201114709 六、發明說明： 【發明戶斤屬之技術領域】 技術領域 本發明係關於一種可由連續供給之熔融玻璃將氣泡去 除之熔融玻璃之減壓脫泡裝置、以及使用該裝置之熔融玻 璃之淨化方法。 L· ^tr ϋ 背景技術 以往以來，為求提高成形玻璃製品之品質，在將已於 炫解爐熔解原料之熔融玻璃於成形裝置成形之前，設有去 除熔融玻璃内產生之氣泡的淨化步驟。 已知一種減壓脫泡方法（參考專利文獻1) ’係於該淨化 程序中將熔融玻璃導入減壓環境氣體内，並於該減壓環境 氣體下，使連續流動之熔融玻璃流内之氣泡大幅成長而使 包含於熔融玻璃内之氣泡上浮，並於熔融玻璃之表面使氣 泡破裂而去除，且於其後由減壓環境氣體排出之。 將實施減壓脫泡時使用之習知減壓脫泡裝置之_般構 造顯示於第5圖。 第5圖所顯示之減壓脫泡裝置1〇〇中，呈圓筒形狀之咸 壓脫泡槽120係以其長軸朝水平方向配向之方式收納配置 於減壓殼體110内。於減壓脫泡槽120之上游側之下面安穿 有朝垂直方向配向之上升管130,而下游側之下面則安裝有 下降管140。又，減壓脫泡槽120之上游側及下游側係意味 於減壓脫泡槽120流動之熔融玻璃G之流動方向的上游側及 201114709 下游側。上升管130及下降管140之其中一部分係位於減壓 设體11 〇内。 上升管130係與減壓脫泡槽120連通，而可將來自溶解 槽300之熔融玻璃G導入減壓脫泡槽120之導入機構。因此， 上升管130之下端部係插入上游池320之開口端，而浸潰至 該上游池320内之熔融玻璃G中。 下降管140係連通於減壓脫泡槽120，而將減壓脫泡後 之熔融玻璃G由減壓脫泡槽120下降並導入至後置程序處理 槽（未圖示）之導出機構。因此，下降管140之下端部係插入 下游池340之開口端，而浸潰至該下游池340内之熔融玻璃g 中。 減壓殼體110内中’減壓脫泡槽120、上升管130及下降 管140之周圍配設有將該等絕熱覆蓋之絕熱用磚等隔熱材 150。 顯示於第5圖之減壓脫泡裝置1〇〇中，減壓殼體11〇之頂 部設有可藉由利用真空果（未圖示）等真空吸引，而將該減 壓殼體110之内部保持於減壓狀態之吸引開口部2〇〇。 該收容配置於減壓殼體11 〇内之減壓脫泡槽丨2〇之頂 部，亦設有用以將該減壓脫泡槽120之内部保持於減壓狀態 之槽開口部160a及160b。槽開口部i6〇a係位於上升管13〇之 上方，而槽開口部160b係位於下降管14〇之上方。 先行技術文獻 專利文獻 【專利文獻1】特開平11 -130442號公報。 201114709 【發明内容】 發明揭示 發明欲解決之課題 減壓脫泡裝置中，宜於減壓殼體之頂部設置用以監視 減壓脫泡槽内部之窗部。第6圖係顯示設有窗部之減壓脫泡 槽之構造之圖。 顯示於第6圖之減壓脫泡裝置100'，係於減壓殼體110 之頂部設有用以監視減壓脫泡槽120内部之窗部170a、 170b。 窗部170a、170b係設於槽開口部[60a、160b上方之減 壓殼體110之頂部，而包含設於該減壓殼體110之頂部的殼 體開口部180a、180b。設於該減壓殼體110之頂部的殼體開 口部180a、180b嵌入有透明窗190a、190b，而可透過槽開 口部160a、160b觀察減壓脫泡槽120之内部。又，窗部170a、 170b係意指包含設於減壓殼體110之頂部的殼體開口部 180a、180b、與已嵌入於該殼體開口部180a、180b之透明 窗190a、190b的構造。 使用顯示於第6圖之減壓脫泡裝置100'來實施減壓脫泡 時，氣泡會在熔融玻璃表面破裂而產生氣體成分（以下稱為 「來自熔融玻璃之氣體成分））），但有時來自熔融玻璃之氣 體成分會做為凝聚物而附著於窗部170a、170b或其周邊之 減壓殼體110之頂部。又，窗部170a、170b或其周邊之減壓 殼體110之構件與來自熔融玻璃之氣體成分發生反應而得 到之生成物、或者該生成物或來自熔融玻璃之氣體成分之 201114709 凝聚物因熱而變性之生成物，有時會附著於減壓殼體110之 頂部。 以下，本說明書中，在前述凝聚物附著於窗部n〇a、 170b、17a、17b或其周邊之減壓殼體110、11之頂部之情況， 除了包含來自熔融玻璃之氣體成分之凝聚物附著於窗部 170a、170b、17a、17b或其周邊之減壓殼體110、11之頂部， 還包含前述反應生成物或熱變性之生成物附著於窗部 170a、170b、17a、17b或其周邊之減壓殼體110、11之頂部 等情況。 當如此之凝聚物附著於窗部170a、170b，特別是附著 於窗190a、190b時，監視減壓脫泡槽120内部會變得困難。 又，若附著於窗部170a、170b或其周邊之減壓殼體110 之頂部的凝聚物朝減壓脫泡槽120内落下，並混入流通於該 減壓脫泡槽120之熔融玻璃中時，會成為熔融玻璃之異物。 因此，有必要定期地去除附著於窗部170a、170b或其 周邊之減壓殼體110之頂部的凝聚物，但該作業必須停止減 壓脫泡裝置之運轉而實施，因此會降低生產性或玻璃製品 之良率。 為解決前述問題點，本發明之目的在於提供一種防止 來自熔融玻璃之氣體成分之凝聚物附著於設於減壓殼體頂 部之窗部、以及附著於其周邊之減壓殼體頂部的減壓脫泡 裝置。 用以解決課題之手段 為達成前述目的，本發明提供一種熔融玻璃之減壓脫 201114709 泡裝置，係包含有：減壓殼體，係可減壓吸引者；減壓脫泡 槽，係設於前述減壓殼體内而可進行熔融玻璃之減壓脫泡 者；導入機構，係設為連通至前述減壓脫泡槽，而可將減 壓脫泡前之熔融玻璃導入至減壓脫泡槽者；及導出機構， 係設為連通至前述減壓脫泡槽，而可將減壓脫泡後之熔融 玻璃由前述減壓脫泡槽導出者；其特徵在於： 前述減壓脫泡槽之頂部設有至少1個槽開口部， 前述減壓殼體之頂部設有至少1個窗部，該窗部係與前 述槽開口部成對而可用以監視前述減壓脫泡槽之内部者， 前述窗部係由設於減壓殼體之頂部的殼體開口部及鑲 嵌於該殼體開口部之透明窗所構成， 且，該熔融玻璃之減壓脫泡裝置具有用以朝前述窗部 内側供給氣體之氣體供給機構。 又，與前述槽開口部成對係意味前述槽開口部之水平 方向位置與前述窗部之水平方向位置呈相對應。此時，包 含前述槽開口部之水平方向位置與前述窗部之水平方向位 置不一致，而由斜方向監視前述減壓脫泡槽内部之情況。 由斜方向監視的情況亦可觀察前述減壓脫泡槽之内部。 又，本發明提供一種熔融玻璃之減壓脫泡裝置，係包 含有：減壓殼體，係可減壓吸引者；減壓脫泡槽，係設於前 述減壓殼體内而可進行熔融玻璃之減壓脫泡者；導入機 構，係設為連通至前述減壓脫泡槽，而可將減壓脫泡前之 熔融玻璃導入至減壓脫泡槽者；及導出機構，係設為連通 至前述減壓脫泡槽，而可將減壓脫泡後之熔融玻璃由前述 201114709 減壓脫泡槽導出者；其特徵在於： 前述減壓脫泡槽之頂部設有至少1個槽開口部， 前述減壓殼體之頂部設有至少1個窗部，該窗部係與前 述槽開口部成對而可用以監視前述減壓脫泡槽之内部者， 前述窗部係由設於減壓殼體之頂部的殼體開口部及鑲 嵌於該殼體開口部之透明窗所構成， 且，該熔融玻璃之減壓脫泡裝置具有用以加熱設於前 述前壓脫泡槽之前述槽開口部之周邊的加熱機構。 又，本發明提供一種熔融玻璃之減壓脫泡裝置，係包 含有：減壓殼體，係可減壓吸引者；減壓脫泡槽，係設於 前述減壓殼體内而可進行熔融玻璃之減壓脫泡者；導入機 構，係設為連通至前述減壓脫泡槽，而可將減壓脫泡前之 熔融玻璃導入至減壓脫泡槽者；及導出機構，係設為連通 至前述減壓脫泡槽，而可將減壓脫泡後之熔融玻璃由前述 減壓脫泡槽導出者；其特徵在於： 前述減壓脫泡槽之頂部設有至少1個槽開口部， 前述減壓殼體之頂部設有至少1個窗部，該窗部係與前 述槽開口部成對而可用於監視前述減壓脫泡槽之内部者， 前述窗部係由設於減壓殼體之頂部的殼體開口部及鑲 嵌於該殼體開口部之透明窗所構成， 且，該熔融玻璃之減壓脫泡裝置具有用以朝前述窗部 内側供給氣體之氣體供給機構，以及用以加熱設於前述減 壓脫泡槽之前述槽開口部周邊之加熱裝置。 又，本發明提供一種熔融玻璃之減壓脫泡裝置，係包 201114709 含有：減壓殼體，係可減壓吸引者；減壓脫泡槽，係設於 前述減壓殼體内而可進行熔融玻璃之減壓脫泡者；導入機 構，係設為連通至前述減壓脫泡槽，而可將減壓脫泡前之 熔融玻璃導入至減壓脫泡槽者；及導出機構，係設為連通 至前述減壓脫泡槽，而可將減壓脫泡後之熔融玻璃由前述 減壓脫泡槽導出者；其特徵在於： 前述減壓脫泡槽之頂部設有至少1個槽開口部， 前述減壓殼體之頂部設有至少1個窗部，該窗部係位於 與前述槽開口部之水平方向之位置一致，而可用以監視前 述減壓脫泡槽之内部者， 前述窗部係由設於減壓殼體之頂部的殼體開口部及鑲 嵌於該殼體開口部之透明窗所構成， 且，該減壓脫泡裝置具有用以朝前述窗部内側供給氣 體之氣體供給機構。 又，本發明提供一種熔融玻璃之減壓脫泡裝置，係包 含有：減壓殼體，係可減壓吸引者；減壓脫泡槽，係設於 前述減壓殼體内而可進行熔融玻璃之減壓脫泡者；導入機 構，係設為連通至前述減壓脫泡槽，而可將減壓脫泡前之 熔融玻璃導入至減壓脫泡槽者；及導出機構，係設為連通 至前述減壓脫泡槽，而可將減壓脫泡後之熔融玻璃由前述 減壓脫泡槽導出者；其特徵在於： 前述減壓脫泡槽之頂部設有至少1個槽開口部， 前述減壓殼體之頂部設有至少1個窗部，該窗部係位於 與前述槽開口部之水平方向之位置一致，而可用以監視前 201114709 述減壓脫泡槽之内部者， 前述窗部係由設於減壓殼體之頂部的殼體開口部及鑲 嵌於該殼體開口部之透明窗所構成， 且，該熔融玻璃之減壓脫泡裝置具有用以加熱設於前 述減壓脫泡槽之前述槽開口部周邊之加熱裝置。 又，本發明提供一種熔融玻璃之減壓脫泡裝置，係包 含有：減壓殼體，係可減壓吸引者；減壓脫泡槽，係設於前 述減壓殼體内而可進行熔融玻璃之減壓脫泡者；導入機 構，係設為連通至前述減壓脫泡槽，而可將減壓脫泡前之 熔融玻璃導入至減壓脫泡槽者；及導出機構，係設為連通 至前述減壓脫泡槽，而可將減壓脫泡後之熔融玻璃由前述 減壓脫泡槽導出者；其特徵在於： 前述減壓脫泡槽之頂部設有至少1個槽開口部， 前述減壓殼體之頂部設有至少1個窗部，該窗部係位於 與前述槽開口部之水平方向之位置一致，而可用以監視前 述減壓脫泡槽之内部者， 前述窗部係由設於減壓殼體之頂部的殼體開口部及鑲 嵌於該殼體開口部之透明窗所構成， 且，該熔融玻璃之減壓脫泡裝置具有用以朝前述窗部 内側供給氣體之氣體供給機構，以及用以加熱設於前述減 壓脫泡槽之前述槽開口部周邊之加熱裝置。 又，本發明提供一種熔融玻璃之減壓脫泡方法，係使 用前述之熔融玻璃之減壓脫泡裝置者。 又，本發明提供一種熔融玻璃之減壓脫泡方法，係使 10 201114709 用前述熔融玻璃之減壓脫泡裝置者， 且其特徵在於至少包含下述（1)及（2)之任一程序， (1) 供給氣體至前述窗部内側之程序； (2) 加熱前述槽開口部周邊之程序。 又，本發明提供一種熔融玻璃製造方法，係使用前述 熔融玻璃之減壓脫泡方法者。 又，本發明提供一種玻璃製品之製造方法，係具有： 減壓脫泡程序，係來自前述減壓脫泡方法者；原料熔融程 序，係作為該減壓脫泡程序之前置程序者；形成程序，係 作為該減壓脫泡之後置程序者；及漸冷程序，係作為該成 形程序之後置程序者。 發明效果 本發明之減壓脫泡裝置可藉由朝設於減壓殼體之頂部 之窗部之内側，亦即朝窗部之槽開口部側供給氣體、及/或 藉由以加熱機構加熱減壓脫泡槽之槽開口部周邊，而防止 來自熔融玻璃之氣體成分之凝聚物附著於該窗部及其周邊 之減壓殼體頂部。 結果，不需要為了去除附著於窗部或其周邊之減壓殼 體頂部之凝聚物，停止減壓脫泡裝置之運轉，而可提高生 產性或玻璃製品之良率。 又，附著於窗部或其周邊之減壓殼體頂部之凝聚物不 會混入流動於減壓脫泡槽之熔融玻璃中成為熔融玻璃之異 物，而製造之玻璃製品之品質會十分優異。 圖式簡單說明 π 201114709 第1圖係顯示本發明之減壓脫泡裝置之一構造例之剖 面圖。 第2圖係第1圖所顯示之減壓脫泡裝置丨〇之窗部17 a附 近之部分擴大圖。 第3圖係顯示本發明之減壓脫泡裝置之另—構造例之 剖面圖。 第4圖係第3圖所顯示之減壓脫泡裝置丨〇 |之槽開口部 16a附近之部分擴大圖。 第5圖係顯示習知例之減壓脫泡裝置之一構造例之剖 面圖。 第6圖係顯示習知例之設有窗部之減壓脫泡裝置構造 例的剖面圖。 C實方包方式;j 用以實施發明之最佳形態 以下’參照圖式說明本發明。 第1圖係顯示本發明之減壓脫泡裝置之一構造例之剖 面圖。第1圖中所示之減壓脫泡裝置1〇中，呈圓筒形狀之減 壓脫泡槽12係以其長軸朝水平方向配向之方式收納配置於 減壓喊體11内。減壓脫泡槽12之上游側下面安裝有朝垂直 方向配向之上升管13，而下游側下面安裝有下降管14。又， 減壓脫泡槽12之上游側及下游側意味流動於減壓脫泡槽i 2 之熔融玻璃G之流動方向的上游側與下游側。上升管13與下 降管14之一部分位於減壓殼體丨丨内。 如第1圖所示，上升管13係與減壓脫泡槽12連通，而可 12 201114709 將來自炫解槽300之熔融玻璃G導入減壓脫泡槽12之導入機 構°因此，上升管13之下端部係插入上游池32〇之開口端， 而浸潰至該上游池320内之熔融玻璃G中。 下降官14係連通於減壓脫泡槽12，而將減壓脫泡後之熔 融玻璃G由減壓脫泡槽12下降並導出至後續程序之處理槽 (未圖示）之導出機構。因此，下降管14之下端部係插入下游 池340之開口端，而浸潰至該下游池34〇内之熔融玻璃〇中。 於減壓殼體11内’減壓脫泡槽12、上升管13及下降管 14之周圍配設有將該等絕熱覆蓋之絕熱用磚等隔熱材15。 顯示於第1圖之減壓脫泡裝置10中，減壓殼體n之頂部 设有可利用真空泵（未圖示）等進行真空吸引，而藉此將該 減壓殼體11之内部保持於減壓狀態之吸引開口部2〇。 該收容配置於減壓殼體讥内之減壓脫泡槽12之頂部， 亦設有用以將該減壓脫泡槽12之内部保持於減壓狀態之槽 開口部16a及16b。槽開口部16&、16b亦可為用以監視減壓 脫泡槽12内部之開口部。 顯示於第1圖之減壓脫泡裝置10中，槽開口部16a位於 上升管13之上方，而槽開口部16b則位於下降管η之上方 惟，本發明之減壓脫泡裝置中，可於減壓脫泡槽之頂 部至少設有1個槽開口部，而設於減壓脫泡槽之頂部之槽開 口部數目以及槽開口部位置並不限定於第i圖所顯示之熊 樣。 因此，槽開口部16a、16b中亦可僅設其中一者。 又，於其等以外之部位（例如減壓脫泡槽12之中間部分） 13 201114709 設置1個槽開口部來代替槽開口部16a ' 16b亦可。 又’除了槽開口部16a、16b，亦可在該等以外之部位（例 如減壓脫泡槽12之中間部分）再設置第3槽開口部（甚至是 第4、第5槽開口部）。 惟，減壓脫泡槽12中，導入來自熔解槽3〇〇之熔融玻璃 G之上升管13與減壓脫泡槽12之連通部分、以及減壓脫泡後 之熔融玻璃G朝後續程序之處理槽導出之下降管14與減壓 脫泡槽12之連通部分，在確認減壓脫泡槽12内之炼融玻璃 之狀態（更具體而言為熔融玻璃表面）上特別重要，因此， 以於減壓脫泡槽12之上游與下游兩方觀察來監視之目的而 設於減壓脫泡槽12之頂部的槽開口部，如第1圖所示之槽開 口部16a、16b，宜至少設於上升管13及下降管14之上方。 設於減壓脫泡槽12之頂部之槽開口部16a、16b之形狀 並未特別受限，只要於監視減壓脫泡槽12内部上不會不方 便，且不會導致減壓脫泡槽12之強度降低，可選擇圓形、 橢圓型、矩形等各種形狀。 設於減壓脫泡槽12之頂部之槽開口部“a、16b之尺寸 亦未特別受限，只要於監視減壓脫泡槽12内部上不會不方 便，且不會導致減壓脫泡槽12之強度降低即可。就圓直徑 或者多角升>之外徑來看’可為3〇〜4〇〇mm，40mm〜350mm為 更佳’且50〜300mm尤為佳。 本發明之減壓脫泡裝置10中，係於減壓殼體丨丨之頂部 設有用以監視減壓脫泡槽12内部之窗部17a、17b。該窗部 17a、17b之位置係與設於減壓脫泡槽12之了員部之槽開口部 201114709 16a、16b之水平方向之位置一致。 窗部17a、17b係由設於減壓殼體11之頂部的殼體開口 部18a、18b、與嵌入至該殼體開口部18a、18b之透明窗19a、 19b所構成。又，該嵌入至該殼體開口部18a、18b之透明窗 19a、19b宜具有耐熱性、耐壓性及耐酸性等。滿足該等條 件之材料有例如石英玻璃、藍寶石玻璃或透明結晶化玻璃 等。 本發明之減壓脫泡裝置中，於減壓殼體之頂部，在與 設於減壓脫泡槽之頂部之槽開口部以水平方向對應之位 置，只要至少設有1個窗部即可，不要求一定要於減壓殼體 之頂部設置與設於減壓脫泡槽之頂部之槽開口部有相同數 目之窗部。故，窗部17a ' 17b中亦可僅設置其中一者。 惟，當考量到於減壓脫泡槽丨2之頂部設置槽開口部 16a、16b之其中1個目的，為考監視該減壓脫泡槽12内部 時，如第1圖所示，宜相對於設於減壓脫泡槽12之頂部之槽 開口部16a、16b，於減壓殻體丨丨之頂部設置相同數目之窗 部17a、17b。 又，監視減壓脫泡槽12之内部時，窗部之水平方向位 置不需一定要與槽開口部之水平方向位置一致，只要槽開 口部之水平方向位置與窗部之水平方向位置對應而成對即 可，且亦可使2者之水平方向位置錯開，而可由斜處監視減 壓脫泡槽内部即可。惟，槽開口部至窗部為止之距離較短 者由於光路較短，結構上宜使窗部之位置與槽開口部之大 致水平方向之位置呈一致。 15 201114709 設於減壓殼體11之頂部之窗部17a、17b之形狀，更具 體而言，作為窗部17a、17b而設於減壓殼體11之頂部之殼 體開口部18a、18b之形狀並未特別受限，只要於監視減壓 脫泡槽12内部上不會不方便，且不會導致減壓脫泡槽12之 強度降低落’可選擇圓形、橢圓型、矩形等各種形狀。惟， 就監視減壓脫泡槽12内部而言，設於減壓脫泡槽12之頂部 之槽開口部16a、16b之形狀、與作為窗部17a、17b而設於 減壓殼體11之頂部之殼體開口部18a、18b之形狀宜一致或 類似。 設於減壓殼體11之頂部之窗部17a、17b之尺寸，更具 體而言，作為窗部17a、17b而設於減壓殼體11之頂部之殼 體開口部18a、18b之尺寸亦未特別受限，只要於監視減壓 脫泡槽12内部上不會不方便，且不會導致減壓脫泡槽12之 強度降低即可。惟，就監視減壓脫泡槽12内部而言，設於 減壓脫泡槽12之頂部之槽開口部i6a、之尺寸、與作為 窗部17a、17b而設於減壓殼體11之頂部之殼體開口部i8a、 18b之尺寸宜大致相同。 故，作為窗部17a、17b而設於減壓殼體丨丨之頂部之殼 體開口部18a、18b之尺寸，宜為關於設於減壓脫泡槽12之 頂部之槽開口部16a、16b之尺寸所記載之範圍。 又，欲觀察本發明之減壓脫泡裝置丨〇之上升管13、下 降管14上方之炫融玻璃之狀態，並監視其狀態時，如第1、 3圖所示，宜將設於減壓殼體11之頂部之窗部17a與設於減 壓脫/包槽12之頂部之槽開口部16a ’或者設於減壓殼體11之 16 201114709 頂部之窗部17b與設於減壓脫泡槽12之頂部之槽開口部16b 構造成透過筒狀體等於縱方向連通以可由窗部17a、17b窺 視來觀察。又，欲觀察並監視朝橫方向流動於減壓脫泡裝 置1〇之減壓脫泡槽12中之熔融玻璃之狀態時，亦可於欲觀 察處’將窗部17a設於減壓殼體11之頂部，且於其垂直下方 或斜下方之減壓脫泡槽12之頂部設置槽開口部16a，構造成 使窗17a與槽開口部16a連通。 第1圖所示之本發明之減壓脫泡裝置10，具有用以供給 氣體至窗部17a、17b之氣體供給機構21a、21b。針對氣體 供給機構，參考第2圖（第1圖所顯示之減壓脫泡裝置10之 窗部17a附近之部分擴大圖）加以說明。又，雖參照第2圖 來說明用以供給氣體至窗部17a之氣體供給機構21a，但用 以供給氣體至窗部17b之氣體供給機構21b實質上亦為相同 構造。 第2圖中，氣體供給機構21a係金屬製，例如不錄鋼製、 黃銅製、鋼製或I呂製等中空管，且其中一端位於窗部〖7a之 内側，更具體而言，位於構成窗部17a之透明窗19a之下方， 而另一端貫通減壓殼體11之壁面而位於減壓殼體丨丨之外 部。 如第2圖所示，本發明之減壓脫泡裝置係由氣體供給機 構21a往窗部17a之内部’亦即窗部17a之槽開口部1&側供 給氣體g。更具體而言’將氣體g供給至構成窗部17a之透明 窗19a之下方。 當將氣體g由氣體供給機構2la往窗部17a(構成窗部17a 17 201114709 之透明窗I9a之下方)時，藉由稀釋存在於窗部⑽近之環 境氣體中的來自㈣_之氣體成分之凝聚物，可防止該 凝聚物附著於窗部17a或其周邊之減壓殼體〗丨之頂部。 又，當將氣體g由氣體供給機構21a往窗部na(構成窗部 17a之透明窗19a之下方）時，供給有氣體g之部位會較減壓殼 體11内之其他部位壓力較高。藉由該壓力差亦可防止該凝 聚物附著於窗部17a或其周邊之減壓殼體〖丨之頂部。 本發明之減壓脫泡裝置之氣體供給機構並無特別受 限，只要是可將氣體供給至設於減壓殼體頂部之窗部的構 造，亦可為圖式所示以外之構造。圖式所示以外之構造之 具體例，有例如將氣體供給機構連結至窗部17&等構造。 又，根據需要’亦可於窗部或窗部附近設置將已供給至窗 部内側之氣體排出之氣體排出機構。 个U之减歷脫泡裝置中’由氣體供給機構供給至窗 部之氣體，只要是不會特概減㈣泡裝置 殼雜沒有U影響者，可使用各種氣體。如此 例有例如乳氣(Η2)、氮氣(Ν2)、氧氣（〇2)、空氣、 破(C0)、二氧化碳(c〇2)'氩氣㈤、氦氣㈣ ― 氣氣(K0 '氣氣(Xe)、煙類氣體、碳氟氣體或 其中以價格便宜之氮氣、空氣等為宜。 H3)荨。 又’由氣體供給機構供給至窗部之氣體供给旦 只要可防止來請融玻璃之氣體 窗部17a及其周邊之減壓殼體u之頂部’並未特別 201114709 舉出由氣體供給機構21a供給至窗部17a之氣體g供給 量之一例，可為0.5〜100公升/分鐘，宜為0.5〜80公升/分 鐘，且以1〜50公升/分鐘為更佳。 又，舉出由氣體供給機構21a供給至窗部17a之氣體g之 流速之一例，可為0.1m/分鐘〜10m/分鐘，且以0.1m/分鐘〜 8m/分鐘為更佳。 第3圖係顯示本發明之減壓脫泡裝置之另外一構造例 之剖面圖。第3圖中所顯示之減壓脫泡裝置10'沒有用以供給 氣體至窗17a、17b之氣體供給機構21a、21b，取而代之者 係具有用以將設於減壓脫泡槽12之頂部之槽開口部16a、 16b周邊加熱之加熱機構22a、22b、22c、22d，而除了具有 加熱機構此點之外，與第1圖中所示之減壓脫泡裝置10相 同。 又，第3圖中所顯示之減壓脫泡裝置10·係顯示減壓脫泡 槽12之構成材料為白金或白金合金時之加熱機構22a、 22b、22c、22d。 針對加熱機構，參照第4圖（第3圖所顯示之減壓脫泡 裝置10'之槽開口部16a附近之部分擴大圖）加以說明。又， 第4圖係針對用以加熱槽開口部16a周邊之加熱機構22a、 22b加以說明，但第3圖所示之用以加熱槽開口部16b周邊之 加熱機構22c、22d亦與前述加熱機構22a、22b實質上具有 相同構造。 第4圖中，加熱機構22a、22b係通電用電極，且該電極 係於減壓脫泡槽12之頂部，以包圍設成連通至窗部17a、nb 19 201114709 之槽開口部16a、16b之入口部分的方式，安裝於上方為凸 狀之入口周邊部（以下僅簡稱凸部）之外周。藉由通電於電極 (加熱機構)22a、22b間，可加熱槽開口部16a之周邊，更具 體而言，可加熱為了設置槽開口部16a而形成於減壓脫泡槽 12頂部之凸部。由於來自流通於減壓脫泡槽12之熔融玻璃G 之氣體成分會由槽開口部16a朝減壓脫泡槽12之外部放 出，而凝聚於窗部17a及窗g[U7a周邊之減壓殼體11之頂 部，因此藉由加熱該槽開口部16a之周邊，可防止來自熔融 玻璃之氣體成分凝聚於窗部17a及窗部17a周邊之減壓殼體 11之頂部。且藉此，可防止來自熔融玻璃之氣體成分之凝 聚物附著於窗部17a及其周邊之減壓殼體11之頂部。 作為通電用電極之加熱機構22a、22b係要求有優異之 耐熱性極優異之導電性。滿足該等條件之材料舉例有白金 或者白金-金合金、白金-錢合金等白金合金。 依據熔融玻璃之組成，來自熔融玻璃之氣體成分會不 同，且依據該氣體成分凝聚之溫度會不同。因此，為了發 揮防止來自熔融玻璃之氣體成分凝聚於窗部17a及其周邊 之減壓殼體11頂部的效果所必要之槽開口部16 a周邊之加 熱溫度，需因應流通於減壓脫泡槽12之熔融玻璃G之組成而 適當選擇。舉例言之，若為使用於製造平板顯示器（FPD) 用之玻璃基板的無鹼玻璃時，藉由將槽開口部16a周圍加熱 至溫度1000〜1300°C，可發揮防止來自熔融玻璃之氣體成 分凝聚於窗部17a及其周邊之減壓殼體11頂部的效果。 本發明之減壓脫泡裝置之加熱機構不特別限定其構 20 201114709 造，只要可加熱設於減壓脫泡槽頂部之槽開口部周邊，亦 可為圖式所示以外之構造。圖式所示之態樣係於安裝在為 了 §又置槽開口部16a而形成於減壓脫泡槽12頂部之凸部外 周的電極(加熱機構)22a、22b間通電，藉此加熱該凸部。作 為其他的例子，亦可於該凸部僅安骏電極(加熱機構)22a， 而相當於電極（加熱機構）22b之電極(加熱機構)則設於凸 部以外之部位，例如設於減壓脫泡槽12之上游側之端部， 並藉由通電於該電極（加熱機構）與電極(加熱機構)22a間來 加熱槽開口部16a周邊。λ，在此所言之上游側意指流通於 減壓脫泡槽12之溶融玻璃g之流動方向之上游側。 又，前述係針對減壓脫泡槽之構成材料為白金或白金 合金之情況，顯示藉由通電加熱來加熱槽開口部周邊之態 樣，但本發明中之減壓脫泡槽，如後所述，亦可為以緻密 耐火材料作為構成材料者。此時，由於無法通電加熱，因 此只要將加熱器(加熱機構)安裝於為了設置槽開口部心而 形成於減壓脫泡槽12頂部之凸部外周，藉此加熱槽開口部 咖之周邊即可。當然，減壓脫泡槽之構成材料為白金或者 為白金合金時’亦可將加熱器（加熱機構)安裝於該凸部之外 周’並藉此加熱槽開口部16a之周邊。 作為用以防止來自熔融玻璃之氣體成分之凝聚物附著 於窗部17a及其周邊之減壓殼體n頂部的機構，已針對具有 用以將氣體供給至窗部之供給機構的減壓脫泡裝置、以及 具有設於減壓脫泡槽之頂部而用以加熱槽開口部周邊之加 熱機構的減壓脫泡裝置加以說明。本發明之減壓脫泡裝置 21 201114709 可僅具有前述氣體供給機構與前述加熱機構的其中之— 者’且亦可具有兩者。為了防止來自熔融玻璃之氣體 之凝聚物附著於窗部17a及其周邊之減壓殼體刀 構’以包含前錢體供給機構以及前述加關構兩者尤2 以下，就氣體供給機構及加熱機構以外之本 壓脫泡裝置之構成要素加以闡述。 之另 第卜3圖所示之減壓脫泡襄置1〇、1〇.中，減 12、上升管13及下降管14由於為炫融玻璃G之導管，因此^ 使用耐熱性及對炼融玻璃之耐歸優異之材料來製作。: 例而3 ’為白金或者白金合金製之中空管、圓筒狀管 他各種形狀之筒狀管。白金合金之具體例有白金金合金、、 合金等° X ’其他例子則可為陶究系之非金屬無機 枓製，亦即，緻密質耐火材料製之中空管、圓筒狀管或 其他各形狀之筒狀管。㈣㈣火材料之具體例有銘電禱 耐火材料、氧化錯電制火材料轴氧化錯二氧化石夕系電 鑄耐火材料等電鑄耐火材料，以及_質糾火材料、緻 费質氧化錯-二氧切系耐火材料及^氧化錯·二氧化石夕系 耐火材料等緻抢質燒製耐火材料。收容減壓脫泡槽12並收 谷上升官13及下降管丨4之一部分之減壓殼體n係金屬製， 例如不鏽鋼製。 本發明之減屋脫泡裝置1〇、1〇，之各構成要素之尺寸， 可因應需要而適當選擇。減壓脫泡槽12之尺寸不論減壓脫 泡槽12為白金製或白金合金製又或者為緻密質耐火材料 22 201114709 製’可根據所使用之減壓脫泡裝置或減壓脫泡槽12之形狀 來適當選擇。為例如第1、3圖所顯示之圓筒形狀之減壓脫 泡槽12時，其尺寸之一例如下。 ◎水平方向之長度：1〜20m ◎内徑：0.2〜3m(圓形剖面） 當減壓脫泡槽12為白金製或白金合金製時，壁厚宜為 4mm以下，而以0.5〜1.2mm尤佳。 減壓脫泡槽不限定為剖面圓形之圓筒形狀，亦可為剖 面形狀為橢圓形或半圓形狀之略圓筒形狀者、或者剖面為 矩形之筒形狀者。 上升管13及下降管14不論為白金製、白金合金製或緻 密質耐火材料製，可因應所使用之減壓脫泡裝置適當選 擇。例如第1、3圖所示之減壓脫泡裝置10、10·之情況中， 上升管13及下降管14之尺寸之一例如下。 ◎内徑：0·05〜0.8m，而以0.1〜〇.6m尤佳 ◎外徑·· 0.2〜6m ’而以0.4〜4m尤佳 上升管13及下降管14為白金製或白金合金製時，壁厚 宜為0.4〜5mm，而以0.6〜4mm尤佳。 使用本發明之減壓脫泡裝置之熔融玻璃之減壓脫泡方 法，可藉由與習知熔融玻璃之減壓脫泡方法同樣之條件而 實施。例如，實施減壓脫泡時，宜加熱減壓脫泡槽12，而 使其内部成為ll〇〇°C〜1600°c、特別為1150Ό〜1500°C之 溫度範圍。又，減壓脫泡槽12之内部宜減壓為絕對壓力38 〜460mmHg(51〜613hPa)，且以減壓至60〜350mmHg(80〜 23 201114709 467hPa)尤佳。 又’由生產性之觀點來看’流動於減壓脫泡槽12之熔 融玻璃G之流量以1〜2〇0〇噸/日為佳^ 使用本發明之減壓脫泡裝置之炫融玻璃製造方法中， 宜包含原料㈣程序來作為本發明之減壓脫泡方法之前置 程序、並包含絲料來作錢續料。料娜融程序 例如可為習知公知者’例如為根據玻璃之種類加熱至約 l4〇〇°C以上総融原料之程序。使狀原料只要是適於製 造玻璃之原材料’並未加以特別受限，例如可使用將石英 紗、硼酸、石灰石等習知物配合最終玻璃製品之組成加以 調合的原材料’亦可包含希望之淨化劑。》，該成形程序 町為例如習知公知者’如浮動成形程序、推出成形程序及 融合成練料。成形後之玻璃係藉由漸冷機構進行漸冷 (漸冷程序），使成形後已固化之玻璃之内部不殘留殘留應 力’並因應需要切斷（切斷程序）及因應其他需要經過研磨 擇序等成為玻璃製品。X ’漸冷㈣、切斷程序及研磨程 序係公眾知悉之公知技術。 根據本發明而製造之熔融玻璃，只要是藉由加熱炼融 法製造之玻璃，組成上並未加以限制。故，可為無驗玻璃， 办可為代表驗石灰玻狀鹼石灰二氧切玻璃或如驗卿 酸鹽玻璃之鹼玻璃。本發明係特別適用於無鹼玻璃，且適 於製造液晶顯示器基板用之無鹼玻璃。 又，根據本發明，可得到泡沫品質極為優異之玻璃製 品，因此非常適於作為FPD用之玻璃基板等玻璃製品之製造 24 201114709 方法。 產業上之利用性 根據本發明之玻璃製造用之減壓脫泡裝置，可防止來 自熔融玻璃之氣體成分之凝結物附著於設於減壓殼體頂部 之窗部或其周邊部，因此可由前述窗部隨時觀察並監視減 壓脫泡槽内之熔融玻璃之狀態，藉此可確實掌握減壓脫泡 裝置之運轉狀況，而有助於生產良率之提高。 又，根據本發明，不會如習知裝置般，附著於減壓殼 體之前述窗部或其周邊之凝結物會落入流動於減壓殼體内 之熔融玻璃面，而成為熔融玻璃之異物，因此可抑制製造 之玻璃因前述異物造成缺點，而有助於品質之提升。 又，在此引用已於2009年6月19日申請之日本專利申請 號2009-146254號之說明書、申請專利範圍、圖式及摘要所 有内容，並採用而作為本發明之發明揭示。 【圖式簡單說明】 第1圖係顯示本發明之減壓脫泡裝置之一構造例之剖 面圖。 第2圖係第1圖所顯示之減壓脫泡裝置10之窗部17a附 近之部分擴大圖。 第3圖係顯示本發明之減壓脫泡裝置之另一構造例之 剖面圖。 第4圖係第3圖所顯示之減壓脫泡裝置1(V之槽開口部 16a附近之部分擴大圖。 第5圖係顯示習知例之減壓脫泡裝置之一構造例之剖 25 201114709 面圖。 第6圖係顯示習知例之設有窗部之減壓脫泡裝置構造 例的剖面圖。 【主要元件符號說明】 10、10’、100、100'...減壓脫泡裝 置 1卜110…減壓殼體 12、 120…減壓脫泡槽 13、 130...上升管 14、 140...下降管 15、 150…隔熱材 16a、16b、160a、160b...槽開口部 17a、17b、170a、170b...窗部 18a、18b、180a、180b...殼體開口 部 19a、19b、190a、190b...透明窗 20、200...吸引開口部 21a、21b…氣體供給機構 22a、22b、22c、22d...加熱機構(通 電加熱用電極） 300…熔解槽 320.. .上游池 340.. .下游池 G"熔融玻璃 g…氣體 26BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum degassing apparatus for molten glass from which bubbles can be continuously supplied by molten glass, and purification of molten glass using the same method. L·^tr ϋ Background Art Conventionally, in order to improve the quality of a molded glass product, a purification step of removing bubbles generated in the molten glass is provided before the molten glass in which the raw material is melted in the drying furnace is molded in the molding apparatus. A vacuum degassing method (refer to Patent Document 1) is known in which a molten glass is introduced into a reduced-pressure atmosphere in the purification process, and bubbles in a continuously flowing molten glass flow are made under the reduced-pressure ambient gas. The bubbles which are contained in the molten glass are floated up, and the bubbles are ruptured and removed on the surface of the molten glass, and are then discharged by the reduced-pressure ambient gas. The conventional structure of a conventional vacuum degassing apparatus used for performing vacuum degassing is shown in Fig. 5. In the vacuum degassing apparatus 1 shown in Fig. 5, the cylindrical pressure degassing tank 120 is housed and disposed in the decompression housing 110 so that its long axis is aligned in the horizontal direction. A riser pipe 130 that is aligned in the vertical direction is attached to the lower side of the upstream side of the vacuum degassing tank 120, and a downcomer pipe 140 is attached to the lower side of the downstream side. Further, the upstream side and the downstream side of the vacuum degassing tank 120 mean the upstream side in the flow direction of the molten glass G flowing through the vacuum degassing tank 120 and the downstream side of 201114709. A part of the riser pipe 130 and the downcomer pipe 140 are located in the decompression chamber 11 〇. The riser pipe 130 is in communication with the vacuum degassing tank 120, and the molten glass G from the dissolution tank 300 can be introduced into the introduction mechanism of the vacuum degassing tank 120. Therefore, the lower end portion of the riser pipe 130 is inserted into the open end of the upstream pool 320, and is immersed in the molten glass G in the upstream pool 320. The downcomer 140 is connected to the vacuum degassing tank 120, and the molten glass G which has been defoamed under reduced pressure is lowered by the vacuum degassing tank 120 and introduced into a derivation mechanism of a post-processing tank (not shown). Therefore, the lower end portion of the downcomer pipe 140 is inserted into the open end of the downstream pool 340 and is immersed in the molten glass g in the downstream pool 340. In the inside of the decompression housing 110, a heat insulating material 150 such as a heat insulating bunker covering the heat insulating defoaming tank 120, the riser pipe 130, and the downcomer 140 is disposed. In the vacuum degassing apparatus 1A shown in Fig. 5, the top of the decompression housing 11 is provided with a vacuum suction by a vacuum fruit (not shown) or the like, and the decompression housing 110 is provided. The inside of the suction opening portion 2 is held in a reduced pressure state. The housing is disposed at the top of the decompression defoaming tank 2 in the decompression housing 11 and is provided with groove openings 160a and 160b for holding the inside of the decompression defoaming tank 120 in a reduced pressure state. The slot opening portion i6〇a is located above the riser tube 13〇, and the slot opening portion 160b is located above the down tube 14〇. Japanese Laid-Open Patent Publication No. Hei 11-130442. DISCLOSURE OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION In the vacuum degassing apparatus, it is preferable to provide a window portion for monitoring the inside of the decompression defoaming tank at the top of the decompression housing. Fig. 6 is a view showing the structure of a vacuum degassing tank provided with a window portion. The vacuum degassing apparatus 100' shown in Fig. 6 is provided with a window portion 170a, 170b for monitoring the inside of the vacuum degassing tank 120 at the top of the decompression housing 110. The window portions 170a and 170b are provided on the top of the pressure-reducing casing 110 above the groove opening portions [60a and 160b, and include housing opening portions 180a and 180b provided at the top of the decompression housing 110. The case opening portions 180a and 180b provided at the top of the decompression housing 110 are fitted with transparent windows 190a and 190b, and the inside of the decompression defoaming groove 120 is observed through the groove opening portions 160a and 160b. Further, the window portions 170a and 170b are intended to include the housing opening portions 180a and 180b provided at the top of the decompression housing 110 and the transparent windows 190a and 190b that are fitted into the housing opening portions 180a and 180b. When the vacuum degassing apparatus 100' shown in FIG. 6 is used to perform vacuum degassing, bubbles are ruptured on the surface of the molten glass to generate a gas component (hereinafter referred to as "a gas component derived from molten glass")). The gas component from the molten glass adheres to the top of the decompression housing 110 of the window portion 170a, 170b or its periphery as agglomerate. Further, the window portion 170a, 170b or a member of the decompression housing 110 around it The product obtained by the reaction with the gas component from the molten glass or the product of the product or the gas component derived from the molten glass, which is denatured by heat, may adhere to the top of the decompression housing 110. Hereinafter, in the present specification, in the case where the agglomerates adhere to the top of the decompression housings 110, 11 of the window portions n?a, 170b, 17a, 17b or the periphery thereof, in addition to the condensation of gas components from the molten glass The object adheres to the top of the decompression housings 110, 11 of the window portions 170a, 170b, 17a, 17b or its periphery, and further includes the reaction product or the thermally denatured product attached to the window portions 170a, 170b, 17a, 17b. The top of the decompression housings 110, 11 around the periphery, etc. When such agglomerates adhere to the windows 170a, 170b, particularly to the windows 190a, 190b, it may become difficult to monitor the inside of the decompression degassing tank 120. Further, the aggregates adhering to the top of the decompression housing 110 attached to the window portions 170a and 170b or the periphery thereof are dropped into the decompression degassing tank 120, and are mixed into the molten glass flowing through the decompression defoaming tank 120. At this time, it becomes a foreign matter of the molten glass. Therefore, it is necessary to periodically remove the aggregates adhering to the top of the decompression housing 110 of the window portions 170a and 170b or the periphery thereof, but the operation must stop the operation of the decompression defoaming device. In order to solve the above problems, an object of the present invention is to provide a method for preventing agglomerates of gas components from molten glass from adhering to a window portion provided at the top of a decompression housing. And a vacuum degassing device attached to the top of the decompression housing at the periphery thereof. Means for Solving the Problems In order to achieve the above object, the present invention provides a decompression device for molten glass, which is a 201114709 bubble device. The pressure reduction casing is a decompressible suction device; the vacuum degassing tank is provided in the decompression casing to perform decompression defoaming of the molten glass; and the introduction mechanism is connected to the foregoing The vacuum degassing tank is depressurized, and the molten glass before vacuum degassing can be introduced into the vacuum degassing tank; and the derivation mechanism is connected to the vacuum degassing tank, and the decompression can be degassed. The molten glass is led out by the decompression degassing tank; wherein at least one groove opening is provided at the top of the vacuum degassing tank, and at least one window portion is provided at the top of the decompression housing. The window portion is paired with the groove opening portion for monitoring the inside of the vacuum degassing tank, and the window portion is provided by a casing opening portion provided at a top portion of the decompression casing and embedded in the casing opening portion The transparent glass defoaming device has a gas supply mechanism for supplying gas to the inside of the window portion. Further, the pair of the groove opening portions means that the horizontal position of the groove opening portion corresponds to the horizontal position of the window portion. At this time, the position in the horizontal direction including the groove opening portion does not coincide with the horizontal position of the window portion, and the inside of the vacuum degassing tank is monitored obliquely. The inside of the vacuum degassing tank can also be observed in the case of monitoring in an oblique direction. Moreover, the present invention provides a vacuum degassing apparatus for molten glass, comprising: a decompression housing which is a decompressible suction; and a vacuum degassing tank which is melted in the decompression housing to be melted a glass decompression defoamer; an introduction mechanism for connecting the molten glass before decompression and degassing to a vacuum degassing tank; and a derivation mechanism Connected to the vacuum degassing tank, and the molten glass defoamed under reduced pressure is exported from the above-mentioned 201114709 vacuum degassing tank; characterized in that: the top of the vacuum degassing tank is provided with at least one slot opening The top of the decompression housing is provided with at least one window portion, and the window portion is paired with the slot opening portion for monitoring the inside of the decompression defoaming tank, and the window portion is provided by a housing opening portion at the top of the pressure housing and a transparent window embedded in the opening portion of the housing, wherein the molten glass degassing defoaming device has a groove for heating the front pressure degassing tank a heating mechanism around the opening. Moreover, the present invention provides a vacuum degassing apparatus for molten glass, comprising: a decompression housing which is a decompressible suction; and a vacuum degassing tank which is melted in the decompression housing to be melted a glass decompression defoamer; an introduction mechanism for connecting the molten glass before decompression and degassing to a vacuum degassing tank; and a derivation mechanism The molten glass which is defoamed under reduced pressure is connected to the vacuum degassing tank, and is characterized in that: at least one groove opening is provided at the top of the vacuum degassing tank The top of the decompression housing is provided with at least one window portion, and the window portion is paired with the slot opening portion for monitoring the inside of the decompression defoaming tank, and the window portion is provided under decompression a housing opening at the top of the housing and a transparent window embedded in the opening of the housing, and the vacuum degassing device for molten glass has a gas supply mechanism for supplying gas to the inside of the window portion, and Used to heat the aforementioned slot opening provided in the aforementioned vacuum degassing tank Heating device around the part. Moreover, the present invention provides a vacuum degassing apparatus for molten glass, and the kit 201114709 includes a decompression housing which is a decompressible attractor, and a vacuum degassing tank which is provided in the decompression housing. a decompression defoaming of molten glass; an introduction mechanism for connecting the molten glass before decompression and degassing to a vacuum degassing tank; and a derivation mechanism In order to communicate with the vacuum degassing tank, the molten glass defoamed under reduced pressure is derived from the vacuum degassing tank; wherein: the top of the vacuum degassing tank is provided with at least one slot opening The top of the decompression housing is provided with at least one window portion, and the window portion is located at a position in the horizontal direction of the slot opening portion, and can be used to monitor the inside of the decompression defoaming tank, the window The part is composed of a housing opening provided at the top of the decompression housing and a transparent window embedded in the opening of the housing, and the decompression defoaming device has a gas for supplying gas to the inside of the window portion. Supply agency. Moreover, the present invention provides a vacuum degassing apparatus for molten glass, comprising: a decompression housing which is a decompressible suction; and a vacuum degassing tank which is melted in the decompression housing to be melted a glass decompression defoamer; an introduction mechanism for connecting the molten glass before decompression and degassing to a vacuum degassing tank; and a derivation mechanism The molten glass which is defoamed under reduced pressure is connected to the vacuum degassing tank, and is characterized in that: at least one groove opening is provided at the top of the vacuum degassing tank The top of the decompression housing is provided with at least one window portion, and the window portion is located at a position in the horizontal direction of the slot opening portion, and can be used to monitor the inside of the decompression defoaming tank of the previous 201114709. The window portion is composed of a housing opening portion provided at the top of the decompression housing and a transparent window embedded in the opening portion of the housing, and the molten glass degassing defoaming device has heating for the reduction Heating device around the opening of the groove of the degassing tankMoreover, the present invention provides a vacuum degassing apparatus for molten glass, comprising: a decompression housing which is a decompressible suction; and a vacuum degassing tank which is melted in the decompression housing to be melted a glass decompression defoamer; an introduction mechanism for connecting the molten glass before decompression and degassing to a vacuum degassing tank; and a derivation mechanism The molten glass which is defoamed under reduced pressure is connected to the vacuum degassing tank, and is characterized in that: at least one groove opening is provided at the top of the vacuum degassing tank The top of the decompression housing is provided with at least one window portion, and the window portion is located at a position in the horizontal direction of the slot opening portion, and can be used to monitor the inside of the decompression defoaming tank, the window portion The utility model comprises a housing opening provided at a top of the decompression housing and a transparent window embedded in the opening of the housing, and the vacuum degassing device of the molten glass has a gas for supplying gas to the inside of the window. a gas supply mechanism, and a heating device provided in the foregoing The heating means around the opening of the groove of the degassing tank is depressurized. Further, the present invention provides a vacuum degassing method for molten glass, which is a vacuum degassing apparatus using the above molten glass. Moreover, the present invention provides a vacuum degassing method for molten glass, which is a vacuum degassing apparatus for the molten glass of 10 201114709, and is characterized by comprising at least one of the following procedures (1) and (2) (1) A program for supplying gas to the inside of the window portion; (2) A program for heating the periphery of the opening of the groove. Further, the present invention provides a method for producing a molten glass, which is a method for using a vacuum degassing method of the molten glass. Moreover, the present invention provides a method for producing a glass product, comprising: a vacuum degassing procedure, which is derived from the vacuum degassing method; and a raw material melting procedure as a pre-programmer of the vacuum degassing procedure; The program is used as the program after the decompression defoaming; and the gradual cooling program is used as the post program for the forming program. Advantageous Effects of Invention The vacuum degassing apparatus of the present invention can be supplied to the inside of the window portion provided at the top of the decompression housing, that is, to the groove opening portion side of the window portion, and/or by heating with a heating mechanism The periphery of the opening of the groove of the degassing vessel is depressurized, and the aggregate of the gas component from the molten glass is prevented from adhering to the top of the decompression housing of the window portion and its periphery. As a result, it is not necessary to stop the operation of the vacuum degassing apparatus in order to remove the aggregate attached to the top of the decompression casing attached to the window portion or the periphery thereof, and the productivity or the yield of the glass product can be improved. Further, the aggregates adhering to the top of the decompression housing of the window portion or the periphery thereof are not mixed with the molten glass flowing in the vacuum degassing tank to become a foreign matter of the molten glass, and the quality of the manufactured glass product is excellent. BRIEF DESCRIPTION OF THE DRAWINGS π 201114709 Fig. 1 is a cross-sectional view showing a structural example of a vacuum degassing apparatus of the present invention. Fig. 2 is a partially enlarged view of the window portion 17a of the vacuum degassing apparatus shown in Fig. 1. Fig. 3 is a cross-sectional view showing another structural example of the vacuum degassing apparatus of the present invention. Fig. 4 is a partially enlarged view of the vicinity of the groove opening portion 16a of the vacuum degassing device 第 shown in Fig. 3. Fig. 5 is a cross-sectional view showing a configuration example of a vacuum degassing apparatus of a conventional example. Fig. 6 is a cross-sectional view showing a structural example of a vacuum degassing apparatus provided with a window portion of a conventional example. C. The best mode for carrying out the invention. Hereinafter, the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing a structural example of a vacuum degassing apparatus of the present invention. In the vacuum degassing apparatus 1A shown in Fig. 1, the cylindrical decompression defoaming tank 12 is housed and disposed in the decompression body 11 so that its long axis is aligned in the horizontal direction. A rising pipe 13 that is aligned in the vertical direction is attached to the lower side of the upstream side of the vacuum degassing tank 12, and a downcomer 14 is attached to the lower side of the downstream side. Further, the upstream side and the downstream side of the vacuum degassing tank 12 mean the upstream side and the downstream side in the flow direction of the molten glass G of the vacuum degassing tank i 2 . A portion of the riser 13 and the downcomer 14 are located within the decompression housing bore. As shown in Fig. 1, the riser 13 is in communication with the vacuum degassing tank 12, and the molten glass G from the drain tank 300 can be introduced into the introduction mechanism of the vacuum degassing tank 12 by the 201114709. Therefore, the riser 13 The lower end portion is inserted into the open end of the upstream pool 32, and is immersed in the molten glass G in the upstream pool 320. The descending member 14 is connected to the vacuum degassing tank 12, and the molten glass G which has been defoamed under reduced pressure is lowered by the vacuum degassing tank 12 and is led to a discharge mechanism of a processing tank (not shown) of a subsequent procedure. Therefore, the lower end portion of the downcomer 14 is inserted into the open end of the downstream pool 340 and is immersed in the molten glass crucible in the downstream tank 34. In the decompression housing 11, a heat insulating material 15 such as a heat insulating brick covered with heat insulation is disposed around the vacuum degassing tank 12, the riser pipe 13, and the down pipe 14. The vacuum degassing apparatus 10 shown in Fig. 1 is provided with a vacuum pump (not shown) or the like at the top of the decompression housing n, whereby the inside of the decompression housing 11 is held by The suction opening portion 2 is in a reduced pressure state. The accommodation is disposed at the top of the decompression degassing tank 12 in the decompression casing, and is provided with groove openings 16a and 16b for maintaining the inside of the decompression defoaming tank 12 in a reduced pressure state. The groove opening portions 16&, 16b may be openings for monitoring the inside of the decompression degassing tank 12. In the vacuum degassing apparatus 10 shown in Fig. 1, the groove opening portion 16a is located above the riser pipe 13, and the groove opening portion 16b is located above the down pipe η. However, in the vacuum degassing device of the present invention, At least one groove opening portion is provided on the top of the vacuum degassing tank, and the number of the groove openings and the position of the groove opening portion provided at the top of the vacuum degassing tank are not limited to the bear samples shown in Fig. i. Therefore, only one of the slot opening portions 16a and 16b may be provided. Further, in place of the other parts (for example, the intermediate portion of the decompression defoaming tank 12) 13 201114709, one groove opening portion may be provided instead of the groove opening portion 16a ' 16b. Further, in addition to the groove opening portions 16a and 16b, the third groove opening portion (even the fourth and fifth groove opening portions) may be further provided at a portion other than the above (e.g., the intermediate portion of the vacuum degassing tank 12). In the vacuum degassing tank 12, the communication portion between the riser 13 and the vacuum degassing tank 12 of the molten glass G from the melting tank 3, and the molten glass G after degassing under reduced pressure are directed to the subsequent process. It is particularly important to confirm the state of the molten glass in the vacuum degassing tank 12 (more specifically, the surface of the molten glass) in the communication portion between the downcomer 14 and the vacuum degassing tank 12 which are taken out from the treatment tank. The groove opening portion provided at the top of the vacuum degassing vessel 12 for the purpose of monitoring the upstream and downstream of the vacuum degassing vessel 12, as shown in Fig. 1, is preferably at least the groove opening portions 16a, 16b. It is disposed above the riser 13 and the downcomer 14. The shape of the groove opening portions 16a, 16b provided at the top of the vacuum degassing tank 12 is not particularly limited as long as it is not inconvenient to monitor the inside of the vacuum degassing tank 12, and does not cause a decompression degassing tank. The strength of 12 is reduced, and various shapes such as a circle, an ellipse, and a rectangle can be selected. The size of the opening portion "a, 16b" provided at the top of the vacuum degassing tank 12 is not particularly limited, and it is not inconvenient to monitor the inside of the vacuum degassing tank 12, and does not cause decompression under reduced pressure. The strength of the groove 12 can be lowered. In the case of the outer diameter of the circle diameter or the multi-angle liter, it can be 3 〇 to 4 〇〇 mm, 40 mm to 350 mm is more preferable, and 50 to 300 mm is particularly preferable. The pressure defoaming device 10 is provided with a window portion 17a, 17b for monitoring the inside of the decompression degassing tank 12 at the top of the decompression housing 。. The position of the window portions 17a, 17b is set at a reduced pressure. The positions of the slot openings 201114709 16a and 16b of the sump 12 are aligned in the horizontal direction. The window portions 17a and 17b are fitted to the housing opening portions 18a and 18b provided at the top of the decompression housing 11, and are embedded therein. The transparent windows 19a and 19b of the case opening portions 18a and 18b are formed. Further, the transparent windows 19a and 19b embedded in the case opening portions 18a and 18b preferably have heat resistance, pressure resistance, acid resistance, and the like. The materials of such conditions are, for example, quartz glass, sapphire glass or transparent crystallized glass, etc. The vacuum degassing device of the present invention In the top of the decompression housing, at least one window portion is provided at a position corresponding to the horizontal opening of the groove opening provided at the top of the decompression degassing tank, and it is not required to be decompressed at all. The top of the casing is provided with the same number of window portions as the groove opening portion provided at the top of the vacuum degassing tank. Therefore, only one of the window portions 17a' 17b may be provided. However, when considering the decompression One of the purpose of providing the groove opening portions 16a and 16b at the top of the defoaming tank 2 is to monitor the inside of the vacuum degassing tank 12, as shown in Fig. 1, preferably with respect to the degassing defoaming tank. The slot opening portions 16a and 16b at the top of the 12 are provided with the same number of window portions 17a and 17b at the top of the decompression housing 丨丨. Further, when the inside of the vacuum degassing tank 12 is monitored, the horizontal position of the window portion is not It is necessary to match the horizontal position of the opening of the slot, as long as the horizontal position of the opening of the slot corresponds to the horizontal position of the window, and the position of the horizontal direction of the two can be shifted. Monitor the inside of the vacuum degassing tank. However, the opening of the tank to the window The shorter distance is due to the shorter optical path, and the structure should be such that the position of the window portion coincides with the position of the horizontal opening of the slot opening portion. 15 201114709 The shape of the window portions 17a, 17b provided at the top of the decompression housing 11 More specifically, the shape of the case opening portions 18a and 18b provided at the top of the decompression housing 11 as the window portions 17a and 17b is not particularly limited as long as the inside of the decompression degassing tank 12 is monitored. It is inconvenient and does not cause the strength of the vacuum degassing tank 12 to decrease. Various shapes such as a circular shape, an elliptical shape, and a rectangular shape can be selected. However, in the case of monitoring the inside of the vacuum degassing tank 12, it is set at a reduced pressure. The shape of the groove opening portions 16a and 16b at the top of the defoaming tank 12 is preferably the same as or similar to the shape of the casing opening portions 18a and 18b provided at the top of the decompression housing 11 as the window portions 17a and 17b. The size of the window portions 17a and 17b provided at the top of the decompression housing 11 is more specifically the size of the housing opening portions 18a and 18b provided at the top of the decompression housing 11 as the window portions 17a and 17b. It is not particularly limited as long as it is not inconvenient to monitor the inside of the vacuum degassing tank 12, and the strength of the vacuum degassing tank 12 is not lowered. However, the inside of the vacuum degassing tank 12 is monitored, and the size of the groove opening i6a provided at the top of the vacuum degassing tank 12 and the top of the decompression housing 11 as the window portions 17a and 17b are provided. The housing opening portions i8a, 18b are preferably substantially the same size. Therefore, the size of the case opening portions 18a and 18b provided at the top of the decompression housing 作为 as the window portions 17a and 17b is preferably the groove opening portions 16a and 16b provided at the top of the decompression defoaming groove 12. The range stated in the dimensions. Further, in order to observe the state of the glazed glass above the riser 13 and the downcomer 14 of the vacuum degassing apparatus of the present invention, and monitor the state thereof, as shown in Figs. The window portion 17a at the top of the pressure-retaining casing 11 and the groove opening portion 16a' provided at the top of the pressure-reducing/unpacking groove 12 or the window portion 17b provided at the top of the decompression housing 11 16 201114709 The groove opening portion 16b at the top of the bubble tank 12 is configured to be viewed through the cylindrical body so as to be connected to the longitudinal direction so as to be peekable by the window portions 17a, 17b. Further, when it is desired to observe and monitor the state of the molten glass flowing in the vacuum degassing tank 12 of the vacuum degassing apparatus 1 in the horizontal direction, the window portion 17a may be provided in the decompression housing at the point of observation. The top of the 11 is provided with a groove opening portion 16a at the top of the vacuum degassing tank 12 vertically downward or obliquely downward, and is configured to communicate the window 17a with the groove opening portion 16a. The vacuum degassing apparatus 10 of the present invention shown in Fig. 1 has gas supply mechanisms 21a and 21b for supplying gas to the windows 17a and 17b. The gas supply means will be described with reference to Fig. 2 (a partial enlarged view of the vicinity of the window portion 17a of the vacuum degassing apparatus 10 shown in Fig. 1). Further, although the gas supply mechanism 21a for supplying the gas to the window portion 17a will be described with reference to Fig. 2, the gas supply mechanism 21b for supplying the gas to the window portion 17b has substantially the same structure. In Fig. 2, the gas supply means 21a is made of metal, for example, a hollow tube such as a steel, brass, steel or Ilu, and one end of which is located inside the window 7a, more specifically, The lower side of the transparent window 19a of the window portion 17a is formed, and the other end penetrates the wall surface of the decompression housing 11 and is located outside the decompression housing. As shown in Fig. 2, the vacuum degassing apparatus of the present invention supplies the gas g from the gas supply mechanism 21a to the inside of the window portion 17a, that is, the groove opening portion 1 & side of the window portion 17a. More specifically, the gas g is supplied to the lower side of the transparent window 19a constituting the window portion 17a. When the gas g is supplied from the gas supply mechanism 2a1 to the window portion 17a (below the transparent window I9a constituting the window portion 17a 17 201114709), the gas component from (4)_ which is present in the ambient gas near the window portion (10) is diluted. The agglomerates prevent the agglomerates from adhering to the top of the decompression housing of the window portion 17a or its periphery. Further, when the gas g is supplied from the gas supply means 21a to the window portion na (below the transparent window 19a constituting the window portion 17a), the portion where the gas g is supplied is higher in pressure than the other portion in the decompression casing 11. By this pressure difference, it is also possible to prevent the gel from adhering to the top of the decompression housing of the window portion 17a or its periphery. The gas supply mechanism of the vacuum degassing apparatus of the present invention is not particularly limited as long as it can supply gas to the window portion provided at the top of the decompression housing, and may have a structure other than that shown in the drawings. Specific examples of the structure other than those shown in the drawings include, for example, a structure in which a gas supply mechanism is coupled to the window portion 17 & Further, a gas discharge mechanism for discharging the gas supplied to the inside of the window portion may be provided in the vicinity of the window portion or the window portion as needed. Among the U-reduced defoaming devices, the gas supplied to the window by the gas supply means can be used as long as it does not substantially reduce (4) the bubble device, and the U-influence does not affect the U. Such as, for example, milk (Η2), nitrogen (Ν2), oxygen (〇2), air, broken (C0), carbon dioxide (c〇2) 'argon (five), helium (four) - gas (K0 ' gas (Xe), a flammable gas, a fluorocarbon gas or a nitrogen gas, an air or the like which is inexpensive. H3) 荨. Further, 'the gas supplied to the window portion by the gas supply means can be prevented from being supplied to the gas window portion 17a of the molten glass and the top portion of the decompression housing u around the glass', and is not particularly supplied by the gas supply mechanism 21a. An example of the amount of gas g supplied to the window portion 17a may be 0. 5 to 100 liters / minute, preferably 0. 5 to 80 liters/minute, and more preferably 1 to 50 liters/minute. Further, an example of the flow rate of the gas g supplied to the window portion 17a by the gas supply mechanism 21a may be 0. 1m / min ~ 10m / min, and 0. 1m / min ~ 8m / min is better. Fig. 3 is a cross-sectional view showing another structural example of the vacuum degassing apparatus of the present invention. The vacuum degassing apparatus 10' shown in Fig. 3 has no gas supply means 21a, 21b for supplying gas to the windows 17a, 17b, but is provided for placing on the top of the decompression degassing tank 12. The heating mechanisms 22a, 22b, 22c, and 22d heated around the groove opening portions 16a and 16b are the same as the vacuum degassing device 10 shown in Fig. 1 except that the heating mechanism is provided. Further, the vacuum degassing apparatus 10 shown in Fig. 3 shows the heating mechanisms 22a, 22b, 22c, and 22d when the constituent material of the vacuum degassing tank 12 is platinum or platinum alloy. The heating mechanism will be described with reference to Fig. 4 (a partial enlarged view of the vicinity of the groove opening portion 16a of the vacuum degassing apparatus 10' shown in Fig. 3). 4, the heating means 22a, 22b for heating the periphery of the opening 16a of the tank are described. However, the heating means 22c, 22d for heating the periphery of the opening 16b of the groove shown in Fig. 3 are also combined with the heating mechanism described above. 22a, 22b have substantially the same configuration. In Fig. 4, the heating means 22a, 22b are electrodes for energization, and the electrodes are attached to the top of the decompression degassing tank 12 so as to surround the groove openings 16a, 16b which are connected to the window portions 17a, nb 19 201114709. The manner of the inlet portion is attached to the outer periphery of the peripheral portion (hereinafter simply referred to as a convex portion) which is convex at the top. By energizing between the electrodes (heating means) 22a, 22b, the periphery of the opening portion 16a of the groove can be heated, and more specifically, the convex portion formed on the top of the reduced pressure degassing tank 12 for heating the groove opening portion 16a can be heated. The gas component from the molten glass G flowing through the vacuum degassing tank 12 is discharged from the groove opening portion 16a toward the outside of the vacuum degassing tank 12, and is condensed on the window portion 17a and the window g [decompression shell around the U7a). Since the top of the body 11 is heated, the gas component from the molten glass is prevented from aggregating on the top of the decompression housing 11 around the window portion 17a and the window portion 17a by heating the periphery of the groove opening portion 16a. Thereby, it is possible to prevent the aggregate of the gas component from the molten glass from adhering to the top of the decompression housing 11 of the window portion 17a and its periphery. The heating means 22a and 22b which are electrodes for energization are required to have excellent electrical conductivity which is excellent in heat resistance. Materials satisfying these conditions are exemplified by platinum alloys such as platinum or platinum alloys and platinum alloys. Depending on the composition of the molten glass, the composition of the gas from the molten glass will be different, and the temperature at which the gas component will agglomerate will vary. Therefore, in order to exhibit a heating temperature around the groove opening portion 16a necessary for preventing the gas component from the molten glass from being aggregated on the top portion of the decompression housing 11 at the window portion 17a and the periphery thereof, it is necessary to flow in the decompression degassing tank. The composition of the molten glass G of 12 is appropriately selected. For example, in the case of an alkali-free glass used for producing a glass substrate for a flat panel display (FPD), by heating the periphery of the groove opening portion 16a to a temperature of 1000 to 1300 ° C, it is possible to prevent gas components from the molten glass. The effect of condensing on the top of the decompression housing 11 of the window portion 17a and its periphery. The heating mechanism of the vacuum degassing apparatus of the present invention is not particularly limited to the structure 20 201114709, and may be a structure other than that shown in the drawings as long as it can heat the periphery of the opening of the groove provided at the top of the vacuum degassing vessel. The pattern shown in the drawing is electrically connected between the electrodes (heating means) 22a, 22b attached to the outer periphery of the convex portion formed on the top of the vacuum degassing tank 12 for the purpose of the groove opening portion 16a, thereby heating the convex portion. unit. As another example, the electrode (heating means) 22a may be provided only in the convex portion, and the electrode (heating means) corresponding to the electrode (heating means) 22b may be provided in a portion other than the convex portion, for example, in decompression. The end portion on the upstream side of the defoaming tank 12 is heated between the electrode (heating means) and the electrode (heating means) 22a to heat the periphery of the groove opening portion 16a. λ, the upstream side as used herein means the upstream side of the flow direction of the molten glass g flowing through the vacuum degassing tank 12. Further, in the case where the constituent material of the vacuum degassing vessel is platinum or a platinum alloy, the state in which the periphery of the opening of the tank is heated by electric heating is shown, but the vacuum degassing tank in the present invention is as follows. As described above, a dense refractory material may be used as a constituent material. In this case, since the heating cannot be performed by the electric current, the heater (heating means) is attached to the outer periphery of the convex portion formed on the top of the decompression degassing tank 12 in order to provide the opening of the groove, thereby heating the periphery of the opening portion of the groove. can. Of course, when the constituent material of the vacuum degassing tank is platinum or a platinum alloy, a heater (heating means) may be attached to the outer periphery of the convex portion to thereby heat the periphery of the groove opening portion 16a. As a mechanism for preventing the aggregate of the gas component from the molten glass from adhering to the top of the window portion 17a and the periphery of the decompression housing n, the decompression defoaming has been provided for the supply mechanism for supplying the gas to the window portion. A device and a vacuum degassing device having a heating mechanism provided on the top of the vacuum degassing vessel for heating the periphery of the opening of the tank will be described. The vacuum degassing apparatus 21 201114709 of the present invention may have only the gas supply mechanism and the heating mechanism described above, and may have both. In order to prevent the agglomerates of the gas from the molten glass from adhering to the window portion 17a and the decompression housing structure of the periphery thereof to include both the front body supply mechanism and the aforementioned addition and closing mechanism, the gas supply mechanism and the heating are provided. The components of the present pressure degassing device other than the mechanism are explained. The vacuum defoaming device shown in Fig. 3 is 1〇, 1〇. In the case of the reduction tube 12, the riser tube 13 and the down tube 14 are made of a material which is excellent in heat resistance and resistance to refractory glass. : For example, 3' is a hollow tube or a cylindrical tube made of platinum or platinum alloy. Specific examples of the platinum alloy include a platinum gold alloy, an alloy, and the like. X 'Other examples may be a non-metallic inorganic tantalum made of a ceramics, that is, a hollow tube, a cylindrical tube, or the like made of a dense refractory material. A tubular tube of various shapes. (4) (4) Specific examples of fire materials include fused refractory materials, oxidized misfired fire materials, axial oxidation oxidized silica dioxide, electroforming refractories, and other electroforming refractories, and _ quality tempering materials, Oxygen-cut refractories and oxidized erbium-doped dioxide refractories, etc. The decompression housing 12 that houses the decompression degassing tank 12 and which is part of the valley riser 13 and the downcomer tube 4 is made of metal, for example, made of stainless steel. The size of each component of the reduced-bulb defoaming device 1〇, 1〇 of the present invention can be appropriately selected as needed. The size of the vacuum degassing tank 12 is either a white gold or a platinum alloy or a dense refractory material 22 201114709. The vacuum degassing device or the vacuum degassing tank 12 can be used according to the vacuum degassing device. The shape is chosen appropriately. For example, in the case of the cylindrical decompression defoaming tank 12 shown in Figs. 1 and 3, one of the dimensions is as follows. ◎ Length in the horizontal direction: 1~20m ◎ Inner diameter: 0. 2~3m (circular cross section) When the vacuum degassing tank 12 is made of platinum or platinum alloy, the wall thickness should be 4mm or less, and 0. 5~1. 2mm is especially good. The vacuum degassing vessel is not limited to a cylindrical shape having a circular cross section, and may have a substantially cylindrical shape having an elliptical or semicircular cross-sectional shape or a rectangular cross-sectional shape. The riser pipe 13 and the downcomer pipe 14 are made of platinum, a platinum alloy or a dense refractory material, and can be appropriately selected in accordance with the vacuum degassing apparatus to be used. For example, in the case of the vacuum degassing apparatus 10, 10· shown in Figs. 1 and 3, one of the sizes of the riser 13 and the downcomer 14 is, for example, lower. ◎Inner diameter: 0·05~0. 8m, and 0. 1 ~ 〇. 6m is especially good ◎ outer diameter · · 0. 2~6m ’ and 0. 4~4m is particularly good. When the riser 13 and the downcomer 14 are made of platinum or platinum alloy, the wall thickness should be 0. 4~5mm, and 0. 6~4mm is especially good. The vacuum degassing method of the molten glass using the vacuum degassing apparatus of the present invention can be carried out under the same conditions as those of the conventional vacuum glass degassing method. For example, in the case of performing vacuum degassing, it is preferred to heat the degassing defoaming tank 12 so that the inside thereof is in a temperature range of ll ° C to 1600 ° C, particularly 1150 Torr to 1500 ° C. Further, the inside of the vacuum degassing tank 12 is preferably reduced to an absolute pressure of 38 to 460 mmHg (51 to 613 hPa), and more preferably to a reduced pressure of 60 to 350 mmHg (80 to 23 201114709 467 hPa). Further, 'from the viewpoint of productivity, the flow rate of the molten glass G flowing in the vacuum degassing tank 12 is preferably 1 to 2 Torr/day. ^ The glazing glass using the vacuum degassing apparatus of the present invention is used. In the production method, the raw material (4) procedure is preferably included as a pre-program of the vacuum degassing method of the present invention, and the yarn is included for the money. The procedure can be, for example, a well-known person's, for example, a procedure for heating a raw material to a temperature of about l4 ° C or more depending on the type of glass. The raw material of the present invention is not particularly limited as long as it is a raw material suitable for the production of glass. For example, a raw material obtained by blending a conventional material such as quartz yarn, boric acid or limestone with a composition of the final glass product may also contain a desired purification. Agent. The forming program is, for example, a well-known person such as a floating forming program, a forming forming program, and a blending material. The formed glass is gradually cooled by a gradual cooling mechanism (gradual cooling process), so that residual stress does not remain in the interior of the solidified glass after forming, and is cut off according to the need (cutting process) and selected according to other needs. Orders become glass products. The X's gradual cooling (4), the cutting procedure and the grinding procedure are known to the public. The molten glass produced according to the present invention is not limited in composition as long as it is a glass produced by a heating and smelting method. Therefore, it can be a non-test glass, which can be used to represent lime-glassy soda-lime dioxy-cut glass or alkali glass such as sulphate glass. The present invention is particularly suitable for use in an alkali-free glass and is suitable for the production of an alkali-free glass for a liquid crystal display substrate. Moreover, according to the present invention, a glass product having excellent foam quality can be obtained, and therefore it is very suitable for the production of a glass product such as a glass substrate for FPD 24 201114709. INDUSTRIAL APPLICABILITY According to the vacuum degassing apparatus for glass production of the present invention, it is possible to prevent the condensation of the gas component from the molten glass from adhering to the window portion provided at the top of the decompression housing or the peripheral portion thereof. The window portion observes and monitors the state of the molten glass in the vacuum degassing tank at any time, whereby the operation state of the vacuum degassing apparatus can be surely grasped, and the production yield can be improved. Further, according to the present invention, the condensate adhering to the window portion of the decompression housing or the periphery thereof does not fall into the molten glass surface flowing in the decompression housing as in the conventional device, and becomes molten glass. The foreign matter can suppress the defects of the manufactured glass due to the aforementioned foreign matter, and contribute to the improvement of the quality. The contents of the specification, the claims, the drawings and the abstract of the Japanese Patent Application No. 2009-146254, filed on Jun. 19, 2009, are hereby incorporated by reference. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a structural example of a vacuum degassing apparatus of the present invention. Fig. 2 is a partially enlarged view of the vicinity of the window portion 17a of the vacuum degassing apparatus 10 shown in Fig. 1. Fig. 3 is a cross-sectional view showing another structural example of the vacuum degassing apparatus of the present invention. Fig. 4 is a partially enlarged view of the vicinity of the groove opening portion 16a of the vacuum degassing apparatus 1 shown in Fig. 3. Fig. 5 is a cross-sectional view showing a configuration example of a vacuum degassing apparatus of a conventional example. Fig. 6 is a cross-sectional view showing a structural example of a vacuum degassing apparatus having a window portion according to a conventional example. [Explanation of main component symbols] 10, 10', 100, 100'. . . Decompression defoaming device 1 Bu 110... Decompression housing 12, 120... Decompression degassing tank 13, 130. . . Rising tube 14, 140. . . Drop pipe 15, 150... heat insulation material 16a, 16b, 160a, 160b. . . Slot opening 17a, 17b, 170a, 170b. . . Window portion 18a, 18b, 180a, 180b. . . Housing opening 19a, 19b, 190a, 190b. . . Transparent window 20, 200. . . The suction openings 21a, 21b...the gas supply mechanisms 22a, 22b, 22c, 22d. . . Heating mechanism (electrode for electric heating) 300... melting tank 320. . . Upstream pool 340. . . Downstream pool G" molten glass g... gas 26