sliding piece is sequentially slid in the direction A in the drawing by 1 mm to define a gap between the resin and the plurality of sliding pieces 6a, 6b, 6c (FIGS. 5 (b) and 5 (c)). ) And FIG. 5 (d)).
[0053]
At the time of sliding movement of the sliding pieces, a compressed gas generator outside the mold passes through a vent pipe, and a 5 MPa pressure is applied between each sliding piece and the resin through a vent provided in each sliding piece. The resin is pressed against the transfer surface 5a, which is the gas-injected gas, and which faces the separation surface.
Then, as shown in FIG. 5D, one continuous gap 8 is finally formed between the plurality of sliding pieces and the resin, and thereafter the resin is completely solidified.
[0054]
FIG. 6 shows the values of the pressure sensors provided on each sliding piece during molding. (A), (b) and (c) on the time axis correspond to the states in FIGS. 5 (b), 5 (c) and 5 (d), respectively.
[0055]
In the first embodiment, as shown in FIG. 6, first, the pressure detected by the sensor provided on the sliding piece 6a becomes 5 MPa. At this time, the sliding piece 6a is separated assuming that the predetermined pressure is reached, Next, the pressure sensed by the sensor provided on the sliding piece 6b becomes 5 MPa. At this time, it is determined that the pressure has reached a predetermined pressure, the sliding piece 6b is separated, and finally sensed by the sensor provided on the sliding piece 6c. At this time, the sliding piece 6c was separated assuming that the pressure reached a predetermined pressure, and a gap 8 was formed as shown in FIG. 5D.
[0056]
Next, when the resin temperature reaches 136 ° C., the mold is opened and the molded product is taken out of the cavity 7 so that the molded product is not deformed. The transfer surface of this molded product had a surface accuracy of 8.7 μm.
[0057]
From the above example, according to the present invention, the resin is brought into close contact with the transfer surface 5a by generating an appropriate resin internal pressure in the cavity 7 by injection filling, and thereafter, an appropriate pressure for maintaining the adhesion is left. In this state, a gap 8 is defined between the resin and the plurality of sliding pieces 6a, 6b, and 6c, so that the resin surface of the resin facing the gap 8 becomes a free surface, and It is easier to move than other surfaces in contact with the mold.
For this reason, the heat conduction from the resin portion is reduced due to the presence of the gap 8, and the cooling rate of the resin portion is the slowest (that is, this portion of the resin has the highest temperature and the lowest viscosity in the cavity 7).
[0058]
As a result, the shrinkage of the resin caused by cooling is absorbed by the movement of this portion of the resin, which has the lowest viscosity, and the portion of the resin facing the void 8 is preferentially shrunk, thereby causing sink on the transfer surface. And the transfer surface is faithfully transferred with high accuracy even in a short molding cycle. Further, since the internal pressure of the resin acting on the transfer surface at the time of cooling can be brought close to the atmospheric pressure, a molded product with small photoelastic distortion can be obtained.
[0059]
Further, in the above example, a polycarbonate resin is used as a molding material, but other resins such as polystyrene, polypropylene, and polymethyl methacrylate may be used as long as they are thermoplastic resins. It is desirable to use an amorphous resin from which a molded article can be easily obtained. Further, in the above description, the moving amount of the sliding piece is 1 mm, but the distance is not limited to 1 mm as long as the gap can be defined between the resin and the plurality of sliding pieces.
[0060]
In addition, if the sink is unevenly formed on the non-transfer surface, a local temperature distribution is generated in the molded product, and the internal strain remaining in the molded product is increased. Since the pieces are continuously provided, continuous shrinkage of a desired size can be uniformly generated on the non-transfer surface by separating the plurality of sliding pieces, so that the internal distortion can be reduced. Although three sliding pieces are provided in the first embodiment, any number of sliding pieces may be provided depending on the area of the non-transfer surface to be separated, the adhesion, and the like.
[0061]
In the first embodiment, the resin pressure in the cavity when the plurality of sliding pieces are separated from the resin is 5 MPa, but may be in the range of 0.5 MPa to 60 MPa. If the sliding piece is separated when the resin pressure is less than 0.5 MPa, sinkage may occur first on the transfer surface, which is not preferable, and when the resin pressure is more than 60 MPa. If the sliding pieces are separated from each other, the internal stress of the molded product itself increases and residual stress remains, which is not preferable.
[0062]
In this embodiment, as described above, since each sliding piece is provided with the pressure detecting means, each sliding piece can be accurately separated from each other with a predetermined pressure to form a gap, thereby increasing internal strain. And the pressure distribution can further prevent a decrease in transferability.
In the above embodiment, when the sliding piece is slid, a gas is injected between the sliding piece and the resin through the vent provided on the surface of the sliding piece in contact with the resin, and the pressure causes the resin to separate the separating surface. By pressing the sliding piece against the opposing surface, it is possible to further prevent deformation due to the resin being pulled by the sliding piece that moves away from the sliding piece due to the adhesion between the resin and the sliding piece when the gap is defined.
[0063]
Here, if the ventilation holes are minute holes and are provided in large numbers on the entire non-transfer surface forming surface of the sliding piece, the ventilation holes are more uniform than the micro holes on the entire non-transfer surface forming surface of the sliding piece. By pressing the resin against the non-transfer surface forming surface of the sliding piece, the resin is pressed onto the sliding piece that moves away from the sliding piece due to the adhesion between the resin and the sliding piece when the gap is defined. Deformation due to being pulled can be more effectively prevented. In addition, if the above-described configuration is achieved by forming at least the non-transfer surface forming surface of the sliding piece and the vicinity thereof by using a porous material, a forming step by mechanical processing of the vent is not required, and low cost is achieved. A vent can be created in
[0064]
In the above example, the diameter of the width (micropore) of the ventilation hole is 0.001 mm or more and 0.1 mm or less. When the width of the vent and the diameter of the micropores are less than 0.001 mm, the effect of pressurizing gas is not sufficient, so that it is not preferable, and when the width of the vent and the diameter of the micropores are 0.1 mm or more. In addition, the molten resin enters the vents or the micropores, which deteriorates the shape of the molded product and shortens the life of the mold.
[0065]
In the first embodiment, the pressure of the gas introduced from the vent is 5 MPa, but may be in the range of 0.01 MPa to 50 MPa. Here, when the pressure of the gas is set to less than 0.01 MPa, the force for pressing the resin against the opposing surface of the separation surface is insufficient, and the sliding that separates and moves by the adhesion force between the resin and the slide piece at the time of defining the gap. If the pressure of the gas is set to 50 MPa or more, it is not preferable because the gas pressure causes a deep sink mark and the shape of the molded product is deteriorated.
[0066]
Here, the shapes formed by a plurality of sliding pieces arranged on one non-transfer surface forming surface are shown in FIG. 7A (a cross-sectional view showing a state of being assembled in a mold), and FIG. As shown in the cross-sectional view (only sliding pieces are shown) at LL in FIG. That is, a plurality of sliding pieces (a sliding piece 6g in this example) and a set of hollow tubular bodies (in this example, sliding pieces) are arranged concentrically around the cylindrical body and each of them. The formation of the columnar composite composed of the pieces 6d to 6f) facilitates processing with less error in the production of the sliding pieces, and as a result, melting between the sliding pieces during molding is performed. Of the molded resin can be prevented, and the deterioration of the shape of the molded product can be prevented.
[0067]
In addition, by applying a surface treatment to the non-transfer surface forming surface of the sliding piece to reduce the adhesive strength with the resin, the adhesive strength between the resin and the sliding piece is further reduced, and the sliding piece is easily separated from the resin. And the shape accuracy of the transfer surface can be improved. Here, as a material for lowering the adhesive force between the molding surface of the sliding piece and the resin, for example, TiN (titanium nitride), TiCN (titanium cyanide), W ₂ C (tungsten carbide) and a fluorine-based resin are mentioned, and the above-described configuration can be easily realized by performing a surface treatment using these.
In addition, as shown in FIG. 3, when the shape of the molded product is not the same thickness as a whole but has a partial difference in wall thickness, and is an uneven thickness shape, the portion corresponding to the outer peripheral portion of the molded product thin portion is quickly formed. The pressure tends to remain because it is cooled.
[0068]
Therefore, if the sliding piece corresponding to the thick part is separated before the sliding piece corresponding to the thin part, and a gap is defined between the resin and the sliding piece, the thickness of the molded product (product in the middle of molding) is increased. The meat portion is separated in a state that still includes a portion having a high temperature close to the melting temperature, that is, in a state having flexibility, and follows the movement according to the separation movement of the sliding piece, and as a result, the periphery thereof And the transferability of the transfer portion is reduced. In addition, since the separation movement of the sliding piece in the thin portion has a large temperature drop, the solidification of the part has considerably progressed, and the above problem does not occur because the movement of the resin in the gap definition due to the separation of the sliding piece is small. However, the internal pressure of the resin already unevenly distributed in the solidified portion in the cavity remains, and the fluidity of the resin is extremely deteriorated, so that the internal distortion that causes optical distortion and the transfer surface accuracy deteriorates.
[0069]
However, if these sliding pieces are sequentially separated from the resin in order from the sliding piece corresponding to the thinnest part of the molded article to the sliding piece corresponding to the thick part, if a gap is sequentially formed, In the case of molding a plastic molded product having portions with different wall thicknesses, after the resin is introduced into the cavity (see FIG. 3A), the resin in the portion corresponding to the thinned portion of the molded product where solidification progresses quickly is still free. As soon as it is possible to move, the sliding piece corresponding to the thin part is preferentially separated from the resin to form an air gap (see FIG. 3B), and then the sliding piece corresponding to the thick part is sequentially removed from the resin. Separation (see FIG. 3 (c)), a gap is sequentially formed, and finally the non-transfer surface forming surface provided with sliding pieces by separating all the sliding pieces of the non-transfer surface forming surface of the mold from the resin. A continuous void 8 having a desired size in contact with each of Let it be to prevent deterioration of transferring property due to the increase and the pressure distribution inside distortion (FIG. 3 (d) see) that to obtain a molded article with excellent accuracy.
[0070]
If the ventilation holes (micro holes) of the sliding piece are formed at positions between the resin and the sliding piece and at positions communicating with the compressed gas generator outside the mold, the sliding piece slides. At that time, gas is injected between the sliding piece and the resin from the vent and the minute hole, and the resin is pressed against the opposing surface of the separating surface to form a gap, thereby further increasing the adhesive force between the resin and the sliding piece. Deformation of the molded product due to the resin being pulled during the movement of the sliding piece due to the close contact force between the resin and the sliding piece at the time of forming the gap by reducing and pressing the resin against the opposing surface of the separation surface Can be more effectively prevented.
[0071]
Next, Comparative Example 1 according to the related art will be described for comparison with Example 1 described above.
A mold having a transfer surface 5a for obtaining the same molded product as in Example 1 was used. The mold is shown in FIG.
[0072]
This mold is a molding die for a plastic molded article having one transfer surface and five non-transfer surfaces, and is slid on the non-transfer surface forming surface of the die that forms the non-transfer surface of the molded product. A moving piece is provided. ,
[0073]
The mold is composed of an upper mold 1 and a lower mold 2. The cavity 7 has cavity pieces 3 and 4 having side surfaces and a cavity piece 5 having a transfer surface 5a which is a mirror surface (the surface accuracy of the transfer surface 5a is PV 0.7 μm). And one sliding piece 6 forming a non-transfer surface corresponding to the transfer surface.
[0074]
The sliding piece 6 is in communication with a driving unit (not shown), and is driven by the driving unit in the direction of arrow A when filling the molten resin and in the direction of arrow B when forming a gap.
The width of the sliding piece is 100 mm.
[0075]
The molding machine used was an electric injection molding machine (Roboshot α100B manufactured by FANUC CORPORATION), and the molding material used was a polycarbonate resin which was an amorphous resin (Palelite L1225L manufactured by Teijin Chemicals Limited, glass transition temperature: about 145 ° C.). . The surface accuracy was evaluated by a laser interferometer (ZYGO manufactured by Canon Inc.).
[0076]
The mold was kept at 136 ° C., which is lower than the softening temperature of the polycarbonate resin, and the resin melted at 280 ° C. was injected and filled into the cavity of the mold (see FIG. 1B).
[0077]
Next, while the average temperature from the surface portion to the center of the resin is equal to or higher than the softening temperature of the resin, the sliding piece 6 is moved by 1 mm to define a gap between the resin and the sliding piece 6, and then the resin is formed. Is completely solidified (see FIG. 1 (c)).
[0078]
Thereafter, when the resin temperature reaches 136 ° C., the mold is opened and the molded product is taken out of the cavity 7. The surface accuracy of the transfer surface of this molded product was 43 μm. Such low surface accuracy is such that when the sliding piece is separated, the resin is pulled in the separating direction by the adhesive force between the resin and the sliding piece, and the molded product is deformed as shown in FIG. Is considered to be due to the concave shape.
[0079]
Next, examples of other molds used in the present invention will be described.
As shown in FIG. 8A, in this example, the ventilation port is slid in a position in contact with the side surface of the sliding piece of the mold (lower die 2) and in a direction in which the sliding piece in contact with the ventilation port is separated from the resin. It is provided at a position where it communicates with the cavity 7 of the mold when moving. Except for the vent, the mold is the same as the mold used in Example 1.
[0080]
After the molten resin is injected and filled into the cavity 7 of such a mold, the pressure of the resin applied to the plurality of sliding pieces 6h, 6i, and 6j reaches a predetermined pressure during cooling to a temperature lower than the softening temperature of the resin. Occasionally, they are sequentially slid so as to be sequentially separated from the resin on the non-transfer surface (FIG. 8B). When the sliding piece slides, the vent communicates with the cavity 7 and a predetermined pressure is applied between the sliding piece and the resin through the vent provided in the mold by a compressed gas generator outside the mold. And the resin is pressed against the opposing surface (transfer surface in this example) of the separation surface by the pressure. Finally, one continuous gap is formed between the plurality of sliding pieces 6h, 6i and 6j and the resin.
[0081]
According to the present invention, the mold is provided at a position where the ventilation port is in contact with the side surface of the sliding piece of the mold (lower mold 2) and when the sliding piece contacting the ventilation port is slid in a direction away from the resin. Is provided at a position communicating with the cavity 7, so that the vent does not come into direct contact with the resin, and it is not necessary to consider the entry of the molten resin into the vent, and the degree of freedom in increasing the diameter of the vent is increased. Get higher. By increasing the diameter of the vent, a sufficient amount of gas can be pressed in and a sufficient pressure can be achieved in a short time, and the resin due to the gas is pressed against the surface opposite to the non-transfer surface forming surface of the sliding piece. The force can be made stronger and wider, and the molding accuracy of the transfer surface can be further increased.
[0082]
In addition, as shown in FIG. 9, when a composite member is formed by insert molding in which another member such as a film different from the molten resin is inserted as an insert and integrally formed as a transfer surface, the other member does not melt at the time of molding. In general, the adhesive force on the transfer surface almost disappears. At this time, the adhesive force between the resin and the sliding piece at the time of forming the gap causes the sliding piece to slide and move. The transfer surface is deformed by the resin being pulled. However, by applying the present invention to such a method of molding a composite molded article by insert molding, a highly accurate composite molded article having almost no deformation can be obtained.
[0083]
In particular, in the case of an insert having a metal film layer formed on the surface by vapor deposition or the like, the adhesion between the metal surface of the insert and the transfer surface (metal) of the mold does not occur at all. The sliding piece that slides due to the adhesive force between the resin and the sliding piece when the air gap is defined has almost no deformation due to the resin being pulled by the sliding piece, and has excellent precision, such as a high-precision integrated mirror. A composite molded article can be obtained.
[0084]
【The invention's effect】
The method for molding a plastic molded article of the present invention is a method for molding a plastic molded article having at least one transfer surface and at least one non-transfer surface, which is performed by introducing a molten resin into a mold cavity. A sliding piece is provided on at least one of the non-transfer surface forming surfaces of the mold that forms the non-transfer surface of the molded product. After the mold is heated to a temperature lower than the softening temperature of the resin, the mold is melted into the cavity. After the resin is introduced and the resin is brought into close contact with the transfer surface by applying pressure, the sliding provided on the non-transfer surface forming surface of the mold is performed until the resin cools below the softening temperature. In the method of molding a plastic molded product in which a piece is moved in a direction away from the resin to define a gap between the sliding piece and the resin, each of the non-transfer surface forming surfaces provided with the sliding piece is provided. The continuous part or the whole of the A plurality of sliding pieces are sequentially slid in a direction away from the resin until the molten resin introduced into the mold cavity is cooled below the softening temperature. A continuous gap having a desired size is formed in contact with each of the non-transfer surface forming surfaces provided with the sliding pieces by separating all the sliding pieces of the non-transfer surface forming surface of the mold from the resin. It is a molding method of a plastic molded article, and by its configuration, a continuous part or the entire non-transfer surface of the mold is formed by a plurality of sliding pieces, and these sliding pieces are not separated from the resin at the same time, By sequentially separating the sliding pieces, the contact area of the sliding pieces moving away from the resin can be reduced, and the adhesive force of the sliding pieces moving away from the resin can be reduced.
[0085]
As a result, it is possible to minimize the force with which the molded product (the half-molded product) in which the resin is being cooled is pulled in the separation direction by the adhesion force to the sliding piece that is moving away. Deformation of a molded product (a product in the middle of molding) can be kept to a minimum, and deterioration of the shape accuracy of the transfer surface can be prevented.
[0086]
Further, in the prior art, the temperature of the non-transfer surface is made lower than the temperature of the transfer surface to promote the solidification of the resin, thereby reducing the adhesive force between the resin and the sliding piece. The temperature difference between the transfer surface and the transfer surface is large, and the molded product is warped after the mold release, and as a result, the shape of the transfer surface is lost. However, in the present invention, a plurality of sliding pieces are provided on the non-transfer surface by the above-described structure, and by sequentially separating them, the adhesive force between the resin and the slide pieces is reduced. The difference in temperature from the surface does not increase, and as a result, deformation due to warpage after mold release can be prevented.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining a problem of a conventional technique.
FIG. 2A is a model cross-sectional view showing a mold and a cavity formed therein.
(B) It is a model sectional view showing the state where resin was injected and filled in (a).
(C) is a model sectional view showing a state where a sliding piece slides in a direction away from resin.
FIG. 2 is an explanatory diagram for explaining a problem of another conventional technique.
FIG. 2A is a model cross-sectional view showing a mold and a cavity formed therein.
(B) It is a model sectional view showing the state where resin was injected and filled in (a).
(C) is a model section showing a state when a sliding piece slides in a direction away from a resin.
FIG. 3 is an explanatory diagram showing an example of an embodiment of the present invention.
(A) is a model sectional view showing a state in which a resin is injected and filled into a mold and a cavity formed therein.
(B) A model section showing a state when the sliding piece 6a slides in a direction away from the resin.
(C) is a model cross-section showing a state where the sliding piece 6b further slides in a direction away from the resin.
(D) The sliding piece 6c slides in the direction away from the resin, and each of the non-transfer surface forming surfaces on which the sliding pieces are provided by separating all the sliding pieces from the resin on the non-transfer surface forming surface of the mold. FIG. 6 is a model cross section showing a state when a single continuous void is formed in contact with.
FIG. 4 is a model perspective view showing a molded product formed in an example of the present invention.
FIG. 5 is an explanatory diagram showing another example of the embodiment of the present invention.
(A) is a model sectional view showing a state in which a resin is injected and filled into a mold and a cavity formed therein.
(B) A model section showing a state when the sliding piece 6a slides in a direction away from the resin.
(C) is a model section showing a state in which the sliding piece 6b further slides in a direction away from the resin.
(D) The sliding piece 6c slides in the direction away from the resin, and each of the non-transfer surface forming surfaces on which the sliding pieces are provided by separating all the sliding pieces from the resin on the non-transfer surface forming surface of the mold. 5 is a model cross section showing a state when a single continuous void is formed in contact with.
FIG. 6 is a graph showing a time change of the pressure of the resin with respect to each sliding piece and a timing when the pressure reaches a predetermined pressure (5MP) in the first embodiment.
FIG. 7 (a) A plurality of sliding pieces form a columnar composite composed of one column and a pair of hollow tubular bodies arranged concentrically around the column and each column. It is a model sectional view showing an example.
(B) It is a model sectional view of the above-mentioned plurality of sliding pieces which form a columnar composite when cut by LL of (a).
FIG. 8 (a) is a position where the ventilation port is in contact with the side surface of the sliding piece of the mold, and when the sliding piece in contact with the ventilation port is slid in a direction away from the resin, it communicates with the cavity of the mold. FIG. 3 is a cross-sectional view of a model of a mold provided at a position where the mold is provided.
(B) It is a model sectional view showing the state when sliding piece 6h of (a) has slid and moved in the direction separating from resin.
FIG. 9 (a) is a model cross-sectional view showing a cross-section of a composite molded product formed by insert molding in which a film is inserted into a transfer surface, which is suitable for the application of the present invention.
(B) A model cross-sectional view showing a cross-section of a composite molded product that is extremely suitable for application of the present invention and is formed by insert molding in which a film having a metal layer is inserted into a transfer surface.
[Explanation of symbols]
1 Upper type
2 lower mold
3,4,5 Cavity pieces
6a-6j Sliding piece

Claims

A method for molding a plastic molded article having at least one transfer surface and at least one non-transfer surface, which is performed by introducing a molten resin into a cavity of a mold,
A sliding piece is provided on at least one of the non-transfer surface forming surfaces of the mold that forms the non-transfer surface of the molded product,
After the mold is heated to a temperature lower than the softening temperature of the resin, the molten resin is introduced into the cavity, and further, the resin is brought into close contact with the transfer surface by pressing, and then the resin is cooled to a temperature lower than the softening temperature. Between the sliding piece and the resin by moving the sliding piece provided on the non-transfer surface forming surface of the mold in a direction away from the resin. In the molding method of the molded article,
Each continuous part or the whole of the non-transfer surface forming surface provided with the sliding piece is constituted by a plurality of sliding pieces, and until the molten resin introduced into the mold cavity is cooled below the softening temperature. The sliding pieces were provided by sequentially sliding the plurality of sliding pieces in a direction away from the resin and finally separating all the sliding pieces of the non-transfer surface forming surface of the mold from the resin. A method for molding a plastic molded article, wherein a continuous gap having a desired size is formed in contact with each of the non-transfer surface forming surfaces.

The molding of the plastic molded product according to claim 1, wherein the pressure of the resin on each of the sliding pieces in the cavity when separating the plurality of sliding pieces from the resin is set to 0.05 MPa or more and 60 MPa or less. Method.

When the plastic molded product to be molded has portions having different thicknesses, and a plurality of sliding pieces corresponding to these portions are provided in the mold, the plastic molded product corresponds to the thinnest portion of the molded product. 3. The plastic according to claim 1, wherein the sliding pieces are sequentially separated from the resin in order from the sliding piece to the sliding piece corresponding to the thick portion, and a gap is sequentially formed. Molding method of molded article.

For each of the plurality of sliding pieces, the pressure of the resin in the cavity with respect to the sliding piece is detected, and the sliding piece whose pressure on the sliding piece of the resin reaches a predetermined value is slid to separate from the resin. The method for molding a plastic molded product according to any one of claims 1 to 3, wherein:

The plurality of sliding pieces form a pair of columnar composites including one column, the column, and a hollow tubular member arranged concentrically around each column. A method for molding a plastic molded product according to any one of claims 1 to 4.

At least one vent is provided on the non-transfer surface forming surface of the sliding piece, and when sliding the sliding piece on the non-transfer surface forming surface of the mold, the resin-side surface of the sliding piece with respect to the resin from the vent is formed. The method for molding a plastic molded product according to any one of claims 1 to 5, wherein the resin is pressurized by injecting a gas into the space between the resin and the resin.

7. The method for molding a plastic molded product according to claim 6, wherein a large number of said ventilation holes are formed in the entire surface of the non-transfer surface forming surface of the sliding piece.

The method for molding a plastic molded product according to claim 6, wherein the diameter of the vent is 0.001 mm or more and 0.1 mm or less.

The sliding port is provided at a position in contact with the side surface of the sliding piece of the mold, and at a position communicating with the cavity of the mold when the sliding piece contacting the vent port slides in a direction away from the resin. The plastic molding according to any one of claims 1 to 5, wherein when the moving piece is slid, the resin is pressurized by pressurizing a gas between the sliding piece and the resin through the vent. Product molding method.

The method for molding a plastic molded product according to any one of claims 6 to 9, wherein the vent is connected to a compressed gas generator provided outside the mold.

The method for molding a plastic molded product according to any one of claims 6 to 10, wherein the gas injection pressure is 0.01 MPa or more and 50 MPa or less.

12. The method according to claim 1, wherein the non-transfer surface forming surface of the sliding piece is subjected to a surface treatment for reducing adhesion to resin.

13. The plastic molding according to claim 1, wherein a molded product is obtained by insert molding in which an insert is inserted into a transfer surface in a resin mold before introducing the molten resin into the cavity. Product molding method.

14. The method according to claim 13, wherein a metal layer is formed on a surface of the insert.

A mold for molding a plastic molded article having at least one transfer surface and at least one non-transfer surface in an internal cavity,
At least one continuous part or entirety of the non-transfer surface forming surface of the mold that forms the non-transfer surface is constituted by a plurality of sliding pieces, each of which is separated from the resin injected and filled into the cavity. After the molten resin is introduced into the mold, when all the sliding pieces on each non-transfer surface forming surface are slid in a direction away from the resin, the molten resin is introduced into the mold. A continuous cavity is formed between the resin and the molded resin.