JP2004107789A - Cleaning method with pressurized fluid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To clean components under an optimized and efficient cleaning condition suitable for the components in a method for cleaning components having recessed structure in contact with super-critical or liquefied carbon dioxide. <P>SOLUTION: Components are cleaned by changing the density of a fluid without changing the phase state of the fluid in a pressurized supercritical condition in contact with the components. In particular, when the density of the components is not more than the liquid density of the fluid, the buoyancy applied to the components is changed by controlling the density of the fluid. Accordingly, the components are vertically moved in the fluid, and the components are efficiently cleaned by generating the agitation effect to prevent the components from being closely attached to each other. Due to the effect, impurities insoluble in the fluid are efficiently removed, and impurities are removed and cleaned to the end of recessed portions of the components with high diffusibility of the super-critical fluid. <P>COPYRIGHT: (C)2004,JPO

Description

【０１１９】
以上の結果から、溶剤洗浄と比較すると残留油分量、パーティクル量ともに低い値が得られている。また、圧力を変化させて二酸化炭素の気体状態、液体状態、超臨界状態を組み合わせることで無機物系のパーティクル除去にも更に洗浄効果が向上することがわかった。
【０１２０】
（実施例２）
実施例１と同様に　プレス成型加工及び切削加工されたケースの洗浄を行った。洗浄用の液化ガスとしては二酸化炭素を用いて行った。図６に示すように材質はＳＵＳ３０４、大きさはφ１２ｍｍ、高さ５ｍｍの凹部構造を有するケースである。このケースを用いて洗浄プロセスの違いによる残留物（油分）の量とパーティクル量を調べた。洗浄プロセスとしては、▲１▼液体状態で圧力一定で温度を変化させた洗浄、▲２▼圧力一定で温度を変化させ、気体状態と液体状態を５回繰り返し状態変化をさせた洗浄、▲３▼超臨界洗浄のみの洗浄、▲４▼▲１▼の工程後超臨界洗浄、▲５▼▲２▼の洗浄後超臨界洗浄の５通りの工程を検討した。それぞれの洗浄工程でケースは１００個ずつ洗浄し分析を行った。残留油分分析は溶剤（四塩化炭素）で油分抽出したのちその抽出油分をＦＴ−ＩＲ（フーリエ変換赤外分光法）で測定した。またパーティクルについては洗浄後パーティクル検査機（ＴｏＰｃｏｎ製ウェーハ表面検査装置　ＷＭ−１７００／１５００）を用いて測定した。表２にその結果を示す。
【０１２１】
【表２】

【０１２２】
以上の結果、温度一定で圧力を変化させて物性変化、状態変化した場合と同様に圧力一定で温度を変化させて洗浄した場合も残留油分量、パーティクル量ともに低い値が得れている。よって、温度を変化させて二酸化炭素の気体状態、液体状態、超臨界状態を組み合わせることで無機物系のパーティクル除去にも洗浄効果が向上することがわかった。
【０１２３】
（実施例３）
実施例１で検討した洗浄方法で最も効果のあった洗浄工程▲６▼「温度一定で圧力を変化させ、気体状態と液体状態を５回繰り返し状態変化をさせた後超臨界洗浄」を用いて材質の異なるケースを洗浄した。ケースの材質は、▲１▼アルミニウム、▲２▼アルミニウム上に有機膜をコートした複合板、▲３▼ステンレスＳＵＳ３０４、▲４▼Ｃｕ、▲５▼Ｔｉである。図７に示すように、ケース形状は縦５ｍｍ×横３０ｍｍ×高さ５０ｍｍである。それぞれの洗浄工程でケースは１００個ずつ洗浄し分析を行った。洗浄用の液化ガスとしては二酸化炭素を用いて行った。残留油分分析は溶剤（四塩化炭素）で油分抽出したのちその抽出油分をＦＴ−ＩＲ（フーリエ変換赤外分光法）で測定した。また、パーティクルについては洗浄後パーティクル検査機（ＴｏＰｃｏｎ製ウェーハ表面検査装置　ＷＭ−１７００／１５００）を用いて測定した。表３にその結果を示す。
【０１２４】
【表３】

【０１２５】
以上の結果、残留油分量とパーティクル量と外観検査で判断したが問題なく洗浄効果が得られた。また、材質の異なるケースにおいても外傷を与えることなく洗浄できることが判明した。
【０１２６】
外見検査、パーティクル量の判断基準は、日本産業洗浄協議会の平成６年度の報告書「一般的な洗浄度評価方法と洗浄度の指標の分類」で示されている「試料２」を用いて説明すると、そこで洗浄度として記されている「一般洗浄」以上を○とした。
【０１２７】
（実施例４）
実施例１で検討した洗浄方法で最も効果のあった洗浄工程▲６▼「温度一定で圧力を変化させ、気体状態と液体状態を５回繰り返し状態変化をさせた後超臨界洗浄」を用いて材質の異なる部品を洗浄した。ただし、有機物系の材質は金属系及びセラミックス系と比べて弱いので時間を短くした。洗浄用の液化ガスとしては二酸化炭素を用いて行った。部品はプレス成型加工、切削を行って形状を加工したものである。部品の材質は、▲１▼エポキシ樹脂、▲２▼ポリイミド樹脂、▲３▼プラスチック、▲４▼エポキシとガラスバルーンの混合、▲５▼ＳｉＯ_２、▲６▼Ｃ（カーボン）である。部品形状は、直径φ１０．８ｍｍ×高さ１．１５ｍｍである。外観検査についてはＳＥＭ（Ｓｃａｎｎｉｎｇ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｙ）を用いて、パーティクルについては洗浄後パーティクル検査機（ＴｏＰｃｏｎ製ウェーハ表面検査装置　ＷＭ−１７００／１５００）を用いて測定した。表４にその結果を示す。
【０１２８】
【表４】

【０１２９】
外見検査、パーティクル量の判断基準は、日本産業洗浄協議会の平成６年度の報告書「一般的な洗浄度評価方法と洗浄度の指標の分類」で示されている「試料２」を用いて説明すると、そこで洗浄度として記されている「一般洗浄」以上を○とした。
【０１３０】
（実施例５）
更に、洗浄効果、特に汚染物の再付着の防止効果を調べるために高圧容器の構造と洗浄対象物の容器固定位置を変えて洗浄を行い残留油分量とパーティクル量測定した。洗浄用の液化ガスとしては二酸化炭素を用いて行った。洗浄工程は実施例１で検討した洗浄方法で最も効果のあった洗浄工程▲６▼「温度一定で圧力を変化させ、気体状態と液体状態を５回繰り返し状態変化をさせた後超臨界洗浄」を用いて洗浄した。部品はプレス成型加工を行って作成したケースで形状は縦５ｍｍ×横３０ｍｍ×高さ５０ｍｍである。高圧容器の構造及び洗浄対象物の容器内固定位置を以下のように変えて洗浄を行った。▲１▼液化ガス導入口＜洗浄対象物＜液化ガス排出口、▲２▼液化ガス導入口＞洗浄対象物＞液化ガス排出口、▲３▼液化ガス導入口＜液化ガス排出口＜洗浄対象物、▲４▼洗浄対象物＜液化ガス導入口＜液化ガス排出口、▲５▼洗浄対象物＜液化ガス排出口＜液化ガス導入口、▲６▼液化ガス排出口＜液化ガス導入口＜洗浄対象物の６通りの検討を行った。それぞれの洗浄工程でケースは１００個ずつ洗浄し分析を行った。残留油分分析は溶剤（四塩化炭素）で油分抽出したのちその抽出油分をＦＴ−ＩＲ（フーリエ変換赤外分光法）で測定した。また、パーティクルについては洗浄後パーティクル検査機（ＴｏＰｃｏｎ製ウェーハ表面検査装置　ＷＭ−１７００／１５００）を用いて測定した。表５にその結果を示す。
【０１３１】
【表５】

【０１３２】
以上の結果、高圧容器の構造と浄対象物の容器内固定位置は液化ガス導入口＜洗浄対象物＜液化ガス排出口にすることで汚染物の再付着防止効果で洗浄効果を向上可能であることがわかった。
【０１３３】
（実施例６）
凹部構造の深さや形状に依存しないかを調べるために凹部構造の形状や深さを変化させて洗浄効果を検討した。洗浄用の液化ガスとしては二酸化炭素を用いて行った。実施例１で検討した洗浄方法で最も効果のあった洗浄工程▲６▼「温度一定で圧力を変化させ、気体状態と液体状態を５回繰り返し状態変化をさせた後超臨界洗浄」を用いて洗浄した。部品はプレス成型加工を行って作成したケースで形状は▲１▼縦５ｍｍ×横３０ｍｍ×高さ５０ｍｍ、▲２▼縦５ｍｍ×横１０ｍｍ×高さ５ｍｍ、▲３▼縦３ｍｍ×横５ｍｍ×高さ２０ｍｍ、▲４▼φ１０．８ｍｍ×高さ５ｍｍ▲５▼φ５ｍｍ×高さ５ｍｍである。それぞれのケース形状でケースは１００個ずつ洗浄し分析を行った。残留油分分析は溶剤（四塩化炭素）で油分抽出したのちその抽出油分をＦＴ−ＩＲ（フーリエ変換赤外分光法）で測定した。またパーティクルについては洗浄後パーティクル検査機（ＴｏＰｃｏｎ製ウェーハ表面検査装置ＷＭ−１７００／１５００）を用いて測定した。表６にその結果を示す。
【０１３４】
【表６】

【０１３５】
以上の結果からケース形状にかかわらず洗浄効果が見られた。よって、ケースの形状によらず洗浄できることがわかった。
【０１３６】
（実施例７）
プレス成型加工及び切削加工されたケースの洗浄工程の検討を行った。洗浄用の液化ガスとしては二酸化炭素と水を用いて行った。材質はＳＵＳ３０４、大きさはφ１２ｍｍ、高さ５ｍｍの凹部構造を有するケースである。このケースを用いて洗浄プロセスの違いによる残留物（油分）の量とパーティクル量、酸化物の変化、接触角測定による濡れ性を調べた。洗浄プロセスとしては、▲１▼二酸化炭素を用いて、温度一定で圧力を変化させ、気体状態と液体状態を５回繰り返し状態変化をさせた洗浄後超臨界状態へ移行して洗浄、▲２▼▲１▼の洗浄後二酸化炭素を追い出して水を導入して２００℃、５Ｍｐａで洗浄、▲３▼▲１▼の洗浄後二酸化炭素中に水を導入して２００℃、５Ｍｐａで洗浄、▲４▼水の２００℃、５Ｍｐａのみの洗浄の４通りの工程を検討した。それぞれの洗浄工程でケースは１００個ずつ洗浄し分析を行った。残留油分分析は溶剤（四塩化炭素）で油分抽出したのちその抽出油分をＦＴ−ＩＲ（フーリエ変換赤外分光法）で測定した。またパーティクルについては洗浄後パーティクル検査機（ＴｏＰｃｏｎ製ウェーハ表面検査装置　ＷＭ−１７００／１５００）を用いて測定した。
【０１３７】
また、酸化物の変化についてはＥＳＣＡ（Ｘ線光電子分光法）を用いて測定した（酸化物の判断基準としては、初期値（脱脂処理後）の酸化物ピーク強度を１として、各洗浄後の酸化物ピーク強度を比で示した）。
【０１３８】
また、接触角については協和界面化学（株）製の自動接触角計ＣＡ−Ｚ型を用いて測定した。接触角とは、物質表面の液体に対するなじみやすさ（親和性、又はぬれ性）を表す指標として、一般に用いられる。図８に示すように接触角とは、固体、液体、気体の三相の界面で液滴の接線と固体面とのなす角のことをいい、液体が表面になじみやすくなるにつれて、接触角は小さくなる。
【０１３９】
表７にその結果を示す。酸化物量は洗浄工程▲１▼を１として規格化した。また、接触角は液体として純水で測定した。
【０１４０】
【表７】

【０１４１】
以上の結果、二酸化炭素の洗浄工程と水の２００℃、５Ｍｐａ洗浄を組み合わせることで油分及び無機物系の酸化物を除去可能であり、さらに接触角も小さくなり濡れ性も改善できることが判明した。
【０１４２】
本発明の第１実施形態によれば、凹部構造を有する部品を液化ガスや超臨界流体の洗浄媒体を用いて洗浄することで、洗浄効果を向上させることができる。
【０１４３】
（第２実施形態）
次に、本発明の第２実施形態で用いられる加圧された流動体、特に超臨界状態の意味について、図２９を参照しながら、説明する。
【０１４４】
この第２実施形態は、第１実施形態で除去した物質を再利用することを考慮したものである。すなわち、従来では、超臨界や亜臨界状態の流体を用いる洗浄において、洗浄効果を高めるためにいろいろな工夫が行われている。例えば、超臨界又は亜臨界状態の流体を急速に状態変化させる方法が開示されている。しかし、これら流体の急激な状態変化は物理的な衝撃を洗浄の対象物に与えるため、部品のゆがみやひどい場合には欠けなどを生じる場合がある。特に、密度の低い部品や、薄板で複雑な構造の凹部を形成した部品などは、その影響を強く受けやすい。
【０１４５】
一方、プレス成型加工で加工される部品、特に電子部品に関しては、精度を高めるため多くの潤滑油を使用する。このため、加工後部品の洗浄液には潤滑油主成分である炭化水素系有機物が大量に含まれる。さらに潤滑油には、加工精度向上を目的として、炭化水素系有機物以外にも界面活性剤等の有機物が含有されている。ところが、通常の洗浄では炭化水素系有機物と界面活性剤等の有機物を分離することが出来ず、再利用はできなかった。
【０１４６】
また、洗浄システムが非常に高価で洗浄時間がかかるため、洗浄物としては金型など非常に高価で繰り返し使用される部品が主たる応用であった。
【０１４７】
これらの問題を解消しようとするものが第２及び第３実施形態である。
【０１４８】
本発明の加圧流動体による洗浄方法は、加圧された流動体を被洗浄物に接触させることによって被洗浄物の表面に付着する不純物を除去する方法であり、被洗浄物に接触している加圧された流動体の相状態を変化させることなく、その流動体の密度を変化させることを特徴とする洗浄方法である。
【０１４９】
特に、被洗浄物の密度が流動体の液体密度以下であって、その流動体の圧力、温度の少なくとも一つの条件を変化することによって、流動体の密度を被洗浄物の密度に対して高低を繰り返すことによって洗浄の効果が得る。この際に、加圧された流動体が超臨界流体であるときに、効果が高くなる。
【０１５０】
また、本発明の加圧流動体による洗浄方法は、加圧された流動体を被洗浄物に接触させることによって被洗浄物の表面に付着する不純物を除去する洗浄方法であり、加圧された第１の流動体の中に浸漬してなる被洗浄物に対して、その第１の流動体に対して密度の異なる加圧された第２の流動体を接触させて洗浄する。その際に、第１の流動体の相状態を変化させることなく、第２の流動体を被洗浄物に接触してなることを特徴とする洗浄方法である。
【０１５１】
この際に、第２の流動体が超臨界流体であるときに好ましい効果が得られる。特に、被洗浄物の密度が第１の流動体の液体密度以下であって、その被洗浄物の密度よりも密度が低い第２の流動体を被洗浄物に接触してなることで洗浄効果が高くなる。また、第１の流動体と第２の流動体とが同一であって、第１の流動体が液体であり、第２の流動体が超臨界流体である場合に特に好ましい効果が得られる。
【０１５２】
本発明の加圧流体による洗浄方法では、用いる流動体が二酸化炭素、水、アンモニア、亜酸化炭素、アルコールの少なくとも１つを含むことによって好ましい効果が得られる。
【０１５３】
また、本発明を適用する被洗浄物の表面に付着する不純物が潤滑油である場合に効果が高くなる。さらに、本発明を適用する被洗浄物が凹部構造を有する部品である場合に効果が高くなる。
【０１５４】
まず、第２実施形態について説明する。
【０１５５】
図２９は、二酸化炭素や水等の流動体（流体）の状態図を示す。図２９において、横軸は温度を表し、縦軸は圧力を表している。温度が臨界温度Ｔｃ１０２で圧力が臨界圧力Ｐｃ１０３の点（Ｔｃ、Ｐｃ）が臨界点１０１である。温度が臨界温度Ｔｃ１０２以上で圧力が臨界圧力Ｐｃ１０３以上の範囲が超臨界状態１０４である。この超臨界状態１０４においては、流動体が気体１０５、液体１０６、固体１０７とは異なる相である。この超臨界状態は、気体、液体、固体などとは異なる性質を示し流体であることが知られている。例えば、超臨界状態の流体の密度は、気体と液体の中間の値を有し、温度と圧力の条件で調整することも可能である。また、超臨界状態は密度だけでなく、洗浄に関して、イオン積、誘電率、拡散なども制御できるため高い洗浄効果を得る方法として用いることができる。
【０１５６】
さらに、洗浄に関しては、液体状態は密度が非常の大きいため、洗浄には効果的な流動体であり、場合によっては液体状態を用いることもある。また、超臨界状態だけでなく比較的高温、高圧の領域で、圧力、温度条件が超臨界状態に近い液体状態を亜臨界領域状態と呼ぶことがあり、この加圧された液体状態も洗浄に用いることがある。
【０１５７】
ここで、例えば、流動体として二酸化炭素の臨界温度Ｔｃ１０２は約３１．１℃であり、二酸化炭素の臨界圧力Ｐｃ１０３は約７．３８ＭＰａである。水の場合は、臨界温度Ｔｃ１０２は約３７４．３℃であり、臨界圧力Ｐｃ１０３は約２２．１ＭＰａである。
【０１５８】
流動体としては、常温常圧で気体の物質が好ましく、二酸化炭素、水、アンモニア、亜酸化炭素等が用いられるが、その他に少し温度を上げると飛散するアルコールを用いても良い。中でも、二酸化炭素や水は人体側面においても無害であるため取り扱い性も良い。さらに二酸化炭素は臨界状態では有機物の分解、除去作用を有し、水は酸化物などのエッチング効果を有するため、それぞれの特徴を生かすことで凹部構造を有する部品の洗浄に有効である。
【０１５９】
本発明の第２実施形態にかかる洗浄方法については、凹部構造を有している部品に適用するのが好ましい。これらの部品は、特に凹部に加工油である潤滑油や不純物（切削くずなど）を付着させやすい。また、この凹部部分は入り組んだ構造であること、加工時に圧力が加わる部分であることから他の平坦な構造部分と比較すると加工油である潤滑油の付着性が高く、洗浄剤などが浸透し難いため洗浄むら、洗浄残りが発生しやすい。そこで、洗浄媒体として浸透性が高く、ある程度の粘性、溶解性を有している液体状態（亜臨界流体を含む）や超臨界状態の加圧された流動体を用いるのが効果が高い。
【０１６０】
次に、本発明の第２実施形態の加圧流体を用いた洗浄方法について説明する。
【０１６１】
本発明の第２実施形態である洗浄方法は、加圧された流動体を被洗浄物に接触させることによって被洗浄物の表面に付着する不純物を除去する方法であり、被洗浄物に接触している加圧された流動体の相状態を変化させることなく、その流動体の密度を変化させて洗浄するものである。特に、被洗浄物の密度が流動体の液体密度以下である場合に、その流動体の密度を制御することによって被洗浄物に加わる浮力を変える。それによって流動体の密度が被洗浄物の密度に対して高低を繰り返すのに伴って、流動体中で被洗浄物を上下に運動させ、攪拌効果を生じさせる方法である。この際に、加圧された流動体が超臨界状態の流体である場合には、密度を大きく変化させることができるので好ましい上に、密度変化に伴って誘電率等が変化して溶解性が変化する効果も有している。
【０１６２】
例えば、二酸化炭素では０．１ＭＰａ、３０℃での気体の密度が約１ｋｇ／ｍ^３であるのに対して、液体では３０℃〜１５℃で約６００〜１６００ｋｇ／ｍ^３、超臨界状態では温度、圧力条件で変わるが臨界圧力以上で約２００ｋｇ／ｍ^３から１０００ｋｇ／ｍ^３以上まで制御することができる。したがって、被洗浄物はこれらの密度範囲を有するものが好ましい。
【０１６３】
被洗浄物の密度は、密度が約２００ｋｇ／ｍ^３から約１５００ｋｇ／ｍ^３の範囲であるものが好ましく、超臨界状態の流動体を用いる場合には、被洗浄物の密度は約２００ｋｇ／ｍ^３から約１０００ｋｇ／ｍ^３の範囲が好適である。被洗浄物としては、樹脂の成型体や内部に中空構造を有する軽量材からなる部品などが適して用いることができる。被洗浄物としては、例えば、中空ガラスビーズをエポキシ樹脂等で固めた部品は超音波センサの音響整合部品として用いられるが、成型する際に切削加工などによって中空ガラスビーズが切断されたり抜けたりしてビーズサイズの凹部構造が加工表面に形成されている。凹部構造の大きさは、幅、深さが数μｍから数百μｍであり、その内部に加工時に割れたガラス片が入っていて、単なる浸漬洗浄では除去することが困難である。また、成型時、加工時の残留油成分も表面や内部に存在することがある。これらの汚れを洗浄するのに本発明の効果を発揮できる。なお、適用できるものとしては、これに限定されるものではない。
【０１６４】
図３０，図３２，図３３は、本発明の第２実施形態にかかる洗浄方法を行う洗浄装置の概略図である。特に、図３２と図３３は、流動体３８０の密度によって、被洗浄物２１４が軽くなったときに密着状態が解けて不純物３８１を除去しやすくなり、それを繰り返すことによって攪拌効果によって洗浄が行われることを示す図である。
【０１６５】
この装置は主な構成要素として、洗浄槽の一例は圧力容器２１０であり、不純物３８１を回収する分離容器２２０、流動体３８０を供給するボンベ（又はタンク）２０１と液体ポンプ２０２と、流動体３８０の温度調整器２０４と各容器を温度制御する温度制御装置２１１、２２１と、圧力制御バルブ２０３、２１３、２２３を制御する圧力制御装置２３０である。
【０１６６】
流動体３８０として二酸化炭素を用い、被洗浄物２１４として中空ガラスビーズのエポキシ樹脂硬化成型体（密度約５５０ｋｇ／ｍ^３）を用いて説明する。被洗浄物２１４を洗浄用治具２１２内に入れて圧力容器２１０内に設置し、温度調整器２０４、圧力制御バルブ２０３で温度、圧力条件を調整して流動体３８０を圧力容器２１０内に液体ポンプ２０２を用いて導入する。圧力容器２１０は、容器用の温度制御装置２１１と圧力制御装置２３０を用いて洗浄条件を制御する。二酸化炭素は、約４７℃、約１２ＭＰａの超臨界状態の流動体３８０として、圧力容器２１０に送られる。この条件での二酸化炭素の密度は約６００ｋｇ／ｍ^３であるために、被洗浄物２１４は、圧力容器２１０中では二酸化炭素の流動体に浮いている状態になっている。この初期状態から温度一定で圧力を制御すると、流動体３８０の密度は約１０ＭＰａで約５００ｋｇ／ｍ^３になり、被洗浄物２１４の密度よりも軽くなるために被洗浄物２１４は沈みはじめる。また、初期状態から圧力一定で温度を制御すると、流動体３８０の密度は約５５℃で約５００ｋｇ／ｍ^３になり、被洗浄物２１４の密度よりも軽くなるために被洗浄物２１４は沈みはじめる。圧力又は温度、あるいは両者を制御して流動体３８０の密度を高くしたり低くしたりすることで、被洗浄物２１４を流動体３８０中で上がったり下がったりさせることができ（図３３参照）、攪拌効果を高めることで洗浄効果を向上させることができる。これによって、超臨界状態の二酸化炭素に溶解しやすい潤滑油などの成分である不純物３８１は、被洗浄物２１４の凹部や狭部まで効果的に溶出除去することが容易になる。また、超臨界状態の二酸化炭素に溶解しにくいガラスや樹脂の切削粉などの成分である不純物３８１は被洗浄物２１４の凹部や狭部から押し出されて除去することが容易になる。
【０１６７】
なお、被洗浄物２１４の密度と流動体３８０の密度とが大略同一のときは、圧力制御装置２３０などの制御装置の動作制御の下に、攪拌羽根３８３を回転させて流動体３８０を攪拌させることにより、密度変化と同様に、被洗浄物２１４に加わえる浮力を変えるようにして、上記したような洗浄効果を奏するようにしてもよい。これは、上記した密度の高低ではなく、両者の密度を限りなく近くすることによって、他のメカニカルな作用で被洗浄物２１４同士の密着を容易に解く例である。この方法によって流動体の密度（圧力、温度）の高低を繰り返す必要が無くなるために、条件の制御は簡便になる。
【０１６８】
また、さらに外力による機械的な変動としては、メカニカルな攪拌だけでなく流動体のノズル噴射によっても実施することができるため、後述する図３１は、本発明の第３実施形態における洗浄装置に適用した例として図３６に流動体のノズル噴射とを組み合わせた例を示す。なお、図３６において、４００は部品毎に洗浄条件を換えるための部品（被洗浄物）情報データベースである。すなわち、情報データベース４００内の情報に基づき、被洗浄物２１４の密度と流動体３８０の密度とが大略同一のときは、ノズル噴射により、被洗浄物２１４同士の密着を容易に解くようにしている。この方法によって流動体の密度（圧力、温度）の高低を繰り返す必要が無くなるために、条件の制御は簡便になる。
【０１６９】
また、本方法では、初期状態で被洗浄物２１４と加圧された流動体３８０の密度をほぼ一致させておくことで、圧力、又は温度の条件をわずかに変化させることで、被洗浄物２１４を加圧された流動体中で上下させることができるため、洗浄効果を発揮させやすくなる。また、図３０では、圧力容器２１０全体の条件を制御する例を示しているが、被洗浄物２１４の近傍に加熱機構を設置して、被洗浄物２１４の近傍の温度を上げることでそこのみの密度を低下させて被洗浄物２１４を沈降させることも可能である。これらの条件は、被洗浄物２１４に付着している不純物の種類等によって使い分ければ良い。本方法の効果に加えて、圧力容器２１０の外部又は内部において攪拌効果を補助する機構を設けておけばさらに効果は高まる。これらの機構としては、回転羽根式の攪拌機構や超音波振動子による攪拌機構などを適宜用いることができる。
【０１７０】
被洗浄物２１４から除去した不純物を含む超臨界状態の二酸化炭素は、分離容器２２０へ送られ、圧力を制御して超臨界状態の二酸化炭素の圧力を低下させ、気体状態に戻す。この時、二酸化炭素に溶解している不純物は溶解度の低下に伴って分離するために洗浄残留物２２２として回収される。また、二酸化炭素に不溶の不純物３８１は沈降して洗浄残留物２２２として回収される。圧力容器２１０と別の容器で不純物３８１を回収することによって、部品への再付着を防ぐことができる。
【０１７１】
図３０において流動体は、気体状態から排気する形になっているが、この気体状態の二酸化炭素を冷却しながら液体ポンプに送り再度加圧して、再使用することもできる。そのため、連続的な洗浄装置を提供することができる。
【０１７２】
（第３実施形態）
次に、本発明の第３実施形態である洗浄方法について説明する。
【０１７３】
第３実施形態も加圧された流動体を被洗浄物に接触させることによって被洗浄物の表面に付着する不純物を除去する方法であり、被洗浄物に接触している加圧された流動体の相状態を変化させることなく洗浄効果を高める方法である。本方法では、第１の流動体の相状態を変化させることなく、第２の流動体を被洗浄物に接触させることによって特に優れた効果が得られる。加圧された第１の流動体の中に浸漬してなる被洗浄物に対して、その第１の流動体に対して密度の異なる加圧された第２の流動体を接触させることによって、被洗浄部に噴射や泡沫等による攪拌効果を向上させる。
【０１７４】
さらに、第２の流動体が超臨界状態の流体である場合には、凹部や狭部を有する部品などの被洗浄物に対しては、超臨界流体の拡散性の高さによって洗浄しにくい部品の奥まで効果的に不純物を除去できる。この際に、加圧された流動体が超臨界状態の流体である場合には、密度を大きく変化させることができるので好ましい上に、密度変化に伴って誘電率等が変化して溶解性が変化する効果も有している。
【０１７５】
また、第１の流動体と第２の流動体とが同一であって、第１の流動体が液体であり、第２の流動体が超臨界流体である場合に特に好ましい効果が得られる。２つの流動体が異なる場合には両者の溶解性の相違を用いて洗浄効果を高めることができるが、二つの流動体が同じ場合には洗浄後の流動体の再利用をするのに流動体を分離する必要が無く効率的な洗浄が可能になるという利点がある。また、被洗浄物の密度が第１の流動体よりも低く第２の流動体よりも高い場合には、第２実施形態と同様に、第２の流動体が被洗浄物に接触させて浮力を制御することによる攪拌効果を与えることができ、洗浄効果が向上できる。
【０１７６】
図３１は、本発明の第３実施形態の洗浄方法を行う洗浄装置の概略図である。この装置は主な構成要素として、洗浄槽は圧力容器３１０であり、不純物を回収する分離容器３２０、第１の流動体を供給するボンベ（又はタンク）３０１と液体ポンプ３０２と、第１の流動体の温度調整器３０４と各容器を温度制御する温度制御装置３１１、３２１と、圧力制御バルブ３０３、３１３、３２３を制御する圧力制御装置３３０である。これに、第２の流動体を供給するボンベ（又はタンク）３４１を液体ポンプ３４２と、第２の流動体の温度調整器３４４と圧力制御バルブ３４３を制御する圧力制御装置３３０を用いて被洗浄物３１４近傍に第２の流動体を接触させる。
【０１７７】
流動体として二酸化炭素を用い、被洗浄物３１４としてハット型のＳＵＳ（ステンレススチール）ケースに代表される凹部を有するプレス成型加工された部品又は切削加工法によって形成された部品を用いて説明する。被洗浄物３１４を洗浄用治具３１２内に入れて圧力容器３１０内に設置し、温度調整器３０４、圧力制御バルブ３０３で温度、圧力条件を調整した流動体を圧力容器３１０内に液体ポンプ３０２を用いて導入する。圧力容器３１０は、容器用の温度制御装置３１１と圧力制御装置３３０を用いて洗浄条件を制御する。二酸化炭素は、液体状態で圧力容器３１０に送り被洗浄物３１４を浸漬して洗浄に用いる。さらに、圧力容器３１０中の凹部構造を有する被洗浄物３１４に対して、第２の流動体を供給するボンベ（又はタンク）３４１を液体ポンプ３４２と、第２の流動体の温度調整器３４４と圧力制御バルブ３４３を制御する圧力制御装置３３０を用いて被洗浄物３１４近傍に噴出し部３４５を通して第２の流動体としての超臨界状態の二酸化炭素を接触させる。
【０１７８】
凹部構造を有する被洗浄物３１４は圧力容器３１０中に配置しており、第１の流動体中で洗浄されながら、第２の流動体によって洗浄効果を促進することになる。第２の流動体の噴出し部３４５が、被洗浄物３１４の開口部に向けて設置している場合は洗浄しにくい奥まで洗浄を行いやすくできる。効果としては、密度の異なる流体の接触による拡散等による攪拌効果とそれに伴う不純物のはく離除去効果、溶解度の異なる流体による様様な溶解度を有する不純物に対する溶解除去効果、両流動体に圧力差がある場合には圧力の均等化への衝撃による振動効果などが働き、洗浄効果が加速されるものと考えられる。これによって、流動体に溶解しやすい潤滑油などの成分は、被洗浄物の凹部や狭部まで効果的に溶出除去することが容易になる。また、流動体に溶解しにくいガラスや樹脂の切削粉などの成分は被洗浄物の凹部や狭部からはく離や押し出されて除去することが容易になる。このときに第２の流動体を接触させるタイミングは連続でも間欠でもよく、一定速度でも、速度変調を行ってもよく、被洗浄物等に応じて設定すればよい。
【０１７９】
また、被洗浄物３１４の密度が第１の流動体の液体状態での密度よりも低い場合には、密度の異なる第２の流動体を接触させることによって、第２実施形態と同じ被洗浄物の上下運動による攪拌効果等が得られ、洗浄効果が向上される。
【０１８０】
また、被洗浄物３１４から除去した不純物を含む第１の流動体と第２の流動体が混合した流動体は、分離容器３２０へ送られ、圧力又は温度を制御して混合流動体を分離して回収すると共に、洗浄残留物３２２を分離回収する。分離した各流動体はそれぞれ加圧して循環利用することができる。また、第１と第２の流動体が同一であれば、洗浄装置及び洗浄操作は簡略化できる。
【０１８１】
本発明の第２及び第３実施形態にかかる洗浄方法及び洗浄装置で洗浄効果が期待できる部品は主にエレクトロニクス関連に用いられる電子部品及びその関連部品である。特に、プレス成形加工及び切削加工による精密加工部品である。これらの部品は、加工精度を向上させるためには必ず加工油である潤滑油が必要不可欠である。しかし、この加工油の残留が次工程の処理、例えばメッキ処理や接着などの性能特性に影響を与え、デバイス及び製品としての性能や信頼性の低下を引き起こす。そのため、高レベルの残留物除去、すなわち精密洗浄を必要とする部品に効果を発揮する。応用商品としては、超音波センサの整合層や電池の電極（特に二次電池など）。その他としては電池用ケース、ＨＤＤ用ケース（筐体ともいう）、電解コンデンサ用のケースなどがある。超音波センサ用の整合層などは無機系のガラスバルーンと有機系のエポキシを混合したもの、無機系のガラスバルーンだけのもの、有機系のエポキシだけのものなど様々な素材が用いられる。また、超音波センサ用ケースなどは素材がステンレス、アルミニウム、エポキシ樹脂である。加工はプレス成型加工による深絞りや樹脂成形、切削加工で加工される。電池用ケースについては一般にアルミニウム又は最近ではアルミニウムにメッキを施した多層鋼材が用いられプレレス成型加工で作製される。ＨＤＤ用ケースとしては素材としてアルミニウムが使用され、最近では特にアルミニウムに有機物系のコートをした複合鋼材が用いられプレス成型加工される。電解コンデンサ用ケースも同様に素材はアルミニウム単体のものやアルミニウム素材の上に有機膜のコートを施した複合鋼板を用いてプレス成形加工される。このように、素材の異なる有機物と無機物が積層された複合材料に対しても工程や使用洗浄媒体であるガス種を選択することで応用可能である。なお、これらの製品分野に限らず、プレス成型加工及び切削加工に加工された凹部構造を有する部品にも効果を有することは論じるまでもない。
【０１８２】
以下具体的な実施例により、この発明の第２及び第３実施形態の効果の説明を行う。
【０１８３】
（実施例８）
中空ガラスビーズ（約３０μｍ）をエポキシ樹脂で含浸して加熱硬化した成型体を所定の部品形状に切削加工した後に洗浄を行った。部品形状は直径φ１０．８ｍｍ×高さ１．１５ｍｍであり、密度は約５５０ｋｇ／ｍ^３であった。この部品は、加工面で中空ガラスビーズが切断されたり、抜けたりしてビーズサイズの凹部構造が多数存在している。
【０１８４】
なお、洗浄の効果は、外観検査と、表面付着した非溶解性のパーティクル量を測定して評価した。外観検査については目視で欠け、割れ等が無いかを確認し、パーティクルについては洗浄後に実体光学顕微鏡及び走査型電子顕微鏡によって部品表面及び凹部内部の不純物の存在を観察した。
【０１８５】
洗浄は、上記の部品１００個ずつをカゴ状の洗浄用治具に入れて、流動体として二酸化炭素を用いて行った。以下の洗浄方法について比較した。
【０１８６】
（１）洗浄なし（２）超臨界状態の二酸化炭素（約５７℃、１３ＭＰａ、密度約５５０ｋｇ／ｍ^３）中に浸漬後、１０分間隔で１２ＭＰａと１４ＭＰａの間の昇降圧を繰返して３時間洗浄（３）超臨界状態の二酸化炭素（約４７℃、１２ＭＰａ、密度約６００ｋｇ／ｍ^３）中に３時間浸漬洗浄（４）液体状態の二酸化炭素（約２０℃、密度約７５０ｋｇ／ｍ^３）に１時間浸漬後、上記（２）の条件で洗浄（５）超臨界状態の二酸化炭素（約４７℃、１２ＭＰａ、密度約６００ｋｇ／ｍ^３）中に１時間浸漬後、温度一定で急激に圧力開放をして容器内を気体状態にすることを３回繰返して洗浄した結果を表８に示す。
【０１８７】
【表８】

【０１８８】
この部品の場合には、洗浄を行っても、（３）、（４）のように単に部品を加圧した二酸化炭素に浸漬しておくだけでは、不純物、特に二酸化炭素に不溶性のものについては洗浄効果が低いことがわかった。これは、部品が流体に浮いてしまっており、部品同士が重なってしまい、その重なりの部分が離れずに洗浄されないためである。また、流体に接触しておくだけでは、部品の微小な凹部の奥まで不純物除去が難しいことがわかった。また、（５）のように、流体の急激な相変化を生じさせることは、その衝撃で不純物の除去は促進されるが、密度の低い本部品では、部品同士の衝突による欠けや割れが見られるものがあった。
【０１８９】
これらに対して、本発明の洗浄方法である（２）では、凹部まで良好に洗浄が行われていることがわかった。この効果は、圧力容器の内部を観察した結果、加圧された二酸化炭素の密度が変化することによって部品が上下して接触面が離れるとともに、それに伴う攪拌効果が作用するために生じるものであることがわかった。
【０１９０】
（実施例９）
プレス成型加工及び切削加工されたケースの洗浄を行った。材質はＳＵＳ３０４、大きさはφ１２ｍｍ、高さ５ｍｍの凹部構造を有するケースである。
【０１９１】
なお、洗浄の効果は、ケースは１００個ずつ洗浄し分析を行い、外観検査と、残留油分検査と、表面付着した非溶解性のパーティクル量を測定して評価した。外観検査については目視で欠け、割れ等が無いかを確認した。残留油分分析は溶剤（四塩化炭素）で油分抽出したのちその抽出油分をＦＴ−ＩＲ（フーリエ変換赤外分光法）で測定した。また、パーティクルについては洗浄後パーティクル検査機（Ｔｏｐｃｏｎ製ウェーハ表面検査装置ＷＭ−１７００／１５００）を用いて測定した。
【０１９２】
洗浄は、上記の部品１００個ずつをカゴ状の洗浄用治具に入れて、１つの流動体だけを用いる場合には二酸化炭素を用いた。また、２つの流動体を用いる場合には、第１の流動体として液体状態の二酸化炭素、第２の流動体として超臨界状態の二酸化炭素を用いて行った。以下の洗浄方法について比較した。
【０１９３】
（１）液体状態の二酸化炭素（約２０℃）に浸漬した状態で、超臨界状態の二酸化炭素（約４７℃、１２ＭＰａ）を噴出して部品にあてながら、３時間洗浄（２）超臨界状態の二酸化炭素（約４７℃、１２ＭＰａ）中に３時間浸漬洗浄（３）液体状態の二酸化炭素（約２０℃）に１時間浸漬後、上記（２）の条件で洗浄（４）超臨界状態の二酸化炭素（約４７℃、１２ＭＰａ）中に１時間浸漬後、温度一定で急激に圧力開放をして容器内を気体状態にすることを３回繰返して洗浄した結果を表９に示す。
【０１９４】
【表９】

【０１９５】
いずれの方法も外観は油分の付着による変色は見られず、加圧した二酸化炭素を用いることで残留油分量は少なくすることができていた。しかし、二酸化炭素に不溶性のパーティクルについては浸漬のみの洗浄では、効果が小さいことがわかった。特に、凹部構造の内部に存在していることが観察された。これらに対して、本発明の洗浄方法である（１）では不純物の除去に対して良好に洗浄が行われていることがわかった。
【０１９６】
【発明の効果】
本発明によれば、凹部構造を有する部品に対して加圧された流動体の密度を制御して接触させることによって、加圧された流動体の溶媒効果による流動体に溶解する潤滑油などの不純物を効率的に除去することができる。さらに、部品に接触させる流動体の密度を制御して攪拌効果を持たせることによって、流動体に不溶の不純物を効率的に除去することができる。したがって、本発明では洗浄処理において、その部品に適した洗浄条件の最適化によって、加圧された流動体の溶媒効果に加えて、攪拌効果を同時に与えることでき、効率的な部品の洗浄を行わせることができため、工業的に価値の大なるものである。
【０１９７】
また、上記した密着を解くための技術を応用することにより、表面改質するために被処理物と被処理物の接している密着を解くことによって、被処理物の表面を均質に、水酸基などの形成による親水化、表面処理剤などによる撥水化、撥油化、表面への他材料のコートすることなどに応用することも可能である。なお、表面改質については、第２流動体を噴射するケースでは、この流動体に処理剤を添加しておくことで、効率的に表面改質が可能になるという効果を得ることもできる。また、抽出するために被処理物と被処理物の接している密着を解くことによって、被処理物の内部からの成分抽出を効率的に行うことが可能になり、潤滑油などの油脂抽出、植物等からのエキス抽出、香料抽出などにも適用することができる。
【０１９８】
上記表面改質では、洗浄処理物であるケースと不純物である潤滑油とＣＯ_２とを加圧することで、流動体であるＣＯ_２の特性が潤滑油など油脂分と親和性になる（溶解度が高くなる）ことを利用している。
【０１９９】
上記抽出では、ミクロ的には分子同士の密着を解き、マクロ的には溶解させるように、ＣＯ_２の温度と圧力を変化させることで、抽出する対象物のＣＯ_２への溶解度を変える（言い換えれば、溶媒であるＣＯ_２の密度を変える）ことを利用して、溶媒中に抽出する対象物を溶かしたのち、温度と圧力を下げて、抽出する対象物を析出させて抽出している。
【０２００】
なお、上記様々な実施形態のうちの任意の実施形態を適宜組み合わせることにより、それぞれの有する効果を奏するようにすることができる。
【０２０１】
本発明は、添付図面を参照しながら好ましい実施形態に関連して充分に記載されているが、この技術の熟練した人々にとっては種々の変形や修正は明白である。そのような変形や修正は、添付した請求の範囲による本発明の範囲から外れない限りにおいて、その中に含まれると理解されるべきである。
【図面の簡単な説明】
【図１】本発明の第１実施形態における洗浄媒体の状態図である。
【図２】（Ａ），（Ｂ），（Ｃ），（Ｄ）は、本発明の第１実施形態における凹部構造を有する部品の例を示す断面図及び斜視図である。
【図３】本発明の第１実施形態のおける洗浄システムを示す説明図である。
【図４】（Ａ），（Ｂ）は、本発明の第１実施形態における洗浄工程を示すグラフである。
【図５】本発明の第１実施形態のおける洗浄状態を示す断面図である。
【図６】本発明の第１実施形態の実施例１における洗浄対象物を示す説明図である。
【図７】本発明の第１実施形態の実施例３における洗浄対象物を示す斜視図である。
【図８】本発明の第１実施形態の実施例３における接触角を説明する説明図である。
【図９】水の物性の温度依存性を示す説明図である。
【図１０】（Ａ），（Ｂ）は、マクロ的に汚れが残りやすい部分を矢印で示す説明図とミクロ的に汚れが残りやすい部分を矢印で示す説明図である。
【図１１】マクロ的に汚れが残りやすい部分を矢印で示す説明図である。
【図１２】本発明の第１実施形態の洗浄方法における洗浄対象物の他の例である超音波センサーケースの概略断面図である。
【図１３】本発明の第１実施形態の洗浄方法における圧力制御時のタイムチャートである。
【図１４】本発明の第１実施形態の洗浄方法における温度制御時のタイムチャートである。
【図１５】本発明の第１実施形態の変形例にかかる洗浄装置において２層式のチャンバーを用いて圧力を高めるときの説明図である。
【図１６】本発明の第１実施形態の変形例にかかる洗浄装置において２層式のチャンバーを用いて圧力を下げるときに２層に分けている扉を開いた状態の説明図である。
【図１７】本発明の第１実施形態の変形例にかかる洗浄装置において液体状態で熱媒体を供給する状態の説明図である。
【図１８】本発明の第１実施形態の変形例にかかる洗浄装置において気体状態で熱媒体を供給する状態の説明図である。
【図１９】本発明の第１実施形態の洗浄装置の制御装置と温度制御用リレーと圧力制御用リレーとの関係を示す説明図である。
【図２０】本発明の第１実施形態の変形例にかかる洗浄装置において洗浄効率を高めるために掻き回し用のプロペラを回転させる状態の説明図である。
【図２１】本発明の第１実施形態の変形例にかかる洗浄装置において洗浄効率を高めるために掻き回し用のプロペラを回転させる状態の説明図である。
【図２２】本発明の第１実施形態の変形例にかかる洗浄装置において洗浄効率を高めるために掻き回し用のプロペラを回転させる状態の説明図である。
【図２３】本発明の第１実施形態の変形例にかかる洗浄装置において洗浄効率を高めるために掻き回し用のプロペラを回転させるとともにノズルからも洗浄媒体を供給する状態の説明図である。
【図２４】本発明の第１実施形態の変形例にかかる洗浄装置において洗浄効率を高めるためにノズルから洗浄媒体を供給する状態の説明図である。
【図２５】本発明の第１実施形態の変形例にかかる洗浄装置において洗浄効率を高めるために掻き回し用のプロペラを回転させるとともに超音波センサーから超音波を供給する状態の説明図である。
【図２６】本発明の第１実施形態の変形例にかかる洗浄装置において洗浄効率を高めるために超音波センサーから超音波を供給する状態の説明図である。
【図２７】（Ａ），（Ｂ），（Ｃ）は、本発明の第１実施形態の変形例にかかる洗浄装置での様々なノズル形状を示す概略断面図である。
【図２８】本発明の第１実施形態の変形例にかかる洗浄装置において洗浄効率を高めるために複数のノズルから洗浄媒体を順に供給して対流を生じさせる状態の説明図である。
【図２９】二酸化炭素や水等の流動体（流体）の状態図である。
【図３０】本発明の第１実施形態における洗浄装置の概略図である。
【図３１】本発明の第２実施形態における洗浄装置の概略図である。
【図３２】被洗浄物の密度が流動体の密度よりも大きい場合の被洗浄物と流動体との関係を示す概略説明図である。
【図３３】被洗浄物の密度が流動体の密度よりも小さい場合の被洗浄物と流動体との関係を示す概略説明図である。
【図３４】被洗浄物の密度と流動体の密度とが大略等しくかつプロペラを回転させない場合の被洗浄物と流動体との関係を示す概略説明図である。
【図３５】被洗浄物の密度と流動体の密度とが大略等しくかつプロペラを回転させる場合の被洗浄物と流動体との関係を示す概略説明図である。
【図３６】図３０の洗浄装置に情報データベースを設けた場合の概略図である。
【符号の説明】
１　洗浄槽（高圧容器）
１ａ　導入口
１ｂ　排出口
２　液化供給槽
３　洗浄媒体供給部（液体ポンプ）
４　ヒータコントローラー
５　ヒータ
６　廃液回収層
７　気化器
８　回収部
２６　付着物
２７，２８，２９，３０，３２　部品
３１　洗浄対象物
１０１　臨界点
１０２　臨界温度Ｔｃ
１０３　臨界圧力Ｐｃ
１０４　超臨界状態
２０１　流動体の供給ボンベ（またはタンク）
２０２　液体ポンプ
２０３　圧力制御バルブ
２０４　温度調整器
２１０　圧力容器
２１１　温度制御装置
２１２　洗浄用治具
２１３　圧力調整バルブ
２１４　被洗浄物（部品）
２２０　分離容器
２２１　温度制御装置
２２２　洗浄残留物
２２３　圧力調整バルブ
２３０　圧力制御装置
３０１　第１の流動体の供給ボンベ（またはタンク）
３０２　液体ポンプ
３０３　圧力制御バルブ
３０４　温度調整器
３１０　圧力容器
３１１　温度制御装置
３１２　洗浄用治具
３１３　圧力調整バルブ
３１４　被洗浄物（部品）
３２０　分離容器
３２１　温度制御装置
３２２　洗浄残留物
３２３　圧力調整バルブ
３３０　圧力制御装置
３４１　第２の流動体の供給ボンベ（またはタンク）
３４２　液体ポンプ
３４３　圧力制御バルブ
３４４　温度調整器
３８０　流動体
３８１　不純物
１０００　制御手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for cleaning an object to be cleaned (for example, a part having a concave structure) such as a precision machined part used in connection with an electronic component, using a pressurized fluid.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, three steps of “cleaning”, “rinsing”, and “drying” are indispensable after processing a component created by machining and pressing, particularly a precision component used for an electronic component. In particular, in the case of precision parts requiring a high cleaning effect, a cleaning agent having a high cleaning ability is of course required, but the final drying step is extremely important. From such a background, in the final step of the precision cleaning field, lubricating oil as a processing oil has been removed by using steam cleaning of Freon 113, 1,1,1-trichloroethane. However, Freon 113 and 1,1,1-trichloroethane cause ozone layer depletion in the environment. In addition, 1,1,1-trichloroethane has a significant effect on the central nervous system of the human body, and further increasing the concentration causes unconsciousness and respiratory arrest. For the above reasons, the regulation on CFCs began in Japan in July 1989, and production was completely abolished in 1995.
[0003]
With the elimination of CFCs 113, 1, 1, 1-trichloroethane, liquid detergents as alternatives to ozone-depleting substances have recently been studied. For non-aqueous solvents, bromine solvents (1-bromopropane and propylpromide), hydrocarbon solvents (normal paraffin, isoparaffin, naphthene, and aromatic), iodine solvents (perfluoro-n-propyl iodide, Fluoro-n-butyl iodide, perfluoro-n-hexyl iodide), chlorinated solvents (aliphatic trichloroethylene, tetrachloroethylene, methylene chloride, trans-1,2-dichloroethylene and aromatic monochlorotoluene, benzotrifluoride) , Para-chlorobenzotrifluoride (PCBTF), 3,4-dichlorobenzotrifluoride (3,4-DCBTF), fluorinated solvents (HCFC-255ca, HCFC-141b, HCFC-123, HCFC-123, HFC-based HFC − 310mee, HFC-356mcf, HFC-338pcc, HFE-based HFE-7100, HFE-7200, cyclic HFC-based OFCPA), siloxane-based solvent (volatile methylsiloxane-based (VMS), dodecamethylcyclohexasiloxane, hexamethyldi- Siloxane, decamethyltetrasiloxane), ketone solvents (methyl ethyl ketone (MEK)), and alcohol solvents (ethanol, isopropanol (IPA), and pentafluoropropanol (5FP)) are used.
[0004]
Examples of the semi-water system include hydrocarbons (normal paraffin, isoparaffin, naphthene, and aromatic), glycol ethers (ethylene glycol ether, isoprene glycol ether), and N-methyl-2-virolidone (NMP). ), Terbenzenes (d-limonene), and siloxanes (volatile methylsiloxanes: VMS, dodecamethylcyclohexane, hexamethyldisiloxane, decamethyltetrasiloxane).
[0005]
Water-free (deoxygenated water, deionized water, ultrapure water), those with improved detergency by additives (alkaline, acidic, ionic surfactants, nonionic surfactants, higher alcohols) Surfactant, ozone-added ultrapure water) and the like.
[0006]
As described above, a number of CFC substitute liquid detergents have been manufactured, and a cleaning method using them has been used for precision parts.
[0007]
As shown in Patent Document 1 (JP-A-9-263994), in a battery case, instead of an organic solvent, annealing is performed at a very high temperature of 700 to 900 ° C. to burn off a lubricating oil as a processing oil. We use cleaning that is harmful. However, in the aluminum plate for film lamination used for aluminum electrolytic capacitors, dirt such as rolling oil and metal powder adhering to the surface of the rolled plate is seized during annealing, which causes defects such as poor appearance and poor adhesion. Therefore, in Patent Document 2 (Japanese Patent Application Laid-Open No. 6-272015), in the annealing of the softening treatment, the surface of the aluminum plate is washed with a mineral acid or an organic acid or a mixed acid thereof before the annealing, and then the annealing treatment is performed.
[0008]
Recently, the following method has been disclosed for cleaning a battery case. In Patent Literature 3 (International Publication No. WO97 / 42668), Patent Literature 4 (International Publication No. WO97 / 42667), Patent Literature 5 (International Publication No. WO98 / 10475) and the like, a steel sheet is formed using an organic solvent or an alkaline degreasing agent. Degreased, acid-washed, heat-treated after plating, heated to the melting point of the petroleum wax-based lubricant to be applied, and the surface-treated steel sheet coated with the molten lubricant on its surface is deep drawn, DI (Drawn & Ironed) It is used for processing, DS (Dry Sanding) processing, and DTR (Drawing & Thin Redrawing). Most of this lubricating oil can be volatilized and removed by heating at a temperature of 200 to 350 ° C. after processing and molding, so that cleaning after processing can be simplified.
[0009]
Further, in Patent Document 6 (Patent No. 3234541), an organic resin film containing a lubricant is formed on one or both sides of an aluminum alloy material such as an HDD (hard disk drive) housing, an electrolytic capacitor, and a precision electronic component. A method is disclosed in which a molding lubricant is improved, a volatile lubricant is applied to the surface thereof, and the lubricant is heated and volatilized and removed after processing.
[0010]
As another cleaning method, as described in Patent Document 7 (Japanese Patent Application Laid-Open No. 2000-225382), when a metal part or a mold is cleaned with water in a supercritical or subcritical state, an organic or a metal acting as a cleaning component is used. It has been proposed to clean and remove dirt by coexisting with an inorganic reducing agent without changing the state of the mold surface or being damaged by a contact object. Further, Patent Document 8 (Japanese Unexamined Patent Application Publication No. 59-502137) proposes a cleaning method for removing organic substances using a supercritical gas. Further, Patent Document 9 (Japanese Patent No. 2832190) discloses a method of improving a cleaning effect by rapidly changing a state of a fluid in a supercritical or subcritical state.
[0011]
[Patent Document 1]
JP-A-9-263994
[Patent Document 2]
JP-A-6-272015
[Patent Document 3]
WO 97/42668 pamphlet
[Patent Document 4]
WO 97/42667 pamphlet
[Patent Document 5]
WO98 / 10475 pamphlet
[Patent Document 6]
Patent No. 3234541
[Patent Document 7]
JP 2000-225382 A
[Patent Document 8]
JP-T-59-502137
[Patent Document 9]
Japanese Patent No. 2832190
[0012]
[Problems to be solved by the invention]
As described above, the lubricating oil for improving the moldability is indispensable in the molding process, and it is not an exaggeration to say that the development of the lubricating oil is the key to the development of the more advanced molding process. However, when the processed precision parts are used as a product, the lubricating oil used in the molding process, if not completely removed, causes a product defect such as deterioration of product performance or contamination. Therefore, in the molding process, it is essential to develop a cleaning method for completely removing the lubricating oil as well as applying the lubricating oil.
[0013]
Regarding the cleaning method using a solvent, particularly for degreasing, a solvent that does not affect the ozone layer destruction, such as an alternative fluorocarbon agent, is used in consideration of the environment, but the effect on the human body is not well understood. For example, 2-bromopropane is an existing substance that has been used as an intermediate for pharmaceuticals, agricultural chemicals, and photosensitizers, as an alkylating agent, and the like. In addition, the time and cost required for cleaning become very problematic. The type of product used for the molded part determines the cleaning level after processing. Therefore, it is desirable to use a solvent having a high detergency, but a solvent having a high detergency has a very high risk of giving a human body surface as described above. Therefore, a solvent having a low risk has a low detergency, so that the time and process (the number of times of cleaning) must be increased.
[0014]
For example, those that are plated after processing, such as battery cases and aluminum electrolytic capacitors, require precise cleaning.To perform degreasing, impurity removal, and activation, it takes a long time to perform the cleaning process. It costs. It is important to prevent degassing during use of a housing or the like used in an HDD, and degreasing treatment is regarded as important. In the case of solvent cleaning, handling is very complicated in terms of management such as solvent management (the Fire Service Law), treatment of the human body (Labor Safety and Sanitation Law), and waste liquid collection processing. The efficiency was reduced.
[0015]
Therefore, as a method of simplifying the cleaning method using a solvent as much as possible or eliminating the need for solvent cleaning, a method of evaporating the volatile lubricating oil by annealing after processing with a combination of an organic resin film and a volatile lubricating oil is used. It is being used. However, this method also does not completely evaporate the lubricating oil. At the micro level, oil or impurities slightly remain on the processed surface. In particular, in the case of deep drawn parts that have been press-formed, parts having a complicated structure such as a concave part, even if annealed to evaporate the lubricating oil, cannot completely evaporate due to the structure. In many cases, impurities are imprinted on the grain boundaries of stainless steel etc. and impurities remain.If annealing is performed in the presence of even a small amount of residue such as oil or impurities, the oil etc. may be carbonized or impurities may seize. In addition, the performance of products applied due to defects due to stains and unevenness and degassing was reduced. Moreover, even in the case of surface-treated steel sheets that are used to simplify cleaning after processing or to prevent deterioration in product performance without using precision cleaning, conventional organic solvents or alkaline degreasing agents are used during the production of surface-treated steel sheets. Since it is degreased, acid-washed, and plated, and then heat-treated, the effect on the environment and human body is hardly improved by the difference between washing before processing or washing after processing. .
[0016]
As another cleaning method in consideration of environmental aspects, a cleaning method of cleaning with supercritical or subcritical carbon dioxide or water has been proposed. In this method, carbon dioxide or water in supercritical or subcritical state is made to coexist with an organic or inorganic reducing agent acting as a cleaning component, so that cleaning can be performed without causing a change in the surface state of the mold and damage due to a contact object. It is only applied to precision molds such as plastic molded lens prisms and parts around the molds that are considered important. In these methods, the recycling of the removed material is not considered. Furthermore, in cleaning using a fluid in a supercritical or subcritical state, various devices have been devised to enhance the cleaning effect. For example, a method for rapidly changing a fluid in a supercritical or subcritical state is disclosed. However, a sudden change in the state of these fluids exerts a physical impact on the object to be cleaned, so that parts may be distorted or chipped if severe. In particular, low-density parts and parts having a thin plate having a concave portion with a complicated structure are easily affected by the influence.
[0017]
On the other hand, many lubricating oils are used for components processed by press molding, especially for electronic components, in order to improve accuracy. For this reason, the cleaning liquid for the processed parts contains a large amount of hydrocarbon-based organic substances, which are the main components of the lubricating oil. Further, the lubricating oil contains an organic substance such as a surfactant in addition to the hydrocarbon-based organic substance for the purpose of improving processing accuracy. However, normal washing cannot separate hydrocarbon-based organic substances and organic substances such as surfactants, and thus cannot be reused.
[0018]
In addition, since the cleaning system is very expensive and requires a long cleaning time, parts that are very expensive and are used repeatedly, such as molds, are mainly used as cleaning objects.
[0019]
Therefore, an object of the present invention is to solve the above-mentioned problems, and a cleaning method using a pressurized fluid that can improve a cleaning effect by cleaning an object to be cleaned using a pressurized fluid. Is to provide.
[0020]
[Means to solve the problem]
The cleaning method using a pressurized fluid according to the present invention is a cleaning method for removing impurities adhering to the surface of the object to be cleaned by bringing the pressurized fluid into contact with the object to be cleaned. Is less than or equal to the liquid density of the fluid, the pressure of the fluid, by changing at least one condition of the temperature, the density of the fluid is repeatedly high and low with respect to the density of the object to be washed, This is a cleaning method using a pressurized fluid in which the fluid is brought into contact with an object to be cleaned.
[0021]
The cleaning method using a pressurized fluid according to the present invention is a cleaning method for removing impurities attached to the surface of the object to be cleaned by bringing the pressurized fluid into contact with the object to be cleaned. Is less than the liquid density of the fluid, and by changing at least one condition of the pressure and temperature of the fluid, the density of the object to be cleaned is substantially equal to the liquid density of the fluid. A cleaning method using a pressurized fluid in which the fluid is subjected to fluctuation by an external force to bring the fluid into contact with the object to be cleaned.
[0022]
At this time, the effect is enhanced when the pressurized fluid is a supercritical fluid.
[0023]
Further, the cleaning method using the pressurized fluid of the present invention is a cleaning method for removing impurities attached to the surface of the object to be cleaned by bringing the pressurized fluid into contact with the object to be cleaned. The object to be cleaned immersed in the first fluid is washed by bringing the first fluid into contact with a pressurized second fluid having a different density. At this time, a cleaning method is characterized in that the second fluid is brought into contact with the object to be cleaned without changing the phase state of the first fluid.
[0024]
At this time, a favorable effect is obtained when the second fluid is a supercritical fluid. In particular, the cleaning effect is obtained by contacting the second fluid having a density lower than the liquid density of the first fluid with the density of the first fluid and having a lower density than the density of the fluid to be cleaned. Will be higher. In addition, a particularly preferable effect is obtained when the first fluid and the second fluid are the same, the first fluid is a liquid, and the second fluid is a supercritical fluid.
[0025]
In the cleaning method using a pressurized fluid of the present invention, a preferable effect is obtained when the fluid used contains at least one of carbon dioxide, water, ammonia, carbon suboxide, and alcohol.
[0026]
Further, the effect is enhanced when the impurities adhering to the surface of the object to be cleaned to which the present invention is applied are lubricating oils. Further, the effect is enhanced when the object to be cleaned to which the present invention is applied is a part having a concave structure.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Before continuing the description of the present invention, the same parts are denoted by the same reference numerals in the accompanying drawings.
[0028]
Hereinafter, before describing embodiments of the present invention with reference to the drawings, an outline of the present invention will be described.
[0029]
The first invention of the present invention is a cleaning method for removing at least deposits adhering to the surface of the concave structure of a component having a concave structure, wherein a cleaning medium is uniformly spread over the surface of the concave structure using a supercritical gas or a liquefied gas. Is a cleaning method for performing cleaning as described above.
[0030]
The second invention of the present invention is the cleaning method according to the first invention, wherein the cleaning is performed such that the cleaning medium is evenly distributed over the entire surface of the component having the concave structure.
[0031]
According to a third aspect of the present invention, there is provided a cleaning method for removing at least a substance adhering to at least the surface of the concave structure of a part having a concave structure, wherein the part having the substance adhered is stored in a cleaning tank, and the part is cleaned in the cleaning tank. A medium is introduced, the parts are present in the cleaning medium atmosphere, and the temperature and pressure of the cleaning medium are changed to alternately change the cleaning medium between a liquid state and a gas state, thereby forming the concave structure. This is a cleaning method in which the cleaning medium is evenly distributed over the surface to perform cleaning.
[0032]
With this configuration, the cleaning efficiency is improved by controlling physical properties such as density and viscosity in a liquid state, and utilizing physical energy contributing to a change in the state of a liquid, gas, or supercritical state.
[0033]
According to a fourth aspect of the present invention, in the third aspect, after the cleaning medium is alternately changed between a liquid state and a gas state, the cleaning medium is changed to a supercritical state to clean the concave structure surface. This is the cleaning method to be performed.
[0034]
According to a fifth aspect of the present invention, in the third aspect, after the cleaning medium is alternately changed between a liquid state and a gas state, the cleaning medium is changed to a sub-supercritical state to change the surface of the concave structure. This is a cleaning method for performing cleaning.
[0035]
A sixth invention of the present invention is the cleaning method according to the third or fourth invention, wherein the pressure is changed from the liquid state to the cleaning medium at a constant temperature and the gas state and the liquid state are alternately and repeatedly changed.
[0036]
A seventh aspect of the present invention is the cleaning method according to the third or fourth aspect, wherein the pressure is changed at a constant temperature with respect to the cleaning medium to alternately repeat the gas state and the liquid state to change the state.
[0037]
According to an eighth aspect of the present invention, there is provided a cleaning method for removing at least a substance adhering to at least the surface of the concave structure of a part having the concave structure, wherein the part having the substance adhering is housed in a cleaning tank, and the part is cleaned in the cleaning tank. The medium is introduced and the parts are present in the cleaning medium atmosphere, the temperature and pressure of the cleaning medium are changed to change the cleaning medium to a supercritical state, and the cleaning medium is evenly distributed over the concave structure surface. Is a cleaning method for performing cleaning as described above.
[0038]
According to a ninth aspect of the present invention, there is provided a cleaning method for removing at least deposits adhering to at least the surface of the concave structure of a component having a concave structure. The medium is introduced and the parts are present in the cleaning medium atmosphere, the temperature and pressure of the cleaning medium are changed to change the cleaning medium to a supercritical state, and the cleaning medium is evenly distributed over the concave structure surface. After the cleaning is performed as described above, a liquid cleaning method is further performed.
[0039]
A tenth aspect of the present invention is the cleaning method according to any one of the first to ninth aspects, wherein the cleaning medium is carbon dioxide gas or water.
[0040]
An eleventh invention of the present invention is directed to a cleaning method for removing at least a substance adhering to at least the surface of the concave structure of a part having a concave structure, wherein the part having the substance adhering is housed in a cleaning tank, and the part is cleaned in the cleaning tank. Carbon dioxide is introduced as a medium, the parts are present in the cleaning medium atmosphere, the temperature and pressure of the cleaning medium are changed to change the cleaning medium to a supercritical state, and the cleaning medium is formed on the concave structure surface. Is a cleaning method in which water is newly introduced as a cleaning medium, and water as the cleaning medium is changed to a supercritical state to clean the surface of the concave structure.
[0041]
A twelfth aspect of the present invention provides a cleaning tank, a cleaning medium supply unit for supplying a cleaning medium to the cleaning tank, a heating device for changing the temperature of the cleaning medium, and a pressurizing device for changing the pressure of the cleaning medium. And a control means for controlling the cleaning medium supply unit, the heating device, and the pressurizing device, and by controlling at least one of the heating device and the pressurizing device, a concave structure accommodated in the cleaning tank is provided. This is a cleaning apparatus that performs cleaning by using a supercritical gas or a liquefied gas as an object to be cleaned so that the cleaning medium is evenly distributed on the surface of the concave structure.
[0042]
According to a thirteenth aspect of the present invention, in the twelfth aspect, by controlling at least one of the heating device and the pressurizing device, the cleaning medium is changed alternately between a liquid state and a gas state, This is a cleaning device for cleaning the surface of the concave structure by changing the cleaning medium to a supercritical state or a subcritical state.
[0043]
According to a fourteenth aspect of the present invention, there is provided a cleaning tank having an inlet for introducing a cleaning medium and an outlet for discharging the cleaning medium and storing an object to be cleaned, and supplying the cleaning medium to the cleaning tank via the inlet. Cleaning medium supply unit, a heating device for changing the temperature of the cleaning medium, a pressurizing device for changing the pressure of the cleaning medium, and control means for controlling the cleaning medium supply unit, the heating device, and the pressurizing device And an extraction / collection container as an example of a collection unit that collects a cleaning medium discharged from the discharge port and collects a removed substance after cleaning, and controls at least one of the heating device and the pressurizing device. By doing so, using a supercritical gas or a liquefied gas to clean the object to be cleaned having a concave structure accommodated in the cleaning tank, the cleaning is performed so that the cleaning medium spreads evenly over the concave structure surface, and the introduction port is Exhaustion Located below the mouth, the discharge port is a cleaning device which is located above the object to be cleaned.
[0044]
A fifteenth invention of the present invention is the cleaning method according to any one of the first to eleventh inventions, wherein the component having the concave structure is a structure formed by press molding or cutting. .
[0045]
According to a sixteenth aspect of the present invention, in any one of the first to eleventh aspects, the component having the concave structure is a structure formed by a press forming method or a cutting method, and the structure is mainly A cleaning method comprising a metal material.
[0046]
A seventeenth aspect of the present invention is the cleaning method according to the sixteenth aspect, wherein the metal material forming the component having the recessed structure is mainly composed of Fe, Al, Cu, or Ti. .
[0047]
According to an eighteenth aspect of the present invention, in any one of the first to eleventh aspects, the component having the concave structure is a structure formed by a press molding method or a cutting method, and the structure is mainly A cleaning method characterized by comprising an organic material.
[0048]
A nineteenth aspect of the present invention is the cleaning method according to the eighteenth aspect, wherein a main component of the organic material forming the component having the concave structure is polyimide or epoxy.
[0049]
According to a twentieth aspect of the present invention, in any one of the first to eleventh aspects, the component having the concave structure is a structure formed by a press molding method or a cutting method, and the structure is mainly A cleaning method comprising a ceramic material.
[0050]
According to a twenty-first aspect of the present invention, in the twentieth aspect, the ceramic material forming the component having the concave structure has SiO 2 as a main component. ₂ , PZT, Ag, or C.
[0051]
According to a twenty-second aspect of the present invention, in any one of the first to eleventh aspects, the component having the concave structure is mainly a composite of a metal and an organic material, a composite of a mainly organic material and a ceramic material, or This is a cleaning method mainly composed of a composite of metal, organic material and ceramic material.
[0052]
According to a twenty-third aspect of the present invention, in any one of the first to eleventh aspects, the component having the concave structure is a matching layer for an ultrasonic sensor, or an electronic component, an ultrasonic sensor, a battery, an HDD ( This is a cleaning method characterized by being various cases for a hard disk drive) and an electrolytic capacitor.
[0053]
Here, as a cleaning medium, for example, a supercritical state or a liquid state (including a subcritical state) of a liquefied gas is used. The type of liquefied gas is mainly carbon dioxide (CO ₂ ) Or water (H ₂ O) A simple substance or a mixture of carbon dioxide and water is used. Select which cleaning medium to use or combine a hard cleaning medium, depending on the main material and contaminant composition of the part.
[0054]
For example, if the main component of the cleaning component is a metal and the contaminants are organic and inorganic oxides such as oils and fats, first clean the organic dirt using carbon dioxide, then introduce water. An inorganic oxide or the like is removed by etching.
[0055]
Further, the present invention improves the cleaning efficiency by controlling physical properties such as density and viscosity in a liquid state, and utilizing physical energy contributing to a change in the state of a liquid, gas, or supercritical state. In particular, in the liquid state of carbon dioxide, by controlling the temperature or pressure in the container, it is easy to control the physical properties such as the density and viscosity of the liquid and to control the state of the gas state, liquid state, and supercritical state. Relatively normal temperature and near atmospheric pressure, easy to handle.
[0056]
There are few adverse effects on the environment and human body. By appropriately combining physical properties and state changes according to the object to be cleaned, physical energy generated due to the physical properties and state changes is given to contaminants (processing oil, cutting waste, etc.) to remove or remove The adhesion of contaminants to water can be reduced and the cleaning efficiency can be improved. For example, the liquid state of carbon dioxide is first introduced into the high-pressure vessel, and the temperature or the pressure is changed to repeat the liquid state and the gas state. In this step, the physical properties of carbon dioxide also change with the state change at the same time, so that physical energy acts on the contaminants to reduce the adhesion strength of the contaminants. Thereafter, by shifting to a supercritical state, organic components such as fats and oils are dissolved and decomposed. It is known that in the supercritical state of carbon dioxide, fats and oils components such as organic substances can be melted and decomposed, but contaminants such as organic substances and inorganic substances, and mixtures of organic and inorganic substances can be combined with gas and liquid state changes. Can be efficiently cleaned.
[0057]
An example of the cleaning object of the present invention is a part processed by press molding or a part processed by cutting, and is characterized by having a concave structure. In particular, in the case of parts with a concave structure, contaminants (such as processing oil and cutting waste) are imprinted on the concave structure part by applying pressure or the like from the surface of the structure or during processing, and cutting debris due to plastic deformation are likely to remain. Even the most difficult to clean. However, by appropriately using the gas, liquid state and supercritical state of the liquefied gas, it is possible to improve the cleaning efficiency, especially for parts having a concave structure, and for carbon dioxide, it becomes a gas at normal temperature, so that a drying step is not necessary. It is characterized by. Parts that are washed are mainly made by press molding or cutting, and the main components of the parts are composed of metal materials, organic materials, ceramic materials, or composites thereof. And The main component of the metal material contains any of Fe, Al, Cu, and Ti. The main component of the organic material is polyimide, epoxy, or thermoplastic resin, and the main component of the ceramic material is SiO. ₂ , Ag, PZT, or C. As a cleaning medium, carbon dioxide, water, and the like are selected according to an object to be cleaned.
[0058]
The cleaning compatible part of the present invention has a concave structure such as a matching layer or case of an ultrasonic sensor, a case or an electrode for a battery, a case (housing) for an HDD, or a case of an electrolytic capacitor. It is an electronic component that requires precision cleaning, has high added value, and has a condition that the volume per unit is small.
[0059]
Hereinafter, a cleaning method and a cleaning apparatus according to a first embodiment of the present invention will be described with reference to FIGS.
[0060]
First, a supercritical fluid and a liquefied gas used in the cleaning method will be described.
[0061]
FIG. 1 shows a state diagram of the cleaning medium in which the temperature T is plotted on the horizontal axis and the pressure P is plotted on the vertical axis. The triple point (black circle 21 in the figure) in FIG. 1 is a state in which three phases of gas, liquid, and solid coexist. At a temperature lower than the temperature of the triple point, the solid and its vapor are in equilibrium, and the pressure of the vapor at that time is given by a sublimation curve (20 in FIG. 1). At pressures below this curve, the solids sublimate to a gas, and at higher pressures the gas solidifies to a solid. At a temperature higher than the triple point, the liquid and its vapor are in equilibrium, and the pressure at this time is represented by a vapor curve (22 in FIG. 1) as a saturated vapor pressure. At a pressure lower than this curve, all the liquid evaporates, and at a pressure higher than this, all the vapor liquefies (region A). Even if the pressure is kept constant and the temperature is changed, if this curve is exceeded, the liquid becomes vapor and the vapor becomes liquid. The end point of this vapor curve is called a critical point (open circle 23 in FIG. 1), and there is a state where it is impossible to distinguish between liquid and gas, and the boundary between gas and liquid also disappears. In a state where the temperature is higher than the critical point, it is possible to transfer between a liquid and a gas without causing a gas-liquid coexistence state. No condensation occurs in this region, no matter how high the density. A state in which the temperature is equal to or higher than the critical temperature (Tc) and equal to or higher than the critical pressure (Pc) (region B) is referred to as a supercritical fluid.
[0062]
In addition, the liquid gas refers to a state where the temperature range as shown in FIG. 1 is higher than the triple junction temperature and lower than the critical temperature, and the pressure is higher than the triple junction pressure and higher than the vapor curve.
[0063]
Then, in the process from the liquefied gas state to the supercritical fluid, the liquid undergoes a subcritical state in which the temperature and pressure are lower than the critical point as shown in FIG. Here, the subcritical state refers to a state within a range of up to 0.6 times the critical temperature (Tc) and the critical pressure (Pc), and accordingly, a state within the range of the next subcritical temperature and subcritical pressure. Is defined.
[0064]
Critical temperature (Tc)> Subcritical temperature ≧ 0.6 × Critical temperature (Tc)
Critical pressure (Pc)> Subcritical temperature ≧ 0.6 × Critical temperature (Pc)
Thus, the cleaning medium changes from a liquid gas to a supercritical state via a subcritical state.
[0065]
The supercritical fluid or liquefied gas used here is carbon dioxide (CO ₂ ) Or water (H ₂ O).
[0066]
The critical temperature (Tc) of carbon dioxide is 31.1 ° C., the critical pressure (Pc) is 7.38 MPa, and the critical temperature (Tc) of water is 374.1 ° C. and the critical pressure (Pc) is 22.04 MPa. .
[0067]
Next, an outline of the cleaning system according to the first embodiment of the present invention will be described with reference to FIG. In the cleaning apparatus according to the first embodiment of the present invention, at least a high-pressure container 1 as an example of a cleaning tank, a liquefaction supply tank (or high-pressure cylinder) 2 holding a cleaning medium, and a liquefaction supply tank 2 serve as a cleaning medium. A liquid pump (corresponding to an example of a cleaning medium supply unit) 3 for supplying a liquefied gas to the high-pressure vessel 1, a heater 5 for heating the inside of the high-pressure vessel 1, and a temperature control of the liquefied gas in the high-pressure vessel 1 by controlling the heater 5 Controller 4, a waste liquid collecting tank 6 for collecting the waste liquid after washing in the high-pressure vessel 1, a vaporizer 7 for vaporizing the liquefied gas collected in the waste liquid collecting tank 6, and a collecting and collecting substance to be removed after washing. It is configured to include an extraction and collection container 8 as an example of the unit. The pressure in the high-pressure vessel 1 is changed by the supply of the liquefied gas by the liquid pump 3, and the temperature of the liquefied gas is controlled by the heater 5 under the control of the heater controller 4. By controlling the temperature and the pressure, a supercritical fluid (supercritical gas in the present embodiment), a subcritical fluid (subcritical gas in the first embodiment), and a liquid gas, which are cleaning media, are generated. Then, the object to be washed is washed with a washing medium. In FIG. 3, reference numeral 1000 denotes a control device for controlling the cleaning operation of the cleaning device, which is connected to the liquid pump 3, the heater controller 4, the vaporizer 7, and the extraction / collection container 8, and controls each operation. I am trying to do it.
[0068]
Here, the liquefied gas is used as the cleaning medium, but a subcritical fluid or a supercritical fluid may be directly supplied into the high-pressure vessel 1, and the vaporizer 7 vaporizes the subcritical fluid or the supercritical fluid. May be used.
[0069]
Next, the cleaning object will be described. As shown in FIGS. 2 (A), 2 (B), 2 (C), and 2 (D), a press-formed part (27, 28, 29, 30) having a concave portion or a cutting process (27, 28, 29, 30) formed by the above-mentioned method are particularly likely to cause the lubricating oil as a processing oil, which is the deposit 26, and impurities (such as cutting chips) to adhere to the concave portions. In addition, since the concave portion has a complicated structure and is a portion to which pressure is applied during processing, the adhesion of lubricating oil as a processing oil and impurities (such as cutting waste) is higher than that of other flat structure portions. In addition, since a cleaning agent or the like does not easily permeate, unevenness in cleaning and residual cleaning are likely to occur.
[0070]
More specifically, as a specific example of the place 40 where the dust of the part to be cleaned or the part to be cleaned remains, in the case of a deep drawn product among the press-formed products, FIG. ), Near the local area bent by press molding, and microscopically, as shown in FIG. 10 (B), there are severely uneven portions (in other words, rough portions of the material surface), and especially, for cleaning. This is the part where the solvent hardly enters. In the case of a stamped product among press-formed products, as shown in FIG. 11, a macroscopic portion 41 is in contact with a punching blade at the time of punching, and a microscopic portion with severe irregularities ( In other words, it is a part where the material surface is rough) or a part where the cleaning solvent is difficult to enter.
[0071]
Examples of the deposit which is particularly difficult to remove and which can be washed by the cleaning method and apparatus of the present invention include, when the deposit is a press molding oil (application type), a deposit which is used during press molding. Among the lubricating oils used are lubricating oils imprinted on the material and lubricating oils that have been deformed due to the application of heat or the like. In addition, when the deposit is a material pre-applied type lubricating oil, the material is a material for processing and molding in which the material is preliminarily coated with lubricating oil. Lubricating oil.
[0072]
In the case of metal, the material of the component to be cleaned or the object to be cleaned of the cleaning method and apparatus of the present invention is various kinds of stainless steel, aluminum, titanium, iron, or the like. Particularly, iron and the like which are easily rusted do not need to be dried, and thus are suitable as a material of a part to be cleaned or a part to be cleaned in the cleaning method and apparatus of the present invention. Other than this, as the metal-organic compound composite material, there is a material in which a sheet of an organic material (PPT, PET, or the like) is attached to a metal surface or a metal is coated.
[0073]
As another example of the object to be cleaned, the shape of another ultrasonic case is shown in FIG.
[0074]
Therefore, a liquefied state (including a subcritical fluid) of carbon dioxide or water having a high permeability and a certain degree of viscosity is first introduced into the high-pressure vessel 1 as a cleaning medium. In particular, carbon dioxide becomes liquid at relatively low temperatures and pressures. Therefore, by controlling the temperature and pressure of the liquid pump 3 and the heater controller 4 by controlling the operation of the liquid pump 3 and the heater controller 4 by the control device 1000, the physical property change between the liquid state and the gas state (here, the physical property change is, for example, a comparison between the gas and the liquid). Then the density is 0.6-1kg / m ³ And 1000kg / m ³ Changes by 3 to 4 orders, and the viscosity is 10 ^-5 Ps · s and 10 ^-3 2 digits in Ps · s, diffusion coefficient is 10 ^-5 And 10 ^-9 4 digits or less below. Thermal conductivity is 10 ^-3 And 10 ^-1 And changes from a liquid state to a gas state and from a gas state to a liquid state.
[0075]
Further, since carbon dioxide and water are harmless even on the side of the human body, they are easy to handle.
[0076]
In addition, carbon dioxide and water have the action of decomposing and removing organic substances in critical conditions, and water has the effect of etching oxides and the like under specific pressure and temperature conditions. It is effective for cleaning.
[0077]
Here, the mechanism by which the supercritical state of carbon dioxide decomposes and removes organic matter and the mechanism by which water has an oxide are not clearly understood at present, but the solubilizing power, ionic product, etc., which can be expressed as a function of density. It is considered to have a macro-average property, which is the equilibrium physical property, and a local structure at the molecular level such as solvation (cluster). In particular, it has been relatively recently that the solvation structure formed around solute molecules has been considered to be relatively recent.If solute molecules are present in a supercritical fluid column where thermal motion and intermolecular force are opposed, The solute-solvent interaction becomes relatively dominant, solvate molecules are attracted around the solute molecules and solvation occurs, and the vicinity of the solute molecules is in a higher density state than the bulk. This is considered to be strongly related to characteristic phenomena such as high selectivity of the dissolving power of the supercritical fluid and promotion of the reaction rate.
[0078]
In addition, the water oxide etching effect shows the temperature dependence (25 Mpa constant pressure) of the physical properties of water shown in FIG. The dielectric constant of water at room temperature is very large, about 80.
[0079]
Therefore, inorganic substances such as electrolytes are dissolved well, but organic substances are hardly dissolved. However, when the temperature is increased, the dielectric constant gradually decreases, and in supercritical water of 374 ° C. or more, the value becomes about 10 and a value comparable to that of an organic solvent having a small polarity. As a result, organic matter is well dissolved but inorganic matter is hardly dissolved. In the etching of an inorganic substance such as an oxide by utilizing such a property change state, an effect can be obtained particularly at a temperature of about 200 ° C. and a pressure of about 5 to 10 Mpa.
[0080]
The manner in which a component having a concave portion as such a cleaning object is cleaned by the cleaning system shown in FIG. 3 will be described. Here, FIGS. 4A and 4B are the same as the state diagram of the cleaning medium shown in FIG.
[0081]
The cleaning object which is a press-formed part (particularly an electronic part) is stored in the high-pressure container 1 with the processing oil and impurities adhered thereto. After the components are introduced into the high-pressure vessel 1, either the temperature or the pressure is changed to change the state from the gaseous state to the liquid state from the liquid state to the gas state.
[0082]
For example, the path 1 shown in FIG. 4A becomes a gas state when the temperature is increased from the liquid state at a constant pressure, and becomes a liquid state when the temperature is returned (lowered) from the state. On the other hand, in the path 2 shown in FIG. 4B, when the pressure is decreased at a constant temperature, the state changes from the liquid state to the gas state, and when the pressure is increased from that state, the state returns from the gas state to the liquid state. By repeating this process several times, especially when changing from the liquid state to the gas state, the processing oil and impurities (cutting waste, etc.) have physical energy (in terms of change in physical properties, for example, the density is compared with gas and liquid). 0.6-1kg / m ³ And 1000kg / m ³ Changes by 3 to 4 orders, and the viscosity is 10 ^-5 Ps · s and 10 ^-3 2 digits in Ps · s, diffusion coefficient is 10 ^-5 And 10 ^-9 4 digits or less below. Thermal conductivity is 10 ^-3 And 10 ^-1 Changes by two digits. Among them, the physical energy caused by the change in surface tension, especially due to the change in density and the change in viscosity, is considered to act), and the adhesion force of processing oil and impurities (such as cutting chips) adhering to the parts Is reduced, and the cleaning effect is improved.
[0083]
Further, by repeating the liquid state and the gas state, convection (arrow 31) of the liquefied gas occurs in the high-pressure vessel as shown in FIG. 5, and the liquefied gas as the cleaning agent permeates every corner of the component 32 having the concave portion. And improve the cleaning effect.
[0084]
Thereafter, the temperature and pressure are changed to the critical point or higher, and the state is shifted to the supercritical state, and the main cleaning is performed. At this time, after passing through several steps of repeating the gas state and the liquid state, the liquefied gas is discharged out of the high-pressure container, and after newly introducing the liquefied gas, the temperature or the pressure is changed to the critical point temperature and the critical point pressure or more. Move to the supercritical cleaning process. In the supercritical state, organic substances are mainly decomposed and removed, and etching of inorganic oxides (in the case of using water) is performed at a specific temperature and pressure.
[0085]
Further, depending on the contamination level of the parts to be cleaned, the cleaning can be performed only by the cleaning step of repeating the liquid state and the gas state without using the supercritical state.
[0086]
The cleaning level of the parts here is explained using "Sample 2" shown in the report of the Japan Industrial Cleaning Council in 1994, "General cleaning evaluation method and classification of cleaning index". Then, it indicates the “coarse cleaning” level or the “general cleaning” level described as the degree of cleaning.
[0087]
The cleaning apparatus according to the first embodiment of the present invention includes a high-pressure vessel 1, a liquid pump 3 for introducing a supercritical gas and a liquefied gas into the high-pressure vessel 1, and controlling the temperatures of the supercritical gas and the liquefied gas in the high-pressure vessel 1. A liquefied gas is introduced into the high-pressure vessel 1 as shown in FIGS. 3 and 5, comprising a heater controller 4 and a heater 5 for performing the operation, an extraction and collection vessel 8 for collecting a substance to be removed after cleaning, and a control device 1000. The inlet 1a is always provided below the outlet 1b for discarding the liquefied gas from inside the high-pressure vessel 1, and the outlet 1b is provided above the object 31 to be cleaned. This is because the specific gravity of the cleaning object 31 is heavier than the specific gravity of the cleaning gas mainly in the liquid state or the supercritical state, whereas organic-based dirt and inorganic oxides are smaller than the specific gravity of the cleaning gas. Therefore, contaminants such as organic substances and inorganic substances tend to float above the cleaning material in a liquid state or a supercritical state. The need for the inlet 1a to be lower than the outlet 1b is to allow the liquefied gas, which is the cleaning gas, to be distributed evenly to the part having the concave structure, which is the cleaning object 31.
[0088]
On the other hand, the need for the exhaust port 1b to be positioned above the inlet port 1a is to prevent the deposits or contaminants once removed from the cleaning component 31 from re-adhering to the component 31.
[0089]
Parts that can be expected to have a cleaning effect in the cleaning method and the cleaning apparatus according to the first embodiment of the present invention are mainly electronic parts used in electronics and related parts. In particular, it is a precision machined part formed by press forming and cutting. For these parts, lubricating oil, which is a processing oil, is indispensable to improve processing accuracy. However, the residue of the processing oil affects the performance characteristics of the next process, for example, the plating process and adhesion, and causes a decrease in the performance and reliability as devices and products. Therefore, it is effective for parts that require high-level residue removal, that is, precision cleaning.
[0090]
Applied products include matching layers of ultrasonic sensors and electrodes of batteries (especially secondary batteries, etc.), and other examples include battery cases, HDD cases (also referred to as housings), and electrolytic capacitor cases. . The matching layer for the ultrasonic sensor and the like are formed with countless fine holes and irregularities, and have a microscopic concave structure. More specifically, various materials such as a mixture of an inorganic glass balloon and an organic epoxy, a material made of only an inorganic glass balloon, and a material made of only an organic epoxy are used.
[0091]
The material for the ultrasonic sensor case or the like is stainless steel, aluminum, or epoxy resin. The processing is performed by deep drawing by press molding, resin molding, or cutting. In general, a battery case is made of aluminum or, more recently, a multi-layered steel material plated with aluminum and formed by press molding. For the HDD case, aluminum is used as a material, and recently, a composite steel material in which aluminum is coated with an organic material is used, and is press-formed. Similarly, the electrolytic capacitor case is press-formed using aluminum alone or a composite steel sheet coated with an organic film on an aluminum material.
[0092]
As described above, the present invention can be applied to a composite material in which an organic substance and an inorganic substance of different materials are laminated by selecting a process and a main gas used as a cleaning medium. It is needless to say that the present invention is not limited to these product fields, and is also effective for parts having a concave structure processed by press molding and cutting.
[0093]
That is, in the cleaning method of the first embodiment, the temperature and pressure of the cleaning medium are changed to alternately change the cleaning medium between a liquid state and a gas state, thereby cleaning the surface of the concave structure. The media is distributed evenly. Further, if necessary, after the cleaning medium is alternately changed between a liquid state and a gas state, the cleaning medium is changed to a supercritical state to clean the concave structure surface. Like that. Alternatively, after the cleaning medium is alternately changed between a liquid state and a gas state, the cleaning medium is changed to a sub-supercritical state to clean the concave structure surface.
[0094]
In summary, there are the following seven methods for distributing the cleaning medium evenly to the parts by changing the pressure or temperature and distributing them by convection. All of these can be performed by controlling the operation of the liquid pump 3 and the heater controller 4 to control the temperature and the pressure by the control device 1000.
[0095]
(1) After at least one cycle of (liquid-gas) as one cycle, the temperature is controlled to a supercritical state.
[0096]
(2) After performing at least one cycle or more with (gas-liquid) as one cycle, pressure control is performed to a supercritical state.
[0097]
(3) After performing at least one cycle with (liquid-gas-liquid) as one cycle, control the temperature to a supercritical state.
[0098]
(4) After performing at least one cycle with (gas-liquid-gas) as one cycle, pressure control is performed to a supercritical state.
[0099]
(5) After performing at least one or more cycles with (liquid-supercritical) as one cycle, control the temperature to the supercritical state.
[0100]
(6) After performing (gas-supercritical) as one cycle for at least one cycle or more, pressure control is performed to a supercritical state.
[0101]
(7) The supercritical state is set at least once during one cycle of (1) to (6). Control pressure or temperature.
[0102]
As shown in FIG. 13, a time chart for controlling the pressure of the control device 1000 based on the operation control of the liquid pump 3 has a vertical axis with respect to the horizontal axis and a vertical axis with respect to the chamber pressure and the CO. ₂ Introducing emissions. When the pressure inside the chamber is high, CO ₂ Is introduced, and when the pressure in the chamber is low, CO ₂ Are discharged, and the pressure is controlled by repeating this periodically.
[0103]
As shown in FIG. 13, the time chart for temperature control of the control device 1000 by the operation control of the heater controller 4 shows the temperature inside the chamber and the heater power ON or OFF with respect to the time axis of the horizontal axis. is there. When the temperature in the chamber is raised, the heater power is turned on, and when the temperature in the chamber is lowered, the heater power is turned off. This is repeated periodically to control the temperature.
[0104]
As another method of the pressure control, FIG. 15 shows a case where the pressure is increased under the operation control of the control device 1000 by using a two-layer type chamber including the main chamber 43 and the sub-chamber 44. In order to increase the pressure easily by closing the door 45 separating the layers, the door 45 separating the layers is opened by the operation control of the control device 1000 as shown in FIG. It is possible. 15 and 16, reference numeral 46 denotes a cleaning medium, and 47 denotes an object to be cleaned.
[0105]
Further, as another method of temperature control, as shown in FIG. 17, a cleaning medium 49 at a temperature higher or lower than the temperature of the cleaning liquid 49 is supplied into a cleaning liquid 49 in a main chamber 48 by a liquid pump. The cleaning medium in the main chamber 48 can be controlled to a predetermined temperature by introducing the cleaning medium 3 in a liquid state. Also, as shown in FIG. 18, a cleaning medium 50 at a temperature higher or lower than the temperature of the cleaning liquid 49 is introduced into the main chamber 48 in a gaseous state by the pump 3A instead of the pump 3, so that the main chamber 48 is cooled. The cleaning liquid 49 in the inside can be controlled to a predetermined temperature.
[0106]
FIG. 19 shows a control device 1000 having a control program for controlling the operation of the above-described cleaning method, a temperature control relay 53 in the heater controller 4 whose operation is controlled by the control device 1000, and a liquid whose operation is controlled by the control device 1000. FIG. 3 is an explanatory diagram showing a pressure control relay 54 in a pump 3 and the cleaning device 60.
[0107]
As shown in FIG. 20, in the first embodiment, as an example of a method for improving the cleaning efficiency, a rotor (a propeller for agitation) 62 disposed on the ceiling side of the main chamber 64 is controlled by the control device 1000. Alternatively, the cleaning medium 65 in the main chamber 64 may be agitated by being rotated by the motor 63 to increase the cleaning efficiency of the cleaning target 47 with the cleaning medium 65.
[0108]
As shown in FIG. 21, in the first embodiment, as another example of a method for improving the cleaning efficiency, a rotor (a propeller for agitation) 62 disposed on the bottom side of the main chamber 64 is provided with a control device. Under the control of 1000, the cleaning medium 65 in the main chamber 64 may be agitated by being rotated by the motor 63 so as to increase the cleaning efficiency of the cleaning target 47 with the cleaning medium 65.
[0109]
Further, as shown in FIG. 22, in the first embodiment, as another example of a method of improving the cleaning efficiency, a rotor (a propeller for agitation) 62 disposed on the side surface of the main chamber 64 is provided with a control device. Under the control of 1000, the cleaning medium 65 in the main chamber 64 may be agitated by being rotated by the motor 63 so as to increase the cleaning efficiency of the cleaning target 47 with the cleaning medium 65.
[0110]
Further, as shown in FIG. 23, in the first embodiment, as another example of a method of improving the cleaning efficiency, a rotor (a propeller for agitation) 62 disposed on the ceiling side of the main chamber 64 is provided with a control device. Under the control of 1000, the cleaning medium 65 in the main chamber 64 is stirred by being rotated by the motor 63, and the liquid pump 3 is driven under the control of the control device 1000 to face the main chamber 64. The cleaning medium may be introduced into the main chamber 64 from the pair of nozzles 66 arranged on the side surface, so that the cleaning efficiency of the cleaning target 65 with the cleaning medium 65 may be increased.
[0111]
Further, as shown in FIG. 24, in the first embodiment, as still another example of a method for increasing the cleaning efficiency, the liquid pump 3 is driven under the control of the The cleaning medium may be introduced into the main chamber 64 from a number of nozzles 66 radially arranged on the cylindrical side surface to increase the cleaning efficiency of the cleaning target 47 with the cleaning medium 65.
[0112]
Further, as shown in FIG. 25, in the first embodiment, as still another example of a method for improving the cleaning efficiency, a pair of the pair of opposite side surfaces of the main chamber 64 are arranged under the control of the control device 1000. The ultrasonic sensor 67 may be driven simultaneously or sequentially to apply ultrasonic waves to the cleaning medium 65 from the side surface of the main chamber 64 to increase the cleaning efficiency of the cleaning target 47 with the cleaning medium 65. Good.
[0113]
Further, as shown in FIG. 26, in the first embodiment, as still another example of a method for improving the cleaning efficiency, under the control of the control device 1000, radially arranged on the cylindrical side surface of the main chamber 64. A large number of ultrasonic sensors 67 are driven simultaneously or sequentially to apply ultrasonic waves to the cleaning medium 65 from the side of the main chamber 64 so as to increase the cleaning efficiency of the cleaning target 47 with the cleaning medium 65. It may be.
[0114]
Further, as shown in FIG. 28, in the cleaning apparatus of FIG. 24, as still another example of a method of increasing the cleaning efficiency, under the control of the controller 1000, the cleaning apparatus is radially arranged on the cylindrical side surface of the main chamber 64. The cleaning medium may be sequentially introduced from the large number of nozzles 66 into the main chamber 64 to increase the cleaning efficiency of the cleaning target 47 with the cleaning medium 65. In this case, the cleaning medium is sequentially introduced into the main chamber 64 from the nozzle 66 in the order of the numbers of the nozzles 1 to 8 or in the order of 8 to 1 shown in FIG. This can further increase the cleaning efficiency. An opening / closing valve or shutter is provided for each nozzle, and the operation of the opening / closing valve or shutter is controlled by the control device 1000, so that the cleaning medium introduction order, opening / closing time, ejection pressure, and ejection amount can be arbitrarily controlled.
[0115]
The tip shape of each nozzle 66 of the first embodiment described above is preferably a shape as shown in FIGS. 27 (A) to 27 (C). As shown in FIGS. 27 (A) to 27 (C), the energy density of the fluid ejected from the nozzle is changed by changing the number of ejection ports, ejection pressure and ejection time as shown in FIGS. And a structure for increasing the stirring efficiency according to the object to be cleaned. For example, when the size of the object to be cleaned is large and the structure is simple, impurities can be easily removed without much stirring, so that a simple nozzle shape as shown in FIG. On the other hand, when the size of the object to be cleaned is small and the structure is complicated, the shape of the nozzle according to the size and complexity is higher than that of FIGS. 27 (B) and 27 (C). Use Further, when the object to be cleaned is a very precise optical component or the like or is very brittle, it is desirable to change the nozzle shape, the ejection pressure, and the ejection time according to the object to be washed. Although shown only two-dimensionally in the drawings, it actually has a three-dimensional structure.
[0116]
Hereinafter, the effects of the first embodiment of the present invention will be described with reference to specific examples.
[0117]
(Example 1)
The press-formed and cut cases were cleaned. The cleaning was performed using carbon dioxide as a liquefied gas. As shown in FIG. 6, the case is made of SUS304, has a size of φ: 12 mm, and a height h: 5 mm. Using this case, the amount of residue (oil) and the amount of particles due to the difference in the cleaning process were examined. The cleaning process includes (1) solvent cleaning (1-bromopropane), (2) cleaning at a constant temperature and changing the pressure in the liquid state, and (3) changing the pressure at a constant temperature to change the gas state and the liquid state. Cleaning with repetition of 5 times, (4) Supercritical cleaning only, (5) Supercritical cleaning after process (2), (6) Supercritical cleaning after cleaning (3), (7) Super After washing in the critical state, seven steps of washing in the liquid state were examined. In each washing step, 100 cases were washed and analyzed. In the residual oil analysis, the oil was extracted with a solvent (carbon tetrachloride), and the extracted oil was measured by FT-IR (Fourier transform infrared spectroscopy). Particles were measured after cleaning using a particle inspection device (ToPcon manufactured wafer surface inspection device WM-1700 / 1500). Table 1 shows the results.
[0118]
[Table 1]

[0119]
From the above results, lower values were obtained for both the residual oil content and the particle amount as compared with the solvent cleaning. Further, it was found that the cleaning effect was further improved in removing inorganic particles by combining the gas state, the liquid state, and the supercritical state of carbon dioxide by changing the pressure.
[0120]
(Example 2)
In the same manner as in Example 1, the case subjected to press molding and cutting was washed. The cleaning was performed using carbon dioxide as a liquefied gas. As shown in FIG. 6, the material is SUS304, the size is φ12 mm, and the height is 5 mm. Using this case, the amount of residue (oil) and the amount of particles due to the difference in the cleaning process were examined. The cleaning process includes (1) cleaning in which the temperature is changed at a constant pressure in the liquid state, (2) cleaning in which the temperature is changed at a constant pressure and the gas state and the liquid state are changed five times, and (3). Five types of processes, i.e., cleaning only with supercritical cleaning, (4) supercritical cleaning after the process of (1), and (5) supercritical cleaning after cleaning of (2) were examined. In each washing step, 100 cases were washed and analyzed. In the residual oil analysis, the oil was extracted with a solvent (carbon tetrachloride), and the extracted oil was measured by FT-IR (Fourier transform infrared spectroscopy). Particles were measured after cleaning using a particle inspection device (ToPcon manufactured wafer surface inspection device WM-1700 / 1500). Table 2 shows the results.
[0121]
[Table 2]

[0122]
As a result, similarly to the case where the physical property changes and the state change by changing the pressure while maintaining the temperature constant, when the cleaning is performed while changing the temperature while maintaining the constant pressure, low values are obtained for both the residual oil content and the particle content. Therefore, it was found that the cleaning effect was improved by removing the inorganic particles by combining the gas state, the liquid state, and the supercritical state of carbon dioxide with changing the temperature.
[0123]
(Example 3)
Using the cleaning process (6) which was the most effective in the cleaning method studied in Example 1, using "supercritical cleaning after changing the gas state and the liquid state five times by changing the pressure at a constant temperature". Cases of different materials were cleaned. The material of the case is (1) aluminum, (2) a composite plate obtained by coating an organic film on aluminum, (3) stainless steel SUS304, (4) Cu, and (5) Ti. As shown in FIG. 7, the case shape is 5 mm long × 30 mm wide × 50 mm high. In each washing step, 100 cases were washed and analyzed. The cleaning was performed using carbon dioxide as a liquefied gas. In the residual oil analysis, the oil was extracted with a solvent (carbon tetrachloride), and the extracted oil was measured by FT-IR (Fourier transform infrared spectroscopy). The particles were measured after cleaning using a particle inspection machine (ToPcon wafer surface inspection apparatus WM-1700 / 1500). Table 3 shows the results.
[0124]
[Table 3]

[0125]
As a result, the cleaning effect was obtained without any problem as judged by the residual oil content, the particle content, and the appearance inspection. In addition, it was found that even cases made of different materials can be washed without causing any damage.
[0126]
Appearance inspection and particle quantity judgment criteria are based on "Sample 2" shown in the FY2006 report of the Japan Industrial Cleaning Council, "General cleaning degree evaluation method and classification of cleaning index". To be more specific, “General cleaning” or more described as the degree of cleaning was evaluated as “○”.
[0127]
(Example 4)
Using the cleaning process (6) which was the most effective in the cleaning method studied in Example 1, using "supercritical cleaning after changing the gas state and the liquid state five times by changing the pressure at a constant temperature". Parts of different materials were cleaned. However, since the organic material was weaker than the metal and ceramic materials, the time was shortened. The cleaning was performed using carbon dioxide as a liquefied gas. The parts are formed by press forming and cutting. The material of the parts is (1) epoxy resin, (2) polyimide resin, (3) plastic, (4) mixture of epoxy and glass balloon, (5) SiO ₂ , (6) C (carbon). The part shape is 10.8 mm in diameter x 1.15 mm in height. The appearance inspection was performed using an SEM (Scanning Electron Microscope), and the particles were measured using a particle inspection machine after cleaning (a wafer surface inspection apparatus WM-1700 / 1500 manufactured by ToPcon). Table 4 shows the results.
[0128]
[Table 4]

[0129]
Appearance inspection and particle quantity judgment criteria are based on "Sample 2" shown in the FY2006 report of the Japan Industrial Cleaning Council, "General cleaning degree evaluation method and classification of cleaning index". To be more specific, “General cleaning” or more described as the degree of cleaning was evaluated as “○”.
[0130]
(Example 5)
Further, in order to examine the cleaning effect, particularly the effect of preventing the reattachment of contaminants, cleaning was performed by changing the structure of the high-pressure container and the position where the container to be cleaned was fixed, and the amount of residual oil and the amount of particles were measured. The cleaning was performed using carbon dioxide as a liquefied gas. The cleaning process was the cleaning process most effective in the cleaning method studied in Example 1. (6) “Supercritical cleaning after changing the gas state and liquid state five times by changing the pressure at a constant temperature” Washed with. The part is a case made by press molding and has a shape of 5 mm long × 30 mm wide × 50 mm high. The cleaning was performed by changing the structure of the high-pressure container and the fixed position of the object to be cleaned in the container as follows. (1) Liquefied gas inlet <Clean target <Liquid gas outlet, (2) Liquefied gas inlet> Clean target> Liquid gas outlet, (3) Liquefied gas inlet <Liquid gas outlet <Clean target , (4) cleaning target <liquefied gas inlet <liquefied gas outlet, (5) cleaning target <liquefied gas outlet <liquefied gas inlet, (6) liquefied gas outlet <liquefied gas inlet <cleaning target Six considerations were made for the product. In each washing step, 100 cases were washed and analyzed. In the residual oil analysis, the oil was extracted with a solvent (carbon tetrachloride), and the extracted oil was measured by FT-IR (Fourier transform infrared spectroscopy). The particles were measured after cleaning using a particle inspection machine (ToPcon wafer surface inspection apparatus WM-1700 / 1500). Table 5 shows the results.
[0131]
[Table 5]

[0132]
As a result, by setting the structure of the high-pressure container and the fixing position of the object to be purified in the container to be the liquefied gas inlet <the object to be cleaned <the liquefied gas outlet, the cleaning effect can be improved by the effect of preventing re-adhesion of contaminants. I understand.
[0133]
(Example 6)
The cleaning effect was examined by changing the shape and the depth of the concave structure in order to examine whether or not it depends on the depth and the shape of the concave structure. The cleaning was performed using carbon dioxide as a liquefied gas. Using the cleaning process (6) which was the most effective in the cleaning method studied in Example 1, using "supercritical cleaning after changing the gas state and the liquid state five times by changing the pressure at a constant temperature". Washed. The parts are cases made by press molding and have the following shapes: (1) 5 mm long x 30 mm wide x 50 mm high, (2) 5 mm long x 10 mm wide x 5 mm high, (3) 3 mm long x 5 mm wide x high The size is 20 mm, (4) φ10.8 mm × height 5 mm, (5) φ5 mm × height 5 mm. In each case shape, 100 cases were washed and analyzed. In the residual oil analysis, the oil was extracted with a solvent (carbon tetrachloride), and the extracted oil was measured by FT-IR (Fourier transform infrared spectroscopy). The particles were measured after cleaning using a particle inspection machine (ToPcon wafer surface inspection apparatus WM-1700 / 1500). Table 6 shows the results.
[0134]
[Table 6]

[0135]
From the above results, a cleaning effect was observed regardless of the case shape. Therefore, it was found that cleaning was possible regardless of the shape of the case.
[0136]
(Example 7)
The cleaning process of the press-formed and cut cases was studied. The cleaning was performed using carbon dioxide and water as a liquefied gas. The case is made of SUS304 and has a concave structure of φ12 mm and height 5 mm. Using this case, the amount of residue (oil), the amount of particles, the change in oxides, and the wettability by contact angle measurement were examined for different cleaning processes. The cleaning process includes: (1) using carbon dioxide, changing the pressure at a constant temperature, changing the gas state and the liquid state five times, and then changing to a supercritical state, and then cleaning; (2) After the washing in (1), carbon dioxide is driven out and water is introduced to wash at 200 ° C. and 5 Mpa. (3) After washing in (1), water is introduced into carbon dioxide and washed at 200 ° C. and 5 Mpa; ▼ Four steps of washing with water at 200 ° C. and 5 Mpa only were examined. In each washing step, 100 cases were washed and analyzed. In the residual oil analysis, the oil was extracted with a solvent (carbon tetrachloride), and the extracted oil was measured by FT-IR (Fourier transform infrared spectroscopy). Particles were measured after cleaning using a particle inspection device (ToPcon manufactured wafer surface inspection device WM-1700 / 1500).
[0137]
The change in oxide was measured by using ESCA (X-ray photoelectron spectroscopy). As a criterion for determining the oxide, the oxide peak intensity of the initial value (after degreasing treatment) was set to 1, and after each cleaning. Oxide peak intensity is shown as a ratio).
[0138]
The contact angle was measured using an automatic contact angle meter CA-Z manufactured by Kyowa Interface Chemical Co., Ltd. The contact angle is generally used as an index indicating the familiarity (affinity or wettability) of a material surface with a liquid. As shown in FIG. 8, the contact angle refers to an angle between a tangent of a droplet and a solid surface at a three-phase interface of a solid, a liquid, and a gas. Become smaller.
[0139]
Table 7 shows the results. The amount of oxide was standardized by setting the washing step (1) to 1. The contact angle was measured with pure water as a liquid.
[0140]
[Table 7]

[0141]
As a result, it was found that by combining the carbon dioxide cleaning step with water at 200 ° C. and 5 Mpa cleaning, oil and inorganic oxides can be removed, and the contact angle can be reduced and the wettability can be improved.
[0142]
According to the first embodiment of the present invention, the cleaning effect can be improved by cleaning the component having the concave structure using the cleaning medium of the liquefied gas or the supercritical fluid.
[0143]
(2nd Embodiment)
Next, the meaning of the pressurized fluid used in the second embodiment of the present invention, particularly the supercritical state, will be described with reference to FIG.
[0144]
The second embodiment is intended to reuse the substance removed in the first embodiment. That is, conventionally, in the cleaning using a fluid in a supercritical or subcritical state, various devices have been devised to enhance the cleaning effect. For example, a method for rapidly changing a fluid in a supercritical or subcritical state is disclosed. However, a sudden change in the state of these fluids exerts a physical impact on the object to be cleaned, so that parts may be distorted or chipped if severe. In particular, low-density parts and parts having a thin plate having a concave portion with a complicated structure are easily affected by the influence.
[0145]
On the other hand, many lubricating oils are used for components processed by press molding, especially for electronic components, in order to improve accuracy. For this reason, the cleaning liquid for the processed parts contains a large amount of hydrocarbon-based organic substances, which are the main components of the lubricating oil. Further, the lubricating oil contains an organic substance such as a surfactant in addition to the hydrocarbon-based organic substance for the purpose of improving processing accuracy. However, normal washing cannot separate hydrocarbon-based organic substances and organic substances such as surfactants, and thus cannot be reused.
[0146]
In addition, since the cleaning system is very expensive and requires a long cleaning time, parts that are very expensive and are used repeatedly, such as molds, are mainly used as cleaning objects.
[0147]
The second and third embodiments are intended to solve these problems.
[0148]
The cleaning method using the pressurized fluid of the present invention is a method for removing impurities attached to the surface of the object to be cleaned by bringing the pressurized fluid into contact with the object to be cleaned. A cleaning method characterized by changing the density of a pressurized fluid without changing the phase state of the fluid.
[0149]
In particular, the density of the object to be cleaned is equal to or less than the liquid density of the fluid, and the density of the fluid is higher or lower than the density of the object to be cleaned by changing at least one of the pressure and temperature of the fluid. By repeating the above, the effect of washing is obtained. At this time, the effect is enhanced when the pressurized fluid is a supercritical fluid.
[0150]
Further, the cleaning method using the pressurized fluid of the present invention is a cleaning method for removing impurities attached to the surface of the object to be cleaned by bringing the pressurized fluid into contact with the object to be cleaned. The object to be cleaned immersed in the first fluid is washed by bringing the first fluid into contact with a pressurized second fluid having a different density. At this time, a cleaning method is characterized in that the second fluid is brought into contact with the object to be cleaned without changing the phase state of the first fluid.
[0151]
At this time, a favorable effect is obtained when the second fluid is a supercritical fluid. In particular, the cleaning effect is obtained by contacting the second fluid having a density lower than the liquid density of the first fluid with the density of the first fluid and having a lower density than the density of the fluid to be cleaned. Will be higher. In addition, a particularly preferable effect is obtained when the first fluid and the second fluid are the same, the first fluid is a liquid, and the second fluid is a supercritical fluid.
[0152]
In the cleaning method using a pressurized fluid of the present invention, a preferable effect is obtained when the fluid used contains at least one of carbon dioxide, water, ammonia, carbon suboxide, and alcohol.
[0153]
Further, the effect is enhanced when the impurities adhering to the surface of the object to be cleaned to which the present invention is applied are lubricating oils. Further, the effect is enhanced when the object to be cleaned to which the present invention is applied is a part having a concave structure.
[0154]
First, a second embodiment will be described.
[0155]
FIG. 29 shows a state diagram of a fluid such as carbon dioxide and water. In FIG. 29, the horizontal axis represents temperature, and the vertical axis represents pressure. The point (Tc, Pc) where the temperature is the critical temperature Tc102 and the pressure is the critical pressure Pc103 is the critical point 101. The supercritical state 104 is a range in which the temperature is equal to or higher than the critical temperature Tc102 and the pressure is equal to or higher than the critical pressure Pc103. In the supercritical state 104, the fluid has a different phase from the gas 105, the liquid 106, and the solid 107. It is known that this supercritical state is a fluid exhibiting properties different from those of a gas, liquid, solid, or the like. For example, the density of a fluid in a supercritical state has an intermediate value between a gas and a liquid, and can be adjusted by temperature and pressure conditions. Further, in the supercritical state, not only the density but also the ionic product, the dielectric constant, the diffusion and the like can be controlled with respect to cleaning, so that the supercritical state can be used as a method for obtaining a high cleaning effect.
[0156]
Further, with respect to cleaning, the liquid state has a very high density, so it is an effective fluid for cleaning, and in some cases, the liquid state is used. In addition to the supercritical state, a liquid state in which the pressure and temperature conditions are close to the supercritical state in a relatively high temperature and high pressure region is sometimes referred to as a subcritical region state, and this pressurized liquid state is also used for cleaning. May be used.
[0157]
Here, for example, the critical temperature Tc102 of carbon dioxide as a fluid is about 31.1 ° C., and the critical pressure Pc103 of carbon dioxide is about 7.38 MPa. In the case of water, the critical temperature Tc102 is about 374.3 ° C., and the critical pressure Pc103 is about 22.1 MPa.
[0158]
The fluid is preferably a substance that is gaseous at normal temperature and normal pressure, and carbon dioxide, water, ammonia, carbon monoxide, and the like are used. Alternatively, alcohol that is scattered when the temperature is slightly increased may be used. Above all, carbon dioxide and water are harmless even on the side of the human body, so they are easy to handle. Further, carbon dioxide has an action of decomposing and removing organic substances in a critical state, and water has an etching effect of an oxide or the like. Therefore, by utilizing the respective characteristics, it is effective for cleaning parts having a concave structure.
[0159]
The cleaning method according to the second embodiment of the present invention is preferably applied to a component having a concave structure. These components are particularly liable to adhere lubricating oil, which is a processing oil, and impurities (such as cutting chips) to the concave portions. In addition, since this concave portion has an intricate structure and is a portion to which pressure is applied during processing, the lubricating oil, which is a processing oil, has higher adhesion than other flat structure portions, and the cleaning agent etc. Since it is difficult, cleaning unevenness and remaining cleaning are likely to occur. Therefore, it is highly effective to use a pressurized fluid in a liquid state (including a subcritical fluid) or a supercritical state having a high permeability and a certain degree of viscosity and solubility as a cleaning medium.
[0160]
Next, a cleaning method using a pressurized fluid according to a second embodiment of the present invention will be described.
[0161]
The cleaning method according to the second embodiment of the present invention is a method of removing impurities adhered to the surface of the object to be cleaned by bringing the pressurized fluid into contact with the object to be cleaned. The washing is performed by changing the density of the pressurized fluid without changing the phase state of the fluid. In particular, when the density of the object to be cleaned is equal to or lower than the liquid density of the fluid, the buoyancy applied to the object to be cleaned is changed by controlling the density of the fluid. In this method, the object to be cleaned is moved up and down in the fluid as the density of the fluid repeats the height of the density of the object to be cleaned, thereby producing a stirring effect. At this time, when the pressurized fluid is a fluid in a supercritical state, the density can be largely changed, which is preferable. It also has changing effects.
[0162]
For example, carbon dioxide has a gas density of about 1 kg / m at 0.1 MPa and 30 ° C. ³ On the other hand, for liquid, about 600 to 1600 kg / m at 30 ° C. to 15 ° C. ³ In the supercritical state, it changes depending on temperature and pressure conditions. ³ From 1000kg / m ³ The control can be performed up to the above. Therefore, the object to be cleaned preferably has these density ranges.
[0163]
The density of the object to be cleaned is approximately 200 kg / m. ³ From about 1500kg / m ³ When a fluid in a supercritical state is used, the density of the object to be cleaned is about 200 kg / m2. ³ From about 1000kg / m ³ Is suitable. As the object to be cleaned, a molded article of a resin or a part made of a lightweight material having a hollow structure therein can be suitably used. As an object to be cleaned, for example, a component obtained by solidifying hollow glass beads with an epoxy resin or the like is used as an acoustic matching component of an ultrasonic sensor, but the hollow glass beads are cut or removed by cutting or the like during molding. Thus, a concave structure having a bead size is formed on the processed surface. The size of the concave structure is from several μm to several hundred μm in width and depth, and a glass piece broken at the time of processing is contained therein, and it is difficult to remove it by simple immersion cleaning. Further, during molding and processing, residual oil components may also be present on the surface or inside. The effects of the present invention can be exerted for cleaning these stains. In addition, what is applicable is not limited to this.
[0164]
FIGS. 30, 32, and 33 are schematic views of a cleaning apparatus that performs the cleaning method according to the second embodiment of the present invention. In particular, FIGS. 32 and 33 show that, due to the density of the fluid 380, when the object 214 to be cleaned becomes lighter, the contact state is released, and the impurities 381 are easily removed. FIG.
[0165]
The main components of this apparatus are a pressure vessel 210 as an example of a cleaning tank, a separation vessel 220 for collecting impurities 381, a cylinder (or tank) 201 for supplying a fluid 380, a liquid pump 202, and a fluid 380. , A temperature controller 204 for controlling the temperature of each container, and a pressure controller 230 for controlling the pressure control valves 203, 213, and 223.
[0166]
Carbon dioxide is used as the fluid 380, and the epoxy resin cured molded body of hollow glass beads (the density is about 550 kg / m ³ ). The object to be cleaned 214 is placed in the cleaning jig 212 and set in the pressure vessel 210, and the temperature and pressure conditions are adjusted by the temperature controller 204 and the pressure control valve 203, and the fluid 380 is placed in the pressure vessel 210. It is introduced using the pump 202. The pressure vessel 210 controls cleaning conditions by using a temperature control device 211 and a pressure control device 230 for the container. The carbon dioxide is sent to the pressure vessel 210 as a supercritical fluid 380 at about 47 ° C. and about 12 MPa. The density of carbon dioxide under these conditions is about 600 kg / m ³ Therefore, the object to be cleaned 214 is floating in the carbon dioxide fluid in the pressure vessel 210. When the pressure is controlled at a constant temperature from this initial state, the density of the fluid 380 is about 10 MPa and about 500 kg / m ³ , And the object to be cleaned 214 begins to sink because the density becomes lighter than the density of the object to be cleaned 214. When the temperature is controlled at a constant pressure from the initial state, the density of the fluid 380 becomes about 500 kg / m at about 55 ° C. ³ , And the object to be cleaned 214 begins to sink because the density becomes lighter than the density of the object to be cleaned 214. By increasing or decreasing the density of the fluid 380 by controlling the pressure and / or temperature, the object to be cleaned 214 can be raised or lowered in the fluid 380 (see FIG. 33), By increasing the effect, the cleaning effect can be improved. This facilitates effective elution and removal of the impurities 381, which are components such as lubricating oil, which are easily dissolved in supercritical carbon dioxide, up to the concave portions and narrow portions of the object 214 to be cleaned. In addition, the impurities 381 which are components which are hardly dissolved in carbon dioxide in a supercritical state, such as cutting powder of glass or resin, are extruded from a concave portion or a narrow portion of the object 214 to be cleaned and can be easily removed.
[0167]
When the density of the object to be cleaned 214 and the density of the fluid 380 are substantially the same, the stirring blade 383 is rotated to stir the fluid 380 under the control of a control device such as the pressure control device 230. Thus, similarly to the density change, the buoyancy applied to the object 214 to be cleaned may be changed to achieve the above-described cleaning effect. This is an example in which the closeness between the objects to be cleaned 214 is easily released by another mechanical action by making the densities of the two as close as possible, instead of the above-mentioned high and low densities. This method eliminates the need to repeatedly increase and decrease the density (pressure and temperature) of the fluid, so that control of the conditions is simplified.
[0168]
Further, the mechanical fluctuation due to the external force can be performed not only by mechanical stirring but also by nozzle injection of a fluid, and therefore, FIG. 31 described below is applied to the cleaning device according to the third embodiment of the present invention. FIG. 36 shows an example in which nozzle injection of a fluid is combined. In FIG. 36, reference numeral 400 denotes a component (subject to be cleaned) information database for changing cleaning conditions for each component. That is, based on the information in the information database 400, when the density of the object to be cleaned 214 and the density of the fluid 380 are substantially the same, the close contact between the objects to be cleaned 214 is easily released by nozzle injection. . This method eliminates the need to repeatedly increase and decrease the density (pressure and temperature) of the fluid, so that control of the conditions is simplified.
[0169]
Further, in the present method, the density of the object to be cleaned 214 and the pressure of the fluid 380 which is pressurized in the initial state are made substantially equal to each other, so that the condition of the pressure or the temperature is slightly changed so that the object to be cleaned 214 Can be moved up and down in the pressurized fluid, so that the cleaning effect can be easily exerted. FIG. 30 shows an example in which the conditions of the entire pressure vessel 210 are controlled. However, a heating mechanism is installed near the object 214 to be cleaned, and the temperature near the object 214 is increased. It is also possible to settle the object to be cleaned 214 by lowering the density of the object. These conditions may be properly used depending on the type of impurities attached to the object to be cleaned 214 and the like. In addition to the effect of this method, if a mechanism for assisting the stirring effect is provided outside or inside the pressure vessel 210, the effect is further enhanced. As these mechanisms, a rotating blade type stirring mechanism, a stirring mechanism using an ultrasonic vibrator, or the like can be appropriately used.
[0170]
The supercritical carbon dioxide containing the impurities removed from the object to be cleaned 214 is sent to the separation vessel 220, where the pressure is controlled to reduce the pressure of the supercritical carbon dioxide and return to a gaseous state. At this time, the impurities dissolved in the carbon dioxide are collected as the cleaning residue 222 to separate as the solubility decreases. Further, impurities 381 insoluble in carbon dioxide settle and are collected as cleaning residues 222. By collecting the impurities 381 in a container different from the pressure container 210, re-adhesion to parts can be prevented.
[0171]
In FIG. 30, the fluid is evacuated from a gaseous state. However, the gaseous carbon dioxide may be sent to a liquid pump while being cooled, pressurized again, and reused. Therefore, a continuous cleaning device can be provided.
[0172]
(Third embodiment)
Next, a cleaning method according to a third embodiment of the present invention will be described.
[0173]
The third embodiment is also a method of removing impurities adhering to the surface of the object to be cleaned by bringing the pressurized fluid into contact with the object to be cleaned. This is a method of increasing the cleaning effect without changing the phase state of the above. In the present method, a particularly excellent effect can be obtained by bringing the second fluid into contact with the object to be cleaned without changing the phase state of the first fluid. The object to be cleaned immersed in the pressurized first fluid is brought into contact with the pressurized second fluid having a different density from the first fluid, Improves the stirring effect by spraying or foaming on the part to be cleaned.
[0174]
Further, when the second fluid is a fluid in a supercritical state, a component to be cleaned such as a component having a concave portion or a narrow portion is difficult to clean due to a high diffusivity of the supercritical fluid. Impurities can be effectively removed all the way to the back. At this time, when the pressurized fluid is a fluid in a supercritical state, the density can be largely changed, which is preferable. It also has changing effects.
[0175]
In addition, a particularly preferable effect is obtained when the first fluid and the second fluid are the same, the first fluid is a liquid, and the second fluid is a supercritical fluid. When the two fluids are different, the difference in solubility between the two can be used to enhance the cleaning effect. However, when the two fluids are the same, it is necessary to reuse the fluid after cleaning. There is an advantage that the washing can be efficiently performed without the necessity of separating the water. When the density of the object to be cleaned is lower than that of the first fluid and higher than that of the second fluid, the second fluid is brought into contact with the object to be cleaned and the buoyancy is increased, as in the second embodiment. Can be given a stirring effect, and the cleaning effect can be improved.
[0176]
FIG. 31 is a schematic diagram of a cleaning apparatus that performs the cleaning method according to the third embodiment of the present invention. The main components of this apparatus are a cleaning vessel which is a pressure vessel 310, a separation vessel 320 for collecting impurities, a cylinder (or tank) 301 for supplying a first fluid, a liquid pump 302, a first fluid A temperature controller 304 for controlling the temperature of the body, a temperature controller 304 for controlling the temperature of each container, and a pressure controller 330 for controlling the pressure control valves 303, 313, and 323. In addition, the cylinder (or tank) 341 for supplying the second fluid is cleaned using the liquid pump 342 and the pressure controller 330 for controlling the temperature controller 344 and the pressure control valve 343 of the second fluid. The second fluid is brought into contact with the object 314.
[0177]
A description will be given using carbon dioxide as the fluid, and a press-formed part having a recess represented by a hat-type SUS (stainless steel) case or a part formed by a cutting method as the object 314 to be cleaned. The object to be cleaned 314 is placed in the cleaning jig 312 and set in the pressure vessel 310, and the fluid whose temperature and pressure conditions have been adjusted by the temperature controller 304 and the pressure control valve 303 are supplied into the pressure vessel 310 by the liquid pump 302. Introduce using. The pressure vessel 310 controls cleaning conditions using a temperature control device 311 and a pressure control device 330 for the vessel. Carbon dioxide is sent to the pressure vessel 310 in a liquid state, and the object to be cleaned 314 is immersed therein and used for cleaning. Further, a cylinder (or tank) 341 for supplying the second fluid to the cleaning object 314 having a concave structure in the pressure vessel 310 is provided with a liquid pump 342, a second fluid temperature controller 344, and the like. The supercritical carbon dioxide as the second fluid is brought into contact with the object to be cleaned 314 through the ejection part 345 using the pressure control device 330 that controls the pressure control valve 343.
[0178]
The cleaning object 314 having the concave structure is disposed in the pressure vessel 310, and the cleaning effect is promoted by the second fluid while being cleaned in the first fluid. When the ejection portion 345 of the second fluid is installed toward the opening of the object to be cleaned 314, it is possible to easily perform cleaning to the back which is difficult to clean. The effects are agitation effect due to diffusion etc. by contact of fluids with different densities and the effect of peeling off impurities, dissolving and removing effect of impurities having similar solubility by fluids with different solubilities, and when there is a pressure difference between both fluids It is considered that the vibration effect due to the impact on the pressure equalization acts on the, and the cleaning effect is accelerated. This facilitates effective elution and removal of components such as lubricating oil, which are easily dissolved in the fluid, up to the concave portions and narrow portions of the object to be cleaned. In addition, components such as glass and resin cutting powder that are difficult to dissolve in the fluid can be easily removed by being peeled off or extruded from a concave portion or a narrow portion of the object to be cleaned. At this time, the timing at which the second fluid is brought into contact may be continuous or intermittent, may be constant, may be subjected to speed modulation, and may be set according to the object to be cleaned.
[0179]
Further, when the density of the object to be cleaned 314 is lower than the density of the first fluid in the liquid state, by contacting the second fluids having different densities, the same object to be cleaned as in the second embodiment is provided. The agitating effect and the like due to the up and down movement of the liquid are obtained, and the cleaning effect is improved.
[0180]
Further, the fluid in which the first fluid and the second fluid containing the impurities removed from the object to be cleaned 314 are mixed is sent to the separation vessel 320, and the mixed fluid is separated by controlling the pressure or the temperature. And the washing residue 322 is separated and collected. Each separated fluid can be circulated and utilized under pressure. Further, if the first and second fluids are the same, the cleaning device and the cleaning operation can be simplified.
[0181]
Parts that can be expected to have a cleaning effect in the cleaning method and the cleaning apparatus according to the second and third embodiments of the present invention are mainly electronic parts used in electronics and related parts. In particular, it is a precision machined part formed by press forming and cutting. For these parts, lubricating oil, which is a processing oil, is indispensable to improve processing accuracy. However, the residue of the processing oil affects the performance characteristics of the next process, for example, the plating process and adhesion, and causes a decrease in the performance and reliability as devices and products. Therefore, it is effective for parts that require high-level residue removal, that is, precision cleaning. Applied products include matching layers for ultrasonic sensors and electrodes for batteries (especially secondary batteries). Other examples include a case for a battery, a case for an HDD (also referred to as a housing), and a case for an electrolytic capacitor. As the matching layer for the ultrasonic sensor, various materials such as a mixture of an inorganic glass balloon and an organic epoxy, an inorganic glass balloon only, and an organic epoxy only are used. The material for the ultrasonic sensor case and the like is stainless steel, aluminum, or epoxy resin. The processing is performed by deep drawing by press molding, resin molding, and cutting. The battery case is generally made of aluminum or, more recently, a multi-layered steel material plated with aluminum, and is made by preless molding. Aluminum is used as a material for the HDD case, and recently, a composite steel material in which aluminum is coated with an organic material is used and press-formed. Similarly, the case for the electrolytic capacitor is press-formed using aluminum alone or a composite steel sheet coated with an organic film on the aluminum material. As described above, the present invention can be applied to a composite material in which an organic substance and an inorganic substance of different materials are laminated by selecting a process or a gas type as a cleaning medium to be used. It is needless to say that the present invention is not limited to these product fields, and is also effective for parts having a concave structure processed by press molding and cutting.
[0182]
Hereinafter, the effects of the second and third embodiments of the present invention will be described with reference to specific examples.
[0183]
(Example 8)
The hollow glass beads (approximately 30 μm) were impregnated with an epoxy resin, and the heat-cured molded body was cut into a predetermined component shape and then washed. The part shape is 10.8mm in diameter x 1.15mm in height, and the density is about 550kg / m ³ Met. This part has a large number of bead-sized concave structures due to cutting or dropping of hollow glass beads on the processing surface.
[0184]
The cleaning effect was evaluated by visual inspection and measuring the amount of insoluble particles adhering to the surface. The appearance was visually inspected to see if there was any chipping or cracking, and for the particles, after cleaning, the presence of impurities on the surface of the component and inside the recess was observed by a stereoscopic optical microscope and a scanning electron microscope.
[0185]
The cleaning was carried out by putting 100 parts of the above-mentioned parts into a basket-like cleaning jig and using carbon dioxide as a fluid. The following cleaning methods were compared.
[0186]
(1) No cleaning (2) Supercritical carbon dioxide (about 57 ° C., 13 MPa, density about 550 kg / m ³ ), And washing for 3 hours by repeatedly raising and lowering the pressure between 12 MPa and 14 MPa at intervals of 10 minutes. (3) Carbon dioxide in a supercritical state (about 47 ° C., 12 MPa, density about 600 kg / m) ³ ) 3 hours immersion cleaning (4) Carbon dioxide in liquid state (about 20 ° C., density about 750 kg / m ³ ) For 1 hour and then washed under the conditions of (2) above. (5) Carbon dioxide in a supercritical state (about 47 ° C., 12 MPa, density about 600 kg / m ³ ) For 1 hour, and the pressure was abruptly released at a constant temperature to bring the inside of the container into a gaseous state, and the cleaning was repeated three times.
[0187]
[Table 8]

[0188]
In the case of this component, even if the component is cleaned, simply immersing the component in pressurized carbon dioxide as in (3) and (4) does not remove impurities, particularly those insoluble in carbon dioxide. It was found that the cleaning effect was low. This is because the parts are floating in the fluid, the parts are overlapped with each other, and the overlapped portions are not separated and are not washed. Further, it was found that it was difficult to remove impurities to the depth of the minute concave portion of the component only by keeping the component in contact with the fluid. In the case of causing a rapid phase change of the fluid as in (5), removal of impurities is promoted by the impact. However, in the case of this low-density part, chipping or cracking due to collision between parts is observed. There was something that could be done.
[0189]
In contrast, in the cleaning method (2) of the present invention, it was found that the recess was well cleaned. This effect occurs because, as a result of observing the inside of the pressure vessel, the density of the pressurized carbon dioxide changes and the parts move up and down to separate the contact surface, and the accompanying stirring effect acts. I understand.
[0190]
(Example 9)
The press-formed and cut cases were cleaned. The case is made of SUS304 and has a concave structure of φ12 mm and height 5 mm.
[0191]
The effect of the cleaning was evaluated by cleaning and analyzing 100 cases at a time, inspecting the appearance, inspecting the residual oil content, and measuring the amount of insoluble particles adhering to the surface. As for the appearance inspection, it was confirmed visually whether there was any chipping or cracking. In the residual oil analysis, the oil was extracted with a solvent (carbon tetrachloride), and the extracted oil was measured by FT-IR (Fourier transform infrared spectroscopy). The particles were measured using a particle inspection machine (Wacon surface inspection apparatus WM-1700 / 1500 manufactured by Topcon) after cleaning.
[0192]
For cleaning, carbon dioxide was used when 100 pieces of the above components were put in a basket-shaped cleaning jig and only one fluid was used. When using two fluids, carbon dioxide in a liquid state was used as the first fluid, and carbon dioxide in a supercritical state was used as the second fluid. The following cleaning methods were compared.
[0193]
(1) Supercritical carbon dioxide (approximately 47 ° C, 12 MPa) is sprayed in a liquid state of carbon dioxide (approximately 20 ° C), and is washed for 3 hours while spraying on parts. (2) Supercritical state (3) immersion in carbon dioxide (about 47 ° C., 12 MPa) for 3 hours, washing (3) immersing in carbon dioxide in a liquid state (about 20 ° C.) for 1 hour, washing under the conditions of (2) above, and (4) supercritical state After immersion in carbon dioxide (about 47 ° C., 12 MPa) for 1 hour, the pressure was rapidly released at a constant temperature to bring the inside of the container into a gas state, and the cleaning was repeated three times.
[0194]
[Table 9]

[0195]
In any of the methods, the appearance did not show any discoloration due to the adhesion of oil, and the amount of residual oil could be reduced by using pressurized carbon dioxide. However, for particles insoluble in carbon dioxide, it was found that cleaning only by immersion had a small effect. In particular, it was observed that it was present inside the concave structure. On the other hand, it was found that the cleaning method (1) of the present invention was excellent in cleaning for removing impurities.
[0196]
【The invention's effect】
According to the present invention, by controlling the density of the pressurized fluid to contact the component having the concave structure, lubricating oil or the like dissolved in the fluid due to the solvent effect of the pressurized fluid. Impurities can be efficiently removed. Further, by controlling the density of the fluid to be brought into contact with the component to have a stirring effect, impurities insoluble in the fluid can be efficiently removed. Therefore, in the present invention, in the cleaning process, by optimizing the cleaning conditions suitable for the part, in addition to the solvent effect of the pressurized fluid, the stirring effect can be simultaneously provided, and efficient cleaning of the part can be performed. Therefore, it is industrially valuable.
[0197]
In addition, by applying the above-described technique for releasing the adhesion, the surface of the object to be treated is uniformly homogenized by releasing the contact between the object and the object to be reformed in order to improve the surface, such as a hydroxyl group. It is also possible to apply the present invention to hydrophilization by formation of water, water repellency and oil repellency by a surface treatment agent, coating of the surface with another material, and the like. In addition, regarding the surface modification, in the case of injecting the second fluid, it is possible to obtain an effect that the surface modification can be efficiently performed by adding a treating agent to this fluid. In addition, by releasing the close contact between the object to be processed and the object to be extracted, it becomes possible to efficiently extract components from inside the object to be processed, and to extract oils and fats such as lubricating oils, The present invention can also be applied to the extraction of extracts from plants and the like, the extraction of flavors, and the like.
[0198]
In the above surface modification, the case which is a cleaning treatment product, the lubricating oil which is an impurity and CO 2 ₂ Is pressurized to obtain the fluid CO ₂ Is used because it has affinity (increases solubility) with oils and fats such as lubricating oils.
[0199]
In the above extraction, CO2 is released so as to dissolve adhesion between molecules on a micro scale and to dissolve on a macro scale. ₂ By changing the temperature and pressure of the ₂ The solubility in water (in other words, the solvent CO ₂ After the target substance to be extracted is dissolved in a solvent, the temperature and pressure are lowered, and the target substance to be extracted is precipitated and extracted.
[0200]
Note that by appropriately combining any of the various embodiments described above, the effects of the respective embodiments can be achieved.
[0201]
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those skilled in the art. It is to be understood that such changes and modifications are included therein unless they depart from the scope of the invention as set forth in the appended claims.
[Brief description of the drawings]
FIG. 1 is a state diagram of a cleaning medium according to a first embodiment of the present invention.
FIGS. 2A, 2B, 2C, and 2D are a cross-sectional view and a perspective view showing an example of a component having a concave structure according to the first embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a cleaning system according to the first embodiment of the present invention.
FIGS. 4A and 4B are graphs showing a cleaning step in the first embodiment of the present invention.
FIG. 5 is a sectional view showing a cleaning state according to the first embodiment of the present invention.
FIG. 6 is an explanatory diagram showing a cleaning target in Example 1 of the first embodiment of the present invention.
FIG. 7 is a perspective view showing an object to be cleaned in Example 3 of the first embodiment of the present invention.
FIG. 8 is an explanatory diagram illustrating a contact angle in Example 3 of the first embodiment of the present invention.
FIG. 9 is an explanatory diagram showing temperature dependence of physical properties of water.
10A and 10B are an explanatory diagram showing a portion where dirt is likely to remain on a macro scale with an arrow and an explanatory diagram showing a portion where dirt is likely to remain on a micro scale with an arrow.
FIG. 11 is an explanatory diagram showing, by arrows, portions where dirt is likely to remain on a macro basis.
FIG. 12 is a schematic sectional view of an ultrasonic sensor case as another example of the cleaning object in the cleaning method according to the first embodiment of the present invention.
FIG. 13 is a time chart at the time of pressure control in the cleaning method according to the first embodiment of the present invention.
FIG. 14 is a time chart at the time of temperature control in the cleaning method according to the first embodiment of the present invention.
FIG. 15 is an explanatory diagram when the pressure is increased using a two-layer chamber in the cleaning apparatus according to the modification of the first embodiment of the present invention.
FIG. 16 is an explanatory view showing a state where a door divided into two layers is opened when a pressure is reduced by using a two-layer chamber in the cleaning apparatus according to the modification of the first embodiment of the present invention.
FIG. 17 is an explanatory diagram of a state in which a heat medium is supplied in a liquid state in a cleaning device according to a modification of the first embodiment of the present invention.
FIG. 18 is an explanatory diagram of a state in which a heat medium is supplied in a gaseous state in a cleaning apparatus according to a modification of the first embodiment of the present invention.
FIG. 19 is an explanatory diagram illustrating a relationship among a control device, a temperature control relay, and a pressure control relay of the cleaning device according to the first embodiment of the present invention.
FIG. 20 is an explanatory diagram of a state in which a stirring propeller is rotated in order to increase cleaning efficiency in a cleaning device according to a modification of the first embodiment of the present invention.
FIG. 21 is an explanatory diagram of a state in which a stirring propeller is rotated in order to increase cleaning efficiency in a cleaning device according to a modification of the first embodiment of the present invention.
FIG. 22 is an explanatory diagram of a state in which a stirring propeller is rotated in order to increase cleaning efficiency in a cleaning device according to a modification of the first embodiment of the present invention.
FIG. 23 is an explanatory view showing a state in which a stirring propeller is rotated to increase the cleaning efficiency and a cleaning medium is supplied also from a nozzle in a cleaning apparatus according to a modification of the first embodiment of the present invention.
FIG. 24 is an explanatory diagram illustrating a state in which a cleaning medium is supplied from a nozzle in order to increase cleaning efficiency in a cleaning device according to a modification of the first embodiment of the present invention.
FIG. 25 is an explanatory diagram of a state in which an agitating propeller is rotated and ultrasonic waves are supplied from an ultrasonic sensor in order to increase cleaning efficiency in a cleaning apparatus according to a modification of the first embodiment of the present invention.
FIG. 26 is an explanatory diagram illustrating a state in which ultrasonic waves are supplied from an ultrasonic sensor in order to increase cleaning efficiency in a cleaning device according to a modification of the first embodiment of the present invention.
FIGS. 27A, 27B, and 27C are schematic cross-sectional views showing various nozzle shapes in a cleaning apparatus according to a modification of the first embodiment of the present invention.
FIG. 28 is an explanatory diagram of a state in which a cleaning medium is sequentially supplied from a plurality of nozzles to generate convection in order to increase cleaning efficiency in a cleaning apparatus according to a modification of the first embodiment of the present invention.
FIG. 29 is a state diagram of a fluid (fluid) such as carbon dioxide or water.
FIG. 30 is a schematic view of a cleaning device according to the first embodiment of the present invention.
FIG. 31 is a schematic view of a cleaning device according to a second embodiment of the present invention.
FIG. 32 is a schematic explanatory view showing the relationship between the object to be cleaned and the fluid when the density of the object to be cleaned is higher than the density of the fluid.
FIG. 33 is a schematic explanatory diagram showing the relationship between the object to be cleaned and the fluid when the density of the object to be cleaned is lower than the density of the fluid;
FIG. 34 is a schematic explanatory view showing the relationship between the object to be cleaned and the fluid when the density of the object to be cleaned is substantially equal to the density of the fluid and the propeller is not rotated.
FIG. 35 is a schematic explanatory view showing the relationship between the object to be cleaned and the fluid when the density of the object to be cleaned is substantially equal to the density of the fluid and the propeller is rotated.
FIG. 36 is a schematic diagram in a case where an information database is provided in the cleaning device of FIG. 30;
[Explanation of symbols]
1 Cleaning tank (high pressure vessel)
1a Inlet
1b outlet
2 Liquefaction supply tank
3 Cleaning medium supply unit (liquid pump)
4 Heater controller
5 heater
6 Waste liquid recovery layer
7 vaporizer
8 Collection section
26 Deposits
27, 28, 29, 30, 32 parts
31 Objects to be cleaned
101 critical point
102 Critical temperature Tc
103 Critical pressure Pc
104 Supercritical state
201 Supply cylinder (or tank) for fluid
202 liquid pump
203 Pressure control valve
204 temperature controller
210 pressure vessel
211 Temperature control device
212 Cleaning jig
213 Pressure adjustment valve
214 Objects to be cleaned (parts)
220 separation container
221 Temperature control device
222 Wash residue
223 Pressure adjusting valve
230 Pressure control device
301 Supply cylinder (or tank) for the first fluid
302 liquid pump
303 Pressure control valve
304 temperature controller
310 pressure vessel
311 Temperature control device
312 Cleaning jig
313 Pressure adjusting valve
314 Items to be cleaned (parts)
320 Separation container
321 Temperature control device
322 Wash residue
323 pressure regulating valve
330 pressure controller
341 Supply cylinder (or tank) for second fluid
342 liquid pump
343 pressure control valve
344 Temperature controller
380 fluid
381 impurities
1000 control means

Claims (10)

A cleaning method for removing impurities (381) attached to the surface of the object to be cleaned by bringing the pressurized fluid (380) into contact with the object to be cleaned (214),
The density of the object to be cleaned is equal to or less than the liquid density of the fluid, and the pressure of the fluid, by changing at least one condition of the temperature, the density of the fluid with respect to the density of the object to be cleaned. A cleaning method using a pressurized fluid in which the fluid is repeatedly brought into contact with the object to be cleaned. A cleaning method for removing impurities (381) attached to the surface of the object to be cleaned by bringing the pressurized fluid (380) into contact with the object to be cleaned (214),
The density of the object to be cleaned is equal to or lower than the liquid density of the fluid, and the pressure of the fluid and at least one condition of the temperature are changed to change the density of the object to be cleaned and the liquid density of the fluid. A cleaning method using a pressurized fluid in which the fluid is brought into contact with the object to be cleaned by applying a variation due to an external force to the fluid in a substantially equal state. 3. The cleaning method according to claim 1, wherein the fluid is a supercritical fluid. A cleaning method for removing impurities attached to the surface of the object to be cleaned by contacting the pressurized fluid with the object to be cleaned,
The object to be cleaned, which is immersed in the pressurized first fluid, is contacted with a pressurized second fluid having a different density from the first fluid for cleaning. A cleaning method using a pressurized fluid in which the second fluid is brought into contact with the object to be cleaned without changing the phase state of the first fluid. 5. The method according to claim 4, wherein the second fluid is a supercritical fluid. The density of the object to be cleaned is lower than the liquid density of the first fluid, and the second fluid having a lower density than the density of the object to be cleaned is brought into contact with the object to be cleaned. The cleaning method using a pressurized fluid according to any one of 4 and 5. 7. The method according to claim 4, wherein the first fluid and the second fluid are the same, the first fluid is a liquid, and the second fluid is a supercritical fluid. The cleaning method using a pressurized fluid according to any one of the first to third aspects. The cleaning method using a pressurized fluid according to any one of claims 1 to 7, wherein the fluid contains at least one of carbon dioxide, water, ammonia, carbon suboxide, and alcohol. The cleaning method using a pressurized fluid according to any one of claims 1 to 8, wherein the impurities attached to the surface of the object to be cleaned are lubricating oils. The cleaning method according to any one of claims 1 to 9, wherein the object to be cleaned is a component having a concave structure.

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